Patent US2859152A successfully refreshed from Google Patents.
Patent US4338012A successfully refreshed from Google Patents.
US4338012A
Expired / Lapsed
US
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Focusing screen
Assignee: Canon Inc
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Filing: 1980-10-31
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Granted: 1982-07-06
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Expires: 2000-10-31
Abstract
Abstract This specification discloses a focusing screen adapted for use with the range finder of a camera, particularly a split image type focusing screen. This screen comprises a pair of portions desposed in the center of the real image plane of the camera, and each portion has a refracting means and a diffracting means. Thereby, in a defocused condition, the images viewed through the portions are split each other and blurred. Further, this screen can be used wth an objective lens having a small aperture ratio.
Inventors
- 👤 Susumu Matsumura
- 👤 Takashi Suzuki
- 👤 Kazuya Matsumoto
- 👤 Kikuo Momiyama
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 11:10
CPC Classifications
G; G02; G02B; G02B27/00; G02B27/40; G01; G01C; G01C3/00; G01C3/02
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
91 words
In a split-image type range finder system having an objective lens for forming an image plane, a focusing screen comprising: a plurality of light deflecting portions in each of which members of prism-like unit structure are arranged with a period "P" in a direction different from the other, said prism-like unit structure, in the cross-section thereof, having the surface thereof formed by a plurality of inclined surfaces having different angles of inclination with respect to the image plane, said period "P" being greater than 10 μm and less than 50 μm.
Claim 2
Dependent Claim
91 words
In a split-image type range finder system having an objective lens for forming an image plane, a focusing screen comprising: a plurality of light deflecting portions in each of which members of prism-like unit structure are arranged with a period "P" in a direction different from the other, said prism-like unit structure, in the cross-section thereof, having the surface thereof formed by a plurality of inclined surfaces having different angles of inclination with respect to the image plane, said period "P" being greater than 10 μm and less than 50 μm.
Claim 3
Dependent Claim
52 words
A focusing screen according to claim 1, wherein the smallest of the angles of inclination which the plurality of inclined surfaces forming the surface of said prism-like unit structure forms with the image plane is less than about 5° and the greatest of said angles of inclination is less than about 16°.
Claim 4
Dependent Claim
47 words
A focusing screen according to claim 1, wherein a pair of said light deflecting portions are semicircular and together form a focus indicating part of circular area, and said members of prism-like unit structure of said pair of light deflecting portions are oriented oppositely to each other.
Claim 5
Dependent Claim
52 words
A focusing screen according to claim 1, wherein four light deflecting portions each are a quarter of a circle and together form a focus indicating part of circular area, and two adjacent light deflecting portions have their respective members of prism-like unit structure oriented in directions different from each other by 90°.
Claim 6
Dependent Claim
26 words
A focusing screen according to claim 3 or 4, wherein a number of microprisms are arranged on the outer peripheral portion of said focus indicating part.
Claim 7
Dependent Claim
77 words
In a split image type range finder system having an objective lens for forming an image plane, a focusing screen comprising: a plurality of light deflecting portions each of which comprises: (a) a prism component having a light deflecting function for providing part of an out-of-focus image with displacement in one direction; and (b) a diffraction lattice component formed on said prism component and having a periodicity in said one direction for diffracting the light incident thereon.
Claim 8
Dependent Claim
77 words
In a split image type range finder system having an objective lens for forming an image plane, a focusing screen comprising: a plurality of light deflecting portions each of which comprises: (a) a prism component having a light deflecting function for providing part of an out-of-focus image with displacement in one direction; and (b) a diffraction lattice component formed on said prism component and having a periodicity in said one direction for diffracting the light incident thereon.
Claim 9
Dependent Claim
20 words
A focusing screen according to claim 6, wherein said diffraction lattice component comprises a relief and phase type diffraction lattice.
Claim 10
Dependent Claim
15 words
A focusing screen according to claim 7, wherein said prism component comprises a Fresnel prism.
