Source: http://www.google.com/patents/US20020044360?dq=5359317
Timestamp: 2017-10-18 13:19:51
Document Index: 672137801

Matched Legal Cases: ['art.\n6', 'art 15', 'art 12', 'art 17', 'art 12', 'art 12', 'art 12', 'art 15', 'art 12', 'art 15', 'art 12', 'art 15', 'art 12', 'art 12', 'art 12', 'art 15', 'art 12', 'art 15', 'art 12', 'art 12', 'art 17', 'art 12', 'art 12', 'arts 12', 'art 62', 'art 12', 'art 17', 'art 12', 'art 12', 'art 12', 'art 12', 'art 12', 'art 17', 'art 12', 'art 12', 'art 12', 'art 15', 'art 15', 'art 15', 'art 15', 'art 15', 'art 17', 'art 17', 'art 17', 'art 17', 'art 17', 'art 12', 'art 50', 'arts 12', 'art 17', 'art 12', 'art 12', 'art 13', 'art 31']

Patent US20020044360 - Lenticular lens sheet and rear projection screen - Google Patents
A lenticular lens sheet having an entrance surface and an exit surface comprises a base part, an entrance lens part forming the entrance surface and having an array of a plurality of convex lens elements capable of gathering light rays. A tinted layer is formed at least in a portion of the entrance lens...http://www.google.com/patents/US20020044360?utm_source=gb-gplus-sharePatent US20020044360 - Lenticular lens sheet and rear projection screen
Publication number US20020044360 A1
Application number US 09/939,648
Also published as EP0978758A1, EP0978758B1, US6421181, US6762883
Publication number 09939648, 939648, US 2002/0044360 A1, US 2002/044360 A1, US 20020044360 A1, US 20020044360A1, US 2002044360 A1, US 2002044360A1, US-A1-20020044360, US-A1-2002044360, US2002/0044360A1, US2002/044360A1, US20020044360 A1, US20020044360A1, US2002044360 A1, US2002044360A1
Inventors Yoshiki Yoshida, K.O. Oda, Hitomu Watanabe
Lenticular lens sheet and rear projection screen
US 20020044360 A1
1. A lenticular lens sheet having an entrance surface and an exit surface comprising:
an entrance lens part forming the entrance surface and having an array of a plurality of convex lens elements capable of gathering light rays; and
a light absorbing layer formed in light-nongathering regions in the exit surface in which light rays refracted by the convex lens elements do not gather;
wherein a tinted layer is formed at least in a portion of the entrance lens part near the entrance surface.
2. The lenticular lens sheet according to claim 1, further comprising an exit lens part formed on the exit surface and having an array of a plurality of lens elements formed respectively in light-gathering regions in which light rays refracted by the convex lens elements of the entrance lens part gather.
4. The lenticular lens sheet according to claim 1 or 2, wherein the tinted layer contains a light diffusing material.
5. The lenticular lens sheet according to claim 1, wherein the tinted layer extends along the light receiving surface of the entrance lens part.
6. The lenticular lens sheet according to claim 1, wherein the tinted layer has portions having the shape of a wedge or a flat plane, and extending from the vertices of the convex lens elements into the entrance lens part.
a lenticular lens sheet having an entrance surface and an exit surface; and
a Fresnel lens sheet disposed opposite to the entrance surface of the lenticular lens sheet facing an image light source,
wherein the lenticular lens sheet has: a base part; an entrance lens part formed on the entrance surface and having an array of a plurality of convex lens elements capable of gathering light rays; and a light absorbing layer formed in light-nongathering regions in the exit surface in which light rays refracted by the convex lens elements do not gather; the entrance lens part being provided with a tinted layer at least in a portion thereof near the entrance surface.
8. The rear projection screen according to claim 7, wherein the lenticular lens sheet further comprises an exit lens part formed on the exit surface and having an array of a plurality of lens elements formed respectively in light-gathering regions in which light rays refracted by the convex lens elements of the entrance lens part gather.
