Patent US5278698A successfully refreshed from Google Patents.
US5278698A
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Magnifying projecting lens
Assignee: Pentax Corp
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Filing: 1993-01-27
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Granted: 1994-01-11
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Expires: 2013-01-27
Abstract
Abstract A magnifying projecting lens has a negative first lens group, a positive second lens group and a positive third lens group that is arranged in this order from a magnifying side. The lens groups are arranged so as to satisfy the following condition: fb/f>1.7, wherein fb equals a back focus when an object distance is (infinity) f equals a focal length of the lens.
Inventors
- 👤 Takashi Iizuka
- 👤 Nobutaka Minefuji
- 👤 Yasunori Arai
- 👤 Kazushi Yoshida
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 19:40
CPC Classifications
G; G02; G02B; G02B9/00; G02B9/12
Claims Analysis
Total Claims: 38
Claim 1
Independent Claim
124 words
A magnifying projecting lens, comprising a negative first lens group, a positive second lens group and a positive third lens group arranged in this order from a magnifying side, wherein the following condition is satisfied: fb/f>1.7, wherein fb equals a back focus when an object distance of the projecting lens is ∞; and f equals a focal length of the projecting lens, and wherein said projecting lens further comprises a positive condenser lens that is disposed nearer a surface to-be-projected than to said third lens group, wherein the following condition is satisfied: 0.3<fc/fb<1.5, wherein fb equals a back focus, except for said condenser lens, when an object distance is ∞; and fc equals a focal length of said condenser lens of said condenser lens.
Claim 2
Dependent Claim
124 words
A magnifying projecting lens, comprising a negative first lens group, a positive second lens group and a positive third lens group arranged in this order from a magnifying side, wherein the following condition is satisfied: fb/f>1.7, wherein fb equals a back focus when an object distance of the projecting lens is ∞; and f equals a focal length of the projecting lens, and wherein said projecting lens further comprises a positive condenser lens that is disposed nearer a surface to-be-projected than to said third lens group, wherein the following condition is satisfied: 0.3<fc/fb<1.5, wherein fb equals a back focus, except for said condenser lens, when an object distance is ∞; and fc equals a focal length of said condenser lens of said condenser lens.
Claim 3
Dependent Claim
35 words
A magnifying projecting lens according to claim 1, wherein the following condition is satisfied: L/f<3.5, wherein L equals an overall length of the projecting lens; and f equals a focal length of the projecting lens.
Claim 4
Dependent Claim
45 words
A magnifying projecting lens according to claim 1, wherein the following condition is satisfied: D12/D23<1.0, wherein D12 equals a distance between said first lens group and said second lens group; and D23 equals a distance between said second lens group and said third lens group.
Claim 5
Dependent Claim
40 words
A magnifying projecting lens according to claim 1, wherein said first lens group comprises at least one negative lens, said second lens group comprises a positive lens, and said third lens group comprises a positive lens and a negative lens.
Claim 6
Dependent Claim
58 words
A magnifying projecting lens according to claim 1, wherein said condenser lens is disposed in such a manner as to turn a strong positive curvature surface toward said magnifying side, and the following condition is satisfied: 0.3<rc/fc<1.0, wherein rc equals a radius of curvature of said positive surface; and fc equals a focal length of said condenser lens.
Claim 7
Dependent Claim
19 words
A magnifying projecting lens according to claim 1, wherein at least one surface of said condenser lens is aspherical.
Claim 8
Dependent Claim
16 words
A magnifying projecting lens according to claim 1, wherein said condenser lens is made from plastic.
Claim 9
Dependent Claim
108 words
A variable power magnifying projecting lens comprising a negative first lens group, a positive second lens group and a positive third lens group having a positive lens and a negative lens, each group being arranged in this order from a magnifying side, wherein a focal length is changed by changing a distance between said second lens group and said third lens group and moving the whole system with respect to an image projected by said projecting lens, the following condition being satisfied: fbw/fw>1.7, wherein fbw equals a back focus in a wide side when an object distance is ∞; and fw equals a focal length in wide side.
Claim 10
Dependent Claim
108 words
A variable power magnifying projecting lens comprising a negative first lens group, a positive second lens group and a positive third lens group having a positive lens and a negative lens, each group being arranged in this order from a magnifying side, wherein a focal length is changed by changing a distance between said second lens group and said third lens group and moving the whole system with respect to an image projected by said projecting lens, the following condition being satisfied: fbw/fw>1.7, wherein fbw equals a back focus in a wide side when an object distance is ∞; and fw equals a focal length in wide side.
