Note: Descriptions are shown in the official language in which they were submitted.
CA 02288034 1999-10-26
Device for measuring fluorescence excited by light,
and the use thereof
The invention relates to a device for measuring
fluorescence excited by light at at least one layer
containing a fluorescing material, and to the use
thereof for measuring fluid materials which effect
fluorescence quenching in at least one of the
fluorescing layers.
Measuring methods and measuring devices
customarily used to date have the disadvantage that the
ratio of fluorescent light to the light required to
excite the fluorescence is very low, with the result
that a separation is required and, consequently, a
miniaturization, which is necessary for many
applications, has so far been ruled out.
Further known solutions do not achieve
satisfactory separation between the exciting light and
the f luore'scent light .
To counter this, use has so far been made of an
expensive, complicated optical design which requires
many optical elements, which are also cost intensive,
the result being, in particular, the appearance of
problems with the miniaturization and process
integration.
The known solutions also have the disadvantage
that the detection of the measuring signal has
proceeded relatively slowly and that furthermore,
errors have occurred due to coupling drift (temperature
fluctuation, mismatching, or due to modem coupling),
and could be taken into account only with difficulty.
DD 106 086 describes a measuring probe in which
fluorescence is excited in a layer, the exciting light
being directed onto the layer by a single optical fibre
which surrounds, in the shape of a ring, at least one
further optical fibre for fluorescent light. The
fluorescent light can be measured with a detector, and
the measured value thereof can be used as a measure of
the content or the concentration of a material, as a
CA 02288034 1999-10-26
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consequence of fluorescence quenching. Use is made for
a reference measurement of a second optical fibre which
directs fluorescent light of a layer region, which is
screened from the measurement medium, onto a second
detector.
However, it is not possible with this solution
to ensure a concrete and accurate local assignment of
the detectable fluorescence intensity over the excited
layer surface, something which is, however, also
necessary for accurate measurements because of an
imprecisely defined local excitation or a non-defined,
inhomogeneous arrangement of the fluorescing material
in the layer. Moreover, an absolute optical separation
is necessary for a simultaneous reference measurement
or further measurements for other materials.
In addition, GB 2265711 A1 describes an optical
fibre sensor in which two optical fibres inclined at a
specific angle to one another are to be used. In this
case, one of the optical fibres serves the purpose of
sending light, and the other optical fibre serves the
purpose of receiving reflected light and directing it
onto a suitable detector. The alignment of the two
optical fibres at an angle to one another is proposed
there in order to achieve enlargement of the possible
detection range of reflected light, since it is
possible to achieve an enlarged overlap of the light
exit cone with the light entrance cone of the two
optical fibres.
US 3,992,631 describes ~a system and a method
for carrying out fluorescence immune tests in which,
inter alia, reference is made to the possibility of
using different optical fibres in a bundle arrangement.
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It is therefore the object of the invention to
propose a device which can be of miniaturized
construction and therefore be adapted flexibly to
different applications and achieves a satisfactory
20 measuring accuracy.
According to the invention, this object is
achieved by means of the features of Patent Claim 1.
Advantageous embodiments and developments of the
invention follow in the case of the use of the features
25 named in the dependent claims.
The device according to the invention for
measuring fluorescence excited by light at at least one
layer containing a fluorescing material essentially
comprises a measuring head in which at least one light
30 source which emits light of wavelengths) exciting
fluorescence(s) in the layer or layers, and at least
one detector which measures the intensity of the
fluorescent light, are held. The light directed onto
the layers) in order to excite the fluorescence is
35 directed onto the fluorescing layer via at least one
optical conductor. In this case, the same optical
conductor can also direct the fluorescent light onto
the detector. A plurality of fluorescing layers can be
arranged next to one another in a fashion separated
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from one another locally or, if appropriate, partially
overlapping, and be irradiated in each case with
exciting light.
