Compressed holographic particle tracking velocimetry for microflow measurements
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SPECIAL SECTION: REGULAR PAPER International Symposium on Imaging, Sensing, and Optical Memory (ISOM ’19), Niigata, Japan
Compressed holographic particle tracking velocimetry for microflow measurements Shuhei Yoshida1 · Kan Itakura1 Received: 28 February 2020 / Accepted: 25 August 2020 / Published online: 24 September 2020 © The Optical Society of Japan 2020
Abstract We have established a holographic particle tracking velocimetry (HPTV) technique based on compressed sensing (CS) for measurement of the velocity field of microflows in this study. In conventional HPTV, where the scattered light field is reconstructed via backpropagation calculations, the particle image spreads greatly in the depth direction and it is then difficult to perform three-dimensional three-component (3D3C) measurements with high accuracy. In the proposed method, CS is applied based on the spatial sparseness of the particle distribution and highly accurate 3D3C measurements are made possible by direct reconstruction of the particle distribution. In this paper, we explain the principle of HPTV based on CS and report the results of evaluation of the velocity vector distribution measurement of a micro linear channel. The experimental results indicate that the proposed method is effective for 3D3C measurements of microflows. Measurement of the velocity field of microflows is becoming increasingly important in the development of microfluidic devices and in the understanding of biological mechanisms. The proposed method is expected to provide an effective technique for use in these applications. Keywords Digital holography · Compressed sensing · Particle tracking velocimetry · PTV
1 Introduction Measurement of the velocity field of microflows, which have a characteristic length of several hundred micrometers or less, is becoming increasingly important in the development of microfluidic devices and in the understanding of biological mechanisms [1]. Particle image velocimetry (PIV) and particle tracking velocimetry (PTV) are widely used as velocity field measurement techniques for microflows and are called micro-PIV/PTV ( μPIV∕μPTV ) in this context [2, 3]. In μPIV∕μPTV , the diffracted light from tracer particles that were placed in the flow is expanded by the optical system and the velocity distribution is then measured by analyzing the motion of the particles. μPIV∕μPTV techniques can measure flows with high spatial resolution when compared with the hot wire anemometer, the hot film anemometer, * Shuhei Yoshida [email protected] 1
Department of Electric and Electronic Engineering, Kindai University, 3‑4‑1 Kowakae, Higashiosaka, Osaka 577‑8502, Japan
and the laser Doppler velocimeter. However, conventional μPIV∕μPTV methods have a deep depth of field (DOF) [4, 5], and it is difficult to apply these methods to high-precision three-dimensional three-component (3D3C) measurements. Holographic PIV/PTV (HPIV/HPTV) [6–9], in which digital holography (DH) is applied to PIV/PTV, is used to perform 3D3C microflow measurements. In HPIV/HPTV,
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