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Volume 22, Issue 7
Displaying 1-8 of 8 articles from this issue
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Hiroo INOKUCHI1994 Volume 22 Issue 7 Pages 527
Published: July 29, 1994
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSDownload PDF (119K) -
Shin YOSHIKADO, Tadashi ARUGA1994 Volume 22 Issue 7 Pages 528-535
Published: July 29, 1994
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSAn infrared interferometer, originally developed for passive observation, can also be used for active coherent imaging (ACI) if we transmit a sensing wave to an object at a finite distance. We present here an ACI method, similar to that of synthetic aperture radars, with a new simple data-processing procedure.
In order to verify our ACI availability, we have investigated various effects of condition changes on processed images through a numerical simulation, and concluded that the ACI is available for high-resolution imaging of an object at ranges within several kilometers in conditions of weak or medium atmospheric turbulence.View full abstractDownload PDF (1012K) -
Masato MATSUBARA, Yushi TAKENAKA, Junichi NISHIMAE, Masaki KUZUMOTO1994 Volume 22 Issue 7 Pages 536-542
Published: July 29, 1994
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSFocusing characteristics of CO2 laser beam affected by an optical distortion are calculated for a Gaussian mode and higher order modes using computer simulation, which gives a theoretical dependence of the optical distortion on the transverse intensity profiles. The theoretical results show that the beam with higher intensity at a center region gives more serious distortion effect for focusing than the beam with lower intensity at a center region.View full abstractDownload PDF (717K) -
Hiroyuki SIMIDZU, Fumito YOSHINO, Akira MATSUNAWA1994 Volume 22 Issue 7 Pages 543-551
Published: July 29, 1994
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSThis paper describes a direct diagnostic technique to measure the 2-dimensional power density distribution in the focal volume of a high-power and pulsed Nd3+: YAG laser for materials processing. A rotating-pinhole laser beam analyzer combined with a signal-pulse generator was used to measure the power density distribution of a 1.06μm wavelength beam, while synchronizing the output of the pulsed laser with the motion of the pinhole. Measurements were carried out with a Nd3+: YAG rod under the thermal stationary conditions and results were obtained.
Reproducibility of measured power density distribution is very good with high temporal and spatial resolution. The focused 1/e2 beam diameter of waveform-controlled pulses has a constant value without depending on the intensity of the laser pulses. Only the mean-power density is proportional to the power of the laser pulses. The power density distribution of a short pulse length of 0.3 ms width can be also measured precisely.View full abstractDownload PDF (1173K) -
Shinichi FUJISAKA, Toshiaki ITO, Katsuhiko SATO1994 Volume 22 Issue 7 Pages 552-558
Published: July 29, 1994
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSThe dynamics of ablation of pig femurs by a KrF excimer laser (248 nm, FWHM 15 ns) was studied using a framing camera with pulsed illumination. A shock wave expanded hemispherically above the exposed surface of the bone. Its velocity was supersonic and increased as fluence increased. Materials began to leave the surface following the shock wave. The obtained photographs indicate that the shock wave and the material removal occur after the end of the laser pulse.View full abstractDownload PDF (1526K) -
Katsuhiko SATO, Takeharu KAKIUCHI, Takashi SUZUKI1994 Volume 22 Issue 7 Pages 559-565
Published: July 29, 1994
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSPig femurs are ablated in air with a KrF excimer laser at several fluences below and above plasma-formation threshold.Ablation craters and debris are examined by means of scanning electron microscopy, infrared spectroscopy and X-ray diffraction analysis.The shape of debris is needle-like and spherical, respectively above and below the plasma-formation threshold. Natural structure of the hard-bone components is observed below and above the plasmaformation threshold. The amounts of H2OandCO32-components of debris are almost unchanged below the plasma-formation threshold, but decrease with sharpening of the X-ray diffraction peak above the plasma-formation threshold.These resultsuggest that in the bone ablation process organic components are decomposed photochemically and vaporized, then entrain and remove the surrounding material, while the debris is thermally influenced above the plasma-formation threshold.View full abstractDownload PDF (1413K) -
Akira TSUNEMI, Ryo HIRAI, Kouji HAGIWARA, Keigo NAGASAKA, Hideo TASHIR ...1994 Volume 22 Issue 7 Pages 566-572
Published: July 29, 1994
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSUsing laser ablation technique, we demonstrated high performance of a TEA CO2 laser with a pulse repetition rate of 1 kHz, for the use of high-speed cleaning of solid surface. Paint, rust, moss and dirt on the surface of solid materials were effectively removed by the irradiation of line focused pulses with an energy of 300 mJ. A cleaning rate reached to 17 m2/hour for a case of paint removal from iron surface.View full abstractDownload PDF (849K) -
Isao OKUDA, Noboru UEHARA, Fumio KOYAMA, Kouji TOMINAGA, Shinki NAKAMU ...1994 Volume 22 Issue 7 Pages 573-601
Published: July 29, 1994
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSDownload PDF (3934K)
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