Study On Optical Flow Shape Measurement Technique By Spatial Line Of View

Three-dimensional surface shape measurement technology plays an important role in optical measurement.Compared with the contact measurement technology,the three-dimensional surface shape measurement technology can obtain object information by analyzing the fringe pattern,realize the non-contact measurement of the complex object surface shape,and restore the morphological characteristics of the object.With the development of science and technology,the needs of related researchers in various fields for measurement are increasing.Three-dimensional surface measurement technology has become one of the main ways to obtain the three-dimensional surface distribution of objects with high precision.The measurement objects usually include static objects and dynamic objects.For objects,the measurement system adopts structured light illumination,which is generally composed of a projection unit and one or more cameras.It has the advantages of non-contact,full-field measurement,high precision,and low cost.It is mainly used in face recognition and detection,industrial and agricultural production,Military communications and biological engineering and other fields.In the actual measurement process,there are certain requirements for the operation process and experimental accuracy.Optical flow is widely used in computer vision.It is the projection of the object's motion in the three-dimensional space on the two-dimensional image plane.It is the medium for obtaining the object motion information on the adjacent frame image sequence.It is widely used in product inspection,object tracking,rigid body and elastic movement,three-dimensional matching,etc.The optical flow caused by the movement of the pixel can be used to measure the height of the object with high precision and restore the shape of the object.Therefore,this paper proposes a method that is different from the traditional surface shape measurement technology,which mainly calculates the fringe deformation by optical flow to obtain the height distribution.The research content is as follows:1.Introduced the main methods of traditional three-dimensional surface measurement,including: phase shift measurement technology and Fourier transform measurement technology.First,introduced their respective technical principles and advantages and disadvantages;Then,explained the optical flow field calculation principles and several differential algorithms under different constraints.2.Proposed a new technique of measuring the normal surface shape based on the L-K local optical flow in the space line of sight coordinate.From the perspective of optical flow,the changes of the two projection fringe patterns after being modulated by the height of the object are studied.The L-K local optical flow algorithm is used to calculate the optical flow generated before and after the stripe is deformed.According to the theoretical relationship between the optical flow and the height of the object,the three-dimensional surface distribution of the measured object is directly calculated.This module gives the measurement principle,designs the experimental light path,and obtains the coordinates of the intersection of the projected light and the observed light under the condition of parallel light projection.The simulation verification is divided into three parts: the first step is to simulate the spherical cap with parallel stripes,which shows that the spatial line-of-sight coordinate method based on the L-K local optical flow can achieve surface shape measurement and is feasible;the second step is to use parallel stripes Simulating a trapezoidal object shows that the method has high resolution for different measurement objects;the third step,using irregular fringes to simulate a spherical cap,shows that the method does not have high requirements for the fringe pattern projected on the surface of the object.Finally,it is verified through experiments that the spatial line-of-sight coordinate method based on the LK local optical flow can measure the three-dimensional surface shape distribution of the object with high accuracy,and compared with the Fourier transform profilometry,it proves the feasibility of the method.3.Proposed a new technology of camera longitudinal motion surface profile measurement based on H-S global optical flow.It also analyzes the change of the projection fringe pattern caused by the longitudinal movement of the camera from the perspective of optical flow.The H-S global optical flow algorithm is used to calculate the optical flow generated before and after the stripe is deformed.By establishing the mathematical relationship between the optical flow and the height of the object,the three-dimensional surface distribution of the measured object is directly calculated.The measurement principle of this method is given,the experimental system is designed,and the simulation and experimental verification are carried out.