9. The rear projection screen according to claim 7, further comprising a front plate disposed opposite to the exit surface of the lenticular lens sheet;
wherein the front plate has a tinted layer formed near an entrance surface thereof or an exit surface thereof, or the front plate is entirely tinted.
10. The rear projection screen according to claim 7, wherein the lenticular lens sheet has a tinted layer formed near the exit surface thereof.
However, further increase in the black strip ratio of the foregoing conventional rear projection screen is difficult, because three color images are projected by separate projectors, such as CRTs, and the angles between the respective optical axes of the projectors are increased progressively for the reduction of the overall thickness of the rear projection television system.
The foregoing lenticular lens sheet is capable of diffusing light only in horizontal directions owing to the shape of its lenses. Therefore, the lenticular lens sheet contains optical diffusing particles(diffusing material) to diffuse light in vertical planes. The optical diffusing particles diffuse image light rays projected on the lenticular lens sheet and external light fallen on the exit surface to generate stray light rays in the lenticular lens sheet. The stray light rays thus generated deteriorates contrast in images. A means for suppressing the deterioration of contrast in images tints the entire lenticular lens sheet (body tinting), the contrast improving effect of which, however, is not necessarily satisfactory, considering reduction in transmittance attributable to tinting.
[0029]FIG. 1 is a typical perspective view of a rear projection screen employing a lenticular lens sheet in a first embodiment according to the present invention;
[0030]FIG. 2 is a fragmentary, enlarged, typical end view of the lenticular lens sheet shown in FIG. 1;
[0031]FIG. 3 is a fragmentary, enlarged, typical end view of a lenticular lens sheet in a second embodiment according to the present invention;
[0032]FIG. 4 is a fragmentary, enlarged, typical end view of a lenticular lens sheet in a third embodiment according to the present invention;
[0033]FIG. 5 is a fragmentary, enlarged, typical end view of a lenticular lens sheet of a tinted body type in a comparative example corresponding to the lenticular lens sheet in the first embodiment shown in FIG. 2 of assistance in explaining a first function of a tinted layer;
[0034]FIG. 6 is a fragmentary, enlarged, typical end view of a conventional lenticular lens sheet provided with black stripes;
[0035]FIG. 7 is a fragmentary, enlarged, typical end view of assistance in explaining a second function of a tinted layer included in the lenticular lens sheet in the first embodiment;
[0036]FIG. 8 is a fragmentary, enlarged, typical end view of a lenticular lens sheet in a comparative example corresponding to the first embodiment shown in FIG. 2 of assistance in explaining the second function of the tinted layer;
[0037]FIG. 9 is a fragmentary, enlarged, typical end view of a lenticular lens sheet in a third embodiment according to the present invention of assistance in explaining the second function of the tinted layer;
[0038]FIG. 10 is a fragmentary, enlarged, typical end view of assistance in explaining the relation between the angle of an entrance lens part included in the lenticular lens sheet in the second embodiment to a screen surface, and the incident angle of external light;
[0039]FIG. 11 is a view of assistance in explaining an optimum distribution of the thickness of a tinted layer included in the lenticular lens sheet in the first embodiment;
[0040]FIG. 12 is a graph comparatively showing light diffusing characteristics of a lenticular lens sheet in which the thickness of a tinted layer is uniform and the lenticular lens sheet in the first embodiment in which the thickness of the tinted layer decreases from a portion thereof corresponding to the vertex of an entrance convex lens element toward a portion of the same corresponding to the peripheral portion of the entrance convex lens element;
[0041]FIGS. 13A, 13B and 13C are fragmentary, enlarged, typical end views of lenticular lens sheets in fourth, fifth and sixth embodiments according to the present invention, respectively;
[0042]FIGS. 14A and 14B are fragmentary, enlarged, typical end views of lenticular lens sheets in seventh and eighth embodiments according to the present invention, respectively; and
[0043]FIGS. 15A to 15D are fragmentary, enlarged, typical end views of rear projection screens in other embodiments according to the present invention, respectively.
