Open AccessMTF improvement for optical synthetic aperture system via mid-frequency compensation
Author(s) -
Yingxin Wu,
Mei Hui,
Weiqian Li,
Ming Liu,
Liquan Dong,
Lingqin Kong,
Yuejin Zhao
Publication year - 2021
Publication title -
optics express
Language(s) - Danish
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.420512
Subject(s) - optics , optical transfer function , synthetic aperture radar , aperture (computer memory) , pupil function , point spread function , spatial frequency , aperture synthesis , physics , image resolution , frequency domain , beam divergence , computer science , diffraction , interferometry , beam diameter , acoustics , laser , laser beams , computer vision
Optical synthetic aperture imaging system has grown out the quest for higher angular resolution in astronomy, which combines the radiation from several small sub-apertures to obtain a resolution equivalent to that of a single filled aperture. Due to the discrete distribution of the sub-apertures, pupil function is no longer a connected domain, which further leads to the attenuation or loss of the mid-frequency modulation transfer function (MTF). The mid-frequency MTF compensation is therefore a key focus. In this paper, a complete mid-frequency compensation algorithm is proposed, which can extract and fuse the frequency of different synthetic aperture systems and monolithic aperture systems according to their special MTF characteristics. The dimensions of the monolithic aperture and optical synthetic aperture system are derived, and the longest baseline of the monolithic aperture is much smaller than that of the optical synthetic aperture system. Then the separated spatial frequency information is extracted and synthesized according to the spatial frequency equivalence point. Finally, the full-frequency enhanced image is recovered by using improved Wiener-Helstrom filter, which adopts specific parameters based on different sub-aperture arrangements. The mid-frequency MTF of Golay-3 increases from 0.12 to 0.16 and that of Golay-6 increases from 0.06 to 0.18. Both the simulation and experiment prove that the proposed method not only realizes the spatial resolution determined by the longest baseline of the optical synthetic aperture system, but also successfully compensates its mid-frequency MTF.