Adept AdeptSight User Guide - Manual (Page 632)

Vision Basics - Resolution
relates the size of the field of view, the distance from the lens to the focal plane, and
the lens size (e.g., 25 mm, 35 mm, etc.) The physical restrictions (see above) deter-
mine the required minimum distance. You can then calculate what lens you need for
that distance.
Vision Basics - Resolution
Pixel
The basic unit of an image is a pixel (picture element). It is the smallest unit of information
that a vision system can return. The number of pixels a system can process determines the
system’s resolution and affects the computer processing time needed to analyze an image.
For area scan cameras, a pixel can be thought of as a single cell in a matrix that the camera
overlays on the field of view (FOV). For a black-and-white camera, the value that is placed in
a cell (pixel) is a shade of grey that represents the intensity of the light reflected from the cor-
responding area in the field of view.
Resolution
The camera representation of our hypothetical 22 x 16 camera shows very poor resolution
due to the low density of pixels.
In addition to the number of pixels in the camera array, the lens focal length combined with
the distance of an object from the camera has the greatest effect on the final resolution of
whatever you are viewing. The following figures show the relationship between focal length
and viewing distance. In general, the best resolution comes when the object of interest fills
as much of the field of view as possible while still being in focus.
An important concept that is illustrated by these figures is the relationship between a pixel
and the physical size of an object. A pixel always has a relative relationship to the size of an
object. It has an absolute relationship only when you fix your viewing distance and focal
length of the lens, and then calibrate the vision system. The camera calibration process
(Standalone Camera Calibration on page 207) establishes an absolute relationship between a
pixel and the actual dimensions of the field of view.
AdeptSight User's Guide, Version 3.2.x, Updated: 8/23/2012
Page 632