Liquid crystal display device

• US 7,161,577 B2
• Filed: 11/15/2001
• Issued: 01/09/2007
• Est. Priority Date: 11/30/2000
• Status: Expired due to Term

• Current Assignee: Panasonic Liquid Crystal Display Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Hitachi Device Engineering Co., Ltd., Hitachi, Ltd.
• Inventors: Ono, Kikuo, Shingai, Akira, Hirakata, Junichi
• Primary Examiner(s): Patel; Nitin
• Application Number:
  US09/987,595
• Publication Number:
  US 20020067332A1
• Time in Patent Office: 1,881 Days
• Field of Search: 345/87, 345/88, 345/89, 345/102, 345/103, 345/84, 345/48, 345/38, 345/211, 345/83, 345/85, 345/99, 345/100, 345/101, 345/90, 345 91- 97, 345/98, 349/61, 349/68, 349/138, 349/139, 315/158
• US Class Current: 345/102
• CPC Class Codes: G09G 2310/0237 Switching ON and OFF the backlight within one frame
• CPC Class Codes: G09G 2310/024 Scrolling of light from the illumination source over the display in combination with the scanning of the display screen
• CPC Class Codes: G09G 2310/08 Details of timing specific for flat panels, other than clock recovery
• CPC Class Codes: G09G 2320/0261 in the context of movement of objects on the screen or movement of the observer relative to the screen
• CPC Class Codes: G09G 2320/041 Temperature compensation
• CPC Class Codes: G09G 2320/0633 by amplitude modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2320/064 by time modulation of the brightness of the illumination source
• 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 2360/145 the light originating from the display screen
• CPC Class Codes: G09G 2360/16 Calculation or use of calculated indices related to luminance levels in display data
• CPC Class Codes: G09G 3/342 using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines

Abstract

In a liquid crystal display device having a backlight, the backlight has a first state which outputs a first amount of light and a second state which generates a second amount of light and the time for the first state and the time for the second state are controlled. Due to such a constitution, the liquid crystal display device can display clear motion picture images in spite of a simple constitution thereof. Further, the liquid crystal display device can display clear and bright motion picture images.

Claims

1. A liquid display device comprising:

a liquid crystal display panel; and

a backlight unit,

wherein the backlight unit repeats lighting and extinguishing a backlight at a constant refresh rate such that a lighting time period is shorter for a motion picture image with a fast-moving subject captured therein than for a motion picture image with a slow-moving subject captured therein, and

the motion picture images have an identical frame rate.

2. A liquid display device according to claim 1, further comprising an image movement degree detection circuit.

3. A liquid display device according to claim 2, further comprising a signal information classifying circuit for classifying signal information into at least a normal movement state and a fast movement state.

4. A liquid display device according to claim 2, further comprising a signal information classifying circuit for classifying signal information into at least a still picture state and a motion picture state.

5. A liquid display device according to claim 1, wherein a current of the backlight is increased when the lighting time period becomes shorter.

6. A liquid display device according to claim 1, wherein the backlight unit includes a lamp, and a current of the lamp is increased when the lighting time period becomes shorter.

7. A liquid display device according to claim 1, wherein the lighting time period is changed based on an image movement at center of the display panel.

8. A liquid display device according to claim 1, wherein the repeating of lighting and extinguishing is synchronized with a scanning signal.

9. A liquid display device according to claim 1, wherein the liquid crystal panel is one of a lateral electric field type, a longitudinal electric field type, and a vertical orientation type, and the longitudinal electric field type has liquid crystal molecules oriented parallel to a surface of a substrate and has a twisted structure.

10. A liquid display device comprising:

a liquid crystal display panel; and

a backlight unit,

wherein the backlight unit controls a backlight to maintain lighting at a constant light amplitude for a still picture image with a non-moving subject captured therein, and repeats lighting and extinguishing for a moving picture image with a moving subject captured therein, and

the still and moving picture images have an identical frame rate.

11. A liquid display device according to claim 10, wherein further comprising an image movement degree detection circuit.

12. A liquid display device according to claim 11, further comprising a signal information classifying circuit for classifying signal information into at least a still picture state and a motion picture state.

13. A liquid display device according to claim 10, wherein a current of the backlight is increased when the lighting time period becomes shorter.

14. A liquid display device according to claim 10, wherein the backlight unit includes a lamp, and a current of the lamp is increased when the lighting time period becomes shorter.

15. A liquid display device according to claim 10, wherein the lighting time period is changed based on an image movement at center of the display panel.

16. A liquid display device according to claim 10, wherein the repeating of lighting and extinguishing is synchronized with a scanning signal.

17. A liquid display device according to claim 10, wherein the liquid crystal panel is one of a lateral electric field type, a longitudinal electric field type, and a vertical orientation type, and the longitudinal electric field type has liquid crystal molecules oriented parallel to a surface of a substrate and has a twisted structure.