ABSTRACT
Ground layer adaptive optics (GLAO) has been widely employed in wide-field observations with ground-based telescopes. However, the present evaluation of GLAO performance lacks a criterion in terms of turbulence layer correction. This deficiency results in a significant gap in understanding the effectiveness of GLAO correction at different heights of the turbulence layer, thereby hindering the optimization of GLAO system performance. To bridge this gap, this Letter introduces a new, to the best of our knowledge, performance criterion for GLAO, termed layer correction efficiency (LCE). This criterion is formulated to quantify the effective compensation of the GLAO system for a specific altitude layer of turbulence, providing support for the further enhancement of GLAO performance. The simulation results indicate that the LCE has high applicability in GLAO performance analysis.
ABSTRACT
The correlation Shack-Hartmann wavefront sensor (SHWFS) is widely used in many fields in addition to solar adaptive optics. The requirement for the SHWFS dynamic range increases with the diameter of the telescope, which means a larger detector array is needed. However, the size of the detector would be restricted by the high frame rate needed for the solar observation. To solve this problem, a new, to the best of our knowledge, method called the region-correlation algorithm (RCA) is proposed. In this method, the sub-image array is divided into several regions, and the slopes of sub-apertures are calculated by referring to a selected sub-image in each region. Note that the final slope over a sub-aperture is obtained by combining the relative slopes between the selected sub-image in different regions. The dynamic range in each region is similar to the conventional correlation algorithm, and the final dynamic range of the RCA would be accumulated from those of the regions. The reconstruction accuracy under large aberration would also be improved due to the extended dynamic range. Meanwhile, the RCA does not require any extra device and the increase in calculation time resulting from the RCA is acceptable. The results of numerical simulation and experiment, compared with conventional correlation algorithm, confirm the advantages in the performance of the RCA as well.
ABSTRACT
Multi-conjugate adaptive optics (MCAO) is the most promising technique currently developed to enlarge the corrected field of view of adaptive optics for astronomy. In this paper, we propose a new configuration of solar MCAO based on high order ground layer adaptive optics and low order high altitude correction, which result in a homogeneous correction effect in the whole field of view. An individual high order multiple direction Shack-Hartmann wavefront sensor is employed in the configuration to detect the ground layer turbulence for low altitude correction. Furthermore, the other low order multiple direction Shack-Hartmann wavefront sensor supplies the wavefront information caused by high layers' turbulence through atmospheric tomography for high altitude correction. Simulation results based on the system design at the 1-meter New Vacuum Solar Telescope show that the correction uniform of the new scheme is obviously improved compared to conventional solar MCAO configuration.