Jamin-type interferometers and components therefor
First Claim
1. A retroreflector having three mutually-orthogonal reflective surfaces arranged around an optical axis, wherein the reflective surfaces stop short of the optical axis to provide a central region of the retroreflector which transmits incident light and a peripheral region of the retroreflector which retroreflects incident light.
2 Assignments
0 Petitions
Accused Products
Abstract
A retroreflector has three mutually-orthogonal reflective surfaces arranged around an optical axis. The reflective surfaces stop short of the optical axis to provide a central region of the retroreflector which transmits incident light and a peripheral region of the retroreflector which retroreflects incident light. When the reflector is used in a Jamin-type interferometer with another reflector, this enables the interferometer to be used for measuring displacement between the reflectors.
In the interferometer, a projected beam is disposed between a pair of return beams and/or one of the return beams is disposed between a pair of the projected beams. This enables a first contiguous area of a face of a beam splitter to be provided with a phase-shifting coating to produce a phase quadrature relationship between a pair of interferogram beams. This simplifies the masking required when applying the coating.
In manufacture of the beam splitting member, a thin-film, beam-splitting, metal coating is applied to the member, and the member and coating are baked so as to modify the phase shift produced by the coating to enable the phase quadrature relationship. During baking a beam of light is projected at the coating with an angle of incidence of substantially π/4 radians so that the beam is split into a transmitted component and a reflected component. The intensities or phases of the transmitted and reflected components are monitored during baking, and the baking is terminated when the monitored intensities or phases have a predetermined relationship. This improves the reliability and/or accuracy of the resulting phase shift.
230 Citations
44 Claims
- 1. A retroreflector having three mutually-orthogonal reflective surfaces arranged around an optical axis, wherein the reflective surfaces stop short of the optical axis to provide a central region of the retroreflector which transmits incident light and a peripheral region of the retroreflector which retroreflects incident light.
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8. A reflector system comprising first and second relatively movable reflectors, wherein:
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the first reflector is a retroreflector having three mutually-orthogonal reflective surfaces arranged around an optical axis, wherein the reflective surfaces stop short of the optical axis to provide a central region of the retroreflector which transmits incident light and a peripheral region of the retroreflector which retroreflects incident light; and
the reflectors are arranged so that light which is transmitted through the central region of the first reflector is reflected by the second reflector and transmitted back through the central region of the first reflector. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16, 17, 23, 24)
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19. A method of manufacturing a retroreflector, comprising the steps of:
- providing a cube corner retroreflector comprising a body of optical material, the body having three mutually-orthogonal reflective surfaces arranged around an optical axis, the reflective surfaces providing internal reflection in the body, and the body having a first transmitting surface for incident light; and
cutting the body in a plane generally orthogonal to its optical axis to form a second transmitting surface which truncates the cube corner so that the reflective surfaces stop short of the optical axis and so that a central region of the retroreflector is provided that transmits incident light and a peripheral region of the retroreflector is provided that retroreflects incident light.
- providing a cube corner retroreflector comprising a body of optical material, the body having three mutually-orthogonal reflective surfaces arranged around an optical axis, the reflective surfaces providing internal reflection in the body, and the body having a first transmitting surface for incident light; and
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20. A method of manufacturing a retroreflector, comprising the steps of:
- providing a cube comer retroreflector comprising a body of optical material, the body having three mutually-orthogonal reflective surfaces arranged around an optical axis, the reflective surfaces providing internal reflection in the body, and the body having a first transmitting surface for incident light; and
forming a passageway through the body generally in the direction of the optical axis so that the reflective surfaces stop short of the optical axis and so that a central region is provided that transmits incident light and a peripheral region of the retroreflector is provided that retroreflects incident light.
- providing a cube comer retroreflector comprising a body of optical material, the body having three mutually-orthogonal reflective surfaces arranged around an optical axis, the reflective surfaces providing internal reflection in the body, and the body having a first transmitting surface for incident light; and
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21. A method of manufacturing a retroreflector, comprising the steps of:
- providing three plane mirrors each having a pair of mutually orthogonal edges;
cutting each mirror along a line intersecting each of its mutually orthogonal edges to form a respective first mirror and a respective second mirror; and
assembling the first mirrors mutually-orthogonally to form a retroreflector having a central region that transmits incident light and a peripheral region of the retroreflector that retroreflects incident light. - View Dependent Claims (22, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 39, 40, 41, 42, 43, 44)
- providing three plane mirrors each having a pair of mutually orthogonal edges;
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25. A Jamin-type interferometer, wherein:
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a beam splitter is arranged to split an incident beam of light into first and second generallyparallel, spaced-apart, projected beams;
a reflector system is arranged to reflect the first and second projected beams to produce first and second return beams, respectively, which are spaced apart from and generally parallel to each other and the first and second projected beams;
the beam splitter is arranged to enable the first and second return beams to be superposed to produce at least one interferogram beam;
the projected beams are projected from, and the return beam returns to, a single face of the beam splitter; and
one of the projected beams is disposed between the return beams and/or one of the return beams is disposed between the projected beams.
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38. A method of manufacture of a beam splitting member, comprising the steps of:
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applying a thin-film, beam-splitting, metal coating to at least part of a surface of the member;
projecting a beam of light at the coating with an angle of incidence of substantially π
/4 radians so that the beam is split into a transmitted component and a reflected component;
baking the member and coating so as to modify the phase shift produced by the coating;
monitoring the intensities or phases of the transmitted and reflected components during the baking step; and
terminating the baking step when the monitored intensities or phases have a predetermined relationship.
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Specification