| In recent years,with the rapid development of modern manufacturing,information technology and cultural relics protection,the requirements for three-dimensional data acquisition are increasing.Structural light three-dimensional measurement method has the advantage of non-contact and high accuracy,and has gradually become the focus of research in the field of three-dimensional measurement.Compared with black-and-white encoding,color-coded structured light measurement system improves the measurement efficiency by introducing color information,but its encoding reliability is affected by the color,shape of the object being measured and ambient light,which is prone to error codes,thus reducing the measurement accuracy.In this thesis,the reliability and efficiency of color coding are studied,and error correction code theory is introduced into communication system to improve the reliability of coding.Firstly,this thesis introduces the principle of structured light three-dimensional measurement,and analyses the cause of error code in structured light measurement and its effect on system measurement accuracy.Based on the Hidden Markov model of the communication system,a model of structured light measurement system is established.Several error correction coding methods in the communication system are analyzed and compared according to the model.The analysis results show that the cyclic code has the advantages of cyclic characteristics,simple encoding and decoding,and is suitable for application in structured light measurement.Secondly,considering both encoding efficiency and encoding reliability,a space-time color encoding method with error correction function is presented based on cyclic code.In this encoding method,code words of cyclic code are generated according to the encoding rules of cyclic code.According to the theory of cyclic code,the code words have error correction ability.The three color channels R,G and B are used as carriers to generate structured light encoding patterns.First,the gray values of the first color channel of the codeword are used to encode them.The second color channel is encoded by the shifted code word,the third color channel is encoded by the shifted code word,and so on.The shift relationship between the three channels can also be used as the basis for error detection and correction,and the error correction performance of the code is enhanced.Finally,the coding information of three channels is combined into a spatial color coding pattern.In order to increase the length of coding,the above pattern can be extended periodically,and color binary can be used for time coding for each cycle.Thirdly,a color coded pattern decoding method is designed for the above coded patterns.In order to improve the anti-noise performance of the measurement,the center of the stripe is positioned using the center of gravity method,and then the color recognition of the center of the coded stripe is implemented using the clustering method to get codewords corresponding to gray scale in three channels.The cyclic code is used to check and correct the code words in three channels,and the shift relationship between the three channels is used to check and correct the code words twice to get the final characteristic code value.In the case of periodic continuation,the color of the coding space corresponding to each period can be recognized,and then the binary decoding method can be used to decode to obtain the coding of each stripe.Finally,an experimental platform for three-dimensional measurement of structured light is designed and set up,and color-coded structured light is analyzed on the experimental platform.The codec scheme proposed in this paper can effectively improve the reliability of encoding. |
