JPH06342140A - Display device - Google Patents

Abstract

PURPOSE:To obtain a clear picture by reducing flicker caused at the time of image synthesizing. CONSTITUTION:As for a display device using a liquid crystal panel which obtains a synthesized picture by synthesizing the picture displayed on two matrix type liquid crystal panels where a picture element is arranged in a matrix state, the polarity of a video signal impressed on one liquid crystal panel out of the matrix type liquid crystal panels in one field is made equal to the polarity of the video signal impressed on another liquid crystal panel in the field that is delayed by one field from the field.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection type display device for projecting an image on a screen by an optical system. More specifically, the present invention relates to a projection display device that projects a display image including pixels in a matrix on a screen.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for a display device larger than a CRT, and various large display devices have been developed and put on the market. One of them is a display device for enlarging and projecting an image composed of pixels arranged in a matrix. FIG. 2 shows the configuration of a projection display device using an LCD (liquid crystal display device) as an image forming means. The LCD 1 has pixels in a matrix, and the transmittance of each pixel is controlled by an external signal to form an original image. This original image is formed on the screen 3 by the projection optical system 2 and displayed.

As the LCD 1, an XY matrix type, an active matrix type or the like is used. Further, another matrix type light modulator or a light emitting type matrix display device (LCD or the like) can be used as the image forming means.

By the way, in such a projection display device, the resolution is controlled by the original image, and in order to increase the resolution, the size of the original image is increased and the number of pixels is increased, or the pixels are reduced to increase the density. Is a must. In the former method of enlarging the original image, the manufacturing cost of the display device is high. Even if a plurality of display devices are arranged side by side, it is difficult to eliminate the discontinuity in the connection portion of the obtained projection images. On the other hand, the latter density increase has a lower limit depending on the mounting of the display device and the external circuit and the manufacturing process. At present, the lower limit is several tens of μm.

As described above, the size and the pixel pitch are determined by the cost, availability of manufacturing, and the number of drivable lines, and there has been a limit in achieving high resolution of the original image.

An object of the present invention is to obtain a projection display with high resolution without increasing the resolution of the original image forming panel. Furthermore, it is to realize high resolution full color display.

The present invention obtains a composite image by displacing a plurality of original images composed of pixels arranged in a matrix and having the same pitch by a fraction of a pixel according to a specific arrangement rule.

Here, the pixels forming the original image may have different sizes but have to have the same pitch. It is assumed that the display information is sampled according to a specific rule and decomposed into a plurality of original images. Interlace, television signals, etc. are examples thereof. Next, a plurality of original images are projected so as to have a displacement according to the regularity described above, and a complete image is reproduced. Further, by combining the original images corresponding to the color display, a high resolution color display device is obtained.

[0009]

【Example】

Example 1 Example 1 is a display device for forming an original image, in which a TFT (thin film transistor) and a matrix liquid crystal panel (hereinafter referred to as TFTLC) are used.
It is a projection type television device using D). The liquid crystal display mode is the field effect of twisted nematic liquid crystal (hereinafter,
FETN), scattering effect (DSM), guest host effect (GH), etc. can be used. In this example, the FETN mode was used. The reason why the matrix driving by the TFT is selected is to improve the performance of the light valve. Therefore, there is no problem even if another matrix type driving method is used. The configuration of this embodiment is shown in FIG. The light source may be provided with two series of condenser lenses 4 and condenser mirrors 5 in the orthogonal direction so as to obtain two illumination light fluxes from one light source 6 in order to increase the utilization efficiency of the light source light. The direction of this illumination light is changed by the mirror 7 and enters the TFTLCD 8. The light modulated by the TFT LCD is imaged on the screen by the projection lens 9. Reference numeral 10 is a correction lens for correcting trapezoidal distortion due to projection. The TV signal is 52 in the vertical direction in the NTSC system.
There are 5 luminance signals for about 700 in the horizontal direction. Therefore, in order to display the luminance signal completely, it is necessary to use a TFT LCD having about 500 × 700 pixels.

However, it is difficult to manufacture such a large-scale matrix array in terms of cost, yield, and manufacturing apparatus, and it is desirable that the number of pixels is as small as possible. The TFT LCD used in FIG. 2 has 240 × 240 pixels and a diagonal size of 2 inches. Therefore, if this TFT LCD is simply projected, only 1/4 of the luminance information is displayed. In this embodiment, a plurality of TFTLCDs (two in this case) are used as shown in FIG. 8, and the resolution is improved by forming an image so that the pixels of the TFTLCD are displaced by a fraction.
FIG. 1 shows the pixel displacement. Panel A is the one with diagonal lines
Pixels of the above, and those with dots are the pixels of panel B. The reason for this displacement is to efficiently disperse the luminance information in the horizontal direction and the luminance information in the vertical direction on the screen.

