Method of operating a surgical microscope arrangement for computer-supported stereotactic microsurgery on a patient

A method of operating a surgical microscope arrangement for computer-supported stereotactic microsurgery patient having a patient coordinate system having known points located at respective positions in an object plane, the arrangement including:

• a multi-link stand and said surgical microscope having magnifying optics defining optical axis and a field of view plane and being mounted on said multi-link stand and said surgical microscope being equipped with optical means operatively connected thereto, and sensor means on said multi-link stand for supplying signals indicative of actual spatial coordinates and orientation of said surgical microscope, the method comprising the steps of:
• obtaining a defined position of selected ones of said known points on said optical axis under direct visual control through said magnifying optics and said selected ones of said known points having coordinates;
• measuring the position of said selected ones of said known points in the patient coordinate system in relation to said surgical microscope by said optical means;
• determining said actual spatial coordinates and the orientation of said surgical microscope by said sensor means;
• determining an absolute position and orientation of the patient in space from said selected ones of said known points which have been measured and said signals of said sensor means;
• correlating the observed field of view with corresponding diagnostic data;
• superposing an image from preoperative diagnostic data on said field of view and while taking into account the magnification of said magnifying optics;
• and,
• said image having coordinates corresponding to said coordinates of said selected ones of said known points.