US5442484A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Retro-focus type lens and projection-type display apparatus
Assignee: Mitsubishi Electric Corp
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Filing: 1992-12-30
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Granted: 1995-08-15
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Expires: 2012-12-30
Abstract
Abstract A retro-focus-type lens is provided from a large conjugate side with a first lens group having a negative refracting power, a second lens group having a positive refracting power which is spaced away from the first lens group at an air interval D1, and a third lens group having a positive refracting power. The following conditions are satisfied when focal lengths of the first lens group, the second lens group, the third lens group, and a total lens system are assumed respectively as f1, f2, f3, and f: 1.8<D1/f<3.0 1.1<f2/f3<1.6 1.5<|f1|/f<2.3. A projection lens constructed by inserting a mirror in a lens system of thus constructed retro-focus type lens is used in a projection-type display apparatus.
Inventors
- 👤 Shinsuke Shikawa
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 22:03
CPC Classifications
H; H04; H04N; H04N9/00; H04N9/12; H04N9/31; H04N9/3102; H04N9/3105; G; G02; G02B; G02B13/00; G02B13/04; G02B13/16; G02B13/22; G02B27/00; G02B27/10; G02B27/1006; G02B27/102; G02B27/1046; G02B27/1066; G02B27/14; G02B27/145; G02B27/149
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
91 words
A retro-focus type lens comprising from a large conjugate side: a first lens group having a negative refracting power; a second lens group having a positive refracting power which is spaced away from the first lens group at an air interval D1; and a third lens group having a positive refracting power; wherein the following conditions are satisfied when focal lengths of the first lens group, the second lens group, the third lens group, and a total lens system are assumed respectively as f1, f2, f3, and f: 1.8<D1/f<3.0 1.1<f2/f3<1.6 1.5<|f1|/f<2.3.
Claim 2
Dependent Claim
91 words
A retro-focus type lens comprising from a large conjugate side: a first lens group having a negative refracting power; a second lens group having a positive refracting power which is spaced away from the first lens group at an air interval D1; and a third lens group having a positive refracting power; wherein the following conditions are satisfied when focal lengths of the first lens group, the second lens group, the third lens group, and a total lens system are assumed respectively as f1, f2, f3, and f: 1.8<D1/f<3.0 1.1<f2/f3<1.6 1.5<|f1|/f<2.3.
Claim 3
Dependent Claim
33 words
A retro-focus type lens according to claim 1, further comprising mirror means which is inserted between the first lens group and the second lens group and is adapted to bend an optical path.
Claim 4
Dependent Claim
35 words
A retro-focus type lens according to claim 1, further comprising diaphragm means arranged in the vicinity of the second lens group and a focal point of the third lens group on the large conjugate side.
Claim 5
Dependent Claim
45 words
A retro-focus type lens according to claim 1, further comprising diaphragm means arranged in the vicinity of the second lens group and a focal point of the third lens group on the large conjugate side, wherein an aperture diameter of the diaphragm means is adjustable.
Claim 6
Dependent Claim
49 words
A retro-focus type lens according to claim 1, further comprising: diaphragm means arranged in the vicinity of the second lens group and a focal point of the third lens group on the large conjugate side; and motor means for causing an aperture diameter of the diaphragm means to vary.
Claim 7
Dependent Claim
29 words
A retro-focus type lens according to claim 1, wherein a lens element on the small conjugate side is an aspherical lens out of those constituting the third lens group.
Claim 8
Dependent Claim
55 words
A retro-focus type lens according to claim 1, wherein a lens element on the small conjugate side is an aspherical lens out of those constituting the third lens group, and the following condition is satisfied when focal lengths of the aspherical lens and the total lens system are assumed respectively as f4 and f: |f4|/f>10.
Claim 9
Dependent Claim
29 words
A retro-focus type lens according to claim 1, wherein a lens element on the large conjugate side is an aspherical lens out of those constituting the first lens group.
Claim 10
Dependent Claim
55 words
A retro-focus type lens according to claim 1, wherein a lens element on the large conjugate side is an aspherical lens out of those constituting the first lens group, and the following condition is satisfied when focal lengths of the aspherical lens and the total lens system are assumed respectively as f5 and f: |f5|/f>100.
Claim 11
Dependent Claim
38 words
A retro-focus type lens according to claim 1, wherein a lens element on the small conjugate side out of those constituting the first lens group and a lens element constituting the second lens group are both aspherical lenses.
Claim 12
Dependent Claim
51 words
A retro-focus type lens according to claim 1, wherein an aberration correction is carried out in a state where a parallel plane plate formed of plastic material in not less than 90% of its thickness is inserted between the third lens group and an image surface on a small conjugate side.
Claim 13
Dependent Claim
91 words
A retro-focus type lens according to claim 1, further comprising diaphragm means arranged in the vicinity of the second lens group and a focal point of the third lens group on the large conjugate side, wherein the second lens group is moved along an optical axis to change the focal length of the total lens system, and the first lens group, the second lens group, and the third lens group are integrally moved along the optical axis to change a projection magnification while compensating for a shift of an image surface.
Claim 14
Dependent Claim
105 words
A retro-focus type lens according to claim 1, further comprising diaphragm means arranged in the vicinity of the second lens group and a focal point of the third lens group on the large conjugate side, wherein the second lens group is moved along an optical axis to change the focal length of the total lens system, and the projection magnification is changed while compensating for a shift of an image surface by integral movement of the first lens group, the second lens group, and the third lens group along the optical axis in combination with movement of the first lens group along the optical axis.
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| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1998-08-14 | 1999-02-13 | 1999-08-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2002-08-14 | 2003-02-13 | 2003-08-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2006-08-14 | 2007-02-13 | 2007-08-15 | $7700.00 | Window Closed / Lapsed |