These and other objects of the invention will be apparent from the following detailed description of the embodiments of the present invention with reference to the accompanying drawings, in which:
Hereinafter, the preferred embodiments of the present invention will be described in detail with reference to
Referring to
The pixels 128 are arranged in a matrix type at the OLED panel 120. Further, a supply pad 110 and a ground pad 112 are disposed at the OLED panel 120. Herein, the supply pad 110 is supplied with a high-level potential voltage from a high-level potential voltage source VDD. The ground pad 112 is supplied with a ground voltage from a ground voltage source GND. In this case, the high-level potential voltage and the ground voltage are supplied to each pixel 128.
The gate driving circuit 122 is comprised of a shift register, a level shift, and an output buffer, etc. Herein, the shift register sequentially generates a scanning signal in response to a gate control signal GDC from the timing controller 127. The level shift shifts a swing width of a scanning signal into a level that is adaptive for a driving of the pixels 128. The gate driving circuit 122 supplies a scanning signal to the gate lines GL to turn-on switching TFTs which are connected to the gate lines CL, thereby selecting the pixels 128 of one horizontal line to be supplied with an analog gamma voltage.
The data driving circuit 124 is comprised of a shift register, a register, a latch, a digital/analog converter, a multiplexer, and an output buffer, etc. Herein, the register temporarily stores digital video data R′G′B′ which are modulated from the timing controller 127. The latch stores data by one line in response to a clock signal from the shift register and, at the same time outputs the stored one line data. The digital/analog converter selects an analog positive polarity/negative polarity gamma voltage corresponding to a digital data value from the latch. The multiplexer selects the data line DL to which the analog positive polarity/negative polarity gamma voltage is supplied. The output buffer is connected between the multiplexer and the data line DL. The data driving circuit 124 is inputted with the modulated digital video data R′G′B′, and supplies the data R′G′B′ to the data lines DL of the OLED panel 120 to be synchronized with a scanning signal under a control of the timing controller 127. As a result, an image having brightness corresponding to a gray scale of the modulated data is displayed at the OLED panel 120.
The gamma voltage generator 126 supplies a plurality of analog gamma voltage to the data driving circuit 124. Herein, the gamma voltage generator 126 generates a positive polarity gamma voltage and a negative polarity gamma voltage which have a predetermined tilt corresponding to a characteristics of the OLED panel 120.
The data modulating circuit 125 analyzes a histogram for each screen, that is, an accumulated density distribution of a pixel for each predetermined gray scale range, and modulates a digital data of an input image to allow a gamma curve tilt within a predetermined gray scale range to be changed on the basis of the analyzed result. Herein, a gamma curve of the entire gray scale ranges regarding digital data of the input image is determined depending upon a reference tilt which is differently set for each gray scale range. The data modulating circuit 125 modulates a digital data of an input image to allow a tilt of a gamma curve of high gray scale range to be lowered than a reference tilt in the case where data of an input image are dominantly shown within the pre-set high gray scale range. The organic light emitting diode display according to the present invention partially reduces brightness of a high-level brightness image using the data modulating circuit 125 to prevent a deterioration of a life span of the organic light emitting diode device. Furthermore, the data modulating circuit 125 modulates a digital data of an input image to allow a tilt of a gamma curve of the specific gray scale range to be heightened than a reference tilt in the case where data of an input image are dominantly shown within the pre-set specific gray scale (low gray scale) range. The organic light emitting diode display according to the present invention partially increases brightness of a low brightness image using the data modulating circuit 125 to prevent a deterioration of uniformity of an image in a low gray scale range. On the other hand, the data modulating circuit 125 modulates a digital data of an input image to allow a tilt of a gamma curve of the high gray scale range and the specific gray scale range to be fixed to a reference tilt in the case where data of an input image are not dominantly shown within the pre-set high gray scale range and the pre-set specific gray scale range. The data modulating circuit 125 can be mounted within the timing controller 127.
The timing controller 127 re-arranges the modulated digital video data R′G′B′ which are supplied from the data modulating circuit 125 in accordance with a resolution of the OLED panel 120 to supply it to the data driving circuit 124. Furthermore, the timing controller 127 generates a data control signal which controls the data driving circuit 124 and a gate control signal which controls the gate driving circuit 122 using a plurality of synchronizing signals. A data control signal generated from the timing controller 127 is supplied to the data driving circuit 124 to control the data driving circuit 124. A gate control signal generated from the timing controller 127 is supplied to the gate driving circuit 122 to control the gate driving circuit 122.
