JP3309422B2 - LCD interlace display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an interlace display of a video signal using a liquid crystal panel.

[0002]

2. Description of the Related Art In recent years, small televisions, laptop OA
The commercialization of devices such as devices using a liquid crystal panel as a display device is remarkable. One of the things that attracts attention among such movements is a liquid crystal video projector. Liquid crystal video projectors can be smaller and lighter than conventional CRT type projectors, have little geometric distortion in terms of display performance, are essentially free from the effects of geomagnetism, and have uniform convergence accuracy over the entire display. It has the advantage that it can be secured. On the other hand, a liquid crystal video projector enlarges and projects an image on a screen, so that the pixel roughness is conspicuous. Therefore, a liquid crystal panel having a larger number of pixels is required as compared with a direct-view type liquid crystal display device. Therefore, a small liquid crystal panel is required from the viewpoint of realization. Hereinafter, a basic configuration of a conventional liquid crystal video projector and driving of a liquid crystal panel will be described.

FIG. 7 shows a conventional example of the basic structure of a liquid crystal video projector. In FIG. 7, reference numeral 1 denotes a light source. 2 is an image display liquid crystal panel, 3 is a polarizer, 4
Is an analyzer, and 5 is a projection lens.

The operation of the liquid crystal video projector constructed as described above will be described below. With the configuration of FIG. 7, the white natural light of the light source 1 passes through the polarizer 3 and becomes linearly polarized light. Here, since natural light is considered as a combined light of two orthogonal vector components (called a P component and an S component), it is assumed that the polarization direction of the polarizer 3 matches the P component and only the P component passes. The image display liquid crystal panel 2 rotates the polarization of the incident P component for each pixel in accordance with the image signal, and controls the polarization direction. The transmittance of the analyzer 4 becomes maximum when the polarization direction of the polarized light passing through the image display liquid crystal panel and the polarization direction of the analyzer 4 coincide with each other, and becomes minimum when the polarization direction is orthogonal, so that the gradation is controlled by the polarization direction control according to the video signal. Can be displayed. The above image is enlarged and projected on the screen by the projection lens 5. FIG. 8 shows an example of the projection image. The number of horizontal display lines of the image display liquid crystal panel 2 is 240
This shows a case where there is only about half of the number of horizontal scanning lines of one frame, that is, an image of an odd field and an image of an even field are overwritten on the same horizontal display line. For color display, a video display liquid crystal panel having a color filter formed in pixel units is used, and three primary color lights of red, green, and blue whose wavelengths are selected by using a dichroic optical filter for white light of a light source are applied to respective optical paths. After passing through the arranged polarizer, image display liquid crystal panel, and analyzer, there is a method of synthesizing again using a dichroic optical filter to form a full color image, but details are omitted because they are not directly related to the principle of the present invention. I do.

FIG. 9 shows a conventional driving circuit for a liquid crystal panel.
0 indicates a timing chart. In FIG. 9, reference numeral 6 denotes a synchronization separation circuit for separating a synchronization signal from a composite video signal, 7 denotes a synchronization control circuit for generating various timing pulses and clocks input to the liquid crystal panel according to the horizontal synchronization signal H and the vertical synchronization signal V, and 8 denotes a software. And 9 denotes a gate driver. In the timing chart of FIG. 10, a indicates a video signal viewed in a horizontal cycle, b indicates a horizontal start pulse SH, and c indicates a sampling clock CK. d indicates a video signal viewed in a vertical cycle, e indicates a vertical start pulse SV, and f indicates a gate clock GK. When viewed in the horizontal cycle, the source driver 8 starts sampling with the horizontal start pulse SH and samples the video signal every time the sampling clock CK rises. When viewed in the vertical cycle, the gate driver 9 starts scanning in the vertical direction with the gate start pulse SV, and sequentially displays the horizontal display lines from the first to the last at every rising of the gate clock GK. I do.

[0006]

However, the above configuration has the following problems. As described above, the liquid crystal panel used in the liquid crystal video projector has a problem that the pixel density is high because the number of pixels and the size are required to be small, and as a result, the production yield is reduced and the cost is increased. .

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems. When displaying an interlaced video signal divided into two fields, a video display having the number of horizontal display lines for one field is provided. Using a liquid crystal panel, an optical rotation control liquid crystal panel, and a birefringent optical plate, the display position in the vertical direction of the image is shifted by one half of the horizontal display line interval for each field to perform an interlaced display, thereby reducing the number of pixels. It is an object of the present invention to enable high-resolution display and downsizing of a liquid crystal panel with a small and inexpensive liquid crystal panel.

