Display device

• US 9,293,088 B2
• Filed: 10/08/2009
• Issued: 03/22/2016
• Est. Priority Date: 10/24/2008
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Yoshida, Yasunori, Kimura, Hajime
• Primary Examiner(s): Lee, Nicholas
• Application Number:
  US12/575,990
• Publication Number:
  US 20100103089A1
• Time in Patent Office: 2,357 Days
• Field of Search: 345/77, 345/589, 345/208, 345/89, 345/102, 345/691, 362 971- 973
• US Class Current: 1/1
• CPC Class Codes: G09G 2310/061 for resetting or blanking
• CPC Class Codes: G09G 2320/0233 Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 2320/0247 Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
• CPC Class Codes: G09G 2320/0252 Improving the response speed
• CPC Class Codes: G09G 2320/062 Adjustment of illumination source parameters
• CPC Class Codes: G09G 2320/066 for control of contrast
• CPC Class Codes: G09G 2320/068 for control of viewing angle adjustment
• CPC Class Codes: G09G 2320/103 Detection of image changes, e.g. determination of an index representative of the image change
• CPC Class Codes: G09G 2320/106 Determination of movement vectors or equivalent parameters within the image
• CPC Class Codes: G09G 2340/16 Determination of a pixel data signal depending on the signal applied in the previous frame
• CPC Class Codes: G09G 3/2022 using sub-frames
• CPC Class Codes: G09G 3/3426 the different display panel areas being distributed in two dimensions, e.g. matrix
• CPC Class Codes: G09G 3/3611 Control of matrices with row and column drivers

Abstract

It is an object to improve image quality in displaying a still image and a moving image by suppressing flickers, a display malfunction, or the like of a display device. A method for controlling the light emission state of a backlight is made different between a still image portion and a moving image portion included in an image to be displayed. In specific, the amount of light emission in the still image portion is made as small as possible in a corresponding divided region of the backlight, and the amount of light emission in the moving image portion is controlled so as not to be changed as much as possible in a corresponding divided region of the backlight.

Claims

1. A display device comprising:

a backlight including a plurality of regions whose brightness can be individually controlled;

a pixel portion including a plurality of pixels provided in the plurality of regions in the backlight;

a control unit for comparing pieces of image data in a plurality of frame periods with each other so as to determine a moving image portion and a still image portion in the plurality of frame periods and for determining light-emission luminance of each of the plurality of regions in the backlight; and

a backlight controller for making the plurality of regions included in the backlight emit light in accordance with a signal from the control unit,

wherein the backlight controller controls light-emission luminance of each of the regions in the backlight corresponding to the moving image portion in a different manner from that corresponding to the still image portion so that a duty ratio of light-emission luminance of a region in the backlight corresponding to the moving image portion is configured to be 100% throughout the entirety of each frame period of the plurality of frame periods in order to be constant in the plurality of frame periods.

2. The display device according to claim 1, wherein, in a case of displaying an image in a kth frame, at least a (k−

2)th frame, a (k−

1)th frame, and the kth frame are used in the plurality of frame periods.

3. The display device according to claim 1, wherein, in a case of displaying an image in a kth frame, at least a (k−

1)th frame, the kth frame, and a (k+1)th frame are used in the plurality of frame periods.

4. A display device comprising:

a backlight including a plurality of regions whose brightness can be individually controlled;

a pixel portion including a plurality of pixels provided in the plurality of regions in the backlight;

a control unit for comparing pieces of image data in a plurality of frame periods with each other so as to determine a moving image portion and a still image portion in the plurality of frame periods and for determining light-emission luminance of each of the plurality of regions in the backlight; and

a backlight controller for making the plurality of regions included in the backlight emit light in accordance with a signal from the control unit,

wherein the backlight controller controls light-emission luminance of each of the regions in the backlight corresponding to the moving image portion in a different manner from that corresponding to the still image portion so that a duty ratio of light-emission luminance of a region in the backlight corresponding to the moving image portion is configured to be 100% throughout the entirety of each frame period of the plurality of frame periods in order to be constant in the plurality of frame periods, and

wherein each of the plurality of regions in the backlight maintains certain brightness in the plurality of frame periods.

5. The display device according to claim 4, wherein, in a case of displaying an image in a kth frame, at least a (k−

2)th frame, a (k−

1)th frame, and the kth frame are used in the plurality of frame periods.

6. The display device according to claim 4, wherein, in a case of displaying an image in a kth frame, at least a (k−

1)th frame, the kth frame, and a (k+1)th frame are used in the plurality of frame periods.

7. A display device comprising:

a backlight including a plurality of regions whose brightness can be individually controlled;

a pixel portion including a plurality of pixels provided in the plurality of regions in the backlight;

a control unit for comparing pieces of image data in a plurality of frame periods with each other so as to determine a moving image portion and a still image portion in the plurality of frame periods and for determining light-emission luminance of each of the plurality of regions in the backlight; and

a backlight controller for making the plurality of regions included in the backlight emit light in accordance with a signal from the control unit,

wherein the backlight controller controls light-emission luminance of each of the regions in the backlight corresponding to the moving image portion in a different manner from that corresponding to the still image portion so that a duty ratio of light-emission luminance of a region in the backlight corresponding to the moving image portion is configured to be 100% throughout the entirety of each frame period of the plurality of frame periods in order to be constant in the plurality of frame periods, and

wherein consecutive frames are used in the plurality of frame periods.

8. The display device according to claim 7, wherein, in a case of displaying an image in a kth frame, at least a (k−

2)th frame, a (k−

1)th frame, and the kth frame are used in the plurality of frame periods.

9. The display device according to claim 7, wherein, in a case of displaying an image in a kth frame, at least a (k−

1)th frame, the kth frame, and a (k+1)th frame are used in the plurality of frame periods.

10. A display device comprising:

a backlight including a plurality of regions whose brightness can be individually controlled;

a pixel portion including a plurality of pixels provided in the plurality of regions in the backlight;

a control unit for comparing pieces of image data in a plurality of frame periods with each other so as to determine a moving image portion and a still image portion in the plurality of frame periods and for determining light-emission luminance of each of the plurality of regions in the backlight; and

a backlight controller for making the plurality of regions included in the backlight emit light in accordance with a signal from the control unit,

wherein the backlight controller controls light-emission luminance of each of the regions in the backlight corresponding to the moving image portion in a different manner from that corresponding to the still image portion so that a duty ratio of light-emission luminance of a region in the backlight corresponding to the moving image portion is configured to be 100% throughout the entirety of each frame period of the plurality of frame periods in order to be constant in the plurality of frame periods,

wherein each of the plurality of regions in the backlight maintains certain brightness in the plurality of frame periods, and

wherein consecutive frames are used in the plurality of frame periods.

11. The display device according to claim 10, wherein, in a case of displaying an image in a kth frame, at least a (k−

2)th frame, a (k−

1)th frame, and the kth frame are used in the plurality of frame periods.

12. The display device according to claim 10, wherein, in a case of displaying an image in a kth frame, at least a (k−

1)th frame, the kth frame, and a (k+1)th frame are used in the plurality of frame periods.