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Optical ranging by phase shift measurement with return signal level compensation

  • US 4,829,172 A
  • Filed: 07/20/1987
  • Issued: 05/09/1989
  • Est. Priority Date: 07/20/1987
  • Status: Expired due to Term
First Claim
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1. An optical ranging system of the type employingmeans for radiating optical energy bearing continuous amplitude modulation,means for gathering a portion of the optical energy returned from an object, andmeans for measuring distance to the object by detecting the phase difference between the modulation of the radiated optical energy and the modulation of the returned optical energy, including means for compensating for variations in the level of the returned optical energy,said system being characterize in that the compensating means includes an optical portion based upon the partial optical blocking of the gathering means by the radiating means and an electronic portion based upon an automatic gain control arrangement in which phase shift occuring in such electronic portion varies negligibly with signal level, and the gathering means includes means for focusing the non-blocked portion of the returned optical energy arriving at the gathering means.

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