Patent GB-835319-A (GB)
Title: Improvements in or relating to anamorphotic optical systems
IPC: G02B13/08
Filed: 1957-08-06
Abstract: 835,319. Anamorphotic optical systems; photographic contact printing. MERIGOLD, P. A., COOK, G. H., and TAYLOR. TAYLOR & HOBSON Ltd. Aug. 6, 1958 [Aug. 6, 1957], No. 24739/57. Classes 97(1) and 98(2) An anamorphotic optical system for illuminating an aperture comprises a source of light, control means operative in an effective aperture intermediate between the source and the final aperture for varying the illumination of such final aperture, a front lens device which in one plane images the light source substantially on the control aperture and in a second plane at right angles to the first plane concentrates the light from the source substantially uniformly on the control aperture, a rear lens device having power only in the second plane and acting in such plane to image the control aperture substantially on the final aperture, and an intermediate lens device located adjacent to the control aperture and acting in the first plane to image an element of the front lens device substantially on the final aperture, and in the second plane to image an element of the front lens device substantially on the rear lens device. This system may be used in a contact printer wherein the light sensitive film and the film to be copied are fed in contact past a printing aperture A, and wherein a control film C, having as shown in Fig. 2, a dark area C<SP>1</SP> and a clear area C<SP>2</SP> (or coloured areas), moving in synchronism with the film to be copied, is fed past a control aperture B for varying the intensity of illumination (or the colour rendering) at the printing aperture. As shown in Fig. 1, the system comprises a front lens device made up of a spherical lens E, which images the light source D on the control aperture B, and a cylindrical lens E<SP>1</SP> which is operative in the plane parallel to the direction of the film movement, and images the front member E on to the control aperture B. The rear lens device consists of two cylindrical lenses F, F<SP>1</SP> operative only in the same plane as the lens E<SP>1</SP> and positioned to image the control aperture B on the printing aperture A. Between the front and rear lens devices there are two cylindrical members G, G<SP>1</SP>, of which member Gl operates in the same plane as member E<SP>1</SP>, while member G is operative in the plane at right angles. These members are arranged adjacent the control aperture B, so that member G images the front member E on the printing aperture A, whilst the member G<SP>1</SP> images the member E<SP>1</SP> substantially on the rear lens device F, F<SP>1</SP>. The front member E may be a single compound spherical component, or be made up of more than one spherical component, but preferably it is as shown a simple lens, having a slightly aspherical rear surface E<SP>2</SP>. The arrangement of Fig. 1 may be modified by the provision of an additional cylindrical lens E<SP>3</SP> operative only in the same plane as the member E<SP>1</SP>, and co-operating with the member E in this plane to image the source of light D on to the rear member E<SP>1</SP>, which image is relayed by the member G<SP>1</SP> on to the rear lens device F, F<SP>1</SP>. In a third arrangement, the light source has a shape generally similar to that of the control aperture B, and the system is simplified by the provision of only a single lens for the front lens device. The members G, G<SP>1</SP> may be combined into a single member having appropriate surface curvatures in the two planes, or may consist of a lens with spherical surfaces, having power equal to that of the weaker of the two cylindrical lenses and a relatively weak cylindrical lens, operative in one plane only and having power equivalent to that of the difference between the powers of the two cylindrical lenses. The control aperture B may be defined by a stop or by the image of a stop elsewhere in the system, or in the case of the third arrangement the control aperture may be defined by the image of the light source.