Results 1 - 10 of 4208
Results 1 - 10 of 4208. Search took: 0.033 seconds
|Sort by: date | relevance|
[en] The thermographic images of laser-heated spots or lines are perturbed by nearby cracks, providing NDE techniques for crack detection. Scanning with a laser line, rather than a laser spot, results in a substantial reduction in inspection time. 3D finite difference modelling results are presented that show the sensitivity of the laser-line thermography technique to cracks of varying lengths, depths and openings. A novel crack imaging technique is presented that is based on assembling the second spatial derivative thermal images of a scanned laser line. Experimental results show the new technique to image cracks with openings as small as a few micrometres. The scanning time of the laser-line thermography technique is shown to be over an order of magnitude smaller than that of the laser-spot thermography technique whilst producing crack images of similar quality
[en] This work is devoted to the technique application of lock-in infrared thermography in the shipbuilding and ocean engineering industry. For this purpose, an exploratory study to find the optimized test conditions is carried out by the design of experiments. It has been confirmed to be useful method that the phase contrast images were quantified by a reference image and weighted by defect hole size. Illuminated optical intensity of lower or medium strength give a good result for getting a phase contrast image. In order to get a good phase contrast image, lock-in frequency factors should be high in proportion to the illuminated optical intensity. The integration time of infrared camera should have been inversely proportional to the optical intensity. The other hand, the difference of specimen materials gave a slightly biased results not being discriminative reasoning
[en] An ultra-precise infrared microscope consisting of a high-resolution infrared objective lens and infrared sensors is utilized successfully to obtain location information on the plane and depth of local heat sources causing defects in a semiconductor device. In this study, multi-layer semiconductor chips are analyzed for the positional information of heat sources by using a lock-in infrared microscope. Optimal conditions such as focal position, integration time, current and lock-in frequency for measuring the accurate depth of the heat sources are studied by lock-in thermography. The location indicated by the results of the depth estimate, according to the change in distance between the infrared objective lens and the specimen is analyzed under these optimal conditions
[en] We present the optical properties of zinc-blende CdSe and ZnSe ¯lms, which have been determined by using vacuum ultra-violet spectroscopic ellipsometry (SE) whose spectral range is from 0.7 to 9.0 eV at room temperature. We observed new critical point energies, whose observation by SE has not been reported so far, in the spectral range above 6 eV. We interpret these new peaks as a previously reported transition from a band-structure calculation. The values of the critical point energies were determined from numerically calculated second energy derivatives of these data.
[en] Ellipsometry and reflection polarimetry are almost synonymous. Therefore it is not surprising that ellipsometry and polarimetry share a common history which is that of optical polarization. The discoveries in the late 1600s by Bartholinus and Huyghens of double refraction by Iceland spar and the unusual properties of the twin beams thus generated presented insurmountable difficulties for the entrenched corpuscular-ray theory of Newton and caused research on polarization to remain stagnant in the 1700s. Major breakthroughs came in the early 1800s when Malus discovered polarization of light by reflection and his cosine-squared law and Fresnel and Arago enunciated their laws of interference of polarized light that helped establish the transverse vector nature of luminous vibrations. Important further research immediately followed on optical rotatory power by Arago, Biot, and Pasteur that ushered fundamental and practical applications of polarimetry in chemistry and biology. Fresnel deserves to be recognized as a founder of ellipsometry by virtue of his laws of reflection of polarized light at interfaces between dissimilar media and his identification and production of circular and elliptical polarization. The later part of the 19th century witnessed significant discoveries of magneto-optic and electro-optic effects by Faraday, Kerr, and Pockels that greatly enriched polarization optics and physics. The 1896 discovery of the Zeeman effect launched the exciting field of solar polarimetry. The 1864 crown achievement of Maxwell's electromagnetic (EM) theory provided a unified framework for the analysis of polarization phenomena across the entire EM spectrum.