Machine Vision

updated 2004-12-07.

Information I've found on "Machine Vision", which I have broadly defined as "Machines are sensitive to photons, the software that runs on them, and objects specifically designed to be viewed by these machines".

This includes

• bouncing photons off the moon
• Oklahoma Imaging Laboratory
• Real-time video processing / image processing
• Real-time digital signal processing / system control
• Available digital cameras (commercial off-the-shelf systems) (includes QuickCam information)
• Building digital cameras (chip-level information)
• Non-Real-time video processing / image processing Image Processing Software, wavelets, theory, etc.
  • mathematical morphology
  • clustering and color quantization
  • demos
• infrared sensors
• circuit board inspection
• 2-way infrared data communication IR protocols
• the Global Positioning System (GPS)
• gps_receivers reviews off-the-shelf GPS receivers
• wireless networking
• the fast Fourier transform (FFT)
• spread spectrum communication
• 1D and 2D Optical Bar Codes and Magnetic Stripe Information Standards (all grouped together because of their close similarity)
• smart cards
• Biometric systems (Retina scanners, Iris scanners, Fingerprint readers, etc.)
• tetrachromate vision
• DTV (digital television) including HDTV
• unsorted

related pages:

• http://visual.wiki.taoriver.net/moin.cgi/PhotoWiki
• primary_colors.html
• holography.html computer-generated holograms
• Visualization tools computer_graphics_tools.html#visualization (medical image visualization, abstract mathematical function visualization, etc.)
• dimension.html#quaternions
• ECC data_compression.html#ecc error correction codes; error detection and correction
• Cool Maps link_farm.html#maps includes some links to satellite images
• standard test image list data_compression.html#benchmark .
• computer_graphics_tools.html#file_formats including JPEG image compression and other image compression information. This file covers the reverse problem -- rather than talking about how to collect and automatically interpret information, it talks about how to display already-collected information for human interpretation.
• data_compression.html#file_formats detailed descriptions of standard image formats and ideas for those who want to improve file formats.
• Astronomy astronomy.html pushes image sensing to its limits.
• For many years humans debated the "wave-like nature" vs. the "particle-like nature" of photons. This page usually takes the particle-like perspective; my emc_faq.html page generally takes the wave-like perspective. Ideally, we would unify this all in one treatment. This page always treats photons as good things that carry information, neglecting what happens when they hit something other than the receiver designed for them. My emc_faq.html always treats photons as bad things that carry energy, focusing on all the bad things that happen when photons of the wrong frequency hit the wrong thing.
• serialportdocs.html documents serial protocols; these might be used over serial photon links like IrDA.
• Some people use Fuzzy Logic and neural nets to process images; I have some links to more information at Robot information as well as more links to some platforms (robots) that carry cameras around.
• data_compression.html has more image compression information, and more information on wavelets.
• webcams and telerobots
• Low-cost lasers (including IR lasers)
• ultrasonic sonar information ultrasonic.html
• free_d.html has links to synthetically generating computer graphics.
• , including Pad++ http://www.cs.umd.edu/hcil/pad++ "zooming 'multiscale interfaces'"
• bignums related to photons, light emitting equipment, and light sensors. bignums.html#photon [FIXME: should that information be moved here ?]
• schematics.html has a photon receiver circuit.

I am particularly interested in real-time mobile-platform machine vision. If you find any relevant links, I'd appreciate you letting me know.

bouncing photons off the moon

bouncing photons off the moon

• http://paintthemoon.org/ an artistic approach
• Moonbounce Weak Signal and Astrophotography by Mike Cook AF9Y http://www.af9y.com/ has EME information; links to other EME sites; software for weak signal detection; explains astronomy photo image processing.
• International laser ranging service (ILRS) http://ilrs.gsfc.nasa.gov/ does constant, continuous distance measurements from base stations to retroreflectors on artificial satellites and the natural satellite.

  Satellite Link Budget Evaluation http://www.wettzell.ifag.de/publ-cgi-bin/linkbudget.py has a list of retroreflector satellites and a on-line calculator ``calculating the absulute return signal strength in terms of photoelectrons with respect to various system, atmospheric and satellite parameters.''

• SETI, EME, Radio Astronomy and Radio Amateurs(W6/PA0ZN) http://www.nitehawk.com/rasmit/welcome1.html "The following Pages are dedicated to: building bridges between the EME, SETI and Radio Astronomy Amateur Interest Groups and the promotion and preservation of Weaksignal Communication." (radio waves are photons too !)
• Inconstant Moon http://www.fourmilab.ch/earthview/moon_ap_per.html by John Walker, has some interesting details about the moon.
• http://www.lpi.usra.edu/expmoon/apollo_landings.html shows where all the Apollo missions landed (Apollo 11, Apollo 14, Apollo 15 all placed retro-reflectors.)
• http://www.qsl.net/k7on/ant/antenn_4.txt ``high performance arrays and more specifically EME (Earth-Moon-Earth) antennas. EME affords a unique property, viz. that due to the approximately 2-1/2 seconds it takes a radio wave to traverse the 450,000 mile path to the Moon and back, the EMEer can make improvements to his antenna system and actually hear the difference by listening for his own echos.''
• http://guthvenus.tripod.com/photongate.htm has some useful numbers on typical illumination and reflection; somewhat paranoid speculation on evolution on Venus. Continued in LASER/PACKETS or simply XENON COMMUNICATIONS "FIRST CONTACT" by Brad Guth, July 05, 2003 http://guthvenus.tripod.com/laser-com.htm

• 
  From: Markus Imhof 
  Subject: Re: Simple/interested electronics project for high school work  experience
  Date: 16 Jun 2000 00:00:00 GMT
  X-Accept-Language: de,en
  Organization: Siemens AG
  Mime-Version: 1.0
  Newsgroups: sci.electronics.design
  
  Brad Albing wrote:
  > > "Russ.Shaw" wrote:
  > > > What about modulating a laser diode led with audio pwm, and using a lens and
  > > photodiode for receive. It'd be interesting to see what range one could get
  > > at night etc.
  > > Hmmm... that would be a good one.  If your air quality down there is better than
  > up here, your line of sight distance would probably be pretty good.
  > > Here's a variation on that that's probably not going to work, but just might.
  > Increase the laser power a bunch.
  
  Irrelevant :-)
  But what you do need for that experiment is a laser with very low
  opening angle, which can (in the range you're going to need for that)
  only be achieved with a large aperture. 'Large' in this case meaning a
  couple of feet, e.g. a suitable telescopic mirror.
  
  > Point it at the moon.  Point a telescope at the
  > moon with your photo-detector installed on the eyepiece (suitably refocused to
  > produce an image on the photo-diode face instead of inside your eyeball).  Do this
  > with a new or nearly new moon so you can visually spot your outbound laser-light.
  > Move around on the moon's surface a little so as to find a good, flat spot for
  > best reflectivity.
  
  Not necessary - see above. For a practical laser, the opening angle will
  be large enough to cover a good sized portion (if not all) of the moon's
  disk, so moving the laser around accomplishes pretty little. As for
  looking for a flat spot for good reflectivity - at an average
  reflectivity below 10% (moon surface is essentially black), that's
  pretty futile. But unless they've degraded too far by now (ask one of
  the astronomy ng's), at least one, maybe several of the Apollo missions
  left some nice high quality retroreflectors on the moon - for exactly
  that purpose (bouncing a laser off them for distance measurements).
  
  Bye
    Markus
  
  
  
  
  From: Roy McCammon 
  Subject: Re: Simple/interested electronics project for high school work  experience
  Date: 16 Jun 2000 00:00:00 GMT
  X-Accept-Language: en
  Organization: C4F
  MIME-Version: 1.0
  NNTP-Posting-Date: Fri, 16 Jun 2000 11:38:38 CDT
  Newsgroups: sci.electronics.design
  
  Markus Imhof wrote:
  
  > But what you do need for that experiment is a laser with very low
  > opening angle, which can (in the range you're going to need for that)
  > only be achieved with a large aperture. 'Large' in this case meaning a
  > couple of feet, e.g. a suitable telescopic mirror.
  > > > Point it at the moon.  Point a telescope at the
  > > moon with your photo-detector installed on the eyepiece (suitably refocused to
  > > produce an image on the photo-diode face instead of inside your eyeball).  Do this
  > > with a new or nearly new moon so you can visually spot your outbound laser-light.
  > > Move around on the moon's surface a little so as to find a good, flat spot for
  > > best reflectivity.
  > > Not necessary - see above. For a practical laser, the opening angle will
  > be large enough to cover a good sized portion (if not all) of the moon's
  > disk, so moving the laser around accomplishes pretty little. As for
  > looking for a flat spot for good reflectivity - at an average
  > reflectivity below 10% (moon surface is essentially black), that's
  > pretty futile. But unless they've degraded too far by now (ask one of
  > the astronomy ng's), at least one, maybe several of the Apollo missions
  > left some nice high quality retroreflectors on the moon - for exactly
  > that purpose (bouncing a laser off them for distance measurements).
  
  I used to for for MacDonald Observatory.  We fired a
  3 Joule ruby laser at the moon.  The chief scientist
  estimated that our average return (gathered by the
  107 inch telescope) was one photon.
  
  As for finding the reflectors, it was difficult.
  It turned out that no one over age 20 could find
  the target and hold the telescope on the target.
  We hired high school kids as night assistants
  (gophers etc).  It turned out, that they were the
  only ones that could hit the target.
  
  
  
  
  From: John  Larkin <jjlarkin@highland_SnipThis_technology.com>
  Subject: Re: Simple/interested electronics project for high school work experience
  Date: 15 Jun 2000 00:00:00 GMT
  Organization: Posted via Supernews, http://www.supernews.com
  MIME-Version: 1.0
  Newsgroups: sci.electronics.design
  
  On Thu, 15 Jun 2000 18:03:03 +1000, "Paul E"
   wrote:
  
  >Hi all,
  > >I have a couple of high school students (16 year old)at work for work
  >experience & are looking for suggestions for simple & interesting electronic
  >projects that they can build.
  > >Any ideas?
  
  
  Paul,
  
  this is kinda fun:
  
  Poke a pair of electrodes into the ground and drive with voice, music,
  or tones through a power amp. Some distance away, poke another pair,
  connected to a high-gain amp and headphones. This is earth
  sheet-resistance communications. It's fun, you get to go outside, you
  can experiment with impedances, potential line shapes, and such stuff,
  and you get to hear all sorts of interesting extraneous sounds. The
  math of the sheet resistance potentials is complex enough to lead into
  other stuff for those inclined. This is audio, and kids like audio.
  
  VLF receivers are interesting, too: a loop antenna and amp is all you
  need. Lots of cool atmospheric sounds might interest a bunch of
  teenagers.
  
