GB1146146A - Optical projector - Google Patents

Abstract

1,146,146. Optical projection apparatus. R. VAN BERLYN (James W. Lucas). May 16, 1966, No. 21549/66. Heading G2J. In a portable overhead projector in which information may be added to a projected image, light from lamp 32 is directed by mirror 35 and condensers 36, 37 through a film-strip or slide at picture gate 38 and leaves projection lens 46 along path P1 to be reflected by mirrors 12 along path P 2 until it passes through a further film-strip 26 mounted on glass plate 48 and is reflected back through that film-strip by a concave mirror 47, to be focused on plate 48, the image focused on the plate and the image on film-strip 26 being projected by reflecting head 49, 50, 51 on to a distant screen. Mirror 47 may be the silvered surface of a plano-convex lens, and a negative Fresnel lens 47A immediately below plate 48 reduces double-imaging. Mirror 12 may be tilted to position 12A, and the hatch 55 raised, to direct images from an external projector 53 on to film 26, or again, the mirror may be tilted further to deflect the projection beam from the internal projector directly on to an external screen. Magazine 45 may contain slides for feeding in at opening 44 to aperture 38, or adaptor 39 may contain a film-strip which is manually advanced. Film-strip 26 is manually wound by crank 56 from spool 57 over plate 48, under mirror 47 and on to spool 62. A blower cools the lamp compartment. The projection head is focused by knob (17), Fig. 1 (not shown), which adjusts rod (16) through friction wheel (18) to set the inclination of pivoted cover (14) to which the head is secured. The head may be tilted relative to lid (14) for screen height adjustment. Lenses 49, 51, Fig.3, are separated by at least two-thirds of their diameter, and the focusing travel is reduced by the use of a hinged supplementary lens 52.