Liquid crystal display apparatus and method therefor

• US 6,693,619 B1
• Filed: 10/26/2000
• Issued: 02/17/2004
• Est. Priority Date: 10/28/1999
• Status: Expired due to Term

• Current Assignee: Saturn Licensing LLC (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Nakagomi, Kazuhiro, Miura, Shinichiro
• Primary Examiner(s): Shankar, Vijay
• Assistant Examiner(s): Patel, Nitin
• Application Number:
  US09/697,686
• Time in Patent Office: 1,209 Days
• Field of Search: 345/102, 345/87, 345/213, 345/148, 345/211, 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 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 3/342 using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines
• CPC Class Codes: G09G 3/3611 Control of matrices with row and column drivers

Abstract

A liquid crystal display apparatus includes a liquid crystal module for displaying an image thereon, a backlight for emitting light from the rear surface of the liquid crystal module, and an inverter for controlling the backlight. The inverter drives the backlight at a predetermined oscillation frequency, based on pulse signals which are pulse-width modulated and are in synchronization with vertical synchronization signals. The backlight is turned off while the liquid crystal module is being scanned for an image of the next field to be displayed, and is turned on when the scanning is complete and the liquid crystal module is ready to display the refreshed image. Accordingly, undesirable afterimages such as trailing do not appear in moving images.

Claims

1. A liquid crystal display apparatus comprising:

a control unit for processing a video signal;

a liquid crystal module controlled by said control unit for displaying an image thereon;

a backlight unit for emitting light onto a rear surface of said liquid crystal module;

a vertical synchronization signal processing unit for generating pulse signals based on a vertical synchronization signal of each field of said video signal, said pulse signals being pulse-width modulated and in synchronization with said vertical synchronization signal; and

an inverter unit for generating, at a predetermined oscillation frequency, a voltage signal for driving said backlight unit, so as to turn on said backlight unit while an image of a field is displayed on said liquid crystal module and to turn off said backlight while scanning an image of a next field on said liquid crystal module, based on said pulse signals.

2. The liquid crystal display apparatus according to claim 1, wherein said vertical synchronization signal processing unit includes a time delay control unit for delaying output of said pulse signals from said vertical synchronization signal processing unit for a predetermined period of time.

3. The liquid crystal display apparatus according to claim 1, wherein said vertical synchronization signal processing unit operates only when said video signal represents a moving image.

4. The liquid crystal display apparatus according to claim 1, wherein said backlight unit includes:

a waveguide member;

a plurality of cold-cathode tubes disposed within said waveguide member; and

a light-blocking member provided in said waveguide member for blocking transmission of light within said waveguide member, wherein the light is emitted from said plurality of cold-cathode tubes.

5. The liquid crystal display apparatus according to claim 4, wherein said inverter unit includes means for controlling each of said plurality of cold-cathode tubes independently.

6. A display method for displaying an image on a liquid crystal module in accordance with a video signal input thereto, the method comprising the steps of:

generating pulse signals based on a vertical synchronization signal of each field of said video signal, said pulse signals being pulse-width modulated and in synchronization with said vertical synchronization signal;

generating voltages based on said pulse signals, at a predetermined oscillation frequency; and

driving, with said voltages, a backlight unit so as to turn on said backlight and emit light onto a rear surface of said liquid crystal module while an image of a field is displayed on said liquid crystal module and to turn off said backlight off when a scanning of an image of a next field on said liquid crystal module is performed.

7. The display method according to claim 6, further comprising the step of:

delaying output of said pulse signals following said step of generating for a predetermined period of time.

8. The display method according to claim 6, wherein said displaying an image is active only when said video signal represents a moving image.