Rapid 3D Reconstruction Method Based On Multi-polarization State Encoding Gray And Sinusoidal Structured Light Fringe In Single Exposure Time

The application of structured light 3D measurement technology is of great significance to industrial production.With the upgrade of industrial production,the measurement environment and optical properties of the surface of the objects to be measured become more and more complicated.How to reduce the structured light measurement error and ensure the stability of the measurement system has become one of the important fileds of the development of structured light measurement system.Most of the up-to-date researches on structured light measurement use light intensity as information transmission channel.However,the intensity of light is easily affected by the optical properties of the environment and object surface’s propertise in the process of transmission,which eventually makes the SNR of structured light encoded data captured by the camera low or even the loss of encoded data,resulting in decoding difficultly.The polarization properties of light provide an additional channel of information.Compared with light intensity,the polarization properties of light are more stable in complex environments.Therefore,two kinds of 3D measurement techniques of multi-polarization coded structured light are proposed to improve the speed and accuracy of three-dimensional measurement of structured light.First,a technique based on multi-polarization state encoding Gray structured light is proposed,which improve the traditional black-white level encoding Gray structured light,analyzes the multi-polarization characteristics of the projected light of the liquid crystal projector,and indicates that the polarization of the projected light has stable transmission characteristics in the structured light measurement system.That is,the polarization of projected light still keep the characteristics of original polarization after being reflected from the surface of the object.This technology encodes the encoded information of Gray structured light in the polarization state of polarized light.During the acquisition of polarization information by the camera,no additional rotate operation of the polarizer is required,and high-quality 3D point cloud data of the surface of a wide range of reflectivity can be obtained in a single exposure time.The polarization enhanced Gray image is not related to the reflectivity of the object’s surface,the sensitivity coefficient of the camera and the exposure time,but related to the polarization intensity of the multi-polarization coded Gray structured light in a certain direction,and the DOLP algorithm to calculate the polarization enhanced Gray fringe pattern is easy to implement.Experimental results implicate that this technique greatly improves the measurement speed and can obtain relatively complete 3D point cloud data of large range of reflectivity objects’ surface within a single exposure time.What’s more,the technology of coding sinusoidal structured light based on multipolarization superposition is proposed.The technology uses liquid crystal projector to construct polarized structured light different from traditional gray sinusoidal structured light to solve the phenomenon of spike,fracture and low signal-to-noise ratio due to overexposure and underexposure of traditional gray sinusoidal structured light coding.Through the projector projection of the color of the light and the polarization model is set up between the polarization states of light,the polarization sinusoidal structure light structure formed by superposition of multiple polarization states,at the same time camera get to contained sine structure light polarization of the phase information without rotating polaroid,makes sinusoidal fringe pattern that waveform quality improved when the measurements of the objects’ surface with a wide range of reflectivity.Because only require one exposure time to obtain high quality sinusoidal fringe patterns,the measurement speed is greatly increased.Experimental results show that this technique improves the quality of sinusoidal structured light fringe,the continuity of unwrapping phase and the accuracy of 3D point cloud data.