KR100815755B1 - Gamma Correction Device and Organic Electroluminescence Display - Google Patents

Abstract

A gamma correction device according to an embodiment of the present invention is a gamma correction device that provides a gamma reference voltage to a display panel, and stores gamma values corresponding to red (R), green (G), and blue sections (B), respectively. A gamma register; A temporary register storing an instruction value for adjusting a part of the gamma value previously stored in the gamma register; A memory for storing a corrected gamma value by reflecting an instruction value of the temporary register; And a gamma output circuit configured to receive the final gamma value stored in the memory, generate a gamma reference voltage corresponding thereto, and apply the gamma output voltage to the data driver.

Description

Gamma correction device and organic light emitting display device having same

1 is a view schematically illustrating a configuration of an organic electroluminescent display device according to an exemplary embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a gamma correction unit illustrated in FIG. 1.

FIG. 3 is a diagram illustrating an example of a register table of the temporary register shown in FIG. 2. FIG.

<Explanation of symbols for the main parts of the drawings>

400: gamma correction unit 410: gamma register

420: temporary register 430: memory

440: gamma output circuit

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescent display, and more particularly, to a gamma correction device for correcting a luminance difference by adjusting a gamma value for each display panel when a luminance difference occurs for each display panel, and an organic electroluminescence display device having the same. .

An organic electroluminescent display is a display device using a phenomenon in which electrons and holes injected through a cathode and an anode are recombined in an organic thin film to form excitons, and light of a specific wavelength is generated from the formed excitons.

Such an organic light emitting display device is configured by using a self-light emitting device, and thus, unlike a liquid crystal display (LCD), it does not require a separate light source. In addition, the luminance of the organic light emitting diode constituting the organic light emitting display device is controlled by the amount of current flowing through the organic light emitting diode.

The organic electroluminescent display includes a passive matrix method and an active matrix method. Among these, the passive matrix method is a method in which the anode and the cathode are formed to be orthogonal and the lines are selected and driven. While the organic EL display device using the passive matrix method is simple in structure and easy to implement, the large screen consumes a large amount of current and reduces the time required to drive each light emitting device.

In contrast, the active matrix method is a method of controlling the amount of current flowing through the light emitting device using the active device. As an active element, a thin film transistor (hereinafter referred to as TFT) is mainly used. The active matrix method is somewhat complicated but has the advantage of low current consumption and long light emission time.

Meanwhile, a general organic electroluminescent display needs to perform gamma correction on an input image signal.

As a gamma correction method, first, an image data value received from the outside is modulated by a controller to generate gamma corrected image data and apply the same to a display panel. According to such a method, the display device manufacturer may set the display device to perform optimal gamma correction even when the display panels have different display characteristics. However, since the image data is modulated, there is a problem in that a part of the image data is lost according to the data modulation method, and thus the gradation step cannot be normally implemented.

In another gamma correction method, a gamma correction is performed by adjusting a gray voltage level corresponding to an image data signal. That is, gamma correction is performed by setting data voltages for the inverse gamma corrected data signal so that the output luminance has a substantially linear characteristic. However, in such a method of adjusting the gradation voltage level, if a voltage level corresponding to the gradation level is already determined, there is no way to change it. Therefore, the display characteristics, which are slightly different for each display panel, are not considered, and thus the display apparatus cannot achieve the optimal display characteristics.

In addition, in the organic electroluminescent display, the light emission characteristics may vary according to the material of the fluorescent layer of the organic EL device, and thus the light emission characteristics may vary according to R, G, and B. Therefore, gamma correction needs to be performed for each of R, G, and B in order to improve display characteristics of the display panel.

An object of the present invention is to provide a gamma correction device for correcting a luminance difference of each display panel by performing gamma correction for each display panel when a luminance difference occurs for each display panel, and an organic electroluminescence display device having the same. have.

In order to achieve the above object, a gamma correction device according to an embodiment of the present invention is a gamma correction device that provides a gamma reference voltage to a display panel, and corresponds to red (R), green (G), and blue section (B). A gamma register which stores gamma values, respectively; A temporary register storing an instruction value for adjusting a part of the gamma value previously stored in the gamma register; A memory for storing a corrected gamma value by reflecting an instruction value of the temporary register; And a gamma output circuit configured to receive the final gamma value stored in the memory, generate a gamma reference voltage corresponding thereto, and apply the gamma output voltage to the data driver.

Here, the gamma values corresponding to the red (R), green (G), and blue sections (B) stored in the gamma register 410 are fixed to a predetermined value initially set, and the number of gamma values stored in the gamma register is displayed on the display panel. It corresponds to the number of colors to be expressed through.

The temporary register may add or subtract R, G, and B gamma values preset in the gamma register to correspond to the command value through a command value corresponding to a predetermined bit, and the command value is a 4-bit signal. Among the bit signals, the MSB is used as a sign bit to add or subtract a predetermined portion to the R, G, and B gamma values preset in the gamma register, and the sum and subtraction of the MSB is controlled by bit values below the MSB.

In addition, the organic electroluminescent display device according to the embodiment of the present invention includes a plurality of scan lines arranged in a first direction and transmitting a selection signal, and a plurality of scan lines insulated from and intersecting the scan lines and arranged in a second direction. A display panel including a data line of the plurality of pixel circuits and a plurality of pixel circuits respectively connected to the scan line and the data line; A scan driver which sequentially generates the selection signals and applies them to the plurality of scan lines; A data driver for generating the data signal and applying the data signal to the data line; A gamma correction unit for providing a gamma reference voltage to the data driver for gamma corrected gray scale display on a display panel, wherein the gamma correction unit

A gamma register which stores gamma values corresponding to red (R), green (G), and blue section (B), respectively; A temporary register storing an instruction value for adjusting a part of the gamma value previously stored in the gamma register; A memory for storing a corrected gamma value by reflecting an instruction value of the temporary register; And a gamma output circuit configured to receive the final gamma value stored in the memory, generate a gamma reference voltage corresponding thereto, and apply the gamma output voltage to the data driver.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a view schematically illustrating a configuration of an organic electroluminescent display device according to an exemplary embodiment of the present invention.

Referring to FIG. 1, an organic light emitting display device according to an exemplary embodiment of the present invention includes a display panel 100, a scan driver 200, a data driver 300, a gamma corrector 400, and a controller 500. do.

The display panel 100 includes a plurality of data lines D1 -Dm extending in a column direction, a plurality of scan lines S1 -Sn extending in a row direction, and a plurality of pixels. The data lines D1 -Dm transfer data signals representing image signals to the pixels, and the scan lines S1 -Sn transfer selection signals to the pixels. The pixel is formed in a pixel region defined by two neighboring data lines D1 -Dm and two neighboring scan lines S1 -Sn, and includes a switching transistor, a driving transistor, and an organic EL element. .

The scan driver 200 receives a control signal including a start signal, a clock signal, and the like from the controller 500 and sequentially generates and applies a selection signal to the scan lines S1 -Sn. The data driver 300 receives a signal such as an image signal, a start signal, a clock signal, and the like from the controller 500 and applies a data voltage corresponding to the image signal to the data lines D1 -Dm.

In addition, the gamma correction unit 400 performs gamma correction on the input image signal, generates a gray voltage corresponding to each gray level, and transmits the gray voltage to the data driver 300.

In the organic EL device (not shown), a cathode is connected to a reference voltage Vss and emits light corresponding to a current applied through a driving transistor. In this case, a ground voltage or the like may be used for the power supply Vss connected to the cathode of the organic EL element.

On the other hand, in most imaging devices (imaging tube, CCD, MOS, etc.), the photoelectric conversion characteristic of incident light has a linear (gamma = 1.0) characteristic, but the photoelectric conversion characteristic of a CRT, LCD, or organic electroluminescent display is nonlinear (gamma). = 2.2) image distortion due to disparity in conversion characteristics.

Thus, gamma correction is performed to compensate for any nonlinear response to cancel the nonlinear (gamma = 2.2) characteristics of the organic electroluminescent display, resulting in luminous sensitivity proportional to the output current.

