System for detecting ice or snow on surface which specularly reflects light
First Claim
1. Apparatus for canceling background light reflected from an object comprising:
- means for producing an image using ambient light reflected from said object;
means for storing light amplitude data of a plurality of pixels of said image;
means for projecting artificial illumination onto said object;
means for producing an illuminated image produced by said artificial illumination plus said ambient light; and
means for subtracting said light amplitude data from corresponding pixels of said illuminated image to compensate for ambient light contribution to said illuminated image.
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Accused Products
Abstract
A system for detecting the presence of an energy polarization altering dielectric material, such as ice or snow, on a surface, such as a part of an aircraft, which normally specularly reflects incident energy, such as light, when there is no such dielectric present. The energy is conveyed from a transmitter along a path to the surface and the incident energy is reflected from the surface along a path to a receiver with a dielectric on the surface destroying any polarization, such as circular, of the energy and that reflected from a specular portion maintaining the polarization. An optical system in one or both of the paths operates in an isolator state to produce an image of the dielectric portion having a first intensity level and that of the specular portion passing through the optical system having a different intensity level. When the optical system is operated alternately in isolator and non-isolator states it produces an image of the dielectric portion having a relatively steady intensity level and that of the specular potion alternating between first and second different intensity levels corresponding to the isolator and non-isolator states of the optical system.
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Citations
11 Claims
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1. Apparatus for canceling background light reflected from an object comprising:
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means for producing an image using ambient light reflected from said object; means for storing light amplitude data of a plurality of pixels of said image; means for projecting artificial illumination onto said object; means for producing an illuminated image produced by said artificial illumination plus said ambient light; and means for subtracting said light amplitude data from corresponding pixels of said illuminated image to compensate for ambient light contribution to said illuminated image.
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2. Apparatus for detecting a material on a surface comprising:
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means for projecting a light source on a transmitting path onto said surface; means for receiving reflected light on a receiving path from at least one of said material and said surface; means in at least one of said transmitting path and said receiving path for alternating between a blocking condition and a non-blocking condition; said blocking condition having a different effect on light transmission than said non-blocking condition, whereby a ratio of light at said means for receiving reflected light from said material and said surface is different between said blocking condition and said non-blocking condition; means for storing an amplitude of reflected light from said surface under ambient light, with said means for projecting turned off; and means for compensating a light received at said means for receiving for said amplitude during operation of said means for projecting, whereby said ambient light in said means for receiving is compensated. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10, 11)
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Specification