US3575082A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Albada viewfinder having three lens components
Assignee: Eastman Kodak Co
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Filing: 1968-06-24
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Granted: 1971-04-13
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Expires: 1988-06-24
Abstract
Abstract An Albada viewfinder comprising a negative aspheric objective and a positive eyepiece between which is located a positive meniscus element having on its rear surface a mirror for forming a virtual image of a reticle mark.
Inventors
- 👤 Gilbert William Mcclune
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 13:32
CPC Classifications
G; G02; G02B; G02B23/00; G02B23/14; G02B13/00; G02B13/18
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
107 words
An Albada-type viewfinder comprising from front to rear a negative objective, a positive meniscus middle element concave toward the rear and a rear positive biconvex eyepiece, wherein the lens elements have substantially the following characteristics and spatial relations in which the lens elements are numbered from the front, R, T and S refer respectively to the radii of curvature of the lens surfaces, the thicknesses of the lens elements and the spacings between the lens elements, numbered by subscript from front to rear, and wherein the lenses have an index of refraction for the D line of substantially 1.49 and a power of dispersion of substantially 57.4:
Claim 2
Dependent Claim
107 words
An Albada-type viewfinder comprising from front to rear a negative objective, a positive meniscus middle element concave toward the rear and a rear positive biconvex eyepiece, wherein the lens elements have substantially the following characteristics and spatial relations in which the lens elements are numbered from the front, R, T and S refer respectively to the radii of curvature of the lens surfaces, the thicknesses of the lens elements and the spacings between the lens elements, numbered by subscript from front to rear, and wherein the lenses have an index of refraction for the D line of substantially 1.49 and a power of dispersion of substantially 57.4:
Claim 3
Dependent Claim
150 words
An Albada-type viewfinder comprising from front to rear a negative objective, a positive meniscus middle element concave toward the rear and a rear positive biconvex eyepiece, a reticle adjacent said eyepiece, and at least a portion of the rear surface of said positive meniscus middle element being coated with a reflective layer for forming a curved mirror facing said reticle to form a virtual image plane of said objective, wherein the lens elements have substantially the following characteristics and spatial relations in which the lens elements are numbered from the front, R, T and S refer respectively to the radii of curvature of the lens surfaces, the thicknesses of the lens elements and the spacings between the lens elements, numbered by subscript from front to rear, and wherein the lenses have an index of refraction for the D line of substantially 1.49 and a power of dispersion of substantially 57.4:
Claim 4
Dependent Claim
150 words
An Albada-type viewfinder comprising from front to rear a negative objective, a positive meniscus middle element concave toward the rear and a rear positive biconvex eyepiece, a reticle adjacent said eyepiece, and at least a portion of the rear surface of said positive meniscus middle element being coated with a reflective layer for forming a curved mirror facing said reticle to form a virtual image plane of said objective, wherein the lens elements have substantially the following characteristics and spatial relations in which the lens elements are numbered from the front, R, T and S refer respectively to the radii of curvature of the lens surfaces, the thicknesses of the lens elements and the spacings between the lens elements, numbered by subscript from front to rear, and wherein the lenses have an index of refraction for the D line of substantially 1.49 and a power of dispersion of substantially 57.4:
References Cited (Backward Citations)
US2923196A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-04-12 | 1974-10-12 | 1975-04-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-04-12 | 1978-10-12 | 1979-04-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-04-12 | 1982-10-12 | 1983-04-13 | $7700.00 | Window Closed / Lapsed |