It is important for the end faces of the
optical conductors of the fluorescent light to be
arranged and/or aligned taking account of the numerical
apertures of all the optical conductors, in order to
achieve an accurate local assignment of the measured
values. A further possibility for achieving this aim
consists in aligning these optical conductors with
reference to one or more layers) containing
fluorescing material(s).
For the measurement, the fluorescing layers)
is/are arranged on the end or ends of the optical
conductors or on a suitable support or a body, or make
contact therewith.
Optical fibres are preferably used as the
optical conductors.
There is thus, in principle, the possibility of
arranging a plurality of different fluorescing layers,
and using them with one or more different light sources
which in each case emit light with wavelengths which
excite fluorescence(s). It is thereby possible with the
aid of only one measurement to detect a plurality of
different fluid materials which effect fluorescence
quenching in the different layers.
However, the invention can also be developed
for the use of a plurality of optical fibres which
direct different types of light to different detectors
arranged separately from one another.
Thus, for example, the light of a light source
can be directed onto a fluorescing layer, from there
the fluorescent light can be directed by a second
optical fibre onto a detector arranged in the measuring
head, and, for the purpose of obtaining a reference
signal, exciting light reflected in the layer can be
directed onto a second detector by a third optical
fibre. The third, or an additional, optical fibre can
also be used for a second fluorescent light.
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In this case, the fluorescing layer or a
plurality of fluorescing layers which are preferably
applied to a substrate serving as support can simply be
plugged onto the measuring head using a cap or an
exchangeable support, thus rendering a simple exchange
possible. In this case, it is particularly advantageous
when a coupling medium is present between the
substrate, to which the fluorescing layers) is/are
applied, and the ends of the optical fibres, in order
to reduce light losses.
It is favourable for various applications when
at least a part of the measuring head, and in this case
at least the part which holds the optical fibres, which
is directed in the direction of the fluorescing
layer(s), is of flexible construction, or the upper
part of the measuring head is at least partially bent.
In order to improve the optical properties of
the device according to the invention, it is
advantageous for a filter and/or a launching optical
system to be arranged between the light source or
sources and the respectively assigned optical fibres,
in order, on the one hand, to avoid light losses and,
on the other hand, to delimit the wavelength region of
the light which is directed onto the respective
fluorescing layer, so that the measuring errors can be
further reduced. It is particularly favourable that the
filters can be exchanged for others which are suitable
for other wavelengths, that is to say other fluorescing
materials, and consequently also other materials to be
detected.
A corresponding arrangement of coupling-out
optical systems and/or filters upstream of the various
detectors acts in the same way.
In the device according to the invention,
however, it is also possible to make use of a bundle of
a plurality of optical fibres, it being possible to
arrange the individual optical fibres in the bundle
differently in order to be able to detect optimum
measuring signals of fluorescent light, and reflected
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light of the light sources) moreover measuring errors
can be minimized. The arrangement of the individual
optical fibres in the bundle can be performed in this
case in the shape of a ring, in one variant, and in the
shape of a star, in a second variant.
In the case of an arrangement in the shape of a
ring, it is possible to arrange next to one another in
an alternating interchanging fashion in an outer ring
optical fibres which, on the one hand, direct exciting
light onto the fluorescing layer and direct light
reflected there as reference signal onto a detector. It
is then possible to arrange in a ring internal thereto
optical fibres which direct fluorescent light onto at
least one detector in the measuring head. An additional
optical fibre which likewise directs exciting light
onto the fluorescing layer can then be arranged at the
centre of the ring.
In an arrangement of the individual optical
fibres in the shape of a star, it is favourable to
arrange at the centre of the star an optical fibre
through which exciting light is directed onto the
fluorescing layer, and to arrange next to one another
in the shape of a star in an alternating interchange,
optical fibres with which reference light and
fluorescent light are directed onto detectors.
