The undisputed understanding of infrared technology and its principles is its temperature measurement. When measuring temperature with a two-color thermometer, the infrared energy emitted by the measured object is converted into an electrical signal on the detector through the optical system of the two-color thermometer. The temperature reading of this signal indicates that several important factors determine the temperature measurement. Important factors are emissivity, field of view, distance from the spot, and spot location.

Emissivity, all objects reflect, transmit and emit energy, and only the emitted energy represents the temperature of the object. When a two-color thermometer measures surface temperature, the instrument can receive all three types of energy. Therefore, all two-color thermometers need to be adjusted to only read the energy emitted. Measurement errors are often caused by reflected infrared energy from other light sources. Some two-color thermometers can vary emissivity, and emissivity values ​​for various materials can be found in published emissivity tables. Compared to the distance spot, the optical system of the bichromatic thermometer collects energy from the circular measurement spot and focuses it on the detector.

Optical resolution is defined as the ratio of the distance from the bicolor thermometer to the object to the size of the point being measured (d:s). The larger the ratio, the better the resolution and the smaller the spot size. The laser aiming is only used to help aim at the measuring point.