METAL HALIDE LAMP AND LIGHTING SYSTEM

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PROBLEM TO BE SOLVED : To provide a metal halide lamp particularly suitable for an automobile headlamp by improving thickness of an arc without enclosing mercury; and to provide a lighting system using it. SOLUTION : This metal halide lamp HPDL is equipped with : a fire-resistant and translucent airtight vessel 1 having a discharge space 1c having an inner volume not more than 0.1 cc; a pair of electrodes 1b, 1b enclosed in the airtight vessel 1 at an electrode-to-electrode distance not longer than 5 mm; and a discharge medium enclosed in the airtight vessel 1 by containing a metal halide containing a first halide of Sc halide and Na halide and at least one kind of second halide of In halide and Zn halide, and a rare gas without essentially containing mercury. In the metal halide lamp, the heat quantity in the discharge space is set above 50 W/cm2 in a stable time; when it is assumed that the spectral intensity of an impurity Cr and the spectral intensity of Sc within a lighting spectrum are A and B, respectively, a condition of A/B≤0.21 is satisfied.