Study On Laser Heterodyne Interferometer For Three Degrees Of Freedom Measurement Based On The Faraday Effect

As the rapid development of the ultra-precision machining technology,precision working stage performance testing,microelectronics technology and biomedical engineering,higher requirements to technology and instrument for displacement and angle detecting are put forword,that is,simultaneous measurement of three degrees of freedom and measuring of nanometer level.The thesis designs a laser heterodyne interferometer for three degrees of freedom measurement method based on the Faraday effect.And the key technologies of this three degrees of freedom measurement method are studied in this thesis.By constructing a measurement system to achieve a long range and high-precision three degrees of freedom measurement simultaneously.This thesis introduces the research status of three degrees of freedom measurement technology at home and abroad.Then a laser heterodyne interferometer for three degrees of freedom measurement method based on the Faraday effect is proposed.The principle of a laser heterodyne interferometer for three degrees of freedom measurement based on the Faraday effect is described in detail.The linearly polarized light reversal method is described.The mathematical model of three degrees of freedom measurement is established.The optical layout of the measurement for three-degree-of-freedom is designed.The signal prosessing system for processing the laser heterodyne interferometric signal is designed.And the software of the system is programmed using Visual Basic language.Lastly,the nonlinearity of the three degree of freedom(X-Y-?)measurement,the influence of the combined mirror and the motion state of the interference module on the optical pathis is analyzed.And the uncertainty of the three degrees of freedom measurement is comprehensively evaluated.In order to verify the feasibility of the proposed system,an experimental setup was constructed and several experiments were conducted as follows:(1)The experiment of stability measurement.The eperimental results show that the displacement measurement system stability is better than 6nm when the experimental setup was still.(2)The comparison experiments of displacement and angle.The displacement measurements were carried out with 10 mm as steps in the range of 200 mm,50?m as steps in the range of 1mm,100 nm as steps in the range of 15?m,respectively.The angle measurements were carried out with 0.01° as steps in the range of 1°,0.1°as steps in the range of 10°,0.1°as steps in the range of 20°.The displacement measuring result is compared with the measuring result of Renishaw interferometer,the maximum and the standard deviation of the measurement error were 52.6nm and 22.3nm,17.1nm and 6.4nm,6.9nm and 1.5nm.The angel measuring result is compared with the measuring result of Renishaw interferometer,the maximum deviation and the standard deviation of the measurement error were 0.27?and 0.05?,10.97?and 3.1?,10.97?and 3.1?.(3)The experiments of X-Y-? simultaneous measurement,which were carried out with 1mm,1?m and 100 nm as steps,respectively.The measuring result of X direction displacement is compared with the value of linear stage,the maximum and the standard deviation of the measurement error were 0.008?m and 0.04?m,0.0026?m and 0.01?m,0.002 nm and 0.013 nm,respectively.The measuring result of Y direction displacement reflecting the straightness error of linear stage were 0.1?m,0.22?m and 14.64 nm which were in error range of ±1?m.The maximum of the measuring yaw ? result were 80.90?rad,-2.11?rad and-0.67?rad which were in yaw error 100?rad(±50?rad)of linear stage.The above experimental results show that the proposed method can achieve long range and high precision three degrees of freedom simultaneous measurement.