GB1439011A - Longrange headlamp - Google Patents

Abstract

1439011 Vehicle headlamps CIBIE PROJECTEURS 3 July 1973 [5 July 1972] 31739/73 Heading F4R A vehicle headlamp comprises a parabolic reflector, a bulb having a cylindrical filament centred on the reflector axis on either side of the focus, and a lens 10 which has at least one refractory surface 28 which lies on the surface of a cone whose axis coincides with the reflector axis, thus forming with the other side of the lens a curved prism which deflects the reflected light rays to give a non-circular shape to the isocandelas of the lamp beam. The angle which the part-conical refracting surface makes with the other side of the lens is sufficiently small to ensure that the light rays are deflected by the surface 28 less than an amount which would diminish the illumination intensity along the reflector axis. This is illustrated by Fig. 5 in which the surface 28 deflects a notional illumination area ABCD to A<SP>1</SP>B<SP>1</SP>C<SP>1</SP>D<SP>1</SP>, the deflection not being so great as to reduce the light passing through the axis at O. the illumination at O thus remaining constant. In the example shown, the part-conical surfaces 28 are grouped in four sectors 16, 18, 20, 22 which give respective light beam deflection of 4 degrees 30 minutes in the directions of the arrows d to flatten the equal illumination curves into atrapezoidal shape, Fig. 6 (not shown). The groups of protrusions 28, which may be formed integrally with the remainder of the lens or separately adhered thereto, are separated from one another by a relative narrow horizontal non-deflecting strip 24 and by a relatively wide vertical diffusion strip 26. By suitable arrangement of the protrusions 28 equal illumination curves of other, e.g. rectangular, shape may be produced.