Illumination – Revolving
Patent
1993-10-26
1995-01-17
Lazarus, Ira S.
Illumination
Revolving
362284, 362321, 250504R, 25033906, F21V 2130, G01J 100
Patent
active
053831012
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a device for generating radiation, which device comprises an electrically operated radiation source to be connected to a power source, a means for regulating the current of the radiation source and an at least partly curvilinearly symmetric cap-like reflector means, which reflector means is positioned round the radiation source in such a way that the radiation source is situated mainly in the centre of curvature of the reflector means or in the vicinity thereof and the cap-like reflector means surrounds the radiation source along a wide sector, the cap-like reflector means comprising an opening for directing radiation out of the reflector means towards a collecting optics positioned in the vicinity of the opening and the size of the opening being arranged to limit the outcoming radiation mainly only to the collecting optics, which device additionally comprises a modulator means rotatable about its rotating axis and including interrupting means for modulating the radiation coming from the radiation source outside the reflector means by interrupting the propagation of the radiation.
A device according to the invention can be used for instance for generating infrared radiation in various spectroscopic measuring devices, by which is measured e.g. on various surfaces how thick a film of impurities or slushing oil or some other substance there is on the surface. It is important to measure the thickness of the film in order to know for painting or otherwise treating the surface, whether the surface shall be cleaned before the painting.
The measuring devices also need a device solution for generating radiation. The measuring devices are based on the fact that the device emits infrared radiation, which is partially reflected back from the surface to be measured. How much reflection occurs, depends on the thickness of the film on the surface and on the properties of the film. The infrared radiation reflected from the surface is measured into a measuring device through optics by means of a detector means.
In measuring devices, a measurement is carried out in several wavelength channels, which makes certain demands on the electrically operated radiation source and associated device solutions, namely that the shape of the spectrum of radiation emitted by the radiation source should remain constant within the area of the object to be measured. The radiation source generally used in infrared spectroscopy is a bulb, the shape of the radiation spectrum of which depends on the temperature of the filament of the bulb. Within the spectrum area, the point of the highest amplitude of a spectrum graph moves somewhat towards a smaller wavelength when the temperature of the filament rises. Infrared spectroscopy presupposes that relative changes in the spectrum would be of pro mille order only, but that is often not the case, depending expressly on changes in the temperature of the radiation source.
For stabilizing the temperature of the filament, a regulating means is generally used, by which the current of the filament can be regulated. Resistance feedback can, for instance, be used as a regulating means, by which feedback the regulating means reduces, at rising temperature of the radiation source and at simultaneously rising resisting power of the filament of the radiation source, the current/voltage of the radiation source, which decreases the temperature of the radiation source. A problem with the realization of the radiation source is also that different parts of the filament itself have different temperatures, which is caused by the fine structure and the radiation balance of the filament compared with the surroundings. In spectroscopic measurements, radiation energy of the radiation source is collected by lenses or mirrors, which direct the radiation energy of the bulb from different parts of the filament in different directions, on account of which the shape of the radiation spectrum varies at an object lighted by optics, depending on which part, or practically, which part with which temperature of
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Lazarus Ira S.
Rautaruukki Oy
Sember Thomas M.
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