JPH0325766B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a transmissive screen, and more particularly to a transmissive screen used in a video projector or the like.

Conventional technology For products using transparent screens,
The performance of this transparent screen greatly influences the performance of the product. This is because important elements of the projected image, such as brightness, contrast, resolution, hue, and viewing area, are greatly affected by the performance of the transmissive screen. By the way, the performance of a transmission screen is greatly influenced by what kind of lenticules are formed on the surface.

FIG. 7 shows the basic configuration of a three-tube in-line color video projector 1, which is a product that uses a transmissive screen. In the same figure, 2,
3 and 4 are red, green and blue images respectively, 5, 6,
7 is a projection lens corresponding to these, and 8 is a transmission screen. Projection lights 9, 10, 11 from each projection tube 2, 3, 4 are projected onto a transmission screen 8 through lenses 5, 6, 7.
Images 3 and 4 are superimposed and formed on a transmissive screen 8. The lights 9, 10, and 11 pass through the transmission screen 8, are diffused, and are emitted in front of the transmission screen 8 as diffused light 12. A portion of the diffused light 12 enters the viewer's eyes 13, and the viewer can see the image on the transmissive screen 8. In the state shown in FIG. 7, the viewer views the image point 14 on the transmission screen 8 from the direction of the diffusion angle θ.

The transmission screen 8 is, for example, a transmission screen shown in Japanese Patent Application Laid-open No. 193436/1987, which was previously filed and published by the applicant, with a concentric Fresnel lens 15 on the back side and a concentric Fresnel lens 15 on the front side. This configuration includes a large number of lenticular units 16, which are shown enlarged in FIG.

The Fresnel lens 15 projects the projected lights 9, 10, 11.
The color video projector 1 functions to refract the light beam so that it becomes a light beam substantially parallel to the central axis Z of the color video projector 1.
However, since the projection tubes 2 and 4 are installed with opening angles φ and −φ with respect to the axis Z, the refraction states of the respective projection lights 9, 10, and 11 at the Fresnel lens 15 are different, and the As shown in the figure, the green projected light 10 is parallel to the axis Z as shown by the ray 10A and travels through the transmissive screen 8 towards the − lenticular unit 16, but the blue projected light 11
is an angle - with respect to axis Z as shown by ray 11A
Lenticular unit 1 with an inclination angle of E _B
6, the red projection light 9 is directed to the lenticular unit 16 with an angle of inclination E _R relative to the axis Z, as shown by the ray 9A.

As shown in FIG. 8, the lenticular unit 16 has inclined surfaces 17 and 18 on both sides that are inclined along the axis α with respect to the Z axis, and a circular arc surface 19 with a radius R ₁ at the center.
It has a shape consisting of circular arc surfaces 20 and 21 of radius R ₂ on both sides.

A green ray 10A parallel to the axis Z is
As shown in Figure 9B, the lenticular unit 1
It is refracted and diffused from the tip surface of 6. In the figure A,
_G is the directional characteristic of the light ray diffused by the central arcuate surface 19, _G is the directional characteristic of the ray diffused by the left and right arcuate surfaces 20 and 21, and _G is the directional characteristic of the ray that is totally reflected by the left inclined surface 17 and reflected by the left arcuate surface. 20. _G is a graph line showing the directional characteristics of the light beam that is totally reflected by the right inclined surface 18 and diffused by the right circular arc surface 21. As for the lenticular unit 16 as a whole, for the green light 10A,
It exhibits a directional characteristic shown by graph line _G , which is a combination of the above directional characteristics.

Further, the red light ray 9A tilted at an angle E _R with respect to the axis Z is diffused as shown in FIG. 10B. The directional characteristics corresponding to the above graph lines _G to _G are as shown by graph lines _R to _R , respectively. When compared with FIG. 9A, the position of graph line _R is closer to graph line _R , while graph line _R is further away from graph line _R. Also, both _R and _R are moving closer to _{the R} side. As a result, the lenticular unit 1
The directional characteristics of 6 for red light 9A are shown in the graph line.
It becomes as shown by _R.

