Imaging Of Extended Objects Research Articles

Richardson–Lucy Iterative Blind Deconvolution with Gaussian Total Variation Constraints for Space Extended Object Images

Richardson–Lucy Iterative Blind Deconvolution with Gaussian Total Variation Constraints for Space Extended Object Images

Phase-contrast imaging of multiply-scattering extended objects at atomic resolution by reconstruction of the scattering matrix

Three-dimensional phase contrast imaging of multiply-scattering samples in X-ray and electron microscopy is extremely challenging, due to small numerical apertures, the unavailability of wavefront shaping optics, and the highly nonlinear inversion required from intensity-only measurements. In this work, we present a new algorithm using the scattering matrix formalism to solve the scattering from a non-crystalline medium from scanning diffraction measurements, and recover the illumination aberrations. Our method will enable 3D imaging and materials characterization at high resolution for a wide range of materials.

Разрешающая способность и радиоизображения стационарных объектов в наземных MIMO-радиокамерах

The study analysed possible resolution of two ground-based MIMO microwave camera designs by means of two-dimensional spatial cross-sections of a generalized ambiguity function. We used stepped-frequency modulated broadband signals as time-orthogonal probing signals for the microwave camera transmitters. We employed a mathematical simulation of the space-time signal processing system pertaining to MIMO microwave camera receivers to illustrate 2D and 3D microwave imaging of stationary extended multipoint objects situated at various altitudes above the earth surface.

Fast Restoration of Aberration-Degraded Extended Object Based on Local Region Abstraction

The compensating capability of wavefront sensorless adaptive optics (WFSless AO) system for extended object images degraded by aberration is severely limited to correction speed due to largely sized images and low frame rate of camera. To improve the correction capability of WFSless AO system, a method based on local region abstraction (LRA) is presented according to the sparse characteristics of extended object imaging. The experiment results of image restoration with WFSless AO system based on LRA show that the correction speed of this method is 8–20 times faster than that of the previous method for the static aberration, the image restoration speed is improved by about 3.5 times under the dynamic aberration.

MWIR imaging experiments with large F-number optics on LEO spacecraft

To determine the feasibility of spacecraft imaging in the mid-infrared region (3.0–5.0μm) utilizing large F-number optics, we create a radiometric simulation of a low-Earth orbit (LEO) extended object, imaging background and noise, in order to predict the signal-to-noise ratio of such objects as viewed from a telescope during the daytime and terminator, etc. We find that the observation of Space Station and other extended targets utilizing large F-number optics for MWIR imaging is possible, given the right conditions. We have developed a large F-number infrared camera with cold stop matched, which is successfully applied to acquire LEO extended object images taken by a 1.23m telescope. We get clear images of International Space Station, Tian-gong, etc. and our proposed the infrared imaging technology can be demonstrated to greatly improve the imaging ability of current ground-based Optoelectric (OE) telescope for the detection of space activities.

Concept of the construction of the optical setup of a panoramic Stokes polarimeter for small telescopes

This article proposes the concept of the construction of an imaging polarizer based on polarization films for measuring the linear polarization of images of celestial extended and point objects. The spectral range of operation of the device is 420–850 nm, and the field-of-view angle is 0.25°×0.25°. The device is intended to be used in telescopes with a primary mirror up to 1 m in diameter and relative aperture f/12. The advantages and disadvantages of the proposed device are analyzed.

Calibration and Performance of the Photon-counting Detectors for the Ultraviolet Imaging Telescope (UVIT) of the Astrosat Observatory11Astrosat is an observatory project of the Indian Space Research Organisation (ISRO), with partnership by the Canadian Space Agency (CSA).

ABSTRACTWe describe calibration data and discuss performance of the photon-counting flight detectors for the Ultraviolet Imaging Telescopes on the Astrosat observatory. This article describes dark current, flat-field, and light-spot images for FUV, NUV, and visible band detectors at more than one wavelength setting for each. We also report on nominal-gain and low-gain operations, full- and subwindow read rates, and non-photon-counting modes of operation, all expected to be used in flight. We derive corrections to the event centroids from the CMOS readout arrays, for different centroid algorithms. We derive spatial resolution values for each detector and plots of point-source signal saturation for different flux levels. We also discuss ways to correct for saturation in extended object images.

Performance of an Off-axis Holographic Lens in the Presence of Aberrations Induced by Construction-reconstruction Wavelength Shift: Extended Object Imaging

In this paper investigations have been carried out on the imaging of extended objects by an off-axis holographic lens operating at a wavelength different from its recording. Aberration balancing and correction techniques have been applied to improve the quality of imaging coherent as well as incoherent bar and edge objects. The light intensity distribution in the Gaussian image plane has been computed numerically and the results have been presented in graphical form. The image quality of the aberration-balanced holo-lens has been found to be comparable to that of the ideal holo-lens.