JPS60179723A - Liquid crystal projection device - Google Patents

Abstract

PURPOSE:To obtain a new useful projection device free from visual angle dependency, by obtaining a display pattern additive-color-mixed by using at least three liquid crystal panels which are driven by an active matrix and independently control the radiation of additive three primary colors. CONSTITUTION:A TFT is constituted by succeesively patterning and piling up a gate electrode 11, gate insulating film 12, semiconductor film 13, source electrode 14, and drain electrode 15 on a transparent insulating substrate 10 of glass, etc. A light shield and orientation film is further installed to the substrate, on which the TFT is formed, to drive a liquid crystal. Then the substrate of a counter electrode is prepared by installing a transparent conductive film and orientation film for orienting liquid crystal to the surface of a transparent substrate, such as glass, etc. These two substrates are stuck together with a spacer in between and liquid crystal is injected into the space between the substrates. Such a liquid crystal panel is prepared by three for red.green. blue colors. Those three liquid crystal panels are not set by laying each picture element accurately one on top of the other, but set by shifting each picture element in two directions by about the 1/3 of the picture element pitch.

Description

[Detailed Description of the Invention] [Technical Field] The present invention is directed to (a) using at least three IJ wax-driven liquid crystal panels to control each of the three additive primary colors (red, green, and blue), and to control the color light in an arbitrary ratio. This invention relates to a small, lightweight projection device that performs additive color mixing.

<Background of the Invention> Matrix liquid crystal panels, which are used as display panels to efficiently display a large amount of information, have a large number of pixel electrodes arranged in at least a dot matrix, and light is emitted according to the voltage applied to them. Generally, the display includes a liquid crystal layer that modulates the image as a component, and displays any monochromatic image including halftones by applying a corresponding video signal to each picture element.

The operating modes of LCD panels include twisted nematic (TN), guest host (GH), dynamic scattering mode (DSM), and birefringence (DA).
There are many modes such as P-cross-ECB, etc.) and phase transition, all of which are applicable to the present invention. In conventional applications of liquid crystals to televisions (TVs), a single panel is used to display monochrome images. MOS-FE
G driven by T integrated Si wafer-substrate
A side watch type LCD TV using an H LCD panel and a pocketable TV using a TN LCD panel have been commercialized. Details about liquid crystals are given in Sasaki, ed., "Basics and Applications of Liquid Crystal Electronics", Ohmsha (1979), etc.

Generally, one of the following three methods is used to individually control each picture element of a liquid crystal panel.

(1) Simple matrix method Striped row and column electrodes are provided on each of two substrates, and they are bonded together so as to cross at right angles to form a panel. A row selection signal is sequentially applied to the row electrodes, and an image signal is applied to the fifth column electrode in synchronization with the row selection signal. The intersection of the row and column electrodes becomes a picture element, and the liquid crystal in the area sandwiched between the two electrodes changes its optical characteristics in response to the potential difference.

Since the liquid crystal is an element that responds to an effective value, driving by the two-voltage averaging method causes a problem of crosstalk, and the number of scanning lines cannot be set very large.

In order to overcome these problems, the following two methods have been developed.

(2) Addition of nonlinear elements Varistor, M I M (Metal /
This method adds a nonlinear element such as In5ulator/Meta+) to suppress crosstalk.

+31 Addition of switching element This is a method in which a switching transistor is added to each picture element and driven individually. A drive voltage is applied during the selection period, charging the storage capacitor and retaining it during the non-selection period. Note that the liquid crystal itself is a capacitive load, and if its time constant is sufficiently larger than the driving repetition period, the storage capacitor can be omitted.

The switching transistor is a thin film transistor (TFr) or M formed on a silicon wafer.
An OS-FET or the like is used.

The present invention provides particularly effective results in the above (2) and (3).

Conventional color liquid crystal panels (for example,
No. 886), the coloring means of the three primary colors are arranged in stripes or mosaics on the same panel, and color cathode ray tubes (No. 886)
Since the colors are mixed additively according to the same principle as CRT), the three additive primary colors (red, green, and blue) are used. It is not a good idea to use subtractive primary colors (yellow, cyan, magenta) in a system where such additive mixing is performed because the color reproduction range becomes narrow.

In the present invention, an arbitrary color image is reproduced by using three liquid crystal panels as light valves that independently control the color light of the three primary colors. The intensity of the light in the red, green, and blue wavelength ranges is modulated by the corresponding liquid crystal panel5, and as a result of combining them, any color is reproduced.

The selection criteria for the wavelength range of colored light used in the present invention are shown below.

Based on the concept of the brightest color, the inventor proposed that the optimal conditions for effectively utilizing a white light source in additive color mixing and satisfying the compatibility of the TV multiplied signal of the NTSC system are as follows. We found that the conditions are

(Absorbs 510 to 665. This is not possible and requires some modification.

