JPH08248381A - Successive color display device for plane - Google Patents

Abstract

PURPOSE: To prevent mixed color and color splitting when color is switched using a liquid crystal shutter. CONSTITUTION: The order of color of green, blue and red is set in a n+1 frame next to (n) frame in which the order of color in a frame is red, blue and green. The number of times with which one side of πcells and the other side of πcell in a liquid crystal shutter is turned OFF from ON is decreased to a half comparing with conventional one in which the fixed order of color switching of red, blue and green is performed. Therefore, mixed color caused by delay of response of a π cell can be reduced. Also, since the same color (red or green) is continued after that even if an afterglow time of blue is long, mixed color by afterglow can be reduced. Further, color splitting in which color is applied on an edge of a white object can be made inconspicuous when the line of sight is moved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a field-sequential color display device capable of color display, for example, by switching images of three primary colors for each field, or for every cycle of an integer fraction of one field.

[0002]

2. Description of the Related Art As a color display device, a color CRT is used.
Although (cathode ray tube) is widely used, it is necessary to adjust the beam convergence and beam landing position because the electron beam of the three primary colors hits the fluorescent screen of the three primary colors, which results in contrast, resolution and cost. There was a problem in terms of. On the other hand, the so-called frame-sequential color display device, which uses a monochrome CRT and a color filter to temporally switch the three primary colors, has an advantage that such a problem does not occur.

A field-sequential color display device which has been put into practical use is a system in which the three primary color signals are temporarily stored in a memory and the switching of color filters and the sequential color signals from the memory are synchronized. As an example, in order to scan the three primary color signals within the time of one field, the horizontal scanning and the vertical scanning are set to three times the normal scanning. As the color filter, a configuration in which the color filter is mechanically rotated and an LCS method in which a liquid crystal shutter including a π cell and a color polarizing plate is switched are put into practical use. That is, the LCS type frame sequential color display device sequentially drives the CRT by the three primary color signals of red (R), blue (B), and green (G) to switch the mode of two π cells.

[0004]

In the field sequential color display device using the liquid crystal shutter described above, there is a problem that color mixing occurs between fields due to the delay of the response speed of the π cell included in the liquid crystal shutter. FIG. 1 shows the response time of a π cell using a nematic liquid crystal. π cell is ON
It takes, for example, 1 ms to switch from ON to OFF, and thus has a characteristic that it does not switch from ON to OFF immediately. For this reason, even if the color is switched during the vertical blanking period, the color is not completely switched within this period, so that another color is mixed at the beginning of the video signal of the next color and color shading occurs. As an example, when the blue image is generated when the two π cells are both in the ON state, immediately after the blue to green switching in which any π cell is turned from ON to OFF, Immediately after switching from green to red, the blue component becomes a mixed color.

Further, as shown in FIG. 2, as the temperature decreases, the particle size of the liquid crystal increases, which increases the viscosity of the liquid crystal, and the response time of the π cell (that is, π).
The time until the cell switches from ON to OFF) further increases.

FIG. 3 shows an image obtained by a frame sequential color display device, for example, color shading in an environment of 0 ° C. As shown in FIG. 3, a considerable amount of color shading SH occurs on the display image P. As one method of preventing color mixture due to such an increase in the response time of the π cell, it has been proposed to divide the electrode of the π cell into a plurality of pieces in the vertical direction (see, for example, US Pat. No. 4,652,087). That is, by sequentially shifting the shutter timing of each of the three divided electrodes within the range of 1/3 field, the switching drive signal is applied to the electrodes prior to the original timing at which the π cell should be switched from ON to OFF. It is possible to do.

However, as shown in FIG.
Below 0 ° C., color shading SH1, SH2, SH3 occurs beyond the correction range of the above-mentioned improvement means and at the boundary of the electrode division lines L1, L2, L3.

Further, in order to divide the electrode of the π cell, a large-scale device such as a photolithography device, an etching device, or a laser beam processing device is required in manufacturing. In addition, the line width of the boundary between electrode divisions is required to be 10 μm or less so as not to obstruct the image, and a high level manufacturing technology is required. Further, a driving device is required according to the number of divided electrodes of the π cell. Considering these points, the above method of dividing the electrode of the π cell is not practical.

