JPH08101672A - Field sequential color display device and its drive circuit - Google Patents

Abstract

PURPOSE: To prevent color split in a field sequential color display. CONSTITUTION: A minimum value is detected from digitized R, G, B signals (three primary colors) for every pixel (a sample) in a minimum value detection circuit 5, and the minimum value is supplied to a four-fold speed signal processing circuit 9 as a Wht signal (achromatic signal). By subtracting the minimum value detected from the R, G, B signals, R', G', B' signals (modified three primary colors signals) are generated, and the modified three primary colors signals are supplied to the four-fold speed signal processing circuit 9. In the four-fold speed signal processing circuit 9, time-division multiplex in which horizontal and vertical synchronizing signals are made four-fold, is performed. By turning on (0 deg. rotation) and/or off (90 deg. rotation) π cells 16, 18 based on the time-division multiplex signal, a color image of which one frame consists of four fields is obtained.

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 and a driving method capable of color display by switching three primary color images for each field or for each one of several sheets.

[0002]

2. Description of the Related Art Conventionally, when two or more colors of light are incident on the human eye, they are mixed on the retina and are perceived as a color different from the incident color. This is called additive color mixing. Color lights that cannot be obtained by using this additive color mixture are R (red), G (green), and B (blue), which are generally called three primary colors of light. An arbitrary color light can be obtained by the additive color mixture of these three independent color lights, which is used as a basic principle of a color display.

Generally in a color display,
Color mixing such as juxtapositional additive color mixing, continuous additive color mixing, and simultaneous additive color mixing is performed. Any of these methods is an additive color mixing method that is caused by the limit of the resolution of the human eye. The above-mentioned continuous additive color mixture is generally called a frame sequential system. This frame sequential system is mainly composed of a color shutter system and a backlight system.
It can be summarized in various types.

FIG. 6 is a block diagram of a conventional example of a frame sequential color display using a color shutter system. Further, FIG. 7 shows an example of the signal waveform of each part of the block diagram shown in FIG. Input terminal 61 to FIG. 7A
The R signal separated from the composite color video signal shown in FIG. 2 is supplied, the same G signal is supplied from the input terminal 62, the same B signal is supplied from the input terminal 63, and the synchronization signal Sync is supplied from the input terminal 64. To be done. Note that FIG.
In A, the illustration of the carrier color signal is omitted for simplicity. These R, G and B signals are digitized by an A / D converter (not shown).

The signals supplied from the input terminals 61 to 64 are supplied to the triple speed signal processing circuit 65. The triple speed signal processing circuit 65 has a field memory 66, compresses the time axis of each signal to 1/3, and time-division-multiplexes the compressed three primary color signals. That is, the triple speed signal shown in FIG. 7B is generated from the triple speed signal processing circuit 65. This triple speed signal is a CRT
(Cathode Ray Tube) It is supplied to the display 67 and the sync separation circuit 68. In the sync separation circuit 68, the sync signal separated from the supplied triple speed signal is supplied to the deflection circuit 69 and L
It is supplied to a CS (Liquid Crystal Switch) drive circuit 70.

In the deflection circuit 69, the CRT display 67 is deflected based on the supplied synchronizing signal, and C
An image is displayed on the RT display 67. Each horizontal and vertical deflection frequency is
R signal, G signal, B within one field
Images of the signals are sequentially displayed. In the LCS drive circuit 70, the drive timing of the π cells 72 and 74 is generated using the supplied synchronization signal.

The drive pulse LCS1 from the LCS drive circuit 70 is supplied to the π cell 72, and the drive pulse LCS2 is supplied to the π cell 74. In this conventional example, the display from the CRT display 67 is a frame-sequential color display by the configuration of three color polarizing plates 71, 73 and 75 and two π cells 72 and 74. FIG. 7C shows a timing chart of the drive pulse LCS1, and FIG. 7D shows a drive pulse LCS.
2 shows a timing chart of No. 2. Here, the π cells 72 and 74 rotate the incident light by 0 ° in the ON state, that is, output the incident light in the state of the incident light, and rotate the incident light by 90 ° in the OFF state and output.