In other words, the spectra of the three colored lights do not overlap,
Moreover, when the three colors are added together, it is necessary to cover the entire visible range.

Considering the above matters, the wavelength range of each color light may be selected as follows.

A conventional projection TV uses a dedicated CRT for each of the three primary colors, and projects images reproduced by the CRT onto a screen using a lens. With the current technology (dcRT), the brightness is not sufficient, so it is not possible to project onto a very large screen.Also, a directional screen is used to make it look as bright as possible, so the viewing angle is very narrow.

Furthermore, since it uses three large CRTs and is integrated with a screen, it becomes a very large-area device and is limited in its installation location.

Laser writing has already been proposed as a projection type liquid crystal display.

Since it is a monochromatic display, it is fundamentally different from the present invention, and the device is still a major loss.

<Objective of the Invention> In view of the above circumstances, the object of the F3A is to provide a new and useful projection device that is small, lightweight, bright, and independent of viewing angle by using at least three 5-LCD panels.

<Example> First, an active matrix substrate on which TPT is integrated is manufactured. FIG. 1+Al is a plan view schematically depicting an example of TPT, and FIG. 1 [Bl is a sectional view thereof. TPT has a gate electrode (11), a gate insulating film (12), a semiconductor film (13), a source electrode (14), and a drain electrode (10) on a transparent insulating substrate (10) such as glass.
15) are sequentially patterned and laminated. A picture element electrode (16) and an optional storage capacitor (17) are connected to the drain electrode (15). As a thin film forming method, a vacuum evaporation method, a sputtering method, a CVD method, a plasma CVD method, a low pressure CVD method, etc. are used, and the pattern is formed using a shadow mask or photolithography technique. A light shield and an alignment film are further provided to drive the liquid crystal on the substrate on which the T'FT is formed. When an n-type semiconductor is used as the semiconductor film C13), when a positive voltage is applied to the gate electrode (11), an electron accumulation layer is formed at the interface of the semiconductor film (13) on the gate insulating film (12) side, and the source electrode (14) and the drain electrode (
15) The resistance between the Figure 1 fcl is TPT
FIG. 2 is a wiring diagram when driving a liquid crystal on a panel. A scanning pulse is periodically applied to the gate electrode (11), and the TP
T is turned on. In synchronization with this, an image signal is applied to the source electrode (14), and is applied to the picture element electrode (16) and storage capacitor (17) provided as necessary through the TPT, thereby driving the liquid crystal. The storage capacitor (17) is for holding the voltage to be applied to the liquid crystal even while the TPT is in the OFF state. If the time constant of the liquid crystal is sufficiently larger than the scanning period, there is no need to provide a storage capacitor. Next, a substrate on the counter electrode side is prepared, in which a transparent conductive film and an alignment film for aligning liquid crystal are provided on a transparent substrate such as glass.

These two substrates are bonded together via a spacer, and liquid crystal is injected into the gap between the two substrates. Three such liquid crystal panels are manufactured for each of red, green, and blue. LCD mode is T
In the case of N, polarizing plates are provided on both sides of each panel. Note that each panel only needs to be able to control red, green, and blue color light, and each panel itself does not necessarily need to be provided with coloring means for the respective colors.

This liquid crystal panel is driven as follows.

An example of a block diagram of the drive circuit is shown in FIG.

TV radio waves are connected to a series of TVs, from the tuner to the color demodulation circuit.
It is processed by a receiving circuit (30) to become red, green, and blue color video signals. The video signal of each color is transmitted to the liquid crystal panels (21) to (23) corresponding to each color with polarity according to the display mode of the liquid crystal.
) are respectively applied. Video signal K (red) of each color
, G (green), and B (blue) are analog line memories (31) consisting of shift registers and sample-hold circuits.
~(33), and one line worth of video signal is stored. Next, this one line worth of video signal is output to the source line (14) in synchronization with the scanning signal generated by the scanning pulse generation circuit (34). Game) - Line (
11), scanning pulses are sequentially applied to turn on the FETs on that line. In this way, video signals are sampled and held at appropriate timings at individual picture element electrodes, and the liquid crystal is controlled. This liquid crystal panel has a light source (40), a condenser lens, ((4)
1), projection lens (42), dichroic mirror (4)
3), (4, 4), and a mirror (45) to configure a projection TV. Incandescent lamps, halogen lamps, xenon lamps, etc. are used as light sources, but the spectrum of the light source does not necessarily have to be a continuous spectrum; instead, it may be a fluorescent tube or discharge tube that emits a bright line spectrum of red, green, and blue. Good too. In this case, the center wavelength of each emission line spectrum is 610 nm.