Here, the color mixture will be described more specifically. Color switching is usually vertical blanking (BLK)
However, when the response speed of the liquid crystal shutter is slow, the colors are not completely switched within the blanking period, as shown in FIG. The colors are mixed, resulting in color shading. FIG. 5 shows how a blue component is mixed due to a delay in the response of the π cell in a device in which one π cell is switched from ON to OFF when switching from blue to green.

Another cause of color mixture is the problem of afterglow of the phosphor of a CRT. FIG. 6 shows a case where the afterglow of the phosphor is long. FIG. 6A shows a color change from red to blue, for example. Figure 6
As shown in B, when the phosphor is made to emit light at a position at the bottom of the screen near the timing of color switching in an impulse,
Even if the driving signal is cut off, the phosphor does not immediately stop emitting light,
Light emission continues to some extent. When the color is switched from red to blue during the vertical blanking period, color mixing occurs at the lower position of the screen, resulting in color shading.

Further, as another problem, when the order of colors in one frame shown in FIG. 7 is changed from red to blue and then to green, when the line of sight of an eye follows a fast moving screen, for example, a white window. The problem arises. In the example of FIG. 7, 1
The CRT is driven by the three primary color signals in a period in which the frame is divided into three. FIG. 7A shows the response state of one π cell, and FIG. 7B shows the response state of the other π cell.
When the π cell switches from ON to OFF, it does not switch immediately as described above, and the response is delayed.

FIG. 8A shows a case where a white (red + blue + green) window moving from left to right on the screen is visually followed. As shown in FIG. 8A, when considering the position of the window driven by the blue signal as the center, the window driven by the red signal of the same frame is shifted by Δx to the right with respect to the blue window, and the green signal is shifted. The window driven by is shifted by Δx to the left with respect to the blue window. In this way, the positions of the afterimages of red, blue, and green change due to the movement of the eyes, and despite the achromatic color, as shown in FIG. 8B, green and cyan are on the front side of the white window, and Seen with magenta and red color. FIG. 8C shows the brightness level in this case. The same problem also occurs when looking outside the screen and quickly gazing at the screen. These phenomena are called color breaks, and are easily noticeable in the case of a white object with high brightness as described above.

As one method of preventing color breakup, it is conceivable to change the frames of the three primary color images faster, but in order to do so, both the horizontal and vertical scanning frequencies must be higher than triple the frequency. I won't. Therefore, the frequency of the horizontal deflection drive and the CRT drive becomes high, which causes a new problem that power consumption increases.

Therefore, an object of the present invention is to provide a field-sequential color display device in which color breakage is prevented while power consumption is suppressed, and the color mixture due to the delay of the response of the π cell and the afterglow of the image generation source is reduced. Especially.

[0015]

SUMMARY OF THE INVENTION According to the present invention, a monochrome image generating means, a drive signal generating means for generating sequential color signals for driving the image generating means from three primary color signals, and an image generating means in series on the optical axis. And a liquid crystal shutter arranged to be switched by an external signal in synchronization with the driving timing of the image generating means, and the sequential color signals generated by the image generating means are plural in one cycle. An area sequential color display device characterized in that the temporal order of color signals is changed.

[0016]

The function of the frame sequential color display device is switched by turning on / off the liquid crystal shutter. By changing the order of the color signals in one field / one frame, the number of times the liquid crystal shutter changes from ON to OFF can be reduced, and color mixing due to a delay in the response of the liquid crystal shutter can be reduced. Further, by making the display periods of the same color continuous, it is possible to prevent color mixture due to afterglow of the image generation source. Further, when a white object that moves fast on the screen is followed with eyes, it is possible to prevent color breakup in which an edge of the object is colored.

[0017]

An embodiment of the present invention will be described below. FIG. 9 shows an embodiment of an LCS type frame sequential color display device to which the present invention can be applied. In FIG. 9, 10
Is a monochrome CRT as an image generation source.
T10 is driven by the video signals of the three primary colors sent in the frame sequential manner. On the front surface of the CRT 10, a liquid crystal shutter 12 including two color polarizing plates 31 and 33, two π cells 32 and 34, and one neutral polarizing plate 35.
Is provided. The π cells 32 and 34 are turned on / off by the drive pulse signals Sd1 and Sd2, respectively.
It is a high-speed response liquid crystal shutter. The liquid crystal shutter 12 performs color selection in synchronization with the video signals of the three primary colors.

