Patent GB-365082-A (GB)
Title: Antidazzle device
IPC: F21S8/10
Filed: 1930-08-13
Abstract: 365,082. Polarizing apparatus ; goggles. COOKE, A. G., 101, Brondesbury Road, and GARDNER, C. F., 1, Balderton Street, both in London. Aug. 13, 1930, Nos. 24271/30, 25380/30, 25381/30, 37569/30, 997/31, and 16805/31. [Class 97 (i).] In an antidazzle system for use with vehicle or other moving or stationary light sources in which one or more projectors are associated with polarizers adapted to produce plane polarized light whilst the observers are equipped with corresponding analysers, each polarizer and analyser consists of four or more strips which are constituted by piles of glass or like plates, or their natural or artificial optical equivalent, and are arranged substantially louvre, dihedral, or zig-zag fashion with their planes at approximately 33‹ to the parallel beam from the projector, and so disposed that the planes of polarization are at 45‹ to the vertical. The analysers may be in the form of a screen mounted on or associated with the windscreen of a vehicle, or they may be formed as spectacle lenses. The polarizers and analysers may be in several sections disposed on an imaginary surface which may be plane, cylindrical, or spherical about the light source or the observer, all the sections being protected by thin glass or like cover-plates. Unpolarized or unsuitably polarized light may be absorbed or deflected by means of prisms or reflectors, and the strips may be secured in their desired relationship by interposing between them prism, wedge, or other shaped members of glass or like transparent material of skeleton or solid formation. Quarter-wave plates may be used to rotate the plane of polarization of the polarizer, the analyser, or both, thus permitting a simple form of analyser to be used. Fig. 3a shows a projector embodying an incandescent electric lamp bulb b containing a very compact filament a and a non-parabolic reflector g, piles of plates c, d, a paraboloidal reflector p which is extended forwardly at k and provided with polished or matt flat lateral surfaces h, and a prismatic front glass e which is preferably inclined backwards. In the form shown in Fig. 15, the projector comprises an apertured spherical reflector r which is slightly out of centre with the coincident foci of a paraboloidal reflector p and an ellipsoidal reflector e, the latter having its second focus coincident with that of a condenser lens l, an apertured plane mirror m and a preferably reflecting tube t. The mirror may be normal to the axis of the projector, it may be inclined as a whole or in two halves, or it may be divided into zones, as shown, each of which may be inclined, The Specification describes numerous modifications of such auxiliary reflecting surfaces which are so shaped and arranged that the secondary bundles of. rays formed by them are paired horizontally or radially with the primary bundles of rays produced by a single reflection from the reflector p. Fig. 18 shows a projector in which the bulb b is spherical with its centre in front of the filament and containing four or more very thin matt vanes v passing through the axis of the bulb and a reflector r in the form of a surface of revolution the cross section of which is an involute to the circular section of the filament. The projector also comprises an ellipsoidal reflector e having its rear edge cut away as at x and a narrow paraboloidal reflector p<1>. The Specification also includes details of other forms of bulbs containing reflectors which are adapted to produce a hemisphere or a narrow .cone of light the envelopes of the bulbs being so shaped that the rays of light pass substantially normally through them. The Specification describes various forms of screens to prevent light passing directly between the edges of the louvres. Fig. 14 shows a cellular black-walled diaphragm a, a placed between the edges of the louvres a2, b2 and short shades b at the forward edges of the louvres. Fig. 23 shows means for purifying the roughly polarized light which has passed through the plates c. It comprises a half-wave plate s or its equivalent, louvred reflectors u, u1, some of which may be replaced by a glass prism g or by translucent barriers, and piles of plates f arranged parallel to the axis of the projector. The reflectors u, u1 are silvered except for small areas which are made matt.