光学系统调制传递函数的敏感性分析

Sensitivity analysis of MTF of optical system

光学元件、结构件的加工和光机系统的装校会导致光学系统的入瞳孔径尺寸和焦距偏离设计值,从而导致光学系统F数的改变,并且光学系统在光谱谱段内成像,光学系统的空间截止频率也在改变。分析了入瞳孔径尺寸D(100～1000mm)、焦距f′(400～2000mm)、F数(4～20)、光谱波长λ(350～800nm)的变化对光学系统MTF的影响。结果表明:增大入瞳孔径尺寸D、空间截止频率foc,有利于提高光学系统的MTF;增大焦距f′、F数、波长λ和规化频率μ,会降低光学系统的MTF。MTF对λ的敏感度是MTF对F的敏感度的F/λ倍,MTF对D的敏感度是MTF对f′的敏感度大小的F倍,且方向相反。对于成像光谱谱段较宽的光学系统,应注意波长λ对MTF的影响。

Optical component and mechanical component manufacture,and assembling and calibration of optical and mechanical system will result in departure of entrance pupil aperture dimension and focus of optical system from their design value,and change of F number of optical system consequently.In addition,imaging of optical system uses spectrum bands,so spatial cutoff frequency of optical system is also in changing.The influence to optical system MTF on change of entrance pupil aperture dimension D（100-1000mm）,focus f′（400-2000mm）,F number（4-20） and spectrum wavelength λ（350-800 nm） is analyzed.The results show that increasing entrance pupil aperture dimension D,spatial cutoff frequency is good to enhance MTF,and increasing focus f′,F number,wavelength λ,and naturalized rate μ will decrease MTF of optical system.Sensitivity of MTF to λ is F/λ times of sensitivity of MTF to F,and sensitivity of MTF to D is F times of sensitivity of MTF to f′,and they have opposite directions.The influence of wavelength λ to MTF is considered when an optical system images in a quite wide spectrum bands.