Laser Speckle Method Research Articles

Thermal conductivity analysis of nanofluid through laser speckle method

Thermal conductivity analysis of nanofluid through laser speckle method

Estimation of reflection loss in a microwave absorbing material based on the laser speckle method

Microwave absorption has received much attention due to its prospective implementation in the extenuation of electromagnetic interference (EMI). The effectiveness of any microwave absorbing material (MAM) is demonstrated by its dielectric dependent properties, such as electric permittivity, magnetic permeability and computed parameters like tangent loss, attenuation and reflection loss (RL) etc. RL is one of the special features of MAMs, allowing the quality of a MAM to be identified by its surface condition and the composition of the fabricated material. As a surface phenomenon, RL depends on factors such as the surface roughness, thickness of the layering of the material and the nature of the surface. The present work emphasizes the effect of surface roughness on RL, studied using the laser speckle technique (LST). Three different compositions of 10 wt%, 30 wt% and 50 wt% of two carbon-based natural fiber composites are studied for microwave absorption. The surface roughness of the material is analyzed, based on the scattering signal of laser speckles recorded in a digital storage oscilloscope. Further, the roughness of the same composition was recorded through a stylus-based profilometer and compared with the measurements from the LST. The results indicate the effectiveness of the laser contrast technique for determining the surface roughness in the design of stealth materials for EMI shielding applications. The RLs of the designed material are found to be greatly enhanced, having a larger surface roughness value with increasing wt%. The RL of the material with 50 wt% composition has been found to be −23.62 dB at 10.498 GHz. This result clearly indicates the applicability of the LST for the estimation of surface conditions to assess the suitability of MAMs in the design of stealth materials.

Refractive index measurement of uniform liquid using an improved laser speckle method

Based on the refraction characteristic of uniform and transparent liquid, the measurement error of the liquid refractive index using the internal standard method is analyzed, and an improved laser speckle method is proposed. This method designs a double-cell structure composed of two identical rectangular parallelepiped glass cells with one cell containing the liquid to be measured and the other one being empty. This double-cell structure is placed in the built optical system based on laser speckle, and then the refractive indices of sodium chloride solution and sucrose solution with various concentrations are measured by the improved method. Compared with the measurement values of the Abbe refractometer and the internal standard method, the results show that the improved method can significantly reduce the measurement error and improve the measurement accuracy.

A review of surface roughness measurements based on laser speckle method

A review of surface roughness measurements based on laser speckle method

Evaluation of Thermal Cycle Durability of Thermal Barrier Coating by Laser Speckle Method and AE Method with Continuous Waveform Recording

Evaluation of Thermal Cycle Durability of Thermal Barrier Coating by Laser Speckle Method and AE Method with Continuous Waveform Recording

Laser speckle imaging in discrimination of zooplanktons from supermicroplastics

The presence of supermicroplastic (SMP) of less than 350 µm is on the rise in oceans, and it is often difficult to discriminate the SMPs from zooplanktons in real-time. In this study, we propose a laser speckle method in differentiating SMPs from brine shrimps, a generally used model zooplankton, and at the same time in distinguishing varied sized SMPs too. The pilot system consisting of a laser diode source of wavelength 635 nm mounted in a submersible glass sphere that has the potential of surveying in deep-sea environments illuminated a cuvette containing either polystyrene microspheres alone or mixed with brine shrimp to produce laser speckles. Such speckles recorded by a CMOS camera at 15 frames/sec for 20sec were analyzed to calculate a parameter of maximum difference between recorded frames. The results clearly differentiated the microplastics and the microplastics from the brine shrimps, thus demonstrating the possible use of the laser speckle method as a potential tool in discriminating planktons from SMPs and has implications for reaching deep-sea environments.

Effect of Chloroplast Movement on Laser Speckle Method

HighlightsThis study investigates the use of laser speckle to evaluate chloroplast movement in plant cells.The analysis value of the laser speckle corresponds to chloroplast movement.The run-length matrix analysis that we propose is more sensitive than existing methods.Abstract. Abiotic and biotic stresses change the cytoplasmic streaming in plant cells. In particular, the state of chloroplast movement changes rapidly in response to environmental changes. Thus, detecting chloroplast movement allows us to comprehend the physiological state of plants. This study investigated the applicability of the laser speckle method for evaluating chloroplast movement. Moreover, we propose a new analysis method for sensitively evaluating chloroplast movement. Leaves of Egeria densa were used, and electrical stimulation was applied as recoverable abiotic stress. Laser speckle measurement and light microscopic observation of the same specimen were performed before and after stimulation. The results showed that the laser speckle method can nondestructively evaluate macroscopic and collective chloroplast movement. The proposed method was more sensitive to chloroplast movement than existing methods. Keywords: Chloroplast, Image processing, Laser speckle, Textual analysis.

Laser beam modulation with a fast focus tunable lens for speckle reduction in laser projection displays

We propose a laser speckle reduction method using a fast focus tunable lens (FTL). Different laser beams are generated after modulating the FTL. Thus, when the laser beams are used to illuminate a diffuser, various speckle images are obtained, and the summed speckle images yield a reduced speckle contrast ratio. To maximize the tuning range of the focal length of the FTL for efficient speckle reduction, the FTL operates in a resonant mode at the resonant frequency at 97 Hz. The effect of the change of the distance between the FTL and the diffuser on the efficiency of speckle reduction is investigated. Experimental results show that the lowest objective speckle contrast ratio is 0.05. After the application of this speckle reduction component in a laser projector, the subjective speckle contrast ratio is reduced from 0.16 to 0.09. In comparison with other speckle reduction methods, the method proposed in this study is simple and effective, and can be used in practice in laser projection displays.

High pressure melting curve of osmium up to 35 GPa

The melting curve of osmium (Os) has been determined up to 35 GPa and 5800 K using a laser heated diamond anvil cell facility. Al2O3 was used as the thermal insulator and pressure transmitting medium. Melting was detected by the laser speckle method, and spectroradiometric technique was employed for determination of melting temperature. The measured melting curve has been compared with available theoretical melting curves. The Simon-Glatzel fit to the experimental data agrees reasonably well with the recently reported theoretical melting curve using Z-method. The melting slope of the measured melting curve is 58.0 K/GPa at P = 0.1 MPa. The melting line of Os is seen to cross that of W around 6 GPa, making it the most refractory metal. The density dependence of Grüneisen parameter [γ(ρ)] has also been determined analytically, using the experimentally obtained melting slope.

Visualization of density difference convection during chemical reaction using laser speckle method

Visualization of density difference convection during chemical reaction using laser speckle method

Postharvest Monitoring of Tomato Ripening Using the Dynamic Laser Speckle.

The dynamic laser speckle (biospeckle) method was tested as a potential tool for the assessment and monitoring of the maturity stage of tomatoes. Two tomato cultivars—Admiro and Starbuck—were tested. The process of climacteric maturation of tomatoes was monitored during a shelf life storage experiment. The biospeckle phenomena were captured using 640 nm and 830 nm laser light wavelength, and analysed using two activity descriptors based on biospeckle pattern decorrelation—C4 and ε. The well-established optical parameters of tomatoes skin were used as a reference method (luminosity, a*/b*, chroma). Both methods were tested with respect to their prediction capabilities of the maturity and destructive indicators of tomatoes—firmness, chlorophyll and carotenoids content. The statistical significance of the tested relationships were investigated by means of linear regression models. The climacteric maturation of tomato fruit was associated with an increase in biospckle activity. Compared to the 830 nm laser wavelength the biospeckle activity measured at 640 nm enabled more accurate predictions of firmness, chlorophyll and carotenoids content. At 640 nm laser wavelength both activity descriptors (C4 and ε) provided similar results, while at 830 nm the ε showed slightly better performance. The linear regression models showed that biospeckle activity descriptors had a higher correlation with chlorophyll and carotenoids content than the a*/b* ratio and luminosity. The results for chroma were comparable with the results for both biospeckle activity indicators. The biospeckle method showed very good results in terms of maturation monitoring and the prediction of the maturity indices of tomatoes, proving the possibility of practical implementation of this method for the determination of the maturity stage of tomatoes.

Measurement of unstable fluid flow during liquid phase reaction using laser speckle method

Measurement of unstable fluid flow during liquid phase reaction using laser speckle method

Study of drying process of paint by dynamic speckle with B/D pixel counting technique

The aim of the work is the assessment of drying process of latex paint by dynamic Laser speckle method. The basic concept of dynamic speckle technique is described. Laser light scattering by water borne sample is a time dependent surface activity. The variation of laser speckle intensity is due to the change of refractive index and the particle movements of the latex paint. A novel method, B/D counting technique to measure the dynamic activity of drying paint using co-occurrence matrix of Time History of Speckle Pattern (THSP) is presented. The result of drying process of latex paint by dynamic laser speckle method is compared with the gravimetric method and agreed well.