The color polarizing plate 31 closest to the screen of the CRT 10 selectively transmits the green and red color lights whose horizontal polarization axes are yellow, and the yellow polarization light whose vertical polarization axes are red and blue, respectively. , Selectively transmit magenta colored light. Π cell 3 for the color polarizing plate 31
The color polarization plates 33 facing each other through 2 selectively transmit red color light with a horizontal polarization axis and selectively transmit green and blue color light with a vertical polarization axis, that is, cyan color light. The neutral polarization plate 35, which faces the color polarization plate 33 via the π cell 34, has a horizontal polarization axis as a light absorption axis and a vertical polarization axis of all color lights of red, blue, and green, that is, Allows white light to pass through.

FIG. 10 shows a circuit configuration of a frame sequential color display device using the above-mentioned liquid crystal shutter 12. A composite color video signal (the waveform of the carrier color signal is omitted for simplicity) is supplied to the input terminal 1, and the A / D converter 2 is supplied.
Are converted into digital signals by. The output signal of the A / D converter 2 is supplied to the Y / C separation circuit 3.

The Y / C separation circuit 3 separates the luminance signal Y and the carrier color signal C. The composite color video signal extracted from the middle of the Y / C separation circuit 3 is supplied to the sync separation circuit 4. The separated carrier color signal C is supplied to the color decoder 5, and the color difference signals RY and BY are output from the color decoder 5. The luminance signal Y and the color difference signals RY and BY are supplied to the matrix circuit 6, and the matrix circuit 6 causes the R signal (red image signal), B signal (blue image signal), and G signal (of the three primary color signals) to be transmitted. A green video signal) is formed.

R signal, B signal from the matrix circuit 6,
The G signal is written in the memory 7, respectively. The signals read from the memory 7 are the γ correction circuits 8R, 8B, 8G.
Is supplied to each. The γ-corrected three primary color signals are D /
It is supplied to the A converter 9 and is converted from a digital signal to an analog signal by the D / A converter 9. By the memory 7, the three-primary-color signals of one field (1V) are time-compressed to approximately 1/3 and converted into sequential color signals in which substantially color signals are sequentially positioned through the blanking period.

Sequential color signals from the D / A converter 9 are supplied to the monochrome CRT 10, and the CRT is operated by the sequential color signals.
10 is driven. That is, the CRT 10 sequentially displays an image of a brightness change corresponding to each level change of the color signal. The CRT 10 includes a horizontal and vertical deflection device 11
have. The liquid crystal shutter 12 described above is arranged in series with the screen surface of the CRT 10 on the optical axis. In addition,
The CRT 10 is not limited to a normal type, but a flat type C
RT is also acceptable. Alternatively, a flat display such as a liquid crystal or a plasma display may be adopted.

The horizontal synchronizing signal HD having the normal horizontal scanning frequency Fh separated by the synchronizing separating circuit 4 is supplied to the PLL 13, and the PLL 13 generates a signal having a frequency (3Fh) tripled in synchronization with the horizontal synchronizing signal HD. It Further, the vertical sync signal VD from the sync separation circuit 4 is PLL1.
4, and a signal having a triple frequency (3Fv) synchronized with the vertical synchronizing signal VD is generated. Then, the composite sync signal from the sync separation circuit 4 and the output signals of the PLLs 13 and 14 are supplied to the timing generation circuit 15.

The timing generation circuit 15 generates a horizontal deflection signal having a frequency of 3Fh and a vertical deflection signal having a frequency of 3Fv. Furthermore, the timing generation circuit 15
Generates a timing signal for the control signal generation circuit 19. The clock generation circuit 16 uses this timing signal to write a clock to the memory 7.
It generates a read clock and a color switching control signal. When the time axis is compressed to 1/3, a read clock having a frequency approximately three times the frequency of the write clock is used. The area used by the memory 7 is selectively switched by the R signal, the B signal, and the G signal by the color switching control signal.