The arrangement of the respective optical
fibres for the various types of light can, however,
also be selected taking account of the arrangement of
different fluorescing layers, it being possible, for
example, to select an arrangement of the optical fibres
in the shape of a circular arc when the fluorescing
layers are preferably constructed as circular arcs and
the local assignment is taken into account.
In another embodiment of the device according
to the invention, the individual optical fibres are
not, however, arranged in parallel but, at least in
their end regions, that is to say in the direction of
the fluorescing layer(s), are inclined at specific
angles to one another, so that, for example,
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fluorescence-exciting light is directed at a specific
angle, which is not equal to 90°, onto the fluorescing
layer, and there is aligned at a second correspondingly
aligned angle at least one optical fibre by which the
reflected reference light can enter and be directed
onto a detector. A third optical fibre can then
preferably be arranged orthogonally relative to the
fluorescing layer through which the fluorescent light
reaches the corresponding detector.
In all these cases, however, it is favourable
to arrange and/or align the optical fibres such that
for the purpose of launching and coupling out exciting
and fluorescent light their end faces permit a local
assignment of the measured fluorescent light, taking
account of their numerical apertures.
It is favourable for specific applications of
the device according to the invention when, at least in
the upper measuring head region, a heater is present
which can prevent condensation of, for example, water
on the fluorescing layer(s). Moreover, it is favourable
to use at least one temperature sensor and a
corresponding controller or regulator to manipulate the
heater in accordance with the ambient conditions, that
is to say the ambient temperature and the atmospheric
humidity, and thereby to be able to set different
prescribable temperatures in the region of the
fluorescing layers) and/or in the upper measuring head
region. The heater can in this case be arranged in the
upper measuring head region, but it is also possible to
arrange appropriate heating elements in the immediate
vicinity of the fluorescing layer(s). One possibility
for this is to fit the heater on the substrate to which
the fluorescing layers) is/are applied.
The device according to the invention can
further be improved when the lower region of the
measuring head is constructed in a thermally insulated
fashion with respect to the upper heated measuring head
region.
CA 02288034 1999-10-26
It can be favourable for various applications
to construct the upper measuring head region not only
in a flexible fashion but also in a tapering fashion,
solely or in conjunction with a flexible design, it
being possible to taper virtually to the diameter of
the optical fibres.
Depending on the actual design of a measuring
device according to the invention, it is then possible
to detect at least one fluid material which effects a
specific quantifiable measure of fluorescence quenching
in the fluorescing layer: It is possible in this case
to detect different materials with different
fluorescing layers which are arranged next to one
another. However, it is also possible in principle to
detect a plurality of materials by directing light of
different wavelengths onto only one fluorescing layer
and carrying out the detection in terms of wavelength
resolution.
Despite an at least partially integrated
electronic evaluation system, the device according to
the invention must be of small and flexible
construction so that the most varied applications are
possible. In particular, the slim and, if appropriate,
flexible construction of the upper measuring head
region has the positive effect that alignment relative
to the measuring location or to the fluorescing
layers) is possible in a simple way.
A further advantage consists in that the
optical fibres can be used without rigid connections,
such as optical connectors, with the result that an
exchange is possible although the optical fibres are
held fixed and therefore can no longer be moved, it
thereby being possible to avoid modal noise.
If a plurality of optical fibres are used as a
bundle, the most varied arrangements at the end of the
measuring head in the direction of the fluorescing
layers) can ensure optimum measuring conditions and
reduce the component of scattered light as well as
greatly minimize crosstalking of exciting light, and it
CA 02288034 1999-10-26
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is also possible in this case to detect a reference
signal.
The spatial separation and additional thermal
insulation of the upper measuring head region can
optimize the temperature control in the region of the
fluorescing layers) with reference to energy
consumption, and unnecessary heating of the lower
region of the measuring head is prevented.
Further advantages of the invention are the
better and more effective illumination of the
fluorescing layer(s), and less influence from
extraneous and scattered light.
