Can Infrared Radiation Detect Extra Glossy or Thick Pages in Scanning Machines?

[dmehling]

I am trying to develop a mechanism for automatically scanning documents which involves picking up pages or sheets of paper. I need a method for determining whether an extra page has been picked up. I have considered using a beam of light that would pass through the page or pages and a sensor on the other side of of the page could determine how much light has passed through. Less light passing through would indicate that the machine has picked up an extra page. What I am wondering is how would this work for very thick or glossy paper like the kind in a magazine? Would visible light be absorbed completely by the paper, and if so what other forms of energy could pass through such paper? Would infrared radiation be a possibility?

 

[mgb_phys]

Infrared might be better because it will have less effect on any optical brightening agents present on the paper. And will be less sensitive to any dye printing.

You will probably have to make some sort of self adjusting system where it constantly measures a running average of the transmission of the paper being used and responds to peaks in this rather than try and determine a fixed transmission value for all paper - which will vary with type. This will also handle both changes in the light source / detector.

Of course you will have a problem if you have a sheet of high gloss paper in the middle of a stack of newsprint.