JPH07159900A - Projection screen - Google Patents

Abstract

PURPOSE:To obtain a screen having a protective function and good picture quality without increasing the number of lens sheet, at a lower cost than a screen using circular Fresnel lenses by using a linear Fresnel lens sheet which focuses light beams in the horizontal direction and a linear Fresnel lens sheet which focuses light beams in the vertical direction instead of circular Fresnel lenses. CONSTITUTION:This screen set is arranged successively from the projection CRT 4 toward the observer side, a linear Fresnel lens sheet 1 comprising a linear Fresnel lens which focuses light beams in the horizontal direction on a film, a lenticular lens sheet 2 to diffuse light, and a linear Fresnel lens sheet 3a which focuses light beams in the vertical direction (or elliptical linear Fresnel lens sheet 3c with tilted axis). Further, the linear Fresnel lens sheet 3a (or elliptical linear Fresnel lens sheet 3c with tilted axis) which focuses light beams in the vertical direction has a linear Fresnel lens on the surface facing the projection CRT 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection screen used for a rear projection type television.

[0002]

2. Description of the Related Art A projection screen used in a rear projection type television is typically disclosed in Japanese Patent Laid-Open No. 48-7783.
No. 0 (US Pat. No. 3,830,556) is cited, which is composed of a Fresnel lens part for condensing the projection light to the observer side and a lenticular lens part for diffusing the projection light and forming an image. Conventionally, since the concentric circular Fresnel lens was formed on one sheet, the Fresnel lens had to be produced in a single-wafer manner, and was less productive than a lenticular lens that can be produced by the extrusion method. ， Also, it was difficult to reduce the production cost. At present, projection screens using a circular Fresnel lens sheet and a lenticular lens sheet are the most common, but as mentioned above, there are difficulties in manufacturing a circular Fresnel lens, and instead of the circular Fresnel lens, a linear Fresnel lens is used. It is also proposed to use them in a crossed manner. However,
Compared to the circular Fresnel lens, there was a problem such as a decrease in gain due to the increase of one sheet.
On the other hand, recently, in a projection screen composed of two lens sheets, a circular Fresnel lens sheet and a lenticular lens sheet, the light shielding layer (black stripe) or the lens formed on the observer side surface of the lenticular lens sheet becomes dirty. ， There is a problem that it is easily scratched, and there is a strong demand from the end user for the protection of the surface of the observer side. In order to respond to this, it is made of acrylic resin that is transparent to the most observer side of the projection screen for surface protection. It is often used that three sheets are arranged and the sheet is arranged. In a projection screen in which two linear Fresnel lens sheets are used orthogonally and combined with a lenticular lens sheet, it is necessary to add one sheet and to add four sheets to form a protection screen. There is a problem that the cost is increased and the gain is further reduced.

[0003]

SUMMARY OF THE INVENTION The present invention uses a circular Fresnel lens by replacing the circular Fresnel lens with a linear Fresnel lens sheet for converging in the horizontal direction and a linear Fresnel lens sheet for converging in the vertical direction. It is an object of the present invention to provide a projection screen which can be manufactured at a lower cost and which has a practically sufficiently good image quality as compared with the projection screen of.

[0004]

