01-10-2016, 03:50 PM
03-10-2016, 09:29 AM
Non Visible Imaging is simply measuring the light that we cannot see. Here we use near and far infrared rays for image acquisition. "Near infrared" light is closest in wavelength to visible light and "far infrared" is closer to the microwave region of the electromagnetic spectrum. The longer, far infrared wavelengths are about the size of a pin head and the shorter, near infrared ones are the size of cells, or are microscopic. Far infrared waves are thermal. In other words, we experience this type of infrared radiation every day in the form of heat! The heat that we feel from sunlight, a fire, a radiator or a warm sidewalk is infrared. The temperature-sensitive nerve endings in our skin can detect the difference between inside body temperature and outside skin temperature. Infrared light is even used to heat food sometimes - special lamps that emit thermal infrared waves are often used in fast food restaurants! Shorter, near infrared waves are not hot at all - in fact you cannot even feel them. These shorter wavelengths are the ones used by your TV's remote control. It has a great advantage that the spectra that we are getting from a living being differs from that of non living beings. Also certain things that are invisible to human eye such as methanol flame etc are visible in infrared. By studying the spectra even machines can identify what the object is.