Research On Structured Light Generation Systems For Three-dimensional Measurements

3D measurement of objects is an effective way to obtain 3D information of objects.How to obtain 3D information accurately and quickly through 3D measurement is the development requirement of modern manufacturing industry.As a new 3D measurement technology,structural light measurement technology has been widely used in industrial production and daily life due to its high precision and real-time characteristics.With the increasing demand of 3D measurement technology for miniaturization of products and diversification of environment,the traditional projector method of generating structured light is gradually replaced by laser projection of structured light in some cases.Whether refractive-generating line structure light or through diffraction to produce surface structured light,There is still a certain deficiency in the structured light projected by the laser.(1)Traditional refraction can only produce a single line of structured light,and multiple lines can only be produced by diffraction and the resulting lines have spot.(2)The distortion of shape in the way of diffraction structure light at large angle will affect the accuracy of measurem ent.Therefore,how to overcome the defects of structured light in this way is also an important research direction to improve the quality of 3D measurement.In this paper,by studying the problems of refraction and diffraction in the 3D measurement of structured light and combining with the actual demand of 3D measur ement,the author have improved and designed the scheme of generating structured light.Firstly put forward a kind of surface structud light diffractive optical element which based on Rilisol Murphy integral can produce large angle without distortion and the light intensity is uniform.And aiming at the deficiency of the existing line structure light generation scheme,put forward a kind of Powell prism and beam splitter are superimposed to produce a multi-line optical optical system with strong uniformity.In addition,according to the practical use of laser generated structured light for 3D measurement,design a laser module with high perpendicularity and good stability,and designed DC Motor Control Scheme based on 51 single Chip Microcomputer,using to control the laser module to keep a constant relative position with the object under test in the laser scanning measurement,so as to improve the measurement accuracy of the 3D measurement system.The main work of the thesis is as follows:(1)Analyzing the shortcomings of the existing structured light source for 3D surface structured light measurement using diffractive optical elements : The light intensity of theprojected structure is unevenly distributed,the resulting structured light pattern is different from the ideal pattern in the case of distortion.According to the problems,proposing a diffraction element design method based on Rayleigh Murphy integral which can produce uniform light intensity and large angle projection without distortion,at the same time,making simulation and testing for the method.(2)Analysed the shortcomings of 3D measurement of linear structured light source:The intensity of the structure ray strips produced by the cylindrical mirror is Gauss distribution,traditional optical systems can only produce single-line structured light.According to the existing problems,proposing an optical system scheme: Powell prism superposition beam splitter produces multi-line structured light,making simulation and testing for the method.(3)According to the design scheme of(1)and(2),designing structured light generation module,to ensure the stability of the relative position between the laser and each optical element during the structural light projection,using loadable design and can be used according to different requirements,adjust the relative position of each device.In the actual process of 3D measurement of line structure light,it is necessary to control the condition of the structured light module to scan the measured object,a control system based on STC89C52 SCM microcomputer is developed.The system can keep constant distance between the module and the measured object during the scanning process.Thus ensuring the clarity of the projection lines to improve the accuracy of the 3D measurement.