Method and apparatus for layer thickness measurement
First Claim
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1. A method for optical measurement of a thickness of a layer on a surface, the method comprising:
- a. sending a focused beam of light onto a spot on the layer whereby a substantial part of the beam is refracted for transmission through the layer to illuminate a region on the surface;
b. detecting diffuse reflections from the spot and the region on the surface using detecting equipment;
c. determine a separation between centers of the detected spot and the region; and
d. using the separation between the centers, and geometric properties of the beam, the surface, and the detecting equipment, and an index of refraction of the layer to compute a thickness of the layer.
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Abstract
A technique for optical measurement of a thickness of a layer on a surface uses diffuse reflections at opposite boundaries of the layer, operates on transparent, or translucent layers. The thickness is determined by computing a separation between the centers of the two diffuse reflections, and using the index of refraction of the layer, and geometric properties of a beam and detector with respect to the surface. The technique is useful for quantifying thickness of a layer of rime ice, glaze ice, frosted ice, or water, for example.
18 Citations
29 Claims
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1. A method for optical measurement of a thickness of a layer on a surface, the method comprising:
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a. sending a focused beam of light onto a spot on the layer whereby a substantial part of the beam is refracted for transmission through the layer to illuminate a region on the surface; b. detecting diffuse reflections from the spot and the region on the surface using detecting equipment; c. determine a separation between centers of the detected spot and the region; and d. using the separation between the centers, and geometric properties of the beam, the surface, and the detecting equipment, and an index of refraction of the layer to compute a thickness of the layer. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 29)
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13. An apparatus for optical measurement of a thickness of a layer on a surface, the apparatus comprising:
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a. an emitter of a focused beam of light arranged to project the focused beam onto a spot on the layer such that a substantial part of the beam is refracted for transmission through the layer to illuminate a region on the surface; b. detection equipment configured with a line of view oriented so that diffuse reflections of the spot and region are in a field of view of the detection equipment; and c. a data processor for computing a separation between centers of the detected spot and the region sensed by the detection equipment, and for computing a thickness of the layer using the separation, an index of refraction of the layer, and geometric properties of the beam, the surface, and the line of view. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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- 24. A kit for measuring a thickness of a layer on a surface, the kit comprising instructions for configuring a laser source and detector equipment with respect to the surface, so that an emitter of a focused beam of light is arranged to project the focused beam onto a spot on the layer such that a substantial part of the beam is refracted for transmission through the layer to illuminate a region on the surface, and the detection equipment is configured with a line of view oriented so that diffuse reflections of the spot and region are in a field of view of the detection equipment.
Specification