KR100743758B1 - Apparatus and Method for controlling dynamic contrast ratio using peak level - Google Patents

Abstract

The present invention relates to an apparatus and method for controlling dynamic contrast ratio using peak level detection of an image displayed on an image display apparatus. The apparatus for controlling dynamic contrast ratio using peak level detection according to the present invention is characterized by displaying a magnitude of an image signal. An effective block check unit for checking whether an output image frame of a scaler that is converted into an image signal having a size suitable for display on the output block is divided into a plurality of local regions and is a target block for measuring average values for brightness adjustment; A peak level determination unit that detects a peak value of a pixel for each pixel in the block for a block determined to be a valid block by the block checker, and determines whether a difference between a peak value and a reference peak value of the corresponding pixel is within a predetermined setting value; And the pixel determined to be a valid pixel in the peak level determination unit. A peak similar level area calculator for calculating and outputting an area determined to be an actual image area according to the present invention, and an inverter level for adjusting the brightness of the corresponding image frame according to the peak similar level area output from the peak similar level area calculator. A frame inverter level determiner for determining and outputting the output, a PWM converter receiving the output of the inverter level determiner and outputting a pulse width modulated signal (PWM) according to a corresponding output level, an output image signal of the scaler, and the inverter And a gamma correction unit configured to receive the output of the level determiner and output image data for compensating for nonlinearity in brightness recognition of the human eye, and an inverter for outputting a voltage having a frequency corresponding to the output of the PWM converter. According to the present invention, the conventional dynamic control while maintaining the emotional contrast The advantage is that the full monochrome contrast ratio, which is the advantage of the last ratio control technology, can be improved.

Dynamic Contrast Ratio Control, Emotion Contrast, Effective Pixel Average

Description

Apparatus and Method for controlling dynamic contrast ratio using peak level

1 is a view for explaining a dynamic contrast ratio control apparatus of a video display device according to the prior art;

2 is a view for explaining a dynamic contrast ratio control apparatus using peak level detection according to the present invention;

3 is a flowchart illustrating a dynamic contrast ratio control method using peak level detection according to the present invention.

4 and 5 are diagrams for explaining a block of an image frame used for detecting a peak level of a pixel for each block according to the present invention.

6 is a flowchart illustrating an inverter level determination process of an image frame using peak level detection according to the present invention.

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

110: scaler 120: gamma compensation

130: LCD panel 140: average calculation unit

150: PWM converter 160: inverter

200: effective average calculation unit 210: effective block check unit

220: peak level determination unit 230: peak similar level area calculation unit

240: frame inverter level determination unit

The present invention relates to an apparatus and method for controlling a dynamic contrast ratio using peak level detection of an image displayed on an image display device.

In the image display device, the image quality setting information for each state constituting the image quality of color temperature, color density, color, sharpness, brightness, contrast, etc. may be changed to maintain an optimal image state desired by the viewer.

The video display device implements and displays an image according to a corresponding setting state according to initial setting information loaded at initial startup or quality setting information changed by a user using a menu function during operation of the video display device.

Since the environment in which the user views the image display device changes according to the image being viewed, it is necessary to change the image quality setting information according to the changed environment in order to enjoy the optimal image. However, whenever the viewing environment changes, it is very inconvenient for the user to change the image quality setting information accordingly.

The sharpness perceived by the human eye depends on how bright and bright areas of the same screen represent dark areas, and the contrast ratio expresses the difference between the brightest part and the darkest part of the image. Therefore, the video display device automatically adjusts the contrast ratio according to the image state. This feature is called Dynamic Contrast Ratio control.

1 is a view for explaining a dynamic contrast ratio control apparatus of a video display device according to the prior art.

Referring to FIG. 1, a dynamic contrast ratio control apparatus according to the related art includes a scaler 110, a gamma correction unit 120, an average calculator 140, a PWM converter 150, and an inverter 160. It is configured to include. In FIG. 1, the LCD panel 130 is a display device for displaying an image according to processed image information.

The detailed configuration and operation of the dynamic contrast ratio control apparatus of the image display apparatus according to the prior art configured as described above will be described.

The scaler 120 converts a video signal selected from a video signal input from a video processor (not shown) into a video signal of a size suitable for display on a display device.

The average calculating unit 140 receives the output image signal of the scaler 120, detects the brightness of each pixel of the image frame for each block, calculates an average brightness value thereof, and converts the calculation result into a DC voltage value DC. Output

The PWM converter 150 receives the output of the average calculator 140 and outputs a pulse width modulated signal PWM according to the output level.

The gamma correction unit 150 receives the output image signal of the average calculation unit 140 and the output voltage of the average calculation unit 150 and compensates for the nonlinearity of the brightness recognition degree of the human eye with respect to the image signal. Is output to the LCD panel 130.

The inverter 160 generates an output having a voltage and a frequency synchronized with the PWM input output from the PWM converter 150, and then outputs the output to the LCD panel 130 to actively display the brightness of the finally displayed image. Will be adjusted.

In the dynamic contrast ratio control apparatus of the image display apparatus according to the prior art as described above, when the local area average brightness value is detected to adjust the brightness of the inverter and control to decrease the brightness, the DC component (DC) of the entire image screen is controlled. Decreases the brightness for the area. The sharpness perceived by the human eye depends on how bright and dark areas of the same screen represent dark areas. In view of the above, the prior art can faithfully express the black level, but has a disadvantage in that the expression of the emotional contrast is disadvantageous.

In order to solve the above problem, the image signal output from the scaler is divided into predetermined image blocks to improve the sensitivity contrast by detecting average brightness values only for valid pixels satisfying the reference values set for each image block. It is an object of the present invention to provide an apparatus and method for controlling dynamic contrast ratio using peak level detection.

It is an object of the present invention to provide an apparatus and method for controlling dynamic contrast ratio using peak level detection that can detect peak levels of an image and adjust brightness of an inverter based on the peak levels.

In order to achieve the above object, a dynamic contrast ratio control apparatus using peak level detection according to the present invention includes a plurality of output image frames of a scaler for converting and outputting an image signal of a size suitable for display on a display device. A valid block check unit that checks whether the average block for brightness adjustment is performed for each block divided into local regions, and a peak value of a pixel for each pixel in the block for a block determined to be a valid block by the effective block check unit. A peak level determination unit that detects and determines whether a difference between a peak value and a reference peak value of the corresponding pixel is within a predetermined setting value, and determines that the image is an actual image area according to the number of pixels determined to be valid pixels by the peak level determination unit. A peak similar level area calculating unit for calculating and outputting an area to be used; A frame inverter level determiner for determining and outputting an inverter level for adjusting the brightness of a corresponding video frame according to the peak pseudo level area output from the pseudo-like level area calculator, and an output level corresponding to the output of the inverter level determiner. PWM converter for outputting the pulse width modulated signal PWM according to the output, and the output image signal of the scaler and the output of the inverter level determiner outputs the image data to compensate for the non-linearity of the brightness recognition degree of the human eye And an inverter for outputting a voltage having a frequency corresponding to the output of the PWM converter.

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A dynamic contrast ratio control method using peak level detection according to the present invention for achieving the above object comprises the steps of checking whether or not a valid block for each block divided into a plurality of local regions according to the start of the dynamic contrast ratio control function; Searching for valid pixels in the block when the check result corresponds to a valid block, calculating an effective average brightness value for the searched valid pixels, and an image frame according to the calculated effective average brightness value And determining and applying the inverter level.

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The checking of the valid block for each block of the image frame divided into a plurality of local areas may include determining that the block that does not include three pixels on the outermost side of the image frame is a valid block.

The searching of the effective pixel may include determining that a pixel having a difference between a peak value of the pixel and a reference peak value within a predetermined setting value is a valid pixel.

The searching of the valid pixel may include changing a peak value of the reference pixel when the valid pixel is greater than or equal to a predetermined threshold.

The calculating of an effective average brightness value for the valid pixels may include obtaining an average brightness value for a block in which the number of pixels whose peak level in the block under search satisfies a criterion exceeds a predetermined threshold.

According to the apparatus and method for controlling dynamic contrast ratio using peak level detection according to the present invention configured as described above, the average brightness value is detected only for valid pixels satisfying the reference value set for each image block, and based on the brightness of the inverter By adjusting, the emotional contrast of the displayed image is improved.

Hereinafter, an apparatus and method for controlling dynamic contrast ratio using peak level detection according to the present invention will be described in detail with reference to the accompanying drawings.

2 is a view for explaining a dynamic contrast ratio control apparatus using peak level detection according to the present invention.

Referring to FIG. 2, an image display device equipped with a dynamic contrast ratio control apparatus using peak level detection according to the present invention includes a scaler 110, a gamma correction unit 120, an LCD panel 130, and an effective display device. The average calculator 200, the PWM converter, and the inverter 160 are included.

The scaler 110 converts the magnitude of the input digital image signal into an image signal of a size suitable for display on the LCD panel 130 as a display device and outputs the converted image signal. The LCD panel 130 used as the display device is just one example, and it is also possible to use another image display device such as a plasma display panel (PDP).

The effective average calculator 200 detects an average brightness value of valid pixels of the output image signal of the scaler 110 and outputs an image adjustment signal. The effective block check unit 210 and peak level determination The unit 220, the peak similar level area calculator 230, and the frame inverter level determiner 240 may be configured.

In the average value measurement for adjusting the brightness of an image frame, the image frame is divided into predetermined local regions for each block. The effective block checker 210 measures the average value for adjusting the brightness of the current block to be checked. Check whether the target block is.

The peak level determiner 220 detects a peak value of a pixel for each pixel in the block for a block determined to be a valid block by the valid block checker 210, and the difference between the peak value and the reference peak value of the pixel is determined. It is determined whether it is within a predetermined setting value.

The peak similar level area calculator 230 calculates and outputs an area determined to be an actual image area according to the number of pixels determined to be valid pixels by the peak level determiner 220.

The frame inverter level determiner 240 determines and outputs an inverter level for adjusting the brightness of a corresponding video frame according to the peak similar level area output from the peak similar level area calculator 230.

The PWM converter 150 receives the output of the frame inverter level determiner 240 of the effective average calculator 200 and outputs a pulse width modulated signal PWM according to the output level.

The gamma correction unit 120 receives the output image signal of the scaler 110 and the output of the effective average calculator 200 and outputs image data that compensates for non-linearity in brightness recognition of the human eye. )

The inverter 160 adjusts the brightness of the LCD panel 130 by outputting a voltage having a constant frequency corresponding to the output of the PWM converter 150.

As described above, the effective average calculation unit 200 detects an average value only for valid pixels in the image frame, adjusts the output to the gamma correction unit 120 and the inverter 160, and controls the brightness of the image frame accordingly. The emotional contrast of the displayed image frame is improved.

An embodiment in which the dynamic contrast ratio control method using the peak level detection according to the present invention is applied to the dynamic contrast ratio control apparatus using the peak level detection configured as described above will be described with reference to FIG. 3.

3 is a flowchart illustrating a method of controlling a dynamic contrast ratio using peak level detection according to the present invention, and FIGS. 4 and 5 illustrate blocks of an image frame used for peak level detection of a pixel for each block according to the present invention. It is a figure for demonstrating.

As shown in FIG. 3, when the image display apparatus starts to operate or a command for executing the dynamic contrast ratio control function is input during the operation, the dynamic contrast ratio control method using peak level detection according to the present invention is performed (S310).

In the present invention, the peak level of the pixel is detected, and the local area of the detected level is sensed to determine whether it is a noisy area or an actual bright area to adjust the output to the inverter for adjusting the brightness level of the frame.

To this end, first, in the effective average calculation unit 200, as shown in FIG. 4, each block in which the image frame is divided into a plurality of local regions is applied to a valid block for checking whether a valid pixel is applied for the present invention. First, it is determined whether (S320).

Each corresponding block is a block of a size of 5 x 5 including two pixels left, right, top, and bottom of the center pixel as shown in FIG. 5 when the center pixel of the block is X (i, j). In this case, the operation is performed by moving (1, 1) pixels around the center pixel X (i, j).

In the present invention, the data of three pixels existing on the edge of the image frame are not valid blocks and are not included in the peak detection operation. This border region is excluded because it can be represented by a sharpening operation of the scaler 110.

As a result of the determination (S320), if a valid block is checked, the peak level is detected for the pixels in the block (S330).

According to the peak level detecting step S330, the number of pixels whose detected peak level is different from the reference peak value is within a predetermined set value is counted, and the peak similar level area is calculated for a block whose corresponding count exceeds a predetermined threshold value. (S340).

The output level of the inverter to adjust the frame brightness is determined based on the peak like level area calculation value (S350).

Thereafter, by controlling the output of the inverter according to the determined output level, an image having improved sensitivity contrast is displayed on display means such as an LCD panel (S360).

6 is a flowchart illustrating a process of determining an inverter level of an image frame using peak level detection according to the present invention.

Referring to FIG. 6, the valid block check unit 210 of the valid average calculator 200 first determines whether a corresponding block corresponds to a valid block (S610).

As a result of the determination (S610), in the case of a valid block, the peak level determination unit 220 first checks whether each pixel has an effective peak level to determine whether the block is a noise component or a valid image component. To this end, the peak level initial determination reference value (Overall_Peak) is set to 0, and the gray level of the pixel currently being checked is read as the current value (Current) (S621).

It is determined whether the current value Current exceeds the determination reference value Overall_Peak (Current> Overall_Peak) (S622). That is, it compares which pixel in the current block is larger than the determination reference value (Overall_Peak) obtained from the blocks performed so far.

As a result of the determination (S622), when the current value (Current) does not exceed the determination reference value (Overall_Peak), the pixel to be checked is moved by one pixel in the block (S623), and the current value (Current) is the determination reference value If (Overall_Peak) is exceeded, the current value of the target pixel is set to the peak level Peak (S624).

Thereafter, it is determined whether the difference between the peak level and the determination reference value Over_Peak falls within a predetermined setting value Diff (S625). The predetermined setting value Diff is a measure of the degree to which the determination reference value Overall_Peak is similar to the peak level of the current pixel, and may be set to gray level difference = 5.

As a result of the determination (S625), if the difference between the peak level and the determination reference value (Overall_Peak) is within a predetermined setting value (Diff) range, the effective pixel count is increased by one (S626), and for every pixel in the block It is determined again whether or not the check is completed (S627). However, if the determination result (S625), out of a predetermined set value (Diff) range, it is determined again whether or not the check for all pixels in the block is completed without increasing the number of effective pixel count (S627).

Subsequently, when the check for all the pixels in the block is not finished, the determination result (S625) moves the pixel to be checked to another pixel in the block so that the difference between the peak level and the current value of the moved pixel is predetermined. The process of determining whether it is within the value Diff is repeated (S625). However, in the determination result (S625), when the check for all the pixels in the block is completed, it is determined whether the count value counted so far exceeds the predetermined threshold Th (S631).

The predetermined threshold Th is the number of pixels similar to the peak value that can be determined to be an effective peak area, and it is preferable that the threshold value Th is set to 9 when each block includes 25 pixels. In this case, it is determined whether the number count value of the pixel whose difference between the peak level of the pixel and the determination reference value (Overall_Peak) is within 5 is 9 or more.

If the count result exceeds the predetermined threshold Th (S631), the threshold reference value (Overall_Peak) is updated to the peak level of the current pixel (S632), and the corresponding block search result is stored (S633). If the count value does not exceed the predetermined threshold Th, the corresponding block search result is stored without updating the determination reference value Overall_Peak (S633).

Thereafter, it is determined whether the check for all blocks in the image frame is finished (S634).

As a result of the determination (S634), if the check for all blocks in the image frame is not finished, the check target block is moved to perform the steps up to now (S622).

However, when the check for all the blocks in the image frame is finished (S634), the peak likelihood level area calculator 230 calculates the peak likelihood level areas for the valid blocks by using the stored block search result. Calculate The average brightness value is calculated for a block in which the number of pixels whose peak level satisfies the criterion in the searched block exceeds a predetermined threshold.

Subsequently, the frame inverter level determiner 240 determines an inverter level to adjust the brightness of the frame in response to the peak similar level areas of the effective blocks (S640).

The dynamic contrast ratio control apparatus and method using the peak level detection according to the present invention has been described in detail above. However, the present invention is not limited to the above embodiments, and many variations are possible by those skilled in the art within the spirit of the present invention. Therefore, changes and modifications are included in the present invention without departing from the spirit of the invention, such facts will be apparent to those skilled in the art.

According to the apparatus and method for controlling dynamic contrast ratio using peak level detection according to the present invention, it is possible to improve the full white-to-full black contrast ratio, which is an advantage of the conventional dynamic contrast ratio control technique, while maintaining the emotional contrast. There is an advantage.

Claims (8)

It is effective to check whether the output image frame of the scaler, which converts the magnitude of the image signal into an image signal of a size suitable for display on the display device, becomes a target block for measuring the average value for brightness adjustment for each block divided into a plurality of local regions. Block check unit; Peak level determination for detecting a peak value of a pixel for each pixel in the block for a block determined to be a valid block by the valid block checker, and determining whether a difference between a peak value of the corresponding pixel and a reference peak value is within a predetermined setting value. part; A peak similar level area calculator configured to calculate and output an area determined as an actual image area according to the number of pixels determined to be valid pixels by the peak level determiner; A frame inverter level determiner configured to determine and output an inverter level for adjusting the brightness of a corresponding video frame according to the peak similar level area output by the peak similar level area calculator; A PWM converter receiving the output of the inverter level determiner and outputting a pulse width modulated signal PWM according to the output level; A gamma correction unit for receiving the output image signal of the scaler and the output of the inverter level determination unit and outputting image data compensating for nonlinearity of brightness recognition degree of a human eye; And Dynamic contrast ratio control apparatus using a peak level detection, characterized in that it comprises an inverter for outputting a voltage of a frequency corresponding to the output of the PWM converter. delete Checking whether a valid block is divided for each block in which the image frame is divided into a plurality of local regions according to the start of the dynamic contrast ratio control function; Searching for valid pixels in the block if the check result corresponds to a valid block; Calculating an effective average brightness value for the searched valid pixels; And, And determining and applying an inverter level of the image frame according to the calculated effective average brightness value. delete The method of claim 3, wherein the checking of the valid block for each block obtained by dividing the image frame into a plurality of local regions comprises determining that the block that does not include three pixels on the outermost side of the image frame is a valid block. A dynamic contrast ratio control method using peak level detection. The method of claim 3, wherein the searching of the effective pixel comprises determining that a pixel whose difference between the pixel peak value and the reference peak value is within a predetermined setting value is a valid pixel. Contrast Ratio Control Method. The method of claim 3, wherein the searching of the valid pixel comprises changing a peak value of the reference pixel when the valid pixel is greater than or equal to a predetermined threshold. 5. The method of claim 3, wherein the calculating of the average effective brightness value for the valid pixel comprises obtaining an average brightness value for a block in which the number of pixels whose peak level in the block under search satisfies a criterion exceeds a predetermined threshold. A dynamic contrast ratio control method using peak level detection.

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