The horizontal deflection signal and the vertical deflection signal from the timing generation circuit 15 are supplied to the horizontal and vertical deflection device 11, and the CRT is horizontally and vertically deflected.
Further, the control signal generation circuit 19 drives the drive signal Sd for the π cells 32 and 34 of the liquid crystal shutter 12.
1 and Sd2, respectively.

Further, in the above-described embodiment, the three primary color signals are serialized. However, an achromatic color signal (black or white signal) is formed from the three primary color signals, and the display is performed by the sequential color signals of the three primary color and achromatic color signals. You may drive. In this case, the horizontal and vertical scanning frequencies are selected to be an integral multiple of 4.

Further, the configuration for signal processing is shown in FIG.
The present invention is not limited to the digital signal processing as shown in (3), and analog signal processing may be performed other than the time base compression by the memory.

Furthermore, in this embodiment, the CRT 10 is used as the image generating source, but it is also possible to use another monochrome pixel display device such as a liquid crystal instead of the CRT 10. When this liquid crystal is used, a color polarizing plate and a π cell may be arranged between the backlight and the liquid crystal.

FIG. 11 is a signal waveform used for explaining a frame sequential color display device using a liquid crystal shutter.
A is an input color video signal. However, FIG. 11A
Are omitted for the chrominance carrier signal for simplicity. From the input color video signal, three primary color signals are formed by Y / C separation, color demodulation, and matrix calculation. Then, by the time axis compression process, as shown in FIG. 11B, the sequential color signal Sg in which the three primary color signals, which are time axis compressed to approximately ⅓ in each period obtained by dividing the period of one field (1V) into three equal parts, are located. It is formed. The CRT 10 is driven by this sequential color signal Sg.

When the above-mentioned liquid crystal shutter 12 is used, the π cells 32 and 34 are turned on in accordance with the relationship between the drive signals Sd1 and Sd2 shown in FIG. 11C in synchronization with the time axis compressed sequential color signal shown in FIG. 11B. / OFF is driven. The horizontal scanning frequency and the vertical scanning frequency of the CRT 10 are set to three times the normal frequency so as to scan one field during each color signal period of the color signal (FIG. 11B).

The switching operation of the above-described embodiment of the present invention will be described with reference to FIG. Here, the polarization direction does not change when passing through the π cells 32 and 34 in the ON state, while the polarization direction is rotated by 90 ° when passing through the π cells 32 and 34 in the OFF state.

Specifically, as shown in the upper diagram of FIG. 12, during the period in which the CRT 10 is driven by the R signal, π
The cell 32 is turned on and the π cell 34 is turned off. Since the polarization direction does not change due to the π cell 32 in the ON state, the color light beams (red) having the same horizontal polarization axis of the color polarization plates 31 and 33 and the color light beam (blue) having these vertical polarization axes have the same color polarization plate 33. Pass through. And π in the OFF state
By passing through the cell 34, the polarization direction is rotated by 90 °, and the horizontal polarization axis of the neutral polarizing plate 35 is the light absorption axis. Therefore, only red color light appears from the neutral polarizing plate 35, and a red image is obtained.

During the period in which the CRT 10 is driven by the B signal, the π cells 32 and 34 are turned on. Therefore,
Blue color light having a polarization axis that coincides with the vertical polarization axes of the color polarizing plates 31 and 33 passes through the π cells 32 and 34, and a blue image is obtained. Further, during the period in which the CRT 10 is driven by the G signal, the π cell 32 is off and the π cell 34 is
Is turned on. Therefore, by the π cell 32, the green color light whose polarization direction is rotated by 90 ° is converted into the color polarizing plates 33, π.
After passing through the cell 34 and the neutral polarizing plate 35, a green image is obtained.

The number of π cells is not limited to two, and the color polarizing plate can be combined with other colors. Further, although the π cell is turned on / off depending on the level of the driving voltage, other driving means such as changing the driving frequency may be used if the above-mentioned two types of modes are set.

Further, in FIG. 11, the color signals are sequentially represented by R, B, and
Although the order of G is used, the order of B, G, and R can also be used to achieve color display by changing the driving mode of the π cells 32 and 34.

