Radiant energy – Luminophor irradiation
Patent
1988-09-26
1990-06-19
Hannaher, Constantine
Radiant energy
Luminophor irradiation
2504591, 2504611, G01J 506, G01T 116, G01T 120
Patent
active
049356313
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to radiation meters, and in particular to radiation meters for measuring the intensity of incident radiation within a predetermined wavelength band against a background of incident radiation within other wavelength bands, for example broadband radiation.
2. Description of Related Art
Such meters are widely used in a number of applications by individual consumers, in industry, and in medicine. One example is in the silicon integrated circuit industry where high-resolution photolithographic processes depend on a source of ultra-violet radiation of known intensity. In order to distinguish between the incident UV radiation and the background wideband radiation, the meters presently used in such an application employ a filter which selectively transmits UV radiation to a UV-sensitive photo-detector. As both these items are quite expensive, this leads to the cost of such a meter being relatively high.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide such a radiation meter which does not necessarily require a filter for selectively transmitting radiation within a predetermined wavelength band nor a detector which is sensitive to radiation within the predetermined wavelength band, the meter thus being of lower cost than previously known meters of this type.
According to the present invention there is provided a radiation meter for measuring the intensity of incident radiation within a selected first wavelength band against a background of incident radiation within a second wavelength band, the radiation meter comprising a body which is substantially transparent to said incident radiation within the second wavelength band and which includes fluorescent material having an absorption spectrum such that the material is effective to select said first wavelength band by absorbing said incident radiation within the first wavelength band and consequently emits radiation within a third wavelength band different from the first wavelength band, the body being effective to direct the emitted radiation on to detector means which is screened from the incident radiation and which detects the emitted radiation and produces an output representative of the intensity of the radiation detected.
The incident radiation within a second wavelength band may be broadband radiation. Even so, in a radiation meter in accordance with the invention the detector means may be a broadband detector.
Preferably the surface of the body on which said incident radiation is incident is larger than the surface of said body to which said emitted radiation is directed.
BRIEF DESCRIPTION OF THE DRAWINGS
Radiation meters in accordance with the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:
FIG. 1 is a pictorial view of the meter;
FIG. 2 is a fragmentary section along a line II--II of FIG. 1 on a larger scale than FIG. 1;
FIG. 3 is a block schematic diagram of electronic circuitry incorporated in the meter; and
FIG. 4 is a schematic view of an alternative form of part of the meter of FIG. 2.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring firstly to FIGS. 1 and 2, the meter, which is designed to measure the intensity of incident UV radiation within the wavelength band 280-320 nm (UVB) against a background of sunlight, comprises a plastics housing 1, in which is mounted a 3 mm thick rectangular sheet 3 of poly(methylmethacrylate), part of the upper surface of which is visible through a window 4 in the end of the housing 1, which window is substantially smaller than the sheet 3. Throughout the sheet 3 there is dispersed an amount of approximately 1 to 3% w/w of, for example, one of the fluorescent dyes shown in Table I below, the absorption spectra of which closely match the erythemal response curve of human skin and the emission peaks of which lie between 325 and 450 nm.
TABLE 1 ______________________________________
Dye Absorption Edge
_____________________________
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Goetzberger et al., "Solar Energy Conversion with Fluorescent Collectors", Applied Physics, vol. 14, No. 123, pp. 123-139 (1977).
Friedman, "Progress on the Development of Luminescent Solar Concentrators", Spie, vol. 248 (1980), pp. 98-104.
"The Sunburning Ultraviolet Meter: Design and Performance", by D. S. Berger, in Photochemistry and Photobiology, 1976, vol. 24, pp. 587-593.
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Clark Michael G.
Kingston Brian L.
Lewis Martin R.
Mosley Alan
Glick Edward J.
Hannaher Constantine
The General Electric Company p.l.c.
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