Apparatus and method for color restoration

1. A color restoration method comprising:

separating multiple band information of a near infrared (NIR) channel from information of an input image by using variables indicating a correlation between a color channel and the NIR channel in the input image;

obtaining estimated invisible light band information of the NIR channel from the multiple band information of the NIR channel and estimated multiple band information of the NIR channel which is estimated from the color channel;

estimating invisible light band information of the color channel based on the estimated invisible light band information of the NIR channel; and

restoring a visible light band image of the color channel by removing the estimated invisible light band information of the color channel from multiple band information of the color channel included in the information of the input image.

2. The color restoration method of claim 1 , further comprising calculating a difference between visible light band information and estimated visible light band information of an input image,

wherein the separating the multiple band information of the NIR channel from the input image is performed based on a case in which the difference is the smallest.

3. The color restoration method of claim 2 , further comprising

obtaining adaptive chromaticity coefficients for the case in which the difference is the smallest; and

suppressing interference between the color channel and the NIR channel using the adaptive chromaticity coefficients.

4. The color restoration method of claim 2 , wherein the obtaining the estimated invisible light band information of the NIR channel is performed by determining and removing noise of the multiple band information of the NIR channel.

5. The color restoration method of claim 4 , wherein the noise is determined by obtaining a difference between the multiple band information of the NIR channel and a value obtained by multiplying the estimated multiple band information of the NIR channel by a value which is greater than 0 and smaller than 1.

6. The color restoration method of claim 1 , wherein the multiple band information of the color channel comprises visible light band information and invisible light band information of the color channel, and

wherein the multiple band information of the NIR channel comprises visible light information and invisible light information of the NIR channel.

7. The color restoration method of claim 1 , wherein the estimated invisible light band information of the NIR channel is obtained by using an equation λK(N all −r{circumflex over (N)} all )={circumflex over (N)} nir ,

wherein

λ

=

1

r

×

N

^

nir

(

1

r

-

1

)

×

N

all

×

K

+

N

^

nir

,

and

wherein N all is the multiple band information of the NIR channel, N^ all is the estimated multiple band information estimated from the color channel, and r is a constant greater than 0 and smaller than 1, and K is another constant.

8. The color restoration method of claim 1 , further comprising suppressing color restoration in a region that exceeds a threshold value by applying a following weight curve to the NIR channel to perform light saturation compensation,

curve

=

e

4

×

(

x

-

threshold

)

2

normal

2

,

wherein x is a pixel value of an NIR image, normal is a constant that is a normalized term, threshold =MAX(N i,j input )*0.7 and N i,j input is a pixel value of the NIR image.

9. The color restoration method of claim 1 , further comprising performing light saturation compensation on the NIR channel in the restored visible light band image.

10. A color restoration apparatus comprising:

a channel correlation checking unit configured to separate multiple band information of a near infrared (NIR) channel from information of an input image by using variables indicating a correlation between a color channel and the NIR channel in the input image;

an adaptive gain control (AGC) unit configured to obtain estimated invisible light band information of the NIR channel from the multiple band information of the NIR channel and estimated multiple band information of the NIR channel which is estimated from the color channel; and

a visible light band information restoring unit configured to estimate invisible light band information of the color channel based on the estimated invisible light band information of the NIR channel, and restore a visible light band image of the color channel by removing the estimated invisible light band information of the color channel from multiple band information of the color channel included in the information of the input image.

11. The color restoration apparatus of claim 10 , further comprising an adaptive chromaticity coefficient generating unit configured to calculate a difference between visible light band information and estimated visible light band information of an input image,

wherein the channel correlation checking unit is configured to separate the multiple band information of the NIR channel from the input image based on a case in which the difference is the smallest.

12. The color restoration apparatus of claim 11 , wherein the adaptive chromaticity coefficient generating unit is configured to obtain adaptive chromaticity coefficients for the case in which the difference is the smallest, and suppress interference between the color channel and the NIR channel using the adaptive chromaticity coefficients.

13. The color restoration apparatus of claim 11 , wherein the AGC unit is configured to obtain the estimated invisible light band information of the NIR channel by determining and removing noise of the multiple band information of the NIR channel.

14. The color restoration apparatus of claim 13 , wherein the AGC unit is configured to determine the noise by obtaining a difference between the multiple band information of the NIR channel and a value obtained by multiplying the estimated multiple band information of the NIR channel by a value which is greater than 0 and smaller than 1.

15. The color restoration apparatus of claim 10 , wherein the multiple band information of the color channel comprises visible light band information and invisible light band information of the color channel, and

wherein the multiple band information of the NIR channel comprises visible light information and invisible light information of the NIR channel.

16. The color restoration apparatus of claim 10 , wherein the AGC unit is configured to obtain the invisible light band information of the NIR channel by using an equation λK(N all −r{circumflex over (N)} all )={circumflex over (N)} nir ,

wherein

λ

=

1

r

×

N

^

nir

(

1

r

-

1

)

×

N

all

×

K

+

N

^

nir

,

and

wherein N all is the multiple band information of the NIR channel, N^ all is the estimated multiple band information estimated from the color channel, and r is a constant greater than 0 and smaller than 1, and K is another constant.

17. The color restoration apparatus of claim 10 , further comprising a light saturation controlling unit configured to suppress color restoration in a region that exceeds a threshold value by applying a following weight curve to the NIR channel to perform light saturation compensation,

curve

=

e

4

×

(

x

-

threshold

)

2

normal

2

wherein x is a pixel value of an NIR image, normal is a constant that is a normalized term, threshold =MAX(N i,j input )*0.7 and N i,j input a pixel value of the NIR image.

18. The color restoration apparatus of claim 10 , further comprising a light saturation controlling unit configured to perform light saturation compensation on the NIR channel in the restored visible light band image.