Jianli Wang

Closed-loop adaptive optics system with a single liquid crystal spatial light modulator

We describe a closed-loop dynamic holographic adaptive optics system. This system can be realized via one liquid crystal spatial light modulator and one CCD camera. The liquid crystal spatial light modulator is used as the wavefront sensor and corrector, as well as imaging element. CCD detects the spots at holographic image plane and at focal plane of imaging channel simultaneously. The basic principle of the system is introduced first, and then the numerical analysis is presented. On this basis, we report a practical implementation of the dynamic holographic adaptive optics system. The results show that a rapid increase of Strehl ratio and improved image quality at focal plane for deliberately introduced aberrations can be achieved, verifying the feasibility of the system.

A three-dimensional point spread function for phase retrieval and deconvolution

We present a formulation of optical point spread function based on a scaled three-dimensional Fourier transform expression of focal field distribution and the expansion of generalized aperture function. It provides an equivalent but more flexible representation compared with the analytic expression of the extended Nijboer-Zernike approach. A phase diversity algorithm combined with an appropriate regularization strategy is derived and analyzed to demonstrate the effectiveness of the presented formulation for phase retrieval and deconvolution. Experimental results validate the performance of presented algorithm.

Pyramid wavefront sensor using a sequential operation method

The pyramid wavefront sensor is a novel slope wavefront sensor that is similar to the Foucault knife-edge test. In this paper, we describe a sequential operation method that can be realized using a micromirror array. The goal of this paper is to discuss the possibility and analyze the features of the method. Geometrical optics calculations are described first to illustrate the principle of the method. Then, more exact diffraction calculations are provided that illustrate the method being equivalent to the pyramid sensor in principle but with a weak diffraction effect. Numerical simulations are also provided to verify the feasibility of using a nonmodulation method in the closed-loop system.

Experimental Demonstration of Sequential Operation Approach for a Three-Sided Pyramid Wavefront Sensor

We describe a sequential operation approach for a three-sided pyramid wavefront sensor (PWFS) based on a micromirror array with hexagonal geometry. The geometrical optics analysis and numerical simulations show that a linear relationship exists between the signals calculated by the sensing data and the local tilt of the wavefront. We discuss the selection of parameter index that is used in our experiment and build a closed-loop system with this wavefront sensor and a 21-element deformable mirror as a wavefront corrector. The experimental results confirm the feasibility of using a nonmodulated sequential three-sided PWFS in adaptive optics systems.

Analysis of a holographic laser adaptive optics system using a deformable mirror

We describe a closed-loop holographic laser adaptive optics system (HLAOS) based on a holographic wavefront sensor (HWFS) and 21-element continuous-surface piezoelectric deformable mirror (DM). The principle behind HWFSs is described, and then the response sensitivity and crosstalk effect on the lowest 12 Zernike modes of aberration are analyzed. Next, the wavefront-correction capability of the 21-element DM is analyzed. The closed-loop correction of the HLAOS to a static aberration is then numerically simulated. We report a practical implementation of the HLAOS and compare the aberration-compensation effect with a traditional adaptive optics system based on a 37-unit Shark-Hartmann sensor. The practically relevant parameters are analyzed and the experimental results show that an HLAOS using a piezoelectric DM can achieve a correction capability comparable to that of a traditional adaptive optics system.

Research of active supporting technology based on 400mm thin mirror

Using a spherical mirror of 400mm diameter and 12mm thickness, active supporting technology of thin mirror is researched. The axial support of the mirror is composed of 12 active supports and 3 fixed supports. The force actuator, which is composed of displacement actuator and force sensor, is installed in the active support. The mirror surface is tested by Zygo interferometer. For calibration, each actuator exerts unit force alone, and the surface variation is tested and taken as the response function of the actuator. The response functions of all actuators compose the stiffness matrix. Then the stiffness matrix is used by damped least square method to determine the correction force of each active support. In order to analyze the correction capability of the active supports, 14 Zernike modes of the mirror surface are generated and tested respectively, and 7 modes are selected for correction. Initially, the RMS error of mirror surface is 1.16λ I(λ =0.6328nm)when all actuators exert the same force. After 5 iterations, the RMS error of mirror surface is reduced to 0.13λ, close to the original surface quality.