Source: https://patents.google.com/patent/US20050104840
Timestamp: 2018-04-27 01:18:29
Document Index: 56301862

Matched Legal Cases: ['art 96', 'art 96', 'art 96', 'art 96', 'art 96', 'art 96', 'art 96', 'art 96', 'art 96', 'art 96', 'art 96', 'art 96', 'art 96', 'art 96', 'art 96', 'art 96']

US20050104840A1 - Method and apparatus for driving liquid crystal display - Google Patents
US20050104840A1
US20050104840A1 US10880218 US88021804A US2005104840A1 US 20050104840 A1 US20050104840 A1 US 20050104840A1 US 10880218 US10880218 US 10880218 US 88021804 A US88021804 A US 88021804A US 2005104840 A1 US2005104840 A1 US 2005104840A1
US10880218
US7466301B2 (en )
A driving method and apparatus for a liquid crystal display stabilizing variations in the brightness of a back light dependent upon brightness components extracted from data to be displayed are disclosed. In the method, the brightness components of each frame are arranged into a histogram, which is divided into a plurality of brightness areas. The most-frequent value of the brightness components or the average value of the brightness components is extracted. The brightness of a back light is controlled to correspond to the brightness areas to which the extracted most-frequent value or the average value belongs. One or more particular areas within the brightness areas are selected such that if the extracted most-frequent value or the average value belongs to the particular areas, the brightness of the back light may not be changed in successive frames.
The present invention provides a driving method and apparatus for a liquid crystal display that is adaptive stabilizing the brightness variation of a back light in correspondence with a gray level value of input data.
FIG. 8 is a block diagram showing a configuration of a third embodiment of the picture quality enhancer shown in FIG. 2; and
FIG. 9 is a block diagram showing a configuration of a fourth embodiment of the picture quality enhancer shown in FIG. 2.
Go=YM−0.396×UD−0.581×VD − (5)
The flag generator 62 applies a control signal of ‘0’ or ‘1’ to the back light controller 64 in correspondence with the most-frequent value F inputted thereto. An operation procedure of the flag generator 62 will be described in detail with reference to FIG. 7 and FIG. 8.
Firstly, the first comparator 80 compares the most-frequent value F and the first boundary value F1 to thereby output ‘1’ when the most-frequent value F is larger than the first boundary value F1 while outputting ‘0’ otherwise. The second comparator 82 compares the most-frequent value F and the second boundary value F2 to thereby output ‘1’ when the most-frequent value F is smaller than the second boundary value F2 while outputting ‘0’ otherwise. The third comparator 84 compares the most-frequent value F and the third boundary value F3 to thereby output ‘1’ when the most-frequent value F is smaller than the third boundary value F3 while outputting ‘0’ otherwise. The fourth comparator 86 compares the most-frequent value F and the fourth boundary value F4 to thereby output ‘1’ when the most-frequent value F is larger than the fourth boundary value F4 while outputting ‘0’ otherwise.
The output part 96 applies a control signal (i.e., a flag signal) of ‘1’ or ‘0’ to the back light controller 64 in correspondence with a value from the logical sum operation array 100. To this end, the output part 96 consists of a D flip-flop. The input D of the D flip-flop receives the output signal of the first AND gate 88 while the clock EN thereof receives the output signal of the second OR gate 94.
An operation procedure of the flag generator 62 will be described assuming that the most-frequency value F is positioned between the first boundary value F1 and the second boundary value F2. If the most-frequency value F is positioned between the first boundary value F1 and the second boundary value F2, then the first and second comparators 80 and 82 output signals of ‘1’ while the third and fourth comparators 84 and 86 output signals of ‘0’.
