Method of scanning documents to read characters thereon without interference from visible marks on the document which are not to be read by the scanner

Abstract

An optical character recognition system including a laser scanner unit adapted to scan a document having preprinted markings to indicate where the characters are to be placed. Variations in light intensity reflected from the document and characters produce scan signals which are processed to determine the characters. The color of the markings on the document is related to the laser frequency such that the light reflected from the markings has the same intensity as the light reflected from the document background, so that the presence of the markings does not interfere with the reading of the characters.

I claim: 
     
       1. The method of machine reading of characters placed on a document form having pre-printed thereon markings visible to the eye but which are not to be read by the character reading machine, said method comprising the steps of: producing by means of a laser small-diameter beam of monochromatic light, the width of said beam being small relative to the size of said characters;   presenting to said beam of monochromatic light a document form having said characters in place on a reflective background and carrying said pre-printed markings in a color related to said monochromatic light such that said beam produces from said markings a reflected light intensity equal to the intensity of reflected light said beam produces from said background, whereby said markings and said background are not distinguishable with respect to the light reflected from said document form in response to impingement of said monochromatic light beam;   scanning said document by sweeping said narrow beam .[.at.]. along a series of consecutive, adjacent paths intersecting said character and said markings;   developing signals representing the amount of light reflected from said document at evenly-spaced points along the scan path throughout the regions of said document containing said characters; and   analyzing said developed signals to determine the nature of the characters on said document. .Iadd.   
     
     
       2.  The method of machine reading of characters placed on a document having presented thereon markings visible to the eye but which are not to be read by the character reading machine, said method comprising the steps of: producing by means of a laser a small-diameter beam of monochromatic light, the width of said beam being small relative to the size of said characters;   presenting to said beam of monochromatic light a document having said characters in place on a reflective background and carrying said markings in a color related to said monochromatic light such that said beam produces from said markings a reflected light intensity equal to the intensity of reflected light said beam produces from said background, whereby said markings and said background are not distinguishable with respect to the light reflected from said document in response to impingement of said monochromatic light beam;   scanning said document by sweeping said narrow beam along a series of consecutive, adjacent paths intersecting said character and said markings;   developing signals representing the amount of light reflected from said document at evenly-spaced points along the scan path throughout the regions of said document containing said characters; and   analyzing said developed signals to determine the nature of the characters on said document. .Iaddend.