JPH0521571U - Color correction device for image projection device - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a color correction device for an image projection device which eliminates the color unevenness of the image on the screen surface due to the light source and makes it possible to obtain a good color tone to the peripheral portion of the image. . An image projection apparatus for projecting a light beam from a light source on a screen surface through a light-transmissive image panel, wherein the image projection apparatus has an uneven spectral distribution on the screen surface by the light source. A color correction device for an image projection device, wherein an optical filter for correcting a non-uniform spectral distribution on a screen surface due to a light source is provided in the optical path of the optical system of the device.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a color correction apparatus for an image projection apparatus, and more specifically, an image projection apparatus for correcting a color tone change on a screen surface due to a light source having a non-uniform spatial spectral distribution at a predetermined distance from a light emitting unit. Color correction device.

[0002]

[Prior art and points in between]

 In recent years, due to the increase in video media in various fields and the reduction in the price of AV equipment (video decks, video cameras, laser disk players, etc.), the penetration rate of AV equipment in general households has shown a remarkable increasing trend. .. Along with this, general home TVs with large screens have become the mainstream. At present, the largest general CRT television for home use is about 40 inches. However, a screen size of about 40 inches is not enough to fully enjoy the image as if it were a theater screen, and the need for larger screens larger than that has increased in recent years. Therefore, what has emerged in response to this need is a liquid crystal projector that is compact and lightweight, and that can easily obtain a large screen image. This liquid crystal projector splits white light emitted from a light source into three primary colors of R (red), G (green), and B (blue) with a dichroic wavelength selection mirror, and three optical shutters corresponding to each of these colors. After passing through the liquid crystal panel that works as a composite, the three monochromatic images are combined into a full-color image, which is enlarged and projected on the screen surface.

Recently, as a light source used in this liquid crystal projector, a metal halide lamp, which is close to a point light source with high brightness and high color temperature, is becoming mainstream in order to realize a bright and clear image. However, the metal halide lamp has a characteristic that the spectral distribution is different between the center and the peripheral part of the arc, and the red component increases as it goes from the central part to the peripheral part. It is known that it appears as a change in the color characteristics (color tone) of. Therefore, when this lamp is used as the light source of a liquid crystal projector, the color characteristics of the image projected on the screen are also affected, and the image around the screen becomes more reddish than the image at the center.

[0004]

[The purpose of the device]

 The present invention has been made in view of the above-mentioned conventional problems, and it is possible to eliminate the color unevenness of the image on the screen surface due to the light source and to obtain an excellent image tone to the peripheral portion of the image. An object is to provide a color correction device for an apparatus.

[0005]

[Outline of the device]

 The present invention is an image projecting apparatus for projecting a light flux from a light source on a screen surface through a light-transmitting image panel, wherein the image projecting apparatus has an uneven spectral distribution on the screen surface. An optical filter for correcting a non-uniform spectral distribution on the screen surface is provided in the optical path of the optical system. Further, the present invention includes a light source having a non-uniform spatial spectral distribution at a predetermined distance from the light emitting unit, a light-transmissive image panel that transmits the light flux from the light source, and a projection lens that projects the light flux. The image projection apparatus is characterized in that an optical filter for correcting a non-uniform spatial spectral distribution at a predetermined distance from the light emitting section of the light source is provided in the optical path of the optical system of the image projection apparatus. With these configurations, it is possible to eliminate the color unevenness of the image on the screen surface due to the light source, and to obtain a good color tone even in the peripheral portion of the image.

When the light source is a metal halide lamp, the red component increases as it goes from the center to the periphery of the arc. Therefore, the transmittance of red light decreases from the center to the periphery. By providing an optical filter designed so that an image on the screen surface can obtain a good color tone.