According to a first aspect of the present invention, in a projection screen used for a rear projection type television, a linear Fresnel lens sheet for horizontally focusing light from a projection tube side, and a lenticular lens for light diffusion. The sheet is composed of three lens sheets, a linear Fresnel lens sheet for collecting light in the vertical direction, and the linear Fresnel lens sheet for collecting light in the vertical direction is characterized in that a linear Fresnel lens is provided on the surface of the projection tube side. This is a projection screen. According to a second aspect of the present invention, the apex of the lens unit of the linear Fresnel lens provided on the surface of the linear Fresnel lens sheet for converging light in the vertical direction on the projection tube side is formed into an arc shape, and the projection light is formed. The projection screen according to claim 1, wherein the light is vertically condensed and diffused. According to a third aspect of the present invention, the lens of the linear Fresnel lens provided on the projection tube side surface of the linear Fresnel lens sheet for converging in the vertical direction is a tilt axis elliptic linear Fresnel lens, and the tilt The axial elliptical linear Fresnel lens is composed of a non-lens surface and a lens surface as a lens unit. The non-lens surface is almost linear, and the lens surface is formed by a part of the ellipse or a combination of a part of the ellipse and a straight line. , The inclination of the major axis of the ellipse changes from the angle near parallel to the sheet to the angle closer to vertical as it goes up and down from the central part of the screen, and condenses and diffuses the projected light in the vertical direction. The projection screen according to claim 1, wherein the projection screen comprises a lens group. According to a fourth aspect of the present invention, the linear Fresnel lens sheet for condensing in the horizontal direction is a film, and the linear Fresnel lens sheet for converging in the vertical direction has a flat emission surface side. The projection screen according to any one of claims 1 to 3. The linear Fresnel lens sheet that collects light in the vertical direction preferably has a sufficient thickness so as to meet the mechanical strength or flame retardancy of the UL standard.

The basic conditions of each lens sheet used in the present invention will be described below. The linear Fresnel lens sheet for horizontally condensing and the linear Fresnel lens sheet for vertically converging used in the present invention are formed of a light-transmitting base material. Here, as the translucent base material, a homopolymer or a copolymer of acrylic acid ester or methacrylic acid ester such as polymethylmethacrylate and polymethylacrylate, polyester such as polyethylene terephthalate and polybutylene terephthalate, polycarbonate,
Thermoplastic resins such as polystyrene and polymethylpentene,
Alternatively, polyfunctional urethane acrylates crosslinked by ultraviolet rays or electron beams, acrylates such as polyester acrylate, transparent resins such as unsaturated polyester, transparent glass, transparent ceramics, etc. are used.

The translucency required for the translucent base material must be selected so that the projected light can be transmitted to the minimum extent to the extent that it does not hinder the use of each application. When used as a lens sheet, it may be colored transparent or matt translucent depending on the application. When used in a projection screen, this light-transmissive substrate is 1.5 to 10% in order to maintain its shape against external force and the like.
The thickness is set to 5 mm, or is set to about 50 to 300 μm, and is held in the TV set by tension or the like. As a method of forming the prism type unit lens groups parallel to each other formed on the surface of the translucent substrate and the film, for example, a known hot pressing method (Japanese Patent Laid-Open No. 56-15
No. 7310), after being embossed with a roll embossing plate on an ultraviolet curable thermoplastic resin film,
A method of irradiating ultraviolet rays to cure the film (Japanese Patent Laid-Open No. 61-156273), applying an ultraviolet ray or electron beam curable resin on a roll intaglio engraved with a lens shape,
After filling the recesses, the roll intaglio is coated with a transparent substrate film through a resin solution, and the resin cured by irradiation with ultraviolet rays or electron beams and the substrate film adhered thereto are rolled.
A method of releasing from the roll intaglio to form the lens shape of the roll intaglio on the cured resin layer (JP-A-3-223883, US Pat. No. 4,576,850) and the like are used. In the case of the method, for convenience of winding and processing the molded lens,
To prevent the occurrence of cracks during processing, select a resin that is relatively flexible and flexible as the ultraviolet or electron beam curing resin. In addition, the size of this prism type unit lens is such that the height at the portion where the lens angle is maximum is 0.05 to
It is about 0.2 mm, and the lens pitch is 0.1 to
Within a range of about 0.5 mm, moire generated between the lenticular lens and the lenticular lens is set to be inconspicuous.

