Abstract
A surface temperature distribution on a metal halide lamp bulb was measured by a thermograph whose original measuring waveband was from 2 to 5μm and limited by a narrow-band interference filter. The lamp bulb made of fused quartz was placed in a vacuum chamber to keep the operating temperature in a range from 800 to 900°C. In order to eliminate intense emission from an arc inside the bulb, the measuring wavelength was selected at an opaque region of the bulb, 4.9μm, after test measurements varying the wavelength from 3.5μm to 5.5μm. Uncertainty of the measured surface temperature was estimated to be smaller than ±15°C in a region near the center of the bulb where the angle of emission was smaller than 50°.