Also, with respect to the axis Z, the above is an angle - to the main body side.
The E _B inclined blue light beam 11A is diffused as shown in FIG. 11B. The directional characteristics corresponding to the above graph lines _G to _G are as shown by graph lines _B to _B , respectively. When compared with Figure 9A, the graph line
_B is approaching graph line _B , and graph line _B
is further away from graph line _B. It is also approaching _B and _B side. As a result, the directivity characteristic of the lenticular unit 16 for the blue light beam 11A becomes as shown by graph line _B.

Problems to be Solved by the Invention Looking at the hue, which is one of the characteristics of the transmissive screen, the hue does not change depending on the viewing position (change in angle θ in Figure 7). This is required. For this, use the above graph line
It is necessary that _G , _R , and _B are approximately the same, and that when superimposed, the brightness of each light is approximately equal at each diffusion angle.

When the above graph lines _G , _R , _{and B} are superimposed, it becomes as shown in Fig. 12, and the discrepancy is noticeable. In particular, between graph lines _R and _B , the intensity of light differs greatly in the diffusion angle ranges A and B, and furthermore, the red component disappears outside the diffusion angle C, and the blue component disappears outside the diffusion angle -C. disappears. Therefore, there was a problem that the hue changed depending on the diffusion angle. The inventor has confirmed that the above-mentioned hue change cannot be improved by mixing a light diffusing substance into the material of the screen 8.

An object of the present invention is to provide a transmission screen that solves the above problems.

Means for Solving the Problems The present invention provides that the top surface of the lenticular unit is
The lenticular unit is composed of a plurality of curved surfaces, and the portions on both sides of the top surface have arcuate surfaces continuous with the rising slopes on both sides of the lenticular unit at the portions that slope downward beyond the top. The shape is as follows.

Effect When obliquely incident light is totally reflected on the rising slope and exits from the top surface, multiple curved surfaces act selectively.

The arcuate surface acts to diffuse the light rays that are totally reflected on the sloped surface and reach them at a large diffusion angle, expanding the viewing area of the transmissive screen and eliminating hue changes.

Embodiment Next, an embodiment of the transmissive screen according to the present invention will be described.

FIG. 1 shows a portion of the transmissive screen 30 on an enlarged scale. In the figure, 31 is a Fresnel lens on the back side, and 32 is a lenticular unit on the front side. On the front, this lenticular unit 32
A large number of them are arranged in series. Further, this transmissive screen 30 is used in a color video projector as shown in FIG.

Note that the transparent screen 30 is made of transparent PMMA.
It is made of (polymethyl methacrylic) resin and does not contain any light-diffusing substances.

The lenticular unit 32 has left and right rising inclined surfaces 33 and 34 inclined at an angle β with respect to the Z axis.
, the central convex curved surface 35, and the radius R ₃ on both sides of this
arc surfaces 36 and 37, arc surfaces 38 and 39 of radius R ₄ connected to the arc surfaces 36 and 37, respectively, between the arc surface 38 and the inclined surface 33, and between the arc surface 39 and the inclined surface 34. Connecting arc surface 40 with radius R ₅ ,
41, and is symmetrical with respect to the axis Z.

The shape of the top surface of this lenticular unit 32 has the following characteristics.

The inclined surfaces 33, 34 do not extend from the tops 44, 45 of the arcuate surfaces 38, 39, but are arranged on the outside of the arcuate surfaces 38, 39 so as to be continuous with the tops 44, 45. It is designed to extend from the middle of 41. That is, the top surface of the lenticular unit 32 has inclined surfaces 33, 3 at the downwardly inclined portions on both the left and right sides.
4 and continuous arcuate surfaces 40 and 41.

The convex curved surface 35 is a pointed non-arc surface such that the apex 42 is located forward of the arc 43 of radius R ₆ inscribed at both ends thereof. That is, the top surface of the lenticular unit 32 has a convex curved surface 35 in the center, which is a non-circular surface that is more pointed than a circular arc surface.
has.

