Undistort Domecam / Fisheye camera image

Hello,

I'm working with the Axis M3007-PV network camera. It has a horizontal angle of view of 187°, vertical of 168° and produces fisheye-like images. I'm trying to undistort/dewarp these images so that straight lines look straight again; I'm not trying to unwrap the image into a panoramic a la Golan's Bloggie unwrap.

So far I've tried two techniques: chessboard calibration/undistort using ofxCv, and the less flexible approach of producing a spherical (partial) map.

With chessboard/undistort, the results vary wildly but I have had some success. The main issues occur around the edge of the image. This is based on adding around 10 calibration images with the chessboard at various positions:

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Screen Shot 2015-09-02 at 09.43.59.png2784x1228 912 KB

With spherical mapping, the centre looks ok but the edges are heavily distorted:

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Clik here to view.

Screen Shot 2015-09-02 at 09.42.38.jpg2784x1554 479 KB

And so to the question: does anyone have any experience with either/both approaches? Is there a way to improve either or is there an alternative approach that I may have missed?

It's for an arts/theatre project BTW, and all code will be open-sourced once it's complete!

Cheers