CCD像元尺寸对傅里叶变换法相位测量精度的影响

Influence of CCD Pixel Size on Phase Measurement Accuracy in Fourier Transform Method

摘要:

针对傅里叶变换分析法中的离散过程理论分析存在的不足，对CCD采样过程中影响相位测量精度的主要因素进行了详细分析和仿真研究。讨论了CCD像元尺寸在采样过程中对傅里叶变换频谱的影响，理论分析了傅里叶变换法中CCD像元的尺寸、随机噪声和量化误差对相位测量精度的影响。计算机仿真和实验结果均表明，用傅里叶变换分析法对具有不同密度的干涉图进行分析时，CCD像元尺寸对采样后输出的光强信号的调制度、信噪比和频谱展宽均有影响，像元尺寸越大，采样后条纹信号的调制度和信噪比越低，其频谱展宽越大，经相位解算后得到的相位测量误差越大。以相位测量误差的RMS值大于0.05λ作为判断基准，信号的信噪比约为20，为扩展傅里叶变换分析法的动态测量范围提供了理论基础。

Abstract:

The main factors affecting the phase measurement accuracy were analyzed and simulated in detail for the process of detecting high-density fringes by CCD in Fourier transform method. The influences of the pixel size of CCD, random noise and quantization series on the Fourier spectrum and the accuracy of phase measurement of interferogram after sampling were discussed. Simulation and experimental results indicate that, when the interferogram with different intensity are analyzed by Fourier transform, with the increase of CCD pixel size and random noise’s RMS, the signal to noise ratio and the spectrum’s width of sequence intensity detected by CCD will be worse, and the phase errors will be greater. When the signal to noise ratio is about 20, the RMS of phase measurement error can be better than 0.05λ.