CA1181272A - Rear projection screen - Google Patents
Rear projection screenInfo
- Publication number
- CA1181272A CA1181272A CA000400430A CA400430A CA1181272A CA 1181272 A CA1181272 A CA 1181272A CA 000400430 A CA000400430 A CA 000400430A CA 400430 A CA400430 A CA 400430A CA 1181272 A CA1181272 A CA 1181272A
- Authority
- CA
- Canada
- Prior art keywords
- rear projection
- projection screen
- flank
- crest
- medium
- Prior art date
- Legal status (The legal status 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 status listed.)
- Expired
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
- G03B21/62—Translucent screens
- G03B21/625—Lenticular translucent screens
Abstract
ABSTRACT OF THE DISCLOSURE
Provided is a rear projection screen having a front surface receiving light rays from a projector and a viewing surface formed with a lenticulated surface in which lenticules each consisting of a crest, a trough and a flank interconnecting the crest and trough are continuously laid. The flank surface is provided with, on at least a part thereof, a total reflecting surface on which all light rays impinging thereto are reflected and then emanate from the crest through a medium inter-face thereof.
Provided is a rear projection screen having a front surface receiving light rays from a projector and a viewing surface formed with a lenticulated surface in which lenticules each consisting of a crest, a trough and a flank interconnecting the crest and trough are continuously laid. The flank surface is provided with, on at least a part thereof, a total reflecting surface on which all light rays impinging thereto are reflected and then emanate from the crest through a medium inter-face thereof.
Description
7~
BACKGROUND OF TE~E INVENTION
The present invention relates to a rear pro-jection screen suitable for use as, for example, a screen for video projectors and, more particularly, to a rear projection screen having a greater angle of field of vision on the viewing side and an increased bright-ness. Still more particularly, the invention is con-cerned with a lenticular lens for use in a rear projec-tion screen of the type mentioned above.
Rear projection screens have been widely available for video projectors, microfilm readers and computer display systems, and various studies and attempts have been made for improving the light transmitting characteristics of the rear projection screen for attaining greater angle of field of vision, higher contrast and higher resolution. As a measure for achieving these objects, it has been proposed to use, solely or in combination with a lens or a diffusion plate, a lenticulated surface having a multiplicity of minute cylindrical lenses (lenticules) arranged con-tinually.
This lenticulated surface is effective in dif--fusing the light impinging thereon. ~ore specifically, a lenticulated surface having a multiplicity of minute Z7~
1 vertically extending cylindrical lenses arranged con-tinually on a vertical plane laterally diffuses the light, while the lenticulated surface having a multipli- ~-city of minute horizontally extending cylindrical lenses ~-arranged continually on a vertical plane longitudinallydiffuses the light. When this lenticulated surface i5 used as a screen, the maximum diffusion angle is varied largely depending on whether the lenticulated surface is faced to the incident light, i.e. towards the light source or to the viewer. Namely, as is known to those skilled in the art, it is possible to obtain a greater diffusion angle when the surface is faced to the light source than when the same is faced to the viewer.
BRIEF DESCRIPTION OF THE D~AWINGS
Fig. 1 is a perspective view of a rear projec-tion screen provided with a lenticulated surface which includes lenticules each having a crest, troughs and flank portions in accordance with an embodiment of the invention, each flank portion being at least partly 20 formed with a total reflection surface;
Fig. 2 is a perspective view of screen as a modified form of the rear projection screen shown in Fig. 17 in which the flank portion has a different form;
Fig. 3 is a perspective view of another embo 25 diment in which concaved lenses are formed on the trough portions of the lenticules of the rear projection screen shown in Fig. l;
7 ~
Fig. 4 is a perspective view of still another embodiment in which concaved lenses are formed on the trough portions of the len~icules of the rear projection screen shown in Fig. 2;
Fig. 5 is a perspective view of a further embodiment in which convexed lenses are formed on the trough portions of the lenticules of the rear projection screen shown in Fig. 2;
Fig. 6 is a sectional view of a still further embodiment in which a Fresnel lens is formed on the pro-jecting side surface of the rear proejction screen shown in Fig. 3;
Fig. 7 is a sectional view of a still further embodiment in which a Fresnel lens is formed in the pro-jecting side surface of the rear projection screen shownin Fig. 5;
Fig. 8 is a sectional view of a still further embodiment in which a light absorbing layer is formed on the total reflecting surface of the rear projection screen shown in Fig. 3;
Fig. 9 is a sectional view of a still further embodiment in which a coating layer and a light - absorbiny layer are laminated on the total reflecting surface of the rear projection screen shown in Flg. 3;
Fig. 10 is a chart for explaining the light 3.~ 7~
transmission characteristics of a total reflection surface;
Fig. 11 is a chart for explaining the light transmission characteristics in the embodiment shown in Fig. 3;
Fig. 12 is an illustration for explaining the characteristics shown in Fig. 11 in more detail;
Fig. 13 is a chart for explaining the light transmission characteristics in the embodiment shown in Fig. 5;
Fig, 14 is a graph showing the light transmitting characteristics of a conventional len-ticulated surface;
Fig. lS is a graph showing the light transmitting characteristics shown in Fig. 12;
Fig. 16 is a graph showing the light transmitting characteristics shown in Fig. 13; and Fig. 17 is a plan view illustrating a general arrangement of a projection system using the rear pro-jection screen embodying the present invention;
In general each lenticule of thelenticulated surface of the kind described has a cir-cular cross-section so that the angle of diffusion of light is considerably small~ In consequence, the brightness is drastically lowered disadvantageously in the region of viewing angles exceeding 30, as will be _~ .
seen from Fig. 14. This reduction of brightness causes not only the problem that the picture surface is darkened when viewed from the region out of the viewing ~~
angle of 30~ but also a problem that the picture surface becomes completely invisible due to a surface reflection in bright circumstance under the influence of ambient light.
SUMMARY OF THE INVE~ITIO~I
Accordingly, an object of the invention is to overcome the above-described problems of the prior art by providing a novel rear projection screen.
To this end, according to the invention, there is provided a rear projection screen having a len-ticulated s~rface formed at least on the viewing side surface of a medium ~a transparent optical medium), and the lenticulated surface includes lenticules each having a crest and troughs interconnected through flanks, wherein at least a portion of the flank is provided with a total reflection surface so that the all light rays impinging thereto are totally reflected and emanate through the crest.
The invention aims, as its another object at providing a rear projection screen which can be readily cast or mo~lded, while having, in addition to the pecu-liar total reflection characteristics mentioned above, agreat diffusion effect by the lenticules.
This object is achieved by a rear projection screen having a plurality of lentic~les formed a~ least on the viewing side surface of the medium, each len-ticule having a crest and troughs interconnected through flanks, wherein at least a portion of the flank is pro-vided with a total reflection surface such that thelight rays impinging thereto are totally reflected and emanate through the crest, and wherein the crest and/or the trough is provided ~itn a lens sur~ace.
