Observation of viscous liquid flow in tobacco substrate during heating using optical coherence tomography.

The present study used optical coherence tomography (OCT) to monitor the dynamics of a highly viscous liquid in a porous tobacco substrate during heating. The OCT technique was integrated with a specially designed heating chamber and an air pump for measuring. Two transitional points in the liquid behaviours at different temperatures were estimated using OCT and statistical analysis of the attenuation coefficient.

Formation of a Giant Anisotropically Ordered Assembled Structure of Inorganic Nanosheets through an Optically Induced Stream.

Formation of a desirable submillimeter-scaled assembled structure of particles in the colloid is a difficult subject in colloidal chemistry. Herein, a submillimeter-scaled ordered assembled structure consisting of highly anisotropic two-dimensional plate-like particles, niobate nanosheets, was obtained through an optical manipulation technique that was assisted by a scattering-force-induced stream. A 532 nm continuous wave laser beam with a power of 400 mW was used to illuminate a liquid crystalline niobate nanosheet colloid from the bottom side of a sample cell, inducing the stream of oriented nanosheets toward the upper side of the sample cell.

Spectral noise reduction and temporal coherence control using a phase unsynchronized wave synthesizing method.

Highly accurate spectrometry requires spectral noise reduction. In this paper, we propose a phase unsynchronized wave synthesizing (PuwS) method that provides different optical path lengths for different wave elements obtained from the division of a wavefront and synthesizes the respective wave elements to have the same propagation direction. PuwS achieves spectral noise reduction and contributes to temporal coherence control.

Microscope Observation of Morphology of Colloidally Dispersed Niobate Nanosheets Combined with Optical Trapping.

Although inorganic nanosheets prepared by exfoliation (delamination) of layered crystals have attracted great attention as 2D nanoparticles, in situ real space observations of exfoliated nanosheets in the colloidally dispersed state have not been conducted. In the present study, colloidally dispersed inorganic nanosheets prepared by exfoliation of layered niobate are directly observed with bright-field optical microscopy, which detects large nanosheets with lateral length larger than several micrometers. The observed nanosheets are not strictly flat but rounded, undulated, or folded in many cases.

Burn depth assessments by photoacoustic imaging and laser Doppler imaging.

Diagnosis of burn depths is crucial to determine the treatment plan for severe burn patients. However, an objective method for burn depth assessment has yet to be established, although a commercial laser Doppler imaging (LDI) system is used limitedly. We previously proposed burn depth assessment based on photoacoustic imaging (PAI), in which thermoelastic waves originating from blood under the burned tissue are detected, and we showed the validity of the method by experiments using rat models with three different burn depths: superficial dermal burn, deep dermal burn and deep burn.

Real-time photoacoustic imaging system for burn diagnosis.

We have developed a real-time (8 to 30 fps) photoacoustic (PA) imaging system with a linear-array transducer for burn depth assessment. In this system, PA signals originating from blood in the noninjured tissue layer located under the injured tissue layer are detected and imaged. A compact home-made high-repetition-rate (500 Hz) 532-nm fiber laser was incorporated as a light source.

Spectroscopic study on appearances of make-up skins using a visible RGB-LED OCT.

Background/purpose: Facial foundation is very effective to correct color irregularities of the skin surface and to protect the skin from harmful light. This depends strongly on both the optical properties and the coating condition of foundation on the skin surface.

Methods: We constructed the full-field optical coherence tomography (OCT) (FF-OCT) microscope with visible light sources of RGB LEDs.

Optical coherence tomography using images of hair structure and dyes penetrating into the hair.

Background/purpose: Hair dyes are commonly evaluated by the appearance of the hair after dyeing. However, this approach cannot simultaneously assess how deep the dye has penetrated into hair.

Methods: For simultaneous assessment of the appearance and the interior of hair, we developed a visible-range red, green, and blue (RGB) (three primary colors)-optical coherence tomography (OCT) using an RGB LED light source.

Highly controllable optical tweezers using dynamic electronic holograms.

Dielectric particles including living cells are trapped within focused laser beam spots, and as a result, they can be transferred by displacing the beam spots. Such the particle manipulating technique is called optical tweezers. Holographic optical tweezers (HOT) enables highly flexible and precise control of particles, introducing holography technique to them.

Low-coherence dynamic light scattering and its potential for measuring cell dynamics.

Fluorescence correlation spectroscopy is a powerful technique for studying the structures and dynamics of living cells. Dynamic light scattering (DLS) is also used to study dynamic characteristics and it has the potential to measure cell dynamics. However, it is difficult to apply DLS to highly scattering media.

Hydrodynamic measurement of Brownian particles at a liquid-solid interface by low-coherence dynamic light scattering.

The hydrodynamics of Brownian particles close to a wall is investigated using low-coherence dynamic light scattering. The diffusion coefficient of the particles in a suspension is measured as a function of distance from the wall. A sudden reduction in the diffusion coefficient near the interface is clearly observed using this method.

Numerical analysis of a path-length-resolved spectrum of time-varying scattered light field.

The path-length-resolved power spectrum of a time-varying scattered light field measured by a time-of-flight method or low-coherence interferometry is evaluated by a new numerical simulation algorithm. The path-length-resolved power spectrum is theoretically derived by combining diffusing-wave-spectroscopy theory and radiative-transfer theory. The proposed algorithm, using the Monte Carlo method, is used to determine the scattering configurations and numerically calculate the power spectrum.

Single-scattering spectroscopy for extremely dense colloidal suspensions by use of a low-coherence interferometer.

Single-scattering spectroscopy by use of a low-coherence interferometer is introduced to measure the power spectra of light scattered from extremely dense colloidal suspensions. The power spectrum of a heterodyne component can be obtained by subtraction of the power spectrum of a homodyne component from the measured power spectrum. The heterodyne power spectrum for light scattered from the medium is shown to coincide with the single-scattering spectrum to a depth of up to a few times the mean-free path length.