Research On Key Technology Of Color Calibration For Typical Color Digital Camera

With the development of digital technology,color digital camera has been widely used and popularized.Because digital imaging equipment is affected by many factors in the imaging process,it is difficult to keep the output image consistent with the actual observation of human eyes.Therefore,how to improve imaging quality has become an important research direction in this field.Color is an important component to reflect the imaging quality of color digital imaging equipment.The reduction of color fidelity will directly affect the evaluation of image quality.Therefore,the research on color calibration system for color digital camera has high theoretical value and wide application prospect.With the improvement of China's space technology and capability,deep space exploration has been gradually developed.As an important payload in deep space detection,color digital camera plays the role of color imaging.Because the working environment of color space camera is affected by various factors such as lighting condition and camera itself,so the color calibration of color space camera has always been the key and difficult point in the design of space digital camera system.As an important part of China's recent aerospace exploration,the detection of terrestrial extraterrestrials poses new challenges to the restoration of image color fidelity by the color cameras on landers and patrols.In this paper,a color calibration system is established to correct the color of the camera by using color correction,white balance correction and color enhancement technology.In order to achieve accurate color reproduction under a variety of lighting and viewing conditions and ensure the accuracy of the color reproduction or the color appearance of the camera's captured image.Since the camera not only needs to carry out the task of navigation,but also has to map and analyze the surface of the earth,so the accurate color reproduction is a basic requirement of the space camera.Because the working environment of the camera is the surface of the outer space star,the space of the lander and the perambulator is limited,and because the device is far from the earth,the data processing and transmission are limited.Therefore,the algorithm used should not use too many training samples,and the calculation amount of the algorithm should not be too large.In view of above problem,based on the s RGB standard of IEC,the CCM color correction base on the polynomials is used to calibrate the color cameras.This method can basically overcome the limitations of most algorithms,such as slow speed and large training sample set,and meet the requirements of processing precision and speed in the process of color correction.By studying the automatic white balance technology of color digital camera,a white balance correction algorithm based on statistical weighted white point method is proposed.In this algorithm,the image is segmented into blocks,the color information of the image is counted by blocks,and the concept of grey area radius is defined.By combining the weight of the light source and the weight of the position,the white point of the image is determined by the method of statistical weighting,and the white balance is judged.The concept of gain adjustment is proposed for the different degree of human adaptation in the environment.Through the gain adjustment,the correction result of the white balance can be further corrected so as to make it more in line with the subjective feelings of the human eye,and improve the overall flexibility of the algorithm.For the special scenes of aerospace cameras,this algorithm can also add specific modules for specific scenes to correct and improve the robustness and adaptability of the white balance algorithm.For some color fidelity declined after color correction module and white balance module,as well as the fixed image target and color of the lander and patrol camera.A color enhancement method for color camera is proposed.This method disassembles the original RGB to YCb Cr space conversion relationship in the YCb Cr space and divides out several tunable parameters.By adjusting the parameter values,the conversion relationship between RGB and YCb Cr was modified and the color of the space converted to YCb Cr is changed.Thus,the enhancement of some colors is realized indirectly.This method can enhance some colors in the image without affecting other colors in the color gamut,and improve the color fidelity,so as to further improve the corrected image quality.