JPH1062783A - Projection liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projection liquid crystal display device having a relatively good utilization factor by using a hologram element as a color resolving means and having less restriction for being assembled into an optical system and being inexpensive and in no danger of color mixture. SOLUTION: A hologram element 14 is arranged between a white light source and a liquid crystal element (LCD) 15 as a color resolving means. The hologram element 14 separates the incident white light at an adaptive angles to picture element array of the liquid crystal elements 15 on the three primaries of red, green, and cyan and transmits them to the side of the liquid crystal elements 15, while it has a function to let the complementary color components (especially, Cyan and Yellow), which may cause color mixture, other than the three primaries pass through in a direction deflecting from the liquid crystal display elements 15. Thus, the liquid crystal display elements 15 are not irradiated with complementary color components of cyan with wavelengths adjacent to blue to green and yellow with wavelengths adjacent to green to red, and there is no danger of color mixture even when white light is used as a source of light.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single-panel projection type liquid crystal display device, and more particularly to a projection type liquid crystal display device using a hologram element as color separation means.

[0002]

2. Description of the Related Art As a liquid crystal display device, there is a projection type display device (liquid crystal projector) for projecting and displaying on a screen together with a direct-view type display device. In this projection type liquid crystal display device, light emitted from a single white light source is separated into three primary colors for color display by color separation means, and each primary color light is divided into pixels of a liquid crystal display element corresponding to the color ( (A liquid crystal cell), where it is modulated according to the reproduced image and then projected on a screen to display a color image. As such a projection type liquid crystal display device, red (Red)
= R), green (Green = G), blue (Blue = B) single-panel method using one liquid crystal display device with color separation means of three colors,
It can be broadly classified into a three-panel system using three monochrome liquid crystal panels for each of the red, green and blue light paths.

[0003] Among them, the single-panel type projection display device has the following two features.
The color separation means separates the light emitted from a single white light source into three primary color lights of red, green and blue. As the color separation means, a color filter, a dichroic mirror and a diffraction grating have been proposed. I have.

[0004]

However, each of these color separation means has the following problems. First, in the color filter type, for example, a red color filter is disposed in a pixel that displays red, but light of other colors (green and blue) is absorbed or reflected by the red color filter. You. This is the same for the green and blue color filters. That is, only one third of the light incident on the liquid crystal display element can be used in the color filter system, the light use efficiency is lower than in the case where the same light source is used in the three-plate system, and the brightness of the screen is similarly reduced by three. There was a problem that it was reduced by a factor of one. Next, a dichroic mirror is formed by alternately laminating about 10 to 20 thin films having a small refractive index and a large thin film on one surface of an optical glass, and utilizes the interference of the optical multilayer film. For this reason, when the dichroic mirror is used as the color separation means, there is a problem that the incident angle dependence of the illumination light is strong, and when the light is incorporated into a set (optical system), the restriction becomes large. Further, regarding the diffraction grating, the diffraction grating performs color separation continuously in principle, so that the possibility of occurrence of color mixture (noise) is very high, and the primary colors (red, green,
There was a problem that it was necessary to shield light components other than blue) by a separate means.

[0005] As another color separation means, there is a method using a hologram element having a diffraction function. When this hologram element is applied as a color separation means, when a laser light source is used as a light source for reproduction, the problem of color mixing unlike the method using a diffraction grating does not occur. However,
If a laser light source is used, the display device becomes expensive, and at present, an inexpensive and bright white light source is used for most display devices. On the other hand, when this white light source is used, there is still a problem of color mixing as in the case of using a diffraction grating. As described above, according to the conventional technology, it is difficult to realize a projection-type liquid crystal display device which can satisfy both the light use efficiency and the color purity and is inexpensive.

The present invention has been made in view of such a problem, and an object of the present invention is to improve the light use efficiency by using a hologram element as color separation means, to reduce restrictions on the incorporation into an optical system, An object of the present invention is to provide an inexpensive projection-type liquid crystal display device that does not cause color mixing.

[0007]

A projection type liquid crystal display device according to the present invention is constituted by regularly arranging a white light source emitting white light and a plurality of pixels corresponding to primary colors for color display. A liquid crystal display element that modulates incident light in accordance with a reproduced image, and a hologram element, and a plurality of primary color lights of white light emitted from a white light source are separated from each other and guided to the liquid crystal display element. And a color separation unit that guides complementary color light that causes color mixing in a direction away from the liquid crystal display element.

