Thermographic cameras are also called Forward Looking InfraRed (FLIR). Such cameras use infrared radiation to form images unlike the normal camera which uses visible light. The infrared energy is a part of the electromagnetic spectrum. This has a longer wavelength than the visible light and so it cannot be seen by naked eyes. The thermographic cameras can even detect objects in total darkness.
The images produced by the thermographic cameras are ideally monochromatic since they use a single type of sensor which responds to a single infrared radiation wavelength range. There are two types of thermographic cameras. They are the ones with cooled infrared image detectors and the other with uncooled detectors. The first types of cameras have cryogenically cooled detectors which are contained within vacuum-sealed flask or case. These cameras are more sensitive since their own temperatures are lower than that of the objects which they detect. The disadvantage of using this camera is that it needs a very expensive maintenance and it takes some time to cool down before it starts working. The other type of camera uses a sensor that operates in ambient temperature. The changes in the voltage, current and resistance are measured and then compared to the values of the operating temperature of the sensor. The image quality and resolution of these cameras are lower than that of the cameras with cooled detectors.
The thermographic cameras are used by manufacturers, engineers, contractors, ranchers, maintenance departments and also in medical fields. Physicians use digital infrared thermal imaging to check the changes in the temperature of skin surface. The scanning infrared camera captures the radiation emitted from skin surface and shows them on a monitor. DITI can also be used to detect neural, vascular, skeletal and muscular systems. Such cameras are also used for home security. While installing an Infrared night vision cameras certain things should be kept in mind. There should be no obstruction in between the camera and the area to be detected. Also, camera should not be placed directly in front of any mirror. The military and police also use these cameras to detect targets. Photography in total darkness is possible with such a camera.
While buying a thermographic camera the specifications that should be taken into consideration are the sensor life time, field of view, number of pixels, dynamic range and spectral band. Thus we see that thermographic cameras can be used in various types of applications.