Tuesday, September 18, 2012

An alternative zoom lens

Every machine vision engineer has a Computar 55mm telecentric lens on his bench. It’s a fine lens that gives a degree of zoom, but I hate to see it used on a real application.

The reason for this is that it’s not repeatable. If it has to be removed for some reason, it’s impossible to guarantee reinstallation with the same mag.

Navitar make a posher version, the Zoom 7000 Macro. That’s a good lens but it suffers the same weakness: it’s impossible to reproduce any particular magnification.

Opto-Engineering, (who else?) has the answer: multi-mag optics. Essentially, it’s a series of lenses that can be indexed round in front of the camera. I’ve seen something similar on microscopes, and I recall old – very old – TV cameras having something similar, but for machine vision this is something of a first.

There’s a video on the Opto Eng website where a young woman explains the merits of this device. The good thing about the video, besides the attractive presenter, is that we are shown the indexing mechanism. I thought that was rather cool.

You could search for the video yourself, but to make your life easier I’ve embedded it below.

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