More particularly, there is provided:
A rear projection screen having a viewing side surface, a projection side surface and a medium therebetween and having a plurality of lenticules which are formed on said viewing side surface so as to form a lenticulated surface thereon, said each lenticule comprising a crest and trough portions interconnected by flank portions wherein at least a portion of each flank has a total reflection surface so that all light rays impinging on said flank are reflected by said total reflection surface and emanate through said medium at portions other than said flank portions.
BACKGROUND OF TE~E INVENTION
The present invention relates to a rear pro-jection screen suitable for use as, for example, a screen for video projectors and, more particularly, to a rear projection screen having a greater angle of field of vision on the viewing side and an increased bright-ness. Still more particularly, the invention is con-cerned with a lenticular lens for use in a rear projec-tion screen of the type mentioned above.
Rear projection screens have been widely available for video projectors, microfilm readers and computer display systems, and various studies and attempts have been made for improving the light transmitting characteristics of the rear projection screen for attaining greater angle of field of vision, higher contrast and higher resolution. As a measure for achieving these objects, it has been proposed to use, solely or in combination with a lens or a diffusion plate, a lenticulated surface having a multiplicity of minute cylindrical lenses (lenticules) arranged con-tinually.
This lenticulated surface is effective in dif--fusing the light impinging thereon. ~ore specifically, a lenticulated surface having a multiplicity of minute Z7~
1 vertically extending cylindrical lenses arranged con-tinually on a vertical plane laterally diffuses the light, while the lenticulated surface having a multipli- ~-city of minute horizontally extending cylindrical lenses ~-arranged continually on a vertical plane longitudinallydiffuses the light. When this lenticulated surface i5 used as a screen, the maximum diffusion angle is varied largely depending on whether the lenticulated surface is faced to the incident light, i.e. towards the light source or to the viewer. Namely, as is known to those skilled in the art, it is possible to obtain a greater diffusion angle when the surface is faced to the light source than when the same is faced to the viewer.
BRIEF DESCRIPTION OF THE D~AWINGS
Fig. 1 is a perspective view of a rear projec-tion screen provided with a lenticulated surface which includes lenticules each having a crest, troughs and flank portions in accordance with an embodiment of the invention, each flank portion being at least partly 20 formed with a total reflection surface;
Fig. 2 is a perspective view of screen as a modified form of the rear projection screen shown in Fig. 17 in which the flank portion has a different form;
Fig. 3 is a perspective view of another embo 25 diment in which concaved lenses are formed on the trough portions of the lenticules of the rear projection screen shown in Fig. l;
7 ~
Fig. 4 is a perspective view of still another embodiment in which concaved lenses are formed on the trough portions of the len~icules of the rear projection screen shown in Fig. 2;
Fig. 5 is a perspective view of a further embodiment in which convexed lenses are formed on the trough portions of the lenticules of the rear projection screen shown in Fig. 2;
Fig. 6 is a sectional view of a still further embodiment in which a Fresnel lens is formed on the pro-jecting side surface of the rear proejction screen shown in Fig. 3;
Fig. 7 is a sectional view of a still further embodiment in which a Fresnel lens is formed in the pro-jecting side surface of the rear projection screen shownin Fig. 5;
Fig. 8 is a sectional view of a still further embodiment in which a light absorbing layer is formed on the total reflecting surface of the rear projection screen shown in Fig. 3;
Fig. 9 is a sectional view of a still further embodiment in which a coating layer and a light - absorbiny layer are laminated on the total reflecting surface of the rear projection screen shown in Flg. 3;
Fig. 10 is a chart for explaining the light 3.~ 7~
transmission characteristics of a total reflection surface;
Fig. 11 is a chart for explaining the light transmission characteristics in the embodiment shown in Fig. 3;
Fig. 12 is an illustration for explaining the characteristics shown in Fig. 11 in more detail;
Fig. 13 is a chart for explaining the light transmission characteristics in the embodiment shown in Fig. 5;
Fig, 14 is a graph showing the light transmitting characteristics of a conventional len-ticulated surface;
Fig. lS is a graph showing the light transmitting characteristics shown in Fig. 12;
Fig. 16 is a graph showing the light transmitting characteristics shown in Fig. 13; and Fig. 17 is a plan view illustrating a general arrangement of a projection system using the rear pro-jection screen embodying the present invention;
In general each lenticule of thelenticulated surface of the kind described has a cir-cular cross-section so that the angle of diffusion of light is considerably small~ In consequence, the brightness is drastically lowered disadvantageously in the region of viewing angles exceeding 30, as will be _~ .
seen from Fig. 14. This reduction of brightness causes not only the problem that the picture surface is darkened when viewed from the region out of the viewing ~~
angle of 30~ but also a problem that the picture surface becomes completely invisible due to a surface reflection in bright circumstance under the influence of ambient light.
SUMMARY OF THE INVE~ITIO~I
Accordingly, an object of the invention is to overcome the above-described problems of the prior art by providing a novel rear projection screen.
To this end, according to the invention, there is provided a rear projection screen having a len-ticulated s~rface formed at least on the viewing side surface of a medium ~a transparent optical medium), and the lenticulated surface includes lenticules each having a crest and troughs interconnected through flanks, wherein at least a portion of the flank is provided with a total reflection surface so that the all light rays impinging thereto are totally reflected and emanate through the crest.
The invention aims, as its another object at providing a rear projection screen which can be readily cast or mo~lded, while having, in addition to the pecu-liar total reflection characteristics mentioned above, agreat diffusion effect by the lenticules.
This object is achieved by a rear projection screen having a plurality of lentic~les formed a~ least on the viewing side surface of the medium, each len-ticule having a crest and troughs interconnected through flanks, wherein at least a portion of the flank is pro-vided with a total reflection surface such that thelight rays impinging thereto are totally reflected and emanate through the crest, and wherein the crest and/or the trough is provided ~itn a lens sur~ace.
More particularly, there is provided:
A rear projection screen having a viewing side surface, a projection side surface and a medium therebetween and having a plurality of lenticules which are formed on said viewing side surface so as to form a lenticulated surface thereon, said each lenticule comprising a crest and trough portions interconnected by flank portions wherein at least a portion of each flank has a total reflection surface so that all light rays impinging on said flank are reflected by said total reflection surface and emanate through said medium at portions other than said flank portions.
2~ There is also provided:
A rear projection screen having a viewing side surface, a projection side surface and a medium therebetween and having a plurality oE lenticules which are Eormed on said viewing side .- surface so as to Eorm a lenticulated surface, said each lenticule comprising a crest and trough portions interconnected by fiank portions wherein at least a portion of each flank has a total -6-~
7~
reflection surface so that all light ravs impinging on said flank are reflected by said total reflection surface and emanate through the crest portion, and wherein at least one of said crest and -trough portions are provided with a lens surface.