According to the present invention, color breakup is prevented and color mixing is further reduced by appropriately arranging one cycle of a color signal, for example, the order of colors in a frame. Regarding the order of colors in a frame in one embodiment of the present invention,
This will be described with reference to FIG.

When the n frames are, for example, in the order of red to blue and then green, in the next n + 1 frames, the order of the first and last colors of the n frame is changed from green to blue and then to red. That is, the last color of the frame is the same as the first color of the next frame. In this case, of course, the next n + 2 frames are made similar to the original n frames from red to blue to green. The colors are sequentially driven in this order. Therefore, in this embodiment, the color order is changed with a cycle of two frames.

As described above, the color order can be controlled by the color switching control signal generated by the clock generation circuit 16. That is, the color switching control signal selects the red signal area, the blue signal area, and the green signal area of the memory 7, and the color signals can be output in the order according to the color switching control signal.

As shown in FIG. 13, by making the last color of the previous frame and the first color of the next frame the same, the .pi. Cell 32 and .pi. Cell 3 shown in FIGS. 13A and 13B are shown.
The number of times 4 is switched from ON to OFF is reduced from 4 times to 2 times per 2 frames, which is half of the conventional case (see FIG. 7), and the above-described color shading is reduced accordingly. That is, the color mixture to the first and last colors of the frame, red and green, is halved.

Further, the CRT is monochrome, but considering the case where the light of the CRT passes through the color polarizing plate, red,
The afterglow characteristics of blue and green are different. However, according to the present invention, even when the afterglow time is different among the red, blue, and green components of phosphor emission, for example, blue is long, as shown in FIG. 13, the color after blue with long afterglow continues. As a result, color shading due to afterglow can be reduced. The same applies when the afterglow of other colors is long.

It should be noted that the inside of the n frame is red, green and blue, and n + 1
Even when the order of blue-green-red within the frame is set, or when the order of blue-red-green is set within the n frame and green-red-blue is set within the n + 1 frame, the above-described effect of the embodiment of the present invention can be obtained. . Further, if the first and last colors of the frame are different depending on the frame, the last color of the frame and the first color of the next frame may not be the same.

FIG. 14A shows white (red + red) moving from left to right on the screen in the color order (FIG. 13) of the embodiment of the present invention.
It shows the case of following the window of (blue + green) with eyes. In this way, the positions of the afterimages of red, blue, and green change due to the movement of the eyes, and despite the achromatic color, yellow and blue are displayed on the front side of the white window shown in FIG. 14B, and blue and yellow are displayed on the rear side. It will be visible with the color of. FIG. 14C shows the luminance level in this case. As can be seen from FIG. 14C,
You can see a white window with yellow at the left and right edges and a blue color inside it (between white and yellow). However, in the past (Fig. 8
As for the luminance level of the portions with cyan and magenta in (1), the luminance level of blue is halved, and the luminance levels of green and red are white. That is, since white and blue are mixed, blue is less noticeable. Also, the yellow at the left and right ends is less noticeable than the green and red seen in conventional color breakup. Visually, color breakup can be reduced.

The order of colors in another embodiment of the present invention is shown in FIG. If the n frames are, for example, in order from red to blue, then green, the next n + 1 frames are green to red, and then blue, with the order of all the colors in the n frames reversed. In addition, the n + 2 frame is changed from blue to green and then red, and the n + 3 frame is changed from red to blue and then green of the original n frame. That is, the order of colors within a frame is such that the first color of the next frame is the same as the last color of the previous frame, and the remaining colors are in a different order than the previous frame. In addition, the first color of the next frame is made the same as the last color of the previous frame, and the remaining colors are made different from the previous frame. The colors are sequentially driven in this order.

As shown in FIG. 15, by making the last color of the previous frame and the first color of the next frame the same, the π cells 32 and π shown in FIGS. 15A and 15B are shown.
The number of times the cell 34 is switched from ON to OFF is reduced to 2/3 of that in the conventional case (see FIG. 7), and the above-described color shading is reduced accordingly.

The last color of the frame may not be the same as the first color of the next frame, such as red-blue-green for n frames, blue-green red for n + 1 frames, and green-red-blue for n + 2 frames.

