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Chapter
4
4.8 Setting up the cameras
•
strong IR sources (e.g. sunlight or sunrays, halogen lamps, ...),
•
mutual blinding of opposing or adjacent cameras
•
any kind of reflective material on clothes or shoes (e.g. reflective tape on safety
vests),
•
blank metal surfaces that act as mirrors, especially curved surfaces and polished
surfaces with 90
◦
angles,
•
some types of packaging foils.
For localising and removing disturbing reflections follow this simple approach:
•
active targets or IR sources: reduce the flash intensity of all cameras to ’0’
Try to localize and remove the remaining markers / reflections which originate from
infrared radiation sources (e.g. sunlight, halogen lamps, ...).
•
mutual blinding: reduce the flash intensity of all cameras to ’0’, then set each cam-
era’s flash intensity to full one after the other
Corresponding / opposing cameras can be easily identified. Re-mount the relevant
cameras until
Monitor 2DOF display does not show markers and the LED bar does
not indicate levels of intensity. You may also assign different syncgroups at this
stage. Please refer to chapter 8.5.1 on page 146 for further information.
•
other non-specific reflections:set the flash intensity of all cameras to ’50’
Try to localize the reflection by moving a target or reflective marker towards the origin
of the reflection (use the
Monitor 2DOF display ) and remove it.
If, by any means, reflections cannot be eliminated completely you may use the static re-
flex suppression of
DTrack2 (please refer to chapter 8.6.1 on page 165).
Z
Be aware that reflex suppression leads to decreased FoV / effective
measurement volume by blocking the area in which the reflection orig-
inated.
4.8.2.1 Mutual blinding
One possible source of disturbing reflections is mutual blinding of adjacent or opposing
cameras that are inside the FoV of each other. This can be well observed in the
Monitor
2DOF display as the cameras falsely identify the IR flashes as numerous flickering mark-
ers (i.e. clusters of crosses or circles). Tracking will be severely affected in the involved
areas of the measurement volume / FoV. The intensity of the simulated LED bar next to
the number of markers seen / used for tracking may serve as another indicator.
In order to distinguish from targets or other reflections please remove all reflective mark-
ers from the measurement volume in the first step. Then check whether the
Monitor 2DOF
display still shows the presence of markers and whether the LED bar shows high levels
of intensity. Try to re-arrange or re-adjust the cameras (i.e. position and orientation).
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