The principle of infrared night vision device

Sales Engineer: Gloria Gao

Email: gloria@bri-elec.com

The principle of infrared night vision device | classification

Infrared night vision device is a night vision device using photoelectric conversion technology. It is divided into two types: active type and passive type: the former uses an infrared searchlight to illuminate the target and receives the reflected infrared radiation to form an image; the latter does not emit infrared rays and relies on the infrared radiation of the target itself to form a "thermal image", so it is also called "thermal image". instrument". The infrared night vision devices currently on the market are all active. Passive infrared night vision devices are generally not called night vision devices, but have been renamed thermal imagers.

The principle and development of infrared night vision device
All objects in nature are constantly radiating infrared rays. The higher the temperature of the object, the stronger the ability to radiate infrared rays. According to the intensity of infrared radiation of the detected object, people have created a precise instrument for determining the position of the object - night vision device.
At night, visible light is very weak, but infrared rays, which are invisible to the human eye, are abundant. The temperature of the human body, rocks, tanks, etc. is different, and the intensity of the infrared rays radiated is also different, and the display on the night vision device is different. Therefore, infrared night vision devices can help people observe, search, target and drive vehicles at night.
Although people discovered infrared light very early, they were limited by infrared components. The development of infrared remote sensing technology is very slow. It was not until 1940 that Germany developed lead sulfide and several infrared transmitting materials that the birth of infrared remote sensing instruments became possible. Since then, Germany has first developed several infrared detection instruments such as active infrared night vision devices. But none of them were actually used in World War II. Almost at the same time, the United States was also developing infrared night vision devices. Although the test was successful later than Germany, it was the first to put it into practical application. In the summer of 1945, the U.S. military landed and attacked Okinawa. The Japanese army hidden in the caves took advantage of the complicated terrain and came out at night to attack the U.S. military. The U.S. military placed a group of guns with infrared night vision devices near the cave, and the Japanese army just climbed out of the cave in the dark. Immediately knocked down by a burst of accurate gunfire. When the infrared night vision device first entered the battlefield, it played an important role in clearing the recalcitrant Japanese army on Okinawa Island.
The active infrared night vision device has the characteristics of clear imaging and simple production, but its fatal weakness is that the infrared light of the infrared searchlight will be detected by the enemy's infrared detection device. In the 1960s, the United States first developed a passive thermal imager, which does not emit infrared light and is not easily detected by the enemy. And has the ability to observe through fog, rain, etc.

Classification of infrared night vision devices
Infrared night vision device is a night vision device that uses photoelectric conversion technology to detect infrared intensity. It is divided into two types: active and passive.

Active infrared night vision device:
1. The instrument emits an infrared beam (IR) outward, irradiates the target, and converts the infrared image reflected by the target into a visible light image.
2. There is also a low-light night vision, which we often say "starlight night vision". Its principle is to use the starry sky and the weak outdoor light source to enlarge and convert it into an image through an electronic intensifier tube, so as to observe at night.
3. At present, almost all active infrared night vision devices in the world have low-light and IR functions, including the first, second, and third generation night vision devices. There are high-end advanced night vision devices with infrared and low-light functions, but there is no problem, in fact, there are.

Passive infrared night vision device:
Passive infrared night vision devices usually refer to "infrared thermal imaging". All objects in nature will not be at zero degrees, and they will emit electromagnetic radiation of different wavelengths. The higher the temperature of the object, the more intense the thermal motion of molecules or atoms. The stronger the infrared radiation. Passive night vision devices are imaged by infrared radiation emitted by the object itself. The key to both is that one is reflected by objects and the other is spontaneous through objects.

Comparison of Active Infrared Night Vision and Passive Infrared Night Vision

Observation distance comparison:
Because the active infrared night vision device wants to find the target in a completely dark environment, it must emit infrared light, and the usual effective distance of infrared light is within 200 meters. So your observation distance will not be greater than 200 meters. The standard passive infrared night vision device is about 300 meters.
Conclusion: Passive infrared night vision device is better than active infrared night vision device.
Image clarity comparison:
To put it simply, the active infrared night vision device can tell whether this person is Zhang San or Li Si. The passive infrared night vision device can only be a person or an animal, a sparrow or a rabbit. (except for level)
Conclusion: Active infrared night vision device is better than passive infrared night vision device.

Price comparison:
The higher the amount of "gold" in the passive infrared night vision device, the more expensive the cost.
Conclusion: Passive infrared night vision device is better than active infrared night vision device.
How to choose:
If you want to observe the target from a long distance in complete darkness without being found by the target, then it is easy to use a passive infrared night vision device. Especially in police investigation and anti-drug, anti-terrorism, firefighter search and rescue, soldiers fighting, security of secret units, etc.
If you need to see the target clearly and distinguish between Zhang San and Li Si, Active Infrared Night Vision is suitable for you. Of course, if you are tall, handsome and rich and want to improve your style by the way, passive infrared night vision is suitable for you. At present, the cheapest passive infrared night vision device is above 5 digits.
As for hunting, it is recommended to consider passive infrared night vision if the funds are sufficient, because some prey can detect infrared light. As soon as you catch it, it runs away!