Abstract: The invention relates to an optical system wherein a masking arrangement removes a component region from an overall region to be viewed while minimizing stray radiation. The improvement afforded by the optical system of the invention is provided by two measures which augment each other in an advantageous manner. The first measure is the use of a component masking arrangement wherein the masked out component region is directed onto a mirror. The second measure is provided by focusing the entering beam with a mirror onto the masking arrangement for masking out the component region. With the controlled removal of the component region, the masked out component region as well as the remaining region can be viewed simultaneously. After an intensity adaptation of one region, which can be carried out if required, both regions can be joined again to a total region.