JP2000347324A - Image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the brightness of light made incident on a screen and the white balance of the light, as for a simply constituted one panel system image display device. SOLUTION: As for the image display device, R, G and B light are derived from white light emitted from a light source 101 through a three-primary color RGB filter 103, and the R, G and B light are successively supplied to one image display element 108 so as to be modulated, then, the modulated light is made incident on a screen. The color filter 103 is constituted so that at least a time for selecting one color among three colors R, G and B may be different from a time for selecting another color.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display device, such as a liquid crystal projector, for enlarging and projecting light from a light source through an image display device onto a screen by a projection lens.

[0002]

2. Description of the Related Art A projection-type image display device using a liquid crystal display device includes a three-panel liquid crystal projection using three liquid crystal display devices and one liquid crystal display device disclosed in Japanese Patent Application Laid-Open No. 1-293385. There is a single-panel type liquid crystal projection used.

[0003] The former three-panel liquid crystal projection is
As shown in FIG. 8, light from a light source 601 is red, green, and blue (hereinafter, referred to as R, G, and B) by a dichroic mirror 602.
Then, the light is respectively incident on the liquid crystal display elements 603R, 603G, and 603B corresponding to the separated colors. The R, G, and B lights modulated by the liquid crystal display element 603 in accordance with the image signal are combined by a cross dichroic prism 604, then enter a projection lens 605, and projected on a screen.

In this method, light from a light source can be used without waste, so that a very bright image can be realized.
Since three liquid crystal display elements 603 corresponding to each of R, G, and B colors are required, and an optical system for color separation and a cross dichroic prism 604 for color synthesis are required, the cost of the system increases. In addition, there is a problem that the system size becomes very large.

As a method for solving this problem, the latter single-panel type liquid crystal projection has been proposed. There are two types of this single-panel type. One type is such that light from a light source is incident on one liquid crystal display element, and R, G, B regularly arranged on pixels of the liquid crystal display element. Since the three pixels R, G, and B are displayed as one group in a method of performing color display using the color filter described above, the resolution is reduced to one third as compared with the three-plate type.

In the other method, as disclosed in Japanese Patent Application Laid-Open No. 8-140107, R, G, and B lights from a light source are sequentially selected by time division using a rotating color filter 701 as shown in FIG. In this method, the light is incident on a black-and-white liquid crystal display element. A signal is input to the liquid crystal display element in synchronization with the incident color, and R, G, and B are displayed as one image segment (one frame). This method is called a time-sequential method or a field-sequential method, and is characterized in that it is very compact and inexpensive, and that the same resolution as that of the three-plate method can be obtained.

[0007]

However, the single-panel type liquid crystal projection has the following problems. In each of the system having a space-divided color filter on the pixel of the liquid crystal display element and the time sequential system, light from the light source is selected by the color filter. For example, white light is incident on the R color filter. Then, the light of G and B incident on this area becomes practically unusable, and the brightness is reduced to 1/3 in principle.

[0008] Further, in the projection for audiovisual (hereinafter referred to as AV), white balance is emphasized. Therefore, if the spectrum of the light source used is biased, light having a strong spectrum must be cut off.
Brightness further decreases. Actually, as a light source currently used for liquid crystal projection, there are a metal halide lamp, a high-pressure mercury lamp (hereinafter referred to as a UHP lamp), a halogen lamp, a xenon lamp, and the like.

The metal halide lamp and the UHP lamp are:
Very high luminous efficiency compared to halogen lamps and xenon lamps, so bright projection can be realized with low power consumption. However, since the emission spectrum of R is weak, G and B colors are cut to obtain a good white balance. Must. Similarly, since the halogen lamp has a weak blue emission spectrum, the R and G colors must be cut off. Xenon lamps are different from the above lamps,
Although the spectrum balance is relatively good, the luminous efficiency is about 1/3 of that of metal halide lamps and UHP lamps. To obtain the same brightness as these lamps, it is necessary to use high power consumption lamps. No.

[0010]

The image display apparatus according to the first aspect of the present invention has a color switch having a function of alternately selecting a light source and three primary colors of red, green and blue contained in the light source. Means, an image display element for displaying an image corresponding to red, green, and blue light from the color switching means, and a projection lens for projecting light modulated by the image display element. The selection time of at least one of red, green and blue in the color switching means is different from the selection time of the other colors.

