Color-sequential display method

This application is a divisional application of U.S. application Ser. No. 11/193,399, filed Aug. 1, 2005, the subject matter of which is incorporated herein by reference.

1. Field of the Invention

The invention relates in general to a display method, and more particularly to a color-sequential display method.

2. Description of the Related Art

With the rapid advance in display technology in recent years, the liquid crystal display (LCD), having the features of slimness, light weight, and low radiation, has gradually become the mainstream display product.

The liquid crystal panel, which includes a number of pixels arranged in a matrix, controls the luminance of the pixel for entire LCD panel to display frames through the input of image data of respective pixels. Since the pixel can only display the grey level from brightness to darkness, other means are needed for the display of colors.

A conventional LCD displays the color through a color filter which displays the three primary color components of a pixel at the same time. Each pixel of the above color filter LCD includes three displaying units respectively corresponding to a red, a green and a blue filters. The red light, green light and blue light displayed via the filter are combined and the colors of the pixel are perceived by the viewer.

Another conventional color-sequential LCD displays color by sequentially displaying the components of the three primary color of a pixel. Each pixel of the above color-sequential LCD includes a displaying unit, which respectively emits red light, green light and blue light respectively from three luminous sources as the backlight source. During a frame time, the pixel sequentially displays three data and red light, green light and blue light sources are correspondingly turned on. Through the persistence of vision, a viewer is able to recognize the color of a pixel.

Compared with the color filter LCD, the color-sequential LCD displays color is without using a color filter, therefore is advantageous in cost saving. Besides, the color-sequential display method, which only requires one pixel to determine the color of a pixel, increases the resolution by three times when used to display the color of an LCD.

However, the color-sequential needs to input image data to a pixel in three times in order to completely input the image data to the pixel, thereby requiring pulses with higher frequency and consequently consuming more power.

On the other hand, an ordinary electronic device would reduce the frame rate of the display to achieve energy saving when at a low power mode. For example, when the frame rate is reduced to 20 Hz from 60 Hz, i.e., from displaying 60 frame data per second to displaying 20 frame data per second. However, due to the decrease in frame rate, the image data displayed according to the conventional color-sequential display method would not be perceived by the viewer as color through the persistence of vision. What the viewer would perceive is the flickering of red, green or blue colors.

It can be seen from the above description that using the color-sequential method to display the LCD color has the advantage of an increased resolution but has its shortcomings at the same time. Therefore, how to reduce the power required for the transmission of image data and enable the color-sequential display method to support a low power mode has become an important issue to be resolved.

According to the object of the invention a color-sequential display method with the advantage of reducing power consumption of image display and having low power mode support is provided.

It is therefore an object of the invention to provide a display method for driving the color-sequential display of the electronic device. When the electronic device is not at low power mode, a first image is displayed first, wherein the first image sequentially uses a second color data and a first color data of the first image to drive the display. Next, a second image is displayed; wherein the second image sequentially uses a second color data and a third color data of the second image to drive the display. When the electronic device is at low power mode, the respective luminance of the first and the second images are obtained. Lastly, the respective luminance of the first image and the second image are sequentially used to drive the display.

Other objects, features, and advantages of the invention will become apparent from the following detailed description of the preferred but non-limiting embodiments. The following description is made with reference to the accompanying drawings.

FIG. 1 is a diagram showing the display process of conventional color-sequential display;

FIG. 2A is a diagram showing the display process of a color-sequential display according to a first embodiment of the invention;

FIG. 2B is a diagram showing the display process of another color-sequential display according to a first embodiment of the invention;

FIG. 3A is a diagram showing the display process of a color-sequential display according to a second embodiment of the invention;

FIG. 3B is a diagram showing the display process of a color-sequential display according to a third embodiment of the invention; and

FIG. 4 is a diagram showing the display process of another color-sequential display according to a second embodiment of the invention.

First Embodiment

Referring to FIG. 1 , a diagram showing the display process of conventional color-sequential display is shown. Take a first image and a second image for example. The first image and the second image respectively include a red data R, a green data G and a blue data B, wherein the first image is displayed at a first frame time FT 1 , and the second image is displayed at a second frame time FT 2 . The display has a red, a green and a blue backlight sources. Conventional color-sequential display method has the first frame time FT 1 from time t 1 to time t 2 divided to time domains TA 1 , TA 2 and TA 3 , and sequentially and respectively displays a red data R 1 , a green data G 1 and a blue data B 1 the first image during the three time domain. So a viewer can recognize the color image of the first frame time FT 1 through the persistence of vision.

