A detection technique which converts invisible heat energy into a visible picture. Objects radiate varying amounts of infrared (IR) heat energy, depending on their temperature. Inside a thermograph, a solid-state detector sees the IR, even in the dark or smoke. TV-style pictures show temperatures by variations in brightness or colour. In printing, thermography simulates the effect produced by printing using a steel die engraving. The image is printed with adhesive ink, then dusted with powdered resin. Heat fuses the resin and ink to produce a raised, embossed effect image.
Thermography can refer to a printing process and an imaging process. A thermogram is an image produced by thermography.
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 900–14,000 nanometers or 0.9–14 µm) and produce images of that radiation. Since infrared radiation is emitted by all objects based on their 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 one to see variations in temperature, hence the name. With a thermographic camera warm objects stand out well against cooler backgrounds.
Thermal imaging photography finds many other uses. Some physiological activities, particularly responses, in human beings and other warm-blooded animals can also be monitored with thermographic imaging.
The appearance and operation of a modern thermographic camera is often similar to a camcorder.
Instead of CCD sensors, most thermal imaging cameras use CMOS Focal Plane Array FPA. Thermographic cameras are much more expensive than their visible-spectrum counterparts, and higher-end models are often export-restricted.
See also: infrared camera, infrared detector
Thermographer training
Aside from test equipment, training is the most important investment a company will make in an infrared inspection program. however, infrared thermography is not a “simply point and shoot” technology. Typically, infrared training courses should cover the topics of infrared theory, heat transfer concepts, equipment selection and operation, how to eliminate or overcome common error sources, and specific applications.
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 called thermal printing and was used in older model fax machines and is used in most 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).
Thermography printing is also a post print process done immediately after printing. Thermography powder is applied to the sheet of paper after it leaves the printing press.
It is commonly used on letterheads, business cards, greetings cards, gift wrap, packaging and can also be used to print braille text.
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