EP0148529A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Rear projection screen
Assignee: Philips North America LLC
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Filing: 1984-12-18
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Granted: —
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Expires: 2004-12-18
Abstract
Abstract A rear projection screen is disclosed which uses a front surface lenticular array to distribute light from projection light sources through a horizontal angle of virtually 180° with uniform luminance. Each lenticular element of the array is characterised by having a height to width ratio of at least 1:1 and a pitch width to tip width ratio of at least 2:1. The lenticular array is further characterized as having the capability of having approximately two-thirds of the front surface area black masked.
Inventors
- 👤 Ralph Hampton Bradley
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 09:11
CPC Classifications
H; H04; H04N; H04N5/00; H04N5/74; G; G03; G03B; G03B21/00; G03B21/54; G03B21/56; G03B21/60; G03B21/62; G03B21/625
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
238 words
5 A rear projection screen comprising, light spreading means on the front surface of said screen for receiving rays from an image source and deflecting respective ones of said rays to display said image with substantial uniform brightness over a wide viewing angle; said light spreading means comprising a plurality of closely spaced generally parallel lenticular lenses; at least some of said lenticular lenses being comprised of a base portion, a first side portion, a second side portion and a tip portion opposite said first side portion; characterized in that, said first side portion has an average slope of between approximately 43 and 85 0 with respect to said base portion; said second side portion has an average slope of between approximately 43° and 85° with respect to said base portion; said first average slope and said second average slope being selected so that said first side portion and said second side portion are substantially internally reflective; in that the ratio of the height of said lenses to the width of said base portion is greater than 1:1 and the ratio of the width of said base portion to the width of said tip portion is greater than 2:1, and in that said tip portion is contiguous with both said first side portion and second side portion, said tip portion comprising two convex cylindrical portions and a central concave cylindrical portion and said t;p portion being substantially refractive.
Claim 2
Dependent Claim
238 words
5 A rear projection screen comprising, light spreading means on the front surface of said screen for receiving rays from an image source and deflecting respective ones of said rays to display said image with substantial uniform brightness over a wide viewing angle; said light spreading means comprising a plurality of closely spaced generally parallel lenticular lenses; at least some of said lenticular lenses being comprised of a base portion, a first side portion, a second side portion and a tip portion opposite said first side portion; characterized in that, said first side portion has an average slope of between approximately 43 and 85 0 with respect to said base portion; said second side portion has an average slope of between approximately 43° and 85° with respect to said base portion; said first average slope and said second average slope being selected so that said first side portion and said second side portion are substantially internally reflective; in that the ratio of the height of said lenses to the width of said base portion is greater than 1:1 and the ratio of the width of said base portion to the width of said tip portion is greater than 2:1, and in that said tip portion is contiguous with both said first side portion and second side portion, said tip portion comprising two convex cylindrical portions and a central concave cylindrical portion and said t;p portion being substantially refractive.
Claim 3
Dependent Claim
27 words
The rear projection screen claimed in Claim 1 characterized in that all of said plurality of closely spaced generally parallel lenticular lenses are of the same construction.
Claim 4
Dependent Claim
25 words
The rear projection screen of Claim 2, characterized in that said first average slope and said second average slope are each greater than 70 .
Claim 5
Dependent Claim
21 words
The rear projection screen of Claim 3 characterized in that said first average slope and said second average slope are equal.
Claim 6
Dependent Claim
28 words
The rear projection screen of Claim 1, characterized in that said two convex cylindrical portions and said central concave cylindrical portion of said tip portion have equal radii.
Claim 7
Dependent Claim
19 words
The rear projection screen of Claim 5 characterized in that said lenticular lenses are symmetrical about their central axes.
Claim 8
Dependent Claim
19 words
The rear projection screen of Claim 7, characterized in that said height to width ratio is greater than 3:2.
Claim 9
Dependent Claim
19 words
The rear projection screen of Claim 7 characterized in that said width to width ratio is greater than 3:1.
Claim 10
Dependent Claim
234 words
The rear projection screen of Claim 6 having said first side portion, said second side portion and said tip portion substantially proportional to a lenticular lens defined as having a width equal to .55mm and symmetry at x=275mm, and each of said symmetrical side portions being constructed from 397 straight line segments which are defined by the expression: where : X 1 =0, Y 1 =0 D =. 2131 ÷ 397 =5.371x10 -4 M 1 = 6.5786 X n =(n-1)xD Y n =Y n- 1 + D x M n-1 the end point of the 397th segment being X 398 =.21310, Y 398 =.88438; the shape of said first side portion being determined by the following interpolation rule: given X, X < .21310 and X i ≤ X < X.+1 then Y=Y i +(X-X i )xM i +D; the shape of said tip portion being defined as follows: for .21310 < x < .25735 the shape is a circle with X 1 =.23971 and Y0 1 =.86896 and R=.03076mm in the formula and ) (the center of the reference lenticular) the shape is a circle with X0 2 = .22750 and Y0 2 = .91936, R is again equal to .03076 mm in the formula and wherein all values of Y are greater than or equal to 0 and the rib is defined as a continuous function for Y and a slope of Y.
Claim 11
Dependent Claim
52 words
The rear projection screen of Claim 1, characterized in that said parallel lenticular lenses define grooves therebetween and said apparatus further comprises means, disposed in said grooves, for absorbing visible light, the means comprising an amount of lightabsorbent discreet particles, whereby reflection of visible ambient light impinged on the system is reduced.
Claim 12
Dependent Claim
19 words
A rear projection screen as claimed in Claim 10 characterized by means for containing the particles within the groove.
Claim 13
Dependent Claim
17 words
A rear projection screen as claimed in Claim 1 characterized in that it further comprises diffusing means.
Claim 14
Dependent Claim
50 words
A rear projection screen as claimed in any of the preceding Claims, characterized by light collimating means on a rear portion of the screen for receiving divergent light rays from an image projector and collimating said rays into parallel rays representative of an image to be displayed by said screen.
References Cited (Backward Citations)
No citation records indexed.
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