Quantitative evaluation on thermal seeing induced 2m ring solar telescope.

Thermal seeing is one of the factors that affect solar telescope observations. A comprehensive analysis method is developed to quantify the thermal seeing effects. A three-dimensional Large Eddy Simulation (LES) turbulence model is used to obtain the transient flow fields around the primary mirror, the secondary mirror and the heat-stop. The thermal seeing is calculated based on the stochastic dynamic influence of turbulence on the light rays. The key parameters of the simulation were calibrated by experiments, and the simulation results were validated by empirical formulas. This method has been applied to evaluate the thermal seeing of the 2m Ring Solar Telescope (2m-RST). Error allocation is performed based on the research results to ensure the Observation effect of 2m-RST.

High robustness single-shot wavefront sensing method using a near-field profile image and fully-connected retrieval neural network for a high power laser facility.

This paper proposes a single-shot high robustness wavefront sensing method based on deep-learning for wavefront distortion measurement in high power lasers. This method could achieve fast and robust wavefront retrieval by using a single-shot near-field profile image and trained network. The deep-learning network uses fully-skip cross connections to extract and integrate multi-scale feature maps from various layers and stages, which improves the wavefront retrieval speed and enhances the robustness of the method. The numerical simulation proves that the method could directly predict the wavefront distortion of high power lasers with high accuracy. The experiment demonstrates the residual RMS between the method and a Shack-Hartmann wavefront sensor is less than 0.01 µm. The simulational and experimental results show that the method could accurately predict the incident wavefront distortion in high power lasers, exhibiting high speed and good robustness in wavefront retrieval.

Hybrid ball-hinged secondary mirror assembly for high-precision surface shape maintenance.

As an essential part of optical telescope, the secondary mirror is subject to the influence of ambient temperature, which leads to temperature-induced distortion on the surface shape. A hybrid ball-hinged secondary mirror assembly (HSMA) is proposed to achieve thermal adaptation over a wide range of temperature. Simulation investigation on the temperature-induced surface shape distortion of the HSMA were carried out by using the finite element model. Simulation results show that the change of secondary mirror surface distortions over a wide range of temperature are minimal and negligible. For the wide ambient temperature range from -30°C to 70°C, the PV and RMS values of the maximum residual distortions can reach as small as 16.31 nm and 3.005 nm, respectively. Furthermore, the influence of gravity-induced distortion on the surface shape is also carried out. Both simulation and experiment results show that the HSMA is able to maintain high-precision surface shape of the secondary mirror over a wide range of temperature and at different attitudes from 0 to 90 ∘.