JPH03150525A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To double the utilization rate of light by splitting the natural light P+S from a light source into P-polarized light and S-polarized light by a beam splitter, and passing them through a liquid crystal and then putting them together into P+S again by a beam splitter. CONSTITUTION:The liquid crystal display device is provided with the 1st beam splitter 1 which splits the natural light from the light source into orthogonal two components (P-polarized light and S-polarized light) perpendicular to the travel direction of the light, a 1st twisted nematic liquid crystal panel 4 (whose orientation direction matches the direction of the P-polarized light) where the P-polarized light is made incident, and a 2nd twisted nematic liquid crystal panel 4 (whose orientation direction matches the direction of the S-polarized light). Further, the device is provided with the 2nd beam splitter 2 which puts the polarized light beams passed through the 1st and 2nd liquid crystal panels together and reflecting mirrors 5 and 6 which are interposed in the optical path from the 1st beam splitter 1 to the 2nd beam splitter 2. Consequently, the utilization rate of light is doubled and a bright display is made with low electric power.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a light transmission type display device using twisted nematic liquid crystal and a light source.

2. Description of the Related Art Over the years, the number of devices using liquid crystals as display devices, such as small televisions, laptop computers, and word processing sensors, has increased significantly. One type of display device that is attracting attention is a liquid crystal projection display device.

A liquid crystal projection display device uses a light source and a liquid crystal panel as a light bulb.Compared to conventional projection display devices using CRTs, it is smaller, lighter, and has superior color reproducibility.
It is extremely promising in that raster geometric distortions related to T and high pressure stability do not occur in principle.

The above-mentioned liquid crystal projection display device will be explained below with reference to the drawings. FIG. 8 shows an example of the basic configuration of a conventional liquid crystal projection display device.

This device includes a light source 11, a condensing lens 12 that places the light source 11 at its focal point and emits parallel light, a first polarizing plate 9 erected in the traveling direction of the parallel light, and a twisted nematic liquid crystal panel 3. , second polarizing plate 10, and projection lens 1
Consists of 3.

Next, the operating principle will be explained. The parallel light from the light source 11 and the condensing lens 12 is natural light with a random vibration direction on a plane perpendicular to the direction of travel of the light, and is expressed as a vector sum of two orthogonal components (P polarized light and S polarized light) on the above plane. be able to. Therefore, when the light exiting the condenser lens 12 is expressed as P+S, the polarizing plate 9 passes only the P-polarized light (or S-polarized light) and enters the liquid crystal panel 3. Here, the alignment direction of the liquid crystal is the incident light (
P or S polarization). A twisted nematic liquid crystal with optical rotation of 90 degrees rotates incident light by 90 degrees when no voltage is applied, and becomes non-rotatable when a voltage is applied.

Therefore, by varying the voltage applied to the liquid crystal, the polarization direction of the light emitted from the liquid crystal can be varied. Since the polarizing plate 10 passes only the component of the polarized light exiting the liquid crystal panel 3 that matches the polarization direction of the polarizing plate 10, the amount of light passing through can be controlled by varying the voltage applied to the liquid crystal panel 3. can. Note that there are two directions for the polarizing plate 10. When the polarizing plate 10 is placed in the same direction as the polarizing plate 8, no voltage is applied to the liquid crystal, especially light is blocked, and when the polarizing plate 10 is placed in the orthogonal direction, light passes through under the same conditions, which are called normally black and normally white, respectively. . Based on the above operating principle, images are displayed using the liquid crystal as a light shutter for each pixel. The projection lens 13 magnifies and forms an image on the screen.

Figure 8 shows the basic configuration of an optical system that displays black-and-white images, but in the case of color images, a dichroic mirror is used to separate the parallel light from the light source into the three primary colors of red, green, and blue. The light is passed through the liquid crystal panel and the polarizing plate's shutter, and the colors are synthesized again using a dichroic mirror. The concept of the optical shutter is exactly the same as that shown in FIG. 8, so details will be omitted.

