Novas configurações de interferômetros de quadratura e de técnicas de detecção de fase óptica baseadas em phase unwrapping

• Ano de defesa: 2014
• Autor(a) principal: Lemes, Andryos da Silva [UNESP]
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Estadual Paulista (Unesp)
• Palavras-chave em Português: Interferometria; Interferometros; Instrumentos oticos; Interferometry
• Link de acesso: http://hdl.handle.net/11449/111112

Optical interferometers with single outputs are very sensitive when operating close to the phase quadrature point of their input-output characteristic curves. However, low frequency environmental fluctuations generate random drifts between the optical paths of the interferometer that deviate the quiescent point from the quadrature condition. This problem causes the phenomenon called signal fading. By electronically processing these two interferometry output signals, shifted by 90º, it is possible to demodulate the signal regardless of environmental drift. These kinds of interferometers, known as quadrature interferometers, are widely used in metrology laboratories, but, due to the large amount of optical components, they are expensive and difficult to design. In this work a low cost homodyne interferometer with two output quadrature beams based on the Michelson configuration is studied, and the procedure to achieve the quadrature signals is mathematically described. Also, a recent technique, not widely known in the literature and that is able to obtain two quadrature signals by using the standard configuration of the Michelson interferometer is explored, exploiting the spatial distribution of the fringe pattern. A new method for optical phase shift demodulation based on phase unwrapping is developed. This approach is able to recover not only the modulation signal waveform, but can also calculate the static phase shift between the interferometer arms when the modulation signal has an average value equal to zero. The method also has the ability to demodulate signals which vary arbitrarily in time. Computational test were done aiming to demonstrate the technique potential. By using this new optical phase shift demodulation method, combined with the proposed interferometer and exploiting the spatial distribution of the fringe pattern, a piezoelectric flextensional actuator is characterized. Displacement versus drive voltage and frequency ...