ABSTRACT
In this paper, we demonstrate that a compact and inexpensive interferometric sensor based on the self-mixing effect in the laser cavity can be used for the characterization of shock waves. The sensor measures the changes in the refractive index induced by the shock wave. It is based on the self-mixing interferometry scheme. We describe the architecture of the dynamic sensor and the design of the experimental setup used for the characterization that involves a shock tube. Thus, we detail the experimental measurements for shock wave pressure amplitude of 5 bar and address their interpretation with regard to the most admitted models for acousto-optics.
ABSTRACT
At the micrometric scale, vessels or skin capillaries network architecture can provide useful information for human health management. In this paper, from simulation to in vitro, we investigate some limits and interests of optical feedback interferometry (OFI) for blood flow imaging of skin vascularization. In order to analyze the tissue scattering effect on OFI performances, a series of skin-tissue simulating optical phantoms have been designed, fabricated and characterized. The horizontal (2D) and vertical (depth penetration) sensing resolution of the OFI sensor have been estimated. The experimental results that we present on this study are showing a very good accordance with theoretical models. In the case of a skin phantom of 0.5 mm depth with a scattering coefficient from 0 to 10.8 mm-1, the presented OFI system is able to distinguish a pair of micro fluidic channels (100 µm × 100 µm) spaced by 10 µm. Eventually, an in vivo test on human skin is presented and, for the first time using an OFI sensor, a 2D blood flow image of a vein located just beneath the skin is computed.
Subject(s)
Interferometry , Optical Devices , Skin/blood supply , Computer Simulation , Feedback , Humans , Phantoms, ImagingABSTRACT
It is established in the optical feedback interferometry (OFI) theory that the shape of the interferometric fringe has an impact on the detector's response to very small displacement measurements. In this paper, we validate-for the first time, to the best of our knowledge, based on experimental results-this statement by comparing experiments to an established model implementation. Through these experiments, we show that the amplitude of the signals induced by sub-λ/2 optical path variations is linearly dependent on the slope of the underlying fringe. Thus, careful control of the phase allows us to maximize the detection amplitude of very small displacements by positioning the phase where the fringe slope is the steepest. These results are directly applicable to established OFI applications that measure sub-λ/2 optical path variations, such as OFI vibrometers or acoustic imaging though the acousto-optic effect.
ABSTRACT
Optical feedback interferometry (OFI) is a compact sensing technique with recent implementation for flow measurements in microchannels. We propose implementing OFI for the analysis at the microscale of multiphase flows starting with the case of parallel flows of two immiscible fluids. The velocity profiles in each phase were measured and the interface location estimated for several operating conditions. To the authors knowledge, this sensing technique is applied here for the first time to multiphase flows. Theoretical profiles issued from a model based on the Couette viscous flow approximation reproduce fairly well the experimental results. The sensing system and the analysis presented here provide a new tool for studying more complex interactions between immiscible fluids (such as liquid droplets flowing in a microchannel).
