Search results for "Near and far field"

Simple Large Scale 3D scanner

2019

Abstract A new 3D measuring device for large dimensions is proposed. It is based on the combination of a simple system consisting of a smartphone that measures in stereo a near field with a robotic total station that tracks the position of the camera on a far field. The calibration method is described and the metrological properties obtained make it possible to measure objects of several tens or even hundreds of meters long with errors of the order of a millimeter. This makes it possible to consider the use of the system for many industrial applications

Extraordinary tuning of a nanocavity by a near-field probe

2011

Abstract We report here an experimental observation of an extraordinary near-field interaction between a local probe and a small-volume solid-state nanocavity. We directly compare the normally observed near-field interaction regime driven by the perturbation theory and then report the extraordinary interaction regime. Subsequently, we show that the cavity can take up to 2 min to recover from this interaction after removing the probe and that leads to an extraordinary blue-shift of the cavity resonance wavelength (∼15 nm) which depends on the probe motion above the cavity and not the position. The reasons for this effect are not fully understood yet but we try to give some explanations.

Subduction‐Induced Back‐Arc Extension Versus Far‐Field Stretching: Contrasting Modes for Continental Marginal Break‐Up

2021

High-resolution far-field integral-imaging camera by double snapshot

2012

In multi-view three-dimensional imaging, to capture the elemental images of distant objects, the use of a field-like lens that projects the reference plane onto the microlens array is necessary. In this case, the spatial resolution of reconstructed images is equal to the spatial density of microlenses in the array. In this paper we report a simple method, based on the realization of double snapshots, to double the 2D pixel density of reconstructed scenes. Experiments are reported to support the proposed approach.

Theoretical study of an absorbing sample in infrared near-field spectromicroscopy

2004

Abstract This paper is devoted to study the near-field spectrometry in the infrared spectral range. To understand the behavior of the infrared light diffracted by an object, numerical calculations have been carried out with Fourier Modale (FM) method within R-matrix algorithm. We consider the case of three-dimensional system including a translational symmetry in one direction, where is included an homogenous layer in which is buried an absorbing object. Using an optical near-field analysis and by calculating the electric field intensity distribution, both of the thickness effect and the lateral size of the absorbing sample are investigated. It is found that the distribution of the intensity…

SNOM study of ferroelectric domains in doped LiNbO3 crystals

2009

Abstract This work shows a study of the periodic ferroelectric domains formed in LiNbO3 crystals doped with rare earths by means of scanning near field optical microscopy (SNOM) technique. It has been observed periodic structures associated with ferroelectric domains with an unexpected high value of the optical contrast working under reflectance SNOM mode. From Raman-Nath diffraction patterns, a refractive index modulation of Δ n ∼ 1 0 − 4 has been calculated. These results were correlated with the ferroelectric periodic domains obtained by the SNOM technique. A light waveguide effects along the ferroelectric domains is suggested to explain the high reflectance contrast observed in SNOM exp…

Accelerating wide-angle converging waves in the near field

2014

We show that a wide-angle converging wave may be transformed into a shape-preserving accelerating beam having a beam-width near the diffraction limit. For that purpose, we followed a strategy that is particularly conceived for the acceleration of nonparaxial laser beams, in contrast to the well-known method by Siviloglou et al (2007 Phys. Rev. Lett. 99 213901). The concept of optical near-field shaping is applied to the design of non-flat ultra-narrow diffractive optical elements. The engineered curvilinear caustic can be set up by the beam emerging from a dynamic assembly of elementary gratings, the latter enabling to modify the effective refractive index of the metamaterial as it is arran…

Computation of near field diffraction by a dielectric grating: a comparison with experiments

1995

We use an eigenmode method to compute the near field diffracted by one-dimensional dielectric gratings. We present a set of easily programmable recurrence relations that give the diffracted field from the incident one. The numerical results are compared with the experimental images obtained with the Photon Scanning Tunneling Microscope (PSTM).

Atomic diffraction from nanostructured optical potentials

2002

We develop a versatile theoretical approach to the study of cold-atom diffractive scattering from light-field gratings by combining calculations of the optical near-field, generated by evanescent waves close to the surface of periodic nanostructured arrays, together with advanced atom wavepacket propagation on this optical potential.

Electromagnetic Singularities and Resonances in Near-Field Optical Probes

2007

Over the last two decades scanning near-field optical microscopy (SNOM) has demonstrated its ability to provide optical resolution significantly better than the diffraction limit (<20 nm). The general principle of SNOM relies on the approach of a nanometer-sized object in the optical near-field of a sample to be studied. This nano-object (NO) is usually the extremity of a probe. Regardless of the nature of the observed SNOM signal (inelastic scattering, fluorescence, etc.), the detection of the light is achieved in the far-field regime where the NO acts as a mediator between the optical near-field and the detector. Figure 1 is a schematic illustration of the SNOM principle.