Night Vision vs Thermal Imaging in Rain: Which Works Better?

Picture from thermal vision on right and picture of night vision on left
Ivaylo Stoyanov
Ivaylo Stoyanov

PhD in Optics, is an expert in the field of gun scopes and thermal optics with years of experience and numerous publications in academic journals.

When it comes to night vision and thermal imaging, they both have their own advantages and limitations. In this article, we’ll explore how both of these technologies work, and which one would work better in rainy weather conditions. Additionally, we’ll discuss the important factors to consider when deciding whether to use night vision optics or thermal imaging devices.

Understanding NV and TV Technologies

Night vision (NV) technology captures and enhances weak night light that is reflected from objects. The lenses of a night vision device can capture the most inefficient light radiation that is invisible to the naked eye. The collected light then enters the photocathode, where it is converted into electrons. These electrons enter the microchannel plate and cause an additional emission of electrons, leading to an increase in the amount of energy.Objects in night vision and thermal vision Finally, these electrons bombard the phosphor screen, which causes the emission of photons of light. This light then forms an image on the screen of the night vision equipment.

On the other hand, thermal imaging (TV) technology works based on the property of any object with a temperature above absolute zero to emit thermal energy. In simpler terms, you can measure the temperature of any object, even a cold one. All thermal imaging devices are capable of recording this temperature. The lenses of a thermal imager can capture minor heat radiation, and the thermal sensor can measure and the processor processes the data to form a heat map of the area to which the device is directed.

NV and TV in Rainy Weather

When it comes to using NV and TV in rainy weather, both have their own strengths and weaknesses. In the case of night vision devices, the light reflected from objects travels a distance from the subject to the lens of the night vision goggles. For a perfect image, nothing should interfere with the passage of light photons. However, in reality, light travels in the atmosphere, not in a vacuum. Impurities of gases, dust, and the smallest particles of water will interfere with the passage of light, creating the effect of partial absorption of light by the atmosphere and causing the photons to scatter. The clearer the air and less saturated with water vapor, the more precise the image on the screen. However, if it’s raining, each particle of water will interfere with the passage of photons of light, creating visual “noise” on the monitor of the night vision monocular. The reflectivity of the water is very high, and the more it rains, the denser the “noise” on the screen looks. Sometimes, it’s almost impossible to see anything due to the thick wall of rain while using a night vision device. In this case, it is much more effective to use any thermal imaging equipment instead of night vision devices.

Deer on night vision scope and a couple of deers on thermal vision camera on the rightRegarding thermal imaging devices, they do not pick up reflected light, but they measure the temperature of the environment and build an image based on the temperature difference. Raindrops are usually negligible for the device to register changes in their core temperature. If the rain is not heavy and does not at all fall like a dense wall, then the thermal imager will not “see” the rain in the air. However, it can detect large drops on the ground or other objects. Water evaporates from surfaces and cools them, and sensitive thermal imaging binoculars detect changes in surface temperatures and display the data as a picture of a running droplet. Light rain will not affect the operation of the thermal imaging equipment in any way. But, when it’s raining heavily, the streams of water act as a protective shield and hide everything behind them. Water perfectly absorbs thermal radiation from objects, and therefore, a thermal imaging device cannot correctly measure the temperature of surfaces. Consequently, anything behind the rain wall will be poorly displayed. Therefore, heavy pouring rain with a dense structure will interfere with observation

Thirdly, we take into account the purpose of observation. If you need to detect the presence of a living organism at a great distance, then it is better to use thermal imaging devices. They work well in detecting the presence of warm-blooded animals, birds, and people. In contrast, night vision devices are better at detecting objects that emit weak reflected light, such as buildings, cars, and other structures.

In Conclusion

When it comes to choosing between night vision and thermal imaging equipment, several factors should be considered, including the task, environment, and weather conditions. In rainy weather, irARM™‘s thermal imaging equipment is the more effective option, detecting temperature differences even through light rain. For clear, dry conditions, night vision equipment may be more suitable. It’s crucial to weigh all factors when selecting an observation device to achieve optimal results, and irARM™ offers quality options for both technologies.

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