Abstract: An optical focusing system having two mirrors with reflecting surfaces in the shape of ellipsoids of revolution. They are positioned relative to each other so that the second mathematical focal point of the first ellipsoid coincides with the first mathematical focal point of the second ellipsoid, counting the focal points in the direction of passage of the light, and the entrance pupil of the system lies at the first mathematical focal point of the first ellipsoid. The ratio of the length of the major axis to the length of the minor axis of the second ellipsoid is selected so that the isoplanasie condition for elimination of coma of third order is satisfied.

Abstract: Adjustable optical apparatus having two optical systems both rotatable about a first axis of rotation. The first optical system has a first deflection element which, in addition to being rotatable about the first axis, is also rotatable about a second axis of rotation arranged at an angle to the first axis. The second optical system has a second light deflecting element which, in addition to being rotatable about the first axis, is also rotatable about a third axis of rotation at an angle to the first axis. The second optical system also includes a partially transmitting mirror, and a prism, both of which move bodily with the second light deflecting element around the first axis of rotation. The arrangement is useful in connection with a sighting system for gunnery control or weapon control, either in actual battle or in simulated situations such as in training apparatus.

Abstract: The invention contemplates a periscope mirror system wherein viewing on a selected one of two 180.degree.-opposed viewing axes is provided to a single exit-mirror for directing exit light in the same direction regardless of the selected viewing axis. The entrance mirror and the exit mirror are angularly positionable on parallel pivot axes which for a first direction of viewing involve direct reflection from the entrance mirror to the exit mirror, and which for the opposite direction of viewing involve indirect reflection from the entrance mirror to the exit mirror via an intermediate image-erecting third mirror.

Abstract: A device for binocular viewing of, for instance, fluorescent screens, image converters, and image intensifiers. Designed to be hand held, the device is light and compact. A single optical system of at least four lens elements provides the desired magnification. Behind the last element (in the direction of travel of the light from the object being viewed to the eyes of the person using the device) there are two rhombic prisms to spread the light beam to the two eyes of the user. In a preferred form, the prisms are adjustable to match the interpupillary distance of the user. At least one of the lens elements of the magnification system preferably has an aspherical surface.