Patent US5218480A successfully refreshed from Google Patents.
US5218480A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Retrofocus wide angle lens
Assignee: 3M Innovative Properties Co
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Filing: 1991-12-03
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Granted: 1993-06-08
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Expires: 2011-12-03
Abstract
Abstract A wide angle lens system of the retrofocus type is provided which includes two lens units. The first lens unit is of negative power and includes a combination of a positive element having a high dispersion and a negative element having a low dispersion for correction of lateral color. The second lens unit is of positive power and includes a combination of a positive element having a low dispersion and a negative element having a high dispersion for correction of longitudinal color. The lens units satisfy the relationship that the magnitude of f 1 is less than about 1.15 times f 2 and preferably satisfy the relationship that the magnitude of f 1 is less than f 0 . The first and second lens units each preferably include an aspheric surface. Applications of the lens system include rear projection television systems wherein a single lens is used to project light from three LCD light valves onto a viewing screen.
Inventors
- 👤 Jacob Moskovich
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 02:58
CPC Classifications
G; G02; G02B; G02B13/00; G02B13/04
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
152 words
A wide angle lens system of the retrofocus type having a focal length f 0 which comprises: (a) a first lens unit of negative power having a focal length f 1 and comprising a negative element and a combination of two elements, one of said two elements being a positive element having a high dispersion and the other of said two elements being a negative element having a low dispersion; and (b) a second lens unit of positive power having a focal length f 2 and comprising a positive element and a combination of two elements, one of said two elements being a positive element having a low dispersion and the other of said two elements being a negative element having a high dispersion; wherein each of the first and the second lens units includes an aspheric surface and the system includes an aperture stop between the first and second lens units.
Claim 2
Dependent Claim
152 words
A wide angle lens system of the retrofocus type having a focal length f 0 which comprises: (a) a first lens unit of negative power having a focal length f 1 and comprising a negative element and a combination of two elements, one of said two elements being a positive element having a high dispersion and the other of said two elements being a negative element having a low dispersion; and (b) a second lens unit of positive power having a focal length f 2 and comprising a positive element and a combination of two elements, one of said two elements being a positive element having a low dispersion and the other of said two elements being a negative element having a high dispersion; wherein each of the first and the second lens units includes an aspheric surface and the system includes an aperture stop between the first and second lens units.
Claim 3
Dependent Claim
153 words
A wide angle lens system of the retrofocus type having a focal length f 0 which comprises: (a) a first lens unit of negative power having a focal length f 1 and comprising a negative element and a combination of two elements, one of said two elements being a positive element having a high dispersion and the other of said two elements being a negative element having a low dispersion; and (b) a second lens unit of positive power having a focal length f 2 and comprising a positive element and a combination of two elements, one of said two elements being a positive element having a low dispersion and the other of said two elements being a negative element having a high dispersion; wherein the absolute value of f 1 is less than about 1.15 times f 2 and the system includes an aperture stop between the first and second lens units.
Claim 4
Dependent Claim
153 words
A wide angle lens system of the retrofocus type having a focal length f 0 which comprises: (a) a first lens unit of negative power having a focal length f 1 and comprising a negative element and a combination of two elements, one of said two elements being a positive element having a high dispersion and the other of said two elements being a negative element having a low dispersion; and (b) a second lens unit of positive power having a focal length f 2 and comprising a positive element and a combination of two elements, one of said two elements being a positive element having a low dispersion and the other of said two elements being a negative element having a high dispersion; wherein the absolute value of f 1 is less than about 1.15 times f 2 and the system includes an aperture stop between the first and second lens units.
Claim 5
Dependent Claim
21 words
The wide angle lens system of claim 2 wherein the absolute value of f 1 is smaller than f 0 .
Claim 6
Dependent Claim
43 words
The wide angle lens system of claim 1, 2, or 3 wherein the second unit's focal point in the direction of the first lens unit and the aperture stop are arranged so that the aperture stop is located inside of the focal point.
Claim 7
Dependent Claim
18 words
The wide angle lens system of claim 4 wherein the aperture stop is located at the focal point.
Claim 8
Dependent Claim
25 words
The wide angle lens system of claim 1, 2 or 3 wherein the negative element of the first lens unit is a negative meniscus lens.
Claim 9
Dependent Claim
36 words
The wide angle lens system of claim 1, 2 or 3 wherein the lens system has a half angle field of view in the direction of the first lens unit of at least about 25° degrees.
Claim 10
Dependent Claim
19 words
The wide angle lens system of claim 2 or 3 wherein the first lens unit includes an aspherical surface.
Claim 11
Dependent Claim
19 words
The wide angle lens system of claim 2 or 3 wherein the second lens unit includes an aspherical surface.
Claim 12
Dependent Claim
143 words
A projection television system comprising three LCD light valves, a screen, and a wide angle lens system which projects light from each of the LCD light valves onto the screen, said wide angle lens system comprising: (a) a first lens unit of negative power having a focal length f 1 and comprising a negative element and a combination of two elements, one of said two elements being a positive element having a high dispersion and the other of said two elements being a negative element having a low dispersion; and (b) a second lens unit of positive power having a focal length f 2 and comprising a positive element and a combination of two elements, one of said two elements being a positive element having a low dispersion and the other of said two elements being a negative element having a high dispersion.
Claim 13
Dependent Claim
143 words
A projection television system comprising three LCD light valves, a screen, and a wide angle lens system which projects light from each of the LCD light valves onto the screen, said wide angle lens system comprising: (a) a first lens unit of negative power having a focal length f 1 and comprising a negative element and a combination of two elements, one of said two elements being a positive element having a high dispersion and the other of said two elements being a negative element having a low dispersion; and (b) a second lens unit of positive power having a focal length f 2 and comprising a positive element and a combination of two elements, one of said two elements being a positive element having a low dispersion and the other of said two elements being a negative element having a high dispersion.
Claim 14
Dependent Claim
21 words
The projection television system of claim 10 wherein each of the first and the second lens units includes an aspheric surface.
Claim 15
Dependent Claim
23 words
The projection television system of claim 10 wherein the absolute value of f 1 is less than about 1.15 times f 2 .
Claim 16
Dependent Claim
20 words
The projection television system of claim 10 wherein the absolute value of f 1 is smaller than f 0 .
Claim 17
Dependent Claim
32 words
The projection television system of claim 10, 11, 12, or 13 wherein the wide angle lens system has an entrance pupil located at a substantial optical distance from the LCD light valves.
Claim 18
Dependent Claim
52 words
The projection television system of claim 14 wherein the wide angle lens system includes an aperture stop and wherein the second unit's focal point in the direction of the first lens unit and the aperture stop are arranged so that the aperture stop is located at or inside of the focal point.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1996-06-07 | 1996-12-07 | 1997-06-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2000-06-07 | 2000-12-07 | 2001-06-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2004-06-07 | 2004-12-07 | 2005-06-08 | $7700.00 | Window Closed / Lapsed |