The invention can take account of a plurality
of material concentrations by means of different
fluorescent dyes and/or reference signals. It is
possible for such layers to be selectively excited and
correspondingly detected.
The temperature control or heating can be
carried out only in the immediate vicinity of the
layers.
There is no need for any external optical
connectors which could lead to coupling problems.
Miniaturization, a lower mass and, in addition,
flexible access to the measuring medium are possible by
optical separation of measuring tip and the detection
and evaluation of measured values.
The device according to the invention is not
only capable of flexible construction, but is also
cost-effective to produce and operate, since some parts
can also be replaced cost-effectively by being
exchanged.
The invention is to be described in more detail
below using exemplary embodiments.
In the drawing:
Figure 1 shows the diagrammatic design of a first
example of a device according to the
invention;
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Figures 2,
2a, 2b show various arrangements of optical fibre
bundles on the upper measuring head;
Figures 3,
3a, 3b show three examples of a measuring head
according to the invention, in two views in
each case;
Figure 4 shows a first example of a support which can
be mounted on a measuring head, in two views;
Figure 5 shows a second example of a support which can
be mounted on a measuring head, in two views;
Figure 6 shows a third example of a support which can
be mounted on a measuring head, in two views;
Figure 7 shows a fourth example of a support which can
be mounted on a measuring head, in two views;
Figure 8 shows a fifth example of a support which can
be mounted on a measuring head, in two views;
Figure 9 shows a support with a symmetrically
constructed planar optical conductor;
Figure 10 shows two symmetrically arranged supports;
Figure 11 shows examples for launching light into and
coupling it out of end faces of supports
which can be mounted on a measuring head;
Figure 12 shows a sixth example of a support which can
be mounted on a measuring head, in two views;
Figure 13 shows a seventh example of a support which
can be mounted on a measuring head, in two
views;
Figure 14 shows an eighth example of a support which
can be mounted on a measuring head, in two
views;
Figure 15 shows a ninth example of a support which can
be mounted on a measuring head, in two views;
Figure 16 shows a body which can be mounted on a
measuring head;
Figure 17 shows a body which can be mounted on a
measuring head;
Figure 18 shows a body which can be mounted on a
measuring head;
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Figure 19 shows a first holder for fluorescent layers,
in three views;
Figure 20 shows a second holder for fluorescent layers
in three views;
Figure 21 shows a measuring head for measuring with
wavelength resolution, and
Figure 22 shows a further measuring head in two views.
The diagrammatic design of a first exemplary
embodiment of a device according to the invention is
represented in Figure 1.
In this case, there is held in the closed
measuring head 1 at least one light source 2 from which
exciting light is directed onto a fluorescing layer 11
via a filter 6, which is preferably also an
exchangeable bandpass filter, by the optical fibre 3,
which is guided through the upper measuring head region
17. Fluorescent light from the fluorescing layer 11
passes through a second optical fibre 15 vi.a an edge
filter 6, possibly likewise exchangeable, onto a
detector 4 with which the intensity of the fluorescent
light can be measured, and the detector 4 is connected
to an electronic evaluation system 9.
Reflected light then passes as reference signal
through a third optical fibre 16, likewise via a filter
8, which can, again, be exchangeable, onto a second
detector 5, which is connected to a second electronic
system 10.
In this case, the exchange of the filters 6, 8
is advantageously to be possible from outside via
openings with a lock.
A heater 12 which is mounted in a metal tip 14
in order to improve the thermal conduction is then
provided in the uppermost region of the upper measuring
head region 17. Likewise held in the metal tip for the
purpose of controlling or regulating the heater 12 is a
temperature sensor 13 whose measuring signal is led to
an electronic control system which then influences the
heat output.
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Two lines at the lower part of the measuring
head 1 indicate connections to an electronic evaluation
system which can further process the preprocessed
signals from the electronic systems 9 and 10, and
display and output them.
Of course, the number of the light sources 2 of
the detectors 4 and 5 can be appropriately increased.
Different variants for possible arrangements of
different optical fibres are then represented in
Figures 2, 2a and 2b. Here, the upper representation in
Figure 2 shows a bundle of different optical fibres,
the filled-in optical fibres 20 directing light of the
light source 2 onto the fluorescing layer. The hatched
optical fibres 21 direct the light reflected at the
layer as reference signal onto the detector 5, and the
optical fibres 22, 23 direct fluorescent light from the
fluorescing layer or layers onto one or more
detectors) 4.
Various arrangements of three optical fibres
are represented in the lower left-hand and middle
representations, the respective function corresponding
to that already explained in the case of the above
representation. Reproduced in the lower right-hand
representation is an arrangement in the shape of a star
of optical fibres in which a central optical fibre 20
for exciting light and, in alternating exchange around
the middle optical fibre 20, optical fibres 21 and 22
are arranged, it being possible for the number of the
optical fibres 21 and 22 arranged in the shape of a
star to be increased at will.
In the lower representations of Figure 2,
furthermore, the guidance of the different optical
fibres 20, 21 and 22 in the upper measuring head region
17 is represented in preferred form. In this case,
different optical fibres, arranged in the outer region,
in particular, are constructed in an angled fashion so
that it is possible to achieve an improved illumination
of the fluorescing layer, and a reduction in the
influence of extraneous light and scattered light.
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The examples represented in Figure 2 are not
only, however, limited to a design of a measuring head,
according to the invention, in which only one
fluorescing layer is used. A plurality of different
fluorescing layers are used on the measuring head
according to the invention, a local assignment of the
different optical fibres required for the measurement
can be performed in a simple way, with the result that
optimum conditions can be obtained in each case for the
various fluorescence and reference signals.
In each case, the optical fibres 22 can,
however, be arranged and/or aligned such that, even
taking account of their own numerical apertures and
those of the optical fibres 20 for exciting light,
locally defined regions can be detected in the layer or
layers.
A second example of a measuring head 1
according to the invention is represented in Figure 3 ,
in two views, from which it emerges that such a
measuring head has a smaller width in relation to its
length, and therefore, in particular, offers more
favourable preconditions for measurement in flowing
media than is the case with, for example, circular or
square shapes, since the flow conditions, and
consequently also the measurement result, can be
negatively influenced by, for example, turbulence which
is produced, higher flow rates or pressure rises.
Exchangeable supports, of which a few examples
are represented in Figures 4 to 15 still to be
described below, can then be mounted on such a
measuring head 1.
As is also to be seen in Figure 3, optical
fibres 3, 15, 16 can be arranged in row arrangements
opposite one another in pairs, the rows being aligned
parallel to the longitudinal axis of such a measuring
head.
It is possible in this case to arrange in one
row exclusively optical fibres 3 for exciting light,
and in the opposite row exclusively optical fibres 15,
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16 for fluorescent light, or at least in one row an
alternating arrangement of optical fibres 3 for
exciting light and optical fibres 15, 16 for
fluorescent light.
Accommodated once again in the measuring head 1
are the light sources 2, preferably exchangeable
filters 6 and 8, launching and coupling-out optical
systems 25, detectors 4 and the corresponding
electronic evaluation and control system 9.
Also represented in Figure 3 are temperature
sensors 13 and heating elements 12 which project from
the upper socket of the measuring head 1 in the form of
a pin or in another suitable form, so that they can be
positioned and fixed in a self-closed fashion in
connection with correspondingly constructed holding
bores in the supports 30 or bodies 40 (still to be
described).
The supports 30 or bodies 40 can be mounted on
the otherwise planar surface of the socket by means of
an optical cement.
A measuring head 1 with a mounted body 40 in
accordance with Figure 16 is to be seen in the right-
hand representation in Figure 3a.
Figure 3b shows an example of a measuring head
1 on which, again, a support 30 or body 40 can be
mounted. The single or a plurality of heating
elements) 12 can be surrounded by a material 12.1
having good thermal conduction.
