Affected by voltage quantification, manufacture technology and environment temperature, the actual deflection accuracy and diffraction efficiency of liquid crystal optical phased arrays (LC-OPA) are in error with the ideal situation when the beam deflected. In this paper, we studied the method of improving the deflection performance of LC-OPA based on stochastic parallel gradient descent (SPGD) algorithm, and choose Strehl ratio (SR) as the performance evaluation function for simulation experiments. We analyzed the influence of the disturbance amplitude δ, the gain coefficient γ and the number of periodic electrodes N on the performance optimization of the SPGD algorithm in the LC- OPA beam. Draw the conclusion: When the number of periodic electrodes N is within a certain range, appropriate adjustment of the disturbance amplitude δ and the gain coefficient γ can achieve better optimization effects, and the larger the deflection angle, the better the optimization effect. When the number of periodic electrodes N is 4, the amplitude of disturbance δ is 0.0009, and the gain coefficient γ is 0.1, the ideal optimization effect of SR of 0.82 can be achieved, which provides a theoretical basis for improving the large-angle deflection precision and diffraction efficiency of LC-OPA.
Based on the processing mechanism of double-sided polishing machine and working mode, conducted intensive research, found that the motion state of the disc and pads can be simplified as a workpiece relative motion, and a complete mathematical model is built for the motion state of any point on the polishing disc. In view of the relationship among the workpiece’s motion characteristics, polishing process parameters and polishing effect, the computer is used to simulate the motion of the polishing disc relative to the workpiece in the state of steady motion. Taking the motion parameters as the control factor, by changing the ratio of different parameters, the different trajectory of the workpiece’s relative motion is obtained, and the regular pattern of the value of each factor on the motion trajectory distribution is explored. Finally, a set of parameters with the best grinding track uniformity and polishing effect were obtained through analysis and summary.
Pneumatic loading system is an important part of the control system of double-sided polishing machine. It realizes ultra-precision polishing of work piece by accurately controlling the pressure of the upper polishing disc loaded on the upper surface of the work piece. Pneumatic loading system is a typical nonlinear, time-varying system. The traditional PID control parameter setting is very complex, and it is difficult to meet the control requirements. In order to accurately control the parameters of the PID control, this paper will join the fuzzy control block in front of the PID control, make error and error change rate as input of fuzzy control, and PID control parameter as output, according to the selected membership functions and fuzzy rules correction the PID control parameters in real time, constitute adaptive fuzzy PID control. This control strategy can effectively control the pneumatic loading system, with strong stability and robustness. To achieve the stable control of polishing pressure, satisfy the accuracy requirements of medium and large diameter double-sided polishing machine.
Beam steering is an important part of achieving target searching, aiming, tracking, capturing and imaging. It has important applications in the fields of new system laser radar and space laser communication. In this paper, the basic principle of optical phased array (OPA) beam steering is detailed, the development status and research results of OPA beam steering technology based on liquid crystal, optical waveguide and MEMS are introduced, and the application of OPA beam steering technology is briefly described. Finally, the prospect of optical phased array beam steering technology is prospected.
In recent years, with the development of modern optics and laser technology, modern industry for optical surface roughness measurement precision of the increasingly high demand, real-time, fast and precise measurement of surface roughness has become constant subject of optical components in processing and test. In this paper, the current method of measuring the surface roughness of optical components were described in detail, including light scattering method, interferometric method, speckle method, and optical stylus method. Besides, the principles and characteristics of different methods were introduced respectively.
This paper introduces the automatic measurement system of laser scattering method based on angular resolution. Discuss the principle of laser in optical element surface scattering, propose the method which use angle resolved scattering (ARS) method to measure surface roughness, at the same time the measurement principle experimental platform is built based on the experimental results after verifying the correctness of the angle resolved scattering method.
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