  
  John
  
  
  
  
  
  
  
  
  
  
  	

Oklahoma Imaging Laboratory

http://oil.okstate.edu/
Telephone:
ES405: 405.744.7590 (David Cary, Zhongxiu Hu, Andrew Segall)
ES404: 405.744.7687 (more research assistants)
icbmto: 36.139584 N, 97.063035 W

The Oklahoma Imaging Laboratory
Engineering South 405
Stillwater OK 74078-5032

is where David Cary is working for Lucent http://www.lucent.com/netsys/worldmap/no_america/us/okm.html

Scott T. Acton, Ph.D.
Associate Professor
School of Electrical & Computer Engineering
202 Engineering South
Oklahoma State University
Stillwater, Oklahoma 74078-5032
Phone:  (405) 744-5250
Fax: (405) 744-9198
Email:  sacton at master.ceat.okstate.edu
Oklahoma Imaging Laboratory: http://OIL.okstate.edu/

Real-time video processing / image processing

• Virtual Tour of Oklahoma State University's Campus! http://www.av.okstate.edu/photography/virtual/ interactively rotate 360 and zoom from selected locations on campus.
• Real-Time Tracking of the Human Body http://www-white.media.mit.edu/vismod/demos/pfinder/
• Postal Address Reading in Real-Time http://www.cedar.buffalo.edu/RCR/IEEE/RCR.html Image segmentation, Handwriting vs. Machine-print recognition.
• Sumitomo Metals Image Processing Products http://smi-lsi.com/first.html $30 morphology chip (26 MHz) (price from ad in _NASA Tech Briefs_ 1997 Aug), 50MHz histogram processor chip
• Interactive Digital Filter Design http://ocala.cs.miami.edu/~loubeau/Filter/home.html
• MDDSP - The Multidimensional Signal Processing Research Group http://www-mddsp.enel.ucalgary.ca/ (real-time video filters; as well as non-real-time fractal compression)
• www.nortech.com high frame rate video capture board
• under $100 (in 25 000 s) TMS320C6x 1600 MIPS (200 MHz x eight 32-bit instructions per cycle) fixed-point digital signal processor (DSP), 1 Mbit on-chip RAM (prices from ad in EDN 1997 April 10 p. 35) http://www.ti.com/sc/c6x
• http://www.ncc.com/misc/dsp_sites.html A long list of Digital Signal Processing resources available online: FAQs, information on DSP chips, manufacturers of DSP boards, etc.

Real-time digital signal processing / system control

• Spectron http://www.spectron.com/ , creator of SPOX, produces several real-time operating systems for most major DSPs (Motorola, Texas Instruments TMS320C6x, etc.) and the Pentium processor
• Visual Solutions http://www.vissim.com/ DSP algorithm design/simulation
• Motorola DSP chips http://mot-sps.com/sps/General/chips-nav.html
• Texas Instruments DSP chips http://dspvillage.ti.com/ /* was http://www.ti.com/sc/docs/dsps/dsphome.htm */

digital cameras

commercial off-the-shelf digital cameras

• digital camera reviews http://chkpt.zdnet.com/chkpt/hpqs022/www.zdnet.com/products/camerauser/798wrapper.html
• Wrist Camera Watches
  • http://www.wristwatch.com/indices.asp,,iid,,77111
  • http://www.starportuk.com/71.htm Casio WQV: digital camera on a wristwatch
  • Wrist watch camera http://www.spiderweb1.com/pi-supply/hardwired/wristwatch.htm
  • ``Take color photos with your watch'' article by Jørgen Sundgot, Saturday, 09.02.02 16:02 GMT (ø) http://www.infosync.no/show.php?id=1138&page=1 Casio WQV-10

    ...capable of both taking and displaying pictures in color ...

    The camera has a resolution of 250,000 pixels (176 x 144) and is capable of taking 16-bit color pictures that can be displayed on the 12-bit STN color display on the watch. Up to a maximum of 100 pictures can be stored on the built-in memory...

  • http://watchfinder.casio.com/
• Steve's digicams http://www.steves-digicams.com/ "digital camera information and news"
• interesting pages for hacking the Kodak DC20 digital camera (serial interface). http://home.t-online.de/home/oliver.hartmann/dc2flash.htm http://home.t-online.de/home/oliver.hartmann/dc20prot.htm http://www.lyot.obspm.fr/~dl/dc20/layout.gif http://aguirre.dsi.unifi.it/~paterno/English/dc20.html
• [what do people want in a digital camera ?]

  Newsgroups: rec.photo.digital
  Subject: Kodak DC20 : bad experience
  
  
  I gave back for refund my 29 days old experience with the Kodak DC20
  because : 
  
  + The resolution 493x373 is NOT the real resolution of the camera
    but a software interpolation. The real absolute per color resolution
    seems to be 120 lines ONLY (but you can extract b&w information at
    of 240 lines but 373 is software only (this explains that the images
    of sharp contours, like text are not sharp/crisp at all)).
  + I wanted to use my camera from any computer and in particular be
    able to transfer the pictures from my notebook running Linux and
    convert them to standard format. Technical protocols (serial com. and
    image format) was hard/impossible to get...:
  + I could get no answer from Kodak support
    (beside "here is the url for dev. plan" (when I just wanted technical
     protocols description and not a plan...), which I finally filled
     with no further informations coming from them...)
  + The 1mb ram which stores only 8 *uncompressed* images (thus the low
    quality and the 'big' resoltion obtained by software) is not enough
    for most of uses.
  + serial link transfers are too slow (even on PC at 115kps and even
    slower on the mac where it seems limited to 57.6kps)
  + you can only erase everything or nothing.
  + I made no more than 50 pictures before having to buy a $10 battery
    this is almost as expensive than using films !
  ...
  
  On the positive side:
  + the camera is extremly light and fits into a pocket; that's great !
  + the sensitivity is very high, suitable for low light indoor.
  + 2 japaneese folks who own Chinon ES1000 (same hardware) have been
    very kind and shared the informations they have ! (not any credit to
    give to kodak for that !)
  
  
  some screen shots and detailed technical infos are on my web page:
  http://www.lyot.obspm.fr/~dl/dc20/
  
  
  now my wish list for my next digital camera:
  + 640x480 real resolution (ie 640x480x3 sensible areas)
  + extendable memory (pcmcia standard card) readable from standard
    card reader
  + standard filter ring, for close up lens and accessories...
  + standard published format for the images stored on cards
  + serial (or better parallel) port transfer of images only as a
    backup / convenience over fast direct cards reading. using published
    protocol.
  + maybe scsi port for real performance ?
  + possible erase of last shot from the camera
  + low cost battery (rechargeable?) / small consumption
  + manual exposure / bulb
  + auto and manual focus
  + TTL / exchangeable lenses
  (ideally it would be a 'digital back' for a camera I already own like
  my Canon ESO-100 ...)
  
  + less than $2000 (if it as all the above, and $500 if it misses some
  features) 
  
  
  Regards
  dl
  --
  Laurent Demailly * http://hplyot.obspm.fr/~dl/ * Pobox email: <dl at mail.dotcom.fr>
  ** job hunting !** please see http://hplyot.obspm.fr/~dl/cv.html or mail me
  

• Fisheye, Inc. http://www.fisheyeinc.com/ specializes in underwater video cameras (check out the shark photos at http://www.fisheyeinc.com/inaction/images.cfm )
• http://www.x10.com/home/offer.cgi?!ABO3,../1index5282.htm $80 "XCam2" battery-powered color video camera, wireless transmitter and receiver. (also does audio) ~30 meter range.
• The SILVACAM Color Infrared Video Camera http://www.vtt.fi/aut/rs/prod/silvacam.html "a modified 3-CCD color video camera ... One of its three channels is dedicated to detect the near infrared (NIR) range of the spectrum. ... Blue: 490 - 580 nm Green: 580 - 680 nm Red: 760 - 900 nm "
• Canon "Optura CCD camera / video recorder ... takes 30 still pictures per second for as long as 60 minutes ...$ 2 499 " (no web site ?)
• http://web-tronics.com/webtronics/small-board-cameras.html sells some low-cost EIA cameras ($62 grayscale/IR, $102 color,
• Ricoh http://www.ricohcpg.com sells some nice digital cameras.
• http://www.photonic-science.ltd.uk/ design, manufacture and supply cameras and complete image acquisition systems.

• Date: Fri, 10 Jul 1998 13:01:26 -0400
  From: Ajay Shekhawat <ajay at cedar.buffalo.edu>
  To: Gerd Truschinski <agni at zedat.fu-berlin.de>
  Cc: quickcam-drivers at crynwr.com
  ...
  I would recommend the EggCam over a QuickCam after seeing the EggCam
  in action.
  
  A colleague bought a refurbed EggCam (w/board) for $71 (+$8 shipping),
  from CompSource at
  	http://www.c-source.com
  (search for "EggCam")
  
  He has been delighted with the frame rate (over 5 full frames/sec including
  saving to disk on Linux). The chipset of the capture board (BT848) is
  well supported in Linux.
  
  Ajay
  

• Markertek Video Supply http://www.markertek.com/ resells "broadcast-quality digital camcorders" for typically $3 000 .
• Hitachi Denshi America, Ltd. http://www.hdal.com/ sells the KP-F100 and KP-F110 "Megapixel 2/3" CCD Black and White Cameras": analog and 10 bit digital outputs; up to 1/ 10 000 second shuttering speed; 1 300 x 1 030 effective pixels.
• Aegis Research http://www.lynx.bc.ca/virtualspy/ CCD Cameras
• News article on Megapixel cameras http://www.news.com/News/Item/0,4,18667,00.html?pt.ms..feed.ne_home
• http://www.connectix.com
• Polaris Industries http://www.polarisusa.com
• Dycam http://www.dycam.com
• Kodak http://www.kodak.com nice digital CCD cameras
• http://www.scx.com
• http://www.sony.com/electronics
• http://www.panasonic.com
• http://www.minoltausa.com
• Marshall cameras http://www.marshall.com/dynamic/search?type=mdesc&search=camera
• http://www.wincam.com/
• "LEDs within the joystick send infrared beams to miniature digital cameras that relay precise data -- accurate to within 1/10th of a millimeter -- about handle and throttle position to the joystick's microprocessor." "Like most SideWinder products, a tiny infrared camera precisely detects handle and throttle motion to within 2/100ths of a degree without any wear or calibration." http://www.microsoft.com/sidewinder

borescopes, fiberscopes and videoscopes

• Instrument Technology, Inc. http://www.scopes.com/ Borescopes, endoscopes, Fiberscopes and Videoscopes (Medical and Veterinary)
• Olympus Industrial Products Group http://www.olympusipg.com/ sells digital high-speed video cameras. Also sells borescopes, fiberscopes, and videoscopes.
• Everest VIT, Inc. http://www.everestvit.com/ sells what it calls "the World's Smallest Video Borescope" and other fiberscopes and video borescopes

Video Phones

• http://www.3com.com/client/pcd/products/bigpicture/

QuickCam details

• Linux got me kicked out of Wal*Mart http://www.honeylocust.com/walmart/
• mini-HOWTO-cqcam How to use a Connectix QuickCam color and Linux to make a webcam http://www.dkfz-heidelberg.de/Macromol/wedemann/mini-HOWTO-cqcam.html
• QuickCam Third-Party Drivers mailing list http://www.crynwr.com/qcpc/ (includes archives)
• the QuickCam http://www.quickcam.com/ is currently manufactured by Logitech http://www.logitech.com/ .
• Quickcam Technical FAQ http://www.cs.duke.edu/~reynolds/quickcam/Quickcam_Technical_FAQ.txt /* was http://www.cs.virginia.edu/~patrick/quickcam/Quickcam_Technical_FAQ.txt */ "Consider it a draft. Updates and suggestions are welcome." -- Date: Fri, 23 Apr 1999 14:02:20 -0400 (EDT) From: Patrick Reynolds <patrick at cs.virginia.edu>
• Texas Instruments http://www.ti.com/ has put the full specs of the TC245, 786- X 488-PIXEL CCD image sensor chip used in the QuickCam online http://focus.ti.com/docs/prod/productfolder.jhtml?genericPartNumber=TC245 /* was http://www-s.ti.com/cgi-bin/sc/device1.cgi?device=TC245&family=CCD+IMAGERS */ http://www-s.ti.com/sc/psheets/socs019a/socs019a.pdf http://www-s.ti.com/sc/ds/tc245.pdf ...
• qcread - Image reader and routines for Connectix QuickCam control http://www.fhttpd.org/pub/qcread/README.html
• /* offline ? */ Connectix Quickcam Developer Resources http://www.kabel.de/~hmueller/qc/
• the communications protocol for the Mac QuickCam: http://www.connectix.com/connect/files/driver/mac.pdf
• QuickCam for Windows FAQ http://www.quickcam2.com/html/html/quickcam_faq__windows_.html
• QuickCam ($99, color, USB and parallel port connectors) http://www.pcworld.com/news/daily/data/1197/971112175225.html?SRC=watch
• Some extremely low-level technical specs on the Mac version of the Connectix QuickCam (918000 bps serial port) http://www.eskimo.com/~hayes/camera.html

• Mailing-List: contact quickcam-drivers-help@crynwr.com; run by ezmlm
  Delivered-To: mailing list quickcam-drivers@crynwr.com
  From: Brian Scearce <bls at pathetique.com>
  Subject: Re: I am trying to get some specific information
  To: finn at sicorp.com, quickcam-drivers@crynwr.com
  Date: Sun, 12 Apr 1998 00:47:59 -0700 (PDT)
  
  Wilho N. Suominen JR asks:
  > How does Brightness, Contrast, and White level quantitatively work?
  
