Error analysis of sub-aperture stitching interferometry

Jia, Xin; Xu, Fuchao; Xie, Wanyi; Xing, Tingwen

doi:10.1117/12.977639

Cited by 6 publications

(3 citation statements)

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“…The subaperture surface random error is caused by random horizontal position error, electronic noise, air disturbance error, and vibration errors. Wiegmann [28] and Jia [29] have analyzed the effect of random horizontal position error to the subaperture stitching in virtual experiments. However, it is difficult for us to separate these environment variables in an experiment.…”

Section: Sensitivity Coefficient In Stitchingmentioning

confidence: 99%

Sensitivity coefficient for monitoring residual surface error in plane subaperture stitching interferometry

Shen

Wang

2018

Meas. Sci. Technol.

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Subaperture stitching interferometry is widely used in large-aperture plane surface measurements. The reference surface error forms a primary reason leading to erroneous stitching surface figures. The methods to remove this error include the normal stitching algorithm with the absolute test and a special algorithm with interlocked compensators without the absolute test. Here, we perform a series of subaperture stitching experiments to demonstrate that the reference surface error can easily be calculated wrongly using the algorithm with interlocked compensators. Consequently, we propose the use of a sensitivity coefficient to describe the sensitivity of the stitching algorithms of the two methods. Next, we perform simulations of pairwise subaperture stitching to illustrate the variations in the sensitivity coefficient with different overlapping area ratios. Finally, two plane surfaces with size of 200 mm × 200 mm are stitched with the reference surface error as reduced by the two methods. Comparisons of the residual surface errors of the two methods show that the algorithm using interlocked compensators is less accurate and less stable, which could be monitored by the sensitivity coefficient. Thus, for reducing the reference surface error in plane subaperture stitching interferometry, the absolute test method should be considered first.

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Section: Sensitivity Coefficient In Stitchingmentioning

confidence: 99%

Sensitivity coefficient for monitoring residual surface error in plane subaperture stitching interferometry

Shen

Wang

2018

Meas. Sci. Technol.

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“…Auto-collimation [7,8] and sub-aperture stitching [9][10][11][12][13][14][15][16][17][18] are two major interferometry methods used for parabolic mirrors. When a concave parabolic mirror is under test, its focal point should be suitable with a standard lens for auto-collimation; if the relative aperture of the parabolic mirror is larger than the standard lens, then the surface of the entire aperture could not be obtained.…”

Section: Introductionmentioning

confidence: 99%

“…In addition, auto-collimation requires the same aperture standard flat mirror as the parabolic mirror under test; however, the requirement of a large aperture and high precision accuracy flat mirror makes it difficult to realise. Sub-aperture stitching is an effective way to extend the lateral and vertical dynamic range of a conventional interferometer; however, when the deviation of a parabolic mirror becomes larger, its corresponding interferograms will be thicker for not only the annular sub-aperture stitching method [9,10] but also for the circular sub-aperture stitching method [11][12][13][14][15][16][17][18], and the corresponding interferogram processing will become more difficult. In addition, sub-aperture stitching requires a precision platform with six degrees of freedom to implement the complex adjustment of the parabolic mirror under test.…”

Section: Introductionmentioning

confidence: 99%

Characterisation of a large aperture steep concave parabolic mirror using SASI based on auto-collimation theory

Liu

Tian

et al. 2014

Meas. Sci. Technol.

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To characterise a large aperture steep concave parabolic mirror, a new sub-aperture stitching interferometry measurement technology (SASI) based on auto-collimation is proposed. The principle of the stitching process is analysed, and the sub-aperture partitioning for a full aperture of a paraboloid is discussed. Next, the overlapped sampled points between sub-apertures are rectified through sampled points realigned in mesh grids. Finally, two experiments, the SASI based on auto-collimation and the full aperture test, were implemented for a parabolic mirror. The stitching result exhibits good agreement with the full-aperture result.

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MEGARA Optics: Sub-aperture Stitching Interferometry for Large Surfaces

Aguirre-Aguirre

Carrasco

Izazaga-Pérez

et al. 2018

PASP

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In this work, we present a detailed analysis of sub-aperture interferogram stitching software to test circular and elliptical clear apertures with diameters and long axes up to 272 and 180 mm, respectively, from the Multi-Espectrógrafo en GTC de Alta Resolución para Astronomía (MEGARA). MEGARA is a new spectrograph for the Gran Telescopio Canarias (GTC). It offers a resolution between 6000 and 20000 via the use of volume phase holographic gratings. It has an integral field unit and a set of robots for multi-object spectroscopy at the telescope focal plane. The output end of the fibers forms the spectrograph pseudo-slit. The fixed geometry of the collimator and camera configuration requires prisms in addition to the flat windows of the volume phase holographic gratings. There are 73 optical elements of large aperture and high precision manufactured in Mexico at the Instituto Nacional de Astrofísica, Óptica y Electrónica (INAOE) and the Centro de Investigaciones en Óptica (CIO). The principle of stitching interferometry is to divide the surface being tested into overlapping small sections, which allows an easier analysis (Kim & Wyant 1981). This capability is ideal for non-contact tests for unique and large optics as required by astronomical instruments. We show that the results obtained with our sub-aperture stitching algorithm were consistent with other methods that analyze the entire aperture. We used this method to analyze the 24 MEGARA prisms that could not be tested otherwise. The instrument has been successfully commissioned at GTC in all the spectral configurations. The fulfillment of the irregularity specifications was one of the necessary conditions to comply with the spectral requirements.

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Error analysis of sub-aperture stitching interferometry

Cited by 6 publications

References 0 publications

Sensitivity coefficient for monitoring residual surface error in plane subaperture stitching interferometry

Sensitivity coefficient for monitoring residual surface error in plane subaperture stitching interferometry

Characterisation of a large aperture steep concave parabolic mirror using SASI based on auto-collimation theory

MEGARA Optics: Sub-aperture Stitching Interferometry for Large Surfaces

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