Claim 11
Dependent Claim
43 words
A variable power magnifying projecting lens according to claim 8, wherein the following condition is satisfied: Lw/fw<3.0, wherein Lw equals an overall length of said lens in a wide side; and fw equals a focal length of said lens in said wide side.
Claim 12
Dependent Claim
58 words
A variable power magnifying projecting lens according to claim 8, wherein the following condition is satisfied: 0.7<|f12|/fw<(ft/fw)·1.5, wherein f12 equals a composed focal length of said first lens group and said second lens group of said lens; and fw and ft equals focal lengths of the whole system in said wide side and in said tele side respectively.
Claim 13
Dependent Claim
53 words
A variable power magnifying projecting lens according to claim 8, wherein the following condition is satisfied: D12/D23<1.0, wherein D12 equals a distance between said first lens group and said second lens group of said lens; and D23 equals a distance between said second lens group and said third lens group of said lens.
Claim 14
Dependent Claim
35 words
A variable power magnifying projecting lens according to claim 8, wherein the following condition is satisfied: rl<0, wherein rl equals a radius of curvature of a most magnifying side surface of said first lens group.
Claim 15
Dependent Claim
28 words
A variable power magnifying projecting lens according to claim 8, wherein said first lens group comprises a negative lens, and said second lens group comprises a positive lens.
Claim 16
Dependent Claim
23 words
A variable power magnifying projecting lens according to claim 8, wherein said third lens group comprises a positive lens and a negative lens.
Claim 17
Dependent Claim
58 words
A variable power magnifying projecting lens according to claim 8, further comprising a positive condenser lens that is disposed near a surface to-be-projected, and wherein the following condition is satisfied: 0.3<fc/fb<1.5, wherein fb equals a back focus, except for said condenser lens, when an object distance is ∞; and fc equals a focal length of said condenser lens.
Claim 18
Dependent Claim
63 words
A variable power magnifying projecting lens according to claim 15, wherein said condenser lens is disposed in such a manner as to turn a strong positive curvature surface toward said magnifying side, and the following condition is satisfied: 0.3<rc/fc<1.0, wherein rc equals a radius of curvature of said positive surface of said lens; and fc equals a focal length of said condenser lens.
Claim 19
Dependent Claim
21 words
A variable power magnifying projecting lens according to claim 15, wherein at least one surface of said condenser lens is aspherical.
Claim 20
Dependent Claim
18 words
A variable power magnifying projecting lens according to claim 15, wherein said condenser lens is made from plastic.
Claim 21
Dependent Claim
20 words
A variable power magnifying projecting lens according to claim 8, wherein an aperture diaphragm moves with said third lens group.
Claim 22
Dependent Claim
32 words
A variable power magnifying projecting lens according to claim 8, wherein a distance between an aperture diaphragm and said third lens group changes according to a change of power of said lens.
Claim 23
Dependent Claim
119 words
A variable power magnifying projecting lens, comprising a negative front lens group, having a positive lens and a negative lens, and a positive rear lens group arranged in this order from a magnifying side, wherein a focal length is changed by changing a distance between said front lens group and said rear lens group and moving the whole system with respect to an image projected by said projecting lens, and the following conditions are satisfied: fbw/fw>1.7, and Lw/fw<3.0, wherein fbw equals a back focus in a wide side when an object distance is ∞; fw equals a focal length of said lens in said wide side; and Lw equals an overall length of said lens in said wide side.
Claim 24
Dependent Claim
119 words
A variable power magnifying projecting lens, comprising a negative front lens group, having a positive lens and a negative lens, and a positive rear lens group arranged in this order from a magnifying side, wherein a focal length is changed by changing a distance between said front lens group and said rear lens group and moving the whole system with respect to an image projected by said projecting lens, and the following conditions are satisfied: fbw/fw>1.7, and Lw/fw<3.0, wherein fbw equals a back focus in a wide side when an object distance is ∞; fw equals a focal length of said lens in said wide side; and Lw equals an overall length of said lens in said wide side.
Claim 25
Dependent Claim
77 words
A variable power magnifying projecting lens comprising a negative front lens group, and a positive rear lens group, said rear lens group consisting of a positive lens and a negative lens, each lens group being arranged in this order from a magnifying side, wherein a focal length is changed by changing a distance between said front lens group and said rear lens group and moving the whole system with respect to image projected by said projecting lens.
