US 11,989,915 B2
Intra-operative determination of a focal length of a camera for medical applications
Sebastian Stopp, Munich (DE); Johannes Zügner, Munich (DE); Johannes Manus, Munich (DE); and José Gardiazabal, Munich (DE)
Assigned to Brainlab AG, Munich (DE)
Filed by Brainlab AG, Munich (DE)
Filed on May 15, 2023, as Appl. No. 18/317,585.
Application 18/317,585 is a continuation of application No. 17/275,052, granted, now 11,694,363, previously published as PCT/EP2019/074155, filed on Sep. 11, 2019.
Claims priority of application No. PCT/EP2018/074664 (WO), filed on Sep. 12, 2018.
Prior Publication US 2023/0281874 A1, Sep. 7, 2023
Int. Cl. G06T 7/00 (2017.01); A61B 34/00 (2016.01); A61B 34/20 (2016.01); A61B 90/00 (2016.01); G06T 7/246 (2017.01); G06T 7/80 (2017.01); H04N 17/00 (2006.01); H04N 23/67 (2023.01)
CPC G06T 7/80 (2017.01) [A61B 34/20 (2016.02); A61B 34/25 (2016.02); A61B 90/39 (2016.02); G06T 7/246 (2017.01); H04N 17/002 (2013.01); H04N 23/67 (2023.01); A61B 2034/2055 (2016.02); A61B 2090/3937 (2016.02); G06T 2200/24 (2013.01); G06T 2207/30004 (2013.01); G06T 2207/30204 (2013.01)] 18 Claims
OG exemplary drawing
 
1. A computer-implemented method of determining a focal length of a camera, the method comprising:
providing uncalibrated camera data of a camera, wherein the uncalibrated camera data comprise an image of at least a part of a tracking system;
specifying an initial value of a focal length of the camera;
specifying a working distance value of a distance between the camera and the at least part of the tracking system;
calculating a distance value of the distance between the camera and the at least part of the tracking system based on the uncalibrated camera data and based on the specified initial value of the focal length of the camera;
calculating a change factor based on the specified working distance value and the calculated distance value;
calculating an adapted value of the focal length of the camera based on the initial value of the focal length and based on the change factor;
detecting one or more optical markers arranged on one or more surfaces of a marker device of the tracking system based on the adapted focal length value and based on the uncalibrated camera data; and
determining a position of a reference point of the marker device, particularly a position of a tip of the marker device, with respect to the camera; and/or
determining an orientation of
the marker device of the tracking system with respect to the camera.