In order to improve the measurement precision of the traditional two-grating measurement system

high density grating is used owing to its configuration and measurement principle.A single grating measurement system using high density grating is introduced.This system uses diffractive light interference to produce original signal.It has optical fourth frequency doubling

using polarization phase-shifting method is used to obtain four signals with ordinal phase delay by 90°.Since the original signals don’t contain other harmonic component.A model machine was designed and made according to the system

in which the grating’s density is 4 17 lp/mm

and the original signal’s period is 0.6 μm.The resolution of the system is 0.586 nm after the 1 024 times electronics subdivision.The measurement results by the machine were compared with HP 5528 interferometer.The experiment results show that the precision of the system is 0.1 μm at 100mm measuring range.This linear displacement measuring system has the advantage of compact structure

high resolution

high precision.It can be used in a number of occasions where high precision linear displacement is required.