The present invention will be more readily understood from the following description of the pre-ferred embodiments thereof with reference to the accom-panying drawings.
DESCRIPTION OF THE PREFERRED EMBODIME~TS
Before the embodiments of the present invention are described, the general arrangement of a projection system using a rear projection screen embodying the pre-sent invention will be first explained with specific reference to Fig. 17.
In Fig. 17, light rays diverging from a pro-jector 172 impinge upon the rear surface of a rear pro-jection screen 171 through a Fresnel lens 173 which con-verts the diverging light rays into parallel light rays.
The light rays transmitted through the medium of the rear projection screen 171 in parallel relation are dispersed from the front surface of the rear proejction ~ screen 171 in a suitable viewing angle.
~ Hereinafter, preferred embodiments of the -6a-~ ~ ~J~
1 - invention will be described with reference to the accom-panying drawings.
Figs. 1 to 5 are perspective views of rear projection screens embodying the invention. As will be seen from these Figures, the rear projection screen of the invention is provided on its viewing side surface a lenticulated surface formed with a plurality of len-ticules each having a crest 1 and troughs 2 intercon-nected by intermediate flanks 3. As will be explained later, the flank 3 is provided at least a portion thereof with a total reflecting surface such that the light rays impinging thereto are totally reflected and then emanate through the crest 1. Figs. 1 to 5 show practical embodiments of the rear projection screen of the invention. More specifically, Fig. 1 shows an embo-diment in which a most part of each flank 3 constitutes a total reflecting surface 31, leaving small portions of non reflecting surfaces 32. Fig. 2 shows another embo-diment in which the entire part of each flank 3 consti-tutes a total reflecting surface 31. Fig. 3 shows stillanother embodiment in which concaved lens surfaces 21 are formed in the troughs 2 of the embodiment shown in Fig. 1. Fig. 4 shows a further embodiment in which con-caved lens surfaces 21 are formed in the trouyhs 2 of the embodiment shown in Fig~ 2. Finally, Fig. 5 shows a further embodiment in which, in place of the concaved lens surfaces 21 in the embodiment shown in Fig. 4, con-;Zt~;~
1 vexed lens surfaces 22 are formed.
In these embodiments, the projecting side sur-face B of the rear projection screen is flat and smooth.
It is, however, effective to form a Fresnel lens on the projecting side surface. Figs. 6 and 7 are sectional vies of embodiments in which a Fresnel lens is formed on the projecting side surface of the rear projection screen. ~ore speciically, Fig. 6 shows a still further embodiment in which a Fresnel lens 4 is formed on the projecting side surface B of the embodiment shown in Fig. 3, while Fig. 7 shows a s-till further embodiment in which a Fresnel lens 4 is formed on the projecting side surface B of the embodiment shown in Fig. 5.
The Fresnel lens in this case is generall~ a circular Fresnel lens and the focal length thereof varies depending on applications of the screen. In the case of a rear projection screen for a large-si2e video projector, for example, the focal length f is usually between 1.0 and 1.2 m. The Fresnel lens 4 can also be incorporated in the embodiments shown in Figs. from 1 through 4.
Figs. 8 and 9 show still further embodiments improved to increase the contrast of image on the rear projection screen. namely, in the embodiment shown in Fig. 8, a light absorbing layer 5 is formed on the total reflecting surface 31. On the other hand, Fig. 9 shows an embodiment in which, in order to prevent the absorp-1 .ion loss in the light absorbing layer 5, a coatinglayer 6 of a substance having a smaller refractive index than the medium is formed beforehand on the total reflecting surface and then the light absorbing layer 5 is formed on the coating layer 6. In the embodiments shown in Figs. 8 and 9, it is possible to make effective use of the total reflecting surface 31 which does not directly transmit the light therethrough to the viewing side surace A, so that the contrast of the image on the rear projection screen is improved considerably.
Although these two embodiments for obtaining higher contrast are explained in connection with the embodiment shown in Fig. 3, it will be clear to those skilled in the art that the above-explained construction for achieving higher contrast can equally be applied to all other embodiments described hereinbefore.
As has been described, the essential feature of the invention resides in the formation of a specific total reflecting surface 31 in each flank 3 of the len-ticule. The light transmission characteristics of theflank having the total reflecting surface will be explained hereinunder with reference to Figs. 10 through 13.
Fig. 10 is an enlarged view of a portion of the len-ticulated s~lrface of a rear projection screen in accordance with the invention. In this case, the flank
A rear projection screen having a viewing side surface, a projection side surface and a medium therebetween and having a plurality oE lenticules which are Eormed on said viewing side .- surface so as to Eorm a lenticulated surface, said each lenticule comprising a crest and trough portions interconnected by fiank portions wherein at least a portion of each flank has a total -6-~
7~
reflection surface so that all light ravs impinging on said flank are reflected by said total reflection surface and emanate through the crest portion, and wherein at least one of said crest and -trough portions are provided with a lens surface.
The present invention will be more readily understood from the following description of the pre-ferred embodiments thereof with reference to the accom-panying drawings.
DESCRIPTION OF THE PREFERRED EMBODIME~TS
Before the embodiments of the present invention are described, the general arrangement of a projection system using a rear projection screen embodying the pre-sent invention will be first explained with specific reference to Fig. 17.
In Fig. 17, light rays diverging from a pro-jector 172 impinge upon the rear surface of a rear pro-jection screen 171 through a Fresnel lens 173 which con-verts the diverging light rays into parallel light rays.
The light rays transmitted through the medium of the rear projection screen 171 in parallel relation are dispersed from the front surface of the rear proejction ~ screen 171 in a suitable viewing angle.
~ Hereinafter, preferred embodiments of the -6a-~ ~ ~J~
1 - invention will be described with reference to the accom-panying drawings.
Figs. 1 to 5 are perspective views of rear projection screens embodying the invention. As will be seen from these Figures, the rear projection screen of the invention is provided on its viewing side surface a lenticulated surface formed with a plurality of len-ticules each having a crest 1 and troughs 2 intercon-nected by intermediate flanks 3. As will be explained later, the flank 3 is provided at least a portion thereof with a total reflecting surface such that the light rays impinging thereto are totally reflected and then emanate through the crest 1. Figs. 1 to 5 show practical embodiments of the rear projection screen of the invention. More specifically, Fig. 1 shows an embo-diment in which a most part of each flank 3 constitutes a total reflecting surface 31, leaving small portions of non reflecting surfaces 32. Fig. 2 shows another embo-diment in which the entire part of each flank 3 consti-tutes a total reflecting surface 31. Fig. 3 shows stillanother embodiment in which concaved lens surfaces 21 are formed in the troughs 2 of the embodiment shown in Fig. 1. Fig. 4 shows a further embodiment in which con-caved lens surfaces 21 are formed in the trouyhs 2 of the embodiment shown in Fig~ 2. Finally, Fig. 5 shows a further embodiment in which, in place of the concaved lens surfaces 21 in the embodiment shown in Fig. 4, con-;Zt~;~
1 vexed lens surfaces 22 are formed.
