Three Types of Night Vision Devices

Three Types of Night Vision Devices

Night vision devices are categorized into infrared night vision, thermal imaging, and image intensifier (I²) night vision. The first two types primarily utilize the principle of infrared radiation, while the third mainly utilizes the principle of low-light amplification.

Type 1: Infrared Night Vision

• Working Principle:The device emits an infrared beam to illuminate the target and converts the infrared image reflected by the target into a visible light image for nighttime observation. Militarily, it is mainly used for nighttime aiming, vehicle driving, reconnaissance photography, etc.  
• Characteristics:Active infrared night vision provides clear imaging and is not limited by ambient light levels. It can be used for observation in complete darkness with good results and is relatively inexpensive. However, its observation range is short. Due to the need for infrared illumination, it has disadvantages such as high energy consumption and the infrared light being easily detected by others' infrared detection devices, leading to exposure. It is now rarely used militarily.

Type 2: Thermal Imaging

• Working Principle:Based on the fundamental principle that any object above absolute zero temperature emits infrared radiation, it utilizes the difference in infrared radiation between the target and the background to detect and identify targets.  
• Characteristics:Because various objects emit infrared radiation of different intensities, people, animals, vehicles, aircraft, etc., can be clearly observed. Furthermore, it is not affected by obstacles such as smoke, fog, and trees, and can work both day and night. However, due to its very high cost, it is currently mainly used in military applications. The application range of thermal imaging is very wide, with a huge market in areas such as power, underground pipelines, fire protection, medical rescue, and industrial inspection.  

Type 3: Image Intensifier (I²) Night Vision

• Working Principle:"Low light" generally refers to weak light at night or under low illumination conditions, with an energy level of 10⁻⁴ lux. At night, under conditions of no artificial lighting, objects (or targets) in the natural environment are illuminated by starlight, moonlight, and airglow. While being illuminated, these objects also emit or reflect light into space. When the objective lens of the night vision device receives light from the object (or target), it forms an image on the photocathode of the image intensifier. When the image intensifier receives this faint optical image, it converts it into an electronic image. This electronic image is then amplified tens of thousands of times by the strong electric field within the image intensifier's electron optics system. A brightness-enhanced optical image is then obtained on the phosphor screen of the image intensifier, thus realizing the conversion of optical image - electronic image - optical image. This image is further magnified by the eyepiece for observation by the human eye.
• Characteristics:Since image intensifier night vision devices work by utilizing natural night sky light and do not have an active light source, they operate passively, thus providing good concealment. Image intensifier night vision devices are most suitable for departments engaged in specialized work, such as military, public security border defense, drug enforcement, anti-smuggling, nighttime surveillance, and security protection applications.