Multi-cavity fabry-perot interferometric thin-film sensor with built-in temperature compensation
First Claim
1. A sensor providing temperature compensation for a measurement of an optical thickness of a film, said sensor comprising at least three partially reflecting surfaces defining at least first and second Fabry-Perot cavities exhibiting different indices of refraction, one of said partially reflecting surfaces being at an end of said sensor and including a surface associated with said second Fabry-Perot cavity for supporting a film, the optical thickness of which is to be measured.
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Accused Products
Abstract
A fiber optic sensor includes at least two Fabry-Perot (FP cavities) defined by at least three partially reflecting surfaces which individually and together are capable of generating different interference spectra which are affected by temperature. One of the FP cavities is formed at an end of the sensor and includes a surface which is capable of supporting a thin film, the optical thickness of which is to be measured. The other FP cavity between the lead-in fiber and the first FP cavity thus does not include the film and can thus independently provide highly accurate temperature information for calibrating the optical length of the second FP cavity and compensation for temperature effects on measurement of the thin film supported thereon, preferably by subtraction of a calibrated temperature-dependent change in optical length of the second FP cavity from the measurement made.
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Citations
20 Claims
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1. A sensor providing temperature compensation for a measurement of an optical thickness of a film, said sensor comprising
at least three partially reflecting surfaces defining at least first and second Fabry-Perot cavities exhibiting different indices of refraction, one of said partially reflecting surfaces being at an end of said sensor and including a surface associated with said second Fabry-Perot cavity for supporting a film, the optical thickness of which is to be measured.
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11. A sensor system providing temperature compensation for a measurement of an optical thickness of a film, said sensor system comprising
a sensor having at least three partially reflecting surfaces defining at least first and second Fabry-Perot cavities exhibiting different indices of refraction, one of said partially reflecting surfaces being at an end of said sensor and including a surface associated with said second Fabry-Perot cavity for supporting a film, the optical thickness of which is to be measured.
Specification