Optimized Golay-9 array configurations for mid-frequency compensation in optical sparse aperture systems

Abstract

Optical sparse aperture (OSA) imaging systems show great potential to generate higher resolution images than those of equivalent single filled aperture systems. However, due to the sparsity and dispersion of sparse aperture arrays, pupil function is no longer a connected domain, which further attenuates or loses the mid-frequency modulation transfer function (MTF), resulting in lower mid-frequency contrast and blurred images. Therefore, an improved traversal algorithm is proposed to optimize Golay-9 array configurations for compensating the mid-frequency MTF. Its structural parameters include diameters of sub-apertures, relative rotation angles between individual sub-apertures, and radius of concentric circles. Then, these parameters are traversed successively in order. Finally, the influences of the obtained optimized array configurations on the mid-frequency MTF are analyzed in detail, and the image performances are evaluated. The experimental results prove the contrast enhancement. Compared with a Golay-9 array at F = 36.5 % , the maximum MTF increases from 0.1503 to 0.307, and the mid-frequency MTF is boosted from 0.0565 to 0.0767. In addition, the peak signal to noise ratio of the degraded image is promoted from 19.75 dB to 20.63 dB. Both quantitative and qualitative evaluations demonstrate the validity of the proposed method.

Image denoising via multi-scale spatial frequency domain convolutional neural network Noise-Net

“…Multiple in-phase circular submirrors in OSA replace the monolithic lenses, and the smaller filled area allows for the same high resolution. It meets the demand for higher resolution and more detailed remote sensing images [2,3] . However, due to the presence of many objective factors such as the influence of harsh environments and the defects of imaging equipment, the acquired images often have noise resulting in poor quality [4,5] .…”