| Budget Amount *help |
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1988: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1987: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Research Abstract |
The laser Doppler velocimeter (LDV), which has some advantages such as non-perturbing quality, capability of remote operation and high spatial resolution, has been well developed to measure flow velocity. However, the LDV needs to seed scattering particles in flow. Recently, to be freed from this problem, velocimeters using photothermal effect have been investigated. Phase graient variation induced by photothermal effect is measured by detecting deflection angle of probe laser beam using a position sensitive device. To measure phase variation, we need to integrate the phase gradient spatially. So accuracy of phase measurement is not good.
In this paper the phase variatiion induced by photothermal effect is measured using an optical fiber interferometer to increase sensitivity and to understand the phenomena directly. Optical fiber heterodyne interferometry have the following features: it is extremely sensitive, can be remotely operated, and has a linear relatioin between detector output and measuring phase. However, the heterodyne system suffered from external disturbance because the reference arm had a different path from the signal arm. We report an optical fiber heterodyne interferometers free from external disturbance in the optical pathes of the fiber used to measure small phase variation. The phase fluctuation in the fiber due to external disturbance is excluded by constructing two Michelson type interferometers which have common pathes of two fibers.
Using jet of air mixed with C_2H_4 it is demonstrated that this method is useful to measurement of flow velocity and concentration. We used a pulse light obtained by chopping CW CO_2 of 10 W as a pump beam. Time of flight method is used for measurement of flow velocity, and the concentration is obtained by analyzing the measured phase variation curve.
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