Halogen light sources are similar to incandescent sources in that halogen lights contain tungsten filament, except a halogen bulb contains halogen gas instead of the inert gas used in incandescent bulbs. The filament in halogen light bulbs typically operates at temperatures over 2,700 Kelvin, producing a spectrum that is shifted left toward the lower wavelengths of the visible region. An example spectral plot can be seen in Figure 5-2, showing that the spectrum of a halogen light bulb peaks in the NIR region.

Figure 5-2 2788K Halogen Bulb