Monday, December 22, 2008

The logo and the line-pair

Let’s wrap up my explanation of the MV4U logo with a short summary.

The logo is a graph of grayscale values across a pair of white lines on a black background, and this serves to illustrate a “line-pair”.

“line-pairs” and “line-pairs per inch” are central concepts in the field of machine vision optics: if you want to see fine detail in your image you need to maximize the number of line-pairs per inch your system can resolve.

I discussed four ways to improve line-pair resolution. These are:

· Use a lens with a small “f” number.
· Open the lens aperture as wide as possible.
· Use shorter wavelength light.
· Use a sensor with small pixels.

Each of these actions has consequences, like reducing the depth of field or requiring a brighter light, so don’t chase resolution needlessly. Just be aware that there are things you can do to improve the optical performance of your machine vision system.

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