An axis-symmetrical optical laser triangulation system was developed by the authors to measure the inner geometry of
long pipes used in the oil industry. It has a special optical configuration able to acquire shape information of the inner
geometry of a section of a pipe from a single image frame. A collimated laser beam is pointed to the tip of a 45° conical
mirror. The laser light is reflected in such a way that a radial light sheet is formed and intercepts the inner geometry and
forms a bright laser line on a section of the inspected pipe. A camera acquires the image of the laser line through a wide
angle lens. An odometer-based triggering system is used to shot the camera to acquire a set of equally spaced images at
high speed while the device is moved along the pipe’s axis. Image processing is done in real-time (between images
acquisitions) thanks to the use of parallel computing technology. The measured geometry is analyzed to identify
corrosion damages. The measured geometry and results are graphically presented using virtual reality techniques and
devices as 3D glasses and head-mounted displays. The paper describes the measurement principles, calibration
strategies, laboratory evaluation of the developed device, as well as, a practical example of a corroded pipe used in an
industrial gas production plant.
This paper presents a new configuration of an optical measurement system using fringe projection for 3D shape
measurement using active photogrammetry. The system was optimized to measure 3D geometries of external surfaces of
pipes. The system was mainly designed for periodic inspections of pipelines submitted to environmental induced
corrosion and local dents. It has a compact design and it is suitable to inspect pipes with diameters 250 mm (10”) and up.
The software is able to compute geometric parameters of the inspected area like depth, volume and length of the
damaged areas. The developed system uses a special compact fringe projector composed of an acrylic tube printed with
two sinusoidal fringe patterns with two different frequencies, a set of LEDs forming a line light source and a special
phase shifting approach with absolute phase calculation procedure. The three-dimensional surface of the pipe is
measured and displayed using virtual reality techniques. The measured area is 300 mm x 200 mm. The paper also
presents results of quantitative evaluations as well application results.