How Thermal Works

How Thermal Works

All bodies with temperature above the absolute zero (0°K, -273°C) emit incoherent electromagnetic waves as the intensity is stronger in the infrared range.

The infrared area of the electromagnetic emission is divided conditionally to four parts:

• Near infrared (0.75 µm  ÷ 3 µm);
• Mid-wave infrared (3 µm ÷ 6 µm);
• Long-wave infrared (6 µm ÷ 15 µm);
• Very-long wave infrared (15 µm ÷ 100 µm).

The emitted quantity and the wave distribution depend on the temperature of the body. The hotter the body, the more IR energy with lower wave length emits. The mathematic relation between the temperature of the body and the wave length of the maximum of the emission is expressed with the low of Wien:
?max=2898/T?
Example:

At temperatures <600 ° C energy emitted is concentrated entirely in the infrared part of spectrum.  Above this temperature human eye is already able to perceive thermal radiation. Of the total emission only a small part is in the visible range. With the escalation of the temperature, the emitted energy seen by the eye is increased too. The object begins to burn with a reddish tinge and when rising the temperature, color crosses the bright red, yellow to white tones.

All objects, both natural and manmade, emit infrared energy as heat. By detecting very subtle temperature differences of everything in view, infrared (or thermal imaging) technology reveals what otherwise would be invisible to the naked eye. Even in complete darkness and challenging weather conditions, thermal imaging gives users the ability to see the unseen.

First developed for military purposes, thermal imaging has since been adopted by law enforcement, fire and rescue teams and security professionals. This technology can be used to detect approaching people or vehicles, to track the footsteps of a fugitive or to learn why a fire resists extinguishment. An electro-optic detector absorbs electromagnetic radiation and outputs an electrical signal that is usually proportional to the irradiance (intensity of the incident electromagnetic radiation). Depending on the type of detector and the way in which it is operated, the output signal can be either a voltage or a current. Radiation at specific wavelengths or within relatively narrow spectral bands can be generated electrically. Short wavelength radiation such as x-rays can be preferentially generated by accelerating electrons to high energy and having them rapidly decelerate by striking a target. Light emitting and laser diodes emit radiation at particular wavelengths by causing electron transitions between specific energy levels of the diode semiconducting material.An electro optical infrared detector absorbs electromagnetic radiation and outputs an electrical signal that is typically proportional to the radiance (intensity of the incident electromagnetic radiation). Depending on the type of infrared detector and its operation, the output signal can be either voltage or supplied current.

Thermal weapon sights and infrared scopes for rifles and other MIL-STD-1913 picatinny rail equipped weapons for forward-looking infrared (FLIR) target acquisition and long range use.

NITEHOG thermal infrared weapon scopes are manufactured to very strict standards. Performance measurements are listed for specific target acquisition and detection using NATO-standard performance charts and calulations. These sights provide superior imaging capability in environments where night vision cannot perform. NITEHOG thermal and infrared products are precision electro-optical instruments and are available to local, state and federal agencies as well as all branches of the United States Military. They are also available to US citizens for purchase within the United States. All systems are subject to strict compliance with all relevant laws and export restrictions.

Thermal Terminology

NUC (Non Uniformity Correction)
Each pixel of the matrix is generating a signal, but different from other pixels signals in the same conditions of observation. This non uniformity leads to some noise artifacts in the picture. This phenomenon is highly expressed in non cooled systems. Therefore it is necessary to be done periodically non uniformity correction (NUC) when the sight is in operating mode. Current infrared focal point arraysare fundamentally limited by their inability to calibrate out component variations. Fixed pattern noise caused by the nonuniform response of the sensors gives the uncorrected images a white-noise-degraded appearance. Nonuniformity correction (NUC) techniques have been developed and implemented to perform the necessary calibration for most IR sensing applications. NUC-algorithm can be activated manually via pressing the button N or automatically, after a set period of time. When holding the button for more than 2 seconds the algorithm is deactivated. NUC is commonly known as activating the “shutter” on thermal systems to refresh the thermal scene.

Image Inversion (Polarity)
In certain scenes of observation is necessary to invert the image colors from white-hot to black-hot and vice versa. Thus can be detected so far undetected fragments and details, merging with the background of the scene, and as well as to improve observation comfort.