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干涉成像系统传递函数的数值分析
Numerical analysis of system transfer function in interferometric imaging system
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摘要: 干涉仪系统传递函数能有效地表征系统相位成像的性能.通过假设干涉成像系统是复振幅的线性平移不变系统,模拟计算正弦相位光栅和相位台阶这两类标准相位物体的成像,确定干涉仪系统传递函数.数值分析结果表明:系统传递函数随着波像差的增加而减小；干涉成像系统对小幅度相位(远小于1 rad)成像是近似线性的,而对大幅度相位(大于0.5 rad)成像则是明显非线性的.当正弦相位的幅度为1时,系统传递函数在1/2和1/3截止频率处出现明显的急剧下降.高度为π/2的相位台阶成像时,系统传递函数随着空间频率的增加而缓慢地降低.Abstract: The performance of phase imaging in interferometric imaging system is well characterized by the system transfer function (STF),The STF of the interferometrie imaging system is analyzed numerically by assuming that the system is linear and shift-invariant for the complex field.Two standard phase objects,sinusoidal phase grating and phase step,are employed and simulated to determine the STF.Numerical simulation results show that the STF decreases as the wavefront aberration of interferometric imaging system increases.It also shows that the interferometric imaging system is approximately linear for small phase (far less than 1 rad) but explicitly nonlinear for large phase (larger than 0.5 rad).The STF has a visible drop at one half or one third of the cut-off frequency of the imaging system when the amplitude of sinusoidal phase is 1 rad.For a phase step with a height of π/2 rad,the STF has no visible drop but decreases slowly with the increasing of spatial frequency.The results provide a useful guidance to the design of interferometer and the measurement of STF and power spectrum density in experiment.
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