In these embodiments, the projecting side sur-face B of the rear projection screen is flat and smooth.
It is, however, effective to form a Fresnel lens on the projecting side surface. Figs. 6 and 7 are sectional vies of embodiments in which a Fresnel lens is formed on the projecting side surface of the rear projection screen. ~ore speciically, Fig. 6 shows a still further embodiment in which a Fresnel lens 4 is formed on the projecting side surface B of the embodiment shown in Fig. 3, while Fig. 7 shows a s-till further embodiment in which a Fresnel lens 4 is formed on the projecting side surface B of the embodiment shown in Fig. 5.
The Fresnel lens in this case is generall~ a circular Fresnel lens and the focal length thereof varies depending on applications of the screen. In the case of a rear projection screen for a large-si2e video projector, for example, the focal length f is usually between 1.0 and 1.2 m. The Fresnel lens 4 can also be incorporated in the embodiments shown in Figs. from 1 through 4.
Figs. 8 and 9 show still further embodiments improved to increase the contrast of image on the rear projection screen. namely, in the embodiment shown in Fig. 8, a light absorbing layer 5 is formed on the total reflecting surface 31. On the other hand, Fig. 9 shows an embodiment in which, in order to prevent the absorp-1 .ion loss in the light absorbing layer 5, a coatinglayer 6 of a substance having a smaller refractive index than the medium is formed beforehand on the total reflecting surface and then the light absorbing layer 5 is formed on the coating layer 6. In the embodiments shown in Figs. 8 and 9, it is possible to make effective use of the total reflecting surface 31 which does not directly transmit the light therethrough to the viewing side surace A, so that the contrast of the image on the rear projection screen is improved considerably.
Although these two embodiments for obtaining higher contrast are explained in connection with the embodiment shown in Fig. 3, it will be clear to those skilled in the art that the above-explained construction for achieving higher contrast can equally be applied to all other embodiments described hereinbefore.
As has been described, the essential feature of the invention resides in the formation of a specific total reflecting surface 31 in each flank 3 of the len-ticule. The light transmission characteristics of theflank having the total reflecting surface will be explained hereinunder with reference to Figs. 10 through 13.
Fig. 10 is an enlarged view of a portion of the len-ticulated s~lrface of a rear projection screen in accordance with the invention. In this case, the flank
3 is provided with a total reflecting surface 31 and 7~
1 non-reflecting surfaces 32. The non-reflecting surfaces 32 are intended for facilitating removal of the medium from the mold in the process of production of the screen. Preferably, the non-reflecting surface 32 is formed in parallel with the optical axis or at an incli-nation angle of 1 to 5 to the optical axis.
On the other hand, the total reflecting sur-face 31 is adapted to make a total reflection of a part of the light rays impinging on the medium and to make the same emanate from the crest 1. It is necessary, however, that the totally reflected light and the light directly impinging on the crest 1 are not totally reflected by the medium interface of the crest 1. The angle ~ of inclination of the total reflecting surface 31 to the optical axis is determined by the refractive index n of the medium. Hereinafter, an explanation will be made as to how the inclination angle a is determined in relation to the refractive index n.
Referring to Fig. 10, light rays Yl and Xl run in parallel with the normal axis N. The light ray Yl out of these two rays impringes on the total reflecting surface 31 at an angle 0 and is totally reflected and emanates through the crest 1 as a ray Y2.
Thus, the total-reflected light intersects the normal axis N at an angle 2~ and emanates through the crest 1.
In order that the whole part of the totally reflected rays emanates through the crest 1, it is 7~
1 essential that this ray should not be totally re~lected by the medium interface of the crest 1. This means that the angle 2~ must be smaller than the total reElection angle.
This relationship is expressed and determined as follows by the formula of total reflection.
n sin 2 a _ sin 2a ~
-- n 2~ _ sin~
~ - 2 sin~l 1 From this relation, it is understood that the angle a formed between the total reflecting surface 31 and the horizontal plane has to meet the following condition.
~5 ~ > 90 - 1 sin-l 1 The angle a of inclination of the total reflecting surface 31 is thus determined. Assuming that the medium is an acrylic resin having a reractive index n of 1.492, the angle a is calculated as follows:
a 2 90 - 1 sin~l - 2 1.4g2 a 2 ~ 2 68.96 Thus, the angle a must be grerater than about 69. However, iE the angle 2~ oE the ray passiny 7~
1 through the crest l approaches the critical angle 42.09, closely, the possibility of total reflection at the medium interface of the crest l is increased unfa-vourably, so that the angle 2~ is preferably smaller than the critical angle. This means that the angle a preferably approximates 90. A too large angle a, however, makes the height of the crest excessively large in comparison with its width so as to make it diEficult to form such a crest. Thus, the angle a is limited also from this point, and is preferably made small in order to facilitate the formation of the crest. As a compro-mise, therefore, the angle a is preferably selected to range between 70 and 80 when an acrylic resin is used as the medium (screen material).
A discussion will be made hereinunder as to the condition for eliminating total reflection of all rays at the crest l. Representing the width of the crest l of the lenticule by Pl, the curvature of the medium interface by r and the rightmost end of the crest 1 by Q, the angle ~ formed between the normal line r and the vertical line N is expressed as follows.
P
sin~ = 2 = Pl r 2r This angle is the angle of incidence of the ray Xl parallel to the ray Yl and passing the point Q.
Therefore, the design should be made to meet the 1 following condition of 1 ~ sin 1 2r n As has been described, by forming the total reflecting surface 31 on the flank 3, the light rays coming from the projecting side surface 8 are transmitted and largely diffused at the viewing side surface A. This phenomenon will be further described with reference to Figs. 11 and 12. These Figures show the embodiment shown in Fig. 3 in a larger scale. In these Figures, there are shown crests 1, troughs 2 and flanks 3. Convexed lenses 11 are formed on the crests 1, while a concaved lenses 21 are formed on the troughs 2. Also, the flank 3 is provided with a total reflecting surface 31.
As parallel light rays come into the len-ticules having the above-described construction from the projecting side surface 8, the ray impinging on the por-tion X corresponding to the crest 1 and the ray impinging on the portion Z corresponding to the trough 2 run straight through the medium, and are refracted and diffused at the surface of the convexed lens 11 on the crest 1 and the surface of the concaved lens 21 on the trough, respectively. This phenomenon will be explained in more detail with specific reference to Fig. 12.
