Display Device, Liquid Crystal Monitor, Liquid Crystal Television Receiver, and Display Method

• US 20090121994A1
• Filed: 02/28/2006
• Published: 05/14/2009
• Est. Priority Date: 03/15/2005
• 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: Miyata, Hidekazu
• Granted Patent: US 7,936,325 B2
• Time in Patent Office: Days
• US Class Current: 345/89
• CPC Class Codes: G09G 2320/0233 Improving the luminance or brightness uniformity across the 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 2320/028 by changing the viewing angle properties, e.g. widening the viewing angle, adapting the viewing angle to the view direction
• CPC Class Codes: G09G 2320/041 Temperature compensation
• CPC Class Codes: G09G 3/2011 by amplitude modulation
• CPC Class Codes: G09G 3/2025 the sub-frames having all the same time duration
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence

Abstract

In one embodiment of the present invention, a display device is disclosed wherein if a frame luminance is less than a maximum value, the device creates a difference between luminance outputs in the two subframes and sets the luminance difference to a value less than a sub-maximum luminance which is a maximum luminance output in one subframe. With the arrangement, no complete switching of the subframes in which luminance outputs are made occurs at a grayscale level where low luminance replaces high luminance or vice versa. Thus, the grayscale level-luminance curve continues smoothly.

Claims

1. A display device displaying an image by dividing each frame into two subframes, i.e., a first subframe and a second subframe, said display device comprising:

a display section displaying an image with luminance in accordance with a luminance grayscale level represented by an incoming display signal; and

a control section generating a first display signal and a second display signal for the first and second subframes, alternately outputting the first and second display signals to the display section, and controlling to output the display signals twice per frame period so that the dividing of the frames does not change a frame luminance which is a sum luminance output of the display section in one frame, wherein

if the frame luminance is less than a maximum value, the control section creates a difference between luminance outputs in the two subframes and sets the luminance difference to a value less than a sub-maximum luminance which is a maximum luminance output in one subframe.

2. The display device of claim 1, wherein:

the control section, if the frame luminance is less than or equal to a predetermined threshold, designates the first subframe for black display in which luminance is a minimum and adjusts luminance for the second subframe to produce a display, and if the frame luminance is greater than the threshold, sets the difference between the luminance outputs in the two subframes to a value less than the sub-maximum luminance; and

the threshold is set to a value less than the sub-maximum luminance.

3. The display device of claim 2, wherein the threshold is set to a luminance range in accordance with luminance grayscale levels from 50% or more to 98% or less of a luminance grayscale level in accordance with the sub-maximum luminance.

4. The display device of claim 2, wherein until the luminance in one of the subframes reaches the sub-maximum luminance, the control section sets the difference between the luminance outputs in the two subframes to a luminance range in accordance with luminance grayscale levels from 50% or more to 98% or less of a luminance grayscale level in accordance with the sub-maximum luminance.

5. The display device of claim 1, wherein the display section is a liquid crystal panel.

6. A liquid crystal monitor, comprising:

the display device of claim 5; and

a signal feeder section for transferring externally supplied image signals to the control section, wherein

the control section in the display device generates the display signals from the image signals.

7. A liquid crystal television receiver, comprising:

the display device of claim 5; and

a tuner section for selecting a channel for television broadcast signals and transferring television image signals for the selected channel to the control section, wherein

the control section in the display device generates the display signals from the television image signals.

9. The display device of claim 1, wherein when the first and second subframes have a ratio of n:

1, the control section;

designates the first subframe for a minimum luminance and adjusts display luminance for only the second subframe, for grayscale display to set an integral luminance per frame to (Minimum Luminance+Luminance of Second Subframe)/(n+1) if the frame luminance is equal to or less than 1/(n+1) times a maximum luminance which is the threshold; and

designates the second subframe for a maximum luminance and adjusts display luminance for the first subframe, for grayscale display to set an integral luminance per frame to (Luminance of First Subframe+Maximum Luminance)/(n+1) if the frame luminance is equal to or more than 1/(n+1) times the maximum luminance.

8. A method of displaying an image by dividing each frame into two subframes, i.e., a first subframe and a second subframe, said method comprising the step of generating a first display signal and a second display signal for the first and second subframes alternately outputting the first and second display signals to the display section, and outputting the display signals twice per frame period so that the dividing of the frames does not change a frame luminance which is a sum luminance output of the display section in one frame,

wherein

if the frame luminance is less than a maximum value, the step creates a difference between luminance outputs in the two subframes and sets the luminance difference to a value less than a sub-maximum luminance which is a maximum luminance output in one subframe.