A miniaturized dual-fibre laser Doppler sensor

Abstract

The integration of laser Doppler velocimeters into small components such as wind tunnel models requires highly miniaturized sensors. This paper presents a novel miniaturization concept, suitable for reducing the dimensions of a fibre-coupled laser Doppler sensor to a millimetre scale. Only a few low-cost, passive elements such as two fibres, a diffraction grating and refractive optics are employed. Preliminary results of a realized sensor head, of about 7 mm diameter and about 15 mm length, are presented. The generated measurement volume of about 0.02 mm diameter and about 0.1 mm length allows highly spatially-resolved velocity measurements. The outstanding features of the sensor are its simplicity, ruggedness and the high optical power of about 0.5 W in the measurement volume.

Touchless underwater wall-distance sensing via active proprioception of a robotic flapper

“…High errors were observed at the higher Rossby numbers, but the median errors were still below 5% of the plate length at all Rossby numbers. Increasing the dimensionless stroke amplitude in the tested ranges (2-4) had a relatively minor impact in increasing prediction accuracy when compared to the effects of the Rossby number (2)(3)(4)(5). Additionally, proximity of the flapper to the walls, whether in front or behind, led to increased prediction accuracy, which is expected due to the likely stronger interactions of the self-generated flow with the wall.…”

“…However, for smallsize Autonomous Underwater Vehicles (AUVs) or bio-inspired underwater robots operating in cluttered shallow water conditions (e.g. in turbulent waters over intertidal zones and rocky river beds and shorelines), conventional acoustic or optical sensing methods [1,2] suffer a number of disadvantages, such as the inability of working in clouded, murky water environment with low visibility [3,4], bulkiness in design [5], high energy consumption [6], and adverse effects on ecosystems [7]. Therefore, it is desirable to develop novel sensing methods to complement or expand the current sensing capabilities of AUVs.…”

Holographic optical element for laser time-of-flight flow sensor

“…Some proposed systems use fiber lasers [3] and others use laser diodes in traditional laser flow sensor systems [4] in order to make the systems more compact. The compactness and high efficiency of laser diodes, makes the use of these an obvious way to miniaturize optical flow sensors.…”

Laser-Doppler velocity profile sensor with submicrometer spatial resolution that employs fiber optics and a diffractive lens

“…The advantages of fiber-optic setups, such as high flexibility and immunity to electromagnetic disturbances, have long been recognized 8,9 and offer great potential for miniaturization. 10 Very small sensor heads can be made if the LDA partial beams are guided to the sensor head by two different fibers. Differences in the fiber arm lengths can, however, result in phase noise or in poor modulation of the Doppler signal, so it is advantageous to use only one fiber for beam delivery and to split the beam in the sensor head.…”