Referring to FIG. 2, the lenticular lens sheet 10 having an entrance surface 11 and an exit surface 14 comprises a base part 15, an entrance lens part 12 forming the entrance surface 11 and having an array of a plurality of entrance convex lens elements capable of gathering light rays, an exit lens part 17 forming the exit surface 14 and formed near a light gathering regions in which light rays refracted by the entrance convex lens elements of the entrance lens part 12 gather, ridges 18 formed in light-nongathering regions on the exit surface 14, and a light absorbing layer 19 formed on the surfaces of the ridges 18. Light rays refracted by the entrance convex lens elements of the entrance lens part 12 do not gather in the light-nongathering regions. The entrance lens part 12 is formed integrally with the base part 15. The entrance lens part 12 and the base part 15 may separately be formed and may be joined together as shown in FIG. 3. A tinted layer 13 is formed at least in a part of the entrance lens part 12 near the entrance surface 11. The tinted layer 13 has a first function to enhance contrast in images displayed on the lenticular lens sheet 10, and a second function to suppress the generation of stray light rays. Those functions of the tinted layer 13 will be described later.
Referring to FIG. 3, a lenticular lens sheet 10A in a second embodiment according to the present invention has an entrance surface 11 and an exit surface 14, and comprises a base part 15, an entrance lens part 12 having an array of a plurality of entrance convex lens elements capable of gathering light rays, and a light absorbing layer 19 formed in light-nongathering regions on the exit surface 14. Light rays refracted by the entrance convex lens elements of the entrance lens part 12 do not gather in the light-nongathering regions. The entrance lens part 12 and the base part 15 are formed separately and joined together. The entrance lens part 12 may be formed integrally with the base part 15. A tinted layer 13 is formed at least in a part of the entrance lens part 12 near the entrance surface 11. The tinted layer 13 has a first function to enhance contrast in images displayed on the lenticular lens sheet 10, and a second function to suppress the generation of stray light ray. Those functions of the tinted layer 13 will be described later.
However, the ambient light falls on the exit surf ace of the lenticular lens sheet from all directions including oblique directions. External light rays B fallen obliquely on the exit surface of the lenticular lens sheet as shown in FIGS. 2 to 4 undergo total reflection in the entrance lens part 12 and travel out of the lenticular lens sheet through the adjacent exit lens elements of the exit lens part 17 in outgoing light rays B1 and B2. As shown in FIGS. 2 to 4, light rays fallen on the entrance lens part 12 at angles of incidence greater than the critical angle go out of the lenticular lens sheet after undergoing total reflection several times (two or three times) in the entrance lens part 12. Therefore, the contrast deteriorating effect of external light can efficiently be eliminated by the tinted layers 13 formed on the surfaces of the entrance lens parts 12 forming the entrance surfaces 11 of the lenticular lens sheets 10, 10A and 10B shown in FIGS. 2 to 4, respectively.
The second function of the tinted layer 13 of each of the lenticular lens sheets 10, 10A and 10B embodying the present invention shown in FIGS. 2 to 4 is to eliminate stray light rays effectively. The second function is more effective when (1) the lenticular lens sheet has an exit lens part, and (2) the focal point of the entrance convex lens elements of the entrance lens part lie substantially on the exit surface.
