Do I understand correctly that each test is run in a short amount of time? Something like:
- put the mirror in the test fixture
- command it to a certain position (with a known voltage)
- measure the position of the laser reflected by the mirror onto the screen
- change the control voltage
- measure the position again (?)
- change the control voltage to the original value
- measure the position of the laser for a third time
- compare the measurements (image position) from steps 3 and 7
- determine if the mirror returned to the original position within some allowed tolerance
If that’s the case, and you can be sure the camera doesn’t move during the test, calibration might not be so important. At the end of the day you are just looking for the laser returning to the original spot within some tolerance? So you don’t really need absolute measurements, but just relative comparisons? Having said that, I do think a calibrated rig would be better overall for a few reasons, particularly because it would support more sophisticated tests in the future…but as a starting point maybe just compare the difference between the two measurements in pixels?
I don’t have any experience with that camera, but I suspect it’s fairly distorted. I also suspect you can find calibration parameters online pretty easily - they won’t match your exact camera, but might be good enough to use for your purposes. I do think you will need to do something to correct the distortion (based on what I’m imagining). The homography can only map linear / projective transformations, and the lens distortion is nonlinear…so you have to handle that separately.
If the laser dot will only be found in a small portion of the image, and you can position your camera so that the laser shows up near the center of the image, you might be able to get away with using a homography for just that part of the image (where distortion is minimal), but there are pitfalls to this approach and really I would suggest a different camera / lens if that’s possible. I don’t think the GoPro was a good choice, but I understand you might be stuck with it. (if so, I’d look for some calibration parameters online for that camera and see how well they work. Calibrating the intrinsics yourself is a bit of a side project and I’d try to avoid it at this stage.)
I think you might be limited in uploading images at first, but you will be allowed to upload images once your post count is a little higher (I think…)