Apparatus and method for compensating for black level

1. An apparatus for compensating for a black level, the apparatus comprising:

a black pixel average value extraction unit, operative to determine a black pixel average value of a current frame by averaging black pixel values of the current frame;

a luminance value extraction unit, operative to extract a luminance value from an analog gain and concentration time information of an image sensor;

a black level extraction unit, connected to the black pixel average value extraction unit and the luminance value extraction unit, operative to calculate a frame weight by using the luminance value and determine a black level value of the current frame by using the frame weight, the black pixel average value, and a black level value of a previous frame; and

a black level compensation unit, connected to the black level extraction unit, operative to compensate for valid pixel values of the current frame by using the black level value of the current frame,

wherein the luminance value extraction unit is operative to determine the luminance value by multiplying the analog gain by the concentration time information to obtain a resultant value, and dividing the resultant value by a normalization factor.

2. The apparatus of claim 1 , wherein the black level extraction unit is operative to determine the black level value of the current frame from an equation:

BL

i

=

w

⁡

(

m

i

-

BL

i

-

1

)

R

w

+

BL

i

-

1

wherein BL i is the black level value of the current frame, w is a frame weight, m i is the black pixel average value of the current frame, BL i-1 is the black level value of the previous frame, and R W is control step resolution of the frame weight, where i is a positive integer.

3. The apparatus of claim 2 , wherein the black level extraction unit is operative to determine the frame weight by using a difference in luminance between the current and previous frames and a luminance value of the current frame.

4. The apparatus of claim 1 , wherein the black level compensation unit is operative to subtract the black level value of the current frame from each of the valid pixel values.

5. The apparatus of claim 1 , wherein the black level compensation unit is operative to calculate an analog offset corresponding to the black level value of the current frame and feedback the analog offset to an analog circuit to remove the black level of the current frame.

6. A method for compensating for a black level, the method comprising:

calculating a frame weight from an analog gain and concentration time information of an image sensor;

extracting a black pixel average value from a black pixel value of a current frame provided by the image sensor;

calculating a black level value of the current frame by using the frame weight, a black pixel average value of the current frame, and a black level value of a previous frame; and

compensating for valid pixel values of the current frame by using the black level value of the current frame,

wherein said calculating the frame weight comprises:

determining a luminance value of the current frame by using the analog gain and the concentration time information;

determining a difference in luminance between frames by comparing the luminance value of the current frame to a luminance value of the previous frame; and

determining the frame weight by using the difference in luminance between the frames and the luminance value of the current frame.

7. The method of claim 6 , wherein said calculating the black level value of the current frame, uses an equation:

BL

i

=

w

⁡

(

m

i

-

BL

i

-

1

)

R

w

+

BL

i

-

1

wherein BL i is the black level value of the current frame, w is a frame weight, m i is the black pixel average value of the current frame, BL i-1 is the black level value of the previous frame, and R W is control step resolution of the frame weight, where i is a positive integer.