US3752575A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Overhead projector
Assignee: Ricoh Co Ltd
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Filing: 1972-10-16
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Granted: 1973-08-14
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Expires: 1992-10-16
Abstract
Abstract An improved overhead projector capable of employing a smaller sized reflecting mirror, thereby making the projector compact in size, wherein a Fresnel condenser lens system, which serves as the stage or is disposed adjacent to a stage, comprises at least two Fresnel lenses having different widths and/or different focal lengths so that the light beams refracted by the different Fresnel lenses may be made incident at different angles upon the projection lens and thus upon the surface of the reflecting mirror, particularly the upper half portion, thereby permitting the reflecting mirror to be shortened. Individual light sources may be used for respective Fresnel lenses so that they may be moved closer together further decreasing the size of the projector.
Inventors
- 👤 H Ataka
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 10:28
CPC Classifications
G; G03; G03B; G03B21/00; G03B21/132; Y; Y10; Y10S; Y10S353/00; Y10S353/03; Y10S353/06
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
171 words
An overhead projector for projecting an image from an imagecontaining means onto a viewing means comprising: a. means for supporting said image-containing means including a Fresnel condenser lens system comprising at least two lenses having characteristic apertures and focal lengths, said lenses differing from each other in at least one of said characteristics, and respectively juxtaposed in the same plane front and rear with respect to said viewing means; b. projection lens means disposed on the opposite side of said image-containing means from said supporting means; c. light source means for directing light through said Fresnel lens system and said image-containing means to said projection lens means; d. reflecting mirror means for redirecting said light toward said viewing means; and e. said projection lens means and said reflecting mirror means being arranged along an axis offset laterally from the central axis of said Fresnel lens system and rearwardly from said viewing means so as to focus both said image and said light from said light source means on said viewing means.
Claim 2
Dependent Claim
171 words
An overhead projector for projecting an image from an imagecontaining means onto a viewing means comprising: a. means for supporting said image-containing means including a Fresnel condenser lens system comprising at least two lenses having characteristic apertures and focal lengths, said lenses differing from each other in at least one of said characteristics, and respectively juxtaposed in the same plane front and rear with respect to said viewing means; b. projection lens means disposed on the opposite side of said image-containing means from said supporting means; c. light source means for directing light through said Fresnel lens system and said image-containing means to said projection lens means; d. reflecting mirror means for redirecting said light toward said viewing means; and e. said projection lens means and said reflecting mirror means being arranged along an axis offset laterally from the central axis of said Fresnel lens system and rearwardly from said viewing means so as to focus both said image and said light from said light source means on said viewing means.
Claim 3
Dependent Claim
20 words
A projector as in claim 1 wherein said light source means is offset laterally and rearwardly from said central axis.
Claim 4
Dependent Claim
37 words
A projector as in claim 1 wherein said light source means comprises two lamps respectively positioned on opposite sides of said central axis of said Fresnel lens system front and rear with respect to said viewing means.
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) | 1976-08-13 | 1977-02-12 | 1977-08-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-08-13 | 1981-02-12 | 1981-08-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-08-13 | 1985-02-12 | 1985-08-14 | $7700.00 | Window Closed / Lapsed |