On Jan 28, 2008 5:41 PM, M. Adam Davis wrote: > The only thing that hasn't been mentioned is that a lot of visible > light scanners modulate the laser or lighting element to seperate > signal and noise, such as from flourescent lights, etc. I don't know that that is true. I've actually not opened one yet that did this. I spent a lot of time working with barcode systems. > So even if you had the simplest barcode scanner (a wand you swiped > across the barcode) if it was modultated you'd be unable to sense and > respond appropriately with a transmit only scenario. If you were able to modulate the reflectance of a target quickly enough, you could. Look at the codes printed on drink cans, where the bar elements are silver and white. The silver looks "black" to the optics because it's a specular, not diffuse reflection. An LCD film over a mirror, might work if it could be thin enough. -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist