Preliminary study of a dispersed fringe type sensing system

Zhang, Yong; Liu, Genrong; Wang, Yuefei; Li, Yeping; Zhang, Yajun; Zhang, Liang

doi:10.1088/1674-4527/9/8/010

Cited by 5 publications

(2 citation statements)

References 14 publications

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“…7 The Keck telescopes show the successful co-phasing of a large segmented aperture using modified SH WFS and curvature WFSing, 8,9 serving as the pathfinder for the JWST Dispersed Fringe Sensor. 10 The phase retrieval and related methods employ high computational complexity; often a multi-parameter merit function is minimized, requiring multiple Fourier transforms for each iteration, and a high-precision mechanized element is required to translate the sensor through the image plane by a known amount with very little run-out. The Dispersed Fringe Sensor is reliant on dispersive optics and requires its own additional optical path.…”

Section: Introductionmentioning

confidence: 99%

Co-phasing primary mirror segments of an optical space telescope using a long stroke Zernike WFS

2016

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Static Zernike phase-contrast plates have been used extensively in microscopy for half a century and, more recently, in optical telescopes for wavefront sensing. A dynamic Zernike wavefront sensor (WFS) with four phase shifts, for reducing error due to spurious light and eliminating other asynchronous noise, has been proposed for use in adaptive optics. Here, we propose adapting this method for co-phasing the primary mirror of a segmented space telescope. In order to extend the dynamic range of the WFS, which has a maximum range of +/ − λ/2, a phasecontrast plate with multiple steps, both positive and negative, has been developed such that errors as large as +/ − 10λ can be sensed. The manufacturing tolerances have been incorporated into simulations, which demonstrate that performance impacts are minimal. We show that the addition of this small optical plate along with a high precision linear translation stage at the prime focus of a telescope and pupil viewing capability can provide extremely accurate segment phasing with a simple white-light fringe fitting algorithm and a closed-loop controller. The original focal-plane geometry of a centro-symmetric phase shifting element is replaced with a much less constrained shape, such as a slot. Also, a dedicated pupil imager is not strictly required; an existing pupil sampler such as a Shack-Hartmann (SH) WFS can be used just as effectively, allowing simultaneous detection of wavefront errors using both intensity and spot positions on the SH-WFS. This could lead to an efficient synergy between Zernike and SH-WFS, enabling segment phasing in conjunction with high-dynamic range sensing.

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Section: Introductionmentioning

confidence: 99%

Co-phasing primary mirror segments of an optical space telescope using a long stroke Zernike WFS

2016

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“…For implementing the above new sensor and utilizing the new dispersed fringe sensing technology, we built an indoor mirror visible phasing experiment system (Zhang et al 2009;Zhang et al 2010a;Zhang et al 2010c,b; based on active optics dispersed fringe sensing technology from 2008 to 2010. Now we have tested the sensor on the original indoor segmented mirror active optics platform and already achieved results reaching the project's requirements of piston measurement accuracy of less than one-tenth of a visible 650 nm wavelength in the piston range from zero to 20 µm.…”

Section: Introductionmentioning

confidence: 99%

An experimental indoor phasing system based on active optics using dispersed Hartmann sensing technology in the visible waveband

Zhang

Liu

Wang

et al. 2011

Res. Astron. Astrophys.

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A telescope with a larger primary mirror can collect much more light and resolve objects much better than one with a smaller mirror, and so the larger version is always pursued by astronomers and astronomical technicians. Instead of using a monolithic primary mirror, more and more large telescopes, which are currently being planned or in construction, have adopted a segmented primary mirror design. Therefore, how to sense and phase such a primary mirror is a key issue for the future of extremely large optical/infrared telescopes. The Dispersed Fringe Sensor (DFS), or Dispersed Hartmann Sensor (DHS), is a non-contact method using broadband point light sources and it can estimate the piston by the two-directional spectrum formed by the transmissive grating's dispersion and lenslet array. Thus it can implement the combination of co-focusing by Shack-Hartmann technology and phasing by dispersed fringe sensing technologies such as the template-mapping method and the Hartmann method. We introduce the successful design, construction and alignment of our dispersed Hartmann sensor together with its design principles and simulations. We also conduct many successful real phasing tests and phasing corrections in the visible waveband using our existing indoor segmented mirror optics platform. Finally, some conclusions are reached based on the test and correction of experimental results.

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Latest progress of LAMOST primary co-phasing experiment in NIAOT, China

Zhang

Cui

et al. 2014

SPIE Proceedings

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Preliminary study of a dispersed fringe type sensing system

Cited by 5 publications

References 14 publications

Co-phasing primary mirror segments of an optical space telescope using a long stroke Zernike WFS

Co-phasing primary mirror segments of an optical space telescope using a long stroke Zernike WFS

An experimental indoor phasing system based on active optics using dispersed Hartmann sensing technology in the visible waveband

Latest progress of LAMOST primary co-phasing experiment in NIAOT, China

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