AT525197A1 - Measuring unit and a method for measuring at least one gaseous or solid substance - Google Patents

Abstract

In order to enable fast, spatially resolved measurement of a gaseous or solid substance in a measurement volume (9), a primary light beam (4) generated by a light source (12) is divided into a plurality of partial beams (3) in a multiplexer unit (2), wherein the partial beams (3) are emitted to different points of a reflection plane (7.1) of a reflection unit (7), and the partial beams (3) penetrate the measurement volume (9) formed between the decoupling units (21) and the reflection unit (7). is, the partial beams (3) being reflected at the reflection unit (7) as return beams (14) and the return beams (14) penetrating the measurement volume (9) a second time and the return beams (14) being detected with at least one detector (11 ) are detected and with the at least one detector (11) a light property characterizing the gaseous or solid substance of at least one detected return beam (14) is measured.

Description

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Measuring unit and a method for measuring at least one gaseous or solid substance

The present invention relates to a measuring unit and a method for measuring

at least one gaseous or solid substance in at least one measurement volume.

Emissions of gaseous or solid substances in exhaust gases, especially in private transport, are a much-discussed topic due to the increasing number of vehicles, not only in the course of global warming, but also in the course of the health burden on people from nitrogen oxides, partially burned fuel components and fine dust particles. Developments in recent decades have aimed on the one hand at avoiding the emission of partially burned compounds in the course of the mandatory installation of catalytic converters in Otto engines, and on the other hand at avoiding the emission of nitrogen oxides in the case of catalytic converters in diesel engines. The allowable values of emitted

Substances are often determined by national and supranational standards.

Nevertheless, there are still vehicles in public use today which, although they met the legal standards for reducing exhaust emissions at the time of their approval, are regarded as high emitters when used over a longer period of time. The reason for this can be, for example, the failure to retrofit a catalytic converter or a lack of maintenance, for example if a diesel catalytic converter is not refilled with urea and a proper function of an SCR (selective catalytic reduction) catalytic converter is no longer given. Among other things, this can also be due to a lack of knowledge regarding the (non) functionality of these

components during the journey.

Exhaust gas measurements are largely limited to systems that measure substances in the exhaust gas, such as gaseous substances or particles, in the vehicle itself, for example in or after the exhaust. However, these systems are limited to a small number of test vehicles and therefore cannot provide a representative image of a large number of different vehicles in real operation. Emission measurements as part of the regular inspection of the vehicle in a workshop are also unrepresentative because such inspections are only carried out at long intervals. Attempts are therefore being made to enable exhaust gas measurements from vehicles in real operation in public spaces. This so-called "remote sensing", also in the sense of "real driving emissions" (RDE) measurements, can be attached to advantageously pre-installed infrastructure, such as toll stations, street lamps, bridges, or building facades in the city and the like. This could be used, for example, to notify vehicle owners of high emission vehicles and/or

provide mandatory maintenance. One must, however, when setting up the devices

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ensure a suitable measuring point in order to obtain representative results. In general, crossing areas with traffic lights and the resulting potential standstill of vehicles should be avoided. Furthermore, it has been shown that a slight incline of the road at the

Measuring point is suitable for generating a positive engine load.

Remote sensing often uses a light source that emits a characteristic wavelength or wavelength range(s) to detect a gaseous substance such as carbon monoxide or nitrogen oxides. A detector allows, for example, a measurement of the attenuation of the light that is sent through the exhaust plume. However, it can also be provided to measure particles, such as soot particles, as a substance. This can then be done, for example, via light scattering or by measuring the attenuation of the

Reflection can be realized in relation to the incident light.

However, the reliable measurement of such substances in exhaust clouds can lead to various difficulties. On the one hand, the emissions of substances from different engines or other energy systems, such as fuel cells, are consistently different and must be measurable with the same system. Furthermore, the concentration range to be measured varies greatly and depends on the vehicle class to be measured (e.g. truck vs. motorcycle). Especially low concentrations cause problems in the evaluation. Also differences in the operating temperature of a

Motors can result in differences in the substances to be measured.

