Optical filter and sensor system

  • US 9,354,369 B2
  • Filed: 07/16/2013
  • Issued: 05/31/2016
  • Est. Priority Date: 07/16/2012
  • Status: Active Grant
First Claim
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1. An optical filter comprising:

  • a filter stack comprising;

    a plurality of hydrogenated silicon layers, wherein the plurality of hydrogenated silicon layers have a refractive index of greater than 3 over a wavelength range of 800 nm to 1100 nm and an extinction coefficient of less than 0.0005 over the wavelength range of 800 nm to 1100 nm; and

    a plurality of lower-refractive-index layers, wherein the plurality of lower-refractive-index layers each have a refractive index of less than 3 over the wavelength range of 800 nm to 1100 nm, and wherein the plurality of lower-refractive-index layers are stacked in alternation with the plurality of hydrogenated silicon layers;

    wherein the optical filter has a passband at least partially overlapping with the wavelength range of 800 nm to 1100 nm,wherein the passband has a center wavelength that shifts by less than 20 nm in magnitude with a change in an incidence angle between 0°

    to 30°

    , thereby providing the optical filter with a wide incidence-angle acceptance range.

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