Measurement And Analysis Of Plane Parameters By Geometrical Optics

For the measurement of rotating objects'small vibration, traditional contact measuring system would make the surface damnify, influence vibration state, result in the measure failed. therefore, just noncontact measurement could achieve measuring demand. Laser measurement techniques based on optics principle are best measurement techniques of vibration. they are high-speeding, high-precision, fargoing. They can settle problems of previous vibration measurement. Vibration displacement measurement of rotating objects is part plane parameters measurement in high frequency, continuous state. So this text study a easy non-contact measurement technique by geometry optics and computer vision. This measurement could applied in any object's.vibration measure which has mirror characteristic. The main work of this text is following several contents:1. principle and structure of measurementplane parameters measurement is mainly divided into two part: The experimental measure part (hardware part) and imge processing and analysis part (software part). The hardware part collects light spot images.Which include semiconductor laser, measure object, receiving screen, CCD camera, PCI card, computer. The software part include image threshold choice, center extraction, calculation and analysis of vibration parameter. Measurement principle: When the laser beam projects light upon plane surface, the reflex ray leave a light spot on receiving screen.the light spot is changing position continuously when the plane vibrating.Useing CCD camera make areal-time capture. Then use software make threshold choice, center extraction, aberrance rectification, coordinate transform. Finally, according to quantificational relation of plane parameters and reflex lightplot ,calculate and analyse of part plane parameter.2. Camera calibrationIn order to extract the geometry information of the space object from the image, we must establish the mutual corresponding relation between the pixel's position and the surface dot of the space object in the photographic measure. The image module of the photograph system decides the mutual corresponding relation. The parameters in the image module of the photograph system are the Camera's parameter. In most conditions, the parameters must be determined through the experiment and the computation. The process of the experiment and the computation is named camera calibration.This text build up a pinhole camera model taking into account radial distortion. Tsai's two-stage calibration is used in system's calibration3. Experimental measurement and analysis of plane parametersThe experimental measure of vibration parameter is divided into two parts. one part is discussing structure design of dynamic measuring system and analysing errors factors: using measurement of this text, measure respectively displacement parameter and corner parameter, validate feasibility of plane parameter measurement; analyse precision of experimental measurement system. forecast error source of dynamic vibration measurement. design dynamic measurement project. the other part is dynamic measure plane parameters: using dynamic measuring system, measure part plane parameters of raw slice, obtaining swing of raw slice vibration. then at the same condition, install eddy current type tranducter, make vibration displacement measurement, obtain the swing. Then compare with the swing measured by this text measurement, Validate correctness and feasibility of this vibration measurement by geometry optics and image processing.4. Errors analysis of plane parameters measurementIn this text, according to many experiments, we find error factors of influencing measuring precision: measuring objects error, Error of geometrical aberrance of imaging system, calibration error, arithmetic error and influence of vibrancy, measuring environment error, data measure error and so on. By analysing thefactors of error, we find methods to decreased and avoid errors, choose a better experiment condition.5. Conclusion and forecastThe key problems of this measurement is the systematic precision and feasibility of plane parameters measurment. In order to testify feasibility, we deal with measuring results of many pictures equally and finalize the results. Higher precision means better measuring result, higher accuracy. In order to improve precision of the system, we do many experiments. Through analyzing experiment process result, we improve the experiment condition as the follow study condition. Experiment results show that the method on laser and computer vision measurement of vibration measurement is correct and feasible.