If the first and second comparators 80 and 82 output signals of ‘1’, then the first and second AND gates 88 and 90 output signals of ‘0’. Herein, the signal of ‘1’ outputted from the first AND gate 88 is applied to the input D of the output part 96. If the second AND gate 90 outputs a signal of ‘1’, then the second OR gate 94 outputs a signal of ‘1’ irrespectively of an output of the first OR gate 92. Herein, the signal of ‘1’ outputted from the second OR gate 94 is applied to the clock EN of the output part 96. Thus, if the most-frequency value F is positioned between the first boundary value F1 and the second boundary value F2, then the flag generator 62 applies a flag signal of ‘1’ to the back light controller 64.
If the most-frequent value F has a gray level less than the third boundary value F3, then the first and fourth comparators 80 and 86 output signals of ‘0’ while the second ‘and third comparators 82 and 84 output signals of ‘1’.
If the first comparator 80 outputs a signal of ‘0’, then the first and second AND gates 88 and 90 output signals of ‘0’ irrespectively of an output of the second comparator 82. Herein, the signal of ‘0’ outputted from the first AND gate 88 is applied to the input D of the output part 96. If the third comparator 80 outputs a signal of ‘1’, then the first OR gate 92 outputs a signal of ‘1’. On the other hand, if the first OR gate 92 outputs a signal of ‘1’, then the second OR gate 94 also outputs a signal of ‘1’. Herein, the signal of ‘1’ outputted from the second OR gate 94 is applied to the clock EN of the output part 96. Thus, the most-frequent value F has a gray level less than the third boundary value F3, then the flag generator 62 applies a flag signal of ‘0’ to the back light controller 64.
On the other hand, if the most-frequent value F has a gray level more than the fourth boundary value F4, then the first and fourth comparators 80 and 86 output signals of ‘1’ while the second and third comparators 82 and 84 output signals of ‘0’. Herein, the signal of ‘0’ outputted from the first AND gate 88 is applied to the input D of the output part 96. If the fourth comparator 86 outputs a signal of ‘1’, then the first OR gate 92 outputs a signal of ‘1’. On the other hand, if the first OR gate 92 outputs a signal of ‘1’, then the second OR gate 94 also outputs a signal of ‘1’. Herein, the signal of ‘1’ outputted from the second OR gate 94 is applied to the clock EN of the output part 96. Thus, the most-frequent value F has a gray level more than the fourth boundary value F4, then the flag generator 62 applies a flag signal of ‘0’ to the back light controller 64.
If the most-frequent value F has a gray level between the third boundary value F3 and the first boundary value F1, then the second comparator 82 outputs a signal of ‘1’ while the remaining comparators 80, 84 and 86 other than the second comparator 82 output signals of ‘0’.
If the first comparator 80 outputs a signal of ‘0’, then the first and second AND gates 88 and 90 output signals of ‘0’ irrespectively of an output of the second comparator 82. Herein, the signal of ‘0’ outputted from the first AND gate 88 is applied to the input D of the output part 96. If the third and fourth comparators 84 and 86 output signals of ‘0’, then the first and second OR gates 92 and 94 output signals of ‘0’. The signal of ‘0’ outputted from the second OR gate 94 is applied to the clock EN of the output part 96. Herein, as the signal of ‘0’ is inputted to the clock EN of the output part 96, the output part 96 does not generate an output. In other words, if the most-frequent value F has a gray level between the third boundary value F3 and the first boundary value F1, then the flag generator 62 maintains a previous flag signal (of ‘0’ or ‘1’)
On the other hand, if the most-frequent value F has a gray level between the second boundary value F2 and the fourth boundary value F4, then the first comparator 80 outputs a signal of ‘1’ while the remaining comparators 82, 84 and 86 other than the first comparator 80 output signals of ‘0’.
If the second comparator 82 outputs a signal of ‘0’, then the first and second AND gates 88 and 90 output signals of ‘0’ irrespectively of an output of the first comparator 80. Herein, the signal of ‘0’ outputted from the first AND gate 88 is applied to the input D of the output part 96. If the third and fourth comparators 84 and 86 output signals of ‘0’, then the first and second OR gates 92 and 94 output signals of ‘0’. The signal of ‘0’ outputted from the second OR gate 94 is applied to the clock EN of the output part 96. Herein, as the signal of ‘0’ is inputted to the clock EN of the output part 96, the output part 96 does not generate an output. In other words, if the most-frequent value F has a gray level between the second boundary value F2 and the fourth boundary value F4, then the flag generator 62 maintains a previous flag signal (of ‘0’ or ‘1’).
In other words, the present flag generator 62 applies a flag signal of ‘1’ to the back light controller 64 when the most-frequent value F is positioned between the first boundary value F1 and the second boundary value F2 while applying a flag signal of ‘0’ to the back light controller 64 when the most-frequent value F has a value less than the third boundary value F3 or a value more than the fourth boundary value F4. On the other hand, the flag generator 62 maintains the previous flag signal when the most-frequent value F is positioned between the third boundary value F3 and the first boundary value F1 or between the second boundary value F2 and the fourth boundary value F4.
(D) extracting at least one of a most-frequent value of the gray levels in the histogram and an average value of the gray levels in the histogram; and
(E) controlling brightness of a back light to correspond to the brightness areas to which the extracted belongs.
2. The method of claim 1, wherein the brightness of the back light is controlled such that a different brightness can be produced for each of the brightness areas.
3. The method of claim 2, wherein the most-frequent value is extracted from the histogram, and the brightness of the back light is controlled to correspond to the brightness area to which the most-frequent value belongs.
4. The method of claim 2, wherein the average value is extracted from the histogram, and the brightness of the back light is controlled to correspond to the brightness area to which the average value belongs.
5. The method of claim 2, further comprising selecting the brightness area to which the most-frequent value belongs to control the brightness of the back light when the number of brightness components occupying the most-frequent value is at least a predetermined percentage of the total brightness components of the frame and selecting the brightness area to which the average value belongs to control the brightness of the back light when the most-frequent value is less than the predetermined percentage.
6. The method of claim 2, wherein the brightness of the back light is controlled such that the brightness supplied increases with an increase in gray level of the extracted value.
7. The method of claim 2, further comprising maintaining the brightness of the back light from the brightness of the back light in a previous frame when the brightness area in which the extracted value belongs is at least one brightness area of the plurality of brightness areas.
8. The method of claim 7, wherein a brightness area of the at least one brightness area separates brightness areas in which the brightness of the back light is allowed to change.
9. A method of driving a display, comprising:
(D) extracting at least one of a most-frequent value of the gray levels of the histogram and an average value of the gray levelsof the histogram;
(E) generating a flag signal to correspond to a brightness area to which the extracted belongs; and
(F) controlling brightness of a back light using the extracted value and the flag signal.
10. The method of claim 9, further comprising maintaining the flag signal from a previous flag signal when the most-frequent value or the average value belongs to at least one brightness area of the brightness areas and otherwise permitting the flag signal to be able to be changed from the previous flag signal when the most-frequent value or the average value does not belong to the at least one brightness area.
11. The method of claim 10, further comprising maintaining the brightness of the back light from a previous brightness of the back light when the flag signal is maintained irrespective of the brightness area to which the most-frequent value or the average value belongs.
12. The method of claim 10, wherein the at least one brightness area is an area in which a brightness value of the back light is not changed.
13. The method of claim 10, further comprising changing the brightness of the back light to correspond to an area to which the most-frequent value or the average value belongs when the flag signal is changed.
14. The method of claim 9, further comprising further comprising selecting the brightness area to which the most-frequent value belongs to control the brightness of the back light when the number of brightness components occupying the most-frequent value is at least a predetermined percentage of the total brightness components of the frame and selecting the brightness area to which the average value belongs to control the brightness of the back light when the most-frequent value is less than the predetermined percentage.
15. A driving apparatus for driving a display, comprising:
a back light control for extracting a most-frequent value or an average value of the gray levels from the histogram and for controlling brightness of a back light using the extracted value, the back light, control dividing the gray levels into a plurality of areas and controlling the brightness of the back light in correspondence with an area to which the extracted value belongs.
16. The driving apparatus of claim 15, wherein the back light control includes:
a back light controller for controlling the brightness of the back light to correspond to the area to which the most-frequent value belongs; and
17. The driving apparatus of claim 15, wherein the back light control includes:
a back light controller for controlling the brightness of the back light to correspond to the area to which the average value belongs; and
18. The driving apparatus of claim 15, wherein the back light control includes:
19. The driving apparatus of claim 16, wherein the back light controller controls the back light such that a different brightness of light can be supplied for each area.
20. The driving apparatus of claims 17, wherein the back light controller controls the back light such that a different brightness of light can be supplied for each area.
21. The driving apparatus of claims 18, wherein the back light controller controls the back light such that a different brightness of light can be supplied for each area.
22. The driving apparatus of claim 15, wherein the back light control includes:
23. The driving apparatus of claim 15, wherein the back light control includes:
24. The driving apparatus of claim 15, wherein the back light control includes:
25. The driving apparatus of claim 22, wherein the back light controller does not change the brightness of the back light when the flag signal has the same value as the previous flag signal.
26. The driving apparatus of claim 23, wherein the back light controller does not change the brightness of the back light when the flag signal has the same value as the previous flag signal.
27. The driving apparatus of claim 24, wherein the back light controller does not change the brightness of the back light when the flag signal has the same value as the previous flag signal.
28. The driving apparatus of claim 22, wherein the flag generator is required to generate a flag signal identical to the previous flag signal when the area to which the most-frequent value belongs is a particular area selected from the plurality of areas.
29. The driving apparatus of claim 23, wherein the flag generator is required to generate a flag signal identical to the previous flag signal when the area to which the average value belongs is a particular area selected from the plurality of areas.
30. The driving apparatus of claim 24, wherein the flag generator is required to generate a flag signal identical to the previous flag signal when the area to which the extracted value belongs is a particular area selected from the plurality of areas.
31. The driving apparatus of claim 28, wherein the particular area lies between areas in which the flag generator is not required to generate a flag signal identical to the previous flag signal.
32. The driving apparatus of claim 29, wherein the particular area lies between areas in which the flag generator is not required to generate a flag signal identical to the previous flag signal.
33. The driving apparatus of claim 30, wherein the particular area lies between areas in which the flag generator is not required to generate a flag signal identical to the previous flag signal.
34. The driving apparatus of claim 22, wherein the flag generator comprises:
35. The driving apparatus of claim 23, wherein the flag generator comprises:
36. The driving apparatus of claim 24, wherein the flag generator comprises:
US10880218 2003-11-17 2004-06-28 Method of driving a display adaptive for making a stable brightness of a back light unit Active 2027-01-02 US7466301B2 (en)
KRP2003-81174 2003-11-17
US20050104840A1 true true US20050104840A1 (en) 2005-05-19
US7466301B2 US7466301B2 (en) 2008-12-16
US10880218 Active 2027-01-02 US7466301B2 (en) 2003-11-17 2004-06-28 Method of driving a display adaptive for making a stable brightness of a back light unit
JP4415172B2 (en) * 2001-03-26 2010-02-17 カシオ計算機株式会社 Image processing apparatus, image processing method, and image processing program
JP3986334B2 (en) * 2002-03-15 2007-10-03 シャープ株式会社 The liquid crystal display device
US7466301B2 (en) 2008-12-16 grant
JP2008134664A (en) 2008-06-12 application
JP4198646B2 (en) 2008-12-17 grant
CN100435202C (en) 2008-11-19 grant
CN1619630A (en) 2005-05-25 application
JP2005148709A (en) 2005-06-09 application
KR20050047357A (en) 2005-05-20 application
JP4738428B2 (en) 2011-08-03 grant
KR100570966B1 (en) 2006-04-14 grant
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:SOHN, MIN HO;BAIK, SEONG HO;REEL/FRAME:015534/0671;SIGNING DATES FROM 20040624 TO 20040626