Further, as shown in FIG. 1B, the effective aperture ratio of the pixel can be reduced in combination to further increase the resolution. In FIG. 1 (b), the shaded area is the effective pixel of panel A, the dotted area is the effective pixel of panel B, and the area enclosed by the broken line and the alternate long and short dash line is the pixel according to the pitch of the matrix. The part is shown.

In order to reduce the effective aperture ratio, the transparent electrode was reduced in size, an opaque wiring material was used for the gate and source electrodes of the TFT, and the electrodes were widened. Furthermore, 90 ° TN (twisted nematic) mode is adopted, which does not allow light to pass when no voltage is applied.

Next, driving of the TFT LCD will be briefly described. The two TFT LCDs have the circuit shown in FIG.
According to the interlace system, they are alternately selected and are AC-driven. The video signal input produces inverted and non-inverted outputs, and this and the black display level VB of the panel are selected by the switch circuits (SW1 to 6) to produce a signal whose polarity is inverted every two fields (2F). This is supplied to the X driver. FIG. 5 is a timing chart thereof. CLf is a shift register clock corresponding to one field (1F), and Df is transmission data. 1 in FIG.
Reference numeral 1 is a shift register for selecting SW1 to SW4, 12 is an inverting buffer, and 13 is a non-inverting buffer. CLx is a clock synchronized with the horizontal synchronizing signal, and Dx is data of the X driver. Similarly, CLy and Dy are the clock and data of the Y driver. In this way, panel A is selected for odd fields (1stF, 8rdF, 5thF in FIG. 5) and panel B is selected for even fields (2ndF, 2ndF in FIG. 6).
4th F). As a result, in the case of Example 1, it was possible to obtain about twice as much resolution as the TFT LCD. Moreover, the utilization efficiency of the light from the light source could be improved.

Embodiment 2 Embodiment 2 is a projection type display device in which a plurality of matrix liquid crystal panels (in the following description, two matrix liquid crystal panels are imaged by one projection optical system. The liquid crystal panel is a TFT LCD similar to that of Embodiment 1).
Was used. FIG. 6 shows the configuration of this embodiment. The liquid crystal layer is a homogeneously oriented black guest-host liquid crystal, and the optical shutter opens when an electric field is applied. Reference numeral 14 is a polarizing plate for improving the optical shutter characteristic. 6 is a light source, 4 is a condenser lens, and 9 is a projection lens. The panel A15 and the panel B16 are arranged in close contact or in close contact with each other and have the same liquid crystal orientation. Images of both panels are formed on the screen 3. For this reason, thin glass (in this case, 0.1 mm thick polished glass) is used as the transparent substrate of the panel on one side. The pixels of both panels are displaced by a half pixel as shown in FIG. Similar to the first embodiment, the television signal is displayed alternately on the panel A and the panel B for every two fields according to the interlace system.

Since the liquid crystal is of a type in which the optical shutter opens when a voltage is applied as described above, it is necessary to apply a voltage to open the optical shutter in an unselected field. Therefore, in driving, as in the first embodiment, the odd field is assigned as panel A and the even field as panel B, and the X driver input is level-selected by the switch circuit so as to take the white level in the unselected field. To do so. The X driver input thus created is shown in FIG. The entire panel driving method can be performed in the same manner as in FIG.

In this way, about twice the resolution can be obtained as compared with the case where one TFTLCD is used. Although the GH mode liquid crystal is used here, any transmission type electro-optical effect that does not use rotation of the polarization plane can be applied.

