Hi all i'm using raspberry pi 2 with raspbian , i'm working on face and eyes detection using opencv and c++ , i want to expand the field of view for the pi official camera module any suggestions will be appreciated :)
if you expand the field distortion will occur and it will make the process of pattern recognition much harder. I think you should stick to the original.
But if you have already decided to use a lens, https://www.youtube.com/watch?v=IPTU8NrVqmQ in the video you can see a view with a fisheye lens (which is for iphone), and also you can see the distortion. You can also check these http://www.raspberrypi-spy.co.uk/2013/06/cheap-interchangeable-lenses-for-the-raspberry-pi-camera-module/ , but they have distortion as well which is inappropriate for recognition applications.