According to a second aspect of the present invention, in the image display apparatus of the first aspect, of the three colors of red, green, and blue light selected by the color switching means, a light from a light source is provided. The selection time of light having a weak spectrum is longer than the selection time of other colors.

According to a third aspect of the present invention, there is provided the image display apparatus according to the first aspect, wherein green is selected from among the three colors of red, green and blue selected by the color switching means. The time is set to be longer than at least one of the selection times of red and blue.

(Operation) The operation of the present invention will be described below. According to the first configuration, by making the selection time of at least one of red, green, and blue in the color switching means different from the selection time of the other colors, the brightness and chromaticity are adjusted according to the spectral distribution of the light source. Can be adjusted.

According to the second configuration, even if there is a bias in the spectral distribution of the light source, by extending the selection time of the weak light among them, a good white balance can be obtained without largely cutting the light. Obtainable.

According to the third configuration, the amount of green light having high visibility can be increased, so that the brightness can be improved.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the drawings. (Embodiment 1) FIG. 1 is a schematic view of a projection type color image display device of the present invention. In the present embodiment, as the light source 101,
120W, 1.4mm arc length UHP manufactured by Philips
A lamp was used. As a light source, a halogen lamp, a xenon lamp, or a metal halide lamp may be used. On the back of the light source 101, an elliptical mirror 102 for condensing light from the light source to its second focal point is arranged. Near the second focal point of the elliptical mirror 102, as shown in FIG.
A rotating color filter 103 having an area for transmitting G and B light is disposed, and the rotating color filter 103 sequentially selects R, G, and B light from white light from a light source in a time-division manner. In this rotating color filter 103, since the emission spectrum of R of the UHP lamp is weak,
The transmission area of each color is set so that the selection time of R is 10% longer than other colors.

In front of the rotating color filter 103,
A glass rod 104 is arranged. The glass rod 104 reflects the light inside and transmits the light, and is arranged such that the light emission slope is substantially focused on a liquid crystal display element 108 described later. On the light emitting slope of the glass rod 104, the light is repeatedly totally reflected inside the rod, so that the illuminance distribution is substantially uniform. Thereby, the illuminance distribution of the light incident on the liquid crystal display element 108 can be improved. The light emitted from the glass rod 104 enters the illumination lens 105 and the field lens 106, is converted into substantially parallel light, and then enters the polarizing plate 107. Polarizing plate 10
In step 7, only the light having one polarization direction among the incident light is transmitted and made incident on the liquid crystal display element 108.

The R, G, and B light modulated by the liquid crystal display element 108 in accordance with the image signal enters a polarizing plate 109 and is projected on a screen via a projection lens 110. As the liquid crystal display element 108, a 0.9 type XGA panel and a nematic liquid crystal having a response speed of 2 msec to 3 msec was used. As the liquid crystal mode, any other liquid crystal mode having a high response speed such as a ferroelectric liquid crystal can be used.

When the projection is configured with the above configuration, the white balance can be greatly improved without greatly lowering the brightness as compared with the case where this method is not used. In the first embodiment, a UHP lamp having a weak R spectrum intensity is used. However, when a lamp having different R, G, and B spectrum intensities is used, a region corresponding to a weak color of the spectrum of the rotating color filter 103 is used. The same effect can be obtained by increasing. For example, when a halogen lamp is used, unlike the UHP lamp, the R light is strong and the B light is weak, so the B region may be increased.

Further, in the first embodiment, the transmission area of the R light is enlarged and the transmission areas of the G and B are set to the same size. The transmission area may be adjusted. Further, Embodiment 1
Although the transmission type liquid crystal display element is used in the above, the same effect can be obtained by using a reflection type liquid crystal display element or a DMD (digital mirror device). In the case of using a polarization mode reflection type liquid crystal display device, a polarizing beam splitter (hereinafter referred to as PBS) 111 is used as shown in FIG.
At 111, light having a polarization component in one direction is incident on the reflective liquid crystal display element 112. When using a reflective liquid crystal display device or DMD that utilizes light scattering or diffraction,
The polarizing plates 107 and 109 described above are in the non-polarizing mode.
It is not necessary to use PBS111.

(Embodiment 2) FIG. 4 is a schematic view of a projection type color image display device according to a second embodiment of the present invention. In the second embodiment, only the characteristics of the light source and the rotating color filter are different from those of the first embodiment. Therefore, in FIG. 4, the portions corresponding to FIG.

