Infrared basic concept

Infrared rays refer to invisible light rays in the range of up to 400 μm longer than the red light wavelength of 0.76 μm. Now, infrared detection and control technology has been widely used in production, environmental protection, medical and household appliances. The near-infrared ray with a wavelength between 0.76 μm is used to transmit the control signal, which has a much better transmission characteristic in the transparent atmosphere than visible light. At the same time, because it is close to the edge of red light, it has some physical properties very similar to the light, such as linear propagation, reflection, refraction, and absorption by matter, so it can also use optical devices such as focusing lenses similar to visible light.

When the object is heated to 400~700 °C, it will emit infrared light with a wavelength of 3~5μm, which belongs to the middle infrared region. The infrared rays emitted by the human body at a body temperature of 36 to 37 ° C have a wavelength of 9-10 μm and belong to the far infrared ray region.

Widely used infrared light-emitting diodes, infrared-receiving photodiodes and photosensitive tubes operate in the near-infrared region with peak wavelengths between 0.88 and 0.94 μm, while pyroelectric infrared sensors can operate effectively in the wavelength range of 2 to 20 μm, as needed Coupled with the right filter made of different materials, it can be used in many different applications in the mid-infrared and far-infrared range.

For the three-wave infrared rays with wavelengths of 2 to 2.6 μm, 3 to 5 μm, and 8 to 14 μm, they are rarely absorbed by the atmosphere. Therefore, these three bands are called "atmospheric windows" and are used for remote sensing technology. National Chapter III In remotely controllable household appliances, the most widely used sensor is a near-infrared sensor.