Multiple-color light-emitting diodes (LEDs) were used for photoacoustic (PA) imaging of printed color specimens, and the obtained PA images agreed well with the corresponding amount of absorbance of the specimens. The LED light sources with wavelengths of 455, 505, 617, and 660 nm were used to evaluate PA images that were obtained for colored specimens printed on the front and rear surfaces of an OHP sheet. The PA images obtained for individual wavelengths were combined to recover the colored image of the specimen, and the recovered image was compared with the original full-color image. The PA signals with amplitudes and phases behave as vectors so that the vectorial addition of PA signals generated from the surface and undersurface well describes the PA signal behavior. Furthermore, imaging of a layered specimen with a surface color layer was also carried out, which lead to successful thermal depth profiling with a colored optical source.
In this study, the nondestructive evaluation (NDE) of an internal defect introduced in the welded region of an aluminum plate has been demonstrated by photoacoustic microscopy (PAM). The internal defect is a blowhole and an incomplete fusion, which were formed in the weld metal during welding. Experiments were carried out at different modulation frequencies. Furthermore, a stereoscopic image of the fractured specimen was obtained by destructive inspection using scanning laser microscopy (SLM) and compared with a photoacoustic (PA) amplitude image. The size of the internal weld defect measured by both methods was approximately the same.
Based on the scaling rule: R(T, H, 6) = R(T, h ) , where h = H(sin2 6 + cos2 8/y2)'/2 and 6 is field angle with respect to the ab-plane, the scaling approach is performed to examine the c-axis resistances of single crystalline La1.86Sro.14CuO4 as functions of field and its orientation at different temperatures. The anisotropy parameter 7 of the system is extracted from the scaling approach, but shows an unusual temperaturedependent behavior, which is not expected by conventional theory. A phenomenological explanation of this temperature dependence is presented. PACC: 7425; '7460E; 74201)
Recently, quality evaluation and control has become increasingly important in biology and agriculture. The evaluation of the quality of food plants has been performed by many inspection methods. To date, the evaluation of the grain of crops by photoacoustic spectroscopy in the infrared region has only been performed for corn. We have developed a method of applying a photoacoustic microscope (PAM) to pollen analysis. In this study, a PAM was used to evaluate the quality of crop grains, rice in this case, for the first time. Due to differences in the absorption of the laser beam, the homogeneity of rice grains was measured and shown as thermal images. The resolution was sufficiently good to evaluate a single grain of rice. This method has an advantage in that it can be used to measure the existence of both the surface and back surface colored regions. In addition to conventional video image evaluation or the macroscopic optical absorption method, PA imaging can enable the evaluation of the quality and condition of rice grains.
A linear-motor-driven photoacoustic microscope, which realizes both rapid response and quiet environment for a gas-microphone detection system, is fabricated as a candidate for the optimum gas-microphone photoacoustic microscopy system.
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