Research On Shaft Diameter Detection Method Based On Structured Light Image

Due to the advantages of non-contact and easy to be integrated in computer,Structured light vision measurement technology has been paid more and more attention in mechanical industry.The key to the development and application of the structured light measurement is to improve the mechanical accuracy measured by the structured light.For online non-contact measuring diameter of step beams,new method of detecting the measuring points on light strip image of the mechanical elements is studied to increase the accuracy of the structured light measurement.Comparing with calibration of the measurement model of the structured light,detecting the measuring points on the light strip image is the key to the improvement of measuring accuracy.According to triangulation-measuring principle of the structured light,imaging position of the point,which is both on the journal surface and on the light plane,is taken as the measuring points on the light strip image.Firstly,in the camera coordinate system involving laser source and step beams,the intersecting line equation between light plane and shaft journal is formulated.By using the pinhole imaging model,the equation of intersecting line between light plane and shaft journal is converted to the theoretical image plane.Then,according to the converted equation,measuring points on the light strip image are detected by nonlinear equation iteration algorithm along the width of the light strip image.Finally,testing the surface roughness and the speed of the journal on the detection accuracy of the new method.Comparing with results of the digital micrometer,the accuracy of the shaft diameter measured by the detected points is verified.In this paper,an online detection method for measuring shaft diameter based on structured light vision technology is investigated.Since the intersection of measured object surface and light plane is a part of an ellipse,a world coordinate system is built to describe the ellipse intersection.According to the calibrated camera parameters,axis equation and structured light plane equation,a conversion method between the world coordinate system and camera coordinate system is derived.Combining ellipse intersecting line equation with camera imaging model,the ellipse intersecting line equation which is both on light plane and shaft surface is also derived.By using geometry constraint method,the center position of original light stripe is selected and the initial value of shaft diameter is measured.Then the optimization of ellipse center position and semi axis length is carried out in the image plane coordinate system,when the radial deviation square reach to minimum value,the shaft radius of measuring model is taken as the final measured value.Innovation of the present work: by using the pinhole imaging model,the detection of the measuring points is finished by converting the intersecting line equation to the theoretical image plane.