Operation and Features
BASLER L304
kc 3-23
Draft
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 = 850 mm
• Conveyor Movement per Encoder Step = 0.25 mm
• Center to Center Spacing Between Sensor Lines = 90 µm
• Pixel Size = 10 µm
• Length of Sensor Line = 40.80 mm (4080 pixels/line x 10 µm/pixel)
•
With an objective lens in place, the direction of travel of the object will cause the image to
cross the blue line in the sensor first.
Step 1 - Calculate the magnification needed to capture the full conveyor width on a sensor line.
β = 1 : 20.83
(
β is the standard symbol for magnification and is usually expressed as a ratio)
Step 2 - Calculate the conveyor movement necessary to move the
image 90 µm.
Step 3 - Calculate the number of encoder steps needed to move the conveyor 1.875 mm.
Since the encoder only counts in whole steps, we have two options. We can move the conveyor
enough to generate seven encoder steps or we can move the conveyor enough to generate eight
encoder steps. In either of these cases, the movement of the conveyor will not result in the image
moving exactly 90 µm. Therefore, we will need to adjust the magnification so that exactly 90 µm
of image movement results. And we must also consider that a change in magnification will result
in a change in the amount of conveyor width that is viewed by each sensor line.
Sensor Line Length
Conveyor Width
----------------------------------------------------
40.80 mm
850 mm
-------------------------- 0 . 0 4 8==
1
0.048
--------------- 20.83=
90 µm 20.83× 1.875 mm=
1.875 mm
0.25 mm/step
------------------------------------ 7.50 steps=
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