The arcuate surfaces 36 and 37 are related to the inclined surfaces 33 and 34, and the rays parallel to the axis Z
For the rays that are totally reflected by the rays, the rays are within the optical path, and the rays are tilted with respect to the axis Z.
It is arranged so that it is out of the optical path for the light beam totally reflected at 34.

Next, the directivity characteristics of the lenticular unit 32 will be explained using an example in which a transmission type screen 30 is installed in place of the transmission type screen 8 shown in FIG. 7.

The green projected light 10A (A _G ~ I _G ) is parallel to the axis Z,
The red projection light 9A (A _R ~ I _R ) is at an angle E _R with respect to the axis Z.
(for example, 5 degrees), and the blue projection light 11A (A _B
~I _B ) is inclined at an angle -E _B (for example 5 degrees) with respect to the axis Z through the transmission screen 30 towards the lenticular unit 32 . Figure 2B, Figure 3B,
In FIG. 4B, A _G , A _R , A _B are rays of light directed toward the inclined surface 33, B _G , B _R , B _B are rays of light directed toward the arcuate surface 40, C _G ,
C _R , C _B are rays heading toward the arcuate surface 38, D _G , D _R , D _B
is a ray of light directed toward the arcuate surface 36, E _G , E _R , E _B is a ray of light directed toward the convex curved surface 35 , F _G , F _R , F _B is the ray of light directed toward the arcuate surface 3
7, G _G , G _R , G _B are rays heading towards the arcuate surface 39 , H _G , H _R , H _B are rays heading towards the arcuate surface 41 , I _G , I _R , I _B are rays heading towards the inclined surface 34 It is a ray of light.

First, with reference to Figure 2 A and B, the green projection light
The directional characteristics of A _G to I _G will be explained.

The rays B _G , C _G , D _G , F _G , G _G , and H _G are each arc surface 4
0, 38, 36, 37, 39, and 41, the light is refracted and diffused as shown in the figure. Arc surface 4 for direct incident light
The overall directional characteristics of 0, 38, 36, 37, 39, and 41 are as shown by graph line _G.

The light ray E _G is refracted by the convex curved surface 35 as shown in the figure, and is diffused as light rays e _G and e _G '. Here, since the convex curved surface 35 is a curved surface that is more pointed than the circular arc surface, the diffusion angle γ is larger than the conventional diffusion surface δ due to the circular arc surface 19 in FIG. 9B. As a result, the directivity of the convex curved surface 35 for directly incident light becomes as shown by the graph line _G , which is flattened compared to the directivity characteristic shown by the graph line _G in FIG. 9A.

The light ray A _G is totally reflected on the inclined surface 33 and returns to the arcuate surface 3
6, 38, 40, and here it is refracted and the angle is
It is diffused mainly in the diagonal direction of 2β. ray _G
is totally reflected by the inclined surface 34 and forms the arcuate surfaces 37, 39,
41, where it is refracted and diffused around an oblique direction of angle -2β. In particular, a part of the light ray refracted by the arcuate surface 40 is shown by a _G in Fig. 9B.
The diffusion angle ζ is considerably larger than the corresponding diffusion angle ε.
It spreads to the right. This large diffusion angle is caused by the sloped surface 33 at the downwardly sloped portion of the arcuate surface 40.
This is obtained because it is continuous. Therefore, the directional characteristics of the arcuate surfaces 36, 38, and 40 for the light beam A _G are as shown by the graph line _G.
It is centered at angle 2β and is flattened compared to the corresponding directional characteristic shown by graph line _G in FIG. 9A, extending gently to the right. Similarly, arc surface 41
A part of the ray refracted by i _G is shown in Figure 9 B.
The diffusion surface ζ is considerably larger than the corresponding diffusion angle ε.
Therefore, the arc surface 37,3
The directional characteristics for the ray _G of rays 9 and 41, as represented by the graph line _G , are flattened and shifted to the left, centering on the angle -2β, compared to the corresponding directional characteristics shown by the graph line _G in FIG. 9A. It becomes a gentle extension.

