Patent ID: 8653731

Claim:
A metal halide lamp of a vertically mounting type comprising a translucent outer tube having a base formed at one end thereof and a light-emitting portion disposed in said outer tube, said metal halide lamp being applied to be mounted such that said base looks toward the upper side, characterized in that said light-emitting portion includes a discharge tube made of translucent ceramics, capillaries extended from both ends of said discharge tube, electrode assemblies enclosed in said capillaries and power supply lead wires extended from both ends of said electrode assemblies, a lamp rated power P [W] is selected so as to satisfy P=100 to 400 [W], if an effective length of said discharge tube is selected to be L and an effective inner diameter is selected to be ID, then 1.8≦L/ID≦2.3 is satisfied, said discharge tube has mercury and metal halides enclosed therein and if a lamp rated power is selected to be P, then a mercury concentration d(Hg) [μmol/cm 3 ] in said discharge tube falls within a range of ±10% of a mercury concentration d(Hg) given by the following equation: d (Hg)=0.0007 P 2 −0.4113 P+ 99.557.