In the projection type liquid crystal display device according to the present invention, white light emitted from a white light source is incident on a hologram element as color separation means. The light is guided to the liquid crystal display element separately from each other according to the pixel arrangement. On the other hand, complementary color light (particularly, cyan and yellow, which causes color mixing with respect to the three primary colors of red, green and blue) contained in the white light is guided by the hologram element in a direction away from the liquid crystal display element. The primary color light guided to the liquid crystal display element is modulated here according to the reproduced image. These modulated lights are projected on a screen to perform color display.

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a schematic configuration of a projection type liquid crystal display device 10 according to an embodiment of the present invention. The projection-type liquid crystal display device 10 according to the present embodiment includes a white light source 11 that emits white light, a reflecting mirror (reflector) 12 that is, for example, a spherical mirror disposed on the back of the white light source 11, and is disposed on the front of the white light source 11. Condensing lens 13, hologram element 14 as color separation means disposed on the front of condensing lens 13, liquid crystal display (LCD) 1 disposed on the front of hologram element 14
5. Projection lens 1 arranged in front of liquid crystal display element 15
6 and a screen 17 for image formation.

The white light source 11 only needs to be capable of emitting white light including the three primary colors of red, green, and blue. For example, a metal halide lamp, a halogen lamp, a xenon lamp, or the like is used. The condenser lens 13 condenses the white light emitted from the white light source 11 and converts the white light into parallel light.
It leads to 4.

The hologram element 14 is not of the type in which the diffraction efficiency does not depend on the wavelength (that is, the type in which only a specific wavelength is diffracted like a Lippmann hologram and the other wavelengths are not diffracted). Hologram element). As such a hologram element, there are, for example, a relief method, a phase method, an amplitude method, and the like. Hologram element 14
For example, a photopolymer (Omnidex 352 manufactured by DuPont) is used as an element material for forming the light-emitting device, and interference fringes corresponding to the wavelengths of the three primary colors and the complementary colors are formed by the method described below. The hologram element 14 according to the present embodiment has the condensing lens 1 as shown in FIG.
The white light condensed by 3 separates the three primary colors of red, green, and blue at an angle suitable for the pixel arrangement of the liquid crystal display element 15 and transmits the separated light to the liquid crystal display element 15 side. Complementary color components other than the primary colors (particularly, cyan (Cy =
Cyan) and yellow (Y = Yellow) have a function of transmitting in a direction away from the liquid crystal display element 15. That is, the above-described color mixing problem is caused by the wavelengths near the wavelengths of the three primary colors originally required for color display, and the cyan color (470 to 520n) having a wavelength close to blue or green.
m) and yellow with a wavelength close to green or red (570-
600 nm), the present embodiment is configured such that the hologram element 14 does not irradiate the liquid crystal display element 15 with complementary colors of these wavelengths.

The liquid crystal display element 15 is a device in which pixels (liquid crystal cells) corresponding to three colors of red, green and blue are regularly arranged in, for example, a delta (triangle) shape. And spatially modulates and outputs. This liquid crystal display element 15 is, specifically,
For example, as shown in an enlarged manner in FIG. 3, it is constituted by an element body 20 and a microlens array 30 as imaging means attached to the front surface of the element body 20. The element body 20 is provided with a liquid crystal layer 2 between two glass substrates 21 and 22.
3 for forming a matrix electrode structure for duty-driving the liquid crystal layer 23.
4R, 24G, 24B and scanning electrode 25 are glass substrate 2
It has a structure arranged on the inner surfaces of 1, 22. The microlens array 30 includes a plurality of microlenses 30a extending in a direction perpendicular to the plane of the paper, and one microlens 30a has three pixels (signal electrodes 24R, 24G, and 24B).
, And is in a state of being arranged to face. Signal electrode 24
R, 24G, 24B and the scanning electrode 25 are each formed of a transparent conductive film, and the signal electrodes 24R, 24G, 2
The drive signals of the respective colors of red, green, and blue are input to 4B. The red light transmitted through the hologram element 14 is applied to the microlens 30 on the signal electrode 24R.
a. Green light transmitted through the hologram element 14 is incident on the signal electrode 24G via the microlens 30a. Further, blue light transmitted through the hologram element 14 is incident on the signal electrode 24B via the microlens 30a. That is, the signal electrodes 24R, 24G,
The intensity of the light of each color incident on each of the lights 24B is modulated according to the input state of the drive signal to the signal electrodes 24R, 24G, and 24B according to the reproduced image.
Note that, for simplicity, a polarizing plate, an alignment film, and the like, which are components of the liquid crystal display element, are omitted here.

The projection lens 16 combines the light that has been modulated and transmitted by the liquid crystal display element 15 and magnifies and forms an image on a screen 17.