Referring to FIG. 8, when image light rays C falls on a conventional lenticular lens sheet 60 provided with black stripes, image light rays C2 equal to about 4% of the incident image light rays C is reflected by the entrance lens part 62 and image light rays C1 penetrate into the lenticular lens sheet 60. Image light rays C4 equal to about 4% of the image light rays C1 are reflected by the exit lens part, and image light rays C3 travels out of the lenticular lens sheet 60. The reflected light rays C4 are reflected several times in the lenticular lens sheet 60 in stray light rays C5 and C6 and travels out of the lenticular lens sheet 60 in light rays C7, which reduces contrast in images
Image light rays A fall on the tinted layer 13 at an incident angle θ of 10°. Generally, red (R) and blue (B) image light rays fall on the lenticular lens sheet at incident angles nearly equal to 10°. As shown in FIG. 7, the image light rays A are gathered by the entrance lens element 12-1 of the entrance lens part 12 on an inclined region of the exit lens element 17-1 of the exit lens part 17 in image light rays A1. Part of the image light rays A1 reflected by the exit lens element 17-1 in image light rays A4 toward the adjacent entrance convex lens element 12-2. The image light rays A4 undergo total reflection several times in image light rays A5 and A6, and the image light rays A6 travels out of the lenticular lens sheet 10 through the next exit lens element 17-3 in image light rays A7. Therefore, stray light rays can more effectively be eliminated by forming the tinted layer 13 along the surface of the entrance lens part 12 than by tinting the entire lenticular lens sheet as shown in FIG. 8.
Referring to FIG. 9, image light rays F fall on the lenticular lens sheet 10B perpendicularly to the entrance surface 11. In the lenticular lens sheet 10B, the focal point of the entrance convex lens element 12-1 lies on the inner side of the exit lens element 17B-1. Therefore, the image light rays F fallen on a left inclined region, as viewed in FIG. 9, of the entrance convex lens element 12-1 of the entrance lens part 12 go out of the lenticular lens sheet 10B through an inclined region of the corresponding exit lens element 17B-1 in image light rays F3. Part of image light rays F1 penetrated into the lenticular lens sheet 10B equal to about 4% of the image light rays F1 are reflected by the exit lens element 17B-1 in image light rays F4 toward the adjacent entrance convex lens element 12-2. The reflected image light rays F4 are reflected repeatedly in a total reflection mode by the entrance convex lens element 12-2 in image light rays F5, F6 and F7, and go out of the lenticular lens sheet 10B through the next exit lens element 17B-3 in image light rays P8.
[0069]FIG. 10 illustrates conditions for reflecting the external light rays B at least twice by the single entrance convex lens element of the entrance lens part 12. The conditions are expressed by:
φ=(π/4)−arcsin[(sin θ)/n]
where n is the refractive index of the material forming the lenticular lens sheet 10A, φ is the angle of a tangent line to the entrance convex lens element of the entrance lens part 12 at a point where the external light rays B fall to a line parallel to the entrance surface 11, and θ is the incident angle of the external light rays B incident on the exit surface 14.
If the angle φis not smaller than an angle φ90=(π/4)−arcsin[(sin 90°)/n]=(π/4)−arcsin (1/n), the effect of the present invention is available.
Method of Forming Tinted Layer
More concretely, it is preferable that the tinted layer 13 is colored in a color density such that the transmittance of each of the lenticular lens sheets 10, 10A and 10B is in the range of 40% to 70%. Whereas the transmittance to the image light rays increases, the intensity of the external light rays reflected in a total reflection mode by the entrance lens part 12 toward the exit surface 14 increase to deteriorate contract in images if the tinted layer 13 is tinted in a low color density such that the transmittance of the lenticular lens sheet is greater than 70%. The transmittance to the image light rays decreases and the relative intensity of the external light rays reflected by the exit lens part 17 increases to deteriorate contrast in images if the tinted layer 13 is tinted in a high color density such that the transmittance of the lenticular lens sheet is smaller than 40%.
Table 1 shows the relation between the transmittance of the lenticular lens sheet 10 in the first embodiment shown in FIG. 2 and contrast in images. Test lenticular lens sheets similar in construction to the lenticular lens sheet 10 shown in FIG. 2 and respectively having tinted layers 13 of different color densities were made, and the transmittance and the reflectance of the test lenticular lens sheets were measured by a haze meter (HR-100 available from Murakami Shikisai Gijutsu Kenkyu-sho), in which the incident angle of image light rays was 45°. Measured values of the transmittance, the reflectance and the transmittance/reflectance ratio are tabulated in Table 1.
