What is the difference between low-light-level night vision and infrared night vision?

1. Different imaging principles

Low-light-level night vision: an optical instrument that amplifies and enhances weak natural light (such as moonlight, starlight, etc.). Its core component is the image intensifier. When working, the photocathode in the image intensifier converts weak light signals into electronic signals. After acceleration and focusing, these electronic signals hit the fluorescent screen and are reconverted into enhanced light signals, so that the observer can see a brighter image than the original scene. For example, in a field environment with only starlight, low-light-level night vision can amplify weak light, allowing users to see the outlines and details of surrounding objects.

Infrared night vision: divided into active and passive types. Active infrared night vision devices emit infrared rays to illuminate the target, and then receive infrared rays reflected by the target to form an image. Passive infrared night vision devices (thermal imaging night vision devices) are based on the principle that all objects will radiate infrared rays as long as the temperature is higher than absolute zero (-273.15℃). The infrared rays emitted by the target object are received by the detector, and then converted into electrical signals. After processing, thermal images are formed. Different colors on the thermal image represent different temperature areas, thereby showing the shape and temperature distribution of the target object. For example, in a completely dark room, a passive infrared night vision device can clearly show the outline of the human body based on the temperature difference between the human body and the surrounding objects.

2. Differences in observation effects

Low-light-level night vision devices:

In an environment with a certain amount of natural light, it can provide relatively clear, detailed and close-to-natural visual images, which helps to observe the shape, characteristics and surrounding environment of the target. For example, using a low-light-level night vision device to observe animals in the woods under moonlight, you can see details such as the appearance and fur color of the animals, and the image color is similar to that of natural scenes.

However, in completely dark or extremely weak light environments, its imaging effect will be greatly limited and may not be able to effectively detect the target. For example, in a basement without any light source, low-light night vision devices basically cannot work properly.

Infrared night vision devices:

Does not rely on external light, can work normally in a completely dark environment, can clearly show the temperature difference between the target and the surrounding environment, even if the target is hidden in the grass, woods or caves, as long as there is a difference between its body temperature and the background, it can be easily found. For example, when looking for prey hidden in the grass at night, passive infrared night vision devices can find it through the heat emitted by the prey's body.

However, the imaging effect of active infrared night vision devices may be affected by the reflectivity of the target, and the imaging of targets with low reflectivity may not be clear; the thermal imaging images of passive infrared night vision devices are usually displayed in pseudo-color, and the details are not as rich as those of low-light night vision devices, which requires users to adapt to and interpret thermal image information for a certain period of time.

3. Different usage scenarios and environmental adaptability

Low-light-level night vision device:

It performs well in clear nights, wide fields of vision and unobstructed environments, but in bad weather, such as heavy rain, fog, thick smoke, etc., its imaging effect will be greatly reduced, and even normal observation will not be possible. For example, in foggy weather, the low light is scattered by the fog, and it is difficult for the low-light-level night vision device to see distant targets clearly.

In a densely vegetated forest, if leaves and other objects block most of the light, it will also affect its observation effect.

Infrared night vision device:

It has strong adaptability to bad weather and complex environments. Whether in rain, fog, snow and other weather conditions, or in an environment with smoke, dust and other obstructions, it can penetrate these obstacles and find the target. For example, in fire scene rescue, passive infrared night vision devices can penetrate thick smoke to observe the location of trapped people.

In a dense forest, it can also effectively detect the target's heat signal without being affected by vegetation. However, if the active infrared night vision device is in an environment with strong light interference (such as strong light reflection or other infrared sources around), its imaging effect may be affected.

4. Different concealment

Low-light night vision device: It does not emit light by itself, but it may be discovered by reflecting the surrounding light when in use, especially when the moonlight is bright or infrared fill light is used, which can easily expose the user's position.

Infrared night vision device: Passive infrared night vision device does not emit visible light when working. It is relatively concealed during use and is not easy to be discovered by the target, which is conducive to the user not being disturbed when approaching the target; while active infrared night vision device can emit infrared rays by itself, so it may be discovered by the opponent's detector to a certain extent.

5. Differences in price and energy consumption

Low-light night vision device: The price is relatively affordable, especially the first and second generation low-light night vision devices. Its energy consumption is relatively low, and it can generally maintain a long working time using ordinary batteries. This is because it mainly amplifies the existing light and does not need to emit infrared rays like active infrared night vision devices.

Infrared night vision device: The price range is wide. Passive infrared night vision devices (thermal imaging night vision devices) are usually more expensive due to their complex technology; active infrared night vision devices are relatively cheaper. At the same time, active infrared night vision devices need to consume a certain amount of energy to emit infrared rays, and the energy consumption is higher than that of low-light night vision devices; the energy consumption of passive infrared night vision devices mainly depends on the detector and signal processing processes, and is generally higher than that of low-light night vision devices.

• Previous: How to use low-light night vision goggles correctly?
• Next: What is the main difference between the third-generation and second-generation night vision devices?