WO2004052024A1

WO2004052024A1 - Device and method of color correction for projection type video image display devices

Info

Publication number: WO2004052024A1
Application number: PCT/IB2003/004991
Authority: WO
Inventors: Willem H. Smits
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2002-12-05
Filing date: 2003-11-04
Publication date: 2004-06-17
Also published as: TW200419293A; AU2003274603A1

Abstract

The present invention relates to the field of projection type video image display devices allowing color correction and a method for such a color correction. The device comprises a light source (1) for emitting a white light luminous flux. It comprises color light separating means (2a, 2b) for separating the white light into three color lights of red, blue and green light. Light valves (3R, 3G, 3B) of essentially equal effective dimensions are provided for modulating lights contained in luminous fluxes from said color light separating means (2a, 2b) and producing a video image. Color light combining means (4) are provided for combining the modulated luminous fluxes, and projection optical means (5) are provided for projecting a combined luminous flux on a screen. Illumination optics are provided in the optical paths for the respective color lights which are arranged to provide different illumination overfill of the light valves (3G, 3B) for modulating green light and blue light than for the light valve (3R) for modulating red light.

Description

Device and method of color correction for projection type video image display devices

FIELD OF THE INVENTION

The present invention relates to the field of projection type video image display devices, and particularly to a projection type video image display device allowing color correction as well as a method for such color correction.

BACKGROUND OF THE INVENTION

Today, many projection type video image display devices having three liquid crystal light valves for modulating red light, blue light and green light are unable to perform a color reproduction which complies with the standard set by the European Broadcasting Union (EBU). This especially applies to reproduction of the standard D65 white point, the reason why the resulting video images often are far from optimal.

One prior-art approach is disclosed in EP 1 058461, which suggests a color image projector for correcting chromatism by changing the sizes or positions of three light valves with respect to each color. In one approach, two or more light valves have different sizes of effective areas where an image is formed. In another approach, the distances between two ore more light valves and the projection lens unit are different from one another.

However, the first prior-art approach is disadvantageous as the number of different components required will be increased thus increasing the production cost. The second prior-art approach is disadvantageous as the physical space requirements will be increased.

OBJECT AND SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide an improved projection type video image display device allowing color correction. This object is achieved through the provision of illumination optics in the optical paths for the respective color lights which are arranged to provide different illumination overfill of the light valves for modulating green light and blue light than for the light valve for modulating red light. It is another object of the invention to provide an improved method for color correction in a projection type video image display.

This object is achieved through a method of providing illumination optics in the optical paths for the respective color lights which are arranged to provide different illumination overfill of the light valves for modulating green light and blue light than for the light valve for modulating red light.

Still other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawing. It is to be understood, however, that the drawing is designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawing is not necessarily drawn to scale and that, unless otherwise indicated, it is merely intended to conceptually illustrate the structures and procedures described herein.

BRIEF DESCRIPTION OF THE DRAWING

The enclosed drawing discloses a schematic view of a projection type video image display device according to a preferred embodiment of the invention.

DESCRIPTION OF EMBODIMENTS The drawing discloses a conceptual diagram showing a basic constitution of a projection type display device according to a preferred embodiment of the present invention. The projection type display device mainly comprises a light source 1, such as a halogen lamp, a metal halide lamp, ultrahigh pressure mercury-vapor lamp, or similar lamp. Furthermore, it comprises color light separating means 2a, 2b, such as dichroic mirrors, for separating a white color luminous flux emitted therefrom into color luminous fluxes of three primaries, red, blue and green. Three liquid crystal light valves 3B, 3G, 3R of essentially equal effective dimensions are provided for optically modulating the separated luminous fluxes of each respective color. Color light combining means 4 are provided, such as a dichroic prism, for combining the modulated luminous fluxes of the optically modulated colors through these liquid crystal light valves 3B, 3G, 3R. A projection lens 5 is provided or magnifying and projecting the combined modulated luminous flux on a projection screen (not shown). The optical paths of the luminous fluxes are illustrated in the drawing using thin solid lines. The process until an image is magnified and projected on the projection screen is described below.