Claim 26
Dependent Claim
77 words
A variable power magnifying projecting lens comprising a negative front lens group, and a positive rear lens group, said rear lens group consisting of a positive lens and a negative lens, each lens group being arranged in this order from a magnifying side, wherein a focal length is changed by changing a distance between said front lens group and said rear lens group and moving the whole system with respect to image projected by said projecting lens.
Claim 27
Dependent Claim
22 words
A variable power magnifying projecting lens according to claim 22, said front lens group comprising a positive lens and a negative lens.
Claim 28
Dependent Claim
63 words
A variable power magnifying projecting glens according to claim 22, wherein the following conditions are satisfied: fbw/fw>1.7, and Lw/fw<3.0, wherein fbw equals a back focus of said lens in a wide side when an object distance is ∞; fw equals a focal length of said lens in said wide side; and Lw equals an overall length of said lens in said wide side.
Claim 29
Dependent Claim
52 words
A variable power magnifying projecting glens according to claim 22, wherein the following condition is satisfied: 0.7<|f12 |/fw<(ft/fw)·1.5, wherein f12 equals a focal length of said front lens group of said lens; and fw and ft equals focal lengths of the whole system in a wide side and in a tele side.
Claim 30
Dependent Claim
41 words
A variable power magnifying projecting lens according to claim 22, wherein the following condition is satisfied: Fw<Ft, wherein Fw equals an F-number of said lens in a wide side; and Ft equals an F-number of said lens in a tele side.
Claim 31
Dependent Claim
20 words
A variable power magnifying projecting lens according to claim 22, wherein an aperture diaphragm moves with said rear lens group.
Claim 32
Dependent Claim
136 words
A variable power magnifying projecting lens, comprising: a variable power lens group conprising a negative front lens group having at least one negative lens, and a positive rear lens group having at least one positive lens and one negative lens that are arranged in this order from a magnifying side; wherein a focal length is changed by changing a distance between said front lens group and said rear lens group and moving the whole system with respect to an image projected by said projecting lens; a positive condenser lens that is disposed in such a manner as to turn a strong positive curvature surface toward said magnifying side; and the following condition is satisfied: 0.3<fc/fb<1.5, wherein fb equals a back focus of said variable power lens, and fc equals a focal length of said condenser lens.
Claim 33
Dependent Claim
136 words
A variable power magnifying projecting lens, comprising: a variable power lens group conprising a negative front lens group having at least one negative lens, and a positive rear lens group having at least one positive lens and one negative lens that are arranged in this order from a magnifying side; wherein a focal length is changed by changing a distance between said front lens group and said rear lens group and moving the whole system with respect to an image projected by said projecting lens; a positive condenser lens that is disposed in such a manner as to turn a strong positive curvature surface toward said magnifying side; and the following condition is satisfied: 0.3<fc/fb<1.5, wherein fb equals a back focus of said variable power lens, and fc equals a focal length of said condenser lens.
Claim 34
Dependent Claim
60 words
A variable power magnifying projecting lens according to claim 28, wherein said condenser lens is disposed in such a manner as to turn a strong positive curvature surface toward said magnifying side, and the following condition is satisfied: 0.3<rc/fc<1.0, wherein rc equals a radius of curvature of said positive surface; and fc equals a focal length of said condenser lens.
Claim 35
Dependent Claim
21 words
A variable power magnifying projecting lens according to claim 28, wherein at least one surface of said condenser lens is aspherical.
Claim 36
Dependent Claim
18 words
A variable power magnifying projecting lens according to claim 28, wherein said condenser lens is made from plastic.
Claim 37
Dependent Claim
35 words
A variable power magnifying projecting lens according to claim 28, wherein the following condition is satisfied: Fw<Ft, wherein Fw equals an F-number in a wide side; and Ft equals an F-number in a tele side.
Claim 38
Dependent Claim
20 words
A variable power magnifying projecting lens according to claim 28, wherein an aperture diaphragm moves with said rear lens group.
References Cited (Backward Citations)
GB1238668A
Cited
JPS58143311A
Cited
JPS59232310A
Cited
US4824223A
Cited
US4838666A
Cited
US4957355A
Cited
JPS6461714A
Cited
US4934794A
Cited
US4938572A
Cited
US4993814A
Cited
JPH01188815A
Cited
US5015077A
Cited
US5042929A
Cited
JPH02284108A
Cited
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