|Thesis abstract: |
During the last years, self-mixing interferometry has been considered even more as a valid alternative to the classical optical instrumentations. Its characteristics such as contactlessly, low-cost and high-resolution, allow to achieve novel kinds of measurement systems dedicated to dimensional measures. This Thesis work describes the development of four different instruments exploiting the self-mixing interferometry; the first one is a vibrometer operating in open-loop mode, which allows spatial resolution down to about 100 nanometres over an undefined spatial range. The second instrument is another kind of vibrometer, based on close-loop technology, which guarantees spatial resolution down to few nanometres, high linearity, but operating on a dynamic range of about 100 microns. A third developed device is oriented to the measure of the speed of a target, based on a particular frequency-domain algorithm; this prototype demonstrated good performances for speed until three meters per second with a resolution better than one millimetre per second. The last shown device is a rangefinder; the device takes the absolute distance measurement of a target, in the spatial range between 10 centimetres and 2 metres, with a resolution of about 100 microns. All the developed instrumentations have been studied, designed and finally implemented in a real-time electronic device, providing the results on an analog or digital output. This work also includes a novel application of the self-mixing interferometry: the holes depth measurements for high-power laser ablating systems. Thanks to its non-invasive property, self-mixing may be used to monitor the ablating processes of industrial texturing systems; different experimental tests are reported, suggesting the feasibility of this novel approach.