Next, FIG. 9 shows an example of a pixel arrangement of a liquid crystal panel. In the figure, A, B, . . . , F indicate each pixel, and the pixels are arranged in a grid pattern in the row and column directions. In addition, there is a part BLA between each pixel that does not allow light to pass through.
Provide CK. FIG. 10 shows an example of a drive circuit for a liquid crystal panel. Transistor switches a, b, . . . Column direction drive is analog sample holder 1 for 2 rows.
5.16 is used. Analog sample holder 15.16
alternately samples and holds the video signal for each row, and while one supplies the held video signal to the liquid crystal, the other samples the video signal for the next row. The output line of the analog sample holder 15,16 is connected to the sources of all transistor switches in the same column and is called the source line. In the row direction, gate lines connected to the gates of all transistor switches in the same row are provided in each row and sequentially driven by a shift register 14. The shift register 14 operates with a gate clock G, and the gate clock G uses, for example, a horizontal synchronization signal depending on the scanning line of a broadcast signal.

As described above, the optical shank operation of the liquid crystal is controlled by the video signal for each pixel selected by the gate line and the source line.

FIG. 11 shows an example of the sampling clock CK and gate clock G of the video signal. The video signal is sampled at the rising edge of the sampling clock CK and stored as a discrete signal in analog sample holders 15 and 16. Further, the gate clock G uses a horizontal synchronization signal.

Problems to be Solved by the Invention However, in the conventional liquid crystal display device shown in FIG. The light utilization rate will be halved. To simply increase the brightness, the total luminous flux of the light source may be increased, but this increases the power consumption and heat generation due to power loss, which prevents the display device from becoming more compact.

On the other hand, in terms of image quality, currently mass-produced liquid crystal panels clearly lack the number of images compared to CRTs, and the roughness of the image display is noticeable when enlarged and projected.

Therefore, the challenge is to devise a method to improve the light utilization rate and achieve a bright display with low power consumption, and a method to improve the display definition on liquid crystal panels with insufficient number of pixels for mass production.

Means for Solving the Problems In order to solve the above problems, the liquid crystal display device of the present invention is configured as follows.

(1) A first beam splitter that splits natural light from a light source into two orthogonal components (P-polarized light and S-polarized light) perpendicular to the direction of travel of the light, and a first twisted nematic liquid crystal panel that receives the P-polarized light ( (the alignment direction matches the P polarized light) and the S
a second twisted nematic liquid crystal panel (the orientation direction of which is aligned with the S-polarized light) into which the polarized light is incident; a second beam splitter that combines the polarized light passing through the first and second liquid crystal panels; This is a liquid crystal display device consisting of a reflecting mirror inserted in a path from one beam splitter to a second beam splitter.

(2) A first beam splitter that splits natural light from a light source into two orthogonal components (P-polarized light and S-polarized light) perpendicular to the traveling direction of the light, and a first twisted beam splitter that receives the P (or S) polarized light. Nematic liquid crystal panel (orientation direction is P or S)
a first half-wave plate that rotates the S (or P) polarized light by 90 degrees to make it P (or S) polarized light; and the P (or S) polarized light that exits the first half-wave plate. a second twisted nematic liquid crystal panel (the orientation direction of which coincides with the P or S polarized light), and a second half-wave plate that rotates the polarized light passing through the second twisted nematic liquid crystal panel by 90 degrees. and a second beam splitter that combines the polarized light passing through the first twisted nematic liquid crystal panel, the second twisted nematic liquid crystal panel, and the polarized light passing through the first and second half-wave plates; This is a liquid crystal display device consisting of a reflecting mirror inserted in a path from a first beam splitter to a second beam splitter.

(3) In the first or second invention, the pixel openings of the first liquid crystal panel and the pixel openings of the second liquid crystal panel are arranged horizontally shifted by one half of the horizontal pixel interval,
and the phase of the video signal sampling clock for displaying the pixels of one liquid crystal panel is shifted by a half wavelength with respect to the video signal sampling clock of the other liquid crystal panel in accordance with the positional deviation of the pixel ports. shall be.

(4) In the first or second invention, the pixel openings of the first liquid crystal panel and the pixel openings of the second liquid crystal panel are arranged vertically shifted by one-half of the vertical pixel interval, and the liquid crystal panel In accordance with the interlace scanning of the television broadcast signal, the gate clock that performs vertical scanning is applied to one LCD panel only in odd-numbered fields and disabled in even-numbered fields, and the other LCD panel is applied only in even-numbered fields. It is characterized in that it is in an applied state and in an odd-numbered field, it is in a prohibited state.

(5) In the first or second invention, the pixel apertures of the first liquid crystal panel and the pixel apertures of the second liquid crystal panel are arranged vertically shifted by one half of the vertical pixel interval, and the liquid crystal panel Regarding vertical scanning of the panel, the same gate clock is applied to the first and second liquid crystal panels and is applied to both odd and even fields of the television broadcast signal.

