Processo de esmerilhamento, polimento e caracterização de um Shear Plate

Shearplate is an optical glass plate having two flat surfaces and a small angle between them. The use of a high quality shear plate is essential to implement shear interferometric technique . The shear interferometry is a technique used to evaluate the light beam collimation. In order to guarantee the shearplate quality , the complete manufacturing process must be thoroughly monitored. In the manufacturing process, the first step consisted of the glass selection. The selected glass has been submitted to the process of cutting, gluing, chamfering, grinding and polishing. Each phase has been strictly monitored. The quality of the final result depends extremely on an appropriate starting condition, which arises from the grinding process, as the polishing process only recovers the brightness of the part, acting on a small scale on the wearing off of the part, as well as not changing the structured obtained in the grinding process. Respecting all stages of the manufacturing process, the quality of the part has evolved to a good result. The best result obtained showed PV distance of 162 nm, slightly less than λ / 4. This result is significant because the dimensions of the piece with respect to the dimensions of the polisher what interferes directly in the results. The closer are the dimensions of piece and the dimensions of the polisher, the greater the difficulty in controlling the propagation of errors

Michelson interferometer vibrometer using self-correcting synthetic-heterodyne demodulation

Synthetic-heterodyne demodulation is a useful technique for dynamic displacement and velocity detection in interferometric sensors, as it can provide an output signal that is immune to interferometric drift. With the advent of cost-effective, high-speed real-time signal-processing systems and software, processing of the complex signals encountered in interferometry has become more feasible. In synthetic heterodyne, to obtain the actual dynamic displacement or vibration of the object under test requires knowledge of the interferometer visibility and also the argument of two Bessel functions. In this paper, a method is described for determining the former and setting the Bessel function argument to a set value, which ensures maximum sensitivity. Conventional synthetic-heterodyne demodulation requires the use of two in-phase local oscillators; however, the relative phase of these oscillators relative to the interferometric signal is unknown. It is shown that, by using two additional quadrature local oscillators, a demodulated signal can be obtained that is independent of this phase difference. The experimental interferometer is aMichelson configuration using a visible single-mode laser, whose current is sinusoidally modulated at a frequency of 20 kHz. The detected interferometer output is acquired using a 250 kHz analog-to-digital converter and processed in real time. The system is used to measure the displacement sensitivity frequency response and linearity of a piezoelectric mirror shifter over a range of 500 Hz to 10 kHz. The experimental results show good agreement with two data-obtained independent techniques: the signal coincidence and denominated n-commuted Pernick method.

Medição interferométrica de fase óptica através do método de segmentação do sinal amostrado

Pós-graduação em Engenharia Elétrica - FEIS