Determine projector focal length

Question

I am trying to run the cvPOSIT algorithm to map points that are projected using an Optoma PK301 with a the Kinect's depth camera. I have already determined the intrinsic parameters of the projector by calibrating it using the Projector-Camera Calibration Toolbox (http://code.google.com/p/procamcalib/) in Matlab. Would I be able to use these intrinsic parameters (in particular the focal lengths fc) to determine the actual focal length of the projector to feed into the POSIT function in OpenCV?

Answer 1

Ok, the quick answer to this is that the POSIT algorithm assumes that the focal length in both the x and y axes are the same (as it would be on an ideal camera). For the purposes of the POSIT algorithm, just take the average of the two: (fx + fy)/2.