  I have one bit of quantitative information, and two pieces of
  qualitative information.
  
  > I understand that Brightness - 255 is auto exposure
  >                          and - 254 is 2.62 seconds
  >                          how does the rest of the range work.
  
  I've appended my code that turns exposure values into exposure times for
  the B&W QuickCam.
  
  > Contrast question: does this set a rail for the ADC or does it
  >   do something else?
  >
  > White Level: does this set bottom, top, or median of levels for the
  >   ADC?
  
  The docs cover this qualitatively.  The CCD signal is a DC bias (fixed
  per device) device with an AC ripple riding on top; the ripple is
  proportional to the light falling on the CCD during the exposure period.
  "White level" is used to subtract the DC bias from the signal; this is
  why there is a single correct white level per Cam.  "Contrast" is a
  scaling factor for the remaining AC ripple.  I don't know what the
  actual qualitative values are, but I suppose you could measure them with
  an oscilliscope if you really needed to know.
  
  Brian
  
  /*
  	This function says how long an exposure takes (in microseconds).
  	It exists to aid synchronization.  The Connectix docs don't
  	include accurate formulas, but Connectix sent me the exposure
  	formula.  -- bls 02/21/97
  */
  unsigned long
  qc_exposure_time(const struct qcam *q)
  {
    int value;
    int shifter;
    unsigned long retval;
  
    value = (q->brightness & 0x0f) | 0x10;
    shifter = (q->brightness & 0xf0) >> 4;
  
    retval = ((unsigned long) value) << (1 + shifter);
    retval *= 4;
    retval /= 3;
    retval /= q->transfer_scale;
    retval += 150;
    return retval;
  }
  

• "How to disassemble a b&w Quickcam" by Hanno Müller http://perso.club-internet.fr/uranos/disassemble_quickcam.htm
• QUICKCAM Astrophotography http://www.astrosurf.com/cidadao/quickcam.htm "The grayscale QuickCam is equipped with a Texas Instruments 255 CCD, a frame-transfer chip with an array of 320x240 10micron-square pixels."
• a program that uses the Connectix black and white Quickcam as the detector for autoguiding an astronomical telescope. http://www.ameritech.net/users/mniemi000/auto.html
• Astrophotography with a QuickCam CCD http://www.vub.ac.be/STER/www.astro/AstroCCD/AstroQC.htm
• http://www.usno.navy.mil/pao/QuickCamAstro.shtml the minimal modification needed to attach the QuickCam to a telescope. using a QuickCam Express, a color USB web-cam with a 320 X 240 CMOS imager chip and later using a Philips Vesta 675K web-cam
• ash's Astronomy Pages http://astro.ai-software.com/ | mirror http://members.cox.net/roeckelein_aap/ has many, many links to CCD astrophotography information (hardware modifications, software, where to buy hardware...)

  ash's Cheap-O Astrocam Page II http://members.cox.net/roeckelein_aap/quickcam.html heavily modified QuickCam: peltier coolers, metal case, etc.

Building and programming a digital camera

Commercial CCD chips; info on how to assemble them and getting single images. see webcam.html for info on putting those images online.

• Tips on Building a CB245 CCD Camera http://astro.martianbachelor.com/CB245/Btips.html /* was http://www.uccs.edu/~cwetheri/Astro/CB245/Btips.html */

  ".BIF - The Best Imaging Format" is an image file format optimized for astronomical images ... yet can be viewed with standard TIFF viewers. http://astro.martianbachelor.com/BIF/ "BIF's basic compression strategy is to use Run Length Encoding (RLE) for the upper byte of an image's data and LZW (Lempel-Ziv & Welch) compression for the lower byte. This assumes 2-byte (16-bit) image data." [FIXME: move to data_compression.html#file_formats ] [other ideas: would it help to ... differencing sounds like a good thing to try out ... convert to gray code before compression (should have no effect on hi byte, but might give better compression on lo byte) ... split into 8 bit "upper image" and 8 bit "lower image"; use lossless .png compression on each one ... ... fractal compression with blurring instead of dilation ... ]

• CCD University http://www.apogee-ccd.com/ccdu.html a very brief overview of each of the little parts of a CCD camera. Explains the language used by people who build CCD cameras. Good overview for people who know nothing about how CCDs work and are curious.
• low-cost linear and rectangular CCD chips (and lots of other robot components) http://members.aol.com/fuboco/optical.htm ??? [FIXME: robot ?]
• Ron Dantowitz todo.html#astro_camera wants better cameras for astronomy, and better software for doing his clever image processing technique.
• Texas Instruments http://www.ti.com/ All current CCD image sensors and support chips from TI http://focus.ti.com/analog/docs/analogprodhome.tsp?templateId=5270&navigationId=9639&familyId=371&path=templatedata/cm/overview/data/video_imaging
• Al Kelly's amateur CCD Astrophotography Page http://www.ghgcorp.com/akelly/
• "A thinned back-illuminated device typically has [ about double ] the quantum efficiency than a front-illuminated device" (because the metal gates reflect light coming from the front, but not from the back).
• http://www.beyondlogic.org/imaging/camera.htm has information on various low-cost CMOS image sensors from about 5 companies (typically with integrated ADC) and simple ways of interfacing them to the robot CPU.
• http://piclist.org/techref/cameras.htm

• From: sales at pixelcam.com
  To: d_cary@my-deja.com
  Subject: (O) RE: Need 'raw' RGB "Bayer" color test image files
  Date: Tue, 22 Jun 1999 17:48:32 -0700
  ...
  Most CCDs for digital cameras use
  
  RGRGRG
  GBGBGB
  
  as their RGB color filter pattern.
  ...
  > Rudi Wiedemann
  > PixelCam, Inc.
  

• the Programmable Digital Camera (PDC) project http://www-isl.stanford.edu/~abbas/group/ talks about designing the CCD itself. [FIXME: VLSI ?]
• ChipDir http://www.ideal.net.au/chipdir/abc/c.htm#camera has some interesting info about digital cameras. [FIXME: more local ChipDir mirror]
• The Cookbook CCD Camera Home Page http://www.wvi.com/~rberry/cookbook.htm "to help amateur astronomers who build their own CCD cameras."

• From: "Phil Humphreys" <Phil at humphreysastro.freeserve.co.uk>
  Subject: Re: cookbook ccd power supply question
  Date: 28 Nov 1999 00:00:00 GMT
  Newsgroups: sci.astro.ccd-imaging
  ...
  Since you are building a CB245 you probably should subscribe to
  the CCD list at WWA.COM . This is mainly composed of
  cookbook builders.
  
  Send a message to LISTSERV@LISTSERV.WWA.COM
  
  In the body of the message place SUBSCRIBE CCD  Scott Hahn
  
  That should get you connected.
  ...
  

• MICROCAM http://www-imt.unine.ch/www/grp_pe/www/projects/Microcam/web_microcam.html 256x256 pixel camera-on-a-chip including 10 bit ADC; a photo of a 64x64 pixel camera that fits *inside* a ball-point pen (designed for endoscopes / endoscopy).
• Very Long-Wavelength Quantum Well red Photodetectors (QWIPs) http://csmt.jpl.nasa.gov/csmtpages/Technologies/QWIPS/qwips.html are being commercially developed into focal plane arrays (infrared cameras) by ViaSpace http://www.ViaSpace.com/
• CMOS active pixel sensors (CMOS APS) http://csmt.jpl.nasa.gov/APS/index.html is being developed into a 256x256 pixel x 10 bit CMOS Camera on a Chip with on-chip ADCs (and eventually a 1024x1024 pixel x 14 bit CMOS Camera on a Chip with on-chip data compression expecting below 50 mW at 30 Hz) by ViaSpace http://www.ViaSpace.com/ "It is the goal of the work to make cameras that are almost all optics and just a single chip for the electronics. ... Digital commands from the computer flow out the cable to the camera, and only digital data flows back to the computer." "The best scientific CCDs achieve noise levels in the 3-5 electrons r.m.s. range. Other CMOS image sensors yield noise levels in the 300-500 electrons r.m.s. range. With the active pixel sensor, we have achieved noise as low as 14 electrons r.m.s. and expect to be able to improve that further."
• Siemens AG http://www.siemens.de/ Supposedly sells "Eyemax", a single chip containing a 720 by 576 pixel CMOS image sensor, 720 monolithically integrated ADCs (one per column), 35 kbits of RAM, and a DSP. It uses less than 0.5 W ... CCDs typically multiplex the pixels to a single high-frequency (hence high-power) ADC, which makes a CCD-based multichip digital camera typically use 5 to 10 times as much as this single-chip digital video camera. [FIXME: find better link directly to this chips product specs.]
• Zoran Corp http://www.eetimes.com/story/OEG19981029S0022 describes the $25 (in high volume) Coach chip, a "digital still camera-on-a-chip" -- -- connects to a CCD sensor, digitizes the analog signals, LCD/TV output, "and a variety of glueless interface blocks to support USB, IrDA, audio and serial ports as well as a microcontroller interface."
• discussion on connecting CCDs to the MC68HC11. (Linear CCDs are under $7). http://www.amc.com/chipdir/oth/ccd.txt
• $4.70 (in 1 000 s) XRD9815ACQ (12-bit, 3-channel analog signal processor and digitizer ADC, designed for 3-channel (RGB) linear CCD and CIS imaging applications) (12 MSamples/s = 4 Mpixels/s) (3V or 5V) (1999 price from http://www.exar.com/pressreleases/press99.html )(32-pin TQFP )
• VLSI Vision Ltd. http://www.vvl.co.uk/ (30 frames/s USB color camera) produces "CMOS image sensors" which it claims are cheaper and have lower power consumption than equivalent CCD image sensors. sells some very interesting chips:
  ($price?) VV5404: monochrome 356x292 pixels, on-chip 8 bit A/D converter, up to 30 frames/s, runs off single 5V power supply, completely digital interfacing. http://www.vvl.co.uk/products/sensors_cameras/404/5404.htm
  "less than $8 in large volumes" VV5300: monochrome 160x120 pixels, on-chip 8 bit A/D converter, up to 60 frames/s runs off single 5V power supply, completely digital interfacing.
  (Also color versions of these chips)
  "people who want to use cameras in hardware projects, and who don't want to deal with the QC's slowness and lack of flexibility, consider ... the VVL 5404... these produce digital data and are very easy to interface to" -- recc. ali at xcf.berkeley.edu Date: 4 Nov 1998 21:19:08 -0000
  

  Path: hermes.rdrop.com!user
  From: d.cary at ieee.org (David A. Cary)
  Newsgroups: comp.robotics.misc
  Subject: CCD with digital output
  Date: Sun, 24 Nov 1996 14:15:50 -0700
  Organization: rarely.
  ...
  I always thought vision would be way too expensive for my robot until I
  read the comp.robotics.* FAQ. It mentioned a "$10... commercially available
  image sensor... built-in A/D converter".
  ...
  --
  David Cary
  Future Technology, PCMCIA FAQ.
  
