流体の非接触計測に向けた光超音波信号の時間相互相関解析に基づく速度計測の基礎特性評価

抄録

Photoacoustic 3D imaging using pulsed light irradiation has been realized for high-resolution three-dimensional visualization of vascular structures from the biological surface to several centimeters in depth. It is currently restricted to morphological imaging with some exceptions. We focused on velocity measurement based on cross-correlation analysis of photoacoustic signals toward realizing blood flow velocity measurement. We used sinusoidal linear motions of a solid object for evaluating the performance of photoacoustic velocity measurement. The object was irradiated with a pair of laser pulses with a time difference, and the generated photoacoustic signals were acquired. Cross-correlation of a successive pair of photoacoustic signals from an object provides a time shift due to the motion of the object. From the time shift, the object moving velocity can be obtained with known sound speed and the time difference between the successive irradiations of the laser pulses. The object motion was independently measured with a laser displacement sensor simultaneously during the measurement. The result of the photoacoustic velocity measurement performance with a standard deviation of about 5 to 10% was obtained for a pre-setting velocity in range of several 100 mm/s.