FIG. 16A shows a case where a white (red + blue + green) window moving from left to right on the screen is visually followed in the color order (FIG. 15) of another embodiment of the present invention. . In this way, the positions of the afterimages of red, blue, and green change due to the movement of the eyes, but white appears on the front side and the back side of the white window shown in FIG. 16B. FIG. 16C shows the brightness level in this case. This will be described by separating the first color, the center color, and the last color of each frame. If the first color is extracted from the nth frame to the n + 2th frame, it becomes red, green and blue. Similarly, if the central color is taken out, it becomes blue, red, and green. further,
If you take out the last color in the same way, you get green, blue and red. This is made to be white on the time average as shown in FIG. 16C. That is, there is no coloring, and color breakup can be prevented as shown in FIG.

Even if there are two or more combinations of colors in one frame, for example, red, blue, green, red, blue, green, or red, blue, green, green, blue, red, etc., one set is a pre-frame and the above-mentioned frame is used. If considered, the same effect according to the present invention can be obtained.

[0048]

According to the present invention, coloring of the front side and the rear side of the moving image in the traveling direction is reduced. Further, color shading due to the slow response of the π cell of the liquid crystal shutter is reduced. Further, color shading due to the long afterglow of the phosphor of the image generation source is reduced.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a response time of a π cell using a nematic liquid crystal.

FIG. 2 is a schematic diagram showing a relationship between a response speed of a π cell and temperature.

FIG. 3 is a schematic diagram showing color shading of an image obtained by a frame sequential color display device.

FIG. 4 is a schematic diagram for explaining an example of a conventional color mixing improvement method.

FIG. 5 is a schematic diagram showing the occurrence of color mixing due to a delay in the response of the π cell.

FIG. 6 is a schematic diagram showing the occurrence of color mixing due to afterglow of a phosphor.

FIG. 7 is a schematic diagram showing a conventional color order and a π cell state.

FIG. 8 is a schematic diagram for explaining a conventional color breakup.

FIG. 9 is a schematic diagram showing an example of a configuration of a liquid crystal shutter of a frame sequential color display device to which the present invention can be applied.

FIG. 10 is a block diagram showing an example of a circuit configuration of a frame sequential color display device to which the present invention can be applied.

FIG. 11 is a waveform diagram showing signal waveforms used for explaining the frame sequential color display device.

FIG. 12 is a schematic diagram showing a color switching operation according to an embodiment of the present invention.

FIG. 13 is a schematic diagram showing a color order and a π cell state according to an embodiment of the present invention.

FIG. 14 is a schematic diagram for explaining the effect of reducing color breakage according to an embodiment of the present invention.

FIG. 15 is a schematic diagram showing a color order and a π cell state according to another embodiment of the present invention.

FIG. 16 is a schematic diagram for explaining the effect of preventing color breakage of another embodiment of the present invention.

[Explanation of symbols]

 10 CRT 12 Liquid crystal shutter 16 Clock generation circuit 31, 33 Color polarizing plate 32, 34 π cell 35 Neutral polarizing plate

Claims (5)

[Claims] 1. A monochrome image generating means, a drive signal generating means for generating sequential color signals for driving the image generating means from three primary color signals, and an image generating means arranged in series with the image generating means on an optical axis. A liquid crystal shutter adapted to be switched by an external signal in synchronization with the drive timing of the means, wherein the sequential color signal generated by the image generating means is
A frame sequential color display device characterized in that the temporal order of a plurality of color signals within the one cycle is changed. 2. The frame sequential color display device according to claim 1, wherein the sequential color signal generated by the image generating means is
Further, the color of the last color signal in the above one cycle and the following 1
A frame sequential color display device characterized in that the color of the first color signal of the cycle is the same. 3. The frame sequential color display device according to claim 2, wherein the color signals of the colors displayed when the liquid crystal shutter is switched from ON to OFF are continuous.
A frame sequential color display device in which the temporal order of a plurality of color signals is changed. 4. The frame sequential color display device according to claim 2, wherein the time of a plurality of color signals is set such that a color signal of a color having a long afterglow time is positioned after color signals of the same color are continuous. A frame-sequential color display device in which the target order is changed. 5. The frame sequential color display device according to claim 1, wherein the temporal order of the color signals is changed every one cycle.