Basic Studies On The Lateral Shearing Interferometry With Globally Random Encoded Grating

Lateral shearing interference measurement technique is one of the most important measurement techniques in the field of optical measurement.It has the advantages of high environmental adaptability,low requirement of coherence and monochromaticity for light-source and wide detection range.The mainstream of today's technology is Quadri-wave lateral shearing interference measurement technique(QWLSIMT).Globally random encoded grating(GREG)lateral shearing interferometry is designed for the lateral shearing interference measurement technique.The basic unit of the GREG is the pixel,which is easy to process and randomly distributed on the grating according to certain constraints.The GREG has the characteristics of approaching the diffraction field of the ideal grating and it can be use as a substitute for any ideal grating,which is difficult to process.Contents of this paper include four parts:(1)In the QWLSIMT with grating as the diffractive elements,the higher-order diffraction of the grating is the most important source of systematic error.The diffractive field of the extended Hartmann mask and the randomly encoded hybrid grating(REHG)is analyzed,and the reason of the high order diffraction light of the REHG is found.(2)On the basis of the REHG,the coding rules are modified,and the globally random encoding constraint is proposed.Based on the globally random encoding constraint,The GREG is designend,which can be use as an approximate substitute for ideal grating with arbitrary transmittance function.According to the QWLSIMT,a globally random encoded hybrid grating(GREHG)is designed as an approximation.The simulation results show that the GREHG can suppress all the higher-order diffraction except the pixel light.Compared with the REHG,the GREHG has the advantages of better suppression of higher-order diffraction,more stable interferogram,more flexible shear ratio and wider bandwidth.(3)Based on the globally random encoding constraint,The globally random encoded phase grating(GREPG)is designed and applied to the QWLSIMT.Compared with the GREHG,the GREPG has the same effect to suppress the high order diffraction order light,but it has the advantages of?~2/4 times optical utilization and relatively small difficulty in processing.For the 9 beam lateral interference measurement technique,a GREPG of 9beam is designed,which shows the universality of the GREG.(4)Experiment of GREHG.It presents the process of GREHG and measure the error of processing.Compare GREHG with cross phase grating in the aspect of the stability of interferogram and the spectrum of interferogram.The result indicate a good compression of high-order diffraction.