1. Field of the Invention
The present invention is related to a driving method and a related display device, and more particularly, to a driving method and a related display device capable of enhancing image brightness and reducing image distortion.
2. Description of the Prior Art
Liquid crystal displays (LCD), characterized in low radiation, small size and low power consumption, have gradually replaced traditional cathode ray tube (CRT) displays and been widely applied in various electronic devices, such as personal digital assistants (PDAs), flat-panel TVs or mobile phones. When used in portable electronic devices, battery duration is a major concern, but the backlight module of an LCD device consumes large amount of power. Therefore, many techniques capable of adjusting the brightness of the backlight module have been developed for power-saving purpose, commonly referred to as content adaptive backlight control (CABC) method. Although lowering the brightness of the backlight module can reduce power consumption, the overall brightness of the display images is also influenced. Therefore, the LCD device needs to enhance the brightness of the display images based on different image contents in order to maintain the image quality after performing the CABC technique.
In n-bit color depth display devices, each pixel has 2n gray levels, each of which corresponds to a specific voltage level. In other words, various degrees of bright/dark visual performances can be achieved by driving each pixel with 2n distinct voltage levels. Reference is made to
Df—i=Ki*Dp—i;
where i represents gray level;
The relationship between the pixel data Dp_i and Df_i can be described by a partial-linear, non-linear or other specific transfer functions. However, all transfer functions aim at improving the brightness of the display images and only differ in the final effects. Since Ki is generally a floating-point value, the integer pixel data Dp_i are transformed into the floating-point pixel data Df_i after performing data slope. Since the digital-to-analog converter (DAC) of the display device only receives integer data, the floating-point pixel data Df_i have to be rounded off to the integer pixel data Do_i. Based on a predetermined gamma curve, the DAC converts the pixel data Do_i into analog voltages, thereby outputting the corresponding gamma voltage Vo_i for driving the display panel and the pixel data Dp_i for driving the backlight module.
Reference is made to
The present invention provides a driving method capable of enhancing image brightness and reducing image distortion, comprising providing a first input pixel data corresponding to a pixel; generating a second input pixel data by multiplying the first input pixel data by a predetermined rate; obtaining an output pixel data corresponding to the second input pixel data from a predetermined gamma curve; and when receiving the first input pixel data, driving a display panel based on the output pixel data for displaying images and driving a light source of the display panel based on the first input pixel data.
The present invention also provides a driving method capable of enhancing image brightness and reducing image distortion, comprising providing a first input pixel data corresponding to a pixel; generating a second input pixel data by multiplying the first input pixel data by a predetermined rate; providing a first integer and a second integer if the second input pixel data is not an integer, wherein the first integer is the largest integer that is smaller than the second input pixel data and the second integer is the smallest integer that is greater than the second input pixel data; obtaining a first output pixel data corresponding to the first integer and a second output pixel data corresponding to the second integer from a predetermined gamma curve; obtaining a third output pixel data corresponding to the second input pixel data based on the first and second output pixel data; and when receiving the first input pixel data, driving a display panel based on the third output pixel data for displaying images and driving a light source of the display panel based on the first input pixel data.
The present invention also provides a display device capable of enhancing image brightness and reducing image distortion, comprising an image content analyzing circuit for generating a first input pixel data based on an image signal; an analog circuit for generating a second input pixel data by multiplying the input pixel data by a predetermined rate, for obtaining an output pixel data corresponding to the second input pixel data from a predetermined gamma curve, and for providing the output pixel data when receiving the first input pixel data; a display panel for displaying images corresponding to the first input pixel data based on the output pixel data; and a backlight module for providing light based on the first input pixel data.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.
Reference is made to
The method for acquiring the relationship between Dp_i and Vo_i will be described in the following paragraphs. In order for an LCD device to display images, external video signals are first converted into digital signals for image-processing, such as gamma correction or image size/chromatic aberration adjustments. Then the digital signals are converted into analog signals for driving the LCD panel. Regarding gamma correction, the gamma characteristic refers to the relationship between the input signal and the output brightness of a display device. Before delivered to the customer, the gamma characteristic of an LCD device has to be measured for gamma correction. Therefore, when driven based on the corrected gamma curve, the LCD device can perform according to various customer demands.
Reference is made to
When the brightness provided by the backlight module is lowered for reducing power consumption, the present invention drives the display device based on the corrected gamma curve γ′ in order to maintain the overall brightness of the display images. Using the concept of data slope for explanation, the display device of the present invention is required to achieve the display effects of the input pixel data Df_i(Ki*Dp_i) when receiving the input pixel data Dp_i. Although the input pixel data Dp_i may have floating-point values, each can be mapped to a corresponding gamma voltage Vo_i based on the predetermined gamma curve γ. For example, assuming the value of the predetermined gamma curve γ equals to VO1 when the gray scale i of the input pixel data Df_i equals to n, and the display device is required to achieve the display effects when the gray scale of the input pixel data Df_i equals to Ki*n. Ki*n can be mapped to a corresponding gamma voltage VO2 based on the predetermined gamma curve γ, no matter Ki*n is an integer or a floating-point. The gamma voltage VO2 can be used as the corrected gamma voltage Vo_i′ when receiving the input pixel data Dp_i having a gray scale of n. Therefore, based on each input pixel data Dp_i and its corresponding Ki, the gamma voltage corresponding to Ki*Dp_i obtained from the predetermined gamma curve γ can be used as the corrected gamma voltage Vo_i′. Thus, the corrected gamma curve γ′ can be obtained based on the input pixel data Dp_i and the corrected gamma voltage Vo_i′. When the brightness provided by the backlight module is lowered for reducing power consumption, the present invention drives the display device based on the corrected gamma curve γ′ in order to maintain the overall brightness of the display images at a level similar to that when driven based on the predetermined gamma curve γ.
Reference is made to
Vn=(VN−VN+1)n−N(VN−VN+1)+VN
In the second embodiment of the present invention, the gamma voltage Vn obtained by means of interpolation is directly outputted for driving the display panel when receiving the input pixel data Dp_i. When the brightness provided by the backlight module is lowered for reducing power consumption, the present invention can still maintain the overall brightness of the display images.
Reference is made to
In the prior art display device, data slope is performed for acquiring new floating-point gray scales, which need to be rounded off into integers before being inputted to the DAC. Due to the limitation of DAC, image distortions may occur. In the present invention, each gray scale is mapped to a corresponding Vo_i (the output voltage of DAC) based on different Ki. In other words, the relationship between Dp_i and Vo_i is directly obtained instead of changing the input voltage of DAC. Since no rounding-off is performed on the floating-point pixel data Df_i, the present invention can reduce power consumption and maintain the overall brightness of display images while retaining the complete variations in 2n gray levels.
Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention.
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