Temperature Measurement Principle of Infrared Thermal Imager

Dec 03, 2021

Temperature Measurement Principle of Infrared Thermal Imager
Discovery of infrared ray
In 1800, William Herschel, the British astronomer, discovered infrared ray.

In theory, the electromagnetic wave whose wavelength is greater than that of infrared ray and less than 1000μm is usually called “infrared ray” and also called “infrared radiation”, which occupies the range from 0.76μm to 1000μm in the electromagnetic spectrum.
Visible light Infrared light
Radio wave Wavelength
X-ray Scope of wavelength of visible light: 0.4--0.76
Ultraviolet light Scope of wavelength of infrared light: 0.76μm-1000μm

Later, scientists classified according to the wavelength of infrared rays:
Near infrared 0.75-3μm
Intermediate infrared 3-6μm
Far infrared 6-15μm
Extreme far infrared 15-1000μm
X-ray Wavelength
Ultraviolet Short wave
Infrared Long wave
Visible light Electromagnetic radiation spectrum map

Several important characteristics of infrared radiation
Universality of infrared radiation - infrared ray exists in any corner of nature. In fact, all living and inanimate objects whose temperature is higher than absolute zero constantly radiate infrared rays.

Infrared radiation is related to temperature - the thermal radiation energy of an object is directly related to the surface temperature of the object. With this characteristic, people can use it to measure the temperature and analyze the thermal state of the object without contact.

Atmospheric windows of infrared radiation - atmosphere and smoke cloud absorb visible light and near infrared rays, but are transparent to thermal infrared rays of 3-5μm and 8-14μm. These two bands are called “atmospheric windows” of thermal infrared rays.

Principle of infrared imaging
Infrared imaging transforms invisible infrared radiation into visible temperature distribution image through a specific device, which can reflect the thermal distribution of the object surface, so it is also called “thermal image”, and this device is called “infrared thermal imager”.
In short, the infrared thermal imager is an infrared camera. It consists of optical system, infrared detector, signal processor, software system and display system.
Detected object Digital signal
Infrared radiation Embedded image processing
Infrared optical system Digital image signal
Optical signal Video signal
Detector Infrared thermal image
Power signal  

Advantages of infrared imaging
Non-contact detection:effectively protect the safety of users and do not affect the target object to be detected.
Intuition of the picture:the temperature of objects in the same area can be compared; can grasp the condition of the target object as a whole; the two-dimensional infrared thermal image can be used to analyze the target object more intuitively.
Real-time of imaging:it is helpful to scan stationary targets quickly and capture fast moving targets and rapidly changing thermal patterns.

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