Among the existing security technologies, low-light and infrared imaging are the most widely used night vision technologies. Low-light imaging is mainly used in anti-terrorist investigations and night vision devices for military operations, while infrared night vision imaging is mainly used for surveillance cameras more monitoring at night.
Low light imaging technology
Low-light night vision technology, also known as image intensification technology, is a photoelectric imaging technology that enhances the faint target image illuminated by night skylight through night vision goggles with image intensifier tubes for observation. In low-light night vision products, the image intensifier is the core device. The image intensifier is used to enhance the weak natural light in the night sky, such as moonlight, starlight, and atmospheric gray light by hundreds of times or tens of thousands of times to enable the human eye to perform long-distance vision. degree of observation. Yellow-green light is the most sensitive wavelength of the human eye, so fluorescent screens of this color are often applied to image intensifiers. When we watch special forces perform night vision imaging in movies and TV, the images in the night vision lens appear yellow-green because of this reason.
Infrared Imaging Technology
Infrared night vision technology is divided into active infrared night vision technology and passive infrared night vision technology. Active infrared night vision technology is a night vision technology that implements observation by actively illuminating and using the infrared light reflected by the target to reflect the infrared source. The corresponding equipment is an active infrared night vision device. Passive infrared night vision technology is an infrared technology that realizes observation by means of infrared radiation emitted by the target itself. It finds the target according to the temperature difference or thermal radiation difference between the target and the background or each part of the target. It is equipped with a thermal imager. At this stage, surveillance cameras are equipped with active infrared systems, and the application of passive infrared systems is still relatively small.
Advantages of Low Light Imaging Technology
The reason why low-light imaging technology is widely used in night vision by armies of various countries is because of its comprehensiveness. Compared with infrared technology, this technology does not require infrared lamps to emit infrared rays, and does not require the observed object to have heat. Therefore, it is well adapted to the army's operations in different environments. When choosing infrared imaging technology, the first thing to consider is the loss and maintenance of the infrared lamp, and the second is to consider whether the observed object itself contains heat. The low-light imaging technology does not need to consider so much, and only needs to use natural light to achieve night vision. At the same time, the low-light night vision device has clear images, small size, light weight, low price, convenient use and maintenance, is not easy to be detected and interfered by electronic devices, and has a wide range of applications. These are also incomparable to infrared night vision imaging.
Disadvantages of low-light imaging technology
The disadvantage of low-light imaging technology is that it is easily affected by the surrounding environment. If you are afraid of strong light, you will have halo phenomenon. When encountering strong light, the night vision device cannot observe, and the observer will feel dizzy. Low-light images have poor contrast, limited gray scale, poor instantaneous dynamic range, flicker at high gain, and are only sensitive to the reflection of the target scene, regardless of the thermal contrast of the target scene.
The advantages of infrared imaging technology
The advantage of infrared imaging technology is that it emits infrared light for night vision imaging without the need for external ambient light. The night vision has a wide range and is less affected by the environment. It is mostly used in building surveillance cameras, mainly because it does not use natural light and is suitable for indoor use. The infrared thermal imaging of passive infrared technology is not affected by harsh environments such as rain, snow, wind and frost, and has clear imaging, high accuracy, and can identify camouflage and anti-interference. The infrared thermal imaging system does not rely on natural light like the low-light night vision device, but relies on the radiation of the target and the background to generate a scene image, so the infrared thermal imaging system can work 24 hours a day. Monitor with thermal imaging even during daylight hours.
Disadvantages of infrared imaging technology
The disadvantage of infrared technology is that infrared images are only sensitive to the radiation of the target scene, but not sensitive to changes in the brightness of the scene. This technology must rely on the infrared rays emitted by infrared lamps. Thermal imaging requires the temperature of objects and the intensity of infrared rays, which cannot adapt to the monitoring requirements in different environments. Moreover, the thermal imaging image is not clear, and the sensitivity to the surrounding environment is not strong. Infrared lamps are easily damaged and require maintenance and replacement.
From the perspective of scientific and technological development, infrared technology has certain advantages. The existence of visible light is conditional, and any object is an infrared source, which is constantly radiating infrared rays, so the application of infrared technology will be everywhere. At present, in terms of short-range night vision, low-light night vision devices still occupy a dominant position due to their low price and better image quality.
With the development of low-light and infrared imaging technology, it has become an effective technical means to synthesize and explore the feature information of low-light and infrared images to fuse them into a more comprehensive image. Night vision image fusion enhances scene understanding, highlights objects, and facilitates faster and more accurate detection of objects in hidden, camouflaged, and disorienting military backgrounds. Displaying the fused image in a natural form suitable for human observation can significantly improve the recognition performance of the human eye and reduce operator fatigue.