Study On Photoelectric Image Measuring Technology For Static Parameters Of Variable Taper Tube

Image measurement technology is a newly high-precision technology growing up in the domain of measurement. It is based on image processing and image analysis, integrated micro-optical imaging, high-precision photoelectric sensor technology, laser technology, computer control technology and other modern science and technology to form a mechatronic measurement system to achieve a high-precision measurement outcome of complex objects.Variable taper tubes are widely used in many fields such as aerospace, weapon, energy, petrochemical industry, hydraulic & electric power and so on. The static parameters of variable taper tube play an important role in the characterization of its capability, including its segmental taper, inflexion and volume. The measurement precision must be reached a high level.This paper gives a comprehensive introduce and the development level of tube image measurement and then gives an in-depth study of the whole design solution to the measurement system of variable taper tube. For the special images, an embedded investigation and analysis for image processing section were mentioned in this paper, especially the image noise removal, image gray-scale transformation, image geometric distortion correction, image segmentation with threshold, straight line fitting and location, measurements processing and the three-dimension tube space reconstruction.Because of the special imaging environment, poor lighting circumstance and other reasons, the problems of noise, narrow dynamic range, as well as geometric distortion in system images. A variety of image enhancement methods were introduced, then the simulation and analysis of the special images were carried through. Based on the analysis, a partial gray enhancement method were presented , which combined exponential with logarithmic transform algorithm and yielded an excellent result. Based on the study of the model of geometric distortion, a correction method due to the linearity of crossing points in the image of grids were also advanced, which gained an ideal correction result.After the pre-processing, the effects of noises and distortion in the special image have been basically eliminated, then the radial information of the tube can be derived. An intensive study of a variety of image segmentation as well as straight line fitting and location algorithm were also given in this paper, it put forward a line location method based on each rows or colums average gray-level, which can achieve a high level location accuracy.Lastly, a three-dimension tube space reconstruction algorithm based on three order NURBS curve interpolation were presented, which provide a further extent to the measurement accuracy of static parameters of the tube.