2006 Fiscal Year Final Research Report Summary
Detection method of sound information in light and development of optical wave microphone
| Project/Area Number |
16560376
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Measurement engineering
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| Research Institution | Kyushu Tokai University |
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Principal Investigator |
SONODA Yoshito Kyushu Tokai University, School of Engineering, Professor, 工学部, 教授 (90117143)
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| Co-Investigator(Kenkyū-buntansha) |
SAMATSU Takashi Kyushu Tokai University, School of Information Science, Assistant Professor, 応用情報学部, 講師 (60299667)
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| Project Period (FY) |
2004 – 2006
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| Keywords | Acoustic engineering / Audible sound / Optical microphone / Interaction between light and sound / Laser applied measurement / Optical information processing / Ultrasonic wave / Microphone |
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| Research Abstract |
The purpose of this research is to develop an optical wave microphone with no diaphragm, which can directly detect audio waves propagating in air by a laser beam. It converts sound signals to electrical signals by detecting the ultra-weak diffraction light generated by phase modulation effect of sounds. In this optical device, the diffraction light having Doppler shifted frequencies by sounds passes through the optical Fourier transform system with a penetrating laser beam and is detected by a photodiode in the optical observing plane. In the present study, the optical information processing system is theoretically and experimentally examined in order to get a best performance of the optical wave microphone. Furthermore, the construction method of laser beam antenna sensing audio waves is experimentally investigated to know how to realize any receiving property needed for practical applications or needs. The obtained main results are as follows :
When sounds interact with a sensing laser beam, the sound signal can be effectively converted to electrical signals by setting the optical observing plane in the proper spatial position, where the optical Fourier transform of the sound incident plane is satisfied. The output signal intensity is proportional to the laser beam waist size, but for the practical uses the beam size of a few mm is desired to easily construct the laser beam transmission.
The relation between the spatial construction or shape of laser beam antenna and the sound receiving property was investigated using double laser beams reflected by a roof mirror. It is shown that the directivity and the signal amplification of the optical wave microphone could be controlled by changing the laser beam construction from one to three dimensions.
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