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Control system for detecting intrusion of a light curtain

  • US 5,404,008 A
  • Filed: 07/16/1993
  • Issued: 04/04/1995
  • Est. Priority Date: 07/16/1993
  • Status: Expired due to Fees
First Claim
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1. A control system adapted to detect intrusion of a control plane by an object;

  • said control system comprising a plurality of light sources arranged along a first margin of said control plane;

    a plurality of light detectors arranged along a second margin of said control plane in generally parallel disposition with respect to said first margin, said light detectors being adapted to receive light emitted from the respective light sources, said light sources being connected in a parallel circuit to a power supply and adapted thereby to broadcast a light curtain across said control plane;

    means for sequentially sampling output signals of said light detectors;

    said parallel circuit including an oscillator circuit means for powering said light sources with a driving voltage of preselected frequency;

    a band pass filter circuit means for establishing an output signal feedback control loop for said sequential sampling means whereby a narrow output signal band frequency near said preselected frequency is established thus reducing extraneous electronic noise and background light effects;

    means for establishing and storing a reference output signal value indicative of a calibrated value;

    means for comparing said output signals with said calibrated value and for developing a control system signal in response to detection of a predetermine difference between said reference signal and said output signals as a result of an intrusion of said light curtain.

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