Next, FIGS. 4A to 4C and FIG.
A specific method of manufacturing the hologram element 14 will be described with reference to (a) and (b).

First, as shown in FIG. 4A, a laser beam for green, that is, a reference beam (Gr) is applied to the hologram substrate 14a having a thickness of, for example, 10 μm, and the reference beam (Gr) is applied to the hologram substrate 14a. object light (Go) is irradiated at an angle theta ₁ which is adapted to the arrangement of the green pixels of the liquid crystal display device 15 Te, forming interference fringes by these lights. Subsequently, FIG.
As shown in (1), together with the laser beam for red, that is, the reference light (Rr), with respect to the same hologram substrate 14a, the angle with respect to this reference light (Rr) conforming to the arrangement of the red pixels of the liquid crystal display element 15. irradiating the object beam (Ro) with theta _2, forming interference fringes by these lights. Subsequently, as shown in FIG. 4C, the same laser beam for blue, that is, the reference light (Br) is applied to the same hologram substrate 14a, and the liquid crystal display element 15 receives the reference light (Br). The object light (B) has an angle θ ₃ that matches the arrangement of the blue pixels.
o) to form interference fringes due to these lights. As described above, interference fringes for the three primary colors of green, red and blue for color display are formed on the hologram substrate 14a.

The incident angle of the reference light (Gr, Rr, Br) with respect to the hologram substrate 14a is such that the white light emitted from the white light source 11 is
The angle is set to be the same as the angle of incidence (in this embodiment, the direction perpendicular to the hologram surface as shown in FIG. 1). In addition, these reference lights (Gr, Rr, B
The incident angles θ _{1 to} θ ₃ of the object light with respect to r) need to be determined in consideration of the focal length of the microlenses 30a in addition to the arrangement pitch of the pixels of each color.

Next, in the present embodiment, these three primary colors are used.
On the hologram substrate 14a on which the interference fringes are formed.
On the other hand, as shown in FIG.
Along with the reference laser beam (Yr).
Angle θ with respect to illumination (Yr) _FourWith object light (Yo)
To form interference fringes due to these lights. Continued
Then, the same hologram substrate 1 as shown in FIG.
4a, a cyan laser beam, that is, a reference beam
(Cyr) and the angle with respect to this reference light (Cyr)
θ_FiveIrradiates the object light (Cyo) with
To form interference fringes. Thus, the hologram substrate 1
Interference fringes for complementary colors (Y, Cy) are formed for 4a
Is done. In addition, each object light (Yo, Cyo) reference
Incident angle θ for light_Four, Θ_FiveAre the same as above (Fig.
Yellow transmitted through the hologram element 14 as in 2) and
Of the extent that the complementary light of cyan deviates from the liquid crystal display element 15.
The angle shall be set. Further, the reference light (Yr, Cy)
r) Incident angle for each hologram element 14
Is also radiated from the white light source 11 as in the case of the three primary colors.
Angle at which the white light is incident on the hologram element 14
In the embodiment, the same as the direction perpendicular to the hologram plane)
The angle shall be set. Note that interference fringes related to complementary colors
For forming a laser, a laser capable of performing multiple oscillations, for example,
Dye lasers can be used.

In the projection type liquid crystal display device 10 of the present embodiment using the hologram element 14 manufactured by such a method, the white light emitted from the white light source 11 and reflected by the reflecting mirror 12 is collected. After being converged by the optical lens 13 to become parallel light, it is incident on the hologram element 14. Each color component of the white light incident on the hologram element 14 advances at a predetermined angle for each wavelength used in the hologram manufacturing process. In other words, of the white light, the three primary colors necessary for the green, red and blue color display are transmitted while being separated at different angles for each color,
The light is incident on the pixel corresponding to each color component of the liquid crystal display element 15 via Oa. On the other hand, complementary color components (cyan and yellow) that cause color mixing other than the three primary colors are transmitted in a direction away from the liquid crystal display element 15. Liquid crystal display element 15
The light of the three primary colors incident on the LCD is spatially modulated by the reproduced image of the liquid crystal display element 15 for each color, and then guided to the projection lens 16. The modulated light that has entered the projection lens 16 is combined here to form an image on the screen 17. Thus, a color image is displayed.