Example 3 Example 3 is a full-color display device using three display panels corresponding to the three primary colors R (red), G (green), and B (blue). R (red) panel 17, G (green) panel 18, B
As shown in FIG. 9, the (blue) panel 19 splits the light flux, and the synthetic mirror 20 (for example, a semi-transmissive mirror or a dichroic mirror)
The light flux is combined by the projection lens 9 and the screen 8
Connect the statue to. Reference numeral 21 is a relay lens, and 4 is a condenser lens. Here, the pixels of the R panel, the G panel, and the B panel are adjusted so as to be regularly displaced as shown in the circle in FIG. Although the pixels are not overlapped in this figure, the pixels may be overlapped by increasing the aperture ratio of the pixels as shown in FIG. Although the TFTLCD is used as the display panel in FIG. 8, any display panel that forms an accurate matrix can be replaced. R,
With a projection television projecting a CRT (cathode ray tube) corresponding to G and B3 primary colors on a screen, it is difficult to obtain a distortion-free image with perfect convergence.
According to the present invention in which image formation is performed by matrix pixels,
Pixel position adjustment between different panels is possible. As a result, the color misregistration between the colors can be reduced, and the luminance information included in R and B can be effectively displayed, so that the resolution can be substantially increased. FIG. 9 shows a drive circuit used in this embodiment. The video signals color-separated into R, G, and B are AC-inverted for each field and input to the X driver.
CLx, Dx, CLy and Dy are clocks and shift data of the X driver and the Y driver. The same circuit as the R circuit is provided for G and B.

In this embodiment, a transmissive TFT LCD is used as a matrix type display device, but it can be implemented as a reflective light valve structure in which light is incident from the same direction as the light source is emitted to modulate light. LCD mode is 9
Of course, other than 0 ° TN can be used. Of course, it is also possible to display a color that is not full color.

[0019]

As described above, according to the present invention, high resolution can be obtained even in a matrix type display device including low density pixels. Since a low-density panel can be used as a component, manufacturing is easy and the cost of the device can be reduced. Further, in color display, due to the accurate address characteristics of the matrix type display device, it is possible to obtain a display with high resolution without color shift.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of pixel displacement according to the present invention, where (a) shows a case where pixels overlap and (b) does not.

FIG. 2 is a configuration diagram of a general projection type display device using an LCD.

FIG. 3 is a diagram showing a configuration example of a synthetic projection method according to the present invention.

FIG. 4 is a diagram showing an example of a drive circuit when two TFTLCDs are used.

5 is a diagram showing a signal waveform of each part of the circuit of FIG.

FIG. 6 is a diagram showing a configuration example of an example in which two TFTLCDs are used.

7 is a diagram showing an X driver input waveform in the case of FIG. 6;

FIG. 8 is a configuration diagram of a full-color projection display device.

FIG. 9 is a diagram showing the drive circuit of FIG. 8;

[Explanation of symbols]

 1 ... Matrix LCD 2 ... Projection optical system 3 ... Screen 4 ... TFT LCD 9 ... Projection lens 15, 16, 17, 18, 19 ... TFT LCD

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[Procedure amendment]

[Submission date] March 22, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction content]

[Document name] Statement

Title: Display device

[Claims]

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a plurality of matrix type liquids.
Table that combines the images formed on the crystal panel to obtain a composite image
Related to the indicating device.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for a display device larger than a CRT, and various large display devices have been developed and put on the market. One of them is a display device for enlarging and projecting an image composed of pixels arranged in a matrix. FIG. 2 shows the configuration of a projection display device using an LCD (liquid crystal display device) as an image forming means. The LCD 1 has pixels in a matrix, and the transmittance of each pixel is controlled by an external signal to form an original image. This original image is formed on the screen 3 by the projection optical system 2 and displayed.

As the LCD 1, an XY matrix type, an active matrix type or the like is used. Further, another matrix type light modulator or a light emitting type matrix display device (LCD or the like) can be used as the image forming means.

[0004]

[Problems to be Solved by the Invention]
The image display device is driven by driving each panel individually.
Although the display image was obtained, driving in this way causes the pattern to be used.
When the number of components increases and drive circuits are needed,
Both have the drawback that the device becomes large.
It was Furthermore, there is a drawback that the manufacturing cost is high.
It was

[0005]

The present invention has the above-mentioned problems
In order to solve the problem,
Images displayed on the first and second matrix type liquid crystal panels
In a display device for synthesizing
The first matrix type liquid crystal of the liquid crystal type liquid crystal panel
A field of the first display signal applied to the panel
Polarity and the field one field behind the above field
Applied to the second matrix type liquid crystal panel in the field.
Characterized by having the same polarity as the second display signal
It

The first display signal and the second display signal
Is formed by one signal, and the one signal is
The polarity is inverted for each field.

The first matrix type liquid crystal panel and the above
The second matrix type liquid crystal panel is switched for each field.
The display signals are driven mutually and the display signal is in a rest period for each field.
It is characterized by having a space.