Green projection light A _G of lenticular unit 32
The directivity characteristic for ~I _G is a combination of the above angular directivity characteristics, and is represented by the graph line _G , and the corresponding graph line A in Figure 9
Compared to the one shown by _G , it extends more gently in the left and right direction.

Note that the inclined surface 3 of the lenticular unit 32
3 and 34 and the shape and dimensions of the top surface, as described above, when the projected light is parallel to the Z axis as described above, the total reflected light at the bottom of the valley of the inclined surfaces 33 and 34 is a circular arc surface. 36, 37 and the convex curved surface 35, and as will be described later, if the projected light is inclined with respect to the Z axis, the projection light will appear on the arcuate surface 36 or 37 depending on the direction of inclination. It is specified that this will not happen.

The directivity characteristics for the red projection lights A _R to I _R are as shown in FIGS. 3A and 3B. Angle E _R with respect to axis Z
_The oblique light rays _{A R} to I _R are totally reflected as _shown in FIG. Rays B _R , C _R , D _R , F _R ,
Arc surfaces 40, 38, 36, 37 for G _R , H _R ,
The directivity characteristics of 39 and 41 are shown in graph line _R in A of the same figure.
This is roughly similar to the graph line _B shifted to the right by an angle E _R . Since the convex curved surface 35 has a shape that is somewhat more pointed than the circular arc surface, the obliquely incident light ray E _R is diffused in substantially the same way as in the case of the light ray E _G , and the directivity characteristics of the convex curved surface 35 with respect to the light ray E _R are as follows. , as shown by the graph line _R , which substantially coincides with the graph line _G described above.

The light ray I _R is totally reflected on the inclined surface 34 and reaches the arcuate surface 37,
39, 41 and diffuses around the diagonal direction of angle -2β-E _R , and the light ray A _R is totally reflected on the inclined surface 33 and is not reflected on the circular arc surface 36 but on the remaining circular arc surfaces 38, 40. It is further refracted and diffused around the diagonal direction of angle 2β−E _R. A part of the reflected light from the inclined surface 34 enters the convex curved surface 35, but this light is totally reflected by the convex curved surface 35 and does not go out forward. That is, since the rays a _R and i _R with large diffusion angles are obtained, and there is no ray diffused from the circular arc surface 36,
The intensity of the diffused light ray to the right is weakened by the arcuate surface 36. As a result, the directivity characteristics for the light beams A _R and I _R become as shown by graph lines _R and _R. That is,
Although graph line _R is lower than graph line _R ,
Since the above rays a _R and i _R exist, the graph line _R moves to the right, the graph line R moves to the left, and the graph line _R moves to the left.
It becomes fully extended like _G.

Red projection light A _R of lenticular unit 32
The directivity characteristic for ~I _R is a combination of the above-mentioned directivity characteristics, and is represented by a graph line _R. As is clear from comparing this graph line _R with the corresponding graph line _R above,
It extends gently from side to side, does not have the concave portion 20a that exists in graph line _R , and has a shallow depth of the valley portion 49a, so that the left-right asymmetry is small. The reason why the left-right asymmetry becomes smaller is because the graph line _R is flattened, and the level of the graph line _R is lower than the level of the graph line _R and extends to the left.

The directivity characteristics for the blue projected lights A _B to I _B are as shown in FIGS. 4A and 4B. Angle relative to axis Z -
E _B Inclined rays A _B ~ I _B are totally reflected and refracted as shown in Figure B, resulting in an angle of −E _B , −2β+E _B or 2β+
Diffuses around the diagonal direction of E _B. This diffusion situation is left and right opposite to the situation shown in FIG. 3B, and will be briefly explained.

The directional characteristics of the arcuate surfaces 40, 38, 36, 37, 39, 41 with respect to the light rays B _B , C _B , D _B , F _B , G _B , H _B are convex with respect to the light ray E _B , as shown by graph line _B. The directional characteristics of the curved surface 35 are as shown by graph line _B. Arc surfaces 36, 38, for ray A _B
Due to the presence of ray a _B , the directional characteristics of 40 become as shown by graph line _B , and the directional characteristics of arcuate surfaces 39 and 41 with respect to ray i _B are as shown by the presence of ray i _B.
It becomes as shown by graph line _B. The directional characteristics of the lenticular unit 32 for the blue projection lights A _B to I _B are as shown by graph line _B. As is clear from a comparison with the corresponding graph line _B described above, this graph line _B extends smoothly from side to side, is free from the concave portion 20b that is present in graph line _B , and has a deep valley portion 49b. It is shallow, and there is little left-right asymmetry.