Therefore, when the drive pulse LCS1 is ON and the drive pulse LCS2 is ON, the G image is displayed, and when the drive pulse LCS1 is ON and the drive pulse LCS2 is OFF, the R image is displayed and the drive pulse LCS1 is displayed. OFF, drive pulse LCS2
When is ON, the B image is displayed. That is, a full-color image is displayed by repeatedly displaying the R, G, and B images.

Further, a two-color light shutter means is arranged in front of the image frame sequential display means disclosed in Japanese Patent Publication No. 5-34672, and a nematic liquid crystal variable optical retarder is provided between two polarizing plates and another polarizing plate. There is known a field-sequential color display device having a means for sandwiching.

[0010]

However, these color displays do not cause any problems when the human line of sight is fixed, but when the human line of sight moves, the retina is used because of the frame sequential method. By changing the positions of the remaining colors of the R, G, and B signals above, there is a problem that colors are attached despite the achromatic color.

In FIG. 8A, since the line of sight is fixed,
The positions of the afterimages of the three primary colors corresponding to the white sphere on the retina do not change. However, as shown in FIG. 8B, when the line of sight moves, the positions of the afterimages of the three primary color images are different on the retina, and as a result, there arises a problem that the white sphere appears to be colored.

Even if the line of sight is fixed as shown in FIG. 8A, if the white sphere moves quickly, it does not follow the movement of the white sphere among the R, G, B signals. For example, the R signal is the G, B signal. If it shifts, the position of the afterimage is different on the retina, and the edge of the white sphere appears to be rounded. These phenomena are called color breaks, and as a property of the color breaks, the higher the brightness of the object, the more easily the color breaks can be seen. In addition, the more achromatic objects have the property that color breaks are more visible.

Therefore, an object of the present invention is to provide an area sequential color display device and a driving method capable of displaying without causing color breakup in an area sequential color display.

[0014]

According to a first aspect of the present invention, a monochrome image display means, a color generating means for generating a three-primary-color signal and an achromatic-color signal from input three-primary-color signals, and three generated color-generating means. With the primary and achromatic signals,
A driving means for sequentially driving the monochrome image display means and a color shutter which is switched by a signal from the outside synchronized with the driving of the generated three primary color signals and the achromatic color signal and arranged in series with the monochrome image display means on the optical axis. And a field sequential color display device.

According to the invention of claim 7, a step of detecting an achromatic color signal from the input three primary color signals,
A step of generating a modified three primary color signal on the basis of the detected achromatic color signal;
A step of generating a double-speed time-division multiplexed signal, and a step of driving a monochrome image display means for switching fields based on the time-division multiplexed signal and a color shutter arranged in series on the optical axis. And a field sequential driving method for a color display device.

[0016]

The monochrome image display device is sequentially driven by the R, G, B signals and the Wht signal, which is composed of three color polarizing plates and two π cells. The Wht signal is R, G, B
Since the level shared by the signals is used, the Wht signal becomes more influential than other signals as it approaches a high-luminance, achromatic image. Therefore, it is possible to prevent the occurrence of color breakup even in a high-luminance, achromatic image. Furthermore, since the contour (edge) is emphasized by performing the contour emphasis (emphasis) process on the Wht signal, it is possible to remove the color breakup at the edge portion of the high luminance signal.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a frame sequential color display using a color shutter system. Further, FIG. 2 shows an example of signal waveforms of respective parts of the block diagram shown in FIG. An R signal separated from the composite color video signal shown in FIG. 2A is supplied from the input terminal 1, a similar G signal is supplied from the input terminal 2, a similar B signal is supplied from the input terminal 3, and the input terminal 4 is further supplied. Is supplied with the synchronization signal Sync. In FIG. 2A, the carrier color signal is not shown for simplicity. These R, G and B signals are digitized by an A / D converter (not shown).

