WO2001014927A1 - Screen for rear projection display - Google Patents

Screen for rear projection display Download PDF

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Publication number
WO2001014927A1
WO2001014927A1 PCT/US2000/023124 US0023124W WO0114927A1 WO 2001014927 A1 WO2001014927 A1 WO 2001014927A1 US 0023124 W US0023124 W US 0023124W WO 0114927 A1 WO0114927 A1 WO 0114927A1
Authority
WO
WIPO (PCT)
Prior art keywords
screen
lenslet array
tan
elements
projection lens
Prior art date
Application number
PCT/US2000/023124
Other languages
French (fr)
Inventor
Roy Auerbach
Joachim Bunkenburg
Brahim Dahmani
E. Gregory Fulkerson
Simon Magarill
John D. Rudolph
Original Assignee
U.S. Precision Lens Incorporated
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by U.S. Precision Lens Incorporated filed Critical U.S. Precision Lens Incorporated
Priority to US10/069,695 priority Critical patent/US6970289B1/en
Publication of WO2001014927A1 publication Critical patent/WO2001014927A1/en

Links

Classifications

    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
    • G03B21/00—Projectors or projection-type viewers; Accessories therefor
    • G03B21/54—Accessories
    • G03B21/56—Projection screens
    • G03B21/60—Projection screens characterised by the nature of the surface
    • G03B21/602—Lenticular screens

Definitions

  • This invention relates to rear screen projection systems including CRT, LCD, and DLP displays, as well as slide projectors.
  • a projection screen is an optical device which does not create an image but provides a required field of view in the vertical and horizontal directions of viewer space. By reducing the field of view in the vertical direction, the screen creates the effect of increasing the brightness of the image within the viewing area, an effect which is referred to in the art as gain.
  • the invention provides a new structure for a compound screen for a rear projection display. More particularly, the invention provides a rear projection screen for use with a projection lens which has an exit pupil (23 in Figure 3), said screen having a light entering side and a light exiting side and comprising in order from said light entering side to said light exiting side: (a) a Fresnel structure (11 in Figure 1);
  • an opaque layer (15 in Figure 1) comprising a plurality of pinholes, said pinholes being at locations which correspond to the images of the exit pupil formed by the combination of the Fresnel structure and the lenslet array.
  • the screen can comprise a protective layer on the light exiting side of the opaque layer.
  • the Fresnel structure, the lenslet array, the opaque layer, and the protective layer can be arranged as subassemblies, e.g., the Fresnel structure and the lenslet array can be arranged in one subassembly and the opaque layer and the protective layer can be arranged in another subassembly.
  • the lenslet array can comprise elements whose size is at least several times smaller than the magnified image of a pixel produced at the array by the projection lens.
  • the lenslet array can comprise elements whose size is at least several times smaller than the magnified image of a dot spot of the cathode ray tube produced at the array by the projection lens.
  • FIG. 1 is a schematic drawing of a rear projection screen constructed in accordance with the invention.
  • Figure 2 is a schematic drawing illustrating the correlation between the size of a lenslet array element and the projected image of a single pixel.
  • Figure 3 is a conceptual ray tracing for the rear projection screen of Figure 1.
  • Figure 4 is a schematic drawing illustrating lenslet array elements having a rectangular aperture.
  • the compound screen has four elements which are: (1) Fresnel structure 11; (2) lenslet array 13; (3) opaque layer 15 with two dimensional structure of precision pinholes; and (4) a protective layer having a smooth outer surface 17.
  • These elements can be arranged in two components as shown in Figure 1, where one component is a substrate with a Fresnel structure on one side and a lenslet array on the other and the other component has an opaque layer with a pinhole structure on one side and a smooth second side which serves as a protective layer.
  • the four elements fisted above can be arranged in any combination of subassembHes but must have the following order from the projection lens to the viewer: Fresnel structure, lenslet array, and opaque layer with pinholes.
  • the protective layer may not be necessary for all applications or may be unnecessary with the selection of a suitable opaque layer.
  • the flat protective layer on the viewer side provides an easy way to clean the screen with typical methods and products for cleaning. Also, this layer adds abrasion and impact resistance to the screen.
  • Figure 2 shows a lenslet array where the shape of each element 19 of the array has a square aperture to collect all light from the projection lens. As illustrated in this figure, the size of each element 19 is much (at least several times) smaller than the magnified image 21 of a projected pixel of a LCD/DLP or the dot spot of a CRT. This provides elimination of moire effects on the screen.
  • Each element of the lenslet array focuses the light in its back focal plane. Light then passes through the holes in the opaque layer and exits into the viewer space as shown at 29.
  • the field of view in the viewer space can be calculated as:
  • ⁇ is the half of field of view (angular dimension)
  • CA is the clear aperture (optical diameter) of a single element of the lenslet array
  • /' is the focal distance of the element. 10
  • Each element of the lenslet array can have a rectangular aperture as shown in Figure 4.
  • the vertical and horizontal fields of view can be determined as:
  • ⁇ v and CCH are the half angular fields of view in the vertical and horizontal directions, respectively, and CA v and CA H are the clear aperture of the element in these directions.
  • Each element of the lenslet array can have a toroidal shape to 0 provide different focal lengths in the vertical and horizontal directions
  • V' and fH are the focal lengths of the element in the vertical and ⁇ horizontal directions.
  • the opaque layer with the sets of pinholes can be done out of photoresist material. This material is exposed with an electromagnetic field and developed with an appropriate chemical process. The process of exposure is done after both components of the screen are assembled.
  • the source of the electromagnetic field is located at the position of the exit pupil of the projection lens (see Figure 3). This provides automatic compensation ⁇ of all inaccuracies in the lenslet array with an appropriate shape and location of the pinholes in the developed opaque layer.
  • the opaque layer can be further improved by the addition of materials which increases the absorption of this layer.
  • All air contact 10 surfaces of the screen can have antireflection coatings that reduce the reflectivity and increase the contrast.
  • the optical properties of the screen can be maintained throughout the temperature and humidity variations which can l ⁇ be expected from seasonal climate conditions and set operation.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Overhead Projectors And Projection Screens (AREA)

