Optical inspection system and method including accounting for variations of optical path length within a sample
First Claim
1. An optical inspection system for optically characterizing a sample, comprising:
- an illuminator/collector assembly configured to deliver multiple incident light rays to the sample and collect multiple return light rays returning from the sample;
a sensor that includes a plurality of zones, each zone measuring ray intensity as a function of ray position and ray angle for the respective collected return light rays;
a ray selector configured to select a first subset of light rays from the collected multiple return light rays at the sensor that meet a first selection criterion, wherein the first selection criterion is associated with a single scattering event; and
a computer including a characterizer configured to determine a physical property of the sample based on the ray intensities, ray positions, and ray angles for the first subset of light rays.
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Abstract
An illuminator/collector assembly can deliver incident light to a sample and collect return light returning from the sample. A sensor can measure ray intensities as a function of ray position and ray angle for the collected return light. A ray selector can select a first subset of rays from the collected return light at the sensor that meet a first selection criterion. In some examples, the ray selector can aggregate ray intensities into bins, each bin corresponding to rays in the collected return light that traverse within the sample an estimated optical path length within a respective range of optical path lengths. A characterizer can determine a physical property of the sample, such as absorptivity, based on the ray intensities, ray positions, and ray angles for the first subset of rays. Accounting for variations in optical path length traversed within the sample can improve accuracy.
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Citations
20 Claims
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1. An optical inspection system for optically characterizing a sample, comprising:
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an illuminator/collector assembly configured to deliver multiple incident light rays to the sample and collect multiple return light rays returning from the sample; a sensor that includes a plurality of zones, each zone measuring ray intensity as a function of ray position and ray angle for the respective collected return light rays; a ray selector configured to select a first subset of light rays from the collected multiple return light rays at the sensor that meet a first selection criterion, wherein the first selection criterion is associated with a single scattering event; and a computer including a characterizer configured to determine a physical property of the sample based on the ray intensities, ray positions, and ray angles for the first subset of light rays. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A method for optically characterizing a sample, comprising:
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illuminating the sample with incident light using an illuminator; collecting multiple return light rays returning from the sample; measuring ray intensities as a function of ray position and ray angle for the respective collected return light rays using a sensor; aggregating at least some of the ray intensities into a plurality of binned signals; and determining a physical property of the sample based on the plurality of binned signals. - View Dependent Claims (19, 20)
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Specification