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24 October, 2021

Speckle-free laser doubles 3D image processing speeds

12 October, 2021

Cognex claims to have eliminated the speckle effect from laser lines, thus improving triangulation-based 3D imaging. It has incorporated its patented speckle-free technology into an embedded vision system which, it says, can achieve inspection speeds twice as fast as rival products.

Laser triangulation is the leading technology for high-resolution 3D image processing. But the projected laser lines produce speckles caused by interference effects in the laser light reflected from the inspection surface, creating light and dark spots on the camera chip or in the eye of the viewer. The speckling creates image noise. A sharp line would be preferable.

For years, developers have been trying to reduce the speckles using various techniques, such as varying the wavelength and camera aperture, or taking multiple images and calculating an average. However, these did not lead to noticeably better results.

Cognex claims that its new process eliminates the speckles and produces straight, clean, bright laser lines. “The basis of the new technology is a blue laser with a wavelength of 450nm,” explains the company’s director of engineering, Thomas Ruhnau. The laser beam is deflected by a vibrating microelectromechanical mirror to create a fanned beam. This is directed onto a diffuser optic that creates a laser fan with a precisely defined width and intensity distribution, eliminating the speckles.

The system is said to be robust enough for harsh industrial environments and to operate within the safety limits for protection class 2M lasers.

Cognex has integrated the speckle-free laser optics into its In-Sight 3D-L4000 3D vision system, resulting in inspection speeds said to be at least twice as fast as rival products. This system has enough built-in computing power and 3D vision tools to inspect 3D point clouds without needing an external PC.

In applications such as 3D inspection of castings – for example, the connecting rod shown here – the speckle-free laser line is said to result in more accurate results than other 3D imaging technologies.

Cognex says that 3D image processing that was previously difficult to achieve, will be easier using the new system. The embedded tools include all of those needed for 3D image processing.

Cognex plans to integrate its speckle-free laser technology into other products. “Users benefit from it, among other things, through improved accuracy and possibly higher inspection speeds, which increases the cost-effectiveness of 3D vision systems,” Ruhnau says. “We therefore see great potential for further products based on this technology and numerous possible uses in a wide range of industrial application fields.”

Cognex:   LinkedIn  Twitter  Facebook




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