Research On Heterodyne Grating Displacement Measurement System With High/Low Displacement Resolution

Precision displacement measurement technology is not only a benchmark of the level of a country's industrialization,but also the foundation of rapid development of a country's advanced manufacturing,advanced processing industry and so on.Since the 21 st century,it has been a challenge about how to develop precision displacement measurement technology with the gradual pace of industrial modernization.As a typical precision displacement measurement device,the grating displacement measurement system has been widely used in many kinds of precision displacement measurement occasions because of its high precision,high resolution,strong anti-interference ability,compact structure and low cost.However,almost all of the grating displacement measurement systems have one displacement measurement resolution,they can not take into account the large range with low displacement resolution and the short range with high displacement resolution,simultaneous.So studing a kind of grating displacement measuring system with high/low displacement resolution is not only a technical solution model of multi-displacement resolution grating displacement measurement system,but also an important practical significance to promote the grating displacement measurement system development.A heterodyne grating displacement measurement system with high/low displacement resolution is proposed.The main contents are as follows:In order to analyze the basic theory of heterodyne grating displacement measurement system,the theory of heterodyne interferometry was analyied.Meanwhile the basic principle of heterodyne method,the principle of shift-frequency and the measurement of phase difference were studied.Then I analyzed the theory of grating displacement measurement including the diffraction characteristics of gratings and the basic principles of grating displacement measurement based on the Multi-slit Diffraction and Doppler Effect.The optical system of heterodyne grating displacement measurement system with high/low displacement resolution is designed.In order to achieve high/low displacement resolution,I designed the optical path structure with three gratings.The effiective grating pitch formulas and the operation method of the displacement information of the high/low displacement resolution part are deduced.The principle of selecting the three gratings' grating pitch is discussed.Meanwhile,the main error sources of the system are discussed,which mainly includes the pitch errors of the grating,the grating structure's error,the periodic nonlinear error caused by the defects of polarized optical elements such as polarized beam spilit and polarizer,etc and the influence of other error sources.Finally,the experimental system was completed.The effiective grating pitch measurement is firstly carried out.The effiective grating pitch of the high displacement resolution part is 0.41 ?m and the low displacement resolution part is 17.02 ?m respectively.The experimental result verified that the system can realize the high / low displacement measurement.Then the long/short range displacement measurement is performed.In long range displacement measurement,the low displacement resolution was 1.2488 ?m,0.9828 ?m and 0.485 ?m displacement deviation with 1000 ?m,500 ?m and 100 ?m displacement respectively.In short range displacement measurement,the high displacement resolution part was 5 nm and 0.4 nm displacement deviation with 100 nm and 20 nm displacement respectively,the experimental data are coincided for the proposed system and HP5529 A in 14 ?m?10 ?m and 5 ?m displacement measurement.Finally,for the system stability,in 7 minutes stability test,the high displacement resolution part and the low displacement resolution part get 0.3 nm and 10 nm stability respectively.All the experimental results show that the designed heterodyne grating high/low displacement measurement system has good ability.