Reflector for vehicular headlight

Abstract

A vehicular headlight reflector for forming a low beam light-distribution pattern by effectively utilizing the entire reflecting surface, and providing a light-distribution control function so that a pattern image generated substantially by a lower half surface of the reflector is located below the horizontal line and as close to the horizontal line as possible. A filament is arranged between a focus F of a reference parabola and a reference point D offset from the focus F so that its central axis extends in parallel with an axis passing through the parabola vertex O and the reference point D. A virtual paraboloid is assumed for each arbitrary point P on the reference parabola, the virtual paraboloid having an optical axis that extends in parallel with a light ray vector of a reflected light ray obtained when a light ray assumed to have been emitted from the reference point D and reflected at the point P, passing through the point P, and having the point D as its focus. A reflecting surface is formed as a collection of intersecting lines obtained when the virtual paraboloid is cut by a plane including the light ray vector and being parallel with the vertical axis (z-axis). Projected images of the light source are located so as to move around a rotation center on the horizontal line with a movement of representative points on an intersecting line in the reflecting surface.