  
  
  Path: hermes.rdrop.com!user
  From: d.cary at ieee.org (David A. Cary)
  Newsgroups: comp.robotics.misc
  Subject: Re: Direct access to CCD camera.
  Date: Fri, 29 Nov 1996 17:59:51 -0700
  Organization: rarely.
  Lines: 42
  
  
  Yes, you're right, the accumulated charge is an analog level, and it must
  be digitized.
  
  However, I want to sample each pixel exactly once with my ADC (why would I
  want anything different ?),
  and it's not obvious to me how to get my ADC properly synchronized with the
  pixel outputs.
  
  It seems pretty silly to convert the 300x400 (or whatever) array of pixels
  into a continuous TV-style analog "composite video output" signal, then
  convert *back* into 299x401 array in my CPU.
  
  The comp.robotics.* FAQ. It mentioned a "$10... commercially available
  image sensor... built-in A/D converter". How convenient, a built-in A/D
  converter, I can just directly wire it to the digital lines of my CPU.
  
  Unfortunately, when I called them up the salesman claimed they didn't sell
  that chip any more.
  
  RWoodward at gnn.com (Ron Woodward) wrote:
  +In article <329ed78b.363673244@138.77.1.23> Paul Hannah wrote:
  +>Has anyone tried to access the CD array directly, instead of running
  +>through a video format of some kind then back to a bitmap.
  +
  +A CCD outputs a stream of voltage/current levels representing the amount
  +of charge accumulated in each pixel well. Because this comes out in a
  serial
  +stream it must be digitized to be put into a bit map. Essentially the only
  way
  +you can get it out of the CCD is in some form of analog video format
  without
  +the sync signals.
  ...
  --
  David Cary
  Future Technology, PCMCIA FAQ.
  
  
  
  
  
  Date: Thu, 22 Sep 1994 07:23:00 -0800
  From: "Steve Meaders" <omnix at infoserv.com>
  X-Mailer: Infoserv Connection's WinMail
  Subject: Re: New CCD Available
  Newsgroups: comp.robotics
  Lines: 38
  
  ...
  >: >The new Digital Video Camera Chip, VVL1070, is ideal for all kinds of
  >: >low-cost computer video imaging applications, such as robotics, pattern
  >: >recognition, highway monitoring of traffic flow, weather conditions and
  >: >consumer applications such as computer snapshots and video telephones.
  >
  >: The designer of the 1070 sensor is VVL.  VVL specializes in CMOS sensor
  >: technology rather than CCD.  Other products from VVL include the Peach
  >: camera (CCIR CMOS camera) and the imputer (CMOS sensor with built in
  >: image processor).
  >
  >: The $10 price is applicable to volume OEM orders.  End users should
  >: be prepared for higher prices for small quantity orders.  If interested,
  >: I can provide VVL's phone, email, etc.
  >
  ...
  
  Iain Kyle
  VLSI Vision, Ltd.
  Aviation House, 31 Pinkhill
  Edinburgh EH12 8BD Scotland
  
  tel: 031-539 7111
  fax: 031-539 7140
  email: ifk at vvl.co.uk
  
  Hope this is of some help.
  
  
  
  
  
  
  
  
  
  
  
  
  

• "Eric B. Olsen" <robojoc at worldnet.att.net> http://home.att.net/~robojoc/ builds camera hardware. "ROBO-CAM(tm) ... The first ever low cost digital vision module! " $99. specifically designed as a module for small robots.
• Discovery Semiconductors http://www.chipsat.com/ high-speed photodetectors
• Infrared Photography by Andy Finney http://www.atsf.co.uk/ilight/ [FIXME: #infrared]
• http://www.ast.cam.ac.uk/~apo/docs/eev-5.html lots of very detailed information (spectral response curves, etc) for the #5383-17-7 CCD at the prime focus of the William Herschel Telescope. (Has a picture of the actual o'scope sequencing waveform !)
• Very nice explaination of how to use a QuickCam for astronomy, with some stunning photos: http://www.vub.ac.be/STER/www.astro/AstroCCD/AstroQC.htm
• How to correct for "barrel distortion" ("Fisheye" distortion):
  • Programs for QuickCam and FreeBSD: http://www.idle.com/~markv/quickcam.shtml
  • Mathematical Theory: http://www.rose.brandeis.edu/users/detector/stanton1992b/paper.html
• Evolving Towards The Perfect CCD http://zebu.uoregon.edu/ccd.html Lots of technical information about CCD manufacture, the current limitations of CCD technology.
• CCD Area Image Sensor MN39470PT/39471PT http://www.panasonic.co.jp/semicon/pr_asa/aee2.html
• Burr Brown http://www.burr-brown.com/ sells, among many other things, the
  $5.75 each (in 1 000s) VSP2000 video signal processor http://www.burr-brown.com/database/CCDVideoSignalProcessing.html : connects to CCD chip and does 10 bit, 18 MHz A/D conversion. (price from 1998 July EEPN p.17)

• 
  Toshiba linear CCDs: 128 pixels: $50 each (in 100s)
  --
  _EDN_ 1995 Oct 12
  "CCDs" article by John Gallant
  
  Panasonic MN3776RE ... 640 x 480 square pixels ...
  expected price $30 in "production quantities" by 1996.
  --
  _EDN_ 1995 Oct 12
  "CCDs" article by John Gallant
  
  Sony Semiconductor Co of America ...
  1/5 inch color and black-and-white CCDs
  ... 362 x 492 pixels, and come in a 14-pin DIP. ... $19 each (in 10,000s).
  --
  _EDN_ 1995 Oct 12
  "CCDs" article by John Gallant
  
  
  
  
  
  From: bales at athena.mit.edu (James W Bales)
  Newsgroups: sci.electronics.components,sci.electronics.design
  Subject: Re: CCD datasheets and ordering information
  Date: 4 Jan 1996 14:23:31 GMT
  Organization: Massachusetts Institute of Technology
  Lines: 16
  
  In article <4cfjfv$nlo@tigger.cc.uic.edu> blin1 at icarus.cc.uic.edu (Bor-tyng Lin) writes:
  >   Where can I get the data sheets for CCD chips?
  
  There is a TI data book - "Area Array Image Sensor Products."
  Published in 1992, the back cover bears the code "SOCC030."
  Lots of data on 2-d CCD arrays.
  
  If you are just starting, consider the TC211, 192 x 165 pixel
  CCD in a 6-pin DIP.  It's about the simplest CCD to operate.
  
  For the data book or chips, try a TI authorized distributer such as:
  Marshall Elecrtonics, 1-800-522-0084, Web page at
  
  http://www.marshall.com/
  .
  
  Jim Bales
  MIT Sea Grant Underwater Vehicles Laboratory
  bales at mit.edu
  
  
  
  
  
  
  
  
  
  
  
  From: Mike Hoffberg <hoffberg at aps.anl.gov>
  Newsgroups: alt.image.medical,
  	rec.photo.digital,
  	sci.electronics.design,
  	sci.engr.advanced-tv,
  	sci.engr.television.advanced,
  	sci.image.processing,
  	sci.physics.accelerators,
  	sci.techniques.xtallography
  Subject: high speed CCD camera
  Date: Wed, 22 May 1996 16:19:50 -0500
  Organization: Argonne National Laboratory, Advanced Photon Source
  Lines: 23
  
  We have developed a CCD camera system capable of over 100 frames/second
  with a 12 bit dynamic range (sigma 1.4).  The software consists of a
  easy to use user interface, and allows the recording and playback of
  images, basic image visualization and real-time display of the image to
  the computer's screen.
  
  The camera is based upon the Thomson TH7895 CCD (512x512, 19 um pixel, 2
  output).
  
  If anyone is interested in more information about this camera, please
  feel free to contact me:
  
  Michael Hoffberg
  Argonne National Laboratory
  tel 708-252-9173
  fax 708-252-9303
  hoffberg at aps.anl.gov
  
  --
  Michael Hoffberg                 /.\ Argonne
  hoffberg at aps.anl.gov            // \\ National
  mike at anl.gov                   //_O_\\ Lab
  Standard Disclaimer Applies   /__| |__\
  
  

Non-Real-time video processing / image processing

Image Processing Software, Digital Image Processing, Machine Vision.

David Cary has some of the fundamental tools (erode, dilate, Huffman compress, linear filtering via FFT) written in MatLab at http://rdrop.com/~cary/program/image_processing/ /* was http://oil.okstate.edu/~caryd/program/ */ .

mathematical morphology

[FIXME: want a easy-to-understand and mathematically correct definition of erode, dilate, open, close here, including gray-scale and binary versions; MatLab implementations can be found at http://rdrop.com/~cary/program/image_processing/ ].

Let b be a structuring element, typically a small picture of a circle or square or horizontal line or vertical line, typically centered on coordinate (0,0). ...

clustering and color quantization

(related to human brain ?)

• Color Image Quantization http://www.cs.ualberta.ca/~oleg/quantization.html reducing the infinity of possible colors (or even the 2^24 possible 24 bit colors) down to a small color palette, typically 2^4 or 2^8 colors in the palette. Often combined with dithering.
• A Spatial Clustering Technique for the Identification of Customizable Ecoregions http://www.esd.ornl.gov/~hnw/esri/
• Mabuse http://www.mabuse.de/ Pixel clustering, wavelet clustering, image compression.
• Clustering Toolboxes http://www.mathtools.com/mtoolbox-clustering.html lots of Matlab source for various clustering algorithms: k-means clustering, fuzzy slustering, etc.
• MPRG Matlab Toolbox http://www.ee.vt.edu/valenti/toolbox.html lots of Matlab source code for: "kmeans.m, Designs a two dimensional vector quantizer using the K-Means algorithm and correlated Gaussian input."; several error-correction-coding (ECC) algorithms including soft-decision Viterbi decoding; and a Pseudo-random Noise (PN) generator for CDMA simulation.
• Bogdan R. Kosanovic http://www.neuronet.pitt.edu/~bogdan/ Bogdan's FTP Site http://www.neuronet.pitt.edu/~bogdan/FTP/ includes a fuzzy clustering MATLAB toolbox (fcmc.v2-0) Fuzzy C-means clustering (FCMC).
• Comparison of Unsupervised Classifiers (ART2, Autoclass and Snob) http://www.cs.ualberta.ca/~upal/cluster/p1/ "Reflecting the large number of applications, unsupervised classification is studied variously as clustering, autoclassification, vector-quantization, numerical taxonomy and conceptual clustering."
• Clusters, Computers And The Human Brain http://sunsite2.dc.stanford.org/releases/wzi-clcpahbn.html "Prof. Eytan Domany ... has developed a new method, or algorithm, for performing "clustering" ... ... The approach has great potential for use in data-heavy scientific and industrial applications. ... Unlike most automated "sorting" processes, in which a computer must be informed of the relevant categories in advance, Domany's algorithm is analogous to human intuition: it doesn't need to be told how the data is structured or how it should be broken down into groups."
• http://www-engr.sjsu.edu/~knapp/HCIRDFSC/C/C_home.htm k-means clustering algorithm the fuzzy k-means procedure Sequential k-Means Clustering
• Color Image Quantization http://web.cs.ualberta.ca/~oleg/quantization.html
• RIOT -- Remote Interactive Optimization Testbed http://riot.ieor.berkeley.edu/riot/ Clustering MacQueen's k-means clustering algorithm Minimum-Cost Spanning Tree Clustering on-line demos (in 3D !)

demos

other

• Image Processing for Teachers (K-12) http://www.umich.edu/~ed626/Image_Processing.html
• A Short Introduction to Digital Image Processing http://www.uct.ac.za/depts/physics/laser/hanbury/intro_ip.html Image Enhancement and Restoration; watershed separation ; ... [FIXME:]
• Computer Vision Online Demos http://www.cs.cmu.edu/afs/cs.cmu.edu/project/cil/www/v-demos.html
• Fast Course of Mathematical Morphology http://www.ime.usp.br/mac/khoros/mmach-1.3/tutor/util/fast.html tells you all about erosion, dilation, "open", "close", and "watershed". The pictures make it easy to understand.
• "histogram flattening" in real time ! adaptive contrast enhancement in real time ! Start at http://www.im.lcs.mit.edu/broch/cam1.html and follow the "next" links for lots of pretty pictures.
• The Wavelet Digest http://www.wavelet.org/wavelet/ a free monthly newsletter
• Steven Pigeon http://www.iro.umontreal.ca/~pigeon (has nice little freeware utility that takes a GIF as input, and outputs a significantly smaller GIF that is hopefully not visually different from the original). Online master's thesis touches on "massively parallel computers based on a reprogrammable architecture (hence the FPGAs) and how they can be used for image processing and neural networks, in particular with the toroidal grid and in applications like automatic digit reading, etc. In french."
• Mathematical Morphology Digest http://www.cwi.nl/projects/morphology/ Some more complicated and theoretical stuff; lots of links.
• DSP Development Corporation http://www.dadisp.com/ is giving a free 30-day trial version of DADiSP (data analysis, math functions, image processing, etc.). The DADiSP Worksheet is normally US$ 1 895.

