scholarly journals Effect of spatial spectrum overlap on Fourier ptychographic microscopy

2017 ◽  
Vol 10 (02) ◽  
pp. 1641004 ◽  
Author(s):  
Qiulan Liu ◽  
Cuifang Kuang ◽  
Yue Fang ◽  
Peng Xiu ◽  
Yicheng Li ◽  
...  
Keyword(s):  
Imaging Technique ◽  
Computing Time ◽  
Spatial Spectrum ◽  
Diffraction Limit ◽  
Optimal Choice ◽  
Synthetic Aperture ◽  
Objective Lens ◽  
Coherent Imaging ◽  
Optical Components ◽  
Imaging Performance

Fourier ptychographic microscopy (FPM) is a newly developed imaging technique which stands out by virtue of its high-resolution and wide FOV. It improves a microscope’s imaging performance beyond the diffraction limit of the employed optical components by illuminating the sample with oblique waves of different incident angles, similar to the concept of synthetic aperture. We propose to use an objective lens with high-NA to generate oblique illuminating waves in FPM. We demonstrate utilizing an objective lens with higher NA to illuminate the sample leads to better resolution by simulations, in which a resolution of 0.28[Formula: see text][Formula: see text]m is achieved by using a high-NA illuminating objective lens (NA[Formula: see text][Formula: see text]) and a low-NA collecting objective lens (NA[Formula: see text][Formula: see text]) in coherent imaging ([Formula: see text][Formula: see text]nm). We then deeply study FPM’s exact relevance of convergence speed to spatial spectrum overlap in frequency domain. The simulation results show that an overlap of about 60% is the optimal choice to acquire a high-quality recovery (520*520 pixels) with about 2 min’s computing time. In addition, we testify the robustness of the algorithm of FPM to additive noises and its suitability for phase objects, which further proves FPM’s potential application in biomedical imaging.

Calculation of structure images of crystalline defects

1978 ◽  
Vol 36 (1) ◽  
pp. 282-283
Author(s):  
M.A. O'Keefe ◽  
Sumio Iijima
Keyword(s):  
Diffuse Scattering ◽  
Computing Time ◽  
Continuous Distribution ◽  
Sampling Interval ◽  
Reciprocal Space ◽  
Objective Lens ◽  
Lattice Images ◽  
Slice Method ◽  
Space Cell ◽  
Beam Lattice

We have extended the multi-slice method of computating many-beam lattice images of perfect crystals to calculations for imperfect crystals using the artificial superlattice approach. Electron waves scattered from faulted regions of crystals are distributed continuously in reciprocal space, and all these waves interact dynamically with each other to give diffuse scattering patterns.In the computation, this continuous distribution can be sampled only at a finite number of regularly spaced points in reciprocal space, and thus finer sampling gives an improved approximation. The larger cell also allows us to defocus the objective lens further before adjacent defect images overlap, producing spurious computational Fourier images. However, smaller cells allow us to sample the direct space cell more finely; since the two-dimensional arrays in our program are limited to 128X128 and the sampling interval shoud be less than 1/2Å (and preferably only 1/4Å), superlattice sizes are limited to 40 to 60Å. Apart from finding a compromis superlattice cell size, computing time must be conserved.

A new method for the observation of Type II magnetic contrast

1990 ◽  
Vol 48 (4) ◽  
pp. 764-765
Author(s):  
R.P. Ferrier ◽  
S. McVitie
Keyword(s):  
Domain Walls ◽  
Incident Beam ◽  
Objective Lens ◽  
Type Ii ◽  
Backscattering Coefficient ◽  
Magnetic Contrast ◽  
Standard Geometry ◽  
Backscattered Electron ◽  
Imaging Performance ◽  
Good Probe

Type II magnetic contrast was first observed by Philibert and Tixier and relies on the change in the effective backscattering coefficient due to interaction of the scattered electrons within the specimen and the local magnetic induction (for a review see Tsuno). Depending on the tilt of the specimen and the position of the backscattered electron detector(s), contrast due to the presence of either or both domains and domain walls can be obtained; in the case of the latter, the standard geometry is for the specimen to be normal to the incident beam and the detectors are positioned above it and close to the optic axis. This is the geometry adopted in our studies, which used a JEOL 2000FX with a special split objective lens polepiece; this permitted the specimen to be in magnetic field-free space, the separate lens gaps above and below allowing good probe forming capabilities combined with excellent Lorentz imaging performance. A schematic diagram is shown in Fig. 1.

