DE9319750U1 - Measuring device in which a light beam is passed through a liquid medium - Google Patents

Description

PATENT ATTORNEYS R" ⁷ ?, ¹ .? ² . Freiburg i.Br.

niPT run H &sfgr;&Ggr;&EEgr;&Mgr;&Tgr;&Tgr;&Tgr; Dreikonigstr. 13

DIPL.-ING. H. SCHMlIl phone mi) losm /toctm

DIPL.-ING. W. MAUCHER ."..*'. .: .**. &tgr;&igr;-y!«* &Lgr;&Agr;&Lgr;»)«?"

Mr/Huh

company

Hellma GmbH & Co.KG

Glass-technical-optical workshops

Monastery Runs 5

79379 Muellheim

Our file * Please always specify

M93 675

Measuring device in which a light beam is passed through a liquid medium

The invention relates to a measuring device in which a light beam is guided through a liquid medium, collected again in whole or in part and, in particular, analyzed spectrophotometrically, the measuring device having two essentially parallel light guides, at the end of which a light deflection by means of a mirror or prism is provided from the mouth of one light guide to that of the other and a measuring section is provided in between, into which measuring section the medium to be examined enters and is penetrated by the light beam.

Such measuring devices are already known. In a solution known from practice, a mirror at 45° is arranged at the end of one light guide, adjacent to which is a slit-shaped access opening for the medium, on the other side of which a second mirror arranged at the same angle ensures that the light fed in and passing between the mirrors through the access opening serving as the measuring section is reflected back into the second light guide parallel to the feed. The light beam can thus be deflected between the two deflections by the mirrors.

pass through the liquid medium so that the recaptured light beam can be analyzed accordingly. This requires very precise manufacture and, above all, assembly of the two mirrors so that the incoming light is actually captured again through the medium and hits the second light guide. The access opening for the medium, which serves as the measuring section, is limited in its dimensions in the direction of the light beam by the distance between the two light guides. A longer measuring section therefore requires a greater distance between the light guides and an even higher precision in the arrangement of the mirrors.

A modified known solution consists in providing a prism in the extension of both light guides, which has a prism surface inclined at 45° opposite the light inlet, on which an air space is created by a cover plate so that this prism surface has a totally reflective effect. Between these two prisms there is again a slit-shaped inlet opening for the medium, which is available as a measuring section. Here too, the length of this measuring section is limited by the distance between the two light guides.

In both cases, the measuring device can advantageously be immersed in any vessel or in open water in order to carry out a specific measurement there, while the actual measuring device used for analysis can be located away from the measuring point, for example in a measuring vehicle or, in the case of measurements within processes, at a sufficient distance or in an adjacent room, unaffected by possibly excessive temperatures or the risk of contamination.

However, in order to obtain a sufficiently long measuring distance for the light beam within the medium with these known measuring devices, the entire measuring device must have a relatively large cross-section due to the larger distance between the two light guides required for this. This is particularly necessary if a liquid is to be examined that absorbs only a small amount of light and therefore requires a correspondingly large measuring distance. Thus, the previously known measuring device cannot be used to examine such liquids under certain circumstances. It is also not possible to insert such a large measuring device through narrow openings in a vessel or into relatively small vessels.

j to be introduced.

The invention is therefore based on the object of creating a measuring device of the type mentioned at the outset, which should have as small an external dimension as possible, in particular a small cross-section, and yet be able to have a measuring distance of almost any size.

The solution to this seemingly contradictory task is that the measuring section or a measuring chamber is arranged as an extension of one of the light guides or the light beam emitted or captured by it outside the light deflection(s). In a surprising way, the

' The measuring section is not placed in the middle between the two light guides and their light deflectors, but rather off-center in the extension of one of the light guides in front of or behind the light deflectors. This means that the light guides 0 can be placed as close to each other as possible, which means that the prism used to deflect the light can be made correspondingly small and inexpensive.

It is useful if one of the two light guides is positioned opposite the light deflection and the parallel

The light guide is shortened and the measuring section is located between the light deflection and the shortened light guide and runs approximately parallel to the non-shortened light guide. A light guide can therefore reach close to the light deflection, while the measuring section is provided parallel to the light deflection, in the extension of which the second light guide is located, whereby either the shortened or the non-shortened light guide serves in any way to supply the light and the other light guide serves to capture the beam guided through the medium.

fc Due to the possible small distance between the two light guides, the entire measuring device has a small external dimension, so that despite the long measuring distance it can also be immersed through narrow openings or in small vessels.

Since the measuring section is not arranged between two light deflections, a particularly inexpensive measuring device can be manufactured by using a single rectangular prism in the incoming and outgoing light beam as a light deflection by 180°, whereby the light entry and exit are arranged at adjacent points on the hypotenuse of this rectangular prism and the reflections on the legs, and that the measuring section is arranged in the area of the light entry or exit.

