GB1370376A - Vehicles having a rear view optical system - Google Patents

Abstract

1370376 Rear view observation devices C E C ROBERTS 27 July 1972 [8 Nov 1971] 51853/71 Heading B7J In a vehicle which may have its own motive power unit or may be a trailer such as a caravan 6, Fig. 5, an optically-transparent prismatic lens 4 is arranged in, on or near the rear window 5 so that parallel light passing through the lens 4 is diverged but generally deflected downwardly (along path 10) relative to its original direction 9. Thus the driver 7 of a towing car 8 can see the road immediately behind the caravan 6 via his driving mirror and the lens 4. As shown in Figs. 1 and 4, the lens may have one or more prismatic sections 1 and one or more concave sections 2, the surfaces of the prismatic sections 1 being parallel and the surfaces of the concave sections 2 being concentric. The lenses are as planoconcave diverging lenses, of which the focal length may be substantially uniform for a whole lens and be between one and six feet, preferably about three feet, or the focal length of a lens may be greater at its central portion than at its edges. The minimum angle of deflection caused by the lens should not be more than 10 degrees and preferably be about 5 degrees. The lenses are circular and have a respective annular lip 3 by which a lens 1 may be attached in a circular hole in the window 5. A prismatic lens may be formed by two contoured transparent sheets bonded around their edges and containing transparent liquid therebetween.