This invention provides a swing-style and high
signal-to-
noise ratio low coherence interference
demodulation devices and the corresponding
demodulation method for the measurement of displacement. In the displacement sensing method, the
optical path difference, which is built by the light reflections from the
reference surface and the
test object, varies with the displacement of the
test object. When the reflected
signal lights is sent to a low coherence polarization interference
system, the birefringent wedge formulates a
spatial distribution of
optical path difference, from which the
optical path difference of the reflection signals thus can be demodulated. In the displacement scanning method, the reflected
signal lights are collimated and transferred to a time
scanner consisting of a rotating mirror and a f-θ lens, to perform thin
light beam scanning along the longitudinal direction of a birefringent wedge. This innovation provides two
demodulation devices that are both applicable for the measurement methods. One uses a linear
camera array and the other uses a linear micropore array and single PIN photoelectric
detector, to receive interference fringes. Since the energy of the
scanning beam is highly concentrated, the signal-to-
noise ratio for low coherence interference signal is significantly higher than that of the traditional devices. In addition, the accuracy of these demodulation devices is significantly improved, because the linear
camera array and the linear micropore array maintain a consistent spatial position of the received
light spot.