Methods and apparatus for analyzing mirror reflectance
First Claim
1. A method of determining the reflectance of a mirror as a function of angle of incidence, comprising:
- (a) measuring the P-polarization reflectance of the mirror at a reference angle of incidence relative to the normal of a reflective surface of the mirror;
(b) measuring the S-polarization reflectance of the mirror;
(c) computing an approximation of at least one of the S-polarization reflectance and the P-polarization reflectance at a proximate angle of incidence other than the reference angle from the measured S-polarization and P-polarization reflectances.
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Accused Products
Abstract
Methods and apparatus are described for assessing the reflective properties of mirrors at different angles of incidence without precise knowledge of the mirror'"'"'s basic optical constants and/or without precise knowledge of the mirror'"'"'s over-coating prescription. Reflectance values can be accurately calculated for multiple angles of incidence based upon measurement data collected for a single angle of incidence. The approach uses equations based on the Fresnel equations for reflectance in which reflectance is calculated as a function of the angle of incidence of incoming light to the scanned mirror used to collect the signal. The angle of incidence-based approach allows accurate reflectance values to be calculated over a broad range of wavelengths and angle of incidences without detailed knowledge of the optical properties of the coating material and the substrate underneath. The described methods and apparatus are particularly useful for calibrating measurements made with remote sensing instruments that use scanned mirrors.
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Citations
36 Claims
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1. A method of determining the reflectance of a mirror as a function of angle of incidence, comprising:
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(a) measuring the P-polarization reflectance of the mirror at a reference angle of incidence relative to the normal of a reflective surface of the mirror; (b) measuring the S-polarization reflectance of the mirror; (c) computing an approximation of at least one of the S-polarization reflectance and the P-polarization reflectance at a proximate angle of incidence other than the reference angle from the measured S-polarization and P-polarization reflectances. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. An apparatus for determining the reflectance of a mirror as a function of angle of incidence, comprising;
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a detector that measures an S-polarization reflectance and a P-polarization reflectance of light reflected from a mirror at a reference angle of incidence; and a processor that computes an approximation of at least one of the S-polarization reflectance and the P-polarization reflectance at a proximate angle of incidence other than the reference angle of incidence from the measured S-polarization and P-polarization reflectances. - View Dependent Claims (23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35)
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36. An apparatus for determining the reflectance of a mirror as a function of angle of incidence comprising:
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a mirror that receives and reflects incident light; a controller that controls positioning of the mirror; a detector that measures an S-polarization reflectance and a P-polarization reflectance of light reflected from a mirror at a reference angle of incidence; and a processor that computes an approximation of at least one of the S-polarization reflectance and the P-polarization reflectance at a proximate angle of incidence other than the reference angle of incidence from the measure S-polarization and P-polarization reflectances.
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Specification