JPH0371186A - Liquid crystal projector - Google Patents

Abstract

PURPOSE:To remove misconvergence by shifting the vertical scanning starting timing of a liquid crystal panel for executing reverse display from a liquid crystal panel for executing normal display only by one line in a liquid crystal projector using three liquid crystal panels formed by triangle array. CONSTITUTION:In a liquid crystal projector for supplying R, G and B video signals respectively to three liquid crystal panels 1 to 3 in which respective picture elements are arranged so as to be shifted by 1/2 picture element in odd and even lines, combining transmitted light beams and projecting the combined light, at least one of the three panels 1 to 3 is allowed to execute reverse display and the other panels are allowed to execute normal display. In the case of scanning the 1st line X1 of the reverse display panel, no video signal is applied, and in the case of scanning the 2nd line X2 of the reverse display panel and the 1st line X1 of the normal display panel, a video signal corresponding to the 1st scanning line is applied. Thereby, the shift pulse X1 to Xn of the normal display panel are delayed from the shift pulses X1 to Xn of the reverse display panel respectively by one clock.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a liquid crystal projector using a liquid crystal display panel.

(B) Prior Art Conventionally, a liquid crystal projector using a liquid crystal display panel is disclosed in Japanese Patent Laid-Open No. 150487/1987.

FIG. 5 shows the configuration of the above-mentioned liquid crystal projector. In the figure, (1) is a projection light source, (2) (3) (4) (5
) are the first to fourth dichroic mirrors (6), (7) are the first and second reflecting mirrors, and (8), (9), and (10) are Actenobumatonox type mirrors for blue, green, and red, respectively. First to third liquid crystal units including a liquid crystal display panel, (11) a projection lens, (12) a screen, and a light source (1).
The light is separated by the first dichroic mirror (2) and the second dichroic mirror (3), and the blue color is reflected by the first reflecting mirror (6) and then transmitted to the first to third liquid crystal units (8). (9) and (10) are respectively modulated by the image information, and then synthesized again by the reflection mirror (7) and the third and fourth dichroic mirrors (4) and (5), and then the projection lens (]1 ) The image is projected onto the screen (12).

? In the optical system described above, the image displayed on the liquid crystal panel (10) needs to be inverted with respect to the image displayed on the liquid crystal panels (8) and (9). Possible methods to achieve this inverted display include simply mounting the liquid crystal panel upside down and reversing the drive direction of the horizontal scanning circuit, but the former method has problems with the preferred viewing angle peculiar to the liquid crystal panel and In the case of a matrix panel, problems with light intensity occur, which is not practical.

On the other hand, the pixel arrangement of a liquid crystal panel is a stripe arrangement in which pixels are simply arranged in the XY direction (Figure 6), and a stripe arrangement in which pixels are simply arranged in
There is a triangular array (FIG. 7) in which each scanning line is shifted by 1/2 pixel. When considering the convergence (alignment of each pixel) between the normal display and the inverted display of two LCD projectors, the stripe arrangement is shown in Figure 8 (
If the inverted display shown in Figure (B) is projected onto the normal display shown in (B), there is no problem since the two will match perfectly.

On the other hand, in a triangular array, if the inverted display in Figure 9 (B) is projected against the normal display in Figure 9 (A), the result will be as shown in Figure 9 (C), where the pixels in the odd rows match, but the pixels in the even rows match. The problem arises that the pixels in the rows do not match.

However, in terms of image quality, the triangular array is superior, so in order to realize a high-image-quality liquid crystal projector, it is desirable to use a triangle array liquid crystal panel.

(c) Problems to be Solved by the Invention The present invention has been made in view of the above-mentioned points, and an object thereof is to obtain good convergence in a liquid crystal projector using three liquid crystal panels arranged in a triangular arrangement.

(d) Means for Solving the Problems The present invention provides R, G,
A liquid crystal projector that supplies a video signal, combines the transmitted light, and projects the image, in which at least one of the three liquid crystal panels performs inverted display and the other liquid crystal panels perform normal display. means for reversing the shift direction of the horizontal scanning circuit of the liquid crystal panel that performs the inverted display; and means for shifting the start timing of vertical scanning by one line between the liquid crystal panel that performs the inverted display and the liquid crystal panel that performs the normal display. Equipped with.

(e) Effect By using the above-mentioned means, the present invention operates so that the positions of each pixel on both panels are aligned by shifting the vertical scanning start timing of the liquid crystal panel that performs inverted display by one line from the liquid crystal panel that performs normal display. do.

(f) Example An embodiment of the present invention will be described below with reference to the drawings.

First, the principle of the present invention will be explained with reference to FIGS. 1 and 2. FIG. 1(A) shows the display state of the normal display panel, and FIG. 1(B) shows the display state of the inverted display panel. Here, the normal display panel displays in the same manner as before, but the inverted display panel sets the first scanning line (the scanning line that first displays an image) to the second line (X,). Furthermore, when installing the image display panel, the position is relatively shifted by one line.

If you project the inverted display in Figure 1 (B), you will see Figure 1 (
The line 1 (Xl) in the same figure (A) and the same figure (
2 lines (X, ) in (c) and 2 lines (X, ) in (a)
, ) and each pixel of the three lines (X, ) in the same figure (c) match. Therefore, no video signal is applied to each pixel in the first line (Xl) of the inversion display panel and the last line of the normal display panel.

Next, the driving circuit for the liquid crystal panel in this embodiment will be explained with reference to FIG. In the figure, (1), (2), and (3”) are active matrix liquid crystal panels in which G, R, and R pixels are arranged in a triangle, respectively, (4), (5, and 6).
) are respectively composed of a shift register and a sample and hold circuit, horizontal scanning circuits (7), (8), and (9) are respectively composed of a shift register, and a vertical scanning circuit (10) is composed of a shift register to demodulate color signals and convert them into R, G, and H. Color demodulation circuit that outputs primary color signals, (
11), (12), and (1, 3) are G signal, B signal, and R signal processing circuits, respectively, and their outputs are supplied to the sample hold of the horizontal scanning circuit corresponding to each color.

In addition, (14) is a synchronization control circuit, and the horizontal synchronization signal (
Hl) and the vertical synchronization signal (V, ).
A start pulse (STY) (STi) and first and second tally pulses (CP,) (CP,) are created. The first start pulse (sT+) and the first clock pulse (CPU) are sent to the horizontal scanning circuit, and the second start pulse (ST, ) and the second clock pulse (CP,
) is supplied to the vertical scanning circuit. (15) is a delay circuit that delays the second start pulse (ST,) by l clocks, and the delayed second start pulse (ST,') is supplied to the G and B vertical scanning circuits (7) ( 8
)−\supplied.

Next, the operation will be explained with reference to the time chart shown in FIG. Each horizontal scanning circuit (4), (5), and (6) has a start pulse (STI) synchronized with the horizontal synchronization signal (HP).
A tarokku pulse (CPU) with a frequency proportional to the number of pixels in one line is supplied, and RlG and B primary color signals are sampled and held to each liquid crystal panel (1) (2).
(3) Drive the column electrodes.

On the other hand, the second start pulse (ST) synchronized with the vertical synchronizing signal (V, ) is supplied to the vertical scanning circuit (9) for R, and the horizontal synchronizing signal (Hl) is supplied to the vertical scanning circuit (9) for R.
The second start pulse (ST,') is delayed by one clock of the second clock pulse (crt) synchronized with the second clock pulse (crt), and is supplied to the G and B vertical scanning circuits (7) and (8).

When scanning one line (Xl) of the inverted display panel, no video signal is applied, and when scanning two lines (X,) and one line (Xl) of the normal display panel, the first
A video signal corresponding to a scanning line is applied.

Therefore, the shift pulses (X+, Xl・
), the normal display panel shift pulse (Xl,
Xl...) will be delayed by one clock. As a result, no video signal is applied when scanning the 1st line [] on the inverted display panel, and the video signal corresponding to the 2nd/jth line, in particular the 1st scanning line when scanning the 1st line on the normal display panel, is applied. applied.

Next, FIG. 4 shows another embodiment of the drive circuit. In the figure, a signal switching circuit (16) is provided for switching the shift direction of the shift register of the horizontal scanning circuit (4) between normal display and inverted display, and a forward/reverse switching signal is used to switch the shift direction of the shift register of the horizontal scanning circuit (4). ) to switch the output states of a plurality of control lines.

Therefore, there is no need to prepare two types of boards for the horizontal scanning circuit as in the past, and the signal switching circuit (
16), each horizontal scanning circuit is driven in the desired shift direction.

The signal switching circuit (16) is the inverter gate I
This can be realized by using C and 3-state buffer ICs.

(G) Effects of the Invention As described above, according to the present invention, it is possible to eliminate misconvergence in a liquid crystal projector using three liquid crystal panels in which pixels are arranged in a triangular arrangement.

Also, since each panel has the same front and back sides relative to the light source,
It is possible to unify the preferred viewing angle.

[Brief explanation of drawings]

Figures 1 (A), (B), and (C) are diagrams showing the principle of the present invention, Figure 2 is a block diagram of one embodiment, Figure 3 is a time chart, and Figure 4 is another embodiment of the drive circuit. FIG. Fig. 5 shows a conventional optical system, Fig. 6 shows a liquid crystal panel with a stripe arrangement, Fig. 7 shows a liquid crystal panel with a triangular arrangement, and Fig. 8 (A) and (B) show a stripe arrangement. FIGS. 9A, 9B, and 9C are diagrams illustrating convergence of a liquid crystal panel arranged in a triangular arrangement. (1)(2)(3)...LCD panel, (4)(5)(
6)...Horizontal scanning circuit, (7)(8)(9)...Vertical scanning circuit, (14)...Synchronization control circuit, (15)...
...Delay circuit.

Claims (1)

[Claims] (1) R, G, and B video signals are supplied to three liquid crystal panels in which each pixel is arranged with a 1/2 pixel offset between odd and even rows, and the transmitted light is combined. In a liquid crystal projector that projects images, in which at least one of the three liquid crystal panels performs inverted display and the other liquid crystal panels perform normal display, horizontal scanning of the liquid crystal panel that performs the inverted display; A liquid crystal projector comprising means for reversing the shift direction of the circuit, and means for shifting the start timing of vertical scanning by one line between the liquid crystal panel that performs the inverted display and the liquid crystal panel that performs the normal display.