The lenticular lens sheet used in the present invention includes, for example, a so-called lenticular lens sheet or a plurality of unit lenses such as hemispherical surfaces in which columnar unit lenses are arranged adjacent to each other with their ridge directions parallel to each other. A so-called fly's eye lens sheet is used. Here, the cross-sectional shape of the unit lens is a circle, an ellipse, a cardioid, a Rankine's oval, a cycloid, a continuous smooth curve such as an involute curve, or a polygon such as a triangle, a quadrangle, or a hexagon. Use part or all. Even if these unit lenses are convex lenses,
It may be a concave lens. Among these, preferred are design, ease of manufacturing, light collection, and light diffusion characteristics (half-value angle, small amount of side-rope light, isotropic half-value angle luminance, and luminance in the normal direction). The point is a cylinder or an elliptic cylinder. In particular, an ellipse whose major axis is the normal direction of the surface light source is preferable because of its high brightness, and the ratio of the major axis to the minor axis is set to 1: 1 to 2: 1. The lens pitch is set in the range of about 0.3 to 1.5 mm. To improve the contrast, these lenticular lens sheets are usually provided with a light absorption layer on the observer side surface, in parallel with the ridgeline, and on the non-condensing part of the incident side lens. . The lenticular lens sheet is formed of a translucent base material. Here, as the translucent base material, the same material as the above-mentioned linear Fresnel lens sheet can be used. Usually, acrylic or polycarbonate resin is used. In addition, in order to scatter light, this translucent substrate is usually made of resin mixed with particles (beads) having a particle diameter of several tens of μm and a refractive index different from that of the resin. To be When this translucent substrate is used as a lenticular lens sheet for a projection screen,
A certain degree of thickness and rigidity are required in manufacturing and use, and a thickness of about 0.5 to 1.5 mm is usually used.

The linear Fresnel lens sheet used in the present invention for focusing light in the vertical direction is typically a normal linear Fresnel lens sheet 3a, a linear Fresnel lens sheet 3b in which the vertices of the lenses are formed in an arc shape, or The tilt axis elliptical linear Fresnel lens sheet 3c is used. The linear Fresnel lens sheet 3a used in the present invention for converging light in the vertical direction is a linear lens array formed by adjoining unit lenses having a triangular cross section on the projection tube side of the sheet with their ridge directions parallel to each other. Then, the slope of the slope is expressed by Snell's formula (see Formula 1 below), and becomes steeper as it goes up and down from the center. Further, the linear Fresnel lens sheet 3b in which the vertices of the lenses are formed in an arc shape is the linear Fresnel lens sheet 3a in which the apex is an arc shape (the apex arc-shaped linear Fresnel), and the circle has a large lens angle. By the way, it is inscribed on the two sides of the triangle created by the straight part of the lens. The radius of the circle is 1/3 to 1 of the lens pitch
If it is about / 10 and is too large, the light condensing property as a linear Fresnel is lost, and if it is too small, the light diffusing property is lost and there is no difference from the linear Fresnel described above. In addition, since the optical path of the diffusing section faces outward from the linear Fresnel lens section as shown in FIG. 4 (a), the circular arc top linear Fresnel has a focal point smaller than that of the linear Fresnel without the arc top. Should be shorter. In this way, by making the vertex of each lens unit of the linear Fresnel lens provided on the projection tube side into an arc shape, it is possible to have a light collecting and diffusing effect. Further, a tilt axis elliptic linear Fresnel lens sheet 3 as described in detail below
The image quality can be further improved by using c. The linear Fresnel lens provided on the projection tube side of the tilt axis elliptical linear Fresnel lens sheet used in the present invention is a linear lens array in which unit lenses of columnar bodies are arranged adjacent to each other with their ridge directions parallel to each other. The cross-sectional shape consists of an ellipse and a straight line, and the inclination angle of the major axis of the ellipse is close to the screen surface in the central part of the screen and gradually increases toward the outside of the central part.

A linear Fresnel lens sheet 3 for focusing light in the vertical direction (hereinafter, unless otherwise specified, a linear Fresnel lens sheet 3a, a linear Fresnel lens sheet 3b in which the vertices of the lenses are formed in an arc shape, an inclined axis elliptical linear Fresnel lens sheet 3c). Etc. are collectively referred to as a linear Fresnel lens sheet for collecting light in the vertical direction), and are formed from a light-transmitting base material. Here, as the translucent base material, the same material as the above-mentioned lenticular lens sheet can be used. Usually, an acrylic resin is used. In addition, the linear Fresnel lens sheet 3 that collects light in the vertical direction has a smooth surface on the exit surface side, and therefore is subjected to scratch prevention processing, stain prevention processing, antistatic processing, and the like to reduce glare. It is used after being subjected to non-reflection treatment, non-glare treatment, and matte treatment. The linear Fresnel lens sheet 3 that collects light in the vertical direction is
In order to secure the structural strength (rigidity) of the entire screen and to meet the UL standard for flame retardancy of plastics, a certain thickness is required, and the thickness is about 3 to 5 mm.

