4 Types Infrared Lens Differents: NIR, SWIR, MWIR, LWIR.

The Differences among Short-Wave Infrared lens, Near-Infrared lens, Mid-Wave Infrared lens  and Long-Wave Infrared lens.

Here is contents:

一、Near-Infrared (NIR)
Wavelength and Definition
Applications in Fiber Communications and Night Vision

Near-Infrared (NIR) lens: Well, the wavelength of near-infrared lens is between 0.75 and 1.4 micrometers. It's defined by the absorption of water. You know, because it has a low attenuation rate in quartz glass, it's usually used in optical fiber communications. And the wavelengths in this area are super sensitive to image enhancement. For example, it's applied in night vision devices like night vision goggles. Night vision goggles can greatly improve the visibility in low light or dark conditions by taking advantage of the features of near-infrared lens. They're widely used in military operations, night security patrols and some outdoor exploration activities where clear vision in the dark is needed.

二、Short-Wave Infrared (SWIR)
Wavelength Range and Water Absorption
Importance in Long-Distance Communications

Short-Wave Infrared (SWIR) lens: Its wavelength is within the range of 1.4 to 3 micrometers. The water absorption rate increases significantly at 1,450 nanometers. And the spectral region from 1,530 to 1,560 nanometers is the main area that dominates long-distance communications.

In a lot of modern telecommunication systems, this specific spectral range plays a really crucial role. It enables signals to be transmitted over long distances with relatively low loss and high stability, which is really important for maintaining efficient and reliable communication links between different places, like between cities or across vast regions.

三、Mid-Wave Infrared (MWIR)
Wavelength and Alternative Name
Applications in Missile Technology and Aircraft Tracking

Mid-Wave Infrared (MWIR) lens, also known as Mid-Infrared lens: The wavelength is from 3 to 8 micrometers. Passive infrared heat-seeking missile technology is designed to work by using the atmospheric window in the 3 - 5 micrometer band. When it comes to the homing of aircraft infrared markers, they usually aim at the plume emitted by the aircraft engines.

In military combat situations, heat-seeking missiles rely on detecting the infrared radiation in this wavelength range to accurately lock onto the target aircraft by sensing the heat signature of the engine plume. And for aircraft identification and tracking systems based on infrared technology, focusing on the infrared emissions from the engine is an important way to tell different aircraft apart and follow them.

四、Long-Wave Infrared (LWIR)
Wavelength and Thermal Imaging
Applications in Search and Rescue and Building

Long-Wave Infrared (LWIR) lens: Its wavelength ranges from 8 to 15 micrometers. This is the area of "thermal imaging". Sensors in this band can get complete passive images of thermal radiation without the need for additional light or external heat sources like the sun, the moon or infrared light sources.

Thermal imaging cameras based on long-wave infrared technology are widely used in all kinds of fields. For instance, in search and rescue operations at night or in areas with poor visibility, they can help rescuers quickly find missing people by detecting body heat. In building inspections, it can be used to identify heat leakage or abnormal heat distribution in walls and roofs, which is good for saving energy and finding potential safety hazards.

Sometimes, NIR and SWIR are called "Reflective Infrared", while MWIR and LWIR are sometimes called "Thermal Infrared".