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Photodetector system for detecting obstacles in aisles between mobile shelving carriages

  • US 5,569,910 A
  • Filed: 11/10/1994
  • Issued: 10/29/1996
  • Est. Priority Date: 11/10/1994
  • Status: Expired due to Term
First Claim
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1. A self-calibrating photodetector protection system comprising:

  • a radiation beam transmitter having an input for electric driving pulses and operative to project a beam of radiation pulses corresponding substantially in width to the width of the driving pulses,a radiation receiver spaced from the transmitter and arranged for receiving the pulsed radiation beam, the receiver having an output and is adapted to respond to receiving radiation pulses of a minimum width and greater than a minimum width by issuing from its output electric pulses corresponding substantially to the width of the received radiation pulses,a digital processor having an electric pulse output coupled to the input of the transmitter and having an input coupled to the output of the receiver,the processor responding to an initializing signal by functioning in a calibration mode wherein the processor is operative to output a series of electric pulses to the input of the transmitter, the first corresponding radiation pulse output in the series by a properly operative transmitter having a preset minimum width and following pulses having successively greater widths up to a predetermined limit to determine the least pulse width in the series that has sufficient width to exceed the pulse width sensitivity threshold of the receiver, which if exceeded, will cause a properly operating receiver to output an electric pulse signal to said input of the processor, said processor having an output and responding to said input of electric pulses by changing the logic level voltage state of said last named output.

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