scispace - formally typeset
Search or ask a question
Topic

Spatial filter

About: Spatial filter is a research topic. Over the lifetime, 6170 publications have been published within this topic receiving 100451 citations.


Papers
More filters
Journal ArticleDOI
TL;DR: A partially and a highly antire ection coated broad area laser are operated in an external cavity Fourier-optical 4f set-up to experimentally investigate transverse mode selection.
Abstract: A partially and a highly antireflection coated broad area laser are operated in an external cavity Fourier-optical 4f set-up to experimentally investigate transverse mode selection. The external cavity consists of a lens and a spatial frequency filter. Running freely the lasers show non-stationary filamentation. Placing the spatial filter unit directly onto the optical axis gives cw fundamental mode operation and a transverse shift of the spatial filter in the plane of the active region allows for selective excitation of higher order modes.

25 citations

Journal ArticleDOI
TL;DR: In this paper, a spatiospectral transfer function is formulated and utilized to describe the beam propagation and the multiple-beam interference occurring in an ideal one-dimensional strip PFP interferometer with no diffraction loss.
Abstract: The transmission of a plane-mirror Fabry–Perot (PFP) interferometer is theoretically modeled and investigated by treating the spatial and spectral features in a unified manner. A spatiospectral transfer function is formulated and utilized to describe the beam propagation and the multiple-beam interference occurring in an ideal one-dimensional strip PFP interferometer with no diffraction loss. The spatial-frequency filtration of a finite-size beam input not only determines the transmitted spatial beam profile but also plays a crucial role in affecting the overall spectral transmittance. The inherent deviations of the spectral transmittance from what we know as the standard Airy’s formula are revealed in diverse aspects, including the less-than-unity peak transmittance, the displacement of a resonance peak frequency, and the asymmetric detuning profile. Our theoretical analysis extends to the misaligned PFP interferometers, such as the cases in which non-normal-incidence beams or wedge-aligned mirrors are used that could severely degrade the effective interferometer finesse.

25 citations

Journal ArticleDOI
TL;DR: Axisymmetric angular filtering of two-dimensional light beams by axisyMMetric photonic microstructures in bulk of glass is proposed and experimentally demonstrated.
Abstract: We propose and show experimentally axisymmetric spatial (angular) filtering of two-dimensional light beams by axisymmetric photonic microstructures. Such three-dimensional microstructures (similar to photonic crystals), in gapless configuration, were recorded in bulk of glass, where the refractive index has been point-by-point modulated using tightly focused femtosecond laser pulses. Axisymmetric angular filtering of approximately 25 mrad is demonstrated experimentally.

25 citations

Patent
13 Jan 1976
TL;DR: In this article, an array for photoelectrically determining the position of at least one focal plane of an image inside an optical instrument comprising an optics for imaging one object on a spatial frequency filter of an optical image correlator and further comprising a measurement display of the light fluxes filtered through the spatial frequency filters.
Abstract: Apparatus for photoelectrically determining the position of at least one focal plane of an image inside an optical instrument comprising an optics for imaging at least one object on at least one spatial frequency filter of an optical image correlator and further comprising a measurement display of the light fluxes filtered through the spatial frequency filter. The apparatus 1-45 for receiving the light fluxes concentrated through optical components 3,4 comprises at least one photoelectric detector system 5, 6, 31, 32. This detector system has at least one row of several detectors 11-15, . . . n, and electrical means 16, 17, 26-28, 33-38 are provided for pairwise interrogation of the photoelectric detectors 11-15, . . . n and also for the analysis of the photoelectric signals generated during the interrogation.

25 citations

Journal ArticleDOI
TL;DR: In this paper, a system combining tomographic PIV (TPIV) and Mach-Zehnder interferometry (MZI) simultaneously measures the time-resolved 3D flow field and 2D distribution of wall-normal deformation in a turbulent channel flow over a transparent compliant surface.
Abstract: A system combining tomographic PIV (TPIV) and Mach–Zehnder interferometry (MZI) simultaneously measures the time-resolved 3D flow field and 2D distribution of wall-normal deformation in a turbulent channel flow over a transparent compliant surface. This paper focuses on the experimental techniques and data analysis procedures, but includes sample results. Standard TPIV analysis resolves the log layer of the mean velocity and the linear decrease in total shear stress with distance from the wall. Single-pixel ensemble correlations reveal the buffer layer and top of the viscous sublayer. Analysis of the MZI data consists of two steps, namely critical spatial filtering of interferograms to remove noise and phase demodulation to calculate the surface shape. A new technique to improve the filtration of noise from interferograms based on spatial correlations of small windows is introduced and optimized. Taking advantage of this enhancement, the phase/deformation distribution is calculated directly from arccosines of the intensity, which avoids edge artifacts affecting spectral calculations. Validations using synthetic noisy interferograms indicate that errors associated with correlation-based enhancement are consistently lower and much less sensitive to fringe shape than spectral band-pass filtering. The experimental wavenumber–frequency spectra show that the deformation consists of patterns that are larger than the field of view, surface waves and small-scale patterns. Some of the latter are advected at the freestream velocity, but mostly at 70 % of the freestream, the mean speed at 10 % of the channel half height. Indeed, spatial correlations of the deformation with velocity components peak at this elevation.

25 citations


Network Information
Related Topics (5)
Optical fiber
167K papers, 1.8M citations
88% related
Resonator
76.5K papers, 1M citations
85% related
Image processing
229.9K papers, 3.5M citations
84% related
Filter (signal processing)
81.4K papers, 1M citations
83% related
Wave propagation
55K papers, 1.1M citations
82% related
Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202321
202265
202181
2020144
2019180
2018179