Due to the differences in the gaseous or solid substances and the expansion of the exhaust cloud, it is difficult to obtain a representative and comparable absorption or concentration or quantity of a gaseous or solid substance in the exhaust cloud

determine.

US Pat. No. 6,171,522 B1 discloses a spatially resolved concentration measurement in an exhaust gas from an aircraft turbine using a plurality of beam paths. In measurement mode (while the engine is running), the hot exhaust gases from the engine emit infrared radiation, which is recorded by receivers and sent to a multiplexer via fiber optic bundles. Each receiving device only detects radiation from the beam bundle assigned to it. The multiplexer forwards the radiation from all fiber bundles sequentially to a spectrometer, where the associated spectrum is determined. The light beams generated by the exhaust gas are thus combined via a multiplexer unit and analyzed in a detector. This enables a spatially resolved measurement of the concentration of various substances in an exhaust cloud. However, the measurement is performed sequentially and can therefore lead to inaccuracies in the analysis of a rapidly volatile

Lead exhaust cloud, as it occurs, for example, in road traffic.

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EP 173 930 A2 discloses an embodiment of an optical multiplexer unit, but here it is divided according to wavelength. However, a wavelength division is disadvantageous for the application in the course of remote sensing, because the absorption of a substance is wavelength-dependent and therefore no spatially resolved measurement of the same

substance is possible.

The object of the present invention is therefore to provide a measuring system that enables a fast, spatially resolved measurement of a gaseous or solid substance

possible in a measuring volume.

This object is achieved according to the invention by a measuring unit mentioned at the outset in that a multiplexer unit and a light source are provided in the measuring unit, the light source generating a primary light beam and sending it to the multiplexer unit and the multiplexer unit generating a plurality of partial beams from the primary light beam, such that the multiplexer unit is designed to emit the partial beams via an optical path and a decoupling unit to different points of a reflection plane of at least one reflection unit, wherein the decoupling units are arranged at a distance from the reflection unit and the at least one measuring volume is arranged between the decoupling units and the reflection unit, that the at least one Reflection unit is provided to reflect the partial beams after their passage through the measurement volume as reflections in the direction of the measurement volume that at least one detector is provided, which detects the return rays after they have passed through the measurement volume and that the at least one detector is provided, one of the at least one gaseous or solid substance

to measure characterizing light property of at least one detected return beam.

By using a multiplexer unit, e.g. in the form of an optical multiplexer, several partial beams can be easily generated, which are sent through the measurement volume at different points and reflected by a reflection unit and, after passing through the measurement volume again, can be detected by a detector as return beams, resulting in a simple spatially resolved measurement in the measurement volume is made possible. The sensitivity of the measurement can also be increased by passing through the measurement volume twice, because each light beam is influenced several times by the gaseous or solid substances in the measurement volume. Due to this integral measurement, a more precise measurement of a gaseous or solid substance in the measurement volume can be made possible and substances can be measured in a lower concentration in the measurement volume. In addition, the measuring unit can be used very flexibly because the positions and directions of the partial beams can be chosen flexibly. This also allows a two-dimensional or three-dimensional measurement in the appropriate arrangement

measurement volume.

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A partial light intensity of each partial beam is advantageously equal to a primary light intensity of the primary light beam or a sum of the partial light intensities of each partial beam is equal to a primary light intensity of the primary light beam. This simplifies the implementation of the multiplexing unit. In one variant, the partial beams have at least partially or completely different partial light intensities, with groups of partial beams having one

can have identical partial light intensity.

The arrangement and the number of detectors in the measuring unit can also be chosen flexibly. For example, the at least one mirroring unit reflects at least two partial beams of the plurality of partial beams as at least two return beams to one detector each, or each partial beam is reflected by the at least one mirroring unit as a

Return beam reflected to one detector each.