The R signal supplied from the input terminal 1 is supplied to the minimum value detection circuit 5 and the subtractor 6. Similarly, the G signal is supplied to the minimum value detection circuit 5 and the subtractor 7, and the B signal is supplied to the minimum value detection circuit 5 and the subtractor 8. The minimum value detection circuit 5 detects the minimum value in the input R, G, B signals, and the detected minimum value is the Wht signal,
It is supplied to the subtracters 6, 7, 8 and the quadruple speed signal processing circuit 9. In the additive color mixture described above, R, G, B of the same level
Since an achromatic signal can be obtained by using the signal, in this embodiment, the levels shared by the three primary color signals,
That is, the minimum value in the R, G, B signals is detected, and the minimum value is supplied as the Wht signal from the minimum value detection circuit 5 to the quadruple speed signal processing circuit 9. This minimum value detection circuit 5
Compares the R signal with the G signal, the G signal with the B signal, and the B signal with the R signal for each digitized pixel (1 sample), and detects the minimum color signal based on the comparison result. To do.

The subtracter 6 supplies the R'signal (corrected R signal) to the quadruple speed signal processing circuit 9 as a result of subtracting the Wht signal from the R signal. Similarly, the subtracter 7 subtracts the Wht signal from the G signal, and as a result, the G ′ signal (corrected G signal) is supplied to the quadruple speed signal processing circuit 9, and the subtracter 8 subtracts the Wht signal from the B signal. , B ′ signals (corrected B signals) are supplied to the quadruple speed signal processing circuit 9. Here, as an example, the R signal is 5
When [V], G signal is 6 [V], and B signal is 4 [V], the minimum value in the minimum value detection circuit 5 is 4 [V].
Is detected, the R ′ signal is 1 [V] and the G ′ signal is 2
The [V] and B ′ signals are 0 [V], and the minimum value, that is, the Wht signal is 4 [V], and the 4 × signal processing circuit 9
Supplied to

The quadruple speed signal processing circuit 9 has a field memory 10, compresses the time axis of each signal to 1/4, and supplies corrected three primary color signals (R ', G', B'signals). Time division multiplexing with an achromatic signal (Wht signal) is performed. That is, the 4 × speed signal shown in FIG. 2B is generated from the 4 × speed signal processing circuit 9. This quadruple speed signal is the CRT display 11
Is supplied to the sync separation circuit 12. In the sync separation circuit 12, the sync signal separated from the supplied quadruple speed signal is supplied to the deflection circuit 13 and the LCS drive circuit 14.

In the deflection circuit 13, the CRT display 11 is deflected on the basis of the supplied synchronizing signal, and C
The image is displayed on the RT display 11, that is, the monochrome display device. Each of the horizontal and vertical deflection frequencies is
It is 4 times the normal one and Wh in one field
Images by the t signal, the R ′ signal, the G ′ signal, and the B ′ signal are sequentially displayed. The LCS drive circuit 14 uses the supplied synchronization signal to generate the drive timing of the π cells 16 and 18.

The drive pulse LCS1 from the LCS drive circuit 14 is supplied to the π cell 16, and the drive pulse LCS2 is supplied to the π cell 18. 2C shows a timing chart of the drive pulse LCS1, and FIG. 2D shows a timing chart of the drive pulse LCS2. The π cells 16 and 18 have the same functions as the π cells 52 and 54 described above. The π cells 16 and 18 are turned on during the high level periods of the drive pulses LCS1 and LCS2, respectively, and the π cells 16 and 18 are turned off during the low level periods.

Here, the description of the three color polarizing plates 15, 17 and 19 and the two π cells 16 and 18 arranged in series on the optical axis of the CRT display 11 will be described with reference to FIG. When the Wht signal (achromatic signal) is taken out, the color light is emitted from the CRT display 11 to the color polarizing plate 1.
5, the vertical axis of the color polarizing plate 15 is R, G,
The B signal is passed and the R signal is supplied to the π cell 16 on the horizontal axis. In the π cell 16, a drive pulse LCS1 (ON) is supplied from the LCS drive circuit 14, and the supplied signal does not change each state according to the drive pulse LCS1 (ON), and the color polarizing plate 17 is supplied.
Supplied to

The vertical axis of the color polarizing plate 17 allows R, G, B signals to pass therethrough, and the horizontal axis allows B signals to pass therethrough. Therefore, the R, G, B signals on the vertical axis of the supplied signals are π cells. 1
8 is supplied. In the π cell 18, the drive pulse LCS2 (ON) from the LCS drive circuit 14 is supplied, and according to the drive pulse LCS2 (ON), the supplied signal is supplied to the color polarization plate 19 without changing each state. It The vertical axis of the color polarizing plate 19 allows R, G, and B signals to pass therethrough, and the horizontal axis allows G signals to pass therethrough. Therefore, from the respective supplied signals, the vertical axes R, G, and
The B signal is output and displayed without changing the respective states. That is, the Wht signal (achromatic signal)
Can be obtained by turning on the π cells 16 and 18. Similarly, turn on the two π cells (0 °
Each of the R, G, B signals, and the Wht signal can be selectively obtained by setting (rotation) and / or OFF (rotation by 90 °).