Referring to
The input part 220 is inputted with digital video data RGB and a synchronizing signal from the exterior. The input part 220 supplies the inputted digital video data RGB to the image analyzing part 240.
The image analyzing part 240 analyzes an image property of digital video data RGB which are supplied from the input part 220, and supplies a control signal corresponding to the analyzed image property to the data modulating part 280. A variety of methods can be used for analyzing an image property of data in the image analyzing part 240. In other words, the image analyzing part 240 arranges data by one frame to be corresponded to a plurality of gray scale ranges to generate a histogram. Herein, the gray scale ranges can diversely divided in accordance with an OLED characteristics. In the embodiment of the present invention, for the sake of explanation, the gray scale ranges will be divided into a minimum gray scale range (min to a) a low gray scale range (a to b), an intermediate gray scale range (b to c), and a high gray scale range (c to max) as shown in
The data modulating part 280 modulates a gray scale value of the digital video data which are supplied from the input part 220 using a look-up table LUT which is stored at the memory 260 in response to the data modulating control signal Cdm from the image analyzing part 240. Output data R′G′B′ are mapped to the look-up table LUT. Herein, the output data R′G′B′ have a second gray scale value corresponding to input data RGB which have a first gray scale value. In this way, the data modulating part 280 modulates the input data RGB to allow a gray scale value of the output data R′G′B′ to be further lowered than a gray scale value of the input data RGB when an accumulated density of a pixel regarding the high gray scale range (c to max) exceeds over the pre-set reference value. Furthermore, the data modulating part 280 modulates the input data RGB to allow a gray scale value of the output data R′G′B′ to be further heightened than a gray scale value of the input data RGB when an accumulated density of a pixel regarding the low gray scale range (a to b) exceeds over the pre-set reference value.
If the data modulating control signal Cdm is supplied from the image analyzing part 240 to the data modulating part 280, the memory 260 supplies a gray scale value of the output data R′G′B′ regarding a gray scale value of the input data RGB at the low gray scale range (a to b) and the high gray scale range (c to max) to the data modulating part 280. A plurality of look-up tables (LUT1, . . . ,LUTi) are stored at the memory 260. Accordingly, the memory 260 to which a control signal is supplied from the image analyzing part 240 supplies look-up table LUT information corresponding to a control signal to the data modulating part 280. The look-up table LUT is experimentally determined in order to realize an optimum image and prevent a deterioration of a life span of the organic light emitting diode device OLED corresponding to a variety of image properties. For example, the look-up table LUT that improves an input versus output ratio at the low gray scale range (a to b) corresponding to data of a dark image property is stored at the memory 260. Furthermore, the look-up table LUT that lowers an input versus output ratio at the high gray scale range (c to max) corresponding to data of a bright image property to prevent a deterioration of a life span of the organic light emitting diode device OLED is stored at the memory 260. The memory 260 may be disposed at the exterior of the timing controller 127, and may be disposed at the interior of the timing controller 127.
A method of modulating a digital data of an input image at the high gray scale range (c to max) according to the embodiment of the present invention will be described with reference to
In order to prevent a deterioration of a life span of the organic light emitting diode device OLED, the data modulating part 280 lowers a tilt of an output gamma curve to narrow down a range of expressing a gray scale at the high gray scale (c to max) area in response to the data modulating control signal Cdm as shown in
A method of modulating a digital data of an input image at the low gray scale range (a to b) according to the embodiment of the present invention will be described with reference to
The data modulating part 280 modulates an input digital data to heighten a tilt of an output gamma curve, so that it becomes possible to prevent a deterioration of a uniformity of an image at the low gray scale range at the low gray scale (a to b) area in response to the data modulating control signal Cdm as shown in
As described above, the organic light emitting diode display and the driving method thereof according to the present invention modulate an input digital data in a high-level brightness image having data of a high gray scale range to decrease brightness of an image, thereby preventing a deterioration of a life span of an organic light emitting diode device, and a driving method thereof.
Furthermore, the organic light emitting diode display and the driving method thereof according to the present invention modulates an input digital data in a low brightness image having data of a low gray scale range to increase brightness of an image, thereby preventing a deterioration of a uniformity of an image at the low gray scale range.
Although the present invention has been explained by the embodiments shown in the drawings described above, it should be understood to the ordinary skilled person in the art that the invention is not limited to the embodiments, but rather that various changes or modifications thereof are possible without departing from the spirit of the invention. Accordingly, the scope of the invention shall be determined only by the appended claims and their equivalents.
Number | Date | Country | Kind |
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10-2006-0060788 | Jun 2006 | KR | national |