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Lost scan line detecting method and device for a handheld scanner having a lost line counter

  • US 5,250,804 A
  • Filed: 09/10/1992
  • Issued: 10/05/1993
  • Est. Priority Date: 09/10/1992
  • Status: Expired due to Fees
First Claim
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1. A lost scan line detecting method for providing lost scan line information to a computer system which is connected to and which receives scan line picture data from a handheld scanner so as to enable said computer system to derive picture data which corresponds to a lost scan line from available scan line picture data, said handheld scanner generating a series of photo receiver pulses and a series of step trigger signals, each of said photo receiver pulses indicating that said handheld scanner has traveled by a distance which is equivalent to one scan line on a document being scanned, said handheld scanner generating each of said step trigger signals after one of said photo receiver pulses has been generated, the period between two said step trigger signals being constant and corresponding to a predetermined maximum scanning speed of said handheld scanner, said method comprising the steps:

  • providing a first counter means to count said photo receiver pulses;

    providing a second counter means to count said step trigger signals; and

    providing a comparator means to compare count outputs of said first and second counter means and to generate a lost scan line signal whenever said count outputs are unequal so as to indicate to said computer system that a lost scan line condition has occurred.

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