When the drive pulse LCS1 is ON and the drive pulse LCS2 is ON, the Wht signal is output,
Drive pulse LCS1 is OFF, drive pulse LC
When S2 is ON, the R signal is output, the drive pulse LCS1 is ON, and when the drive pulse LCS2 is OFF, the G signal is output and the drive pulse LCS1 is OF.
When F and the drive pulse LCS2 are OFF, the B signal is output. That is, the three color polarizing plates 15 and 17
And 19, two π cells 16 and 18, respectively. In this way, since the level shared by the R, G, and B signals (three primary color signals) is the Wht signal (achromatic color signal), the influence of the Wht signal is the strongest when displaying an image of high brightness and achromatic color. Therefore, the cause of color breakage can be eliminated.

Here, FIG. 4 shows a detailed block diagram of an example of the quadruple speed signal processing circuit 9 of the present invention. Input terminal 2
The R ′ signal supplied from 1 is supplied to the field memory 26, the G ′ signal supplied from the input terminal 22 is supplied to the field memory 27, and the B ′ signal supplied from the input terminal 23 is the field memory. Supply to 28,
Further, the Wht signal supplied from the input terminal 24 is supplied to the field memory 29. The synchronization signal Sync supplied from the input terminal 25 is supplied to the write control circuit 30 and the clock generation circuit 32. This synchronization signal Syn
c is a composite sync signal including a horizontal sync signal and a vertical sync signal.

In the clock generation circuit 32, a clock signal is generated based on the synchronization signal Sync, and the generated clock signal is supplied to the write control circuit 30 and the read control circuit 31. In the write control circuit 30,
A write signal for storing the signal supplied to each field memory in the memory is generated from the supplied synchronization signal Sync and the clock signal, and is supplied to each field memory. In the field memories 26, 27, 28 and 29 to which the write signal is supplied, the supplied signals are stored for each field. Each signal stored in each field memory is read in response to the read signal supplied from the read control circuit 31, and the switch 33
Is selected, the time division multiplexing is performed and the data is taken out from the output terminal 34.

As an example, the frequency of the read clock signal is four times the frequency of the write clock signal. As a result, the time axis is compressed to 1/4, and
A 4 × speed signal as shown in B is taken out from the output terminal 34. Further, the read control circuit 31 outputs a selection signal and a synchronization signal. The selection signal is used as a switching signal of the switch 33, and is further taken out from the output terminal 35 as a signal for field identification or LCS driving. Further, the sync signal output from the read control circuit 31 is taken out from the output terminal 36 as a composite sync signal for driving the deflection system of the CRT display.

FIG. 5 is a block diagram showing another embodiment of the frame sequential color display using the color shutter system of the present invention. In FIG. 5, R, G,
A block diagram from the input of the B signal to the quadruple speed signal processing circuit 9 is shown, and the quadruple speed signal processing circuit 9 and subsequent components have the same configuration as the block diagram of FIG. The digitized R signal supplied from the input terminal 1 has already been γ-corrected, and therefore is supplied to the inverse γ-correction circuit 41 and converted into a signal before γ-correction. Similarly, input terminal 2
The digitized G signal supplied from the input terminal 3 is supplied to the inverse γ correction circuit 42, and the digitized B signal supplied from the input terminal 3 is supplied to the inverse γ correction circuit 43.