In order to measure the measurement volume from different directions, a further variant of the invention provides that at least two partial beams of the plurality of partial beams have different directions and the at least two partial beams in different directions are each directed to a reflection unit with a reflection plane, and the respective reflection unit each incident partial beam is reflected as a return beam to the at least one detector. In other words, in this variant, at least two partial beams of the plurality are oriented in partial beams in directions that differ from one another. This means that, for example, a partial beam can be oriented in a first direction and all other partial beams are oriented in a second direction, but in exactly the same way one partial beam can also be directed in a first direction, another partial beam in a second direction and the remaining partial beams in one be oriented in third or more other directions. In such an arrangement, for example, two groups of partial beams can be emitted, with the partial beams of the groups having different directions (e.g. being normal to one another) and penetrating the measurement volume in different directions. In other words, in such a variant, two groups of partial beams are provided and the partial beams of a first group penetrate the measurement volume in a different direction than the partial beams of a second group. The return beams of the respective group can be detected by one detector or by different detectors. This allows a two-dimensional

Measurement of a measurement volume can be achieved.

The detection of several return beams with one detector can be simplified if at least two optical paths have different optical path lengths and the partial beams of the plurality of partial beams running over these at least two optical paths due to the different optical path lengths after passing through the

Measuring volume, the reflection at the at least one reflection unit and the passage

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by the measurement volume as reflections with a time offset at the at least one detector

arrive. This allows such return beams to be recorded at clearly separate times.

In one variant, all optical paths have different optical path lengths. In other words, each optical path has an optical path length that differs from the

optical path lengths of all other optical paths differs.

If the measuring unit is designed to emit at least one partial beam at an angle deviating from a normal to the reflection plane of the at least one reflection unit, this can be used in a wide variety of ways. On the one hand, a specifically arranged detector can be targeted with the return beam, which can facilitate the detection of the return beam. On the other hand, multiple passages of the partial beam, and possibly also of the return beam, can be realized through the measurement volume. For this purpose, the partial beam can be reflected back and forth multiple times between two reflection units arranged at a distance from one another and facing one another, and the partial beam can thus penetrate the measurement volume multiple times. with

With such an arrangement, the sensitivity of the measurement can be increased even further.

Several measurement volumes that are different or spaced apart can be measured if the multiplexer unit is designed to direct a number of partial beams to at least one deflection unit, with the at least one deflection unit being provided to direct the number of partial beams in the direction of the at least one reflection unit and the reflection unit reflects the partial beams as return beams. In other words, the at least one deflection unit is designed to change the direction of a partial beam exiting from it in relation to its entry direction. The return beams can also be guided to at least one detector via the multiplexer unit. Each deflection unit can have its own measuring volume

be formed.

In a further variant of the invention, the multiplexer unit can be pivoted about an axis, the axis being normal to the reflection plane of the at least one reflection unit or normal to a surface on which the measuring unit is arranged.

is arranged to run.

The detection of multiple return beams in a detector can also be simplified if a modulation unit is provided in the measuring unit in order to split the primary beam and/or at least two partial beams and/or at least two return beams into individual light packets. In other words, at least one modulation unit is provided, with which continuous light beams can be divided into a large number of separate light packets that are separate from one another. Come at the detector that detects the return rays

then individual light packets on. If these light packets are additionally separated in time

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from each other, the detection of the return beam at the detector can be simplified even further

will.

In a particularly advantageous embodiment, at least one imaging unit is provided in the measuring unit in order to record at least part of the exhaust gas cloud from different directions if an exhaust gas cloud is present in the measuring volume, with an evaluation unit being present to combine the multiple images recorded with the imaging unit from different directions into one to reconstruct the image of at least part of the exhaust gas cloud and to determine a passage distance of at least one partial beam of the plurality of partial beams and/or the return beam through the exhaust gas cloud in the measurement volume from the image of at least one part of the exhaust gas cloud, with the at least one detector that detects the return beam detected, a decrease in intensity of the return beam due to the at least one gaseous or solid substance is detected and the evaluation unit is provided, from the decrease in intensity and the determined passage distance a concentration of the at least one gaseous or to determine the solid substance in the measuring volume. This enables a more precise determination of a concentration of a gaseous or solid substance in the measurement volume. A plurality of cameras and/or one or more lidar units can advantageously be used as the imaging unit. The plurality of cameras and/or the one or more lidar units are preferably arranged at different positions. In other words, the plurality of cameras and/or the one or more lidar units are arranged in such a way that the part of the exhaust gas cloud can be imaged from different spatial directions. In this way, they can image part of the exhaust cloud from different directions.

