High contrast wide-field evanescent wave illuminated sub-diffraction imaging (Conference Presentation)

2018 ◽  
Author(s):  
Chenlei Pang ◽  
Xiaowei Liu ◽  
Minghua Zhuge ◽  
Liu Xu ◽  
Qing Yang
Keyword(s):  
Evanescent Wave ◽  
Wide Field ◽  
High Contrast ◽  
Diffraction Imaging

High-contrast wide-field evanescent wave illuminated subdiffraction imaging

2017 ◽  
Vol 42 (21) ◽  
pp. 4569 ◽  
Author(s):  
Chenlei Pang ◽  
Xiaowei Liu ◽  
Minghua Zhuge ◽  
Xu Liu ◽  
Michael Geoffrey Somekh ◽  
...  
Keyword(s):  
Evanescent Wave ◽  
Wide Field ◽  
High Contrast

Seismic diffraction separation in the near-surface: Detection of high contrast voids in unconsolidated soils

Geophysics ◽  
2021 ◽  
pp. 1-72
Author(s):  
Parsa Bakhtiari Rad ◽  
Craig J. Hickey
Keyword(s):  
Soft Soil ◽  
Processing Parameters ◽  
Imaging Method ◽  
Data Sets ◽  
High Contrast ◽  
Near Surface ◽  
Time Migration ◽  
Diffraction Imaging ◽  
Dip Angle ◽  
Scattering Time

Seismic diffractions carry the signature of near-surface high-contrast anomalies and need to be extracted from the data to complement the reflection processing and other geophysical techniques. Since diffractions are often masked by reflections, surface waves and noise, a careful diffraction separation is required as a first step for diffraction imaging. A multiparameter time-imaging method is employed to separate near-surface diffractions. The implemented scheme makes use of the wavefront attributes that are reliable fully data-derived processing parameters. To mitigate the effect of strong noise and wavefield interference in near-surface data, the proposed workflow incorporates two wavefront-based parameters, dip angle and coherence, as additional constraints. The output of the diffraction separation is a time trace-based stacked section that provides the basis for further analysis and applications such as time migration. To evaluate the performance of the proposed wavefront-based workflow, it is applied to two challenging field data sets that were collected over small culverts in very near-surface soft soil environments. The results of the proposed constrained workflow and the existing unconstrained approach are presented and compared. The proposed workflow demonstrates superiority over the existing method by attenuating more reflection and noise, leading to improved diffraction separation. The abundance of unmasked diffractions reveal that the very near-surface is highly scattering. Time migration is carried out to enhance the anomaly detection by focusing of the isolated diffractions. Although strong diffractivity is observed at the approximate location of the targets, there are other diffracting zones observed in the final sections that might bring uncertainties for interpretation.

scholarly journals MEMS Deformable Mirrors for Space-Based High-Contrast Imaging

Micromachines ◽  
2019 ◽  
Vol 10 (6) ◽  
pp. 366 ◽  
Author(s):  
Rachel E. Morgan ◽  
Ewan S. Douglas ◽  
Gregory W. Allan ◽  
Paul Bierden ◽  
Supriya Chakrabarti ◽  
...  
Keyword(s):  
High Altitude ◽  
Space Environment ◽  
Optical Systems ◽  
Sounding Rocket ◽  
Deformable Mirrors ◽  
Wide Field ◽  
High Contrast ◽  
Contrast Imaging ◽  
Wavefront Control ◽  
High Contrast Imaging

Micro-Electro-Mechanical Systems (MEMS) Deformable Mirrors (DMs) enable precise wavefront control for optical systems. This technology can be used to meet the extreme wavefront control requirements for high contrast imaging of exoplanets with coronagraph instruments. MEMS DM technology is being demonstrated and developed in preparation for future exoplanet high contrast imaging space telescopes, including the Wide Field Infrared Survey Telescope (WFIRST) mission which supported the development of a 2040 actuator MEMS DM. In this paper, we discuss ground testing results and several projects which demonstrate the operation of MEMS DMs in the space environment. The missions include the Planet Imaging Concept Testbed Using a Recoverable Experiment (PICTURE) sounding rocket (launched 2011), the Planet Imaging Coronagraphic Technology Using a Reconfigurable Experimental Base (PICTURE-B) sounding rocket (launched 2015), the Planetary Imaging Concept Testbed Using a Recoverable Experiment - Coronagraph (PICTURE-C) high altitude balloon (expected launch 2019), the High Contrast Imaging Balloon System (HiCIBaS) high altitude balloon (launched 2018), and the Deformable Mirror Demonstration Mission (DeMi) CubeSat mission (expected launch late 2019). We summarize results from the previously flown missions and objectives for the missions that are next on the pad. PICTURE had technical difficulties with the sounding rocket telemetry system. PICTURE-B demonstrated functionality at >100 km altitude after the payload experienced 12-g RMS (Vehicle Level 2) test and sounding rocket launch loads. The PICTURE-C balloon aims to demonstrate 10 - 7 contrast using a vector vortex coronagraph, image plane wavefront sensor, and a 952 actuator MEMS DM. The HiClBaS flight experienced a DM cabling issue, but the 37-segment hexagonal piston-tip-tilt DM is operational post-flight. The DeMi mission aims to demonstrate wavefront control to a precision of less than 100 nm RMS in space with a 140 actuator MEMS DM.

