LOCAL-DIMMING METHOD, LIGHT SOURCE APPARATUS PERFORMING THE LOCAL-DIMMING METHOD AND DISPLAY APPARATUS HAVING THE LIGHT SOURCE APPARATUS

• US 20100060671A1
• Filed: 03/31/2009
• Published: 03/11/2010
• Est. Priority Date: 09/05/2008
• Status: Active Grant

• Current Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Kwon, Yong-Hoon, Park, Se-Ki, Kim, Gi-Cherl, Park, Sang-Il, Song, Si-Joon
• Granted Patent: US 8,629,831 B2
• Time in Patent Office: Days
• US Class Current: 345/690
• CPC Class Codes: G09G 2320/064 by time modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2360/145 the light originating from the display screen
• CPC Class Codes: G09G 3/3413 Details of control of colour illumination sources
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence

Abstract

A light source module of a display device comprises light-emitting blocks each of which comprises multiple sets of light sources, with different sets emitting different colors (e.g. red, green and blue). Each set is independently controllable according to one or more driving parameters. A local-dimming method comprises: (a) in each color-dimming period, driving each light-emitting block by the first color-dimming process; (b) in each compensating period, driving each light-emitting block by a full-color process which is independent of the image; (c) in each compensating period, sensing emitted light and determining the one or more driving parameters'"'"' reference driving values operable to generate a reference color; (d) in at least one of the color-dimming and compensating periods, driving each light-emitting block using the one or more driving -parameters'"'"' values which depend on the reference driving values; and (e) between a color-dimming period and an adjacent compensating period, gradually switching the light-source module between the first color-dimming process and the full-color process.

Claims

1. A local-dimming method for driving a light source module in a display device, the light source module comprising a plurality of independently controllable light-emitting blocks, each of the light-emitting blocks comprising a plurality of sets of light sources, each set of light sources consisting of one or more light sources, different sets of light sources of each light-emitting block emitting different colors, different sets of light-sources being independently controllable according to one or more driving parameters to allow each light-emitting block to be driven by a first color-dimming process in which each light-emitting block'"'"'s output chromaticity and luminance depend on an image displayed by the display device, the local-dimming method comprising:

(a) in each of one or more color-dimming periods of time, driving each said light-emitting block by the first color-dimming process;

(b) in each of one or more compensating periods of time, driving each said light-emitting block by a full-color process which is independent of the image;

(c) in each of said one or more compensating periods of time, while driving each said light-emitting block by the full-color process, sensing light emitted by at least one of the light sources, and based on the sensing, determining the one or more driving parameters'"'"' reference driving values operable to generate a reference color by the light-emitting blocks;

(d) in at least one of the color-dimming and compensating periods of time, driving each said light-emitting block using the one or more driving parameters'"'"' values which depend on the reference driving values; and

(e) between at least one of the color-dimming periods and an adjacent one of the compensating periods, gradually switching the light-source module between a state in which the luminance of each said light-emitting block is determined by the first color-dimming process and a state in which the luminance of each said light-emitting block is determined by the full-color process.

2. The method of claim 1 wherein:

operation (e) is performed during one or more transitional periods between a color-dimming period and an adjacent compensating period, each said transitional period comprising a plurality of frames in each of which the luminance L of each set of the light sources is a function of;

(i) the set'"'"'s luminance L_cd as determined by the first color-dimming process;

(ii) the set'"'"'s luminance L_fc as determined by the full-color process; and

(iii) the current frame; and

for each fixed value of L_cd and each fixed value of L_fc greater than L_cd, all of said functions either gradually increase or gradually decrease with each subsequent frame of the transitional period.

3. The method of claim 2 wherein operation (e) is performed in a transitional period immediately preceding a compensating period and with all of the functions gradually increasing, and operation (e) is also performed in another transitional period immediately preceding a color-dimming period with all of the functions gradually decreasing.

4. The method of claim 1 wherein operation (d) is performed in at least one color-dimming period.

5. The method of claim 4 wherein the one or more reference driving values obtained in each said compensating period in operation (c) are used in the operation (d) performed in the immediately following color-dimming period.

6. The local-dimming method of claim 1, wherein the sets of the light sources in each said light-emitting block comprise a set of one or more red light sources, a set of one or more green light sources, and a set of one or more blue light sources, and wherein the reference color is a white color.

7. The local-dimming method of claim 6, wherein each red light source emits red light in the wavelength range of about 580 nm to about 700 nm, each green light source emits green light in the wavelength range of about 460 nm to about 630 nm, and the blue light source emits blue light in the wavelength range of about 400 nm to about 520 nm.

8. The local-dimming method of claim 1, wherein operation (e) is performed immediately before and immediately after at least one compensating period, the total luminance of the light-emitting blocks gradually increasing before the at least one compensating period and gradually decreasing after the at least one compensating period.

9. The local-dimming method of claim 1, wherein operation (c) comprises:

driving each said light-emitting block by the full-color process with the one or more driving parameters having previously obtained reference driving values;

obtaining a result of the sensing in a digital format;

comparing the result of the sensing to reference color data corresponding to the reference color;

determining new reference driving values for the one or more driving parameters based on a comparison of the result of the sensing to the reference color data; and

driving each said light-emitting block by the full-color process with the one or more driving parameters having the new reference driving values.

