Operation and Features
BASLER L304
kc 3-13
Draft
To better understand the concept of spatial correction, consider a simple example. In our
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 0.10 mm x 0.10 mm on the
object will create a 10 µm x 10 µm image on one pixel.
• We have an encoder on our system and each step of the encoder represents a 0.10 mm
movement of the conveyor. Given our 1 to 10 magnification, this means that the image on the
sensor will move 10 µm for each step of the encoder.
• We trigger an exposure on each step of the encoder.
Now, consider a single 0.10 mm wide area on the object and call this point A. Assume that the
image of point A is falling directly on the green line of the sensor and that we have just performed
an exposure. In order to move the image of point A from the line of view of the green sensor line
to the line of view of the red sensor line, we will need 9 steps of the encoder. That is:
9 steps x 0.10 mm/step x 1/10 magnification = 90 µm movement of the image on the sensor
(90 µm is the exact center-to-center spacing between lines in the sensor.)
To move the image of point A from the red sensor line to the blue sensor line, we will need 9 more
steps of the encoder. Remember that we are performing an exposure on each encoder step.
To get full RGB data for point A, we must take the green line data and combine it with the red data
from 9 exposures later and the blue data from 18 exposures later. In order to do this, the data from
the last 19 exposures must be stored in the camera and the camera must be able to combine the
information from the appropriate exposures.
Figure 3-11 sums up the exposures that must be combined to get full RGB data for point A. It also
shows what must be done to get full color information for point B, that is, a 0.10 mm area on the
object immediately after point A.
A parameter called the Spatial Correction Amount is used to tell the camera which exposures
should be combined (see Section 3.5.2). In the case of our example, the Spatial Correction
Amount parameter should be set to 9. This setting would tell the camera to combine the data from
each green line exposure with the red data from 9 exposures later and the blue data from 18
exposures later.
Figure 3-11: Sequence of Exposures for Point A and Point B
To Next Page
Loading...
Need help?
General
