Headlamp unit for motor vehicles

A slant type headlamp unit for a motor vehicle, comprising a reflector having an optical axis and as its inner reflecting surface a reflecting area taking the form of a part of a paraboloid of revolution, a lamp bulb having at least a coil filament disposed nearly parallel with the optical axis of said reflector and which has the center thereof disposed in a position slightly spaced frontwardly from the focus of said paraboloid of revolution, a front lens slantably disposed with respect to said optical axis, said front lens covering the front opening of said reflector and defining a front lens plane which includes a horizontal, X axis and a Y axis perpendicular thereto, said X and Y axes lying in said front lens plane and intersecting with the optical axis, said front lens having provided on its inner surface a plurality of prism areas which refract the rays of light emitted from said lamp bulb and reflected at said reflector, thereby forming horizontally elongated illumination patterns and slanted illumination patterns frontwardly with respect to said horizontally elongated illumination patterns, each of said prism areas being composed of a plurality of concave cylindrical prism elements having a bottom line extending along the deepest portion of said concave cylindrical prism elements, and each of said prism elements having a predetermined curvature required for forming respective illumination patterns;

• said reflector having light-diverging reflecting areas formed in positions above said optical axis and nearly symmetrical with respect to a vertical plane in which said optical axis lies, said light-diverging reflecting areas being composed of a plurality of light-diverging reflecting elements which diverge in the horizontal plane the rays of light emitted from said lamp bulb;
• said prism areas of the front lens comprising first and second prism areas, said first prism areas forming horizontally elongated illumination patterns in a frontward direction, said second prism areas forming slanted illumination patterns in a frontward direction and being located adjacent said first prism area;
• said first prism areas further comprising a finite prism area in which said bottom lines of said cylindrical prism elements are disposed parallel to the Y axis of said front lens plane, said finite prism area being positioned in the Y direction above said second prism areas, said second prism areas having bottom lines of its cylindrical prism elements disposed at an angle with respect to the Y axis thereby forming said slanted illumination patterns whereby said illumination patterns are superposed to produce a luminous intensity distribution pattern having a cut-off line which does not extend to a traffic lane running in the opposite direction of said motor vehicle.