US3998553A
Expired / Lapsed
US
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Device and method for testing high reflectivity autostigmatic optical elements and systems
Assignee: Zygo Corp
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Filing: 1975-05-12
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Granted: 1976-12-21
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Expires: 1995-05-12
Abstract
Abstract An optical device and method for testing high reflectivity autostigmatic optical elements and systems is disclosed. A thin, partially transmissive optical element, e.g., a pellicle with an optical coating having a transmission factor determined by the nominal reflectivity of the test article, is placed in the measurement leg of a spherical wavefront Fizeau interferometer so that high contrast, two-beam interference fringes can be obtained from a high reflectivity autostigmatic optical element or system.
Inventors
- 👤 George C. Hunter
- 👤 Paul F. Forman
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 17:48
CPC Classifications
G; G01; G01B; G01B9/00; G01B9/02; G01B9/02034; G01B9/02038; G01B9/02039
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
157 words
In a spherical wavefront interferometer for testing a highly reflective autostigmatic test article consisting of (1) a source of light (2) means for passing said light, as an expanded beam, through (3) a partially transmissive, partially reflective spherical reference surface to produce a reflected reference wavefront, and a transmitted converging spherical test wavefront which is directed toward (4) the common center of curvature of said reference surface and said highly reflective autostigmatic test article, and said test wavefront then probes (5) said test article and is reflected therefrom back through said reference surface and (6) means for interfering both said reflected reference wavefront and said reflected test wavefront, the improvement which consists in placing, between said reference surface and said test article a partially transmissive, thin coated pellicle which has a transmission factor T which approximates ##EQU3## where R rs is the reflectivity of the reference surface, and R ta is the reflectivity of the test article.
Claim 2
Dependent Claim
157 words
In a spherical wavefront interferometer for testing a highly reflective autostigmatic test article consisting of (1) a source of light (2) means for passing said light, as an expanded beam, through (3) a partially transmissive, partially reflective spherical reference surface to produce a reflected reference wavefront, and a transmitted converging spherical test wavefront which is directed toward (4) the common center of curvature of said reference surface and said highly reflective autostigmatic test article, and said test wavefront then probes (5) said test article and is reflected therefrom back through said reference surface and (6) means for interfering both said reflected reference wavefront and said reflected test wavefront, the improvement which consists in placing, between said reference surface and said test article a partially transmissive, thin coated pellicle which has a transmission factor T which approximates ##EQU3## where R rs is the reflectivity of the reference surface, and R ta is the reflectivity of the test article.
Claim 3
Dependent Claim
16 words
The device of claim 1, in which the said source of light is a gas laser.
Claim 4
Dependent Claim
43 words
The device of claim 1, in which said reference surface is uncoated optical glass or fused silica, with a reflectivity of 3.5%, and the transmission factor of said pellicle is 34%, and said test article range in reflectivity is from 11% to 100%.
Claim 5
Dependent Claim
40 words
The device of claim 1, in which said reference surface is uncoated fused silica with a reflectivity of 3.5%, and the transmission factor of said pellicle is 52%, and said test article range in reflectivity is from 7% to 27%.
Claim 6
Dependent Claim
40 words
The device of claim 1, in which said reference surface is uncoated fused silica with a reflectivity of 3.5%, and the transmission factor of said pellicle is 27%, and said test article range in reflectivity is from 27% to 100%.
Claim 7
Dependent Claim
27 words
The device of claim 1, in which said test article has a convex test surface and is placed between said pellicle and said common center of curvature.
Claim 8
Dependent Claim
32 words
The device of claim 1, in which said test article has a concave test surface and is placed on the opposite side of said common center of curvature from said reference surface.
References Cited (Backward Citations)
US3028782A
Cited
US3506361A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1979-12-21 | 1980-06-21 | 1980-12-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-12-21 | 1984-06-21 | 1984-12-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-12-21 | 1988-06-21 | 1988-12-21 | $7700.00 | Window Closed / Lapsed |