Research On Binocular Stereoscopic Deflection Measurement Technology Based On Reflection Law

With the rapid development of modern industrial manufacturing technology,mirror object components are widely used in many industrial production and manufacturing fields such as aerospace,national defense and precision optics.The industry has high quality and performance requirements for mirror object components,so the threedimensional(3D)shape measurement of mirror object components has attracted the attention of many researchers at home and abroad.The traditional contact coordinate measuring machine(CMM)cannot meet the requirements of modern industrial measurement due to the possibility of damage to the surface of mirror object components.The fringe projection 3D topography measurement method based on modern optical technology is no longer applicable due to the special reflection characteristics of the component surface.On this basis,the evolution of the fringe reflection 3D topography measurement technology can avoid the influence of mirror surface reflection.And it is widely used for 3D morphometry of mirror surface object components because of its high accuracy,fast measurement speed,non-contact and simple structure.The main research contents of this paper are as follows:Since camera calibration is a necessary step before the vision measurement system can carry out the measurement task,the measurement accuracy of the system is directly affected by the calibration accuracy,so this paper first studies the traditional camera calibration technology,and then studies the specific calibration method of smartphone camera.As the front and rear cameras of smartphones are integrated in the form of back-to-back installation inside the phone,there is no common field of view between the front and rear cameras,and the traditional camera calibration method is difficult to solve the smartphone front and rear camera calibration problem.In this paper,a calibration method of over-the-horizon camera based on plane mirror reflection is proposed.Firstly,the front camera with target in the field of view is calibrated directly by the traditional plane calibration method.Then,a plane mirror coated on the reflector is introduced,which reflects the target only appearing in the front camera field of view in the rear camera field of view to calibrate the rear camera.In turn,the pose relationship between the same target and the front and rear cameras is obtained to complete the system calibration.Finally,a binocular measurement system composed of a single smartphone and a multi-camera measurement system composed of two smartphones are built for experimental verification.The experimental results show that the proposed camera calibration method for smartphones with no common field of view is feasible.Analysis of the causes of reflection point ambiguity in the application of monocular fringe reflection measurement technique to specular reflection measurements,and the elimination method of the ambiguity of reflection points is researched.A method based on the law of reflection is designed to eliminate the ambiguity.The principle of this method is to introduce an auxiliary camera to form a binocular measurement system.On the basis of the normal consistency of the reflection point,a parameter equation is constructed to determine the 3D coordinates of the reflection point through onedimensional parameter search on the known visual light of the measurement camera.In this paper,a detailed derivation of the proposed method is presented.An experimental system is built to verify the feasibility of the proposed method,and a 3D surface shape measurement is performed on a concave mirror with specular reflection characteristics.The experimental results confirm that the method can effectively solve the ambiguity problem in the measurement system.