# Optimized Passive Defense Measures via IR Imaging
## 1 Introduction  
Thermal spectroscopy lies in the heart of the radiation science [1]. In particular, the thermal radiation arises as the propagation of the energy [2]. In general, it travels in the form of the electromagnetic radiation, which is emitted by a hot surface that spreads heat waves in all possible directions [3]. Such waves travel from the source to the points of absorption with the speed of light. Hereby, the thermal radiation does not require an intervening medium for its propagation. In this regard, infrared techniques play an important role [4; 5; 6]. At a given length scale, infrared radiation takes place in a definite portion of the electromagnetic spectrum, where the radiation wavelengths lie in the range of about 700 nm to 1 mm. From the physical viewpoint, it is worth emphasizing that infrared waves have a longer wavelength than that of the visible light as perceived by our naked eyes [7; 8]. However, it has a shorter wavelength than that of the radio waves. Notice that the frequencies falling in the range of the infrared radiation are larger than the frequencies of the microwaves. Indeed, these frequencies are lower than those of the visible light that lie in the frequency band of about 300 GHz to 400 THz, see [9] and [6] concerning the passive infrared detection techniques. As far as the radiation effects over human bodies are considered, the IR portion of the electromagnetic spectrum is harmful in general. Fundamentals behind an optimized instrumental designing lie in the properties of emission spectra of black bodies [10; 11]. Ideally, an object is termed as a black body when it absorbs all radiation that falls on it. That is, it absorbs all wavelengths of the electromagnetic radiation [3]. Black bodies are the simplest object for testing our analysis in order to have an optimized electromagnetic radiation. In order to have an apt thermal coating [12], we address the issue of optimization of the radiation energy function with respect to the surface temperature of the body and wavelength of the radiation. It is worth mentioning that the emission of such radiations possesses a characteristic wavelength distribution that depends on the temperature of the black body [13]. In the vicinity of a given equilibrium,the radiation distribution can be viewed as a function of the wavelength of the radiation and temperature of the radiating body. An optimization of the energy is further supported because the body emitting the radiation attains a uniform temperature distribution in a few milliseconds to a few microseconds [14,15]. Regarding an apt design of thermal instruments, the black body radiation serves as the standard basis to explore radiation properties of real surfaces [7]. We consider optimization of the radiation distribution of a black body [13] because it is fully absorptive and acts as a complete diffuser. Herewith, the purpose of thermal detectors is achieved via the radiant energy that is radiated from a given body due to its temperature gradient. At temperatures above the absolute zero, all bodies emit thermal radiation [1,2]. On the other hand, a physical body reaches a hotter state by absorbing certain number of electromagnetic quanta [3]. Apart from the visible spectrum, it is worth mentioning that we have low and high energy radiation zones [7,9,10]. Namely, the infrared portion of the electromagnetic radiation is emitted naturally by a heated object that possesses wavelengths greater than the red end of the visible light, but less than that of the microwaves, viz. the range of 800 nm to 1 mm. Notice that there exist other radiations in the electromagnetic spectrum such as ultraviolet radiation, X-rays, and microwaves [3]. Ultraviolet radiation is an important element of the electromagnetic radiation that is radiated from the Sun, and other artificial energy sources, e.g., solarium [16]. Importantly, the Sun is among the main sources of the UV radiation.