Liquid level measurement system based on a coherent optical sensor

A liquid level sensor based on a new optical technique is proposed and demonstrated. By using the wavelength modulation which takes place in the laser diode it´s possible to extract the absolute distance of a target from the induced self-mixed effect. The optical properties of liquid surface have been studied both in static and dynamic conditions, in order to optimize the back-reflected light. This point has determined the guidelines for the optical and electronic project. The prototypal device developed has allowed to measure and track the liquid level during a filling process.