JPH02189537A - Projection type liquid crystal display device - Google Patents

Abstract

PURPOSE:To display an image plane which is good in the unformity of image plane brightness by using a beam splitter and a luminous flux reflecting element which are provided between a light source and a liquid crystal display element, and lighting the liquid crystal display element with two pieces of luminous flux obtained by splitting the luminous flux from the light source. CONSTITUTION:The light source 1 emits the projection light 7, which are split by the beam splitter 4 into projection light 8 and projection light 9. The projection light 8 illuminates the liquid crystal display element 2 as it is and the projection light 9, on the other hand, illuminates the liquid crystal display element 2 as the projection light 10 after being reflected by the mirror 5 so that its traveling direction is almost equal to the traveling direction of the projection light 8. For the purpose, the beam splitter 4 and mirror 5 are arranged between the light source 1 and liquid crystal display element 2 and the liquid crystal display element 2 can be lighted with the two pieces of luminous flux obtained by splitting the projection light 7 from the light source 1. Consequently, while an area which is not utilized to project an image plane becomes small, the difference of an intensity distribution from the peripheral part decreases and even when a laterally long image plane is projected, the light utilization efficiency of the light source 1 is increased and uniform image plane brightness is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a projection type liquid crystal display device, and more particularly to a projection type liquid crystal display device that projects a display image of a liquid crystal display element onto a screen surface.

[Conventional technology]

A projection type liquid crystal display device projects a display image of a liquid crystal display element onto a screen surface, and is also capable of enlarging and projecting the image.

FIG. 3 shows a conventional projection type liquid crystal display device.

As shown in FIG. 3, the projection type liquid crystal display device in this case includes a light source 41 such as a halogen lamp or a xenon lamp, and a TN
A liquid crystal display element 42 that forms an image using a (twisted nematic) type liquid crystal, and a projection lens 43 that enlarges and projects the displayed image of the liquid crystal display element 42 onto a screen 44 using projection light 45 from a light source 41. It mainly consists of Such a projection type liquid crystal display device can easily obtain a large screen image by enlarging and projecting the display screen of a small liquid crystal display element 42 onto a screen 44 to an arbitrary size using a projection lens 43. , and the device is very compact.

In addition, compared to projectors that enlarge and project slide film, 8mm film, etc., projection type liquid crystal display devices use an electronic display called a liquid crystal display element, so they can reproduce images from television broadcast signals, video signals, etc. It has the characteristic of being

[Problem to be solved by the invention]

However, in conventional projection-type liquid crystal display devices, problems arise in terms of light utilization efficiency and the like when attempting to obtain a more horizontally elongated screen.

Generally, when displaying images on a large screen, it is said that it is better to make the screen horizontally elongated, like in a movie, to reduce viewer fatigue and to create a sense of realism and the power of the screen. The usefulness of such a screen shape can be said for other general display screens, but it is especially true for high-definition, which is expected to provide high resolution and high image quality. The ratio is 9:16, and the screen shape is longer than the 3:4 aspect ratio of a normal TV screen.

Therefore, when a projection type liquid crystal display device has such a screen shape, it is necessary to use a horizontally long liquid crystal display element as the liquid crystal display element and illuminate it with the projection light from a light source to form a horizontally long screen. However, when trying to realize such a horizontally long screen using a conventional projection type liquid crystal display device, in order for the projected light from the light source to illuminate the entire horizontally long liquid crystal display element, at least the circumference of the liquid crystal display element must be It will be illuminated in a circle larger than a circle. Here, the light of the portion other than the liquid crystal display element is not used for the projection screen, and the more the shape of the liquid crystal display element becomes a horizontally long rectangle, the more the amount of unused light increases. As a result, the efficiency of using light from the light source decreases, and the projection screen inevitably becomes dark. Further, a problem arises in that there is a large difference in brightness between the center of the projection screen and both left and right ends.

Furthermore, these difficulties will be explained in more detail using figures.

FIG. 4 is a diagram for explaining the problems of the conventional example.

In FIG. 4(a), projected light 27 from a light source 2 is condensed by a condenser lens 23 and illuminates a liquid crystal display element 22. In FIG. Here, if the screen shape of the liquid crystal display element 22 is long horizontally, the aspect ratio of the screen is 9:16, for example, similar to high-definition.
In this case, the projected light 27 illuminates the liquid crystal display element 22 as shown in FIG.
) will be illuminated as shown. As is clear from the figure, the hatched portion of the projection light 27 in the figure is not used for projecting the screen, and the longer the shape of the liquid crystal display element 22 becomes horizontally long, the wider the area becomes. Therefore, the efficiency of using light from the light source is inevitably lower than when the aspect ratio is 3=4.

Furthermore, since the intensity distribution of the projected light 27 is strong at the center and weak at the periphery, the illuminance on the liquid crystal display element 22 is as shown in FIG. 4(c).
As shown in the figure, the distribution has a large difference between the center and both left and right ends. Since this illuminance distribution is reflected in the brightness distribution of the projection screen, a problem arises in that the center of both projection surfaces is bright and the peripheral areas are extremely dark.