A white light luminous flux emitted from the light source 1 passes through an illuminating optical system composed of a first lens 6, and goes toward a first dichroic mirror 2a which passes blue light and reflects green and red light.

The blue light passing through the first dichroic mirror 2a is reflected by a first reflection mirror 7a, and reaches liquid crystal light valve modulating means 3B. The green light is reflected by a second dichroic mirror 2b which reflects green light and passes red light, and reaches liquid crystal light valve modulating means 3G. The red light passes through the second dichroic mirror 2b, and is brought through a first relay lens 8, and is reflected by a second reflection mirror 7b, is brought through a second relay lens 9, and is reflected by a third reflection mirror 7c, and reaches liquid crystal light valve modulating means 3R. Herein, the color lights modulated by the liquid crystal light valve modulating means 3B, 3G, 3R according to a video signal corresponding to the colors are put into the dichroic prism color light combining means 4. Color lights modulated according to the video signal corresponding to the colors by the liquid crystal light valve modulating means 3B, 3G, and 3R are combined by the dichroic prism color light combining means 4, and projected on a projection screen (not shown) through a projection lens 5 which is a projection optical means. hi order to facilitate color correction of the projection type display device, illumination optics are provided in the optical paths for the respective color lights, which illumination optics are arranged to provide different illumination overfill of the light valves 3G, 3B for modulating green light and blue light than for the light valve 3R for modulating red light. The illumination optics of the red light luminous path comprising the first relay lens 8, second reflection mirror 7b, second relay lens 9, and third reflection mirror 7c, are illustrated in the Figure by the broken-line frame 10.

Through insertion of first and second relay lenses 8, 9 in the optical path for the red luminous flux, the illumination overfill of the liquid crystal light valve modulating means 3R for modulating the red luminous flux is reduced with respect to the illumination overfill of the liquid crystal light valves 3G, 3B for modulating the blue and green luminous fluxes, respectively. With equal effective dimensions of the liquid crystal light valve modulating means 3B, 3G and 3R, more green and blue light will now be blocked at the light valves, increasing the relative contribution of red light. Due to the relay optics 8, 9, the red illumination overfill is reduced with respect to green and blue, resulting in larger illumination angles, i.e. at the projected image the effective system throughput for green and blue is smaller than for red, resulting in a reduced brightness contribution for green and blue, enabling achievement of e.g. a D65 white point. As all light valves 3B, 3G, 3R can be operated to utilize their full driving ranges between a black state and a white state, the projector contrast can be maximized and the lifetime of the light valves 3B, 3G, 3R is optimized.

The following description relates to a method for color correction of a projection type video image display device comprising: a light source 1 for emitting a white light luminous flux in one direction, color light separating means 2a, 2b for separating the white light from said light source 1 into three color lights of red light, blue light and green light, modulating means 3B, 3G, 3R comprising liquid crystal light valves of essentially equal effective dimensions for modulating lights contained in luminous fluxes from said color light separating means 2a, 2b, and producing a video image, color light combining means 4 for combining the modulated luminous fluxes after being modulated by said modulating means 3B, 3G, 3R, and projection optical means 5 for projecting a combined luminous flux obtained by said color light combining means 4 on a projection screen. According to any one of the above described embodiments, the method comprises the step of: providing illumination optics in the optical paths for the respective color lights which are arranged to provide different illumination overfill of the light valves 3G, 3B for modulating green light and blue light than for the light valve 3R for modulating red light.

In a further embodiment, the method further comprises the step of arranging said illumination optics to provide a larger illumination overfill of the light valves 3G, 3B for modulating green light and blue light than for the light valve 3R for modulating red light. In another embodiment, the method comprises the step of providing illumination optics comprising relay optics 8, 9 in the optical path for the red light which are arranged to provide a smaller illumination overfill of the light valve 3R for modulating red light than the illumination overfill of the light valves 3G, 3B for modulating green light and blue light provided by the illumination optics in the optical paths for these color lights.

