The development of large-aperture telescopes employing monolithic mirrors has been greatly limited by technical constraints and the difficulty of processing and manufacturing. The sparse aperture imaging system employing multiple small-sub apertures arranged and combined onto a co-phasing surface can achieve the equivalent resolution to the fullyfilled aperture system, which brings new research ideas for astronomical observation and ground survey. However, the sparsity of apertures will result in blurred imaging. In this paper, we focus on the high-resolution imaging from the geostationary orbit and propose a restoration method for blurred images obtained by the sparse aperture system with a 12- sub-aperture annular-like structure. A SASDeblurNet, containing U-shaped structures and skip connections, is proposed to rapidly restore blurred images end-to-end. MAE, MSE, DSSIM, Charbonnier, and edge loss functions are attempted to train a small amount of data sets in anticipation of better imaging results. The simulation results show that the image restored by the proposed method improves the PSNR by an average of 11 dB and the SSIM of the restoration image improves from 0.77 to 0.94, achieving a high resolution comparable to that of a full-aperture optical system. Compared with traditional non-blind deconvolution algorithms, SASDeblurNet can effectively remove the effect of artifacts. Our work shows that the proposed method has good real-time performance, generalization ability, and noise immunity, which can provide the corresponding data support for on-orbit and real-time observation of sparse aperture imaging systems.
Space-based high-resolution imaging system has a trend to broadband spectrum imaging in geosynchronous orbits. The resolution of an imaging system is related to the aperture size, the height of the orbit of the system, and the detection wavelength. For traditional imaging system, it is difficult to increase the aperture size due to the limitation of manufacturing level, processing cost and load weight. The optical sparse aperture (OSA) system uses a number of independent subaperture systems with a smaller size and the same standard to collect light from objects and synthetizes a blur image in focal plane, which can achieve a large equivalent aperture size. However, with the increasing number of the sub-aperture systems, the system structure becomes more complicated, which is difficult to be used in practice. This paper presents an approach to search for an optimal OSA system based on annular pupil structure and reduce the number of sub-aperture systems by rotating the pupil to compensate PSF information and improve the image quality in OSA system. In this paper, a 12-aperture OSA system applied for earth observation in geosynchronous orbit are designed optimally to realize the resolution of 1m. The optimal scheme for rotating the pupil with twelve apertures under the threesymmetric structure was determined, and the MTF of the hexagonal structure was obtained. The simulation results show that the method can be applied to design a OSA system with a rotating pupil, synthesize all images within the rotation period, collect all frequency information, and restore high-resolution images using image restoration techniques.
The superresolving pupil filters are utilized to modulate amplitude or phase, which can compress the central main lobe of the diffracted spot below the diffraction limit. The mature pupil filter is mainly made by binary optical processing technology or liquid crystal spatial light modulators. Compared with these two types, the superresolving pupil filters based on deformable mirror(DM) have the advantages of programmability, no wavelength and polarization limitation. In this paper, the design of superresolving continuous phase filters using DM eigenmodes as the basis function is studied by simulation. The DM eigenmodes are constructed by the coupling relationship between the actuators, and the first, sixth, fifteenth and 30th order eigenmodes are selected for interpolation to obtain the continuous phase function. Superresolution gain factor (Gt), Strehl ratio (S) and axial displacement of focus (UF) are chosen as performance evaluation index. Using multi-objective optimization genetic algorithm to solve the constrained multi-objective optimization problem, the spot size is reduced by approximately 30% compared to the diffraction-limited spot, and the corresponding Strehl ratio is approximately 0.4. Using DM as the continuous phase filter, we analyzed the effects of defocus and astigmatism on the super-resolution performance of the filter. The fitting accuracy of pupil filters designed by DM eigenmodes and Zernike polynomials are also compared, which proves that the eigenmode-based superresolving pupil filters are more suitable for fitting with a deformable mirror.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.