In this paper

we propose a color balancing method for correcting uneven illuminations of sub-images of a combined four-head camera. First

the radiometric response function is estimated via a process of camera calibration. Then

based on the overlapped areas of the four sub-images a color correction model is established. Furthermore

a robust estimation method is used to compute the differences of exposure amounts pertaining to the four sub-cameras. Hence

the process of color balancing for a stitched image is accomplished. Finally

a linear weight function is defined to smooth the stitching line. The experiments show that the proposed method is capable of eliminating or compensating the differences of exposure amounts

which guarantees the color unity of the stitched image without unacceptable boundaries.