Development of 3-D electromagnetic field intensity measurement system using infrared 2-D lock-in amplifier

Abstract

We have developed a 3-D electromagnetic field measurement system using 2-D lock-in amplifier. In this system, a modulated amplitude of electromagnetic wave is illuminated to an absorption screen to generate a heat distribution. A very small change of temperature on a screen illuminated with the modulated electromagnetic wave is measured using an infrared thermograph camera. To show the usefulness of the developed system, we compare the observed temperature change distribution to the optical power distribution emitted from LED light source. From the result, we found that the system is well working and it is possible to measure the temperature change in order of several mK (milli-Kelvin). Furthermore, we tried to use it for measuring an invisible GHz electromagnetic wave. We illuminated the electromagnetic wave to a conductor with shape of ldquoOrdquo. When we observed the temperature change on the screen putting behind the conductor, we can have a clear image of the shape of ldquoOrdquo.