To put it more precisely, the red data R 1 of the first image is written to all pixels of the display first during a write period R 1 W of the time domain TA 1 . Next, the red backlight source is turned on during a turn-on period RL of the time domain TA 1 for the red data R 1 to be displayed on the display. Similarly, the green data G 1 of the first image is written to all pixels of the display during a write period G 1 W of the time domain TA 2 . Then, the green backlight source is turned on for the green data G 1 to be displayed on the display during a turn-on period GL of the time domain TA 2 . The blue data B 1 of the first image is written to all pixels of the display during write period B 1 W of the time domain TA 3 . Then, the blue backlight source is turned on for the blue data B 1 to be displayed on the display during a turn-on period BL of the time domain TA 3 .

The second frame time FT 2 from time t 2 to time t 3 is also divided to three time domains, which are time domains TB 1 , TB 2 and TB 3 respectively. The method for displaying the second image during the second frame time FT 2 , which is basically the same with the method for displaying the first image during the first frame time FT 1 , sequentially and respectively displays a red data R 2 , a green data G 2 and a blue data B 2 of the second image during time domains TB 1 , TB 2 and TB 3 .

Referring to FIG. 2A , a diagram showing the display process of a color-sequential display according to a first embodiment of the invention is shown. Like the conventional color-sequential display method, the color-sequential display method of the present embodiment also divides the first frame time and the second frame time respectively to three time domains. However, unlike the conventional color-sequential display method which displays the first image and the second image according to the sequence of red data R, green data G and blue data B, the color-sequential display method of the present embodiment does not display the first image and the second image according to a fixed order of red data R, green data G and blue data B.

In the display method according to the first embodiment, the first frame time FT 1 is divided to three time domains TA 1 , TA 2 and TA 3 , and the red data R 1 , the green data G 1 and the blue data B 1 of the first image is sequentially and respectively displayed during the three time domains. Although the second frame time FT 2 is also divided to three time domains, namely time domains TB 1 , TB 2 and TB 3 respectively, the blue data B 2 , the green data G 2 and the red data R 2 of the second image are sequentially and respectively displayed during the three time domains of the second frame time FT 2 .

Referring to FIG. 2B , a diagram showing the display process of another color-sequential display according to a first embodiment of the invention is shown. When the electronic device is at low power mode, the display method of FIG. 2B instead of FIG. 2A is used to drive the color-sequential display of the electronic device. The display method of FIG. 2B obtains the luminance of the to-be-displayed image first and uses the luminance of the image to drive the display accordingly.

That is, when the electronic device is at low power mode and would like to display the first image during the first frame time FT 1 , the first image in an RGB domain for instance is converted to an YUV image data and written to all pixels of the display during a write period Y 1 W of the first frame time FT 1 using an Y component of the YUV image data as the luminance, then a backlight source is turned on during a turn-on period TL of the first frame time FT 1 for the first luminance of the image to be displayed on the display. In the method of converting the image data from the RGB domain to the YUV domain, the mode of turning on a backlight source during the turn-on period TL of the first frame time FT 1 can use different turn-on modes to turn on backlight source according to the required level of energy saving. For example, turn on the red backlight source, the green backlight source and the blue backlight source at the same time; turn on the three backlight sources with low luminance; turn on at least one of the three backlight sources; or not turn on the backlight source. By doing so, the display method of the first embodiment is able to support the low power mode.

Second Embodiment

Referring to FIG. 3A , a diagram showing the display process of a color-sequential display according to a second embodiment of the invention is shown. Compared with the conventional color-sequential display method, the color-sequential display method of the second embodiment respectively divides the first frame time FT 1 and the second frame time FT 2 to two time domains. The first frame time FT 1 , which is divided to time domains TA 1 and TA 2 , sequentially and respectively displays the green data G 1 and the red data R 1 of the first image during the two time domains. The second frame time FT 2 , which is divided to time domains TB 1 and TB 2 , sequentially and respectively displays the green data G 2 and the blue data B 2 of the second image during the two time domain.

