Research On The Method Of Improving Reliability Of Color Coded Structured Light

In recent years,with the rapid development of manufacturing,biomedicine,cultural relic protection,virtual reality and other fields,the requirements of ThreeDimensional(3D)measurement technique are becoming much higher now.Typical 3D measurement methods cannot meet the requirements of high efficiency,non-contact and high precision.The 3D measurement methods based on structured light has the advantages of high efficiency,no contact,simple system,low cost,and has a good application prospect in industry and other fields.At present,structured light system based on black-and-white coded has high reliability and has been applied in the industrial field,but it has low coding efficiency and cannot adapt to high-speed or realtime measurement scenarios.The structured light system based on color coded improves the measurement efficiency,but the reliability of its coding is easily affected by the ambient light,the color and shape of the measured object,and the decoding error will greatly reduce the accuracy of the measurement system.Therefore,this thesis studies the low reliability of color coded structured light,introduces the concept of error correction coding in communication system,in order to ensure the accuracy of the measurement system.The thesis introduces the measurement principle of structured light system,and establishes the mathematical model of the system while the reason of error code in color structured light coding is analyzed.The model of communication system is compared with the model of structured light system,and the basis of the application of error correction coding in communication system is given.This thesis studies on several typical error correction codes in communication system,and makes a comparative analysis.According to the analysis results,convolutional codes are selected as the research object.The Markov process of digital signal transmission in 3D measurement of structured light system is studied,and the transmission model is established.In this thesis,the coding principle of convolutional code is studied,and gives the reason of its error correction function.Combining the transmission model and the error correction principle of convolutional code,the decoding method is compared and analyzed.Study the principle of MLE decoding method with high efficiency and reliability.Based on the research above,this thesis focuses on how to introduce convolutional coding and maximum likelihood decoding into color coded structured light system from two aspects of coding efficiency and reliability.There are two coding schemes are designed based on the color channel:(1)multi group convolutional code scheme is realized by shifting a group of convolutional code sequence to three groups of convolutional code R,G and B channels.The scheme uses the color sequence of three adjacent coding stripes to correct the coding sequence.And it uses the local transposition characteristics of three groups of convolutional code to carry out error correction and verification.(2)convolutional code and Gray Code are combined to ensure reliability and improve coding efficiency.Aiming at the common types of error codes.An error correction scheme based on MLE decoding method is designed,which improves the reliability of coding.In order to further improve the reliability of decoding,the common color recognition algorithms are compared.And the performance analysis of the algorithm is given to provide reference for further improving the reliability of decoding.The simulation of error correction coding is carried out with 3ds Max,the common types of error codes are simulated,and the effectiveness of the coding method,decoding method and error correction scheme proposed in this thesis to improve the reliability of structured light system is verified.