IMAGE DISPLAY DEVICE AND IMAGE DISPLAY METHOD

• US 20140225943A1
• Filed: 08/31/2012
• Published: 08/14/2014
• Est. Priority Date: 09/07/2011
• Status: Active Grant

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Murakami, Hirofumi, Shiobara, Naoki
• Granted Patent: US 9,076,397 B2
• Time in Patent Office: Days
• US Class Current: 345/694
• CPC Class Codes: G09G 2320/0233 Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 2320/0646 Modulation of illumination source brightness and image signal correlated to each other
• CPC Class Codes: G09G 2360/16 Calculation or use of calculated indices related to luminance levels in display data
• CPC Class Codes: G09G 3/3413 Details of control of colour illumination sources
• CPC Class Codes: G09G 3/3426 the different display panel areas being distributed in two dimensions, e.g. matrix
• CPC Class Codes: G09G 3/3607 for displaying colours or for displaying grey scales with a specific pixel layout, e.g. using sub-pixels display of colours in flat matrix panels other than liquid crystal displays G09G3/2003; grey scales specific for television H04N3/127

Abstract

An object is to moderate the occurrence of mura in an oblique view in an image display device that conducts area active driving. An emission luminance calculator (151) computes a luminance (first emission luminance) (32) of LEDs in respective areas on the basis of an input image (31). The emission luminance corrector (152) applies a correction to the first emission luminance (32) on the basis of correction data (33) in an LED filter (155). Herein, provided that a first image is defined as an image displayed in the case of being externally given an image in which a high-gradation region and a low-gradation region neighbor each other as the input image (31), the emission luminance corrector (152) uses the LED filter (155) to compute a second emission luminance (34), thereby setting the values of correction data (33) stored in the LED filter (155) so as to yield a constant degree of spatial variation in the output gradations between the high-gradation region and the low-gradation region in the case of viewing the first image from a designated oblique direction.

Claims

1. An image display device including a backlight made up of a plurality of light sources, and having a function of controlling the luminance of each light source of the backlight, the image display device characterized by comprising:

a display panel, including a plurality of display elements, that displays an image based on an externally given input image;

an emission luminance calculator that divides the input image into a plurality of areas, and on the basis of an input image corresponding to each area, computes a luminance during emission of light sources corresponding to each area as a first emission luminance;

a correction filter that stores correction data for a designated number of areas near a single area;

an emission luminance corrector that computes a second emission luminance by applying the correction filter to each area and correcting the first emission luminance on the basis of the correction data;

a display data calculator that, on the basis of the input image and the second emission luminance, computes display data for controlling optical transmittance of the display elements;

a panel driving circuit that, on the basis of the display data, outputs to the display panel a signal controlling the optical transmittance of the display elements; and

a backlight driving circuit that, on the basis of the second emission luminance, outputs to the backlight a signal controlling the luminance of each light source;

wherein, provided that a first image is defined as an image displayed on the display panel in the case of being externally given an image in which a high-gradation region and a low-gradation region neighbor each other as the input image, the emission luminance corrector uses the correction filter to compute the second emission luminance, thereby setting each correction data value stored in the correction filter so as to yield a constant degree of spatial variation in output gradations between the high-gradation region and the low-gradation region in the case of viewing the first image from a designated oblique direction.

2. The image display device according to claim 1, characterized in that

provided that a target output gradation distribution is defined as a distribution of output gradations that yields a constant degree of spatial variation in output gradations between the high-gradation region and the low-gradation region in the case of viewing the first image from a designated oblique direction,

the target output gradation distribution between the high-gradation region and the low-gradation region is expressed by a straight line that passes through an outermost edge portion at which the first emission luminance is correctable by applying the correction filter to areas of the high-gradation region, and a maximal portion of output gradations expressed between the high-gradation region and the low-gradation region while viewing the first image from a designated oblique direction in a hypothetical case of not applying correction to the first emission luminance.

3. The image display device according to claim 2, characterized in that

a value of the correction data is set to a value of a difference between a luminance of the backlight obtained on the basis of a system of equations made up of a first equation expressing a distribution of output gradations in the case of viewing the first image from a front direction and a second equation expressing the target output gradation distribution, and a luminance of the backlight in a hypothetical case of not applying a correction to the first emission luminance.

4. The image display device according to claim 3, characterized in that the first equation is expressed by the following formula (Eq1):

5. The image display device according to claim 1, characterized in that

the emission luminance corrector computes the second emission luminance so that the difference between the second emission luminance and the first emission luminance is less than or equal to a predetermined limit.

6. The image display device according to claim 1, wherein

the emission luminance corrector computes the second emission luminance so that the second emission luminance is equal to or greater than a predetermined lower limit.

7. The image display device according to claim 1, characterized in that

a plurality of correction filters are provided in advance, and

the emission luminance corrector selects a correction filter to use while correcting the first emission luminance according to the input image.

8. The image display device according to claim 1, characterized in that

every time an input image is externally given, each correction data value stored in the correction filter is computed on the basis of that input image.

9. An image display method for an image display device equipped with a display panel that includes a plurality of display elements and displays an image based on an externally given input image, and a backlight made up of a plurality of light sources, the image display method characterized by comprising:

an emission luminance calculating step that divides the input image into a plurality of areas, and on the basis of an input image corresponding to each area, computes a luminance during emission of light sources corresponding to each area as a first emission luminance;

an emission luminance correcting step that computes a second emission luminance by applying a correction filter storing correction data to each of a designated number of areas near a single area, and correcting the first emission luminance on the basis of the correction data;

a display data calculating step that, on the basis of the input image and the second emission luminance, computes display data for controlling optical transmittance of the display elements;

a panel driving step that, on the basis of the display data, outputs to the display panel a signal controlling the optical transmittance of the display elements; and

a backlight driving step that, on the basis of the second emission luminance, outputs to the backlight a signal controlling the luminance of each light source;

wherein, provided that a first image is defined as an image displayed on the display panel in the case of being externally given an image in which a high-gradation region and a low-gradation region neighbor each other as the input image, the emission luminance correcting step uses the correction filter to compute the second emission luminance, thereby setting each correction data value stored in the correction filter so as to yield a constant degree of spatial variation in output gradations between the high-gradation region and the low-gradation region in the case of viewing the first image from a designated oblique direction.