Waveplates are widely used in solar physics for polarization measurements in solar telescopes. Accurate calibration of the fast-axis azimuth and retardance of waveplates is crucial for improving the precision of these measurements. In this paper, we suggest that the spatial polarization characteristics of the analyzer in waveplate calibration system, using the intensity method, can introduce errors in calibrating the fast-axis and retardance. Therefore, we propose a correction method that introduces an analyzer model during the waveplate calibration process to address these errors. Numerical simulations demonstrated that the impact of these characteristics of the analyzer on the waveplate calibration depends on the form of these characteristics and the parameters of the waveplate itself, leading to calibration errors over 0.1° in fast-axis orientation and 1° in retardance in some cases. We conducted simulations using a calibration system as an example. The simulations indicate that, in certain cases, the correction method can reduce these errors significantly: from-0.27°to-0.08° for fast-axis orientation and from -3.8° to -0.01° for retardance. This method effectively reduces calibration errors of waveplate parameters induced by the spatial polarization characteristics of the analyzer in intensity-based methods.
The wide field adaptive optics system for solar observations had been developed and put in routine operation at the 1-meter New Vacuum Solar Telescope (NVST) in Fuxian Lake, Yunnan Observatory. This system adopts the configuration based on the high order ground layer correction loop and the low order high altitude correction loop. Three correction modes, namely the conventional adaptive optics (CAO), ground layer adaptive optics (GLAO), and multi-conjugate adaptive optics (MCAO) with three layers correction, can be chosen with the science requirement. The DM for ground layer correction is inherited from the 151-element AO system, and two new DMs are added and conjugated to 2~5km and 7~10km, respectively. The opto-mechanical design allows for changing the conjugate height of the two DMs independently. Two multi-direction Shack-Hartmann wavefront sensors are employed for sensing the aberration from ground layer and high-altitudes turbulence. The control system is based on multi-core CPUs platform, which is flexible for testing various control approaches. We summarize the design and report the observational results of different correction modes.
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