GB669774A - Improvements in or relating to prism systems - Google Patents

Abstract

669,774. Optical systems. LEITZ, E. May 31, 1949 [Nov. 1, 1948], No. 14587/49. Class 97 (i). In a prism system which comprises a prism having a partially reflecting surface for splitting a light beam incident thereon and image erecting means, the image erecting means in the path of one split beam is a Porro system of the first kind, the image erecting means in the path of the other split beam is a Porro system of the second kind and the partially reflecting surface of the beam splitting prism acts also as a reflecting surface of one of said Porro systems. In the system shown in Fig. 1, the prisms 2 and 6 constitute a beam splitting cube, the prisms 1, 2 and 3 comprise the Porro system of the first kind and the prisms 1, 3 and 5 comprise the Porro systems of the second kind and emergent beams A and B are parallel to the incident beam C. In order to make the optical parts of the beams A and B equal a glass block a is positioned in the path of beam A. Prism 1 may be omitted and, in such a case, a prism is placed immediately below the glass block a and another prism is placed below the prism 5. If, it is desired that the emergent beams be inclined at an angle to the incidentbeam, the latter may first pass through a prism having three internally reflecting surfaces - as described with reference to Fig. 5 of- SpeÚification 11556/99, [Class 97]. Various other forms of prism system are described. Fig.- 6 illustrates a microscope in which light from the objective 8 is incident on a prism 9 so that it is deflected through an angle of 45 degrees before striking the beam splitting surface of the prism system 10. The emergent beams pass through two rhomboidal prisms 11, 12 so that the distance therebetween is made equal to the interocular distance.