US3864111A
Expired / Lapsed
US
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Reducing Stress Birefringence in Fused Silica Optical Elements
Assignee: Individual
•
Filing: 1973-08-08
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Granted: 1975-02-04
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Expires: 1993-08-08
Abstract
Abstract Stress-birefringence in light transmitting fused-silica optical elements is reduced by the etch removal of surface layers stressed by mechanical abrasion and thermal effects in the fabrication of the optical elements. The etch is applied selectively to the non-light-transmitting surfaces of the optical element to relieve stress-birefringence inducing uniaxial strain directed in the plane of the light-transmitting faces.
Inventors
- 👤 James C Kemp
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 22:11
CPC Classifications
G; G02; G02B; G02B1/00; G02B1/10; G02B1/12; C; C03; C03C; C03C15/00
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
100 words
THE METHOD OF REDUCING STRESS-BIREFRINGENE IN FUSEDSILICA AND FUSED-QUARTZ LIGHT-TRANSMITTING ELEMENTS BY ETCH REMOVAL OF STRESSED SURFACE LAYERS OF THE LIGHT-TRANSMITTING ELEMENTS COMPRISISNG: COVERING LIGHT-TRANSMITTING SURFACE AREAS OF THE OPTICAL ELEMENT WITH AN ETCHANT RESISTANT SUBSTANCE, SUBJECTING THE SELECTIVELY COVERED OPTICAL ELEMENT TO AN ETCHANT CORROSIVE TO THE OPTICAL ELEMENT SUBSTRATE FOR A PERIOD OF TIME SUFFICIENT TO REMOVE MECHANICALLY ABRADED OR THERMALLY EFFECTED LAYERS OF THE SUBSTRATE UNDER STATIC COMPRESSIONAL STRESS (TYPICALLY 0.001 INCH TO 0.004 INCH), AND REMOVING BY MEANS OF THE ETCHANT UNIAXIAL STRAIN DIRECTED IN THE PLANE OF LIGHT-TRANSMITTING FACES WHICH STRAIN GIVES RISE TO STRESS-BIREFRINGENCE.
Claim 2
Independent Claim
100 words
THE METHOD OF REDUCING STRESS-BIREFRINGENE IN FUSEDSILICA AND FUSED-QUARTZ LIGHT-TRANSMITTING ELEMENTS BY ETCH REMOVAL OF STRESSED SURFACE LAYERS OF THE LIGHT-TRANSMITTING ELEMENTS COMPRISISNG: COVERING LIGHT-TRANSMITTING SURFACE AREAS OF THE OPTICAL ELEMENT WITH AN ETCHANT RESISTANT SUBSTANCE, SUBJECTING THE SELECTIVELY COVERED OPTICAL ELEMENT TO AN ETCHANT CORROSIVE TO THE OPTICAL ELEMENT SUBSTRATE FOR A PERIOD OF TIME SUFFICIENT TO REMOVE MECHANICALLY ABRADED OR THERMALLY EFFECTED LAYERS OF THE SUBSTRATE UNDER STATIC COMPRESSIONAL STRESS (TYPICALLY 0.001 INCH TO 0.004 INCH), AND REMOVING BY MEANS OF THE ETCHANT UNIAXIAL STRAIN DIRECTED IN THE PLANE OF LIGHT-TRANSMITTING FACES WHICH STRAIN GIVES RISE TO STRESS-BIREFRINGENCE.
Claim 3
Dependent Claim
38 words
The method of reducing stress-birefringence of claim 1 further comprising subjecting the seLectively covered optical element to an etchant corrosive to the optical element substrate in the form of an immersing in an aqueous solution of hydrofluoric acid.
Claim 4
Dependent Claim
30 words
The method of reducing stress-birefringence of claim 2 wherein the subjecting of the optical element to hydrofluoric acid comprises immersing in an aqueous solution of approximately 50 percent hydrofluoric acid.
Claim 5
Dependent Claim
33 words
The method of reducing stress-birefringence of claim 2 wherein the subjecting of the optical element to hydrofluoric acid comprises immersing in a bath of hydrofluoric acid which is agitated during the etching operation.
Claim 6
Dependent Claim
32 words
The method of reducing stress-birefringence of claim 2 wherein the subjecting of the optical element to hydrofluoric acid comprises immersing in a bath of hydrofluoric acid which is maintained at approximately 25*C.
Claim 7
Dependent Claim
19 words
The method of reducing stress-birefringence of claim 2 wherein the covering step comprises selectively covering the substrate with paraffin.
Claim 8
Dependent Claim
84 words
The method of reducing stress birefringence of claim 1 wherein the selective covering of the light transmitting faces of the optical element is accomplished by: immersing the optical element in a liquified, etchant resistant substance, solidifying the etchant resistant substance cutting or scraping the etchant resistant substance from the non-light-transmitting surfaces, and beveling the etchant resistant substance back from the edges demarcating the protected faces so that the etchant resistant substance contacting the protected faces is thinest near the edges demarcating the protected faces.
Claim 9
Dependent Claim
34 words
The method of reducing stress-birefringence of claim 1 wherein the removing of stressed surface layers comprises removing stressed surface layers created by mechanical cutting or polishing processes in the fabrication of the optical element.
Claim 10
Dependent Claim
46 words
The method of reducing stress-birefringence of claim 1 wherein the technique for etching optical elements described in claim 2 is employed in the fabrication of optical elements where it is desirable to minimize residual stress-birefringence such as in the fabrication of optical elements for photoelastic modulators.
Claim 11
Dependent Claim
25 words
The method of reducing stress-birefringence of claim 1 further comprising the initial step of severing the optical elements from a larger block of fused silica.
Claim 12
Dependent Claim
23 words
The method of reducing stress birefringence of claim 1 further comprising the ultimate step of joining the stress-reduced element to a electromechanical transducer.
References Cited (Backward Citations)
US1981815A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-02-03 | 1978-08-05 | 1979-02-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-02-03 | 1982-08-05 | 1983-02-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-02-03 | 1986-08-05 | 1987-02-04 | $7700.00 | Window Closed / Lapsed |