Represented in two different views in Figure 4
is a first example of a support 30 which, as
represented in Figure 3 , can be mounted on a measuring
head 1, and is made from an optically transparent
material.
It is to be noted here that, as also holds for
the following pictorial representations 5 to 13, the
proportions do not correspond to the actual ones,
rather, to simplify and improve comprehension, the
width is represented to be substantially larger than is
the case in a practical design, and in that for use in
CA 02288034 1999-10-26
14
flowing fluid media the width of such a support 30 is
substantially smaller in relation to its length, with
the result that the flow resistance is kept
correspondingly low.
The support 30 in accordance with Figure 4
comprises two limbs 30', 30" which are optically
separated from one another at least partially by an
interposed, preferably reflecting layer 36.
In this example, layers 32 containing
fluorescing materials are applied to both outer sides
of the support 30, and the remaining outer surfaces 37
are likewise constructed or coated to be reflective.
The exciting light is now irradiated via
optical fibres 3 into at least one of the two end faces
of the limbs 30', 30 " into the transparent support 30,
and the fluorescence is e:~cited there in the layers 32
by multiple reflection. A portion of the fluorescent
light is irradiated again into the support 30 and, by
reflection at the outer surfaces of the support 30,
directed onto optical fibres 15, 16 for fluorescent
light by the lower end faces of one or both limbs 30',
" , and the intensity of the fluorescent light is
detected by detectors 4 and, consequently, the material
concentration can be measured as a consequence of
25 fluorescence quenching.
Also to be seen in the left-hand representation
of Figure 4 is the fact that the upper bounding
surfaces of the support 30 are constructed inclined at
an angle to one another, the angle being selected such
30 that optimum reflection conditions can be achieved in
accordance with the wavelengths used.
Represented in the right-hand representation of
Figure 4 is a view orthogonal to the longitudinal axis
of such a support 30, from which it may be seen that a
plurality of regions can be separated optically from
one another (also possible in the following examples)
by, for example, reflecting layers 38, and different
layers 32.1, 32.2 and 32.3 are applied or constructed
in the regions. Given these different layers 32.1 to
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32.3, it is possible to use a measuring head 1
according to the invention to determine a plurality of
material concentrations simultaneously and/or to carry
out at least one reference measurement in one of these
regions. The same reference numerals are used for
identical elements in the following figures.
A further variant of a support 30 is
represented in Figure 5, this variant differing from
those previously described only in the outer contour.
The example, represented in Figure 6 likewise
in two views, of a support 30 which can be mounted on a
measuring head 1 according to the invention corresponds
essentially to parts of the support 30 already
mentioned in the description of Figure 4.
The only point is that a cavity reaching over
the entire length of the support 30, or one or more
cutouts, whose surfaces are also provided with a
reflecting coating 36 is/are constructed between the
limbs 30' and 30" .
A self-closing fastening on the measuring head
1 can be achieved with this cavity or the cutout(s).
Constructed for this purpose on the surface of
the measuring head 1 is an appropriate longitudinal web
which can engage in a self-closed fashion in the cavity
constructed in the support 30, and can hold it
correspondingly.
If one or more cutouts are constructed in the
support 30, the correspondingly shaped and contoured
heating elements 12 and temperature sensors 13, or
other, for example, pin-shaped elements without a
further function, can, constructed exclusively for
fastening such a support 30 on the measuring head 1, be
inserted into the cutouts or cavities in a self-closed
fashion and be held there fastened appropriately.
The support 30 likewise represented in two
views in Figure 7 differs from the support 30 shown in
Figure 6 once again only in the web-like flattening in
the upper region.
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In the support 30 represented in Figure 8, the
layers 32 containing fluorescing materials are applied
in the inclined upper region, with the result that they
are not aligned parallel to one another, but are
inclined relative to one another.
