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Calibrating fisheye lenses above 180 degrees

asked 2015-07-02 17:42:56 -0500

TAXfromDK gravatar image

Hi Guys,

I am working on a fisheye lens that has a extreme fov around 220 degrees. An example can be seen here:

image description

I have been looking at lens correction in opencv before, but the models as I know them does not make sense when the fov crosses 180 degrees, as the image can not be represented as a plane anymore.

I have currently made a radial model, where i measure pixel distance from center while following a point in the horizon. This is a tedious task, and I hope a better method is around. Hopefully something with a checkerboard or something.

I am therefore looking to see if OpenCV has any tools in that direction?

Kind regards

Jesper

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Did you had a look at this ?

Ice_T02 gravatar imageIce_T02 ( 2016-12-12 06:29:17 -0500 )edit

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answered 2016-12-12 05:43:17 -0500

Treer gravatar image

updated 2016-12-12 23:42:49 -0500

I'm in the same boat.

Ninghang said the existing model and checkerboard calibration can still be used as a good approximation if you mask off everything beyond 180° during the calibration process.

I'd like to try this method and see how it compares to a manually calibrated radial model. But before reinventing this wheel yet again... has anyone written a fisheye calibrater that allows masking off beyond 180 degrees?

I don't expect OpenCV's model to stay a close approximation past 180, but for my task I can live with that, it will also be interesting to see the divergence.


Edit: Ninghang's post was written in 2012, and OpenCV's fisheye camera model appears to have been added in 2014, so he might not have been referring to the current model. However, I was under the impression that OpenCVs fisheye calibration model is the same as this paper (2007), "known to approximate a large range of fisheye lenses" but looks to me like it will start deviating from lens behaviour beyond 180°, so I assume TAXfromDK's question is still valid for OpenCVs fisheye calibration model, and Ninghang's answer might be a solution if you don't need acurracy beyond 180°. I could be wrong - I'm still learning and haven't tried this yet, I intend to once I find/write calibration software that allows masking.

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Asked: 2015-07-02 17:42:56 -0500

Seen: 1,255 times

Last updated: Dec 12 '16