| Optical wavefront testing technology plays an important role in industry,aerospace,biomedicine and other fields.The dynamic range and sensitivity of traditional Twyman-Green and Fizeau interferometric systems are fixed values,which cannot be adjusted dynamically for different requirments.The system structure is complex and sensitive to environmental vibrations,which is not suitable for testing in situ.The Shack-Hartman sensor holds the features of simple structure,large dynamic range,and good stability,but the lateral resolution is extremely low.The point diffraction interferometer,three-wavefront lateral shearing interferometer and cross grating lateral shearing interferometer all involve the problem of pinhole or order selection mask alignment difficulties.The modified Hartmann mask lateral shearing interferometer has periodic Talbot effect,and high-contrast interferograms can only be obtained at specific locations.Randomly encoded hybrid grating(REHG)lateral shearing interferometer based on luminous flux shows features of strong anti-vibration ability,high dynamic range,high resolution,continuous adjustable shear ratio with no order selection mask and Talbol effect.It has a broad application prospect in the testing of optical surface,optical system aberration and quantitative phase imaging.In this dissertation,the design principles of REHG lateral shearing interferometric wavefront testing system,as well as key parameters such as shear ratio,dynamic range,sensitivity and wavefront retrieval accuracy,are discussed.The shear ratio calibration algorithm based on shearing wavefront feature extraction is proposed.An aspheric non-null general testing system and a wideband sensitivity enhanced real-time quantitative phase imaging system using REHG lateral shearing interferometer are established.The main research contents are as follows:The background of optical wavefront detection technology and its important significance in aerospace,military,industrial and biomedical imaging are discussed.The current commonly used wavefront testing technology and application research progress are described and the advantages and disadvantages of each technology are analyzed.The necessity of studying the REHG lateral shearing interferometric system is proposed.The model of REHG lateral shear interference system is discussed and a shear ratio calibration algorithm based on shearing wavefront feature extraction(SWFE)is proposed.The mathematical model,system characteristics and main machining errors of REHG are analyzed,and the wavefront retrieval algorithm of REHG lateral shearing interferometer is discussed.The formula for calculating the shear ratio of the system is given,the main factors that determine the shear rate are clarified,and key parameters such as the relative sensitivity and dynamic range of the system are discussed in detail.A high-precision calibration algorithm for shear ratio based on SWFE is proposed.The error of the simulation result of shear ratio relative to the initial setting value is only 0.2%,which has a very high calibration accuracy.A generalized detection system for aspheric non-zero position based on REHG lateral shearing interferometer is proposed.Firstly,the structural characteristics of the system and the mechanis:m of return error are elaborated,and the universal detection ability of the system is analyzed.The iterative reverse optimization backhaul error correction algorithm based on actual detection system modeling is discussed.Based on the principle simulation of the aspheric surface detection by this system,the root mean square(RMS)value of the surface reconstruction residual is about 5×10-3 ?,under ideal conditions,which demonstrates the feasibility and accuracy of the system.The posture errors of key components of the system are analyzed,and the error control methods are givenA wideband sensitivity enhanced interferometric microscope(WSEIM)based on REHG lateral shearing interferometer is proposed,which can be used for real-time quantitative phase imaging.In view of the shortcomings of the spectral leaking in the single shear quantitative phase imaging system,a novel dual-shear wideband sensitivity enhancement interferometric microscope is introduced,the constraint for the optimal shear ratio selection is obtained.To accelerate the phase retrieval algorithm for real-time visualization,a fully vectorized path-independent differential leveling phase unwrapping algorithm is proposed.The phase retrieval frame rate for each pair of two 4 mega pixel interferograms can reach 54.91 fps.The standard deviation of the phase retrieval residual error in WSEIM simulation experiment is 0.751 nm,which demonstrates the phase imaging accuracy of the systemExperiments are carried out to verify the research content of this dissertation.First,the shear ratio calibration experiment is carried out by using the quartz phase plate fused with a specific pattern,and the etching depth of the phase plate and the spherical surface are characterized.The comparison with the testing results of the ZYGO interferometer demonstrates the accuracy of the shear ratio calibration.Then,an aspheric non-null testing experimental system is built,and the control of the posture and position errors of key components is completed.The RMS error measured by ZYGO interferometer is 2×10-3?,which demonstrates the feasibility and accuracy of the system.Finally,a wideband sensitivity-enhanced quantitative phase imaging system based on two REHG lateral shearing interferometers with different shear ratios is established.The standard deviation of the characterization of the fused silica substrate by WSEIM and the testing result of the Wyko NT9100 white light profiler is 4.164 nm,which verifies the high accuracy of the phase retrieval of the system.Compared with the traditional quantitative phase imaging system based on single shear quadriwave lateral shearing interferometer,WSEIM can eliminate the periodic error caused by the lack of spectrum and reduce the time standard deviation by about 50%,providing an effective method for label free real-time dynamic quantitative phase imaging of biological cells. |
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