Claim 11
Dependent Claim
27 words
A focusing screen according to claim 8, wherein a unit structure of said relief type diffraction lattice is mounted on a strip portion of said Fresnel prism.
Claim 12
Dependent Claim
18 words
A focusing screen according to claim 7, wherein said diffraction lattice component comprises a rectangular type diffraction lattice.
Claim 13
Dependent Claim
18 words
A focusing screen according to claim 7, wherein said diffraction lattice component comprises a saw-tooth type diffraction lattice.
Claim 14
Dependent Claim
22 words
A focusing screen according to claim 6, wherein said periodicity is not more than 50 μm and not less than 10 μm.
Claim 15
Dependent Claim
120 words
In a single lens reflex camera having means for selectively mounting interchangeable objective lenses having different relative aperture ratios, a focus indicating system comprising: a focusing screen including a pair of light deflecting portions each having a plurality of prism-like unit structures arranged with a periodicity in one direction opposite to the direction of the periodicity of the unit structures in the other light deflecting portion, each said prism-like unit structure having its surface formed by a plurality of inclined surfaces of different inclinations in the direction of periodicity, whereby an out-of-focus image is split and blurred in the direction of periodicity; and means for supporting said focusing screen in an image plane in a view finder of the camera.
Claim 16
Dependent Claim
120 words
In a single lens reflex camera having means for selectively mounting interchangeable objective lenses having different relative aperture ratios, a focus indicating system comprising: a focusing screen including a pair of light deflecting portions each having a plurality of prism-like unit structures arranged with a periodicity in one direction opposite to the direction of the periodicity of the unit structures in the other light deflecting portion, each said prism-like unit structure having its surface formed by a plurality of inclined surfaces of different inclinations in the direction of periodicity, whereby an out-of-focus image is split and blurred in the direction of periodicity; and means for supporting said focusing screen in an image plane in a view finder of the camera.
Claim 17
Dependent Claim
90 words
In a split image type rangefinder system having an objective lens for forming an image plane, a focusing screen comprising: a plurality of light deflecting portions, each of which comprises: (a) a prism component having a light deflecting function for providing part of an out-of-focus image with a displacement in a first direction, and (b) a diffraction lattice component formed on said prism component and having a periodicity in a second direction at a right angle to said first direction of said image displacement, for diffracting the light incident thereon.
Claim 18
Dependent Claim
90 words
In a split image type rangefinder system having an objective lens for forming an image plane, a focusing screen comprising: a plurality of light deflecting portions, each of which comprises: (a) a prism component having a light deflecting function for providing part of an out-of-focus image with a displacement in a first direction, and (b) a diffraction lattice component formed on said prism component and having a periodicity in a second direction at a right angle to said first direction of said image displacement, for diffracting the light incident thereon.
Claim 19
Dependent Claim
15 words
A focusing screen according to claim 14, wherein said prism component comprises a Fresnel prism.
Claim 20
Dependent Claim
26 words
A focusing screen according to claim 15, wherein a unit structure of said diffraction lattice component is mounted on a strip portion of said Fresnel prism.
Claim 21
Dependent Claim
26 words
A focusing screen according to claim 14, wherein said diffraction lattice component has a pitch not more than 50 μm and not less than 10 μm.
Claim 22
Dependent Claim
23 words
A focusing screen according to claim 17, wherein a unit structure of said diffraction lattice component comprises a rectangular type relief diffraction lattice.
Claim 23
Dependent Claim
23 words
A focusing screen according to claim 17, wherein a unit structure of said diffraction lattice component comprises a saw-tooth type relief diffraction lattice.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1985-07-05 | 1986-01-04 | 1986-07-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1989-07-05 | 1990-01-04 | 1990-07-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1993-07-05 | 1994-01-04 | 1994-07-06 | $7700.00 | Window Closed / Lapsed |