LIQUID CRYSTAL DISPLAY DEVICE

• US 20110292018A1
• Filed: 04/25/2011
• Published: 12/01/2011
• Est. Priority Date: 05/28/2010
• Status: Active Grant

• Current Assignee: Maxell, Ltd.
• Original Assignee: Hitachi Consumer Electronics Company Limited (Hitachi, Ltd.)
• Inventors: Tsuru, Yasutaka, KUBOTA, Hidenao
• Granted Patent: US 8,736,543 B2
• Time in Patent Office: Days
• US Class Current: 345/211
• 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 2360/144 the light being ambient light
• CPC Class Codes: G09G 2360/16 Calculation or use of calculated indices related to luminance levels in display data
• CPC Class Codes: G09G 3/3426 the different display panel areas being distributed in two dimensions, e.g. matrix

Abstract

An area control section individually sets illumination intensity (light control value) of each backlight cell corresponding to each area of the display screen. A spatial filter corrects the light control values so that spatial distribution of the light control values becomes more moderate between adjoining areas. A black area control section sets the minimum value of the light control value based on a “black area” in the screen. A power control section corrects the light control values so that power consumption of the backlight does not exceed a limit value. A shading control section corrects the light control values to relatively lower brightness in the peripheral part of the screen compared to the central part of the screen. A micro-controller switches the operations of the above light control value correcting sections according to an image display mode selected by the user.

Claims

1. A liquid crystal display device comprising a liquid crystal panel and a backlight which illuminates the liquid crystal panel with light, wherein:

the liquid crystal panel is segmented into a plurality of areas of pixels by dividing the pixels on the panel into a plurality of pixel groups, and

the backlight is formed by a plurality of backlight cells corresponding to the areas, respectively, and

the liquid crystal display device comprises a backlight light-control section which executes area control for independently controlling illumination intensity of each backlight cell based on a brightness level of an image signal for the area corresponding to the backlight cell and a controller which controls the backlight light-control section, and

the backlight light-control section has multiple area control modes, and

the controller controls the backlight light-control section to switch the area control mode according to an image display mode selected by a user.

2. A liquid crystal display device comprising a liquid crystal panel and a backlight which illuminates the liquid crystal panel with light, wherein:

the liquid crystal panel is segmented into a plurality of areas of pixels by dividing the pixels on the panel into a plurality of pixel groups, and

the backlight is formed by a plurality of backlight cells corresponding to the areas, respectively, and

the liquid crystal display device comprises;

an area control section which sets a light control value, as a value for individually controlling illumination intensity of each backlight cell, based on a brightness level of an image signal for the area corresponding to the backlight cell;

light control value correcting sections which corrects the light control values set by the area control section; and

a controller which controls operations of the area control section and the light control value correcting sections, and

the controller controls the illumination by the backlight by switching the operations of the light control value correcting sections according to an image display mode selected by a user.

3. The liquid crystal display device according to claim 2, wherein:

the light control value correcting sections include at least two selected from the following;

a spatial filter which corrects the light control values so that spatial distribution of the light control values becomes more moderate in consideration of effect of leaking of light between adjoining areas;

a black area control section which measures a black area based on the number of pixels whose brightness signal level is a black level threshold value or less, compares the calculated black area with a black area threshold value, and sets a minimum value of the light control value based on result of the comparison;

a power control section which calculates power consumption of the backlight and corrects the light control values so that the power consumption does not exceed an electric power limit value; and

a shading control section which corrects the light control values so as to relatively lower brightness in a peripheral part of a screen of the liquid crystal panel in comparison with a central part of the screen.

4. The liquid crystal display device according to claim 3, wherein the controller sets the black area threshold value of the black area control section, the electric power limit value of the power control section or a power reduction value of the shading control section according to selection by the user.

5. The liquid crystal display device according to claim 2, wherein the image display modes selectable by the user include an in-store demonstration mode, a power reduction mode and a high image quality mode.

6. The liquid crystal display device according to claim 2, further comprising an illuminance sensor which detects illuminance around the device,

wherein the controller controls the illumination by the backlight by switching the operations of the light control value correcting sections according to the illuminance detected by the illuminance sensor.