Abstract

A rear projection screen for use with a projection lens which has an exit pupil (23) is provided. The screen has a light entering side and a light exiting side and comprises in order from said light entering side to said light exiting side: (a) a Fresnel structure (11); (b) a lenslet array (13); and (c) an opaque layer (15) comprising a plurality of pinholes, said pinholes being at locations which correspond to the images of the exit pupil formed by the combination of the Fresnel structure and the lenslet array.

Description

SCREEN FOR REAR PROJECTION DISPLAY
I. FIELD OF INVENTION
This invention relates to rear screen projection systems including CRT, LCD, and DLP displays, as well as slide projectors.
II. BACKGROUND OF THE INVENTION
A projection screen is an optical device which does not create an image but provides a required field of view in the vertical and horizontal directions of viewer space. By reducing the field of view in the vertical direction, the screen creates the effect of increasing the brightness of the image within the viewing area, an effect which is referred to in the art as gain.
III. SUMMARY OF THE INVENTION
The invention provides a new structure for a compound screen for a rear projection display. More particularly, the invention provides a rear projection screen for use with a projection lens which has an exit pupil (23 in Figure 3), said screen having a light entering side and a light exiting side and comprising in order from said light entering side to said light exiting side: (a) a Fresnel structure (11 in Figure 1);
(b) a lenslet array (13 in Figure 1); and
(c) an opaque layer (15 in Figure 1) comprising a plurality of pinholes, said pinholes being at locations which correspond to the images of the exit pupil formed by the combination of the Fresnel structure and the lenslet array. The lenslet array can comprise elements which have a square aperture in which case, in viewer space, the screen's half field of view α can be described by the equation: α = tan_1(0.5»CA/f ) where CA and f are, respectively, the clear aperture and the focal length of the elements.
Alternatively, the lenslet array can comprise elements which have a rectangular aperture in which case the screen's vertical half field of view αv and horizontal half field of view CIH, in viewer space, can be described by the equations: αv = tan_1(0.5*CAv/f ) and αH = tan_1(0.5»CAH/f) where CAv, CAH, and f are, respectively, the vertical clear aperture, the horizontal clear aperture, and the focal length of the elements.
As a further alternative, the lenslet array can comprise anamorphic elements in which case the screen's vertical half field of view αv and horizontal half field of view αH, in viewer space, can be described by the equations: αv = tan_1(0.5»CA/f v) and αH = tan_1(0.5«CA/f H) where CA, f y, and f H are, respectively, the clear aperture, the vertical focal length, and the horizontal focal length of the elements. The screen can comprise a protective layer on the light exiting side of the opaque layer. The Fresnel structure, the lenslet array, the opaque layer, and the protective layer can be arranged as subassemblies, e.g., the Fresnel structure and the lenslet array can be arranged in one subassembly and the opaque layer and the protective layer can be arranged in another subassembly. When the screen is used with a pixelized panel, the lenslet array can comprise elements whose size is at least several times smaller than the magnified image of a pixel produced at the array by the projection lens. Similarly, when the screen is used with a cathode ray tube, the lenslet array can comprise elements whose size is at least several times smaller than the magnified image of a dot spot of the cathode ray tube produced at the array by the projection lens.
The accompanying drawings, which are incorporated in and constitute part of the specification, illustrate the various aspects of the invention, and together with the description, serve to explain the principles of the invention. It is to be understood, of course, that both the drawings and the description are explanatory only and are not restrictive of the invention.
TV. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic drawing of a rear projection screen constructed in accordance with the invention.
Figure 2 is a schematic drawing illustrating the correlation between the size of a lenslet array element and the projected image of a single pixel.
Figure 3 is a conceptual ray tracing for the rear projection screen of Figure 1.
Figure 4 is a schematic drawing illustrating lenslet array elements having a rectangular aperture.
The reference numbers used in the drawings refer to the following:
11 Fresnel structure 13 lenslet array
15 opaque layer with pinholes
17 smooth surface of protective layer
19 elements of lenslet array
21 magnified image of single pixel 23 exit pupil of projection lens
25 light from projection lens 27 parallel beam 29 light in viewer space V. DESCRIPTION OF THE INVENTION
The structure of a screen constructed in accordance with the invention is shown in Figure 1.