540 nm and 460 nm are desirable in terms of color reproduction range and compatibility with NTSC signals. Dichroic mirror (43),
(44) divides the light from the light source into three wavelength bands: red, green, and blue,
This is to modulate each color light using a liquid crystal panel and then synthesize it again.

A dichroic mirror is a stack of multiple thin films with different refractive indexes, and uses an interference effect to reflect only light in a specific wavelength range and transmit the rest. (43) selectively reflects red light and transmits other light. (44) selectively reflects blue light and transmits other light. With this configuration, it is possible to effectively utilize the light of each wavelength from a single light source, and the light utilization efficiency is higher than that of a method in which only light in the necessary wavelength range is transmitted through an absorption filter.

The resolution of the reproduced image is determined by the number of picture elements of each panel, but it cannot be increased indefinitely due to the manufacturing technology, yield, cost, etc. of the liquid crystal panel.

If the number of pixels is small, the quality of the reproduced image will be poor.

When the number of picture elements in a horizontal line is smaller than the horizontal resolution of an NTSC TV signal (approximately 350 pixels), the spatial resolution of human vision is high for brightness and low for hue. , an apparently smooth image can be obtained by doing the following.

The three liquid crystal panels are set so that the images of each picture element are not exactly superimposed, but are shifted from each other by about % of the picture element pitch in two directions, as shown in FIG. 4 FB+. Figure 4 (
If the picture elements of each color are shifted and overlapped accurately as shown in A), shadows of gates, lines, sources, and lines will appear between the picture elements in a grid pattern, and the reproduced image will be rough, but If they are shifted by % pitch, the grid-like shadows described above will be filled in, and a smooth image will be obtained. In the diagram, R, G
, B are red, green, and blue picture elements, respectively. At this time, color,
A phase change produces a high spatial frequency component, but this is hardly perceptible to the human eye due to visual characteristics. It goes without saying that sampling of the video signal to be applied to the picture elements of each color is better if it is performed at a timing that corresponds to the shifted position of each picture element.

When the light from the light source is strong, to prevent the liquid crystal panel from heating up and changing its operating characteristics, air cooling is performed using a fan or liquid cooling is performed as necessary by immersing the liquid crystal panel in insulating oil.

A projection TV configured in this way is as compact as a slide projector, and has more freedom in installation location than conventional projection TVs.For example, it can be projected onto the ceiling, or hung from the ceiling and projected onto a wall. You will be able to do things like Furthermore, it is also possible to freely change the screen size by changing the projection distance or replacing the projection lens.

Note that if the projection plane is perpendicular to the optical axis of the optical system, problems such as the rectangular screen deforming into a trapezoid or the focus shifting may occur. This can be solved by changing the angle between the optical axis of the liquid crystal panel and the optical system.

<Effects of the Invention> As described above, the present invention constitutes a liquid crystal projection device that is small, lightweight, bright, and independent of viewing angle, and has great practical value.

It should be noted that the scope of application of the present invention is not limited to TVs, and it is clear that it can also be applied to character displays and graphic displays as displays for various information processing devices.

[Brief explanation of the drawing]

FIG. 1 (Δ1tBlFC1 is a schematic plan view, schematic cross-sectional view, and wiring diagram of a TFT. FIG. 2 is a block diagram of a liquid crystal projection television apparatus showing an embodiment of the present invention. FIG. FIG. 4 is an explanatory diagram illustrating the arrangement of picture elements. FIG. 5 is an explanatory diagram of the "tilt mechanism" in the liquid crystal projection television device. 1. 1"1: Gate electrode, 12: Gate insulating film. 13: Semiconductor film, 14: Source electrode, 15 Nidrain electrode, 16: Pixel electrode, 17: Storage capacitor, 21.
22.23: Liquid crystal panel, 30: TV signal receiving circuit,
31.32.33: Analog line memory, 34
: Scanning pulse generation circuit, 4o: Light source, 41: Condenser lens, 42: Throwing T lens, 43.44: Dichroic mirror 145: Mirror.

Claims (1)

[Claims] 1. A display pattern in which additive colors are mixed using at least three liquid crystal panels that are driven by active matrix links and each independently controls the emission of three additive primary colors (red, green, and blue). A liquid crystal projection device characterized in that: 2. The liquid crystal projection device according to claim 1, wherein the wavelength range of the colored light controlled by each panel is selected to be as follows. 3. The liquid crystal projection device according to claim 1 or 2, wherein the colored light incident on each liquid crystal panel is light obtained by separating white light from a single light source into three primary colors by a dichroic mirror. 4. The liquid crystal projection device according to claim 1, wherein the projected images of each liquid crystal panel Φ picture element overlap each other with a shift of about the picture element pitch. 5. The liquid crystal projection device according to claim 1, further comprising a mechanism for changing the angle between the liquid crystal panel and the optical axis of the optical system.