[0008]

In order to achieve this object, a liquid crystal interface display of the present invention has the following arrangement.

[0009] and the image display liquid crystal panel for opening and closing to the video display for each pixel the light from a light source, an analyzer disposed between the polarizer on the exit side disposed on the incident side of the light to the image display liquid crystal panel, horizontal One pixel per line, analyzer
Of the linearly polarized light passing through the analyzer arranged on the exit side of
The direction is changed for each horizontal line by the horizontal sync pulse of the video signal.
Next, horizontal independent rotation control LCD panel that controls rotation
And a birefringent optical element disposed on the emission side of the horizontally independent optical rotation control liquid crystal panel and having a refractive index that varies depending on the polarization direction.

[0010]

[0011]

[0012]

[0013]

With this configuration, when displaying an interlaced video signal divided into two fields, the vertical display position of the video is set to two horizontal display line intervals for each field.
By moving the display by one-half and performing interlaced display, high-resolution display and downsizing of the liquid crystal panel can be realized with an inexpensive liquid crystal panel having a small number of pixels.

[0014]

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

FIG. 1 shows the basic optical system of the first embodiment of the present invention, FIG. 2 shows a structural diagram of the optical rotation control liquid crystal panel 6, FIG. 3 shows a drive circuit block diagram, and FIG. In FIG. 1, reference numeral 18 denotes an optical rotation control liquid crystal panel, and 19 denotes a birefringent optical element. In FIG. 2, 20 is a liquid crystal, 21 is a glass substrate, and 10 and 11 are transparent electrodes. In FIG. 3, reference numeral 12 denotes a first video signal field memory, 13 denotes a second video signal field memory, 14 denotes a scan conversion control circuit, 15 denotes a blanking circuit, 16 denotes an AD converter, and 17 denotes a DA converter. is there.

Next, the basic operation of the first embodiment will be described. As shown in FIG. 2, the optical rotation control liquid crystal panel 18 has a structure in which both surfaces of a liquid crystal 20 are sandwiched between transparent electrodes 10 and 11, respectively. Therefore, the transparent electrode 10 is driven in the field cycle by the optical rotation control liquid crystal panel drive signal DD shown in FIG.
When the voltage between 11 is turned on and off, the liquid crystal 20 repeats non-rotation and 90-degree rotation of incident light. Here, the voltage polarity at the time of ON is alternately inverted between positive and negative, and AC driving is performed. As described above, the P component exiting the analyzer 4 (the polarization direction of the analyzer 4 is assumed to coincide with the P component) is converted into a P component (non-rotation) and an S component (90-degree rotation) in the field cycle. Rotates. If the birefringent optical element 19 sets the direction of the optical axis of the crystal using an anisotropic crystal such as quartz or calcite, the P component and the S component can be used as shown in FIG.
The light of the S component can be separated in the vertical direction. In addition,
The separation interval is set by the thickness of the birefringent optical element 19.
As described above, according to the interlaced scanning of the video signal,
Interlaced display is possible by moving the image of the even field relative to the odd field vertically by half the horizontal display line interval. FIG. 5 shows a display example on the screen.

Next, a method of driving the image display liquid crystal panel 2 will be described. As shown in the timing diagrams of FIGS. 4a to 4f, the horizontal scanning frequency is 15.75 KHz, and the vertical scanning frequency is 6.
A video signal having a horizontal scanning frequency of 31.5 KHz and a vertical scanning frequency of 120 Hz obtained by double-speed conversion of a video signal of 0 Hz is input to the video display liquid crystal panel 2, and horizontal and vertical scanning are performed twice in one field period. However, the video signal is erased during the second vertical scanning as shown in FIG.
Note that the odd-numbered and even-numbered horizontal scanning lines are overwritten on 240 horizontal display lines as in the conventional case. As described above, the image display liquid crystal panel 2 displays an image of one field, and once erases, displays the next field, and the rotation control liquid crystal panel 18 scrolls at each field change. By moving the vertical display position on the screen, accurate interface display is possible. Incidentally, when the image display liquid crystal panel 2 is driven by the conventional method, for example, the image of the 240th horizontal display line written in the first field is immediately after the writing and the second field is displayed.
Since the written content is held in the liquid crystal until it is written again in the field, the image of the first field is erroneously displayed as the image of the second field at a position shifted from the vertical position for most of the time. Become. For this reason, the double speed drive of the present invention is required. In the drive circuit block diagram of FIG. 3, the first video signal field memory 12 and the second video signal field memory 13 alternately write and read video signals in odd and even fields. . The read clock RCK is twice as fast as the write clock WCK, and is read twice in one field period. The blanking circuit 15 is used for two fields in one field period.
The video signal is erased for the second reading. As a result, a double-speed video signal shown in FIG. 4D is obtained. The scan conversion control circuit 14 includes the field memory write clock WCK, read clock RCK, double-speed sampling clock 2CK required for horizontal and vertical double-speed scanning of the video display liquid crystal panel 2, double-speed horizontal start pulse 2SH, and double-speed gate.
2GK and a double speed vertical start pulse 2SV.

