No abstract

Abstract. This paper presents a novel method for defect detection in pipes using a mobile laser-optics technology and conventional digital-geometry-based image processing techniques. The laser-optics consists of a laser that projects a line onto the pipe's surface, and an omnidirectional camera. It can be mounted on a pipe crawling robot for conducting continuous inspection. The projected laser line will be seen as a half-oval in the image. When the laser line passes over defected points, the image moments on the pixel information would change. We propose a B-spline curve fitting on the digitally-convoluted image and a curvature estimation algorithm to detect the defects from the image. Defect sizes of 2 mm or larger can be detected using this method in pipes of up to 24 inch in diameter. The proposed sensor can detect 180-degree (i.e., upper half surface of the pipe). By turning the sensor 180 degrees, one will be able to detect the other half (i.e., lower half of the pipe's surface). While, 360-degree laser rings are available commercially, but they did not provide the intensity needed for our experimentation. We also propose a fast boundary extraction algorithm for real time detection of defects, where a trace of consecutive images are used to track the image features. Tests were carried out on PVC and steel pipes.

Achieving optimal spatial resolution in imaging systems plays a major role in the design of vision-based industrial inspection tools. Single-view omnidirectional imaging systems provide a cost-effective and computationally-traceable solution for real-time inspection of infrastructure with a favorable size factor. We formulate, for the first time, the spatial cylindrical resolution of omnidirectional Catadioptric and Dioptric imaging systems with the focus on pipe inspection applications. We also provide a design guideline to achieve the highest resolution in these systems. First, we deliver a comprehensive study on optimal resolution in Catadioptric imaging systems which consist of a perspective pinhole camera, a collimated laser as the light source, and a reflective surface (i.e., hyperbolic mirror). Variation of the spatial resolution in terms of the camera's focal length, the mirror curvature, and the relative position between the laser projector and the camera is fully investigated via simulation and experiments. Also, the optimal resolution in Dioptric systems, which consist of a camera with compound refractive lenses (i.e., fish-eye lens) is studied and compared with that in Catadioptric systems. Tests were conducted on a 40-cm-diameter PVC pipe in a controlled laboratory environment.

No abstract

No abstract