JPH04147290A - Projection type display device - Google Patents

Abstract

PURPOSE:To obtain a small-sized projection unit which generates no color shade by performing image modulation by three light valves which are arranged at positions equal in optical path length from a light source, mixing two colors by a color mixing means, and projecting the composite color on a screen together with other one color. CONSTITUTION:The projection light from the light source 6 is reflected by a reflector 7 and diffracted spectrally into the primary colors by dichroic mirrors 14a and 14b. Here, the mirrors 14a and 14b are arranged so that the optical path lengths from the light source 6 to the three liquid crystal light valves 9a, 9b, and 9c are equal. Then the spectrally diffracted color lights of the primary colors are image-modulated by the valves 9a, 9b, and 9c and the green light is projected on the screen by a 2nd projection lens 15b. The red light and blue light are put together by the mirror 14d and projected on the screen through a 1st projection lens 15a, so that the image is put together with the image of the green light. Consequently, the small-sized projection unit which generates no color shade and enables excellent picture element matching is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a projection display device that enlarges and projects images of a plurality of light valves onto a screen to obtain a large-screen image. (Prior Art) In recent years, there has been a trend toward larger screens for image display devices, especially television monitors, and various display devices that achieve this larger screen have been developed. Among these, projection devices using liquid crystal light valves are relatively popular because they are highly practical for being compact and lightweight, and they allow ordinary households to easily enjoy large screen displays.

FIG. 4 and subsequent figures show a rear projection display device as an example of a projection display device using a conventional liquid crystal light valve.

In this rear projection type display device, an image projected from a projection unit 1 is reflected by a plurality of reflecting mirrors 2 and projected onto a transmission screen 3 to display the image.

Conventional examples of this projection unit 1 include a three-tube projection unit 4, which uses three projection lenses to synthesize images on a screen, as shown in FIG. 5, and a three-tube projection unit 4, as shown in FIG. A single-tube projection unit l-5, etc., which performs image synthesis within the projection unit and projects the synthesized image onto a screen, is known.

First, regarding the projection principle of the three-tube projection unit 4,
This will be explained with reference to FIG.

In the figure, reference numeral 6 denotes a light source, for example, a white light source with high color rendering such as a metal halide lamp, and the beam of the emitted light is 7.
, and enters the dichroic mirror 8a. The dichroic mirror 8a is, for example, a mirror with spectral characteristics that reflects the red <R> wavelength region and transmits the blue (B) and green (G) wavelength regions. Only wavelength range is incident. In addition, the front (B) and green (G) wavelength ranges that have passed through the dichroic mirror 8a are, for example, reflected from the green (G) wavelength range to become blue (B).
The wavelength range is split into a blue (B) wavelength range and a green (G) wavelength range by a dichroic mirror 8b which has a spectral characteristic of transmitting light, and these blue (B) wavelength ranges are separated by a liquid crystal light valve 9b.
In addition, the green (G) wavelength region is reflected by the mirror 8C and enters the liquid crystal light valve 9C. The above three liquid crystal light valves 9a, 9b, and 9C are each driven by a video signal corresponding to an incident wavelength range, and image-modulate the incident color light. These three liquid crystal lights) and valves 9a, 9
The three color lights that have been image-modulated in b and 9C are transmitted through the corresponding projection lenses 10a, 10b, and 10c of the respective optical path lights.
The images are enlarged and projected, combined and displayed on the screen. Since such a three-tube projection unit 4 has a simple and compact configuration, it has the advantage that the main body of the rear projection display device can be made smaller.

Next, the projection principle of the single tube type projection unit 5 will be explained with reference to FIG. 9. In the figure, the same components as the three-tube projection unit 4 described above are given the same reference numerals.

Reference numeral 6 denotes a light source, which is, for example, a high color rendering white light source such as a metal halide lamp, and its emitted light beam is reflected by the flutter 7 and enters the dichroic mirror 11a. This dichroic mirror 11a is, for example, a mirror with spectral characteristics that transmits the red (R) wavelength region and reflects the blue (B) and green (G) wavelength regions, and this dichroic mirror 11a
The red (R) wavelength region transmitted through the light is reflected by the mirror 11b and enters the liquid crystal light valve 9a. The blue (B) and edge (G) wavelength regions reflected by the dichroic mirror 11a are, for example, the dichroic mirror 11 that has spectral characteristics of reflecting the green (G) wavelength region and transmitting the blue (B) wavelength region.
It is separated into blue (B) wavelength region and green (G) wavelength region at C,
The green (G) wavelength range is in the liquid crystal light valve 9b, and the blue (B) wavelength range is in the liquid crystal light valve 9b.
The wavelength range is incident on the liquid crystal light valve 9C. The above three liquid crystal light valves 9a, 9b, and 9c are each driven by video signals corresponding to the incident wavelength range,
Image modulation is performed on the incident colored light. Next, the red (R) color light is image-modulated by the liquid crystal light valve 9a that modulates the red (R) color light, and the green (G) color light is image-modulated by the liquid crystal light valve 9b that modulates the green (G) color light. Color light is green (G
) wavelength region is reflected and the red (R) wavelength region is transmitted by a dichroic mirror 11d, which has spectral characteristics, and the dichroic mirror 11. incident on e. Also, blue (
B) The blue (B) color light image-modulated by the liquid crystal light valve 9c that modulates color light is reflected by the mirror 11f, and the blue (B) color light is reflected by the mirror 11f.
) The dichroic mirror 11e has spectral characteristics that reflects the wavelength range and transmits the red (R) and green (G) wavelength ranges.
Then, it is combined with red (R) and edge (G) color light, and is enlarged and projected onto the screen by the projection lens 12. Such a single-tube projection unit 5 has an advantage over the three-tube projection unit 4 described above in that pixel alignment (registration alignment, convergence) in synthesis can be performed with high precision. Also,
Another advantage is that it can also be used as a front projection display device that projects onto a reflective screen.

