Chinese Optics Letters, Volume. 17, Issue 12, 121101(2019)

Piston sensing via a dispersed fringe sensor with a merit-function-based active scanning algorithm at low light levels

Yongfeng Zhang1,2,3 and Hao Xian1,2,*
Author Affiliations
  • 1Key Laboratory on Adaptive Optics, Chinese Academy of Sciences, Chengdu 610209, China
  • 2Institute of Optics and Electronics, Chinese Academy of Sciences, Chengdu 610209, China
  • 3University of Chinese Academy of Sciences, Beijing 100049, China
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    Dispersed fringe sensors are a promising approach for sensing the large-scale physical step between adjacent segments with acceptable accuracy. However, the nature of dispersion in a dispersed fringe sensor leads to the ideal dispersed fringe pattern becoming vulnerable to noise, particularly at low light levels. A reliable merit-function-based algorithm with an active actuation is introduced here. The feasibility of our algorithm is numerically demonstrated, and Monte Carlo experiments for different signal-to-noise ratios are conducted to assess its robustness. The results show that the method is valid even when the signal-to-noise ratio is as low as 1.

    It has been a trend that a segmented mirror is employed to construct extremely large telescopes. Up to this date, several large segmented telescopes have been completed, such as the Keck I/II[1], Giant Magellan Telescope (GMT)[2], South African Large Telescope (SALT)[3], Hobby-Eberly Telescope (HET)[4], and Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST)[5]; and several programs are being planned, such as the Thirty Meter Telescope (TMT)[6], European Extremely Large Telescope (E-ELT)[7], and Advanced Technology Large-Aperture Space Telescope (ATLAST)[8]. For the purpose of making a segmented mirror act as an equivalent monolithic mirror, the rigid misalignment errors in the segmented mirror must be corrected within the tolerance limit, especially the piston error; if not, the image quality will not be better than that of a single segment[9].

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    Yongfeng Zhang, Hao Xian. Piston sensing via a dispersed fringe sensor with a merit-function-based active scanning algorithm at low light levels[J]. Chinese Optics Letters, 2019, 17(12): 121101

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    Paper Information

    Category: Imaging Systems

    Received: Jun. 24, 2019

    Accepted: Aug. 6, 2019

    Published Online: Nov. 26, 2019

    The Author Email: Hao Xian (xianhao@ioe.ac.cn)

    DOI:10.3788/COL201917.121101

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