Imaging principle of thermal imaging night vision device

1. Principle of infrared radiation

All objects will radiate infrared rays as long as their temperature is higher than absolute zero (-273.15℃). The higher the temperature of the object, the stronger the infrared energy it radiates. Thermal imaging night vision devices are based on this principle and form images by detecting infrared rays emitted by objects.

2. Working process of detectors

Absorbing infrared rays: The core component of thermal imaging night vision devices is the infrared detector, which can absorb infrared rays radiated by target objects. The detector is usually composed of many tiny detection units, which can be made of materials such as mercury cadmium telluride (HgCdTe), quantum well infrared detectors (QWIP) or type II superlattice detectors. When infrared rays are irradiated on the detector, the material in the detector undergoes physical changes, such as generating electron-hole pairs or changing the electrical properties of the material.

Signal conversion: 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 detectors 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 various parts of the target object.

3. Signal processing and imaging

Signal amplification and processing: 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, and reduce noise 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: The processed signal is sent to the image processing unit, where the signal is converted into an image through a certain algorithm. Generally, pseudo-color coding is 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, users can intuitively see the thermal contour and temperature distribution of the target object.

4. Optical system assistance

Thermal imaging night vision devices are also equipped with an optical system, which collects infrared radiation from the target object and focuses 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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