**2.1. Brief history of IR imaging**

In 1829, Nicéphore Niépce (1765–1833, who was a French inventor) and Louis-Jacques-Mandé Daguerre (1787–1851, who was a French artist and photographer) had developed a photo‐ graphic plate sensitive to NIR radiation. Based on this invention, Sir William de Wiveleslie Abney (1843–1920, who was an English astronomer, chemist and photographer) and Edward Robert Festing (1839–1912, who was an English army officer and chemist) performed NIR radiation measurements in history [7]. In 1860, Gustav Robert Kirchhoff (1824–1887, who was an American physicist) recorded the atomic spectra of many elements and defined that "a hot solid object produces light with a continuous spectrum, a hot tenuous gas produces light with spectral lines at discrete wavelengths (i.e., specific colors) which depend on the energy levels of the atoms in the gas and a hot solid object surrounded by a cool tenuous gas (i.e., cooler than the hot object) produces light with an almost continuous spectrum, which has gaps at discrete wavelengths depending on the energy levels of the atoms in the gas" [12]. Kirchhoff's law of thermal radiation, Stefan-Boltzmann law, Planck's law and Wien's displacement law defined four basic laws of IR radiation [13].

The first thermal camera was invented by Kálmán Tihanyi (1897–1947, who was a Hungarian physicist, electrical engineer and inventor) in 1929. It was used for anti-aircraft defense in Britain [13, 14]. An evaporograph, which is considered the ancestor of thermal imaging, was initially discovered in 1956. In this technique, a thermal imaging device converts an IR image into a visible image via the differential evaporation or condensation of oil on a thin membrane [15].

In the following years, especially after the year 2000, the IR image capture conversion kits of digital cameras began to be developed. In 2006, the first professional digital camera, which was developed using ultraviolet (UV) and IR technology, was introduced [16].
