GB699331A - Optical system for photo-composing machines - Google Patents

Abstract

699,331. Optical projection system for photocomposing machines. MONOTYPE CORPORATION, Ltd. Jan. 2, 1952, No. 121/52. Classes 97 (i) and 98 (i). Between fixed object and image planes two reflectors are situated in spaced staggered relation to reflect the image of a master character or symbol from the first to the second reflector along a path parallel to the path of incidence of the first reflector, and from the second reflector to the image plane along a third parallel path, the reflectors being adjustable along guides parallel to the aforesaid paths, and a projection lens is adjustable along a guide arranged parallel to the reflector guides and is mounted also for rotation about an azis parallel to these guides to place the lens either in the path of incidence of the first reflector or in the path of reflection of the second reflector, mechanisms also being provided for adjusting the reflectors and the lens individually along their respective guides in accordance with the desired magnification or reduction of the image. As shown, prisms A, B mounted in holders A<SP>1</SP>, B<SP>1</SP> with their hypotenuse faces towards each other and partly overlapping are moved by knob controlled rack-and-pinion drive along parallel vertical guides A<SP>3</SP>, B<SP>3</SP> in a housing C which is located between a master character at E and an image-receiving support H (not shown). A projection lens F in a holder F<SP>1</SP> is rack-andpinion mounted on a further vertical guide F2 which is itself rotatable in bearings F<SP>9</SP>, F<SP>10</SP> so that by rotating a plate F<SP>11</SP> secured to the guide the lens may be placed in either of the light paths el, e<SP>3</SP>, the plate F<SP>11</SP> being latched in the position chosen. The prisms and lens are positioned appropriately for a chosen magnification by sets of distance-pieces A<SP>9</SP>, B<SP>9</SP> (not shown) between the casing C and the bottom of the mounts A<SP>1</SP>, B<SP>1</SP> and a distance-piece F<SP>16</SP> between the bearing F<SP>10</SP> and the bottom of the mount F<SP>1</SP>. Alternatively adjustable distancepieces may be used or the lens and prism holders may be adjusted by externally operable screw rods passing through threaded holes in the holders which bear pointers co-operating with scales on the exterior of the casing C. The casing C has a hinged door which when opened to allow access to the lens and prisms allows a spring-loaded pivoted shutter-plate to close the aperture C<SP>2</SP> leading to the light-sensitive material, closing of the door pivoting the plate clear of the aperture.