scholarly journals High Precision Crowded Field Photometry

1989 ◽  
Vol 8 ◽  
pp. 651-656
Author(s):  
Peter Linde
Keyword(s):  
High Precision ◽  
List Type ◽  
Point Spread Functions ◽  
Error Sources ◽  
Point Spread ◽  
Spread Function ◽  
Star Group ◽  
Local Background ◽  
Definition Of

AbstractMethods have been developed for high precision photometry in crowded stellar fields. The procedure includes the following steps:• Determination of a two-dimensional point spread function• Definition of groups of stars with mutually overlapping images• Determination of local background for each star group• Simultaneous fitting of point spread functions, one for each star in the groupThe Lund approach emphasizes interactivity. Many fundamental procedures are facilitated by the use of an optimised image display. Extensive modelling has been done to study the influence of various error sources.

Determination of the Point Spread Function of a Computer-Generated Lens Formed by a Phase Light Modulator

2020 ◽  
Vol 128 (7) ◽  
pp. 1036-1040 ◽  
Author(s):  
N. G. Stsepuro ◽  
G. K. Krasin ◽  
M. S. Kovalev ◽  
V. N. Pestereva
Keyword(s):  
Point Spread Function ◽  
Light Modulator ◽  
Point Spread ◽  
Spread Function

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.

Paleokarst reservoirs: Efficient and flexible characterization using point-spread function-based convolution modeling

2021 ◽  
pp. 1-65
Author(s):  
Kristian Jensen ◽  
Martin Kyrkjebø Johansen ◽  
Isabelle Lecomte ◽  
Xavier Janson ◽  
Jan Tveranger ◽  
...  
Keyword(s):  
Seismic Data ◽  
Convolution Operators ◽  
Point Spread Functions ◽  
Point Spread ◽  
Spread Function ◽  
Open Cavities ◽  
Modeling Experiment ◽  
Seismic Characterization ◽  
Seismic Images

Paleokarst originate from collapse, degradation and infill of karstified rock, and typically feature spatially heterogeneous elements such as breakdown products, sediment infills and preserved open cavities on all scales. Paleokarst may further contain aquifer or hydrocarbon reservoirs as well as pose a drilling hazard during exploration. Seismic characterization of paleokarst reservoirs therefore remains both a challenging and important task. We illustrate how the application of 2(3)D spatial convolution operators, referred to as point-spread functions (PSFs), allows for seismic modeling of complex and heterogeneous paleokarst geology at a cost equivalent to conventional repeated 1D convolution. Unlike the latter, which only considers vertical resolution effects, PSF-based convolution modeling yields simulated prestack depth migrated images accounting for 3D resolution effects both vertically and laterally caused by acquisition geometries, frequency-band limitations, and propagation effects in the overburden. We confirm the validity of the approach by a comparison of modeled results to results obtained from a published physical modeling experiment. Finally, we present four additional separate case studies to highlight the usability and flexibility of the approach by assessing different issues and challenges pertaining to characterizing and interpreting seismic features of paleokarst. Through PSF-based convolution modeling, geoscientists working with paleokarst seismic data may be better able to understand how various acquisition and modeling parameters affect seismic images of paleokarst geology.

Spatial Sampling in Monostatic Subsurface Radar Imaging

2020 ◽  
Author(s):  
Maria Antonia Maisto ◽  
Rocco Pierri ◽  
Raffaele Solimene
Keyword(s):  
Sampling Strategy ◽  
Data Sampling ◽  
Subsurface Scattering ◽  
Point Spread Functions ◽  
Point Spread ◽  
Measurement Domain ◽  
Standard Sampling ◽  
The One ◽  
Space Case

<div>This paper deals with microwave subsurface imaging obtained by a migration-like inversion scheme, for a 2D monostatic scalar configuration and a two-layered background medium. The focus is on the determination of a data sampling strategy which allows to reduce the number of required measurements and at the same time keep the same performance in the reconstructions. To this end, the measurement points are determined in order to approximate the point-spread function corresponding to the ideal continuous case (i.e., the case in which the data space is not sampled at all). Basically, thanks to suitable variable transformations the point-spread functions is recast as a Fourier-like operator and this provides insight to devise the sampling scheme. It is shown that resulting measurement spatial positions are non-uniformly arranged across the measurement domain and their number can be much lower than the one provided by some literature standard sampling criteria. The study also contains a comparison with the free space case so as to highlight the role played by the half-space that schematized the subsurface scattering scenario on the number and the locations of the measurement points. Numerical examples are also included to check the theoretical arguments.</div>

Determination of Generalized Coordinates and Forces for Generation of the Three Dimensional Curves with Torsion by PKM (Parallel Kinematik Machines)

2010 ◽  
Vol 166-167 ◽  
pp. 15-26
Author(s):  
N.V. Orlandea
Keyword(s):  
High Precision ◽  
Reference System ◽  
Three Dimensional ◽  
Control Parameters ◽  
Kinematic Control ◽  
Generalized Coordinates ◽  
Definition Of

The paper describes the definition of a set of generalized coordinates and forces (kinematic control parameters) necessary to satisfy a specific job. Specifically, the generation of a three dimensional curve with torsion described by a Frenet reference system. The method employed to accomplish this task is using the Original ADAMS program alias MCADA. The analysis results indicate that the method can be successfully applied when designing motion simulators; however, there are accuracy restrictions for high precision six axis machining.

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