6.3 Camera Alignment 6 HARDWARE SETUP
Figure 6: Example for standard epipolar geometry.
•IDS uEye ML; model UI-3240ML-M-GL
•IDS uEye CP; model UI-3140CP-M-GL Rev.2
•IDS uEye CP; model UI-3240CP-M-GL
All cameras must have a gray scale sensor.
6.3 Camera Alignment
Both cameras have to be mounted on a plane with a displacement that is
perpendicular to the cameras’ optical axes. Furthermore, both cameras must
be equipped with lenses that have an identical focal length. This arrangement
is known as the standard epipolar geometry. An example for such a camera
mounting is shown in Figure 6.
The distance between both cameras is referred to as baseline distance. Us-
ing a large baseline distances improves the depth resolution at high distances.
A small baseline distances, on the other hand, allows for the observation of
very close objects. The baseline distance should be adjusted in conjunction
with the lenses’ focal length. An online tool for computing desirable combina-
tions of baseline distance and focal length can be found on the Nerian Vision
Technologies website1.
6.4 External Trigger
For stereo matching it is important that both cameras are synchronized, mean-
ing that both cameras record an image at exactly the same point of time. Many
industrial cameras already feature the ability to synchronize themselves, by
having one camera produce a trigger signal for the respective other camera.
As an alternative, the SP1 can produce up to two trigger signals. The
signals are provided through the trigger port, which can receive a standard
3.5 mm phone connector. The pin assignment for this connector is shown in
Figure 7.
The peak voltage of both trigger signals is at +3.3 V. To protect the trigger
port from short circuits, each signal line is connected through a 220 Ωseries
1http://nerian.com/products/sp1-stereo-vision/calculator/
8