A particular design has been selected in the
example of a support 30 represented in Figure 9. Use is
made in this case only of a support 30 to which
layers) 32.1 to 32.3 containing one or more
fluorescing materials are applied, and, at a spacing
therefrom, an otherwise symmetrically constructed
planar optical conductor 35 which both have, above the
layers) 32 containing fluorescing materials, a surface
which is inclined at an angle and at which both the
exciting light and the fluorescent light are reflected.
In this example, exciting light is launched exclusively
into the lower end face of the support 30 and reflected
therein, so that fluorescence is excited in the
layers) 32. Since the opposite surfaces of the support
30 and of the planar optical conductor 35 are
constructed or coated in a reflecting fashion only in
the lower part, at least a portion of the fluorescent
light can pass by reflection at the inclined surface of
the support 30 into the planar optical conductor 35 and
be directed from the lower end face thereof via the
appropriately arranged optical fibres onto the
detectors for the purpose of measuring the fluorescence
intensity. However, instead of the reflecting layers
36, it is also possible to introduce a less strongly
refracting medium into the interspace in a fashion
producing the same effect, this state of affairs also
being valid for the examples according to Figures 6 to
8.
Moreover, instead of the planar optical
conductor 35, it is also possible to use a second
support 30, so that a symmetrical arrangement can be
achieved, in which case it is then also possible
thereby to apply different layers 32.
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In the example represented in Figure 10, by
contrast, for example in accordance with Figure 9, the
layers 32 containing fluorescing materials are
constructed or applied in the upper, inclined region of
the supports 30.
In the supports 30 represented in Figure 4 to
Figure 15, the layers 32 containing fluorescing
materials can be applied directly to the corresponding
surfaces of the supports 30. In another variant,
however, the layers 32 containing fluorescing materials
can be applied in advance to a preferably plate-shaped
transparent substrate and be fastened subsequently
thereto on the respective support 30 at the respective
location, it being possible for this purpose to make
use of mechanically acting self-closed and/or force-
closed connections alone or in conjunction with an
optically suitable binding agent, or of such a binding
agent alone.
Figure 11 represents possible variants of the
construction of end faces of the supports 30 or of the
planar optical conductors 35 into which or from which
the exciting light or the fluorescent light can
respectively be launched or coupled out, these end
faces being correspondingly inclined in all these
examples such that the reflection in the limbs 30',
" of the supports 30 can be optimized, on the one
hand, for the excitation of the fluorescence and, on
the other hand, for the alignment of the fluorescent
light to be measured.
30 In these cases, the upper part of the measuring
head 1, on which such a support 30 is to be mounted,
must be of complementary shape in order to avoid
optical losses. The same also applies to the supports
30 of the examples according to Figures 14 and 15.
Figures 12 and 13 show further possibilities of
how a support 30 can be constructed, only slightly
modified U shapes having been represented here by way
example.
CA 02288034 1999-10-26
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Figures 14 and 15 show rotationally symmetrical
supports 30 whose upper part is of conical
construction, and in which the layers 32.1 and 32.2
containing fluorescing materials are arranged or
constructed in the shape of a circular ring around the
outer lateral surface of the support 30, if appropriate
on an additional, appropriately constructed support, or
directly on the surface.
The two examples of Figures 14 and 15 differ
only in the construction of the reflecting coating 36.
In both examples, the light is launched into and
coupled out of the support 30 through conically
recessed end faces.
Represented in Figure 16 is a body 40 made from
an optically scattering material such as, for example,
a polyester filled with titaniu.-n oxide, aluminium oxide
or zirconium oxide, to which, in turn, layers 32.1 and
32.2 containing fluorescing materials are applied
directly or on a flat substrate.
