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incandescent lamps (see also sources of light)
For an infrared source based upon the principle of an incandescent lamp, light is an unavoidable by-product that should be minimised as much as possible. The amount of emitted radiation in the visible part of the electromagnetic spectrum increases with the temperature of the filament. For this reason the filament
quartz- and metal tubulars
Quartz tubes consist of heat resistant quartz glass in which a coiled filament is placed, whether as an open coil or wrapped around a solid core of for instance quartz glass. The filament most commonly is fabricated out of Kanthal, a metal that starts glowing at relatively low temperatures and that, most importantly, does not burn in atmospheric conditions. The radiation range of quartz tubes is roughly from 2000 to 2300 nm which is well above that of infrared
infrared radiation lays in the near infrared area, ranging from 700 to 1400 nm, infrared incandescent lamps are much more effective for therapeutic purposes and the use of quartz tubes is more dedicated to cosmetic applications. Quartz tubes most often have a straight or bent shape that resembles very
much that of metal tubular radiators. These tubulars however consist of a coiled nickel-chromium wire in an electrical isolating binder of for instance magnesium-oxide or aluminium powder, mounted in a sealed tube of brass or stainless steel. Compared with quartz tubes metal tubular radiators have an even greater output in the far infrared areas and less in the more desirable near infrared areas (approximately 15% IR-A, 40% IR-B and 45% IR-C, see electromagnetic spectrum) making them more suitable for heating applications.
Quartz tubes have a better shock resistance than incandescent lamps and are more compact as well. For this reasons quartz tubes, despite their lower performance, are commonly applied in combined infrared- and ultraviolet sun-lamp applications, the quartz tube acting as the serial ballast for the ultraviolet device.
metal wired elements
Around 1920 the first electric elements for heating and for therapeutic use became available. The elements were made of Chromel-wire, an invention done in 1905 by William Hoskins en Albert Marsh. Chromel (also known as nichrome) is an alloy of
nickel and chrome. Is has a stable and slightly positive temperature coefficient at high temperatures and when heated it forms a protective layer of chromium-oxide on the surface of the wire. This allows the wire to glow under atmospheric conditions without burning or further corrosion. The wire was wound into a spiral and than wrapped around a ceramic body. It could be heated to about 1100 ºC. Around 1930 elements made of Kanthal appeared on the market. Kanthal is an alloy made of iron, chrome and aluminium that was discovered by
Hans von Kantzow from Hallsthammar. Like Chromel, Kanthal forms a protective layer at the surface of the wire, a layer made of aluminium-oxide. It can withstand higher temperatures than Chromel and it is easier to process.
incandescent lamps, being 1000 to 1400 nm (see infrared emission). Since the most beneficial
temperature of a typical infrared incandescent lamp for drying purposes is about 1900 ºC, well below the filament temperature of an incandescent lamp for lighting purposes which is about 2500 ºC (see infrared emission). For therapeutic applications like pain relieve and wound healing however, a short wave infrared radiation is needed which requires a high
temperature of the filament. The unwanted surplus of light is than damped with a red filter. Compared with incandescent lamps for lighting purposes, infrared incandescent lamps for therapeutic use are relatively large for their typical dissipation of 100 to 150 Watts, thus enabling the creation of a sufficient broad beam. To force the
650 nm. From the 1950's on, pressed, impact-proof glass lamps became popular. These lamps are often equipped with a segmented spherical lens, a so-called fresnel lens, to bundle the infrared rays even better. The yield of infrared incandescent lamps is about 45% IR-A, 45% IR-B and 10% IR-C (see electromagnetic spectrum).
