JP2006145881A - Reflection type projection screen - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reflection type projection screen where the effect of external light is lessened, efficiency of light is improved, and configuration is made simple. <P>SOLUTION: The reflective projection screen includes, in order from the side of a light source such as a projector 4 for projecting projection light 5: a diffusing plate 2 having at least a transmission diffusion face 2a for turning transmission light into diffusion light; and a corner cube array 3, by which the light transmitted through the diffusing plate 2 is reflected to a position which is almost the same as the transmitting position of the transmission diffusion face 2a. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a reflective projection screen. For example, the present invention relates to a reflective projection screen that can be suitably used for a front projector system that reflects a projection light of a projector, a projector, or the like arranged on the viewer's side so that an image can be viewed.

Conventionally, when viewing images such as movies and still images on a screen with a projector or projector, for example, if the room is bright, the outside light is reflected on the screen and the contrast of the image deteriorates, making it difficult to view. There was a problem. In order to improve this, a reflection type projection screen with improved reflection characteristics has been proposed.
For example, Patent Document 1 includes a mat layer including an organic spherical filler and a metal thin film layer, a reflection luminance of white light is 10% or more, and a half value angle of the reflection luminance is 30 ° or more. The screen is listed.
Patent Document 2 discloses a reflective screen provided with a bead diffusion layer, a cholesteric liquid crystal (CLC) layer, and a light shielding layer from the light source side, and a CLC layer and a CLC layer from the light source side to form a diffuse reflection surface. A substrate for forming irregularities, a reflective screen provided with a light shielding layer, a CLC layer from the light source side, a substrate for forming irregularities for the CLC layer to form a corner cube structure, a reflective screen provided with a light shielding layer, Is described.
In Patent Document 3, a color filter, a scattering liquid crystal layer that can be switched between reflection and scattering, and a corner cube reflector are provided from the light source side. By switching the scattering liquid crystal layer between reflection and scattering, recursion is performed. There is described a display device having a corner cube array that realizes only a state in which light reflected from a light source is blocked and a state in which light emitted from a light source is scattered and reflected.
Further, Patent Document 4 includes a corner cube mirror in which two reflecting surfaces are concave curved surfaces, thereby diffusing the light reflected by the concave curved surface and providing a reflection directionality that is narrow in the vertical direction and wide in the horizontal direction. A reflective screen having a retroreflective characteristic is described.
JP-A-6-148747 (page 2-3) JP 2003-287818 A (page 5-16, FIGS. 1, 6, and 7) Japanese Patent Laying-Open No. 2003-195788 (page 5-10, FIGS. 4 and 15) Japanese Patent Laid-Open No. 5-150368 (page 2-4, FIG. 1-5)

However, the conventional reflective projection screen as described above has the following problems.
In the technique described in Patent Document 1, although the reflection luminance is 10% or more, which is slightly improved as compared with the conventional technique, it cannot be said that the light utilization efficiency is sufficiently improved. Therefore, there is a problem that a high output light source is required.
In the technique described in Patent Document 2, although the light use efficiency can be improved by providing the CLC layer, it is necessary to control the layer thickness and orientation direction of the CLC layer over the entire screen. There is a problem of becoming. Therefore, it is a technique that is difficult to apply to a large projection screen.
Further, the technology described in Patent Document 3 describes a display device that can switch between retroreflection and scattering reflection using a corner cube reflector and a scattering type liquid crystal layer, and is applied to a reflection type projection screen. There is a possibility that the light utilization efficiency can be improved. However, since it is necessary to arrange the scattering type liquid crystal layer on the back side of the corner cube reflector and to electrically control the scattering type liquid crystal layer, there is a problem that the configuration becomes very expensive.
Further, in the technique described in Patent Document 4, although a concave curved surface is provided on the corner cube mirror, light having a relatively high directivity can be reflected in the incident direction, but an accurate concave curved surface shape is processed on the corner cube mirror. Therefore, there is a problem that a very expensive reflective screen is required.
Further, if the processing error of the concave curved surface is bad, there is a problem that the image is disturbed and high image quality cannot be obtained.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a reflective projection screen that can reduce the influence of external light, improve light utilization efficiency, and can be simply configured.

In order to solve the above-mentioned problems, in the invention described in claim 1, a reflection type projection screen that diffuses and reflects projection light from a light source, at least a transmission diffusion surface that uses transmission light as diffusion light, and the light source And a corner cube group that is disposed on the rear surface side of the transmission diffusion surface as viewed from the side and reflects the projection light transmitted through the transmission diffusion surface toward the transmission diffusion surface.
According to the present invention, when the projection light is imaged on the transmission diffusion surface, the light transmitted through the transmission diffusion surface is converted into the diffusion light and is incident on the corner cube group. Since the corner cube group is a retroreflective element, the diffused light is reflected in the direction of 180 ° with respect to the direction incident on the corner cube group, and is incident again at substantially the same position on the transmission diffusion surface. And when this transmitted light permeate | transmits a diffuse transmission surface, each is diffused again and is radiate | emitted to the light source side. Therefore, the image of the projection light can be viewed within the angle range where the diffused light spreads.
On the other hand, since external light incident from a direction different from the direction of the light source is substantially retroreflected in the incident direction, it does not interfere with viewing without being mixed with the image of the projection light.
Further, since the transmitted light is transmitted twice through the transmission diffusion surface, it is possible to form diffusion light that spreads over a relatively wide range even if the degree of diffusion per transmission diffusion surface is small. Therefore, it is possible to reduce light quantity loss during the diffusion process and easily realize diffuse light with strong directivity.
Further, since the reflecting surface is composed of the corner cube group, the light loss can be reduced and the light utilization efficiency can be improved as compared with the case where the reflecting diffusion surface is arranged.

  Here, the corner cube group is a group of corner cubes arranged side by side without a gap or with a minute interval.

According to a second aspect of the invention, in the reflective projection screen according to the first aspect, when light having wavelengths λ _B = 485 nm, λ _G = 550 nm, and λ _R = 650 nm is incident, the following formula is satisfied. To do.
0.8 ≦ (R _B / I _B ) / (R _G / I _G ) ≦ 1.25 (1)
0.8 ≦ (R _R / I _R ) / (R _G / I _G ) ≦ 1.25 (2)
_{Here, I B, I G, I} R are each wavelength lambda _B, lambda _G, the incident intensity of light _{λ R, R B, R G} , R R are each wavelength lambda _B, lambda _G, lambda _This is the emission intensity of _R light.
According to the present invention, λ _B , λ _G , and λ _R are selected as wavelengths representing the three primary colors of blue, green, and red, and the ratio (reflectance) of the output intensity to the respective incident intensities is expressed by equation (1). Therefore, the reflectance representing blue and red is set in a range close to 1 with respect to the reflectance representing green. Therefore, since the balance of the reflectance representing blue, green and red of the projection light becomes good, a reflective projection screen with excellent color reproducibility can be obtained.

  It goes without saying that the expressions (1) and (2) may be established for an arbitrary incident angle, but it is sufficient that the expressions (1) and (2) are established within a range of incident angles provided for actual use. For example, it is sufficient if the incident angle is in the range of 45 ° with respect to the normal line of the transmission diffusion surface, and in some cases, the range may be 30 ° or 20 °.

In order to realize better color reproducibility, it is preferable that the ranges of the formulas (1) and (2) are narrower. For example, it is more preferable to set within the range of the following formula.
0.9 ≦ (R _B / I _B ) / (R _G / I _G ) ≦ 1.15 (1a)
0.9 ≦ (R _R / I _R ) / (R _G / I _G ) ≦ 1.15 (2a)

According to a third aspect of the present invention, in the reflective projection screen according to the first or second aspect, when light having wavelengths λ _B = 485 nm, λ _G = 550 nm, and λ _R = 650 nm is incident on the transmission diffusion surface. The structure satisfies the following formula.
0.5 ≦ R _B / I _B ≦ 1 (3)
0.5 ≦ R _G / I _G ≦ 1 (4)
0.5 ≦ R _R / I _R ≦ 1 (5)
_{Here, I B, I G, I} R are each wavelength lambda _B, lambda _G, the incident intensity of light _{λ R, R B, R G} , R R are each wavelength λ _B, λ _G, λ _This is the emission intensity of _R light.
According to the present invention, λ _B , λ _G , and λ _R are selected as wavelengths representing blue, green, and red, and the output intensity with respect to each incident intensity satisfies the expressions (3) to (5). Therefore, a bright image can be obtained.

  It goes without saying that the expressions (3) to (5) may be established for an arbitrary incident angle, but it is sufficient that the expressions (3) to (5) are established within a range of incident angles provided for actual use. For example, it is sufficient if the incident angle is in the range of 45 ° with respect to the normal line of the transmission diffusion surface, and in some cases, the range may be 30 ° or 20 °.

According to a fourth aspect of the present invention, in the reflective projection screen according to any one of the first to third aspects, the corner cube group is constituted by a prism group.
According to the present invention, the reflecting surface of the corner cube can be used as the internal reflecting surface, so that the reflecting surface can be easily formed. Moreover, depending on use conditions, it can be used as a total reflection surface. In that case, good reflectance can be obtained without applying a mirror coat or the like. For this reason, the light utilization efficiency can be improved, and it can be manufactured inexpensively and easily.

According to a fifth aspect of the present invention, in the reflective projection screen according to the fourth aspect, the incident surface of the prism group also serves as the transmission diffusion surface.
According to the present invention, since the incident surface of the prism group also serves as a transmission diffusion surface, the number of parts can be reduced. Further, since there is no optical surface between the transmission diffusion surface and the internal reflection surface of the prism group, the light amount loss can be reduced.

According to a sixth aspect of the present invention, in the reflective projection screen according to any of the first to fourth aspects, the light-transmitting surface has the transmission diffusion surface formed on one surface and a smooth flat surface or curved surface formed on the other surface. A diffusion element is provided, and the other surface of the diffusion element is arranged facing the light source side.
According to the present invention, the light transmissive diffusing element having the transmission diffusing surface on one surface and the smooth surface or the curved surface on the other surface is disposed with the other surface facing the light source side. The diffusion surface can be configured not to be exposed to the light source side. Therefore, it is possible to prevent dust, dirt, and the like from attaching to the transmission diffusion surface from the outside.
Further, even if dust, dirt, or the like adheres to the smooth flat surface or curved surface exposed to the light source side, it can be easily wiped off and cleaned. Therefore, even if the transmission diffusion surface is configured as a fine uneven surface that is easy to manufacture, it can be configured to be resistant to dust and dirt.

Here, the smooth flat surface or curved surface may be smooth to such an extent that dirt is difficult to adhere and cleaning is easy even if it adheres.
In order to make it more difficult to get dirty, it is preferable to apply an antistatic coating to a smooth flat surface or curved surface.

According to a seventh aspect of the present invention, in the reflective projection screen according to any one of the first to sixth aspects, the corner cube group is a corner cube formed of one corner cube or a plurality of corner cubes integrally formed. A structure in which a plurality of units are joined is used.
According to the present invention, since the corner cube group is formed by joining a plurality of corner cube units, a large screen can be easily produced by joining small corner cube units that are easy to produce.
Here, one corner cube means a member having three reflecting surfaces that function as a corner cube.

  In this case, for the convenience of assembling and positioning, it is preferable that each corner cube unit has an uneven shape that fits in the joint portion. In particular, it is preferable that the corner cubes have a divided shape in which the outer shapes fit each other.

In the invention according to claim 8, in the reflection type projection screen according to any one of claims 1 to 7, the corner cube constituting the corner cube group is subjected to a light shielding process on adjacent ridge line portions. And
According to this invention, since the light shielding process is performed on the ridge line part adjacent to the corner cube, the light scattering at the ridge line part is prevented, and the deterioration of the image quality due to the scattered light can be prevented. Although this light-shielding portion is long, it has a small area and therefore has little light loss.

In the invention according to claim 9, in the reflective projection screen according to any one of claims 1 to 8, when the transmission diffusion surface is an uneven surface, the pitch of the uneven surface is that of the corner cube group. The pitch is smaller than the corner cube vertex pitch.
According to this invention, since the pitch of the concavo-convex surface of the transmission diffusion surface is smaller than the pitch of the apex of the corner cube, a plurality of concavo-convex surfaces are positioned with respect to one corner cube. For this reason, deterioration in resolution is suppressed, and a high-quality reflective projection screen can be obtained.
In order to obtain higher resolution, it is preferable that the pitch of the concavo-convex surface of the transmission diffusion surface is smaller than 1/3 of the pitch of the apex of the corner cube.

  According to the reflection type projection screen of the present invention, the corner cube group and the transmission diffusion surface have a relatively simple configuration, and the influence of external light incident from a direction different from the direction of the light source is caused by the retroreflective of the corner cube group. In addition to being able to be removed, the diffused light that has passed through the transmissive diffusion surface is reflected at substantially the same position by the corner cube group and emitted to the light source side, so that the light utilization efficiency can be improved.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In all the drawings, even if the embodiments are different, the same or corresponding members are denoted by the same reference numerals, and common description is omitted.
A reflective projection screen according to an embodiment of the present invention will be described.
FIG. 1A is a schematic explanatory view in a side view for explaining a schematic configuration of a projector system using a reflective projection screen according to an embodiment of the present invention. FIG. 1B is a partially enlarged view for explaining the configuration of the reflective projection screen according to the embodiment of the present invention. 2A and 2B are a schematic plan view and a cross-sectional view taken along line AA for explaining the schematic configuration of the corner cube group according to the embodiment of the present invention. However, in FIG. 2A, all the ridge lines are shown as solid lines in order to also explain the planar arrangement of a reflector-type corner cube group described later. Moreover, the black circle in a figure shows the vertex of the recessed part depressed in the paper surface back | inner side.

As shown in FIG. 1A, the reflective screen 1 (reflective projection screen) of the present embodiment reflects an image when an appropriate image is projected as projection light 5 by a projector 4 (light source), for example. It can be suitably used as a projection screen for a front projector system or the like that reflects the light 6 toward the light source and allows the viewer 7 to view the image.
The schematic configuration of the reflective screen 1 is composed of a diffusion plate 2 (diffuse element) and a corner cube array 3 (corner cube group), which are arranged in this order from the light source side (the right side in the figure) while maintaining a constant spacing therebetween. ing.

As shown in FIG. 1 (b), the diffuser plate 2 has a light diffusing surface 2 a that diffuses and transmits incident light on the light source side, and transmits light on the side opposite to the light source facing the corner cube array 3. Is a plate member having a substantially rectangular shape in plan view, on which a transmission surface 2b for emitting light is formed. The shape of the diffusing plate 2 may be a flat plate or may be slightly curved so that it can be easily appreciated.
As a material of the diffusion plate 2, for example, a synthetic resin, a glass plate, or the like can be adopted.
The transmission diffusing surface 2a is light transmissive and may be formed in any way as long as the transmitted light is diffused. For example, the transmission diffusing surface 2a is manufactured by forming fine irregularities on the surface by mat relief processing or the like. be able to.
Moreover, you may form by sticking the permeation | transmission diffusion sheet formed in the shape of a thin layer sheet on a transparent flat plate.
Further, a light-transmitting fine powder having a refractive index different from that of the substrate material may be provided on the surface or dispersed within the plate thickness. In the latter case, strictly speaking, the transmission diffusion surface is not formed. However, when the thickness of the diffusion plate 2 is thin, it can be regarded that the transmission diffusion surface is approximately formed at the center of the plate thickness.
The transmission surface 2b preferably has a high transmittance in order to improve the light utilization efficiency, and an antireflection coating may be applied as necessary.

As shown in FIGS. 2A and 2B, the corner cube array 3 is provided with a flat plate portion 3B on the bottom surface side of a triangular pyramid portion 3A in which three reflecting surfaces 3b are orthogonal to each other and the bottom surface forms an equilateral triangle. The plurality of corner cube prisms 30 that are formed are plate-like members that are arranged so that adjacent ridge line portions 3d that are ridge lines on the bottom surface of each triangular pyramid portion 3A are adjacent to each other. The size in plan view is substantially the same as that of the diffusion plate 2.
On the diffusion plate 2 side of the flat plate portion 3B, an incident surface 3a is formed that is disposed substantially parallel to the transmission surface 2b of the diffusion plate 2.

In order to achieve such an arrangement, when the shortest distance between the apexes 3c of the adjacent corner cube prisms 30 is expressed as a pitch L _C , the length of the adjacent ridge line portion 3d is expressed as L _T and is expressed by the following equation.
L _C = 2 · L _T / √3 (6)
Pitch L _C is a bore diameter of the bottom surface of the triangular pyramid portion 3A, and has a substantial size of the representative values of the corner cube prism 30.
The size of the L _C can be set according to the required resolution. For example, in order to set a resolution for resolving a pattern in which a black line having a width W and a white line having a width W are interchanged on the reflective screen 1, it is necessary to satisfy the following equation.
L _C <W (7)
Even if the expression (7) is satisfied, the range of the diffusion region of the diffusion plate 2 is large, and if the diffusion is performed in a range exceeding the size of the corner cube prism 30, the resolution is lowered. Therefore, it is preferable to satisfy the following expression, where L _d is the pitch of the unevenness of the diffusion plate 2.
L _C > L _d (8)
In order to improve the resolving power, L _d is preferably even smaller, and more preferably satisfies the following formula.
L _c > 2 · L _d (8a)

Such a corner cube array 3 is formed, for example, by cutting a metal from three directions to form a triangular pyramid mold, molding a transparent synthetic resin material having a refractive index greater than 1, and forming a mold shape. Can be produced by transferring.
Further, the transparent substrate can be manufactured by etching by a photolithography process.
When the corner cube array 3 is manufactured, a corner cube unit obtained by dividing the corner cube array 3 into several parts may be manufactured and joined at the boundary. In this way, it becomes easy to manufacture a large corner cube array 3. In addition, for example, when a mold is manufactured, there is an advantage that the mold can be easily manufactured and a highly accurate mold can be manufactured.

An example of such a corner cube unit will be described with reference to FIG.
FIG. 3 is a schematic plan view for explaining an example of the corner cube unit according to the embodiment of the present invention.
The corner cube unit 31 is formed by integrally molding 32 corner cube prisms 30 and has a joint surface formed so that the entire outer shape passes through the adjacent ridgeline portion 3d.
In the outer shape, concave and convex shapes such as a concave fitting portion 31A, a convex fitting portion 31B, a concave and convex fitting portion 31C, and a concave and convex fitting portion 31D are formed. As the fitting portion 31C and the uneven fitting portion 31D, the adjacent corner cube units 31 are fitted together in a plane to be positioned.
By forming such an outer shape having a concavo-convex shape, there is an advantage that when the corner cube unit 31 is joined, assembly and positioning are facilitated, and even the large reflective screen 1 can be easily manufactured.

Note that the outer shape and size of the corner cube unit 31 are merely examples, and can be modified as necessary.
Further, all of the corner cube array 3 may be configured by the same shape corner cube unit 31 or may be combined with different shapes.
If necessary, a single corner cube prism 30 may be used as a corner cube unit.

The reflective screen 1 satisfies the expressions (1) and (2) by appropriately setting the wavelength dependence of the transmission characteristics and reflection characteristics of the diffuser plate 2 and the corner cube array 3 in order to maintain good color reproducibility. A configuration is preferable. For example, the wavelength characteristics of transmittance and reflectance can be controlled by applying a multilayer coating to the transmission surface 2b and the reflection surface 3b.
Then, in the reflection screen 1, the reflectances of wavelengths λ _B and λ _R representing blue and red, respectively, are set to be substantially equal to the reflectance of wavelength λ _G representing green. Reflective characteristics can be obtained. Therefore, the color reproducibility is good.
In order to obtain better color reproducibility, it is more preferable to satisfy the expressions (1a) and (2a).

  In addition, in order to appreciate a bright image of the projection light 5, it is preferable that the reflectivity of each of blue, green, and red is high. For example, the transmission characteristics and reflection characteristics of the diffuser plate 2 and the corner cube array 3 depend on the wavelength. It is preferable to satisfy the expressions (3), (4) and (5) by appropriately setting the properties. For example, the wavelength characteristics of transmittance and reflectance can be controlled by applying a multilayer coating to the transmission surface 2b and the reflection surface 3b.

Next, the effect | action of the reflective screen 1 of this embodiment is demonstrated.
FIG. 4A is a schematic explanatory diagram for explaining the operation of the reflective projection screen according to the embodiment of the present invention. FIG. 4B is a schematic explanatory diagram for explaining the directivity of the reflective projection screen according to the embodiment of the present invention. FIG. 4C is a schematic graph for explaining the light intensity distribution of the reflected light in FIG. The horizontal axis of the graph is the reflection angle, and the vertical axis is the light intensity.

As shown in FIG. 4A, it is assumed that the projection light 5 represented by one light beam enters the point P on the transmission diffusion surface 2a at an incident angle θ.
When the projection light 5 is incident on the transmissive diffusion surface 2a, if the antireflection coating is not applied to the transmissive diffusion surface 2a, the projection light 5 is reflected while being partially diffused.
Other light passes through the transmission diffusion surface 2a and enters the corner cube array 3 as diffused light 50 that diffuses in the range of, for example, angles φ ₁ and φ ₂ with respect to the optical axis.
Since the reflecting surfaces 3b of the corner cube array 3 are orthogonal to each other, the diffused light 50 is retroreflected. That is, regardless of the incident angle, the light is reflected in the direction of 180 ° with respect to the incident direction and returns to the substantially diffused position. Accurate to return to a position slightly shifted from the point P in plan view, since the pitch L _C representing the size of the corner cube prism 30 is set sufficiently small, the amount of deviation is negligible.
Therefore, as shown in FIG. 4A, the point P may be approximated. That is, the diffused light 50 re-enters the point P within an incident angle range of (θ + φ ₁ ) to (θ−φ ₂ ). Then, each light beam is again subjected to the diffusing action of the transmissive diffusion surface 2a, and the screen reflected light in an angle range (θ + θ ₂ ) to (θ−θ ₁ ) slightly wider than (θ + φ ₁ ) to (θ−φ ₂ ). The process proceeds to the light source side (right side in the figure) as 6c.
Thus, in this embodiment, since the transmitted light of the transmission diffusion surface 2a is reflected by the corner cube array 3 and emitted from the transmission diffusion surface 2a, a reflection type projection screen with little light loss and excellent light utilization efficiency is obtained. Yes.

Here, the angle range (θ + θ ₂ ) to (θ−θ ₁ ) is 0.2% or more with respect to the peak value I _max of the light intensity distribution, and 0.4% or more of the average value I _ave of the light intensity distribution. It is defined as an angle range that satisfies any of the above.

When the light intensity distribution of the screen reflected light 6 is schematically shown, a light intensity distribution having directivity in the angle θ direction is obtained as shown in FIG.
An example of this light intensity distribution is shown as a curve 500 in FIG. A curved line 501 indicated by a broken line shows a light intensity distribution of a general diffuse reflection surface whose emission angle is the angle θ direction for comparison.
The curve 500 takes a peak value I _max at θ, has a relatively flat light intensity distribution between the angle ranges (θ + θ ₂ ) to (θ−θ ₁ ), and has a direction in which the intensity sharply decreases outside. It has a strong light intensity distribution. The threshold value I _{th at which the} angle is (θ + θ ₂ ) or (θ−θ ₁ ) is a value that satisfies any of I _th ≧ I _max * 0.02 and I _th ≧ I _ave * 0.04. . Here, I _ave represents the average value of the light intensity.
Such intensity of directivity is represented by the magnitudes of the angles θ ₁ and θ ₂ , and can be varied by setting the degree of diffusion of the transmission diffusion surface 2 a. For example, 0 ° <θ ₁ ≦ 30 ° and 0 ° <θ ₂ ≦ 30 ° can be set. For example, the degree of directivity is adjusted by changing the values of θ ₁ and θ ₂ to 20 °, 10 °, and the like.
In the present embodiment, most of the screen reflected light 6 is light that passes through the transmission diffusion surface 2a twice, so that the diffusion degree of the transmission diffusion surface 2a is halved compared to a general diffusion plate. Can do. Therefore, since the transparency of the diffusion plate 2 can be improved accordingly, the light loss due to the diffusion plate 2 can be greatly reduced.
As a result, it becomes easy to satisfy the expressions (1) to (5) between the projection light 5 and the screen reflected light 6, and the color reproducibility and brightness can be improved.

Further, the corner cube array 3 provided for improving the light utilization efficiency can be configured in a simple manner as compared with a case where a liquid crystal reflective layer is provided, for example.
In the present embodiment, since the corner cube array 3 is constituted by the corner cube prism 30, the reflection surface 3b can be constituted as an internal reflection surface, and depending on use conditions, it can be used as a total reflection surface. Therefore, there is an advantage that the reflective coat or the like can be simplified or omitted.

Next, first, second, and third modifications of the present embodiment will be described.
FIGS. 5A, 5B, and 5C are schematic partial cross-sectional views for describing the reflective projection screens of the first, second, and third modifications of the embodiment of the present invention, respectively. .

  As shown in FIG. 5A, the corner cube array 10 of the first modification example of the present embodiment omits the diffusion plate 2 of the above embodiment and replaces the incident surface 3 a of the corner cube array 3 with transmission diffusion. By providing the surface 10a, the corner cube group and the transmission diffusing surface are integrated to form a reflective projection screen with a single member. Hereinafter, a description will be given focusing on differences from the above embodiment.

The transmission diffusion surface 10a may be formed in any manner as long as it can be formed on the incident surface 3a of the corner cube array 3, and the same configuration as that of the transmission diffusion surface 2a can be adopted. For example, it is possible irregularities pitch is formed by a mat relief working of L _d.
Even in this case, in the corner cube unit 31, instead of the incident surface 3a, a transmission diffusion surface 10a is formed so that a plurality of corner cube units 31 are joined and, after joining, a corner cube array that functions as one member. Needless to say, 10 can be configured.

According to such a configuration, since the reflection type projection screen can be configured with one member, a simple and inexpensive reflection type projection screen can be obtained.
In this case, since the number of optical surfaces is constituted only by the transmission diffusion surface 10a and the reflection surface 3b, there is an advantage that the light amount loss is remarkably reduced.

  As shown in FIG. 5B, the corner cube array 11 of the second modification of the present embodiment includes a diffusion plate 8 (a diffusion element) instead of the diffusion plate 2 of the above embodiment. Hereinafter, a description will be given focusing on differences from the above embodiment.

The diffusing plate 8 is a flat plate or a curved plate provided with a transmissive surface 8b and a transmissive diffusing surface 2a each having a smooth plane or a curved surface in order from the light source side (right side in the figure).
The smoothness of the transmissive surface 8b may be smooth enough to allow dust or dirt to hardly adhere to the surface, and when it adheres, the surface can be easily cleaned by wiping the surface.

According to such a configuration, since the transmission diffusion surface 2a is directed to the corner cube array 3 side and is not exposed to the outside, there is no possibility of dust or dirt being attached or damaged. Therefore, since the defect of the transmissive diffusion surface 2a that affects the resolution and image quality of the screen reflected light 6 does not occur, there is an advantage that it is easy to maintain high image quality over time.
Further, since the transmissive surface 8b exposed on the surface is formed of a smooth flat surface or curved surface, when dust or dirt adheres, there is an advantage that it can be easily cleaned by wiping, for example, and maintenance is easy.
In addition, it is more preferable to apply an antistatic coat to the transmission surface 8b, because it is possible to suppress the adhesion of dust. Furthermore, if an antireflection coating is applied, it is advantageous in terms of light loss.
In addition, since the surface is formed of a smooth flat surface or curved surface, it is easy to perform a strengthening treatment, coat a protective film, or attach a protective sheet to the surface in order to prevent generation of scratches.

  As shown in FIG. 5C, the corner cube array 12 of the third modification example of the present embodiment has a reflector type corner cube array 9 (corner cube group) instead of the corner cube array 3 of the second modification example. It is to be prepared. Hereinafter, a description will be given focusing on differences from the above embodiment.

The reflector type corner cube array 9 is composed of a reflector type corner cube 90 with three reflecting surfaces 9b, which are surface reflecting surfaces orthogonal to each other and intersecting at a vertex 9c, as a unit, and adjacent ridges 9d are joined together. . The planar arrangement is a planar arrangement as shown in FIG.
The reflector-type corner cube array 9 has a concave-convex relationship opposite to that of the corner cube array 3, but can be manufactured by substantially the same manufacturing method. However, when a light transmissive material is used, it is necessary to apply a reflective coat to the reflective surface 9b. If a material having a low light transmittance and capable of forming a reflecting mirror surface, such as a metal or a silicon wafer, is employed as the material, it is possible to form the reflecting surface 9b without applying a reflecting coat only by mirror finishing.

This modification has the same effect as that of the second modification by the action of the diffusion plate 8, and the reflector-type corner cube is used as the corner cube group by providing the transmission diffusion surface 2 a on the diffusion plate 8. It is an example that can.
The reflector-type corner cube array 9 does not require transparency as a material, so that there is an advantage that the degree of freedom in selecting the material is increased.

Next, fourth, fifth, and sixth modifications of the present embodiment will be described.
FIGS. 6A and 6B are a schematic plan view for explaining a reflection type projection screen of a fourth modification of the embodiment of the present invention and a BB cross-sectional view thereof, respectively. FIGS. 7A and 7B are cross-sectional views corresponding to the line BB in FIG. 6A for explaining the reflective projection screens of the fifth and sixth modifications of the embodiment of the present invention. is there.

In the fourth modification of the present embodiment, a light shielding layer 3e is provided on the adjacent ridge line portion 3d of the corner cube array 3 of the above embodiment. Hereinafter, a description will be given focusing on differences from the above embodiment.
As shown in FIG. 6B, the light shielding layer 3e is formed, for example, by performing a light shielding process, for example, by application of a light-absorbing paint, in the vicinity of the adjacent ridge line portion 3d from the back side of the corner cube array 3. .

According to such a configuration, the light incident on the adjacent ridge line portion 3d is absorbed, so that irregular reflection at the adjacent ridge line portion 3d can be suppressed. Therefore, it is possible to suppress a decrease in contrast of the screen reflected light 6 due to irregularly reflected light at the adjacent ridge line portion 3d.
In general, the adjacent ridge line portion 3d is easily affected by manufacturing errors. However, by providing the light shielding layer 3e in this way, the allowable width of the manufacturing error of the adjacent ridge line portions 3d can be widened, so that the manufacturing efficiency, yield, etc. There is an advantage that can be improved.

In the fifth modification of the present embodiment, as shown in FIG. 7A, instead of the adjacent ridge line portion 3d, a flat surface portion 3f substantially parallel to the incident surface 3a is formed, and light shielding is performed on the back surface side of the flat surface portion 3f. The layer 3e is formed.
According to this configuration, since the flat portion 3f is provided instead of the adjacent ridge line portion 3d, which is highly difficult to manufacture, the manufacture is facilitated, and the reflection and scattering at the flat portion 3f can be prevented by providing the light shielding layer 3e. it can. Further, there is an advantage that the light shielding layer 3e can be easily formed by providing the flat portion 3f.

As shown in FIG. 7 (b), the sixth modification of the present embodiment has a light shielding layer 3e on the incident surface 3a located on the upper surface side of the adjacent ridge line portion 3d in the corner cube array 3 of the fourth modification. It is provided.
According to this configuration, the incident light is shielded by the light shielding layer 3e and does not reach the adjacent ridge line portion 3d, so that scattering at the adjacent ridge line portion 3d can be prevented.
Further, since the light shielding layer 3e is provided on the incident surface 3a that is flat or slightly curved, there is an advantage that the light shielding layer 3e can be easily formed and the manufacturing efficiency of the corner cube array 3 can be improved. .

  In the above description of the embodiment and the modified example, the corner cube group has been described mainly using a prism group. However, if possible, these may be appropriately replaced with a reflector-type corner cube array. Needless to say, it is good.

In the above description, in the formulas (1) to (5), (1a), (2a), etc., the wavelengths λ _B = 485 nm, λ _G = 550 nm, λ _R = 650 nm are used as wavelengths representative of the three primary colors of light. However, these are merely examples, and if the values are close to these, the same effect is obtained, and other representative values may be employed instead.
For example, as the wavelengths λ _B , λ _G , and λ _R , the Fraunhofer line F line (486.1 nm), e line (546.1 nm), and C line (656.3 nm) can be used instead of the above values. .
Further, when three-color (blue, green, red) LED light sources or the like are used as the light source, the respective emission wavelengths of these LED light sources can also be employed.
In addition, when using a configuration in which RGB color separation is performed by a dichroic prism, a color filter, or the like as a light source, the wavelength of RGB color separation light itself may be used.

In the above description, as an example of the corner cube group, an example has been described in which ridge lines adjacent to each other form a regular triangle. However, as another example, ridge lines adjacent to each other have a regular hexagon in plan view. An arrangement may be used.
FIGS. 8A and 8B are a schematic plan view and a perspective schematic view for explaining the configuration of the reflective surface of another corner cube group that can be used in the reflective projection screen according to the embodiment of the present invention. It is explanatory drawing. In FIG. 8A, the black circle at the apex indicates the apex that sinks to the back side of the paper, and the white circle indicates the apex that protrudes toward the front side of the paper. A broken line is located at an intermediate position between these vertices and indicates a virtual line connecting other vertices on the same plane.

The corner cube array 40 (corner cube group) is formed by joining corner cubes each having a square reflecting surface 40b orthogonal to each other and intersecting at a vertex 3c at adjacent ridge line portions 40d. In this case, the pitch L _C, in the same manner as mentioned above, can be defined as the shortest distance connecting the vertices 3c of each corner cube.
The corner cube array 40 may be manufactured as a prism or a reflector.
For example, in the case of manufacturing as a prism, the plate-shaped corner cube array 40 can be formed by forming a flat plate portion of the same material above the apex of the white circle in the figure and using it as an incident surface.

  In the above description, the example of the plate member is used as the diffusion element. However, the plate member is not limited to the plate member as long as it has a smooth flat surface or curved surface and a transmission diffusion surface. For example, forms other than plate members, such as a film and a sheet member, can also be adopted.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic explanatory view in a side view and an enlarged partial cross-sectional view for explaining a schematic configuration of a projector system using a reflective projection screen according to an embodiment of the present invention. It is a plane view schematic explanatory drawing and its AA sectional drawing for demonstrating schematic structure of the corner cube group which concerns on embodiment of this invention. It is a plane view schematic explanatory drawing for demonstrating an example of the corner cube unit which concerns on embodiment of this invention. It is the model explanatory drawing for demonstrating the effect | action and directivity of the reflective projection screen which concern on embodiment of this invention, and a schematic graph for demonstrating the light intensity distribution of the reflected light. It is a typical fragmentary sectional view for demonstrating the reflection type projection screen of the 1st, 2nd, 3rd modification of embodiment of this invention. It is a plane view schematic explanatory drawing for demonstrating the reflection type projection screen of the 4th modification of embodiment of this invention, and its BB sectional drawing. It is sectional drawing corresponding to the BB line of Fig.6 (a) for demonstrating the reflection type projection screen of the 5th and 6th modification of embodiment of this invention. It is a plane view schematic explanatory drawing and a perspective schematic explanatory drawing for demonstrating the structure of the reflective surface of the other corner cube group which can be used for the reflective projection screen which concerns on embodiment of this invention.

Explanation of symbols

1,11 Reflective screen (reflective projection screen)
2, 8 Diffuser (Diffusion element)
2a Transmission diffusion surface 2b, 8b Transmission surface 3, 10, 40 Corner cube array (corner cube group)
3A Triangular pyramid part 3a Incident surfaces 3b, 9b, 40b Reflecting surface 3c Vertex 3d Adjacent ridge line part (adjacent ridge line part)
3e Light-shielding layer 3f Plane part 4 Projector (light source)
5 Projection light 6 Screen reflection light 9 Reflector type corner cube array (corner cube group)
30 Corner cube prism 31 Corner cube unit 50 Diffused light (transmitted light)

Claims (9)

A reflective projection screen for reflecting projection light from a light source,
A transmission diffusing surface having at least transmitted light as diffused light; and
Reflection comprising: a corner cube group disposed on the rear surface side of the transmission diffusion surface as viewed from the light source side and reflecting the projection light transmitted through the transmission diffusion surface toward the transmission diffusion surface. Type projection screen. The reflective projection screen according to claim 1, wherein the following expression is satisfied when light having wavelengths λ _B = 485 nm, λ _G = 550 nm, and λ _R = 650 nm is incident.
0.8 ≦ (R _B / I _B ) / (R _G / I _G ) ≦ 1.25 (1)
0.8 ≦ (R _R / I _R ) / (R _G / I _G ) ≦ 1.25 (2)
_{Here, I B, I G, I} R are each wavelength lambda _B, lambda _G, the incident intensity of light _{λ R, R B, R G} , R R are each wavelength λ _B, λ _G, λ _This is the emission intensity of _R light. 3. The reflective projection screen according to claim 1, wherein when light having wavelengths λ _B = 485 nm, λ _G = 550 nm, and λ _R = 650 nm is incident on the transmission diffusion surface, the following expression is satisfied. .
0.5 ≦ R _B / I _B ≦ 1 (3)
0.5 ≦ R _G / I _G ≦ 1 (4)
0.5 ≦ R _R / I _R ≦ 1 (5)
_{Here, I B, I G, I} R are each wavelength lambda _B, lambda _G, the incident intensity of light _{λ R, R B, R G} , R R are each wavelength λ _B, λ _G, λ _This is the emission intensity of _R light.   The reflection type projection screen according to claim 1, wherein the corner cube group is constituted by a prism group.   The reflection type projection screen according to claim 4, wherein an incident surface of the prism group also serves as the transmission diffusion surface. A light transmissive diffusion element in which the transmission diffusion surface is formed on one surface and a smooth flat surface or curved surface is formed on the other surface,
The reflective projection screen according to claim 1, wherein the other surface of the diffusing element is disposed toward the light source.   The reflection type according to any one of claims 1 to 6, wherein the corner cube group has a configuration in which a plurality of corner cube units each including one corner cube or a plurality of corner cubes integrally formed are joined. Projection screen.   The reflection type projection screen according to claim 1, wherein a light shielding process is performed on ridge lines where the corner cubes constituting the corner cube group are adjacent to each other.   The reflection type according to any one of claims 1 to 8, wherein when the transmission diffusion surface is an uneven surface, a pitch of the uneven surface is smaller than a pitch of corner vertices of the corner cube group. Projection screen.

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