SIGNAL CONVERSION METHOD FOR DISPLAY IMAGE

• US 20150348500A1
• Filed: 12/17/2014
• Published: 12/03/2015
• Est. Priority Date: 05/29/2014
• Status: Active Grant

• Current Assignee: AU Optronics Corporation
• Original Assignee: AU Optronics Corporation
• Inventors: Lin, Hui-Feng, Cheng, Sheng-Wen
• Granted Patent: US 9,484,000 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06T 7/90 Determination of colour characteristics
• CPC Class Codes: G06V 10/56 relating to colour
• CPC Class Codes: G06V 20/36 Indoor scenes
• CPC Class Codes: G06V 20/38 Outdoor scenes
• CPC Class Codes: G09G 2320/0276 for the purpose of adaptation to the characteristics of a display device, i.e. gamma correction
• CPC Class Codes: G09G 2320/064 by time modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2320/0646 Modulation of illumination source brightness and image signal correlated to each other
• 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 2340/06 Colour space transformation
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336
• CPC Class Codes: G09G 5/02 characterised by the way in which colour is displayed details of colour display specific for CRTs G09G1/28; specific for flat matrix panels other than liquid crystal displays G09G3/2003; specific for liquid crystal displays G09G3/3607
• CPC Class Codes: G09G 5/06 using colour palettes, e.g. look-up tables
• CPC Class Codes: G09G 5/10 Intensity circuits

Abstract

A signal conversion method for a display image is provided. The signal conversion method includes: receiving an image data of the (N−1)th frame; converting the (N−1)th image data to obtain a luminance data; determining a signal tuning gain of an image data of Nth frame according to the image data of the (N−1)th frame, the luminance data and a backlight duty adjusting table; adjusting an image data of Nth frame according to the signal tuning gain of Nth frame so as to generate an output image data of Nth frame; and displaying pixels according to the output image data of Nth frame.

Claims

1. A signal conversion method for a display image adapted for a display comprising a plurality of pixels, each of the pixels having red, blue, green and brightness sub-pixels, the method comprising:

receiving an image data of the (N−

1)th frame through the display, wherein the image data comprises a red pixel data, a blue pixel data and a green pixel data corresponding to each pixel;

obtaining a luminance data according to the image data of the (N−

1)th frame;

determining a signal tuning gain of the Nth frame according to the image data and the luminance data of the (N−

1)th frame and through a backlight duty adjusting table, wherein the backlight duty adjusting table comprises a plurality of backlight luminances and a plurality of gains respectively corresponded by a plurality of luminance distribution ranges;

adjusting an image data of the Nth frame according to the signal tuning gain of the Nth frame so as to generate an output image data of the Nth frame, wherein the output image data comprises a red output sub-pixel data, a green output sub-pixel data, a blue sub-output pixel data and a luminance output sub-pixel data; and

displaying the pixel by the display according to the output image data of the pixel.

2. The signal conversion method for the display image as recited in claim 1, wherein determining the signal tuning gain according to the image data and the luminance data of the (N−

1)th frame and through the backlight duty adjusting table comprises;

generating the a plurality of backlight duties (BL DUTY) of the RGBW display according to the luminance data of the (N−

1)th frame;

calculating a plurality of cumulative pixel numbers corresponding to the backlight duties of the (N−

1)th frame based on the backlight duties, and sorting the cumulative pixel numbers in order of magnitude of the backlight duties;

when the cumulative pixel numbers sorted at the front are greater than a critical number, determining an optimum among the backlight duties corresponding to the cumulative pixel numbers sorted at the front; and

determining the signal turning gain of the Nth frame according to the backlight duty adjusting table and the optimum among the corresponding backlight duties.

3. The signal conversion method for the display image as recited in claim 1, wherein adjusting the image data of the Nth frame according to the signal tuning gain of the Nth frame so as to generate the output image data of the Nth frame comprises:

converting the image data of the Nth frame into a luminance data of the Nth frame by a gamma conversion;

after multiplying the luminance data with the signal tuning gain of the Nth frame, performing a signal conversion to generate an output luminance data of the Nth frame; and

converting the output luminance data of the Nth frame into the output image data of the Nth frame via an inverse gamma conversion.

4. The signal conversion method for the display image as recited in claim 3 further comprising:

determining a backlight duty of the Nth frame according to the signal tuning gain of the Nth frame.

5. The signal conversion method for the display image as recited in claim 1 further comprising:

determining whether the display operates under an indoor mode or an outdoor mode.

6. The signal conversion method for the display image as recited in claim 5 further comprising:

when the display operates under the outdoor mode, computing the image data according to a fixed gain so as to generate an adjusted image data of the Nth frame.

7. The signal conversion method for the display image as recited in claim 6, wherein the fixed gain equals to 2.

8. The signal conversion method for the display image as recited in claim 1, wherein the backlight duty is a reciprocal of the gain.

9. The signal conversion method for the display image as recited in claim 5, wherein when the display operates under the indoor mode, the backlight duty of the Nth frame satisfies:

10. The signal conversion method for the display image as recited in claim 5, wherein when the display operates under the indoor mode, the backlight duty of the Nth frame satisfies:

11. The signal conversion method for the display image as recited in claim 5, wherein when the display operates under the indoor mode, the backlight duty of the Nth frame satisfies:

12. The signal conversion method for the display image as recited in claim 5, wherein the backlight duties satisfy:

when the display operates under the outdoor mode, the image data of the Nth frame is a white image, and the red output sub-pixel data, the green output sub-pixel data, the blue sub-output pixel data and the luminance output sub-pixel data after being normalized by the gamma conversion respectively generate a normalized red output pixel data R, a normalized green output pixel data G, a normalized blue output pixel data B and a normalized luminance output pixel data W, wherein 0.45<

=R=G=B=W<

=0.5, the backlight duty of the Nth frame equals 100%, and a NTSC color gamut value of the display is greater than 90%.

13. The signal conversion method for the display image as recited in claim 12, wherein the backlight duty is controlled by current modulation or pulse width modulation.