JP2006285096A - Reflective projection system, reflective screen - Google Patents

Abstract

A reflection type projection system and a reflection screen capable of obtaining an image with high contrast, high luminance, and no reflection are provided.
The polarization direction of the substantially linearly polarized image light projected from the image source L substantially coincides with the horizontal direction in which the unit prism shape 12 and the light absorbing portion 14 extend while maintaining the same cross-sectional shape. Provided. The reflective layer 13 is formed of a polarizing reflective material that reflects only the horizontal polarization component, and further, the polarizing layer 16 is provided so that the passable polarization direction is the horizontal direction.
[Selection] Figure 2

Description

  The present invention relates to a reflective projection system and a reflective screen for observing image light from an image source by reflecting the image light with a reflective screen.

  Conventionally, this type of reflection screen has been known in which a light transmission diffusion layer is provided on the front side of a transparent sheet and a linear Fresnel lens surface for light reflection is provided on the back side (for example, Patent Document 1). Patent Document 2 discloses a configuration of a reflective screen that can suppress a decrease in contrast due to external light and obtain a suitable viewing angle. Further, Patent Document 3 describes a reflective screen by combining a lenticular lens and a linear Fresnel lens arranged in a direction orthogonal to the back surface provided with a reflective portion.

However, there has been a request to obtain an image with higher contrast and a request to obtain an image with the highest possible brightness even when the amount of light from the projection-side light source is small. Even when a high-brightness image is obtained, it is always required to eliminate unnecessary reflections.
Furthermore, the above-described conventional reflective screen has a problem that the manufacturing process becomes complicated, resulting in an increase in manufacturing cost.

Further, Patent Document 4 relates to a reflective screen that reflects and observes light projected obliquely from the front, and a reflection surface and a light absorption surface are formed on a screen surface having a sawtooth cross section so that image light and external light can reach. A reflective screen having different surfaces is disclosed.
However, in the reflection screen described in Patent Document 4, it is necessary to manufacture the reflection surface and the light absorption surface clearly on a screen surface having a sawtooth cross section, but one of the sawtooth peaks is a reflection surface, It is difficult to make the other as a light-absorbing surface, and there is a problem that the manufacturing unit price becomes high.
JP-A-8-29875 Japanese Patent Laid-Open No. 10-62870 JP 2002-31507 A JP-A-2-262134

  An object of the present invention is to provide a reflective projection system and a reflective screen that can obtain an image with high contrast, high brightness, and no reflection.

The present invention solves the above problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to the Example of this invention is attached | subjected and demonstrated, it is not limited to this.
The invention according to claim 1 is a reflection type projection system comprising: an image source (L) that projects image light; and a reflection screen (10) that reflects the image light to enable observation; , In a cross section orthogonal to the screen surface, a light transmission part (12) that can transmit light, and a light absorption part (14) that absorbs light, wherein the light transmission part and the light absorption part, A reflection layer (13) that is alternately formed along the screen surface and reflects the image light that has passed through the light transmission portion is provided on the back side of the light transmission portion, and the image light is substantially linearly polarized light. The polarization direction (A) of the image light substantially coincides with the direction in which the light transmitting portion and the light absorbing portion extend while maintaining the same cross-sectional shape. It is.

According to a second aspect of the present invention, in the reflective projection system according to the first aspect, the light transmission section (12) has a width on the image source side that is wider than a width on the back surface side in a cross section orthogonal to the screen surface. The reflection type projection system is characterized in that it has a wide, substantially wedge shape, and a unit prism shape formed in a large number along the screen surface in a direction orthogonal to the polarization direction (A) of the image light.
A third aspect of the present invention is the reflection type projection system according to the first or second aspect, further comprising a polarizing layer (16) for aligning a polarization state of light passing therethrough with linearly polarized light in a predetermined polarization direction. The reflection type projection system is characterized in that a predetermined polarization direction aligned by the layers substantially coincides with a polarization direction (A) of the image light.
According to a fourth aspect of the present invention, in the reflective projection system according to any one of the first to third aspects, the reflective layer (13) is a polarized reflection that selectively reflects only polarized light in one direction. The reflection type projection system is characterized in that the polarization direction that is formed of a material and is selectively reflected by the polarization reflector substantially matches the polarization direction (A) of the image light.
The invention of claim 5 is the reflection type projection system according to any one of claims 1 to 4, further comprising an illumination light source (G) for illuminating at least a space where the reflection screen is installed, The illumination projection of the illumination light source is substantially linearly polarized light, and the polarization direction (B) of the illumination light is substantially orthogonal to the polarization direction (A) of the image light. System.

The invention according to claim 6 is a reflection screen that allows the image light projected from the image source to be reflected and observed, and is a light transmission portion (12) capable of transmitting light in a cross section orthogonal to the screen surface. And a light absorbing part (14) for absorbing light, wherein the light transmitting part and the light absorbing part are alternately formed along the screen surface, and at least on the back side of the light transmitting part In a reflective screen including a reflective layer (13) that reflects the image light that has passed through the light transmitting portion, the reflective screen includes a polarizing layer (16) that aligns the polarization state of light passing therethrough with linearly polarized light in a predetermined polarization direction, The reflection screen (10) is characterized in that a predetermined polarization direction aligned by the polarizing layer substantially coincides with a direction in which the light transmission part and the light absorption part extend while maintaining the same cross-sectional shape. .
The invention according to claim 7 is a reflection screen that allows the image light projected from the image source to be reflected and observed, and is capable of transmitting light in a cross section orthogonal to the screen surface. And a light absorbing part (14) for absorbing light, wherein the light transmitting part and the light absorbing part are alternately formed along the screen surface, and at least on the back side of the light transmitting part In a reflective screen including a reflective layer (13) that reflects the image light that has passed through the light transmitting portion, the reflective layer is formed of a polarized reflective material that selectively reflects only polarized light in one direction, A reflective screen (10) characterized in that a polarization direction selectively reflected by a polarizing reflector substantially coincides with a direction in which the light transmitting portion and the light absorbing portion extend while maintaining the same cross-sectional shape. It is.

  The invention according to an eighth aspect is the reflective screen according to the sixth or seventh aspect, wherein the light transmission portion (12) is closer to the image source side than a width on the back side in a cross section orthogonal to the screen surface. The reflection screen (10) is characterized in that it has a substantially wedge shape with a wide width and a unit prism shape formed in a line along the screen surface in a direction perpendicular to the polarization direction of the image light.

According to the present invention, the following effects can be obtained.
(1) The image light is substantially linearly polarized light, and the polarization direction of the image light is substantially the same as the direction in which the light transmitting portion and the light absorbing portion extend while maintaining the same cross-sectional shape. It can reflect more efficiently. This is because the light transmission part and the light absorption part have a difference in refractive index, so that the reflectance varies depending on the polarization direction incident on the interface. Since the polarization direction of the image light is S-polarized with respect to the interface, the reflectance is high. Therefore, it is possible to minimize the rate of incidence and loss on the light absorption layer.

(2) The light transmitting portion is substantially wedge-shaped with a width on the image source side wider than the width on the back surface side, and is formed side by side in the direction orthogonal to the polarization direction of the image light along the screen surface. Can absorb the extraneous light and display high contrast images.

(3) Since the predetermined polarization direction aligned by the polarization layer substantially matches the polarization direction of the image light, it is possible to prevent an external light component that does not match the polarization direction of the image light from reaching the reflection layer. High-contrast video can be displayed.

(4) Since the polarization direction selectively reflected by the polarizing reflector is substantially the same as the polarization direction of the image light, an image with high contrast without reflecting external light components that do not match the polarization direction of the image light. Can be displayed.

(5) Since the polarization direction of the illumination light is substantially orthogonal to the polarization direction of the image light, it is possible to clearly distinguish between the image light and the illumination light and reflect only the illumination light so that observation is possible. High contrast images can be displayed even in a bright room with lit.

  The purpose of obtaining an image with high contrast, high brightness, and no reflection was realized by utilizing the fact that the image light from the image source is linearly polarized light.

FIG. 1 is a sectional view showing a reflective projection system in the present embodiment.
FIG. 2 is a perspective view showing the reflective projection system in the present embodiment. However, FIG. 2 shows a state where the reflective layer 13 is not formed for the sake of explanation. 1 and 2 show exaggerated dimensions and shapes as appropriate for the sake of explanation, and the interior lighting G, the image source L, and the reflection screen 10 are schematically shown together. Are different in arrangement relation, and include portions where the incident angle of each light ray is different from the magnitude relation in the following description.

The reflective screen 10 in this embodiment is configured such that a projector optical engine unit (image source) L for projecting image light is disposed below the center of the screen 10 and image light is projected obliquely upward. Most of the screens were developed considering that the light enters the screen from above. Then, the image light from below is efficiently reflected to the viewer side, and unnecessary light from above is selectively absorbed by a light absorbing unit described later, so that the reflection screen for a front projector having a very high contrast can be obtained. It is a thing.
The projector optical engine unit (image source) L is a liquid crystal projector, and the polarization state of the projected image light is linearly polarized, and the polarization direction A indicated by the arrow in FIG. 2 is the horizontal direction. Are arranged as follows.
FIG. 1 shows a vertical cross-section when the screen is in use. The reflective screen 10 includes a base portion 11, a unit prism shape 12, a reflective layer 13, a light absorbing portion 14, a regular reflection preventing layer 15, a polarizing layer 16, and the like.

  The base portion 11 is a portion that becomes a base material necessary for forming the unit prism shape 12, and is a light-transmitting portion formed from a resin sheet or film such as acrylic, polycarbonate, or polyethylene terephthalate. In this embodiment, acrylic is used. Note that the base portion 11 may be colored (tinted) with a dye, pigment, or the like such as gray so as to reduce the transmittance to a predetermined transmittance as necessary.

  The unit prism shape 12 is a light transmitting portion having a substantially wedge shape in which the width on the image source side is wider than the width on the back surface side in the cross section of FIG. A large number of unit prism shapes 12 are formed along the screen surface (in the vertical direction in FIG. 1). The unit prism shape 12 is vertically symmetric in the vertical direction, and the angle between the upper and lower slopes and the normal of the screen surface is 5 °, the top width is 40 μm, and the valley bottom The height from the top to the top is 200 μm. The unit prism shape 12 is made of an ultraviolet curable resin having a refractive index of 1.56. Here, the screen surface indicates a surface in the plane direction of the screen when viewed as the entire screen, and is used as the same definition in the following description and in the claims.

The light absorbing portion 14 is a portion having an action of absorbing light formed while the unit prism shapes 12 are arranged. In this embodiment, the light absorbing portion 14 is formed by uniformly filling black beads (not shown). This black bead is a microbead having an action of absorbing light, and a gap where the bead does not exist in the light absorbing portion 14 is a void. With this configuration, the light absorbing portion 14 can be easily deformed, which is convenient for obtaining the necessary flexibility when the reflective screen 10 is a roll-up type.
The unit prism shape 12 and the light absorbing portion 14 extend in the horizontal direction while maintaining the cross-sectional shape shown in FIG. As described above, since the polarization direction of the image light is the horizontal direction, the polarization direction of the image light coincides with the direction in which the unit prism shape 12 and the light absorbing portion 14 extend while maintaining the same cross-sectional shape. ing. The reason for this will be described later.

The reflection layer 13 is provided on the back side of the substantially wedge-shaped top of the unit prism shape 12, and is a layer that reflects video light and returns it to the front side (video source side), and is filled in the light absorption unit 14. In order to hold a black bead (not shown), it is formed so as to cover the entire back side.
In addition, the reflective layer 13 in the present embodiment is formed of a polarized reflector that selectively reflects only polarized light in one direction. The reflective layer 13 of this embodiment is formed by using a wire grid polarizer in which dielectrics and conductors are alternately arranged in the plane direction, and the polarization direction selectively reflected by the reflective layer 13 is the horizontal direction. And coincides with the polarization direction of the image light. Accordingly, while the image light is efficiently reflected, the outside light and the like whose polarization directions do not match hardly reflect. This wire grid polarizer is a reflective layer having polarization selectivity, and it is not necessary to provide a separate reflective layer. In addition, since the light which is not reflected is transmitted in the back surface direction, in order to prevent external light from being reflected on any surface on the back side of the screen (for example, on the wall), for example, a black light absorption layer is further provided on the back surface. You may arrange. In addition to the wire grid polarizer, for example, DBEF (manufactured by Sumitomo 3M Limited) may be used for the reflective layer 13.
The reflectivity of the reflective layer 13 of this example is 81.1% on average for 400 to 700 nm for polarized light with the same polarization direction, and 3.4% for polarized light in a direction orthogonal thereto. is there.

The regular reflection preventing layer 15 is a layer in which a number of fine irregularities are randomly formed on the surface. In this embodiment, the total transmission efficiency is approximately 90%, the diffuse transmittance is approximately 37%, and the haze value is approximately 42%. A certain commercially available diffusion film (TL-4 manufactured by Kimoto Co., Ltd.) was used. For the measurement of the haze value and the haze value shown below, a haze / transmission / reflectometer HR-100 type (manufactured by Murakami Color Research Laboratory Co., Ltd.) was used.
The regular reflection preventing layer 15 has the following functions.
(1) The image source L is prevented from being reflected and observed on the outermost surface of the reflection screen.
(2) Widen the observable angle of the image projected on the reflective screen.

Here, the function (1) cannot be achieved by using a diffusion layer (diffusion film) of a type in which a diffusion material is mixed inside the layer. In order to achieve this function, it is necessary that the surface has a fine uneven shape. The degree of the reflection prevention effect of the image source can be adjusted according to the light diffusion degree due to the fine uneven shape. If the degree of diffusion is too small, the reflection cannot be suppressed. However, if the degree of diffusion is too strong, the screen is observed as white. Therefore, when a number of diffusion films having different diffusivities were evaluated, the haze value of the regular reflection preventing layer 15 was 25% or more and 90% or less. It was found that it can be effectively prevented.
Various surface treatments such as antistatic treatment, hard coat treatment, and antifouling treatment may be additionally applied to the surface side of the regular antireflection layer 15, but in that case, the surface has a fine uneven shape. It is necessary to leave.

The polarizing layer 16 is a layer that is provided between the base portion 11 and the regular reflection preventing layer 15 and aligns the polarization state of light passing therethrough with linearly polarized light in a predetermined polarization direction. Specifically, the polarization component that coincides with the predetermined polarization direction is passed as it is, but the polarization component other than the predetermined polarization direction is an absorbing polarizer that absorbs.
The predetermined polarization direction aligned by the polarizing layer 16 in the present embodiment is provided to be a horizontal direction. Therefore, the polarization direction that can pass through the polarizing layer 16 is substantially the same as the polarization direction of the image light. In this way, the image light can pass through the polarizing layer 16 and proceed to the reflecting layer 13 side, but light having a polarization component in a direction other than the predetermined polarization direction of the polarizing layer 16 (for example, outside) Most of the light is absorbed by the polarizing layer 16.

In the reflection screen 10 described above, the image light beams L1 and L2 projected from the image source L are guided in the unit prism shape 12 and totally reflected at the boundary surface with the light absorbing portion 14 as shown in FIG. Do. The light absorbing portion 14 is filled with black beads, but since the gap is a gap, the refractive index of the light absorbing portion 14 is lower than the refractive index of the unit prism shape 12, and therefore, Light incident at an angle larger than the critical angle at this interface is totally reflected.
Then, the image light totally reflected by the boundary surface between the unit prism shape 12 and the light absorbing portion 14 reaches the reflection layer 13 and is reflected, and then further totally reflected, for example, as an observable light ray toward the observer. Returned.

  On the other hand, the external lights G1 and G2 from the room lighting G provided above the reflection screen 10 have a large incident angle with respect to the reflection screen 10, and therefore, incident on the boundary surface between the unit prism shape 12 and the light absorbing portion 14. The angle becomes smaller and there are many components that do not exceed the critical angle, and the light enters the light absorbing portion 14 without being totally reflected, and is absorbed by the black beads. Therefore, the rate at which external light returns to the observation position can be greatly reduced.

Here, the reason why the polarization direction of the image light coincides with the direction in which the unit prism shape 12 and the light absorbing portion 14 extend while maintaining the same cross-sectional shape will be described.
When polarized light is reflected, it is already known that the reflectance varies depending on the relationship between the polarization state (polarization direction) and the reflecting surface, and S-polarized light is more reflective than P-polarized light. High reflectivity.
In the reflective screen 10 of the present embodiment, total reflection is used at the interface between the unit prism shape 12 and the light absorbing portion 14, so that the light that reaches this interface is closer to S-polarized light in relation to the interface, the efficiency is higher. Image light can be reflected.
FIG. 3 is a graph plotting the results of actually measuring the change in reflectance due to the difference in the polarization direction for each incident angle with respect to the screen surface of the reflective screen 10 of this embodiment.
FIG. 3 shows a case where the polarization direction of the image light is the vertical direction and a case where the polarization direction is the horizontal direction, based on the image light having the polarization direction of the horizontal direction and an incident angle of 0 °. FIG. 3 shows that the reflection intensity is higher when the polarization direction of the image light is the horizontal direction than when the polarization direction is the vertical direction. The reason for this is that when the polarization direction of the image light is horizontal, the polarization state of the image light that reaches the interface between the unit prism shape 12 and the light absorber 14 is S-polarized light in relation to this interface. Because there will be more.

Therefore, in the present embodiment, the incident direction on the total reflection surface (interface) is such that the polarization direction of the image light coincides with the direction in which the unit prism shape 12 and the light absorbing portion 14 extend while maintaining the same cross-sectional shape. The relationship between the plane and the polarization direction of the image light is close to that of S-polarized light so that the image light is reflected with a higher reflectance.
Note that if the reflecting screen 10 is rotated in accordance with the polarization direction of the image light, the positional relationship between the original video source L and the room lighting G is lost. In the example, an image source L in which image light is projected with horizontal linearly polarized light is used.

In the present embodiment, the polarization direction of the image light is limited to the horizontal direction as described above, and the reflection layer 13 and the polarization layer 16 are arranged in accordance with this. Therefore, even when external light having no polarization characteristic reaches the reflection screen 10, light other than the component having the same polarization direction as that of the image light is not reflected. Therefore, the image displayed on the reflective screen 10 is a high contrast image.
Furthermore, in the present embodiment, in order to make it possible to observe a high-contrast image in a brighter indoor environment, the room illumination G is also improved as described below as part of the reflective projection system.

  The illumination light that illuminates the room emitted from the room illumination G is linearly polarized light, and its polarization direction is set to a direction orthogonal to the polarization direction of the image light (the direction of arrow B in FIG. 2), that is, the vertical direction. Yes. Specifically, the polarizing filter 17 is disposed at a position where the light from the room illumination G is emitted, and the polarization direction of the room illumination light is set to be substantially orthogonal to the polarization direction of the image light. In this way, if there is no other light source, only two types of light reaching the screen 10 can be used, that is, image light that is linearly polarized light in the horizontal direction and illumination light that is linearly polarized light in a direction orthogonal thereto. Can be. Therefore, it is possible to selectively reflect only the image light by using the reflection screen 10 of the present embodiment, and it is possible to display a high-quality image with very high contrast in a bright environment.

When image light was actually projected onto the reflective screen 10, the projected image had a high reflectance, and most of the external light could be absorbed.
Thus, according to this embodiment, even in a bright room, it is possible to obtain an image with high contrast, high brightness, and no reflection.

(Modification)
The present invention is not limited to the embodiments described above, and various modifications and changes are possible, and these are also within the equivalent scope of the present invention.
In the present embodiment, an example in which the reflection layer 13, the polarization layer 16, the polarization filter 17 and the like are used in combination with the unit prism shape 12 and the light absorption unit 14 corresponding to the polarization direction of the image light has been described. For example, a part of them may be omitted as appropriate, such as omitting the polarizing layer 16.

It is sectional drawing which showed the reflection type projection system in a present Example. It is the perspective view which showed the reflection type projection system in a present Example. It is the figure which plotted the change of the reflectance by the difference in a polarization direction for every incident angle with respect to a reflective surface.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Reflective screen 11 Base part 12 Unit prism shape 13 Reflective layer 14 Light absorption part 15 Regular reflection prevention layer 16 Polarizing layer 17 Polarizing filter

Claims (8)

An image source for projecting image light;
A reflective screen that reflects the image light and enables observation;
In a reflective projection system with
The reflection screen includes a light transmission part capable of transmitting light and a light absorption part for absorbing light in a cross section orthogonal to the screen surface, and the light transmission part and the light absorption part are provided on the screen surface. Are alternately formed along
A reflective layer that reflects the image light that has passed through the light transmission part is provided on the back side of the light transmission part,
The image light is substantially linearly polarized light, and the polarization direction of the image light substantially coincides with the direction in which the light transmitting portion and the light absorbing portion extend while maintaining the same cross-sectional shape;
Reflective projection system characterized by The reflective projection system according to claim 1, wherein
The light transmission portion has a substantially wedge shape in which a width on the image source side is wider than a width on the back surface side in a cross section orthogonal to the screen surface, and a direction orthogonal to the polarization direction of the image light along the screen surface A unit prism shape formed side by side,
Reflective projection system characterized by The reflective projection system according to claim 1 or 2,
A polarizing layer that aligns the polarization state of light passing therethrough with linearly polarized light in a predetermined polarization direction;
A predetermined polarization direction aligned by the polarizing layer substantially coincides with a polarization direction of the image light;
Reflective projection system characterized by The reflective projection system according to any one of claims 1 to 3, wherein
The reflective layer is formed of a polarized reflector that selectively reflects only polarized light in one direction,
The polarization direction selectively reflected by the polarizing reflector is substantially the same as the polarization direction of the image light;
Reflective projection system characterized by The reflective projection system according to any one of claims 1 to 4, wherein:
An illumination light source that illuminates at least a space in which the reflective screen is installed;
The illumination light of the illumination light source is substantially linearly polarized light,
The polarization direction of the illumination light is substantially orthogonal to the polarization direction of the image light,
Reflective projection system characterized by A reflection screen that reflects image light projected from an image source so that the light can be observed, and a light transmission portion that can transmit light and a light absorption portion that absorbs light in a cross section orthogonal to the screen surface The light transmission part and the light absorption part are alternately formed along the screen surface, and reflect the image light that has passed through the light transmission part at least on the back side of the light transmission part In a reflective screen comprising a reflective layer,
A polarizing layer that aligns the polarization state of light passing therethrough with linearly polarized light in a predetermined polarization direction;
The predetermined polarization direction aligned by the polarizing layer substantially coincides with the direction in which the light transmitting portion and the light absorbing portion extend while maintaining the same cross-sectional shape;
Reflective screen featuring. A reflection screen that reflects image light projected from an image source so that the light can be observed, and a light transmission portion that can transmit light and a light absorption portion that absorbs light in a cross section orthogonal to the screen surface The light transmission part and the light absorption part are alternately formed along the screen surface, and reflect the image light that has passed through the light transmission part at least on the back side of the light transmission part In a reflective screen comprising a reflective layer,
The reflective layer is formed of a polarized reflector that selectively reflects only polarized light in one direction,
The polarization direction selectively reflected by the polarizing reflector is substantially the same as the direction in which the light transmission part and the light absorption part extend while maintaining the same cross-sectional shape,
Reflective screen featuring. The reflecting screen according to claim 6 or 7,
The light transmission portion has a substantially wedge shape in which a width on the image source side is wider than a width on the back surface side in a cross section orthogonal to the screen surface, and a direction orthogonal to the polarization direction of the image light along the screen surface A unit prism shape formed side by side,
Reflective screen featuring.

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