GB2293044A

GB2293044A - Excimer radiator

Info

Publication number: GB2293044A
Application number: GB9517476A
Authority: GB
Inventors: John Anthony Byatt
Original assignee: ABB Research Ltd Switzerland
Current assignee: ABB Research Ltd Switzerland
Priority date: 1994-08-26
Filing date: 1995-08-25
Publication date: 1996-03-13
Anticipated expiration: 2015-08-25
Also published as: GB9517476D0; GB2293044B; DE4430300C1

Description

EXCIMER RADIATOK 2293044 The invention is based on an excimer radiator

according to the preamble of claim 1.

The preamble of claim 1 relates to prior art as is known from EP-A 1 -0 385 205, wherein a plurality of high-power excimer radiators are arranged side by side in a straight line or in a curve. The individual radiators can contain different gas fillings for different UV wavelengths. At least one of the electrodes and/or dielectric layers delimiting the discharge space can be formed as a UV transparent, electrically conductive coating. A partly aluminium coating, vapour-deposited on the outer periphery of the respective radiator, acts as an outer electrode and, simultaneously, as a reflector.

The Swiss company periodical ABB Technik 3 (1991), p. 21-28 describes cylindrical UV excimer radiators for different wavelengths having an annular discharge gap and two cylindrical electrodes for industrial applications, e.g. UV drying, UV hardening and metal coating. These excimer radiators are operated at frequencies of approximately 50 kHz and with voltage amplitudes of 5 kV - 10 kV, wherein the hot discharge plasma does not come into contact with the electrodes. It is pointed out that flat UV sources and special geometdes for photochemical reactors are also realisable. With a short pulse duration, excimer radiators produce a defined wavelength with high point intensity and high repetition frequency.

The periodical: Meas. Sci. Technol. 4 (1993), p. 668-676 discloses a portable, diffusely reflecting spectrophotometer for rapid and automatic measurements on tissue, wherein light from a tungsten-halogen lamp is transmitted to the tissue via an IR filter and optical fibres and transmitted back to a spectrometer, 2 where it is detected by means of a one-dimensional CCD layer of 1024 photodetector elements and the measured value obtained is recorded by a MOS shift register.

The book by Clifton C. Thompson, ULTRAVIOLET-VISIBLE ABSORPTION SPECTROSCOPY, 1974, Willard Grant Press, 20 Newbury Street, Boston, Massachusetts 02116, p. 39-45, describes a double-beam spectrophotometer, wherein monochromatic light is transmitted through a sample on the one hand and through a comparison absorber on the other by means of a chopper and a beam splitter alternately. Depending on the desired wavelength range, a tungsten or hydrogen broad-band lamp is used as a UV light source, a narrow wavelength band being selected from the spectrum emitted by the lamp by means of an optical system, normally by an interference filter or diffraction grating.

The disadvantages are the short life and low stability of these expensive, broad-band radiation sources.

The invention, as defined in claim 1, solves the problem of further developing an excimer radiator of the type initially mentioned in such a manner that it radiates a plurality of narrow wavelength ranges from a relatively small surface. An advantageous use of the multi-wavelength excirner radiator is in spectrophotorneters.

Advantageous embodiments of the invention are defined in the dependent claims.

3 One advantage of the invention consists in the fact that a complex optical system can be replaced by a single radiation source. Compact spectrophotometers can be produced by means of the invention.

A fiu-ther advantage is the long life of the excimer radiators. High intensities are unnecessary.

According to an advantageous embodiment of the invention, there are no light losses from slits, diffraction gratings, filters, etc.

The invention is further explained in the following with reference to embodiments shown in the drawings, in which:

Fig. 1 shows a two-bearn spectrophotometer with an excimer radiation source; Fig. 2 shows a layer-type excimer radiator having two layer electrodes; Fig. 3 shows a compact spectrophotometer with an excimer radiation source; Fig. 4 shows a disassembled view of a compact spectrophotometer according to Fig. 3; Fig. 5 shows a disassembled view of a layer-type excimer radiator having a common transparent mesh electrode and a plurality of excimer radiation sources which are individually activatable; Fig. 6 showsan arrangement of a plurality of excimer radiation sources provided with gas storage containers, and Fig. 7 shows an excimer radiation source, according to Fig. 6, provided with a gas storage container.

In the figures, like parts are designated by the same reference numerals.

4 The two-beam spectrophotometer shown in Fig. 1, the structure of which is known from the aforementioned book by Clinton C. Thompson, comprises a multi-wavelength excimer radiation source I instead of one or more conventional broad-band radiation sources. The light, emitted by this multiwavelength excimer radiation source I and having a plurality of narrow wavelength ranges, is selected by a diffiaction grating 2 according to wavelength and transmitted through a light gap 3 onto a chopper and bearn splitter 4, on which is mounted a mirror 5. By means of this mirror 5, the incident light is fed via a prism 12 to a light detector 13, alternately via a mirror 6, a comparison object 7 and a mirror 8 on the one hand and via a mirTor 9, a sample 10 and a mirror I I on the other hand.

Fig. 2 shows a perspective view of a layer-type multi-wavelength excimer radiation source 1 as is useable in the two-way spectrophotometer according to Fig. 1. Between a first electrode or mirror electrode 14, the surface of which can be silver-coated, and an at least partially transparent second electrode or wire or mesh electrode 15 are provided a plurality of flat cylinders or excimer lamps L 11 - Lrim filled with different gases and arranged in rows and columns in the manner of a matrix side by side and one below another, only the excimer lamps L l 1 - L41 in the first row and L41 - L44 in the fourth column being, partly, visible. Generally, n excimer lamps per row and m excimer lamps per column can be provided, n and m being whole numbers. On application of an alternating electric field, the different gas fillings of the flat cylindrical excimer lamps L 11 - Lnin, which are made of glass or, if necessary, quartz, produce different wavelength ranges with the light radiated by the mesh electrode 15 having a narrow bandwidth. The multi- wavelength excimer radiation source 1 is operated with voltage amplitudes M the range of 5 kV - 10 kV at frequencies of approximately 50 kHz.

