line segment structure 502 of one lateral wall of the shaped reflector 50 comprises a plurality of inclined faces 502 a u02dc 502 n that respectively incline in such a manner that one upper inclined face inclines toward the center of the shaped reflector 50 at a relatively greater angle than the adjacent lower inclined face the first stepped straight line segment structure 502 has its top edge connected to an outer edge of a planar wall 504 which has its inner edge connected to the bottom edge of the second stepped straight line segment structure 505 the second stepped straight line segment structure 505 comprises a plurality of inclined faces 505 a u02dc 505 n that respectively incline in such a manner that one upper inclined face inclines toward the center of the shaped reflector 50 at a relatively greater angle than the adjacent lower inclined face the second stepped straight line segment structure 505 has its top edge connected to an outer edge of a slope 506 which slopes downwardly and inwardly toward the center of the shaped reflector having its inner edge connected to the bottom edge of the third stepped straight line segment structure 506 the third stepped straight line segment structure 508 comprises a plurality of inclined faces 508 a u02dc 508 n that respectively incline in such a manner that one upper inclined face inclines toward the center of the shaped reflector 50 at a relatively greater angle than the adjacent lower inclined face the other lateral wall of the shaped reflector comprises first second and third stepped straight line segment structures 518 519 520 a planar.