If a thermal camera specifies minimum focusing distance as 20m/50m (based on the lens), it means that the bare minimum distance required to provide parallel beam on to the lens is 20m/50m to form image on to FPA.
As collimators with off-axis parabolic mirror provides parallel beam of cavity sources, is it possible to use the IR collimators for calibrating thermal imagers?
Research paper/ technical note, if available in this regard is requested
Thanks
Hi Nagarajan, Theoretically, you can move the target closer to the off-axis parabola to replicate a finite conjugate. However, the further the conjugate is away from infinity, the larger the aberrations become. The magnitude of the aberrations depend on the focal length of the collimator and the aperture of the camera lens you are using. You really need optical design software to quantify the aberrations. A simpler option is to not use the collimator but to set the target 20m from your camera. If you do not have access to a controlled area this long, it is generally easier anyway to set up a flat mirror approximately half the distance required and then the target can be placed close to the camera.
- Badges
- Science topic
- Similar topics
- Organizational Psychology
- Training