The difference between infrared thermal imaging and night vision


What is the difference between thermal imaging and night vision? I believe many people don't know, so let us understand the difference between the two together!

The reflected light that our eyes see, daylight cameras, night vision devices, and human eyes all follow the same basic principle: visible light energy hits and reflects, and then the detector receives and converts it into an image. Whether it is the eyeball or in the camera, these detectors must receive enough light, otherwise they will not be able to image. Obviously, no sunlight can reflect anything at night, so they are limited to the light provided by starlight, moonlight and artificial light. If it is not enough, they will be of no avail.

Thermal imaging camera

Thermal imaging cameras are completely different from ordinary cameras. We call them "cameras", but they are actually sensors. To understand how they work, the first thing you have to do is to forget all your previous knowledge of camera photos. FLIR uses heat instead of visible light to take pictures. Both heat (also called infrared or thermal energy) and light are part of the electromagnetic spectrum, but cameras that can detect visible light will not see thermal energy, and vice versa.

Thermal imaging cameras can not only detect heat, but also detect small heat differences (as low as 0.01°C) and display them as shades of gray or different colors. Many people just don't understand this concept, let's explain its principle below.

Everything we encounter in our daily lives releases heat, even ice. The hotter something is, the more heat it emits. The heat emitted is called the "heat signal". When the thermal characteristics of two objects next to each other are slightly different, they are displayed very clearly to FLIR regardless of the lighting conditions. Heat energy comes from a variety of energy sources, depending on what you are looking at at the time. Some things, such as warm-blooded animals (including humans), engines, and machinery, generate their own heat through biological or mechanical means. Other things-land, rocks, buoys, vegetation absorb heat from the sun during the day and emit heat at night.

Since different materials absorb and radiate heat energy at different rates, the area that we consider to be a temperature actually has a subtle difference in temperature. This is why the wood recorded in the water for several days looks different from the temperature in the water, so it is visible to the thermal imager. FLIR can detect these temperature differences and convert them into images. Although all of this may seem a bit complicated, the reality is that thermal imaging cameras are very convenient to use. Their images are clear and easy to understand, and no training or explanation is required. If you can watch TV, you can use a FLIR thermal imaging camera.

Night vision

Night vision

The green pictures we see in movies and TV come from night vision goggles (NVG). NVG absorbs a small amount of visible light, magnifies it a lot, and then projects it onto the display.

Cameras made of NVG technology have the same limitations as the naked eye: that is, if there is not enough visible light, their line of sight will not be good. The imaging performance of anything that depends on reflected light is limited by the amount and intensity of reflected light. NVG and other low-light cameras are not very useful at dusk because they have too much light to work effectively, but the naked eye cannot see enough light. Thermal imagers are not affected by visible light, so they can provide you with clear images even in the sunset.

Infrared lighting camera

The infrared illumination camera attempts to project a beam of near-infrared energy to produce its own reflected light, which can be seen by its imager when it bounces off an object. This is feasible, but this camera still needs to rely on reflected light to image, so they have the same limitations as other night vision cameras that rely on reflected light in short distance and poor contrast.


All these visible light cameras (daylight cameras, NVG cameras and infrared illumination cameras) work by detecting reflected light energy. However, the amount of reflected light they receive is not the only factor that determines whether you can see with these cameras: image contrast is also important.

If the thing you are looking at has a lot of contrast compared to its surroundings, then you will have more chances to see it with a visible light camera. If there is no good contrast, you will not see clearly no matter how bright the sun is. White objects seen on a dark background have a lot of contrast, but darker objects will be difficult to see in a dark environment with these cameras, which is poor contrast. At night, when the lack of visible light naturally reduces the image contrast, the performance of the visible light camera decreases a lot.

Thermal imaging cameras do not have these shortcomings. First of all, they have nothing to do with the reflected light energy. In daily life, everything you see has a heat signal. This is why compared to using a visible light camera (or even a night vision camera), the chance of seeing things at night with a thermal imager is much greater.

In fact, many objects you may be looking for (such as people) will produce their own contrast because they will generate their own heat. Thermal imaging cameras can see them well, because they can not only take images through thermal energy, but also image thermal energy. They use the tiny thermal differences between objects to take photos. Night vision devices have the same disadvantages as daylight and low-light cameras: they need enough light and enough contrast to create usable images. On the other hand, thermal imaging cameras can clearly observe day and night while creating their own contrast. There is no doubt that thermal imaging cameras are the best 24-hour imaging option.