SUMMARY OF THE INVENTION An object of the present invention is to provide a projection type liquid crystal display device that can have a high light utilization efficiency of a light source and improve the uniformity of screen brightness even when projecting a horizontally long screen.

[Means to solve the problem]

The present invention provides a projection type liquid crystal display device that has a light source and a liquid crystal display element and projects a display image of the liquid crystal display element onto a screen surface, and includes a beam splitter that separates a luminous flux from the light source into two luminous fluxes.
The ivy and a light beam reflecting element that deflects at least one of the two light beams are provided between the light source and the liquid crystal display element, and the liquid crystal display element is illuminated with the two light beams. .

[Effect]

In the present invention, by installing a beam splitter and a light beam reflecting element, it is possible to illuminate a liquid crystal display element with three beams of light, which reduces the area that is not used for screen projection, and at the same time, the intensity distribution has a small difference from the surrounding area. Therefore, even when projecting a horizontally long screen, it is possible to realize a projection type liquid crystal display device that can improve the light utilization efficiency of the light source and provide uniform screen brightness.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a plan view of a projection type liquid crystal display device for explaining one embodiment of the present invention.

As shown in FIG. 1, the device of this embodiment includes a light source 1, a liquid crystal display element 2, and a projection lens 3, and a display image of the liquid crystal display element 2 is projected in front of the projection lens 3. A screen 6 is arranged.

As will be described later, the liquid crystal display element 2 is a horizontally long liquid crystal display element with an aspect ratio of, for example, 9216, and a beam splitter is provided between the liquid crystal display element 2 and the light source 1 in this embodiment. 4 and a mirror 5 are provided. These are used to illuminate the liquid crystal display element 2 with two beams of light, the beam splitter 4 is used to separate the beam from the light source 1 into two beams, and the mirror 5 is This constitutes a light beam reflecting element that deflects at least one of the two light beams.

In the illustrated example, a beam splitter 4 separates a projection light 7, which is a light beam from a light source 1, into two light beams, a projection light 8 and a projection light 9, and a mirror 5
The mirror 5 reflects the projected light 9 into the projected light 10, and
The liquid crystal display element 2 is illuminated together with the projection light 8.

The projection lens 3 is arranged so that the display image of the liquid crystal display element 2 illuminated with the projection light 8 and the projection light 10 is formed on the screen 6.

As described above, in this embodiment, in a projection type liquid crystal display device that includes at least a light source 1, a liquid crystal display element 2, and a projection lens 3, and projects a display image of the liquid crystal display element 2 onto a screen surface, the light source 1 and the liquid crystal display element 2, there is a beam splitter 4 that separates the light beam from the light source 1 into two light beams, and a mirror 5 as a light beam reflecting element that deflects one of the two light beams. is provided, and the liquid crystal display element 2 is illuminated with the two luminous fluxes.

In the projection type liquid crystal display device having the above configuration, the display image of the liquid crystal display element 2 is projected onto the screen 6 in the following manner.

In FIG. 1, a light source 1 generates a projection light 7;
is separated by the beam splitter 4 into two beams, projection light 8 and projection light 9. The projected light 8 is directly transmitted to the liquid crystal display element 2.
On the other hand, the projected light 9 is reflected by the mirror 5 so that its traveling direction is approximately equal to the traveling direction of the projected light 8,
The liquid crystal display element 2 is illuminated as projection light 10.

In this way, the beam splitter 4 and the mirror 5 are arranged between the light source 1 and the liquid crystal display element 2, and the liquid crystal display element 2 can be illuminated with two luminous fluxes obtained by separating the projected light 7 from the light source 1. . That is, the liquid crystal display element 2 having a horizontally long screen shape is irradiated with two light beams, the projection light 8 and the projection light IO.

As mentioned above, the projection lens 3 allows the projection light 8 and the projection light 1 to be
It is arranged so that the display image of the liquid crystal display element 2 illuminated at 0 is formed on the screen 6, and when the liquid crystal display element 2 is illuminated as described above, the image displayed on the liquid crystal display element 2 By enlarging and projecting onto the screen 6, a large screen image can be displayed, and even in the case of a horizontally long display screen, the light utilization efficiency of the light source 1 is high, and the uniformity of the screen image is also good. It is possible to perform large screen display in the state.

This can be explained as follows.

FIG. 2 is a diagram for explaining the principle of the present invention in comparison with the case of FIG. 4.

As mentioned above, in the case of the configuration using the conventional device, the fourth
As shown in Figures (b) and (C), the light utilization efficiency is low and the intensity distribution has a large difference, whereas the configuration according to the present invention using a beam splinter and a light flux reflecting element , as shown in FIG. 2(a), the light source 31
The projected light is separated into two light beams, projection light 37 and projection light 38, by the beam splitter 34, and then the projected light 38 is reflected by the light beam reflecting element 35 so that its traveling direction is almost the same as that of the projected light 37. The projected light 37 and the projected light 39 illuminate the liquid crystal display element 32, respectively. In this case, the projected light 37 and the projected light 39 are
), the liquid crystal display element 32 is illuminated.

