| Project/Area Number |
60550027
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
物理計測・光学
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| Research Institution | Waseda University, School of Science and Engineering |
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Principal Investigator |
KOMATSU Shin'ichi Waseda University, School of Science and Engineering, Professor, 理工学部, 教授 (00087446)
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| Co-Investigator(Kenkyū-buntansha) |
KUME Yuichiro Waseda University, School of Science and Engineering, Assistant, 理工学部(昭和60年度のみ分担), 助手 (20161713)
OHZU Hitoshi Waseda University, School of Science and Engineering, Professor, 理工学部, 教授 (10063520)
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| Project Period (FY) |
1985 – 1986
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| Project Status |
Completed (Fiscal Year 1986)
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| Budget Amount *help |
¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1986: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1985: ¥1,700,000 (Direct Cost: ¥1,700,000)
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| Keywords | Optical Heterodyne / Light Scattering / Optical Beat / Optical Prote / Defect Detection / 形状測定 |
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| Research Abstract |
A laser heterodyne probing system is constructed to measure the distribution of lightscattering particles or defects fixed within a partially transparent object, and the fundamental properties of this system are examined experimentally.
The optical part of this system is similar to the differential laser Doppler velocimeter in which a probe volume is formed by crossing two converging laser beams at some finite angle, besides the probe volume in this case can be made so small that it is occupied with only one interference fringe in a most extreme case.
The two beams have been frequency-shifted to each other, therefore the photo-current due to the light scattered by a particle within the probe volume contains a beat signal whose center frequency is equal to the frequency shift. Since a light-scattering particle existing in only one beam produces no beat signal and the beat signal possibly produced by the interference effect among some particles outside the probe volume can be suppressed with sufficiently large photo-detecting angle, the beat detection gives a higher signal to noise ratio compared with conventional light-intensity detection.
A Zeeman-laser is used to obtain two coherent beams whose frequencies are mutually shifted by a small amount(88kHz). Because the beat frequency is fairly low, the signal detection can be performed easily with a lock-in amplifier. A simple optical unit consisting of some polarizing elements is required to separate the two orthogonally polarized beams with different frequencies.
Experimental results obtained with a latex sphere target shows that high SNR has been achieved by the present method even when some interfering particles exist in front of the probe volume.
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