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Can thermal imaging cameras really see people through walls?
- 2019-01-25-

Thermal imaging technology is based on the fact that everything is hot. Although many objects can't see anything from the outside, there are still hot and cold on it. With the help of the colors on the heat map, we can see the temperature distribution. Red and pink indicate higher temperatures, and blue and green indicate lower temperatures.

All objects that are not at absolute zero will emit electromagnetic radiation of different wavelengths. The higher the temperature of the object, the more intense the thermal movement of molecules or atoms, and the stronger the infrared radiation. The spectral distribution or wavelength of radiation is related to the nature and temperature of the object. The quantity that measures the radiation capacity of an object is called the radiation coefficient. Objects with a dark color or a darker surface have a larger emissivity and stronger radiation; objects with a bright color or a lighter surface have a smaller emissivity and weaker radiation.

The human eye can only see a very narrow range of electromagnetic radiation, called the visible spectrum. For radiation with a wavelength below 0.4um or above 0.7um, the human eye is powerless. The wavelength of the infrared region in the electromagnetic spectrum is between 0.7um ~ 1mm, and the human eye cannot see the infrared radiation. Modern thermal imaging devices work in the mid-infrared region (wavelength 3 ~ 5um) or far-infrared region (wavelength 8 ~ 12um). By detecting the infrared radiation emitted by an object, the thermal imager produces a real-time image, which provides a thermal image of the scene. The invisible radiation image is transformed into a clear image that is visible to the human eye. The thermal imager is very sensitive and can detect temperature differences of less than 0.1 ° C.

When working, the thermal imager uses optics to focus the infrared energy emitted by the objects in the scene on the infrared detector, and then the infrared data from each detector element is converted into a standard video format, which can be used on a standard video monitor Is displayed, or recorded on a tape. Since the thermal imaging system detects heat rather than light, it can be used around the clock; and because it is a passive device, there is no light radiation or radio frequency energy, so it does not expose the user's location.