US5086353A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Variable magnification viewfinder optical system
Assignee: Minolta Co Ltd
•
Filing: 1990-11-20
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Granted: 1992-02-04
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Expires: 2010-11-20
Abstract
Abstract The present invention provides a variable magnification viewfinder optical system, comprising from the object side: objective lens group of a positive refractive power, including a first lens unit of a negative refractive power and a second lens unit of a positive refractive power, said first and second lens units being shiftable along the optical axis of the optical system for changing the magnification of the optical system; condenser lens group of a positive refractive power; and eyepiece lens group of a negative refractive power; wherein the objective lens group forms a real image of an object and the real image can be observed through the eyepiece lens group; and wherein the optical system fulfills the following conditions; -0.09/mm<1/f.sub.1 <-0.03/mm 0.04/mm<1/f.sub.2 <0.11/mm -0.1/mm<fe/(f.sub.1 ·f.sub.2)<-0.035/mm wherein: f 1 represents focal length of the first lens unit of the objective lens group in millimeters; f 2 represents focal length of the second lens unit of the objective lens group in millimeters; and f e represents focal length of the eyepiece lens group in millimeters.
Inventors
- 👤 Hiromu Mukai
- 👤 Kagumi Kojiya
- 👤 Kohtaro Hayashi
- 👤 Taro Shibuya
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 17:09
CPC Classifications
G; G02; G02B; G02B23/00; G02B23/14
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
173 words
Variable magnification viewfinder optical system, comprising from the object side: an objective lens group of a positive refractive power, including a first lens unit of a negative refractive power and a second lens unit of a positive refractive power, said first and second lens units being shiftable along the optical axis of the optical system for changing the magnification of the optical system; a condenser lens group of a positive refractive power; and an eyepiece lens group of a positive refractive power; wherein the objective lens group forms a real image of an object and the real image can be observed through the eyepiece lens group; and wherein the optical system fulfills the following conditions; -0.09/mm<1/f.sub.1 <-0.03/mm 0.04/mm<1/f.sub.2 <0.11/mm -0.1/mm<f.sub.e /(f.sub.1 ·f.sub.2)<-0.035/mm wherein: f 1 represents the focal length of the first lens unit of the objective lens group in millimeters; f 2 represents the focal length of the second lens unit of the objective lens group in millimeters; and f e represents the focal length of the eyepiece lens group in millimeters.
Claim 2
Dependent Claim
173 words
Variable magnification viewfinder optical system, comprising from the object side: an objective lens group of a positive refractive power, including a first lens unit of a negative refractive power and a second lens unit of a positive refractive power, said first and second lens units being shiftable along the optical axis of the optical system for changing the magnification of the optical system; a condenser lens group of a positive refractive power; and an eyepiece lens group of a positive refractive power; wherein the objective lens group forms a real image of an object and the real image can be observed through the eyepiece lens group; and wherein the optical system fulfills the following conditions; -0.09/mm<1/f.sub.1 <-0.03/mm 0.04/mm<1/f.sub.2 <0.11/mm -0.1/mm<f.sub.e /(f.sub.1 ·f.sub.2)<-0.035/mm wherein: f 1 represents the focal length of the first lens unit of the objective lens group in millimeters; f 2 represents the focal length of the second lens unit of the objective lens group in millimeters; and f e represents the focal length of the eyepiece lens group in millimeters.
Claim 3
Dependent Claim
150 words
Variable magnification viewfinder optical system as claimed in claim 1, wherein the optical system further fulfills the following conditions; |r.sub.1B /r.sub.1F |<6 |r.sub.2B /r.sub.2F |<2 0.9<f.sub.oT /f.sub.e <3 wherein: r 1B represents a radius of curvature of a lens surface located at the object side in the first lens unit of the objective lens group; r 1F represents a radius of curvature of a lens surface located at the eye side in the first lens unit of the objective lens group; r 2B represents a radius of curvature of a lens surface located at the object side in the second lens unit of the objective lens group; r 2F represents a radius of curvature of a lens surface located at the eye side in the second lens unit of the objective lens group; and f oT represents the focal length of the objective lens group at the largest magnification condition.
