Search results for "Microscope"
showing 10 items of 1412 documents
Characterization of a compact low-cost Stokes lens for astigmatism compensation in optical instruments
2020
Variable power cross-cylinder lenses (or Stokes lenses) have been widely known in the literature for decades. In this paper, we describe how to build a low-cost Stokes lens and discuss its calibration and its application to two significant cases. The construction is in virtue of a phoropter’s Risley prism mount for assembling a couple of equal but opposite sign cylindrical lenses (we have selected ± 1.50 D). Thus, variable astigmatic power is achieved by relative rotation of the lenses in opposite directions, and the resulting astigmatic axis is defined by the global rotation of the device. Calibration measurements are performed using an automatic lensmeter (Topcon CL-300) and an aberromete…
Aberration compensation for objective phase curvature in phase holographic microscopy: comment
2014
In a recent Letter by Seo et al. [Opt. Lett. 37, 4976 (2012)], the numerical correction of the quadratic phase distortion introduced by the microscope objective in digital holographic microscopy (DHM) has been presented. In this comment, we would like to draw to the attention of the authors and the readers in general that this approach could not be the optimal solution for maintaining the accuracy of the quantitative phase via DHM. We recall that the use of telecentric imaging systems in DHM simplifies the numerical processing of the phase images and produces more accurate measurements.
Resolution improvements in integral microscopy with Fourier plane recording
2016
Abstract: Integral microscopes (IMic) have been recently developed in order to capture the spatial and the angular information of 3D microscopic samples with a single exposure. Computational post-processing of this information permits to carry out a 3D reconstruction of the sample. By applying conventional algorithms, both depth and also view reconstructions are possible. However, the main drawback of IMic is that the resolution of the reconstructed images is low and axially heterogeneous. In this paper, we propose a new configuration of the IMic by placing the lens array not at the image plane, but at the pupil (or Fourier) plane of the microscope objective. With this novel system, the spa…
Shift-variant digital holographic microscopy: inaccuracies in quantitative phase imaging
2013
Inaccuracies introduced in quantitative phase digital holographic microscopy by the use of nontelecentric imaging systems are analyzed. Computer modeling of the experimental result shows that even negligible errors in the radius and center of curvature of the numerical compensation needed to get rid of the remaining quadratic phase factor introduce errors in the phase measurements; these errors depend on the position of the object in the field-of-view. However, when a telecentric imaging system is utilized for the recording of the holograms, the numerical modeling and experimental results show the shift-invariant behavior of the quantitative-phase digital holographic microscope.
Superresolution digital holographic microscopy for three-dimensional samples.
2009
An approach that allows superresolution imaging of three-dimensional (3-D) samples by numerical refocusing is presented in the field of digital holographic microscopy. Based on the object's spectrum shift produced by tilted illumination, we present a time multiplexing superresolved approach to overcome the Abbe's diffraction limit. The proposed approach uses a microscope in a Mach-Zehnder interferometric architecture with the particularity that the output plane does not coincide with the image plane. Thus, a set of off-axis non-image plane holograms are sequentially recorded for every tilted beam used in the illumination stage. After that and by using simple digital post-processing and nume…
Inhomogeneous-strain-induced magnetic vortex cluster in one-dimensional manganite wire
2020
Abstract Mixed-valance manganites with strong electron correlation exhibit strong potential for spintronics, where emergent magnetic behaviors, such as propagation of high-frequency spin waves and giant topological Hall Effects can be driven by their mesoscale spin textures. Here, we create magnetic vortex clusters with flux closure spin configurations in single-crystal La0.67Sr0.33MnO3 wire. A distinctive transformation from out-of-plane domains to a vortex state is directly visualized using magnetic force microscopy at 4 K in wires when the width is below 1.0 μm. The phase-field modeling indicates that the inhomogeneous strain, accompanying with shape anisotropy, plays a key role for stab…
Einzelnachweis von Elektronen (15 bis 50 keV) in Kernphotoplatten
1960
Nuclear track emulsions (Ilford G 5) were used for counting of single slow electrons. They had to be accelerated by high voltage of about 30 kV and were incident vertically. The pulsed electron-beam was measured in a cage, single pulses were shot on the emulsion. The developed plates were photographed under the microscope and the tracks counted on the enlarged copies. The results are: about 40% of incoming electrons can be found as tracks in the emulsions. This number varies between different emulsions (of same type G 5), within one plate the number of tracks is better proportional to the number of electrons than between different plates. With a counting resultx one may expect the true resu…
Time-of-flight photoelectron emission microscopy TOF-PEEM: first results
1998
The time structure of the synchrotron radiation at BESSY (Berlin) is used to operate a photoemission electron microscope in a time-of-flight (TOF) mode. The electrons which are emitted from the sample surface with different energies are dispersed in a drift tube subsequent to the imaging optics. The screen of the microscope was replaced by a fast scintillator (tau = 1.4 ns) and the light is detected by an ultra fast gated intensified CCD camera (800 ps gate 1 MHz repetition rate). The resolving power in the energy domain is demonstrated and possible implications on the spatial resolution (chromatic correction) are discussed. Additionally, an improved contrast at very low emission energies i…
Detection of the optical magnetic field by circular symmetry plasmons
2000
We report on the influence of coating a sharpened optical fiber tip with Au when observing nanofabricated dielectric structures with a Photon Scanning Tunneling Microscope (PSTM) in constant-height mode. For well-defined incident wavelengths and coating thicknesses, we found that such tips detect the distribution of the magnetic field associated with the optical wave in the near-field zone. A simple tip model indicates that this phenomenon is related to the excitation of circular symmetry plasmons in Au coated tips.