US4345838A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Apparatus for spectrometer alignment
Assignee: Department of National Defence
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Filing: 1980-07-30
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Granted: 1982-08-24
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Expires: 2000-07-30
Abstract
Abstract A Fourier transform spectrometer in which an alignment system is provided for keeping the moving mirror accurately parallel to its original orientation. A reference laser beam is supplied to the spectrometer and if the moving mirror tilts to become out of parallelism then bars appear in the output field. Three detectors arranged at the vertices of a right-angled triangle detect such bars and provide error signals to a mirror control system. The detectors also receive spurious signals caused by stray reflections at the beamsplitter-compensator plate. By providing a square-shaped reference beam which is masked by an L-shaped opening such spurious signals are eliminated.
Inventors
- 👤 Henry L. Buijs
- 👤 Garry L. Vail
- 👤 Jean-Noel Berube
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 04:13
CPC Classifications
G; G02; G02B; G02B27/00; G02B27/0018; G01; G01J; G01J3/00; G01J3/28; G01J3/45; G01J3/453
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
121 words
In a spectrometer having a laser reference source providing a generally square-shaped beam, a beamsplitter-compensator, a fixed mirror and a moving mirror, a system for detecting variations in alignment between the mirrors including three detectors located adjacent the output field and arranged at the vertices of a triangle, and wherein stray reflections at the beamsplitter-compensator create laterally displaced ghost images of the reference source, the improvement comprising means orienting the beamsplitter-compensator with respect to the reference beam so that the ghost images are displaced along a diagonal of the square-shaped beam and a mask in the input laser beam restricting the laser beam to an L-shaped area which when it impinges on the output field includes the vertices of the triangle.
Claim 2
Dependent Claim
121 words
In a spectrometer having a laser reference source providing a generally square-shaped beam, a beamsplitter-compensator, a fixed mirror and a moving mirror, a system for detecting variations in alignment between the mirrors including three detectors located adjacent the output field and arranged at the vertices of a triangle, and wherein stray reflections at the beamsplitter-compensator create laterally displaced ghost images of the reference source, the improvement comprising means orienting the beamsplitter-compensator with respect to the reference beam so that the ghost images are displaced along a diagonal of the square-shaped beam and a mask in the input laser beam restricting the laser beam to an L-shaped area which when it impinges on the output field includes the vertices of the triangle.
Claim 3
Dependent Claim
17 words
The improvement of claim 1 wherein the detectors are arranged at the vertices of a right-angled triangle.
References Cited (Backward Citations)
US4053231A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1985-08-23 | 1986-02-22 | 1986-08-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1989-08-23 | 1990-02-22 | 1990-08-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1993-08-23 | 1994-02-22 | 1994-08-24 | $7700.00 | Window Closed / Lapsed |