Evaluation of Imaging Performance for Sub-Y-type Interferometric Synthetic Aperture Radiometer

PIERS Online ◽  
2005 ◽  
Vol 1 (5) ◽  
pp. 543-546
Author(s):  
Ho-Jin Lee ◽  
Hyuk Park ◽  
Sung-Hyun Kim ◽  
Yong-Hoon Kim
Keyword(s):  
Synthetic Aperture ◽  
Imaging Performance

scholarly journals Sub-Diffraction Visible Imaging Using Macroscopic Fourier Ptychography and Regularization by Denoising

Sensors ◽  
2018 ◽  
Vol 18 (9) ◽  
pp. 3154 ◽  
Author(s):  
Zhixin Li ◽  
Desheng Wen ◽  
Zongxi Song ◽  
Gang Liu ◽  
Weikang Zhang ◽  
...  
Keyword(s):  
Phase Retrieval ◽  
State Of The Art ◽  
Imaging Technique ◽  
Speckle Noise ◽  
Laser Speckle ◽  
Coherent Imaging ◽  
Quantitative Metrics ◽  
Visible Imaging ◽  
Flow Algorithm ◽  
Diffraction Imaging

Imaging past the diffraction limit is of significance to an optical system. Fourier ptychography (FP) is a novel coherent imaging technique that can achieve this goal and it is widely used in microscopic imaging. Most phase retrieval algorithms for FP reconstruction are based on Gaussian measurements which cannot extend straightforwardly to long range, sub-diffraction imaging setup because of laser speckle noise corruption. In this work, a new FP reconstruction framework is proposed for macroscopic visible imaging. When compared with existing research, the reweighted amplitude flow algorithm is adopted for better signal modeling, and the Regularization by Denoising (RED) scheme is introduced to reduce the effects of speckle. Experiments demonstrate that the proposed method can obtain state-of-the-art recovered results on both visual and quantitative metrics without increasing computation cost, and it is flexible for real imaging applications.

scholarly journals A Novel Sub-Bottom Profiler and Signal Processor

Sensors ◽  
2019 ◽  
Vol 19 (22) ◽  
pp. 5052
Author(s):  
Tan ◽  
Zhang ◽  
Yang ◽  
Sun
Keyword(s):  
Real Data ◽  
Synthetic Aperture ◽  
Motion Error ◽  
Buried Objects ◽  
Synthetic Aperture Sonar ◽  
Receiver Array ◽  
Sonar System ◽  
Data Processing Method ◽  
Imaging Performance ◽  
Along Track

In this paper, we introduce a novel sub-bottom profiler, making good use of the Mills cross configuration of multibeam sonar and synthetic aperture techniques of the synthetic aperture sonar system. The receiver array is mounted along the ship keel, while the transmitter array is mounted perpendicular to the receiver array. With the synthetic aperture technique, the along-track resolution can be greatly improved. The system often suffers from motion error, which severely degrades the imaging performance. To solve this problem, the imaging algorithm with motion compensation (MC) is proposed. With the presented method, the motion error is first estimated based on overlapped elements between successive pulses. Then, the echo data is processed by using the range migration algorithm based on the phase center approximation (PCA) method, which simultaneously performs the MC with the estimated motion error. In order to validate the proposed sub-bottom profiler and data processing method, some simulations and lake trial results are discussed. The processing results of the real data further indicate that the presented configuration has great potential to find buried objects in seabed sediments.

New synthetic aperture imaging technique with dynamic apodization window

2012 ◽  
Author(s):  
Dongwon Kim ◽  
Jongho Park ◽  
Jeong Cho ◽  
Tai-Kyong Song ◽  
Yangmo Yoo
Keyword(s):  
Imaging Technique ◽  
Synthetic Aperture ◽  
Synthetic Aperture Imaging
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