Liquid crystal display device having multi-speed drive modes and image interpolation

• US 8,842,140 B2
• Filed: 08/06/2010
• Issued: 09/23/2014
• Est. Priority Date: 08/07/2009
• Status: Expired due to Fees

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Oniki, Motoyuki
• Primary Examiner(s): Boddie, William
• Assistant Examiner(s): Gyawali, Bipin
• Application Number:
  US13/389,415
• Publication Number:
  US 20120162289A1
• Time in Patent Office: 1,509 Days
• Field of Search: 345/690, 345/102
• US Class Current: 345/690
• CPC Class Codes: G02F 1/133601 for spatial active dimming
• CPC Class Codes: G02F 1/133602 Direct backlight
• CPC Class Codes: G02F 1/133603 with LEDs
• 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 2340/0435 Change or adaptation of the frame rate of the video stream
• 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: H04N 7/0132 the field or frame frequency of the incoming video signal being multiplied by a positive integer, e.g. for flicker reduction

Abstract

To provide a liquid crystal display device capable of reducing the occurrence of a multi-contour in the display of a moving image to the minimum, the cycle of execution of an intermittent lighting operation in backlight scanning and the cycle of a vertical synchronization signal are made equal when an interpolation image insertion mode in which an interpolation image signal generated on the basis of two or more continuous frame images is inserted between frames and written into a liquid crystal panel is executed, and the cycle of the execution of the intermittent lighting operation in the backlight scanning is made longer than the cycle of the vertical synchronization signal (or the backlight scanning is disabled) when an overlapped image output mode in which the same frame image is written into the liquid crystal panel continuously n times is executed.

Claims

1. A liquid crystal display device comprising:

an image writing portion that writes an image signal onto a liquid crystal panel in accordance with a given clock signal;

a backlight source having a plurality of sub-light-sources arranged in rows in correspondence to a plurality of display areas in a vertical direction of the liquid crystal panel;

a backlight control portion that executes a backlight scanning that causes each of the sub-light-sources to sequentially and repeatedly execute an intermittent turning-on action consisting of an action of a given consecutive turning-off period and an action of a given consecutive turning-on period in connection with an image signal writing action by the image signal writing portion; and

an interpolation image generating portion that generates an interpolation image signal based on two or more consecutive frame images, wherein

the image writing portion writing an image signal onto the liquid crystal panel in synchronization with a vertical synchronization signal having a frequency n times (n represents an integer of 2 or larger one) a frame frequency of a video signal containing the image signal, the image writing portion, when in a first multi-speed drive mode, executing an interpolation image insertion process in which the interpolation image signal generated by the interpolation image generating portion is inserted between frames and is written onto the liquid crystal panel, and, when in a second multi-speed drive mode, the image writing portion executing an overlapped image output process in which the same frame image is written onto the liquid crystal panel n times in a row, and wherein

the backlight control portion matches an execution cycle of the intermittent turning-on action in the backlight scanning to a cycle of the vertical synchronization signal when the image writing portion executes the first multi-speed drive mode, while increasing the execution cycle of the intermittent turning-on action in the backlight scanning to a cycle longer than the cycle of the vertical synchronization signal or invalidates the backlight scanning when the image writing portion executes the second multi-speed drive mode;

an interpolation image precision determining portion that determines whether precision of an interpolation image signal generated by the interpolation image generating portion is equivalent to preset precision, wherein

even when the image writing portion executes the first multi-speed drive mode, if the interpolation image precision determining portion determines the precision of the interpolation image signal to be not equivalent to the preset precision, the backlight control portion increases an execution cycle of the intermittent turning-on action in the backlight scanning to a cycle longer than a cycle of the vertical synchronization signal or invalidates the backlight scanning.

2. The liquid crystal display device as defined in claim 1, wherein

when the image writing portion executes the second multi-speed drive mode, the backlight control portion determines an execution cycle of the intermittent turning-on action in the backlight scanning to be n times a cycle of the vertical synchronization signal.

3. The liquid crystal display device as defined in claim 1, wherein

when the image writing portion executes the second multi-speed drive mode, the backlight control portion so shortens an execution cycle of the intermittent turning-on action in the backlight scanning that the backlight scanning is invalidated substantially.

4. The liquid crystal display device as defined in claim 2 or 3, wherein

the backlight control portion keeps a turning-on ratio in n frames in the backlight scanning constant.

5. The liquid crystal display device as defined in claim 1, wherein

when the interpolation image generating portion generates candidates for an interpolation image signal in number equal to or greater than preset number of candidates, the interpolation image precision determining portion determines precision of the interpolation image signal to be not equivalent to the preset precision.