Transmittance (%) 45 53 61 68 76
Reflectance (%) 5.0 5.4 5.6 5.8 8.5
Transmit- 9.0 9.8 10.9 11.7 8.9
The lenticular lens sheet 10 do not absorb external light rays reflected by the exit surface 14 on the viewing side. Therefore, the transmittance/reflectance ratio decreases as the color density increases to decrease the transmittance. Accordingly, it is preferable to tint the tinted layer 13 in a color density such that the transmittance is in the range of 40% to 70%.
When the transmission LCD is used as an image light source, the reduction of the transmittance is limited because the output capacity of the transmission LCD is not very large Therefore, it is preferable that the tinted layer 13 is tinted in a color density such that the transmittance is in the range of 45% to 60%.
Preferably, the thickness t2 of a portion of the tinted layer 13 corresponding to a peripheral portion of the convex lens element of the entrance lens part 12 is smaller than the thickness t1 of a portion of the same corresponding to a central portion of the convex lens element (t1>t2) in FIG. 11. If the tinted layer 13 is formed in a uniform thickness, the length of image light rays incident on a peripheral portion 12 b of the entrance convex lens element of the entrance lens part 12 is greater than that of the optical path of image light rays incident on the vertex 12 a of the entrance convex lens element of the entrance lens part 12. Consequently, the image light rays incident on the peripheral portion 12 b are absorbed more greatly than those incident on the vertex 12 a, and the intensity of image light rays diffused in the range of a diffusion angle in the range of 30° to 40° is reduced.
[0087]FIG. 12 is a graph comparatively showing light diffusing characteristics of a lenticular lens sheet in which the thickness of the tinted layer of the lenticular lens sheet is uniform and the lenticular lens sheet 10 in the first embodiment in which the thickness of the tinted layer decreases from a portion thereof corresponding to the vertex of an entrance convex lens element toward a portion thereof corresponding to the peripheral portion of the entrance convex lens element. In the lenticular lens sheet 10, the thickness of a portion of the tinted layer 13 corresponding to the peripheral portion of the entrance convex lens element is smaller than that of a portion of the same corresponding to the vertex of the entrance convex lens element. Therefore, the reduction of the intensity of the outgoing image light rays diffused in a range of a diffusion angle in the range of 30° to 40° can be suppressed.
The light diffusing material may be dispersed not only in the tinted layer 13 but may also be dispersed in the baser part 15. It is preferable that the light diffusing material concentration of the base part 15 is small because the external light rays are diffused before reaching the tinted layer 13 by the base part 15 and reflected toward the exit surface if the light diffusing material concentration of the base part 15 is large. Preferably, the light diffusing material concentration C1 of the tinted layer and the light diffusing material concentration C1 of the base part 15 meet an inequality: 0≦C0<C1.
In each of the lenticular lens sheets 10, 10A and 10B embodying the present invention and shown in FIGS. 2 to 4, the surface of the exit lens part 17 forming the exit surface 14 (the surface near light-gathering regions in the case of the lenticular lens sheet 10A shown in FIG. 3) is either a smooth surface or a matte surface. If the surface of the exit lens part 17 is a smooth surface, images displayed on the lenticular lens sheet gives a clear sensation, any transparent flat panel need not be disposed in front of the rear projection screen, and images can be displayed in a satisfactory picture quality because images are not spoiled by the reflection of matters reflected by the entrance surface 11 on the flat panel. When the surface of the exit lens part 17 forming the exit surface 14 (the surface near light-gathering regions in the case of the lenticular lens sheet 10A shown in FIG. 3) is a smooth surface, an antireflection layer, a low-reflection layer and/or a polarizing filter layer may be formed on the surface of the exit lens part 17 (the surface near light-gathering regions in the lenticular lens sheet 10A shown in FIG. 3) to enhance contrast in images. A hard coating layer, an antiglare layer and/or an antistatic layer may be formed on the surface of the exit lens part 17.
