JP4552397B2 - Image processing apparatus and method - Google Patents

Description

  The present invention relates to an image processing apparatus, such as an organic EL (Electroluminescence) display, and a method for performing a predetermined process on an input image and displaying the input image on a display unit.

In an image display device, such as a liquid crystal display, an image is displayed by arranging a large number of pixels in a matrix and controlling the light intensity for each pixel in accordance with image information to be displayed.
This is the same for an organic EL display or the like, but the organic EL display is a so-called self-luminous display having a light emitting element in each pixel circuit, and has a higher image visibility than a liquid crystal display. There are advantages such as unnecessary and high response speed.
Further, the brightness of each light emitting element is controlled by the value of the current flowing therethrough, that is, it is greatly different from a liquid crystal display or the like in that the light emitting element is a current control type.

  In the organic EL display, as with the liquid crystal display, a simple matrix method and an active matrix method can be used. However, although the former has a simple structure, it is difficult to realize a large and high-definition display. There's a problem. For this reason, active matrix systems have been actively developed in which the current flowing through the light emitting elements inside each pixel is controlled by active elements (typically TFTs: thin film transistors) provided inside the pixels.

  FIG. 5 is a circuit diagram showing a first configuration example of a pixel circuit in an active matrix organic EL display (see, for example, Patent Documents 1 and 2).

The pixel circuit 10 in FIG. 5 includes a p-channel thin film field effect transistor (hereinafter referred to as TFT) 11, an n-channel TFT 12, a capacitor C 11, and an organic EL element (OLED) 13 as a light emitting element. In FIG. 5, DTL indicates a data line, and WSL indicates a scanning line.
Since organic EL elements often have rectifying properties, they are sometimes called OLEDs (Organic Light Emitting Diodes). In FIG. 5 and others, the symbol of a diode is used as a light-emitting element. It does not require rectification.
In FIG. 5, the source of the TFT 11 is connected to the power supply potential VCC, and the cathode (cathode) of the light emitting element 13 is connected to the ground potential GND. The operation of the pixel circuit 10 of FIG. 5 is as follows.

When the scanning line WSL is in a selected state (here, at a high level) and the write potential VDATA is applied to the data line DTL, the TFT 12 becomes conductive and the capacitor C11 is charged or discharged, and the gate potential of the TFT 11 becomes VDATA.

  When the scanning line is in a non-selected state (here, low level), the data line DTL and the TFT 11 are electrically disconnected, but the gate potential of the TFT 11 is stably held by the capacitor C11.

The current flowing through the TFT 11 and the light emitting element 13 has a value corresponding to the gate-source voltage Vgs of the TFT 11, and the light emitting element 13 continues to emit light with a luminance corresponding to the current value.
The operation of selecting the scanning line WSL and transmitting the luminance information given to the data line to the inside of the pixel as described above is hereinafter referred to as “writing”.
As described above, in the pixel circuit 10 of FIG. 5, once VDATA is written, the light emitting element 13 continues to emit light with a constant luminance until the next rewriting.

  FIG. 6 is a circuit diagram showing a second configuration example of the pixel circuit in the active matrix organic EL display.

The pixel circuit 20 in FIG. 6 includes p-channel TFTs 21 and 22, n-channel TFTs 23 and TFT 24, a capacitor C 21, and an organic EL element OLED 25 that is a light emitting element. In FIG. 6, DTL indicates a data line, WSL indicates a scanning line, and ESL indicates an erase line.
The operation of the pixel circuit 20 will be described below with reference to the timing chart shown in FIG.

  First, in the state (period) <1>, as shown in FIGS. 7C and 7D, the scanning signal WS applied to the scanning line WSL and the erase signal ES applied to the erase line ESL are set to the high level. The As a result, the TFTs 24 and 23 are turned on and the TFT 22 is turned off, and the electric charge corresponding to the amount of data VDATA is charged to the capacitor C21 from the data line DTL.

  In the state (period) <2>, as shown in FIGS. 7C and 7D, the scanning signal WS to the scanning line WSL and the erasing signal ES to the erasing line ESL are set to a low level. As a result, the TFTs 24 and 23 are turned off and the TFT 22 is turned off, and a current corresponding to the electric charge charged in the capacitor C21 flows to the EL light emitting element 25 through the TFT 21. This current is maintained until the signal ES applied to the erase line ESL becomes high level.

