Going back in time here.... If you focus a video camera on a paper test pattern with regular spaced vertical stripes It will generate very accurate pulses when that area is scanned. Remember that the total scan line time is about 65 micro seconds. This allowed us to work on the frequency response of video amplifiers way back when. Raster scanning has not always been the dominate method for OCR either. I have an unreasonable amount of experience with flying spot scanners that worked really well thirty years back. John Ferrell 6241 Phillippi Rd Julian NC 27283 Phone: (336)685-9606 Dixie Competition Products NSRCA 479 AMA 4190 W8CCW "My Competition is Not My Enemy" ----- Original Message ----- From: "Russell McMahon" To: Sent: Friday, August 10, 2001 8:31 AM Subject: [EE]: Video Camera as head position indicator - ideas sought > I have been asked to investigate providing a disabled user with the means to > operate an existing book-page turner. > This device usually uses a suck / blow switch with two levels (hard / soft) > of suck and blow providing 4 commands. > The user has Multiple Sclerosis and is unable to reliably use the suck/blow > system > Other users would also have similar needs. > A complication is that minimal funding is available. This is not necessarily > a limitation but a lower cost solution would be nice. > > The user has reasonable head position control and it was suggested that I > could provide a light beam pointing system where the user pointed a head > mounted light beam at 4 optical receptors mounted above the page turner. > This should be a reasonably straight forward solution: > - Use a laser pointer > - Possibly modified to provide beam modulation.although this should not bee > necessary at such short range. > - Optical saturation from ambient light should be easy to avoid in this > application. > - Provision of a timed "beam on" period with turn on enabled by eg looking > upwards at a greater than usual angle would remove the otherwise annoying > red spot on the reading material :-) > > HOWEVER > > It occurred to me that the availability of low cost video cameras in various > forms (serial port, parallel, USB, separate video ...) should allow a > reasonably low cost solution where the camera monitored a target and > detected head orientation. This could still include a head mounted target or > source but this could be more discrete and if active it could be infrared > and pulsed. While this sounds eminently achievable there would almost > certainly prove to be "more to it" than meets the eye at this stage. Such a > system is notionally more expensive in material cost than a headpointer / > beam system but would be more flexible, more easily adapted to related uses > and less user intrusive. > A rudimentary camera based defined-object location system could have a range > of other uses in disability aid applications. > > On reflection (no pun intended) it might be easier to use the camera to > detect where a beam falls on a target than to look at the user and attempt > to determine where the beam is pointing. The "target" could be a wall or > screen above the page turner. The user need not necessarily be able to see > the beam. While this is effectively just replacing optical detectors with a > single wide area detector the above points re flexibility etc still apply. > > Has anyone had experience of similar systems and / or can offer useful > suggestions that may help reduce design time. > > > > regards > > Russell McMahon > > -- > http://www.piclist.com hint: PICList Posts must start with ONE topic: > [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads > > -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads