Search results for " Color"
showing 10 items of 770 documents
Multi-domain spectral approach with Sommerfeld condition for the Maxwell equations
2021
We present a multidomain spectral approach with an exterior compactified domain for the Maxwell equations for monochromatic fields. The Sommerfeld radiation condition is imposed exactly at infinity being a finite point on the numerical grid. As an example, axisymmetric situations in spherical and prolate spheroidal coordinates are discussed.
Wave propagation in optical systems
1974
The intensity distribution in the image space of an optical system, due to an arbitrary object, is calculated by solving the problem of the propagation of a monochromatic light wave through the system. The system is assumed to be cylindrically symmetric with an arbitrary number of spherical surfaces. Analytic techniques based on the principle of stationary phase are used, and several advantages over ray-tracing techniques are obtained.
Bistable phase locking of a laser via monochromatic signal injection
2009
In free running lasers the field phase is not fixed and any value possible value is equally likely (invariant), but can be locked to an external reference by injecting a monochromatic signal field into the cavity. In this way the phase of the slave laser locks to a single value resulting in a monostable phase locking. It could be however of practical interest that the laser field be locked not to a single value but to two different possible values, hence the name bistable phase locking.
Cavity solitons in lasers with spatially modulated injected signal
2009
The injection of a monochromatic signal into a laser is a well-known technique for locking the laser phase to that of the injection. Some years ago another type of injection, called rocking [1,2], was introduced to render the laser phase-locking bistable. Rocking consists of the modulation of the amplitude injection so that its sign changes periodically, or even randomly [3], in time. Here we present an alternative to rocking that leads to the same type of behaviour, namely the appearance of bistable phase locking and, in the case of large Fresnel number lasers, to stable (phase bistable) cavity solitons and extended patterns. The new type of injection we present here is monochromatic, unli…
Wavelength dependence of visual acuity in goldfish.
2003
Visual acuity was measured in a two-choice training experiment with food reward. Four goldfish were trained to select a homogeneously illuminated testfield when a high-contrast grating (transparency) was shown for comparison at the second testfield. Measurements were performed for white and monochromatic testfield illuminations in the light adapted state. Fourteen wavelengths between 404 nm and 683 nm were tested. For each wavelength (and white light) the testfield intensity was determined for which spatial resolution was highest. Between 446 nm and 683 nm maximal values of 2.0 cycles/deg (corresponding to a visual acuity of 15' of arc) were found. At 404 nm and in the ultraviolet resolutio…
Small field motion detection in goldfish is red-green color blind and mediated by the M-cone type
2007
Large field motion detection in goldfish, measured in the optomotor response, is based on the L-cone type, and is therefore color-blind (Schaerer & Neumeyer, 1996). In experiments using a two-choice training procedure, we investigated now whether the same holds for the detection of a small moving object (size: 8 mm diameter; velocity: 7 cm/s). In initial experiments, we found that goldfish did not discriminate between a moving and a stationary stimulus, obviously not taking attention to the cue “moving.” Therefore, random dot patterns were used in which the stimulus was visible only when moving. Using black and white random dot patterns with variable contrast between 0.2 and 1, we found…
Stabilizing effect of driving and dissipation on quantum metastable states
2018
We investigate how the combined effects of strong Ohmic dissipation and monochromatic driving affect the stability of a quantum system with a metastable state. We find that, by increasing the coupling with the environment, the escape time makes a transition from a regime in which it is substantially controlled by the driving, displaying resonant peaks and dips, to a regime of frequency-independent escape time with a peak followed by a steep falloff. The escape time from the metastable state has a nonmonotonic behavior as a function of the thermal-bath coupling, the temperature, and the frequency of the driving. The quantum noise-enhanced stability phenomenon is observed in the investigated …
Fractal square zone plates
2013
[EN] In this paper we present a novel family of zone plates with a fractal distribution of square zones. The focusing properties of these fractal diffractive lenses coined fractal square zone plates are analytically studied and the influence of the fractality is investigated. It is shown that under monochromatic illumination a fractal square zone plate gives rise a focal volume containing a delimited sequence of two-arms-cross pattern that are axially distributed according to the self-similarity of the lens.
The Capabilities of monochromatic EC neutrino beams with the SPS upgrade
2007
The goal for future neutrino facilities is the determination of the U(e3) mixing and CP violation in neutrino oscillations. This will require precision experiments with a very intense neutrino source and energy control. With this objective in mind, the creation of monochromatic neutrino beams from the electron capture decay of boosted ions by the SPS of CERN has been proposed. We discuss the capabilities of such a facility as a function of the energy of the boost and the baseline for the detector. We conclude that the SPS upgrade to 1000 GeV is crucial to reach a better sensitivity to CP violation iff it is accompanied by a longer baseline. We compare the physics potential for two different…
RGB Photoelasticity: Review and Improvements
2010
: This paper considers the main developments of RGB photoelasticity with reference to the maximum measurable retardation. In this paper, a new procedure based on the standard error function evaluated on a subset of the calibration array is also proposed and experimentally tested. The experiments show that the filament lamp makes it possible to find retardations until approximately 4 fringe orders while the fluorescent lamp makes it possible to determine higher fringe orders (12 fringe orders in this paper) owing to the discrete spectrum of the source. The paper shows that, by using the incandescent lamp, the primary limiting factor is the lack of modulation of the R, G and B signals wherea…