FL=(d/2)/tan(a/2)
where FL is the focal length, d is the sensor diagonal and a is the diagonal field of view.
The resolution (Nx and Ny) and the other parameters of the camera don't have any incidence on the focal length.
N.B. this formula is true in the other side of the lens too. For example to get the height of the image (the object that fits in the image) OH at a given distance D given a vertical angle of view av:
OH=2*D*tan(av/2)
More details on angle of view, focal length and image area here.
Thanks for your answer. The problem is that I don't have d and a, in your formula. Maybe I can do something with intrinsic matrix?. It's something like this: K =[1. 3, 0, 0.3; 0, 1.3, 0.3; 0, 0,0.001]; Thanks again.
That is probably not enough. The intrinsic camera matrix doesn't contain any information about the physical dimensions of the sensor, which is needed to get the focal distance.
Take a look at this document for explanation of the camera matrix and how to get the focal length from it.
Asked: 2018-10-26 03:51:55 -0600
Seen: 1,264 times
Last updated: Oct 26 '18
