What is the principle of thermal imaging technology in night vision devices?

(1) Basic principles of infrared radiation

All objects will radiate infrared radiation as long as the temperature is higher than absolute zero (-273.15℃), which is the basis of thermal imaging technology. The temperature of the object is different, and the intensity and wavelength distribution of the infrared radiation it radiates are also different. Thermal imaging night vision devices use this feature to obtain its thermal information by detecting the infrared radiation emitted by the target object, and then form an image.

(2) The detector's perception of infrared radiation

The role of the infrared detector: The core component of thermal imaging night vision devices is the infrared detector. It can absorb infrared radiation from the target object. The detector is generally composed of many tiny detection units, which are usually made of materials such as mercury cadmium telluride (HgCdTe), quantum well infrared detector (QWIP) or type II superlattice detector. When infrared light is irradiated on the detector, the material in the detector will undergo physical changes, such as generating electron-hole pairs or changing the electrical properties of the material.

Signal conversion process: The detector converts the absorbed infrared energy into an electrical signal. This conversion is based on the photoelectric effect or other physical mechanisms. For example, in a detector based on the photoconductivity effect, the absorption of infrared light causes the conductivity of the detector material to change, thereby generating an electrical signal corresponding to the intensity of the infrared light. The size and change of these electrical signals reflect the difference in the intensity of infrared light radiated by different parts of the target object.

(3) Signal processing and imaging process

Signal amplification and optimization: The electrical signal generated by the detector is usually very weak and needs to be amplified and processed. There is a special signal processing circuit in the thermal imaging night vision device, which can amplify, filter, reduce noise and other operations on the electrical signal. The amplified signal can more accurately reflect the thermal information of the target object. At the same time, the signal processing circuit can also digitize the signal for subsequent image processing and display.

Image processing and pseudo-color display: The processed signal is sent to the image processing unit, where it is converted into an image through a certain algorithm. Pseudo-color coding is generally used to display thermal images, that is, infrared signals of different intensities (corresponding to different temperatures) are represented by different colors. For example, hotter areas may be represented by red or white, and colder areas by blue or black. In this way, the user can intuitively see the thermal contour and temperature distribution of the target object.

(4) Optical system assisted imaging

Thermal imaging night vision device is also equipped with an optical system, whose function is to collect infrared radiation radiated by the target object and focus it on the detector. The optical system usually includes optical components such as lenses and reflectors. The materials and designs of these components need to be able to effectively transmit infrared rays. With the assistance of the optical system, the detector's reception efficiency of the target object can be improved, and the clarity and accuracy of the imaging can be enhanced.

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