Study On The Temperature Compensation Of Videometrics And Pose Relay Camera Network

Videometrics develops fast and is widely applied because of its impersonality, high precision and non-contact feature with the development of computer, image processing and automatic control technologies in recent years, especially for the image sensors such as CCD/CMOS becoming increasingly performance-cost. However, there are two difficulties encounterd in applying videometrics to measure the pose deformations of large structures. Firstly, video cameras have temperature effects as well as other high precision sensors such as the ring laser gyroscopes, the accelerometers, and so on, then thermal errors will be introduced when the videometrics apllying in a long period where the temperature of environment will change unavoidably. Secondly, traditional videometrics cannot be used to measure the pose deformation of objects in a large viewing field or non-intervisible objects in large structures, which are commonly used in technological and engineering construction today. To overcome the aforementioned difficulties, this thesis proposes a temperature compensation method to reduce the thermal errors in long time videometrics and develops the pose relay videometrics method using camera network to measure multiple non-intervisible objects.Firstly, principles and real applications of the monocular videometrics methods are introduced in chapter 1 as well as the binocular ones. Orthogonal iterative algorithm, which is one of the most popular monocular pose estimation algorithms, is presented in detail for the monocular pose estimation method is the base of pose relay in camera series and camera network. Furthermore, a new data fusion method is proposed to improve the precision of translation measurements along the optical axis of camera with a high precision laser rangefinding sensor.Secondly, mathematic relations between the image drift and the intrinsic/exterior parameters of the camera are studied targeted on the plane grid based on the classic pinhole camera model in chapter 3. The linear image drift model as well as the simplified one used in close range applications are farther proposed by analyzing and simulating the coupling between the varieties of camera parameters. Experiments of camera warm-up as well as experiments of environment temperature variations are implemented to validate the image drift models, in which the fact is found out that parameters of the camera rises immediately after camera startup for about 1 hour. So cameras had better to be warm-up for about 1 hour before calibrating and measuring in order to reduce the thermal errors introduced by the temperature rising of the camera.Then temperature compensation methods of videometrics are studied in chapter 4. Linear dynamic system modeling based system identification is particular introduced, with which the variety models of camera parameters are calibrated and verified under temperature variety environments. Experimental results show that image drift is reduced strongly under the temperature compensation method. Feasibility and validity of the method are further confirmed by comparing the pose estimations on plane object with/without temperature compensations.Principles of the pose relay videometrics using camera network are studied in chapter 5 as well as the representation methods. Software design and hardware realization of the pose relay videometrics using camera series as well as its application in the large ship deformation measurements are introduced firstly, then measurements of the pose relay videometrics using parallel camera series are studied and an adjustment based data optimization method is proposed to reduce the measurement errors. In the end, the pose relay videometrics using camera network is proposed, in which the graph theory is used in representing the camera network and optimizing the measurements.Lastly, the optimization calibration of multi-cameras relay station as well as the data optimization in the videometric using camera network are studied in chapter 6. An adjustment optimization method based redundancy calibrations is proposed by analyzing the structure of the multi-camera relay station. Simulation results show that the method could suppress noises effectively and improve the calibration precision because the full utilizing of constraint conditions in the relay station. Adjustment based method as well as SPGD (Stochastic Parallel Gradient Descent) based method are proposed in optimizating the measurements of pose relay videometrics system using camera network. Simulation results show that both methods could suppress noises and improve the measurement precision effectively because they can take full advantages of the constraint conditions intrinsic in the camera network, however, it is noticeable that complexity of the adjustment based algorithm will increase drastically as the complexity of the camera network increases, while complexity of the SPGD based method remains same, so the latter one is expected to find wide applications in the attitude angular deformation measurements of large structures.