As shown in this figure, the compound screen has four elements which are: (1) Fresnel structure 11; (2) lenslet array 13; (3) opaque layer 15 with two dimensional structure of precision pinholes; and (4) a protective layer having a smooth outer surface 17. These elements can be arranged in two components as shown in Figure 1, where one component is a substrate with a Fresnel structure on one side and a lenslet array on the other and the other component has an opaque layer with a pinhole structure on one side and a smooth second side which serves as a protective layer.
The four elements fisted above can be arranged in any combination of subassembHes but must have the following order from the projection lens to the viewer: Fresnel structure, lenslet array, and opaque layer with pinholes. The protective layer may not be necessary for all applications or may be unnecessary with the selection of a suitable opaque layer. When used, the flat protective layer on the viewer side provides an easy way to clean the screen with typical methods and products for cleaning. Also, this layer adds abrasion and impact resistance to the screen.
Figure 2 shows a lenslet array where the shape of each element 19 of the array has a square aperture to collect all light from the projection lens. As illustrated in this figure, the size of each element 19 is much (at least several times) smaller than the magnified image 21 of a projected pixel of a LCD/DLP or the dot spot of a CRT. This provides elimination of moire effects on the screen.
The work of the screen is illustrated in Figure 3. Light 25 from the exit pupil 23 of the projection lens illuminates the Fresnel structure which has a front focal distance equal to the distance from the exit pupil of the projection lens to the screen. This means that after refraction on the Fresnel structure, the light becomes parallel to the optical axis as shown at
27. Each element of the lenslet array focuses the light in its back focal plane. Light then passes through the holes in the opaque layer and exits into the viewer space as shown at 29.
5 The field of view in the viewer space can be calculated as:
/ N O.δxC tan(α>= — - —
where α is the half of field of view (angular dimension), CA is the clear aperture (optical diameter) of a single element of the lenslet array, and /'is the focal distance of the element. 10 To provide a different field of view in the vertical and horizontal directions two different solution can be implemented:
(1) Each element of the lenslet array can have a rectangular aperture as shown in Figure 4. In this case the vertical and horizontal fields of view can be determined as:
. , __ / \ O.δxCA, , -v O.δxCA, lδ tan(av)= — _ϋ>tan(αff>= — -JL
where αv and CCH are the half angular fields of view in the vertical and horizontal directions, respectively, and CA v and CA H are the clear aperture of the element in these directions.
(2) Each element of the lenslet array can have a toroidal shape to 0 provide different focal lengths in the vertical and horizontal directions
(anamorphic property). For this case the equations for the vertical and horizontal fields of view are:
, / O.δxCA , / O.δxCA tan( v )= , tan(aH )= , tv In where V' and fH are the focal lengths of the element in the vertical and δ horizontal directions.
The opaque layer with the sets of pinholes can be done out of photoresist material. This material is exposed with an electromagnetic field and developed with an appropriate chemical process. The process of exposure is done after both components of the screen are assembled. The source of the electromagnetic field is located at the position of the exit pupil of the projection lens (see Figure 3). This provides automatic compensation δ of all inaccuracies in the lenslet array with an appropriate shape and location of the pinholes in the developed opaque layer.
To increase the contrast and reduce the reflection of ambient light in the viewer space the opaque layer can be further improved by the addition of materials which increases the absorption of this layer. All air contact 10 surfaces of the screen can have antireflection coatings that reduce the reflectivity and increase the contrast.
By using identical materials or materials with appropriate thermal coefficients of expansion, the optical properties of the screen can be maintained throughout the temperature and humidity variations which can lδ be expected from seasonal climate conditions and set operation.
From the foregoing, it can be seen that the benefits of the screen design of the invention include:
• elimination of moire effect;
• full control of vertical and horizontal field of view in viewer space; 0 • low loss for fight propagation from the projection lens to the viewer space and high loss of light (opaque property) in reverse direction; and
• a protective layer on the outside side of the screen.
Although specific embodiments of the invention have been described δ and illustrated, it will be apparent to those skilled in the art that modifications and variations can be made without departing from the invention's spirit and scope. The following claims are thus intended to cover the specific embodiments set forth herein as well as such modifications, variations, and equivalents. 0

