A method of modulating an infrared radiation (IR) source that includes applying a time-varying, periodic voltage signal to the IR source, measuring a parameter of the voltage signal, and adjusting the voltage signal to maintain a substantially constant delivered power to the IR source. Adjusting the voltage signal is done based on the measured parameter and a predetermined relationship between the measured parameter of the voltage pulse and a resistance of such an infrared radiation source. Alternatively, the method includes applying a the voltage pulse, measuring a first parameter of the voltage pulse and a second parameter of a current passing through the infrared radiation source resulting from the applying step, and adjusting the voltage pulse to maintain a substantially constant delivered power to the infrared radiation source based on the first parameter and the second parameter.