JP2001249407A - Prism sheet, projection screen, and multi-projection system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a prism sheet, a projection screen, and a multi-projection system in which the luminance difference of projected video image light is not caused irrespective of the direction to observe. SOLUTION: The multi-projection system is equipped with rear projectors PJ1-PJ4 and the projection screen 4, and the projection screen 4 has a diffusion plate 1, a horizontal prism sheet 2, and a vertical prism sheet 3. The horizontal prism sheet 2 and the vertical prism sheet 3 have linear Fresnel lens areas 2a, 2c, 3a, and 3c, and prism areas 2b and 3b whose cross sections are isosceles triangle shapes, and because the video light is vertically emitted to the diffusion plate 1, the diffused light diffused by the diffusion plate 1 becomes equal irrespective of the position on the screen. Thus, when observing from any direction, the video image having no luminance unevenness on a picture is observed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a prism sheet, a projection screen, and a multi-projection system on which image light is projected by a plurality of rear projectors.

[0002]

2. Description of the Related Art FIG. 5 is a perspective view illustrating a conventional multi-projection system. The multi-projection system uses the diffuser 1
01 and rear projectors PJ1 and PJ2. The rear projectors PJ1 and PJ2 project images onto the regions 101a and 101c of the diffusion plate 101, respectively, and project a large image on the diffusion plate 101. The diffusion plate 101 is a sheet that diffuses image light by adding a diffusing agent or forming a lenticular lens on the exit surface side, the entrance surface side, or both.

A region 101a provided on a diffusion plate 101,
At the boundary of 101c, there is an overlapping area 101b where both images of the rear projectors PJ1 and PJ2 are projected, so that there is no break in the image. FIG. 6 is a plan view showing a conventional multi-projection system. The amount of the image light projected on the overlapping area 101b is smaller than that of the area 10b.
The light amount is adjusted so as to be half the light amount of 1a and 101c and projected, and when viewed from the front, only the image light emitted from the overlapping area 101b is prevented from having high brightness.

[0004]

However, in the above-described conventional multi-projection system, the image light projected from the rear projectors PJ1 and PJ2 is diffused as it is. The main emission directions were different. Therefore, the diffusion state of the image light in the vicinity of the optical axis, near the end, and in the overlapping area 101b of the rear projectors PJ1 and PJ2 is different (diffuse light A to E), and depending on the direction in which the diffuser plate 101 is observed, the screen may be different. There is a problem that a luminance difference occurs depending on the upper position.

[0005] A to E in FIG. 6 indicate diffused light in each part. In the overlapping area 101c, the diffused lights C1 and C2 having a half light amount of the diffused lights A, B, D, and E near the optical axis and near the ends are diffused at the same position with the main emission directions being different directions. The diffused light C in which these are combined differs from the diffused lights A, B, D, and E particularly in the diffusion state. Therefore, especially, the overlapping area 101C is compared with the other areas.
There is a problem that the luminance difference from other parts may be conspicuous depending on the viewing direction.

SUMMARY OF THE INVENTION The object of the present invention is to
An object of the present invention is to provide a prism sheet, a projection screen, and a multi-projection system in which a difference in luminance of projected image light does not occur.

[0007]

The present invention solves the above-mentioned problems by the following means. In addition, in order to make it easy to understand, description is given with reference numerals corresponding to the embodiment of the present invention, but the present invention is not limited to this. That is, the invention of claim 1 includes a plurality of rear projectors (PJ1 to PJ1).
PJ4) is a prism sheet (2, 3) used for a projection screen (4) irradiated with image light projected by a first and second rear projectors arranged adjacent to each other. Of the overlapping areas (4b, 4e, 4g, 4h, 4i) where the first and second image light overlap, and at least the adjacent directions among the emission directions of the first and second image light projected on the overlapping area. A prism sheet comprising: an emission direction matching section (2b, 3b) for making the emission direction the same direction.

According to a second aspect of the present invention, in the prism sheet according to the first aspect, the emission direction matching portion includes a prism region (2b, 2b, 2) in which unit prisms having a cross-sectional shape of an isosceles triangle are arranged in the adjacent direction. 3b), the area other than the prism area is a linear Fresnel lens area (2a, 2c, 3) in which scalene triangles are arranged in the adjacent direction.
a, 3c).

[0009] The invention of claim 3 is claim 1 or claim 2.
In the prism sheet described in the above, the incident angles of the first and second image light incident on the prism sheet is α, the angle between the exit surface and the incident surface is β, and the refractive index of the prism sheet is n,

[0010]

(Equation 2)

A prism sheet characterized by the following relationship:

According to a fourth aspect of the present invention, at least one of the prism sheets according to any one of the first to third aspects is provided, and an image light is provided on the viewer side of the prism sheet. And a diffusion plate (1) for diffusing the light.

According to a fifth aspect of the present invention, in the projection screen according to the fourth aspect, the prism sheet includes a horizontal prism sheet (2) for controlling the image light in a vertical direction;
A vertical prism sheet (3) for controlling the image light in a horizontal direction.

The invention of claim 6 is the invention of claim 4 or claim 5.
And a multi-projection system having a plurality of rear projectors (PJ1 to PJ4).

According to a seventh aspect of the present invention, in the multi-projection system according to the sixth aspect, the projection screen (4).
The optical axis of the image light projected from the rear projectors (PJ1 to PJ4) passes through the center of the linear Fresnel lens, and the overlapping area (4b, 4e, 4g, 4h, 4i) and the prism area (2b, 3b) is the same as the multi-projection system.

[0016]

Embodiments of the present invention will be described below in more detail with reference to the drawings. FIG.
1 is a perspective view showing a multi-projection system according to the present invention. The multi-projection system according to the present embodiment includes rear projectors PJ1 to PJ4 and a projection screen 4.

Each of the rear projectors PJ1 to PJ4 is a projector for projecting a separate image to an assigned position on the projection screen 4, and is arranged in a grid of four, and has a projection distance L = 1000 mm. The screen size projected by one projector is 52 inches diagonally.

The projection screen 4 includes rear projectors PJ1 to PJ1.
This is a screen that displays the image projected by PJ4. FIG.
Is a view of the projection screen 4 as viewed from the front. One projector has an aspect ratio of 3: 4, performs projection of X2 = 52 inches, and is arranged so as to overlap by X4 = 4 inches in a diagonal direction. Therefore, the projection screen 4
As a whole, the screen is X1 = 100 inches. The projection screen 4 overlaps the areas 4a, 4c, 4d, and 4f (all diagonal X3 = 48 inches) where only the image light from one rear projector is projected, and the image light from a plurality of rear projectors. The overlapping areas 4b, 4e, 4g, 4h,
4i. The position P indicates a position corresponding to the optical axis of the projector, and is located at X5 = 22 inches and X6 = 26 inches. The projection screen 4 is in the form of a screen by superposing the diffusion plate 1, the horizontal prism sheet 2, and the vertical prism sheet 3 on each other.

The diffusing plate 1 is a sheet that diffuses image light by adding a diffusing agent or forming a lenticular lens on the exit surface side, the entrance surface side, or both.

The horizontal prism sheet 2 is a sheet having a prism shape for controlling image light in the vertical direction.
FIG. 3 is a side view illustrating the horizontal prism sheet 2, and the vertical prism sheet 3 is omitted for simplicity. The horizontal prism sheet 2 has a prism area 2b and linear Fresnel lens areas 2a and 2c.

The prism area 2b is an area in which unit prisms each having a vertical cross-sectional shape of an isosceles triangle are vertically arranged, and the rear projectors PJ2 and PJ4 which are vertically adjacent to each other.
(PJ1 and PJ3) are located at positions coincident with overlapping areas 4g, 4h, and 4i where the projected image light overlaps (see FIG. 2), and an emission direction matching unit that controls the vertical emission direction of this image light is used. is there.

The shape of the prism area 2b is an isosceles triangle such that the image lights projected by the adjacent rear projectors PJ2 and PJ4 (PJ1 and PJ3) are emitted substantially in parallel. FIG. 4 is a diagram illustrating the shape of the prism region 2b. When the incident angle of the image light on the horizontal prism sheet 2 is α, in order for the exit angle to be perpendicular to the horizontal prism sheet 2, the angle β between the exit surface and the entrance surface of the prism region 2 b must be Is given by the following equation, where n is the refractive index of the horizontal prism sheet 2.

[0023]

(Equation 3)

Here, overlapping areas 4g, 4h, 4i (= prism area 2b) are determined from the optical axes of rear projectors PJ1 to PJ4.
Are 22 inches diagonally apart from each other (FIG. 2). When α is obtained from this value, α = 18.5 °. Therefore, if the angle β between the exit surface and the entrance surface of the prism region 2b in the horizontal prism sheet 2 is 34.8 °,
The emission angle is perpendicular to the horizontal prism sheet 2.
In the present embodiment, unit prisms having a cross-sectional shape having an angle of 34.8 ° at a position corresponding to the base angle of the isosceles triangle are vertically arranged to form a prism region 2b.

The image light projected by the rear projectors PJ1 to PJ4 onto the overlapping regions 4g, 4h, 4i (prism region 2b) is about half of the image light projected on the linear Fresnel lens regions 2a, 2b. The light is reduced and projected by a light amount limiting means (not shown) so that the light amount is obtained.

The linear Fresnel lens regions 2a and 2c are
A region in which the linear Fresnel lens shape whose vertical cross-sectional shape is the cross-sectional shape of the Fresnel lens is formed on the emission side. The image light that spreads in the vertical direction is emitted substantially parallel in the vertical direction, and the diffusion plate 1 is formed. Lead to. Specifically, the angle β is determined according to the vertical light incident angle α, and the unit shape is determined. If this is performed for each position and the angle β is changed, the shape of the linear Fresnel lens regions 2a and 2c that emits the incoming image light substantially parallel in the vertical direction can be formed. Therefore, each of the rear projectors PJ1 to PJ4
In the portion corresponding to the position of the optical axis, β = 0 °, and a vertically symmetrical shape with that as the axis of symmetry.

The vertical prism sheet 3 is a sheet having a prism area 3b and linear Fresnel lens areas 3a and 3c like the horizontal prism sheet 2. The horizontal prism sheet 2 has a direction for controlling image light. The difference is that it is horizontal.

In the vertical prism sheet 3, the rear projector P
From the optical axes of J1 to PJ4, overlapping regions 4b, 4e, and 4i (=
It is 22 inches diagonally away from the prism area 3b) (FIG. 2), and from this value, the incident angle α in the horizontal direction is α = 24.1 °. Therefore, as in the case of the horizontal prism sheet 2, if the angle β between the exit surface and the entrance surface of the prism area 3 b in the vertical prism sheet 3 is 43.3 °, the exit angle with respect to the vertical prism sheet 3 Vertical. In the present embodiment,
The angle at the position corresponding to the base angle of the isosceles triangle is 43.3 °
The unit prisms having the cross-sectional shape of are arranged in the left-right direction to form a prism region 3b.

The linear Fresnel lens regions 3a and 3c are
In the horizontal direction, the image light that spreads in the horizontal direction is emitted in a direction substantially parallel to the diffusion plate 1, and is guided to the diffusion plate 1. The linear Fresnel lens regions 2a and 2c in the horizontal prism sheet 2 are provided.
The shape is produced in the same manner as described above.

The horizontal prism sheet 2 having the configuration described above
In addition, two types of vertical prism sheets 3 were produced by changing the material, thickness, and pitch. (1) An acrylic resin was used as the material, and the thickness was 5 mm and the pitch was 0.2 mm, and both prism sheets were produced by casting. (2) A UV-curable resin (urethane acrylate) was laminated on a PET (polyethylene terephthalate) base material, and the lens shape was shaped. Both prism sheets were produced by casting with a thickness of 0.1 mm and a pitch of 0.1 mm. Using these two types of prism sheets, two types of multi-projection systems equipped with projection screens having these are manufactured, and as a result of observing from various angles, an image without luminance unevenness is obtained over the entire screen including the overlapping area. It was confirmed that it could be done.

According to the present embodiment, as shown in FIG.
Since the direction of the image light reaching the diffuser is in the same direction regardless of the position, the diffused light F to J of the image light emitted from the diffuser is obtained.
However, even if the viewing angle changes, it is possible to obtain an image without unevenness in luminance on the screen.

(Modifications) Various modifications and changes are possible without being limited to the above-described embodiments, and they are also within the equivalent scope of the present invention. (1) In the present embodiment, an example is shown in which four rear projectors are arranged in a grid, but the present invention is not limited to this, and for example, nine or sixteen rear projectors may be used. Instead of arranging the rear projectors in a grid pattern, for example, two projectors may be arranged horizontally. In this case, even if the horizontal prism sheet for controlling the image light in the vertical direction is omitted, the luminance unevenness in the overlapping area is not noticeable.

(2) In this embodiment, the shape of the linear Fresnel lens is obtained by calculating the angle of the slope for each position, and each slope is a plane. However, the present invention is not limited to this. Each of the slopes may be a curved surface in a form in which a cylindrical lens that can emit light in parallel is divided for each pitch and the vertices are aligned.

[0034]

As described above in detail, according to the present invention, among the emission directions of the image light projected on the overlapping area,
It is provided with an emission direction matching portion that makes at least the emission direction in the adjacent direction the same direction, and in particular, the emission direction matching portion is a prism region in which unit prisms having a cross-sectional shape of an isosceles triangle are arranged in the adjacent direction. The image light can reach the diffuser plate so that the light is emitted in the same direction. In addition, since the relationship between the incident angle of the image light and the angle between the emission surface and the incidence surface is defined as a predetermined relationship, the image light is surely aligned on the diffusion plate so that the emission direction is the same direction. Can be reached. Further, since the projection screen includes the diffusion plate, the horizontal prism sheet, and the vertical prism sheet, even if the image is from a rear projector arranged in a two-dimensional direction, luminance unevenness does not occur regardless of the position. You can do so.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a multi-projection system according to the present invention.

FIG. 2 is a view of the projection screen 4 as viewed from the front.

FIG. 3 is a side view illustrating the horizontal prism sheet 2.

FIG. 4 is a diagram illustrating the shape of a prism area 2b.

FIG. 5 is a perspective view illustrating a conventional multi-projection system.

FIG. 6 is a plan view showing a conventional multi-projection system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Diffusion plate 2 Horizontal prism sheet 3 Vertical prism sheet 4 Projection screen PJ1-PJ4 Rear projector

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) H04N 5/74 H04N 5/74 C

Claims (7)

[Claims] 1. A prism sheet used for a projection screen on which image light projected by a plurality of rear projectors is irradiated, wherein the first and second rear projectors arranged adjacent to each other project light. An overlapping area in which the first and second image lights overlap each other; and an emission direction matching unit for making at least the adjacent one of the emission directions of the first and second image lights projected onto the overlapping area the same direction. And a prism sheet comprising: 2. The prism sheet according to claim 1, wherein the emission direction matching section is a prism area in which unit prisms having a cross-sectional shape of an isosceles triangle are arranged in the adjacent direction, and other than the prism area. The prism sheet is a linear Fresnel lens area in which scalene triangles are arranged in the adjacent direction. 3. The prism sheet according to claim 1, wherein an incident angle of the first and second image light to be incident is α, and an angle between an exit surface and an incident surface is β. Assuming that the refractive index of the sheet is n, A prism sheet characterized by the following relationship: 4. A projection comprising: the prism sheet according to claim 1; and a diffusion plate provided closer to an observer than the prism sheet and diffusing image light. screen. 5. The projection screen according to claim 4, wherein the prism sheet includes: a horizontal prism sheet that controls the image light in a vertical direction; and a vertical prism sheet that controls the image light in a horizontal direction. A projection screen, characterized in that: 6. A multi-projection system comprising: the projection screen according to claim 4; and a plurality of rear projectors. 7. The multi-projection system according to claim 6, wherein the projection screen passes through the center of the linear Fresnel lens, the optical axis of the image light projected from the rear projector, and the overlapping area and the prism area. A multi-projection system characterized by: