1. A surgical microscope comprising: microscopy optics; a camera; a display system; and a controller; wherein the microscopy optics are configured to image a field of view onto the camera; wherein the camera is configured to obtain two-dimensional camera images of the field of view and to generate image data representing the camera images; wherein the microscopy optics are variable optics configured to change an imaging scale of the imaging of the field of view onto the camera; wherein the controller comprises a data memory storing object data of each member of a group of plural different surgical tools; wherein the controller is configured to: receive the image data from the camera and to process the camera images represented by the image data; determine an expected size of a surgical tool in the camera images based on the object data of the members of the group of plural different surgical tools and the imaging scale; and use the determined expected size of the surgical tool to identify the surgical tool in the camera images by object recognition, the object recognition including: limiting a search space of the object recognition by using the determined expected size of the surgical tool in the camera images; using the object data of the members of the group of plural different surgical tools and the imaging scale; and within the limited search space, selecting, from the members of the group of plural different surgical tools, a member corresponding to the surgical tool in the camera images.