Rotating optical geometry sensor for inner pipe-surface reconstruction

Abstract

The inspection of sewer or fresh water pipes is usually carried out by a remotely controlled inspection vehicle equipped with a high resolution camera and a lightning system. This operator-oriented approach based on offline analysis of the recorded images is highly subjective and prone to errors. Beside the subjective classification of pipe defects through the operator standard closed circuit television (CCTV) technology is not suitable for detecting geometrical deformations resulting from e.g. structural mechanical weakness of the pipe, corrosion of e.g. cast-iron material or sedimentations. At Fraunhofer Institute of Optronics, System Technologies and Image Exploitation (IOSB) in Karlsruhe, Germany, a new Rotating Optical Geometry Sensor (ROGS) for pipe inspection has been developed which is capable of measuring the inner pipe geometry very precisely over the whole pipe length. This paper describes the developed ROGS system and the online adaption strategy for choosing the optimal system parameters. These parameters are the rotation and traveling speed dependent from the pipe diameter. Furthermore, a practicable calibration methodology is presented which guarantees an identification of the several internal sensor parameters. ROGS has been integrated in two different systems: A rod based system for small fresh water pipes and a standard inspection vehicle based system for large sewer Pipes. These systems have been successfully applied to different pipe systems. With this measurement method the geometric information can be used efficiently for an objective repeatable quality evaluation. Results and experiences in the area of fresh water pipe inspection will be presented

The calibration method of the circle-structured light measurement system for inner surfaces considering systematic errors

“…Among them, circle-structured light measurement is a special kind of structured light measurement method that uses laser triangulation. Compared to common point-or line-structured light measurement methods [14,15], it can directly form a 360 • projection light stripe on an inner surface and measure the whole inner surface with high efficiency and without complicated operations or using a complex system structure [16]. However, the measurement accuracy of the circle-structured light system is mainly affected by two sources of systematic error: light plane deviation and motion direction deviation of the stage system.…”

Corrected unwrapping method based on the tangential and radial distortion centre for the panoramic annular image

“…Among them, ultrasonic testing [1], eddy current testing [2] and optical testing [3] are three main detection methods. The first two are easy to be interfered by external factors for its contacting pattern, which lead to inaccurate testing result.…”

“…Flaw detection techniques for the pipe inner wall are very important in many real industry and defence production fields, such as oil transporting pipe, gun tube [1–3]. Among them, ultrasonic testing [1], eddy current testing [2] and optical testing [3] are three main detection methods. The first two are easy to be interfered by external factors for its contacting pattern, which lead to inaccurate testing result.…”