10. A light source apparatus comprising:

a light source module comprising a plurality of light-emitting blocks, each of the light-emitting blocks comprising a plurality of sets of light sources, each set of light sources consisting of one or more light sources, different sets of light sources of each light-emitting block emitting different colors, each set of light-source being associated with respective one or more driving parameters determining an input power provided to each light-source of the set to allow each light-emitting block to be driven by a first color-dimming process in which each light-emitting block'"'"'s output chromaticity and luminance depend on an image displayed by the display device; and

a local-dimming driving part providing the one or more driving parameters to the sets of the light-sources, the local-dimming part comprising a light sensing part sensing light emitted by the light source module and comprising circuitry for;

(a) in each of one or more color-dimming periods of time, determining each said set'"'"'s driving parameters using the image to perform the first color-dimming process on each said light-emitting block;

(b) in each of one or more compensating periods of time, determining each said set'"'"'s driving parameters independently of the image to drive each said light-emitting block by a full-color process;

(c) in each of said one or more compensating periods of time, while driving each said light-emitting block by the full-color process, determining the one or more driving parameters'"'"' reference driving values based on the light sensing part'"'"'s output, the one or more driving parameters'"'"' reference driving values generating a reference color by the light-emitting blocks;

(d) in at least one of the color-dimming and compensating periods of time, driving each said light-emitting block using the one or more driving parameters'"'"' values which depend on the reference driving values; and

(e) between at least one of the color-dimming periods and an adjacent one of the compensating periods, gradually switching the light-source module between a state in which the luminance of each said light-emitting block is determined by the first color-dimming process and a state in which the luminance of each said light-emitting block is determined by the full-color process.

11. The light source apparatus of claim 10, wherein the sets of the light sources in each said light-emitting block comprise a set of one or more red light sources, a set of one or more green light sources, and a set of one or more blue light sources, and wherein the reference color is a white color.

12. The light source apparatus of claim 11, wherein each red light source emits red light in the wavelength range of about 580 nm to about 700 nm, each green light source emits green light in the wavelength range of about 460 nm to about 630 nm, and the blue light source emits blue light in the wavelength range of about 400 nm to about 520 nm.

13. The light source apparatus of claim 11, wherein the local-dimming driving part comprises:

an image analysis part analyzing an image signal corresponding to each light-emitting block and determining a color-dimming level; and

a light source driving part driving the light sources of each light-emitting block based on the color-dimming level.

14. The light source apparatus of claim 13, wherein the local-dimming driving part further comprises a compensating control part driving the light source module by the full-color process during the one or more compensating periods, and controlling the light source driving part to gradually change the luminance generation of the light-emitting blocks during transitions between a state in which the luminance of each said light-emitting block is determined by the first color-dimming process and a state in which the luminance of each said light-emitting block is determined by the full-color process.

15. The light source apparatus of claim 14, wherein the compensating control part comprises:

a storage part storing reference data including color reference data corresponding to a reference color to be generated by the light-emitting blocks in the full-color process, the reference data also including duty-ratio reference data causing the light sources to emit the reference color; and

a control part using sensing data from the light sensing part and the color reference data during each compensating period to adjust the duty-ratio reference data.

16. The light source apparatus of claim 14, further comprising:

a first printed circuit board (PCB) having the image analysis part disposed on the first PCB;

a second PCB having the light source driving part disposed on the second PCB; and

a third PCB disposed between the first and second PCBs and having the compensating control part disposed on the third PCB.

17. The light source apparatus of claim 16, further comprising a sub-PCB disposed between the second and third PCBs, and having connectors mounted on the sub-PCB, the connectors connecting an output signal of the third PCB to an input signal of the second PCB.

18. The light source apparatus of claim 14, wherein:

operation (e) is performed during the transitional periods between a color-dimming period and an adjacent compensating period, each said transitional period comprising a plurality of frames in each of which the luminance L of each set of the light sources is a function of;

(i) the set'"'"'s luminance L_cd as determined by the first color-dimming process;

(ii) the set'"'"'s luminance L_fc as determined by the full-color process; and

(iii) the current frame; and

the compensating control part controlling the light source driving part so that in each transition from a color-dimming period to a compensating period, all of said functions are gradually increasing functions of the current frame for each fixed value of L_cd and each fixed value of L_fc greater than L_cd, and in each transition from a compensating period to a color-dimming period, all of said functions are gradually decreasing functions of the current frame for each fixed value of L_cd and each fixed value of L_fc greater than L_cd.

19. The light source apparatus of claim 14, wherein the light sensing part comprises:

a light sensor sensing the light emitted the light sources during the full-color process and outputting a color sensing signal;

an amplifier amplifying the color sensing signal and outputting a color amplified sensing signal; and

an analog-to-digital converter (ADC) converting the color amplified sensing signal into digital-type color sensing data.

20. A display apparatus comprising:

a display panel displaying an image;

a light source module including a plurality of light-emitting blocks, each of the light-emitting blocks including a plurality of color light sources; and

a local-dimming driving part driving the light source module by a first color-dimming process using color-dimming levels determined based on an image portion corresponding to each of the light-emitting blocks, adjusting the light emitted by the color light sources in a full-color process during a compensating period, and driving the light-emitting blocks to have to gradually change the total luminance of the light-emitting blocks during transitions between a state in which all the light-emitting blocks are driven by the first color-dimming process and a state in which all the light-emitting blocks are driven by the full-color process.

21. The display apparatus of claim 20, wherein the local-dimming driving part comprises:

an image analysis part analyzing an image signal corresponding to each light-emitting block and determining the color-dimming levels;

a light source driving part driving the color light sources of each light-emitting block based on the color-dimming levels;

a compensating control part driving the light source module by the full-color process during the compensating period, and controlling the light source driving part so that the light-emitting blocks have the gradually changed total luminance during the transitional period; and

a light sensing part sensing the amount of the light emitted by the color light sources during the full-color process and outputting color sensing data.

22. The display apparatus of claim 21, wherein the compensating control part controls the light source driving part, so that when an image is unchanged during a first period before the compensating period and an image is unchanged during a second period after the compensating period, then the total luminance of the light source blocks is gradually increased during the first period and the total luminance of the light source blocks is gradually decreased during the second period.