scholarly journals Wide field-of-view, high-resolution Solar observation in combination with ground layer adaptive optics and speckle imaging

2020 ◽  
Vol 637 ◽  
pp. A99
Author(s):  
Libo Zhong ◽  
Lanqiang Zhang ◽  
Zhendong Shi ◽  
Yu Tian ◽  
Youming Guo ◽  
...  

Context. High angular resolution images at a wide field of view are required for investigating Solar physics and predicting space weather. Ground-based observations are often subject to adaptive optics (AO) correction and post-facto reconstruction techniques to improve the spatial resolution. The combination of ground layer adaptive optics (GLAO) and speckle imaging is appealing with regard to a simplification of the correction and the high resolution of the reconstruction. The speckle transfer functions (STFs) used in the speckle image reconstruction mainly determine the photometric accuracy of the recovered result. The STF model proposed by Friedrich Wöger and Oskar von der Lühe in the classical AO condition is generic enough to accommodate the GLAO condition if correct inputs are given. Thus, the precisely calculated inputs to the model STF are essential for the final results. The necessary input for the model STF is the correction efficiency which can be calculated simply with the assumption of one layer turbulence. The method for calculating the correction efficiency for the classical AO condition should also be improved to suit the GLAO condition. The generic average height of the turbulence layer used by Friedrich Wöger and Oskar von der Lühe in the classic AO correction may lead to reduced accuracy and should be revised to improve photometric accuracy. Aims. This study is aimed at obtaining quantitative photometric reconstructed images in the GLAO condition. We propose methods for extracting the appropriate inputs for the STF model. Methods. In this paper, the telemetry data of the GLAO system was used to extract the correction efficiency and the equivalent height of the turbulence. To analyze the photometric accuracy of the method, the influence resulting from the distribution of the atmospheric turbulence profile and the extension of the guide stars are investigated by simulations. At those simulations, we computed the STF from the wavefront phases and convolved it with the high-resolution numerical simulations of the solar photosphere. We then deconvolved them with the model STF calculated from the correction efficiency and the equivalent height to obtain a reconstructed image. To compute the resulting photometric precision, we compared the intensity of the original image with the reconstructed image. We reconstructed the solar images taken by the GLAO prototype system at the New Vacuum Solar Telescope of the Yunnan Astronomical Observatory using this method and analyzed the results. Results. These simulations and ensuing analysis demonstrate that high photometric precision can be obtained for speckle amplitude reconstruction using the inputs for the model STF derived from the telemetry data of the GLAO system.

2021 ◽  
Vol 41 (2) ◽  
pp. 0208002
Author(s):  
李江勇 Li Jiangyong ◽  
冯位欣 Feng Weixin ◽  
刘飞 Liu Fei ◽  
魏雅喆 Wei Yazhe ◽  
邵晓鹏 Shao Xiaopeng

2020 ◽  
Author(s):  
Florian Willomitzer ◽  
Prasanna Rangarajan ◽  
Fengqiang Li ◽  
Muralidhar Balaji ◽  
Marc Christensen ◽  
...  

Abstract The presence of a scattering medium in the imaging path between an object and an observer is known to severely limit the visual acuity of the imaging system. We present an approach to circumvent the deleterious effects of scattering, by exploiting spectral correlations in scattered wavefronts. Our Synthetic Wavelength Holography (SWH) method is able to recover a holographic representation of hidden targets with high resolution over a wide field of view. The complete object field is recorded in a snapshot-fashion, by monitoring the scattered light return in a small probe area. This unique combination of attributes opens up a plethora of new Non-Line-of-Sight imaging applications ranging from medical imaging and forensics, to early-warning navigation systems and reconnaissance. Adapting the findings of this work to other wave phenomena will help unlock a wider gamut of applications beyond those envisioned in this paper.


