Patent ID: 6467931
Filing Date: 2002-10-22
Classification: F21V,G03B

Abstract:
An illumination device comprising:light source means; and an optical member having an entrance surface which a light beam from said light source means is made to enter and an exit surface from which the light beam having entered the entrance surface is made to exit, wherein a plurality of prism portions each having an apical angle are arranged at the exit surface of said optical member, wherein a part of the plurality of prism portions totally reflect a part of the flight beam having entered the entrance surface, wherein said light source means has a tube-like shape, and the plurality of prism portions are formed such that a ridgeline forming each apical angle of the plurality of prism portions is approximately perpendicular to the longitudinal direction of the tube-like shaped light source means; and wherein each apical angle of prism portions located in a central region of the optical member is an obtuse angle and approximately equal, and each apical angle of prism portions located in regions surrounding the central region is an acute angle and approximately equal, among a plurality of prism portions.