What
Does The Infrared Show Us?
This is an infrared
image of the Earth taken by the GOES 6 satellite in 1986. A scientist used
temperatures to determine which parts of the image were from clouds and which
were land and sea. Based on these temperature differences, he colored each
separately using 256 colors, giving the image a realistic appearance.
Why use the infrared to
image the Earth? While it is easier to distinguish clouds from land in the
visible range, there is more detail in the clouds in the infrared. This is
great for studying cloud structure. For instance, note that darker clouds are
warmer, while lighter clouds are cooler. Southeast of the Galapagos, just west
of the coast of South America, there is a place where you can distinctly see
multiple layers of clouds, with the warmer clouds at lower altitudes, closer to
the ocean that's warming them.
Introduction
Near infrared light
consists of light just beyond visible red light (wavelengths greater than
780nm). Contrary to popular thought, near infrared photography does not allow
the recording of thermal radiation (heat). Far-infrared thermal imaging
requires more specialized equipment. Infrared images exhibit a few distinct
effects that give them an exotic, antique look. Plant life looks completely
white because it reflects almost all infrared light (because of this effect,
infrared photography is commonly used in aerial photography to analyze crop
yields, pest control, etc.) The sky is a stark black because no infrared light
is scattered. Human skin looks pale and ghostly.
How
can we "see" using the Infrared?
Since the primary source of
infrared radiation is heat or thermal radiation, any object which has a
temperature radiates in the infrared. Even objects that we think of as being
very cold, such as an ice cube, emit infrared. When an object is not quite hot
enough to radiate visible light, it will emit most of its energy in the
infrared. For example, hot charcoal may not give off light but it does emit
infrared radiation which we feel as heat. The warmer the object, the more
infrared radiation it emits.
Near infrared imaging applications
v Semiconductor
analysis
v Pharmaceutical
formulation analysis
v Textiles
Abstract
It 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.
Conclusion
Near infrared light
consists of light just beyond visible red light (wavelengths greater than
780nm). Contrary to popular thought, near infrared photography does not allow
the recording of thermal radiation (heat). Far-infrared thermal imaging
requires more specialized equipment. Infrared images exhibit a few distinct
effects that give them an exotic, antique look.
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