To achieve a full-aperture, diffraction-limited image, a telescope’s segmented primary mirror must be properly phased. Furthermore, it is crucial to detect the piston errors between individual segments with high accuracy. Based on the diffraction imaging theory, the symmetrically shaped aperture with an arbitrarily positioned entrance pupil would focus at the optical axis with a symmetrical diffraction pattern. By selecting a single mirror as a reference mirror and regarding the diffraction image’s center as the calibration point, a function can be derived that expresses the relationship between the piston error and the distance from the center of the inference image to the calibration point is linearity within one-half wavelength. These theoretical results are shown to be consistent with the results of a numerical simulation. Using this method, not only the piston error, but also the tip–tilt error can be detected. This method is simple and effective; it yields high-accuracy measurements and requires less computation time.
To determine parameters of the Segmented Mirror Telescope is quite essential for the design, manufacture, testing and construct of the telescope system, especially the F-number parameters and curvature radius of the primary mirror, as well as the asphericity. A model of Sub-segmented mirror was established in this paper, based on which, using the feature points combined with lagrange condition extreme, the asphericity calculation of the asymmetrical hexagon off-axis parabolic mirror in different central points is solved. The 8m and 11m segmented mirror telescope were taken for example in the calculation, and got the relation curve between F-number of primary mirror and Asphericity of segmented mirror, respectively. This work is useful for the design, manufacturing and testing of the large diameter Segmented Mirror Telescope.
The pyramid wavefront sensor is an innovative device with the special characteristics of variable gain and adjustable
sampling in real time to enable an optimum match of the system performance, which make it an attractive option for next
generation adaptive optics system compared with the Shack-Hartmann. At present most of the pyramid wavefront sensor
are used with modulation based on oscillating optical component in order to give a linear measurement of the local tilt,
but the PWFS without modulation would greatly simplify the optical and mechanical design of the adaptive optics
system and also give highest sensitivity as expected to be achieved. In this paper we describe the optical setup of our
adaptive optics system with nonmudulated pyramid wavefront sensor. In this system, the pyramid wavefront sensor with
8×8 sub-apertures in the pupil diameter has been designed, and the deformable mirror with 61 actuators based on the
liquid-crystal spatial light modulator is used to introduce aberrations into the system, as well as to correct them
afterwards. The closed-loop correction results of single order Zernike aberrations and the Kolmogorov turbulence phase
screen are given to show that the PWFS without modulation can work as expected for closed-loop system.
The 127-element adaptive optical system for the 1.8m astronomical telescope is being developed. In this system, the
wavefront correction loop consists of a 127-element deformable mirror, a Hartmann-Shack (H-S) wavefront sensor, and
a high-speed digital wavefront processor. The tracking system consists of a tip-tilt mirror, a tracking sensor and a
tracking processor. The wavelength for the H-S wavefront sensor ranges from 400-700nm. The imaging observation
wavelengths range from 700-1000nm and 1000-1700nm respectively. In this paper, the optical configuration of 1.8m
telescope will be briefly introduced. The 127-element adaptive optical system is described in detailed. Furthermore, the
preliminary performances and test results on the 127-element adaptive optical system is reported.
A kind of Multiple-Detecting-Branch (MDB) Shack-Hartmann wavefront sensor (SHWFS) with extremely large number
of subapertures, in which the pupil is split into spatially several branches by a beam splitter and each branch is detected
by a SHWFS with less subapertures comparatively, is proposed to use for the wavefront sensing of the adaptive optics
system for extremely large telescope. All the signals from the CCDs of SHWFS must be synchronized by the specially
developed hardware system. There are the angular error of the beam splitter and the circum-optical-axis rotary of CCDs
besides of the error of the conventional SHWFS. In this paper, the principle of the MDB SHWFS is introduced and its
errors are analyzed. The simulation and experimental results show that this kind of MDB SHWFS can be used to
measure effectively the wavefront aberration of the total pupil.
The 61-element upgraded adaptive optical system for the 1.2m telescope of Yannan Observatory for astronomical observation had been in operation since May 2004. In this paper, the 61-element upgraded adaptive optical system for 1.2m telescope of Yunnan Observatory will be briefly described. The performance on the 61-element upgraded adaptive optical system is analyzed. Furthermore, the observational results for the stars will be presented.
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