  DSP Development Corporation http://www.dadisp.com/ "markets DADiSP, a popular graphical data analysis software program for scientists and engineers." FREE Student Edition Download.

• Mars Global Surveyor -- photos of "The Face" http://www.jpl.nasa.gov/marsnews/mgs/cydonia/ The raw image and the processed image are both shown. It's amazing how much better these simple tools -- "stretch" and "box filter" -- make it look. The exact processing steps taken are listed, so you can duplicate it. Can you do any better ? http://mars.jpl.nasa.gov/mgs/target/CYD1/
• Jos B.T.M. Roerdink, Ph.D. http://www.cs.rug.nl/~roe/ Lots of papers here (in postscript format) on image processing, mathematical morphology, wavelets, computer vision, and graphics for scientific visualization.
• Mathematical Morphology Digest http://www.cwi.nl/projects/morphology/ Includes pointers to Skeletonization Software and other computer vision source code.
• http://www.dpi.inpe.br/dpi/morpho/Papers_and_Books/Papers/applications/remote_sensing/B_remote_sensing.html ? What software is this ?
• Rotation Invariant Neural Network-Based Face Detection (Technical Report: CMU-CS-97-201) From: Shumeet Baluja <baluja at jprc.com>
  Abstract: ... Unlike similar systems which are limited to detecting upright, frontal faces, this system detects faces at any degree of rotation in the image plane. ... preliminary results for detecting faces which are rotated out of the image plane, such as profiles and semi-profiles. ...
  Questions and comments are welcome.
  http://www.cs.cmu.edu/~har/faces.html
  http://www.cs.cmu.edu/~baluja/techreps.html
• The Journal of Electronic Imaging (JEI) http://www.imaging.org/jei/online.html
• PATTERN ANALYSIS AND APPLICATIONS journal http://www.soc.plym.ac.uk/soc/sameer/paa.htm
• Precision Digital Images http://www.precisionimages.com/ DSP image processing
• http://www.mathworks.com/
• TWAIN is a software interface standard that allows the sending of bit maps and the output of character recognition programs directly into many software programs (Weinberg, 1994).

infrared sensors

"robot IR"

• infrared goggles for under $10 http://amasci.com/amateur/irgoggl.html fun. points to
  • The overall spectral sensitivity of the human eye http://www.4colorvision.com/files/photopiceffic.htm "The spectral absorption characteristics of the four chromophores of (human) vision" (yes, 4). which has lines for scotopic vision (normal vision), plus the extra sensitivity humans have with photopic vision (extremely dim light -- starlight -- extra infrared sensitivity) and aphakic vision (without the ultraviolet-absorbing lens). It claims that "the CIE (1931) Photopic Luminosity Function ... acquired using instrumentation of the 1920's ... Such instrumentation is completely inadequate" and "The equal-flux curve has a peak 10-20 nm to the left of the nominal (and often quoted) 555 nm peak of the equal-energy curve." i.e., the human eye is most sensitive to photons of about 545 nm.
• I.S.I. Group, Inc. http://www.isigroup.com/ sells infrared cameras
• Infrared Imaging Abstracts http://www.atsf.co.uk/ilight/ilightabstracts.html many interesting periodicals.
• [FIXME: Todo:] how to measure temperature from infrared measurements.

  one method: * assume standard broad-band black-body-radiation curve * Measure with 2 sensors with different frequency response ... * By convolving the black-body-radiation curve with the 2 sensors response curve at various temperatures, construct ratio vs. temperature curve.

  Other methods ?

• Phoenix Contact Inc. http://www.phoenixcontact.com sells a interesting PSM-ODL long-distance (200 yards) infrared data transmission system. (connects to RS-485 bus interface)
• "analog hack" of the Sharp IR sensors to get a signal proportional to the ammount of IR we were getting back from the sheet/tape.
• Experimental InfraRedCam http://www.rcd-net.com/infrared/ir1.html
• infrared remote controls http://falcon.arts.cornell.edu/~dnegro/IR/IR.html http://plop.phys.cwru.edu/repairfaq/REPAIR/F_irrfaq.html

• Date:         Tue, 11 Feb 97 14:41:24 PST
  From:         Rodrigo Dib <1RFD1642 at ibm.MtSAC.edu>
  Organization: Mt. San Antonio College
  Subject:      Re: I capture the IR signals thru my SB16, now what ?
  To:           David Cary <cary at agora.rdrop.com>
  
  On Tue, 11 Feb 1997 08:23:03 -0700 you said:
  >Would you mind telling me how to use a SB16 to capture signals like this ?
  
  I used the "Line-in" of the SB16. I have an old IR Rx module so i
  connected its output to the "line-in" of the card. Then run Wave Studio
  which comes with the SB16 and recorded at highest sampling rate (44kHz),
  while i press the key in yhe remote control i wanted to see the signals.
  I had to press the key for just a fraction of a second so i just hit it
  a couple of times. I kept on pressing the first time and got the signal
  a bunch of times and thought it didn't work. In the bottom window of the
  Wave program i cut everything else but one burst of signal....as soon as
  i started to cut , it fit the signal in the window until i was left with
  just the pulses which were in the burst but i coudn't see because i was
  looking at them like in a "zoom-out" way, you can't see any details until
  you zoom in. Oh ..one more thing....while pressing the remote the speakers
  are going to make one hell of a noise!! you could mute them but you won't
  know if you got one burst or more.
  For other URLs .... no clue, thanks for yours.
  

circuit board inspection

circuit board inspection

DAV did a project with infrared circuit board inspection ... I thought I had collected more links on the subject.

• http://www.uct.ac.za/depts/physics/laser/laserres.html circuit board inspection software.

2-way infrared data communication

infrared communication

see also infrared sensors #infrared

[Do I have more IrDA info in my "Organizations" file ?] [Do I have more IR protocol information in a "DAV's photons FAQ" file ?]

pulsed LED communication (IR serial communication).

• The Infrared Data Association (R) http://www.irda.org/ ``The Association for Defining Infrared Standards'' has many interesting protocols and hardware standards ... including IrWW (Infrared Wrist Watch) protocol (for synchonizing the wristwatch time to a PC, and for synchronizing one wristwatch time to another wristwatch). [FIXME: protocols]
• IrDA 1.1 (synchronous) is a 4000 Kbps infrared wireless communication standard. (This is *far* faster than the fastest 56 Kbps modems).
• 10 Mbit/s full duplex optical 1 Km data link http://www.infosite.com/~jkeyzer/piclist/2001/Dec/1961.html ... http://atrey.karlin.mff.cuni.cz/~clock/twibright/ronja/ [machine vision # ir ? serial ? todo ?]
• "Laser Communications" by Samuel M. Goldwasser http://www.laserfaq.org/slf/laserlia.htm#lialco points to "the Laser Reflector. It is run by ham radio operators who do long distance free-space communications. One is working on laser EME (Earth-Moon-Earth), and another is into non-line-of-site weak signal operation using low baud rate long term integration and advanced DSP techniques with coherent signals" http://www.qsl.net/wb9ajz/laser/laser.htm [FIXME: make a backup copy of the circuit here; link from schematic.html]
• "Our Ir is more reliable than IrDa" http://www.perfectsolutions.com/pc6f.asp [FIXME: What's the difference ?]
• "Low Cost IR Data Link Controls Model Train" article by Jim Walker. http://www.elecdesign.com/Pages/magpages/mar2299/ifd/0322id.htm shows the full schematic for IR transmitter, IR receiver, and a H-bridge motor controller.
• Philips infrared remote control protocol http://ustr.net/infrared/infrared1.shtml
• Siemens Wireless Infrared Data Transfer http://www.smi.siemens.com/opto/daa/

• IEEE 802.11 ... allows an IR link ... at 850 to 950 nm. One point in IR data communication's favor is that it does not require FCC certification, which has often slowed the introduction of RF wireless products.

  Unlike IrDA version 1.0's point-to-point nature, the 802.11 IR link uses diffuse-infrared transmission. So the receiver and the transmitter ... don't need a clear line-of-sight. ...

  IEC 825 is the standards group that sets safety limits for IREDs. Currently, IREDs are grouped with lasers. The emission limits for IREDs are 325 mW/steradian to 500 mW/steradian ... work is under way to break out IREDs from lasers and put them with visible light devices. The allowed power levels for IREDs will them probably raise to 1000 mW/steradian. ...

  ... an increasing fraction of cellular phones, digital watches, palmtop computers, and notebook PCs will begin sporting IrDA ports. ...

  -- Charles H. Small, 1998-02
• Motorola http://www.mot.com/SPS/IRDA/ seems to have a lot of support for IrDA.
• Hewlett Packard http://www.hp.com/go/IR sells some tiny IrDA transceivers
• 38-kHz IR LED Circuit http://www.robotroom.com/Infrared555.html very good, step-by-step instructions with lots of pictures ... so even someone relatively new to electronics should be able to build one up on a solderless breadboard. [FIXME: move to circuits ? Or move all IR circuits here, and just leave link from there to here ?] Compares using a 555 timer to a NAND oscillator. No significant difference for this application.
• Notes on Infra-Red Remotes by Dave Negro http://www.gis.net/~dnegro/IR/ /* was http://falcon.arts.cornell.edu/~dnegro/IR/ */ has lots of information about remote control signals (~40 KHz carrier), table of manufacturers and their IR standards, code and information for using your HP calculator as a remote control, software for 68HC11 and 8052 to transmit and receive standard codes, and pointers to several related schematics (RS-232 to IR transmitters, receiver to RS-232, etc.)
• STV3012 infrared remote control transmitter for audio and video applications http://us.st.com/
• http://www.hut.fi/Misc/Electronics/ lots of electronics info -- Amateur science experiments, robotics, GPS, Barcode technology (printed and magnetic stripe), infrared circuits (including information on lots of IR remote control protocols, and information on IrDA -- distance boost using lasers) smart cards
• Free Space Digital Optics Research http://sipi.usc.edu/~kuznia/FSDOhomepage/FSDO.html Free space optical interconnections within VLSI systems, using "smart pixel"s that contain an optical detector and transmitter along with CMOS circuitry.
• Echelon network (I believe it is called LonWorks) ... Neuron Chips implement a complete 7-layer protocol (based on the OSI architectural model), ... plus memory (ROM, SRAM, and EEPROM) on a single chip, and run internode communication at up to 1.25 Mbits/s (depending on the medium: already implemented and available from multiple suppliers are twisted pair, power line, coax, RF, infrared, and optical fiber).
• The ALT.COMP.HARDWARE.HOMEBUILT FAQ http://www.gl.umbc.edu/~msokos1/achh20.txt mentions:

  2.19 Where can I find information on IR standards?
     * http://falcon.arts.cornell.edu/~dnegro/IR/IR.html
     * http://www.hut.fi/~then/electronics.html#irremote
     * http://149.170.200.3/Physics/Acorn/About.html For a linux driver, see
       http://www.thp.uni-koeln.de/~rjkm/lirc/lirc.tar.gz
     * computer controlled IR remote control:
       http://www.geocities.com/CapeCanaveral/6552
     * There's an application note entitled "IrDA-Compliant Transmitter/
       Receiver," with lots of detail about the standard, at the SHARP web
       site, http://www.sharpmeg.com/datasheets/rf-ir/#0 and data sheets at
       http://www.sharpmeg.com/datasheets/rf-ir/#4
     * http://www.irda.org/ The home of the IRDA standards organisation,
       somewhat messy, but they do provide the standards free for     downloading.
     * ftp://ftp.armory.com./pub/user/rstevew/IR/
     * http://www.misty.com/~don/irfilter.html
  

From: (Tom Maier)
Newsgroups: comp.robotics.misc
Subject: Re: Digital Remote Control
Date: Thu, 20 Mar 1997 13:35:29 GMT
Organization: MindSpring Enterprises, Inc.

