Principle and practice of high-resolution imaging with a field-emission TEM

1992 ◽  
Vol 50 (1) ◽  
pp. 138-139
Author(s):  
Max T. Otten ◽  
Wim M.J. Coene
Keyword(s):  
High Resolution ◽  
Field Emission ◽  
Incidence Angle ◽  
Temporal Coherence ◽  
Energy Spread ◽  
High Resolution Imaging ◽  
Major Improvement ◽  
High Resolution Images ◽  
Resolution Imaging

High-resolution imaging with a LaB6 instrument is limited by the spatial and temporal coherence, with little contrast remaining beyond the point resolution. A Field Emission Gun (FEG) reduces the incidence angle by a factor 5 to 10 and the energy spread by 2 to 3. Since the incidence angle is the dominant limitation for LaB6 the FEG provides a major improvement in contrast transfer, reducing the information limit to roughly one half of the point resolution. The strong improvement, predicted from high-resolution theory, can be seen readily in diffractograms (Fig. 1) and high-resolution images (Fig. 2). Even if the information in the image is limited deliberately to the point resolution by using an objective aperture, the improved contrast transfer close to the point resolution (Fig. 1) is already worthwhile.

High-Resolution Imaging of the Ocean Surface Backscatter by Inversion of Altimeter Waveforms

2011 ◽  
Vol 28 (8) ◽  
pp. 1050-1062 ◽  
Author(s):  
Jean Tournadre ◽  
Bertrand Chapron ◽  
Nicolas Reul
Keyword(s):  
High Resolution ◽  
Significant Wave Height ◽  
Basic Assumption ◽  
Sea Surface ◽  
Small Scale ◽  
High Resolution Imaging ◽  
Small Islands ◽  
Backscatter Coefficient ◽  
High Resolution Images ◽  
Resolution Imaging

Abstract This paper presents a new method to analyze high-resolution altimeter waveforms in terms of surface backscatter. Over the ocean, a basic assumption of modeling altimeter echo waveforms is to consider a homogeneous sea surface within the altimeter footprint that can be described by a mean backscatter coefficient. When the surface backscatter varies strongly at scales smaller than the altimeter footprint size, such as in the presence of surface slicks, rain, small islands, and altimeter echoes can be interpreted as high-resolution images of the surface whose geometry is annular and not rectangular. A method based on the computation of the imaging matrix and its pseudoinverse to infer the surface backscatter at high resolution (~300 m) from the measured waveforms is presented. The method is tested using synthetic waveforms for different surface backscatter fields and is shown to be unbiased and accurate. Several applications can be foreseen to refine the analysis of rain patterns, surface slicks, and lake surfaces. The authors choose here to focus on the small-scale variability of backscatter induced by a submerged reef smaller than the altimeter footprint as the function of tide, significant wave height, and wind.

scholarly journals Detection Capability Verification and Performance Test for the High Resolution Imaging Camera of China’s Tianwen-1 Mission

2021 ◽  
Vol 217 (6) ◽  
Author(s):  
Wei Yan ◽  
Jianjun Liu ◽  
Xin Ren ◽  
Chunlai Li ◽  
Qiang Fu ◽  
...  
Keyword(s):  
High Resolution ◽  
Data Processing ◽  
High Resolution Imaging ◽  
Martian Surface ◽  
Detection Capability ◽  
High Quality ◽  
Mars Exploration ◽  
Imaging Camera ◽  
High Resolution Images ◽  
Resolution Imaging

AbstractHigh-resolution optical cameras have always been important scientific payloads in Mars exploration missions, which can obtain detailed images of Martian surface for the study of geomorphology, topography and geological structure. At present, there are still many challenges for Mars high-resolution images in terms of global coverage, stereo coverage (especially for colour images), and data processing methods. High Resolution Imaging Camera (HiRIC) is a high-quality, multi-mode, multi-functional, multi-spectral remote sensing camera that is suitable for the deep space developed for China’s first Mars Exploration Mission (Tianwen-1), which was successfully launched in July 2020. Here we design special experiments based on the in-orbit detection conditions of Tianwen-1 mission to comprehensively verify the detection capability and the performance of HiRIC, from the aspects of image motion compensation effect, focusing effect, image compression quality, and data preprocessing accuracy. The results showed that the performance status of HiRIC meets the requirements of obtaining high resolution images on the Martian surface. Furthermore, proposals for HiRIC in-orbit imaging strategy and data processing are discussed to ensure the acquisition of high-quality HiRIC images, which is expected to serve as a powerful complementation to the current Mars high-resolution images.

