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Optical encoder

  • US 4,319,134 A
  • Filed: 04/21/1980
  • Issued: 03/09/1982
  • Est. Priority Date: 06/16/1978
  • Status: Expired due to Term
First Claim
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1. A method of making an optical shaft encoder of a type that produces an electrical signal having a phase angle representative of the relative position of a movable shaft, said encoder including a source of light, a photocell positioned to receive the light, means coupled to the movable shaft for blocking transmission of the light to the photocell in accordance with the relative position of the shaft, and amplifier means coupled to the photocell for producing the electrical signal, said amplifier means including variable resistance means for use in controllably adjusting the peak amplitude of the electrical signal, said method comprising the steps of:

  • mounting said photocell and said amplifier means on a circuit board,energizing said source of light and said amplifier means and moving said movable shaft in a prescribed fashion,monitoring the peak amplitude of the electrical signal produced by said amplifier means, and comparing it to a prescribed level,directing a laser beam onto the variable resistance means in said amplifier means, while continuing to monitor the peak amplitude of the electrical signal and to compare it to the prescribed level, said laser beam having an intensity sufficient to alter the resistance of the variable resistance means, thereby controllably adjusting the peak amplitude of the electrical signal, andterminating the step of directing a laser beam when it has been determined in said step of comparing that the peak amplitude of the electrical signal is substantially equal to the prescribed level.

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