低干渉光源を利用した流動計測システムの開発

抄録

A new measurement system for velocity distribution based on a low-coherent interferometry is examined. A low-coherent source has a broad spectrum in the oscillating frequency. That is, an interference output with the low-coherent source is obtained only when the path lengths of both a reference light and a scattered light are coincident in an interferometer. Therefore, a depth with the scattered light can be specified by adjusting a path difference in the interferometer. A superluminescent diode (SLD) provides an optical source with a low temporal coherence. In the present paper, the measurement system with interferometric technique by use of SLD has been successfully developed to be an anemometer which is capable of travers measuring a velocity distribution along a depth in a flow passage. The light beam emitted from the SLD forms a Michelson type interferometer, in which to move a mirror reflecting the reference light means to traverse a velocity profile along the depth at each chosen location. A fluctuation of the interference output is detected and is Fourier-processed. A flow velocity is calibrated by the width of the half peak value of the Fourier spectrum. The measurement result agrees well with the theoretical velocity profile.