JP3054423B2 - LCD projector - Google Patents

Description

The present invention relates to a liquid crystal projector using a liquid crystal display panel.

(B) Conventional technology A conventional liquid crystal projector using a liquid crystal display panel is disclosed in JP-A-61-150487.

FIG. 6 shows the configuration of the above-mentioned liquid crystal projector. In the figure, (1) is a projection light source, (2), (3) and (4).
(5) is the first to fourth dichroic mirrors, (6)
(7) is first and second reflection mirrors, (8), (9) and (10) are first to third liquid crystal units including active matrix type liquid crystal display panels for blue, green and red, respectively.
(11) is a projection lens, (12) is a screen, light from a light source (1) is split by a first dichroic mirror (2) and a second dichroic mirror (3), and blue is a first reflection mirror (6). ), And after being modulated by the first to third liquid crystal units (8), (9), (10) according to image information, respectively, the third reflecting mirror (7) and the third and fourth dichroic mirrors ( 4) The images are combined again by (5), and an image is projected on the screen (12) via the projection lens (11).

(C) Problems to be Solved by the Invention In the above-mentioned liquid crystal projector, it is necessary to increase the number of pixels of each liquid crystal display panel in order to realize high image quality.
For example, if a 480 × 720 panel is used, NTSC full line display can be performed. However, the yield was low and the panel was expensive.

In view of the above, it is an object of the present invention to provide a liquid crystal projector capable of obtaining a high-quality image without using a liquid crystal display panel having a large number of pixels for all three liquid crystal display panels.

(D) Means for Solving the Problems The present invention provides a light source that emits light of at least three components of red, green, and blue; a light separating unit that separates light from the light source into green, red, and blue light; First and second liquid crystal display panels that are inserted in the optical paths of red and blue light and that are luminance-modulated by red and blue image information, respectively, and that are inserted in the optical path of the green light and emit light according to the green image information. A third liquid crystal display panel that is modulated and has more pixels than the first and second liquid crystal display panels, a light combining unit that combines light transmitted through the first to third liquid crystal display panels, And a projection means for projecting the light synthesized by the means on a screen.

(E) Function The present invention assumes that the liquid crystal display panel for green, which has the highest luminosity, has a large number of pixels, and the liquid crystal display panels for blue and red, which have a luminosity lower than green, each have a smaller number of pixels than for green. Thus, even if the resolution of blue and red slightly decreases, the resolution of the synthesized image does not decrease so much.

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

First, before explaining the embodiments, the principle of the present invention will be described.

The human eye has a maximum visibility range in the green wavelength range, has higher resolution for green light than red and blue light, and has higher sensitivity for light and dark.

Therefore, the applicant has confirmed through experiments that if the resolution of the green color is the same as the conventional one, the image quality does not deteriorate much even if the resolutions of the red and blue colors are reduced. The optical system in this embodiment is basically the same as that in FIG.

Next, a driving circuit of the liquid crystal panel in this embodiment will be described with reference to FIG. In the figure, (13) indicates that the number of pixels is 480 vertical x 720 horizontal
The liquid crystal display panels for G, (14) and (15) are the liquid crystal display panels for B and R with 240 × 480 pixels, respectively (16)
(17) and (18) are first to third horizontal scanning circuits each including a shift register and a sample and hold circuit, and (19) and (2)
0) and (21) represent first to third shift registers, respectively.
A vertical scanning circuit, (22) is a color demodulation circuit that demodulates color signals and outputs R, G, B primary color signals, and (23), (24), (25) are G signal, B signal, and R signal processing, respectively. The output is supplied to a horizontal scanning circuit corresponding to each color.

Reference numeral (26) denotes a synchronization control circuit, based on the horizontal synchronization signal (Hp) and the vertical synchronization signal (Vp), the first and second start pulses (ST1) and (ST2) and the first to third clock pulses (ST2). Create CP1) (CP2) (CP3).

Next, the operation will be described with reference to the time chart of FIG.

The first horizontal scanning circuit (16) has a first start pulse (ST1) synchronized with the horizontal synchronizing signal (Hp), and a first having a frequency corresponding to the number of horizontal pixels (720) of the G liquid crystal display panel (13). A clock pulse (CP1) is supplied to sample the G signal.

Both the second and third horizontal scanning circuits (17) and (18) have the first
A start pulse (ST1) and a second clock pulse (CP2) having a frequency corresponding to the number of horizontal pixels (480) of the B and R liquid crystal display panels (14, 15) are supplied.
The signal and the R signal are sampled.

The first vertical scanning circuit (19) performs an interlaced shift operation every other line based on the second start pulse (ST2) synchronized with the vertical synchronization signal (Vp) and the third clock pulse (CP3) of the horizontal cycle. That is, in the odd field, 240 odd lines of the G liquid crystal panel (13) are sequentially selected, and in the even field, 240 even lines are sequentially selected.

In addition, the second and third vertical scanning circuits (20) and (21) use the B and R liquid crystal display panels (1) based on the second start pulse (ST2) and the third clock pulse (CP3) of the horizontal cycle.
4) The 240 lines in (15) are sequentially selected by the shift operation.

The R, G, and B lights transmitted through the liquid crystal display panels driven as described above are combined, and an image is projected on a screen.

(G) Effects of the Invention As described above, according to the present invention, all the three liquid crystal display panels do not use a large number of pixels but use only a green panel having a high visibility with a large number of pixels. Thereby, a high-quality image can be obtained at a low price.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a driving circuit of a liquid crystal projector according to an embodiment of the present invention, FIG. 2 is a time chart thereof, and FIG. 3 is a diagram showing an optical system of the liquid crystal projector. (13) (14) (15) ... G, B and R liquid crystal display panels, (16) (17) (18) ... First, second and third horizontal scanning circuits, (19) ( 20) (21): first, second and third vertical scanning circuits, (26): synchronization control circuit,

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04N 9/31 G02F 1/13 505 G03B 21/00 G03B 33/12 G09F 9/35 G09G 3/36

Claims (2)

(57) [Claims] 1. A light source that emits at least three component lights of red, green, and blue; light separating means for separating light from the light source into green, red, and blue light; First and second liquid crystal display panels inserted and respectively modulated in luminance by red and blue image information; and inserted in an optical path of the green light and luminance-modulated by green image information; (2) a third liquid crystal display panel having more pixels than the number of pixels of the liquid crystal display panel; a light combining means for combining light transmitted through the first to third liquid crystal display panels; and a light combined by the light combining means on a screen. And a liquid crystal projector comprising: 2. The image information supplied to the first and second liquid crystal display panels converts red and blue video signals into first and second predetermined frequency signals.
Along with sampling by the sampling clock,
2. The liquid crystal projector according to claim 1, wherein the image information supplied to the third liquid crystal display panel is obtained by sampling a green video signal with a second sampling clock having a higher frequency than the first sampling clock.