Apparatus and Method For Nanoradian Metrology of Changes In Angular Orientation of A Vibrating Mirror Using Multi-Pass Optical Systems
First Claim
1. A metrology system for measuring changes in orientation of a vibrating mirror, comprising an optical cavity that includes reflection of a measurement beam from the vibrating mirror, the optical cavity configured such that an object space that includes the vibrating mirror is a conjugate image of the same object space.
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Abstract
A new and useful metrology system is provided, of a type that comprises an optical cavity of the hemispherical or spherical type, with a vibrating mirror not located at or near a focus of the optical cavity, and which is particularly useful as a non interferometric metrology system. In one of its basic aspects, the metrology system measures changes in orientation of a vibrating mirror, by providing an optical cavity that includes reflection of a measurement beam from the vibrating mirror, where the optical cavity is configured such that an object space that includes the vibrating mirror is a conjugate image of the same object space. In another of its basic aspects, a metrology system according to the present invention has a measurement beam that is reflected from the vibrating mirror, where the vibrating mirror and a reference mirror are in a relationship in which reflection of the measurement beam from the vibrating mirror is then reflected from the reference mirror in a manner that establishes a local reference system for measuring changes in the orientation of the vibrating mirror.
12 Citations
12 Claims
- 1. A metrology system for measuring changes in orientation of a vibrating mirror, comprising an optical cavity that includes reflection of a measurement beam from the vibrating mirror, the optical cavity configured such that an object space that includes the vibrating mirror is a conjugate image of the same object space.
- 8. A metrology system for measuring changes in the orientation of a vibrating mirror, comprising an optical cavity in which a measurement beam is reflected from the vibrating mirror, and wherein the vibrating mirror and a reference mirror are in a relationship in which reflection of the measurement beam from the vibrating mirror is then reflected from the reference mirror in a manner that establishes a local reference system for measuring changes in the orientation of the vibrating mirror.
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11. A metrology system for measuring changes in the orientation of a vibrating mirror, comprising
a. an optical cavity in which a pair of measurement beams are reflected from the vibrating mirror and imaged at an image plane during each of a plurality of passes of the measurement beams through a portion of the optical cavity, b. the optical cavity including a vibrating mirror subsystem in which the pair of measurement beams are reflected from the vibrating mirror and from a reference mirror during each of a plurality of passes of the measurement beams through a portion of the optical cavity, and c. wherein the vibrating mirror subsystem and the paths of the measurement beams directed into and out of the vibrating mirror subsystem are configured to reduce the influence of air turbulence on the measurement beams in at least one predetermined reference plane.
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12. A metrology system for measuring changes in the orientation of a vibrating mirror, comprising
a. an optical cavity in which a pair of measurement beams are (i) reflected from the vibrating mirror and from a reference mirror and (ii) imaged at an image plane, during each of a plurality of passes of the measurement beams through a portion of the optical cavity, and b. an input beam subsystem comprising an input beam source that produces a single input beam and an input beam conditioner that (i) produces a pair of measuring beams from the single input beam, (ii) focuses the pair of measurement beams as spots on a first plane and (iii) directs the pair of measurement beams into the portion of the optical cavity; - and
c. wherein the portion of the optical cavity and the input beam conditioner are configured such that the common mode component of the locations of the focused spots on the first plane is invariant to displacements and/or changes in the orientation of either the input beam conditioner or the input beam subsystem, and the differential mode component of the locations of the corresponding focused spots on the image plane is not invariant and is sensitive to displacements and/or changes in orientation and/or location of either the input beam conditional or the input beam subsystem.
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Specification