METHOD OF LOCAL DIMMING, BACKLIGHT ASSEMBLY FOR PERFORMING THE METHOD AND DISPLAY APPARATUS HAVING THE BACKLIGHT ASSEMBLY

• US 20090189543A1
• Filed: 12/16/2008
• Published: 07/30/2009
• Est. Priority Date: 01/25/2008
• Status: Active Grant

• Current Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Kwon, Yong-Hoon, Kim, Gi-Cherl, Yang, Byung-Choon, Yeo, Dong-Min
• Granted Patent: US 8,111,223 B2
• Time in Patent Office: Days
• US Class Current: 315/297
• CPC Class Codes: G09G 2320/064 by time modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2320/0673 for control of gamma adjustment, e.g. selecting another gamma curve
• CPC Class Codes: G09G 2340/06 Colour space transformation
• CPC Class Codes: G09G 3/3413 Details of control of colour illumination sources
• CPC Class Codes: G09G 3/3426 the different display panel areas being distributed in two dimensions, e.g. matrix

Abstract

In order to perform local dimming, a driving dimming duty cycle is generated using a target gamma curve (TGV), wherein the driving dimming duty cycle corresponds to a representative grayscale value (RGV) of each of a plurality of dimming unit areas. Each of a plurality of light unit blocks of a light source is driven based on the driving dimming duty cycle, wherein the light unit blocks correspond to the dimming unit areas, respectively. Therefore, a display apparatus may display an image having a higher contrast ratio than normal.

Claims

1. A method of local dimming for a display panel, comprising:

generating a driving dimming duty cycle corresponding to a representative grayscale value (RGV) of each of a plurality of dimming unit areas using a target gamma curve (TGV); and

driving each of a plurality of light unit blocks of a light source based on the driving dimming duty cycle, the plurality of light unit blocks corresponding to the plurality of dimming unit areas, respectively.

2. The method of claim 1, wherein the driving dimming duty cycle is generated by:

generating the RGV of each of the plurality of dimming unit areas based on input image data;

generating a target luminance value (TLV) corresponding to the RGV using the TGV;

generating a light luminance value of each of the plurality of light unit blocks using the TLV; and

generating the driving dimming duty cycle corresponding to the light luminance value.

3. The method of claim 2, wherein the light luminance value is generated by:

calculating the light luminance value from the TLV taking into consideration interaction between the light-emitting unit blocks.

4. The method of claim 3, wherein the light luminance value is calculated by:

calculating the light luminance value from the TLV using a point spread function corresponding to the interaction between the light-emitting unit blocks.

5. The method of claim 2, wherein the driving dimming duty cycle has a duty cycle value that is decreased by a difference between a real observed luminance value of a maximum driving duty corresponding to a maximum luminance and the TLV.

6. The method of claim 2, wherein the RGV is generated by:

calculating the RGV from a plurality of individual grayscale values (IGVs) corresponding to unit pixels in each of the plurality of dimming unit areas, respectively.

7. The method claim 6, wherein the RGV is at least one of values consisting of an average value of the IGVs, a maximum value of the IGVs, a minimum value of the IGVs, and a root mean square of the IGVs.

8. The method of claim 1, wherein the RGV is calculated by:

calculating a red RGV from red individual grayscale values (IGVs) for displaying a red image;

calculating a green RGV from green IGVs for displaying a green image; and

calculating a blue RGV from blue IGVs for displaying a blue image.

9. The method of claim 8, wherein the TLV is generated by:

generating a red TLV corresponding to the red RGV using a red TGV;

generating a green TLV corresponding to the green RGV using a green TGV; and

generating a blue TLV corresponding to the blue RGV using a blue TGV.

10. The method of claim 9, wherein each of the plurality of light unit blocks is driven by:

driving each of a plurality of red unit light sources for generating red light using the red TLV;

driving each of a plurality of green unit light sources for generating green light using the green TLV; and

driving each of a plurality of blue unit light sources for generating blue light using the blue TLV.

11. The method of claim 9, wherein each of the plurality of light unit blocks is driven by:

driving each of a plurality of white unit light sources for generating white light using the red TLV, the green TLV and the blue TLV.

12. A backlight assembly comprising:

a light source including a plurality of light-emitting unit blocks corresponding to a plurality of dimming unit areas, respectively;

a local dimming control part generating a driving dimming duty cycle corresponding to a representative grayscale value (RGV) of each of the plurality of dimming unit areas using a target gamma curve value (TGV); and

a light-driving part driving each of the plurality of light-emitting unit blocks by a local dimming method in response to the driving dimming duty cycle.

13. The backlight assembly of claim 12, wherein the local dimming control part comprises:

a representative value output part generating the RGV of each of the plurality of dimming unit areas based on image data;

a target value output part generating a target luminance value (TLV) corresponding to the RGV using the TGV;

a light luminance output part generating a light luminance value of each of the plurality of light unit blocks using the TLV; and

a dimming duty cycle output part generating the driving dimming duty cycle corresponding to the light luminance value.

14. The backlight assembly of claim 13, wherein the local dimming control part further comprises:

a lookup memory storing a lookup table having information about the TGV.

15. The backlight assembly of claim 13, wherein the target value output part comprises:

a lookup memory storing a lookup table having information about the TGV.

16. The backlight assembly of claim 12, wherein the plurality of light-emitting unit blocks comprises:

red light-emitting diodes (LEDs) generating red light;

green LEDs generating green light; and

blue LEDs generating blue light.

17. The backlight assembly of claim 12, wherein the light-emitting unit blocks comprises a plurality of white LEDs generating white light.

18. A display apparatus comprising:

a display panel displaying an image in response to image data applied from outside; and

a backlight assembly supplying light to the display panel, the backlight assembly comprising;

a light source including a plurality of light-emitting unit blocks corresponding to a plurality of dimming unit areas, respectively;

a local dimming control part generating a driving dimming duty cycle corresponding to a representative grayscale value (RGV) of each of the dimming unit areas using a target gamma curve value (TGV); and

a light-driving part driving each of the plurality of light-emitting unit blocks by a local dimming method in response to the driving dimming duty cycle.

19. The display apparatus of claim 18, wherein the local dimming control part comprises:

a representative value output part generating the RGV of each of the plurality of dimming unit areas based on image data;

a target value output part generating a target luminance value (TLV) corresponding to the RGV using the TGV;

a light luminance output part generating a light luminance value of each of the plurality of light unit blocks using the TLV; and

a dimming duty cycle output part generating the driving dimming duty cycle corresponding to the light luminance value.

20. The display apparatus of claim 18, further comprising:

a timing control part controlling the display panel and the local dimming control part in response to the image data.