Research On Polarization Measurement Method Of Transparent Object With 3-D Profile

In today’s situation,high-precision measurement technology plays an indispensable role in the machine-building industry,precision measuring instruments,and high-precision processing instruments.As the need for increased measurement accuracy grows,measurement methods become more complex.These industries with high precision measurement needs have undergone profound developments and innovations.It is difficult to achieve the high precision reconstruction of transparent objects to be measured for many measurement targets.The low reflection ability of transparent objects to be measured and the complex reflection and refraction of internal light will cause the missing texture of transparent objects to be measured,and the traditional 3D reconstruction methods are difficult to achieve the reconstruction of their surfaces.Therefore,it is of great theoretical and practical significance to study the high-precision contour reconstruction of the surface contour of transparent objects.In this paper,we study the measurement method of the 3D contour of a transparent object,take the transparent optical glass made of H-K9 as the research object,conduct polarization analysis on its surface contour to obtain the normal distribution,then use the normal vector of the measured surface as the research object,use 3D reconstruction algorithm to realize the contour reconstruction of the measured transparent object,and finally conduct experimental verification.The details of the study are as follows:(1)When measuring the surface of transparent objects,due to the surface reflection characteristics of transparent objects,their surfaces have weak reflected light,and the second surface has strong interference reflection,the CCD collects less reflected light,and there is a loss of surface information,causing measurement errors.Therefore,this topic introduces the idea of polarization measurement and establishes a polarization measurement model with reduced interference from other reflected light.(2)Stokes vector is used to describe the polarization state of reflected light on the surface of a transparent object under right circularly polarized light illumination conditions,to represent the angle of incidence and the azimuth of the incident surface by the Stokes vector obtained by the rotating wave sheet method,to fix the position structure of the illumination system in the measurement system,and to eliminate the ambiguous values of the azimuth of the incident surface that exist.The mathematical model of the normal vector gradient is established on the surface of the transparent object according to the polarization state of the incident light by the polar coordinate form of the incident angle and azimuth angle.(3)The pixel plane is projected onto the object plane according to the Zhang Zhengyou camera calibration method.The normal vectors in the pixel coordinate system are projected to the object surface coordinate system for subsequent contour reconstruction using the coordinate transformation relationship.(4)A Fourier gradient integration reconstruction method based on the improved Southwell model is proposed to reconstruct the normal vector gradient data in three dimensions.Since the Fourier gradient integration reconstruction needs to make the gradient data meet the periodicity condition,an antisymmetric periodicity method is used to expand the gradient matrix to realize the periodicity requirement of the discrete Fourier gradient integration method for the integration surface type.The accuracy of the reconstructed contour height is compared with that of the traditional Southwell model and the differential sampling model to verify the accuracy of the height reconstruction of the improved model.(5)By building an experimental platform,the surface profile normal vector data of transparent objects are measured and reconstructed.