scholarly journals Holographic representation: Hologram plane vs. object plane

2018 ◽  
Vol 68 ◽  
pp. 193-206 ◽  
Author(s):  
Marco V. Bernardo ◽  
Pedro Fernandes ◽  
Angelo Arrifano ◽  
Marc Antonini ◽  
Elsa Fonseca ◽  
...  
Keyword(s):  
Object Plane ◽  
Hologram Plane

scholarly journals A Comparison of Different Counting Methods for a Holographic Particle Counter: Designs, Validations and Results

Sensors ◽  
2020 ◽  
Vol 20 (10) ◽  
pp. 3006
Author(s):  
Georg Brunnhofer ◽  
Isabella Hinterleitner ◽  
Alexander Bergmann ◽  
Martin Kraft
Keyword(s):  
Three Dimensional ◽  
Nano Particles ◽  
The Novel ◽  
Computational Speed ◽  
Hologram Plane ◽  
Detection And Counting ◽  
Sampling Volume ◽  
Fringe Patterns ◽  
Selection Of

Digital Inline Holography (DIH) is used in many fields of Three-Dimensional (3D) imaging to locate micro or nano-particles in a volume and determine their size, shape or trajectories. A variety of different wavefront reconstruction approaches have been developed for 3D profiling and tracking to study particles’ morphology or visualize flow fields. The novel application of Holographic Particle Counters (HPCs) requires observing particle densities in a given sampling volume which does not strictly necessitate the reconstruction of particles. Such typically spherical objects yield circular intereference patterns—also referred to as fringe patterns—at the hologram plane which can be detected by simpler Two-Dimensional (2D) image processing means. The determination of particle number concentrations (number of particles/unit volume [#/cm 3 ]) may therefore be based on the counting of fringe patterns at the hologram plane. In this work, we explain the nature of fringe patterns and extract the most relevant features provided at the hologram plane. The features aid the identification and selection of suitable pattern recognition techniques and its parameterization. We then present three different techniques which are customized for the detection and counting of fringe patterns and compare them in terms of detection performance and computational speed.

scholarly journals Modelling a Holographic Particle Counter

Proceedings ◽  
2018 ◽  
Vol 2 (13) ◽  
pp. 967 ◽  
Author(s):  
Georg Brunnhofer ◽  
Alexander Bergmann
Keyword(s):  
Aerosol Particle ◽  
Dynamics Simulation ◽  
Particle Model ◽  
Particle Counter ◽  
Volume Of Interest ◽  
Hologram Plane ◽  
Essential Components ◽  
Sampling Volume ◽  
Detection Unit ◽  
Aerosol Volume

In order to design an imaging unit of a novel holographic particle counter an aerosol particle model was developed to generate a virtual hologram plane of an aerosol volume of interest. The herein presented model combines the three essential components to help dimensioning a target detection unit: (i) an In-Line holography model with a reference light source and a basic transfer function of an imager to take into account imager size, pixel pitch and exposure time; (ii) an aerosol particle model with particles of variable count, size and spatial distribution; and (iii) the possibility to import fluid dynamics simulation data to simulate the particle flow in an arbitrary sampling volume.

Sizing and Positioning Algorithm for 1 µm to 10 µm Particles Using Shadowgraphy

2013 ◽  
Author(s):  
Michael J. Robinson ◽  
Zakaria Mahmud ◽  
Orven F. Swenson ◽  
Justin Hoey
Keyword(s):  
Relative Position ◽  
Scientific Community ◽  
Aerosol Particles ◽  
Measurement Range ◽  
Object Plane ◽  
The Past ◽  
Current State ◽  
Imaging Camera ◽  
Positioning Algorithm ◽  
State Of Art

Measuring flows of aerosol particles of less than 10 μm diameter has proven a challenge in the past. Previously, our work included a brief review of the current state-of-art for aerosol measurements where accurate sizing was limited to particles greater than 5 μm. We developed a sizing and positioning algorithm (SPA) to accurately calculate both the diameter of a spherical particle, and the relative position of that particle to the object plane of the imaging camera for particles down to 3 μm in diameter. Our current work further extends the measurement range down to 1 μm particles. This algorithm has great benefit for the scientific community interested in small-particle aerosol flows.

scholarly journals Microscope 3D Point Spread Function Evaluation Method on a Confirmed Object Plane Perpendicular to the Optical Axis

2020 ◽  
Vol 10 (7) ◽  
pp. 2430
Author(s):  
Shuai Mao ◽  
Zhenzhou Wang ◽  
Jinfeng Pan
Keyword(s):  
Point Spread Function ◽  
Evaluation Method ◽  
Optical Axis ◽  
Incident Beam ◽  
Function Evaluation ◽  
Object Plane ◽  
Point Spread ◽  
Spread Function ◽  
3D Point Spread Function

