US3768900A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Slide projectors
Assignee: Thorn Lighting Ltd
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Filing: 1970-12-16
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Granted: 1973-10-30
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Expires: 1990-12-16
Abstract
Abstract A bowl reflector of modified ellipsoidal shape is suitable for a slide projector, eliminates the need for a condenser and, when used with a flat-coil type filament lamp, enables a substantially uniform light distribution to be obtained. The regions of an ellipsoidal reflector responsible for imaging the cool, dark ends of the filament are effectively omitted from the present reflector.
Inventors
- 👤 Lintic W Mc
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 22:48
CPC Classifications
G; G03; G03B; G03B21/00; G03B21/14; G03B21/20; G03B21/208; G03B21/001
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
118 words
A screen projector comprising: a projection lens, a gate, a light source, said light source having a flat-coil filament, and a bowl shaped reflector, said reflector having a reflecting surface comprising two segments of ellipsoids of revolution symmetric about and meeting in a meridional plane of said reflector, the axes of revolution for said segments being symmetrically displaced on either side of said meridional plane with at least a portion of said meridional plane lying between each segment and its respective axis of revolution, and said coil filament being located with the principal axis of said coil lying in said meridional plane, whereby said reflector is unable to produce an image on the ends of said coil filament.
Claim 2
Dependent Claim
118 words
A screen projector comprising: a projection lens, a gate, a light source, said light source having a flat-coil filament, and a bowl shaped reflector, said reflector having a reflecting surface comprising two segments of ellipsoids of revolution symmetric about and meeting in a meridional plane of said reflector, the axes of revolution for said segments being symmetrically displaced on either side of said meridional plane with at least a portion of said meridional plane lying between each segment and its respective axis of revolution, and said coil filament being located with the principal axis of said coil lying in said meridional plane, whereby said reflector is unable to produce an image on the ends of said coil filament.
Claim 3
Dependent Claim
29 words
A screen projector according to claim 1, wherein said axes of revolution are parallel and spaced apart by a distance at least equal to the width of said filament.
Claim 4
Dependent Claim
50 words
A screen projector according to claim 2, wherein said axes of revolution diverge from one another with their spacing increasing away from the rim of said reflector, the spacing between said axes of revolution in the region of said filament being at least equal to the width of said filament.
Claim 5
Dependent Claim
26 words
A screen projector according to claim 1, wherein the reflecting surface of said reflector has a dichroic coating which is only partially reflective to heat radiation.
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) | 1976-10-29 | 1977-04-30 | 1977-10-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-10-29 | 1981-04-30 | 1981-10-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-10-29 | 1985-04-30 | 1985-10-30 | $7700.00 | Window Closed / Lapsed |