Sevcik  wrote:

Hi Sevcik,

>> I've been able to get them to work up to 35 feet.  You probably
>> need to boost your transmission power.
>>
>Tom, you may be right.  Do you remember what your LED current was ?

About 200 milliamps peak, if I remember right.

>>
>> I get them to run at 1200 Baud with no problems.  Are you
>> using the type that Radio Shack is selling?
>>
>>I did not get mine from Radio Shack.  I get 1200 baud, but can not
>send a string of 9 bits of light on.  The AGC reduces the gain till
>the last bits drop off.  So - I send every bit followed by it's
>compliment.  The line speed is 1200 baud, but half is redundant.
>How did you avoid this problem ?

I haven't noticed any of the dropping of the last bits.  The modules
I was using were from LITEON and I bought them from Digikey.
It's solid as a rock at 1200 Baud.  I did some designs for a company
and they run it at 1200 Baud and have not reported any problems.

Are you sure this is the AGC kicking in?  Could it be that the output
of your transmit LED is actually drooping during the transmission?
One thing to check is to see if you are getting droop on your drive
voltage to the LED during the last bits of the transmission.  Connect
a scope to the limiting resistor and see if this is happening.

A large cap right across the transmit LED circuit from V+ to ground is
also important.  About 100 uF or greater.  This helps to give better
instantaneous current to the transmit circuit.  This is especially
important if you are using a battery power source.

Maybe it's just a difference in the receiver module.

Tom

IR components:

• ??? http://optics.org/
• Hamamatsu Photonics http://www.hamamatsu.com/ 4-element photodiodes, synchronous optical detectors, other clever photodiodes.
• http://www.optodiode.com/ GaAlAs detectors
• Fieldpiece Instruments http://www.fieldpice.com/ $129 "ATIR1" non-contact temperature accessory.
• Oxford Semiconductor http://www.oxsemi.com/ has some very fast UARTs (up to 15 Mbps !), some specifically designed for IrDA.

photon sources

photon_sources (except for lasers laser.html )

[FIXME: consider moving this entire section to laser.html ?]

• What is Electromagnetic (EM) Radiation? http://imagine.gsfc.nasa.gov/docs/teachers/lessons/xray_spectra/background-em.html
• LED Flashlights http://www.equipped.org/led_lights.htm reviews from a non-technical, rugged survival point of view: "We've run over the lights with a truck and they have still functioned afterwards"
• The LED Museum by Craig S. Johnson http://ledmuseum.home.att.net/ reviews LED flashlights and individual LEDs.
• Dan's Data http://dansdata.com/ reviews LED flashlights
• http://www.luxeonstar.com/ "The world's brightest LED"
• The Brightest and Most Efficient LEDs and where to get them! http://www.misty.com/~don/led.html by Don Klipstein (Jr).
• LED Pulser circuit http://www.misty.com/people/don/ledbl.html [FIXME: move to schematic.html ]
• HP Application Note AN-1005 (is linked from http://www.semiconductor.agilent.com/led_lamps/app_index.html ) has a section titled "DC Operation is Better than Pulsed Operation for Light Output".
• ZXSC100 Single cell DC-DC converter LED driving applications. http://www.zetex.com/applicat.shtm http://www.zetex.com/pdf/apps/an33.pdf claims that ``the eye and the brain believes the [pulsed] LED is brighter [than a continuous current with the same average power]''. [FIXME: make section on pulsed LED flashlights ?]

  ??? http://www.zetex.com/pdf/design/dn5.pdf http://www.zetex.com/design.shtm [FIXME: short description]

• Pulsing LEDs to make them look brighter? http://www.misty.com/people/don/ledp.html
• LED PWM circuit for automobile http://www.lumileds.com/pdfs/an1149-3.pdf
• White LED users http://clubs.yahoo.com/clubs/whiteleds ???
• JKL Lamps Corporation JKL components http://www.JKLlamps.com/ sells CCFL lamps and inverters
• surface mount leds
  • Surfee-Leds http://surfeeleds.com/
  • Chicago Miniature Lamp, Inc. http://www.chml.com/ sells surface-mount LEDs.
• Flourescent tubes and ballast http://www.xtronics.com/fluorescent-tubes.htm mentions that some ballast circuits generated light flicker that interfere with IR remote controls and IrDA.
• The LED FAQ by Paul Mathews "questions and answers relating to Light Emitting Diodes and their Infrared Emitter cousins." http://www.pioneernet.net/optoeng/LED_FAQ.html /* was http://www2.whidbey.net/optoinfo/LED_FAQ.html */ answers the questions "How Hard Can I Drive LEDs?" "What Is the Best Way to Pulse Modulate LEDs?", and "Can I Increase LED Brightness by Using Pulsed Operation?". (The answer to that last question is : Sometimes. "At very low and very high current levels, you get less light per milliamp than you do at intermediate currents." So if you're trying to maximize the number of photons (optical power), use DC. On the other hand, if you want some fixed dim light (say, enough to see to put your keys in the lock), far below the max. brighness of the LED, you can minimize battery power by pulsing.)
• [photon sources] Fluorescent Lamps by Louis A. Bloomfield http://howthingswork.virginia.edu/fluorescent_lamps.html

GPS, the Global Positioning System

(uses #spread_spectrum )

Here I just talk about getting the (x,y,z,t) information. Technically interesting, but useless by itself. This is just the first step -- next you either find your location on a map 3d_design.html#maps or you use your location in building a new map.

This is mostly technical details for people who want to *build* a GPS receiver. See #gps_receivers if you want to *buy* a GPS receiver.

• http://massmind.org/techref/microchip/gps.htm [FIXME: consider moving all my information there]
• ``GPS = Big Brother?'' article http://www.geek.com/news/geeknews/2001july/gee20010702006611.htm ``You can't call it paranoia if it's already happened.''

  http://www.geek.com/news/geeknews/2001oct/gee20011001008112.htm talks a lot about the ethical implications of the FCC-mandated enhanced 911 location. Some more-or-less scenarios discussing what happens when this information falls into the wrong hands.

  DAV: Because of my Brinist leanings, I think this is over-reacting. Yes, people could do bad things with that information -- if it's one-sided. However, if we can get enough information flowing the other way, then the threat can be negated. [FIXME: do I need a new ``societal implications of GPS'' section for stuff like this ?]

• http://www.sustainableworld.com/y2kgps/gpseng/general_info.html points to lots of simple tutorials/primers and more thorough descriptions of GPS.
• http://ourworld.compuserve.com/homepages/BevHoward/gpsart.htm has a nice discussion of what GPS can do for you, the different types of receivers (recommends no-display units, so you can hook them to a palmtop computer ... and put the antenna outside on the roof)
• Introduction to GPS Applications http://www.redsword.com/GPS/ is a very brief introduction to GPS for someone who knows absolutely nothing about it. It has some good links to other sites for more details.
• ``How stuff works'' http://www.howstuffworks.com/gps.htm has a good explaination of how GPS works.
• http://dmoz.org/Science/Earth_Sciences/Geomatics/GPS_-_Global_Positioning_System/
• 'Quantum Weirdness' May Lead to More Accurate GPS http://www.extremetech.com/article/0,2997,s%253D201%2526a%253D12774,00.asp ``CAMBRIDGE, Mass., Aug. 22 (AScribe News) -- Exploiting "quantum weirdness" would dramatically improve the precision of radar, sonar, the global positioning system (GPS) and other object locators, Massachusetts Institute of Technology researchers report. ... Seth Lloyd ... Vittorio Giovannetti and Lorenzo Maccone ... ''
• "Quirks in Nature Enhance Global Positioning System: Quantum properties may improve precision of object locators while adding security." article by Sharon Berry 2002-01 http://cartome.org/quirks.htm "quantum positioning system (QPS)" points at Quantum Information Technology http://rleweb.mit.edu/quantummuri/
• the Global Positioning System Primer http://www.aero.org/publications/GPSPRIMER/index.html
• GPS (Global Positioning System) http://www.business2.com/webguide/0,1660,16537,00.html?ref=rhs links to a bunch of nice resources.
• [FIXME: http://www.navcen.uscg.mil/gps/default.htm ??? ]
• the GPS Applications Exchange http://gpshome.ssc.nasa.gov/ talks about the many things people *do* with GPS receivers. "If you know of an interesting GPS application that isn't listed on this site, please tell us about it."
• the Global Positioning System Primer http://www.aero.org/publications/GPSPRIMER/
• United States Coast Guard (USCG) Navigation Center GPS PAGE http://www.navcen.uscg.mil/gps/
• The full NMEA-0183 standard http://vancouver-webpages.com/peter/nmeatype.txt as of Nov. 94 [FIXME: is this link relevant ?
• http://www.knightsys.com/ "The vision of Knight Systems is to bring tightly-coupled GPS/INS into the mainstream of navigation systems."
• _GPS World_ magazine http://www.gpsworld.com/ | http://www.gpsworld.com/gpsworld/ has lots of information about GPS products and interesting things people do with GPS.
• (lots of GPS and other electronic mapping information) http://canoe.miningco.com/msub24.htm
• http://www.spacecom.af.mil/hqafspc/library/facts/gps.htm
• http://www.trimble.com/gps/index.htm lots of information on GPS.
• http://ideosphere.com/fx-bin/Claim?claim=GPSSA some comments on GPS.
• http://dir.yahoo.com/Science/Geography/Navigation/Global_Positioning_System__GPS_/ more about GPS.
• From: quark at ds9.com (Quark)
  Newsgroups: sci.physics.relativity
  Subject: Re: Is this the sort of question witch i can ask on sci.physics.relativity or will i be flamed ?
  Date: Fri, 28 Feb 1997 17:47:49 GMT

  On Fri, 28 Feb 1997 11:07:23 +0000, Keith Stein
  <sthbrum at sthbrum.demon.co.uk> wrote:
  
  >
  >
  >  Does anyone happen to know what the actual figure for
  >the total time dilation on the GPS satellites per day is ?
  