The difference in the spectral distribution at each point at a predetermined distance from the light emitting portion of the light source, or the difference in the spectral distribution at each point on the screen surface due to the light source is measured by measuring the light distribution at each point on the image panel surface. Can also be found by measuring the spectral distribution of each point on the screen surface. Therefore, an optical filter for correcting different spectral distributions at each point on the screen surface can be installed at any position of the optical system, but the screen that is finally evaluated for image quality It is easier to evaluate and design if it is placed adjacent to the image panel that is conjugate with the surface.

[0008]

【Example】

 The present invention will be described below with reference to illustrated embodiments. FIG. 3 shows an outline of an optical system of a conventional liquid crystal projector. The white light emitted from the light source 11 is reflected by the cold mirror 13 in the visible light component excluding the infrared light component. As for the visible light reflected by the cold mirror 13, one primary color light (for example, blue light) of the three primary colors is reflected by the first dichroic mirror 15, and the other two primary color lights are transmitted.

The blue light reflected by the first dichroic mirror 15 is reflected by the total reflection mirror 17, and passes through the condenser lens 21 and the translucent first liquid crystal panel 23. Then, the light is transmitted through the third and fourth dichroic mirrors 35 and 47, and the image of the first liquid crystal panel 23 is formed at a predetermined position (for example, the screen surface) by the projection lens 49.

On the other hand, the other primary color lights (green light and red light) that have passed through the first dichroic mirror 15 are reflected by the second dichroic mirror 25, and one of the primary color lights (eg, green light) is reflected. The primary color (eg red light) is transmitted. The green light reflected by the second dichroic mirror 25 passes through the condenser lens 31 and the translucent second liquid crystal panel 33. Then, the light is reflected by the third dichroic mirror 35, passes through the fourth dichroic mirror 47, and is projected by the projection lens 49 onto the image of the first liquid crystal panel 23 at the predetermined position so as to overlap the image of the second liquid crystal panel 33. Form an image.

The red light that has passed through the second dichroic mirror 25 passes through the condenser lens 41 and the transmissive third liquid crystal panel 43. Then, it is reflected by the total reflection mirror 45, is reflected by the fourth dichroic mirror 47, and is projected by the projection lens 49 onto the images of the first liquid crystal panel 23 and the second liquid crystal panel 33 at the predetermined position. The image of the liquid crystal panel 43 of No. 3 is formed.

In the liquid crystal projector described above, the projected image is decomposed into three primary colors, images of respective components are formed by three liquid crystal panels, and the images are projected in the corresponding three primary colors and superimposed.

Here, FIG. 4 shows the state of spectral distribution on the screen surface when the light source 11 is a metal halide lamp. FIG. 4 (a) shows a screen, and FIG. 4 (b) is a spectral distribution diagram of spectra at points a to d on the screen surface of FIG. 4 (a). As a result, the relative illuminance at about 600 nm to 700 nm tends to increase in the radial direction of the screen surface. From this, it can be seen that the red component of the spectrum increases in the radial direction from the center of the image projected on the screen.

FIG. 1 shows an optical system configuration diagram of a liquid crystal projector to which a color correction device of an image projection device of the present invention is applied. The optical system of the liquid crystal projector shown here is basically the same as the optical system of the liquid crystal projector shown in FIG. 3 of the conventional example described above, and the same members in both drawings are denoted by the same reference numerals. .. 1, a portion different from the optical system shown in FIG. 3 is located between the condenser lens 41 that transmits red light and the third liquid crystal panel 43, and is provided adjacent to the liquid crystal panel 43. The circular gradient dichroic filter 60 (optical filter) is provided.

As described above, when a metal halide lamp is used as the light source 11, the color tone of the image on the screen surface becomes reddish from the center of the image to the periphery due to the emission characteristics of the lamp. In the present invention, a circular gradient dichroic filter 60 designed to reduce the transmittance of the red component from the center to the periphery is provided with a circular gradient dichroic filter 60 corresponding to the emission characteristics of the metal halide lamp. It is characterized by being installed in the optical path to improve the color tone of the image on the screen surface, especially in the peripheral area of the screen.

