JP2009180907A - Color light sources for field sequential color display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that the conventional color display cannot easily make the color reproduction gamut as required. <P>SOLUTION: The color display of a field sequential system has a light regulator 10 to control the light amount of each color light source 2-4 in the three primary colors and the light amount in each color field. It changes the chromaticity coordinates in each color field by regulating the light amount of each color light source in each color field and the light amount of other color light sources by using the light regulator, and, further, obtains the white balance by regulating the light amount ratio between the color fields while maintaining the light amount ratio in each color field, and changes the color gamut (from 6 color gamut to 7 color gamut). <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a color light source for a field sequential color display device.

  A field sequential color display device usually has a display element (display panel) for sequentially displaying monochrome video signals divided for three different wavelengths and a light source provided for each different wavelength, for example, an LED light source. A color image is displayed by causing the light source to emit light in synchronization with display of a video signal of a corresponding wavelength (for example, Patent Document 1).

  In the above-described conventional configuration, the color reproduction range in the CIE color system chromaticity diagram is limited to an area range that can be reproduced by three color light sources of RGB (red, green, and blue), and there is a color range that cannot be displayed. In order to expand the color reproduction range, an additional E (emerald) LED can be added to drive the four fields using four color light sources, but the color reproduction range can be expanded. In addition, there is an increase in cost due to the addition of a control circuit therefor. As means for expanding the color reproduction range without increasing the cost, the emission wavelength other than the three primary color light sources is intentionally shifted by changing the peak value and width of the current driving the LED of the specific color. It is known that four fields are constituted by the emission color and the three primary colors of the light source, and the colors are mixed with the number of colors exceeding the three primary colors of RGB to obtain white balance (Patent Document 2). .

In the field sequential method, three primary color components (one more color in Patent Document 2) of display colors of individual color display pixels are time-divided into three (four in Patent Document 2) in the display color display period (one frame). ) In a divided time range (field or color field), and multi-color display or full-color display is performed by sequential additive color mixing within one frame.
On the other hand, different color filter type LCDs (liquid crystal display devices) are widely used. In the color filter system, three color liquid crystal cells having a black and white bidirectional display optical shutter function and RGB three primary color micro color filters are combined in a one-to-one manner to form individual color display pixels, and each color display pixel is spatially divided. Multi-color display and full-color display are performed by the simultaneous additive color mixture of the three colors. In the color filter type LCD, the total light transmittance is considerably low, so that it is essential to add a backlight. As the backlight, a white light source or a three-color light source (three-wavelength fluorescent lamp) is used. However, since the RGB absorption spectrum of the color filter is broad, a three-color light source may be used to obtain high color purity (non-light source). Patent Document 1).

Compared to the RGB micro color filter method, the field sequential type LCD requires a response speed of the liquid crystal panel (cell) that is three times faster, but it does not require a color filter that absorbs light in addition to the polarizer. A bright display can be realized. In addition, since each electrode dot itself of the liquid crystal panel corresponds to each color display pixel on a one-to-one basis, an RGB micro color filter system in which a set of three electrode dots corresponds to one color display pixel Compared to the above, a color display with a resolution three times as high can be realized (Non-Patent Document 1).
JP 2003-280607 A JP 2007-101802 A Shoichi Matsumoto, "Liquid Crystal Display Technology-Active Matrix LCD-" 1996.11.8 first edition, published industrial books

On the other hand, the color gamut required for a color display device varies depending on the application. For example, sRGB for broadcasting equipment, DTP (desktop publishing), and Adobe RGB standard for the printing industry. Therefore, the color display device itself is required to have a color adjustment function, that is, a color management function.
In LCDs typified by ordinary color filter types, color specifications such as color gamut and white balance are fixed at the time of design, so it is difficult to arbitrarily adjust the light source during use. Therefore, at present, color adjustment is performed by correcting pixel data by calculation as an alternative, but for that purpose, a high-performance and expensive dedicated image processing LSI must be developed and mounted. When this correction is performed, the amount of light is reduced because the light is reduced, and the display gradation of the liquid crystal is lowered, so that the color adjustment is not essential.

In addition, the color gamut (gamut :: an area that can be represented by chromaticity coordinates of three primary colors in a chromaticity coordinate space) of a display device that uses an LED as a backlight with respect to sRGB or the like assumed in broadcasting equipment. Widely, when video data is displayed without being processed, a color with a different color from the original color is displayed, so there is a demand for narrowing the color reproduction range.
However, although the conventional field sequential color display device has been devised to expand the color reproduction range as in Patent Document 2, color management is performed in accordance with the demand for narrowing the color reproduction range as described above. I can't find anything to try.

  As described above, the conventional color display device has a problem that it is not easy to adjust the color gamut to the required one.

The present invention made to solve the above problems is as follows.
(1) A color light source for use in a field sequential color display device, comprising a light control means capable of controlling the amount of light for each light source of each of the three primary colors and for each color field. Color light source.
2. A color light source for a field sequential color display device according to claim 1, wherein a color group of four or more primary colors is used instead of the three primary colors, and the number of the color fields is three or four or more. .
(Claim 3) A method of driving a color light source according to claim 1 or 2, wherein the dimming means is used to adjust the color light source responsible for the color field in each color field and other colors. By adjusting the light quantity of the light source, the chromaticity coordinates represented by the color field are changed, and the white light balance is obtained by adjusting the light quantity ratio between the color fields while maintaining the light quantity ratio in the color field. A method for driving a color light source for a field sequential color display device, wherein the area is changed.

  According to the present invention, it is easy to match the color gamut to the required specifications, and it is also easy to switch between color and monochrome.

  FIG. 4 is a schematic block diagram showing an example of the color light source of the present invention. 2, 3, and 4 are light sources (R light source, G light source, and B light source) that emit light of RGB colors, and are configured by LEDs, for example. Each of the light sources 2 to 4 is provided with a light control means 10 capable of controlling the light amount (= light emission time × light intensity) for each light source and each color field of the three primary colors. Such dimming means 10 can be constituted by a small-scale dimming control circuit using an IC (a circuit for controlling the current applied to the light source and the on / off timing of the current), and the cost burden is light.

In the case of a three-color field configuration, only RGB three-color light sources are used. However, in the case of a four-color field configuration, a light source (X light source) 5 that emits a color X other than RGB is added and adjusted in the same manner. The light means 10 may be provided. The X light source 5 may be an E light source described in Patent Document 2.
The color light source of the present invention having these light sources 2, 3, 4 (or 5) and dimming means 10 allows the display panel 20 to sequentially display black and white (including halftone) images corresponding to each color field. Driven synchronously.

The display panel 20 is preferably a liquid crystal panel composed of liquid crystal cells, but is not limited to this. For example, the display panel 20 is a DLP (digital light processing: registered trademark of TI) system using a DMD (digital mirror device). There may be.
Next, a color light source driving method according to the present invention will be described. Hereinafter, the case of a three-color field configuration will be described as an example.

For example, as shown in FIG. 3, the conventional field sequential light source driving sequence is such that only the light source of the responsible color is turned on in each of the red, green, and blue color fields. In such a light source driving sequence, the chromaticity of the lighting color in each color field cannot be changed.
On the other hand, in the present invention, since the color light source includes the light control means 10, the light control means controls the light quantity for each light source of each color by using the light control means, thereby taking a light source drive sequence as shown in FIG. be able to. That is, not only the light source of the color in charge in each color field but also light sources of other colors are turned on. At the time of lighting, the chrominance coordinates represented by the color field are adjusted by adjusting the light quantity of the light source of the color responsible for the color field and the light source of the other colors by the dimming means. The color gamut is changed by adjusting the light quantity ratio between the color fields while maintaining the ratio of the light quantity in the color field and adjusting the light quantity ratio between the color fields.