When the above graph lines _G , _R , and _B are superimposed, it becomes as shown in Fig. 5. As can be seen from the figure, graph lines _R and _B are close to each other over the entire wide diffusion angle range from angle F to -F, and graph lines _R and _B are also close to glass line _G. There is. Therefore, the above-mentioned transparent screen 3
0 is an ideal screen in which the viewing area is wide and the hue change is not noticeable even in the diffusion angle ranges A and B shown in FIG. 12, for example.

In addition, the above transparent screen 30 can be replaced with PMMA.
It is also possible to adopt a structure in which a light-diffusing substance is appropriately mixed into the resin. By doing so, the directional characteristics are further flattened or smoothed, and the screen has more ideal characteristics.

Furthermore, since the vertical directivity of the transmissive screen only needs to satisfy the viewing area of approximately ±10 degrees in practical terms, it is sufficient to mix a light-diffusing substance into the screen. Incidentally, the inclusion of a light-diffusing substance also helps prevent scintillation.

In addition, 46 in FIG. 1 is a coating, and the inclined surface 3
3 and 34. This film 46 is coated with a substance having a lower refractive index than the screen material, such as silicone resin or fluorine resin. 47 is a black film, which is formed on the above-mentioned film 46. This black coating 47 makes the transmission screen 30 have a black stripe configuration.
Image contrast is improved. Incidentally, instead of the black film described above, the V-shaped groove 48 formed between adjacent lenticular units may be filled with a black material. Here, the width W of the V-shaped groove 48 with respect to the pitch P of the lenticular unit
When the ratio of (W/P) is taken as the blackening rate, V
The depth of the grooves 48 can be increased, the blackening rate can be increased, and the contrast can be greatly improved. Further, although not shown, a transparent thin cured film is applied to the surface of the transmission screen 30 to prevent scratches.

By using the transmissive screen 30 described above in place of the transmissive screen 8 shown in FIG. 7, the color video projector 1 has good performance regarding important image-related elements such as hue, contrast, and viewing area. Become.

The above-mentioned transmission screen 30 has a Fresnel lens 31 on the back side, but when the projection distance is long and the angles φ, E _R and E _B in FIG. 7 are small,
The Fresnel lens 31 is not necessarily necessary,
The back surface may be a flat surface. Furthermore, it has been experimentally confirmed that even when this transmission screen 30 is used upside down, it exhibits practically acceptable characteristics.

FIG. 6 shows a modification of the lenticular unit 32 described above.

The lenticular unit 50 has a configuration in which the convex curved surface 35 in FIG. , there is an arc surface 5 on the left side of this
3, 54, and has arcuate surfaces 55, 56 on the right side. The portions to the right of the tops of the arcuate surfaces 53 and 54 correspond to the arcuate surfaces 36 and 38 in FIG. 1, the portions to the left correspond to the arcuate surface 40, and the portions to the left of the tops of the arci This corresponds to the arcuate surfaces 37 and 39 in the figure, and the right side portion corresponds to the arcuate surface 41. This lenticular unit 50 has substantially the same directivity characteristics as the lenticular unit 32 described above,
The detailed explanation will be omitted.

Furthermore, the fact that the transmission screen 30 can be realized as a single-piece structure as described above is easier and cheaper to manufacture than a two-piece structure of a Fresnel lens plate and a lenticular plate. In addition, in the case of a two-panel screen, an area is required for peripheral edge processing (including bonding processing), so an ineffective area of 1 cm to several cm is created outside the effective area of the screen. This does not occur with the screen 30, and products can be manufactured with dimensions close to the screen width. This is very important when several video projectors are lined up and images are connected and synthesized, as it allows the border size of the joint to be reduced.

