| The planar displacement measurement system based on two-dimensional grating,which is referred to as two-dimensional grating measurement system hereinafter,has the advantages of high precision and high environmental stability,and it is widely used in high-precision planar displacement measurement occasions.The calibration of twodimensional grating measurement system is the key to ensure its measurement accuracy.However,the calibration of two-dimensional gratings mostly relies on the atomic force microscope to measure the microstructure parameters,whose measurement range is limited,and it is not suitable for large-scale two-dimensional gratings;the calibration of two-dimensional grating measurement systems mostly uses laser interferometer to calibrate in one direction,which can not calibrate two directions at the same time.Therefore,a two-dimensional grating calibration system based on the principle of coplanar orthogonal dual-axis laser interferometer was designed in this paper.The structure and hardware of the experimental device was built.The error model of the experimental device was established,and the geometric error analysis of the calibration device was studied.The two-dimensional grating calibration experiment device can achieve the simultaneous dual axis calibration of two-dimensional grating measurement system more than 100mm×100mm.The main research work of this article is as follows:(1)The calibration requirements of the two-dimensional grating measurement system were analyzed.The key technologies to realize the two-dimensional grating calibration function and calibration accuracy improvement were clarified.And the overall implementation scheme based on dual-axis laser calibration was designed.(2)The two-dimensional grating calibration method based on orthogonal dualaxis laser interferometer was proposed.The laser interferometer measurement method of the coplanar orthogonal two-dimensional plane mirror interferometer was described.In this method,the two-dimensional grating performs planar movement with the movement platform,and the probe of grating was fixed to the device.Each direction was measured using a differential interferometer and a long plane mirror to ensure the signal continuous within the two-dimensional measurement range.An environmental parameter compensation system based on the Edlen formula was set to achieve realtime correction of the laser wavelength.A synchronous control system was used to realize the synchronous recording of the laser and the grating indication under the external trigger pulse control.And the calibration function of two-dimensional grating was realized.(3)The main geometric error sources of the experiment device were analyzed.The models including straightness errors and angle errors were established.According to the structural characteristics of the two-dimensional grating system,the influence of the installation error of the two-dimensional grating was analyzed.A coordinate transformation model for installation error was established.The rotation and coordinate system of the two-dimensional grating installation plane were proposed respectively.A three-point level adjustment support device was designed.(4)The two-dimensional grating calibration experiment device was built.The automatic control measurement software based on C# was developed.The functional modules were realized by using host computer communication.The two-dimensional grating calibrating experiment was carried out using incremental two-dimensional grating to test the function of the device.The experimental results showed that the measurement error in the x and y directions of the experimental device was effectively reduced after correction.The principle validity of the error correction method was verified,and the function feasibility of the experiment device was verified. |
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