US3797938A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Optical apparatus for measuring deformation of parabolic antennas
Assignee: Northrop Grumman Space and Mission Systems Corp
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Filing: 1972-10-16
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Granted: 1974-03-19
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Expires: 1992-10-16
Abstract
Abstract An optical apparatus for recording by double exposure either a hologram or a holographic contour map of a parabolic antenna. The holographic apparatus requires a laser and is arranged so as to function with practical lasers such as a ruby laser having limited coherence and limited light power. Although the antenna is a paraboloid it may be considered an ellipsoid with conjugate foci for purposes of this invention. Accordingly, the scene beam is reflected onto the antenna from a point image source close to one of the foci of the parabolic antenna while the hologram is at the conjugate focal point of the antenna. The path length of the reference beam is matched to that of the scene beam to provide temporal coherence matching. The light may be scattered by a diffuse reflecting ball in one of the foci of the antenna or alternatively a specularly reflecting ball may be used. This ball may be gold plated to improve the reflection of the ruby light. For contouring of the antenna one of the reflectors in the path of the reference beam may be hinged to change the angle of the reference beam between exposures, each being taken at a different wavelength.
Inventors
- 👤 L Heflinger
- 👤 R Wuerker
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 21:48
CPC Classifications
G; G01; G01B; G01B9/00; G01B9/02; G01B9/021; Y; Y10; Y10S; Y10S359/00; Y10S359/902
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
154 words
An optical apparatus for recording holographic interferograms of a parabolic antenna, the antenna having a shape approximating that of an ellipsoid, whereby the antenna has conjugate foci, said apparatus comprising: a. a light source for generating a coherent light beam; b. means for splitting said light beam into a reference beam and a scene beam; c. a recording material disposed substantially in one of the foci of the antenna; d. means disposed substantially in the conjugate focus of the antenna for reflecting said scene beam onto the antenna; e. means for directing said scene beam onto said means for reflecting said scene beam; and f. means for directing said reference beam onto said recording material in such a manner that the path length of said reference beam from said means for splitting to said recording mAterial substantially equals the path length of said scene beam from said means for splitting to said recording material.
Claim 2
Dependent Claim
154 words
An optical apparatus for recording holographic interferograms of a parabolic antenna, the antenna having a shape approximating that of an ellipsoid, whereby the antenna has conjugate foci, said apparatus comprising: a. a light source for generating a coherent light beam; b. means for splitting said light beam into a reference beam and a scene beam; c. a recording material disposed substantially in one of the foci of the antenna; d. means disposed substantially in the conjugate focus of the antenna for reflecting said scene beam onto the antenna; e. means for directing said scene beam onto said means for reflecting said scene beam; and f. means for directing said reference beam onto said recording material in such a manner that the path length of said reference beam from said means for splitting to said recording mAterial substantially equals the path length of said scene beam from said means for splitting to said recording material.
Claim 3
Dependent Claim
28 words
Optical apparatus as defined in claim 1 wherein said means for reflecting said scene beam consists of a light scattering medium having substantially the shape of a sphere.
Claim 4
Dependent Claim
21 words
Optical apparatus as defined in claim 1 wherein said means for reflecting said scene beam consists of a specularly reflecting sphere.
Claim 5
Dependent Claim
32 words
Optical apparatus defined in claim 3 wherein said light source is a pulsed ruby laser and wherein said sphere is gold coated to maximize its reflectivity for light from said ruby laser.
Claim 6
Dependent Claim
40 words
Optical apparatus as defined in claim 1 wherein the antenna has a central feed hole and wherein said means for directing said scene beam directs said scene beam through said feed hole onto said means for reflecting said scene beam.
Claim 7
Dependent Claim
182 words
Optical apparatus for recording holographic interferograms of a parabolic antenna of large size, the antenna having substantially the shape of an ellipsoid to provide conjugate foci, said apparatus comprising: a. a laser for generating a coherent light beam; b. means for splitting said light beam into a reference beam and a scene beam; c. means disposed substantially in one of the foci of the antenna for reflecting the scene beam onto the antenna; d. a recording material disposed substantially in the conjugate focus of the antenna; e. means for directing said scene beam onto said means for reflecting said scene beam, whereby the scene beam is reflected substantially equally from all portions of the antenna onto the recording material; and f. means for directing said reference beam onto said recording material, said means for directing said reference beam including a reflector, and being so arranged that the path length of said reference beam from said means for splitting to said recording material substantially equals the length of the path of said scene beam from said means for splitting to said recording material.
Claim 8
Dependent Claim
182 words
Optical apparatus for recording holographic interferograms of a parabolic antenna of large size, the antenna having substantially the shape of an ellipsoid to provide conjugate foci, said apparatus comprising: a. a laser for generating a coherent light beam; b. means for splitting said light beam into a reference beam and a scene beam; c. means disposed substantially in one of the foci of the antenna for reflecting the scene beam onto the antenna; d. a recording material disposed substantially in the conjugate focus of the antenna; e. means for directing said scene beam onto said means for reflecting said scene beam, whereby the scene beam is reflected substantially equally from all portions of the antenna onto the recording material; and f. means for directing said reference beam onto said recording material, said means for directing said reference beam including a reflector, and being so arranged that the path length of said reference beam from said means for splitting to said recording material substantially equals the length of the path of said scene beam from said means for splitting to said recording material.
Claim 9
Dependent Claim
61 words
Optical apparatus as defined in claim 6 adapted for providing a holographic contour map of the antenna, wherein means is provided for adjusting said reflector in the path of said reference beam to change the angle of the reference beam at said recording material in accordance with changes of the frequency of the laser beam used for recording the contour map.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-03-18 | 1977-09-17 | 1978-03-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-03-18 | 1981-09-17 | 1982-03-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-03-18 | 1985-09-17 | 1986-03-19 | $7700.00 | Window Closed / Lapsed |