GB558315A - Improvements in or relating to optical projection apparatus - Google Patents

Abstract

558,315. Optical-projection apparatus. SOC. GENEVOISE D'INSTRUMENTS DE PHYSIQUE. Oct. 5, 1942, Nos. 13940 and 13941. Convention dates. Feb. 5 and April 16. [Class 97 (i)] In apparatus for episcopic or diascopic projection of small objects for examination, and comprising objectives of different focal lengths alternatively movable into position for use, a movable support carries the objectives of short focal length and also one or more reflectors capable of being interposed between the object and an objective of long focal length, the objectives of long focal length being mounted independently of this support with their axes at an angle to the axes of the other objectives and the arrangement being such that the direct distance between the object and projection screen may be reduced. As shown, a support 4, slidable in guides 5, carries short focus lenses 3, 3<SP>1</SP>, 3" and a mirror 14, any of which may be brought into the projection axis through an object support 2. The projection beam through any of these lenses is reflected by mirrors 7, 10 on to a projection screen 12 located close above the support 2. A long focus objective 15, or one of two or more such objectives carried by a slide so as to be alternatively in projection position, is located with its axis substantially horizontal and receives the image beam by reflection from the mirror 14; the beam emergent from the objective 15 is reflected by mirrors 17, 20, when their pivoted carrier 18 is moved so that they are in the broken line positions indicated in Fig. 5, to the mirror 10 and thence to the screen 12. Lighting of the object may be effected by a fixed lamp 22, condensers 23, 24, and, when projection is through one of the lenses 3, 3<SP>1</SP>, 3", by a reflector 21 and transparent reflecting plate 25 mounted on the support 4. If projection is through a lens 15, a transparent reflecting plate in the position of the reflector 21, and the mirror 14 itself, effect the illumination by light received from the condenser 24. For diascopic projection, a fixed reflector 30 and one of condensers 31, 31<SP>1</SP> may transmit light from the lamp 2. A modification is described in which the mirrors 17, 20 are omitted and the mirror 10 is movable into either of two positions in which it reflects directly from the mirror 7 or from the objective 15 to the screen 12.