为了分析电荷耦合元件(CCD)在成像过程以及彩色插值算法引起的图像退化问题,提出CCD彩色插值的调制传递函数(MTF)研究方法.分析CCD在传递图像时的退化情况,选取常用的插值算法,如双线性插值,梯度插值,计算插值算法对图像退化影响,用MTF来表征CCD彩色成像时的传递能力.实验结果表明,即使只考虑插值算法的影响,CCD彩色成像时的调制传递能力将在非彩色插值CCD的基础上进一步退化,在奈奎斯特频率下只有非插值CCD的1/2左右.因此CCD的空间离散采样特性使图像在传递时出现退化,当CCD前面置入彩色滤波片(CFA)后,由于彩色插值算法的影响,MTF将进一步减弱.
In order to analyze the problem of degeneration of charge-coupled device(CCD) caused by imaging process and color interpolation,the research method of modulation transfer function(MTF) of color interpolation has been proposed.The degeneration of general CCD was firstly analyzed,and general interpolation algorithm,such as bilinear interpolation,gradient interpolation,were selected to compute the degeneration of images.The MTF was used to characterize the transfer capability of CCD in the color imaging process.Experimental results show that even if only to consider the impact of the interpolation algorithm,the MTF of CCD,in the color imaging process,would be degenerated comparing to non-interpolation CCD.The value of MTF was only half of non-interpolation CCD.Therefore the image degeneration occurs in the transmission caused by the discrete sample feature of CCD.When the color filter array(CFA) was placed in front of CCD,the MTF would be worse because of interpolation algorithm.