3D Reconstruction Of Insulators Based On Binocular Vision With Structured Light

3D reconstruction technology based on binocular vision uses two cameras,taking photos of an object simultaneously,then reconstructs a 3D model of the object.Image matching is not only the key technology but also a hard problem of binocular vision technology,especially when it comes to the featureless objects in images.To solve the problem of 3D reconstruction of featureless objects,people widely use the strategy of projecting structured light on the surface of an object in order to add features on it.Structured light projected by a laser generator can keep concentrated in a very long distance which makes it suitable for adding features on the surface of an object in distance,thus,the problem of image matching is simplified.Creep distance and umbrella distance of insulators influence their antifouling property and the security of the electric power system.In order to avoid power failures caused by pollution flashover of insulators,staff at transformer substations have to measure and examine related parameters of insulators working outdoor at stations every year.To reduce human labor for measuring shape parameters of insulators outdoor,this paper proposes a 3D reconstruction method,combining binocular-vision technology and structured light,of insulators and obtains shape parameters of insulators by computing the related parameters of the 3D models.As a featureless object,an insulator's profile is outlined by a structured-light stripe projected on its surface which adds surface features on it.Since the accuracy of structured light matching will affect the measuring accuracy of 3D models of insulators,this paper proposes a method named multi-threshold segmentation combined with geometrical center extraction which overcomes the disturbance of background noise in images and the variation of light strength.The method extracts a complete and successive center line of structured light.The coordinates of the insulator will be obtained by matching center lines of structured light in a pair of photographs.Taking an advantage of an insulator as a solid of revolution,if already knowing the profile curve and the central axis of an insulator,rotate the profile curve around the central axis and a 3D model of the insulator will be constructed.This paper proposes a segmentation method,combining Canny and region growing method,to extract the edges in an image of an insulator,find the outlines among them,and growing from candidate seeds selected from the center line of structured light into a region of an insulator.After that,the outline of the insulator is obtained.According to the condition that the most protruding points on two sides of an umbrella is on a circle in an umbrella plane,these points' spatial coordinates will be obtained by selecting the two most protruding points on both sides of each umbrella and matching them.Structured light in the right image is composed by several curves corresponding to several umbrellas of an insulator.So,the most protruding point of each curve is on the same plane with the two edge points of this umbrella extracted before.Calculate the coordination of the center of an umbrella by equations of three points,not on a line,on a plane and on the circumference of a circle.Theoretically,these center points are on the central axis of the insulator,so if more than one center points' coordinates are obtained,the linear equation of the central axis will be figured out by line fitting.Obtain the profile curve of an insulator by projecting the reconstructed structured light on the plane passing the central axis.With the central axis and the profile curve of an insulator,the 3D model of an insulator can be rebuild.When 3D models reconstructed in this way are used for measurement of insulators' shape parameters,the measuring accuracy is within 1.5%which proves the pragmatic nature of these 3D models and this measuring method can replace outdoor manual measurement.