Thermography
From Freepedia
Thermography can refer to a printing process and a imaging process.
Thermographic Imaging
Thermography, or thermal imaging, is a type of infrared imaging. Thermographic cameras detect radiation in the infrared range of the electromagnetic spectrum (roughly 900-10,000 nanometer) and produce images of that radiation. Since infrared radiation is emitted by all objects at ambient temperature, according to the black body radiation law, thermography makes it possible to "see" one's environment with or without visible illumination. The amount of radiation emitted by an object increases with temperature, therefore thermography allows you to see variations in temperature, hence the name. With a thermographic camera warm objects stand out well against cooler backgrounds. Humans and other warm-blooded animals become easily visible against the environment day or night, hence historically its extensive use can be ascribed to military and security services.
Thermal imaging photography finds many other uses. For example, firefighters use it to see through smoke, find persons, and localize hotspots of fires. With thermal imaging, power lines maintenance technicians locate overheating joints and parts, a telltale sign of their failure, to eliminate potential hazards. Where thermal insulation becomes faulty, building construction technicians can see heat leaks to improve the efficiencies of cooling or heating air-conditioning. Thermal imaging cameras are also installed in some luxury cars to aid the driver, the first being the 2000 Cadillac DeVille. Some physiological activities, particularly responses, in human beings and other warm-blooded animals can also be monitored with thermographic imaging. [1]
The appearance and operation of a modern thermographic camera is often similar to a camcorder. Enabling the user to see in the infrared spectrum is a function so useful that ability to record their output is often optional. A recording module is therefore not always inbuilt.
Instead of CCD sensors, thermal imaging cameras use microbolometer arrays. Their resolution is considerably lower than of optical cameras, mostly only 160x120 or 320x240 pixels. Thermographic cameras are much more expensive than their visible-spectrum counterparts, and higher-end models are often export-restricted. Older bolometers or more sensitive models require cooling; only the modern uncooled arrays allow construction of small, rugged handheld devices.
See also: infrared camera
Thermographic Printing
Thermographic printing refers to two types of printing, both of which rely on heat to create the letters or images on a sheet of paper.
The simplest type is where the paper has been coated with a material that changes colour on heating. This is the thermal printing in old fashioned fax machines and can still be seen in some shop till receipt printers.
More complex is thermographic printing that melts print off a ribbon and onto the sheet of paper (thermal ink transfer printing). This type of printing is used to create the raised bumpy print on expensive business cards, the raised rubbery print on some T-shirts and the magnetic print on cheques.