The flat cylindrical excimer lamps L 11 - L41 are miniature lamps and preferably have a diameter in the range of 0.5 cm - 3 cm and a depth or thickness in the range of 2 mm - 5 mm.

Fig. 3 shows a cross-section through a compact spectrophotometer with a multi-wavelength excimer radiation source 1 according to Fig. 2 and Fig. 4 shows a disassembled view.

The multi-wavelength excimer radiation source 1 is arranged in series with a vessel or a cuvette 16; 16a, 16b, a vessel provided with a fluorescent material 17 and a light detector 18; D 11 - Dnm. The cuvette 16 comprises a vessel part with a sample 16a and an adjacent vessel part with a comparison material 16b. It is laterally displaceable in such a manner that only either the vessel part with the sample 16a to be tested or the vessel part with the comparison material 16b is located in the beam path of the multi-wavelength excimer radiation source 1. The vessel provided with a fluorescent material 17 has the function of converting UV light into visible light so as to be able to use an inexpensive light detector 18; D 11 - Dmn, sensitive to visible light, in tests using UV light. The vessel provided with a fluorescent material 17 can optionally be omitted. The light detector 18; D 11 - Drim, equipped with diodes for visible light comprises fight detectors D 11 - Dmn arranged in the manner of a matrix in a plane n x m, the said light detectors D 11 - Drim being arranged in accordance with the matrix-type arrangement of the excimer lamps L 11 Lrim and being associated therewith in such a manner that each light detector D 11 - Dmn substantially only receives the light from one of the excimer lamps L 11 - Lrim.

This application corresponds to that of a spectrophotometer having a twobeam system according to Fig. 1. If one wished to avoid the movement or 6 displacement of the cuvette 16; 16a, 16b, the arrangement would have to be duplicated.

Fig. 5 shows a disassembled view of a mulfi-wavelength excimer radiation source 1 according to Fig. 2, but with n x m mutually electrically insulated, separately activatable mirror electrodes E 11 - E44 (E 11 Enm) arranged behind the excimer lamps L 11 -L44 (L 11 - Lnin) in such a manner that each mirror electrode E 11 - E44 is arranged in series with an excimer lamp L 11 L44. Consequently, this multi-wavelength excitner radiation source 1 can be used as a monochromatic radiation source and can radiate individual narrowband wavelength ranges. However, it can also radiate a plurality of narrowband wavelength ranges if a plurality of mirror electrodes E 11 - E44 are activated simultaneously. This simply constructed multi-wavelength excimer radiation source 1 can therefore be used for many purposes, preferably for measuring the colour content of tissue, in particular paper webs, in a wavelength range of preferably 200 nm - 1 gm. For many applications, the beam generation system of conventional photometers can be replaced by this multi-wavelength excimer radiation source 1.

Fig. 6 shows an arrangement of a plurality of excimer lamps L 11 - Lnm provided with gas storage containers 19 on their edges beyond the active optical region. The gas storage containers 19 prolong the fife of the excimer lamps L 11 - Lrun.

Fig. 7 shows a cross-section through an excimer lamp L having an angled gas storage container 19, as can optionally be used for inner exciMer lamps L22 L33 according to Fig. 6.

7 It goes without saying that the excimer lamps L 11 - Lnin, instead of being in the form of a circular cylinder, can be rectangular in crosssection or, for example, pentagonal or oval or have another form. They also do not necessarily have to be arranged in horizontal and vertical rows. The important factor is that a plurality of flat, miniature excimer lamps for different wavelength ranges are combined to form a single multiwavelength excimer radiation source 1.

8

Claims

CLAIMS:

1. An excimer radiator a) having a plurality of separate excimer radiation sources b) between at least one first electrode and c) one at least partially transparent second electrode, d) wherein a plurality of excimer radiation sources, which emit radiation in different, narrow wavelength ranges under discharge conditions, are combined to form a multi-wavelength excimer radiation source, characterised in that e) the excimer radiation sources are formed as flat cylindrical miniature lamps and f) for all excimer radiation sources of the excimer radiator, only one at least partially transparent second electrode, common to all, is provided.

2. An excimer radiator according to claim 1, characterised in that the excimer radiation sources are arranged in the manner of a matrix side by side and one below another.

3. An excimer radiator according to claim 1 or 2, characterised in that at least some of the excimer radiation sources are provided with a gas storage container.

An excimer radiator according to any one of the preceding claims, characterised in that a separately activatable, mutually electrically insulated first electrode is associated with each excimer radiation source.

9 5. A spectrophotometer including a light source comprising an excimer radiator according to any one of the preceding claims.

6. A spectrophotometer according to claim 5, characterised in that the spectrophotometer is a compact spectrophotometer, wherein the light source is arranged optically in series with a cuvette, containing a sample and a comparison material side by side, and at least one light detector.

7. A spectrophotometer according to claim 6, characterised in that a vessel provided with a fluorescent material, for converting invisible light into visible light, is arranged between the cuvette and the at least one light detector.

8. A spectrophotometer according to any one of claims 5 to 7, characterised in that a separate light detector is associated with each light source of the excimer radiator.

9. An excimer radiator constructed and arranged to operate substantially as hereinbefore described with reference to Figures 2, 5, 6 and 7 of the accompanying drawings.

10. A spectrophotometer constructed and arranged to operate substantially as hereinbefore described with reference to Figures 3 and 4 of the accompanying drawings.