Device for the measurement of a displacement of an object using a self-mixing technique

摘要

A device for the measurement of a displacement of an object (2) uses a self-mixing technique. A laser (1) such as a laser diode having a laser cavity and allowing mode hopping to occur is used in conduction with an external cavity (12) encompassing the laser cavity (11) and being linked to said object (2). A first photo detector (31) is provided to measure the AM variation of the laser signal of the laser (1). The device further comprises an optical-frequency-to-intensity-converter (3) receiving a laser signal of the laser (1). This converter can be a Fabry-Perot resonator eg. in the form of a PMMA film. A second photo detector (4) is provided receiving the converted signal (24) transmitted through the optical-fequency-to-intensity-converter (3) to generate a frequency modulated output signal representing the displacement or velocity to be measured.