JP2004325749A - Image processing circuit for organic el display, method for driving the image processing circuit and electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make it possible to convert the gradation data to be supplied to an organic EL display without providing another correction circuit, to perform gamma correction and to flexibly change the conversion mechanism of gradation data. <P>SOLUTION: An electro-optical device A is provided with an organic EL display 1, a processor 2 as a peripheral circuit, a RAM 3, and a ROM 4. A gradation conversion module as software is stored in the ROM 4. When the processor 2 executes the gradation conversion module, gamma correction is applied to input picture data to obtain converted picture data. Hence the contents of gradation conversion can be flexibly and easily changed by changing the gradation conversion module. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention belongs to a technical field related to an image processing circuit of an organic EL display and a driving method thereof, and an electronic device using the same.
[0002]
[Prior art]
In recent years, since the performance of the organic EL element has reached a practical level, development on an organic EL display has been actively conducted. Up to now, three types of methods have been proposed for full-color organic EL displays. These methods use an inkjet device to pattern red, blue, and green light emitting organic EL elements using an inkjet device, and use a color filter from the light emitted from an organic EL element that emits white light. A method of extracting each color of red, blue, and green, or a method of causing an organic EL element that emits blue light to emit light and converting the light into red and green in an organic layer called a color conversion layer.
[0003]
However, in a method using an ink jet device, a known organic EL element material does not realize a red material having a high luminous efficiency, and a difference occurs in luminance for each color. Also in the method using a color filter, there is a difference in efficiency in extracting each color, and a difference occurs in luminance for each color. Further, also in the method using the color conversion layer, there is a difference in conversion efficiency to each color, and a difference occurs in luminance for each color.
[0004]
As described above, in the full-color organic EL display, a difference in luminance for each color is a problem. Further, with the development of full-color organic EL displays, developments relating to the improvement of the visibility have also been actively carried out. As a known method for improving the visibility of an organic EL display, performing gamma correction is known.
[0005]
Thereby, display quality can be improved. At this time, since there is a difference in luminance for each color as described above, it is desired to perform gamma correction independently for each color in consideration of this. 2. Description of the Related Art Conventionally, a display device having a correction circuit has been known as a method of realizing a display device with high visibility by appropriately performing gamma correction for each color in an organic EL display (see Patent Document 1).
[0006]
[Patent Document 1] JP-A-2001-92413
[0007]
[Problems to be solved by the invention]
However, in order to perform gamma correction in a conventional driving device, it is necessary to develop a new correction circuit, and the cost and time involved in the development have been increased. In addition, small electronic devices such as mobile phones have a history of development in which the peripheral circuits of the display are reduced and the display area of the display is further expanded, and the addition of a new correction circuit does not comply with this background. there were. Furthermore, since the correction means is configured by hardware, it has been difficult to flexibly change the correction method according to the display.
[0008]
Therefore, the present invention has been made in view of the above-described circumstances, and an object of the present invention is to make it possible to convert gradation data to be supplied to an organic EL display without providing a new correction circuit. Perform the correction. Another object is to make it possible to flexibly change the conversion mechanism of gradation data.
[0009]
[Means for Solving the Problems]
In order to solve the above-described problem, an image processing circuit of an organic EL display according to the present invention is configured such that a pixel having an organic EL element and a circuit for controlling light emission of the organic EL element is provided at an intersection of a scanning line and a data line. For supplying converted image data to an organic EL display arranged in a matrix corresponding to the above, and storing a gradation conversion program for converting an input gradation value according to a predetermined rule to generate an output gradation value. Means for executing the gradation conversion program, converting the gradation value of the input image data to generate the converted image data, and outputting the converted image data to the organic EL display.
[0010]
According to the present invention, since the gradation conversion can be executed by software, it is not necessary to add a new conversion circuit for performing the gradation conversion as hardware. Therefore, as compared with the case where a new conversion circuit is developed, the cost and time required for the development can be significantly reduced. Also, when a conversion circuit as hardware is mounted on an organic EL display, the display becomes larger and a display area becomes smaller. However, if a gradation conversion program as software is used, there is a problem of securing a space. Is eliminated. Furthermore, the conversion method can be flexibly changed according to the gradation / luminance characteristics of the newly developed organic EL display. Note that an organic light emitting diode (OLED: Organic Light Emitting Diode) can be used as the organic EL element.
[0011]
Here, the input image data is composed of first to third input image data respectively corresponding to red, blue, and green, and the control unit executes the gradation conversion program to execute the first to third input image data. It is preferable that the third input image data is independently converted to generate first to third converted image data and output to the organic EL display. In this case, different conversion characteristics can be provided for each color.
[0012]
In the above-described image processing circuit for an organic EL display, the predetermined rule is preferably gamma correction. Thereby, the visibility of the organic EL display can be improved. In particular, if gamma correction is performed for each color, it is possible to correct the luminance by adjusting the difference in luminance for each color.
[0013]
Next, in the method for driving an organic EL display according to the present invention, pixels having an organic EL element and a circuit for controlling light emission of the organic EL element are arranged in a matrix corresponding to intersections of scanning lines and data lines. A method of driving an arranged organic EL display, wherein a CPU executes a gradation conversion program for converting an input gradation value according to a predetermined rule to generate an output gradation value, thereby obtaining a gradation value of input image data. And a second step of supplying a drive signal to the data line based on the converted image data. According to the present invention, since the gradation conversion can be executed by software, it is possible to flexibly change the conversion method.
[0014]
Further, when the input image data is composed of first to third input image data respectively corresponding to red, blue and green, the first step is to execute the gradation conversion program by a CPU. It is preferable that the first to third input image data be independently converted to generate first to third converted image data as the converted image data. Further, it is preferable that the predetermined rule is gamma correction.
Next, an electronic apparatus according to the present invention includes the above-described image processing circuit of the organic EL display, and includes, for example, a mobile phone, a PDA, a notebook personal computer, a pager, and electronic paper. Applicable.
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of an electro-optical device according to one embodiment of the present invention. In FIG. 1, the electro-optical device A includes an organic EL display 1, a processor 2 as a peripheral circuit, a RAM 3, and a ROM 4.
[0015]
The organic EL display 1 includes a panel unit 100, a scanning line driving circuit 140, and a source line driving circuit 150. In the panel section 100, a plurality of scanning lines 111 are formed extending in the X (row) direction in the drawing, and a plurality of data lines 112 extend in the Y (column) direction. It is formed. Further, a plurality of current supply lines 113 are provided in parallel with each data line 112. The pixels 130 are provided at respective intersections of the scanning lines 111 and the data lines 112 and are arranged in a matrix. For convenience of explanation, in this embodiment, the total number of the scanning lines 110 is m and the total number of the data lines 120 is n (m and n are integers of 2 or more), and the electro-optical device is m rows × n Although described as a matrix display device with columns, the present invention is not limited to this.
[0016]
The scanning line driving circuit 140 supplies a scanning signal to sequentially activate the m scanning lines 111. The data line driving circuit 150 supplies the gradation data to each data line 112. The operation of the scanning line driving circuit 140 and the operation of the data line driving circuit 150 are synchronized with each other by a synchronization signal 160.
[0017]
FIG. 2 shows an embodiment of a pixel 130 formed on the panel unit 100 of the organic EL display shown in FIG. As shown in the figure, the pixel 130 is formed in a region surrounded by the scanning line 111, the data line 112, and the current supply line 113, and includes a switching transistor 203 including an N-channel transistor, a data holding capacitor 204, and an N-channel transistor. It includes a driving transistor 205 and an organic EL element 206. Each transistor can be constituted by a TFT (Thin Film Transistor). Further, an organic light emitting diode can be used as the organic EL element 206.
[0018]
As a method of expressing an intermediate gradation using the organic EL element 206, for example, there is an analog method. In the analog system, when the scanning signal supplied from the scanning line driving circuit 140 is activated and the scanning line 111 is selected, the switching transistor 203 is turned on. While the scanning line 111 is selected, the grayscale data of the analog signal is written to the storage capacitor 204 via the data line 112.
[0019]
When the scanning signal becomes inactive and the scanning line 111 becomes non-selected, the driving transistor 205 is controlled by the gradation data written in the storage capacitor 204 and supplies a current corresponding to the gradation data to the organic EL element 206. I do. Thereby, the light emission of the organic EL element 206 is controlled according to the gradation data written in the storage capacitor 204. Further, a method for expressing the intermediate gradation of the organic EL element 206 may be a digital method.
The applicant has also applied for a method of expressing such an intermediate gradation in Japanese Patent Application No. 2002-319677, and such a driving method can be applied to the present invention.
[0020]
The description returns to FIG. The ROM 4 stores a control program for controlling the electro-optical device A. The processor 2 includes a CPU and controls the electro-optical device A according to a control program. The RAM 3 functions as a work area for the CPU 2, and stores input image data Din and converted image data Dout supplied from an external device via an interface circuit (not shown). The converted image data Dout is data obtained by executing the gradation conversion module, which is a part of the control program, by the processor 2 and converting the gradation of the input image data Din according to a predetermined rule. The tone conversion module of this example employs gamma correction as a predetermined rule. The gamma correction means a correction performed on the gradation characteristics of the device so that a natural gradation can be obtained in multi-gradation display with reference to human vision. The input image data Din and the converted image data Dout represent 6 bits and 64 gradations.
[0021]
FIG. 3 shows a processing example of the gradation conversion module. In this example, it is assumed that the relationship between gradation and luminance in the organic EL display 1 has linearity as shown in FIG. That is, when the input image data Din stored in the RAM 3 is supplied to the organic EL display 1 as it is, the luminance changes in proportion to the input gradation.
[0022]
The processor 2 converts the input image data Din according to the gradation conversion module as described below. 0 → 0, 1 → 0, 2 → 0, 3 → 0, 4 → 1, 5 → 1, 6 → 1, 7 → 1, 8 → 2, 9 → 2, 10 → 2, 11 → 2, 12 → 3, 13 → 3, 14 → 3, 15 → 3, 16 → 5, 17 → 5, 18 → 5, 19 → 5, 20 → 7, 21 → 7, 22 → 7, 23 → 7, 24 → 9, 25 → 9, 26 → 9, 27 → 9, 28 → 12, 29 → 12, 30 → 12, 31 → 12, 32 → 16, 33 → 16, 34 → 16, 35 → 16, 36 → 21, 37 → 21, 38 → 21, 39 → 21, 40 → 26, 41 → 26, 42 → 26, 43 → 26, 44 → 31, 45 → 31, 46 → 31, 47 → 31, 48 → 37, 49 → 37, 50 → 37, 51 → 37, 52 → 45, 53 → 45, 54 → 45, 55 → 54, 56 → 54, 57 → 54, 58 → 54, 60 → 63, 61 → 63, 62 → 63 63 → 63. In each case, the left side of the arrow is the gradation of the input image data Din before the conversion, and the right side of the arrow is the converted image data Dout after the conversion. When such conversion is performed, the relationship between gradation and luminance is as shown in FIG. 3B, and gamma correction is performed. The above-described relationship between the input tone and the output tone is an example, and the processing content of the tone conversion module may be determined from the relationship between the tone and the brightness before the conversion and the relationship between the desired tone and the brightness after the conversion. .
[0023]
The conversion means of the gradation data realized by the processor 2 is realized by a gradation conversion module as software. Therefore, as compared with the case where a new correction circuit is developed, the cost and time required for the development can be significantly reduced. In addition, if a correction circuit as hardware is mounted on the organic EL display 1 or its panel unit 100, the display becomes larger and the display area becomes smaller. However, if a gradation conversion module as software is used, The problem of securing space is eliminated. Furthermore, according to the gradation and brightness characteristics of the newly developed organic EL display, the conversion module can perform the conversion process independently for each color, and can flexibly change the correction method for each color of red, blue, and green. It is.
[0024]
The present invention is not limited to the embodiments described above, and for example, the following applications are possible.
(1) The input image data may include input image data DRin, DBin, and DGin corresponding to each of red, blue, and green, and may generate converted image data DRin, DBin, and DGin corresponding to gradation. In this case, if the gradation / luminance characteristics of the organic EL display 1 are different for each color, a gradation conversion module may be provided for each color. Conversely, if the gradation and luminance characteristics of the organic EL display 1 are the same for each color, gradation conversion may be performed using one gradation conversion module.