  It's around 38,000 nanoseconds  if uncorrected.
  See:
  http://vishnu.nirvana.phys.psu.edu/mog/mog9/node9.html#SECTION00090000000000000000
  

  General relativity in the global positioning system http://vishnu.nirvana.phys.psu.edu/mog/mog9/node9.html
• http://www.whitehouse.gov/WH/EOP/OSTP/html/gps-factsheet.html
• http://www.trimble.com:80/gps/index.htm http://www.yahoo.com/Science/Geography/Navigation/Global_Positioning_System/ [FIXME]
• National Geodetic Survey's CORS http://www.ngs.noaa.gov/CORS/cors-data.html "Surveyors, GIS/LIS professionals, engineers, scientists, and others can apply CORS data to position points at which GPS data have been collected. The CORS system enables positioning accuracies that approach a few centimeters relative to the National Spatial Reference System, both horizontally and vertically."

• NAVSTAR GPS	GLONASS
  Week of validity	Day of validity
  Identifier	Channel number
  Eccentricity	Eccentricity
  Inclination	Inclination
  Time of almanac	Equator time
  Health	Validity of almanac
  Right ascension (RA)	Equator longitude
  Rate of change of RA	---
  Root of semimajor axis	Orbital period
  Argument of perigee	Argument of perigee
  Mean anomaly	---
  ---	Luni-solar term
  Time offset	Time offset
  Frequency offset	---

  -- from p. 254 _Global Positioning System: Theory and Applications: Volume II_, ed. Bradford Parkinson and James Spilker Jr. (c)1996
• "A sidereal day is defined as the time for the Earth to complete one revolution on its axis in ECI space and consists of 24 mean sidereal hours where 1 mean sidereal day is slightly shorter than a mean solar day. One sidereal day is 23 h, 56 min, 4.009054 s or 86 164.09054 s of mean solar time." -- p. 38 _Global Positioning System: Theory and Applications: Volume I_, ed. Bradford Parkinson and James Spilker Jr.
• "The period of an orbit in seconds of mean solar time is Tp = (2π/sqrt(µ))^3/2 where a is the semimajor axis in meters and µ is the Earth's gravitational parameter µ = 3.986005 x 10^14 m^3/s^2. ... Orbit velocity (circular) (ECI) = sqrt( µ / a ). -- p. 40 _Global Positioning System: Theory and Applications: Volume I_, ed. Bradford Parkinson and James Spilker Jr.
• NAVSTAR GPS HOMEPAGE http://www.laafb.af.mil/SMC/CZ/homepage/
• See Usenet Newsgroup sci.geo.sattelite-nav
• Sam's GPS Raw Data Pages http://callisto.worldonline.nl/~samsvl/
• GPS/GLONASS http://home.t-online.de/home/bgalitzki/gps.htm
• ``Global Positioning System Overview'' by Peter H. Dana http://www.colorado.edu/geography/gcraft/notes/gps/gps.html This gives a little more detail that I haven't seen elsewhere online. For example, it gives details of the CA code of GPS ( 10 bit shift registers (LFSR) and the particular code tap assignments of each satellite (PRN ID 1 through 32) and the first 10 bits of each satellite's sequence. ).
• Global Positioning System (GPS) Resources by Samuel J. Wormley 2002 http://www.cnde.iastate.edu/staff/swormley/gps/gps.html links to lots of technical GPS information.
• ``Using GPS to Synthesize A Large Antenna Aperture When the Elements are Mobiles '' http://waas.stanford.edu/~wwu/ssjan/ [FIXME: read this .ppt presentation] [useful for radio astronomy]

gps_receivers

reviews and general information on off-the-shelf GPS receivers.

[FIXME:]

See also A few GPS receivers that caught my eye .

see also 3d_design.html#maps for mapping software.

• GPS humor in the comics http://rev-fun.gospelcom.net/index.php?date=19981216
• Consumer Search http://www.consumersearch.com/www/sports_and_leisure/handheld_gps/index.html summarizes lots of other reviews of handheld GPS receivers. Good.
• Joe Mehaffey and Jack Yeazel's GPS Information Website http://joe.mehaffey.com/ tons of links, comparisons between various receivers, etc.
• http://www.handhelds.org/z/wiki/GPS DAV: the only wiki with a GPS section I know of ... perhaps I should move more of my stuff there ?
• http://flight.com/dir/viewresources.asp?categoryID=2000 lists all the major GPS manufacturers.
• http://www.gpsnuts.com/ has some software reviews, and tips and tricks for using some GPS receivers.
• Motorola GPS Products http://www.motorola.com/ies/GPS/gpswho.html
• Trimble: OEM Boards and Chipsets http://trimble.com/oem.html
• Trimble sells GPS receivers for crop duster aircraft http://trimble.com/aggps_trimflight3.html (see [GPS - IFR] )
• [GPS - IFR]
• GPS and Mapping Info From WE7U http://www.eskimo.com/~archer/gps.html has a long list of GPS receivers, including prices.
• ``How stuff works'' http://www.howstuffworks.com/gps.htm points to a few GPS receiver reviews, and lets you share your own experiences. [FIXME: ask Marshall Brain to link Where to Buy http://www.howstuffworks.com/gps6.htm to somewhere that has a wider variety of GPS receivers]
• http://www.cnet.com/ has some GPS related stuff. Search for GPS on cnet: http://cnet.search.com/search?timeout=3&q=gps and you'll see reviews of stand-alone GPS receivers, GPS programs for your PalmPilot, GPS programs for the PC ... especially check out the zdnet link. This page is the best I've found for finding good prices, and The mySimon link here takes you to more prices, but that's only helpful if you already know the exact model number.
• http://www.gpsw.co.uk/acatalog/GPS_Categories___PDA_Navigation_Systems___54.html
• _GPS World_ Buyers Guide http://www.gpsworld.com/gpsworld/static/staticHtml.jsp?id=3159
• GPS/Compass Reviews http://gearreview.com/navreviews.asp

  We recommend always using a map and compass with a GPS receiver. Using a compass to navigate to a bearing is quicker and more accurate than relying on the GPS to lead you to your destination. Going anywhere in the backcountry without an adequate map is just stupid.

  DAV thinks that a *real* compass you can actually see (really nice ones for $40) is still superior to the ``digital compass'' some GPS units have built-in (typically tacking $100 onto the price).
• ??? http://search.dmoz.org/cgi-bin/search?search=GPS&morecat=1 ???
• Overview of low-cost GPS receivers which output raw data http://home-2.worldonline.nl/~samsvl/oemtable.htm While these are technically ``off-the-shelf'', many of these are raw modules that need to be hooked up to some more processing, a display, etc.
• Garmin http://www.garmin.com/ sells some GPS receivers.

a few GPS receivers that caught my eye

a few GPS receivers that caught my eye See also reviews and general information on off-the-shelf GPS receivers .

• GPS wristwatches
  • $199.60 Casio Watch PAT2GP-1V with GPS receiver http://www.wristwatch.com/depot.asp,,sku,,cas-PAT2GP1V,,idx,,71031,,slt,,37579.6678356482 | http://www.casio.co.jp/ww-e/pdf/qw2240.pdf | http://www.casio.com/watches/product.cfm?section=14&product=3682&display=
  • $400 http://news.com.com/2100-1040-807614.html One of the more heavily promoted items at CES was the GPS Personal Locator from Wherify Wireless , a Global Positioning System transmitter encased in a fairly bulky wristwatch designed to be worn by a child. When you want to know where your kid is, use a phone or Wherify's Web site to get the coordinates, a map, and aerial photos. Such security measures probably sound a lot less excessive after Sept. 11. http://www.wherifywireless.com/prod_watches.htm
• Texas Instruments TCS2500 [FIXME:]
• Earthmate http://www.delorme.com/earthmate/ [FIXME: http://www.sammysoft.com/gpsreview/ ???] "Get the Earthmate GPS receiver for only $89.95 (may have slight cosmetic blemishes). " I think Earthmate is the lightest and cheapest off-the-shelf GPS receiver I've seen. This is just a receiver. All 4 coordinates come out its serial port. It has no LCD display. KA9MVA Hacks the Earthmate http://www.qsl.net/ka9mva/earthmate.htm includes the Rockwell Zodiac protocol PDF.
• GPS2020 - world's smallest fully integrated GPS module http://sychip.com/32-rf.html
• u-blox http://www.u-blox.com/products/index.html sells many GPS receivers, including

  "GPS-MS1 - World's smallest GPS Receiver" http://www.u-blox.ch/gps-ms1/ "the form factor of a PLCC84 package (30mm x 30mm), the module provides complete GPS signal processing from antenna input to serial data output (NMEA or SiRF proprietary format) at a single operating voltage of 3.3 Volts. A second serial port accepts differential GPS data (RTCM). And, featuring the GRF1/LX RF front-end chip with integrated low-noise amplifier (LNA), the module connects seamlessly to low-cost passive antennas. General purpose I/Os and sufficient CPU power allow integration of additional customer specific functionality into the module. Based on Hitachi's SH-series RISC CPU ... low-power"

• http://www.electronsoup.com/xcom/Network/GPS/ has a lot of GPS receivers (without displays) ... some raw modules ... do they already have all the ones I list here ? most of them connect to a PDA.
• Overview of low-cost GPS receivers which output raw data http://callisto.worldonline.nl/~samsvl/oemtable.htm (includes approximate price, currently from US$ 140 to US$ 250)
• GPS receivers in a Springboard module: (Handspring) http://www.handspring.com/products/sbmodules/travelandleisure.jhtml (should, but doesn't ?) lists receivers from 3 different companies and where to buy them. The lowest 2 prices are both $149.99 (list).

  Search for GPS on cnet: http://cnet.search.com/search?timeout=3&q=gps and you'll see reviews of GPS modules for the Handspring Visor

  http://www.visorcentral.com/content/Products/detail-41.htm lists receivers (and prices) from 4 different companies (this is the only place I've seen the ``WebGPS by Nexian'' )

  • Magellan's GPS Companion(TM) for the Handspring(TM) Visor(TM) http://www.magellangps.com/ | http://www.magellangps.com/en/products/product.asp?PRODID=109
    $126.65 http://staples.com/Catalog/Browse/skuset.asp?PageType=2&SkuSetID=987982&bcFlag=True&bcSCatId=3&bcSCatName=Technology&bcCatId=59&bcCatName=PDAs+%26+Handhelds&bcDeptId=1776&bcDeptName=Accessories&bcClassId=141605&bcClassName=GPS

    apparently, no matter who you buy it from, as long as it's before 2002-12-31, Magellen will give a $50 rebate http://www.magellangps.com/en/store/promotions/visor.asp | http://www.marcosoft.com/

  • http://www.marcosoft.com/ $149 (+$12 shipping) Magellan GPS companion ... for other PalmOS and laptops, has serial-port based GPS units. ``the Magellan Map Companion software is a rebranded version of our Quo Vadis(TM) 2.1 and 2.1c software''
  • the manufacturer points me to local distributors. In Tulsa, that would be: BEST BUY TULSA COMPUSA GADGET CO THE: 1702 UTICA SQUARE WAL-MART and a surprisingly large number of other stores.

    $142.78 ... $129.94 http://zdnetshopper.cnet.com/shopping/resellers/0-9491702-1411-5894190.html (the low price is from Amazon, but they only seem to have 1 used device, no new ones ...)

    latest prices from several distributors: ($129.94 as of 2002-12) http://shopper.cnet.com/shopping/resellers/1,10231,0-9491702-311-5894190,00.html unfortunately, 2 of them seem to be offline, and http://www.cdw.com/shop/products/default.asp?edc=286017 tells me ``GPS Companion for the Handspring Visor Note: This product has been discontinued as of Tuesday, December 17, 2002.''

