Modulation of Radiated Light from Incandescent Lamp (I)

When the incandescent lamp is energized with alternating current, its tilament temperature riuctuates at twice the frequency of the power source. Consequently, radiant flux, luminous flux, color, etc. fluctuate. The magnitude of fluctuation is affected with the specific heat, size and average temperature of the filament ;Anti the frequency of the power source.In this paper. a discussion has been made for the fluctuation. Now. the energy flow from 'electric input to light output is considered as a transfer element to quantify the fluctuationin the communication system.Accrdingty. when transfer function G(s)=α/s+α is introduced to clarify the relation of the input power with the radiant energy, the output response to the alternating input W(t)=Wm(1-cos ω t) is given approximatety by J(t)=Jm{1-(α/ω) cos (ωt-π/2)} where; ω=4πf. f: frequency of the power source and luminous flux response is given by I(t)=Im{1-2(α/ω) cos (ωt-π/2)} where:a=1/τ τ: time constant of incandescent lamp.Modulation coefficient of luminous flux is a few percent to ten percent or so in 40-500 W lamps.(at 100 V. 60-cps.) for general use and these nearly coincided with experimental values. And the relation between “Modulation coefficients” of radiant energy mj, luminous flux mi, and temperature mt is given by mj=m/2=4.6mt=α/ω