The melting curve of Ni to 1 Mbar

The melting curve of Ni has been determined to 125 GPa using laser-heated diamond anvil cell (LH-DAC) experiments in which two melting criteria were used: firstly, the appearance of liquid diffuse scattering (LDS) during in situ X-ray diffraction (XRD) and secondly, plateaux in temperature vs. laser power functions in both in situ and off-line experiments. Our new melting curve, defined by a Simon–Glatzel fit to the data where TM(K)=[(PM18.78±10.20+1)]1/2.42±0.66×1726, is in good agreement with the majority of the theoretical studies on Ni melting and matches closely the available shock wave melting data. It is however dramatically steeper than the previous off-line LH-DAC studies in which determination of melting was based on the visual observation of motion aided by the laser speckle method. We estimate the melting point (TM) of Ni at the inner-core boundary (ICB) pressure of 330 GPa to be TM=5800±700 K(2σ), within error of the value for Fe of TM=6230±500 K determined in a recent in situ LH-DAC study by similar methods to those employed here. This similarity suggests that the alloying of 5–10 wt.% Ni with the Fe-rich core alloy is unlikely to have any significant effect on the temperature of the ICB, though this is dependent on the details of the topology of the Fe–Ni binary phase diagram at core pressures. Our melting temperature for Ni at 330 GPa is ∼2500 K higher than that found in previous experimental studies employing the laser speckle method. We find that those earlier melting curves coincide with the onset of rapid sub-solidus recrystallization, suggesting that visual observations of motion may have misinterpreted dynamic recrystallization as convective motion of a melt. This finding has significant implications for our understanding of the high-pressure melting behaviour of a number of other transition metals.

Precipitation phenomenon of nanoparticles in power-law fluids over a rotating disk

The steady flow and mass transfer of nanofluids with power-law type base fluids over a free-rotating disk are investigated. Previously, we have modeled the volume fraction of nanoparticles and verified the experimental conclusion through the numerical simulation of particle distribution in nanofluid in a Petri dish under the influence of movement using a power-law model of mass diffusivity. We further this study by a similar model of the mass diffusivity following a power-law type to consider the laminar non-Newtonian power-law flow in a rotating infinite disk with angular velocity about the z-axis. The coupled governing equations are transformed into ODEs. Homotopy analysis method (HAM) is applied to solve the ODEs while special attention is paid to deal with the nonlinear items in the ODEs. In the last section, we provide images of nanoparticles suspended in power-law fluids in a rotating disk as obtained using the laser speckle method. When they are compared with the analytical results gained by the HAM, they qualitatively matched the solutions of the concentration equation of nanofluids.

104 レーザスペックル法による局所変形発生評価の実験的検証(材料力学I)

104 レーザスペックル法による局所変形発生評価の実験的検証(材料力学I)

Measurement of the Velocities of Nanoparticles in Flowing Nanofluids using the Zero-Crossing Laser Speckle Method

A zero-crossing dynamic speckle method is proposed to determine the velocities of nanoparticles in nanofluids. A Gaussian laser beam is used to illuminate nanofluids in a pipe, and the dynamic speckles are detected by a spatially integrating detector with an aperture. The integrated speckle intensity signal is processed by a computer and the zero-crossing rate is counted. The velocity of the nanoparticles can be determined from its relationship to zero-crossing rate. The results show that the nanoparticles exhibit features of flowing nanofluids, and when the average velocity of the nanofluids is 53.4mm/s, the average velocity of the nanoparticles is 51.8 ± 5.1 mm/s.

Sensitivity to experimental errors in evaluating the thermal expansion coefficient of a thermal barrier coating by using coating system specimens

The coefficients of thermal expansion (CTEs) of coatings were necessary to evaluate the thermal stresses of the coated component. In general, the CTEs were measured from the free-standing coatings. It is useful if the CTEs of the coatings are able to be measured from the coating system specimens. The resulting CTE of a coating by the coating system is sensitive to experimental errors when compared with that for the free-standing coating. In this study, the sensitivity to experimental errors in evaluating the CTEs from the coating system specimens was investigated. The experimental study was also carried out on six kinds of specimens with different sensitivities. The surface strain during thermal cycling from 850 °C to 300 °C measured by a laser speckle method was used to evaluate the CTE. The CTEs of Yttria-stabilized-zirconia thermal barrier coating and CoNiCrAlY bond coatings were measured by a composite cylinder model. It was found from the sensitivity calculation that the errors of the CTE of the substrate and the measuring slope between strain and temperature caused a large error in the resulting CTE of the coating. The sensitivity calculation also showed that the increase of the thickness of the coating was effective in decreasing the sensitivities. A reasonable estimation was experimentally obtained if the specimens had low sensitivities.

108 レーザースペックル法による局所変形発生評価(材料力学II)

108 レーザースペックル法による局所変形発生評価(材料力学II)

Discrimination of motile bacteria from filamentous fungi using dynamic speckle

We present a dynamic laser speckle method to easily discriminate filamentous fungi from motile bacteria in soft surfaces, such as agar plate. The method allows the detection and discrimination between fungi and bacteria faster than with conventional techniques. The new procedure could be straightforwardly extended to different micro-organisms, as well as applied to biological and biomedical research, infected tissues analysis, and hospital water and wastewaters studies.