System and method for color imaging under low light
A camera for enhanced color imaging in a low light environment including: one or more illuminators for illuminating a R, a G, and a B light at different time periods; an image sensor for capturing R G and B image frames; and a processor configured to generate an intermediate color frame from each of the R, G and B image frames; determine moving pixels in the each of the intermediate color frames; determine a true color for the moving pixels in each intermediate color frame; generate a true color frame for each intermediate color frame by substituting color of the moving pixels with respective true colors of the moving pixels, in intermediate color frame; calculate scene color metrics from the true color frame or intermediate color frame; and adaptively adjust illumination of one or more of the R, G, and B lights to enhance a next frame.
1. A method for enhanced color imaging in a low light environment, the method comprising:
illuminating a first color, a second color, and a third color light at different time periods;
capturing a first color image frame, a second color image frame and a third color image frame, in response to the illumination;
determining moving pixels in each of the color image frames;
generating a true color frame for each of the color image frames by substituting respective colors of the moving pixels with respective majority colors of the moving pixels, in each of the color image frames; and
adaptively adjusting illumination of one or more of the first, second, and third color lights to enhance color quality of a next true color frame.
2. The method of claim 1 , wherein the first color is red, the second color is blue, and the third color is green.
3. The method of claim 1 , wherein the first color is yellow, the second color is magenta, and the third color is cyan.
4. The method of claim 1 , further comprising turning off the illumination of the first, second and third lights for a time period to generate a dark (D) frame; and subtracting the D frame from each of the first, second, and third color image frames to compensate for ambient lighting.
5. The method of claim 1 , wherein determining moving pixels comprises subtracting a current color image frame for a given color from a previous color image frame of the same given color to identify the pixels that are present in the current color image frame, but not in the previous color image frame.
6. The method of claim 5 , further comprising using a threshold value to separate moving pixels from non-moving pixels in a given color image frame, wherein the threshold value is determined based on an amount of noise present in the given color image frame.
7. The method of claim 1 , wherein the majority color of the moving pixels is determined by determining a majority color of a moving pixels' non-moving neighborhood.
8. The method of claim 7 , wherein a final size of the non-moving neighborhood is determined by adaptively varying a current size of the non-moving pixels' neighborhood until a statistically significant value for the majority color of the moving pixels is determined.
9. The method of claim 7 , wherein a final size of the non-moving neighborhood is determined by increasing a current size of the non-moving pixels' neighborhood until a predetermined number of non-moving pixels with similar colors are detected.
10. The method of claim 1 , further comprising calculating scene color metrics for each of the true color frames that quantifies a spectral profile of a scene in a respective true color frame; and adaptively adjusting said illumination responsive to said scene color metrics.
11. The method of claim 10 , wherein calculating scene color metrics comprises calculating scene color statistics including a total number and energy of said first, second and third colors.
12. The method of claim 1 , wherein adaptively adjusting illumination comprises adaptively adjusting a sensor exposure time.
13. The method of claim 1 , wherein adaptively adjusting illumination comprises adaptively adjusting one or more of brightness, and duty cycle of one or more of said first, second and third color lights.
14. The method of claim 1 , further comprising enhancing resolutions of the true color frames.
15. A camera for enhanced color imaging in a low light environment comprising:
a lens;
one or more illuminators for illuminating a first color, a second color, and a third color lights at different time periods;
an image sensor for capturing a first color image frame, a second color image frame and a third color image frame, in response to the illumination; and
a processor for determining moving pixels in each of the color image frames; generating a true color frame for each of the color image frames by substituting respective colors of the moving pixels with respective majority colors of the moving pixels, in each of the color image frames; and adaptively adjusting illumination of one or more of the first, second, and third color lights to enhance color quality of a next true color frame.
16. The camera of claim 15 , wherein a field of view of each of the one or more of illuminators is matched to a field of view of the lens.
17. The camera of claim 15 , wherein the processor turns off the one or more illuminators for a time period to generate a dark (D) frame, and subtracts the D frame from each of the first color image frame, the second color image frame and the third color image frame to compensate for ambient lighting.
18. The camera of claim 15 , wherein the processor adaptively adjusts illumination of one or more of the first, second, and third color lights by adaptively adjusting an exposure time of the image sensor.
19. The camera of claim 15 , wherein the processor adaptively adjusts illumination of one or more of the first, second, and third color lights by adaptively adjusting one or more of brightness, and duty cycle of the colors of the first color, second color, and third color lights.