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.