Research On Embedded High-speed 3D Shape Measuring Technology Based On Single Binary Code Structured Light Pattern

The three-dimensional measurement technology of structured light has been widely used in many fields of material processing engineering,which solves a large number of three-dimensional measurement and detection problems in the process of material processing.Three-dimensional measurement technology for the material forming performance evaluation,forming accuracy evaluation and improvement of the forming process to provide basic data.With the development of technology,the industry also on the three-dimensional measurement technology put forward higher and higher requirements.Three-dimensional measuring device used in industry will be upgrade to the next line,and implementation of embedded high-speed measurements and make decisions for the production line,instand of the offline measurements in the past.Embedded high-speed three-dimensional measurement equipment will become an indispensable part of a variety of materials processing production line,to achieve full product testing,and even feedback control of the production system to repair product defects.In addition,auricle defect identification,traffic accident measurement,oral denture customization and other fields on the three-dimensional measurement speed,computational efficiency and integration also made the same requirements.Therefore,it is urgent to study and develop the embedded high-speed three-dimensional measurement technology and equipment to meet the above three-dimensional surface measurement needs.However,the existing three-dimensional measurement technology of surface structure light still has the following challenges:(1)the three-dimensional measurement technology of various surface structures has different emphasis on measurement speed,measurement accuracy and spatial resolution because of its coding quantity and coding form,difficult to balance.Single frame coding method for high-speed measurement,but there are still low spatial resolution,poor stability and other issues.The multi-frame coding method has a high spatial resolution,but it is necessary to reduce the number of coded images to increase the measurement speed.(2)the existing three-dimensional measurement system is generally used X86 computer platform for three-dimensional reconstruction of the calculation,high-speed measurement brings huge amounts of data and computing on the computer’s high-speed data transmission and floating-point computing power put forward higher requirements.In the application of material processing engineering,the use of X86 architecture as a platform for low integration,is not conducive to integration with other systems.In order to the key problems in embedded high-speed precision 3D measurement system realization,this paper makes a study on:the PMP algorithm based on FPGA(Field Programmable Gate Array),single-frame coded light three-dimensional measurement algorithm,high-speed three-dimensional measurement application development.These research contents provide an important technical basis for the realization of industrial embedded 3D measuring equipment,which has important theoretical and technical value.The single-frame coding method based on neighborhood avoids the influence of motion error and is suitable for high-speed measurement.However,its stability and spatial resolution in complex surface need to be solved by reasonable coding design.Therefore,the coding method of 2 × 2 minimum neighborhood based on De Bruijn queue is proposed,and the coding pattern of black and white binary is designed.The designed coding pattern is suitable for high-speed projection and has the maximum density of feature points.An accurate corner extraction algorithm based on the principle of double path symmetry is proposed to realize the accurate extraction of corner points under projection defocusing conditions.A template decoding method based on gradient extremum is designed to realize high accuracy decoding.The final realization of single-frame structure of light-coded three-dimensional measurement,measurement results with high accuracy,good stability.The key to implementing embedded high-speed measurement is the customization of low-power embedded computing units.This paper proposes a high-speed FPGA architecture for the phase measuring profilometry(PMP)algorithm.The whole PMP algorithm is designed and implemented based on the principle of full-pipeline and parallelism.The results show that the accuracy of the FPGA system is comparable with those of current top-performing software implementations.The FPGA system achieves 3D sharp reconstruction using 12 phase-shifting images and completes in 21 ms with 1024 ×768 pixel resolution.To the best of our knowledge,this is the first fully pipelined architecture for PMP systems,and this makes the PMP system very suitable for high-speed embedded industrial 3D shape measurement applications.Based on the above-mentioned technical research and theory,this paper develops a set of high-speed three-dimensional surface measurement system based on FPGA.In view of the application requirements of forensic disability identification and automatic robot arm measurement,a high speed measurement system is developed in the application of methods and techniques,and achieved good results.On the one hand,an automated data processing algorithm for auricle defect measurement is developed to achieve accurate calculation of the maximum projection area and the auricle defect ratio.In the forensic clinical made a good application.On the other hand,the hardware linkage program based on the industrial robot arm has been developed,and the good connection between the measuring system and the industrial robot has been achieved,and the application has been made well in the industrial field.