title: Optical system for liquid level measurements.
abstract: This work describes the development of a novel laser instrument for non-contact liquid level measurements. The physical principle of operation is based on the self-mixing effect induced in the laser diode by modulating the laser wavelength. The frequency main tone of the resulting fringes is proportional to the absolute target distance. A high speed FPGA (Field Programmable Gate Array) electronic performs the data acquisition and elaboration. The high elaboration/acquisition speed improves the chance of acquiring good signal also on a moving liquid target. The optical characteristics of the liquid surface have been studied in order to identify the optimal optical configuration when the surface is flat as well as when the surface is rippled. The final low-cost instrument works in real time and is able to track a filling process with 2.5 cm/s of speed, with resolution better than 1 mm for distances up to 50 cm.
authors.affiliation: Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milan, Italy.
authors.forename: D
authors.initials: D
authors.lastname: Melchionni
authors.affiliation: Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milan, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Norgia