US5042929A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Projection lens and projection system
Assignee: Panasonic Holdings Corp
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Filing: 1990-03-16
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Granted: 1991-08-27
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Expires: 2010-03-16
Abstract
Abstract A projection lens enlarges and projects optical images in a matrix type light valve onto a screen. The projection lens includes a front lens group of the retrofocusing type; a rear lens with aspherical surfaces whose radii of curvature in the peripheral portion are shorter than that in the central portion; and a reflecting mirror which is positioned between the front lens group and the rear lens and diverts the optical axis. This projection lens enables the optical images in the light valve to be projected with a high contrast and a wide field angle. A projection system is provided which includes a light source; a light valve; a converging optical apparatus; a transmission type screen; diverting place mirrors; and a projection lens to enlarge and project the optical images in the light valve onto the screen. Since the projection lens has a wide field angle and has the reflecting mirror provided therein, the projection system can be very compact.
Inventors
- 👤 Takaaki Tanaka
- 👤 Yoshito Miyatake
- 👤 Yuichi Kimura
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 12:24
CPC Classifications
G; G02; G02B; G02B13/00; G02B13/18; G02B13/04
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
88 words
A projection lens for enlarging and projecting optical images in a light valve onto a screen, comprising: a front lens group of a retrofocusing type which is positioned on the screen side; a rear lens which is positioned on the light valve side and comprises aspherical surfaces whose radii of curvature in the peripheral portion are shorter than that in the central portion; and a reflecting mirror which is positioned between said front lens group and said rear lens and diverts the optical axis of said projection lens.
Claim 2
Dependent Claim
88 words
A projection lens for enlarging and projecting optical images in a light valve onto a screen, comprising: a front lens group of a retrofocusing type which is positioned on the screen side; a rear lens which is positioned on the light valve side and comprises aspherical surfaces whose radii of curvature in the peripheral portion are shorter than that in the central portion; and a reflecting mirror which is positioned between said front lens group and said rear lens and diverts the optical axis of said projection lens.
Claim 3
Dependent Claim
124 words
A projection lens according to claim 1, wherein the front lens group is constructed with six lenses and comprises, from the screen side, a positive first lens, a second lens of a negative meniscus, a third lens whose both side surfaces are formed in a convex shape, a fourth lens whose both side surfaces are formed in a concave shape, a fifth lens of a positive meniscus whose concave surface faces the screen side, and a positive sixth lens, and satisfy the following condition -2.0<f.sub.1ν1 /f.sub.2ν2 <-1.0 where, f 1 and ν 1 denote a focal distance and an Abbe's number of said first lens and f 2 and ν 2 indicate a focal distance and an Abbe's number of said second lens, respectively.
Claim 4
Dependent Claim
21 words
A projection lens according to claim 1, wherein a paraxial power of said rear lens is set to a negative value.
Claim 5
Dependent Claim
21 words
A projection lens according to claim 1, wherein a peripheral power of said rear lens is set to a positive value.
Claim 6
Dependent Claim
15 words
A projection lens according to claim 1, wherein said rear lens is a plastic lens.
Claim 7
Dependent Claim
45 words
A projection lens according to claim 1, wherein the relative positions of said rear lens and said reflecting mirror are fixed and the position of said front lens group against said rear lens can be adjusted along the optical axis of said front lens group.
Claim 8
Dependent Claim
73 words
A projection system comprising: a light source; a light valve in which optical images corresponding to picture signals are formed; a converging optical apparatus for irradiating a light beam emitted from said light source into said light valve; a transmission type screen; diverting plane mirrors; and a projection lens for enlarging and projecting said optical images onto said screen; wherein a projection lens according to claim 1 is used for said projection lens.
Claim 9
Dependent Claim
98 words
A projection system comprising: a light source; three light valves in which optical images corresponding to picture signals are formed; a converging optical apparatus for irradiating light beam emitted from said light source into said light valves; dichroic mirrors for separating the light from said converging optical apparatus into red, green, and blue light rays; a transmission type screen; diverting plane mirrors; and three projection lenses for enlarging and projecting said optical images from each of the light valves onto said screen; wherein a projection lens according to claim 1 is used for each of said projection lenses.
Claim 10
Dependent Claim
24 words
A system according to claim 8, wherein a single reflecting mirror is shared by said three projection lenses in place of respective reflecting mirrors.
Claim 11
Dependent Claim
23 words
A system according to claim 8, wherein optical image forming surfaces of the three light valves are located on a same flat surface.
Claim 12
Dependent Claim
21 words
A system according to claim 8, wherein optical axes of said front lens group of said three projection lenses are parallel.
References Cited (Backward Citations)
US4099850A
Cited
JPS575488A
Cited
US4526442A
Cited
JPS62125791A
Cited
US4764806A
Cited
US4744641A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1994-08-26 | 1995-02-25 | 1995-08-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-08-26 | 1999-02-25 | 1999-08-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-08-26 | 2003-02-25 | 2003-08-27 | $7700.00 | Window Closed / Lapsed |