The Research On Radial Shearing Interference Technology With Respect To Laser Wavefront

Interference testing technology is a technology which is based on light interference principle. Compared with general optical testing technology, interference testing technique has higher accuracy and smarter sensitivity, and most of the interference testing does not contact surface directly which will not bring additional damage and error to the measured element. Compared with the traditional interference testing techniques, the radial shearing interferometry technology measuring wavefront does not require a reference beam, and is not sensitive to the change of the temperature, the air flow, the ground vibration environment. With changing the ratio of radial shearing, the measurement accuracy is also changed, so it is suitable for field measurement of the gas temperature field, the human eye corneal topography, the aspheric machining, laser quality parameter diagnosis. Considering the radial shearing interferometer has the advantage in measurement of laser wavefront parameters than traditional interferometer, thereby the radial shearing interference technology of laser wavefront has been a hot research. Therefore, in order to further optimize the radial shearing interferometer system, it is necessary to deeply study the radial shearing interference technique. The main contents of this thesis can are summarized as the following aspects:(1) The basic technology of the wavefront testing is investigated and their characteristics and application range are analyzed and compared, radial shearing interferometry is chosen as a high precision testing method of high power laser transient wavefront; the measurement principles of radial shearing interferometer are summarized. The characteristics of the shearing wavefront are analyzed, wavefront reconstruction of several methods for radial shearing interferometry are described, finally the iterative method is chosen to the simulation and analysis of the accuracy of wavefront reconstruction.(2) Several factors affecting the precision of wavefront reconstruction are analyzed: First, the conversion between Zernike coefficient and Seidel aberration coefficient is deduced. Secondly, the influence of the order of Zernike polynomial on the wavefront fitting precision under simple and complex wavefront condition is analyzed. Then the influence of the choice of the radial shearing ratio b on the wavefront fitting precision is analyzed. Finally, the influence of the number of iterations on the wavefront fitting precision is analyzed. The simulation comes to conclusion that: 1) Properly selecting the shearing ratio can simplify the computational complexity. 2) Compared with the small distortion wavefront reconstruction, more but appropriate iteration number in large distortion wavefront reconstruction is needed. 3) Preferred shearing ratios for different measured wavefront PV values are summarized: a. beta > 0.7, if WPV>10λ; b. 0.5 < beta < 0.7, if 6λ < WPV < 10λ; c. beta < 0.5, if WPV < 6λ.(3) According to the theoretical analysis and practical engineering, the radial shearing interference optical system is designed using ZEMAX.