CCD非线性效应对剪切干涉法波前检测的影响

利用径向剪切干涉法检测高功率激光波前时,由于探测器CCD非线性效应,在频谱中引入了除基频外的二级、三级等高次频谱分量,增加了频谱混叠的可能,使得对有用信息提取困难,降低了波前检测精度。从理论上分析了CCD非线性效应产生高次频谱分量和导致频谱混叠的原因,给出非线性条件下避免频谱混叠的条件,提出了通过提高空间载频的方法来减小或消除CCD非线性效应导致的频谱混叠。计算机模拟和实验结果表明,该方法能够有效抑制频谱混叠并显著提高波前检测精度。

Effect of CCD nonlinearity on wavefront detection by shearing interferometry

When radial shear interferometer is used in high-power laser wavefront detection, due to the influence of the nonlinearity of CCD, there exist not only the first order frequency with wave-front information but also the second and the third order frequency. They may lead to overlapping spectrum, which makes it difficult to extract useful information and reduces the detection accuracy of wavefront. A theoretical analysis on mechanisms of high-order spectral component and spectrum aliasing caused by the nonlinearity of CCD is established, and the condition to avoid spectrum aliasing is pointed out. Finally, a method by increasing the spatial carrier frequency to reduce or eliminate the spectrum aliasing is proposed. Computer simulation and experimental results have verified the feasibility of