JP2007163547A - Projection display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rear projection display device capable of improving light use efficiency even in an oblique projection system using a Scheimpflug principle. <P>SOLUTION: The projection display device includes: an illuminating optical system that modulates light from an illuminating light source, thereby making the light incident on a light valve regulating a display image; and a projecting optical system that magnifies and projects the light of display image formed by the light valve, onto a screen. In the projection display apparatus, when the light valve, projecting optical system, and screen face are regarded as a subject face, lens principal face, and image face respectively, planes obtained by extending these three faces are made to cross in one place, thereby satisfying the Scheimpflug principle, and making the optical axis of the illuminating optical system almost coincide with the optical axis of the projecting optical system. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a transmissive projection TV (transparent TV, rear projection TV,
Although there are various names such as rear projection type TV, they are all synonymous, and may be used afterwards. The present invention relates to an improvement in a display that generates display image light by causing illumination light to enter a light valve that defines a display image.

Attention has been focused on an enlargement projection system that uses a display panel (hereinafter referred to as a light valve) using a transmissive or reflective dot matrix liquid crystal, and enlarges and projects an image displayed on the light valve on a screen to display it as a large screen. ing.
A rear transmissive screen for rear projection television (TV) is generally configured by a combination of a light diffusing sheet disposed on the viewer side and a Fresnel lens sheet positioned on the light source side.
A Fresnel lens sheet in which unit lenses are concentrically arranged serves to emit projection light from a small projector called an engine (with a built-in light valve) to the light diffusing sheet as substantially parallel light.
The light diffusive sheet spreads the projection light, which has been made approximately parallel light by the Fresnel lens sheet, in a specific direction due to the characteristics of a cylindrical lens group arranged in parallel in a specific direction, and widens the viewing area as display light on the viewer side. Has the function of emitting light.

  The conventional rear projection display device has a structure in which the light beam transmitted through the light valve is converted into an optical path by a reflection mirror and guided to the back of the screen. Since distortion occurs, the installation conditions of the reflecting mirror are severely restricted, and due to this, the volume occupied by the projection optical system, in particular the dimension in the depth direction (the thickness of the cabinet), increases with respect to the screen. It had the subject that it could not be set as the rear projection type display apparatus by a cabinet.

As a means for solving the above problems, an “oblique projection method” has been considered.
In the oblique projection method, as shown in FIG. 1, the second lens 10 having the optical axis 17 bent at the imaging plane 9 (for example, reflecting means) with respect to the optical axis 16 of the first lens 8 is formed on the imaging plane 9. Is placed in between. The second lens 10 obliquely projects the image formed on the imaging surface 9 by the first lens 8 onto the screen 3 arranged so as to be inclined to the side opposite to the inclination of the imaging surface 9 with respect to the optical axis 17. Thus, an enlarged image is obtained. In this case, if a reflection mirror is bent in the middle of the optical path from the second lens 10 to the screen 3, and a screen is provided on the front surface of the cabinet and guided to the back surface, a display device using rear projection is provided as a compact optical system. can get.

However, when the display device is configured using the projection optical system, the image formed on the imaging surface 9 by the first lens 8 is extended, and this is corrected by the second lens 10 and imaged on the screen 3. If the stretch is not corrected properly, the image becomes distorted and unsightly, and faithful reproducibility cannot be obtained.
Here, “stretching” means that the final image on the screen extends in either the horizontal direction or the vertical direction because the enlargement ratio differs between the horizontal direction and the vertical direction. This is still a distortion that remains after the correction, and for example, a rectangular “image” is formed on a square “object”.
Therefore, Patent Document 1 that aims to provide a projection type display device having a projection optical system that uses a projection optical system and does not cause an image to be extended on a screen when a large screen is obtained with a compact configuration. There is a proposal concerning.
Japanese Patent No. 2893877 (JP-A-4-57014)

The projection display device according to Patent Document 1 is
A light source, a light valve that modulates light from the light source, an anamorphic optical system that forms a corrected intermediate image in which one direction of an image formed by the light valve is compressed or expanded, and the corrected intermediate image is distorted, And an enlargement projection optical system for enlarging and projecting an image having no extension.

  In an embodiment (see FIG. 2) in which the projection display device according to Patent Document 1 is used for a transmission type projection optical system (see FIG. 2), an optical axis 17 that is bent at the imaging plane 9 with respect to the optical axis 16 of the first lens 8. The second lens 10 having the image forming surface 9 is disposed therebetween. The image formed on the image plane 9 can be enlarged through the second lens 10 and can be enlarged and projected from an oblique direction onto the screen 3 inclined to the opposite side of the image plane.

The above-described “oblique projection method” and the projection type display device according to Patent Document 1 employ an optical system that satisfies “Shineproof conditions”.
The Scheimpflug rule (Shcheimpflugrule Scheimpflug principle) is, as shown in FIG. 3, when the subject surface and the optical axis (horizontal direction in the figure) are not orthogonal, This is a condition that the entire image plane is in focus if the planes obtained by extending the three members meet at one place (S).

According to the projection type display device described in Patent Document 1, a correction intermediate that is compressed or expanded in one direction with a cylindrical lens system interposed before and after a real image that is disposed on the same optical axis as the light valve and formed by a convex lens. Since the image is formed, no delay occurs when the image is enlarged and projected onto the screen, and the quality of the image on the screen can be remarkably improved.
In addition, a corrected intermediate image that is compressed or expanded in one direction is formed before and after the real image that is arranged on the same optical axis as the light valve and is formed by a convex lens. Therefore, the quality of the image on the screen can be remarkably improved.

