Lens shading correction circuit, lens shading correction method, and image processing system
A lens shading correction circuit includes an elliptical gain generation circuit configured to extract a position of a pixel and generate an elliptical gain value using elliptical gain parameters and the extracted position and a multiplier configured to output an output value by multiplying the elliptical gain value by a weight for the pixel. The lens shading correction circuit corrects the lens shading based on the first output value and a gain increment value.
1 . A lens shading correction circuit for correcting lens shading, the lens shading correction circuit comprising:
an elliptical gain generation circuit configured to extract a position of a pixel and generate an elliptical gain value using elliptical gain parameters and the extracted position;
a first multiplier configured to output a first output value by multiplying the elliptical gain value by a weight for the pixel; and
a second multiplier configured to output a final output value based on an initial input value and the first output value;
the lens shading correction circuit correcting the lens shading based on the final output value.
2 . The correction circuit of claim 1 , further comprising:
an adder configured to output a second output value by adding a gain increment value to the first output value,
wherein the final output value is generated by multiplying the second output value by the initial input value.
3 . The lens shading correction circuit of claim 1 , wherein the elliptical gain generation circuit is further configured to generate different elliptical gain values according to the position of the pixel.
4 . The lens shading correction circuit of claim 3 , wherein the pixel is located on a two-dimensional (2D) plane, and the position of the pixel comprises a first position value in a first direction and a second position value in a second direction orthogonal to the first direction.
5 . The lens shading correction circuit of claim 4 , wherein the elliptical gain generation circuit is further configured to generate the elliptical gain value using an nth degree equation, the elliptical gain parameters, and the first and second position values of the pixel.
6 . The lens shading correction circuit of claim 5 , wherein the elliptical gain parameters comprise first to fourth parameters,
the first parameter and the second parameter are parameters of the nth degree equation,
the third parameter is an ellipse parameter in the first direction, and
the fourth parameter is an ellipse parameter in the second direction.
7 . The lens shading correction circuit of claim 1 , further comprising a register storing the elliptical gain parameters.
8 . The lens shading correction circuit of claim 6 , wherein the first to fourth parameters minimize error of the pixel.
9 . A lens shading correction method comprising:
extracting a position of a pixel;
generating an elliptical gain value using the extracted position of the pixel and elliptical gain parameters;
generating a first output value by multiplying the elliptical gain value by a weight for the pixel;
generating a second output value by adding the first output value and a gain increment value together;
generating a final output value by multiplying the second output value by an initial input value; and
correcting lens shading based on the final output value.
10 . The lens shading correction method of claim 9 , wherein the generating of the elliptical gain value comprises generating different elliptical gain values according to the position of the pixel.
11 . The lens shading correction method of claim 9 , wherein, in the extracting of the position of the pixel, the pixel is located on a two-dimensional (2D) plane, and the position of the pixel comprises a first position value in a first direction and a second position value in a second direction orthogonal to the first direction.
12 . The lens shading correction method of claim 11 , wherein the generating of the elliptical gain value comprises generating the elliptical gain value using an nth degree equation, the elliptical gain parameters, and the position value of the pixel.
13 . The lens shading correction method of claim 12 , wherein, in the generating of the elliptical gain value using the elliptical gain parameters, the elliptical gain parameters comprise first to fourth parameters, the first parameter and the second parameter are parameters of the nth degree equation, the third parameter is an ellipse parameter in the first direction, and the fourth parameter is an ellipse parameter in the second direction.
14 . An image processing system comprising an image sensor and an image signal processor,
wherein the image signal processor comprises a register storing elliptical gain parameters and a lens shading correction circuit,
wherein the lens shading correction circuit comprises:
an elliptical gain generation circuit configured to extract a position of a pixel and generate an elliptical gain value using the elliptical gain parameters; and
a first multiplier configured to output a first output value by multiplying the elliptical gain value by a weight for the pixel,
wherein the weight for the pixel is determined based on characteristics of the image sensor, and
wherein the lens shading circuit corrects lens shading using the first output value and a gain increment value.
15 . The image processing system of claim 14 , wherein the lens shading correction circuit further comprises:
an adder configured to output a second output value by adding the first output value and the gain increment value together; and
a second multiplier configured to output a final output value by multiplying the second output value and an initial input value together,
wherein the lens shading circuit corrects the lens shading using the final output value.
16 . The image processing system of claim 14 , wherein the elliptical gain generation circuit is further configured to generate different elliptical gain values according to the position of the pixel.
17 . The image processing system of claim 16 , wherein the pixel is located on a two-dimensional (2D) plane, and the position of the pixel comprises a first position value in a first direction and a second position value in a second direction orthogonal to the first direction.
18 . The image processing system of claim 17 , wherein the elliptical gain generation circuit is further configured to generate the elliptical gain value using an nth degree equation, the elliptical gain parameters, and the first and second position values of the pixel.
19 . The image processing system of claim 18 , wherein the elliptical gain parameters comprise first to fourth parameters,
the first parameter and the second parameter are parameters of the nth degree equation,
the third parameter is an ellipse parameter in the first direction, and
the fourth parameter is an ellipse parameter in the second direction.