A point spread function evaluation method for a microscope on the object plane that is perpendicular to the optical axis is proposed. The measurement of the incident beam direction from the dual position-sensitive-detector (PSD)-based units, the determination of the object plane perpendicularity and the paraxial region, and evaluation methods for the point spread function (PSF) are presented and integrated into the proposed method. The experimental verification demonstrates that the proposed method can achieve a 3D PSF on the perpendicular object plane, as well as magnification, paraxial region evaluation, and confirmation for any microscopic system.

scholarly journals Dielectric metasurfaces for complete and independent control of the optical amplitude and phase

2019 ◽  
Vol 8 (1) ◽  
Author(s):  
Adam C. Overvig ◽  
Sajan Shrestha ◽  
Stephanie C. Malek ◽  
Ming Lu ◽  
Aaron Stein ◽  
...  
Keyword(s):  
High Efficiency ◽  
Three Dimensional ◽  
Iterative Algorithms ◽  
Object Plane ◽  
Complete Control ◽  
Surface Textures ◽  
Computer Generated Holography ◽  
Form Birefringence ◽  
Phase Amplitude ◽  
Dielectric Metasurface

Abstract Metasurfaces are optically thin metamaterials that promise complete control of the wavefront of light but are primarily used to control only the phase of light. Here, we present an approach, simple in concept and in practice, that uses meta-atoms with a varying degree of form birefringence and rotation angles to create high-efficiency dielectric metasurfaces that control both the optical amplitude and phase at one or two frequencies. This opens up applications in computer-generated holography, allowing faithful reproduction of both the phase and amplitude of a target holographic scene without the iterative algorithms required in phase-only holography. We demonstrate all-dielectric metasurface holograms with independent and complete control of the amplitude and phase at up to two optical frequencies simultaneously to generate two- and three-dimensional holographic objects. We show that phase-amplitude metasurfaces enable a few features not attainable in phase-only holography; these include creating artifact-free two-dimensional holographic images, encoding phase and amplitude profiles separately at the object plane, encoding intensity profiles at the metasurface and object planes separately, and controlling the surface textures of three-dimensional holographic objects.

scholarly journals Calibration of the Cloud Particle Imager Probes Using Calibration Beads and Ice Crystal Analogs: The Depth of Field

2007 ◽  
Vol 24 (11) ◽  
pp. 1860-1879 ◽  
Author(s):  
Paul J. Connolly ◽  
Michael J. Flynn ◽  
Z. Ulanowski ◽  
T. W. Choularton ◽  
M. W. Gallagher ◽  
...  
Keyword(s):  
Particle Size ◽  
Calibration Method ◽  
Depth Of Field ◽  
Strong Positive Correlation ◽  
Size Distributions ◽  
Ice Crystal ◽  
Particle Size Distributions ◽  
Object Plane ◽  
Cloud Particle ◽  
Sample Mean

Abstract This paper explains and develops a correction algorithm for measurement of cloud particle size distributions with the Stratton Park Engineering Company, Inc., Cloud Particle Imager (CPI). Cloud particle sizes, when inferred from images taken with the CPI, will be oversized relative to their “true” size. Furthermore, particles will cease to be “accepted” in the image frame if they lie a distance greater than the depth of field from the object plane. By considering elements of the scalar theory for diffraction of light by an opaque circular disc, a calibration method is devised to overcome these two problems. The method reduces the error in inferring particle size from the CPI data and also enables the determination of the particles distance from the object plane and hence their depth of field. These two quantities are vital to enable quantitative measurements of cloud particle size distributions (histograms of particle size that are scaled to the total number concentration of particles) in the atmosphere with the CPI. By using both glass calibration beads and novel ice crystal analogs, these two problems for liquid drops and ice particles can be quantified. Analysis of the calibration method shows that 1) it reduces the oversizing of 15-μm beads (from 24.3 to 14.9 μm for the sample mean), 40-μm beads (from 50.0 to 41.4 μm for the sample mean), and 99.4-μm beads (from 103.7 to 99.8 μm for the sample mean); and 2) it accurately predicts the particles distance from the object plane (the relationship between measured and predicted distance shows strong positive correlation and gives an almost one-to-one relationship). Realistic ice crystal analogs were also used to assess the errors in sampling ice clouds and found that size and distance from the object plane could be accurately predicted for ice crystals by use of the particle roundness parameter (defined as the ratio of the projected area of the particle to the area of a circle with the same maximum length). While the results here are not directly applicable to every CPI, the methods are, as data taken from three separate CPIs fit the calibration model well (not shown).

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