[0008]

Embodiment 1 Embodiment 1 is a display device for forming an original image, in which a TFT (thin film transistor) and a matrix liquid crystal panel (hereinafter, referred to as TFTLC) are used.
It is a projection type television device using D). The liquid crystal display mode is the field effect of twisted nematic liquid crystal (hereinafter,
FETN), scattering effect (DSM), guest host effect (GH), etc. can be used. In this example, the FETN mode was used. The reason why the matrix driving by the TFT is selected is to improve the performance of the light valve. Therefore, there is no problem even if another matrix type driving method is used. The configuration of this embodiment is shown in FIG. The light source may be provided with two series of condenser lenses 4 and condenser mirrors 5 in the orthogonal direction so as to obtain two illumination light fluxes from one light source 6 in order to increase the utilization efficiency of the light source light. The direction of this illumination light is changed by the mirror 7 and enters the TFTLCD 8. The light modulated by the TFT LCD is imaged on the screen by the projection lens 9. Reference numeral 10 is a correction lens for correcting trapezoidal distortion due to projection. The TV signal is 52 in the vertical direction in the NTSC system.
There are 5 luminance signals for about 700 in the horizontal direction. Therefore, in order to display the luminance signal completely, it is necessary to use a TFT LCD having about 500 × 700 pixels.

However, it is difficult to manufacture such a large-scale matrix array in terms of cost, yield, and manufacturing equipment, and it is desirable that the number of pixels is as small as possible. The TFT LCD used in FIG. 2 has 240 × 240 pixels and a diagonal size of 2 inches. Therefore, if this TFT LCD is simply projected, only 1/4 of the luminance information is displayed. In this embodiment, a plurality of TFTLCDs (two in this case) are used as shown in FIG. 8, and the resolution is improved by forming an image so that the pixels of the TFTLCD are displaced by a fraction.
FIG. 1 shows the pixel displacement. Panel A is the one with diagonal lines
Pixels of the above, and those with dots are the pixels of panel B. The reason for this displacement is to efficiently disperse the luminance information in the horizontal direction and the luminance information in the vertical direction on the screen.

Further, as shown in FIG. 1B, the effective aperture ratio of the pixel can be reduced in combination to further increase the resolution. In FIG. 1 (b), the shaded area is the effective pixel of panel A, the dotted area is the effective pixel of panel B, and the area enclosed by the broken line and the alternate long and short dash line is the pixel according to the pitch of the matrix. The part is shown.

In order to reduce the effective aperture ratio, the transparent electrode was reduced in size, an opaque wiring material was used for the gate and source electrodes of the TFT, and the electrodes were widened. Furthermore, 90 ° TN (twisted nematic) mode is adopted, which does not allow light to pass when no voltage is applied.

Next, driving of the TFT LCD will be briefly described. The two TFT LCDs have the circuit shown in FIG.
According to the interlace system, they are alternately selected and are AC-driven. The video signal input produces inverted and non-inverted outputs, and this and the black display level VB of the panel are selected by the switch circuits (SW1 to 6) to produce a signal whose polarity is inverted every two fields (2F). This is supplied to the X driver. FIG. 5 is a timing chart thereof. CLf is a shift register clock corresponding to one field (1F), and Df is transmission data. 1 in FIG.
Reference numeral 1 is a shift register for selecting SW1 to SW4, 12 is an inverting buffer, and 13 is a non-inverting buffer. CLx is a clock synchronized with the horizontal synchronizing signal, and Dx is data of the X driver. Similarly, CLy and Dy are the clock and data of the Y driver. In this way, panel A is selected for odd fields (1stF, 8rdF, 5thF in FIG. 5) and panel B is selected for even fields (2ndF, 2ndF in FIG. 6).
4th F). As a result, in the case of Example 1, it was possible to obtain about twice as much resolution as the TFT LCD. Moreover, the utilization efficiency of the light from the light source could be improved.

Embodiment 2 Embodiment 2 is a projection type display device in which a plurality of matrix liquid crystal panels (in the following description, two matrix liquid crystal panels are imaged by one projection optical system. The liquid crystal panel is the same TFT LCD as that of Embodiment 1).
Was used. FIG. 6 shows the configuration of this embodiment. The liquid crystal layer is a homogeneously oriented black guest-host liquid crystal, and the optical shutter opens when an electric field is applied. Reference numeral 14 is a polarizing plate for improving the optical shutter characteristic. 6 is a light source, 4 is a condenser lens, and 9 is a projection lens. The panel A15 and the panel B16 are arranged in close contact or in close contact with each other and have the same liquid crystal orientation. Images of both panels are formed on the screen 3. For this reason, thin glass (in this case, 0.1 mm thick polished glass) is used as the transparent substrate of the panel on one side. The pixels of both panels are displaced by a half pixel as shown in FIG. Similar to the first embodiment, the television signal is displayed alternately on the panel A and the panel B for every two fields according to the interlace system.