(6) In the first or second invention, the pixel openings of the first panel and the pixel openings of the second liquid crystal panel are shifted by half the horizontal pixel interval in the horizontal direction, and the vertical pixel interval is shifted in the vertical direction. The phase of the video signal sampling clock that displays the pixels of one liquid crystal panel is shifted by half the interval, and the phase of the video signal sampling clock that displays the pixels of one liquid crystal panel is adjusted relative to the video signal sampling clock of the other liquid crystal panel according to the horizontal positional shift of the pixel aperture. The gate clock that scans the liquid crystal panel in the vertical direction is applied to one liquid crystal panel only in odd-numbered fields and disabled in even-numbered fields in accordance with the interlaced scanning of the television broadcast signal. The other liquid crystal panel is characterized in that it is applied only in even fields and prohibited in odd fields.

(7) In the first or second invention, the pixel entrance part of the first liquid crystal panel and the pixel opening part of the second liquid crystal panel are shifted by half the horizontal pixel interval in the horizontal direction, and vertically in the vertical direction. The pixels are arranged with a half pixel interval shifted, and the phase of the video signal sampling clock that displays the pixels of one liquid crystal panel is changed to the video signal sampling clock of the other liquid crystal panel according to the horizontal positional shift of the pixel aperture. For vertical scanning of the liquid crystal panel, the same gate clock is applied to the first and second liquid crystal panels and applied to both odd and even fields of the television broadcast signal. It is characterized by being in a state of

With this configuration, it is possible to double the light utilization rate and realize a bright display with low power consumption, and furthermore, it is possible to double the definition of image display by using a liquid crystal panel with a small number of pixels, which is intended for mass production.

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

FIG. 1 shows a first embodiment of a liquid crystal display device of the present invention.

Natural light from a light source is divided into two orthogonal components (
The first beam splitter 1 separates the light into P-polarized light and S-polarized light.
, the first twisted nematic liquid crystal panel 3 into which the P-polarized light is incident (the alignment direction matches the P-polarized light), and the S-polarized light.
A second twisted nematic liquid crystal panel 4 into which polarized light is incident (the alignment direction matches the S-polarized light) and a first beam splitter 2 which combines the polarized light passing through the first and second liquid crystal panels 3.4. and a reflecting mirror 5.6 inserted in the path from the first beam brick 1 to the second beam splitter 2.

Natural light P+S from the light source is separated into P-polarized light and S-polarized light by beam splitter 1, each passes through liquid crystal panels 3 and 4, and then combined again as P+S by beam splitter 2, so only one of P-polarized light or S-polarized light is used. The light utilization rate is doubled compared to the conventional example shown in FIG.

FIG. 2 shows a second embodiment of the liquid crystal display device of the present invention.

Comparing with Figure 1, the S-polarized light exiting the first beam block 1 is turned into P-polarized light with a 90-degree plane rotation using a half-wave plate 7.8, and then enters the liquid crystal panel 4 (the orientation direction matches the P-polarized light). However, the difference is that the polarized light exiting the liquid crystal panel 4 is again incident on the second beam splitter with a 90-degree plane rotation. With such a configuration, the alignment direction of the liquid crystal panels 3.4 can be aligned in the P direction. Here, the half-wave plate 7.8 may be inserted on both sides of the liquid crystal panel 3, and in this case, the P-polarized light is
By polarizing the light, the alignment direction of the liquid crystal panels 3.4 can be aligned in the S direction.

In FIGS. 1 and 2, the angle of optical rotation of the liquid crystal panel 3.4 is at most 90 degrees (or an odd multiple of 90 degrees).

Further, in the figure, the light emitted from the beam splitter 2 shown by a solid line is the light emitted when a voltage is applied to the liquid crystal panel 3.4, and the broken line is the light emitted when no voltage is applied. Therefore, when configuring the system as normally black, the output light shown in the solid line is used, and when the system is configured as normally white, the output light shown in the broken line is used.

FIG. 3 shows an embodiment of the liquid crystal display device of the present invention shown in FIG. FIG. 3 shows the pixel apertures of the first liquid crystal panel 30 (solid lines AB...) and the pixel apertures of the second liquid crystal panel 4 (dashed lines A', B', etc.) in the first and second embodiments described above.・・）
This is a liquid crystal display device characterized in that the pixels are arranged shifted by half the horizontal pixel interval H in the horizontal direction.

