COMPENSATION FOR READOUT NOISE IN CCD IMAGES
COMPENSATION FOR READOUT NOISE IN CCD IMAGES
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DOI：
10.1364/josaa.12.000272
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发表时间：
1995-02-01
影响因子：
1.9
通讯作者：
WHITE, RL
中科院分区：
文献类型：
--
作者：
SNYDER, DL;HELSTROM, CW;WHITE, RL
用CCD相机采集的数据建模为添加剂泊松-高斯混合物，泊松分量表示对象相关的光电子，对象无关的光电子，偏置电子和热电子的累积计数，高斯分量表示读出噪声。两种方法检查用于补偿读出噪声。一种方法依赖于通过泊松噪声近似高斯读出噪声，然后使用修改的Richardson-Lucy算法来实现补偿。该方法已被用于恢复与CCD的原始宽视场/行星相机搭载哈勃太空望远镜获得的图像。第二种方法直接使用的期望最大化算法推导出的泊松-高斯混合数据。这就需要确定的条件均值估计的泊松成分的混合物，这是完成了一个非线性函数的数据的评价。第二种方法比第一种方法需要更多的计算，但在数学上更精确，并且在质量上有适度的改进，特别是对于较暗的物体。作为一个具体的例子，我们比较了这两种方法的代表性的图像采集与该相机，它们包含过多的模糊，这是由于球面像差和均方根读出噪声水平的13个电子。
Data acquired with a CCD camera are modeled as an additive Poisson-Gaussian mixture, with the Poisson component representing cumulative counts of object-dependent photoelectrons, object-independent photoelectrons, bias electrons, and thermoelectrons and the Gaussian component representing readout noise. Two methods are examined for compensating for readout noise. One method relies on approximating the Gaussian readout noise by a Poisson noise and then using a modified Richardson-Lucy algorithm to effect the compensation. This method has been used for restoring images acquired with CCD's in the original Wide-Field/Planetary Camera aboard the Hubble Space Telescope. The second method directly uses the expectation-maximization algorithm derived for the Poisson-Gaussian mixture data. This requires the determination of the conditional-mean estimate of the Poisson component of the mixture, which is accomplished by the evaluation of a nonlinear function of the data. The second method requires more computation than the first but is more accurate mathematically and yields modest improvements in the quality of the restorations, particularly for fainter objects. As a specific example, we compare the two methods in restorations of images representative of those acquired with that camera; they contain excess blurring that is due to spherical aberration and a rms readout noise level of 13 electrons.