Obstruction position detecting system with comparison and memory means
First Claim
1. In a presence detection apparatus having a plurality of sets of light beam sources and photodetectors, the source and photodetector of each set defining a light beam channel and being disposed so the light beam from the source impinges upon the photodetector in the absence of an obstruction in the light beam channel, said sets of light beam channels being arranged at predetermined locations to define a screen, the improvement comprising:
- sensing means for sensing the output of each photodetector to detect blocked light beam channels;
memory means coupled to said sensing means for storing the location of blocked light beam channels; and
comparison means coupled to said sensing means and said memory means for comparing the location of sensed blocked light beam channels with stored locations of blocked light beam channels.
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Accused Products
Abstract
The present invention employs a plurality of spaced light beam sources and corresponding photodetectors to form a light screen. A programmed microprocessor and memory circuitry senses the photodetector output and stores information on the position of an allowed obstruction. During operation of the equipment, the microprocessor repeatedly senses the photodetector output to determine which channels are blocked. When dangerous changes occur in the size, position or presence of an obstruction, the system alerts the operator or stops the equipment.
46 Citations
11 Claims
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1. In a presence detection apparatus having a plurality of sets of light beam sources and photodetectors, the source and photodetector of each set defining a light beam channel and being disposed so the light beam from the source impinges upon the photodetector in the absence of an obstruction in the light beam channel, said sets of light beam channels being arranged at predetermined locations to define a screen, the improvement comprising:
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sensing means for sensing the output of each photodetector to detect blocked light beam channels; memory means coupled to said sensing means for storing the location of blocked light beam channels; and comparison means coupled to said sensing means and said memory means for comparing the location of sensed blocked light beam channels with stored locations of blocked light beam channels. - View Dependent Claims (2, 4, 5, 6)
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3. The presence detection apparatus of claim 3 further comprising switch means coupled to said comparison means for providing a switched output signal in response to a predetermined change in said blocked light beam channels.
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7. In a presence detection method, wherein the presence detection apparatus includes a plurality of sets of light beam sources and photodetectors, the source and photodetector of each set defining a light beam channel and being disposed so the light beam from the source impinges upon the photodetector in the absence of an obstruction in the light beam channel, said sets of light beam channels being arranged at predetermined locations to define a screen, the improvement comprising the steps of:
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sensing the initial output of said photodetectors to determine whether a light beam channel is blocked and thereby detect an allowable obstruction; storing the location of blocked light beam channels in memory; sensing the subsequent output of said photodetectors to determine whether a light beam channel is subsequently blocked; and comparing the location of subsequently blocked light beam channels to said stored locations. - View Dependent Claims (8, 9, 10, 11)
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Specification