2019 ◽  
Vol 85 (11) ◽  
pp. 815-827 ◽  
Author(s):  
Mi Wang ◽  
Beibei Guo ◽  
Ying Zhu ◽  
Yufeng Cheng ◽  
Chenhui Nie

The Gaofen-1 (GF1) optical remote sensing satellite is the first in China's series of high-resolution civilian satellites and is equipped with four wide-field-of-view cameras. The cameras work together to obtain an image 800 km wide, with a resolution of 16 m, allowing GF1 to complete a global scan in four days. To achieve high-accuracy calibration of the wide-field-of-view cameras on GF1, the calibration field should have high resolution and broad coverage based on the traditional calibration method. In this study, a GF self-calibration scheme was developed. It uses partial reference calibration data covering the selected primary charge-coupled device to achieve high-accuracy calibration of the whole image. Based on the absolute constraint of the ground control points and the relative constraint of the tie points of stereoscopic images, we present two geometric calibration models based on paired stereoscopic images and three stereoscopic images for wide-field-of-view cameras on GF1, along with corresponding stepwise internal-parameter estimation methods. Our experimental results indicate that the internal relative accuracy can be guaranteed after calibration. This article provides a new approach that enables large-field-of-view optical satellites to achieve high-accuracy calibration based on partial calibration-field coverage.


2007 ◽  
Vol 364-366 ◽  
pp. 550-554
Author(s):  
Jun Chang ◽  
Zhi Cheng Weng ◽  
Yong Tian Wang ◽  
De Wen Cheng ◽  
Hui Lin Jiang

In this paper, we are presenting a design method and its results for a space optical system with high resolution and wide field of view. This optical system can be used both in infrared and visible configurations. The designing of this system is based on an on-axis three-mirror anastigmatic (TMA) system. Here the on-axis concept allows wide field of view (FOV) enabling a diversity of designs available for the Multi-Object Spectrometer instruments optimized for low scattered and low emissive light. The available FOVs are upto 1º in both spectrum ranges, whereas the available aperture range is F/15 - F/10. The final optical system is a three-mirror telescope with two on-axis and one off-axis segment and its resolution is 0.3m or even lower. The distinguished feature of this design is that it maintains diffraction-limited image at wide wavelengths. The technological developments in the field of computer generated shaping of large-sized optical surface details with diffraction-limited imagery have opened new avenues towards the designing techniques. Such techniques permit us to expand these technological opportunities to fabricate the aspherical off-axis mirrors for a complex configuration.


2011 ◽  
Author(s):  
Kazuhiro Sasaki ◽  
Kazuhiro Kurokawa ◽  
Shuichi Makita ◽  
Daiki Tamada ◽  
Yiheng Lim ◽  
...  

2002 ◽  
Vol 2 (10) ◽  
pp. 134-134
Author(s):  
R. W. Massof ◽  
L. Brown ◽  
M. D. Shapiro ◽  
G. D. Barnett ◽  
F. H. Baker

2006 ◽  
Vol 18 (6) ◽  
pp. 787-794
Author(s):  
Xiaodong Tao ◽  
◽  
Hyungsuck Cho ◽  
Youngjun Cho ◽  

Vision techniques used in automatic microassembly are limited by inherent problems such as small depth of focus and small field of view. Microassembly must, however, initially detect microparts in a wide field of view and large depth of field while maintaining high resolution. We propose microassembly using active zooming that can overcome these limitations. For a small field of view, active zooming prevents the target from getting out of the field of view during microassembly. For a small depth of focus, our proposal is based on focus measure to maintain clear target image in the field of view during microassembly. Two-step assembly thus ensures zoom microscopy maintaining a wide field of view and large depth of field initially and high resolution at the end. Peg-in-hole assembly experiments confirmed the feasibility of our proposal.


Author(s):  
K. Ogura ◽  
J. Teshima

Observation of extremely thin insulating layers of silicon oxide and silicon nitride formed on a trench with a conventional EE SEM cannot be satisfactorily carried out by the conventional method to mechanically polish and chemically etch the wafer cross section and then investigate the state of layer formation from the uncvenness appearing on the cross section. One reason is that the resolution of the conventional FE SEM is not enough for the observation of several nm thick layers even if they arc etched. Another reason is that true layer thickness may be obscured by chemical etching. Those are why TEMs have been used for the observation of extremely thin insulating layers on trenches with atomic resolution. However, TEM application includes complicated specimen preparation, and does not allow observation of wide field of view. Therefore, the ultra-high resolution SEM (UHR SEM) has recently been used for similar purposes, using a simply cleaved plane of a wafer.


2018 ◽  
Vol 26 (3) ◽  
pp. 2390 ◽  
Author(s):  
M. Tumarina ◽  
M. Ryazanskiy ◽  
S. Jeong ◽  
G. Hong ◽  
N. Vedenkin ◽  
...  

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