In order to protect sensitive reflection areas from dirt or damage, a protective film can advantageously be exchanged over a reflection unit

arranged. This means that necessary maintenance intervals can be reduced.

The above-described object is also achieved according to the invention by a method mentioned at the outset in that a primary light beam generated by a light source is divided into a plurality of partial beams in a multiplexer unit, with the partial beams each traveling via an optical path and a decoupling unit to different points of a reflection plane reflection unit, and the partial beams penetrate the measurement volume, which is formed between the decoupling units and the reflection unit, the partial beams being reflected at the reflection unit as return beams, and the return beams penetrating the measurement volume a second time, and the return beams having at least

be detected by a detector and with the at least one detector a gaseous

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or solid substance characterizing light property of at least one detected return beam

is measured.

The subject invention is explained in more detail below with reference to FIGS. 1 to 6, which are advantageous by way of example, diagrammatically and not by way of limitation

Show configurations of the invention. 1 shows a measuring unit with a multiplexer unit,

2 and 3 each with a possible embodiment of the measuring unit

Multiplexer unit, Fig. 4 a multiple measurement with multiple measurement volumes,

5 shows a concentration measurement of a substance in an inventive

measuring unit, and FIG. 6 shows a protective film unit for the measuring unit according to the invention.

1 shows a measuring unit 1 for measuring a gaseous or solid substance in a measuring volume 9 which is emitted from an emission source, such as a vehicle. In the measurement volume 9 there can be, for example, an exhaust gas cloud 5 which is emitted by the emission source. A wide variety of gaseous and solid (e.g. particles) substances can occur in the measuring volume 9 . For example, an exhaust gas cloud 5 from a car can be present in the measurement volume 9 . However, the substances in the measurement volume 9 can come from any type of emission source, for example on a surface 8 . For example, the emission source is a vehicle such as passenger cars (passenger cars), trucks (trucks), but also a single-track vehicle such as a motorcycle, moped, and the like that have an internal combustion engine. Emissions from other emission sources, such as a fuel cell, which as a rule only emit water vapor and no pollutants, can also be measured using such a measuring unit 1 . The detection of gaseous or solid substances in a measurement volume 9 can be helpful, for example, to determine the proportion of vehicles with

to determine low or high emission values in road traffic.

The measurement can take place on a surface 8, for example a road, advantageously at a certain distance d above a surface 8. However, it is also conceivable that the measuring unit 1 is arranged to the side of a measuring volume 9 and the measurement takes place parallel to the surface 8, or that the measuring unit 1 is also installed in the surface 8 itself. Also combinations of measurements from several sides

are imaginable.

The measuring unit 1 can also have a measuring volume 9 at other remote locations, for example

a surface 8 measure. It is conceivable that a measuring unit 1 in the measuring volume 9

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measures an exhaust cloud from an aircraft when taking off or landing on a runway at an airport. It is also conceivable that an exhaust gas cloud 5 from a ship

measured in a harbor basin or in a lock, for example.

The invention is not limited to the applications mentioned above, but rather all possible uses of the measuring unit 1 that are apparent to a person skilled in the art

imaginable.

The exhaust gas cloud 5 does not necessarily have to come from a vehicle either, but can in principle come from any emission source. An example is an exhaust cloud 5 from

an industrial process, which is emitted, for example, in a chimney.