(Problems to be Solved by the Invention) In the conventional three-tube projection unit 4, as shown in FIG.
, 9C (optical path length) are different, there is a problem that color unevenness occurs on the display screen. This is the 6th
As shown in the figure, since parallel light cannot be obtained because the light source 6 has an arc length, the reflected light from the reflector 7 is directed along the optical axis connecting the light source 6 and the centers of the projection lenses 10a, 10b, and 10c. This is because the condensing angle θ is set at a constant angle so that the focal point is focused at .

Furthermore, since the pixel shapes of the three liquid crystal light valves 9a, 9b, and 9c are fixed and the shape of the display screen cannot be electrically controlled, the projection lenses 10a, 10 shown in FIG.
0b, 10c and the liquid crystal light valves 9a, 9b, 9c
are arranged as shown in FIGS. 7 and 8, and images are synthesized on the screen 13. As shown in FIGS. 7 and 8, the above three projection lenses], Oa, 10b, 10c
It can be seen that the shift amount d of the optical axes of the two projection lenses 10a, 10c at both ends and the liquid crystal light valves 9a, 9c becomes large, and that the periphery of the projection lenses 10a, 10C is used considerably. In this way, using the lens to the periphery increases aberrations on the screen,
There is also the problem that distortion occurs at the edges of the combined display image, causing pixels to no longer match.

Next, in the conventional single-tube projection unit 5 shown in FIG.
The three-tube projection unit 4 described above does not suffer from color unevenness due to differences in optical path length or pixel alignment problems during image composition. However, since there are many parts and the configuration is complex, adjustments during manufacturing are difficult. It gets complicated. In addition, since the projection lens 12 is separated from the liquid crystal light valves 9a, 9b, and 9c, the back focus becomes long, making lens design difficult, expensive, and large in size. As a result, the projection unit becomes large, and the rear projection display device itself also becomes large, making it impossible to achieve miniaturization, which is the greatest advantage of using a liquid crystal light valve.

The present invention was made in view of the above circumstances, and does not cause color unevenness due to differences in optical path length from the light source to the three liquid crystal light valves, and also has better pixel alignment during composition than a three-tube projection unit. It is an object of the present invention to provide a projection unit which can be used for various purposes and whose shape is smaller than that of a single tube type projection unit.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, a projection type display device according to the present invention includes a color separation means for separating white light emitted from a light source into three primary colors, and a color separation means for separating white light emitted from a light source into three primary colors. The three light valves are disposed at positions having equal optical path lengths from the light source, and two of the three color lights image-modulated by the three light valves are image-modulated. a first projection lens for projecting the two-color light combined by the color combination means onto a screen; and a second projection lens for projecting the one-color light not combined by the color combination means onto the screen. Preferably,
The wavelength range of the monochromatic light projected by the second projection lens is
The first projection lens and the second projection lens may be arranged in a vertical direction, and the first projection lens and the second projection lens may be in a green wavelength region.
The projection lens may be configured by arranging the projection lenses in a row in the horizontal direction.

(Function) With the above configuration, the white light emitted from the light source is separated into three primary colors by the color separation means, and these three primary colors are separated from the light source by three light valves disposed at positions that share an equal optical path. Each image is modulated, two of the three image-modulated three-color lights are combined by a color synthesis means, and these two
The first projection lens projects the colored light onto the screen, and the second projection lens projects the one-color light that is not combined by the color combining means onto the screen. Furthermore, it is desirable that the monochromatic light projected by the second projection lens be in the green wavelength region.

Since the optical path length from the light source to the three light valves is the same, color unevenness does not occur, and the configuration is simplified by using two projection lenses and arranging them vertically or horizontally. The projection unit is more compact than a tube-type projection unit. Also, a 3-tube projection unit)
- The projection lens can be made smaller even when compared to -.

(Example) Hereinafter, the present invention will be described in detail with reference to the drawings.

1 to 3 show an embodiment of the present invention, FIG. 1 is a projection unit configuration diagram, and FIGS. 2(a) and 2(b) are rear projection type display device configurations with a vertically arranged projection unit. Figure, Figure 3 (
Figures a) and (b) are configuration diagrams of a rear projection display device with a horizontally arranged projection unit.

