1. Field of the Invention
The present invention relates to a color value converting technique of a color sequential display. More particularly, the present invention relates to a technique for converting three color values to four color values.
2. Description of Related Art
In a conventional liquid crystal display (LCD), a light source of backlight module is generally designed to be a white light source, for example, a cold cathode tube. Such white light source can provide a backlight source for each pixel through color filters. Regarding a pixel array, a red (R) color filter, a green (G) color filter and a blue (B) color filter are disposed at each pixel position, which may lead to a high cost. Moreover, since the color filters are applied to the LCD, the white light source can be blocked by the color filters, so that a luminance of the LCD is decreased.
Accordingly, a color sequential display applying a color sequentially method and a control circuit is developed according to the conventional techniques. The color sequential display uses light-emitting diodes (LEDs) with various colors to replace the conventional white backlight source, in which the light sources of different colors are alternately lighted on timing to display the colors of the pixels. The conventional LCD uses the color filters to mix colors on a spatial axis, while the color sequential display mixes colors on a time axis through different color light sources, and a principle thereof is that within a time range of a visual staying principle, the R, G and B colors are swiftly switched on the time axis to achieve the color mixing effect.
The color sequential display does not require the color filters, so that the light source is not blocked, and therefore image luminance is increased. Moreover, since the color sequential display applies the LEDs as the light sources, and in coordination with a color display technique of the color sequential method, the color sequential display may have features of lightness, slimness, shortness and smallness, so that a large spatial resolution can be obtained with a low cost. Though the color sequential display has advantages of high resolution, high luminance, high color and small size, disadvantages thereof such as a color break-up (CBU) phenomenon are also derived.
The CBU phenomenon is generated due to that different color fields of an object of an image will fall on different retina points of human eyes due to the features of random saccade and instinct of tracing moving object of human eyes. Therefore, the CBU phenomenon occurs on edges of the object. FIG. 1 is a schematic diagram illustrating a color breakup phenomenon. Referring to FIG. 1, a full color image can be divided into red (R), green (G) and blue (B) sub-images. Display of the full color image can be achieved by swiftly and sequentially displaying the R, G and B sub-images. Taking a white image as an example, when the white image is required to be displayed, a left edge of the white image 100 observed from a moving observation point is a color combination of blue (B) and blue plus green (B+G), and a right edge thereof is a color combination of red (R) and red plus green (R+G), which are not the white (W) color required to be displayed.