GB1453829A - Projection or viewing apparatus - Google Patents

Abstract

1453829 Projectors and viewers LUCAS INDUSTRIES Ltd 30 Jan 1974 [9 Dec 1972] 56955/72 Heading G2J A projector or viewer comprises a light source 11, a transparency carrier 12, a transparent plate 19 positioned in the light path and movable in a plane perpendicular thereto and along mutually perpendicular axes, and means on the screen for superimposing on an image of the transparency a further image e.g. a triangle acting as a pointer, which is movable with the plate 19. In Fig. I light from a further source 21, mounted on plate 19, is reflected by the surface 23 of a prism 20, also mounted on the plate, and shows up as a bright area on the image of the transparency projected on to a screen 18. Alternatively projection lens 17 may be replaced by a magnifying lens for direct viewing. In alternative embodiments light is conducted from the light source 11 to the edge of the plate 19 by a fibre optic element and then reflected by the surface of a prism shaped recess, or a prism inserted in a recess, in the plate. Alternatively the end of the fibre optic element is mounted directly in the plate and provides the further image. If the reflecting surfaces are not illuminated they appear as black areas on the image. The plate is slidably mounted in a first guide which in turn is slidably mounted in a second guide, the two directions of sliding movement being mutually perpendicular.