In this case, as shown in FIG. 6, the phase of the video signal sampling clock GK2 used for pixel display on the liquid crystal panel 4 is changed by 2 minutes with respect to the video signal sampling clock CK1 on the liquid crystal panel 3, depending on the positional shift of the pixel aperture. With a configuration of 9 or more, the number of pixels in the horizontal direction is 2.
It will be doubled.

FIG. 4 shows a fourth embodiment of the liquid crystal display device of the present invention.
FIG. 4 shows the pixel apertures (solid lines A, B...) of the first liquid crystal panel 3 and the pixel apertures b (dashed lines A') of the second liquid crystal panel 4 in the first and second embodiments described above. , B', . . . ) are arranged vertically shifted by half the vertical pixel interval.

In this case, when scanning the liquid crystal panel in the vertical direction, as shown in FIG. The gate clock C2 is applied only in even fields and disabled in odd fields. With the above configuration, in the vertical direction, it is possible to display the entire number of lines by interlace scanning on a liquid crystal panel that has half the number of display lines as the scanning lines of a television broadcast signal.

FIG. 7b shows the vertical scanning method in the fifth embodiment of the liquid crystal display device of the present invention.
It is equivalent to the figure. In this case, in order to scan the liquid crystal panel in the vertical direction, the first liquid crystal panel 3 and the second liquid crystal panel 4 are driven by the same gate clock G. The gate clock G is applied to both odd and even fields of the television broadcast signal. With the above configuration, in the vertical direction, it is possible to perform simple two-sided scanning in which the entire number of lines is displayed in one field period on a liquid crystal panel that has half the number of display lines as the scanning lines of a television broadcast signal. .

FIG. 5 shows a sixth embodiment of the liquid crystal display device of the present invention.

FIG. 5 shows the pixel apertures (solid lines A, B, . . . ) of the first liquid crystal panel 3 and the image apertures (broken lines A', . . . ) of the second liquid crystal panel 4 in the first and second embodiments described above. B'...)
This is a liquid crystal display device characterized in that the pixels are arranged so as to be shifted by half the horizontal pixel interval in the horizontal direction and by half the vertical pixel interval in the vertical direction.

In this case, as shown in FIG. 6, the phase of the video signal sampling clock CK2 used for the pixel cover of the liquid crystal panel 4 is adjusted according to the horizontal positional shift of the pixel opening.
It is assumed that the video signal sampling clock CKI is delayed by a half wavelength with respect to the video signal sampling clock CKI. When scanning in the vertical direction, as shown in FIG. 7a, the gate clock G1 of the liquid crystal panel 3 is applied only in odd fields and disabled in even fields, and the gate clock G2 of the liquid crystal panel 4 is applied only in even fields. It is applied only in fields and disabled in odd fields. With the above configuration, a delta arrangement of pixels is possible on a liquid crystal panel having one-half the number of display lines of the scanning lines of a television broadcast signal, and the definition is improved in both the horizontal and vertical directions. Further, in this case, the vertical scanning is interlaced scanning.

The seventh embodiment uses the gate clock G shown in FIG. 7 in the pixel arrangement shown in FIG. In this case, the first liquid crystal panel 3 and the second liquid crystal panel 4 are driven by the same gate clock G to perform vertical scanning of the liquid crystal panel. The gate clock G is applied to both odd and even fields of the television broadcast signal.

With the above configuration, a delta arrangement of pixels is possible on a liquid crystal panel having one-half the number of display lines of the scanning lines of a television broadcast signal, and the definition is improved in both the horizontal and vertical directions. In this case, the vertical scanning is a simple two-sided scanning that displays all lines in one field period.

Effects of the Invention As described above, by using the liquid crystal display device of the present invention, it is possible to improve the light utilization efficiency and realize a bright display with low power consumption, and it is possible to improve the efficiency of using the liquid crystal display device of the present invention. It becomes possible to improve the definition of display.

[Brief explanation of the drawing]

FIG. 1 is a basic configuration diagram of a first embodiment of a liquid crystal display device of the present invention, FIG. 2 is a basic configuration diagram of a second embodiment, FIG. 3 is a pixel arrangement diagram of a third embodiment, and FIG. Figure 4 is a pixel arrangement diagram in the fourth and fifth implementations;
9 is a diagram showing an example of the pixel arrangement of a conventional liquid crystal panel; FIG. 10 is a basic configuration diagram of a liquid crystal drive circuit; The figure is 1
．． 2...beam splitter, 3 string nematic liquid crystal panel, 5 color, 7.8...half wave plate.