The rays Xl and X2 which pass in the medium towards bath marginal ends of the portion x of the crest 1 run straight and are refracted as illustrated when ~ 8~2t~
1 leaving the convexed lens surface 11 of the crest 1, while the rays Zl and Z2 passing through both ends of the trough 2 are diffused. On the other hand, most por-tion of the rays coming into both ends of the portion Y
of each flank 3, i.e. the rays in the region between Yl and Y2 or between Yl, and Y2, are reflected on each total reflecting surface 31 and emanates through the convexed lens surface 11 on the crest 1.
~n explanation will be made hereinunder as to the uniformity of brightness within the region of pro-jection angle of the projected rays, with specific reference to Fig. 12. If there is any non-uniformity in the brightness, the brightness of a picture element is varied depending on the direction of viewing of the pic-ture element. Referring to Fig. 12, the rays passingthrough the convexed lens surface 11 are diffused within the range ~ after emanating through the crest 1, as in the cases of rays Xl and X2. On the other hand, the rays coming into the total reflecting surface 31, i.e.
the rays between the rays Yl and Y2, are totally reflected and emanate through the crest 1 as strong light rays within the range ~ . On the other hand, the light rays which pass through the concaved lens surEace 21 of the trough 2, i.e. the rays between Zl and Z2' are diffused by the concaved lens surface 21 and emanate within the region ~p. The resultant rays in the regions ~ and (~ exhibit brightness characteristics (~ + ~) 1 shown in Fig. 15. As understood from this charac-teristics (~ + ~), the brightness of the resultant rays is drastically lowered in the angle region exceeding 30 from the center line of the crest 11. On the other hand, the rays ~ reflecting from the total reflecting surface 31 and then emaniating from the crest 11 form a strong light which represents brightness characteristics ~ shown in Fig. 15. This ray advantageously compen-sate for the reduction of brightness in the above-mentioned characteristics (~ + ~ ), thereby to furtheruniformalize the brightness within the reasonable viewing angle range. The curve shown by broken line in Fig. 15 shows total brightness characteristics due to ~ , ~ and ~ with the assistance of a light diffusing means ~hich will be mentioned hereinunder. The most suitable optical system for obtaining these charac-teristics can be selected by properly selecting optimum values to factors such as the height of the flank 3~
pitches P, Pl and P2 of the lenticules, and the focal lengthes of the convexed lens surface 11 and the con-caved lens surface 21.
Fig. 13 shows the optical system of the rear projection screen as shwon in Fig. 7. The ra~s in the range be-tween Yl and Y2 among the parallel light rays coming from the projecting side are totally reflected and emanate, as ~ , from the crest. On the other hand, the rays in the range between Zl and Z2 are diEfused as `7~
1 ~ after passing the focal point. Also, as shown in Fig.
12, the rays in the range between Xl and x2 are diffused as illustrated with the region ~ . The rays between Y2 and Xl and the rays between X2 and Y2, are made to S partially emanate and partially repeat reflection and refraction before emanation to the outside.
In this rear projection screen, the rays from the total reflecting surEace 31 serves to increase the angle of field of vision and provides, in com-bination with the other rays ~ and ~ , brightnesscharacteristics as shown in Fig. 16.
In the foregoing description of the embodi-ment, the material of the medium is stated as being an acrylic resin. This is because the acrylic resin exhi-bits superior optical properties and easy processabi-lity. It is possible, however, to use other materials such as vinyl chloride resins, polycarbonate resins, olefin resins, stylene resins and so forth. With these synethtic resins, the rear projection screen of the invention can be produced by extrusion, heat press, injection molding and so forth.
The sizes of every parts of the screen vary depending on its applications. For information, in the case of the lenticules of the screen shown in Fig. 11, the width Pl of the crest 1 is selected to range between 0.2 and 1.5 mm, while the width P2 of the trough 2 is selected to be between 0.3 and 1.5 mm. Thus, the pitch Z7~
1 P is selected to fall between 0.5 and 3 mm, while the height H is selected to range between 0.2 and 2 mm.
The rear projection screen of the invention can easily be formed even when the lenticulated surEace has a narrow or restricted trough 2 as in the case of screens shown in Figs. 1 and 2. From the view point of manuEacture, however, it is preferred that the lens sur-face is formed also in the trough 2 as in the case of the embodi~ents shown in Figs. 3 thru 7, because of ready removal from the mold as compared with the case where the crests are interconnected through the Elank to the comparatively narrow trough 2. The flank 3 need not always be straight but can have a curvilinear profile.
In order to further increase the diffusion of light in both vertical and horizontal directions in the rear projection screen, it is advisable to provide the medium with additional light diffusing means. For instance, it is possible to uniformly mix and disperse in the medium one, two or more additives which are neither molten in the liquid medium such as molten acry-lic resin nor make chemical reaction therewith.
Examples of such additives are inorganic diffusion agents such as SiO2, CaCO3, A12O3, TiO2, BaSO~, ZnO and fine powdered glass, and organic diffusion agents such as polystylene, stylene-acrylonitrile copolymer or the like. It is also eEfective to Eorm a layer containing such diffusion agents. Alternatively, minute roughness q ~
1 is made in the incidence surface or the surface of the crest. By employing such diffusion means, it is possible to effect a greater diffusion of light in the angle region of ~ and ~ in Fig. 12, and also to increase the diffusion of light in the vertical direc-tion in Fig. 1.
It is also effetive to add a sultable dye or pigment in the medium to control the color tone. As a measure for preserving a large diffusion of ligh~ in the vertical direction, it is effective to integrally in corporate a horizontally extending cylindrical lenses (lenticules) with the above-mentioned lenticules (lenticules).
The contrast of the picture element is reduced by ambient light impinging one side surface of the screen. In order to avoid such a reduction in the contrast, it is possible to enhance the contrast of the picture element by forming, on the total reflection sur-face 31l a light absorbing layer 5 which prevents the transmission of light, as in the case of the embodiment shown in Fig. 8. There is a fear, however, that the light absorbing layer 5 inconveniently absorbs a part of the light reflec-ted by the total reflection surface 31, although such a part is negligibly small. tn order to avoid such an absorption of light, it is preferred to form on the total reflection surface a coating layer 6 of a refractive index smaller than that of the medium 1 and then provide the light absorbing layer 5 on the coating layer 6. By so doing, it is pssible to elimi-nate the absorption of even small part of the light reflected by the total reflection surface 31 and to pro-ject the rays from the picture elements more effec-tively. As -the material having smaller refractive index, for example, it is possible to use a resin con-taining fluorine when the medium is made of an acrylic resin. It is possible to use a reflecting layer of, for example, aluminum as the coating layer 6.
Practical examples of rear projection screens of the invention are shown below.
