A conventional sealed beam headlamp equipped with a polarization plate of the absorption type (Dichrom) gives too weak illumination for driving, and the one with a sodium nitrate polarization plate, which scarcely, absorbs light, does not give the light distribution required by JIS for the passing beam, resulting in glare to a driver of oncoming car.
To get a polarization headlamp with sufficiently strong illumination and no-glare, a head-lamp system is constructed of a square reflector wide in horizontal direction, a bulb with a filament stretched vertically, a prism system and a cylindrical lens system.
Light beams refracted by the prism system proceed downwards under the horizontal plane which passes through the axis of the reflector, the beams directed upwards being cut off nearly perfectly.
A sodium nitrate polarization plate is arranged before the headlamp to construct a polarization headlamp. The polarization headlamp thus constructed is bright and satisfies the JIS for the driving beam, and the light intensities measured by an illuminometer covered by Dichrom are weak in upward directions, satisfying the requirments of JIS for the passing beam.
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