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Does anything like that exist?:

A4 or bigger sized plate which would with ca. 1 mm precision detect regions of the plate which were covered. So if you place your hand on the plate you will obtain a binary image of the hand with

0 = no light = hand

1 = light = no hand.

I would be a very simple binary scanner of plate or strip dimensions.

Which technology would you recommend to do the task? Preferably, it should be possible to buy the strip or plate and it should be connectable to PC.

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  • \$\begingroup\$ Maybe something with a matrix of photoresistors, but with 1cm resolution...something similar with silicon is not realistic, and with the resolution you require would require a too large area or a great number of small devices that would be difficult to build. \$\endgroup\$ – clabacchio Jan 27 '12 at 16:25
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People did detect a hand touching a glass surface via infrared light. They had the light shine on the edge of a glass plate and the light was then reflected internally. Where the hand touched the glass plate, the infrared light left the glass plate and could be detected via a digital camera behind the glass.

enter image description here

Your can read about it here.

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  • \$\begingroup\$ I seriously doubt you can get the required 1 mm precision this way, but of course it wouldn't be the first time I was wrong ;-) \$\endgroup\$ – JonnyBoats Jan 27 '12 at 18:35
  • \$\begingroup\$ @JonnyBoats: A sheet of A4 paper is about 210 by 300mm. This means 63000 individal "pixels" have to be looked at. Sounds doable with a 2MP webcam or better. Or do I overlook an issue other than resolution? \$\endgroup\$ – 0x6d64 Jan 28 '12 at 22:48
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Sounds like you are looking for a scanner of some sort, probably a flatbed type.

These use a CCD (charge coupled device) based scanning device that moves along under whatever is being scanned and converts light levels to digital data.

If your application requires some function they don't provide, you could maybe grab a cheap scanner and hack it as necessary for prototyping.

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