User`s manual

Spatial Correction on Color Cameras AW00049313000
134 Basler runner
To better understand the concept of spatial correction, consider a simple example. In this example,
we will make the following assumptions:
 The optics and the distance between the camera and the conveyor have been arranged so
that we have a 1 to 10 magnification. This means that an area of 0.14 mm x 0.14 mm on the
object will create a 14 µm x 14 µm image on one pixel.
 We have an encoder on our system and each step of the encoder represents a 0.14 mm
movement of the conveyor. (This means that the image on the sensor will move 14 µm for
each step of the encoder).
 We trigger a line acquisition on each step of the encoder (when a line acquisition is triggered,
all three lines in the sensor acquire data at the same time).
Now, consider a single 0.14 mm wide area on the object and call this area A. Assume that the image
of area A is falling directly on the red line of the sensor and that we have just performed an
acquisition. In order to move the image of area A from the line of view of the red sensor line to the
line of view of the green sensor line, we will need 8 steps of the encoder. That is:
8 steps x 0.14 mm/step x 1/10 magnification = 112 µm movement of the image on the sensor
(112 µm is the exact center-to-center spacing between lines in the sensor)
To move the image of area A from the green sensor line to the blue sensor line, we will need 8 more
steps of the encoder. Remember that we are performing an acquisition on each encoder step.
To get full RGB data for area A, we must take the red line data and combine it with the green data
from 8 acquisitions later and the blue data from 16 acquisitions later. In order to do this, the data
from the last 17 acquisitions must be stored in the camera and the camera must be able to combine
the information from the appropriate acquisitions.
Figure 49 sums up the line acquisitions that must be combined to get full RGB data for area A. It
also shows what must be done to get full color information for area B, that is, a 0.14 mm area on
the object immediately after area A.
The Spatial Correction parameter is used to tell the camera which lines should be combined. In the
case of our example, this parameter should be set to +8. This setting would tell the camera to
combine the red line data with the green line data from 8 line acquisitions later and the blue line
data from 16 acquisitions earlier
Fig. 49: Sequence of Exposures and Line Readouts for Point A and Point B
Acquisition
Point A
(Red Line)
Point A
(Blue Line)
Point A
(Green Line)
Point B
(Red Line)
Point B
(Blue Line)
Point B
(Green Line)