Obviously, compared to FIG. 4(b), the area of the shaded portion in the figure that is not used for screen projection is very small, and the efficiency of using light from the light source is high.

Furthermore, regarding the illuminance distribution of the liquid crystal display element 32, the three beams of projection light 37 and projection light 39 illuminate positions separated from the center of the liquid crystal display element 32 to the left and right. Compared to the case C), the uniformity can be significantly improved as shown in FIG. 2(C). Therefore, the uniformity of the brightness of the projection screen is also improved compared to the conventional example.

In this way, in a projection type liquid crystal display device, a beam splitter and a light beam reflecting element are installed between the light source and the liquid crystal display element, and the liquid crystal display element is illuminated with three beams of light, thereby projecting a horizontally long screen. It is possible to increase the light utilization efficiency of the light source and obtain uniform screen brightness.

The following are specific examples of the light source 1, liquid crystal display element 2, beam splinter 4, mirror 5, etc. used in the projection type liquid crystal display device having the configuration shown in FIG.

As for the light source 1, in this example, a high brightness white light source such as a halogen lamp or a xenon lamp was used. Further, although not clearly shown in the drawings, in order to prevent other components from being deteriorated by the projection light 7, the projection light 7 is passed through a filter that transmits only visible light.

The beam splitter 4 is a half mirror formed by depositing a metal film such as aluminum or chromium, a dielectric multilayer film, etc. on a glass substrate, and uniformly splits the visible wavelength light into transmitted light. A device that can separate the reflected light and the reflected light so that the intensities of the three beams are approximately equal was used. In addition, it is also possible to use a Kuipkuip beam splitter in which one slope of two right-angled prisms is coated with a semi-permeable membrane and the slopes are joined together.

Furthermore, although the mirror 5 is an aluminum surface mirror, an enhanced reflection mirror whose reflectance is particularly increased by a dielectric multilayer film or the like is used. Furthermore, the loss of reflected light can be reduced by using a right-angle prism that satisfies the total reflection condition on the slope.

Furthermore, regarding the liquid crystal display element 2, in this embodiment, it is a TN (twisted nematic) type liquid crystal cell, and is an active matrix type in which thin film transistors are arranged in a matrix for each pixel to drive the liquid crystal. However, other types of liquid crystal display elements, such as a simple matrix type or an active matrix type in which thin film diodes are arranged, may be used. Here, as described above, the shape of the display screen used was one with an aspect ratio similar to that of a high-definition screen, that is, a horizontally long one with an aspect ratio of 9:16.

When we actually performed enlarged projection using the above configuration, we found that by illuminating the liquid crystal display element 2, which has a horizontally long screen shape, with the two luminous fluxes of the projection light 8 and the projection light 10, the light source could be It is possible to increase the light usage efficiency of the screen and improve the uniformity of screen brightness.

In the configuration shown in FIG. 1, the image displayed by the liquid crystal display element 2 can be displayed in black and white or in color with a built-in color filter. Also, the projection light 8. A similar projection type liquid crystal display is used when the projected light 10 is separated into three colors of red, blue, and green by a dichroic filter, and is incident on three liquid crystal display elements respectively, and then combined again by a dichroic filter to display a color display. A display device is obtained.

Furthermore, the display screen may be one reproduced by inputting a television broadcast signal or a video signal, or may display characters, graphs, etc. created with a personal computer or word processor.

〔Effect of the invention〕

As explained above, according to the present invention, a beam splitter and a light flux reflecting element provided between a light source and a liquid crystal display element are used to illuminate the liquid crystal display element with two light fluxes obtained by separating the light flux from the light source. Therefore, even in the case of a horizontally long display screen, it is possible to obtain a projection type liquid crystal display device that can realize a screen display with high light utilization efficiency of a light source and good uniformity of screen brightness.

[Brief explanation of the drawing]

FIG. 1 is a plan view for explaining a projection type liquid crystal display device according to an embodiment of the present invention, FIG. 2 is a diagram for explaining the principle of the present invention, and FIG. 3 is a diagram for explaining a conventional example. , FIG. 4 is a diagram for explaining the problems of the conventional example. 1.31...Light source 2.32...Liquid crystal display element 3...Projection lens 4.34...Beam splinter 5...Mitsu-6...Screen 7-10 .37-39... Projection light 35... Luminous flux reflecting element

Claims (1)

[Claims] (1) In a projection type liquid crystal display device that has a light source and a liquid crystal display element and projects the display image of the liquid crystal display element onto a screen surface, a beam splitter that separates the light flux from the light source into two light fluxes and the two light fluxes are used. A projection type liquid crystal display device, characterized in that a light beam reflecting element for deflecting at least one of the light beams is provided between the light source and the liquid crystal display element, and the liquid crystal display element is illuminated with the two light beams.