Effects of the Invention As described above, according to the transparent screen of the present invention, on both sides of the top surface, the downwardly sloping portions are provided with a circular arc surface continuous with the rising slope surface or a convex shape similar to a circular arc surface. Since the shape has a curved surface, a part of the light rays that are totally reflected on the inclined surface and refracted toward the circular arc surface are diffused at a large diffusion angle, making it difficult to see. It is possible to expand the viewing area.

Further, the arcuate surface or the convex curved surface similar to the arcuate surface provided between both ends and substantially the center can diffuse the totally reflected light from the inclined surface.

By adding the diffusion effect of the circular arc surface provided between both ends and approximately the center to the diffusion effect of the circular arc surface continuous with the rising slope in the downwardly sloped portion, this transmission screen has a directional characteristic. For example, even if the red, green, and blue projection tubes are individually arranged in-line and the angles of light incident on the screen are different, the hue change can be improved even when the screen image is viewed from any direction. It is possible to obtain natural images that cannot be felt.

In addition to the above, by creating a shape with a non-circular surface that is sharper than the circular arc surface at the approximate center, this non-circular surface has a wider diffusion angle than the circular arc surface, further expanding the viewing area. It has the advantage of being able to be expanded and further improving hue change.

[Brief explanation of drawings]

Fig. 1 is an enlarged view of a part of an embodiment of the transmissive screen according to the present invention, and Figs. 2B and A show the diffusion situation and directional characteristics of a ray parallel to the axis Z in the lenticular unit. The corresponding figures, FIGS. 3B and A and FIGS. 4B and A, show the diffusion situation in the lenticular unit of a light ray tilted in one direction and a light ray tilted in the opposite direction with respect to the axis Z, respectively. FIG. 5 is a diagram showing the directional characteristics of the lenticular unit in relation to each other. FIG. 6 is a diagram showing a modification of the lenticular unit. FIG. 7 is a diagram showing a modification of the lenticular unit. 8 is a diagram showing the basic configuration of a three-tube in-line color video projector to which the transmission screen of the present invention can be applied; FIG. 8 is an enlarged view of the shape of the lenticular unit in FIG. 7; 9B and A, FIG. 10B and A, and FIG. 11B and A are diagrams correspondingly showing the diffusion situation and directional characteristics of green, red, and blue light in the lenticular unit of FIG. 8, respectively. FIG. 12 is a diagram showing the above-mentioned directional characteristics superimposed. 1...Color video projector, 2, 3,
4... Projection tube, 5, 6, 7... Projection lens, 13
...Viewer's eyes, 30...Transparent screen, 3
1...Fresnel lens, 32...lenticular unit, 33, 34...rising inclined surface, 35...
...Convex curved surface, 36, 37, 38, 39, 40,
41... Arc surface, 42, 44, 45... Top, 4
6... Coating, 47... Black coating, 48... V-shaped groove, 49a, 49b... Valley portion.

Claims (1)

[Scope of Claims] 1. A tapered lenticular unit in which the front surface from which the incident light from the back side is emitted, the rising inclined surfaces on both sides serve as total reflection surfaces for the incident light, and the top surface serves as the emission surface. In a transmission type screen formed by a plurality of consecutively arranged transmission screens, the top surface of the lenticular unit is configured by five or more curved surfaces arranged in a row, and the curved surfaces located at both ends of the top surface are curved in a downwardly sloping portion. A circular arc surface continuous with the rising inclined surface or a convex curved surface similar to a circular arc surface, and one or more curved surfaces located approximately in the center of the top surface have their tops inscribed at both ends of the curved surface. It is a convex non-arc surface that protrudes forward from the arc of a circle, and the one or more curved surfaces located between the curved surfaces located at both ends and the curved surface located approximately at the center are arc surfaces or arcs. A transparent screen characterized by a convex curved surface that approximates a surface. 2. The transmission screen according to claim 1, wherein the rising inclined surface of the lenticular unit has a black coating. 3. The transmission screen according to claim 1, wherein the lenticular unit has a surface treated with a highly hard transparent film.