Claim 4
Dependent Claim
164 words
Variable magnification viewfinder optical system as claimed in claim 1, wherein the eyepiece lens group consists of one positive lens element and one negative lens element, and wherein the optical system further fulfills the following conditions; ν.sub.eP >45 ν.sub.eN <40 0.5<r.sub.eP /r.sub.eN <0.95 -0.8<r.sub.eB /f.sub.e <-0.35 -0.9<f.sub.eN /f.sub.e <-0.4 wherein: ν eP represents Abbe number of the positive lens element included in the eyepiece lens group; ν eN represents Abbe number of the negative lens element included in the eyepiece lens group; r eP represents a radius of curvature of a lens surface of the positive lens element faced to the negative lens element; r eN represents a radius of curvature of a lens surface of the negative lens element faced to the positive lens element; r eB represents a radius of curvature of a lens surface located at the eye side in the eyepiece lens group; and f eN represents the focal length of the negative lens element of the eyepiece lens group.
Claim 5
Dependent Claim
34 words
Variable magnification viewfinder optical system as claimed in claim 3, wherein one of the positive and negative lens elements in the eyepiece lens group is shiftable for adjusting the diopter of the optical system.
Claim 6
Dependent Claim
21 words
Variable magnification viewfinder optical system as claimed in claim 1, wherein the objective lens group includes at least one aspheric surface.
Claim 7
Dependent Claim
44 words
Variable magnification viewfinder optical system as claimed in claim 1, wherein the condenser lens group includes at least one aspheric surface whose radius of curvature decreases in proportional to the height measured from the optical axis in a direction perpendicular to the optical axis.
Claim 8
Dependent Claim
44 words
Variable magnification viewfinder optical system as claimed in claim 1, wherein the eyepiece lens group includes at least one aspheric surface whose radius of curvature decreases in proportional to the height measured from the optical axis in a direction perpendicular to the optical axis.
Claim 9
Dependent Claim
144 words
Variable magnification viewfinder optical system, comprising from the object side: objective lens group of a positive refractive power, including a first lens unit of a negative refractive power and a second lens unit of a positive refractive power, said first and second lens units being shiftable along the optical axis of the optical system for changing the magnification of the optical system; condenser lens group of a positive refractive power; and eyepiece lens group of a positive refractive power; wherein the objective lens group forms a real image of an object and the real image can be observed through the eyepiece lens group; and wherein the optical system fulfills the following condition; 0.9<f.sub.oT /f.sub.e <3 wherein: f oT represents a focal length of the objective lens group at the largest magnification condition; and f e represents a focal length of the eyepiece lens group.
Claim 10
Dependent Claim
144 words
Variable magnification viewfinder optical system, comprising from the object side: objective lens group of a positive refractive power, including a first lens unit of a negative refractive power and a second lens unit of a positive refractive power, said first and second lens units being shiftable along the optical axis of the optical system for changing the magnification of the optical system; condenser lens group of a positive refractive power; and eyepiece lens group of a positive refractive power; wherein the objective lens group forms a real image of an object and the real image can be observed through the eyepiece lens group; and wherein the optical system fulfills the following condition; 0.9<f.sub.oT /f.sub.e <3 wherein: f oT represents a focal length of the objective lens group at the largest magnification condition; and f e represents a focal length of the eyepiece lens group.
Claim 11
Dependent Claim
114 words
Variable magnification viewfinder optical system, comprising from the object side: objective lens group of a positive refractive power, including a first lens unit of a negative refractive power and a second lens unit of a positive refractive power, said first and second lens units being shiftable along the optical axis of the optical system for changing the magnification of the optical system; condenser lens group of a positive refractive power; and eyepiece lens group of a positive refractive power, consisting of one positive lens element and one negative lens element; wherein the objective lens group forms a real image of an object and the real image can be observed through the eyepiece lens group.
