Method and apparatus for reducing or eliminating stray light in an optical test head
First Claim
1. Apparatus comprising:
- at least one input path for receiving light from a light source and communicating said light to a workpiece;
a light detector for receiving light and generating a signal in response thereto;
at least one output path for receiving light reflected from said workpiece and communicating said light to said detector;
wherein at least one of said at least one output path or at least one input path includes a light-absorptive layer for absorbing and/or trapping stray light.
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Accused Products
Abstract
An optical test head comprises one or more optical input paths by which a beam of light is communicated from a light source to a workpiece and one or more optical output paths by which light reflected off of the workpiece is communicated to a detector. The input optical path and the output optical path can include one or more mirrors and one or more lenses. At least one of the optical paths includes a layer for trapping and/or absorbing stray light. One or more of the lenses includes an anti-reflective coating for reducing noise caused by unwanted light reflection off of the lenses. The optical paths include one or more masks reducing stray light. The one or more masks can have an adjustable aperture (e.g. an iris).
25 Citations
21 Claims
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1. Apparatus comprising:
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at least one input path for receiving light from a light source and communicating said light to a workpiece;
a light detector for receiving light and generating a signal in response thereto;
at least one output path for receiving light reflected from said workpiece and communicating said light to said detector;
wherein at least one of said at least one output path or at least one input path includes a light-absorptive layer for absorbing and/or trapping stray light. - View Dependent Claims (2, 3, 4, 5)
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6. Apparatus comprising:
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at least one input path for receiving light from a light source and communicating said light to a workpiece;
at least one output path for receiving light reflected from said workpiece and communicating said light to a detector; and
one or more masks within at least one of said paths for reducing or eliminating stray light in said at least one of said paths, said stray light being a component of light that would exist even in the absence of defects on said workpiece, said one or more masks not substantially affecting light that exists in said one of said at least one of said paths as a result of said defects. - View Dependent Claims (7)
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8. Apparatus comprising:
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at least one input path for receiving light from a light source and communicating said light to a workpiece;
at least one output path for receiving light reflected from said workpiece and communicating said light to a detector; and
at least one mask within said at least one output path for minimizing or preventing light stray light from reaching said detector. - View Dependent Claims (9)
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10. Apparatus comprising:
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a light source for generating a light beam, said light beam being directed toward a workpiece;
a detector for receiving light reflected from said workpiece; and
one or more lenses in the optical path of said light beam, at least one of said lenses being coated with a V-type AR coating. - View Dependent Claims (11)
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12. Apparatus comprising:
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a light source for generating a light beam, said light beam being directed toward a workpiece;
a detector for receiving light reflected by said workpiece; and
one or more lenses in the optical path of said light beam, at least one of said lenses being coated with an antireflection coating that reflects less than about 0.25% of the light striking said lens. - View Dependent Claims (13, 14)
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15. Method comprising:
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communicating light through at least one input path to a workpiece;
communicating light reflected by said workpiece through at least one output path to a detector;
wherein at least one of said at least one output path or at least one input path includes a light-absorptive layer for absorbing and/or trapping stray light. - View Dependent Claims (16)
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17. Method comprising:
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communicating light through at least one input path to a workpiece;
communicating light reflected from said workpiece through at least one output path to a detector;
wherein one or more masks are within at least one of said paths, said one or more masks reducing or eliminating stray light in said at least one of said paths, said stray light being a component of light that would exist even in the absence of defects on said workpiece, said one or more masks not substantially affecting light that exists in said one of said at least one of said paths as a result of said defects. - View Dependent Claims (18)
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19. Method comprising:
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providing a light beam traveling toward a workpiece;
detecting light reflecting off of said workpiece with a detector; and
passing said light beam through at least one lens in the optical path between a source of said light beam and said detector, said at least one lens being coated with a V-type AR coating.
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- 20. Method of claim 19 wherein said workpiece is a platter and said light beam is a laser beam, said method further comprising passing said light beam through a plurality of lenses in the optical path between said source and said detector, said V-type AR coating causing said at least one lens to exhibit a reflectivity less than 0.25%, said V-type AR coating reducing or eliminating stray light.
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20-1. Method comprising:
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providing a light beam traveling toward a workpiece;
detecting light reflecting off of said workpiece with a detector;
passing said light beam through at least one lens in the optical path between a source of said light beam and said detector, said at least one lens being coated with an antireflective coating that causes the lens to exhibit a reflectivity less than about 0.25%.
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Specification