Aberration Measurement On Optical Imaging Element With Ptychographic Iterative Engine

Optical imaging is the most common technical means of obtaining external information in many fields such as military,scientific research,production and life.The performance of imaging systems can be accurately described by OTF(optical transfer function).Mathematically,OTF is the normalized autocorrelation of the aperture function P(x,y) of the imaging system,while the P(x,y) of most practical imaging systems is a two-dimensional complex-valued function including intensity and phase.The measurement of the OTF is actually a measure of the strength and phase of P(x,y).With the rapid advancement of advanced technologies such as computational optical imaging,in theory,as long as the OTF of an optical system is accurately known,the optical image produced by the numerical calculation can be numerically corrected to obtain an ideal high-resolution image,and the conventional measurement is performed.The method has been unable to meet the actual needs of these new technologies,and new methods must be developed to accurately measure the optical properties of imaging systems.In order to accurately measure the exit pup il transmission function P(x,y) of the imaging system,two measurement methods based on spatial superposition scanning imaging(PIE)and frequency domain PIE are proposed.Wherein,based on the spatial PIE measurement method,when the imaging system to be tested is not introduced,the scanning diffraction object records a series of diffraction intensity distributions,reconstructs the complex amplitude distribution of the illumination light wavefront and the diffraction object;and then introduces the imaging system to be tested into the measurement system.Scanning the same diffractive object again records a series of diffraction intensity distributions,thereby reconstructing the wavefront information containing the information of the optical component to be tested.The method directly measures the phase difference between the beam front of the system and the ideal spherical front wavefront when the system is imaging the point object to obtain the phase distribution of P(x,y),and based on this,the various levels are decomposed.Geometric aberration coefficient.The frequency domain-based PIE measurement method uses a light-emitting diode(LED)array instead of a conventional illumination source to generate different emission direction illumination lights,collects multiple low-resolution images,and realizes the scanning of the spectrum information of the sample to be measured.Based the Fourier relationship between the objects,images and system's coherent transfer functions(CTF),using a series of angle illumination methods and iterative image reconstruction methods,the method can directly reconstructs the two-dimensional CTF complex amplitude distribution and super-resolution images.Compared with the traditional wavefront measurement method,the proposed two methods use a common optical path system,and do not depend on the additional reference beam,not only have a compact optical structure,but also avoid the reference light and system vibration.The error has the advantages of convenient use,high resolution and high precision.Numerical calculations show that the aberration coefficients of the imaging systems obtained by these two methods are less than 0.1%.The experimental results show that the actual measurement error is less than 1%.The proposed two technologies solve the key technical problems that the traditional method is difficult to realize the accurate measurement of the two-dimensional complex-valued exit function,provide a new detection method for the detection of optical imaging components,and further develop new imaging technologies such as optical imaging.Development provides new technical means.