JP2003287809A - Rear projection type video display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rear projection type video display device which has a screen causing no Moire fringes in an off-axis optical system of the large eccentricity. <P>SOLUTION: The Fresnel lens used for the off-axis optical system is constituted so as to satisfy the following conditional relations; for example, when δ<p1, 0.51<δ/p1<0.59, 0.61<δ/p1<0.65, 0.67<δ/p1<0.74, 0.76<δ/p1<0.79. Therein, Δ>V, δ=H-(H<SP>2</SP>+p<SP>2</SP>-2pr)<SP>1/2</SP>, Δ is the eccentricity of the perpendicular direction, 2V is the perpendicular dimension of a screen, δ is the horizontal component of a braze pitch on the right (or left) end of the screen, 2H is the horizontal dimension of the screen, (p) is the braze pitch, (r) is the radius of the blade passing the left and right and the lower end of the screen and p1 is pixel pitch. <P>COPYRIGHT: (C)2004,JPO

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rear projection type video display device. [0002] Conventionally, a rear projection type video display device using a screen has been known. The screen is composed of a combination of a Fresnel lens and a lenticular lens. Generally, a so-called on-axis optical system in which the center of the screen exists on the optical axis of the Fresnel lens is used. Here, the pitch of the Fresnel lens is defined by the pitch in the diameter direction of the blaze grooved on a concentric circle centered on the optical axis in both the vertical and horizontal directions of the screen (hereinafter, referred to as the blaze pitch). And a pixel pitch on the screen, a pitch at which the vertical stripes of the lenticular lens are arranged (hereinafter, referred to as a lenticular pitch),
A condition that moire fringes do not occur is defined between the above-mentioned blaze pitch. [0003] Even in a so-called off-axis optical system in which the center of the screen is deviated from the optical axis of the Fresnel lens, generation of moiré fringes is avoided even under the above specified conditions when the amount of eccentricity is small. In some cases, large moiré fringes may be generated when the off-axis optical system with a large eccentricity is applied under the condition that moiré fringes do not occur in the on-axis optical system. In view of the above circumstances, an object of the present invention is to provide a rear projection type video display apparatus having a screen which does not generate moire fringes in an off-axis optical system having a large eccentricity. [0005] In order to solve the above problems, a rear projection type video display apparatus of the present invention uses a screen provided with a Fresnel lens and a lenticular lens and emits light from an image projection optical system. In the rear-projection image display device that receives the image light on the back side of the screen and displays an image, the center of the screen is located at a position vertically decentered from the optical axis center of the Fresnel lens. And Δ: vertical eccentricity 2V: vertical dimension of the screen δ: horizontal component of the blaze pitch at the lower right (or left) end of the screen 2H: horizontal dimension of the screen p: blaze pitch r: blade passing through the lower right and left ends of the screen Radius p1: pixel pitch p2: wrench pitch, Δ> V δ = H− (H ² + p ² −2pr) ^1/2 δ <p1 0.51 <δ / p1 <0.59 0.61 <δ / p1 <0.65 0.67 <δ / p1 <0.74 0.76 <δ / p1 <0.79 or δ <p2 0.51 <δ / p2 <0.59 0.61 <δ / p2 <0.65 0.67 <δ / p2 <0.74 0.76 <δ / p2 <0.79 > P1, 0.51 <p1 / δ <0.59 0.61 <p1 / δ <0.65 0.67 <p1 / δ <0.74 0.76 <p1 / δ <0.79 or , Δ> p2, 0.51 <p2 / δ <0.59 0.61 <p2 / δ <0.65 0.67 <p2 / δ <0.74 0.76 <p2 / δ <0. 79 is satisfied. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A rear projection type video display according to an embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is an internal structural view of a rear projection type video display device viewed from the side. An optical engine 2 is finely adjusted and fixed on a lower chassis 1 of the rear projection display. The optical engine 2 includes an illumination optical system, an image light generation optical system, a projection lens, and the like. The illumination optical system includes a light source such as a metal halide lamp, an integrator lens including a pair of lens pairs, a polarization conversion device for aligning the polarization direction of the light from the light source, and the like. In this embodiment, the image light generation optical system uses a three-plate type transmission liquid crystal type color separation / synthesis optical system. The center of the projected image light is off-axis with respect to the optical axis of the projection lens (oblique projection optical system). The aspherical mirror 3 is integrally fixed to the optical engine 2 by a support member 7 on the projection image light emission side of the optical engine 2. The aspherical mirror 3 receives the projected image light from the optical engine 2 and reflects it. The projection video light reflected by the aspherical mirror 3 is reflected by the folding mirror 4 and guided to the rear mirror 5. The upper end of the folding mirror 4 is located near the lower end of the screen 6. The screen 6 receives the projected image light reflected by the rear mirror 5 on the rear side, and projects an image. FIG. 2 is a perspective view showing the Fresnel lens 6a and the lenticular lens 6b on the screen 6 with some separation. Matting processing is performed on the image light incident surface of the Fresnel lens 6a, and a lens portion is formed on the emission surface. The lenticular lens 6b has a lens portion in a vertical stripe shape, and a black stripe is formed on the flat surface side in accordance with the arrangement of the lens portion. FIG. 3 is a diagram schematically showing the front side of the Fresnel lens 6a on the screen 6. FIG. In the figure, a screen s indicated by a dotted square frame indicates a case where the screen is an on-axis optical system. In this case, a screen center o exists on the optical axis ax of the Fresnel lens F (6a). On the other hand, a screen S indicated by a solid rectangular frame is an off-axis optical system according to this embodiment, and is a position shifted by an eccentricity Δ in the vertical direction from the optical axis ax of the Fresnel lens F (6a). Has a screen center O. Here, the horizontal size of the screen S is 2H, and the vertical size of the screen is 2V. At this time, Δ> V. As shown in FIG. 1, the screen S according to this embodiment uses only a portion of the Fresnel lens F that does not include the optical axis ax. That is, the blaze pitch p in the horizontal direction is not included. Here, the inventor of the present application has experimentally shown that the horizontal component of the blaze pitch at the left and right ends of the lower side of the screen obtained by cutting out the screen S from the Fresnel lens F is used as a parameter to have the strongest correlation with the occurrence of moire fringes. In addition to finding from these results, attention was paid to the fact that the horizontal component of the blaze pitch is determined by the amount of eccentricity and the size of the screen of the screen. Specific examples are shown below. FIG. 4 is a diagram schematically showing a method of deriving a horizontal component of the blaze pitch at the lower right end of the screen of the screen. In the figure, the horizontal component of the blaze pitch at the lower right corner of the screen S is denoted by δ. Here, the lower right corner of the screen S is A1,
Assuming that the blade passing through No. 1 is B1, the blade one inside of B1 is B2, and the intersection of B2 and the lower side of the screen S is A2, δ is the distance between A1 and A2. At this time, the following equation is established. H ² + a ² = r ² (H−δ) ² + a ² = (rp) ² ∴δ = H− (H ² + p ² −2pr) ^1/2 where 2H: Screen horizontal dimension p: Blaze pitch r : The radius of the blade passing through the lower right and left ends of the screen a: The distance from the optical axis of the Fresnel lens to the lower end of the screen. Then, a configuration satisfying the following conditional expression is adopted. When δ <p1, 0.51 <δ / p1 <0.59 0.61 <δ / p1 <0.65 0.67 <δ / p1 <0.74 0.76 <δ / p1 <0.79 Alternatively, when δ <p2, 0.51 <δ / p2 <0.59 0.61 <δ / p2 <0.65 0.67 <δ / p2 <0.74 0.76 <δ / p2 <0. 79 When δ> p1, 0.51 <p1 / δ <0.59 0.61 <p1 / δ <0.65 0.67 <p1 / δ <0.74 0.76 <p1 / δ < 0.79 Or, when δ> p2, 0.51 <p2 / δ <0.59 0.61 <p2 / δ <0.65 0.67 <p2 / δ <0.74 0.76 <p2 / δ <0.79 where p1: pixel pitch (projected liquid crystal pixel pitch on the screen) p2: wrench pitch. By determining the horizontal dimension 2H of the screen and the amount of eccentricity Δ in the vertical direction as the components of the rear projection type video display apparatus, the radius r of the blade passing through the lower right and left ends of the screen is determined, and the pixel pitch p1 and the wrench pitch p2 are determined. Is given, satisfying the above condition, the Fresnel lens F (6