This projection type liquid crystal display device 10 has the advantage of using the hologram element 14 as the color separation means, that is, the incident light is blocked by absorption and reflection as compared with the color filter as other color separation means. As a result, the incident light can be efficiently used and the cost is low. In addition, the complementary color component of the wavelength causing the color mixture is removed from the liquid crystal display element 15 and only the three primary colors are efficiently transmitted to the liquid crystal display element 15. I can guide you. Therefore, there is an effect that a bright image display with good color reproducibility can be performed. Further, by forming a hologram element by the above method, even if it is desired to exclude a specific wavelength in the set (optical system) configuration, it can be easily realized without increasing the number of optical elements. Further, there is also an effect that the emission energy can be used efficiently by matching the wavelength of the object light at the time of hologram creation with the set light source spectrum.

Although the present invention has been described with reference to the embodiment, the present invention is not limited to the above-described embodiment and can be variously modified. For example, in the above embodiment, in the process of manufacturing the hologram element 14, green, red,
Although multiple exposures are performed in the order of blue, yellow, and cyan, the arrangement order is arbitrary because the arrangement order is determined by the incident angle in the manufacturing process. Further, the hologram element 14 may be manufactured not by the multiple exposure method but by the collective exposure method. Further, the complementary colors may include not only yellow and cyan colors but also other magenta colors and the like.

In the above embodiment, the liquid crystal display element 15 has a delta (triangle) pixel arrangement. However, other liquid crystal arrangements (for example, stripes) may be used. The interference fringes of the hologram element 14 may be formed.

Further, in the above embodiment, the white light emitted from the white light source 11 is perpendicular to the hologram element 14 by arranging the components such as the white light source 11 and the condenser lens 12 on the same axis. However, the arrangement of the optical system such as the white light source 11 and the condenser lens 13 may be changed so that white light is incident on the hologram element at an angle. 14 may be arranged to be inclined with respect to the liquid crystal display element 15. In any case, in the process of forming interference fringes of the hologram, the incident angle of the reference light on the hologram surface may be changed according to the incident angle of the white light from the white light source 11.

In addition, in the above-described embodiment, an example has been described in which a transmission type hologram element in which diffracted light is emitted to the opposite side to the light source with the hologram surface as a boundary is applied. A hologram element of a mold type can also be used. The reference light for producing the reflective hologram element may be incident from a direction conjugate with the reference light for producing the transmission hologram element.

In the above embodiment, the complementary color component of the white light incident on the hologram element 14 is guided upward or downward in the xy plane (on the plane of FIG. 2) of the primary color light. In the z direction (the direction perpendicular to the plane of FIG. 2).
May be separated from the liquid crystal display element 15. Further, in the above-described embodiment, the interference fringes are formed by using the laser light in the process of manufacturing the hologram element. However, light other than the laser can be used as the reference light and the object light.

In the above embodiment, the interference fringes of the hologram element 14 are optically formed by two-beam interference. However, a desired hologram interference fringe can be obtained by a computer. In this computer generated hologram, a hologram element similar to that in the above embodiment may be manufactured by adding the conditions in the above embodiment at the time of calculation.

[0027]

As described above, according to the projection type liquid crystal display device of the present invention, the hologram element is used as the color separation means, and the primary color light out of the white light emitted from the white light source by the hologram element is used. Are separated from each other and guided to the liquid crystal display element, and the complementary light that causes color mixing is guided in a direction deviating from the liquid crystal display element, so that the light use efficiency is improved and the incorporation into a set (optical system) is improved. It is possible to provide an inexpensive projection-type liquid crystal display device with reduced restrictions and no risk of color mixing.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating an overall configuration of a projection type liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a configuration diagram for explaining functions of a hologram element used in the display device shown in FIG.

FIG. 3 is a configuration diagram for explaining a structure of a liquid crystal display element used in the display device shown in FIG.

FIG. 4 is a process chart for explaining a manufacturing process of a hologram element used for the display device shown in FIG.

FIG. 5 is a process drawing for explaining a manufacturing process of the hologram element.

[Explanation of symbols]

11: white light source, 12: reflecting mirror, 13: condenser lens, 1
4 Hologram element 15 Liquid crystal display (LCD), 16 Projection lens, 1
7 ... Screen

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location H04N 9/31 H04N 9/31 C

Claims (2)

[Claims] 1. A white light source that emits white light, and a liquid crystal display element that is configured by regularly arranging a plurality of pixels corresponding to primary colors for color display and that modulates incident light according to a reproduced image. A plurality of primary color lights out of the white light emitted from the white light source are guided to the liquid crystal display element while being complementary to each other. A projection type liquid crystal display device comprising: color separation means for guiding the element in a direction away from the element. 2. The projection type liquid crystal display device according to claim 1, wherein the complementary light separated by the hologram element includes at least cyan and yellow light.