Study On 2D Processing And 3D Reconstruction Of CT Log Images At Different Temperatures

In recent years,wood nondestructive testing technology and digital image processing technology have developed rapidly.As an advanced method of wood nondestructive testing,Computed tomography(CT)has advantages including image without overlapping,high spatial resolution,accurate and intuitive,and direct digital processing.Therefore,CT detection technology has been widely applied in the field of wood nondestructive testing.In this paper,three disks of Abies fabri、Cunninghamia lanceolata and Pinus koraiensis were used as specimens.The samples were scanned at different temperatures(15℃.-5℃ and-20℃),and a series of CT 2D tomography images were obtained.On this basis,combined with CT technology and digital image processing,the research included:the study of the distribute regulations of CT values in log tomography images,the study of pseudo color processing of log tomography images,and the study of 3D reconstruction of log tomography images.Through these studies,thg paper was expected to provide new ideas and technical means for identifying internal structural changes(including water state,etc.)of logs and living trees at different temperatures(especially at low temperatures),and laid the foundation for further research.The main research works were summarized as follows:(1)By picking up CT values of the characteristic points in different directions on the log CT images,the variations of CT values on the log CT images were summed up.The correlation between temperature and CT values of cross section in logs was analyzed,and the changes of CT values with temperature and its reasons were discussed.It can quantitatively reflect the changes of wood interior at different temperatures,and provide a basis for further study of temperature on the changes of wood internal moisture state and content.(2)Based on the idea of CT image intuitive analysis,using the gray level-color transform method,image pseudo color enhancement based on two coding methods of rainbow code and hot metal code is implemented.Then,the enhancements and characteristics of two methods for CT images at different temperatures are compared,analyzed and evaluated.The evaluation results show that pseudo color enhancement can significantly improve the visual resolution,reduce visual judgment error,and provide a new idea for studying of the changes of internal structure and components at different temperatures.(3)Using 3D reconstruction technology to reconstruct the log CT images,all kinds of information inside the wood can be accurately obtained.In this paper,MIMICS software was used to reconstruct the 3D model of logs.Comparative analysis of the changes of the 3D models in different intervals and the colour profile of different perspectives inside the models at different temperatures were made.The changes of the internal structure of the logs at different temperatures are discussed.All this lays a good foundation for further study of the temperature changes in the internal structure and moisture distribution of logs.At the same time,by segmenting heartwood and sapwood of the logs,the corresponding 3D model was established.The method has the advantages of simple and easy to use,better 3D reconstruction and faster calculation speed.It can be further applied to the rational utilization and virtual sawing of wood.