Hardware manual

Camera Impact Reference Guide
Datalogic Automation Inc. 2-32
• Real World Points: The "real-world" location (in X and Y coordinates) corresponding to each Polygon
Point should be entered. Double-click on a field to edit it. Click the appropriate button to Append,
Insert, or Delete a Real World point.
Calibrate From Entered Points
Use this option when it is difficult to calibrate with a target or when the inspected image contains perspec-
tive distortion and you need to manually enter the pixel grid points for the calibration. This option will cor-
rect for pixel size and perspective distortion, but not radial distortion. To calibrate for radial distortion you
must use a calibration target.
The entered points and real-world points must correspond one-to-one, meaning that there must be the same
number of points and they must be in the same order.
To calibrate for real-world origin and pixel size calibration the points you select should represent at least
three distinct X and Y locations on the part. For acceptable distortion correction, select at least four distinct
X and Y locations on the part. For example, if you only use points along the top and bottom edges, the dis-
tortion correction in the vertical direction is ill-defined and will likely be unacceptable because only two dis-
tinct Y locations are represented. You should try to space the points into at least four distinct X and Y
locations.
The calibration algorithm will automatically determine whether to calibrate for distortion or not. If there is
not detectable distortion, or if there are too few points, it will calibrate for real-world origin and pixel size. If
there is detectable distortion and enough points, it will also calibrate for distortion. The current setting is dis-
played after the Lens Distortion label in the “Current Calibration” box below the image window.
It is possible to “confuse” the distortion calibration algorithm by defining certain point positions. If you get
“odd” calibration results, you should first check that you entered the correct real-world coordinates in the
correct order. If these are correct, use more points to better define the distortion.
NOTE: Since the image origin (0,0) is in the upper-left corner of the image, the X and Y coordinate values
use a "left-handed" coordinate system. This means that the X coordinate value increases to the right and the
Y coordinate value increases downward. See “Point Settings” below.
To calibrate from entered points
1. From the Calibrate drop-down, select From Entered Points.
2. In the Entered Points table, enter the X and Y coordinates of each point on the image that you want to
use for calibration. To append, insert, and delete points, use the buttons next to the fields. The points
are NOT marked on the image.
3. When all the Entered Points have been entered, enter the "real-world" measured locations that corre-
spond to each Entered Point. The measurement units are not necessary.
For example, in the image below, Real World Point 1 (0,0) corresponds to Entered Point 1 (39,200);
Point 2, in real-world units, is 2, -2 (+2X and -2Y from Point 1); Point 3 is 6, -2 (+6X and -2Y); Point
4 is 8, 0; Point 5 is 6, 2; and Point 6 is 2, 2. To append, insert, and delete Real World Points, use the but-
tons next to the fields.