In the inverse γ correction circuit 41 supplied with the R signal, the γ correction is canceled. Similarly, the reverse γ correction circuit 42 supplied with the G signal cancels the γ correction, and the reverse γ correction circuit 43 supplied with the B signal cancels the γ correction. The minimum value detection circuit 5 detects the minimum value in the R, G, B signals for which the γ correction has been canceled, and this minimum value detection circuit 5 outputs R for each digitized pixel (1 sample), for example. The signal and the G signal, the G signal and the B signal, the B signal and the R signal are compared, and the minimum color signal is detected based on the comparison result. The detected minimum value is supplied to one selected terminal of the emphasis circuit 45 and the switch 46 as the Wht signal as in the above-described embodiment. In the emphasis circuit 45, the supplied Wht signal is subjected to contour emphasis processing to emphasize the contour (edge), and is supplied to the other selected terminal of the switch 46.

In the brightness detection / motion detection circuit 44, brightness detection is first performed, and a brightness level showing a value higher than the set threshold value is detected as high brightness, and motion is detected only when high brightness is detected. Detection is done. The motion detection performed by the luminance detection / motion detection circuit 44 is detected from the motion amount from the inter-field difference, and the switch 46 is controlled based on the motion amount. That is, the switch 46
When transmitting the Wht signal, whether or not to transmit the Wht signal subjected to the emphasis processing is selected.
Then, the Wht signal is supplied to the subtractors 6, 7, 8 and the γ correction circuit 50 via the selection terminal of the switch 46.

The subtracter 6 subtracts the Wht signal from the R signal for which the γ correction has been canceled, and as a result, an R ′ signal (corrected R signal) is generated. The R ′ signal is the γ correction circuit 47.
Supplied to Then, in the γ correction circuit 47, the R ′ signal is subjected to γ correction and then supplied to the quadruple speed signal processing circuit 9. Similarly, in the subtractor 7, a G ′ signal (corrected G signal) is generated as a result of subtracting the Wht signal from the G signal for which the γ correction has been canceled, and the G ′ signal is supplied to the γ correction circuit 48. Then, in the γ correction circuit 48, G
The γ signal is subjected to γ correction and then supplied to the quadruple speed signal processing circuit 9.

Further, in the subtractor 8, a B'signal (corrected B signal) is generated as a result of subtracting the Wht signal from the B signal in which the γ correction is canceled, and the B ′ signal is supplied to the γ correction circuit 49. To be done. Then, in the γ correction circuit 49,
After the B ′ signal is subjected to γ correction, it is supplied to the quadruple speed signal processing circuit 9. Further, the Wht signal supplied to the γ correction circuit 50 is subjected to γ correction and then supplied to the quadruple speed signal processing circuit 9. The quadruple speed signal processing circuit 9 is based on the Sync signal supplied from the input terminal 4 as shown in FIG. 1, and is based on the R ′ signal, the G ′ signal, the B ′ signal and the W ′ signal.
The ht signal is processed.

According to another embodiment, in the case of a white sphere as shown in FIG. 8, when the minimum value is detected and the minimum value (Wht signal) detected from each R, G, B signal is subtracted, the white sphere is detected. Since the inside is the same level, the subtraction result must be 0. However, when the white sphere moves fast, especially at the edge portion, the difference between the minimum value and the R, G, B signals does not become 0, so that color breakup occurs at the edge portion. In order to prevent this color breakup, the emphasis circuit 45 performs emphasis processing for edge enhancement on the Wht signal. Further, by subtracting each R, G, B signal by using the Wht signal which has been subjected to the emphasis processing, it is possible to obtain the effect that each R, G, B signal is band-limited. That is, from R, G, B signals to W
By subtracting the ht signal, the effect of rounding the edges can be obtained. As a result, the color breakup at the edge portion becomes inconspicuous.

Further, when the white sphere moves as shown in FIG. 8, according to human visual characteristics, when the white sphere moves very slowly, the rounding of the edge cannot be recognized, and the white sphere moves further. Even if it is very fast, it is not possible to recognize the rounding of edges. Therefore, the motion detection used in this embodiment detects whether or not there is a motion amount capable of recognizing an edge dullness according to human visual characteristics,
It is determined whether the emphasis process is performed.

Here, in this embodiment, a CRT display is used for the frame sequential color display device, but an LCD (Liquid Cry) is used instead of the CRT display.
Other monochrome pixel display devices such as stalDisplay) can also be used.

