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Benjamin Halkon

Publications and source records attributed to Benjamin Halkon.

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Optically interrogated liquid crystal-based, charge-mode accelerometer telemetry

A hybrid optoelectronic vibration sensing system is presented, combining a conventional charge-mode piezoelectric accelerometer with an optical fiber interface via a liquid crystal-based electrical-to-optical transducer. This configuration allows the accelerometer's electrical output to be converted into an optical signal, enabling remote signal transmission over optical fiber. The same fiber could also be used to supply power to the system, offering a compact and interference-resistant solution suitable for challenging environments such as those with high voltages or explosive risks. Experimental results demonstrate a displacement resolution ranging from \Delta z = 0.015 nm at 0.160 nm displacement, up to \Delta z = 0.720 nm at 351 nm displacement, or equivalently, from \alpha = 0.0005 m/s2 to 0.057 m/s2 in acceleration. Despite undergoing electrical-to-optical and optical-to-electrical signal conversion, the system maintains high sensitivity, low noise levels, and signal integrity. This proof-of-concept optically interrogated accelerometer highlights a path toward reducing sensor infrastructure requirements by eliminating the need for conventional power supplies and electromagnetic shielding, which are typically required in fully electrical accelerometer systems.

physics.optics

Ultra-broadband local active noise control with remote acoustic sensing

One enduring challenge for controlling high frequency sound in local active noise control (ANC) systems is to obtain the acoustic signal at the specific location to be controlled. In some applications such as in ANC headrest systems, it is not practical to install error microphones in a person's ears to provide the user a quiet or optimally acoustically controlled environment. Many virtual error sensing approaches have been proposed to estimate the acoustic signal remotely with the current state-of-the-art method using an array of four microphones and a head tracking system to yield sound reduction up to 1 kHz for a single sound source. In the work reported in this paper, a novel approach of incorporating remote acoustic sensing using a laser Doppler vibrometer into an ANC headrest system is investigated. In this 'virtual ANC headphone' system, a lightweight retro-reflective membrane pick-up is mounted in each synthetic ear of a head and torso simulator to determine the sound in the ear in real-time with minimal invasiveness. The membrane design and the effects of its location on the system performance are explored, the noise spectra in the ears without and with ANC for a variety of relevant primary sound fields are reported, and the performance of the system during head movements is demonstrated. The test results show that at least 10 dB sound attenuation can be realised in the ears over an extended frequency range from (500 Hz to 6 kHz) under a complex sound field and for several common types of synthesised environmental noise, even in the presence of head motion.

eess.SY