2017/04/27 by Joss Bland‐Hawthorn, Joss Bland-Hawthorn, Janez Kos +9
Engineering · Physics and Astronomy · #Advanced Fiber Laser Technologies #Cardinal point #Computer science #Diffraction #Distortion (music) #Image plane #Optical Coherence Tomography Applications #Optical transfer function #Optics #Optoelectronics #Photonic Crystal and Fiber Optics #Physics #Point spread function #Spectral line #Spectrograph #Telescope #Wavefront #astro-ph.IM
paper · pdf · doi:10.1364/oe.25.015614
Optics Express, Special Issue on Astrophotonics (10 pages, 6 figures)
arxiv created 2017/04/27 · openalex publication_date 2017/06/26 · arxiv updated 2017/08/02 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We demonstrate a new approach to calibrating the spectral-spatial response of a wide-field spectrograph using a fibre etalon comb. Conventional wide-field instruments employed on front-line telescopes are mapped with a grid of diffraction-limited holes cut into a focal plane mask. The aberrated grid pattern in the image plane typically reveals n-symmetric (e.g. pincushion) distortion patterns over the field arising from the optical train. This approach is impractical in the presence of a dispersing element because the diffraction-limited spots in the focal plane are imaged as an array of overlapping spectra. Instead, we propose a compact solution that builds on recent developments in fibre-based, Fabry-Perot etalons. We introduce a novel approach to near-field illumination that exploits a 20cm aperture commercial telescope and the propagation of skew rays in a multimode fibre. The mapping of the optical transfer function across the full field is represented accurately (<0.5% rms residual) by an orthonormal set of Chebyshev moments. Thus we are able to reconstruct the full 4K × 4K CCD image of the dispersed output from the optical fibres using this mapping, as we demonstrate. Our method targets one of the largest sources of systematic error in multi-object spectroscopy, i.e. spectral distortion due to instrumental aberrations, and provides a comprehensive solution to their calibration and removal.