In the second embodiment, a xenon lamp (400) having a relatively good spectral balance is used as the light source 401.
W) was used. As a light source, a halogen lamp, a xenon lamp, or a metal halide lamp may be used. As the rotating color filter 402, FIG.
As shown in the figure, the G area is about 10% higher than the R and B areas.
The larger one was used.

As a result of using the rotating color filter 402, the visibility is high and the amount of G light greatly contributing to the brightness is increased. Therefore, the conventional rotating color filter having the same R, G, and B transmission regions is used. The brightness was increased about 1.2 times as compared with the case. As a result, the white balance slightly deviates from that of G. However, since a xenon lamp having a relatively good spectral balance is used as a light source, this does not cause a serious problem.

Even when a lamp having a biased emission spectrum such as a UHP lamp or a metal halide lamp is used in addition to the xenon lamp, it is useful for data projection in which white balance is not so important. In the second embodiment, the transmission area of G light is increased,
Although the R and B transmission regions are set to the same size, the R, G, and B transmission regions may be adjusted according to the spectral distribution of the light source.

Furthermore, in the second embodiment, the first embodiment
Similar effects can be obtained by using a reflective liquid crystal display element or a DMD in the same manner as described above.

In the first and second embodiments, a rotary color filter divided into R, G, and B regions is used.
As shown in (1), in order to increase the brightness, the present invention can be applied to a case where a transparent region is added to the R, G, B regions. In the first and second embodiments, the rotating color filter is used as the color switching means. However, any color switching can be applied as long as the color switching can be performed in a time-division manner.
For example, a color filter may be switched by inserting a cylindrical color filter as shown in FIG. 7A into the optical path and rotating the same, and a strip-shaped color filter as shown in FIG. Alternatively, color switching may be performed by reciprocating on the optical path.

[0027]

As described above, according to the present invention, the screen of the three colors of R, G, and B passing through the rotating color filter is adjusted so that the other performances are not greatly reduced. The white balance of the incident light can be adjusted and the brightness can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a projection type color image display device according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of a rotating color filter used in Embodiment 1 of the present invention.

FIG. 3 is a schematic diagram when a reflective liquid crystal display element is used in Embodiment 1 of the present invention.

FIG. 4 is a schematic diagram of a projection type color image display device according to a second embodiment of the present invention.

FIG. 5 is an explanatory diagram of a rotating color filter used in Embodiment 2 of the present invention.

FIG. 6 is an explanatory diagram of another rotating color filter used in Embodiment 2 of the present invention.

FIG. 7 is an explanatory diagram of another color switching unit used in Embodiment 2 of the present invention.

FIG. 8 is an explanatory view of a conventional three-panel liquid crystal projection.

FIG. 9 is an explanatory diagram of a conventional rotating color filter.

[Explanation of symbols]

 Reference Signs List 101 light source 102 elliptical mirror 103 rotating color filter 104 glass rod 105 illumination lens 106 field lens 107 incident side polarizing plate 108 liquid crystal display element 109 emission side polarizing plate 110 projection lens 111 PBS 112 reflection type liquid crystal display element 401 light source 402 rotating color filter

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G09G 3/20 642 G09G 3/20 642L 3/34 3/34 J F-term (Reference) 2H088 EA13 EA14 EA16 EA19 HA12 HA13 HA18 HA20 HA24 HA28 JA17 MA02 MA06 2H093 NA65 ND04 ND08 NE06 NF17 NG02 5C080 AA10 BB05 CC03 CC06 DD03 DD27 DD30 EE29 EE30 FF07 FF09 JJ06

Claims (3)

[Claims] 1. A light source, a color switching unit having a function of alternately switching and selecting three primary colors of red, green, and blue contained in the light source; and a light source for red, green, and blue light from the color switching unit. An image display device for displaying a corresponding image, and a projection lens for projecting light modulated by the image display device, wherein at least one of red, green, and blue in the color switching means is provided. An image display device, wherein a selection time is different from a selection time of another color. 2. A method according to claim 1, wherein, among the three colors of red, green and blue light selected by said color switching means, the selection time of light having a weak spectrum from the light source is made longer than the selection time of other colors. The image display device according to claim 1. 3. A method according to claim 1, wherein, of the three colors of red, green and blue light selected by said color switching means, a green selection time is longer than at least one of the red and blue selection times. The image display device according to claim 1.