Incorporation of a spatial source distribution and a spatial sensor sensitivity in a laser ultrasound propagation model using a streamlined Huygens' principle.

The near-field, surface-displacement waveforms in plates are modeled using interwoven concepts of Green's function formalism and streamlined Huygens' principle. Green's functions resemble the building blocks of the sought displacement waveform, superimposed and weighted according to the simplified distribution. The approach incorporates an arbitrary circular spatial source distribution and an arbitrary circular spatial sensitivity in the area probed by the sensor.

Laser triangulation measurements of scoliotic spine curvatures.

Background: The main purpose of this research was to develop a new method for differentiating between scoliotic and healthy subjects by analysing the curvatures of their spines in the cranio-caudal view.

Methods: The study included 247 subjects with physiological curvatures of the spine and 28 subjects with clinically confirmed scoliosis. The curvature of the spine was determined by a computer analysis of the surface of the back, measured with a non-invasive, 3D, laser-triangulation system.

Wound perimeter, area, and volume measurement based on laser 3D and color acquisition.

Background: Wound measuring serves medical personnel as a tool to assess the effectiveness of a therapy and predict its outcome. Clinically used methods vary from measuring using rules and calipers to sophisticated methods, based on 3D measuring. Our method combines the added value of 3D measuring and well-known segmentation algorithms to enable volume calculation and achieve reliable and operator-independent analysis, as we demonstrate in the paper.

From laser ultrasonics to optical manipulation.

During the interaction of a laser pulse with the surface of a solid object, the object always gains momentum. The delivered force impulse is manifested as propulsion. Initially, the motion of the object is composed of elastic waves that carry and redistribute the acquired momentum as they propagate and reflect within the solid.

Determination of the human spine curve based on laser triangulation.

Background: The main objective of the present method was to automatically obtain a spatial curve of the thoracic and lumbar spine based on a 3D shape measurement of a human torso with developed scoliosis. Manual determination of the spine curve, which was based on palpation of the thoracic and lumbar spinous processes, was found to be an appropriate way to validate the method. Therefore a new, noninvasive, optical 3D method for human torso evaluation in medical practice is introduced.

Optical coherence tomography for an in-vivo study of posterior-capsule-opacification types and their influence on the total-pulse energy required for Nd:YAG capsulotomy: a case series.

Background: Posterior capsule opacification (PCO) is the most common post-operative complication associated with cataract surgery and is mostly treated with Nd:YAG laser capsulotomy. Here, we demonstrate the use of high-resolution spectral-domain optical coherence tomography (OCT) as a technique for PCO analysis. Additionally, we evaluate the influence of PCO types and the distance between the intraocular lens (IOL) and the posterior capsule (PC), i.

Synthesis of Er- and Yb-doped gadolinium oxide polymorphs and influence of their structures on upconversion properties.

Nanocrystalline Gd(2)O(3) products doped with Er(3+) and Yb(3+) cations were synthesized by combustion method. We showed that the temperature of combustion can be tuned by using different types of organic fuels within reaction mixture. The combustion process is performed at lower temperature in the presence of urea as an organic fuel leading to pure cubic Gd(2)O(3):Er,Yb phase, on the other hand higher combustion temperature, yielding pure monoclinic Gd(2)O(3):Er,Yb polymorph is achieved in the mixture of urea and b-alanine.

3D laser measurements of bare and shod feet during walking.

This article presents a new system for 3D foot-shape measurements during walking. It is based on the laser-triangulation, multiple-line-illumination and color-modulation techniques. It consists of a walking stage and four measuring modules that simultaneously acquire the foot shape from the top, bottom and side views.

Characterization of the head-to-trunk orientation with handheld optical 3D apparatus based on the fringe projection technique.

Background: Knowing the orientation of the head is important in many fields, including medicine. Many methods and measuring systems exist, but usually they use different markers or sensors attached to the subject's head for head orientation determination. In certain applications these attachments may represent a burden or a distraction to the subject under study which may have an unfavourable impact on the measurement.

A homodyne quadrature laser interferometer for micro-asperity deformation analysis.

We report on the successful realization of a contactless, non-perturbing, displacement-measuring system for characterizing the surface roughness of polymer materials used in tribological applications. A single, time-dependent, scalar value, dubbed the collective micro-asperity deformation, is extracted from the normal-displacement measurements of normally loaded polymer samples. The displacement measurements with a sub-nanometer resolution are obtained with a homodyne quadrature laser interferometer.

Optodynamic energy-conversion efficiency during an Er:YAG-laser-pulse delivery into a liquid through different fiber-tip geometries.

When an erbium-laser pulse is directed into water through a small-diameter fiber tip (FT), the absorption of the laser energy superheats the water and its boiling induces a vapor bubble. We present the influence of different FT geometries and pulse parameters on the vapor-bubble dynamics. In our investigation, we use a free-running erbium: yttrium aluminum garnet (Er:YAG) (λ=2.

Measurement of spinal sagittal curvatures using the laser triangulation method.

The purpose of the first part of the study was to establish the variability of repeated measurements in different measuring conditions. In the second part, we performed in a large number of patients, a measurement of thoracic kyphosis and lumbar lordosis and compared them to age, gender, and level of nourishment. In the first part, measurements were performed on a plastic model of the back of a patient with a rigid and a normal spine.

Dual-probe homodyne quadrature laser interferometer.

We present a dual-probe homodyne quadrature laser interferometer for the measurements of displacement at two separate spatial locations. This is a coupled homodyne interferometer with inverted polarity of probe signals featuring a wide dynamic range and constant sensitivity. As an application of this dual-probe interferometer, we demonstrate how to locate the pulsed-laser interaction site on a plate without knowing the propagation velocities of the laser-induced mechanical waves.

Optodynamic monitoring of laser tattoo removal.

The goal of this research is to use the information contained in the mechanisms occurring during the laser tattoo removal process. We simultaneously employed a laser-beam deflection probe (LBDP) to measure the shock wave and a camera to detect the plasma radiation, both originating from a high-intensity laser-pulse interaction with a tattoo. The experiments were performed in vitro (skin phantoms), ex vivo (marking tattoos on pig skin), and in vivo (professional and amateur decorative tattoos).

Laser 3-D measuring system and real-time visual feedback for teaching and correcting breathing.

We present a novel method for real-time 3-D body-shape measurement during breathing based on the laser multiple-line triangulation principle. The laser projector illuminates the measured surface with a pattern of 33 equally inclined light planes. Simultaneously, the camera records the distorted light pattern from a different viewpoint.

Synthesis and fluorescent properties of chromium-doped aluminate nanopowders.

Nanocrystalline chromium-doped Al2O3 and MgAl2O4 products were synthesised by combustion method in the presence of urea. The powders were characterised by X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), BET surface area analysis, induction coupled plasma analysis (ICP) and mapping energy dispersive X-ray analysis (EDX). Fluorescence properties of the products were investigated in order to find the applications in fluorescent sensor and in the production of transparent polycrystalline ceramic materials for laser and optical application.

Power scaling of AOM-switched lasers with SCPEM-based time-multiplexing.

Power Scaling of a Q-switched laser designed for internal frequency conversion is demonstrated by combining two Nd:YVO4-gain-channels with a time-multiplexing scheme based on a single crystal photo elastic modulator (SCPEM). Both channels are coupled with a polarizer and share an output-coupler and acousto-optic modulator (AOM). In order to combine two channels by time multiplexing, the single crystal photo elastic modulator is used which switches between two channels, while the acousto-optic modulator conducts the Q-switching.

High-speed two-frame shadowgraphy for velocity measurements of laser-induced plasma and shock-wave evolution.

We describe a high-speed, two-frame shadowgraph method for the two-dimensional visualization of an expanding laser-induced plasma and shock wave in two time instances. The developed experimental method uses a 30 ps, green-laser, polarized pulse for the direct and delayed illumination separated by a variable time delay in the range from 300 ps to 30 ns. Since the exposed images of a single event are captured with two CCD cameras, the established method enables velocity measurements of the fast laser-induced phenomena within the nanosecond excitation-laser pulse as well as at later times-when the excitation-laser radiation has already ended.

Interference effects at a dielectric plate applied as a high-power-laser attenuator.

The interference effects caused by the Fresnel reflections of a Gaussian beam on the boundaries of a dielectric plate, which can be considered as a Fabry-Perot etalon, were theoretically and experimentally investigated. In addition to the incident angle and the polarization of the incident light, two additional parameters--the plate's parallelism and the temperature--which are often neglected, were analyzed. Based on the theoretical predictions and the measured behavior of the transmittance of the dielectric plate a new, temperature-controlled variable high-power-laser attenuator is proposed.