In designing the circular gradient dichroic filter 60, when measuring the difference in the spectral distribution on the screen surface of the light source 11, even if the spectral distribution on the screen surface is measured, the spectral distribution on the liquid crystal panel surface is also measured. The distribution may be measured. The circular gradient dichroic filter 60 can be installed at any position in the optical system, but the design is easier if it is installed next to the liquid crystal panel that is conjugate with the screen surface where the quality of the image is finally evaluated. Moreover, it is advantageous to install the circular gradient dichroic filter 60 compactly in the liquid crystal projector. FIG. 2 shows an experimental result of the spectral distribution state on the screen surface when the circular gradient dichroic filter 60 is installed between the liquid crystal panel 43 and the condenser lens 41. From the results shown in FIG. 2B, it can be seen that the relative illuminance of the spectrum of about 600 nm to 700 nm, which tends to increase in the radial direction of the screen surface, is clearly improved.

In this embodiment, the metal halide lamp is used as the light source, but any light source may be used as long as it has a non-uniform spatial spectral distribution at a predetermined distance from the light emitting section.

Further, when using a light source having a different light emitting characteristic other than the metal halide lamp used in this embodiment, it goes without saying that an optical filter corresponding to the light emitting characteristic of the light source is designed and installed.

[0019]

[Effect of the device]

 As described above, according to the present invention, it is possible to obtain a good color tone even at the periphery of the image by correcting the color unevenness of the image on the screen surface due to the light source with the optical filter.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an optical system of a liquid crystal projector to which a color correction device of the present invention is applied.

FIG. 2 is a diagram showing a spectral distribution of an image on the screen surface of FIG.

FIG. 3 is a diagram showing a configuration of an optical system of a conventional liquid crystal projector.

FIG. 4 is a diagram showing a spectral distribution of an image on a screen surface in the case where the light source of FIG. 3 is a metal halide lamp.

[Explanation of symbols]

11 Light Source 13 Cold Mirror 15 First Dichroic Mirror 17 Total Reflection Mirror 21 Condenser Lens 23 First Liquid Crystal Panel (Image Panel) 25 Second Dichroic Mirror 31 Condenser Lens 33 Second Liquid Crystal Panel (Image Panel) 35 Third Dichroic mirror 41 Condenser lens 43 Third liquid crystal panel (image panel) 45 Total reflection mirror 47 Fourth dichroic mirror 49 Projection lens 60 Circular gradient dichroic filter (optical filter)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takayuki Iizuka 2-36-9 Maenocho, Itabashi-ku, Tokyo Asahi Kogaku Kogyo Co., Ltd.

Claims (4)

[Scope of utility model registration request] 1. An image projection apparatus for projecting a light beam from a light source on a screen surface through a light transmission type image panel, wherein the image projection apparatus has a non-uniform spectral distribution on the screen surface. A color correction apparatus for an image projection apparatus, comprising an optical filter for correcting a non-uniform spectral distribution on a screen surface in the optical path of the optical system of the apparatus. 2. A light source having a non-uniform spatial spectral distribution at a predetermined distance from a light emitting section; a light transmissive image panel for transmitting a light beam from the light source; and a projection lens for projecting the light beam. In the image projection apparatus, an optical filter is provided in the optical path of the optical system of the image projection apparatus to correct a non-uniform spatial spectral distribution at a predetermined distance from the light emitting section of the light source. Color correction device. 3. A metal halide lamp as a light source;
A light-transmissive image panel that transmits the light flux from the metal halide lamp; a projection lens that projects the light flux;
In an image projection apparatus including the above-mentioned image projection apparatus, an optical filter is provided in the optical system optical path of the image projection apparatus, in which the transmittance of red light decreases from the center to the periphery. Color correction device. 4. The method according to any one of claims 1 to 3,
The optical filter is a color correction device of the image projection device provided adjacent to the image panel.