' light exit is immediately adjacent to this prism and, in particular, is arranged at right angles to the hypotenuse. In this way, on the one hand, a device with the smallest possible cross-section is obtained, but the measuring section can be practically any length, whereby this length is only limited by the total length of the device, or for a measuring section of any length, the device must be designed to be correspondingly long without making it necessary to increase the cross-section. It is particularly advantageous that a single prism is used for the

Light deflection is sufficient, whereby this can be small and therefore inexpensive due to the small distance between the two light guides. Furthermore, the possibility of sources of error is significantly reduced by using a single prism as a light deflection element compared to a solution with two prisms and a measuring section in between.

The housing that accommodates the two light guides and the prism can be open at the side in the area of the measuring section and the measuring section can be separated from the non-shortened light guide and the front side of the shortened light guide. The measuring section is thus easily accessible from three sides and is only limited at the front sides and the side adjacent to the second light guide. Compared to a gap-like opening as a measuring section, the accessibility for the medium to be examined is also significantly improved when immersed in a vessel, a pipe or even in open water.

In order to ensure an accurate measurement, it is advisable if the measuring section is separated from the light guide arranged parallel to it by an opaque, particularly black, partition. A transparent cover plate can be provided between the measuring section and the light guide aligned with it. This allows the measuring beam to enter the measuring section unhindered or to exit from it into the light guide without the light guide coming into contact with the medium.

A modified solution to the problem for a measuring device, with which scattered light or fluorescence in a liquid medium hit by a light beam is to be detected by one of the parallel light guides, can consist in that behind the incident light beam a

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only one light deflection is provided and in continuation of the second light guide in the angular space between the exit from the light deflection and this second light guide a free space is provided as a measuring space. This again makes use of the advantages of being able to provide two light guides with the smallest possible distance from each other parallel to the device, since the light emanating from one light guide reaches the measuring space through a single deflection and causes the medium there to fluoresce or to partially reflect and scatter this light. In a sense, one half of the prism of the first-described solution can be omitted in order to achieve a

k measuring device for fluorescence measurements or scattered light measurements.

It is advantageous if the only light deflection from the incoming light guide is provided by a mirror and/or a prism by 90° and the measuring space is delimited by a cover plate before entering the second light guide and exiting the light deflection, in particular a prism surface arranged approximately parallel to the two light guides, and is otherwise open. This in turn results in good accessibility for the medium.

Since the scattering of light or fluorescence at the

^ If the light exits behind the prism, the two light guides within the device can be approximately the same length and a transparent cover plate can be provided in front of the outgoing light guide to delimit the measuring area, which is located approximately at the height of the measuring device across the light guides, where the supplied light beam enters the light deflection. The second light guide could also be shortened, but for a fluorescence or scattered light measurement, a greater distance from the actual measuring point is not necessary.

In both solutions according to the invention, it is expedient if an adapter with a converging lens is provided at the end of the light guide facing the measuring point, which parallelizes the beam emerging from the light-carrying light guide and focuses the beam arriving at the receiving light guide onto the entry opening in the light guide. This avoids light losses and measurement distortions as best as possible. In addition, it is possible for the diameter of the exit and/or entry opening for the light on the light guides to have a diameter of less than 1mm, in particular about 1/2mm, preferably about 0.6mm. This results in light guides that themselves have a relatively small external dimension, thus favoring the smallest possible external dimension of the entire measuring device, but still allow good light output and thus a sufficiently accurate measurement.

Above all, the combination of one or more of the features and measures described above results in a measuring device that enables either a measuring path of almost any length through the medium or a scattered light or fluorescence measurement in a very small space, whereby free access to the measuring space is available for the medium 5 and the production is inexpensive.

Exemplary embodiments of the invention are described in more detail below with reference to the drawing. It shows in part

schematic representation:
30

Fig.l a side view of a measuring arrangement with a measuring device which has two parallel light guides which, after exiting the measuring device, are guided to a remote measuring device

5, whereby in the measuring device the

The light coming from the light guide is deflected twice and then captured again by the other light guide, and in between there is a measuring section open for the access of the medium to be measured in the extension of one of the shortened light guides,

on an enlarged scale

Fig.2 a longitudinal section of the measuring device with double

Light deflection and measuring section arranged in extension of a light guide, whereby the

the optical fibre to be arranged in the measuring section before it is inserted into a receiving opening provided for it ) is still shown outside the measuring device,

Fig.3 a top view of the measuring device and

Fig.4 a longitudinal section of a modified measuring device for fluorescence or scattered light measurement.

Two light guides 3 run between a measuring device, designated as a whole with 1, and a measuring device 2 for analyzing the measurement results. This allows a larger distance to be bridged between the measuring device 1 and the actual measuring device 2.

The measuring device 1, in which a light beam 4 is to be guided through a liquid medium 25, completely or partially captured again and analyzed spectrophotometrically in the measuring device 2, has two light guides 3 which are essentially parallel in their interior, at the ends of which a light deflection by means of a prism 5 from the mouth 6 of one light guide 3 to the inlet opening 7 of the other light guide 3 and a measuring section 8 in between are provided. The

The medium 25 to be examined enters through lateral openings and is penetrated by the light beam 4 in the measuring section 8.

It can be seen, particularly from Fig.2, that the measuring section 8 is arranged outside the light deflection in the extension of one of the light guides 3 or the light beam 4 emitted or captured by it. If one takes the direction of the light indicated by the arrows Pf in Fig.1 and 2, the measuring section in the exemplary embodiment is located immediately in front of the receiving light guide 3, which in Fig.2 is shown shortly before it is mounted, i.e. before it is plugged into

} a receiving opening 9 within the measuring device 1 is shown.

This light guide 3 is therefore shortened in the position of use compared to the other light guide 3 and the measuring section 8 is located between the light deflection, i.e. the prism 5, and this shortened light guide. The measuring section therefore runs approximately parallel to the non-shortened light guide 3.

According to Fig. 2, a single rectangular prism 5 is provided in the outgoing and outgoing light beam 4 as a light deflection by a total of 180°, whereby the inclined prism surfaces on which

' in each case a deflection of the light by 45° takes place, are designed to be totally reflective by a cover plate 10 and an air space 11 located between them. The light entry and exit takes place at 0 adjacent points of the hypotenuse of this rectangular prism 5 and the reflections take place at the legs where the mentioned cover plates 10 and air spaces 11 are arranged. In this embodiment, the measuring section 8 is located in the area of the light exit immediately adjacent to this prism 5 and is arranged at right angles to the hypotenuse,

i.e. at the same angle as the light ray 4 to the hypotenuse.

The housing 12 of the measuring device 1, which accommodates the two light guides 3, is open at the side in the area of the measuring section 8 and the measuring section 8 is separated from the non-shortened light guide 3 and the front side of the shortened light guide 3 in order to keep the medium away from the light guides.

The measuring section 8 is separated from the light guide 3 arranged parallel to it by an opaque, in particular black, partition wall 13. Between the measuring section 8 and the light guide 3 aligned with it, a transparent

) cover plate 14 is provided.

It should be mentioned at this point that under certain circumstances the light guide that is not shortened in the embodiment could also end at the same height as the shortened light guide, i.e. both light guides could be shortened, so that the incident light would then travel a distance corresponding to the length of the measuring section up to the prism. However, for a measurement that is as free from interference as possible, the embodiment shown with two light guides 3 is more favorable, the ends of which are offset from one another in the longitudinal direction of the device 1 by the length of the measuring section 8.

' From Fig. 3 it is clear that due to the described arrangement the external dimensions of the measuring device 1 or its cross-sectional dimensions can be relatively small, although a relatively long measuring section 8 is made possible.

A modified embodiment of the measuring device 1, which in turn has two parallel light guides 3 in a housing 12, serves to detect scattered light or fluorescence in a liquid medium hit by a light beam 4 using one of the parallel light guides. In this case, this

receiving light guide 3 is shown outside the housing 12, wherein the arrow Pf2 indicates that it can be inserted into a corresponding opening 9 to complete the measuring device 1.
5

In this embodiment, which is largely similar to that shown in Fig. 2, the difference is that behind the incident light beam 4, a single light deflection is provided on a prism surface designed accordingly with a cover plate 10 and an air space 11 and, in continuation of the second light guide, in an angular space between the exit from the light deflection

} or the prism 5 and the second light guide 3, a free space is provided as a measuring space 15. The only light deflection is caused by a prism 5 by 90° and the measuring space 15 is in turn limited by a cover plate 14 before entering the second light guide. The further limitation of this measuring space 8, which is otherwise accessible from all sides, is the light exit of the prism 5.

In this case, the two light guides 3 within the measuring device 1 have approximately the same length. In front of the outgoing light guide 3, the transparent cover plate 14 is provided as a boundary of the measuring space 15, which is located approximately at the height of the measuring device 1 across from the light guides 3, where the supplied light beam 4 enters the light deflection or the prism 5. It can be seen in Fig. 4 that the cover plate 14 rests slightly on the prism 50 next to the incoming light guide. The thickness of the cover plate 14 can also result in a slight shortening of the receiving light guide 3.

In a practical manner, a light beam can be guided from a remote measuring device 2 through a light guide to the

Prism 5, from which it is deflected at right angles to the side, where a measuring chamber 15 is located in front of the mouth of the receiving second light guide 3, in which the light can cause fluorescence or scattered light effects, which this second light guide directs to the measuring device 2. In this case too, the measuring device 1 advantageously has good accessibility for the medium and small external dimensions, so that it can even be immersed in small vessels or vessels with narrow openings.

In both embodiments it is provided that at the

An adapter 16 with a converging lens 17 is provided at the end of the light guide 3 facing the measuring point, which parallelizes the beam spreading out from the light-supplying light guide 3 and focuses the light arriving at the receiving light guide 3 onto the inlet opening 18 in the light guide. The diameter of the exit or inlet opening 18 for the light at the light guide 3 has a diameter of less than 1 mm, preferably 0.6 mm.

It should also be mentioned that the light used does not have to be exclusively or only visible light, but that waves from a non-visible spectrum could also be used depending on the type of measurement.

The measuring device 1, with which optical or spectrophotometric measurements 0 are carried out at a greater distance from a measuring device 2, has two parallel light guides, through one of which the light is fed and through the other of which the light passed through the medium or scattered by the medium is returned to the measuring device for analysis. The measuring section 8 or the measuring chamber 15 is located in front of the mouth of one of the light guides, be it the emitting one or the

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prefers the receiving light guide 3. The light deflection is therefore located adjacent to the actual measuring section and is not divided by the measuring section. The external dimensions of the cross section of the measuring device 1 can be correspondingly small.

Expectations

Claims (11)

Expectations l. Measuring device (1) in which a light beam (4) is guided through a liquid medium (5), is collected again in whole or in part and is analyzed spectrophotometrically, in particular, the measuring device having two essentially parallel light guides (3), at the end of which a light deflection by means of a mirror or prism (5) from the mouth (6) of one light guide (3) to the mouth (7) of the other and in between a ) measuring section (8) are provided, in which measuring section (8) the medium to be examined (5) enters and is penetrated by the light beam (4), characterized in that the measuring section (8) or a measuring space (15) is arranged in extension of one of the light guides (3) or of the light beam (4) emitted or captured thereby, outside the light deflections. 2. Measuring device according to claim 1, characterized in that one of the two light guides is shortened compared to the light deflection and the parallel light guide and the measuring section (8) is located between the light deflection and the shortened light guide and runs approximately parallel to the non-shortened light guide (3). 3. Measuring device according to claim 1 or 2, characterized 0 in that a single rectangular prism (5) is provided in the outgoing and outgoing light beam (4) as a light deflection by 180°, the light entry and the light exit being arranged at adjacent points of the hypotenuse of this rectangular prism (5) and the reflections at the catheti, and that the measuring section (8) in the The area of light entry or exit is immediately adjacent to this prism (5) and in particular arranged at right angles to the hypotenuse. 4. Measuring device according to one of claims 1 to 3, characterized in that the housing (12) accommodating the two light guides (3) is open at the side in the region of the measuring section (8) and the measuring section (8) is separated from the non-shortened light guide (3) and the front side of the shortened light guide (3). 5. Measuring device according to one of claims 1 to 4, characterized in that the measuring section (8) is parallel to the the light guide (3) arranged therein is separated by an opaque, in particular black, partition wall (13). 6. Measuring device according to one of claims 1 to 5, characterized in that a transparent cover plate (14) is provided between the measuring section (8) and the light guide (3) aligned therewith. 7. Measuring device according to the preamble of claim 1, with which scattered light or fluorescence in a liquid medium struck by a light beam (4) is detected by one of the parallel light guides, characterized in that a single light deflection is provided behind the incoming light beam (4) and in continuation of the second light guide in an angular space between the exit from the light deflection and this second light guide a free space is provided as a measuring space (15). 8. Device according to claim 7, characterized in that the only light deflection from the incident Light guide is provided by a mirror and/or a prism (5) by 90° and the measuring space (15) is delimited by a cover plate (14) before entering the second light guide and exiting the light deflection, in particular a prism surface arranged approximately parallel to the two light guides and is otherwise open. 9. Measuring device according to claim 7 or 8, characterized in that the two light guides (3) within the measuring device (1) have approximately the same length and a transparent cover plate (14) is provided in front of the outgoing light guide as a boundary of the measuring space (15), which is located approximately at the height of the measuring device (1) transversely to the light guides (3) at which the supplied light beam (4) enters the light deflection. 10. Measuring device according to one of the preceding claims, characterized in that an adapter (16) with a converging lens (17) is provided at the end of the light guide (3) facing the measuring point, which directs the beam emerging from the light-guiding light guide (3) in parallel and focuses the light arriving at the receiving light guide (3) onto the inlet opening (18) in the light guide. 11. Measuring device according to one of the preceding claims, characterized in that the diameter of the exit or entry opening (18) for the light at the light guides (3) has a diameter of less than 1mm, in particular about 1/2mm, preferably 0.6mm. 5 Godfather