US4725130A
Expired / Lapsed
US
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Zoom finder
Assignee: Ricoh Co Ltd
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Filing: 1986-03-20
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Granted: 1988-02-16
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Expires: 2006-03-20
Abstract
Abstract A compact zoom finder suitable for compact cameras, video cameras and the like whose zoom ratio is about 2. While the zoom lens is composed of three units having positive, negative and positive refracting powers in order from an object side, the third unit is preferably composed of an ante-component having a negative refracting power and a post-component having a positive refracting power. In this case, an arrangement is made so that one surface in the ante-component of the third unit comprises a half mirror, and one surface in the post-component is provided with a frame to thereby provide for an albada finder.
Inventors
- 👤 Toshiro Ozawa
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 08:56
CPC Classifications
G; G02; G02B; G02B15/00; G02B15/14; G02B15/16; G02B15/177; G02B15/143; G02B15/1435; G02B15/143503; G02B23/00; G02B23/14; G02B23/145
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
90 words
A zoom finder including, in order from an object side, a first unit having a negative refracting power, a second unit having a positive refracting power and a third unit having a negative refracting power, wherein a space between the first unit and the second unit and a space between the second unit and the third unit are relatively varied to vary the magnification of the finder, the zoom finder fulfilled by the following conditions: Mmax <1; and 10<f.sub.2 <20; where: Mmax is a maximum magnification of the finder; and
Claim 2
Dependent Claim
90 words
A zoom finder including, in order from an object side, a first unit having a negative refracting power, a second unit having a positive refracting power and a third unit having a negative refracting power, wherein a space between the first unit and the second unit and a space between the second unit and the third unit are relatively varied to vary the magnification of the finder, the zoom finder fulfilled by the following conditions: Mmax <1; and 10<f.sub.2 <20; where: Mmax is a maximum magnification of the finder; and
Claim 3
Dependent Claim
10 words
f 2 is a focal length of the second unit.
Claim 4
Dependent Claim
10 words
f 2 is a focal length of the second unit.
Claim 5
Dependent Claim
38 words
A zoom finder according to claim 1, wherein the finder is fulfilled by the following condition: -10<Dw<10; where: Dw is the space between principal points of the second and third units at the minimum magnification of the finder.
Claim 6
Dependent Claim
38 words
A zoom finder according to claim 2, wherein the finder is fulfilled by the following condition: -10<Dw<10; where: Dw is the space between principal points between the second and third units at the minimum magnification of the finder.
Claim 7
Dependent Claim
29 words
A zoom finder according to claim 1, wherein the third unit is composed of an ante-component having a negative refracting power and a post-component having a positive refracting power.
Claim 8
Dependent Claim
38 words
A zoom finder according to claim 4, wherein one surface in the ante-component of the third unit comprises a half mirror, and a frame is formed in one surface of the post-component to provide for an albada finder.
Claim 9
Dependent Claim
85 words
A zoom finder according to claim 1, wherein the first unit comprises a negative lens L 1 and a negative lens L 2 with a surface having a sharp curvature faced to a pupil side; and the finder is fulfilled by the following condition: r.sub.2 <0.4|r.sub.1 |; where: r 1 is the paraxial radius of curvature on the object side of the lens L 1 ; and r 2 is the paraxial radius of curvature on the pupil side of the lens L 1 .
Claim 10
Dependent Claim
53 words
A zoom finder according to claim 6, wherein the first surface of the lens L 1 is formed into an aspherical surface such that the lens surface is to be positioned on the pupil side than the spherical surface having the paraxial radius of curvature as the distance from the optical axis increases.
Claim 11
Dependent Claim
53 words
A zoom finder according to claim 6, wherein the second surface of the lens L 1 is formed into an aspherical surface such that the lens surface is to be positioned on the object side than the spherical surface having the paraxial radius of curvature as the distance from the optical axis increases.
Claim 12
Dependent Claim
53 words
A zoom finder according to claim 6, wherein the fourth surface of the lens L 2 is formed into an aspherical surface such that the lens surface is to be positioned on the object side than the spherical surface having the paraxial radius of curvature as the distance from the optical axis increases.
Claim 13
Dependent Claim
105 words
A zoom finder according to claim 1, wherein the second unit comprises a positive lens L 3 with a surface having a sharp curvature faced toward the pupil and a positive lens L 4 with a surface having a sharp curvature faced to the object side; and the finder is fulfilled by the following condition: r.sub.7 <0.4|r.sub.8 |; where: r 7 is the paraxial radius of curvature of the surface on the object side of the lens L 4 in the second unit, and r 8 is the paraxial radius of curvature of the surface on the pupil side of the lens L 4 .
Claim 14
Dependent Claim
79 words
A zoom finder according to claim 6, wherein in the second unit, the fifth and seventh surfaces are formed into an aspherical surface such that the lens surface is to be positioned on the object side than the spherical surface having the paraxial radius of curvature whereas the sixth and eighth surfaces are formed into an aspherical surface such that the lens surface is to be positioned on the pupil side, as the distance from the optical axis increases.
Claim 15
Dependent Claim
21 words
A zoom finder according to claim 2, wherein in the third unit, the ninth surface is formed into an aspherical surface.
Claim 16
Dependent Claim
24 words
A zoom finder according to claim 1, wherein the second unit is fixed, and the first and third units are moved to perform zooming.
Claim 17
Dependent Claim
24 words
A zoom finder according to claim 1, wherein the third unit is fixed, and the first and second units are moved to perform zooming.
References Cited (Backward Citations)
US4303311A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-02-15 | 1991-08-17 | 1992-02-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-02-15 | 1995-08-17 | 1996-02-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-02-15 | 1999-08-17 | 2000-02-16 | $7700.00 | Window Closed / Lapsed |