Digital Demodulation Using I/Q Signals and Optical Phase Control Applied to a Vibrometer

• Autor(a) principal: Galvez-Limaco, Angel Manuel [UNESP]
• Data de Publicação: 2020
• Outros Autores: Galeti, Jose Henrique, Nelli Silva, Emilio Carlos, Higuti, Ricardo Tokio [UNESP], Connelly, Michael J., Kitano, Claudio [UNESP]
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Institucional da UNESP
• Texto Completo: http://dx.doi.org/10.1109/JSEN.2020.2997900; http://hdl.handle.net/11449/209603
• topic: Optical interferometry; Optical sensors; Laser beams; Adaptive optics; Piezoelectric materials; Semiconductor device measurement; piezoelectric transducers; signal processing; metrology

An efficient and cost effective optical phase detection vibrometer based on a modified closed loop homodyne Michelson interferometer is presented. Real-time phase demodulation is carried out, using an embedded platform that performs data acquisition, signal processing, PI (proportional-integral) control and the generation of signals that drive the electrooptic Pockels cell phase shifter and the piezoelectric actuator under test. Two phase quadrature signals are generated from a single interferometric output, using the interleaving action, in alternation, of a digitally generated modulating signal, and then the well-known differential-cross-multiplication technique is applied to perform the computation of the phase shift of interest. The quadrature condition is reached using the PI loop based on an error signal obtained from a Lissajous figure derived from out-of-phase signals. The vibrometer is capable of measuring nanometric displacements, and is simple, inexpensive, accurate, immune to fading and self-consistent. The new method was used to determine the displacement frequency response curves of two prototypes of multi-actuated flextensional piezoelectric actuators. Measurements were made between 500 Hz and 15 kHz, and the results agreed with those obtained by the standard SCM-Signal Coincidence Method.