Tuesday, April 3, 2012

A better linescan light

I had the misfortune recently of watching an engineer set up a light for a linescan inspection system. If you’ve ever had to do this you’ll know that it’s far from easy. The angle of the light is critical to get the required contrast on the target, the working distance has to be right to minimize the line width and maximize the intensity, and the line has to align perfectly with the sensor in the camera. In short, there are just too many degrees of freedom.

This is what first drew me, like a moth, to the Corona II from German light and camera manufacturer, Chromasens. Instead of a rod lens, this uses a mirror to create the narrow focused line. And to make life easier for the integration engineer, the light has flat mounting surfaces with the mirror directing the beam out at a known and fixed angle.

As all you mechanical types will know, it’s much easier to construct mounting brackets and surfaces that are flat, square and parallel than at some complex angle, so this feature of the design seems a simple yet useful advance.

Another point I really like is the ability to control the output of the light automatically. Using what Chromasens call an ““Illumination Setup Tool” it’s possible to have the output altered in response to the image quality. This way the impact of dust on the light cover or reduced LED output (yes, it does happen,) is automatically compensated and the vision engineer gets fewer service calls in the middle of the night.

I doubt these lights are cheap, but this might be one of those cases where you spend more to save more. And that includes saving on installation time.

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