  For example, in the red field, not only the R light source but also the other two color light sources are set to a light amount lower than that of the R light source and are lit. As a result, the chromaticity of the lighting color in the red field can be adjusted to a desired level (even if red, R is green, G, blue, or B). The white balance can be arbitrarily controlled by adjusting the light quantity ratio between the color fields while maintaining the light quantity ratio among the three color light sources in each color field. Therefore, the color gamut can be easily narrowed, and the white balance can be easily maintained at a desired level.

In FIG. 1, for each light source and each color field, the light intensity is changed by changing the light intensity with a constant light emission time. However, the present invention is not limited to this, and the light emission time is changed without changing the light intensity. The amount of light may be changed by changing both the intensity and the light emission time.
As a result, for example, as shown in the chromaticity diagram of FIG. 2, it is easy to control the chromaticity coordinates of RGB to change the color gamut 6 before the change to a narrower color gamut 7, and this The white balance can be maintained at a desired level while maintaining the color gamut 7. Therefore, the color gamut can be easily adapted to the required specifications.

On the other hand, in the color filter system of a single light source (for example, a white light source), the chromaticity coordinates of the three primary colors are almost uniquely determined by the transmission wavelength characteristics of the color filter, and there is no room for adjustment.
In addition, white balance adjustment is possible with a color filter system having a plurality of color light sources, but the chromaticity coordinates of the three primary colors shift in an unintended direction along with the white balance adjustment, so complex pixel data Unless the calculation is performed, it is difficult to independently control the chromaticity coordinates of the three primary colors and the white balance.

  Comparing the color management method based on the present invention with that based on pixel data calculation, as shown in Table 1, it can be said that the method based on the present invention is much more advantageous.

  Further, in the conventional field sequential color system, since the color of the light source that emits light in one color field is limited to one primary color as shown in FIG. 3, monochrome display cannot be performed. Thus, since two or more primary colors can be emitted simultaneously in one color field, it is easy to switch between color and monochrome.

  The color light source of the present invention is a combination of each light source composed of LEDs that emit light of each color of R, G, and B and a dimming control circuit configured to realize the control function of the dimming means using an IC. This was used for the backlight of an OCB (optical compensation bend) mode liquid crystal display panel to produce a field sequential type liquid crystal display (FS-LCD) having a three-field configuration. In this FS-LCD, by adjusting the chromaticity of the emission color by lighting the three-color light source in each of the red, green, and blue color fields in the dimming control circuit, a color gamut that meets the requirements of sRGB was obtained. .

It is explanatory drawing which shows one example of the light source drive sequence by this invention. It is a chromaticity diagram of the CIE color system. It is explanatory drawing which shows an example of a normal (conventional) field sequential system light source drive sequence. It is a schematic block diagram which shows an example of the color light source of this invention.

Explanation of symbols

1 Visible color region 2 Light source (R light source)
3 Light source (G light source)
4 Light source (B light source)
5 Light source (X light source; X is a color other than RGB)
6 color gamut (before change)
7 color gamut (after change)
10 Light control means (light control circuit)
20 Display panel

Claims (3)

  A color light source for use in a field sequential color display device, comprising a light control unit capable of controlling the amount of light for each light source of each of the three primary colors and for each color field.   The color light source for a field sequential color display device according to claim 1, wherein a color group of four or more primary colors is used instead of the three primary colors, and the number of the color fields is three or four or more.   3. A method of driving a color light source according to claim 1 or 2, wherein the light control means adjusts the light quantity of a color light source in charge of the color field and a light source of other colors in each color field. By changing the chromaticity coordinates represented by the color field and adjusting the light quantity ratio between the color fields while maintaining the light quantity ratio in the color field, the white balance is obtained and the color gamut is changed. A method for driving a color light source for a field sequential color display device.

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