a) The blaze pitch p is determined, and a screen 6 that can prevent moiré can be obtained by producing a Fresnel lens F having such a blaze pitch p and cutting out a predetermined area (solid-line square area in FIG. 2). become. Here, as mentioned in the related art, it is a known matter that the condition for preventing the occurrence of moire fringes is defined between the pixel pitch p1, the wrench pitch p2, and the blaze pitch p. However, this condition is only effective in an on-axis optical system or an off-axis optical system having a small eccentricity. A rear projection type video display according to the present invention includes an off-axis optical system in which Δ> V. For this off-axis optical system, the screen S
The horizontal component δ of the blaze pitch at the lower left and right edges of the screen is determined to be an important element, and the horizontal component δ is determined by the screen size and the eccentricity Δ. In the case of configuring a rear projection type video display device, a horizontal component δ obtained by a screen size and an eccentricity Δ,
A Fresnel lens F (6a) having an appropriate blaze pitch p is defined by defining conditions under which moiré fringes do not occur between the pixel pitch p1 and the wrench pitch p2, and a predetermined area is cut out and used. A display device is realized. In this embodiment, the optical engine 2
As for the above, the one having a three-plate type transmissive liquid crystal type color separation / synthesis optical system was shown, but a single-plate type or a type using a reflective liquid crystal panel may be used. The present invention is also applicable to the case where a video display element of the following type is used. As described above, according to the present invention,
There is an effect that it is possible to provide a rear projection type video display device having a screen that does not generate moire fringes in an off-axis optical system having a large amount of eccentricity.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an internal structural diagram of a rear projection type video display device according to the present invention as viewed from a side. FIG. 2 is a perspective view showing a Fresnel lens and a lenticular lens in the screen with some separation therebetween. FIG. 3 is a diagram schematically showing a front side of a Fresnel lens in a screen. FIG. 4 is a diagram schematically illustrating a method of deriving a horizontal component of a blaze pitch at a lower right end of the screen of the screen. [Description of Signs] 2 Optical engine 3 Non-curved mirror 4 Folding mirror 5 Rear mirror 6 Screen

Claims (1)

Claims: 1. A rear-projection image that uses a screen having a Fresnel lens and a lenticular lens, receives image light emitted from an image projection optical system on the back side of the screen, and displays an image. In the display device, the center of the screen is located at a position decentered in the vertical direction from the center of the optical axis of the Fresnel lens, and Δ: vertical eccentricity 2V: screen vertical dimension δ: screen Horizontal component 2H of the blaze pitch at the lower right (or left): horizontal dimension of the screen p: blaze pitch r: radius p of the blade passing through the lower left and right edges of the screen p1: pixel pitch p2: wrench pitch Δ> Vδ = H− ( under H ² + p ² -2pr) ^1/2 conditions, when δ <p1, 0.51 <δ / p1 <0.59 0.61 <δ / p1 <0.65 0.67 < When /p1<0.74 0.76 <δ / p1 <0.79 or δ <p2, 0.51 <δ / p2 <0.59 0.61 <δ / p2 <0.65 0.67 < δ / p2 <0.74 0.76 <δ / p2 <0.79 When δ> p1, 0.51 <p1 / δ <0.59 0.61 <p1 / δ <0.65 0. 67 <p1 / δ <0.74 0.76 <p1 / δ <0.79 or δ> p2, 0.51 <p2 / δ <0.59 0.61 <p2 / δ <0.65 0.67 <p2 / δ <0.74 0.76 <p2 / δ <0.79.