[0010]

According to the present invention, the lens unit of the linear Fresnel lens sheet for converging in the horizontal direction on the side of the most projection tube and the lens unit of the linear Fresnel lens sheet for converging in the vertical direction on the side of the most observer are linearly parallel. Because of the continuous shape, the extrusion molding method, the roll film and the lens type roll are used in the same way as the lenticular lens sheet.
It is possible to carry out continuous production by letting a radiation-curable resin flow down between the two and treating it with radiation.

Further, in the present invention, the linear Fresnel lens for converging in the horizontal direction is arranged on the most projected light side, and the linear Fresnel lens for converging in the vertical direction is provided on the most observer side, whereby the protective plate At the same time as adding functions
By substantially reducing the number of lens sheets by one, it becomes possible to have the same three-lens structure as the projection screen using the circular Fresnel lens.

Further, the linear Fresnel lens sheet for converging light in the vertical direction has a flat emission surface side in consideration of its role as a screen protection plate. It is possible to apply antistatic treatment, anti-reflection treatment, anti-glare treatment, and matte treatment to reduce glare.

[0013]

Embodiments of the present invention will now be described in more detail with reference to the drawings. FIG. 1 is a perspective view illustrating the concept of a projection screen according to an embodiment of the present invention. FIG. 1A shows the linear Fresnel lens sheet 3a as shown in FIG.
(B) is an inclined axis elliptical linear Fresnel lens sheet 3c
Is shown. FIG. 2 is a diagram for explaining the arrangement and the optical path concept of FIG. 1, and FIGS. 2 (a) and 2 (b) show a plan view and a side view in which the linear Fresnel lens sheet 3a is arranged, and FIG. c) and FIG. 2D show a plan view and a side view in which the tilt axis elliptical linear Fresnel lens sheet 3c is arranged. 1 and 2, the screen set is C
A linear Fresnel lens sheet with a linear Fresnel lens provided on the film for converging in the horizontal direction from the RT projection tube 4 toward the viewer side, a lenticular lens sheet for light diffusion 2, a vertical direction to the most viewer side The linear Fresnel lens sheet 3 for condensing the light is sequentially arranged, and
The linear Fresnel lens sheet 3 for collecting light in the vertical direction is provided with a linear Fresnel lens provided on the projection tube side surface.

(Example 1) As the linear Fresnel lens sheet 3 for converging light in the vertical direction, a linear Fresnel lens sheet 3a having a linear Fresnel lens for converging the projection light in the vertical direction is arranged on the surface of the projection tube. However, a projection screen composed of three pieces was used. The linear Fresnel lens sheet 3a has a sufficient thickness to secure the mechanical strength and / or flame retardancy (UL94HB) of the entire screen.

The specific numerical value of the above configuration is 40 to 60.
If you select only consumer products of inch, the following table 1
Indicated by.

[Table 1]

With the above structure, the linear Fresnel lens sheet 3a has a structure as shown in FIGS. 3 (a) and 3 (b).
It had a light-condensing effect, and it was possible to reduce the amount of diffusing agent contained in the lenticular lens sheet and produce a clear image. FIG. 3 is an example in which the linear Fresnel lens sheet 3a of Example 1 is used. FIG. 3 (a) is a part of an optical path diagram and FIG. 3 (b) is an explanatory diagram showing its diffusion characteristics. In FIG. 3 (b), the horizontal axis represents the angle of the emitted light beam, and the vertical axis represents the intensity thereof. The intensity of the outgoing light emitted at the horizontal position in FIG.
At the value of the emission angle of 0 in FIG. 3B, the light emitted upward in FIG. 3A is on the (+) side of FIG. 3B, and the light emitted downward in FIG. It is shown on the (−) side of (b).

