Shigeyoshi Hisada

Visualization and Measurements of Sound Pressure Distribution of Ultrasonic Wave by Stroboscopic Real-Time Holographic Interferometry

The sound pressure distribution of underwater ultrasonic waves is measured by real-time stroboscope holographic interferometry using bismuth silicon oxide single crystal. Stroboscopic sub-microsecond irradiation of laser light enables the recording of the stationary holographic interferogram of refractive index changes of water by ultrasonic waves for the frame time of a charge coupled device camera. The fringe order distribution is calculated from the interferogram by Fourier transform fringe analysis. The optical path differences caused by sound field along the optical path are converted into local field values of sound pressure, which is displayed as a gray scale distribution image. In the experiment, the sound pressure distributions of ultrasonic waves through rectangular and circular apertures are observed. They are compared with the theoretical sound pressure distribution. The sound pressure values obtained by a hydrophone show good agreement with the measured values obtained by this method. The converging and diverging sound pressure fields realized by an acoustic lens are measured.

Thermal Contraction Coefficient Measurement Technique of Several Materials at Low Temperatures Using Electronic Speckle Pattern Interferometry

Electronic speckle pattern interferometry has been applied to the measurement of the thermal expansion coefficient of a sample in the form of a plate of several commercial available metallic materials at low temperatures. Interference fringe patterns are mapping contours of constant in-plane displacement difference between two temperatures. They are dependent on the cooling rate and the temperature gradient of the specimen. The fringe separation shows the thermal strain. The temperature of specimens are simultaneously monitored using thermocouples during the cooling process. Analysis of the thermal strains and temperatures allows for the measurement of the thermal expansion of the specimen.

Deformation Measurements of Materials at Low Temperatures Using Laser Speckle Photography Method

We observed deformations of several materials during cooling down process from room temperature to liquid nitrogen temperature using the laser speckle photography method. The in-plane displacements were measured by the image plane speckle photography and the out-of-plane displacement gradients by the defocused speckle photography. The results of measurements of in-plane displacement are compared with those of FEM analysis. The applicability of laser speckle photography method to cryogenic engineering will also be discussed.

Strain Measurements of Stainless Steel at Low Temperatures Using Electronic Speckle pattern interferometry

Publisher Summary This chapter applies electronic speckle pattern interferometry to the measurements of out-of plane deformation and in-plane, and strain of some kinds of stainless steel during the cooling down process from room temperature to liquid nitrogen temperature. Interference fringe patterns represent in-plane and out-of-plane deformation (warp), depend on cooling rate, temperature gradient at the surface of the specimen, and on the rolling direction of the specimen. The deformation and temperature of the specimen are also monitored by using resistance strain gauges and thermocouples, respectively. The thermal contraction as the thermal behavior of materials in the cooling down process, is one of the most important properties. From this point of view, the deformation process has been studied by using various techniques. The deformation and strain of materials has conventionally been measured by applying resistance type strain gauges.

Laser soldering of Sn-Ag-Cu and Sn-Zn-Bi lead-free solder pastes

It has reported that a waste of an electronics substrate including lead and its compound such as 63Sn-37Pb has polluted the environment with acid rain. For that environment problem the development of lead-free solder alloys has been promoted in order to find out the substitute for Sn-Pb solders in the United States, Europe, and Japan. In a present electronics industry, typical alloys have narrowed down to Sn-Ag-Cu and Sn-Zn lead-free solder. In this study, solderability of Pb-free solder that are Sn-Ag-Cu and Sn-Zn-Bi alloy was studied on soldering using YAG (yttrium aluminum garnet) laser and diode laser. Experiments were peformed in order to determine the range of soldering parameters for obtaining an appropriate wettability based on a visual inspection. Joining strength of surface mounting chip components soldered on PCB (printed circuit board) was tested on application thickness of solder paste (0.2, 0.3, and 0.4 mm). In addition, joining strength characteristics of eutectic Sn-Pb alloy and under different power density were examined. As a result, solderability of Sn-Ag-Cu (Pb-free) solder paste are equivalent to that of coventional Sn-Pb solder paste, and are superior to that of Sn-Zn-Bi solder paste in the laser soldering method.

Direct laser marking on ROM media for identification

In order to attempt the direct laser marking for ROM media like a compact disk for identification, various laser heating was carried out against a thin metallic film in the transparent medium. As heat sources for the processing, a semiconductor laser excitation YAG laser (532 nm wavelength of second harmonic, max 150 mW), semiconductor lasers (780 nm, up to 2 W), and an Ar ion laser (514.5 nm, max 2000 mW), etc. were used. The media under consideration on laser marking is an aluminum thin film reflector layer, which was sandwiched between a polycarbonate (PC) of 1.2 mm and a protection film of 5 μm thickness. The aluminum thin film (Al) is 100 nm in thickness. The obtained laser marking sizes were less than 1 μm and were evaluated using SEM and AFM. The observation samples inside a transparency resin were obtained by tearing off a protection film, and the surfaces of the bared PC and protection film were examined. The surface conditions and cross sections of laser-marking area were observed. It seems that the heated aluminum thin film were melted and a hole arose. Then a cavity was not observed from SEM cross-section observation in the marking area. It became clear that the holes were filled with PC by SEM and AFM observation. These results indicate the possibility of heat localization at the Al-PC interface and also significant heat penetration into the PC substrate itself.

Holographic optical element for laser soldering

Experimental studies on the characteristics of holographic lens were carried out, aiming at the simultaneous soldering of multi-spots in electronic assembly by the use of YAG laser. Holograms were recorded on the commercial available photographic plates, and converted into transparent phase type holographic lens by chemical processing. The dependencies of the diffraction efficiency on the recording conditions and two chemical treatment methods of silver halide sensitized gelatin and rehalogenating bleaching were examined in CW YAG laser system ((lambda) equals 1.06 micrometers ).

Measurements of Thermal Expansion of Nonmetallic Materials at Low Temperature using ESPI

The electronic speckle pattern interferometry (ESPI) is applied to measure the thermal expansion for several nonmetallic materials (GFRP, A12O3, PTFE, and SiO2) during heating from low temperatures to ambient. Between two temperatures, the thermal strains were acquired by ESPI and the temperature of the surface by thermocouples. The results allow for the determinative of the thermal expansion coefficient. Since nonmetallic materials like fiber reinforced plastic (FRP), plastics and ceramics are translucent to light, a speckle pattern is formed by the interference between the light not only scattered at the surface but also multiple-scattered in the inner part of the specimen. As the temperature changes, the totality of the scatter movements exceeds a certain limit to keep the correlation between the speckle patterns. Loss of ESPI fringes results in the image process. Satisfactory results were obtained by coating the specimen surface by a vacuum-evaporated aluminum film. The thermal expansion coefficient of a SiO2 specimen could be acquired by calculating the phase map caused by the transformation of the object using ESPI with Fourier transform method (FTM). The thermal expansion coefficients obtained by ESPI were in the range of 1 x 10-7 to 1 x 10-4(l/K) between 100K and 300K.