[0025]
(2) When a digital method is used for the intermediate gradation of the organic EL element 206, a subfield driving method may be used. In the subfield driving method, one frame is divided into a plurality of subfields, and pixels are turned on (lit) and turned off (turned off) in units of subfields according to the gray scale to be displayed. In this case, the voltage supplied to the data line 112 is binary. Also, when representing the gray level of K bits, weighted ^{subframe, 2 0, 2 1, 2} 2, ... 2 K - 1 become.
[0026]
FIG. 4 shows the relationship between subfields and frames. In this example, the converted image data Dout has 6 bits, and each bit is represented by D0 to D5. The horizontal axis indicates time, and the vertical axis indicates the scanning direction in the pixel matrix. In the example shown in FIG. 4A, the length of the subfield corresponding to D5 is 32 times the length of the subfield corresponding to D0. The presence of such a long subfield makes it easier for human eyes to detect the on / off state of the pixel 130, which may be seen as flicker. Therefore, as shown in FIG. 4B, it is preferable to divide the subfield corresponding to D5 into three parts and disperse them in one frame. Thereby, flicker can be prevented and the image quality of the organic EL display 1 can be significantly improved.
[0027]
(3) The above-described electro-optical device A can be applied to electronic equipment. For example, the present invention may be applied to a mobile phone 1300 as shown in FIG. The mobile phone 1300 includes an electro-optical device A having the organic EL display 1 together with a plurality of operation buttons 1302. In addition, the electro-optical device A includes a notebook personal computer, a PDA, a television, a view finder, a monitor direct-view video tape recorder, a car navigation device, a pager, an electronic notebook, a calculator, a word processor, a workstation, and a POS terminal. The present invention can be applied to a device including a touch panel.
[Brief description of the drawings]
FIG. 1 is a block diagram of an electro-optical device according to an embodiment of the present invention.
FIG. 2 is a circuit diagram illustrating an embodiment of a pixel of an organic EL display.
FIG. 3 is an explanatory diagram illustrating a processing example of a gradation conversion module.
FIG. 4 is a diagram showing the relationship between subfields and frames.
FIG. 5 is a perspective view of a mobile phone as an electronic device.
DESCRIPTION OF SYMBOLS A: electro-optical device, 1: organic EL display, 100: panel unit, 111: scanning line, 112: data line, 130: pixel, 140: scanning line driving circuit, 150: data line driving circuit.

Claims (7)

An organic EL that supplies converted image data to an organic EL display in which pixels each having an organic EL element and a circuit that controls light emission of the organic EL element are arranged in a matrix corresponding to intersections of scanning lines and data lines. An image processing circuit for a display,
Storage means for storing a gradation conversion program for converting an input gradation value according to a predetermined rule to generate an output gradation value;
Control means for executing the gradation conversion program, converting the gradation value of the input image data to generate the converted image data, and outputting the converted image data to the organic EL display;
An image processing circuit for an organic EL display, comprising: The input image data includes first to third input image data corresponding to red, blue, and green, respectively.
The control means executes the gradation conversion program, converts the first to third input image data independently to generate first to third converted image data, and outputs the first to third converted image data to the organic EL display. The image processing circuit for an organic EL display according to claim 1, wherein: 3. The image processing circuit for an organic EL display according to claim 1, wherein the predetermined rule is gamma correction. A method for driving an organic EL display, in which pixels each having an organic EL element and a circuit for controlling light emission of the organic EL element are arranged in a matrix corresponding to intersections of scanning lines and data lines,
A first step of converting a gradation value of input image data to generate converted image data by executing, by a CPU, a gradation conversion program for converting an input gradation value according to a predetermined rule to generate an output gradation value;
Supplying a drive signal to the data line based on the converted image data. The input image data includes first to third input image data corresponding to red, blue, and green, respectively.
In the first step, the first to third input image data are independently converted by executing the gradation conversion program by a CPU, and the first to third converted image data are used as the converted image data. The method of driving an organic EL display according to claim 4, wherein the driving method is generated. The method according to claim 4, wherein the predetermined rule is gamma correction. An electronic apparatus comprising the image processing circuit for an organic EL display according to claim 1.

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