Line Laser Thickness and 3D Inspection

I recently implemented a project where we were using a SICK Ranger camera to measure a part. This camera works by measuring the position of light from a line generating laser on its 2D field of view and translating that to a height position. This works because features that are higher and closer to the camera will be closer to the top of the camera's 2D field of view and things that are lower will be closer to the bottom. This is the same effect can easily be seen in shadows when the sun is low in the sky.

The unobtainable ideal would be for the laser line to be exactly one pixel thick across our field of view with no laser speckle causing dropouts in the measurement. This would result in a perfect measurement with no noise. This is unobtainable, however, so the best we can do is minimize line thickness and speckle as much as possible.

The original laser delivered with the camera was a standard SNF model laser. Results were not as consistent as was desired and we researched alternatives. It turns out there is a version of the same SNF model laser with a narrow line thickness option. Swapping the laser dramatically improved our measurement quality with no other changes to the system.