JPH0756541B2 - Projection type color display device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a projection type color display device using a plurality of matrix type display panels for image formation.

[Conventional technology]

A conventional projection type color display device synthesizes a single color image by a reflection type light valve and a dichroic mirror as disclosed in JP-A-58-150937.

[Problems to be Solved by the Present Invention]

However, in the prior art, when a general television signal is received and displayed, the light valve is a cathode ray tube (CRT).
It was a large-scale device because it was controlled by the light of, and there were a lot of flickering on the screen, and the image quality was never sufficient.

Therefore, the present invention solves such a problem,
It is an object of the invention to provide a projection type color display device which has no flicker on the screen and has a high contrast.

[Means for solving problems]

The projection color display device of the present invention phase-inverts each RGB color signal for each field or each frame, and at the same time, one of the RGB color signals is converted into another signal.
Selecting means for selecting and outputting each of the RGB color signals so as to invert the phase in synchronization with the signal, and the RGB color signals selected by the selecting means,
It is characterized by comprising three liquid crystal light valves for modulating and outputting RGB color lights from the light source system, and a combining means for combining the RGB three color lights modulated through the liquid crystal light valves.

Further, the selecting means is configured to invert the G color signal of the RGB color signals with respect to the R color signal and the B color signal.
The feature is that each of the RGB color signals is selectively output.

[Action]

According to the above configuration of the present invention, crosstalk and flicker of the projection type color display device are prevented, and further the contrast is improved.

〔Example〕

FIG. 1 is a perspective view showing the configuration of a matrix type display panel of a projection type color display device in an embodiment of the present invention. The transparent substrate 1 is made of quartz, glass or the like, thin film transistors (TFT) 2 are formed in a matrix on the substrate, and the pixel electrode 3 is a transparent electrode such as ITO or SnO ₂ . The counter substrate 4 is a TFT liquid crystal type light valve in which a common electrode 5 is formed and a liquid crystal is filled between the substrates. The polarizing plate 6 is laminated on each substrate,
The light transmissivity is controlled by the voltage applied between the pixel electrodes.

FIG. 2 is an equivalent circuit diagram of the TFT based on FIG. 1 (a)
Is a circuit diagram of one picture element configured by connecting two stages of TFTs in series, and (b) is a circuit diagram converted into an equivalent circuit.

The equivalent circuit of a liquid crystal is usually regarded as a parallel connection of C and R, and the pixel capacitance C _{LC of the} liquid crystal is the overlap capacitance C _G1 , C _G2 , C _G3 of the gate electrodes.
Therefore, it is desirable that the size is sufficiently large. Furthermore, the liquid crystal resistance R
_{By making LC} sufficiently high, the amount of charge accumulated in the liquid crystal can be sampled and held for a long time. or,
It is desirable that the transistor resistances R _TR1 and R _TR2 are sufficiently small. Especially, when analog sample and hold of image data is performed, the frequency response is 1H (μSec) ÷ (number of horizontal pixels ).

Therefore, increasing the number of pixels reduces the pixel area and leads to a decrease in the pixel capacitance C _LC of the liquid crystal, while increasing the performance of the transistor may increase the overlapping capacitances C _{G1 to} C _G3. .

FIG. 3 is a diagram showing a TFT sample hold.

As shown in FIG. 2, in reality, when the source potential Vs is sampled at the sampling time Δt due to the overlapping capacitance of the gate electrode and the impedance of the liquid crystal sending, the voltage V _LC applied to the liquid crystal is as shown in the figure. In addition, since signals of opposite polarities are supplied for each one field or one frame, impedances due to the polarities of the overlapping capacitors are different and asymmetry occurs.

Therefore, for a unit time (about 16 msec) of one field of the NTSC system, which is the same as that of the television receiver, a slight flicker of low frequency component occurs. In the case of an active matrix panel (for example, an active matrix made of amorphous silicon or polysilicon), these flicker is likely to occur, and the matrix configuration is 1000 × 10.
When the density is increased to around 00, the time constants of C _LC and R _LC become smaller, and the flicker phenomenon increases.

Therefore, a driving method that prevents these flicker and crosstalk is required.

FIG. 4 is a block diagram of a drive circuit of the projection type color display device of the present invention.

The video signal is amplified by the video amplifier 10 and separated by the sync separator 11 into a horizontal sync signal H and a vertical sync signal V. Also, color separation is performed by the video chroma circuit 12,
Converted to R, G, B color signals. The even / odd field judgment circuit 13 performs a field judgment and a data select circuit.
The signal G / K of even field and odd field is sent to 14. The timing control 15 is a timing control circuit of the light valve 16.

The light valve 16 composed of a matrix panel (hereinafter referred to as a light valve) is composed of a plurality of TFT panels that independently control color signals of R, G, and B colors.

