| Project/Area Number |
16360027
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Applied optics/Quantum optical engineering
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| Research Institution | Tokyo University of Agriculture and Technology |
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Principal Investigator |
KUROKAWA Takashi Tokyo University of Agriculture and Technology, Institute of Symbiotic Science and Technology, Professor (40302913)
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| Co-Investigator(Kenkyū-buntansha) |
TANAKA Yosuke Tokyo University of Agriculture and Technology, Institute of Symbiotic Science and Technology, Associate Professor (20283343)
SHIODA Tatsutoshi Tokyo University of Agriculture and Technology, Institute of Symbiotic Science and Technology, Assistant Professor (10376858)
TAKEDA Mitsuo The University of Electro-Communications, Department of Information & Communication Engineering, Professor (00114926)
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| Project Period (FY) |
2004 – 2005
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| Project Status |
Completed (Fiscal Year 2005)
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| Budget Amount *help |
¥15,300,000 (Direct Cost: ¥15,300,000)
Fiscal Year 2005: ¥3,300,000 (Direct Cost: ¥3,300,000)
Fiscal Year 2004: ¥12,000,000 (Direct Cost: ¥12,000,000)
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| Keywords | OCT / octical freauencv comb / interferometer / FRM / 段差計測 / ファラデー回転鏡 |
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| Research Abstract |
A range of techniques, including coherence scanning microscopy, three-dimensional sensing by coherence radar, and scanning white-light interferometry, have been developed for simultaneous measurement of the three-dimensional step height of discontinuous objects and tomographic imaging. These techniques, however, require mechanical scanning with a piezoelectric transducer or a precision translator. Spectral interferometry, on the other hand, potentially offers a powerful means for high-speed absolute threedimensional shape measurement of objects without moving mechanical parts. The practical applicability of such methods, however, remains limited due to the high cost of tunable lasers with sufficiently wide range (e.g., external cavity laser diodes and dye lasers) and the slow speed of data acquisition because of the large number of calculations in the Fourier transform. As an alternative interferometry-based approach, synthesis of the coherence functions has been reported to be suitable for distance measurements. This method involves pseudo-frequency comb generation by frequency modulation of a laser diode. Yet this method is not suitable for surface profilometry because the frequency-comb interval is limited to the order of megahertz.
In this Letter, a novel frequency comb-based interferometry technique for profilometry and tomography is proposed. The optical frequency comb employed by this method can be adjusted simply, allowing interferometry to be performed at frequency intervals of up to gigahertz order. The method is therefore suitable for measurement of absolute distances of several micrometers to several meters without the need for mechanical movement.
Step-height measurement with 9 μm accuracy was successfully performed by sweeping the comb interval frequency. Thickness measurement of a glass plate was also demonstrated. This profilometry method is expected to be useful for both surface profilometry and tomography.
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