GB320693A - An improvement in glare free headlamps for motor cars, lorries and similar vehicles - Google Patents

Abstract

320,693. Holloway, S. P. April 8,1929. Vehicle lamps.-A vehicle lamp comprises an electric lamp bulb L having its filament approximateJy coincident with the proximate focus f<1> of a substantially hemiellipsoidal reflector R, and one or more relatively small concave lenses D disposed between the conjugate focus f<2> and the bulb, the arrangement being such that rays of light from all parts of the filament pass through the lens after a single reflection without traversing the glass of the bulb a second time. The lamp-holder H is shown passing through an aperture at the apex of the reflector, but it may be arranged inclined or at right angles to the longitudinal axis of the reflector. The portion r of the reflector between its apex and latus rectum may approach, in a continuous curve or in steps, nearer to the focus f<1> than the truly elliptical form y, so that rays of light reflected by the portion r pass through the lens in zones nearer to its margin. The centre of the lens may then be obscured or partly obscured as at 0 with negligible loss. Also, the bulb L may be silvered or otherwise obscured as at 0<1>. The transverse section of the retlector may be progressively modified from the top and bottom towards the sides into an elliptical or other form to cause lateral rays of light to pass through the lens nearer to its centre. With such a reflector a narrow helical coil filament could be arranged vertically and the lens more strongly curved in a horizontal plane passing through its centre, without causing undue divergence. The lens could also be of elliptical, rectangular, or other non-circular shape, or it may be circular and provided with a stop or diaphragm of the desired shape. It may have one or both surfaces spherically or cylindrically concave, or it may be of meniscus, toric, of other figured form, and it may be irregularly roughened on one surface to avoid striations. It may be supported by a screen S provided with a window W through which some of the unreflected light can pass to illuminate the foreground.