However, in Patent Document 1 (the optical system shown in FIG. 2), since the direction of the principal ray does not coincide with the optical axis of the second lens 10 that is a projection lens, the light ray directed toward the second lens (projection lens) 10 diverges. In many cases, the light becomes light and does not enter the second lens (projection lens) 10 at all, and there is a problem that the light use efficiency is very poor.
An object of the present invention is to provide a rear projection type display device capable of improving the light utilization efficiency even in the oblique projection method employing the Scheinproof condition.

A projection type display device according to the present invention as set forth in claim 1 comprises:
An illumination optical system that enters a light valve that defines a display image by modulating light from the illumination light source; and
In a projection display device comprising a projection optical system that projects and enlarges display image light formed by the light valve onto a screen,
When the light valve, the projection optical system, and the screen surface are a subject surface, a lens main surface, and an image surface, respectively, the extended surface of these three members intersects at one place, and satisfies the Scheinproof condition.
The optical axis of the illumination optical system is characterized by being coincident with or substantially coincident with the optical axis of the projection optical system.

By making the optical axis of the illumination optical system coincide (or substantially coincide) with the optical axis of the projection optical system, the image light directed to the projection optical system (projection lens) does not need to be divergent light and enters the projection lens. It is easy to ensure the amount of light, and it is avoided that the efficiency of using illumination light is reduced.
Accordingly, there is provided a thin (compact in the depth direction) projection display device that is free from video defects such as keystone distortion and trapezoidal distortion and can project high-luminance video light on a large screen.

<Embodiment 1>
A first embodiment using a transmissive panel (light valve) is shown in FIG.
Normally, in the optical system as shown in FIG. 4, when the Scheimpflug condition is satisfied, an image having a size indicated by I2 forms an image through the lens system as a size indicated by I1 without aberration.
The enlargement ratio is α1 / α2.
Under the Scheimpflug condition, I2 is the object plane and I1 is the image plane.

In the above optical system, a transmissive light valve (liquid crystal panel) is installed at a portion indicated by Im2, and a screen is installed at a portion indicated by Im1.
The center of Im1 and Im2 is the optical axis.
A projection lens is installed at L1.
Here, the optical axis of the illumination optical system is made to coincide with the optical axis described above.
The illumination light from the lamp (illumination light source) is made uniform through an integrator such as a fly eye or a light tunnel.

Then, the panel is illuminated with a parallel light beam through a condenser lens.
Thereafter, spatially modulated light (image light) enters the projection lens from the panel.
At this time, the illumination light may be converged by a lens so that the light amount of the illumination light can be maximized before the panel.
The shaded portion in the figure corresponds to the path of the light beam from the illumination light source to the screen. However, there is no light loss before and after the projection lens L1.

Here, the NA of the illumination light needs to be larger than the NA of the projection optical system.
An image is formed on the screen through the projection optical system, and here an off-optical axis offset Fresnel lens is used. (Not shown)
For example, a TIR (total reflection) Fresnel lens may be used.
Further, in order to fit the optical system in the projection TV, the light beam may be bent at the position of the dotted line as necessary (by arranging the mirror at the dotted line position, the screen becomes a position symmetrical to the dotted line. ) This will affect the downsizing (depth direction) of the display device.

<Embodiment 2>
A second embodiment using a reflective panel (light valve) is shown in FIG.
In this case, since the optical axis of the illumination optical system and the optical axis of the projection optical system are on the same axis or in the vicinity, it is necessary to use a certain optical means-prism.
When trapezoidal distortion occurs, optical means having a correction function may be used for the projection lens optical system.

  In this way, by matching the optical axes of the illumination optical system and the projection optical system and using an offset Fresnel screen, the problem of light loss can be solved, and as with aerial photography (Scheinproof), the resolution is high. Can be displayed on the screen.

Explanatory drawing which shows the optical system by an oblique projection system. (Conventional technology) FIG. 3 is an explanatory diagram illustrating an optical system that satisfies the Scheinproof condition including an anamorphic optical system that forms a corrected intermediate image. (Conventional technology) Explanatory drawing which shows an outline about the conditions of Shineproof. Explanatory drawing which shows one Embodiment of this invention at the time of using a transmissive | pervious light valve. Explanatory drawing which shows one Embodiment of this invention at the time of using a reflection type light valve.

Explanation of symbols

3 Screen 8 1st lens (constitution of illumination optical system)
9 Imaging surface
10 Second lens (constructs a projection optical system)
16 Optical axis of the first lens
17 Optical axis of the second lens

Claims (5)

An illumination optical system that enters a light valve that defines a display image by modulating light from the illumination light source; and
In a projection display device comprising a projection optical system that projects and enlarges display image light formed by the light valve onto a screen,
When the light valve, the projection optical system, and the screen surface are a subject surface, a lens main surface, and an image surface, respectively, the extended surface of these three members intersects at one place, and satisfies the Scheinproof condition.
A projection display device, wherein an optical axis of an illumination optical system is coincident with or substantially coincides with an optical axis of a projection optical system.   The projection display device according to claim 1, wherein the screen surface serving as the image surface is formed at a position shifted from the optical axis.   The projection display device according to claim 1, wherein an offset Fresnel lens with an optical axis removed is used for the screen.   4. The projection type display device according to claim 1, wherein an optical means inserted into the projection optical system is used for correcting the distortion of the display image light formed by the light valve.   5. The projection display device according to claim 1, wherein one or more reflection mirrors are present in the projection optical system.