Research On Several Key Technology For Multi-camera And Fringe Projection Threedimensional Measurement System

Three-dimensional imaging has been one of the hottest areas in computer vision.Fringe projection measurement uses a combination of sinusoidal grating and phase shift technology.It adopts image processing technology and the internal and external parameters of the camera to get the three-dimensional information of the surface.While the detection range of the single-camera measurement system is limited due to measurement angle of view.Multicamera measuring system which consists of multiple cameras can break through the measurement angle and detection limits,thus widen the range of applications.In this paper,we do some research of the key technology in multi-camera fringe projection measurement system,put forward some new solutions to some key problems,finally set up the actual measurement system.The main innovations are as follows:1?There existed problems such as wide distribution of the camera in the space,no public perspective between cameras,calibration of complex model in the Multi-camera measurement system.In order to overcome these problems,we propose a new multi-camera calibration method in this paper,combines of one-dimensional calibration objects and two-dimensional calibration objects to perform step-by-step calibration.First,a projector and a camera can be regarded as a measurement group,a two-dimensional planar target which has special feature points is used to perform off-line calibration of camera and projector internal parameters of a single measurement group.Second,a one-dimensional target is used to solve the relative positional relationship between all measurement groups.The one-dimensional target is placed several times in front of the measurement system,with the internal and external parameters of calibrated camera,projector and the geometry knowledge to acquire the three-dimensional coordinates of the feature points under different measurement group.With the 3D point set corresponding to the neighboring measurement groups and Least-squares to obtain the rotation and translation matrix of the adjacent measurement group.To apply this method to multi-camera measurement systems,rapid and accurate multi-camera parameter calibration is achieved.2?Current algorithm that solve the phase error caused by the Gamma nonlinearity of the projector only consider a single gamma value caused the over-compensation and undercompensation.In this paper,we analyzed the influence of the phase error caused by different Gamma values due to the influence of different luminance distributions,then proposed a phase compensation method.The projector projects a single grayscale image on a homogenous whiteboard.Using a histogram to analyze the grayscale distribution of the image collected by the camera,next the image is divided into different regions,then the phase information is used to map the sub-region information of the image to the projector plane,and the phase error model of different regions is established by the least squares method.In the actual measurement,the region information of the phase is first coarsely positioned according to the initial phase,a corresponding error compensation model is obtained,and the initial phase is compensated to solve the standard phase.Experimental results show that our method can greatly reduce the phase error and improve the accuracy of the measurement.3?In order to guide the actual grating projection measurement system design.In this paper,we elaborate the influence of the system structure and parameters such as camera parameters,baseline length,the angle between the camera optical axis and the optical axis of the projector,and the measurement distance to the measurement results;Then we discuss the relationship between the measurement error and the measurement system structural design and parameters in the two measurement models of the axis-parallel structure and the axis-convergence structure and established the error analysis model;Finally,a multi-camera structured light measurement system was built and verified by experiments for theoretical analysis.Experiments show that the theoretical analysis used in the design of multi-camera measurement systems can effectively improve the measurement accuracy of the measurement system.