Ultraviolet sensing apparatus

Details Ultraviolet sensing apparatus Ultraviolet sensing apparatus

1998-04-30

2000-11-07

Ham, Seungsook

Radiant energy

Invisible radiant energy responsive electric signalling

Ultraviolet light responsive means

G01J 500

Patent

active

061440353

DESCRIPTION:

BRIEF SUMMARY
This invention relates to an ultraviolet (UV) sensing apparatus.
UV radiation is produced artificially by special fluorescent tubes for numerous applications. A characteristic of such tubes is that, while of limited effective life in terms of UV production, they also produce visible light but continue to do so, without apparent change in intensity or colour, long after useful production of UV radiation has ceased. Thus, the visible output gives no indication of the condition of such a tube in terms of its continuing effectiveness in producing the desired intensity of UV radiation.
Excessive exposure to UV radiation from the sun causes burning of the skin, and is known to be a cause of melanoma.
Currently available effective devices for measuring UV intensity are bulky, costly and inconvenient for on-site checking of UV tube output. Available low-cost devices for the indication of the intensity of UV produced by the sun are unreliable due to their sensitivity to infra red (IR) radiation and their inability to exclude its corrupting effect.
The aim of the invention is to provide an improved UV sensing apparatus.
Throughout this specification, the term electromagnetic radiation should be taken to mean radiation in the range encompassing UV, visible light and IR.
The present invention provides UTV sensing apparatus comprising a housing which is substantially opaque to electromagnetic radiation, an aperture formed in the housing, a filter positioned within the housing at the internal mouth of the aperture, a fluorescent member positioned within the housing on that side of the filter remote from that adjacent to the aperture, and a light sensor positioned within the housing to receive light emitted by the fluorescent member, wherein the filter is such that it substantially removes visible light, the fluorescent member is such as to fluoresce when subjected to UV radiation, and the light sensor is positioned so that substantially none of any electromagnetic radiation entering the housing via the aperture impinges upon the light sensor.
The filter is necessary to remove visible light, otherwise this could cause fluorescence unrelated to the amount of incident UV radiation, and this would be undesirable.
Preferably, the internal geometry of the apparatus and the refractive indices of IR within the apparatus are such that IR is not reflected internally within the fluorescent member at angles which allow the IR to egress towards the light sensor. Advantageously, the light sensor is shielded an internal housing wall in such a manner that substantially none of any electromagnetic radiation entering the housing via the aperture impinges upon the light sensor.
Conveniently, the aperture is sized so that the electromagnetic radiation entering the sensing apparatus is insufficient to cause saturation of the fluorescent member, and so that the light sensor is not saturated by the light emitted by the fluorescent member. Conveniently, the aperture is circular and has a diameter lying within the range of from 0.25 mm to 3 mm. Preferably, the aperture has a diameter lying within the range of from 0.75 mm to 2 mm.
The filter may be made of a dark blue glass.
In a preferred embodiment, the fluorescent member is an acrylic slab coated on one side with an organic dye which fluoresces when subjected to UV radiation. In this case, the coated side of the acrylic slab may be that side adjacent to the filter. Alternatively, the fluorescent member is an acrylic slab which is doped with an organic dye which fluoresces when subjected to UV radiation. In either case, the dye may be a phosphor.
Advantageously, the dye is such as to emit light of a predetermined frequency when subjected to UV radiation. Preferably, the dye is such as to emit green light.
The fluorescent member may be such that the intensity of fluorescent light emitted is substantially linearly proportional to the intensity of UV radiation received.
Advantageously, for reasons of cost and size, the light sensor is a light-dependent resistor. Preferably, the resistance of the

REFERENCES:
patent: 3427489 (1969-02-01), Walsh

Affiliated with

Also associated with

Rating

Ultraviolet sensing apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Ultraviolet sensing apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Ultraviolet sensing apparatus will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-1643571