Machine Vision Anlaysis Of Laser Marking Quality

As the maturity and wide applications of laser marking technology, demands of laser marking quality online detection are increasing. Laser triangulation method can be obtain depth, width, and other information. Laser triangulation method is based on the traditional triangulation to acquire three-dimensional surface information. because of its non-contact, non-destructive, high speed and high accuracy, as well as intellectualization, laser triangulation has been widely used in industrial inspection, machine vision.In this thesis, laser triangulation involved in the BIV (Bulit In Vision) system used in the laser marking quality detection to extensively investigated. The methods of eleminating laser speckle are suggested and a new measure arithemetic for the computing of diffuse reflectance to proposed which can improve the detection accuracy. The main research and innovations are as follow:1.A general formula for marking depth is eatablished with laser triangulation, for different angle between the CCD array and optical axis,a simplified formula is obtained,the maximal match condition is also obtained.2.Various factors affecting the detection accuracy are analysed and corresponding measures for the improvement of accuracy are suggested.3.The determination of the center line of the intensity of diffuse reflectance is the key to find the closly depth of marking. The accuracy of center line is correlated with the detection accuracy. The real intensity distribution of diffuse reflectance is not normal distribution and there are other scatter light interfering the sampling signal, traditional methods fail to put there factors into account, the detection accuracy is not high enough. A new arithmetic is proposed to make the point nearer the center with greater weight.