Patent ID: 6908218

Claim:
A light source unit comprising: a lamp comprising a light emitting element and a lamp valve enclosing the light emitting element; and a reflector having a reflective surface for reflecting rays of light emitted by the lamp and refracted by the lamp valve so as to focus the rays of light on a predetermined focal point; wherein the reflector is larger than the light emitting element, and the reflective surface has a cross-sectional shape containing an optical axis and determined such that the following expression (1) takes a substantially constant value C when: (i) a point (x 2 , y 2 ) on an outer surface of the lamp valve is calculated through which a ray of light emitted from a position (s, 0 ) of the light emitting element and refracted at a point (x 1 , y 1 ) on an inner surface of the lamp valve passes, (ii) a point (x 3 , y 3 (=f(x 3 ))) on the reflective surface of the reflector is calculated where the ray of light refracted at the point (x 2 , y 2 ) intersects with the reflector, and (iii) said calculations are carried out by changing (x 1 , y 1 ) little by little: ( I - x 3 ) 2 + f ⁡ ( x 3 ) 2 + ( x 3 - x 2 ) 2 + ( f ⁡ ( x 3 ) - y 2 ) 2 + n · ( x 2 - x 1 ) 2 + ( y 2 - y 1 ) 2 + ( x 1 - s ) 2 + y 2 2 = C ( 1 ) where (I, 0 ) is a position of the focal point, and n is a refractive index of the lamp valve.