[0097]FIGS. 13A, 13B and 13C show lenticular lens sheets 10C, 10D and 10E in fourth, fifth and sixth embodiments according to the present invention, respectively. Each of the lenticular lens sheets 10C, 10D and 10E has an entrance lens part 12 formed of a tinted ultraviolet curable resin on a base part 50.
[0101]FIGS. 14A and 14B show lenticular lens sheets 10F and 10G in seventh and eighth embodiments according to the present invention, respectively. The lenticular lens sheets 10F and 10G have entrance lens parts 12 including entrance convex lens elements provided in portions around vertices thereof with tinted layers 13F and 13G, respectively.
[0105]FIGS. 15A to 15D show rear projection screens 1A, 1B, 1C and 1D in other embodiments according to the present invention, respectively. Each of the rear projection screens 1A, 1B, 1C and 1D employs the lenticular lens sheet 10, 10H, and a front panel 30A, 30B, 30C and 30D disposed on the exit side of the lenticular lens sheet 10.
Most lenticular lens sheets are formed of a material containing a light diffusing material to provide the lenticular lens sheets with a vertical diffusion characteristic. Part of image light rays is diffused in stray light rays and the stray light rays goes out of the lenticular lens sheet through exit lens elements other than intended ones. In the lenticular lens sheet 10 shown in FIG. 2, some of the external light rays B incident on the exit lens part 17 goes out of the lenticular lens sheet 10 through the entrance lens part 12 without being reflected in a total reflection mode by the entrance lens part 12.
The rear projection screen 1D shown in FIG. 15D has a lenticular lens sheet 10B similar in construction to the lenticular lens sheet 10 and provided with a tinted exit lens part 13H forming an exit surface 14. The rear projection screen 1D is constructed by disposing a front panel 30D formed entirely of a transparent base part 31D in front of the lenticular lens sheet 10H. The front panels 30A, 30B, 30C and 30D may be provided with functional layers, such as an antireflection layer, a low-reflection layer, a polarizing filter layer, an antistatic layer, a glareproof layer and/or hard coating layer.
Lenticular lens sheets with black stripes in Example, Comparative examples 1 and 2 were made. The lenticular lens sheets were similar in construction to the lenticular lens sheet 10 shown in FIG. 2. In each of the lenticular lens sheets in Example, Comparative examples 1 and 2, the pitch of the lenticular lenses of the entrance lens part was 0.72 mm, the distance between the entrance lens part and the exit lens part was 0.87 mm, the lenticular lenses of the entrance and the exit lens part were convex lenticular lenses, and the black strip ratio was 50%. The lenticular lens sheet in Example was provided with a tinted layer of 0.14 mm in thickness. The lenticular lens sheet in Comparative example 1 was provided with a lightly tinted layer, and the lenticular lens sheet in Comparative example 2 was not provided with any tinted layer. The properties of the lenticular lens sheets were measured. Measured results are tabulated in Table 2.
Example Ex. 1 Ex. 2
Transmittance (%) 68 76 67
Reflectance (%) 6.8 8.5 7.0
Transmittance/ 11.7 8.9 9.5
Contrast 56 49 53
Bright room 0° 5.7 5.8 5.7
luminance (TV-OFF) 40° 5.7 6.9 6.3
Bright room luminance (TV-OFF) is the luminance of a central region of the rear projection screen measured from directions at 0° and 40° to the rear projection screen in a bright room with the illuminating fluorescent lamps of the room turned on and the television projector disconnected from the power source. Since the television projector is disconnected from the power source, the bright room luminance is a measurement of the intensity of ambient light reflected from the rear projection screen. The lenticular lens sheets in Example and Comparative examples 1 and 2 are scarcely different from each other in the reflection of the ambient light in the 0°-direction. The reflection of the ambient light in the 40°-direction by the rear projection screen provided with the lenticular lens sheet in Example is smaller than that by the rear projection screens respectively provided with the lenticular lens sheets in Comparative examples 1 and 2.
Although the invention has been described in its preferred embodiments with a certain degree of particularity, obviously many changes and variations are possible therein.