That is, the green data G 1 of the first image is written to all pixels of the display first during the write period G 1 W of the time domain TA 1 , and then the green backlight source is turned on for the green data G 1 to be displayed on the display during the turn-on period GL of the time domain TA 1 . The red data R 1 of the first image is written to all pixels of the display during the write period R 1 W of the time domain TA 2 , and then the red backlight source is turned on for the red data R 1 to be displayed on the display during the turn-on period RL of the time domain TA 2 . The green data G 2 of the second image is written to all pixels of the display during the write period G 2 W of the time domain TB 1 , and then the green backlight source is turned on for the green data G 2 to be displayed on the display during the turn-on period GL of time domain TB 1 . The blue data B 2 of the second image is written to all pixels of the display during the write period B 2 W of the time domain TB 2 , and then the blue backlight source is turned on for the blue data B 2 to be displayed on the display during the turn-on period BL of the time domain TB 2 .

Of the three color data during a frame time, only two color data are displayed in the display method of the second embodiment, thereby reducing the power for transmitting image. For example, refer to FIG. 2A , in the first embodiment, the display sequentially displays two color data, i.e., the blue data B 1 of the first image and the blue data B 2 of the second image. The two color data are at adjacent frames, and thus have little differences. Since both of the two color data use the blue backlight source as the backlight, the second data of the two sequential color data can be left out in the second embodiment without deteriorating image quality. Furthermore, the power consumption can be effectively reduced. As shown in FIG. 3A , only the red data R 1 of the first image is written to all pixels of the display with the red data R 2 of the second image being left out during the write period R 1 W of the time domain TA 2 ; then, the red backlight source is turned on for the red data R 1 to be displayed on the display during the turn-on period RL of the time domain TA 2 .

According to the display method of the second embodiment, the green backlight source is turned on twice as much as the red backlight source and the blue backlight source. In order to keep the display content intact, the backlight sources of three colors of the display are preferably be adjusted accordingly. For example, the luminance of the green backlight source is adjusted to be a half of the red backlight source and blue backlight source. That is, the ratio among the luminance of the red backlight source, the luminance of the green backlight source and the luminance of the blue backlight source is adjusted as 2:1:2, or as shown in FIG. 4 , the turn-on period GL of the time domains TA 1 and TB 1 can be adjusted to be a half of the turn-on period RL of the time domain TA 2 and the turn-on period BL of the time domain TB 2 . That is, the ratio among the turn-on time of the red backlight source, the turn-on time of the green backlight source and the turn-on time of the blue backlight source is adjusted to be 2:1:2.

It can be seen from the above disclosure that the color-sequential display method of the second embodiment only display two color data no matter during the first frame time FT 1 or the second frame time FT 2 , not only effectively reducing the number of color data to be transmitted, but also reducing the power for transmitting the image.

Refer to FIG. 3A , the display method of the second embodiment can keep and have the red data R 2 of the second image written to the write period R 2 W after the red data R 1 is written to the write period R 1 W for the turn-on period RL of the time domain TA 2 to display the red data R 1 and the red data R 2 . Consequently, the color data of the second image is more complete. It is noteworthy that write period R 2 W to which the red data R 2 is written does not necessarily to be immediate next to the write period R 1 W; a time interval is allowed. Besides, the write period R 2 W does not need to begin at turn-on period RL; an earlier start is allowed.

Third Embodiment

Referring to FIG. 3B , a diagram showing the display process of a color-sequential display according to a third embodiment of the invention is shown. FIG. 3B is a variation of the second embodiment, and the same elements with the second embodiment are not repeated here. As shown in FIG. 3B , during a write period R 2 W of the time domain TB 1 , only the red data R 2 of the second image is written to all pixels of the display with the red data R 1 of the first image being left out. Then, during the turn-on period RL of the time domain TB 1 , the red backlight source is turned on for the red data R 2 to be displayed on the display. In short, the second embodiment omits the red data R 2 , while third embodiment omits the red data R 1 instead from the original sequential display of data B 1 , G 1 , R 1 , R 2 , G 2 , B 2 .

On the other hand, in second embodiment or third embodiment, when the electronic device is at low power mode, none of the display method of FIG. 3A , FIG. 3B or FIG. 4 is used to drive the color-sequential display of the electronic device. The to-be-displayed luminance of the image is obtained first, and then the luminance of the image is used to drive display. When the electronic device is at low power mode, the color-sequential display method of the second embodiment or third embodiment is similar to FIG. 2B , and is not repeated here. It can be seen form the above disclosures that the display method of the second embodiment or the third embodiment also supports the low power mode.

The display method disclosed in the above embodiments of the invention has the advantage of reducing power consumption of image display and having low power mode support.

While the invention has been described by way of example and in terms of a preferred embodiment, it is to be understood that the invention is not limited thereto. On the contrary, it is intended to cover various modifications and similar arrangements and procedures, and the scope of the appended claims therefore should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements and procedures.