Since the liquid crystal is of a type in which the optical shutter opens when a voltage is applied as described above, it is necessary to apply a voltage to open the optical shutter in an unselected field. Therefore, in driving, as in the first embodiment, the odd field is assigned as panel A and the even field as panel B, and the X driver input is level-selected by the switch circuit so as to take the white level in the unselected field. To do so. The X driver input thus created is shown in FIG. The entire panel driving method can be performed in the same manner as in FIG.

In this way, about twice the resolution can be obtained as compared with the case where one TFTLCD is used. Although the GH mode liquid crystal is used here, any transmission type electro-optical effect that does not use rotation of the polarization plane can be applied.

8 and 9 show three primary colors R (red), G (green),
Full color using 3 display panels corresponding to B (blue)
-This is a configuration example when a display device is used. The R (red) panel 17, the G (green) panel 18, and the B (blue) panel 19 split the light flux as shown in FIG. 9, and the light flux is combined by a combining mirror 20 (for example, a semi-transmissive mirror or a dichroic mirror) and projected. An image is formed on the screen 8 by the lens 9. Reference numeral 21 is a relay lens, and 4 is a condenser lens. Here, the pixels of the R panel, the G panel, and the B panel are adjusted so as to be regularly displaced as shown in the circle in FIG. In this figure, there is no overlap between pixels, but in Figure 1 (a)
As described above, the aperture ratio of the pixels may be increased to overlap the pixels. Although the TFTLCD is used as the display panel in FIG. 8, any display panel that forms an accurate matrix can be replaced. With a projection television that projects a CRT (cathode ray tube) corresponding to R, G, and B primary colors on a screen, it is difficult to obtain a distortion-free image with perfect convergence. According to the present invention in which image formation is performed using matrix pixels, pixel position adjustment between different panels can be performed. As a result, the color misregistration between the colors can be reduced, and the luminance information included in R and B can be effectively displayed, so that the resolution can be substantially increased. FIG. 9 shows a drive circuit used in this embodiment. The R, G, B color separated video signals are AC-inverted for each field,
Input to the X driver. CLx, Dx, CLy,
Dy is a clock and shift data for the X driver and the Y driver. The same circuit as the R circuit is provided for G and B.

In this embodiment, a transmissive TFT LCD is used as a matrix type display device, but it can be implemented as a reflection type light valve structure in which light is incident from the same direction as the light source is emitted to modulate light. LCD mode is 9
Of course, other than 0 ° TN can be used. Of course, it is also possible to display a color that is not full color.

[0018]

As described above, according to the present invention, the image
It is possible to reduce flicker when compositing and create a clear image.
It has an effect that an image can be obtained. Moreover,
Holds data by providing a pause period for each field
Therefore, the field memory becomes unnecessary and
This has the effect of reducing the number of parts on the road.

Further, the number of parts of the display device is reduced to manufacture.
This has the effect of reducing costs.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of pixel displacement according to the present invention, where (a) shows a case where pixels overlap and (b) does not.

FIG. 2 is a configuration diagram of a general projection type display device using an LCD.

FIG. 3 is a diagram showing a configuration example of a synthetic projection method according to the present invention.

FIG. 4 is a diagram showing an example of a drive circuit when two TFTLCDs are used.

5 is a diagram showing a signal waveform of each part of the circuit of FIG.

FIG. 6 is a diagram showing a configuration example of an example in which two TFTLCDs are used.

7 is a diagram showing an X driver input waveform in the case of FIG. 6;

FIG. 8 is a configuration diagram of a full-color projection display device.

FIG. 9 is a diagram showing the drive circuit of FIG. 8;

[Explanation of Codes] 1 .. matrix LCD 2 .. projection optical system 3 .. screen 4. TFTLCD 9 .. projection lens 15, 16, 17, 18, 19 .. TFTLCD

Claims (4)

[Claims] 1. In a projection display device for obtaining a display image by projecting an image formed by a matrix display device in which pixels are arranged in a matrix, a display image synthesized from a plurality of images of the matrix display device. A projection-type display device characterized in that it is displaced. 2. The projection display device according to claim 1, wherein the displacement of the display image is substantially one pixel or less. 3. The projection display device according to claim 1, wherein the images of the matrix display device have the same pitch geometrically. 4. The projection display device according to claim 1, wherein the matrix display device displays an image corresponding to a display color.