In the second embodiment of the present invention, potassium dihydrogen phosphate (KD) is used in place of the rotation control liquid crystal panel 18 shown in FIG.
The polarization direction is rotated by applying a voltage having a field period using an electro-optic crystal plate 16 having an electro-optic effect, such as the crystal plate P). Other configurations and operations are the same as those of the first embodiment.

In a third embodiment of the present invention, a horizontally separated optical rotation control liquid crystal panel 1 is used instead of the optical rotation control liquid crystal panel 18 of FIG.
7 is used. Horizontally separated optical rotation control liquid crystal panel 1
7 is separated by each horizontal line and driven by a gate driver 9 so that the liquid crystal can be rotated on each horizontal line as shown in FIG. That is, the image display liquid crystal panel 2 has a structure in which the horizontal pixel separation is eliminated and the source side electrode is made one. Then, the output light of one horizontal display line of the image display liquid crystal panel 2 is converted to the horizontal separation optical rotation control liquid crystal panel 17.
It is arranged close to the image display liquid crystal panel 2 so as to be incident on one horizontal line. In the third embodiment, the timing chart for driving the video display liquid crystal panel 2 is exactly the same as that of the conventional example shown in FIG. The horizontal separation optical rotation control liquid crystal panel 17 is driven on the source side using the same signal as the optical rotation control liquid crystal panel drive signal DD of the first embodiment, and is input to the image display liquid crystal panel 2 on the gate side. The same game as the one
The clock signal GK and the vertical start pulse SV are used. As described above, the vertical display position on the screen is sequentially moved line by line in accordance with the horizontal line display of the video display liquid crystal panel 2, thereby enabling an interlaced display. In the third embodiment, the vertical display position can be moved line by line as in the case of the CRT display, so that it is clear that accurate interface display is possible. Needless to say, the present invention can provide an extremely effective means even for a high-definition video display device.

[0020]

As described above, according to the present invention, the vertical display position of an image is shifted by one-half of the horizontal display line interval for each field and displayed interlacedly, whereby the number of pixels can be reduced. It is possible to achieve high-resolution display and downsizing of the liquid crystal panel with less and less expensive liquid crystal panels.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a basic optical system of a liquid crystal interlace display device according to a first embodiment of the present invention.

FIG. 2 is a structural diagram of an optical rotation control liquid crystal panel according to the first embodiment of the present invention.

FIG. 3 is a block diagram of a driving circuit according to the first embodiment of the present invention.

FIG. 4 is a drive timing chart according to the first embodiment of the present invention.

FIG. 5 is a diagram showing a display example on a screen according to the present invention.

FIG. 6 is a configuration diagram of a horizontally separated optical rotation control liquid crystal panel of a liquid crystal interlace display device according to a second embodiment of the present invention.

FIG. 7 is a configuration diagram showing a basic optical system of a conventional liquid crystal video projector.

FIG. 8 is a diagram showing a display example on a conventional screen.

FIG. 9 is a block diagram of a conventional liquid crystal panel drive circuit.

FIG. 10 is a conventional drive timing chart.

[Description of Signs] 2 Video display liquid crystal panel 3 Polarizer 4 Analyzer 12 First video signal field memory 13 Second video signal field memory 14 Scan conversion control circuit 15 Blanking circuit 16 Electro-optic crystal plate 17 Horizontally independent optical rotation Control liquid crystal panel 18 Optical rotation control liquid crystal panel 19 Birefringent optical element

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02F 1/13 505 G02F 1/133 505 G02F 1/1347

Claims (1)

(57) [Claims] 1. An image display liquid crystal panel for displaying an image by opening and closing light from a light source for each pixel, a polarizer disposed on a light incident side and an analyzer disposed on an output side with respect to the image display liquid crystal panel. And one pixel for each horizontal line,
A horizontally independent optical rotation control liquid crystal panel that controls the optical rotation of the linearly polarized light passing through the analyzer on the emission side of the analyzer sequentially for each horizontal line with a horizontal synchronization pulse of a video signal, and the horizontal independent optical rotation A liquid crystal interlaced display device comprising a birefringent optical element arranged on the emission side of a control liquid crystal panel and having a different refractive index depending on the polarization direction.