Further, by providing the linear Fresnel lens sheet 3a arranged on the observer side with a sufficient thickness, the linear Fresnel lens sheet for focusing light in the horizontal direction can be made into a thin film, and as a result, Previously, we were able to reduce the rainbow eye and double image (ghost) that were caused by stray light inside the circular Fresnel lens.

(Embodiment 2) As the linear Fresnel lens sheet 3 for converging light in the vertical direction, the lens unit is a linear Fresnel lens sheet 3b in which the vertices of the lenses of the linear Fresnel lens are formed in an arc shape, and three sheets are formed. It was a projection screen. The linear Fresnel lens sheet 3b that collects light in the vertical direction has a sufficient thickness to ensure the mechanical strength and / or flame retardancy (UL94HB) of the entire screen.

The specific numerical value of the above configuration is 40 to 60.
Table 2 below is a list when focusing on inch consumer products.
Indicated by.

[Table 2] (Below margin)

FIG. 4 is an example in which the linear Fresnel lens sheet 3b of Example 2 is used. FIG. 4 (a) is a part of the optical path diagram and FIG. 4 (b) is an explanatory diagram showing its diffusion characteristics. is there.
In FIG. 4B, the horizontal axis represents the angle of the emitted light beam, and the vertical axis represents the intensity thereof. The intensity of the outgoing light emitted at the horizontal position in FIG. 4 (a) is the value of the outgoing angle 0 in FIG. 4 (b), and the light emitted upward in FIG. 4 (a) is (+) in FIG. 3 (b). ) Side, and light emitted downward in FIG. 4A is shown on the (−) side in FIG. 3B. With the above configuration, the linear Fresnel lens sheet 3b that collects and diffuses light in the vertical direction is shown in FIGS. 4 (a) and 4 (b).
It has the effect of condensing and diffusing, as seen in, and reduces the diffusing agent contained in the lenticular lens sheet,
It was possible to produce a clear image.

Further, the linear Fresnel lens sheet 3b in which the vertex of the lens arranged on the observer side is formed in an arc shape.
With a sufficient thickness, the linear Fresnel lens sheet that collects light in the horizontal direction can be made into a thin film, and as a result, stray light in the circular Fresnel lens has conventionally been the cause. , It was possible to reduce rainbow eyes and double images (ghosts).

(Embodiment 3) Next, the tilt axis elliptic linear Fresnel lens sheet used in the present invention will be described in more detail with reference to the drawings. Like the Fresnel lens, the tilt axis elliptic linear Fresnel lens is composed of a lens surface and a non-lens surface that act optically. FIG. 5 is a conceptual diagram for explaining the lens unit of the tilt axis elliptical linear Fresnel lens sheet of the embodiment of the present invention. The lens unit is composed of the non-lens surface linear portion, the elliptical lens portion, and the linear lens portion. . The optical axis of the projected light is corrected and diffused mostly by an elliptical lens. Therefore, the linear lens portion may not be necessary or may be omitted.

FIG. 6 (a) is a partial perspective view for schematically explaining the inclination of the major axis of a plurality of lens units near the central portion and the peripheral portion of the tilt axis elliptic linear Fresnel lens sheet used in the present invention. A lens that changes the inclination of the major axis of the ellipse vertically from the center of the screen to an angle closer to vertical to a sheet, and condenses and diffuses the projection light in the vertical direction. It is shown to consist of groups. In the present invention, the tilt axis elliptical linear Fresnel lens sheet is used for correction and diffusion of the optical axis in the vertical direction. Normally, the vertical diffusion angle of the rear projection screen is smaller than the horizontal diffusion angle, and at most 1
It is about 0 degrees. In order to suppress the diffusion angle within this range and perform effective optical axis correction, it is necessary to increase the average radius of curvature of the lens. Therefore, the ratio of the major axis to the minor axis of the ellipse of the lens should be large (at least 3). It is necessary to provide a linear lens part. Since the lens has an elliptical or linear lens portion having a large diameter ratio as described above, the non-lens surface is substantially linear. FIG. 6B is a conceptual diagram for explaining the inclination θ of the ellipse's long axis, and the inclination θ of the ellipse's long axis is θ = 90 ° −φ−tan ^{−1 when the} direction perpendicular to the screen is zero. It is shown by b / a. Here, a is the major axis of the ellipse, and b is the minor axis of the ellipse. φ is the lens angle and is calculated by the following formula from Snell's formula.