In a still further embodiment, the method comprises the step of arranging said illumination optics to provide such a difference in illumination overfill of the light valves 3G, 3R for modulating green light and blue light with respect to the illumination overfill of the light valve 3R for modulating red light that a resulting combined luminous flux would be rendered a D65 white point. As illustrated by the above, a projection type video image display device and a method for color correction of a projection type video image display device have been described, where a desired color correction is easily achievable. The general advantages of commonly occurring projection type video image display devices are largely retained, as liquid crystal light valve modulating means of essentially equal effective dimensions are used in standard positions equally distant from the dichroic prism color light combining means. The approach according to the present invention is advantageous in comparison with the previously discussed prior-art approach, which prescribes use of liquid crystal light valve modulating means of different effective dimensions or alternatively placed in non-standard positions with different distances from the dichroic prism color light combining means. The present invention eliminates these restrictions of such a prior-art approach by enabling color correction in projection type video image display devices using equivalent liquid crystal light valve modulating means placed in standard positions which reduces component cost and provides a more compact design. Thus, while fundamental novel features of the invention as applied to a preferred embodiment thereof have been shown, described and pointed out, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.

Claims

CLAIMS:

1. A projection type video image display device comprising: a light source (1) for emitting a white light luminous flux in one direction; color light separating means (2a, 2b) for separating the white light from said light source (1) into three color lights of red light, blue light and green light; modulating means (3R, 3G, 3B) comprising light valves of essentially equal effective dimensions for modulating lights contained in luminous fluxes from said color light separating means (2a, 2b) and producing a video image; color light combining means (4) for combining the modulated luminous fluxes after being modulated by said modulating means (3R, 3G, 3B); and projection optical means (5) for projecting a combined luminous flux obtained by said color light combining means (4) on a screen, wherein illumination optics are provided in the optical paths for the respective color lights which are arranged to provide different illumination overfill of the light valves (3G, 3B) for modulating green light and blue light than for the light valve (3R) for modulating red light.

2. The projection type video image display device of claim 1, wherein said illumination optics are arranged to provide a larger illumination overfill of the light valves (3G, 3B) for modulating green light and blue light than for the light valve (3R) for modulating red light.

3. The proj ection type video image display device of claim 1 , wherein said illumination optics comprises relay optics (8, 9) provided in the optical path for the red light which are arranged to provide a smaller illumination overfill of the light valve (3R) for modulating red light than the illumination overfill of the light valves (3G, 3B) for modulating green light and blue light provided by the illumination optics in the optical paths for these color lights.

4. The projection type video image display device of claim 1, wherein said illumination optics are arranged to provide such a difference in illumination overfill of the light valves (3G, 3B) for modulating green light and blue light with respect to the illumination overfill of the light valve (3R) for modulating red light that a resulting combined luminous flux would be rendered a D65 white point.

5. A method for color adjustment of a projection type video image display device comprising: a light source for emitting a white light luminous flux in one direction; color light separating means for separating the white light from said light source into three color lights of red light, blue light and green light; modulating means comprising light valves for modulating lights contained in luminous fluxes from said color light separating means and producing a video image; color light combining means for combining the modulated luminous fluxes after being modulated by said modulating means; and projection optical means for projecting a combined luminous flux obtained by said color light combining means on a screen, wherein said method comprises the step of: providing illumination optics in the optical paths for the respective color lights which are arranged to provide different illumination overfill of the light valves for modulating green light and blue light than for the light valve for modulating red light.

6. The method of claim 5, further comprising the step of arranging said illumination optics to provide a larger illumination overfill of the light valves for modulating green light and blue light than for the light valve for modulating red light.

7. The method of claim 5, further comprising the step of providing illumination optics comprising relay optics in the optical path for the red light which are arranged to provide a smaller illumination overfill of the light valve for modulating red light than the illumination overfill of the light valves for modulating green light and blue light provided by the illumination optics in the optical paths for these color lights.

8. The method of claim 5, further comprising the step of arranging said illumination optics to provide such a difference in illumination overfill of the light valves for modulating green light and blue light with respect to the illumination overfill of the light valve for modulating red light that a resulting combined luminous flux would be rendered a D65 white point.