In particular, as the technology of digitally processing image signals is widely applied, a gamma correction device made of digital circuits is generally used. Typically, gamma correction characteristics of an input-to-output are changed by mapping an input image signal to a specific address of a memory. BACKGROUND OF THE INVENTION A mapping system that obtains a gamma characteristic of a video signal by storing it in advance in a memory and outputting a gamma corrected output signal stored at a corresponding address in the memory according to the level of the input video signal is well known.

That is, the gamma correction is performed by adjusting the gray voltage level corresponding to the input image signal. The gamma correction is performed by setting data voltages so that the output luminance has a substantially linear characteristic with respect to the inverse gamma corrected data signal. It is.

However, in such a method of adjusting the gradation voltage level, if a voltage level corresponding to the gradation level is already determined, there is no way to change it.

Therefore, there is a problem that the display device cannot achieve the optimal display characteristics because the display characteristics that differ slightly from one display panel to another are not considered.

Embodiments of the present invention provide a gamma correction apparatus for correcting a luminance difference by adjusting a gamma value for each display panel when a luminance difference occurs for each display panel, and an organic electroluminescence display device having the same.

FIG. 2 is a schematic diagram of a gamma correction unit illustrated in FIG. 1.

Referring to FIG. 2, the gamma correction unit 400 according to an embodiment of the present invention stores a gamma register corresponding to red (R), green (G), and blue section (B), respectively. A temporary register 420 for storing a part of a gamma value preset in the gamma register; A memory 430 for storing a corrected gamma value by reflecting the command value of the temporary register; The gamma output circuit 440 is configured to receive the final gamma value stored in the memory, generate a gamma reference voltage corresponding thereto, and apply the generated gamma reference voltage to the data driver 300.

Here, the gamma values corresponding to the red (R), green (G), and blue sections (B) stored in the gamma register 410 are fixed to a predetermined value.

In this case, the gamma value corresponds to a data voltage in an organic light emitting display device driven by a voltage driving method.

For example, the gamma value corresponds to a 6-bit video signal for each of R, G, and B for 260,000 colors, and a value corresponding to 8-bit video signal for each of R, G, and B for 16 million colors. In this case, the number of gamma values stored in the gamma register corresponds to the number of colors to be expressed.

However, when the gamma correction is performed based on the gamma value previously stored in the gamma register 410, as described above, since the voltage level corresponding to the corresponding gradation level is already determined, there is no way to change it, for each display panel. There is a disadvantage that the display device cannot achieve the optimal display characteristics because the display characteristics that are slightly different are not considered.

In order to overcome this problem, an embodiment of the present invention uses a command value stored in the temporary register 420 to quickly adjust a gamma value for each display panel when a luminance difference occurs for each display panel. The difference can be corrected.

That is, when a luminance difference is generated for each panel by a preset value gamma value in the gamma register 410, a gamma value of the gamma register 410 through a command command value stored therein using the temporary register 420. By adjusting, the luminance difference can be corrected by adjusting the gamma value for each display panel even when the luminance difference occurs for each display panel.

FIG. 3 is a diagram illustrating an example of a register table of the temporary register illustrated in FIG. 2.

Referring to FIG. 3, which is an example of a register table of a temporary register 420, the command value may be a predetermined value of a predetermined R, G, and B gamma value, that is, a constant value with respect to a data voltage. Luminance can be controlled by adding or subtracting values corresponding to bits.

More specifically, the temporary register 420 stores a command value of 4 bits for each of R, G, and B. Here, the MSB is used as a sign bit among the four bits, and accordingly, the upper seven levels and the lower eight levels can be adjusted based on the center [0000].

That is, if MSB is 0, the gamma register 410 sums the R, G, and B gamma values, that is, bits corresponding to bits of a predetermined value, with respect to the data voltage. If MSB is 1, the gamma register is initially added. The R, G, and B gamma values, that is, values corresponding to bits of a predetermined value are subtracted from the data voltage.

In addition, the sum of the sum and the subtraction is controlled by a bit value less than or equal to MSB. As a result, the sum of the R, G, and B gamma values initially set in the gamma register through the command value of 4 bits is fixed. Luminance can be controlled by adding or subtracting a value corresponding to a bit of a value.

For example, when the command value is [0111], a gamma value of the corresponding gamma register is added to a value corresponding to +7, and when the command value is [1111], a gamma value of the corresponding gamma register is −. It is possible to adjust the brightness by subtracting the value corresponding to 8.

In addition, since the R, G, and B gamma values respectively stored in the gamma register are separately controlled, the problem of white balance can be solved.

The gamma value corrected by reflecting the command value of the temporary register 420 is finally stored in the memory 430, and the gamma output circuit 440 receives the final gamma value stored in the memory 430 and corresponds thereto. The gamma reference voltage is generated and applied to the data driver 300. At this time, the memory 430 is preferably implemented as a ROM.

According to the present invention, when the luminance difference occurs for each display panel, by performing gamma correction for each display panel, the luminance difference of each display panel is corrected, and the luminance difference occurs for each panel by providing a separate temporary register for the gamma correction. The advantage is that the gamma value can be adjusted more quickly.

Claims (11)

In the gamma correction device for providing a gamma reference voltage to the display panel, A gamma register which stores gamma values corresponding to red (R), green (G) and blue (B), respectively, A temporary register storing an instruction value for adjusting a part of the gamma value previously stored in the gamma register; A memory for storing a corrected gamma value by reflecting an instruction value of the temporary register; A gamma output circuit which receives the final gamma value stored in the memory and generates a gamma reference voltage corresponding to the final gamma value and applies the data to the data driver; And the temporary register adds or subtracts R, G, and B gamma values preset in the gamma register to correspond to the command value through a command value corresponding to a predetermined bit. The method of claim 1, A gamma correction device, characterized in that the gamma value corresponding to red (R), green (G), and blue section (B) stored in the gamma register (410) is fixed to a predetermined value initially set. The method of claim 2, And a number of gamma values stored in the gamma register corresponds to the number of colors to be expressed through the display panel. delete The method of claim 1, And the command value is a 4-bit signal. The method of claim 5, The MSB of the 4-bit signal is used as a sign bit to add or subtract a predetermined portion to the R, G, and B gamma values preset in the gamma register, and the sum and subtraction of the 4-bit signal is controlled by a bit value less than or equal to the MSB. Correction device. A plurality of scan lines arranged in a first direction and transmitting a selection signal, a plurality of data lines insulated from and intersecting the scan lines and arranged in a second direction, and a plurality of data lines respectively connected to the scan line and the data lines A display panel including a pixel circuit; A scan driver which sequentially generates the selection signals and applies them to the plurality of scan lines; A data driver for generating the data signal and applying the data signal to the data line; A gamma correction unit configured to provide a gamma reference voltage to the data driver for displaying gamma corrected gray scales on a display panel, The gamma correction unit, A gamma register which stores gamma values corresponding to red (R), green (G), and blue section (B), respectively; A temporary register storing an instruction value for adjusting a part of the gamma value previously stored in the gamma register; A memory for storing a corrected gamma value by reflecting an instruction value of the temporary register; A gamma output circuit which receives the final gamma value stored in the memory and generates a gamma reference voltage corresponding to the final gamma value and applies the data to the data driver; And the temporary register adds or subtracts R, G, and B gamma values preset in the gamma register to correspond to the command value through a command value corresponding to a predetermined bit. The method of claim 7, wherein And a gamma value corresponding to red (R), green (G), and blue sec (B) stored in the gamma register (410) is fixed to a predetermined value initially set. delete The method of claim 7, wherein And the command value is a 4-bit signal. The method of claim 10, Among the 4-bit signals, the MSB is used as a sign bit to add or subtract a predetermined portion to the R, G, and B gamma values preset in the gamma register, and the sum of the sum and the subtraction is controlled by a bit value less than or equal to the MSB. Electroluminescent display.

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