opencv - How do I convert focal length in pixels to millimeter (mm)? -


i using opencv calibration method determine focal length of endoscope.

http://docs.opencv.org/doc/tutorials/calib3d/camera_calibration/camera_calibration.html

and getting focal length in pixels. want in millimeter , not know sensor dimensions. how can calculate focal length in millimiter (mm)?

refer this article, , this answer.

the intrinsic matrix contains 5 intrinsic parameters. these parameters encompass focal length, image format, , principal point. parameters \alpha_{x} = f \cdot m_{x} , \alpha_{y} = f \cdot m_{y} represent focal length in terms of pixels, m_{x} , m_{y} scale factors relating pixels distance , f focal length in terms of distance.

so if know size of sensor , hence physical size of every pixel, can derive focal length in mm, albeit approximation. still best endoscope's datasheet if need more precise number.


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