Display apparatus containing controller driver with correcting circuit and method of driving display panel

1. A display apparatus comprising:

a display panel;

a correcting circuit configured to carry out a gamma correction on input gradation data in response to correction data which specifies a shape of a gamma curve to generate output gradation data;

a correction data storage section configured to receive and store said correction data, supplied externally, and to transfer the stored correction data to said correcting circuit; and

a driving circuit configured to drive said display panel in response to said output gradation data from said correcting circuit,

wherein said correcting circuit:

selects a correction calculation equation from among a plurality of correction calculation equations based on a value of said input gradation data and said correction data, the selected correction calculation equation including a parameter which is determined based on a maximum value of the input gradation data, and a coefficient which is determined based on said correction data; and

carries out an approximation calculation for said gamma correction based on said input gradation data by using the selected correction calculation equation; and

wherein said correction data comprises correction point data CP 0 to CP 5 ,

if said input gradation data is D IN , said output gradation data is D OUT and an intermediate data value D IN Center is defined by a following equation (1) by using a permissible maximum value D IN MAX of said input gradation data:

D IN Center =D IN MAX /2  (1)

(1) when said correction point data CP 0 to CP 5 are determined for said input gradation data D IN to be smaller than said intermediate data value D IN Center and for a gamma value of said gamma correction to be less than one, said output gradation data D OUT is calculated from the following equation (2a):

D OUT =2( CP 1 −CP 0) PD INS /K 2 +( CP 3 −CP 0) D INS /K+CP 0  (2a)

(2) said correction point data CP 0 to CP 5 are determined for said input gradation data D IN smaller than said intermediate data value D IN Center and for a gamma value of said gamma correction to exceed one, said output gradation data D OUT is calculated from the following equation (2b):

D OUT =2( CP 1 −CP 0) ND INS /K 2 +( CP 3 −CP 0) D INS /K+CP 0  (2b)

(3) when said input gradation data D IN is larger than said intermediate data value D IN Center , said output gradation D OUT is calculated from the following equation (2c):

D OUT =2( CP 4 −CP 2) ND INS /K 2 +( CP 5 −CP 2) D INS /K+CP 2  (2c)

where when a parameter R is defined by the following equation:

R=K 1/2 ·D INS 1/2 ,

said K, D INS , PD INS , and ND INS take values defined by the following equations:

K =( D IN MAX +1)/2,

D INS =D IN (in case of D IN <D IN Center )

D INS =D IN +1 −K (in case of D IN >D IN Center )

PD INS =( K−R )· R

ND INS =( K−D INS )· D INS .

2. The display apparatus according to claim 1 , wherein

a first calculation equation of said plurality of calculation equations has a term proportional to D IN n1 (D IN is said input gradation data and 0<n1<1) without having a term proportional to D IN n2 (n2>1), and

a second calculation equation of said plurality of calculation equations has a term proportional to D IN n2 without having a term proportional to D IN n1 .

3. The display apparatus according to claim 2 , wherein said n1 is ½, and said n2 is 2.

4. The display apparatus according to claim 2 , wherein said correction data is determined for a gamma value for said gamma correction to be less than one, and when said input gradation data is smaller than a predetermined value, said first calculation equation is selected as said correction calculation equation.

5. The display apparatus according to claim 4 , wherein said correction data is determined for the gamma value for said gamma correction to exceed one, and said second calculation equation is selected as said correction calculation equation when said input gradation data is smaller than said predetermined value or when said input gradation data is larger than said predetermined value.

6. The display apparatus according to claim 2 , wherein said first calculation equation is defined such that said output gradation data calculated through said gamma correction from said first calculation equation and said output gradation data calculated from an exact equation for the gamma correction are coincident with each other when said input gradation data is a value of a first value range, and

said second calculation equation is defined such that said output gradation data calculated through said gamma correction from said second calculation equation and said output gradation data calculated from said exact equation of the gamma correction are coincident with each other, when said input gradation data is a value of a second value range, and

said first value range is smaller than said second value range.