Claims (7)

[Claims] (1) A first beam splitter that separates natural light from a light source into two orthogonal components (P-polarized light and S-polarized light) perpendicular to the traveling direction of the light, and the P-polarized light is incident thereon, and the orientation direction matches that of the P-polarized light. a first twisted nematic liquid crystal panel, a second twisted nematic liquid crystal panel into which the S-polarized light is incident and whose alignment direction coincides with the S-polarized light;
A liquid crystal display device comprising: a second beam splitter that combines polarized light passing through a second liquid crystal panel; and a reflecting mirror inserted in a path from the first beam splitter to the second beam splitter. (2) A first beam splitter that splits natural light from a light source into two orthogonal components (P polarized light and S polarized light) perpendicular to the direction of travel of the light;
a first twisted nematic liquid crystal panel that matches polarized light or S-polarized light; a first half-wavelength that rotates the S- or P-polarized light by 90 degrees to become P- or S-polarized light; and a first half-wavelength plate that outputs the first half-wavelength plate; a second twisted nematic liquid crystal panel into which P or S polarized light is incident and whose alignment direction matches that of the P or S polarized light; and a second twisted nematic liquid crystal panel which rotates the polarized light passing through the second twisted nematic liquid crystal panel by 90 degrees again. a half-wave plate, and a second beam splitter that combines the polarized light passing through the first twisted nematic liquid crystal panel, the second twisted nematic liquid crystal panel, and the polarized light passing through the first and second half-wave plates. and a reflecting mirror inserted in a path from the first beam splitter to the second beam splitter. (3) An image in which the pixel openings of the first liquid crystal panel and the pixel openings of the second liquid crystal panel are shifted horizontally by half the horizontal pixel interval, and the pixels of one liquid crystal panel are displayed. 3. The liquid crystal panel according to claim 1, wherein the phase of the signal sampling clock is shifted by a half wavelength with respect to the video signal sampling clock of the other liquid crystal panel in accordance with the positional shift of the pixel aperture. LCD display device. (4) A gate in which the pixel apertures of the first liquid crystal panel and the pixel apertures of the second liquid crystal panel are vertically shifted by half the vertical pixel interval, and which scans the liquid crystal panel in the vertical direction. In accordance with the interlaced scanning of the television broadcast signal, the clock is applied to one liquid crystal panel only in odd fields and disabled in even fields.
3. The liquid crystal display device according to claim 1, wherein the other liquid crystal panel is applied only in even fields and prohibited in odd fields. (5) The pixel apertures of the first liquid crystal panel and the pixel apertures of the second liquid crystal panel are vertically shifted by half the vertical pixel interval, and the vertical scanning of the liquid crystal panel is the same. 3. The liquid crystal display device according to claim 1, wherein the gate clock is applied to the first and second liquid crystal panels and applied to both odd and even fields of the television broadcast signal. . (6) The pixel apertures of the first liquid crystal panel and the pixel apertures of the second liquid crystal panel are shifted by half the horizontal pixel pitch in the horizontal direction and by half the vertical pixel pitch in the vertical direction. and shift the phase of a video signal sampling clock for displaying the pixels of one liquid crystal panel by a half wavelength with respect to the video signal sampling clock of the other liquid crystal panel in accordance with the horizontal positional shift of the pixel aperture, In addition, the gate clock that scans the liquid crystal panel in the vertical direction is applied only in odd fields to one liquid crystal panel and disabled in even fields, and is disabled in even fields to the other liquid crystal panel, depending on the interlaced scanning of the television broadcast signal. 3. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is applied only in the field and is prohibited in the odd field. (7) The pixel openings of the first liquid crystal panel and the pixel openings of the second liquid crystal panel are shifted by half the horizontal pixel interval in the horizontal direction and by half the vertical pixel interval in the vertical direction. and shift the phase of a video signal sampling clock for displaying the pixels of one liquid crystal panel by a half wavelength with respect to the video signal sampling clock of the other liquid crystal panel in accordance with the horizontal positional shift of the pixel aperture, Further, regarding the vertical scanning of the liquid crystal panels, the same gate clock is applied to the first and second liquid crystal panels, and is applied to both odd and even fields of the television broadcast signal. A liquid crystal display device according to claim 1 or claim 2.