infrared rays into a parallel beam, the inside of the lamp is covered with an infrared reflective coating. At first the lamps were commonly fabricated as clear, blown glass bulbs and eye protectors where necessary to cover the eyes from the intense light of the filament. To overcome this disadvantage the lamps were soon equipped with filters that stopped light with wavelengths below
Since the working temperature of infrared- and normal
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appearances and combinations
By far the most common appearance of infrared armatures for therapeutic use is that of the tabletop model. Generally the armature can be turned or tilted in order to allow for a comfortable
body position during the treatment. Some armatures are equipped with clips allowing fastening to the armrest of a chair or to a cabinet door. Infrared armatures mounted on a standard had never become very popular although Philips for some time offered a tripod with an adapter allowing a standard tabletop model to be mounted on the tripod. Also from Philips is the HP2001, a model with the lamp mounted on a swan's neck. Some armatures came with a set of interchangeable elements. Common elements were dull radiators, metal
mineral lamps and dull radiators
A mineral lamp consists of a metal- or ceramic plate coated with minerals that is heated by a separate electrical heat source. The
indirectly heated plate emits infrared radiation in a range from 2 to 50 micrometers, which is in the not visible middle- and far infrared part of the electromagnetic spectrum. Mineral lamps emerged in China in the 1980's after it was noticed that employees of a badly maintained ceramic factory hardly suffered from the moist environment they
A halogen lamp in fact is an incandescent lamp filled with a highly pressurised inert gas. To this gas a small amount of halogen
(mostly bromine or iodine) is added, causing an ingenious process of regeneration from the wolfram atoms that had been emitted by the filament of the lamp. In the relatively cold outer zones of the lamp these atoms will bind themselves to the halogens. The quality of these chemical combinations is that they do not condense on the inside of the glass bulb, making the bulb to remain clear throughout the lifetime of the lamp. Natural circulation of the gas within the lamp ultimately will cause the halogen combinations to enter the hottest zone
surrounding the filament of the lamp. There the combination will break up and the released wolfram atoms will reduce further
evaporation of the filament. Thanks to this process of regeneration the average lifetime of a halogen lamp is significant longer than that of a conventional incandescent lamp. Because of the high pressure and -temperature halogen lamps usually are relatively small and made out of quartz glass. The melting temperature of quartz glass is much higher than that of standard glass (about 1100 ºC instead of about 500 to 800 ºC). The filament temperature of a halogen lamp may rise as high as 2600 ºC. Halogen lamps are applied in tabletop infrared
devices but especially in infrared cabins where the produced convection heat is likewise useful as the infrared radiation.
chronic wounds, joint pain, back pain and so on. Less poetic but at least as effective is the infrared radiation that is emitted by dull radiators, radiators who emit long-waved and therefore invisible infrared rays. Dull radiators mostly consist of a highly heat resistant shell that houses a glowing metal wired element embedded in an electric isolator, for instance a ceramic shell that contains a metal filament embedded in sand. Such small ceramic elements are for instance applied for warming little animals while larger elements are used in
incandescent lamps is in the same order of magnitude no special restrictions are imposed on their armatures. Small incandescent lamps with a dissipation between 15 to 25 Watt are used in massage devices were they indirectly heat up the synthetic or metal outside of the device to a temperature of about
40 ºC at most.
too but the effect of those is mainly based on the common well being caused by a rise of ambient temperature. Dull radiators with a relatively low surface temperature of about 40 ºC at most are used for massage applications. The low temperature allows for the use of synthetic shells like the shown Pifco massage device.
had to work in. The claimed application area of mineral lamps is contributed to the complex composition of the applied minerals and includes every ailment that profits from soothing warmth like
saunas. Specific dull radiators were developed for therapeutic use
The heart of a laser is formed by a solid-, a fluid- or a gaseous medium enclosed by two mirrors, forming a so-called resonation chamber. The medium has to posses free electrons that can be excited from a lower to a higher orbit by absorption of a photon. This excited electrons will almost immediately return to their ground state under the emission of another photon whose wavelength is characteristic for the used medium. This is called a spontaneous photon emission and since the wavelength of the emitted photons is always the same, the emitted radiation is monochromatic. When such a photon hits an already excited electron this electron will return to its ground state while releasing a second photon. This is called a stimulated emission and the two resulting photons will be identical both in wavelength and in phase, resulting in a monochromatic coherent radiation. A stimulated emission is initiated by one photon, resulting in the emission of an identical second one. In an environment where there are more excited free electrons in the medium than ground-state free electrons an avalanche may occur which will last until the number of excited electrons has become too low. The situation in which there exist more excited than ground state free electrons is called population inversion. Typically the medium is forced and maintained into this state with help of an external radiation source or an electric current in a process that is called pumping. Once the laser is "pumped" to "inversion", avalanches of monochromatic coherent radiation occur and this irregular process is transformed into a continuous process by the two mirrors on both sides of the medium. One of the mirrors, the output coupler, reflects most of the radiation but it also allows a small part of the radiation to pass through it. The two mirrors are placed in an exactly opposite position resulting in an ever increasing number of photons bouncing between the two mirrors. A part of these photons will be responsible for the release of new photons while another part passes through the output coupler. This radiation travels in only one direction, perpendicular to the surface of the mirrors and the result is therefore a monochromatic, coherent and collimated bundle of radiation, a laserbeam. The wavelength of this laserbeam depends on the nature of the medium and may vary from X-ray, ultraviolet, visible light, near- and far infrared to
microwaves. Many lasers operate in the visible part of the electromagnetic spectrum (called light) and this is where the original acronym LASER stands for: Light Amplification by Stimulated Emission of Radiation. In medical science infrared lasers are used for soft- and hard tissue surgery, for treatment of nail fungus and acne scars and for hair
wired elements, quartz elements, infrared- and coloured incandescent lamps, blended lamps and even discharge lamps (see also ultraviolet-radiators).