FIG. 5 is a timing chart of the projection type color display device of the present invention.

In the block diagram shown in FIG. 4, the vertical synchronizing signal V, which has been synchronized and separated, is used as a constant cycle to convert the video signal VIDEO into R, G, B
The data are modulated into R-DATA, G-DATA, and B-DATA of three colors of each color, and those signals have a phase between the light valves so that R and B are in phase and G is in phase. , Supply to flip.

As a result, flicker and crosstalk generated in each light valve for each color can cancel each other due to the reciprocal relationship. FIG. 6 is a diagram using three light valves in the embodiment of the present invention, (a)
Shows a plan view and (b) shows a front view.

The light source 20 uses a halogen lamp, an Xe lamp, a metal halide lamp, or the like, and has R, G, and B color filters 21,
The light valves 24, 25, 26 are illuminated via 22, 23. The light valve is configured by a TFT liquid crystal panel that electrically modulates the transmittance of light, and projects each color information of R, G, and B on a screen 28 by a projection lens 27 in an enlarged manner. With the above configuration, the image on the screen 28 is R, G, B
It is possible to cancel flicker and crosstalk by applying data in which the phases of the R and B light valves are opposite in phase to the crossover cycle of the G light valve for each image information.

FIG. 7 is a diagram showing a projection type color display device using a single lens of another embodiment of the present invention, (a) is a plan view and (b) is a front view.

The white light emitted from the light source 30 is separated into three primary colors of R, G, and B by a color separation method in which two dichroic mirrors 31 having red selective reflection and blue selective reflection are orthogonal to each other. , Each color light is reflected by the mirror 32 and the light valve 33
Is irradiated. The light valve 33 is a TFT liquid crystal panel that electrically modulates information of each color into light transmittance. The cube prism 34 is constructed by bonding four prisms having selective reflection characteristics of red and blue to the two sides of the right-angled prism that sandwich the right angle with an optical adhesive, and the light modulated by the light valve 33 is a cube prism. Color combination is performed in 34, and an image is formed on the screen 36 by the projection lens 35.

With the above configuration, the image information of the light valve that performs color synthesis controls the light transmissivity by the number that intersects with each field or each frame. It is possible to cancel flicker and crosstalk by using the crossover signal of the opposite phase as the phase.

This device can be applied when an amorphous type liquid crystal panel, a polysilicon type, an active type liquid crystal panel using MIM or a diode ring, or a simple matrix type liquid crystal panel is used as a light valve.

〔The invention's effect〕

The projection color display device of the present invention phase-inverts each RGB color signal for each field or each frame, and at the same time, one of the RGB color signals is converted into another signal.
Since the RGB color signals are selected and output so as to be phase-inverted in synchronization with the signals, the phase inversion is caused by the parasitic capacitance of the liquid crystal element of each liquid crystal light valve to which each color signal to be phase-inverted is applied. There is an effect that the occurrence of low-frequency flicker due to the asymmetry of the waveform is canceled after the color combination, and the flicker can be prevented without causing color shift.

Further, the selecting means sets the RG so that the G color signal of the RGB color signals is phase-inverted with respect to the R signal and the B color signal.
Since the B color signals are selectively output, the color energy ratios of G and R and B, which have high visibility and high energy, are substantially equal to each other, and flicker is offset.

[Brief description of drawings]

FIG. 1 is a perspective view showing a configuration of a matrix type display panel of the present invention. 2 (a) and 2 (b) are circuit diagrams of one pixel of the TFT in FIG. 2 (a), and FIG. 2 (b) is a transparent circuit diagram of the TFT. FIG. 3 is a diagram showing a sample hold of the TFT of the present invention. FIG. 4 is a block diagram of a drive circuit of the projection type color display device of the present invention. FIG. 5 is a timing chart of the projection type color display device of the present invention. FIGS. 6 (a) and 6 (b) are views using three light valves in the embodiment of the present invention, FIG. 6 (a) is a plan view, FIG. 6 (b) is a front view, and FIGS. 2B is a diagram showing a projection display device using a single lens according to another embodiment of the present invention. FIG. 6A is a plan view and FIG. 1 ... Transparent substrate 2 ... Thin film transistor 3 ... Pixel electrode

Claims (2)

[Claims] 1. The RGB color signals are phase-inverted field by field or frame by frame, and one of the RGB color signals is reversed.
Selection means for selectively outputting the RGB color signals so as to invert the phase in synchronization with the other two signals, and the RGB color signals selected by the selection means,
A projection color including three liquid crystal light valves for modulating and outputting RGB color lights from a light source system, and combining means for combining RGB three color lights modulated through the liquid crystal light valves. Display device. 2. The selecting means performs phase inversion of a G color signal of the RGB color signals with respect to an R color signal and a B color signal.
The projection type color display device according to claim 1, wherein each of the RGB color signals is selectively output.