Claims

What is claimed is:
1. A rear projection screen for use with a projection lens which has an exit pupil, said screen having a light entering side and a light exiting side and comprising in order from said light entering side to said fight exiting side:
(a) a Fresnel structure;
(b) a lenslet array; and
(c) an opaque layer comprising a plurality of pinholes, said pinholes being at locations which correspond to the images of the exit pupil formed by the combination of the Fresnel structure and the lenslet array.
2. The screen of Claim 1 wherein the lenslet array comprises elements which have a square aperture.
3. The screen of Claim 2 wherein, in viewer space, the screen has a half field of view α given by: α = tan_1(0.δ»CA/f) where CA and f are, respectively, the clear aperture and the focal length of the elements.
4. The screen of Claim 1 wherein the lenslet array comprises elements which have a rectangular aperture. δ. The screen of Claim 4 wherein, in viewer space, the screen has a vertical half field of view αv given by: αv = tan-1(0.δ»CAv/f) and a horizontal half field of view αH given by: αH = tan_1(0.δ»CAH/f) where CAv, CAH, and f are, respectively, the vertical clear aperture, the horizontal clear aperture, and the focal length of the elements.
6. The screen of Claim 1 wherein the lenslet array comprises anamorphic elements.
7. The screen of Claim 6 wherein, in viewer space, the screen has a vertical half field of view αv given by: αv = tan-1(0.δ»CA/fv) and a horizontal half field of view αH given by: αH = tan_1(0.δ«CA/fH) where CA, f v, and fΗ are, respectively, the clear aperture, the vertical focal length, and the horizontal focal length of the elements.
8. The screen of Claim 1 further comprising a protective layer on the light exiting side of the opaque layer.
9. The screen of Claim 8 wherein the Fresnel structure, the lenslet array, the opaque layer, and the protective layer are arranged as subassembHes.
10. The screen of Claim 9 wherein the Fresnel structure and the lenslet array are arranged in one subassembly and the opaque layer and the protective layer are arranged in another subassembly.
11. The screen of Claim 1 wherein the screen is for use with a pixelized panel and the lenslet array comprises elements whose size is at least several times smaller than the magnified image of a pixel produced at the array by the projection lens.
12. The screen of Claim 1 wherein the screen is for use with a cathode ray tube and the lenslet array comprises elements whose size is at least several times smaller than the magnified image of a dot spot of the cathode ray tube produced at the array by the projection lens.
13. A rear screen projection system comprising a projection lens having an exit pupil and the screen of Claim 1.
14. The rear screen projection system of Claim 13 wherein the Fresnel structure has a front focal distance and the distance from the exit pupil of the projection lens to the screen is equal to said front focal distance.
PCT/US2000/023124 1999-08-24 2000-08-23 Screen for rear projection display WO2001014927A1 (en)

