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DISTANCE MEASURING DEVICE

  • US 3,779,645 A
  • Filed: 05/13/1971
  • Issued: 12/18/1973
  • Est. Priority Date: 05/20/1970
  • Status: Expired due to Term
First Claim
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1. A distance measuring device comprising:

  • a source of amplitude-modulated light, wherein a light beam produced from said source is modulated at predetermined modulation frequency;

    a light receiver for converting said light beam incident thereon into an electrical signal having a magnitude corresponding to the intensity of said incident light beam;

    a reception optical system for directing said light beam from said source to a reflective object spaced from said course at a distance to be measured, and for directing the light beam reflected from said object to said receiver, wherein said receiver converts said light beam passing through said reception optical system into a reception electrical signal;

    a reference optical system having a predetermined optical path and operable to direct said light beam from said source through said predetermined optical path to said receiver, wherein said receiver converts said light beam passing through said reference optical system into a reference electrical signal;

    change-over means for selectively passing said light beam through said reception and reference optical systems one at a time;

    phase difference measuring means for measuring the phase difference between said reception electrical signal and said reference electrical signal to determine the distance to be measured;

    comparison means connected to said receiver for comparing the magnitudes of said reception and reference electrical signals and including memory means connected to said receiver for storing the magnitude of the electrical signal corresponding to the light beam passing through the other of said two optical systems while said change-over means selectively prevents the light beam passing through said one of said optical systems from entering said receiver, and a comparator connected to said receiver and said memory means for comparing the magnitude of the electrical signal corresponding to the light beam passing through said one of said optical systems with the said magnitude stored in the memory means while said change-over means prevents the light beam passing through said optical system from Entering said receiver, wherein said comparator provides said output of said comparison means; and

    a light quantity regulator responsive to an output of said comparison means and disposed in one of said reception and reference optical systems for regulating the quantity of light entering said receiver through one of said optical systems so that the magnitude difference between said signals is within a predetermined range.

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