scholarly journals Introduction to the Joint Commission Meeting on High Resolution Imaging from the Ground

1989 ◽  
Vol 8 ◽  
pp. 545-546
Author(s):  
John Davis
Keyword(s):  
High Resolution ◽  
Angular Resolution ◽  
High Angular Resolution ◽  
High Resolution Imaging ◽  
Wide Range ◽  
High Resolution Images ◽  
Resolution Imaging ◽  
Optical Wavelengths ◽  
To Come ◽  
Very High

As a result of advances in instrumentation and techniques, from radio through to optical wavelengths, we have before us the prospect of producing very high resolution images of a wide range of objects across this entire spectral range. This prospect, and the new knowledge and discoveries that may be anticipated from it, lie behind an upsurge in interest in high resolution imaging from the ground. Several new high angular resolution instruments for radio, infrared, and optical wavelengths are expected to come into operation before the 1991 IAU General Assembly.

High-resolution imaging on a field emission TEM

1993 ◽  
Vol 48 (1-2) ◽  
pp. 77-91 ◽  
Author(s):  
Max T. Otten ◽  
Wim M.J. Coene
Keyword(s):  
High Resolution ◽  
Field Emission ◽  
High Resolution Imaging ◽  
Resolution Imaging

High-resolution SE-I imaging of biological membranes using a Schottky field-emission in-lens SEM

1991 ◽  
Vol 49 ◽  
pp. 516-517
Author(s):  
R.P. Apkarian
Keyword(s):  
High Resolution ◽  
Field Emission ◽  
Emission Sources ◽  
High Resolution Imaging ◽  
Cold Cathode ◽  
Research Facility ◽  
Isolated Cells ◽  
Whole Cells ◽  
Resolution Imaging ◽  
Definition Of

Previous notes have described efforts to routinely collect quality SE-I image contrasts of biologically significant particulate membrane features (1-10 nm) in the context of whole cells and tissue fragments. Utilizing SEMs equipped with in-lens specimen stages and field emission sources (Schottky and cold cathode) operated at 15-30 kV and in conjunction with specimens coated with 1 nm Cr films (Z=24), nanometer resolution of biological samples may be attained. This note describes the definition of optimal electron source conditions for the high resolution imaging of cell membrane features μ 10 nm. The Schottky field emitter equipped ISI DS-130F SEM, in-house at the Yerkes Research Facility, was operated at 5-20 kV accelerating voltages (A.V.) and at 4 or 4.8 kV extraction voltages (E.V.). Although we have published images of soft and hard biological sections and isolated cells containing 1-10 nm particle contrasts by operating the SEM at 25-30 kV A.V., we have maintained 4 kV extraction voltage and not attempted using 4.8 kV above 25 kV A.V.

High-resolution imaging with the schottky emitter FEG TEM

1993 ◽  
Vol 51 ◽  
pp. 1072-1073
Author(s):  
Max T. Otten
Keyword(s):  
Spatial Coherence ◽  
Temporal Coherence ◽  
Energy Spread ◽  
Total System ◽  
High Resolution Imaging ◽  
A Value ◽  
High Tension ◽  
Two Factors ◽  
Resolution Imaging ◽  
Improved Performance

The Philips CM-series Field Emission TEMs, equipped with the Schottky field emitter and operating at 200 kV (CM20 FEG and the newer CM200 FEG) and 300 kV (CM30 FEG) have a dramatically improved performance in HRTEM imaging relative to their LaB6 equivalents (Table 1). The spatial and temporal coherence of these microscopes far exceeds that of similar microscopes equipped with LaB6 filaments. As a result, the information in the HRTEM images proceeds well beyond the point resolution (the information limit for the 200 kV microscopes typically lies around 0.6× their point resolution) (Fig. 1).The information limit is determined by brightness (controlling the illumination semi-angle α and thus the spatial coherence) and the energy spread (controlling the temporal coherence). These two factors are inversely related — if one goes up, the other goes down. The energy spread under HRTEM conditions is ∼0.8 eV, a value that is not inherent to the Schottky emitter but is due to the total system including the emitter and high-tension tank and accelerator.

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