Wednesday, September 1, 2010

Novel machine vision illumination

If you’re on the lookout for clever lighting ideas, recently issued US patent number 7,782,513 might be of interest. This is for “Fast variable angle of incidence illumination for a machine vision inspection.” The inventor is one Paul Gladnick of Seattle and his invention is assigned to Mitutoyo.

The problem Mr. Gladnick is trying to address is common to many machine vision applications: the task demands light from different directions to highlight different features – darkfield for some, brightfield for others – yet we have neither space nor time nor budget for multiple systems. What we’d really like to be able to do is switch back and forth very quickly between different lighting schemes, but the hardware to make this possible doesn’t exist.

And that of course is something this invention seeks to remedy. You should read the patent to really understand it (download the document in its entirety from the US Patent & Trademark Office,) but here’s a brief description:

From the outside this light looks like a cloudy day illuminator – a big upturned bowl – but inside there’s a central column that the camera looks through. The outside of this column is lined with reflective rings, each at a slightly different angle. Likewise, the inside surface of the bowl consists of a series of reflecting rings, each arranged at a different angle.

The inside of this bowl is divided into four quadrants, and part way down each quadrant there is a flat mirror. This mirror reflects light piped in from above onto one of the rings on the center column. The angle of each ring is different, so different rings bounce the light onto a different region of the interior surface of the bowl, and from there the light is reflected onto the workpiece.

Confused? Well if I could describe this properly I’d be writing patents for a living. Suffice to say that it’s very clever, although I am just a little skeptical as to how well it will work in practice. Guess I need to keep an eye on Mitutoyo’s product range.

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