Patent GB-843888-A (GB)
Title: Improvements in or relating to stereoscopic microscopes
IPC: G02B21/22
Filed: 1958-06-26
Abstract: 843,888. Microscopes. ABBEY, A. (American Optical Co.). June 26, 1958, No. 20571/58. Class 97(1) In a stereoscopic microscope which comprises a head part movably mounted on a column secured to a base and embodying an optical system for forming a pair of spaced images of an object, said system including a pair of erecting prisms and a pair of eyepieces, the spacing between which can be altered to vary the interocular distance, such variation of the eyepiece spacing causing corresponding rotation of the images, the erecting prisms each have a roof surface of a dihedral angle which compensates for the image rotation when the eyepieces are spaced at the average interocular distance. As shown in Fig. 1, the microscope comprises a column 21 on which an arm 22 is movably mounted, this arm carrying a head part 23 and two housings 27, 28, pivoted about a common pivot pin 26 and enclosing erecting prisms and supporting inclined eyepieces 33, 34, the spacing of which is adjusted by rotation of the housings about the pivot pin 26. Light from the object on stage 20 is collimated by objective lens 24; and two images of the object are formed for viewing through the eyepieces by separate Galilean systems and lenses 31, 47 and 32, 48, Fig. 3, disposed at opposite ends of the associated roof prisms 29, 30. Several Galilean systems are provided for selective use, these systems being housed in a turret in the head part 23, which turret is rotatable by external knob 35, having a click indicator associated therewith. As shown in Fig. 5, each erecting prism is such that the light rays incident at one roof face are reflected to the other roof face 55 and thence internally reflected at inclined surface 56 to a silvered part 57 of the prism base, whence they are reflected through the lenses 47 or 48 into the eyepieces 33 or 34. Each prism is cemented to a mounting plate 51 or 52 which is detachably secured to the housing 27 or 28 and is apertured at 51a for engagement by locating pins 51b on the housing, so that the prism is properly positioned in the light path. The roof angle between the faces 54, 55 of each prism is such as to cause an image rotation which substantially offsets that due to the spacing between the eyepieces corresponding to an average inter-. ocular adjustment. As shown in Fig. 8 for the lens 47, each of the lenses at the eyepiece end of the erecting prism is held in an aperture in the housing 27 or 28 by a threaded member 63 which presses a shoulder 62 against the underside of the housing surface and has a passage 64 which is filled as with a low melting point metallic alloy 64a. To the upper end of this member 63 is threaded an eyepiece carrier 65, so that it can be adjusted for focusing, a setscrew 66 being provided to hold it in adjusted position. The microscope system is movable for focusing by a rack and pinion mechanism, Fig. 2, in which the rack 71 is secured to a dovetailed member 69, secured to the arm 22, and on which the pinion 76 extends through a second dovetailed member 73 which is fastened to the column 21. The pinion 76 is supported in bearings in each limb of a bifurcated spring 79 supported within the column 21.