  In state (period) <3>, as shown in FIG. 7D, the erase signal ES to the erase line ESL is set to a high level. As a result, the TFT 23 and TFT 22 are turned on, so that the charge charged in the capacitor C21 is discharged through the TFT 23 and TFT 22, and the light emission of the EL light emitting element 25 is turned off there.

  Thus, in the circuit of FIG. 6, each pixel uses one erase line ESL to uniquely control the light emission period (DUTY) of the light emitting element 25.

By the way, it is generally known that a light emitting element in an organic EL display has a characteristic of deteriorating in proportion to the amount of light emission and time, and improvement of the characteristic of the light emitting element is expected.
On the other hand, since the display screen of the display is not always uniform, the deterioration of the light emitting elements in the screen is not uniform, which causes the light emitting elements to partially deteriorate.
In particular, in the display of a watch or the like, since only that portion is extremely deteriorated and a decrease in luminance is seen, it is generally called “burn-in”. (Hereafter, partial pixel deterioration is expressed as “burn-in”)
In addition, when a plurality of types of light-emitting elements are used or when a single light-emitting element has a plurality of emission wavelength components, there are many cases where the respective deterioration characteristics do not match.
In this case, in the deteriorated pixel portion, the white balance is shifted and it appears to be colored.

It has been considered that the image burn-in caused by the deterioration of the display element with respect to the light emission time is most preferably suppressed by improving the light emission lifetime of the display element material.
Other than improving the material, conventionally, in order to prevent burn-in, a circuit that actively discharges the storage capacitor of the pixel (for example, see Patent Document 3) is used. Reduces unnecessary light emission time and prevents burn-in.
In addition, a device for reducing the burn-in by devising how to use a screen saver or the like has been proposed (for example, see Patent Document 4).
USP 5,684,365 JP-A-8-234683 JP 2002-169509 A JP 2002-207475 A

However, by improving the light emission lifetime of the display element material, in principle, it is impossible to eliminate burn-in completely in the self-luminous display, no matter how much the light emission lifetime of the display element material is extended. In some cases, only a video signal that is likely to be burned in is input as a video signal displayed on the display device. In other words, burn-in cannot be prevented simply by improving the life of conventional materials.
Also, unless the life of the material is extended, the screen burn-in is not improved, and it can only depend on the development of the field such as the speed and cost of material development.

  The circuit that positively discharges the storage capacitor of the pixel described in Patent Document 3 and the circuit described in Patent Document 4 compensate for the burn-in, that is, the deterioration of the light emission luminance due to the deterioration of the pixel to the extent that it can be practically used. And cannot be mitigated.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an image processing apparatus and method that can delay the progress of the degree of deterioration of a light emitting element of a pixel due to deterioration in characteristics over time. It is in.

In order to achieve the above object, an image processing apparatus according to a first aspect of the present invention includes a luminance frequency calculating means for calculating the luminance frequency of an input image signal, and an image fixed in the input image signal. A fixed image recognition means for recognizing whether or not there is, and an image processing method for determining whether or not to perform γ conversion processing based on the luminance frequency obtained by the luminance frequency calculation means and the recognition result of the fixed image recognition means the selected image processing designation means for designating, have a, and an image processing means for processing for the input image based on the specified the image processing method by the image processing designation means, the fixed image recognition means, The input image is binarized, the binarized image is divided into a plurality of areas, the sum of the binarized values is calculated for each divided area, and the calculated values are stored for each area before the stored plural Frame value Comparison determines the total value of each frame and is within a certain range, and the fixed pixel are out.

Preferably, the fixed image recognizing unit binarizes the input image, divides the binarized image into a plurality of areas, calculates a total of binarized values for each divided area, and calculates the calculated value. Are compared with the values of a plurality of previous frames stored for each area, and if the total value of each frame is within a certain range, it is determined that a fixed pixel has appeared.
Preferably, the luminance frequency calculating means calculates a frequency distribution with respect to gradation for the image in the frame, and the fixed image recognizing means obtains a binarization threshold value from the luminance frequency calculating means. Calculate and set from the obtained luminance frequency distribution value.

Preferably, the image processing designating unit recognizes that one frame image is not gathered on the high gradation side and there is a fixed image at a high gradation by the information obtained from the luminance frequency calculating unit. Select and specify a method for performing a predetermined γ conversion .
In addition, the image processing designation unit may perform γ conversion even if it is recognized that there is a fixed image at a high gradation when one frame image is gathered on the high gradation side based on the information obtained from the luminance frequency calculation means. Specify not to perform.

The image processing method according to the second aspect of the present invention recognizes whether there is a fixed image in the input image signal, and a first step of calculating the luminance frequency of the input image signal. A second step and a third step of selecting and specifying an image processing method for performing or not performing the γ conversion processing based on the luminance frequency obtained by the first step and the recognition result of the second step. a step, have a, a fourth step of performing processing for the input image based on the specified the image processing method by the third step, in the second step binarizes the input image The binarized image is divided into a plurality of areas, the sum of the binarized values is calculated for each divided area, and the calculated values are compared with the values of a plurality of previous frames stored for each area. And for each frame Determining a total value and falls within a certain range, and the fixed pixel are out.

According to the present invention, for example, the luminance frequency of the image signal input by the luminance frequency calculating means is calculated and output to the image processing specifying means.
The fixed image recognition means recognizes whether or not there is a fixed image in the input image signal, and the result is output to the image processing designation means.
In the image processing designation means is designated for optimum image processing method selected image processing means on the basis of the recognition result of the brightness degree and fixing the image recognition unit obtained by the luminance frequency computing means.
Then, the input image is processed based on the optimum image processing method designated by the image processing designation means.

ADVANTAGE OF THE INVENTION According to this invention, the progress of the deterioration degree of the light emitting element of a pixel can be delayed, and the partial pixel deterioration by fixed displays, such as a displayed clock, can be suppressed.
By limiting the case where γ conversion is performed, it is possible to realize image sticking prevention that minimizes the sense of discomfort in image quality.

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

  FIG. 1 is a block diagram showing an embodiment of an image processing apparatus according to the present invention.

  As shown in FIG. 1, the image processing apparatus 30 includes an image input unit 31, a luminance frequency conversion unit 32 as a luminance frequency calculation unit, a fixed image recognition unit 33, an image processing designation unit 34, an image processing unit 35, and an output. Part 36.

  The image input unit 31 causes the input image IM to be input to the luminance frequency conversion unit 32, the fixed image recognition unit 33, and the image processing unit 35.

The luminance frequency conversion unit 32 performs a process of calculating a frequency distribution with respect to gradation for an image in one frame that is input as needed by the image input unit 31, and uses the calculated luminance frequency distribution as a fixed image recognition unit 33 and an image process. The data is output to the designation processing unit 34.

The fixed image recognition unit 33 detects whether the image input by the image input unit 31 includes a pattern that can be fixedly displayed. For example, on a television, patterns such as subtitles and clock display at the time of a movie are recognized.
The fixed image recognition unit 33 outputs the recognition result to the image processing designation unit 34.

FIG. 2 is a block diagram illustrating a specific configuration example of the fixed image recognition unit according to the present embodiment.
As shown in FIG. 2, the fixed image recognition unit 33 includes a binarization circuit 331, an area division circuit 332, a calculation unit 333, a comparison unit 334, and a memory 335.

The binarization circuit 331 binarizes the image from the image input unit 31 and outputs it to the area division circuit 332.
The binarization circuit 331 calculates and sets a binarization threshold value, for example, from the luminance frequency distribution value obtained from the previous luminance frequency conversion unit 32.

The area dividing circuit 332 divides the image binarized by the binarizing circuit 331 into several to several tens of areas and supplies it to the calculation unit 333.
The area dividing method in the area dividing circuit 332 can be arbitrarily changed.

The calculation unit 333 calculates the sum of the binarized values for each area divided by the area division circuit 332 and outputs the sum to the comparison unit 334.
The total value of the binarized values for each divided area calculated by the calculation unit 333 can be stored in a plurality of frames in the memory 335.

The comparison unit 334 compares the value calculated by the calculation unit 333 with the value group of the previous frame stored in the memory 335 for each area, and the total value of each frame is within a certain range. It is determined that a fixed pixel has appeared, and if it is not within a certain range, it is determined that no fixed pixel has been output, and the determination result is output to the image processing designation unit 34.
By doing so, it is not necessary to record frame image information using a memory of several megabytes to several hundred megabytes, and the frame screen information can be saved with a small memory. In addition, since the data capacity is extremely reduced, it is possible to perform frame image calculation processing in a short time.

The image processing designation unit 34 determines an image processing selection method based on the luminance frequency distribution value obtained from the luminance frequency conversion unit 32 and the determination result of the fixed image recognition unit 33. In the image processing according to the present embodiment, a γ conversion process is performed, so a γ table is designated.
The image processing designation unit 34 selects the γ table from information on the luminance frequency distribution of the input image and the fixed image.
Specifically, the image processing designation unit 34 recognizes that one frame image is not gathered on the high gradation side by the information obtained from the luminance frequency conversion unit 32 and there is a fixed image with high gradation. A method for converting γ is selected as shown in FIG. In this way, a method of performing γ correction that suppresses gradation on the high luminance side and suppresses burn-in, which is so-called pixel luminance deterioration, is selected.
On the contrary, the image processing designating unit 34 recognizes that there is a fixed image with a high gradation when images of one frame are gathered on the high gradation side based on the information obtained from the luminance frequency conversion unit 32. Select a method that does not perform gamma correction. This is because data is gathered on the high gradation side, so that when the γ correction is performed, the image is converted into an uncomfortable image.
In this case, there is also a possibility that image sticking hardly occurs in principle.

The image processing unit 35 performs γ conversion of the image input from the image input unit 31 based on the image processing method selected and specified by the image processing specifying unit 34. Conversion method performs table conversion, it is possible to cope for any γ conversion.

  The output unit 36 outputs the image input from the image processing unit 35 at the same timing as the format of the input signal.

  The operation of the image processing apparatus configured as described above will be described below.

First, the input image IM is input by the image input unit 31 to the luminance frequency conversion unit 32, the fixed image recognition unit 33, and the image processing unit 35.
In the luminance frequency conversion unit 32, a frequency distribution with respect to gradation is calculated for an image in one frame that is input as needed by the image input unit 31, and the calculated luminance frequency distribution value is used as the fixed image recognition unit 33 and the image processing designation. The data is output to the processing unit 34.
The fixed image recognition unit 33 detects whether the image input by the image input unit 31 does not include a pattern that can be fixedly displayed. Specifically, the input image is first binarized. The binarized image is divided into several to several tens of areas. A total of binarized values is calculated for each divided area, and the values are stored in a plurality of frames and in a memory. Then, the calculated value is compared with the value of the previous frame stored for each area, and when the total value of each frame is within a certain range, it is determined that a fixed pixel is output. . The determination result of the fixed image recognition unit 33 is output to the image processing designation unit 34.

In the image processing designation unit 34, an image processing selection method is determined based on the luminance frequency distribution value obtained from the luminance frequency conversion unit 32 and the determination result of the fixed image recognition unit 33. Specifically, if information obtained from the luminance frequency conversion unit 32 recognizes that one frame image is not gathered on the high gradation side and there is a fixed image with high gradation, γ conversion is performed. Selected. On the other hand, if one frame image is gathered on the high gradation side based on the information obtained from the luminance frequency conversion unit 32, it is determined that γ correction is not performed even if it is recognized that there is a fixed image with high gradation. The Then, the determination result of the image processing designation unit 34 is output to the image processing unit.
In the image processing unit 35, γ conversion of the image input from the image input unit 31 is performed based on the image processing method selected and specified by the image processing specification unit 34. Then, the output unit 36 outputs the image input from the image processing unit 35 at the same timing as the format of the input signal.

As described above, according to the present embodiment, the luminance frequency conversion unit 32 that performs the process of calculating the frequency distribution with respect to the gradation for the image in one frame that is input as needed, and the input image is fixedly displayed. Image processing based on the fixed image recognition unit 33 that detects whether or not a pattern is included, the luminance frequency distribution value obtained from the luminance frequency conversion unit 32, and the determination result of the fixed image recognition unit 33. An image processing designation unit 34 that determines a selection method of (γ conversion), and an image that performs γ transformation of an image input from the image input unit 31 based on the image processing method selected and designated by the image processing designation unit 34 Since the processing unit 35 is included, the following effects can be obtained.

That is, the following effects can be obtained by recognizing that a fixed display pattern on the high gradation side is included in the input image signal and performing γ correction for each frame.
Partial pixel deterioration due to a fixed display such as a clock displayed on a television screen or the like can be suppressed.
Further, by limiting the cases where γ conversion is performed, it is possible to realize image sticking prevention that suppresses the uncomfortable feeling of image quality as much as possible.
In addition, it is possible to suppress partial pixel deterioration when there are many fixed images such as personal computer (PC) games.
Further, by controlling in units of one field, it is possible to operate for a wide range of time from ten milliseconds to minutes, and it is possible to realize control without a sense of incongruity.

In addition, for example, by adopting an FPGA with a built-in CPU core as shown in FIG. 4, this function can be realized without requiring any special peripheral circuit and without affecting the existing display mechanism. There is an advantage of being.
In the example of FIG. 4, the function of the image processing device 30 according to the present embodiment is incorporated into a timing generator 40 used in a flat panel display such as a general LDC, thereby improving the function and performance without changing the appearance. be able to.

  Since partial pixel deterioration due to fixed display of a clock or the like displayed on a television screen or the like can be suppressed, the invention can be applied to a timing generator used for a flat panel display such as an organic EL display or a liquid crystal display.

1 is a block configuration diagram showing an embodiment of an image processing apparatus according to the present invention. It is a block diagram which shows the specific structural example of the fixed image recognition part which concerns on this embodiment. It is a figure for demonstrating the selection method of the gamma conversion process of the image process designation | designated part which concerns on this embodiment. It is a figure which shows the application example of the image processing apparatus which concerns on this invention. It is a circuit diagram which shows the 1st structural example of the pixel circuit in an active matrix type organic EL display. It is a circuit diagram which shows the 2nd structural example of the pixel circuit in an active matrix type organic electroluminescent display. 7 is a timing chart for explaining the operation of the circuit of FIG. 6.

Explanation of symbols

DESCRIPTION OF SYMBOLS 30 ... Image processing apparatus, 31 ... Image input part, 32 ... Luminance frequency conversion part, 33 ... Fixed image recognition part, 331 ... Binarization circuit, 332 ... Area division circuit, 333 ... Calculation part, 334 ... Comparison part, 335 ... Memory, 34 ... Image processing designation part, 35 ... Image processing part, 36 ... Output part.

Claims (8)

Luminance frequency calculating means for calculating the luminance frequency of the input image signal;
Fixed image recognition means for recognizing whether there is a fixed image in the input image signal;
Image processing designating means for selecting and designating an image processing method of whether or not to perform γ conversion processing based on the luminance frequency obtained by the luminance frequency calculating means and the recognition result of the fixed image recognizing means;
Have a, and an image processing means for processing for the input image based on the specified the image processing method by the image processing designation means,
The fixed image recognition means includes
The input image is binarized, the binarized image is divided into a plurality of areas, the sum of the binarized values is calculated for each divided area, and the calculated values are stored for each area before the stored plural An image processing apparatus that determines that a fixed pixel appears when the total value of each frame is within a certain range compared to the value of the frame . The luminance frequency calculation means includes
For the image in the frame, calculate the frequency distribution for the gradation,
The fixed image recognition means includes
The image processing apparatus according to claim 1, wherein a threshold value for binarization is calculated and set from a luminance frequency distribution value obtained from the luminance frequency calculating means. The image processing designation means
If the information obtained from the luminance frequency calculation means recognizes that one frame of image is not gathered on the high gradation side and there is a fixed image with high gradation, a method for performing a predetermined γ conversion is selected. The image processing apparatus according to claim 2. The image processing designation means
When one frame image is gathered on the high gradation side based on the information obtained from the luminance frequency calculation means, it is designated not to perform γ conversion even if it is recognized that there is a fixed image with high gradation. Item 4. The image processing apparatus according to Item 2 or 3. A first step of calculating a luminance frequency of the input image signal;
A second step of recognizing whether there is a fixed image in the input image signal;
A third step of selecting and specifying an image processing method for performing or not performing the γ conversion processing based on the luminance frequency obtained by the first step and the recognition result of the second step;
Have a, a fourth step of performing processing for the input image based on the specified the image processing method by the third step,
In the second step,
The input image is binarized, the binarized image is divided into a plurality of areas, the sum of the binarized values is calculated for each divided area, and the calculated values are stored for each area before the stored plural An image processing method for determining that a fixed pixel appears when the total value of each frame is within a certain range as compared with the value of each frame . In the first step,
For the image in the frame, calculate the frequency distribution for the gradation,
In the second step,
The image processing method according to claim 5, wherein a threshold value for binarization is calculated and set from the luminance frequency distribution value obtained from the first step. In the third step,
When the information obtained in the first step recognizes that one frame image is not gathered on the high gradation side and there is a fixed image with high gradation, a method for performing a predetermined γ conversion is selected. The image processing method according to claim 6. In the third step,
If one frame image is gathered on the high gradation side according to the information obtained in the first step, the gamma conversion is designated not to be performed even if it is recognized that there is a fixed image with a high gradation. Item 8. The image processing method according to Item 6 or 7.

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