| 摘要 |
PURPOSE:To remove noise components to a high degree by equalizing the resonance frequency and phase of a measurement-side photoacoustic cell to those of a reference-side cell and generating the difference signal between both of them. CONSTITUTION:Cells consisting of the measurement-side photoacoustic cell 1 and a reference-side cell 2 are pressed against the surface of a sample by a sample contacting rubber O ring 3 to constitute measurement-side and reference-side airtightness holding parts 4 and 5. Further, modulating light is guided into the cell 1 by an optical fiber 6 to illuminate the sample surface locally. Optical sound and a noise generated in the sample are transduced by the holding parts 4 and 5 into compressional waves of gas, which are received by measurement-side and reference-side microphones 7 and 8 mounted on the other surfaces of the holding parts 4 and 5. Then, the position of the microphone 8 is adjusted by the movement of a thread-cut block 9 to make the resonance frequency and phase of the cell 2 coincident with the resonance frequency of the measurement side. Thus, the difference signal is generated to remove noise components to a high degree.
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