Fumio Ohtani

Relative Spectral Distribution of Tungsten Coil Lamps

Our studies have been made on the relative spectral distribution over a visible region of coiled fi lament tungsten lamps compared with M-shaped coiled filament lamps. In three laboratories, precise measurement was made with a significant variety of lamp types. All data obtained were reduced into specific curves against the graybody distribution.General standard lamps for luminous intensity and also tungsten-halogen lamps having a single coil and coiled coil filament showed almost unique distribution. This was noted to be the same as that of the M-shaped lamp. A small discrepancy was observed in the shortest wavelength region between the samples and M-shaped lamp. The lower values in the M-shaped lamp were found to have been resulted from the larger absorption of its glass bulb. The type “JC” small projection lamp was the only exception in this case. It has a rather rough and scattered distribution similar to that of the ribbon filament lamp.This paper also presents the numerical analysis and further discussion on the overall emissivity of the coiled filament.