Single‐Crystalline Perovskite Microlasers for High‐Contrast and Sub‐Diffraction Imaging

2019 ◽  
Vol 29 (39) ◽  
pp. 1904868 ◽  
Author(s):  
Kaiyang Wang ◽  
Shuai Wang ◽  
Shumin Xiao ◽  
Nan Zhang ◽  
Yujie Wang ◽  
...  
Keyword(s):  
High Contrast ◽  
Single Crystalline ◽  
Diffraction Imaging

Pretectal Neurons Optimized for the Detection of Saccade-Like Movements of the Visual Image

2001 ◽  
Vol 85 (4) ◽  
pp. 1512-1521 ◽  
Author(s):  
N.S.C. Price ◽  
M. R. Ibbotson
Keyword(s):  
Spatial Frequency ◽  
Second Harmonic ◽  
Temporal Frequency ◽  
Receptive Fields ◽  
High Spatial Frequency ◽  
Sine Wave ◽  
Wide Field ◽  
Visual Response ◽  
High Contrast ◽  
Sine Wave Gratings

The visual response properties of nondirectional wide-field sensitive neurons in the wallaby pretectum are described. These neurons are called scintillation detectors (SD-neurons) because they respond vigorously to rapid, high contrast visual changes in any part of their receptive fields. SD-neurons are most densely located within a 1- to 2-mm radius from the nucleus of the optic tract, interspersed with direction-selective retinal slip cells. Receptive fields are monocular and cover large areas of the contralateral visual field (30–120°). Response sizes are equal for motion in all directions, and spontaneous activities are similar for all orientations of static sine-wave gratings. Response magnitude increases near linearly with increasing stimulus diameter and contrast. The mean response latency for wide-field, high-contrast motion stimulation was 43.4 ± 9.4 ms (mean ± SD, n = 28). The optimum visual stimuli for SD-neurons are wide-field, low spatial frequency (<0.2 cpd) scenes moving at high velocities (75–500°/s). These properties match the visual input during saccades, indicating optimal sensitivity to rapid eye movements. Cells respond to brightness increments and decrements, suggesting inputs from on and off channels. Stimulation with high-speed, low spatial frequency gratings produces oscillatory responses at the input temporal frequency. Conversely, high spatial frequency gratings give oscillations predominantly at the second harmonic of the temporal frequency. Contrast reversing sine-wave gratings elicit transient, phase-independent responses. These responses match the properties of Y retinal ganglion cells, suggesting that they provide inputs to SD-neurons. We discuss the possible role of SD-neurons in suppressing ocular following during saccades and in the blink or saccade-locked modulation of lateral geniculate nucleus activity to control retino-cortical information flow.

High-contrast epi-fluorescence wide-field imaging of biological cells using integrating-bucket method

2015 ◽  
Vol 355 ◽  
pp. 427-432 ◽  
Author(s):  
K.S. Park ◽  
W.J. Choi ◽  
J.B. Eom ◽  
K.S. Chang ◽  
B.H. Lee
Keyword(s):  
Wide Field ◽  
Biological Cells ◽  
High Contrast ◽  
Field Imaging ◽  
Wide Field Imaging

scholarly journals Coherent-hybrid STED: high contrast sub-diffraction imaging using a bi-vortex depletion beam

2019 ◽  
Vol 27 (6) ◽  
pp. 8092 ◽  
Author(s):  
António Pereira ◽  
Mafalda Sousa ◽  
Ana C. Almeida ◽  
Luísa T. Ferreira ◽  
Ana Rita Costa ◽  
...  
Keyword(s):  
High Contrast ◽  
Diffraction Imaging

Development of a Computer-Controlled 120kV High-Performance Tem

1996 ◽  
Vol 54 ◽  
pp. 446-447
Author(s):  
H. Kobayashi ◽  
I. Nagaoki ◽  
E. Nakazawa ◽  
T. Kamino
Keyword(s):  
High Resolution ◽  
High Performance ◽  
Spherical Aberration ◽  
Focal Length ◽  
Chromatic Aberration ◽  
Objective Lens ◽  
Wide Field ◽  
High Contrast ◽  
Computer Controlled ◽  
The Magnetic Field

A new computer controlled 120kV high performance TEM has been developed(Fig. 1). The image formation system of the microscope enables us to observe high resolution, wide field,and high contrast without replacing the objective lens pole-piece. The objective lens is designed for high- contrast (HC) and high-resolution(HR) modes, and consists of a double gap and two coils. A schematic drawing of the objective lens and the strength of the magnetic field of the lens is described in Fig.2. When the objective lens is used in HC mode, upper and lower coils are operated at a lens current of same polarity to form the long focal length. The focal length(fo), spherical aberration coefficient(Cs) and chromatic aberration coefficient (Cc) in HC mode at 100kV are 6.5, 3.4 and 3.1mm, respectively. Magnification range at HC mode is × 700 to × 200,000. The viewing area with an objective aperture of a diameter of 10μm is 160mm in diameter. In HR mode, the polarity of lower coil current is reversed to form a shorter focal length for high resolution image observation. The fo, Cs and Cc of the objective lens in HR mode at lOOkV are 3.1, 2.8 and 2.3mm, respectively. The highest magnification in HR mode is × 600,000.

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