When an LCD is used, it is possible to arrange a color polarizing plate and a π cell between the backlight and the liquid crystal.

Further, in this embodiment, the R ', G', B'signals (corrected three primary color signals) and the Wht signal (achromatic color signal) are generated by detecting the minimum value.
There is no problem even if the maximum value is used instead of the minimum value.

[0039]

According to the present invention, R, G, B signals (3
In a frame sequential color display in which four fields of primary color signal) and Wht signal (achromatic color signal) make up one frame, R, Since the influence of the Wht signal, which is a shared level of the G and B signals, is the strongest, it is possible to eliminate the cause of color breakup.

Further, according to the present invention, the edges are blurred by limiting the frequency bands of the R, G and B signals,
Since the edge is emphasized by performing the emphasis processing on the Wht signal, it is possible to remove the color breakup which has occurred at the high brightness, achromatic edge portion.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a frame sequential color display using a color shutter system of the present invention.

FIG. 2 is a timing chart showing an example of a color display according to the present invention.

FIG. 3 is a schematic diagram showing an example for explaining a π cell.

FIG. 4 is a block diagram showing an example of a 4 × speed processing device according to the present invention.

FIG. 5 is a block diagram showing another embodiment of a frame sequential color display using the color shutter system of the present invention.

FIG. 6 is a block diagram showing an example of a frame sequential color display using a conventional color shutter system.

FIG. 7 is a timing chart of an example of a conventional color display.

FIG. 8 is a schematic diagram showing an example for explaining color breakup.

[Explanation of symbols]

 5 Minimum value detection circuit 9 4x signal processing circuit 11 CRT display 12 Sync separation circuit 13 Deflection circuit 14 LCS drive circuit 15, 17, 19 Color polarization plate 16, 18 π cell

Claims (7)

[Claims] 1. A monochrome image display means, a color generation means for generating a three-primary-color signal and an achromatic color signal from an input three-primary-color signal, and the generated three-primary-color signal and an achromatic color signal,
It is switched by a driving means for sequentially driving the monochrome image display means and an external signal synchronized with the driving of the generated three primary color signals and the achromatic color signal, and is arranged in series on the optical axis with the monochrome image display means. A frame sequential color display device consisting of a color shutter. 2. The frame sequential color display device according to claim 1, wherein the color generating means detects a minimum value or a maximum value from the input three primary color signals and detects the detected minimum value or An achromatic color signal determining means having a maximum value as an achromatic color signal, and a difference value between the determined achromatic color signal and the input three primary color signals is used as a modified three primary color signal. apparatus. 3. The frame sequential color display device according to claim 1, wherein the color generating means detects a minimum value or a maximum value from the input three primary color signals, and the detected minimum value or An achromatic color signal determining means for making the maximum value an achromatic color signal, a means for performing edge enhancement processing on the achromatic color signal from the achromatic color signal determining means, and the achromatic color signal with the separation emphasis input A frame sequential color display device, characterized in that a difference value from the three primary color signals is used as a modified three primary color signal. 4. The frame sequential color display device according to claim 3, wherein the luminance levels for detecting the luminance levels of the three primary color signals and the motion /
A frame-sequential color display device, characterized in that it comprises a motion detecting means and the contour enhancement processing is performed when the detected brightness level is high. 5. The frame sequential color display device according to claim 4, wherein the motion level from the brightness / motion detecting means is larger than a first threshold value and smaller than a second threshold value. A frame-sequential color display device characterized in that the above-mentioned contour enhancement processing is performed. 6. The frame sequential color display device according to claim 1, wherein said driving means time-division-multiplexes said three primary color signals and achromatic color signals generated by said color generating means at a quadruple speed. A field-sequential color display device characterized by sequentially driving the monochrome image display means. 7. A step of detecting an achromatic color signal from the input three primary color signals, a step of generating a modified three primary color signal based on the detected achromatic color signal, the achromatic color signal and the modified A step of generating a time-division multiplexed signal at a speed four times higher than that of the three primary color signals, and a monochrome image display means for switching fields based on the time-division multiplexed signal and a color shutter arranged in series on the optical axis are driven. And a step-sequential driving method for a color display device, which comprises: