Apparatus for overdrive computation and method therefor

1. An overdrive computation apparatus for generating a desired overdrive gray-level value, the apparatus comprising:

a first addition/subtraction device for receiving a first overdrive gray-level value OD 1 and a second overdrive gray-level value OD 2 , and outputting a difference value indicating a difference between the first overdrive gray-level value OD 1 and the second overdrive gray-level value OD 2 , wherein the first overdrive gray-level value OD 1 corresponds to an ith first gray-level index value X(i) and a second gray-level index value Y 1 in an overdrive lookup table, the second overdrive gray-level value OD 2 corresponds to an (i+1)th first gray-level index value X(i+1) and the second gray-level index value Y 1 in the overdrive lookup table, the overdrive lookup table includes M first gray-level index values from X( 1 ) to X(M), the ith first gray-level index value X(i) and the (i+1)th first gray-level index value X(i+1) are included in the M first gray-level index values, where i is smaller than M, and i and M are integers, the difference value lies in one of a plurality of intervals, and each of the intervals has a respective corresponding computation for an overdrive gray-level value;

a priority encoder for generating a first decision signal according to the one of the intervals in which the difference value lies;

a computation device for receiving first gray-level data and converting the first gray-level data to operated gray-level data by at least one of a bit-shifting operation and a first adding/subtracting operation, by the respective corresponding computation according to the first decision signal, wherein the first gray-level data indicates a value lying between the ith first gray-level index value X(i) and the (i+1)th first gray-level index value X(i+1); and

a second addition/subtraction device, for receiving the operated gray-level data and the first overdrive gray-level value OD 1 and for generating the desired overdrive gray-level value by a second adding/subtracting operation on the operated gray-level data and the first overdrive gray-level value OD 1 .

2. The overdrive computation apparatus according to claim 1 , wherein the first gray-level data is either previous gray-level data or current gray-level data.

3. The overdrive computation apparatus according to claim 1 , wherein the computation device further includes a comparator, the comparator is for receiving second gray-level data and the first gray-level data, the second gray-level data are gray-level data in a previous computation of the desired overdrive gray-level value or gray-level data in a current computation of the desired overdrive gray-level value while the first gray-level data are the gray-level data in the current computation of the desired overdrive gray-level value or the gray-level data in the previous computation of the desired overdrive gray-level value, respectively, and generating a second decision signal according to the second gray-level data and the first gray-level data, and the computation device generates the operated gray-level data according to the first decision signal and the second decision signal.

4. The overdrive computation apparatus according to claim 1 , wherein the operated gray-level data are converted by operating on a portion of bits of the first gray-level data.

5. The overdrive computation apparatus according to claim 1 , wherein the desired overdrive gray-level value lies between the first overdrive gray-level value and the second overdrive gray-level value.

6. The overdrive computation apparatus according to claim 1 , wherein the first overdrive gray-level value and the second overdrive gray-level value are obtained from a look up table.

7. The overdrive computation apparatus according to claim 1 , wherein the desired overdrive gray-level value is used for driving a liquid crystal molecule.

8. A method for generating a desired overdrive gray-level value by using an overdrive computation apparatus, the overdrive computation apparatus comprising a first addition/subtraction device, a priority encoder, a computation device and a second addition/subtraction device, the method comprising:

computing a difference value by the first addition/subtraction device, wherein

the difference value indicates a difference between a first overdrive gray-level value OD 1 and a second overdrive gray-level value OD 2 ,

the first overdrive gray-level value OD 1 is a corresponding value with respect to an ith first gray-level index value X(i) and a second gray-level index value Y 1 in an overdrive lookup table,

the second overdrive gray-level value OD 2 is a corresponding value with respect to an (i+1)th first gray-level index value X(i+1) and the second gray-level index value Y 1 in the overdrive lookup table,

the overdrive lookup table includes M first gray-level index values from X( 1 ) to X(M), and

the ith first gray-level index value X(i) and the (i+1)th first gray-level index value X(i+1) are included in the M first gray-level index values, where i is smaller than M, and i and M are integers, the difference value lies in one of a plurality of intervals, and each of the intervals has a respective corresponding computation for an overdrive gray-level value; generating by the priority encoder a first decision signal according to the one of the intervals in which the difference value lies;

converting by the computation device the first gray-level data to operated gray-level data by at least one of a bit-shifting operation and an adding/subtracting operation by the respective corresponding computation according to the first decision signal , wherein the first gray-level data indicates a value lying between the ith first gray-level index value X(i) and the (i+1)th first gray-level index value X(i+1); and

generating by the second addition/subtraction device the desired overdrive gray-level value according to the operated gray-level data and the first overdrive gray-level value OD 1 .

9. The method according to claim 8 , wherein the first gray-level data is either previous gray-level data or current gray-level data.

10. The method according to claim 8 , further comprises:

receiving second gray-level data, wherein the second gray-level data are gray-level data in a previous computation of the desired overdrive gray-level value or gray-level data in a current computation of the desired overdrive gray-level value while the first gray-level data are the gray-level data in the current computation of the desired overdrive gray-level value or the gray-level data in the previous computation of the desired overdrive gray-level value, respectively;

generating a second decision signal according to the first gray-level data and the second gray-level data; and

generating the operated gray-level data according to the first decision signal and the second decision signal.

11. The method according to claim 8 , wherein the step of converting by the computation device the first gray-level data to the operated gray-level data further comprises:

selecting a portion of bits of the first gray-level data and converting the first gray-level data to the operated gray-level data by operating on the portion of bits.

12. The method according to claim 8 , wherein the desired overdrive gray-level value lies between the first overdrive gray-level value and the second overdrive gray-level value.

13. The method according to claim 8 , wherein the first overdrive gray-level value and the second overdrive gray-level value are obtained by looking up a table.

14. The method according to claim 8 , further comprising driving a liquid crystal molecule according to the desired overdrive gray-level value.