User`s manual

AW00049313000 Spatial Correction on Color Cameras
Basler runner 145
Example 2
There is a second approach to calculating system design criteria that is less concerned with aspect
ratio. This approach is more tuned towards matching the line of view of the sensor to the width of
your conveyor. Example 2 illustrates this approach.
Assume the following conditions:
 Conveyor Width = 350 mm
 Conveyor Movement per Encoder Step = 0.2 mm
 Center to Center Spacing Between Sensor Lines = 112 µm
 Pixel Size = 14 µm
 Length of Sensor Line = 29.372 mm (2098 pixels/line x 14 µm/pixel)
 With an objective lens in place, the direction of travel of the object that will cause the image
to cross the blue line in the sensor first.
1. Calculate the magnification needed to capture the full conveyor width on a sensor line.
( is the standard symbol for magnification and is usually expressed as a ratio)
2. Calculate the conveyor movement necessary to move the image
112 µm.
3. Calculate the number of encoder steps needed to move the conveyor 1.335 mm.
Since the encoder only counts in whole steps, you have two options, move the conveyor enough to
generate six encoder steps or move the conveyor enough to generate seven encoder steps. In
either of these cases, the movement of the conveyor will not result in the image moving exactly 112
µm. Therefore, you will need to adjust the magnification so that exactly 112 µm of image movement
results. And you must also consider that a change in magnification will result in a change in the
conveyor width that is viewed by each sensor line.
The calculations below look at the outcomes of the two options:
Sensor Line Length
Conveyor Width
----------------------------------------------------
29.372 mm
350 mm
------------------------------ 0.08392==
1
0.08392
--------------------- 1 1 . 9 1 6=
 1 : 11.916=
112 µm 11.916 1.335 mm=
1.335 mm
0.2 mm/step
--------------------------------- 6.675 steps=