When you calibrate a FLIR Blackfly S camera, the default settings usually result in a good calibration. These notes are provided to help you to understand FLIR Blackfly S camera parameters and behavior.
Set a large enough Area of Interest window
We strongly recommend setting the Area of Interest window at least as large during calibration as will be used during capture. If in doubt, use the default setting of the whole image for both calibration and capture.
Set an appropriate frame rate
We recommend calibrating using at least the video rate that will be used for capture. The calibration of FLIR cameras in Nexus does not check for timing offsets (unlike say, calibrating an SDI camera in Shogun Live), as the timing of the camera is controlled directly using the Vicon Lock unit. This means you can change the frame rate and exposure of the video camera after calibration or decrease the Area of Interest window size. However, do not alter the aperture of the lens without re-calibrating.
A known issue results in warnings being briefly generated when you change camera parameters, including when you enter and exit calibration mode. If continual warnings about timing, missing triggers or black frames being inserted occur, calibration is unlikely to be successful, so ensure that the video is stable before continuing.
Use Video Calibration Mode
- To tune the video threshold and calibration shutter duration, from the Calibration panel, select Video Calibration Mode.
This activates a number of parameters in the System panel. In video calibration mode, the image becomes much darker, ideally so that only the strobes can be seen.
- Power on the wand in Strobe mode.
- Check that centroids can be seen in the video image.
If not, you may need to adjust the parameters until the centroids become visible.
Adjust the threshold if required
In most cases, the default threshold usually works well. However, in extreme circumstances, you can adjust this setting if the wand LEDs are not reliably detected.
Check camera masks
Check that masks are sensible (ie, covering any bright objects, but not covering a very large portion of the image). If masks are too large, it is likely that the calibration settings are inappropriate.
Carry out wand wave
Calibrate the system as normal (see Calibrate Vicon cameras), making sure that the video camera receives sufficient wand waves. The best way to do this is to leave the Auto Stop option selected with the default settings.
Check the calibration
After calibrating, you can carry out a quick check.
- Start a capture.
- Wave the wand quickly in front of the video camera.
- Stop the capture.
- Transfer the capture to AVI so it can be played back and stepped through.
- Step through and verify that reconstructions are shown in the correct place.
(They will still be very slightly offset, owing to the difference between the physical position of the visible and IR strobe LEDs on the wand.)