US3915568A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Overhead projector
Assignee: Ricoh Co Ltd
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Filing: 1974-07-16
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Granted: 1975-10-28
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Expires: 1994-07-16
Abstract
Abstract A truncated conical reflector reflects an annular image of a light source disposed therewithin through an annular-convex or circular-cylindrical lens, which may be a Fresnel lens, and through the slide being projected into a projection lens, which projects an image of the slide onto a screen.
Inventors
- 👤 Isao Yamada
- 👤 Satoshi Yamauchi
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 16:25
CPC Classifications
G; G03; G03B; G03B21/00; G03B21/132
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
164 words
An overhead projector comprising: a frame for supporting a document being projected; a truncated conical reflector having an internal reflector surface, the base of said conical reflector being arranged to face said frame; a light source disposed within said conical reflector on the axis thereof; projection lens means spaced from said frame and arranged to project an image of the document onto a viewing surface; a circular-cylindrical lens disposed between the base of said conical reflector and said frame with the axis of said conical reflector perpendicularly passing through the center of said circular-cylindrical lens to focus an image of said light source into said projection lens means; and a converging lens disposed between said circular-cylindrical lens and said frame, whereby the document is illuminated by light radiated by the light source, reflected by the conical reflector and refracted by the circular-cylindrical lens and the converging lens, and the image of the document is projected onto the viewing surface by the projection lens means.
Claim 2
Dependent Claim
164 words
An overhead projector comprising: a frame for supporting a document being projected; a truncated conical reflector having an internal reflector surface, the base of said conical reflector being arranged to face said frame; a light source disposed within said conical reflector on the axis thereof; projection lens means spaced from said frame and arranged to project an image of the document onto a viewing surface; a circular-cylindrical lens disposed between the base of said conical reflector and said frame with the axis of said conical reflector perpendicularly passing through the center of said circular-cylindrical lens to focus an image of said light source into said projection lens means; and a converging lens disposed between said circular-cylindrical lens and said frame, whereby the document is illuminated by light radiated by the light source, reflected by the conical reflector and refracted by the circular-cylindrical lens and the converging lens, and the image of the document is projected onto the viewing surface by the projection lens means.
Claim 3
Dependent Claim
20 words
An overhead projector according to claim 1, in which both the circular-cylindrical lens and the converging lens are Fresnel lenses.
Claim 4
Dependent Claim
47 words
An overhead projector according to claim 2, in which the axis of said conical reflector and the viewing surface are arranged vertically, the document is arranged horizontally, and said projection lens means is arranged to project the image of the document substantially vertically onto the viewing surface.
Claim 5
Dependent Claim
170 words
In an overhead projector having a frame for supporting a document being projected and projection lens means arranged to project an image of the document onto a viewing surface, the improvement of an illumination system for illuminating the side of the document opposite to the side facing the projection lens means, said illumination system comprising: a truncated conical reflector havinG an internal reflector surface, the base of said conical reflector being arranged to face the frame; a light source disposed within said conical reflector on the axis thereof; a circular-cylindrical lens disposed between the base of said conical reflector and the frame with the axis of said conical reflector perpendicularly passing through the center of said circular-cylindrical lens to focus an image of said light source into said projection lens means; and a converging lens disposed between said circular-cylindrical lens and the frame, whereby the document is illuminated by light radiated by said light source, reflected by said conical reflector and refracted by said circular-cylindrical lens and the converging lens.
Claim 6
Dependent Claim
170 words
In an overhead projector having a frame for supporting a document being projected and projection lens means arranged to project an image of the document onto a viewing surface, the improvement of an illumination system for illuminating the side of the document opposite to the side facing the projection lens means, said illumination system comprising: a truncated conical reflector havinG an internal reflector surface, the base of said conical reflector being arranged to face the frame; a light source disposed within said conical reflector on the axis thereof; a circular-cylindrical lens disposed between the base of said conical reflector and the frame with the axis of said conical reflector perpendicularly passing through the center of said circular-cylindrical lens to focus an image of said light source into said projection lens means; and a converging lens disposed between said circular-cylindrical lens and the frame, whereby the document is illuminated by light radiated by said light source, reflected by said conical reflector and refracted by said circular-cylindrical lens and the converging lens.
Claim 7
Dependent Claim
19 words
The improvement according to claim 4, in which both the circular-cylindrical lens and the converging lens are Fresnel lenses.
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) | 1978-10-27 | 1979-04-28 | 1979-10-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-10-27 | 1983-04-28 | 1983-10-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-10-27 | 1987-04-28 | 1987-10-28 | $7700.00 | Window Closed / Lapsed |