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Optical sensor apparatus and method for remotely monitoring a utility meter or the like

  • US 4,680,704 A
  • Filed: 12/28/1984
  • Issued: 07/14/1987
  • Est. Priority Date: 12/28/1984
  • Status: Expired due to Fees
First Claim
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1. An apparatus for optically sensing the angular position of a pointer member fixedly mounted on a rotatable shaft for rotational movement therewith about an axis of rotation, the apparatus comprising:

  • a. an infrared light source means for providing a source of infrared light;

    b. mirror means cooperating with the infrared light source means for directing the infrared light generally toward the pointer member from a location generally forward of the pointer member;

    c. retroreflective surface means disposed on generally one of two locations selected from a faceplate in back of the pointer member and the pointer member for providing a contrast between the pointer member and the faceplate in back of the pointer member, the retroreflective surface means reflecting the infrared light generally back in the direction from which it came toward the mirror means;

    d. lens means for focusing the infrared light reflected by the retroreflective surface means;

    e. optically sensitive image detector means including an array of light sensitive elements for receiving the infrared light focused thereon by the lens means, the optically sensitive image detector means including control circuitry means for controlling the operation of the image detector means, the control circuitry means including;

    i. means for presetting each of the light sensitive elements to a predetermined voltage;

    ii. means for initiating the exposure of the light sensitive elements to the infrared light;

    iii. refreshing means for refreshing the light sensitive elements after a predetermined exposure interval wherein the voltage of each of the light sensitive elements is compared to a predetermined threshold voltage value and each of the light sensitive elements are provided with one of two nominal voltage values representative of the respective light sensitive elements having a voltage less than the threshold voltage value or greater than the threshold voltage value; and

    iv. means for reading the nominal voltage value of each of the light sensitive elements and providing a binary output signal representative of the nominal voltage value; and

    f. control means operatively interconnected to the image detector means for receiving the binary output signal and storing the binary output signal in memory means whereby a binary image of the pointer member is stored, the control means including;

    i. exposure control means for controlling the exposure of the image detector means to the infrared light;

    ii. location means for locating the axis of rotation of the pointer member, the location means including means for correlating the binary image of the pointer member stored in the memory means to a first predetermined geometric shape;

    iii. angular position means cooperating with the location means for determining the angular position of the pointer member, the angular position means including means for correlating the binary image of an end portion of the pointer member with a second geometric shape rotatable relative to the binary image of the pointer member about the axis of rotation of the pointer member; and

    iv. means for storing in memory means digital data representative of the angular position of the pointer member.

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