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Application Number Priority Date Filing Date Title
US10/069,695 US6970289B1 (en) 2000-08-23 2000-08-23 Screen for rear projection display

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US15045199P 1999-08-24 1999-08-24
US60/150,451 1999-08-24

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2003069407A1 (en) * 2002-02-18 2003-08-21 Synelec Telecom Multimedia Display screen and its method of production
US10379265B2 (en) 2015-05-11 2019-08-13 Corning Incorporated Surface display units with opaque screen
US10838255B2 (en) 2014-10-07 2020-11-17 Corning Incorporated Direct view display device and light unit for direct view display device

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3580661A (en) * 1969-04-10 1971-05-25 Bell & Howell Co Rear projection viewing screen for close viewing
US3830556A (en) * 1971-12-15 1974-08-20 Y Bratkowski Rear projection screen
US4184762A (en) * 1978-06-16 1980-01-22 Oscar Guzman Variable definition projection systems
US4526439A (en) * 1968-03-21 1985-07-02 Takanori Okoshi Three-dimensional image display apparatus and a screen therefor
US4666248A (en) * 1985-12-20 1987-05-19 U. S. Philips Corporation Rear-projection screen
US5111337A (en) * 1991-01-04 1992-05-05 Eugene Martinez Enhanced contrast, maximum gain front and rear projection screens
US5210641A (en) * 1992-05-01 1993-05-11 Lewis Richard B High contrast front projection display screen

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4526439A (en) * 1968-03-21 1985-07-02 Takanori Okoshi Three-dimensional image display apparatus and a screen therefor
US3580661A (en) * 1969-04-10 1971-05-25 Bell & Howell Co Rear projection viewing screen for close viewing
US3830556A (en) * 1971-12-15 1974-08-20 Y Bratkowski Rear projection screen
US4184762A (en) * 1978-06-16 1980-01-22 Oscar Guzman Variable definition projection systems
US4666248A (en) * 1985-12-20 1987-05-19 U. S. Philips Corporation Rear-projection screen
US5111337A (en) * 1991-01-04 1992-05-05 Eugene Martinez Enhanced contrast, maximum gain front and rear projection screens
US5210641A (en) * 1992-05-01 1993-05-11 Lewis Richard B High contrast front projection display screen

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2003069407A1 (en) * 2002-02-18 2003-08-21 Synelec Telecom Multimedia Display screen and its method of production
US10838255B2 (en) 2014-10-07 2020-11-17 Corning Incorporated Direct view display device and light unit for direct view display device
US10379265B2 (en) 2015-05-11 2019-08-13 Corning Incorporated Surface display units with opaque screen

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