JP2002149129A - Color sequential display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To alleviate such problems as color break, high subframe frequency and memory capacity increase of the conventional color sequential type display and to provide a method of realizing this display easily. SOLUTION: In the color sequential type display device that is constituted of light sources which emit the light of the primary colors sequentially and light valves which control the transmittance of every pixel in synchronism with the light emission of the light sources and reproduce color images by displaying the primary color images sequentially, the light valves have pixels using color filters which transmits a plurality of primary colors simultaneously.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color sequential display device for reproducing a color image by sequentially displaying basic color images.

[0002]

2. Description of the Related Art In recent years, a color sequential display having a configuration as shown in FIG. 7 has been used as an example. This display has a light source 11 that sequentially emits three primary colors.
And a light valve 12 that displays an image as a change in transmittance in synchronization with the light emission of the light source. light source
Numeral 11 is used as a surface-emitting light source in which the brightness is made uniform over the entire surface by a scattering plate or the like.

FIG. 8 shows a time sequence. Light sources of three primary colors (R: red, G: green, B: blue) are sequentially emitted 22 during one frame 21 for displaying one entire color image,
Display the corresponding color image on the light valve in synchronization with it
A sub-frame 24 is provided. In the sub-frame, first, electrical writing 23 of data to each pixel of the light valve is performed. Second, when data is written to each pixel, the liquid crystal of each pixel responds, but the response requires a certain time. Normally, writing is performed sequentially from the top of the light valve, so the liquid crystal response starts in order from the top,
The liquid crystal of the whole light valve completes the response, and the image is prepared on the light valve as a pattern of transmittance.
The last pixel written at the bottom is the end of writing,
This is the timing at which the liquid crystal at that position completes the response. Therefore, thirdly, in the color sequential display, the backlight emits light at this timing 22, and the image is displayed as a luminance pattern.

As an example, in the case of a video signal, one frame is about 16.7 msec.
6msec. By making the one-frame time sufficiently short, the primary colors become indistinguishable to human vision, and the colors overlap to achieve color display.

In this method, one dot corresponds to one color pixel as a result, so that three times higher resolution can be obtained as compared with a method in which a liquid crystal panel is provided with a color filter, and no color filter is used. Therefore, since this absorption can be omitted, the transmittance can be tripled, and as a result, the power consumption can be reduced to ３.

In the following, the color emitted by the light source between sub-frames will be referred to as a basic color.

[0007]

However, the conventional color sequential display has the following problems.

(1) Occurrence of a color break As shown in FIG. 9, when a line of sight tracks a moving object, there is a color break phenomenon in which the outline 31 is colored, and in the color sequential system, it occurs in principle. . If the frame frequency is increased, the frequency is reduced, but a high-speed response is required for the display device, and the following problem (2) occurs instead.

(2) Insufficient liquid crystal panel high-speed driving performance and liquid crystal high-speed response performance Liquid crystal panel high-speed driving three times faster than the color filter system and liquid crystal responsiveness are required. If this is insufficient, problems such as a decrease in contrast occur.

(3) Increase in Cost of Adding Memory to Convert to Field Sequential Signal The field sequential system requires a drive circuit shown in FIG. 42 is an RGB sync separation circuit, 43 to 45
Is a scanning speed conversion circuit for R, G, B including a memory, respectively, and 47 is a backlight drive circuit for causing the light source 11 to sequentially emit light.

As shown in FIG. 10, a scanning speed conversion circuit 43 separates an input video signal 41 into image signals of three primary colors of RGB and sequentially displays the separated image signals on a liquid crystal panel at triple speed. , 44, 45, and a memory for storing temporary information in this circuit is required. In the above conventional example, the memory needs three primary colors and three screens.

An object of the present invention is to solve the above-mentioned problems of the conventional color sequential system and to provide a color sequential display device which can be easily realized.

[0013]

According to a first aspect of the present invention, there is provided a light source for sequentially emitting light of a basic color, and a light valve for controlling transmittance of each pixel in synchronization with light emission of the light source. In a color sequential display device that reproduces a color image by sequentially displaying images,
The light valve is a color sequential display device including pixels using a color filter that transmits a plurality of basic colors simultaneously.

According to a second aspect, in the color sequential display device according to the first aspect, the basic colors are three primary colors of red, green, and blue, and the color filter is:
The color sequential display device is characterized by two types of filters: a filter that transmits red and green simultaneously and a filter that transmits green and blue simultaneously.

According to a third aspect of the present invention, in the color sequential display device according to the first or second aspect, the light source comprises a light emitting diode (LED).

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a diagram showing a configuration example of a color sequential display device according to the present invention.

In this embodiment, a backlight (light source) 51,
It comprises a liquid crystal panel 52 as a light valve and a color sequential drive circuit 53. Further backlight
Reference numeral 51 designates three types of LEDs (light emitting diodes) 54 for emitting three primary colors of red, green and blue, which are arranged in sufficient numbers to emit necessary luminance. A scattering plate 55 for preventing color unevenness of a light beam is disposed on the LED. With this configuration,
The LED backlight emits the necessary primary colors according to the signal from the drive circuit, and has a uniform brightness with the scattering plate 55, and serves to illuminate the liquid crystal panel 52 disposed above.

Since the LED can be driven at a high response speed of about 1 μsec, it is most suitable for pulse emission of about 1 msec required by the color sequential method. Further, since the spectrum width is narrow, there is an advantage that a filter for transmitting two colors used in the present invention can be easily designed.

