Infrared light is electromagnetic radiation with a wavelength between 700 nanometers and out to 300 micrometres. The beginning region of the infrared spectrum is referred to as the near-IR or ‘NIR’ for short and begins at 700 nanometers (‘nm’) which is also toward the ending point of the visible spectrum. The typical human eye will respond to wavelengths from about 390 to 750 nm. The ending point of NIR and start of the SWIR wavelength is often cause for confusion and debate depending on application.
The generally agreed to categories of wavelength from UV-SWIR are listed below.
The short wave infrared (‘SWIR’) waveband is a highly interesting spectral region for many reasons. This wavelength operates entirely outside of human vision yet the images created from SWIR cameras have the familiar appearance of monochromatic imaging done in the visible spectrum. SWIR cameras are being used in numerous applications ranging from military to medical imaging. For military imaging a SWIR camera is able to operate in low-light, see ‘through’ fog and haze, and detect hot objects while allowing operators to benefit from familiar types of images. An increasing number of high-end industrial inspection systems have discovered NIR-SWIR cameras. Using these cameras allows much greater penetration depth compared to normal visible CCD or CMOS cameras. Therefore, in applications such as wafer inspection a NIR-SWIR camera can penetrate the wafer material and detect defects unseen by standard industrial machine vision cameras. The most highly sensitive NIR-SWIR cameras utilize an InGaAs based detector which allows high quantum efficiency in the 900-1700nm band. For more information please contact our Sales Department.
As the wave band moves farther out into other infrared regions, we encounter the Mid-IR (MWIR) region at around 2.5 micron. In guided missile technology the 3-5 µm portion of this band is the atmospheric window in which the homing heads of passive IR 'heat seeking' missiles are designed to work, homing on to the IR signature of the target aircraft, typically the jet engine exhaust plume.
For practical purposes when we refer to ‘IR cameras’ in the industrial camera world we mean cameras existing in the non-visible regions indicated above. However, an important distinction and to be more correct scientifically speaking, thermal imaging is referred to as imaging in the MWIR and LWIR bands. The reason for this is that terrestrial objects emit light at those wavelengths. Quite simply the higher the object’s temperature the brighter the object will appear in thermal imaging.
For more information on all the NIR – LWIR cameras offered by Rice Camera Technologies, please refer to our military ISR camera product section or click on the links below. We provide cameras which are ideal for high-end machine vision or military applications where performance and reliability are key concerns.