Study Of 3D Point Cloud Acquisition Based On Laser Interference Fringe

With the development of Internet and the entry of Intelligent Manufacturing in the field of industrial manufacturing,the measurement of physical information such as volume,color and shape of objects becomes more and more important in industrial measurement.The research of object shape measurement or three-dimensional information reconstruction technology is very active in the field of industrial measurement.In object contour measurement technology,it can be divided into contact and non-contact measurement methods according to the measurement methods;contact measurement such as traditional mechanical probe method,non-contact measurement such as grating projection,laser interference and so on.Non-contact measurement is especially studied in the field of fast and efficient measurement because of its fast and adaptable to various sizes of object measurement,combined with computer vision algorithm which is very convenient for automation.According to the principle of the above three-dimensional measurement,the measuring accuracy and range are also different,and the measuring speed and accuracy are also quite different.For example,the traditional mechanical probe method is time-consuming and has high accuracy.Although the commonly used grating projection method can achieve high accuracy and real-time,it can only measure objects in close range due to the external illumination environment and small measuring range.Physical and other shortcomings.In addition,multi-view method is often used in passive three-dimensional measurement.This method does not need to transmit measurement signals to the surface of the measured object,but it requires a higher algorithm for camera equipment and image processing part,and has a worse error rate.Laser,as a coherent light source with good monochrome and high brightness,has irreplaceable advantages in the field of three-dimensional measurement of objects.In this paper,laser fringes are used as light source in three-dimensional measurement,including laser fringes based on laser shearing interferometry and linear laser fringe arrays spliced together.The software and hardware system based on laser shearing interferometry and linear laser array is built.The former uses interference to produce fringes,which can produce very fine interference fringes.It can be used with microscopic equipment to achieve high-precision measurement.The use of line laser can improve the measurement of environmental light interference,and does not need to use the advantages of band-pass filter,in the rapid measurement has great advantages.Phase profilometry and monocular camera calibration are used to reconstruct the measurement algorithm.The former obtains fine modulated object information for small size and rich details,obtains two-dimensional phase distribution of small object by Fourier transform profilometry,and reflects the actual phase relationship of measured object by unwrapping algorithm.Then,according to the relationship between height and phase of shearing interference object surface,the smaller object profile information can be obtained.The method of monocular camera calibration and reconstruction can quickly acquire the three-dimensional information of the object under test,and the point cloud information of the object can be accurately acquired by high-precision calibration.In this way,the camera parameters at any position can be obtained by multi-position calibration along the depth of field.The relative position of each laser line can be determined by the calibration of the depth plane,and then the laser fringes can be extracted.The corresponding depth information is restored,and then OPENGL is used to reconstruct the point cloud to generate the surface contour.