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Bar code reading systems having electrical power conservation and laser radiation power limiting means

  • US 5,019,698 A
  • Filed: 08/07/1989
  • Issued: 05/28/1991
  • Est. Priority Date: 08/07/1989
  • Status: Expired due to Term
First Claim
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1. In a bar code reader having means for providing pulsed light beam adapted to be incident upon a bar code and which is returned therefrom, and means for providing an electrical bar code signal corresponding to such bar code in response to light returned from said bar code so as to enable decoding thereof, the improvement wherein said producing means comprises a light source having an optical power output (P) vs. electrical current (I) characteristic having a slope efficiency Δ

  • P/Δ

    I which is non-linear and characterized by an abrupt positive change between an initial region of low slope efficiency and a subsequent region of higher slope efficiency, and means for applying repetitive current pulses to said source to operate said source at a point on said characteristic in said region of higher slope efficiency and with a duty cycle such that the average optical power output is no greater than a certain level which does not exceed radiological health restrictions, and said electrical signal providing means comprises means for removing signal components of said electrical signal at the repetition rate of said current pulses.

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