Multi-conjugate adaptive optics (MCAO) has been proved to obtain the high resolution images with a large field of view in solar observation. A solar MCAO experiment system had been successfully developed and tested at the 1-meter New Vacuum Solar Telescope (NVST) of Fuxian Solar Observatory. It consists of two deformable mirrors (DMs), a multidirection Shack-Hartmann wavefront sensor (MD-WFS), and a real-time controller. In order to command the two DMs, five guide regions were selected from the MD-WFS to retrieve a three-dimensional measurement of the turbulent volume based on atmospheric tomography. This system saw the first light in October, 2017, and a series of MCAO-corrected high resolution sunspots images were acquired. In this presentation, the MCAO experiment system is introduced, and the observation results are presented. Furthermore, a new MCAO system based on our proposed MCAO configuration with a high order ground layer adaptive optics and low order high altitude correction will be developed for the NVST as a regularly operating instrument for scientific observations of the sun.
Correlating Shack-Hartmann wavefront sensor is widely used in solar adaptive optics in which the relative shift between
different subapertures by correlation algorithm is computed, and then the control voltage by wavefront
reconstruction can be estimated to use for correcting the wavefront distortion induced by atmospheric turbulence. In this
paper, several different correlation algorithms including Cross-Correlation Coefficient, Absolute Difference Function,
Absolute Difference Function-Squared and Square Difference Function are used to estimate relative shift in correlating
Shack-Hartmann wave-front sensor with the different observed solar structure such as sunspot, solar pore and solar
granulation. The measurement noise RMS error is computed to compare the performance of the correlation algorithms.
The results show the correlation algorithm precision is directly related to the solar structure. The measurement noise is
relatively small with the relatively high contrast target, and vice versa. At the same time, the size of reference image also
could influence the measurement noise, the larger size of the reference image, the smaller the measurement noise is.
Solar observation with high resolution in large field of view (FoV) is required for some solar active regions with the typical sizes of 1’ to 3’. Conventional adaptive optics (AO) could not satisfy this demand because of the atmospheric anisoplanatism. Through compensating the turbulence in different heights, multi-conjugate adaptive optics (MCAO) has been proved to obtain a larger corrected FoV. A MCAO experimental system including a conventional 151-element AO system and a 37-element MCAO part is being developed. The MCAO part contains a 37-element deformable mirror conjugated into the 2km to 5km height and a multi-direction Shack-Hartmann wavefront sensor (MD-SHWFS) with 7×7 subaperture array and 60 arcsec FoV, the frame rate of the MD-SHWFS is up to 840Hz. Three-dimensional (3-D) wavefront sensing utilizing atmospheric tomography had been validated by solar observation. Based on these results, a ground layer adaptive optics (GLAO) experimental system including a 151-element deformable mirror and the MD-SHWFS has been built at the 1m New Vacuum Solar Telescope (NVST). In this paper, the MCAO experimental system will be introduced. The preliminary experimental results of three-dimensional wavefront sensing and GLAO on the NVST of Full-shine Lake Solar Observatory are presented.
Adaptive Optics (AO) has become the requisite equipment of the ground-based large solar telescope to correct the wavefront aberration induced by the atmospheric turbulence. Two generation solar AO systems, one is the 37-element loworder AO system with 2100Hz frame rate and the other is 151-element high-order AO system with 3500Hz frame rate, were successfully developed in 2013 and 2015 respectively. In this presentation, the development of the two AO systems for 1-m New Vacuum Solar Telescope (NVST) at Fuxian Solar Observatory (FSO) will be introduced and the solar high resolution observational results are presented.
The AO progresses for astronomy in the Key Laboratory of Adaptive Optics, Chinese Academy of Sciences are reported in this presentation. For night-time astronomical observations, the recent AO technological developments, such as Laser Guide Star, Pyramid Sensor and Deformable Secondary Mirror, are introduced. The solar AO researches are also presented for day-time astronomical observations. Furthermore, we will show the on-sky high resolution observational results in the 1.8m telescope at Gaomeigu site, Yunnan Observatory and the 1-m New Vacuum Solar Telescope (NVST) at Fuxian Lake Solar Observatory respectively.
For better understanding and forecasting of solar activity, high resolution observations for the Sun are needed. Therefore, the Chinese Large Solar Telescope (CLST) with a 1.8-m aperture is being built. The CLST is a classic Gregorian configuration telescope with an open structure, alt-azimuth mount, retractable dome, and a large mechanical de-rotator. The optical system with an all reflective design has a field of view of larger than 3 arc-min. The 1.8-m primary mirror is a honeycomb sandwich fused silica lightweight mirror with an ultra lower expansion material and active cooling. The adaptive optics system will be developed to provide the capability for diffraction-limited observations at visible wavelengths. The CLST design and development phase began in 2011 and 2012, respectively. We plan for the CLST’s start of commission to be in 2017. A multiwavelength tomographic imaging system, ranging from visible to near-infrared, is considered as the first light scientific instrument. The main system configuration and the corresponding postfocal instruments are described. Furthermore, the latest progress and current status of the CLST are also reported.
Phase diversity (PD) can not only be used as wavefront sensor but also as image post processing technique. However, its computations have been perceived as being too burdensome and it is difficult to achieve its real time application on a PC platform. In this paper, we carried out parallel analysis on the algorithm and task assignments on the heterogeneous platform of CPU-GPU, and then implement parallel programing optimization on GPUs. The optimization strategies of the cost function on GPU are introduced. The process of OTF is improved to make the amount of calcuation reduced by 11% compared to the original method. In order to demonstrate the speedup of PD, two images, 128x128 pixels and 256x256 pixels in dimension, are tested on CPU platform and CPU/GPU heterogeneous platform respectively. The results show the time costs have the improvenments of 13x and 28x for the implementation of PD based on GPU in contrast with that based on CPU.
A novel adaptive optics vision simulator (AOVS) is presented and characterized for several design features, including automated measuring and compensating eye’s aberrations up to the fifth order, which fully cover aberrations typically found in the human eye, even for the cases of highly aberrated eyes. Especially, it is equipped with 35 elements bimorph deformable mirror with bigger stroke and smaller size, which could help establish near-diffraction-limited ocular optics condition. To investigate the validity of this apparatus, pilot data under different aberration correction pattern from one subjects are collected, and contrast sensitivity function (CSF), an important psychophysical function in vision, is obtained also. Results from living eyes show a practically perfect aberration correction and demonstrate the utility of this system.
For better understanding and forecasting of the solar activity and the corresponding impacts human technologies and life on earth, the high resolution observations for Sun are needed. The Chinese Large Solar Telescope (CLST) with 1.8 m aperture is being built. The CLST is a classic Gregorian configuration telescope with open structure, alt-azimuth mount, retractable dome, and a large mechanical de-rotator. The optical system with all reflective design has the field of view of larger than 3 arc-minute. The 1.8 m primary mirror is a honeycomb sandwiches fused silica lightweight mirror with ULE material and active cooling. The adaptive optics system will be developed to provide the capability for diffraction limited observations at visible wavelengths. The CLST design and development phase began in 2011 and 2012 respectively. We plan for the CLST’s starting of commission in 2017. A multi-wavelength tomographic imaging system with seven wavelengths range from visible to near-infrared wavelength is considered as the first light scientific instruments. In this paper the main system configuration and the corresponding post focal instruments are described. Furthermore, the latest progress and current status of the CLST are also reported.