GB900285A - Prism or mirror system for the adjusting of parts of optical instruments - Google Patents

Abstract

900,285. Prism systems; microscopes. ZEISSSTIFTUNG, CARL, [trading as ZEISS, C. [firm of]]. June 7, 1960 [June 9, 1959], No. 19868/60. Class 97 (1). An optical instrument includes a beam splitter and recombiner including partially transmitting as well as full reflectors so arranged that the part beam reflected by the first semi-reflecting surface travels (before re-combining therewith) through a different optical path length from the part beam which is transmitted by said surface, this beam splitter being arranged in use between two objects (e.g. diaphragms) at different axial distances from an image forming system so that an image of one object is formed in coincidence with an image of the other object. As shown in Fig. 2, as applied to a microscope having an objective 3, incident light from the axially spaced fixed diaphragm 1 and aperture is diaphragm 2 is split at a semireflecting surface 4<SP>1</SP>. The transmitted part beam a is again transmitted at 5<SP>1</SP> so that the objective 3 forms an image of the diaphragms 1, 2 at la, 2a respectively. The part beam b, which is reflected at 4<SP>1</SP> is internally reflected by a prism 6<SP>1</SP> on to the surface 5<SP>1</SP> and thence into the objective 3, whereby further images 1b, 2b are formed of the diaphragms 1, 2 respectively. The prism 6<SP>1</SP> is mounted on a carriage 18 slidable under the control of a screw 19 in a direction at right angles to the optical axis of the objective 3 so that the image 1a of diaphragm 1 is brought into coincidence with the image 2b of the diaphragm 2. Alternatively, the prism 6<SP>1</SP> may be fixed to the prisms having the semireflecting surfaces 4<SP>1</SP>, 5<SP>1</SP>. In another form, Fig. 3, the incident light is reflected at 13 on to a semi-reflector 15 whereby part of the light is returned through the semireflector 13, while part of the light is incident on a tetrahedral mirror 16 and reflected thereby through surfaces 15 and 13. A further form is described (Fig. 4, not shown), in which the semi-reflecting surface 15 is omitted and a second tetrahedral mirror is provided to return along its own path the part beam which is transmitted at the surface 13.