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3D laser scanner `overcomes drawbacks`

23 March, 2009

A British company has announced a 3D digital laser scanner that, it claims, overcomes some limitations of conventional laser stripe scanners. Oxfordshire-based Meta Vision Systems originally developed the system for use with automated welding equipment, but it believes that it could have other manufacturing applications, such as profile measurement and scanning for reverse engineering.

Conventional laser vision systems based on the triangulation principle use a laser stripe projected onto a target. This is processed by a 2D camera to produce a 3D profile of the target.

But this technique has limitations because constant laser power is used for the whole stripe. It is not possible to vary the laser intensity to increase the amount of light reflected from dark areas, or to decrease the reflections from lighter areas. Also, the camera views the area on either side of the stripe, which can lead to further problems with dynamic range and unwanted reflections.

Meta’s new DLS300 sensor still uses triangulation, but is based on a scanning spot rather than a stripe. The company says that this solves the two main problems of stripe-based triangulation. First, it is easy to implement automatic gain control to compensate for changes in reflectivity. And second, the imaging is done by a linear charge-coupled device which looks only at the region of interest and is not affected by reflections. Other benefits include a programmable field of view, and a depth of field that is independent of the width of field.

Much of the signal processing is done inside the sensor head. A built-in Ethernet port allows the data to be transmitted rapidly, as well as allowing the scanner to be controlled digitally by an external device.

Bob Beattie, Meta’s managing director, reports that performance of the sensor “has exceeded our expectations and the initial design specification. Trials in various welding applications, including adaptive submerged arc welding of nuclear vessels and wind tower production, have been extremely successful.”

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