US3712707A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Composite back projection screen and method of forming
Assignee: General Electric Co
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Filing: 1970-02-27
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Granted: 1973-01-23
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Expires: 1990-02-27
Abstract
Abstract A composite back projection screen exhibiting a highly uniform intensity distribution and reduced scintillation is formed by embossing a Fresnel lens along either the front or back face of a thermoplastic sheet to focus projected light upon a predetermined viewing location and coating the front face of the sheet with a layer of bulk diffusing material to effect a multiple scattering of light passing through the layer. Desirably, either the risers of the Fresnel lens and/or the layer of bulk diffusing material is blackened to enhance the ambient rejection of the projection screen.
Inventors
- 👤 J Henkes
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 14:07
CPC Classifications
G; G03; G03B; G03B21/00; G03B21/54; G03B21/56; G03B21/60; G03B21/62; G03B21/625
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
104 words
A back projection screen for viewing on the front face of the screen an image projected upon the back face of the screen comprising a sheet of transparent plastic having a Fresnel lens embossed along one face of said screen for focusing light rays passing therethrough and an approximately 1.0 - 5.0 mil thick layer of a bulk diffusing material, containing sufficient blackening to reduce the transmission of the screen by an amount between 5 and 35 percent, coated atop said front face of said screen to produce multiple scattering of projected light rays therein during passage of said light rays through said layer.
Claim 2
Dependent Claim
104 words
A back projection screen for viewing on the front face of the screen an image projected upon the back face of the screen comprising a sheet of transparent plastic having a Fresnel lens embossed along one face of said screen for focusing light rays passing therethrough and an approximately 1.0 - 5.0 mil thick layer of a bulk diffusing material, containing sufficient blackening to reduce the transmission of the screen by an amount between 5 and 35 percent, coated atop said front face of said screen to produce multiple scattering of projected light rays therein during passage of said light rays through said layer.
Claim 3
Dependent Claim
32 words
A back projection screen according to claim 1 wherein said Fresnel lens is embossed along the back face of said screen and further including blackening on the risers of the Fresnel lens.
Claim 4
Dependent Claim
50 words
A back projection screen according to claim 1 wherein said diffusing layer comprises a resin and light diffusing particles in substantially equal amounts by weight, said resin having an index of refraction differing from the index of refraction of said light diffusing particles by an amount between 0.03 and 0.15.
Claim 5
Dependent Claim
45 words
A back projection screen according to claim 1 wherein said Fresnel lens is a spiral prism having a light transmitting face exhibiting a gradually increasing angle relative to the plane of the screen with increased departure of The prism from the center of the screen.
Claim 6
Dependent Claim
46 words
A back projection screen according to claim 1 wherein said Fresnel lens is a plurality of concentric prismatic surfaces, said surfaces exhibiting a gradually increasing angle relative to the plane of the screen with increased departure of the prismatic surfaces from the center of the screen.
Claim 7
Dependent Claim
67 words
A back projection screen according to claim 1 wherein said Fresnel lens comprises a plurality of prismatic sections extending longitudinally across one face of said thermoplastic sheet and latitudinally across the opposite face of said sheet, the angular disposition of the light transmitting surface of each prismatic section increasing relative to the plane of the screen with increase departure of the prismatic elements from the screen center.
Claim 8
Independent Claim
121 words
A method of forming a back projection screen comprising the steps of: embossing a face of a transparent thermoplastic sheet into a Fresnel lens having a desired focal point with a master producing a Fresnel lens having optically smooth light transmitting surfaces with surface roughened risers, coating said selectively roughened Fresnel lens with a fluid blackening agent; and coating the face of said sheet facing said focal point with an approximately 1.0 - 5.0 mil thick layer of a bulk diffusing material by immersing the face of said sheet in a bath of said diffusing material and withdrawing said sheet from the bath at a controlled rate to provide a substantially uniform layer of said bulk diffusing material along said face.
Claim 9
Independent Claim
121 words
A method of forming a back projection screen comprising the steps of: embossing a face of a transparent thermoplastic sheet into a Fresnel lens having a desired focal point with a master producing a Fresnel lens having optically smooth light transmitting surfaces with surface roughened risers, coating said selectively roughened Fresnel lens with a fluid blackening agent; and coating the face of said sheet facing said focal point with an approximately 1.0 - 5.0 mil thick layer of a bulk diffusing material by immersing the face of said sheet in a bath of said diffusing material and withdrawing said sheet from the bath at a controlled rate to provide a substantially uniform layer of said bulk diffusing material along said face.
Claim 10
Dependent Claim
90 words
A method of forming a back projection screen according to claim 7 wherein said Fresnel lens is embossed in a longitudinal direction across said thermoplastic sheet, and further including juxtaposing said embossed sheet in a back to back configuration with a second thermoplastic sheet having an embossed Fresnel lens extending in a direction perpendicular to the Fresnel lens disposition of said first sheet and flowing a solvent for said thermoplastic sheets at the nip of the flat confronting faces of said sheets to bond said sheets into a unitary screen.
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) | 1976-01-23 | 1976-07-24 | 1977-01-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-01-23 | 1980-07-24 | 1981-01-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-01-23 | 1984-07-24 | 1985-01-23 | $7700.00 | Window Closed / Lapsed |