Light collection system

In a short focal length light projection system of the light valve and film gate type for projecting light from an arc lamp through lenticular lens means to project a uniformly distributed image on the image forming plane of said light projection system, a compound reflector for said arc lamp comprising:

• an ellipsoidal reflector formed of an uninterrupted full surface of revolution about a central axis and positioned to collect a portion of the light from said arc and reflect a direct image of light from said arc in a beam between an inner cone and an outer cone, and
• a spherical reflector formed of an uninterrupted full surface of revolution about said central axis and positioned to collect another portion of the light from said arc and reflect the light back to said ellipsoidal reflector to be reflected by said ellipsoidal reflector as a secondary image of light from said arc in said beam,
• said light beam being directed through said lenticular lens means to project said direct image and said secondary image onto said image forming plane,
• said arc lamp having an anode electrode and a cathode electrode positioned in line along said central axis and including means for establishing said arc in the gap between said electrodes, said arc having its hottest portion adjacent said cathode electrode and a less intense more transparent portion of said arc adjacent said anode electrode,
• said ellipsoidal reflector being positioned relative to said arc lamp such that the adjacent focus of said ellipsoidal reflector is substantially located in the hottest portion of said arc on said central axis adjacent said cathode electrode and said spherical reflector being positioned relative to said arc lamp such that the center of said spherical reflector is substantially located on said central axis in the lens intense region of said arc, whereby light reflected to said ellipsoidal reflector passes through said gap in the more transpartent region of said arc.