Reflector for illumination lamp capable of producing a stellate light

Abstract

The xyz orthogonal coordinate system is set so that the x-axis coincides with the optical axis of a reflecting surface. A fundamental surface has a reference point on the x-axis and a reference parabola included in a plane inclined, in a generalized form, from the xy-plane and having a vertex on the origin of the coordinate system and a focus on the x-axis in the rear of the reference point. The fundamental surface is a collection of intersecting lines each obtained by cutting an imaginary paraboloid of revolution having an axis extending in parallel with a ray vector direction taken by a reflected ray after being emitted from the reference point and then reflected at a reflecting point on a parabola that is an orthogonal projection of the reference parabola onto the xy-plane, passing through the reflecting point, and having a focus at the reference point by a plane in parallel with the z-axis and including the ray vector. The reflecting surface is formed by periodically arranging identical sectors of the number of apices of an intended stellate light distribution pattern around the optical axis. Each sector has a shape of a generally fan-shaped portion of the fundamental surface having a central angle of 360.degree. divided by the number of apices of the stellate pattern and located in the vicinity of the xy-plane or xz-plane.