Claim 12
Dependent Claim
114 words
Variable magnification viewfinder optical system, comprising from the object side: objective lens group of a positive refractive power, including a first lens unit of a negative refractive power and a second lens unit of a positive refractive power, said first and second lens units being shiftable along the optical axis of the optical system for changing the magnification of the optical system; condenser lens group of a positive refractive power; and eyepiece lens group of a positive refractive power, consisting of one positive lens element and one negative lens element; wherein the objective lens group forms a real image of an object and the real image can be observed through the eyepiece lens group.
Claim 13
Dependent Claim
58 words
Variable magnification viewfinder optical system as claimed in claim 9, wherein the optical system further fulfills the following conditions; ν.sub.eP >45 ν eN <40 wherein; ν eP represents Abbe number of the positive lens element included in the eyepiece lens group; and ν eN represents Abbe number of the neative lens element included in the eyepiece lens group.
Claim 14
Dependent Claim
30 words
Variable magnification viewfinder optical system as claimed in claim 10, wherein the eyepiece lens group consists of, from the object side, one positive lens element and one negative lens element.
Claim 15
Dependent Claim
122 words
Variable magnification viewfinder optical system as claimed in claim 11, wherein the optical system further fulfills the following conditions; 0.5<r.sub.eP /r.sub.eN <0.95 -0.8<r.sub.eB /f.sub.e <-0.35 -0.9<f.sub.eN /f.sub.e <-0.4 wherein: r eP represents a radius of curvature of a lens surface of the positive lens element faced to the negative lens element; r eN represents a radius of curvature of a lens surface of the negative lens element faced to the positive lens element; r eB represents a radius of curvature of a lens surface located at the eye side in the eyepiece lens group; f eN represents a focal length of the negative lens element of the eyepiece lens group; and f e represents a focal length of the eyepiece lens group.
Claim 16
Dependent Claim
34 words
Variable magnification viewfinder optical system as claimed in claim 9, wherein one of the positive and negative lens elements in the eyepiece lens group is shiftable for adjusting the diopter of the optical system.
Claim 17
Dependent Claim
30 words
Variable magnification viewfinder optical system as claimed in claim 13, wherein the positive lens element of the eyepiece lens group is shiftable for adjusting the diopter of the optical system.
Claim 18
Dependent Claim
44 words
Variable magnification viewfinder optical system as claimed in claim 13, wherein the eyepiece lens group includes at least one aspheric surface whose radius of curvature decreases in proportional to the height measured from the optical axis in a direction perpendicular to the optical axis.
Claim 19
Dependent Claim
120 words
Variable magnification viewfinder optical system, comprising from the object side: objective lens group of a positive refractive power, including a first lens unit of a negative refractive power and a second lens unit of a positive refractive power, said first and second lens units being shiftable along the optical axis of the optical system for changing the magnification of the optical system; image reverse optical system including a condenser lens group of a positive refractive power; and eyepiece lens group of a positive refractive power, consisting of one positive lens element and one negative lens element; wherein the objective lens group forms a real image of an object and the real image can be observed through the eyepiece lens group.
Claim 20
Dependent Claim
120 words
Variable magnification viewfinder optical system, comprising from the object side: objective lens group of a positive refractive power, including a first lens unit of a negative refractive power and a second lens unit of a positive refractive power, said first and second lens units being shiftable along the optical axis of the optical system for changing the magnification of the optical system; image reverse optical system including a condenser lens group of a positive refractive power; and eyepiece lens group of a positive refractive power, consisting of one positive lens element and one negative lens element; wherein the objective lens group forms a real image of an object and the real image can be observed through the eyepiece lens group.
Claim 21
Dependent Claim
25 words
Variable magnification viewfinder optical system as claimed in claim 16, wherein the objective lens group forms the real image out of the condenser lens group.
Claim 22
Dependent Claim
20 words
Variable magnification viewfinder optical system as claimed in claim 16, wherein the image reverse optical system is a parro prism.
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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) | 1995-02-03 | 1995-08-05 | 1996-02-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1999-02-03 | 1999-08-05 | 2000-02-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2003-02-03 | 2003-08-05 | 2004-02-04 | $7700.00 | Window Closed / Lapsed |