基于岭回归的四带图像偏色校正算法

Four-Band Image Color Cast Correction Algorithm Based on Ridge Regression

对于在可见光范围拍摄的图像中混入近红外光引起的图像偏色问题,传统监控系统采用机械切换的红外截止滤镜来实现日夜拍摄模式的切换,但这容易产生机械故障,影响成像.本文在不改变原来CCD或CMOS传感器的基础上,采用可见光加850 nm双峰滤镜替代传统机械切换滤镜,但仍存在850 nm红外串扰问题.为解决红外干扰,本文抛弃传统的红外干扰图像偏色校正分析方法,从传感器受近红外光的影响分析入手,通过岭回归的彩色定标方法对相机自身的光谱特性进行校正.这个过程即拟合了摄像头拍摄三带图像时启用红外截止滤镜的状态.首先在实验室黑暗环境中,使用D65标准光源箱,并用850 nm的近红外光源直射已经移除红外截止滤镜的摄像头,在棚中拍摄潘通色卡的四带图像(RGB三带与IR近红外带);随后关闭近红外光源,同机位拍摄潘通色卡的三带图像.根据岭回归算法进行彩色定标,获取三带图像与四带图像之间的校正矩阵,用于四带图像色彩校正,获得色彩自然的图像.

For the problem of color deviation caused by mixing near-infrared light into the images taken in the visible light range, the traditional monitoring system uses the mechanically switched infrared cut-off filter to achieve the switching of day and night shooting mode, which is prone to produce mechanical faults and affect the imaging. On the basis of not changing the original CCD or CMOS sensor, this study adopts visible light and 850 nm dual-peak filter to replace the traditional mechanical switching filter, but there is still the 850 nm infrared crosstalk problem. In order to solve the infrared interference, this study abandons the traditional color deviation correction analysis method of infrared interference image, starts with the analysis of the influence of near-infrared light on the sensor, and corrects the spectral characteristics of the camera by ridge regression color calibration method. This process simulates the state of using the infrared cut-off filter when the camera takes the three-band image. First, in the dark environment of the laboratory, use the D65 standard light source box, and use the 850 nm near-infrared light source to directly shoot the camera that has removed the infrared cut-off filter, and shoot the four-band image of the Pantone color card in the shed (RGB three-band and IR near Infrared band);then close the near-infrared light source, taking the three-band image of the Pantone color card with the same position. Color calibration is performed according to the ridge regression algorithm, and a correction matrix between the three-band image and the four-band image is obtained, which is used for color correction of the four-band image to obtain a natural color image.