Next, in this embodiment, the liquid crystal panel 52
A TN (twisted nematic) mode TFT (thin film transistor) liquid crystal panel was used. The configuration consists of a TFT glass substrate provided with a polarizing plate and a pixel driving circuit, a counter glass substrate, and a TFT glass substrate.
N-mode liquid crystal and color filters.

However, the scope of application of the present invention is not limited to the above. The following method can be applied to all light valves that control light transmittance for each pixel.

A first feature of the present invention is a color filter.
61,62. The color filters are arranged as a set of two pixels as shown in FIG. 2, and the spectral transmission characteristics of each are as shown in FIG. The first filter 61 is
The second filter 62 transmits green and blue as shown in FIG. 3 (b), while transmitting red and green as shown in FIG. 3 (a). The two-dimensional arrangement method can be either FIG. 4A in which the filters 61 and 62 are arranged alternately in one row or FIG. 4B in which the filters 61 and 62 are alternately arranged for each filter, and can be selected according to the purpose of use.

The second feature of the present invention resides in a method of emitting a backlight and a method of displaying an image on a liquid crystal panel. FIG. 5 shows a timing chart.

One frame 91 constituting the entire image is composed of two types of subframes 92 and 93. First subframe 92
First, the separated green signal is supplied to the liquid crystal panel 52 from the input signal in the color sequential driving circuit 53 in advance, and a green image is displayed 94. The reason why there is an interval 95 between writing and backlight emission in the timing chart is to secure the liquid crystal response time,
It can be changed depending on the liquid crystal used. With the transmittance pattern corresponding to the green image prepared on the liquid crystal panel 52 in this way, only the green LED 510 emits light 96 at the end of the first sub-frame. Then, the color filters of the liquid crystal panel both transmit the green color, so that a green image is displayed.

Next, in the second sub-frame 93, the red and blue separated by the color sequential drive circuit 53
A filter that is supplied with a kind of video signal and transmits red and green
A circuit in the liquid crystal panel is configured so that a red signal is written to a pixel having 57 and a blue signal is written to a pixel having a filter 58 that transmits green and blue. As a result, after the liquid crystal response time 98, transmittance patterns corresponding to red and blue images are prepared on the liquid crystal panel 52. So, at the end of the second subframe 93, the red and blue
When the LEDs 511 and 512 are turned on at the same time, the red and blue images are correctly displayed simultaneously through the corresponding filters of the pixels.

Of course, the resolution of the red and blue images is half that of green, but human visibility is highest in green and the resolution is mainly determined by green. Has little effect on resolution.

The structure of the sub-frames 92 and 93 is as follows.
It is not limited to the configuration of the above embodiment. The order of the first and second sub-frames 92 and 93 can be exchanged, and the sub-frames 92 and 93 can be repeated a plurality of times to prevent a color break.

Next, FIG. 6 shows an example of a circuit configuration of the color sequential drive circuit 53 of the present embodiment. 71 is an RGB sync separation circuit, 72 is a G scanning speed conversion circuit including a memory, 73 is an R and B scanning speed conversion circuit, 74 is a timing control circuit, and 75 is a backlight drive circuit. The difference from the prior art is that, as described above, in the present embodiment, the memory is reduced to two screens because it is composed of two types of subfields.

Finally, the performances of the present system, the conventional color sequential system, and the color filter system are compared using a table.

[0030]

[Table 1]

As is apparent from Table 1, in this embodiment,
As with the conventional sequential system, the most important green that determines the resolution and brightness is three times the color filter system, while the color break, subframe frequency, and memory usage are 1/2, 2/3, and 3/3 respectively. It has been reduced to 2/3. From the above results, by using this method, it is possible to provide a color sequential type display device which can solve the problems such as color break, subframe frequency, and memory usage while maintaining most of the advantages of the color sequential method. .

[0032]

According to the present invention, the subframe 2/3, the color break 1/2, the used memory 2 /
3, a color sequential display device with few disadvantages can be realized.

[Brief description of the drawings]

FIG. 1 is a diagram showing one configuration example of the present invention.

FIG. 2 is a diagram illustrating a configuration example of a color filter.

FIG. 3 is a diagram illustrating spectral characteristics of a color filter.

FIG. 4 is a diagram illustrating an example of the arrangement of color filters.

FIG. 5 is a timing chart illustrating a display method.

FIG. 6 is a block diagram illustrating a configuration example of a driving circuit.

FIG. 7 is a diagram showing a conventional configuration example.

FIG. 8 is a timing chart illustrating a conventional display method.

FIG. 9 is a diagram for explaining a conventional color break.

FIG. 10 is a block diagram illustrating a configuration example of a conventional driving circuit.

[Explanation of symbols]

 Reference Signs List 51 backlight 52 liquid crystal panel 510 red LED 511 green LED 512 blue LED 53 color sequential drive circuit 61 first color filter 62 second color filter

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Claims (3)

[Claims] 1. A light source that sequentially emits basic colors and a light valve that controls the transmittance of each pixel in synchronization with the light emission of the light source. A color sequential display device for reproducing, wherein the light valve has pixels using a color filter that transmits a plurality of basic colors at the same time. 2. The color sequential display device according to claim 1, wherein the basic colors are three primary colors of red, green, and blue, and the color filters are a filter that transmits red and green simultaneously, and a filter that transmits green and blue. A color sequential display device comprising two types of filters that transmit light simultaneously. 3. The color sequential display device according to claim 1, wherein the light source comprises a light emitting diode (LED).