IMAGE DISPLAY APPARATUS

• US 20100295879A1
• Filed: 05/17/2010
• Published: 11/25/2010
• Est. Priority Date: 05/19/2009
• Status: Active Grant

• Current Assignee: Maxell, Ltd.
• Original Assignee: Hitachi Consumer Electronics Company Limited (Hitachi, Ltd.)
• Inventors: OGI, Yuya, TANAKA, Kazuhiko, TSURU, Yasutaka
• Granted Patent: US 9,047,829 B2
• Time in Patent Office: Days
• US Class Current: 345/690
• CPC Class Codes: G02F 1/1336 Illuminating devices
• CPC Class Codes: G02F 1/133601 for spatial active dimming
• CPC Class Codes: G09G 2320/0238 Improving the black level
• CPC Class Codes: G09G 2320/0247 Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
• CPC Class Codes: G09G 2320/0646 Modulation of illumination source brightness and image signal correlated to each other
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 3/3426 the different display panel areas being distributed in two dimensions, e.g. matrix

Abstract

An image display apparatus includes a dimming value determination circuit for determining a dimming value of a backlight based on an input image signal, an image signal compensation circuit for compensating the input image signal supplied to a liquid crystal panel in accordance with the dimming value, and a backlight drive circuit for driving and controlling the backlight in accordance with the dimming value. When the light emitting luminance of the present frame of the backlight increases relative to the light emitting luminance of the previous frame, the backlight drive circuit delays the timing for applying the dimming value of the present frame. This makes it possible to reduce power consumption of the backlight by suppressing deterioration in the image quality in spite of the sharp change in the display image luminance.

Claims

1. An image display apparatus for displaying an image using a display panel formed by arranging plural transmittance variable elements each having a light transmittance variable in accordance with a signal of an input image and a light source unit for generating a light irradiated to the display panel, comprising:

a dimming value determination unit which determines a dimming value for setting a light emitting luminance of the light source unit based on the signal of the input image;

an image signal compensation unit which compensates the signal of the input image supplied to the display panel in accordance with the dimming value determined by the dimming value determination unit; and

a drive control unit which drives and controls the light source unit in accordance with the dimming value determined by the dimming value determination unit, wherein;

the drive control unit compares the light emitting luminance of the light source unit obtained when applying the dimming value of a present frame with the light emitting luminance obtained when applying the dimming value of a previous frame; and

when the light emitting luminance of the present frame increases, the drive control unit delays a timing for applying the dimming value of the present frame compared with the timing when the light emitting luminance of the present frame decreases for driving the light source unit.

2. The image display apparatus according to claim 1, wherein:

when the light emitting luminance of the present frame of the light source unit increases relative to the light emitting luminance of the previous frame, the drive control unit delays the timing for applying the dimming value of the present frame behind an end of a transmittance transition time of the transmittance variable element for forming the display panel; and

when the light emitting luminance of the present frame of the light source unit decreases relative to the light emitting luminance of the previous frame, the drive control unit advances the timing for applying the dimming value of the present frame earlier than the end of the transmittance transition time of the transmittance variable element for forming the display panel.

3. The image display apparatus according to claim 1, wherein the drive control unit sets the timing for applying the dimming value of the present frame to be within a transmittance transition time of a transmittance variable element for forming the display panel.

4. The image display apparatus according to claim 1, wherein:

the light source unit is formed of plural light sources each for irradiating each one of plural regions formed by dividing the display panel;

the dimming value determination unit determines the dimming value for setting the light emitting luminance of each of the light sources for irradiating the regions based on the signals of the input image in the respective regions;

the image signal compensation unit compensates the signal of the input image supplied to the display panel for each of the regions in accordance with the dimming value corresponding to the light source, which has been determined by the dimming value determination unit; and

the drive control unit compares the light emitting luminance obtained when applying the dimming value of the present frame with the light emitting luminance obtained when applying the dimming value of the previous frame in each of the light sources, and when the light emitting luminance of the present frame increases, the drive control unit delays the timing for applying the dimming value of the present frame compared with the timing when the light emitting luminance of the present frame decreases for driving the respective light sources.

5. The image display apparatus according to claim 2, wherein:

the light source unit is formed of plural light sources each for irradiating each one of plural regions formed by dividing the display panel;

the dimming value determination unit determines the dimming value for setting the light emitting luminance of each of the light sources for irradiating the regions based on the signals of the input image in the respective regions;

the image signal compensation unit compensates the signal of the input image supplied to the display panel for each of the regions in accordance with the dimming value corresponding to the light source, which has been determined by the dimming value determination unit; and

when the light emitting luminance of the present frame increases relative to the light emitting luminance of the previous frame in each of the respective light sources, the drive control unit delays the timing for applying the dimming value of the present frame behind an end of a transmittance transition time of the transmittance variable element for forming the region irradiated by the light source of the display panel, and when the light emitting luminance of the present frame decreases relative to the light emitting luminance of the previous frame, the drive control unit advances the timing for applying the dimming value of the present frame earlier than the end of the transmittance transition time of the transmittance variable element for forming the region irradiated by the light source of the display panel.

6. The image display apparatus according to claim 3, wherein:

the light source unit is formed of plural light sources each for irradiating each one of plural regions formed by dividing the display panel;

the dimming value determination unit determines the dimming value for setting the light emitting luminance of each of the light sources for irradiating the regions based on the signals of the input image in the respective regions;

the image signal compensation unit compensates the signal of the input image supplied to the display panel for each of the regions in accordance with the dimming value, which has been determined by the dimming value determination unit; and

the drive control unit sets the timing for applying the dimming value of the present frame to be within the transmittance transition time of the transmittance variable element for forming the region irradiated by the light source of the display panel in each of the respective light sources.

12. The image display apparatus according to claim 1, wherein the display panel uses a liquid crystal element as the transmittance variable element.

7. An image display apparatus for displaying an image using a display panel formed by arranging plural transmittance variable elements each having a light transmittance variable in accordance with a signal of an input image and a light source unit for generating a light irradiated to the display panel, comprising:

a dimming value determination unit which determines a dimming value for setting a light emitting luminance of the light source unit based on the signal of the input image;

an image signal compensation unit which compensates the signal of the input image supplied to the display panel in accordance with the dimming value determined by the dimming value determination unit; and

a drive control unit which drives and controls the light source unit in accordance with the dimming value determined by the dimming value determination unit,

wherein the drive control unit compares the light emitting luminance of the light source unit when applying the dimming value of the present frame with the light emitting luminance when applying the dimming value of the previous frame to apply the dimming value of the previous frame as that of the present frame when the light emitting luminance of the present frame increases, and to directly apply the dimming value of the present frame when the light emitting luminance of the present frame decreases for driving the light source unit.

8. The image display apparatus according to claim 7, wherein:

the light source unit is formed of plural light sources each for irradiating each one of plural regions formed by dividing the display panel;

the dimming value determination unit determines the dimming value for setting the light emitting luminance of each of the light sources for irradiating the regions based on the signals of the input images in the respective regions;

the image signal compensation unit compensates the signal of the input image supplied to the display panel for each of the regions in accordance with the dimming value corresponding to the light source, which has been determined by the dimming value determination unit; and

the drive control unit compares the light emitting luminance when applying the dimming value of the present frame with the light emitting luminance when applying the dimming value of the previous frame in each of the light sources to apply the dimming value of the previous frame as that of the present frame when the light emitting luminance of the present frame increases, and to directly apply the dimming value of the present frame when the light emitting luminance of the present frame decreases for driving the respective light sources.

13. The image display apparatus according to claim 7, wherein the display panel uses a liquid crystal element as the transmittance variable element.

9. An image display apparatus for displaying an image using a display panel formed by arranging plural transmittance variable elements each having a light transmittance variable in accordance with a signal of an input image and a light source unit for generating a light irradiated to the display panel, comprising:

a dimming value determination unit which determines a dimming value for setting a light emitting luminance of the light source unit based on the signal of the input image;

an image signal compensation unit which compensates the signal of the input image supplied to the display panel in accordance with the dimming value determined by the dimming value determination unit;

a dimming value correction unit which corrects the dimming value to have a time taken for an intermediate value between the dimming values before and after switching of the dimming value determined by the dimming value determination unit; and

a drive control unit which drives and controls the light source unit in accordance with the dimming value corrected by the dimming value correction unit.

10. The image display apparatus according to claim 9, wherein the dimming value correction unit corrects the dimming value at the switching time point to have a time for which plural values as the intermediate values change stepwise.

11. The image display apparatus according to claim 9, wherein:

the light source unit is formed of plural light sources each for irradiating plural regions formed by dividing the display panel;

the dimming value determination unit determines the dimming value for setting the light emitting luminance of each of the light sources for irradiating the regions based on the signals of the input images in the respective regions;

the image signal compensation unit compensates the signal of the input image supplied to the display panel for each of the regions in accordance with the dimming value corresponding to the light sources, which has been determined by the dimming value determination unit;

the dimming value correction unit corrects the dimming value to have the time taken for the intermediate value between the dimming values before and after switching of the dimming value of each of the light sources, which has been determined by the dimming value determination unit; and

the drive control unit drives and controls the respective light sources in accordance with the dimming values corrected by the dimming value correction unit.

14. The image display apparatus according to claim 9, wherein the display panel uses a liquid crystal element as the transmittance variable element.