I need to calibrate some wide angle pictures taken underwater ?

[FraserD]

I have been looking at the calibration VIs with IMAQ, but haven't found one which is suitable for my (quite simple) case.

I need one which takes my image (taken with my imaging setup of the grid of dots) and works out the lookup table needed to make the spatial information correct, in order to correct some other images taken with the same camera but at a much greater range.

The images have radial distortion and also pincushion distortion from looking through a plane port into water, but the camera axis is perpendicular to the image plane.

Furthermore, the grid image i have acquired for calibration purposes was taken at a range of only 30 cm while the images i am trying to correct were taken at a
range of 8 metres, 6 metres and 4 metres. Will this make the calibration innaccurate ?

Does anyone know of an example VI which does this, or have any advice ?

I have enclosed my grid image.

[Kyle_V]

Your distortion doesn't seem too bad from a short distance, but if you're going to apply this distortion information to an object that is 8 meters away, I would recommend getting a more accurate grid of dots (one with more dots). Also, the distances between the dots at 8 inches from the camera will look a lot different from the distance at 6 meters. So, I don't think you'll be able to make very accurate real world measurements with this method.

I think your best bet is to use special lenses that may lessen the fish-eye effect (no water pun intended). Edmund Optics (edmundoptics.com) and Graftek Imaging (graftek.com) are great sources for lens information.

Kyle V