Nonmechanical axial scanning laser Doppler velocimeter with directional discrimination

Abstract

An axial scanning laser Doppler velocimeter (LDV) with directional discrimination not requiring any moving mechanism in its probe is proposed. The proposed LDV utilizes frequency shift induced by acousto-optic modulators (AOMs) for discriminating the direction of velocity. The measurement position is axially scanned by changing the wavelength of the light input to the probe. The experimental result reveals that both the axial scan and the directional discrimination can be realized by using the proposed method without any moving element in the probe.

Nonmechanical cross-sectional scanning laser Doppler velocimeter with directional discrimination of transverse velocity component

“…4,5 An LDV with a compact sensor probe is desirable for practical applications. [9][10][11] In these LDVs, acousto-optic modulators (AOMs) or electro-optic phase shifters were employed for optical frequency shifting. However, these techniques have disadvantages because the moving mechanism can be easily damaged by mechanical impact on the probe and is subject to abrasion.…”

Non-mechanical scanning laser Doppler velocimetry with sensitivity to direction of transverse velocity component using optical serrodyne frequency shifting

“…Several non-scanning LDVs with sensor probes have been reported [7][8][9][10]. To realize a scanning LDV with a compact and reliable sensor probe, we have proposed scanning LDVs without any moving mechanism in their probes [11][12][13][14][15]. In these non-mechanical scanning LDVs, the measurement position is scanned by changing the wavelength input to the probe, and diffraction gratings are used inside the probe instead of a moving mechanism.…”

“…measurement of the sign of the velocity component, is indispensable. For introducing directional sensitivity into an LDV, optical frequency shifting [8,13,[16][17][18][19][20][21][22] is commonly used. The fiber-optic LDV with a compact probe capable of providing directional information has been proposed [8], although this LDV was a non-scanning type.…”

“…The fiber-optic LDV with a compact probe capable of providing directional information has been proposed [8], although this LDV was a non-scanning type. We have proposed a non-mechanical scanning LDV with directional sensitivity [13]. In these LDVs, Bragg cells using the acousto-optic effect were employed for optical frequency shifting.…”

Nonmechanical scanning laser Doppler velocimeter for cross-sectional two-dimensional velocity measurement

“…To overcome these drawbacks in conventional scanning techniques, the authors have proposed scanning LDVs without any moving mechanisms in their probes [7][8][9][10]. In these LDVs, the scanning function is obtained by changing the wavelength of the light input to the probe, and diffraction gratings are included in the probe for scanning beams instead of using a moving mechanism.…”