Driver's vision enhancer and DRS Technologies. All objects above Absolute zero (−273.15 °C / −459.67 °F) emit infrared radiation (IR), an invisible form of light beyond the optical spectrum. The optical spectrum is part of the electromagnetic energy spectrum which consists of ultraviolet, visible, and near, middle, and far-infrared energy. Only a small part of the optical spectrum is visible to the unaided eye. The Sun emits energy across the entire electromagnetic spectrum. Solar energy strikes the surface of objects. Some of that energy is absorbed and stored as heat (thermal energy). After sunset, this thermal energy remains and is emitted in the
Photoacoustic effect added steady light does not produce any photoacoustic effect by itself, but changes the photoacoustic response due to the modulated/pulsed probing light. The resulting signal serves as a reference to all other measurements in absence of the background light. The photothermal part of the reference signal is maximal, since at photosynthetic saturation no energy is stored. At the same time the contribution of the other mechanisms tends to zero at saturation. Thus the reference signal is proportional to the total absorbed light energy. In order to separate and define the photobaric and photothermal contributions in spongy samples (leaves, lichens) one