    $153.08 Magellan GPS Companion Springboard Module http://www.expansys.com/product.asp?code=90270320&curr=USD 2002-10-12

    automobile PDA Navigation System http://www.gpsw.co.uk/acatalog/GPS_Categories___PDA_Navigation_Systems___54.html lists the Magellan GPS Companion (for Handspring Visor) (using Springboard slot) and other GPS receivers for Palm, iPAQ, EPOC, and other PDAs. (using serial port or Compact Flast slot)

  • the HandyGPS Pro (Springboard module) from nexian http://www.nexian.com/ review: http://www.visorcentral.com/content/Stories/1304-1.htm a review by Scott Hanselman ( Tue Oct 30, 2001 ) ``I have to say that I VERY MUCH prefer the interface to StreetFinder over UbiGo.''

    		$229.99 (with Street Finder)
    		$199.00 (with UbiGo)
    		

    $172.26 Nexian HandyGPS Pro Springboard Module http://www.expansys.com/product.asp?code=NEX_HGPS1&curr=USD 2002-10-12 (without either UbiGo or Street Finder ?)

    ??? is this the same thing ? http://www.visorvillage.com/hardware/Nexian-HandyGPS-2001-1-11-visor-.html claims that it's useless without UbiGo or other additional-cost software ... which no longer comes with the unit.

  • GeoDiscovery's Geode http://www.geodiscovery.com/ review: http://www.ihpva.org/pipermail/hpv/2001-March/013963.html

  reviews of them:

  • GPS Springboard Comparison September 28, 2001 11:42 AM Rick & Lynn Cousins review the Geodiscovery, Magellan and Nexian GPS Springboard modules and provide an exclusive comparison with Casio GPS watch. http://www.palmgear.com/news/shownews.cfm?sid=90505620021217083619&resID=18560 ... http://www.pmn.co.uk/springboard/ [unfortunately ... seems to have gone offline.]
  • http://www.pocketaprs.com/faq.html mentions the 3 GPS springboard modules (magellan, nexian, geodiscovery), but only works with the magellan. This is DAV's main reason for picking magellan. (OK, so my first GPS was geodiscovery -- when I thought it was the only GPS that would work with a handheld computer). [FIXME: link #maps with this ``Obtaining and Creating Map Files'' section] (negative on PayPal ?) (PocketAPRS claims to work with the magellen in the springboard slot ... and also with a TNC in the springboard slot ... but of course both won't fit at the same time.)

  GPS related software for Palm OS (including Handspring)

  • NavCalc / GPS Point2Point http://www.visorvillage.com/software/pc/NavCalc-2002-1-24-palm-pc.html
  • http://www.visorvillage.com/software/pc/Flight-Buddy-2000-10-16-palm-pc.html | http://www.aspenleaf.com/palm/
• cool gadget that adds the 4 coordinates from a GPS receiver to photos taken by a digital camera: http://come.to/Stelios_Cellar
• http://www.gpsworld.com/gpsworld/product/productList.jsp?categoryId=1390 lots of very small GPS modules

wireless networking

• http://www.networkcomputing.com/ ????
• http://www.networkcomputing.com/1006/1006r2side2.html ???
• http://www.networkcomputing.com/1006/1006r2side3.html ???
• http://www.networkcomputing.com/1006/1006r2.html ???
• "no strings attached" http://www.networkcomputing.com/1004/1004buyers2.html ???
• "Where's 802.11 heading ?" http://www.networkcomputing.com/1004/1004buyerside2.html ???
• "Planning and implementing wireless LANs" http://www.networkcomputing.com/netdesign/wlan1.html ???
• "Wireless no longer a niche" http://www.iplanetit.com/techcenters/docs/Mobile_Computing/Technology/PIT19981221S0022 ???
• http://www.aironet.com/ ???
• ???

the fast Fourier transform (FFT)

• "Fastest Fourier Transform in the West." http://www.fftw.org/ /* was http://theory.lcs.mit.edu/~fftw/ */ "FFTW is a C subroutine library for computing the Discrete Fourier Transform (DFT) in one or more dimensions, of both real and complex data, and of arbitrary input size. We believe that FFTW, which is free software, should become the FFT library of choice for most applications." "Works on any platform with a C compiler. Documentation in HTML and other formats. Callable from Fortran and MATLAB (via wrapper routines included with FFTW). "
• The FXT library: FFT code and related stuff and other algorithms by Jörg Arndt http://www.jjj.de/fxt/
• 2D FFT in C http://www.coe.ou.edu/~havlicek/ece5273/handouts/ho1/ho1.html
• AtSpec http://www.trump.net.au/~paavo/ The FFT code used in this application is available for peer review ("open source") at http://www.trump.net.au/~paavo/sfreebee.htm "a high performance low cost spectrum analyzer that runs under Windows ... providing the major features of hardware based spectrum analyzers ... power spectrum, cross spectrum, frequency response, auto correlation, cross correlation and probability density measurements". . Free demo versions of the application are available for download. The "driver source code" used in this application is included to let you write your own device driver to interface with it. [FIXME: this might be cool for the Sunset Lab AIB board).
• http://www.tinyboot.com/fft.txt FFT using integer arithmetic. ( 16:16 fixed-point ?). In Forth. by Brad Eckert. computer_architecture.html#forth
• 1D fft routine in Java http://www.idiom.com/~zilla/Computer/Javanumeric/fft.java uses ``sine recursion'', i.e., given the values of sin(x) and cos(x) at a couple of specially selected points, it derives all the other values it needs by simple multiplication and addition, no more calls to the trig library. [FIXME: Is this the same as the ``sin table'' calculation described in 1d_design.html#trig ?]

Other mathematical algorithms

• the Numerical Recipes Home Page http://www.nr.com/ mirror: http://cfata2.harvard.edu/numerical-recipes/

laser time of flight

Photons travel at about 1 foot / ns =~= 1 mm / 3 ps. I used to think that would be far too difficult to measure accurately with reasonably-priced equipment, but I'm starting to hear rumors that clever tricks can do it with low-cost equipment. How ?

Can the same tricks be used to reduce the cost of transillumination unknowns_faq.html#transillumination equipment ? Or does transillumination equipment *already* use these tricks ?

Date: Thu, 19 Mar 1998 01:25:00 -0800 (PST)
From: Robert Freitas 
...

It is fairly well-known that the mean free path of a photon in soft human tissue is 10-100 microns, "depending...". Thus in typical soft tissue, after ~150 microns some 99% of all photons have suffered at least one scattering event. By contrast, the characteristic range for absorption in typical human soft tissue is on the order of a few millimeters. So what you're seeing coming through your thumb is photons that have been scattered many many times, but have not yet been absorbed by the tissue. That's why you get a generalized diffuse glow rather than a sharp image showing internal structures like an x-ray. (Blue is preferentially absorbed, which is why the glow appears red.)

It may interest you to know that transillumination is being actively investigated as a way to look for subdermal tumor masses noninvasively. They use extremely fast flashes and various shutter-timing tricks to filter out the scattered photons, so that their sensors can preferentially accumulate those exceedingly few "ballistic photons" that have not yet been scattered, and which therefore still contain useful information about absorbers (e.g. bones, dense tumor masses, etc.) lying in the beam path.

There's tons of literature references on all this stuff -- it's really quite "old hat"!

...

Robert A. Freitas Jr.

• Time-of-Flight Laser Rangefinder using CCD Camera http://www.laserfaq.org/slf/laserlia.htm#liarccd

  ...

  Next, the light source is pulsed for a length of time equal to the round-trip time based for the maximum distance of interest and electronic shutter is gated with the same pulse. The accumulated charge would then be inversely related to distance and proportional to intensity. But the intensity contribution could be subtracted out since it is known from the reference frame.

  ... either direct control of the electronic shutter is needed, bypassing any synchronous logic, or a "sync" output from the camera must be available. Also note that the charge integration times involved -- 10s or 100s of ns -- are orders of magnitude smaller than those normally used on all but very specialized CCD cameras, even with a fast shutter. ...

  Since the electronic shutter is held open precisely the same amount of time that the laser is pulsed, pixels corresponding to very close objects "catch" the entire pulse, while pixels corresponding to distant objects "catch" less of the pulse -- by the time the photons near the end of the pulse travel all the way out and back, the shutter has already closed. Pixels corresponding to very distant objects may miss the entire pulse -- so "inversely related to distance" is not exactly the right equation.

• laser TOF http://www.city.ac.uk/omc/laser_time.htm ``This tutorial gives an overview of time-of-flight distance measurement. ... typical applications ... how these systems work, and some of their benefits and limitations.''
• Time-of-flight laser range scans http://idefix.ikp.liu.se/rames/LIDAR.htm (Pretty pictures, but where's the hardware data on how they were made ?)

[FIXME: seems to be overlap / mixing between TOF and spread spectrum. Should I just mash into one big category ? How to properly seperate into 2 or more categories ?]

spread spectrum

related local links:

• Switching power converters switching_power.html have a few similarities to spread-spectrum communication. (especially ``Magic Sine Wave'' generators)
• Bluetooth

Spread-Spectrum, patented in 1942 by Hedy Lamarr (actor) and George Anthiel (composer).

Also miscellaneous semi-related information on range finding, and linear-feedback shift-registers (LFSRs).

• http://c2.com/cgi/wiki?LinearFeedbackShiftRegister
• _Introduction to Spread Spectrum Communications_ book (c) 1995 by Peterson, Ziemer, and Borth.
• "some of the best introductions to Linear Feedback Shift Registers (LFSR's)" http://www.ciphersbyritter.com/BOOKSHOP.HTM#CodingTheory
• LFSR (Linear Feedback Shift Register) http://www.ciphersbyritter.com/GLOSSARY.HTM#LinearFeedbackShiftRegister a brief definition.
• Spread Spectrum Scene http://www.sss-mag.com/ also has articles on utra-wideband (UWB) communications and radar
• LFSR Pseudo Random Number Generator for AVR-RISC http://www.tu-harburg.de/~setb0209/cpu/avrlfsr.html
• Spread Spectrum http://www.nuhorizons.com/home/tech/newspe.html-ssi
• Pulse communications and pulse radar

  DAV: pulse communication and pulse radar have some similarities to spread spectrum: (a) both are wideband, and (b) both can be used to tell the distance between 2 communicators (or 1 station and a reflector).

  DAV: While pulse radar is certainly easier to understand than fully-general spread-spectrum, it seems to have about the same (and in some cases worse) performance than other modulation schemes.

  • ``Take a Number'' article by Rory J. O'Connor (May 7, 2001) http://www.interactiveweek.com/article/0,2997,s%253D619%2526a%253D6706,00.asp discusses the FCC and its effect on companies trying to sell ultrawideband transmitters such as Fantasma and Time Domain
  • Time Domain Corporation http://www.time-domain.com/ | http://www.timedomain.com/ has patented one version of pulsed communication.
  • ``The origins of Ultra-Wideband Technology (UWB), also known as nonsinusoidal communication technology, impulse radar, ground-penetrating radar, impulse radio, baseband pulse technology, and other designations.'' May 1998. http://www.aetherwire.com/CDROM/Welcome1.html
  • http://ideosphere.com/fx-bin/Claim?claim=PlsCom
  • A 10 GHz (0.1 ns/tick) timer can measure (RADAR) distances to objects with an accuracy of about 0.1 foot. (0.1 ns/tick --> 0.1 foot/tick =~= 1 inch per tick, which is 1/2 inch out + 1/2 inch back, detecting the leading edge of the pulse). Jeff Fox writes a little about pulse radar at http://www.ultratechnology.com/echo.htm
  • http://www.tinaja.com/glib/muse135.pdf are one particular form of spread-spectrum communication. (lots of further links here).
• Random number generators, such as Rollo Silver's favorite, which use SHIFTs and XORs, and give as values only some part of their internal state, can be inverted. See HAKMEM 1d_design.html#hakmem item 25 http://www.inwap.com/pdp10/hbaker/hakmem/random.html#item25
• bps_faq.html for some information on the "EIA IS-60 standard", a chirped spread-spectrum protocol.