Image processing device and image processing method

Patent metadata

Field	Value
Publication number	US-9805663-B2
Application number	US-201514797096-A
Country	US
Kind code	B2
Filing date	Jul 11, 2015
Priority date	Jul 30, 2014
Publication date	Oct 31, 2017
Grant date	Oct 31, 2017

Abstract

The image processing device includes a luminance modulator, a backlight control gain adjustment unit, a peak value detector, and a histogram detector. The peak value detector calculates a peak value as a maximum luminance value in a prescribed region of the video input signal inputted. The histogram detector calculates frequency distribution about the luminance value of the video input signal. Based on the peak value calculated by the peak value detector and the frequency distribution calculated by the histogram detector, the luminance modulator converts a luminance value of the video input signal into a luminance value of the video output signal and outputs the video output signal, for every pixel. The backlight control gain adjustment unit creates the backlight control signal based on the peak value.

First claim

What is claimed is:

1. An image processing device comprising:
a luminance modulator operable to receive a video input signal and operable to calculate a video output signal to be supplied to a display panel coupled;
a backlight control gain adjustment unit operable to calculate a backlight control signal to be supplied to a backlight controller provided in the display panel;
a peak value detector operable to calculate a peak value as a maximum luminance value in a prescribed region of the video input signal;
a histogram detector operable to calculate frequency distribution about the luminance value of the video input signal in the prescribed region,
wherein the luminance modulator converts a luminance value of the video input signal into a luminance value of the video output signal for every pixel, based on the peak value and the frequency distribution, and
wherein the backlight control gain adjustment unit calculates the backlight control signal based on the peak value;
a peak Automatic contrast level (ACL) control gain calculation unit;
a pattern-adaptive gamma characteristic calculation unit; and
a total control gain calculation unit,
wherein the peak ACL control gain calculation unit calculates a peak ACL control gain with which the luminance of each pixel of the video input signal is amplified, based on a ratio of the peak value to the maximum possible value of the video output signal,
wherein the pattern-adaptive gamma characteristic calculation unit calculates a luminance modulation gain with which the luminance of each pixel of the video input signal is modulated, based on the frequency distribution,
wherein the total control gain calculation unit calculates a product of the peak ACL control gain and the luminance modulation gain as a total control gain, and
wherein the luminance modulator converts the luminance value of the video input signal into the luminance value of the video output signal for every pixel based on the total control gain.

2. The image processing device according to claim 1 ,
wherein the pattern-adaptive gamma characteristic calculation unit calculates the luminance modulation gain based on at least one of a first function, a second function, and a third function,
wherein the first function has no point of inflection and enhances the luminance for every pixel of the video input signal,
wherein the second function has one point of inflection and enhances the luminance about a high luminance pixel above a barycenter of the frequency distribution among the video input signal, and reduces the luminance about a low luminance pixel below the barycenter, and
wherein the third function linearizes the relation of a cumulative value of the frequency to a luminance value of the frequency distribution.

3. The image processing device according to claim 2 further comprising:
a frequency distribution rate calculation unit,
wherein, when no localized distribution is observed in the frequency distribution, the frequency distribution rate calculation unit derives the first function and supplies it to the pattern-adaptive gamma characteristic calculation unit,
wherein, when the frequency distribution is locally distributed at one place, the frequency distribution rate calculation unit derives the second function and supplies it to the pattern-adaptive gamma characteristic calculation unit, and
wherein, when the frequency distribution is locally distributed at several regions, the frequency distribution rate calculation unit derives the third function with which a gamma value is specified based on the cumulative value of the frequency in the frequency distribution, and supplies the third function to the pattern-adaptive gamma characteristic calculation unit.

4. The image processing device according to claim 1 further comprising:
a bottom value detector operable to calculate a bottom value as a minimum luminance value of the video input signal in a prescribed region,
wherein the luminance modulator converts a luminance value of the video input signal into a luminance value of the video output signal for every pixel, based on the peak value and the frequency distribution, and additionally based on the bottom value.

5. The image processing device according to claim 1 ,
wherein the image processing device evaluates the enhancement amount of the luminance value of the video output signal to the luminance value of the video input signal, the enhancement being performed by the luminance modulator based on the frequency distribution, and readjusts the backlight control signal based on the enhancement amount, the backlight control signal being created by the backlight control gain adjustment unit based on the peak value.

6. The image processing device according to claim 1 ,
wherein the image processing device evaluates the enhancement amount of the luminance value of the video output signal to the luminance value of the video input signal, the enhancement being performed by the luminance modulator based on the frequency distribution, and readjusts the backlight control signal based on the enhancement amount, and
wherein, in lieu of or combining with the readjustment, the luminance modulator converts the luminance value of the video input signal into the luminance value of the video output signal for every pixel, based on the peak value and the frequency distribution, and additionally based on the enhancement amount.

7. The image processing device according to claim 1 ,
wherein the backlight controller adjusts a backlight luminance for every region corresponding to the prescribed region, and
wherein the backlight control gain adjustment unit calculates a backlight control signal to adjust the backlight luminance of the region corresponding to the prescribed region.

8. The image processing device according to claim 1 further comprising:
a processor operable to execute software,
wherein the processor performs the operation of the luminance modulator and the backlight control gain adjustment unit by executing the specified software.

9. The image processing device according to claim 1 , wherein a generation of a quantization error to the video signal is suppressed to a smaller amount than performing sequentially a conversion using the luminance modulation gain, and a conversion using luminance modulation gain.

10. An image processing device comprising:
a luminance modulator operable to receive a video input signal and operable to calculate a video output signal to be supplied to a display panel coupled;
a backlight control gain adjustment unit operable to calculate a backlight control signal to be supplied to a backlight controller provided in the display panel;
a peak value detector operable to calculate a peak value as a maximum luminance value in a prescribed region of the video input signal;
a histogram detector operable to calculate frequency distribution about the luminance value of the video input signal in the prescribed region,
wherein the luminance modulator converts a luminance value of the video input signal into a luminance value of the video output signal for every pixel, based on the peak value and the frequency distribution, and
wherein the backlight control gain adjustment unit calculates the backlight control signal based on the peak value;
a peak Automatic contrast level (ACL) control gain calculation unit;
a pattern-adaptive gamma characteristic calculation unit; and
a total control gain calculation unit,
wherein the peak ACL control gain calculation unit calculates a peak ACL control gain with which the luminance of each pixel of the video input signal is amplified, based on a ratio of the peak value to the maximum possible value of the video outp

Assignees

• Renesas Electronics Corp

Inventors

• Kawaguchi Hirofumi

Classifications

• G09G3/342

  using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines · CPC title

• G09G2320/062

  Adjustment of illumination source parameters · CPC title

• G09G2330/021

  Power management, e.g. power saving · CPC title

• G09G3/3406 Primary

  Control of illumination source (illumination devices structurally associated with liquid crystal cells G02F1/1336) · CPC title

• G09G3/36

  using liquid crystals · CPC title