There are three types of special scopes for night hunting. Night vision devices are based on electro-optical converters, digital (similar in principle to a digital camera or camera), thermal imagers.
Thermal imaging sights are significantly superior inefficiency to their counterparts. It looks like a video camera. Instead of light, it registers heat. All items emit infrared radiation, which creates a heat map. It is shown on the screen with a contrasting image. In complete darkness, people, animals, and relief details are visible.
The bolometric sensor is the «heart» of the thermal imaging sight. It is sensitive to heat radiation. A microbolometer is a semiconductor matrix of thermistors deposited on a crystal. The distance between the elements is no more than 20 microns, and the sensitivity is hundredths of a degree.
Ordinary glass does not allow thermal radiation to pass through, so the scope lenses are made of rare-earth monocrystalline germanium. Infrared optics are black and have a characteristic luster. The matrix (its material, size, and resolution limit) and the size of the germanium lens determine the cost of thermal imaging scopes.
The eyepieces of thermal imaging sights are made of optical glass with diopter adjustment and a soft eyecup. They focus on the screen.
The sight is designed for firing. It is rigidly attached to the weapon, has a reticle, and is not afraid of shock loads during recoil.
When you buy the thermal scope for hunting, you need to pay attention to:
- Matrix resolution. Sensors differ in the number of sensing elements. Usually, matrices of the VGA 640×480 and QVGA 384×288 standards are used. The higher the resolution, the clearer the image on the screen and the more accurate the scope itself.
- Lens multiplicity, optical magnification. The number in front of the «x» shows how many times the image in the scope is larger than that visible to the naked eye. Usually, this is an increase of 1-4 times
- The angle of view. It Can be observed without moving the aiming point. It is inversely proportional to lens magnification. The higher the magnification, the lower the field of view and contrast.
- Frame frequency. The image in the sight eyepiece is updated cyclically. The higher the frame rate, the shorter the latency.
- Accurate shot range. The manufacturers indicate the range are three values that differ from model to model. Detection range is the maximum distance to the target at which they can be seen. The object must overlap at least two adjacent pixels in the scope to be considered detected. Recognition range is the distance at which it is still impossible to judge the details, but you can determine the type of target. The size of the recognized object on the screen must be at least 5-6 pixels. Identification range is the distance to the target from which all significant details can be distinguished. It can be judged by them if the visible size is more than 10-12 pixels.
Thermal imaging scopes manufacturers interpret target and shot identification distances differently. Atmospheric conditions also add uncertainty.
However, the detection range of biological targets and an accurate shot, even with inexpensive thermal imaging sights, is not lower than that of the most modern classic night sights.