Error analysis and optimal design of polarization calibration unit for solar telescope
                    <sup>*</sup>

Hou, Jing; Wang, Dongguang; Deng, Yuanyong; Sun, Yue; Zhang, Zhiyong

doi:10.1088/1674-1056/26/8/089501

Cited by 2 publications

(2 citation statements)

References 16 publications

(26 reference statements)

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“…This technique has been utilized by several telescopes, such as the Advanced Stokes Polarimeter at the vacuum tower telescope of National Solar Observatory (Skumanich et al 1997), the Domeless Solar Telescope at Hida Observatory (Kiyohara et al 2004;Anan et al 2012;Anan et al 2018), the German Vacuum Tower Telescope at Tenerife (Beck et al 2005), the Solar Optical Telescope aboard Hinode (Ichimoto et al 2008), the 1.5 m solar telescope GREGOR (Hofmann et al 2012) and so on. An ICU designed by the staff at Huairou Solar Observing Station has been equipped on the NVST since 2017 (Hou et al 2017) in order to precisely determine the matrix X.…”

Section: ⋆ Corresponding Authormentioning

confidence: 99%

Spectro-polarimetric observations at the NVST: I. instrumental polarization calibration and primary measurements

Hou

Yuan

et al. 2020

Res. Astron. Astrophys.

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This paper is devoted to the primary spectro-polarimetric observation performed at the New Vacuum Solar Telescope of China since 2017, and our aim is to precisely evaluate the real polarimetric accuracy and sensitivity of this polarimetry by using full Stokes spectro-polarimetric observations of the photospheric line Fe I 532.4 nm. In the work, we briefly describe the salient characteristic of the NVST as a polarimeter in technology and then characterize its instrumental polarization based on the operation in 2017 and 2019. It is verified that the calibration method making use of the instrumental polarization calibration unit (ICU) is stable and credible. The calibration accuracy can reach up to 3×10 −3 . Based on the scientific observation of the NOAA 12645 on April 5th, 2017, we estimate that the residual cross-talk from Stokes I to Stokes Q, U and V , after the instrumental polarization calibration, is about 4×10 −3 on average, which is consistent with the calibration accuracy and close to the photon noise. The polarimetric sensitivity (i.e., the detection limit) for polarized light is of the order of 10 −3 with an integration time over 20 seconds. Slow modulation rate is indeed an issue for the present system. The present NVST polarimeter is expected to be integrated with an high-order adaptive optics system and a field scanner to realize 2D magnetic field vector measurements in the following instrumentation update.

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Section: ⋆ Corresponding Authormentioning

confidence: 99%

Spectro-polarimetric observations at the NVST: I. instrumental polarization calibration and primary measurements

Hou

Yuan

et al. 2020

Res. Astron. Astrophys.

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“…[24,25] A Mueller matrix measurement and calibration system is used to measure both LCVRs and the polarization response matrix 𝑋 with an ac-curacy of 0.01. [30,31] Figure 11 shows the relationship between the measured Mueller matrix of both LCVRs and the derived voltages at 500 nm, where A, B, C, and D are Mueller matrix's four parameters as described in Eq. (21).…”

Section: Measurement and Optimization Of The Lcvrs-based Stokes Polar...mentioning

confidence: 99%

Interference effect on the liquid-crystal-based Stokes polarimeter*

et al. 2020

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The Stokes polarimeter based on liquid crystal variable retarders (LCVRs) is envisaged as a promising novel technique for polarization measurement in space applications due to the inherent advantage of eliminating the need for conventional rotating polarizing optics and increasing the measuring speed. However, the intrinsic multi-beam interference in LCVRs limits its polarization accuracy by several percent. How to eliminate the influence of the interference effect becomes an urgent issue for the liquid-crystal-based Stokes polarimeter. The present study introduces a simplified but effective interference model based on the thin-film optics and polarized light theory to simulate the relationship between the interference effect of the LCVRs-based Stokes polarimeter and the polarization accuracy. The simulation results show that the transmittance variation of LCVR with the derived voltage is caused by multi beam interference between the indium tin oxide (ITO) film and the liquid crystal within LCVR, which produces a few percent of instrumental polarization. The instrumental polarization is about 0.01 and different for different wavelengths. An optimization method was proposed to reduce the instrumental polarization to 0.002, effectively improving the polarization sensitivity of the Stokes polarimeter limited by the interference. In addition, an experimental setup was built up to measure and analyze the influence of the interference effect of the LCVRs-based Stokes polarimeter on the polarization accuracy before and after the optimization. The experiment results are in good agreement with the simulation.

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Error analysis and optimal design of polarization calibration unit for solar telescope ^*

Cited by 2 publications

References 16 publications

Spectro-polarimetric observations at the NVST: I. instrumental polarization calibration and primary measurements

Spectro-polarimetric observations at the NVST: I. instrumental polarization calibration and primary measurements

Interference effect on the liquid-crystal-based Stokes polarimeter*

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Error analysis and optimal design of polarization calibration unit for solar telescope *

Cited by 2 publications

References 16 publications

Spectro-polarimetric observations at the NVST: I. instrumental polarization calibration and primary measurements

Spectro-polarimetric observations at the NVST: I. instrumental polarization calibration and primary measurements

Interference effect on the liquid-crystal-based Stokes polarimeter*

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Error analysis and optimal design of polarization calibration unit for solar telescope ^*