Such a body 40, which can also be designated as
a diffuser plate, can have cutouts or cavities 42 which
are dimensioned and arranged such that the body 40 can
be mounted on a measuring head 1 as represented, for
example, in Figure 3. In this case, the exciting light
is radiated into the body 40 by the optical fibre 3 and
distributed there diffusely, as a result of which a
uniform excitation of fluorescence is achieved in the
layers 32 and at least a portion of the fluorescent
light is redirected into the body 40, and directed from
there into the optical fibres 16 and 15 onto the
detectors 4 for the purpose of measuring the
fluorescence intensity.
It is also possible that the fluorescent light
can be launched into the optical fibres 15, 16 from an
end face of the layers) 32, and can thereby be
directed onto the detectors) 4, 5.
Such a body 40 can, however, also consist of an
optically transparent material which is provided on the
exposed surfaces with a reflecting coating, and the
CA 02288034 1999-10-26
- 19 -
surface of the body 40 is constructed in an optically
scattering fashion in the region of the layers 32
containing fluorescing materials.
A cap 41 with a body 40, which can be
constructed, in turn, as already set forth in the
description of Figure 16, is shown in Figure 17, and on
the body 40, in turn, at least one layer 32 containing
a fluorescing material is arranged or constructed
there. As was represented, for example, in Figure 1,
the cap 41 can then be mounted on a measuring head 1,
and in this case the arrangement and alignment of the
optical fibres 15 and 16 for the fluorescent light
should be performed to correspond with those of the
respective layers 32.1 or 32.3.
A further example of a body 40 which can
already be constructed, as mentioned above, is
represented in Figure 18.
Such a body 40, can, in turn, easily be made
available in a simple way as an exchangeable part, as
is also the case for the cap 41 in accordance with
Figure 17 and the body 40 in accordance with Figure 16.
If, as also represented in Figure 3a, the body
40 according to Figure 18 is mounted on a measuring
head 1, the light of the light source 2 passes
relatively accurately into the middle of the body 40
and is scattered there diffusely and fluorescence is
excited in the layers 32.1 and 32.3 virtually
simultaneously. The fluorescent light retroreflected
into the body 40 passes via the limbs 40' and 40 " of
the body 40 and the optical fibres 15 via an optical
system 25 onto a photodetector 4, it being possible for
an optical filter 8 to be arranged upstream of the
latter, and the evaluation of the measuring signals
being carried out with the electronic system 9
integrated in the measuring head 1.
Figures 19 and 20 represent two examples of
holders 43 on which it is possible to fasten layers
32.1 and 32.2 containing fluorescing materials. These
layers 32.1 and 32.2 are preferably applied to a plane,
CA 02288034 1999-10-26
- 20 -
flat, transparent substrate which can be fastened on
the holder 43 in a self-closed fashion and/or with a
binding agent.
A holder 43 thus prepared can then readily be
mounted and fastened on, for example, a body 40 which
can, if appropriate, be a permanent component of a
measuring head 1, as is represented in Figure 3a.
Represented in Figure 21 is a further example
of a measuring head 1 according to the invention, on
whose upper tip there is arranged, in turn, a layer 11
in which at least one fluorescing material is
contained. Arranged, in turn, below this layer 11 is a
temperature sensor 13 and a heating element 12, the aim
being, if required, to prevent the formation of
condensate on the layer 11.
The exciting light .s once again launched into
an optical fibre 3 starting from the light source 2 via
an optical system 53 and ,an exchangeable filter 6, and
directed onto the layer 11. The excited fluorescent
light passes via the optical fibre 15, the optical
systems 52 and the exchangeable filter 8 into a
spectrometer 50, for the purpose of wavelength-resolved
measurement, to different detectors 54' and 54 " via an
optocoupler 51.
A further example of a measuring head 1
according to the invention is represented in Figure 22,
in two views. In this case, the exciting light of the
light source 2 is launched only on one side into a limb
30' or 30" of a support 30 such as is represented in
Figures 4 to 15, and coupled out again from the
respective other limb 30' or 30 " or both limbs 30' and
30 " , and directed onto detectors 4 in order to
determine the fluorescence intensity.
