Research On Optical Mirror Position Detection And Active Correction

The China Giant Solar Telescope(CGST)is the proposed next generation large ground-based solar telescope in China.It is to use the segmented mirror active optical technology to realize a circular mirror surface with a diameter of 8 meters.Pose detection of the segment mirrors is one of the key technical requirements for co-phasing observation of the CGST.This paper focuses on segmented mirror position detection and active correction method.The main contents are summarized as follows:(1)The principle of segmented-mirror active optics was introduced.In terms of the degree of freedom detection and control requirements of CGST,a new 8-m ring-segmented solar telescope control system was introduced.Then the segmented mirror experimental prototype of 8m ring-segmented solar telescope was introduced.(2)In this method,the degree of freedom(normal translation of the mirror and two tilts)are detected by the combination of the adjacent segmented-mirror edge mounted displacement sensor(also called edge sensor)and the tilt sensor.At the same time,the displacement of the actuator is actively corrected by the displacement actuator.The tilt sensor is a two-dimensional precision angle measurement system based on digital camera and laser.According to the proposed angular measurement scheme,a test platform is built and calibrated with a high-precision interferometer.The angular measurement accuracy can reach 0.05?.According to the proposed measurement method,the hardware and software systems are also designed.(3)A segmented-mirror control system based on displacement and tilt detection is built and tested.The theoretical control matrix and the measured control matrix are calibrated by the test system actively.The experimental results show that in the static environment,the measured control matrix and the theoretical control matrix correction effect are comparable;in the presence of disturbances,the convergence rate of the measured control matrix is better than that of the theoretical control matrix.However,the mean square error of piston can be stabilized within 20 nm by both control matrices,and the mean square error of tip and tilt between sub-mirrors can be stabilized within 0.2?,which fully meets the control requirements.