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Compact moisture sensor with efficient high obliquity optics

  • US 5,898,183 A
  • Filed: 10/16/1997
  • Issued: 04/27/1999
  • Est. Priority Date: 10/16/1997
  • Status: Expired due to Term
First Claim
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1. A moisture sensor for mounting on a first surface of a sheet of glass to detect moisture in a sensing area on a second surface of the sheet of glass, said moisture sensor comprising:

  • a) a coupler for mounting on the first surface of the sheet of glass for optically coupling light rays into and out of the glass;

    b) a housing secured to said coupler;

    c) a planar circuit board secured in said housing and having a device surface which is disposed generally parallel to the first surface of the sheet of glass;

    d) an emitter mounted on said device surface for emitting light rays about an emission axis extending from said emitter approximately perpendicular to said device surface;

    e) a collimator optically coupled to said coupler for collimating light rays from said emitter into a collimated light beam, said collimator having a light receiving aperture with a physical center and an optical center such that an optical axis extends through said optical center and said optical center is spaced apart from said physical center, said collimator being disposed such that the optical axis forms a first oblique angle with respect to the emission axis;

    f) a detector having a detection surface and a detection axis extending from the detection surface for detecting light striking the detection surface about the detection axis and for generating signals in response to the detected light, said detector mounted on the device surface of said planar circuit board such that the detection axis is approximately perpendicular to the device surface; and

    g) a focuser optically coupled to said coupler for focusing the collimated light beam into a convergent fan of rays onto said detection surface, said focuser having a light transmitting aperture with a physical center and an optical center such that an optical axis extends through said optical center and said optical center is spaced apart from said physical center, said focuser being disposed such that said optical axis forms a second oblique angle with respect to said detection axis.

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