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Some facts about thermal and night vision optics

Understanding night vision devices can be quite simple if you know what factors to pay attention to. There are a lot of terminologies here, several generations of equipment and its varieties.

We will tell you further about which product is suitable for your needs and how to determine it.

What are night vision devices?

This is special equipment that enhances the existing color in low light conditions. Some devices allow you to see in complete darkness, intensifying the infrared illumination of any object. The image is displayed on the monitor or eyepiece. Such goods are used in various fields, from military affairs to hunting or security. They differ from each other in price and technological features.

Principles of Amplification of Light of Night Vision Devices

The principle of operation of night vision scopes is to amplify the available light by 1000 times. The illumination visible to the human eye ranges up to 760 nm. Infrared devices have been seen from 760. A person or an animal does not see this anymore. Each generation of fixtures can display an image in its own unique spectrum. Therefore, we will talk about what they are later.

Generation of night vision devices

Generations are divided depending on the technologies that were used in the manufacture. Exists:

  • first;
  • 1+;
  • 2+;
  • 3;
  • 3+;
  • digital

The quality of the resulting image depends on the gradation of growth. But if we consider standard equipment, it consists of:

  • electro-optical converter;
  • eyepiece;
  • power supply unit.

An electro-optical converter amplifies the light many times over. This is determined by the generation of night vision sight. In terms of design, performance, and cost, the latest developments differ significantly from those that entered the market five years ago. Moreover, in recent years, they have practically ceased to develop. The fact is that there has appeared equipment called «best thermal scope for hunting». Its production is significantly cheaper than that of night vision devices. Accordingly, the final cost of the product decreases.

Among the main characteristics of the image converter, it is worth noting the possibility of increasing the luminous flux, the sensitivity of the photocathode, and the resolution.

Light Gain

The range of vision depends on it. For devices of 1 and 1+ generations, the light amplification factor can be in the range of 500 to 1000 times. It depends on the sensitivity of the photocathode and the light output of the phosphor. In fact, this coefficient shows how many times the image will be brighter after light passes through the equipment. The higher the sensitivity of the photocathode, the greater the light gain.

Photocathode sensitivity

The second most important characteristic, which is calculated as the ratio of the photocurrent to the value of the luminous flux. The photocathode reacts to the intensity of the light flux and its frequency, therefore its sensitivity is divided into integral and spectral.

Integral sensitivity characterizes the photocathode’s ability to respond to the entire light flux. The spectral sensitivity of the photocathode is the ratio of the photocurrent to the monochromatic radiant flux.


Depending on the modification of the device and the quality of its manufacture, the resolution in the center of the field of view, as a rule, can be from 30 lines/mm to 50 lines/mm. Consider all these characteristics in order to choose the perfect device for you.


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