[0024]

[Equation 1]

Here, n is the refractive index of the lens, r is the height of the lens from the center of the screen, f ₁ is the projection distance, and f ₂ is
Focusing distance. FIG. 7 is a conceptual diagram for explaining the tip shape of a die cutting blade for cutting an inclined axis elliptical linear Fresnel lens unit used in the present invention. As shown in the figure, the cutting edge has more than half of the ellipse "buried". It takes a shape, and therefore,
Sufficient strength is obtained at the cutting edge, from the center to the edges of the periphery,
Cutting is possible with one blade. Lens pitch is 0.3 ~
It is set to 1.0.

As the linear Fresnel lens sheet 3 for converging light in the vertical direction, an inclined axis elliptic linear Fresnel lens sheet 3c was used, and a projection screen having a three-piece construction was used. Inclined axis elliptical linear Fresnel lens sheet 3c
Has a sufficient thickness to secure the mechanical strength and / or flame retardancy (UL94HB) of the entire screen.

The specific numerical value of the above configuration is 40 to 60.
If you select only consumer products of inch, Table 3 below
Indicated by.

[Table 3] (Margins below)

FIG. 8 shows an example in which the inclined axis elliptic linear Fresnel lens sheet of FIG. 5 is used. FIG. 8 (a) is a part of an optical path diagram, and FIG. 8 (b) is an explanatory diagram showing its diffusion characteristics. Is. In FIG. 8B, the horizontal axis shows the angle of the emitted light beam, and the vertical axis shows the intensity thereof. The intensity of the outgoing light emitted at the horizontal position in FIG. 8A is the value of the outgoing angle 0 in FIG. 8B, and the light emitted upward in FIG. 8A is (+) in FIG. 8B. ) Side, and the light emitted downward is shown on the (-) side of FIG. 8B. As shown in FIG. 8B, when there is a linear lens portion, the diffusion characteristic has a protruding shape and more light can be emitted in a desired direction. May stand out too much, resulting in an unfavorable result on the image.
FIG. 9 is a conceptual diagram illustrating a lens unit of an inclined axis elliptical linear Fresnel lens sheet according to another embodiment of the present invention,
The one having a linear lens portion between the elliptical lens portions is also shown in FIG.
Although the same effect as that of the lens shown in FIG. 8 is obtained, the position of the protrusion as shown in FIG. 8B appears at a position different from that of FIG. 6B.

With the above structure, the tilt axis elliptic linear Fresnel lens sheet 3c has a light diffusing action at the same time as condensing as shown in FIGS. 8 (a) and 8 (b), and is contained in the lenticular lens sheet. It was possible to reduce the amount of diffusing agent and create a clear image.

Further, by providing the tilt axis elliptic linear Fresnel lens sheet 3c arranged on the observer side with a sufficient thickness, the linear Fresnel lens sheet for focusing light in the horizontal direction can be made into a thin film, As a result, we were able to reduce rainbow eyes and double images (ghosts) that were previously caused by stray light inside the circular Fresnel lens.

[0031]

According to the present invention, it is possible to obtain a projection screen which is cheaper than a projection screen using a circular Fresnel lens and has a good image quality with a protection function without increasing the number of lens sheets.

[Brief description of drawings]

FIG. 1 is a perspective view illustrating the concept of a projection screen according to an embodiment of the present invention. FIG. 1A shows a linear Fresnel lens sheet 3a, and FIG. 1B shows an inclined axis elliptical linear Fresnel lens sheet 3c.

