In last month’s column, I talked about the accuracy funnel, which shows that in a measurement system where the sensor or the part is moved in one or more axes, the greater the distance, the larger the potential inaccuracies in the measured distance. In the case of an imaging system as used in a video or vision measurement system, there are other accuracy considerations that are important even when there’s no motion.

What am I measuring?
To understand what can affect accuracy at this level one must understand that video systems do not measure parts—they measure images of parts.

Yes, you see the part in an eyepiece or on a monitor, but what you see is an image of the part. Fundamental? Maybe. But it is important to the understanding of sources of measurement error in imaging. The entire image area is called the field of view.

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