Example 1:
A sheet of 3 mm thick was formed from a material mainly consisting of a partially polymerized methacrylate with an additive of SiO2 as a diffusion agent. With this sheet, a screen having lenticules on the projecting side surface as sho,wn in Fig. 1 was formed by a heat press. The pitch of the lenticules was 2~ 0.75 mm, the radius of curvature of the crest was 0.4R
and the angle ~ was 70. Also, the focal length f of the Fresnel lens was 1.2 m.
Brightness characteristics of the thus formed screen were evaluated. It was confirmed that the value Go and the angle ~ are 8 and 24, respectively. The screen exhibited a superior performance to make the '7~
1 image visible over a wide angle of field of vision which materially exceeds 55.
Example 2:
Using a similar sheet as Example 1, a screen was formed by a heat press to have lenticules substan-tially identical to those in Fig. 2 and provided in the projecting side surface thereof with a Fresnel lens similar to that of Example 1. The pitch and height of the lenticules were 0.7 mm, while the angle 75. The Go value and the angle ~ were 5.3 and 22, respectively, but the screen showed good characteristics to make the image visible within the range of angle of field of vision up to 50.
Example 3:
Using a similar sheet as Example 1, a screen having a form substantially equal to that shown in Fig.
7 was formed. The pitches of the lenticules having the total reflection surfaces was 0.5 mm, the pitch of the circular lenticules was 0.7 mm and the height was 0.5 mm. The angle ~ and the focal length f o~ the Fresnel lens were 75 and 1.2 m, respectively. The thus obtained screen showed high Go value and large angle ~ which are 6.6 and 32, respectively. The screen had good performance to make the image visible over a wide angle of field of vision of up to 60, advantageously.
1 non-reflecting surfaces 32. The non-reflecting surfaces 32 are intended for facilitating removal of the medium from the mold in the process of production of the screen. Preferably, the non-reflecting surface 32 is formed in parallel with the optical axis or at an incli-nation angle of 1 to 5 to the optical axis.
On the other hand, the total reflecting sur-face 31 is adapted to make a total reflection of a part of the light rays impinging on the medium and to make the same emanate from the crest 1. It is necessary, however, that the totally reflected light and the light directly impinging on the crest 1 are not totally reflected by the medium interface of the crest 1. The angle ~ of inclination of the total reflecting surface 31 to the optical axis is determined by the refractive index n of the medium. Hereinafter, an explanation will be made as to how the inclination angle a is determined in relation to the refractive index n.
Referring to Fig. 10, light rays Yl and Xl run in parallel with the normal axis N. The light ray Yl out of these two rays impringes on the total reflecting surface 31 at an angle 0 and is totally reflected and emanates through the crest 1 as a ray Y2.
Thus, the total-reflected light intersects the normal axis N at an angle 2~ and emanates through the crest 1.
In order that the whole part of the totally reflected rays emanates through the crest 1, it is 7~
1 essential that this ray should not be totally re~lected by the medium interface of the crest 1. This means that the angle 2~ must be smaller than the total reElection angle.
This relationship is expressed and determined as follows by the formula of total reflection.
n sin 2 a _ sin 2a ~
-- n 2~ _ sin~
~ - 2 sin~l 1 From this relation, it is understood that the angle a formed between the total reflecting surface 31 and the horizontal plane has to meet the following condition.
~5 ~ > 90 - 1 sin-l 1 The angle a of inclination of the total reflecting surface 31 is thus determined. Assuming that the medium is an acrylic resin having a reractive index n of 1.492, the angle a is calculated as follows:
a 2 90 - 1 sin~l - 2 1.4g2 a 2 ~ 2 68.96 Thus, the angle a must be grerater than about 69. However, iE the angle 2~ oE the ray passiny 7~
1 through the crest l approaches the critical angle 42.09, closely, the possibility of total reflection at the medium interface of the crest l is increased unfa-vourably, so that the angle 2~ is preferably smaller than the critical angle. This means that the angle a preferably approximates 90. A too large angle a, however, makes the height of the crest excessively large in comparison with its width so as to make it diEficult to form such a crest. Thus, the angle a is limited also from this point, and is preferably made small in order to facilitate the formation of the crest. As a compro-mise, therefore, the angle a is preferably selected to range between 70 and 80 when an acrylic resin is used as the medium (screen material).
A discussion will be made hereinunder as to the condition for eliminating total reflection of all rays at the crest l. Representing the width of the crest l of the lenticule by Pl, the curvature of the medium interface by r and the rightmost end of the crest 1 by Q, the angle ~ formed between the normal line r and the vertical line N is expressed as follows.
P
sin~ = 2 = Pl r 2r This angle is the angle of incidence of the ray Xl parallel to the ray Yl and passing the point Q.
Therefore, the design should be made to meet the 1 following condition of 1 ~ sin 1 2r n As has been described, by forming the total reflecting surface 31 on the flank 3, the light rays coming from the projecting side surface 8 are transmitted and largely diffused at the viewing side surface A. This phenomenon will be further described with reference to Figs. 11 and 12. These Figures show the embodiment shown in Fig. 3 in a larger scale. In these Figures, there are shown crests 1, troughs 2 and flanks 3. Convexed lenses 11 are formed on the crests 1, while a concaved lenses 21 are formed on the troughs 2. Also, the flank 3 is provided with a total reflecting surface 31.
As parallel light rays come into the len-ticules having the above-described construction from the projecting side surface 8, the ray impinging on the por-tion X corresponding to the crest 1 and the ray impinging on the portion Z corresponding to the trough 2 run straight through the medium, and are refracted and diffused at the surface of the convexed lens 11 on the crest 1 and the surface of the concaved lens 21 on the trough, respectively. This phenomenon will be explained in more detail with specific reference to Fig. 12.
The rays Xl and X2 which pass in the medium towards bath marginal ends of the portion x of the crest 1 run straight and are refracted as illustrated when ~ 8~2t~
1 leaving the convexed lens surface 11 of the crest 1, while the rays Zl and Z2 passing through both ends of the trough 2 are diffused. On the other hand, most por-tion of the rays coming into both ends of the portion Y
of each flank 3, i.e. the rays in the region between Yl and Y2 or between Yl, and Y2, are reflected on each total reflecting surface 31 and emanates through the convexed lens surface 11 on the crest 1.
