Thursday, December 18, 2008

Improving line pair resolution (Part 1)

Previously I discussed why some folks pay so much attention to the ability of a machine vision system to resolve line-pairs. I wrapped up by hinting that there are ways to improve the line-pair resolving ability of your system. Let’s talk about two of them now.

The minimum line-pair spacing that your system can resolve is determined partly by the lens you use. A lens with a small “f” number, (a “fast” lens,) will give better line pair resolution than a slower lens. So if you need to see fine detail, buy a lens with the smallest “f” number you can find/afford.

Now if you look at any lens with an adjustable aperture you’ll notice that the “f” number varies with the aperture opening: closing down the aperture, (as you might want to do to increase depth of field,) increases the “f” number and so reduces the ability to resolve line-pairs. So to see fine detail, open up that aperture, but expect to lose depth of field.

Want more tips on improving line-pair resolution? Check back soon!

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