In high power laser system, the wavefront quality of large optic elements in the mid-frequency region plays a critical role in the system performance and safe operation. A simple and efficient measurement method for mid-frequency wavefront error is used, which employs the extended ptychographical iterative engine algorithm and has simple structure, low environment requirement and flexible adjustable frequency ranges. This method has been successfully implemented for the wedge focused lens to achieve accurate mid-frequency measurement. Further it can be extended to a wide range of large optical components, especially for which the wavefronts are not easy to be measured using interferometers.
Wavefront distortion induced by structure design must be minished to raise the quality of output beam in ICF facility.
The support system of large octagonal Nd:glass in main amplifiers of SG-II is optimized with finite element analysis
software ANSYS, and wavefront distortion in aperture of amplifier is calculated with Zernike polynomials fitting in
different parameters combination. The transmission wavefront distortion induced by optimal support system is less than
tenth wavelength and meets the requirement of system.
The factors affecting the removal rate and surface shape in CMP is introduced. The edge effect is a critical problem in CMP process, which behaves on the global planarization of workpiece-pad interface and change on local planarization and results in collapse or rise in workpiece edges. One of the main factors of edge effect is Von Mises stress, which is a composition stress. The main affecting factor of Von Mises is the axial stress component. The factors affecting the material removal rate (MRR) of workpiece surface and surface nonuniformity include shape, material properties and thickness of pad and polishing media. Factors of load and relative velocity in CMP are also discussed.
As the resolution of the interferometer is rapidly increasing, the higher requirement is proposed to the interferometry. For avoiding losing of the useful information of the actual interferogram, an algorithm is presented based on singular value decomposition (SVD) which is more stable than other algorithms to some extent. The weight coefficients of the orthogonal polynomials can be worked out directly, which can eliminate the computational error. Then an evaluation criterion is developed to choose the optimum Zernike polynomial number. The computer simulations of this algorithm are also made. The simulation experiments have proved that it is an efficient algorithm and can reconstruct the wavefront accurately and stably.
This article describes briefly the optical surface profileometry in China, including several result of its theory research, optical profiler development and some problems using the optical profiler.
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