US3622218A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Two-element objective for use in the infrared range
Assignee: Eltro GmbH and Co
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Filing: 1969-12-08
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Granted: 1971-11-23
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Expires: 1989-12-08
Abstract
Abstract A two-element objective for operation in the infrared range of 8 Mu and 14 Mu is constituted by a convex-concave front condensing lens of cesium bromide spaced in front of a rear dispersive lens of polycrystalline zinc sulfide fritted under pressure. The objective has a resolving power of 0.8 milliradians on the optical axis with an aperture ratio of 1:2.5.
Inventors
- 👤 Hans Gerhard Kruger
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 21:47
CPC Classifications
G; G02; G02B; G02B13/00; G02B13/14; G02B13/146
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
118 words
An achromatic two-lens objective for the infrared range, comprising; a front condensing lens formed of cesium bromide, wherein said lens has a front surface exposed to the atmosphere and includes a protective coating on said front surface impervious to water and permeable to radiation of a wavelength between 8 Mu and 14 Mu , and a rear dispersive lens constituted of polycrystalline zinc sulfide frittered under pressure spaced from said condensing lens so as to provide air separation therebetween, the combination of said condensing and dispersive lenses forming an infrared range objective between 8 Mu and 14 Mu and having a resolving power of about 0.8 milliradians on the optical axis with an aperture ratio of about 1:25.
Claim 2
Dependent Claim
118 words
An achromatic two-lens objective for the infrared range, comprising; a front condensing lens formed of cesium bromide, wherein said lens has a front surface exposed to the atmosphere and includes a protective coating on said front surface impervious to water and permeable to radiation of a wavelength between 8 Mu and 14 Mu , and a rear dispersive lens constituted of polycrystalline zinc sulfide frittered under pressure spaced from said condensing lens so as to provide air separation therebetween, the combination of said condensing and dispersive lenses forming an infrared range objective between 8 Mu and 14 Mu and having a resolving power of about 0.8 milliradians on the optical axis with an aperture ratio of about 1:25.
Claim 3
Dependent Claim
18 words
An objective as claimed in claim 1 wherein said lens has the following data in mm.: f 100
Claim 4
Dependent Claim
29 words
An objective as claimed in claim 2 wherein the Abbe index gamma 10 is wherein: n8 and n14 are the refractive indexes at wavelengths of 8 and 14 respectively.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-11-22 | 1975-05-24 | 1975-11-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-11-22 | 1979-05-24 | 1979-11-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-11-22 | 1983-05-24 | 1983-11-23 | $7700.00 | Window Closed / Lapsed |