Apparatus and method for surface inspection with test and reference channel comparison
First Claim
1. Apparatus for comparing a test surface with a reference surface comprisingdetector means;
- a test channel means for receiving radiation from the test surface;
reference channel means for receiving radiation from the reference surface;
selector means to pass radiation from the test channel means and the reference channel means to the detector means,varying means being provided to vary the radiation passed to or from at least one of the test channel means or reference channel meanscycle means being provided to cycle the selector means between a first state in which more radiation from the test channel than the reference channel is passed to the detector means and a second state in which more radiation from the reference channel than the test channel is passed to the detector means;
control means being provided to control the radiation varying means to provide a zero or minimum variation of radiation received by the detector means as the selector means is cycled by the cycle means.
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Accused Products
Abstract
Apparatus for comparing a test surface 23 with a reference surface 8 comprising detector means 16.17, a test channel TC for receiving radiation from the test surface 23 and a reference channel RC for receiving radiation from the reference surface 8. A selector means 12 is provided to pass radiation from the test channel means TC and the reference channel means RC to the detector means. Varying means 5 is provided to vary the radiation passed along the test channel TC and reference channel RC. Cycle means is provided to cycle the selector means 12 between a first state in which more radiation from the test channel TC than the reference channel RC is passed to the detector means and vice versa. Control means is provided to control the radiation varying means 5 to provide a zero or minimum variation of radiation received by the detector means as the selector means 12 is cycled.
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Citations
20 Claims
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1. Apparatus for comparing a test surface with a reference surface comprising
detector means; -
a test channel means for receiving radiation from the test surface; reference channel means for receiving radiation from the reference surface; selector means to pass radiation from the test channel means and the reference channel means to the detector means, varying means being provided to vary the radiation passed to or from at least one of the test channel means or reference channel means cycle means being provided to cycle the selector means between a first state in which more radiation from the test channel than the reference channel is passed to the detector means and a second state in which more radiation from the reference channel than the test channel is passed to the detector means; control means being provided to control the radiation varying means to provide a zero or minimum variation of radiation received by the detector means as the selector means is cycled by the cycle means. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification