JPH07261278A - Transmission type screen and back projection type picture display device - Google Patents

Abstract

PURPOSE:To improve contrast by reducing color shift and cutoff and eliminating stray light in a transmission type screen used for a back projection type picture display device. CONSTITUTION:The shape of the cross section of a longitudinal lenticular lens constituting the light incident surface 10 of a lenticular lens sheet constituting a transmission type screen is formed so that a position 9a to which a red light beam 17 made incident on a point 10a on the lens surface at a light beam concentration angle theta1 goes after it is made incident thereon may be nearly the same as a position 9b to which the red light beam made incident on a point 10b at the same concentration angle goes after it is made incident thereon, and all the red light beams made incident between the points 10a and 10b on the lens surface at the same concentration angle may go to a position nearer to an optical axis side than the position 9a after they are made incident thereon.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmissive screen constituted by combining a lenticular lens sheet and a Fresnel lens sheet, and a rear projection type image display device provided with the transmissive screen.

[0002]

2. Description of the Related Art In recent years, a rear projection type image display apparatus having a structure in which an image displayed on a projection type cathode ray tube as a small image generation source or a liquid crystal display device is magnified by a projection lens and projected on a transmission type screen has been recently developed. Since the image quality is remarkably improved and you can enjoy the powerful presence on a large screen, it is becoming popular as a home projection TV and a commercial monitor TV.

In this rear projection display apparatus, when a projection type cathode ray tube (hereinafter referred to as a projection tube) is used as an image generation source, in order to sufficiently brighten the brightness on the transmissive screen, conventionally, a red color is generally used. A method has been adopted in which a projection tube and a projection lens are combined for the three primary colors of green, green, and blue, and the three primary colors are combined on a transmissive screen.

FIG. 23 is a top view showing the arrangement of a general optical system in a rear projection type image display device.
As shown in the figure, the projection tube is arranged in the green projection tube 21.
A blue projection tube 20 and a red projection tube 22 are laterally arranged in-line with the center of as a center, and image light is combined on a transmissive screen 24. At this time, the optical axis 25 of the blue image light and the optical axis 27 of the red image light respectively form an angle θ ₁ with the normal line direction of the transmissive screen 24.

This angle θ ₁ is called a light beam convergence angle. Also,
A projection lens 23 which is connected to the blue projection tube 20 and a red projection tube 22, respectively, will be arranged with a normal direction and theta ₂ of the angle of the transmissive screen 24, the lens focus the angle theta ₂ Called a horn. Reference numeral 26 is the optical axis of the green image light.

FIG. 24 is a perspective view showing a main part of a conventional transmissive screen used in such a rear projection type image display device. In the figure, the transmissive screen is composed of two sheets, and comprises a Fresnel lens sheet 4 and a lenticular lens sheet 7.

The Fresnel lens sheet 4 has a light incident surface 5 which is a flat surface, and a light emitting surface 6 which is a Fresnel convex lens shape. The Fresnel lens sheet 4 uses the Fresnel convex lens of the light emitting surface 6 to emit the luminous flux of the image light incident on the entire light incident surface 5 as a substantially parallel luminous flux from the entire light emitting surface 6 to thereby form the lenticular lens sheet 7.
It has a function of converting the light to be incident on, and has an effect of improving the brightness distribution of the entire screen of the transmissive screen.

The light-incident surface 10 of the lenticular lens sheet 7 has a surface shape in which a plurality of vertically elongated lenticular lenses whose longitudinal direction is the vertical direction of the screen screen are continuously arranged in the horizontal direction of the screen screen. The light emitting surface has a shape in which a plurality of vertically elongated lenticular lenses 9 having a screen screen vertical direction as a longitudinal direction and light absorption bands 8 having a finite width having a screen screen vertical direction as a longitudinal direction are alternately and continuously arranged. Is done.

The light incident surface 10 and the light emitting surface (8, 9)
The cross-sectional shape of the vertical lenticular lens that constitutes
Each has a substantially elliptical shape, and its shape and characteristics are described in detail, for example, in Japanese Patent Laid-Open No. 58-59436. In addition, the light diffusion material 15 is mixed inside the lenticular lens sheet 7,
It mainly plays the role of improving the directional characteristics in the vertical direction of the screen.

FIG. 25 is a ray tracing diagram showing a locus of a light flux when light fluxes of green light rays substantially parallel to each other are incident on the lenticular lens sheet 7 shown in FIG. 24, and FIG. 26 is also shown in FIG. FIG. 6 is a ray tracing diagram showing a locus of a light flux when light fluxes of red light rays substantially parallel to each other are incident on the lenticular lens sheet 7. In these figures, 16 is a green ray and 17 is a red ray.

As shown in FIGS. 25 and 26, the light incident surface 1
0 and the vertical lenticular lens are arranged on both sides of the light emission surface (9), so that the emission position of the light emitted from the lenticular lens sheet 7 is within a certain width range on the light emission surface (9). You can collect. Then, the position where the light is not emitted is dyed with black paint to form the light absorption band 8, so that the external light reflection of the transmissive screen can be significantly reduced and the contrast of the image can be improved.

Further, by arranging the vertically long lenticular lenses on both the light incident surface 10 and the light emitting surface (9), the directional characteristics of the viewing luminance of the image light of the three primary colors emitted from the transmissive screen 24. Can be made to have the same tendency to some extent, so that the balance of the three primary colors of red, green and blue can be corrected to some extent. However, strictly speaking, the directional characteristics of the visual luminosity of the image lights of the three primary colors do not completely match, but have different characteristics.

As a result, the balance of the three primary colors of red, green and blue changes depending on the horizontal angle at which the viewer looks at the image,
The color of the image changes and appears. This phenomenon is called color shift. This color shift is expressed by the logarithm of the ratio of the relative value of the luminance of red light and the luminance of blue light when the viewing angle is 0 ° and the luminance is 100%. Shall be evaluated.

[0014]

[Equation 1]

Where R is the brightness of red light at a certain viewing angle, B is the brightness of blue light at a certain viewing angle, and R ₀ is the brightness of red light at a viewing angle of 0 °. , B ₀ is the brightness of blue light at a viewing angle of 0 °. Color shift is dB
It is expressed in units of, and the closer to 0 dB the better. For example, when the ratio of the relative brightness of red light and blue light is 1: 1 it is 0 dB, and when it is 2: 1 it is about 3 dB.

FIG. 27 is a characteristic diagram showing directional characteristics of light in the horizontal direction of the screen screen in the transmissive screens shown in FIGS. It should be noted that in FIG.
_{1 is set} to 9 °, and the viewing luminance is represented by a relative value when the viewing angle at 0 ° is 100%.

As shown in FIG. 27, the transmissive screen of the related art, that is, the longitudinal lenticular lenses constituting the light entrance surface 10 and the light exit surface (9) are each formed to have an almost elliptical cross section. In a transmissive screen having a different lenticular lens sheet 7, the color shift due to the lenticular lens sheet 7 causes a viewing angle of 35 °.
It is 2.3 dB.

On the other hand, conventionally, the transverse cross-sectional shape of the vertically long lenticular lens constituting the light incident surface 10 and the light emitting surface (9) of the lenticular lens sheet 7 is described in, for example, Japanese Patent Application Laid-Open No. 1-182837. As described above, the cross-sectional shape of the vertically long lenticular lens of the light incident surface 10 is set such that the light condensing position is farther in the peripheral portion than in the vicinity of the optical axis, and the color shift is reduced,
Changes in the characteristics of the vertical lenticular lens forming the light incident surface 10 and the vertical lenticular lens 9 forming the light emitting surface (9) with respect to the optical axis shift, and the surface between the light incident surface 10 and the light emitting surface (9). A technique has been proposed in which any change in the characteristics due to a manufacturing error that occurs in the distance (that is, the thickness of the lenticular lens sheet 7) is suppressed.

[0019]

By the way, the conventional rear projection type image display device has a diagonal screen size of 36.
Although it was limited to inches or more, one goal was to make the set (display device) compact and to reduce the space required for installation. Therefore, FIG.
In addition to the structure in which the optical path of the arrangement shown in FIG. 2 is folded back by a reflecting mirror, when the screen size is about 40 inches diagonal, the projection distance of the projection lens is designed to be as short as about 650 to 700 mm from about 800 mm in the past. As a result, the depth of the set housing was reduced, but it was around 450 mm at the minimum.

On the other hand, when the projection tubes having substantially the same outer dimensions as the conventional projection tubes are used as the red, green, and blue projection tubes, the distance between adjacent projection tubes is the same as the conventional one due to the structure. (For example, in the case of a projection tube having a diagonal size of about 7 inches, the projection size is about 140 mm) It is difficult to set it to be equal to or less than that, so that both the light beam convergence angle θ ₁ and the lens convergence angle θ ₂ become large. For example, the light beam convergence angle θ ₁ was previously about 8 to 9 °, but has recently been expanded to about 10 to 11 °.

On the other hand, in order to further reduce the depth of the set casing and reduce the installation space, the depth of the casing is 4
One specification is a specification of 00 mm or less. this is,
This is because furniture having a depth of about 400 mm has become quite popular in recent years, and a clean arrangement can be taken when a rear projection type image display device is installed side by side with such furniture.

To realize this specification, the screen size is 33 inches or more diagonally, the screen aspect ratio is 16: 9, the height of the screen center is 750 mm or less, and the projection distance of the projection lens is 640 mm or less. Is preferable from the viewpoint of installation at home, but the light beam convergence angle θ ₁ is larger than that in the above case and is about 12 °.

However, when the conventional transmissive screen as described above is used for the rear projection type image display device having such a large light beam convergence angle θ ₁ and a large lens convergence angle θ ₂ , the following problems occur. Occurs. That is, as described above, when the light beam converging angle θ ₁ and the lens converging angle θ ₂ become large, the deviation of the optical axes of the red and blue lights incident on the lenticular lens sheet 7 becomes large. The problem of increased color shift arises.

Further, the light beam convergence angle θ ₁ and the lens convergence angle θ ₂
Becomes larger, the divergence angle of the red light and the blue light inside the lenticular lens sheet 7 also becomes larger. Therefore, it is necessary to widen the width of the vertically long lenticular lens 9 forming the light emitting surface (9). However, if the width of the vertically long lenticular lens 9 forming the light emitting surface (9) is increased,
External light reflection by the vertically long lenticular lens surface is increased, which causes a problem that the contrast of an image is lowered.

Moreover, if the width of the vertically long lenticular lens 9 constituting the light exit surface (9) is widened, the width of the light absorption band 8 is narrowed conversely, so that the contrast of the image is further lowered.

Therefore, when constructing a lenticular lens sheet of a transmissive screen used for a rear projection type image display device having a large light beam converging angle θ ₁ and a large lens converging angle θ ₂ , the color shift is reduced and the It is necessary to reduce the width of the vertically long lenticular lens 9 forming the emission surface (9) to the minimum necessary to prevent deterioration of contrast.

On the other hand, however, if the width of the vertically long lenticular lens 9 constituting the light emitting surface (9) is made too narrow, a part of the light incident on the vertically long lenticular lens constituting the light incident surface 10 will be part of the light emitting surface (9). ) May not reach the vertically long lenticular lens 9 and become stray light.

This is not a big problem for green image light whose optical axis is parallel to the normal line of the transmissive screen (the light beam converging angle θ ₁ is 0 °), but the optical axis is transmissive. This is a serious problem for red and blue image lights having a light beam convergence angle θ _{1 of} more than about 11 ° with respect to the screen normal.

As an example, in FIG. 28, a conventional lenticular lens forming a light incident surface has a lateral cross-sectional shape such that a light collecting position is more distant in the peripheral portion than in the vicinity of the optical axis. FIG. 29 shows a locus of a light flux when light fluxes of green light rays substantially parallel to each other are incident on the lenticular lens sheet according to FIG. 29. FIG. 29 also shows a light flux of red light rays substantially parallel to each other on the lenticular lens sheet. The locus | trajectory of a light beam in case the light beam convergence angle (theta) ₁ injects at 12 degrees is shown.

That is, as shown in FIG. 28, even when stray light is not generated for the green image light 16,
As shown in FIG. 29, a part of the red image light 17 may become stray light.

Such stray light is a problem because it deteriorates the contrast and focus characteristics of the image due to internal reflection on the transmissive screen. In addition, when a part of the light becomes stray light, the light transmittance is reduced, which causes the image to be dark, and the contrast is reduced when the image is viewed in a bright room. .

Such stray light is generated by the light emitting surface (9).
It can be reduced by widening the width of the vertically long lenticular lens 9 constituting the light emitting surface (9).
When the width of the vertically long lenticular lens 9 constituting the above is widened, as described above, the external light reflection by the vertically long lenticular lens surface increases, and the problem of lowering the contrast of the image occurs.

In addition to the above problems, as shown in FIG.
The directional characteristics of red image light and blue image light in the conventional transmissive screen have a so-called cut-off in which the viewing luminance sharply decreases at viewing angles outside about 40 ° and −40 °, respectively. To do. In FIG. 27, the magnitude of the relative luminance at the viewing angle at which the cutoff begins is
About 90% of each is red and blue.

When there is a cutoff, at a viewing angle outside the viewing angle at which the cutoff occurs, the viewing brightness sharply decreases due to the cutoff, so that the viewer sees a difference in brightness on the screen. May be felt as a sudden change in color. Therefore, the existence of the cutoff is a problem as well as the increase of the color shift.

Further, in the conventional transmissive screen, there is a problem that when the light beam convergence angle θ ₁ and the lens convergence angle θ ₂ become large, the color breakup of the screen becomes large. Color breakup is a phenomenon in which the images on the left and right halves of the screen are bordered red and bluish, respectively. This phenomenon is very well visually recognized when white is displayed on the entire screen of the screen by the test image signal of all white.

As described above, in the conventional transmissive screen, when it is used for a rear projection type image display device having a large light beam concentration angle θ ₁ and a large lens concentration angle θ ₂ , color shift, cutoff, and It is difficult to solve the problem of color breakage and to improve the contrast. Therefore, when the screen size is a diagonal size of 40 inches, the depth is at least about 450 mm or more.

Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art, reduce color shift, cutoff, and color breakup, eliminate stray light, and improve contrast. It is an object of the present invention to provide a transmissive screen that can be used, and a rear projection type image display device including the same.

Another object of the present invention is that the screen size is a diagonal of 33 inches or more and the projection distance of the projection lens is 640.
When the height is less than or equal to mm, the screen aspect ratio is 16: 9, the height at the center of the screen is 750 mm or less, and the depth of the housing is 400.
It is to provide a rear projection type image display device having a size of less than or equal to mm.

[0039]

According to the present invention, in order to achieve the above object, the shape of the light incident surface is such that a vertically long lenticular lens whose longitudinal direction is the vertical direction of the screen screen is continuous in the horizontal direction of the screen screen. And a vertically elongated lenticular lens having a light emitting surface whose longitudinal direction is in the vertical direction of the screen,
In the lenticular lens sheet, the light incident surface is formed by alternately arranging a plurality of light absorption bands of finite width whose longitudinal direction is the screen screen vertical direction and alternately arranged in the horizontal direction of the screen screen. This is achieved by adopting a high-order aspherical surface shape having the following conditions as the cross-sectional shape (cross-sectional shape in the horizontal direction of the screen screen) of the vertically long lenticular lens.

Here, FIG. 30 shows a coordinate system for defining the cross-sectional shape of the vertically long lenticular lens. Figure 3
At 0, the optical axis direction of the vertically long lenticular lens is Z
The direction from the light incident surface (lens surface) to the light emitting surface is defined as the positive direction. Further, the axis in the radial direction (transverse direction) of the vertically long lenticular lens, which is perpendicular to the Z axis, is the X axis, and the upper direction in FIG. 30 is the positive direction.

Further, let x be the distance in the radial direction from the certain reference point O on the Z axis along the X axis (the positive direction of the X axis is the positive direction of x), and Z from the X axis. The distance in the axial direction (the direction from the light incident surface to the light emitting surface is a positive direction) is defined as a function Z (x) of x. At this time, the cross-sectional shape of the vertically long lenticular lens is defined by the following equation (2).

[0042]

[Equation 2]

In the equation (2), x, Z (x)
Are expressed in units of mm. Further, RD is a radius of curvature, CC is a conic constant, and AD, AE, AF, and AG are aspherical coefficients. In equation (2), the term x is 10
Although only the next term is shown, the present invention is not limited to this, and the terms up to the even-order terms of 12th and higher may be used.

In the present invention, the longitudinal lenticular lens forming the light incident surface of the lenticular lens sheet has a lateral cross-sectional shape that is convex on the side on which image light is incident, and the optical axis of the longitudinal lenticular lens is the axis of symmetry. As a line symmetry, and in the same plane as the horizontal cross section of the screen screen of the vertical lenticular lens,

An angle of 8 ° or more with respect to the optical axis of the vertical lenticular lens in the horizontal direction of the screen screen, which is incident on the lens surface of the vertical lenticular lens across the extension line of the optical axis, is substantially parallel to each other. When a light flux composed of light rays exists, among the light rays included in the light flux, a light ray incident on a point (hereinafter, referred to as a first point) intersecting the optical axis on the lens surface of the vertically long lenticular lens, After a light ray incident on a point (hereinafter, referred to as a second point) near a boundary between adjacent vertically long lenticular lenses is incident, the light rays are almost the same on the lens surface of the vertically long lenticular lens constituting the light exit surface. As you head to the position,

On the lens surface of the vertically long lenticular lens forming the light incident surface, all the light rays incident on the respective other points between the first point and the second point after the incidence, A shape is adopted such that it goes toward a position closer to the optical axis than the position on the lens surface of the vertically long lenticular lens that constitutes the light emitting surface.

In addition to the above conditions, when the maximum absolute value of x (hereinafter referred to as the effective radius) is defined as x _MAX as the transverse cross-sectional shape of the vertically elongated lenticular lens forming the light incident surface of the lenticular lens sheet. , The second derivative function Z ″ (x) of the function Z (x) with respect to x is
A shape that takes a minimum value at x = 0 and a maximum value at x where 0 <| x | <x _MAX is adopted.

[0048] Further, the distance from the center of the transmissive screen to screen diagonal corners and R _MAX, at a position of distance 0.4R _MAX from the center in the screen horizontal direction of the screen, and the principal ray from the red projection tube , The direction of emission of the chief ray from the blue projection tube from the light emitting surface of the Fresnel lens sheet is respectively the angles θ _R , θ with respect to the optical axis direction of the longitudinal lenticular lens forming the light incident surface of the lenticular lens sheet. When forming _B , of angles θ _R and θ _B ,
If the absolute value of one is 14 ° or more, preferably 15 ° or more,
Further, the Fresnel convex lens shape having a configuration in which the other absolute value is 11 ° or less, preferably 10 ° or less is provided on the Fresnel lens sheet.

The above-mentioned cross-sectional shape of the vertically long lenticular lens forming the light incident surface of the lenticular lens sheet according to the present invention will be further described below with reference to FIG. FIG. 1 is an explanatory diagram for explaining a cross-sectional shape of a vertically long lenticular lens that constitutes a light incident surface of a lenticular lens sheet according to the present invention.

As shown in FIG. 1, in the present invention, a light beam converging angle θ ₁ is provided at a point 10a on the lens surface of a vertically long lenticular lens which constitutes the light incident surface 10 and intersects with the optical axis of the vertically long lenticular lens. When a red light beam 17 is incident on the
Longitudinal lenticular lens 9 constituting the light emitting surface (9)
Position 9a on the lens surface of

Similarly, on the lens surface of the vertically long lenticular lens forming the light incident surface 10, a boundary with an adjacent vertically long lenticular lens (that is, when the effective radius of the vertically long lenticular lens is defined as a relative radius 1.0, the relative radius thereof is defined as 1.0). 10 near the position where is 1.0)
When a red light ray 17 is incident on b with a light beam convergence angle θ ₁ , the position 9b on the lens surface of the vertically long lenticular lens 9 forming the light exit surface (9) is directed toward the rear side of the red light ray 17 after the incidence. And are almost at the same position.

Further, the point 1 on the lens surface of the vertically long lenticular lens which constitutes the light incident surface 10 is further added.
All the red light rays that are incident with the light ray convergence angle θ ₁ between 0a and the point 10b are, after the incidence, higher than the position 9a on the lens surface of the vertically long lenticular lens 9 that constitutes the light emission surface (9). It goes to the inner position, that is, the position on the optical axis side.

[0053]

The present invention has been made mainly based on the following matters found as a result of studying the problems of stray light generation, color shift, and cutoff.

With the lenticular lens sheet in the conventional transmissive screen, as shown in FIG. 28, the green image light 16 has a red color as shown in FIG. 29 even when stray light is not generated. Part of the image light 17 may become stray light. Further, in the conventional transmissive screen, as shown in FIG. 27, there is a cutoff mainly in the directional characteristics of the red image light and the blue image light. Therefore, in order to investigate the problems of stray light generation, color shift, and cutoff,
It is necessary to study mainly red and blue image lights.

As shown in FIG. 1, at a point 10a intersecting the optical axis on the lens surface of the vertically long lenticular lens forming the light incident surface 10, the inclination of the lens surface is perpendicular to the optical axis. Therefore, the red ray 17 incident on the point 10a is
The light rays incident on the flat plate perpendicular to the optical axis are subjected to the same refraction and reach the position 9a on the lens surface of the vertically long lenticular lens 9 forming the light emitting surface (9).

Since the refraction angle of the red ray 17 at this time is the same as the refraction angle of the ray incident on the flat plate perpendicular to the optical axis, the arrival position 9a of the ray on the light exit surface (9) is the lenticular lens. The light beam incident on the flat plate having the same thickness as the thickness t of the sheet 7 is almost the same as the arrival position on the light emission surface.

Therefore, the reaching position 9a is substantially constant regardless of the cross-sectional shape of the vertically long lenticular lens that constitutes the light incident surface 10, and the refractive index N of the base material that constitutes the lenticular lens sheet 7 and the lenticular lens sheet. It is determined only by the thickness t of FIG. That is, assuming that the distance from the optical axis to the reaching position 9a is h, h is given by the following equation (3).

[0058]

[Equation 3]

Therefore, at the light exit surface (9),
Regardless of the cross-sectional shape of the vertically long lenticular lens that constitutes the light incident surface 10, it is necessary to secure the arrival position 9a of the light beam, so the width of the vertically long lenticular lens 9 that constitutes the light emitting surface (9) is the minimum. However, a width twice the distance h is required.

Further, among the luminous fluxes of red rays which are parallel to each other and are incident on the lens surface of the longitudinal lenticular lens forming the light incident surface 10, the point 10a and the above-mentioned boundary are crossed across the extension line of the optical axis. In the case of the lenticular lens sheet in the conventional transmissive screen, the red light flux incident between the point 10b near the point of and the point 10b is, for example, as shown in FIG.
As shown in, a part of the light may not reach the vertically long lenticular lens 9 forming the light emitting surface (9) and may become stray light. However, as shown in FIG. 29, for the red light flux that is incident between the point 10a and the point 10c near the other boundary without crossing the extension line of the optical axis,
All have reached the vertically long lenticular lens 9 which comprises the light-projection surface (9).

Therefore, crossing the extension line of the optical axis, point 1
All the red light fluxes incident between 0a and the point 10b are
If the red light ray incident on the point 10a can be refracted inside or at the same position as the locus of the red light ray, part of the red or blue light will not be stray light.

Moreover, the width of the vertically long lenticular lens 9 forming the light exit surface (9) is theoretically sufficient to be twice the distance h obtained by the above equation (3). Therefore, the width of the vertically long lenticular lens 9 constituting the light emitting surface (9) can be minimized. Therefore, the width of the light absorption band 8 can be widened, and an image with good contrast without stray light can be provided.

On the other hand, in order to reduce the cut-off in the directional characteristic of the red image light, adjacent vertically long lenses are formed on the lens surface of the vertically long lenticular lens forming the light incident surface 10 in the peripheral portion away from the optical axis. Near the boundary with the lenticular lens (hereinafter simply referred to as the boundary)
Therefore, it is effective to increase the incident light flux by moving the condensing position of the lens far.

That is, a conventional transmissive screen, for example, as shown in FIG. 26, has a lenticular lens sheet having a cross-sectional shape of a vertically long lenticular lens forming the light incident surface 10 that is substantially elliptical. In the transmissive screen, the red light ray 17 incident on the point 10c near the boundary on the lens surface of the longitudinal lenticular lens forming the light incident surface 10 is incident on the point 10b near the other boundary. Compared with 17, the vertical lenticular lens 9 forming the light exit surface (9) does not provide sufficient refraction.

Therefore, when the red ray 17 incident on the point 10c is emitted from the light emitting surface (9), the viewing angle is 40.
Does not diffuse more than ° and cutoff occurs. Therefore, the condensing distance by the lens is increased in the vicinity of the boundary on the lens surface of the vertically long lenticular lens that constitutes the light incident surface 10, and the red ray incident on the point 10c constitutes the light emitting surface (9). It is necessary to make the vertical lenticular lens 9 near the point where it intersects the optical axis on the lens surface, and to increase the refraction angle given by the vertical lenticular lens 9 forming the light exit surface (9).

However, if the converging distance by the lens is simply increased in the vicinity of the boundary on the lens surface of the vertically long lenticular lens forming the light incident surface 10, the light is incident on the point 10b as shown in FIG. Red ray 1
Since 7 is often stray light, there is a trade-off relationship between the cutoff and the generation of stray light.

In contrast to this relationship, in the present invention, as shown in FIG. 1, the red ray 17 incident on the point 10b near the boundary on the lens surface of the vertically long lenticular lens forming the light incident surface 10 is incident. , The position 9b in the vicinity of the boundary with the light absorption band 8 is reached on the lens surface of the vertically long lenticular lens 9 that constitutes the light exit surface (9), and therefore the balance of the above trade-off relationship is achieved. Will be the best.

That is, since the red ray incident on the point 10b reaches the position 9b, part of the light does not become stray light. Further, the red light ray incident on the point 10c in the vicinity of the other boundary is sufficiently refracted by the vertically long lenticular lens 9 forming the light emitting surface (9), and the viewing angle at which the cutoff starts to occur becomes large. , The relative luminance at that viewing angle becomes smaller. Temporarily, point 10
If the light incident on b passes through the inside of the above condition, the cutoff for the red and blue light incident on the point 10c becomes large.

By making the cross-sectional shape of the vertically long lenticular lens forming the light incident surface 10 into a shape satisfying the above conditions, the cutoff is inconspicuous, the color shift is small, and there is no stray light. It is possible to obtain a lenticular lens sheet having high transmittance and good contrast.

The width of the vertically long lenticular lens 9 forming the light exit surface (9) is set to be twice the distance h obtained by the above equation (3), so that stray light is not generated. Although the width can be suppressed and the width can be minimized, in actual implementation, the deviation of the optical axis of the lenticular lens sheet and the thickness error are taken into consideration.
It should be as wide as 1 to 1.4 times.

However, even in that case, it is possible to make the width narrower than that of the vertically long lenticular lens forming the light emitting surface of the lenticular lens sheet in the conventional transmission type screen, the contrast is high, and the cutoff is small. A characteristic transmission screen can be obtained.

[0072] On the other hand, the distance from the center of the transmissive screen to screen diagonal corners and R _MAX, at a position of distance 0.4R _MAX from the center in the screen horizontal direction of the screen, and the principal ray from the red projection tube , The emission direction of the chief ray from the blue projection tube from the light emission surface of the Fresnel lens sheet, respectively, with respect to the optical axis direction of the longitudinal lenticular lens constituting the light incident surface of the lenticular lens sheet, the angle θ _R , When forming θ _B ,

Of the angles θ _R and θ _B , the absolute value of one is 1
When a Fresnel convex lens shape having a configuration in which the absolute value of the other is 5 ° or more, preferably 16 ° or more, and 11% or less, preferably 10 ° or less, is provided on the Fresnel lens sheet, a red or blue In the longitudinal lenticular lens that constitutes the light emitting surface of the lenticular lens sheet, the chief ray will pass through a position farther from the optical axis, and the entire luminous flux of that color will pass outside the effective radius of the light emitting surface and will be lost. The color breakup is reduced because more light is emitted.

[0074]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS. FIG. 2 shows a case where light fluxes of red light rays having a light ray converging angle θ ₁ of 12 ° and substantially parallel to each other are incident on the lenticular lens sheet 7 in the transmissive screen according to the first embodiment of the present invention. FIG. 3 is a ray tracing diagram showing the trajectory of the light flux, and FIG. 3 is a ray tracing diagram showing the trajectory of the light flux when light fluxes of green light rays substantially parallel to each other are incident on the lenticular lens sheet 7 of FIG. .

Further, in Table 1 below, when the cross-sectional shape of the lenticular lens sheet 7 shown in FIGS. 2 and 3 is defined by the function shown in the above-mentioned (Equation 2), constants and coefficients in the function are given. An example of each numerical value and others are shown. In this embodiment (design example), the light beam convergence angle θ ₁ is 12 °.
This is an example suitable for front and rear optical systems.

[0076]

[Table 1]

The transmissive screen of this embodiment is composed of the Fresnel lens sheet 4 and the lenticular lens sheet 7, like the conventional transmissive screen shown in FIG.

Now, as shown in FIG. 2, the longitudinal cross section of the vertically long lenticular lens forming the light incident surface 10 of the lenticular lens sheet 7 in this embodiment has a parallel red color with a light beam converging angle of 12 °. Of the light flux composed of light rays, the light rays incident on a point 10a intersecting the optical axis of the vertically long lenticular lens on the lens surface of the vertically long lenticular lens forming the light incident surface 10 and the boundary between the adjacent vertically long lenticular lens Near point 1
The light ray incident on 0b substantially intersects at a position 9a on the lens surface of the longitudinal lenticular lens 9 forming the light emitting surface (9), and also at other points between the points 10a and 10b. The shape is such that all the incident light rays reach the inside, that is, the optical axis side, of the position 9a on the lens surface of the vertically long lenticular lens 9 forming the light emitting surface (9).

FIG. 4 shows a design example of the lenticular lens sheet 7 shown in Table 1 above, where the light beam converging angle is 12 °.
FIG. 6 is a characteristic diagram showing a relationship between an incident position on the light incident surface 10 and an emission position on the light emitting surface (9) of red light incident on the horizontal axis. The relative radius r of x and the relative radius r ′ of the emission position x ′ on the light emission surface (9) are plotted on the vertical axis.

Here, the relative radius r of the light incident surface 10 and the relative radius r'of the light emitting surface (9) are the effective radii of the light incident surface 10 and the light emitting surface (9), respectively, x _MAX ,
When _x'MAX is given, it is given by the following equation (4).

[0081]

[Equation 4] r = x / x _MAX

[0082]

## EQU5 ## r '= x' / x ' _MAX

In FIG. 4, r = 0 and r ′ = 0 are points on the optical axis of the vertically long lenticular lens 9 constituting the light incident surface 10 and the light emitting surface (9), respectively. Further, the point 10a corresponds to r = 0, the point 10b corresponds to r = r ₁ and the point 9a corresponds to r ′ = r ₁ ′, and the cross-sectional shape of the vertically long lenticular lens forming the light incident surface 10 is It shows that the shape is the same as the above-mentioned gist of the present invention.

In the transmissive screen of this embodiment, as shown in FIGS. 2 and 3, part of the light in the lenticular lens sheet 7 does not become stray light and the light utilization rate is high. , Good contrast of the image can be obtained. Here, although some stray light may be generated by mixing the light diffusing material into the sheet base material, it is at a level that does not pose a practical problem.

FIG. 5 shows numerical values for defining the cross-sectional shape of the lenticular lens sheet 7 shown in FIG. 2 and FIG.
It is a characteristic view which shows the directional characteristic of the light of a screen horizontal direction in a transmissive screen when the numerical value shown in the said Table 1 is used. The directional characteristics of FIG. 5 are derived by calculation with the light beam convergence angle θ ₁ of 12 °, and the influence of the light diffusing material is ignored.

As shown in FIG. 5, the color shift in the directional characteristic of light in the horizontal direction of the screen screen is determined by the viewing angle ±
1.7 dB at 35 °, 4.0 d at a viewing angle of ± 55 °
B, the conventional lenticular lens sheet 7, that is, the vertical lenticular lens has a substantially elliptical cross-sectional shape, even though the rear projection type image display device has a large light beam focusing angle and a large lens focusing angle. The color shift is less than the lenticular lens sheet 7.

Further, the viewing angle at which the cutoff begins to occur is about ± 50 °, and the relative luminance at that time is as small as about 50%, so that an image of high quality with no noticeable cutoff is obtained. There is.

By the way, in the following Table 2, when the cross-sectional shape of the lenticular lens sheet 7 shown in FIG. 2 is defined by the function shown in the above-mentioned (Equation 2), each constant and coefficient in the function are shown. Other examples of numerical values are shown.

[0089]

[Table 2]

FIG. 6 shows the directional characteristics of light in the horizontal direction of the screen in the transmissive screen when the numerical values shown in Table 2 are used as the numerical values for defining the cross-sectional shape of the lenticular lens sheet 7 shown in FIG. It is a characteristic view to show. The directional characteristics of FIG. 6 are also derived by calculation with the light beam convergence angle θ ₁ of 12 °, and the influence of the light diffusing material is ignored.

In Tables 1 and 2, the longitudinal lenticular lens forming the light exit surface (9) has an elliptical cross-sectional shape, which is a color shift in the directivity of light in the horizontal direction of the screen. Although the design example is optimized so that the color unevenness on the screen is reduced, it may be a circle or an appropriate aspherical shape as in the case of the conventional transmissive screen. Regarding the width of the vertically long lenticular lens 9 forming the light exit surface (9), when the light beam convergence angle θ ₁ is 12 °, it is 2 h which is twice the distance h given by the formula (3). It is set to 1.1 to 1.4 times 2h.

As can be seen from FIG. 6, even when the numerical values shown in Table 2 above are used as the numerical values for defining the cross-sectional shape of the lenticular lens sheet 7 shown in FIG. When a directional characteristic of a screen screen with a small off-state can be obtained, and when it is used in a rear projection type image display device with a large light beam concentration angle and a large lens concentration angle, as in the case of using the numerical values shown in Table 1 above. However, there is an effect that a part of light does not become stray light and an image with good contrast can be obtained.

As described above, according to this embodiment,
The balance between color shift, cutoff and contrast is excellent, and a more preferable image can be provided for viewing. Next, a second embodiment of the present invention will be described with reference to FIGS.

FIG. 7 shows a lenticular lens sheet 7 in a transmissive screen as a second embodiment of the present invention.
FIG. 7 is a ray tracing diagram showing a locus of a light flux when light fluxes of red light rays having a light ray converging angle θ ₁ of 12 ° and being substantially parallel to each other enter.

Further, Table 3 below shows an example of each numerical value when the cross-sectional shape and the like of the lenticular lens sheet 7 shown in FIG. 7 is defined by the above formula (Equation 2). This example (design example) is an example suitable for an optical system having a light beam convergence angle θ _{1 of} about 12 °.

[0096]

[Table 3]

The transmissive screen of this embodiment is also composed of the Fresnel lens sheet 4 and the lenticular lens sheet 7 as in the conventional transmissive screen shown in FIG.

The difference between this embodiment and the above-mentioned first embodiment is that in the first embodiment, the cross-sectional shape of the vertically long lenticular lens forming the light incident surface 10 of the lenticular lens sheet 7 is " Light incident surface 1 of the bundle of red parallel rays incident with a ray converging angle of 12 °
On the lens surface of the vertically long lenticular lens constituting 0, a ray incident on a point 10a intersecting the optical axis of the vertically long lenticular lens and a ray incident on a point 10b near the boundary between adjacent vertically long lenticular lenses. , Substantially intersect at the position 9a on the lens surface of the longitudinal lenticular lens 9 forming the light exit surface (9), and all the rays incident on the other points between the points 10a and 10b are Position 9 on the lens surface of the vertically long lenticular lens 9 forming the light emitting surface (9)
In contrast to the shape which satisfies the condition of "inward of a, that is, reaching the optical axis side", in the present embodiment,
In addition to the above-mentioned conditions, the cross-sectional shape of the vertically long lenticular lens that constitutes the light-incident surface 10 has the following condition: "In the light-incident surface 10, when the effective radius is x _MAX , the function Z (x) that defines the cross-sectional shape is Second derivative function Z ″ (x) with respect to x
Takes a minimum value of positive value at x = 0, and 0 <| x | <
It has a shape that satisfies the condition that "a maximum value is obtained at x that is x _MAX ."

FIG. 8 shows a design example of the lenticular lens sheet 7 shown in Table 3 above, where the light beam converging angle is 12 °.
FIG. 6 is a characteristic diagram showing the relationship between the incident position on the light incident surface 10 and the emission position on the light emitting surface (9) of red light that is incident with the horizontal axis on the horizontal axis as in FIG. 4 described above. The relative radius r of the incident position x on the light incident surface 10 and the relative radius r ′ of the outgoing position x ′ on the light emitting surface (9) are plotted on the vertical axis.

In FIG. 8 as in FIG. 4, the point 10a is r = 0, the point 10b is r = r ₁ , and the point 9a is r ′ =.
Corresponding to r ₁ ′, it is shown that the cross-sectional shape of the vertically long lenticular lens forming the light incident surface 10 is a shape that satisfies the same conditions as those of the first embodiment described above.

FIG. 9 is a graph showing the design example of the lenticular lens sheet 7 shown in Table 3 above, where x is a value of the function Z (x) that defines the cross-sectional shape of the vertically long lenticular lens forming the light incident surface 10. Second derivative function Z ″ (x)
Is shown. However, the horizontal axis represents the relative radius r of the incident position x on the light incident surface 10 described above.

In FIG. 9, the second derivative function Z ″ (x)
Takes a positive minimum value at x = 0, a maximum value near r = 0.8 (that is, x = about 0.8x _MAX ), becomes 0 near r = 0.95, and at r = 1. It is a negative value.

In the transmissive screen of this embodiment, as shown in FIG. 7, a part of the light is not stray light in the lenticular lens sheet 7, and the light utilization rate is high, and Good contrast can be obtained. Here, although some stray light may be generated by mixing the light diffusing material into the sheet base material, it is at a level that does not pose a practical problem.

FIG. 10 shows a case where the numerical values shown in Table 3 above are used as the numerical values for defining the cross-sectional shape of the lenticular lens sheet 7 shown in FIG. 3 is a characteristic diagram showing the directional characteristics of FIG. The directional characteristic of FIG. 10 is derived by calculation with the light beam convergence angle θ ₁ of 12 °, and the influence of the light diffusing material is ignored.

As shown in FIG. 10, the color shift in the directional characteristic of light in the horizontal direction of the screen screen is 1.7 dB at a viewing angle of ± 35 °, and 2.9 dB at a viewing angle of ± 55 °.
Even though the rear projection type image display device has a large light beam focusing angle and a large lens focusing angle, the conventional lenticular lens sheet 7, that is, the longitudinal lenticular lens has a substantially elliptical cross section. The color shift is smaller than that of the lenticular lens sheet 7, and the color shift at the viewing angle of ± 55 ° is smaller than that of the first embodiment described above. Further, unlike the first embodiment, since there is no cutoff, there is an effect that an image of extremely high quality is obtained.

In Table 3, the longitudinal lenticular lens 9 forming the light exit surface (9) has an elliptical cross-sectional shape, which is a color shift in the directivity of light in the horizontal direction of the screen and the screen. Although the design example is optimized so that the color unevenness is reduced, similar to the conventional transmissive screen, a circle or an appropriate aspherical shape may be used as compared with the case of the first embodiment. It is the same.

Regarding the width of the vertically long lenticular lens 9 forming the light exit surface (9), when the light beam convergence angle θ ₁ is 12 °, it is twice the distance h given by the equation (3). It is set to 1.1 to 1.4 times 2h for a certain 2h.

Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 11 is a perspective view showing a main part of a transmissive screen as a third embodiment of the present invention. The transmissive screen of this embodiment has substantially the same configuration as the transmissive screen of the first embodiment. The difference from the transmissive screen of the first embodiment is that the light incident surface 13 of the Fresnel lens sheet 12 is The point is that a plurality of horizontally long lenticular lenses having the horizontal direction of the screen screen as the longitudinal direction are arrayed in the vertical direction of the screen screen. The cross-sectional shape of the lenticular lens sheet 7 is the same as the shape shown in FIG.

Also in this embodiment, as in the first embodiment, the directional characteristic in the horizontal direction of the screen screen is obtained in which the color shift is small and the cutoff is almost inconspicuous.
Further, a part of light does not become stray light, and an image with high light transmittance and good contrast can be provided for viewing.

Further, in the present embodiment, the diffusion of light in the direction perpendicular to the screen screen is not limited to the light diffusing material mixed in the sheet base material, but also the laterally long light formed on the light incident surface 13 of the Fresnel lens sheet 12. Also done with a lenticular lens. Therefore, the mixing amount of the light diffusing material can be reduced, and in this case, the reflection of external light by the light diffusing material is reduced, so that an image with better contrast can be obtained.

On the other hand, in this embodiment, the cross-sectional shape of the lenticular lens sheet 7 may be the same as the cross-sectional shape of the lenticular lens sheet 7 of the second embodiment shown in FIG. At this time, the color shift is further reduced and the cutoff is almost eliminated in the directional characteristics of light in the horizontal direction of the screen screen.

Next, a fourth embodiment of the present invention will be described with reference to FIG. FIG. 12 is a perspective view showing a main part of a transmissive screen as a fourth embodiment of the present invention. The difference between the transmissive screen of the present embodiment and the transmissive screen of the first embodiment is that the transmissive screen of this embodiment has a Fresnel lens sheet 4 and a lenticular lens sheet 7.
And a second lenticular lens sheet 1, 3
The point is that it is composed of one sheet. The cross-sectional shape of the lenticular lens sheet 7 is the same as the shape shown in FIG.

In the present embodiment, the second lenticular lens sheet 1 has a shape in which the light incident surface 2 has a shape in which a plurality of horizontally long lenticular lenses having the horizontal direction of the screen screen as the longitudinal direction are continuously arranged in the vertical direction of the screen screen. And has a function of diffusing the incident light flux in the vertical direction of the screen screen. Further, the shape of the light emitting surface 3 is a plane.

Also in this embodiment, as in the first embodiment, the directional characteristic in the horizontal direction of the screen screen is obtained in which the color shift is small and the cutoff is almost inconspicuous.
Furthermore, part of the light does not become stray light, and an image with high light transmittance and good contrast can be provided for viewing.

Further, in the vertical direction of the screen screen, the light is diffused by the horizontally long lenticular lens of the light incident surface 2 as in the third embodiment.
The amount of the light diffusing material mixed in can be reduced, and an image with better contrast can be obtained.

On the other hand, in this embodiment, the cross-sectional shape of the lenticular lens sheet 7 may be the same as that of the lenticular lens sheet 7 of the second embodiment shown in FIG. At this time, the color shift is further reduced and the cutoff is almost eliminated in the directional characteristics of light in the horizontal direction of the screen screen.

In each of the above embodiments, the light diffusing material may or may not be mixed in the lenticular lens sheet 7. Compared with the case where the light diffusing material is not mixed, the color shift is slightly improved, and the ghost due to unnecessary reflection of light between each sheet that constitutes the transmissive screen is reduced. But there is
On the other hand, there are disadvantages such as a slight decrease in image contrast and focus characteristics.

When the above-mentioned light diffusing material is mixed into the lenticular lens sheet 7, the light diffusing material is simply mixed into the lenticular lens sheet 7, and the light emitting surface (9 The light diffusing material may be unevenly distributed on the side of). With such a configuration, compared to a configuration in which a light diffusing material is uniformly mixed, even if the amount of the light diffusing material is increased to expand the directional characteristics of light in the screen screen vertical direction, the image The effect is that the deterioration of the focus characteristics is not so much seen.

A specific manufacturing method of the lenticular lens sheet 7 having a light diffusing material unevenly distributed on the light emitting surface (9) side is disclosed in JP-A-3-39944 or JP-A-5-61120. There is a method based on the technique as disclosed in the publication.

Among them, in JP-A-5-61120, the thickness of the layered portion including the light diffusing material on the side of the light emitting surface (9) of the lenticular lens sheet 7 is measured in the vicinity of the optical axis of the vertically long lenticular lens. Although a technique of making the thickness thinner in the peripheral portion is disclosed, in the present invention, in the case where the light diffusing material is further unevenly distributed in the vicinity of the optical axis of the light emitting surface (9) by the above-mentioned conventional technique, each of the embodiments described above is used. There is a new effect, which is unexpected in the above-mentioned conventional art, that the color shift is further reduced.

The reason for this will be described with reference to FIGS. 13 to 15. FIG. 13 shows the lenticular lens sheet 7 of the transmissive screen of the second embodiment of the present invention shown in FIG. 7, in which light diffusion as a layered portion including a light diffusion material is provided on the light emission surface (9) side. It is a figure which shows the cross-sectional shape of the example of the structure which provided the material layer 19 and made the thickness of the layered part thin in the peripheral part rather than the optical axis vicinity.

In FIG. 13, looking at the light rays emitted in the + 35 ° direction and the −35 ° direction in the horizontal direction of the screen screen on the viewing side, the red light ray traveling in the + 35 ° direction has a distance passing through the layered portion. About 0.24 mm, -35 °
The red light ray traveling in the direction has a distance of about 0.18 mm passing through the layered portion.

In the figure, only the red light ray 17 is shown, but since the blue light ray exists substantially symmetrically with the red light ray with respect to the optical axis, there is a blue light ray traveling in the + 35 ° direction,
The blue light rays traveling in the -35 ° direction have distances of passing through the layered portions of about 0.18 mm and about 0.24 mm, respectively.
Becomes

Therefore, the red ray of the rays traveling in the + 35 ° direction passes through the layered portion for a distance about 1.3 times longer than that of the blue ray. The longer the passing distance of the layered portion, the more light is diffused by the light diffusing material and travels in the other direction, so that less light travels in the original direction.

FIGS. 14 and 15 are characteristic diagrams showing the directional characteristics in the horizontal direction of the screen screen in comparison at this time.
FIG. 14 shows the case without the light diffusing material, and FIG. 15 shows the case with the light diffusing material layer. In FIG. 14, + 35 °
The color shift in the direction is 1.7 dB, but in FIG. 15, the color shift in the + 35 ° direction is reduced to 1.3 dB.

This is because the light diffusion material layer 19 diffuses more red light than blue light.
In FIG. 5, the relative luminance of red is much lower than the relative luminance of blue as compared with FIG. To be more accurate, it is necessary to consider the light rays near the above-mentioned light ray traveling in the + 35 ° direction as well, but even in that case, the tendency is generally as described above.

Next, the Fresnel lens sheet in each of the above embodiments will be described. FIG. 16 shows a transmission screen having a configuration in which the lenticular lens sheet 7 according to the second embodiment of the present invention is combined with the conventional Fresnel lens sheet 4, and the entire screen on the screen is white by a test image signal of white. FIG. 6 is a characteristic diagram showing the distribution of relative luminance from the center of the screen to the right end and the left end of the screen in the horizontal direction when viewed from the front of the screen for each color of red, green, and blue. The horizontal axis indicates the relative distance in the horizontal direction from the center of the screen, where the distance from the center of the screen to the diagonal corner of the screen is 1, and the right side of the screen is the positive direction and the left side of the screen is the negative direction.

As shown in FIG. 16, in the right half of the screen, red,
The relative brightness of blue is larger than that of green, and it looks bluish,
Further, in the left half of the screen, the relative brightness of red is larger than that of green and blue, and the image appears reddish, causing color breakup.

FIG. 17 shows that when the distance from the center of the screen to the diagonal corner of the screen of the above-mentioned transmission screen is R _MAX , the relative distance from the center of the screen to the horizontal right direction is 0 when viewed from the image viewing side. 4 is a ray tracing diagram showing loci of chief rays of red, green, and blue at a position of 4R _MAX , which is drawn without a light diffusing material.

In FIG. 17, among the chief rays of red, green and blue, the chief ray of blue is the point 9 farthest from the optical axis on the light emitting surface (9) of the lenticular lens sheet 7.
It has passed p. At this time, Fresnel lens sheet 4
The direction of emission of the chief ray of each color from the Fresnel convex lens on the light emission surface is about 11.0 ° for red, about 0.1 ° for green, and about 13. for blue with respect to the optical axis direction of the lenticular lens sheet.
It is 5 °, and the position of the point 9p is 0.
The distance is 126 mm.

FIGS. 18 and 19 show the principal rays of red, green and blue at the position of 0.4 R _{MAX in} the horizontal right direction from the center of the screen when viewed from the image viewing side of the transmissive screen of the present invention. FIG. 4 is a ray tracing diagram showing a locus, which is drawn without a light diffusing material.

In FIG. 18, the direction of emission of the chief ray of each color from the Fresnel convex lens is about 10.4 ° below 11 ° for red and about 0.5 ° for green with respect to the optical axis direction of the lenticular lens sheet. Blue is configured to have an angle of 14 ° or more and approximately 14.5 °. At this time, as in the case of FIG.
Of the red, green, and blue chief rays, the blue chief ray passes through a point 9p farthest from the optical axis on the light exit surface (9) of the lenticular lens sheet 7, and its position is 0 from the optical axis. The distance is .137 mm.

In this case, as compared with FIG. 17, the passing point 9p of the blue principal ray is located farther from the optical axis, and the entire blue light flux passes through the outside of the effective radius of the light emitting surface and becomes loss light. Since the light is increased, the color breakage is effectively reduced. At this time, when the lenticular lens sheet 7 has a light diffusing material, the light loss of the blue luminous flux is further increased by the diffusion, and thus the color breakup is further reduced.

In FIG. 19, the emission direction of the principal ray of each color from the Fresnel convex lens is about 9.5 ° which is less than 10 ° for red and about 1.6 ° for green with respect to the optical axis direction of the lenticular lens sheet. Blue is configured to be about 15.5 °, which is 15 ° or more. At this time, the blue chief ray passes through the point 9p farthest from the optical axis on the light exit surface (9) of the lenticular lens sheet 7 as in FIG. 18, and its position is 0.147 mm from the optical axis. Has become the distance.

In this case, the passing point 9p of the blue principal ray is located farther from the optical axis than in the case of FIG. 18, and the light which becomes the lost light of the blue luminous flux is further increased. It is further reduced.

Finally, a rear projection type image display device equipped with the transmissive screen of the present invention will be described.
20 is a front view schematically showing the outer appearance of an embodiment of a rear projection type image display apparatus equipped with a transmissive screen according to the present invention, and FIG. 21 is an external view of the rear projection type image display apparatus of FIG. It is the side view which showed roughly.

20 and 21, reference numeral 31 is a rear projection type image display device, and 37 is a transmissive screen. In this embodiment, the rear projection type image display device 31 has a screen size of 38 inches diagonal and an aspect ratio of 16: 9. Further, the width, height and depth of the main body of the rear projection type image display device 31 are 900 mm, 990 mm and 390 mm, respectively, and the center height of the screen is set to 725 mm.

FIG. 22 is a sectional view schematically showing the positional relationship of the components related to the optical system in the rear projection type image display device 31 of FIG. 20 when viewed from the side. In the figure, 32 is a projection tube, 33 is a projection lens, 34 is a reflecting mirror, 38 is a coupler that connects the projection tube 32 and the projection lens 33, 39 is an electric circuit section, 40 is a housing, and 46 is the projection tube 3.
CPT boards for supplying power and signals to the two, 47, 48,
49 are casters forming part of the housing 40,
Main plate and wire mesh part.

In the rear projection type image display apparatus of the present invention, the transmissive screen of the present invention described above is used, and other parts are arranged at high density as shown in FIG. There is an effect that a compact set (rear projection type image display device) as shown can be realized.

[0140]

As is apparent from the above description, according to the present invention, in the lenticular lens sheet that constitutes the transmissive screen, the cross-sectional shape of the vertically long lenticular lens that constitutes the light incident surface of the sheet is specified. By adopting the shape of
Even when used in a rear projection image display device with a large ray concentration angle θ ₁ and lens concentration angle θ ₂ , color shift, cutoff, and color breakage can be reduced, and stray light is eliminated to improve image contrast. Can be made.

That is, a part of the light does not become stray light, and the light transmittance can be increased as compared with the case of the transmissive screen using the conventional lenticular lens sheet. Further, as compared with the conventional lenticular lens sheet in which the longitudinal lenticular lens has a substantially elliptical cross-sectional shape, it is possible to obtain a directional characteristic with less color shift and a smaller cutoff. Also,
Since the light transmittance can be increased, even when a light diffusing material is mixed in the base material of the lenticular lens sheet, little light becomes stray light and good contrast characteristics can be obtained.

Further, at a position of 0.4 R _{MAX in} the horizontal direction of the screen screen from the center of the screen, the chief ray from the red projection tube and the chief ray from the blue projection tube are emitted from the light exit surface of the Fresnel lens sheet. The emitting directions are angles θ _R and θ _{B with} respect to the optical axis direction of the longitudinal lenticular lens that constitutes the light incident surface of the lenticular lens sheet.
Of the angles θ _R and θ _B , the absolute value of one is 1
Since the Fresnel lens sheet is provided with a Fresnel convex lens shape of 4 ° or more, preferably 15 ° or more and the other absolute value is 11 ° or less, preferably 10 ° or less, red or blue In the longitudinal lenticular lens that constitutes the light-emitting surface of the lenticular lens sheet, the chief ray of the light passes through a position further away from the optical axis, and the entire luminous flux of that color passes outside the effective radius of the light-emitting surface and is lost. The light that becomes light is increased, and the above-mentioned color breakup is reduced.

In the rear projection type image display device of the present invention, a compact set can be realized by using the above-mentioned transmission screen of the present invention and arranging each of the other parts at a high density.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a cross-sectional shape of a vertically long lenticular lens that constitutes a light incident surface of a lenticular lens sheet 7 according to the present invention.

FIG. 2 is a ray tracing diagram showing a trajectory of a light flux when red light fluxes substantially parallel to each other are incident on a lenticular lens sheet 7 in a transmissive screen as a first embodiment of the present invention.

FIG. 3 shows the lenticular lens sheet 7 shown in FIG.
It is a ray tracing diagram which shows the locus | trajectory of the light beam in case the light beam which consists of a green light ray substantially parallel to each other injects.

FIG. 4 is a diagram showing a cross-sectional shape of the lenticular lens sheet 7 shown in FIG. FIG. 6 is a characteristic diagram showing the relationship between the incident position on the light incident surface 10 and the emission position on the light emitting surface (9).

5 is a characteristic showing directivity of light in a screen screen horizontal direction in a transmissive screen when the numerical values shown in Table 1 are used as numerical values for defining the cross-sectional shape and the like of the lenticular lens sheet 7 shown in FIG. It is a figure.

6 is a characteristic showing a directional characteristic of light in a screen screen horizontal direction in a transmissive screen, when the numerical values shown in Table 2 are used as numerical values for defining the cross-sectional shape of the lenticular lens sheet 7 shown in FIG. It is a figure.

FIG. 7 is a ray tracing diagram showing a locus of light flux when light fluxes of red light rays substantially parallel to each other are incident on the lenticular lens sheet 7 in the transmissive screen according to the second embodiment of the present invention.

8 is a diagram showing the cross-sectional shape of the lenticular lens sheet 7 shown in FIG. 7 as a numerical value that defines the cross-sectional shape, etc. of the red light incident on the light incident surface 10 of the lenticular lens sheet 7, It is a characteristic view which shows the relationship between the incident position in the light-incidence surface 10 and the emission position in the light-exit surface (9).

9 is a cross-sectional shape of a vertically elongated lenticular lens forming a light-incident surface 10 when the numeric values shown in Table 3 are used as the numeric values that define the cross-sectional shape of the lenticular lens sheet 7 shown in FIG. It is a characteristic view which shows the secondary differential function Z ″ (x) with respect to x of the function Z (x) to be defined.

10 is a characteristic showing the directional characteristic of light in the horizontal direction of the screen screen in the transmissive screen when the numerical values shown in Table 3 are used as the numerical values that define the cross-sectional shape of the lenticular lens sheet 7 shown in FIG. It is a figure.

FIG. 11 is a perspective view showing a main part of a transmissive screen as a second embodiment of the present invention.

FIG. 12 is a perspective view showing a main part of a transmissive screen as a third embodiment of the present invention.

13 shows a case where a layered portion containing a light diffusing material is provided on the light emitting surface (9) side in the lenticular lens sheet 7 of the transmission screen of the second embodiment of the present invention shown in FIG. FIG. 3 is a ray tracing diagram showing the loci of light fluxes of red light rays that are substantially parallel to each other when they enter.

FIG. 14 is a lenticular lens sheet 7 shown in FIG.
FIG. 7 is a characteristic diagram showing the directional characteristics of light in the horizontal direction of the screen screen in the case where there is no light diffusion material layer in the transmissive screen using.

FIG. 15 is a lenticular lens sheet 7 shown in FIG.
FIG. 6 is a characteristic diagram showing the directional characteristics of light in the horizontal direction of the screen screen in the case where there is a light diffusing material layer in the transmissive screen using.

FIG. 16 is a relative in the horizontal direction of the screen when an all-white image is projected on a transmissive screen having a configuration in which the lenticular lens sheet 7 of the second embodiment of the present invention and the conventional Fresnel lens sheet 4 are combined. It is a characteristic view showing a distribution of luminance.

17 is a perspective view showing a transparent screen shown in FIG. 16 with a relative distance of 0.
It is a ray tracing figure which shows the locus | trajectory of the chief ray of red, green, and blue in the position of 4.

FIG. 18 is a perspective view of the transmission screen of the present invention in which the relative distance is 0.
It is a ray tracing figure which shows the locus | trajectory of the chief ray of red, green, and blue in the position of 4.

FIG. 19 is a perspective view of the transmission type screen of the present invention, wherein the relative distance is 0.
It is a ray tracing figure which shows the locus | trajectory of the chief ray of red, green, and blue in the position of 4.

FIG. 20 is a front view schematically showing the outer appearance of an embodiment of a rear projection type image display device having a transmissive screen according to the present invention.

21 is a side view schematically showing the outer appearance of the rear projection type image display device shown in FIG. 20. FIG.

22 is a cross-sectional view schematically showing a positional relationship of components related to an optical system in the rear projection type image display device shown in FIG. 20, as seen from a side surface.

FIG. 23 is a top view showing the arrangement of general optical systems in a rear projection type image display device.

FIG. 24 is a perspective view showing a main part of a conventional transmissive screen used in a rear projection type image display device.

FIG. 25 is a lenticular lens sheet 7 shown in FIG.
FIG. 3 is a ray tracing diagram showing a locus of a light flux when green light fluxes that are substantially parallel to each other are incident on FIG.

FIG. 26 is a lenticular lens sheet 7 shown in FIG.
FIG. 4 is a ray tracing diagram showing a locus of a light flux when red light fluxes that are substantially parallel to each other are incident on the optical path.

27 is a characteristic diagram showing directional characteristics of light in the horizontal direction of the screen in the transmissive screen shown in FIG.

FIG. 28 is a cross-sectional shape of a vertically long lenticular lens,
A conventional lenticular lens sheet that has a shape such that the light collecting position is farther in the peripheral part than in the vicinity of the optical axis.
It is a ray tracing diagram which shows the locus | trajectory of the light beam in case the light beam which consists of a green light ray substantially parallel to each other injects.

FIG. 29 shows a cross-sectional shape of a vertically long lenticular lens,
A conventional lenticular lens sheet that has a shape such that the light collecting position is farther in the peripheral part than in the vicinity of the optical axis.
It is a ray tracing diagram which shows the locus | trajectory of the light beam when the light beam which consists of red light rays substantially parallel to each other injects.

FIG. 30 is an explanatory diagram showing a coordinate system for defining the cross-sectional shape of the vertically long lenticular lens.

[Explanation of symbols]

1 ... landscape lenticular lens sheet, 2, 5, 10,
13 ... Light incident surface, 3, 6, 14 ... Light emitting surface, 4, 12 ...
Fresnel lens sheet, 7 ... Lenticular lens sheet, 8 ... Light absorption band, 9 ... Longitudinal lenticular lens, 1
0 ... Light incident surface, 10a ... Point of the vertically long lenticular lens that constitutes the light incident surface, intersecting with the optical axis of the vertically long lenticular lens on the lens surface, 10b, 10c ... Lens surface of the vertically long lenticular lens that constitutes the light incident surface Points near the boundary with the adjacent vertically long lenticular lens above, 16 ... Green ray, 17 ... Red ray, 18 ...
Stray light, 19 ... Light diffusion material layer, 20 ... Blue projection tube, 21 ... Green projection tube, 22 ... Red projection tube, 23 ... Projection lens, 24
... Transmissive screen, 25 ... Optical axis of blue image light, 26
… Optical axis of green image light, 27… Optical axis of red image light, 3
1 ... Rear projection type image display device, 32 ... Projection tube,
33 ... Projection lens, 34 ... Reflecting mirror, 37 ... Transmissive screen, 38 ... Coupler, 39 ... Electric circuit section, 40 ... Housing,
46 ... CPT substrate, 47 ... Casters, 48 ... Base plate, 4
9 ... Wire mesh part.

Claims (16)

[Claims] 1. A transmissive screen which is composed of at least a Fresnel lens sheet and a lenticular lens sheet, transmits the image light incident from the image generation source side, and emits the image light to the image viewing side. The Fresnel lens sheet has a Fresnel convex lens in which one of the surface on which the image light is incident (hereinafter referred to as a light incident surface) and the surface on which the image light is emitted (hereinafter referred to as a light emission surface) is a Fresnel convex lens. The lenticular lens sheet has a shape in which the light-incident surface has a shape in which a vertically long lenticular lens having a screen screen vertical direction as a longitudinal direction (hereinafter referred to as a light-incident surface vertically long lenticular lens) is continuously formed in the screen screen horizontal direction. The light emitting surface has a vertical lenticular shape whose longitudinal direction is perpendicular to the screen screen. (Hereinafter, referred to as “longitudinal lenticular lens for light emission surface”) and a light absorption band having a finite width whose longitudinal direction is in the vertical direction of the screen screen are alternately arranged in the horizontal direction of the screen screen. The cross-sectional shape of the incident surface vertical lenticular lens in the horizontal direction of the screen screen is convex on the side on which the image light is incident, and forms a line-symmetric shape with the optical axis of the light incident vertical lenticular lens as the axis of symmetry. And, in the same plane as the cross section of the light incident surface vertical lenticular lens in the horizontal direction of the screen screen, an angle of 8 ° or more with respect to the optical axis of the light incident surface vertical lenticular lens in the horizontal direction of the screen screen, There is a substantially parallel luminous flux that is incident on the lens surface of the light incident surface vertical lenticular lens across the extension of the optical axis. In this case, among the light rays included in the light flux, the light rays incident on a point (hereinafter, referred to as a first point) intersecting the optical axis on the lens surface of the light incident surface vertical lenticular lens are adjacent to each other. A light incident surface at a point near the boundary with the vertically long lenticular lens (hereinafter referred to as a second point);
After being incident, the light exit surface and the first and second points on the lens surface of the light-incident surface vertical lenticular lens are moved to almost the same position on the lens surface of the light-incident surface vertical lenticular lens. All of the light rays incident on the other points in between are formed so that, after incidence, they are directed to a position on the optical axis side with respect to the position on the lens surface of the light emission surface longitudinal lenticular lens. Characteristic transmissive screen. 2. The transmissive screen according to claim 1, wherein a cross-sectional shape of the light incident surface vertical lenticular lens along the horizontal direction of the screen screen is based on a position on the optical axis of the light incident surface vertical lenticular lens. The position has a curved shape represented by a function Z (x) of the distance x along the horizontal direction from the position (where the sign of Z (x) is positive in the direction from the light incident surface to the light emitting surface). , And the maximum absolute value of x (hereinafter referred to as the effective radius) is x _MAX , the second derivative function Z ″ of x of the function Z (x) above.
(X) takes a minimum value at x = 0, and 0 <| x | <
A transmissive screen having a curved shape such that a maximum value is obtained at x that is x _MAX . 3. The transmissive screen according to claim 1, wherein the cross-sectional shape of the light incident surface vertical lenticular lens along the horizontal direction of the screen screen is based on the position on the optical axis of the light incident surface vertical lenticular lens. The position has a curved shape represented by a function Z (x) of the distance x along the horizontal direction from the position (where the sign of Z (x) is positive in the direction from the light incident surface to the light emitting surface). , And the maximum absolute value of x (hereinafter referred to as the effective radius) is x _MAX , the second derivative function Z ″ of x of the function Z (x) above.
(X) is a positive value and a minimum value at x = 0,
<| X | <x _MAX takes a maximum value at x, and x =
A transmissive screen having a curved shape such that x _MAX takes a negative value. 4. The transmissive screen according to claim 1, wherein the cross-sectional shape of the light-incident surface vertical lenticular lens along the horizontal direction of the screen screen is based on the position on the optical axis of the light-incident surface vertical lenticular lens. The position has a curved shape represented by a function Z (x) of the distance x along the horizontal direction from the position (where the sign of Z (x) is positive in the direction from the light incident surface to the light emitting surface). , And the maximum absolute value of x (hereinafter referred to as the effective radius) is x _MAX , the function Z (x) is 0 <| x | <x _MAX.
A transmissive screen having a curved shape having an inflection point in. 5. The transmissive screen according to claim 1, wherein the width of the vertically long lenticular lens on the light exit surface is twice the distance h given by the following equation (3). A transmissive screen having a width set to be 1.1 to 1.4 times longer than a certain 2h. Note [Equation 3] Where t is the thickness of the lenticular lens sheet, θ ₁
Is the light beam convergence angle, and N is the refractive index of the base material forming the lenticular lens sheet. 6. The transmissive screen according to claim 1, wherein the Fresnel lens sheet is one of the light incident surface and the light emitting surface that has the Fresnel convex lens shape. A different type of surface is a transmissive screen characterized in that it is a surface shape formed by arranging a plurality of horizontally-long lenticular lenses whose longitudinal direction is the horizontal direction of the screen screen in a vertical direction of the screen screen. 7. The transmission screen according to claim 1, wherein the shape of at least one surface is such that a horizontal lenticular lens whose longitudinal direction is the screen screen horizontal direction is continuous in the screen screen vertical direction. The transmissive screen is characterized in that a second lenticular lens sheet having a planar shape formed by arranging a plurality of such elements is further arranged in the optical path. 8. The transmissive screen according to claim 1, wherein the lenticular lens sheet includes a light diffusing material. 9. The transmission screen according to claim 1, wherein the lenticular lens sheet includes a light diffusing material unevenly distributed on a side of the light emitting surface. screen. 10. The transmission screen according to claim 1, wherein the lenticular lens sheet has a light diffusing material unevenly distributed on the light emitting surface side, and the light emitting surface lenticular. A transmissive screen characterized in that it is unevenly distributed near the optical axis of the lens. 11. A rear projection type image display device comprising the transmissive screen according to any one of claims 1 to 10. 12. A rear projection type image display device having a screen size of 33 inches or more diagonal and a screen aspect ratio of approximately 16: 9, wherein the transmissive screen according to claim 1 and a plurality of screens are provided. Of the image generation source, a projection lens for projecting a display image of the image generation source on the transmissive screen, and a reflecting mirror that folds back the projection light flux from the projection lens; A rear projection type image display device, characterized in that an electric circuit for displaying an image on a source is fixedly housed at a predetermined position inside a casing, and the depth of the casing is 400 mm or less. 13. The rear projection type image display device according to claim 12, wherein the height of the center of the screen is 750 mm or less. 14. The rear projection type image display device according to claim 12,
A rear projection type image display device, wherein the projection distance of the projection lens is 640 mm or less. 15. The rear projection type image display device according to claim 12,
As the plurality of image generation sources, red, green, and blue image generation sources are arranged in this order in the horizontal direction of the screen, and the distance from the center of the screen on the transmissive screen to the diagonal corner of the screen is R _MAX. Of the chief ray from the red image source and the chief ray from the blue image source of the Fresnel lens sheet at a position of 0.4 R _{MAX in} the horizontal direction of the screen from the screen center of the screen. When the emission direction from the light emission surface forms an angle θ _R , θ _B with respect to the optical axis direction of the light incident surface vertical lenticular lens of the lenticular lens sheet, respectively, among the angles θ _R , θ _B , A rear projection type image display device, wherein one absolute value is 14 ° or more and the other absolute value is 11 ° or less. 16. The rear projection type image display device according to claim 12,
As the plurality of image generation sources, red, green, and blue image generation sources are arranged in this order in the horizontal direction of the screen, and the distance from the center of the screen on the transmissive screen to the diagonal corner of the screen is R _MAX. Of the chief ray from the red image source and the chief ray from the blue image source of the Fresnel lens sheet at a position of 0.4 R _{MAX in} the horizontal direction of the screen from the screen center of the screen. When the emission direction from the light emission surface forms an angle θ _R , θ _B with respect to the optical axis direction of the light incident surface vertical lenticular lens of the lenticular lens sheet, respectively, among the angles θ _R , θ _B , A rear projection type image display device, wherein one absolute value is 15 ° or more and the other absolute value is 10 ° or less.