~n explanation will be made hereinunder as to the uniformity of brightness within the region of pro-jection angle of the projected rays, with specific reference to Fig. 12. If there is any non-uniformity in the brightness, the brightness of a picture element is varied depending on the direction of viewing of the pic-ture element. Referring to Fig. 12, the rays passingthrough the convexed lens surface 11 are diffused within the range ~ after emanating through the crest 1, as in the cases of rays Xl and X2. On the other hand, the rays coming into the total reflecting surface 31, i.e.
the rays between the rays Yl and Y2, are totally reflected and emanate through the crest 1 as strong light rays within the range ~ . On the other hand, the light rays which pass through the concaved lens surEace 21 of the trough 2, i.e. the rays between Zl and Z2' are diffused by the concaved lens surface 21 and emanate within the region ~p. The resultant rays in the regions ~ and (~ exhibit brightness characteristics (~ + ~) 1 shown in Fig. 15. As understood from this charac-teristics (~ + ~), the brightness of the resultant rays is drastically lowered in the angle region exceeding 30 from the center line of the crest 11. On the other hand, the rays ~ reflecting from the total reflecting surface 31 and then emaniating from the crest 11 form a strong light which represents brightness characteristics ~ shown in Fig. 15. This ray advantageously compen-sate for the reduction of brightness in the above-mentioned characteristics (~ + ~ ), thereby to furtheruniformalize the brightness within the reasonable viewing angle range. The curve shown by broken line in Fig. 15 shows total brightness characteristics due to ~ , ~ and ~ with the assistance of a light diffusing means ~hich will be mentioned hereinunder. The most suitable optical system for obtaining these charac-teristics can be selected by properly selecting optimum values to factors such as the height of the flank 3~
pitches P, Pl and P2 of the lenticules, and the focal lengthes of the convexed lens surface 11 and the con-caved lens surface 21.
Fig. 13 shows the optical system of the rear projection screen as shwon in Fig. 7. The ra~s in the range be-tween Yl and Y2 among the parallel light rays coming from the projecting side are totally reflected and emanate, as ~ , from the crest. On the other hand, the rays in the range between Zl and Z2 are diEfused as `7~
1 ~ after passing the focal point. Also, as shown in Fig.
12, the rays in the range between Xl and x2 are diffused as illustrated with the region ~ . The rays between Y2 and Xl and the rays between X2 and Y2, are made to S partially emanate and partially repeat reflection and refraction before emanation to the outside.
In this rear projection screen, the rays from the total reflecting surEace 31 serves to increase the angle of field of vision and provides, in com-bination with the other rays ~ and ~ , brightnesscharacteristics as shown in Fig. 16.
In the foregoing description of the embodi-ment, the material of the medium is stated as being an acrylic resin. This is because the acrylic resin exhi-bits superior optical properties and easy processabi-lity. It is possible, however, to use other materials such as vinyl chloride resins, polycarbonate resins, olefin resins, stylene resins and so forth. With these synethtic resins, the rear projection screen of the invention can be produced by extrusion, heat press, injection molding and so forth.
The sizes of every parts of the screen vary depending on its applications. For information, in the case of the lenticules of the screen shown in Fig. 11, the width Pl of the crest 1 is selected to range between 0.2 and 1.5 mm, while the width P2 of the trough 2 is selected to be between 0.3 and 1.5 mm. Thus, the pitch Z7~
1 P is selected to fall between 0.5 and 3 mm, while the height H is selected to range between 0.2 and 2 mm.
The rear projection screen of the invention can easily be formed even when the lenticulated surEace has a narrow or restricted trough 2 as in the case of screens shown in Figs. 1 and 2. From the view point of manuEacture, however, it is preferred that the lens sur-face is formed also in the trough 2 as in the case of the embodi~ents shown in Figs. 3 thru 7, because of ready removal from the mold as compared with the case where the crests are interconnected through the Elank to the comparatively narrow trough 2. The flank 3 need not always be straight but can have a curvilinear profile.
In order to further increase the diffusion of light in both vertical and horizontal directions in the rear projection screen, it is advisable to provide the medium with additional light diffusing means. For instance, it is possible to uniformly mix and disperse in the medium one, two or more additives which are neither molten in the liquid medium such as molten acry-lic resin nor make chemical reaction therewith.
Examples of such additives are inorganic diffusion agents such as SiO2, CaCO3, A12O3, TiO2, BaSO~, ZnO and fine powdered glass, and organic diffusion agents such as polystylene, stylene-acrylonitrile copolymer or the like. It is also eEfective to Eorm a layer containing such diffusion agents. Alternatively, minute roughness q ~
1 is made in the incidence surface or the surface of the crest. By employing such diffusion means, it is possible to effect a greater diffusion of light in the angle region of ~ and ~ in Fig. 12, and also to increase the diffusion of light in the vertical direc-tion in Fig. 1.
It is also effetive to add a sultable dye or pigment in the medium to control the color tone. As a measure for preserving a large diffusion of ligh~ in the vertical direction, it is effective to integrally in corporate a horizontally extending cylindrical lenses (lenticules) with the above-mentioned lenticules (lenticules).
The contrast of the picture element is reduced by ambient light impinging one side surface of the screen. In order to avoid such a reduction in the contrast, it is possible to enhance the contrast of the picture element by forming, on the total reflection sur-face 31l a light absorbing layer 5 which prevents the transmission of light, as in the case of the embodiment shown in Fig. 8. There is a fear, however, that the light absorbing layer 5 inconveniently absorbs a part of the light reflec-ted by the total reflection surface 31, although such a part is negligibly small. tn order to avoid such an absorption of light, it is preferred to form on the total reflection surface a coating layer 6 of a refractive index smaller than that of the medium 1 and then provide the light absorbing layer 5 on the coating layer 6. By so doing, it is pssible to elimi-nate the absorption of even small part of the light reflected by the total reflection surface 31 and to pro-ject the rays from the picture elements more effec-tively. As -the material having smaller refractive index, for example, it is possible to use a resin con-taining fluorine when the medium is made of an acrylic resin. It is possible to use a reflecting layer of, for example, aluminum as the coating layer 6.
Practical examples of rear projection screens of the invention are shown below.
Example 1:
A sheet of 3 mm thick was formed from a material mainly consisting of a partially polymerized methacrylate with an additive of SiO2 as a diffusion agent. With this sheet, a screen having lenticules on the projecting side surface as sho,wn in Fig. 1 was formed by a heat press. The pitch of the lenticules was 2~ 0.75 mm, the radius of curvature of the crest was 0.4R
and the angle ~ was 70. Also, the focal length f of the Fresnel lens was 1.2 m.
Brightness characteristics of the thus formed screen were evaluated. It was confirmed that the value Go and the angle ~ are 8 and 24, respectively. The screen exhibited a superior performance to make the '7~
1 image visible over a wide angle of field of vision which materially exceeds 55.
Example 2:
Using a similar sheet as Example 1, a screen was formed by a heat press to have lenticules substan-tially identical to those in Fig. 2 and provided in the projecting side surface thereof with a Fresnel lens similar to that of Example 1. The pitch and height of the lenticules were 0.7 mm, while the angle 75. The Go value and the angle ~ were 5.3 and 22, respectively, but the screen showed good characteristics to make the image visible within the range of angle of field of vision up to 50.
Example 3:
Using a similar sheet as Example 1, a screen having a form substantially equal to that shown in Fig.
7 was formed. The pitches of the lenticules having the total reflection surfaces was 0.5 mm, the pitch of the circular lenticules was 0.7 mm and the height was 0.5 mm. The angle ~ and the focal length f o~ the Fresnel lens were 75 and 1.2 m, respectively. The thus obtained screen showed high Go value and large angle ~ which are 6.6 and 32, respectively. The screen had good performance to make the image visible over a wide angle of field of vision of up to 60, advantageously.
Claims (15)
1. A rear projection screen having a viewing side surface, a projection side surface and a medium therebetween and having a plurality of lenticules which are formed on said viewing side surface so as to form a lenticulated surface thereon, said each lenticule comprising a crest and trough portions interconnected by flank portions wherein at least a portion of each flank has a total reflection surface so that all light rays impinging on said flank are reflected by said total reflection surface and emanate through said medium at portions other than said flank portions.
2. A rear projection screen having a viewing side surface, a projection side surface and a medium therebetween and having a plurality of lenticules which are formed on said viewing side surface so as to form a lenticulated surface, said each lenticule comprising a crest and trough portions interconnected by flank portions wherein at least a portion of each flank has a total reflection surface so that all light rays impinging on said flank are reflected by said total reflection surface and emanate through the crest portion, and wherein at least one of said crest and trough portions are provided with a lens surface.
3. A rear projection screen as claimed in claim 1 or 2 wherein a Fresnel lens is formed on the projecting side of said medium.
4. A rear projection screen as claimed in claim 1 or 2 wherein said total reflection surface is formed over the entire area of said flank.
5. A rear projection screen as claimed in claim 1 or 2 wherein the angle .alpha. between said total reflection surface and the plane of the projection surface is selected to meet the conditions of:
.alpha. ? 90° -(1/2)sin-1(1/n) where, n represents the refractive index of said medium.
.alpha. ? 90° -(1/2)sin-1(1/n) where, n represents the refractive index of said medium.
6. A rear projection screen as claimed in claim 1 wherein said medium includes a light diffusion means for diffusing light impinging on the projection surface to increase the angular field of view at the viewing surface.
7. A rear projection screen as claimed in claim 6, wherein said light diffusion means includes a pigment dispersed in said medium.
8. A rear projection screen as claimed in claim 1 or 2 wherein a light absorbing layer is formed on the outer side of said reflection surface to improve the contrast of the projected image.
9. A rear projection screen as claimed in claim 1 or 2 wherein a coating layer of a substance having a refractive index smaller than the refractive index of said medium, and a light absorbing layer are applied on the outer surface of said total reflection surface.
10. A rear projection screen as claimed in claim 7, wherein said pigment comprises organic material.
11. A rear projection screen as claimed in claim 7, wherein said pigment comprises inorganic material.
12. A rear projection screen as claimed in claim 2, wherein both of said crests and troughs are provided with a lens surface.
13. A rear projection screen as claimed in claim 1 or 2 wherein said trough portions have a concave surface.
14. A rear projection screen as claimed in claim 1 or 2 wherein said trough portions have a convex surface.
15. A rear projection screen as claimed in claim 1 or 2 wherein said flank has a generally straight, flat surface.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP51194/81 | 1981-04-07 | ||
| JP56051194A JPS57165830A (en) | 1981-04-07 | 1981-04-07 | Lenticular lens for screen |
| JP56090544A JPS57205727A (en) | 1981-06-12 | 1981-06-12 | Renticular lens for screen |
| JP90544/81 | 1981-06-12 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1181272A true CA1181272A (en) | 1985-01-22 |
Family
ID=26391729
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000400430A Expired CA1181272A (en) | 1981-04-07 | 1982-04-05 | Rear projection screen |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US4418986A (en) |
| EP (2) | EP0166262B1 (en) |
| CA (1) | CA1181272A (en) |
| DE (2) | DE3280211D1 (en) |
| DK (1) | DK156019C (en) |
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| CN101470221B (en) * | 2007-12-26 | 2011-01-19 | 颖台科技股份有限公司 | Diffusion plate and backlight module using the same |
| US9557445B2 (en) | 2015-02-24 | 2017-01-31 | Arkema France | Optical diffusion blend materials for LED lighting |
| EP3262461A4 (en) | 2015-02-24 | 2018-10-03 | Arkema France | High efficiency diffusion lighting coverings |
Family Cites Families (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2510344A (en) * | 1945-03-17 | 1950-06-06 | Rca Corp | Viewing screen |
| US2529701A (en) * | 1947-05-13 | 1950-11-14 | Rca Corp | Rear projection viewing screen |
| GB656651A (en) * | 1947-05-13 | 1951-08-29 | Rca Corp | Improvements in rear projection viewing screen |
| US2738706A (en) * | 1952-04-04 | 1956-03-20 | Jr Harvey A Thompson | Back-lighted projection screens |
| US2870673A (en) * | 1954-11-26 | 1959-01-27 | Schwesinger Gerhard | Lenticulated rear projection screen |
| US3218924A (en) * | 1962-06-25 | 1965-11-23 | Wendell S Miller | Rear projection screen |
| US3257900A (en) * | 1963-10-25 | 1966-06-28 | Goodbar Isaac | Projection screen |
| US3279314A (en) * | 1965-10-23 | 1966-10-18 | Wendell S Miller | High contrast projection screens |
| BE792745A (en) * | 1971-12-15 | 1973-03-30 | Freen Ltd | TRANSPARENCY PROJECTION SCREEN |
| FR2276605A1 (en) * | 1974-06-28 | 1976-01-23 | Bachelot Andre | Double sided optical projection surface - improved image contrast transfer and improved luminous transfer efficiency |
-
1982
- 1982-03-31 US US06/364,193 patent/US4418986A/en not_active Expired - Lifetime
- 1982-04-05 CA CA000400430A patent/CA1181272A/en not_active Expired
- 1982-04-06 EP EP85106693A patent/EP0166262B1/en not_active Expired
- 1982-04-06 DE DE8585106693T patent/DE3280211D1/en not_active Revoked
- 1982-04-06 DE DE8282102985T patent/DE3274155D1/en not_active Expired
- 1982-04-06 EP EP82102985A patent/EP0063317B1/en not_active Expired
- 1982-04-06 DK DK158582A patent/DK156019C/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| DE3274155D1 (en) | 1986-12-11 |
| EP0166262B1 (en) | 1990-07-11 |
| DK156019C (en) | 1989-10-16 |
| DK156019B (en) | 1989-06-12 |
| DK158582A (en) | 1982-10-08 |
| US4418986A (en) | 1983-12-06 |
| DE3280211D1 (en) | 1990-08-16 |
| EP0166262A1 (en) | 1986-01-02 |
| EP0063317A1 (en) | 1982-10-27 |
| EP0063317B1 (en) | 1986-11-05 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEC | Expiry (correction) | ||
| MKEX | Expiry |