Philips Historische Producten museum Eindhoven (39/52)

Shown here is a series of three special incandescent lamps intended for laboratory use, for the calibration of optical instrument to be more precise. The one on the left is a ribbon lamp whose peculiar shape is designed to limit parasitic light reflections in the direction of the measuring instrument. Because of the configuration of its filament, this source is used primarily as a luminance and spectral standard. The two other lamps are flux standards of the vacuum type with straight filament (right) and of the gas-filled type with coiled filament (center).