Search results for "Filter"
showing 10 items of 1019 documents
Nonlinear spectral compression in fibre as a power-limiting device
2017
Spectral compression (SC) by self-phase modulation in optical fibre has been known for a long time and has since been reported for various parameters [1]. In this paper, we analyse the impact of amplitude fluctuations and a degraded optical signal-to-noise ratio (OSNR) of the seed pulses on the SC process by means of extensive nonlinear Schrodinger equation numerical simulation. Remarkably, our results show that the SC is rather stable against these pulse degradation factors, thereby revealing its potential for use in the context of optical regeneration of intensity-modulated signals. We therefore propose an optical scheme combining SC with an optical bandpass filter (OBPF) centred at the c…
Monitoring the stability of thin and medium back-up filters of the Newton-XMM EPIC camera
2003
We are conducting a measurement program on back-up filters of the XMM-Newton EPIC camera aimed at monitoring possible aging effects during the mission lifetime. One thin and one medium EPIC back-up filters have been stored since 1997 in an environment similar to that one of the flight filters (dry nitrogen box before launch, high vacuum after launch). The transmission of the two filters has been measured periodically in the 1900-10000 angstrom wavelength range where effects of aging would be clearly evident. The preliminary results, after 5 years of monitoring, show that a slight aging effect has occurred on both filters which, however, has no significant impact onto the EPIC calibration fo…
The γ5-problem and anomalies — A Clifford algebra approach
1990
Abstract It is shown that a strong correspondence between noncyclicity and anomalies exists. This allows, by fundamental properties of Clifford algebras, to build a simple and consistent scheme for treating γ 5 without using ( d −4)-dimensional objects
Strehl ratio versus defocus for noncentrally obscured pupils.
1994
We discuss from the viewpoint of the Strehl ratio versus defocus, or the normalized axial-irradiance distribution, the influence of decentering the dark mask of an annular pupil. Our treatment, which is valid for pupil apertures with any Fresnel number, permits us to infer that the axial behavior of a noncentrally obscured pupil is equivalent to that of an apodizer with continuous amplitude variations. Hence the Strehl ratio versus defocus of an optical system can be shaped by use of noncentered dark masks that act as continuous gray apodizers. Several numerically evaluated examples are presented.
Focal-shift formula in apodized nontelecentric focusing systems
2007
A single analytical formulation for evaluating the focal shift in any apodized nontelecentric focusing setup is reported. The formulation is also useful in the case of imaged paraxial beams. We show explicitly that the magnitude of the focal shift is determined by only one parameter that depends on the effective width of the pupil filter and its axial position. To illustrate our approach we examine different focusing setups.
Interferometric Phase Retrieval in Optical Transient Detection
2021
A transient detection imaging system (TDI), also known as optical novelty filter, is an adaptive interferometric device that detects temporal changes in a scene while suppressing its static parts. Removal of background improves contrast and helps visualizing and measuring intensity and phase. Following the first TDI proposal by Cudney et al. [1] , most TDI systems are based on photorefractive two-wave mixing [2] . Previous works rely on conventional intensity measurements, where partial information about input signal phase changes are obtained by previous calibration using an input phase-output intensity transfer function of the particular system.
Spontaneous fission of rutherfordium isotopes - total kinetic energies
2019
The isotopes 255,256,258Rf were produced in the fusion-evaporation reactions 50Ti + 207,208Pb and 50Ti + 209Bi at GSI Darmstadt, using the velocity filter SHIP. Total kinetic energies of fragments from spontaneous fission for these isotopes were evaluated with a correction to pulse-height defect.
Projection-invariant pattern recognition with a phase-only logarithmic-harmonic-derived filter.
2010
A phase-only filter based on logarithmic harmonics for projection-invariant pattern recognition is presented. This logarithmic-harmonic-derived filter is directly calculated in the Fourier plane. With respect to normal logarithmic-harmonic filters it provides a smaller variation of the correlation intensity with the projection factor of the target. Computer and optical experiments are presented.
Filter performance parameters for vectorial high-aperture wave fields.
2008
Performance parameters have been presented that can be used to compare the focusing performance of different optical systems, including the effect of pupil filters. These were originally given for the paraxial case and recently extended to the high-aperture scalar regime. We generalize these parameters to the full vectorial case for an aplanatic optical system illuminated by a plane-polarized wave. The behavior of different optical systems is compared.
Event reconstruction methods for the HypHI Phase 0 experiment at GSI
2010
WOS: 000282530300034