FIG. 2 is a view for explaining the concept of the arrangement and the optical path of FIG. 1 for the projection screen of the embodiment of the present invention,
2 (a) and 2 (b) are a plan view and a side view in which the linear Fresnel lens sheet 3a is arranged, and FIG.
FIG. 2D shows a plan view and a side view in which the tilt axis elliptic linear Fresnel lens sheet 3c is arranged.

FIG. 3 is an example using the linear Fresnel lens sheet 3a of Example 1 of the present invention, FIG. 3 (a) is a part of an optical path diagram, and FIG.
(B) is an explanatory view showing the diffusion characteristic.

4 is an example using a linear Fresnel lens sheet 3b of Example 2 of the present invention, FIG. 4 (a) is a part of an optical path diagram, and FIG.
(B) is an explanatory view showing the diffusion characteristic.

FIG. 5 is a conceptual diagram illustrating a lens unit of an inclined axis elliptical linear Fresnel lens sheet 3c according to a third embodiment of the present invention.

FIG. 6 is a tilted-axis elliptic linear Fresnel lens sheet 3c used in the present invention, and FIG. 4A is a partial perspective view schematically illustrating the tilt of the long axis of a plurality of lens units near the central portion and the peripheral portion of the sheet. FIG. 4B is a conceptual diagram illustrating the inclination θ of the major axis of the ellipse of each lens.

FIG. 7 is a conceptual diagram illustrating a tip shape of a die cutting blade that cuts a lens unit of an inclined axis elliptical linear Fresnel lens 3c used in the present invention.

8 is an example in which the tilt axis elliptic linear Fresnel lens sheet 3c of FIG. 5 is used. FIG. 8A is a part of an optical path diagram, and FIG.
(B) is an explanatory view showing the diffusion characteristic.

FIG. 9 is a conceptual diagram illustrating a lens unit of an inclined axis elliptical linear Fresnel lens sheet 3c according to another embodiment of the present invention.

[Explanation of symbols]

1 Linear Fresnel lens sheet for converging in the horizontal direction 2 Lenticular lens sheet 3 Linear Fresnel lens sheet for converging in the vertical direction 3a Linear Fresnel lens sheet 3b Linear Fresnel lens sheet in which the apex of the lens is formed in an arc shape 3c Inclination axis elliptic linear Fresnel lens sheet 4 Projection tube

Claims (4)

[Claims] 1. A projection screen used for a rear-projection television, comprising three sheets, a linear Fresnel lens sheet for horizontally focusing light from a projection tube side, a lenticular lens sheet for light diffusion, and a linear Fresnel lens sheet for vertically focusing light. The projection screen is characterized in that the linear Fresnel lens sheet, which is composed of the lens sheet of (1) and is focused in the vertical direction, is provided with a linear Fresnel lens on the surface of the projection tube side. 2. The linear Fresnel lens sheet for collecting light in the vertical direction is formed in a circular arc shape at the apex of the lens unit of the linear Fresnel lens provided on the projection tube side surface, and the projection light is collected in the vertical direction. The projection screen according to claim 1, wherein the projection screen is diffused. 3. The lens of the linear Fresnel lens provided on the surface of the linear Fresnel lens sheet for converging light in the vertical direction on the projection tube side is an inclined axis elliptical linear Fresnel lens, and the inclined axis elliptical linear Fresnel lens is a lens. The unit is composed of a non-lens surface and a lens surface, the non-lens surface is almost linear, and the lens surface is formed by a part of an ellipse or a combination of a part of an ellipse and a straight line, and As the inclination goes up and down from the center of the screen, it changes from an angle close to parallel to the sheet to an angle closer to vertical, and it consists of a group of lenses that focus and diffuse the projection light in the vertical direction. The projection screen according to claim 1. 4. The linear Fresnel lens sheet for converging in the horizontal direction is a film, and the linear Fresnel lens sheet for converging in the vertical direction has a flat emission surface side. The described projection screen.