7. The display apparatus according to claim 1 , wherein said correction point data CP 0 to CP 5 are calculated:

(1) from the following equation (3a) when the gamma value γ of said gamma correction is smaller than one,

CP 0

CP 1=(4Gamma[ K/ 4]−Gamma[ K ])/2

CP 2=Gamma[ K− 1]

CP 3=Gamma[ K]

CP 4=2Gamma[( D IN MAX +K− 1)/2]−D OUT MAX

CP 5 =D OUT MAX   (3a)

(2) from the following equation (3b) when said gamma value γ exceeds one:

CP 0

CP 1=2Gamma[ K/ 2]−Gamma[ K]

CP 2=Gamma[ K− 1]

CP 3=Gamma[ K]

CP 4=2Gamma[( D IN MAX +K− 1)/2]−D OUT MAX

CP 5 =D OUT MAX   (3b)

where Gamma[x] is a function defined by the following equation when D OUT MAX is a maximum value of said output gradation data:

Gamma[ x]=D OUT MAX ( x/D IN MAX ) γ   (4).

8. The display apparatus according to claim 1 , wherein said correcting circuit comprises:

an order switching circuit having a function to generate a first data value which depends on D IN n1 (D IN is said input gradation data and 0<n1<1) and a second data value which depends on D IN n2 (n2>1), and configured to output one of said first data value and said second data value; and

an output gradation data calculating circuit configured to use said one of said first and second data values as a variable, and to generate said output gradation data by using a calculation equation whose coefficients are determined from correction data which specifies a shape of a gamma curve for the gamma correction.

9. The display apparatus according to claim 1 , wherein the correcting circuit determines the coefficient for the correction calculation equation based on whether said correction data is greater than or less than, an intermediate data value.

10. The display apparatus according to claim 1 , wherein said correcting circuit:

calculates a plurality of variables for the correction calculation equation; and

selects a variable from the plurality of variables based on whether a gamma value of said gamma correction is greater than one and whether the input gradation value is greater than an intermediate data value.

11. The display apparatus according to claim 10 , wherein said correcting circuit:

carries out the approximation calculation for said gamma correction using the correction calculation equation including the selected variable and the determined coefficient; and

generates output gradation data based on the approximation calculation.

12. A controller driver comprising:

a correcting circuit configured to carry out gamma correction on input gradation data in response to correction data which specifies a shape of a gamma curve;

a correction data storage section configured to receive said correction data from outside said controller driver to store therein the received correction data, and to transfer the stored correction data to said correcting circuit; and

a driving circuit configured to drive a display panel in response to output gradation data which is outputted from said correcting circuit,

wherein said correcting circuit:

selects a correction calculation equation from among a plurality of correction calculation equations based on a value of said input gradation data and said correction data, the selected correction calculation equation including a parameter which is determined based on a maximum value of the input gradation data, and a coefficient which is determined based on said correction data; and

uses said input gradation data as a variable and carries out approximation calculation of said gamma correction by using the selected correction calculation equation; and

wherein said correction data comprises correction point data CP 0 to CP 5 ,

if said input gradation data is D IN , said output gradation data is D OUT and an intermediate data value D IN Center is defined by a following equation (1) by using a permissible maximum value D IN MAX of said input gradation data:

D IN Center =D IN MAX /2  (1)

(1) when said correction point data CP 0 to CP 5 are determined for said input gradation data D IN to be smaller than said intermediate data value D IN Center and for a gamma value of said gamma correction to be less than one, said output gradation data D OUT is calculated froth the following equation (2a):

D OUT =2( CP 1 −CP 0) PD INS /K 2 +( CP 3 −CP 0) D INS /K+CP 0  (2a)

(2) when said correction point data CP 0 to CP 5 are determined for said input gradation data D IN to be smaller than said intermediate data value D IN Center and for a gamma value of said gamma correction to exceed one, said output gradation data D OUT is calculated from the following equation (2b):

D OUT =2( CP 1 −CP 0) ND INS /K 2 +( CP 3 −CP 0) D INS /K+CP 0  (2b)

(3) when said input gradation data D IN is larger than said intermediate data value D IN Center , said output gradation data D OUT is calculated from the following equation (2c):

D OUT =2( CP 4−CP2) ND INS /K+CP 2  (2c)

where when a parameter R is defined by the following equation:

R=K 1/2 ·D INS 1/2 ,

said K, D INS , PD INS , and ND INS take values defined by the following equations:

K =( D IN MAX +1)/2,

D INS =D IN (in case of D IN <D IN Center )

D INS =D IN +1 −K (in case of D IN >D IN Center )

PD INS =( K·R )· R

ND INS =( K−D INS )· D INS .

13. The controller driver according to claim 12 , wherein a first calculation equation of said plurality of calculation equations has a term proportional to D IN n1 (D IN is said input gradation data and 0<n1<1) without having a term proportional to D IN n2 (n2>1), and

a second calculation equation of said plurality of calculation equations has a term proportional to D IN n2 without having a term proportional to D IN n1 .

