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Low noise photoelectric detector apparatus

  • US 3,996,476 A
  • Filed: 09/10/1975
  • Issued: 12/07/1976
  • Est. Priority Date: 09/10/1975
  • Status: Expired due to Term
First Claim
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1. A low noise photoelectric sensing apparatus comprising a framework, a lens mounted in one end of said framework for focusing light impinging thereupon at a focal point located on the rear side of said lens on a central axis passing therethrough, said lens having a front side exposed to the exterior of said framework and having a central hole therein,a photodetector mounted in said framework on said central axis positioned toward the rear of said lens for receiving the focused light and providing an output signal related thereto,a light source mounted on said central axis positioned toward the front of said lens for emitting light away from said lens,an opaque collar formed to fit in said central hole for shielding said lens from said emitted light to reduce noise in said output signal resulting from spurious light from said light source impinging on said photodetector, said lens serving to receive emitted light only after reflection from objects in front of said lens, whereby said output signal provides a low noise indication thereof.

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