The invention relates to a
heterodyne type two / three-dimensional
grating displacement coarse / fine measuring
system. The
system comprises a single-frequency
laser light source, an electro-optic modulator, five
beam splitter prisms, a two-dimensional transmission type measuring
grating, seven one-dimensional transmission type measuring gratings, six
polarization beam splitter prisms, twelve polaroids, twelve photoelectric detection and
signal processing components and five plane mirrors;
laser emitted by the single-frequency
laser light source is linearly polarized single-frequency laser, the polarization direction of the laser forming a 45-degree angle with an x axis; the laser is modulated through the electro-optic modulator of which the
fast axis direction is parallel to the x axis, so that
heterodyne laser can be outputted; the
heterodyne laser is composed of an
s wave component of which the polarization direction is along a y axis and a
p wave component of which the polarization direction is along the x axis; and the
s wave component and the
p wave component have a
phase difference which changes with the change of modulated
voltage loaded by the electro-optic modulator. With the heterodyne type two / three-dimensional
grating displacement coarse / fine measuring
system of the invention adopted, errors caused by factors, such as ambient temperature and
humidity change, can be avoided; and the coarse / fine conversion of displacement measurement resolution in two / three-dimensional directions can be realized, and different measurement needs can be fully satisfied.