In FIG. 1, the light source 6 may be the same as in the conventional example, for example, a high color rendering white light source such as a metal halide lamp, and the light emitted from this light source 6 is transmitted through a reflector 7 as in the conventional single tube projection unit. Two dichroic mirrors that reflect and serve as color separation means 14. The light is separated into three primary colors at a and 14b. However, these two dichroic mirrors 14a, 14, b have an optical path length from the light source 6 to the three liquid crystal light valves 9a, 9b, 9c (L+ in the figure).
1) are arranged so that they are equal. Also, for example,
The dichroic mirror 14a has a spectral characteristic that transmits the red (R) wavelength region and reflects the blue (B) and green (G) wavelength regions, and the dichroic mirror 14b reflects the blue (B) wavelength region and reflects the green (green) wavelength region. (G) The wavelength region is a spectral characteristic that is transmitted. Furthermore, the mirror 14c may be a mirror with a heat-insulating effect such as an infrared transmitting mirror instead of the total reflection mirror.Next, the above-mentioned separated three primary color lights can be used as the incident light as in the conventional example. The liquid crystal light valves 9a, 9 are driven by a video signal corresponding to the color light to perform image modulation of the color light incident thereon.
b, enters 9c. These liquid crystal light valves 9a, 9
Of the three color lights that have been image-modulated in the images b and 9c, the green (G) color light is projected onto the screen by the second projection lens 15b.

Further, the red (R) and blue CB) color lights are synthesized by a dichroic mirror 14d, which is a color synthesis means with spectral characteristics in which the red (R>wavelength region is transmitted and the blue (B) wavelength region is reflected). The light is projected onto the screen by the first projection lens 15a and combined with the previously recorded (G) color light image.

When the projection unit 16 of the present invention is incorporated into a rear projection type display device, there are two cases in which the projection unit 16 is arranged horizontally as shown in FIGS.
A case can be considered in which the projection unit 16 is arranged vertically, as shown in (b).

First, when the projection unit 16 is arranged horizontally as shown in FIGS. Although the height of unit 16 is lower,
Width and depth become longer.

Therefore, the back focus of the first projection lens 15a becomes long, making it expensive.

In contrast, when the projection unit 16 is arranged vertically as shown in FIGS. Therefore, the width of this projection unit 16 becomes thicker, but the depth becomes shorter. Therefore, the first projection lens 15
Since the back focus of a can be shortened, the cost can be reduced compared to the case where the projection unit 16 is arranged horizontally.

[Effects of the Invention] As explained above, according to the present invention, since the optical path lengths from the light source to the three liquid crystal light valves are equal, color unevenness does not occur, and compared to a three-tube projection unit, the pixels at the time of composition are Good alignment can be achieved.

Furthermore, since the shift amount of the optical axes of the projection lens and the liquid crystal light valve can be smaller than that of a conventional three-tube projection unit, the aperture of the projection lens can be made smaller.

Furthermore, the structure of the projection unit is simpler than that of a conventional single-tube projection unit, and the main body of the projection display apparatus can be made smaller and lighter.

[Brief Description of the Drawings] Figures 1 to 3 show an embodiment of the present invention, with Figure 1 being a configuration diagram of a projection unit, and Figures 2 (a) and (b) showing a vertically arranged projection unit. A configuration diagram of the rear projection type display device, Figure 3 (
a) and (b) are configuration diagrams of a rear projection type display device with a horizontally arranged projection unit, FIG. 4 is a configuration diagram of a conventional rear projection type display device, and FIG. 5 is a configuration diagram of a conventional three-tube projection unit. 6th
The figure is an explanatory diagram of the condensing angle of a conventional 3-tube projection unit, Figure 7 is an explanatory diagram of the optical path length problem of a conventional 3-tube projection unit, and Figure 8 is an explanation of the problem when combining images with a conventional 3-tube projection unit. figure,
FIG. 9 is a configuration diagram of a conventional single tube type projection unit. 6... Light source, 9a, 9b, 9C... Light valve,
14a, 14b...color separation means, 14. d... Color synthesis means, 15a... First projection lens, 15b...
・Second projection lens Figure 1 Figure 4 Figure 9

Claims (4)

[Claims] (1) A color separation means for separating white light emitted from a light source into three primary colors; and a color separation means for image modulating each of the three color lights separated by the color separation means, and disposed at a position having equal optical path lengths from the light source. the three light valves, a color synthesis means for synthesizing two of the three color lights image-modulated by the three light valves, and a first projection for projecting the two-color light synthesized by the color synthesis means onto a screen. A projection type display device comprising: a lens; and a second projection lens that projects one color light that is not combined by the color combining means onto a screen. (2) The projection display device according to claim 1, wherein the wavelength range of the monochromatic light projected by the second projection lens is a green wavelength range. (3) The projection type display device according to claim (1), wherein the first projection lens and the second projection lens are arranged side by side in a vertical direction. (4) The projection display device according to claim (1), wherein the first projection lens and the second projection lens are arranged side by side in a horizontal direction.