GB618376A - Improvements in or relating to collimators - Google Patents

Abstract

618,376. Optical gauging apparatus. REID & SIGRIST, Ltd., and CANTLE, L. G. H. Oct. 29,.1946, No. 32110. [Class 106 (ii)] [Also in Group XX] A device for testing the parallelism of two surfaces comprises a collimating lens with a light source in the focal plane thereof so that parallel light from the lens strikes a mirror which is disposed at right angles to the lens axis and is located by one of the surfaces, and also strikes another mirror located by the other surface; the parallelism between the surfaces is determined by measurement of the distance between the two images of the light source formed by reflection in the mirrors, these two images being focused on a scale in the focal plane of the lens, or in the space adjacent the light source, in which case the distance between them is found by using an eyepiece, for example. In the form shown, the collimating lens 14 and a glass disc 15, the surface 16 of which is silvered and which is apertured at 17 (or the disc may be silvered at its margin, the centre being clear), are carried by the part 12 of a telescoping tube 11, 12. Rotatable around the part 11 is a head 19, which slidably carries a magnifying eyepiece 21 and has fixed thereto a plate 30 bearing a scale, which is illuminated by light from a lamp and condenser unit, that is reflected by the surface 31 of a prism, through a slit in opaque material, disposed between the prism and the plate 30 on which it is mounted. The mirror 15 is placed on the surface 38 of the lens mount 37 of a photographic camera, while a mirror 34 is placed in contact with the film guide 39. Looking through the eyepiece, two images are seen on the scale and the separation thereof indicates the angle between the lens mount and film guide. Hence, one or other of these elements can be positioned correctly so that they are parallel.