Patent Application
20110074751
The present invention relates to a contrast ratio improving device and a contrast ratio improving method for use with a display panel. The present invention also relates to an image display system having such a contrast ratio improving device and using such a contrast ratio improving method.
A contrast ratio is a measure of a liquid crystal display (LCD) panel. When the LCD panel is in a dark room, the contrast ratio is defined as the ratio of the luminance value of the brightest color (white) to the luminance value of darkest color (black). As the brightness of the white color and the darkness of the black color are increased, the contrast ratio is increased. A high contrast ratio indicates a better image quality of the LCD panel. Nowadays, the LCD manufacturers make efforts in designing LCD panels with high contrast ratios.
Ideally, the contrast ratio is defined as the ratio of the luminance value obtained when the pixel voltage is zero to the luminance value when the pixel voltage is equal to the reverse voltage. In other words, a highest contrast ratio of the LCD panel is obtained when the maximum pixel voltage (i.e. the black voltage) is set to the reverse voltage. Due to the process variations of LCD panels, the relationships between the pixel voltage and the transmittance of different LCD panels are usually distinguished. For example, the Curve 1 has a first reverse voltage (RV1), the Curve 2 has a second reverse voltage (RV2), and the Curve 3 has a third reverse voltage (RV3). The first reverse voltage (RV1), the second reverse voltage (RV2) and the third reverse voltage (RV3) fall into a voltage range 10. For preventing from occurrence of the gray level inversion, the LCD manufacturers usually define a constant value below the lower limit of the voltage range 10 as the common black voltage of different LCD panels. In other words, there is a shift between the common black voltage and the reverse voltage. Under this circumstance, the obtained contrast ratio is not optimal.
Therefore, there is a need of providing a contrast ratio improving device and a contrast ratio improving method so as to obviate the drawbacks encountered from the prior art.
In accordance with an embodiment of the present invention, there is provided a contrast ratio improving method for use with a display panel. Firstly, multiple voltage values are applied to the display panel. Then, the brightness values corresponding to the voltage values applied to the display panel are detected. Afterwards, a voltage value corresponding to a specified value of the brightness values is selected as a peak voltage of the display panel.
In accordance with another embodiment of the present invention, there is provided a contrast ratio improving device for use with a display panel. The contrast ratio improving device includes a controller and a photo detector. The controller is electrically connected to the display panel for applying multiple voltage values to the display panel, so that the display panel exhibits multiple brightness values corresponding to the voltage values applied to the display panel. The photo detector is electrically connected to the controller for detecting the brightness values, converting the brightness values into corresponding electronic signals, and transmitting the electronic signals to the controller. According to the electronic signals, the controller selects a voltage value corresponding to a specified value of the brightness values as a peak voltage of the display panel.
In accordance with another embodiment of the present invention, there is provided an image display system. The image display system includes a display device and a power supply. The display device has a display panel and the contrast ratio improving device of the present invention. The power supply is electrically connected to the display device for providing electric energy to power the display device.
In accordance with another embodiment of the present invention, there is provided an image display system. The image display system includes a display panel, a memory and a power supply. The memory stores a peak voltage obtained by the contrast ratio improving method of the present invention. The power supply is electrically connected to the display panel for providing electric energy to power the display panel.
The above contents of embodiments of the present invention will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed description and accompanying drawings, in which:
The present invention will now be described more specifically with reference to the following embodiments. It is to be noted that the following descriptions of preferred embodiments of this invention are presented herein for purpose of illustration and description only. It is not intended to be exhaustive or to be limited to the precise form disclosed.
If these voltage values fall into the voltage range 10 as shown in
In a case that the display panel 20 is a normally white LCD panel, the extreme value of the brightness values is the minimum value of the brightness values and the peak voltage is a black voltage. In response to the voltage ranged from zero to the peak voltage (i.e. the black voltage), the driver IC 24 will drive the normally white LCD panel to exhibit multiple values of the brightness values. Whereas, in a case that the display panel 20 is a normally black LCD panel, the extreme value of the brightness values is the maximum value of the brightness values and the peak voltage is a white voltage. In response to the voltage ranged from zero to the peak voltage (i.e. the white voltage), the driver IC 24 will drive the normally black LCD panel to exhibit multiple values of the brightness values.
The memory 23 is for example a non-volatile memory such as an erasable non-volatile memory (e.g. a flash memory) or a one-time programming (OTP) non-volatile memory. The memory 23 can be integrated into the driver IC 24 or other IC. Alternatively, the memory 23 can be separated from the driver IC 24. An example of the image display system 600 includes but is not limited to a mobile phone, a digital camera, a personal digital assistant, a notebook computer, a desktop computer, a TV set, a global positioning system (GPS), an automotive display system, a flight display system, a digital photo frame, a portable DVD player, and the like. Some embodiments of the present invention are illustrated by referring to a LCD device. Nevertheless, the present invention is applicable to other display device such as an organic light emitting diode (OLED) device.
While the invention has been described in terms of what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention needs not to be limited to the disclosed embodiment. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.