14. The controller driver according to claim 13 , wherein said correction data is determined for a gamma value of said gamma correction to be less than one, and when said input gradation data is smaller than a predetermined value, said first calculation equation is selected as said correction calculation equation.

15. The controller driver according to claim 12 , wherein said correcting circuit comprises:

an order switching circuit having a function to generate a first data value which depends on D IN n1 (D IN is said input gradation data and 0<n1<1) and a second data value which depends on D IN n2 (n2>1) in response to said input gradation data, and configured to output one of said first and second data values; and

an output gradation data calculating circuit configured to use said one data value outputted from said order switching circuit as a variable and to generate said output gradation data by using a calculation equation whose coefficients are determined from said correction data which specifies a shape of gamma curve for said gamma correction.

16. A method of driving a display panel, comprising:

generating output gradation data from input gradation data by:

selecting a correction calculation equation from among a plurality of correction calculation equations based on a value of said input gradation data and a value of correction, data which specifies a shape of a gamma curve, the selected correction calculation equation including a parameter which is determined based on a maximum value of the input gradation data, and a coefficient which is determined based on the correction data; and

carrying out an approximation of gamma correction on the input gradation data by using the selected correction calculation equation; and

driving a display panel in response to said output gradation data; and

wherein said correction data comprises correction point data CP 0 to CP 5 ,

if said input gradation data is D IN , said output gradation data is D OUT and an intermediate data value D IN Center is defined by a following equation (1) by using a permissible maximum value D IN MAX of said input gradation data:

D IN Center =D IN MAX /2  (1)

(1) when said correction point data CP 0 to CP 5 are determined for said input gradation data D IN to be smaller than said intermediate data value D IN Center and for a gamma value of said gamma correction to be less than one, said output gradation data D OUT is calculated from the following equation (2a):

D OUT =2( CP 1 −CP 0) PD INS /K 2 +( CP 3 −CP 0) D INS /K+CP 0  (2a)

(2) when said correction point data CP 0 to CP 5 are determined for said input gradation data D IN to be smaller than said intermediate data value D IN Center and for a gamma value of said gamma correction to exceed one, said output gradation data D OUT is calculated from the following equation (2b):

D OUT =2( CP 1 −CP 0) ND INS /K 2 +( CP 3 −CP 0) D INS /K+CP 0  (2b)

(3) when said input gradation data D IN is larger than said intermediate data value D IN Center , said output gradation data D OUT is calculated from the following equation (2c):

D OUT =2( CP 4 −CP 2) ND INS /K 2 +( CP 5 −CP 2) D INS /K+CP 2  (2c)

where when a parameter R is defined by the following equation:

R=K 1/2 ·D INS 1/2 ,

said K, D INS , PD INS , and ND INS take values defined by the following equations:

K =( D IN MAX +1)/2

D INS =D IN (in case of D IN <D IN Center )

D INS =D IN +1 −K (in case of D IN >D IN Center )

PD INS =( K−R )· R

ND INS =( K−D INS )· D INS .

17. A display apparatus comprising:

a display panel;

a correcting circuit configured to carry out a gamma correction on input gradation data in response to correction data which specifies a shape of a gamma curve to generate output gradation data;

a correction data storage section configured to receive and store said correction data, supplied externally, and to transfer the stored correction data to said correcting circuit; and

a driving circuit configured to drive said display panel in response to said output gradation data from said correcting circuit,

wherein said correcting circuit:

selects a correction calculation equation from among a plurality of correction calculation equations based on a value of said input gradation data and said correction data, the selected correction calculation equation including a parameter which is determined based on a maximum value of the input gradation data, and a coefficient which is determined based on said correction data; and

carries out an approximation, calculation for said gamma correction based on said input gradation data by using the selected correction calculation equation; and

said correction calculation equation is of a form:

D

OUT

=

B

·

D

IN

sel

(

K

2

/

2

)

+

C

·

D

INS

K

+

A

,

wherein:

D OUT represents output gradation data,

D IN represents input gradation data,

D IN MAX represents a maximum value of D IN ,

K=(D IN MAX +1)/2,

D INS =D IN if a most significant bit of D IN is 0,

D INS =D IN +1−K if a most significant bit of D IN is 1, and

values of A, B, C, and D IN se1 are determined according to said input gradation data and said correction data.