How to find sx and sy and F intrinsix matrix in camera calibration

I have a problem where I need to find the focal length of the camera at hand. I have calibrated the camera and obtained the parameters including fx = sx*F and fy=sy*F. But I have situation where I need to find the focal length 'F'.

How should I do it?

[William Rose]

@Suraj Sudhakar, This is an interesing question, but not a Matlab question, at least not yet. I recommend tha t you figure out an algorithm you want to try, then trying wirting a Matlab script for it. If you are having trouble turning it into Matlab, post your initial attempt at a Matlab script, and explain what does not work about it. That would be a good Matlab question, and I'm sure you would get help.

[Suraj Sudhakar]

@William Rose I see, since fx and fy was given by matlab during calibration, I assumed there could be a function which I was not aware of that could give the desired result. But it does not seem to be the case. I shall delete the question then, thank you for your time

[William Rose]

@Suraj Sudhakar, you're welcome, and in my opinion there's no need to delete a reasonable question, which yours is.

[William Rose]

@Suraj Sudhakar, I'm curious: how did Matlab give you fx=sx*f and fy=sy*f? In other words, what input data and what script or function did you use?

This site looks like it could be helpful to you. https://www.cse.unr.edu/~bebis/CS791E/Notes/CameraCalibration.pdf

[Suraj Sudhakar]

@William Rose I used the camera calibration toolbox, but I have realised I do not need the focal length information. Thank you for your help.

[William Rose]

@Suraj Sudhakar, you're welcome.

Answer 1

[Matt J]

You can only find the focal length if you know the pixel sizes at the image plane. There's probably no way you can get it, but I also tend to doubt that you really need it. Why do you think you do?

[Suraj Sudhakar]

@Matt J I wanted to locate the sharpest object in an image using the distance and focal length information. But you are correct. It is not really necessary. I have found other easier methods. But thank you for the answer.