Patent ID: 8277054

Claim:
A reflecting mirror that is for attaching to a high-pressure discharge lamp including a bulb and a pair of electrodes provided in the bulb, and has a reflecting surface that reflects toward the pair of electrodes some of light rays emitted by the high-pressure discharge lamp, the pair of electrodes opposing each other in a common axis thereof, wherein the reflecting surface has been corrected from a spherical surface at given reflection points on the reflecting surface such that within an area surrounded by line segments connecting points P 1 (Z 1 , Y 1 ) to Pn(Zn, Yn), Pp(Zn, 0 ), Pq(Z 1 , 0 ) and the point P 1 (Z 1 , Y 1 ) in the stated order, a part corresponding to a distance between the pair of electrodes is enlarged, where (i) a Z-Y rectangular coordinate system is defined with the common axis as a Z-axis and an axis intersecting the Z-axis at a right angle as a Y-axis, (ii) a Z-coordinate of a point Pi(Zi,Yi)(1≦i≦n) on the Z-Y rectangular coordinate system represents a position of an intersection point with the Z-axis of an ith reflection light ray that has been emitted from an ith one of 1st to nth points (n ≧3) arranged in the common axis in number order and has been reflected at the reflection point, and a Y-coordinate of the point Pi(Zi,Yi) represents an illuminance at the intersection point, and (iii) the point Pp (Zn, 0 ) and the point Pq (Z 1 , 0 ) respectively represent intersection points with the Z-axis of an nth reflection light ray and a 1 st reflection light ray, wherein, a cross section of the reflecting mirror, taken along the Z-axis, has the plurality of reflection points corrected to a position offset from the spherical surface to provide the reflecting surface.