Scanning Technologys

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I am designing a scanner to digitize and reprint old pictures/documents. Because of the age of the media high light levels are not permitted. Are there any scanning technologies other than CCD (high light levels needed) and digital cameras (expensive) that I could use?

Thanks

-- Andy Cardiff (Cards_999@iclway.co.uk), October 22, 1999

Answers

Well this may be no help but Canon make an inexpensive scanner called the FB 620P. It uses a CIS ( Contact Image Senor) and 3 RGB LED's as the light source. They do nice work and are not nearly as bright as a regular scanner bulb if I remember correctly. I don't profess to know the technical jargon well but it's kind of a unique scanner in that mechanical sence. The 620P is the parallel version and the 620U is the USB version. They cost $100 and $130 respectively. Good luck.

-- Cris Daniels (danfla@gte.net), October 22, 1999.

There are photomultiplier tubes which is the technology that drum scanners are based on. The sensitivity of these can go all the way down to capturing a single photon, but they are bulky and expensive items that couldn't be used as an array. You'd have to use a raster scanning technique instead of line by line.

If colour accuracy is not an issue, you could steal Nikon's idea of illuminating with three colour LEDs.

Frankly, I'm not sure what the problem is. The time that any part of a document is exposed to light under a normal flatbed scanner must be less than a second, and modern high-frequency discharge tubes generate very little heat. Also, normal plate glass will filter out most of the damaging UV. One second at (say) 1000 Lux will do no more damage than 20 seconds in normal room lighting.

-- Pete Andrews (p.l.andrews@bham.ac.uk), November 11, 1999.


Andy - an answer for REALLY dim light: the Toshiba PDR-M4 digital camera (about $400), which has a "bulb" setting which does two things: 1) very long exposures, and 2) dark-current correction - meaning that after the exposure, the camera takes a second shot, of the inside of the lens cap, and digitally subtracts it from the first, to balance for noise generally present in extremely low-light shots.

Haven't tried it, but you could literally work by the light of a single candle. Hard to believe the curators would complain - except maybe about that open flame!

-mark grebner

-- Mark Grebner (Mark@Grebner.com), December 21, 1999.


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