The substances to be measured in the measuring volume 9 can be gaseous substances such as carbon dioxide (CO), carbon monoxide (CO), nitrogen oxides (NOx), sulfur dioxide (SO2), gaseous polycyclic aromatic hydrocarbons (PAH) and the like. However, it is also conceivable to measure solid substances, such as solid particles, such as soot particles, in the measuring volume 9 . The substances and their quantities and/or concentrations in the measuring volume 9 are usually dependent on the emission source, for example the type of fuel, the internal combustion engine, the operating state of the internal combustion engine and the status of a catalytic converter or exhaust gas aftertreatment system (if present). For example, an internal combustion engine that is not yet up to operating temperature often emits a higher concentration of partially combusted substances, such as polycyclic aromatic hydrocarbons, than at normal operating temperature. Likewise, in different operating states (e.g. given by current speed and current

Torque) emits different substances.

These gaseous or solid substances in the measuring volume 9 are to be measured according to the invention. "Measuring a substance" can mean recognizing the presence of the substance in the measuring volume 2, but also measuring a quantity or concentration of the

gaseous or solid substance in the measuring volume 2.

A light source 12 is provided in the measuring unit 1 and is arranged in close proximity to a detector 11 in the exemplary embodiment shown. The light source 12 and the detector 11 are preferably arranged in a common housing. The light source 12 can, for example, emit monochromatic light, for example as laser light, which emits a defined wavelength with a predetermined light intensity. In particular, quantum cascade lasers (QCL) can be used, but other types and combinations of lasers are also conceivable in order to cover different wavelength ranges. It is also conceivable that the light source 12 comprises a polychromatic emitting lamp, such as a lamp in the ultraviolet (UV) or

also in the infrared range (IR). There is also a monochromator in the light source 12 or on

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other suitable location of the measuring unit 1 conceivable in order to select specific wavelengths. A monochromator, for example, a Bragg grating, a prism, a

be a movable mirror or an optical filter.

The light source 12 generates a primary light beam 4 with a predetermined primary light intensity Ip. The primary light beam 4 has at least a predetermined wavelength. The primary light beam 4 can be routed to at least one multiplexer unit 2 via an optical primary path 10 . The multiplexer unit 2 and the light source 12 can also be designed as one unit, in which case the primary optical path 10 would be implemented in this common unit. However, the light source 12 can also be arranged locally separately from the multiplexer unit 2 (as in FIG. 1). The primary optical path 10 can be, for example, a light guide, such as a fiber optic cable, a mirror system or another suitable optical system that directs the primary light beam 4 from the light source 12 to the

Multiplexer unit 2 conducts.

The primary light beam 4 is divided in the multiplexer unit 2 into a plurality n of partial beams 3 with a predetermined partial light intensity I+ (in FIG. 1 only some of them are provided with reference symbols). In one variant, at least two of the plurality n

Sub-beams 3 different partial light intensities.

A multiplexer unit 2 is an optical system or device in the form of an electrical or optical or electro-optical circuit or arrangement, which divides an incoming primary light beam 4 into a plurality n of outgoing partial beams 3 with partial light intensities, the wavelength of the partial beams 3 preferably being the same as the primary light beam 4 remains. However, the wavelength of the partial beams 3 can also be different from the wavelength of the primary light beam 4 . Depending on the application, the partial light intensity I+ can be the same as the primary light intensity Ip, but it can also be different. In principle it is also conceivable that certain partial beams 3 have the same wavelength as the wavelength of the primary light beam 4 and/or the primary light intensity Ip and others do not. However, it is also conceivable that the sum of the partial intensities I; of the partial beams corresponds to the primary light intensity Ip, and thus a simultaneous beam splitting in the multiplexer unit 2 can take place. The partial light intensities I} of the partial beams 3 are

preferably the same.

A multiplexer unit 2 can be implemented, for example, by an “optical fiber multiplexer” or also “optical coupler” or “optical splitter”. A realization of the multiplexer unit 2 as a “Fiber Optic Switching Network” is also conceivable. In doing so, he will

Primary light beam 4 successively to a plurality n by means of an electronic circuit

Partial beams 3 divided. Various versions of a multiplexer unit 2 are

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well known and the person skilled in the art can choose one suitable for the respective application

Select.

In one variant, the multiplexer unit 2 is designed in such a way that an optical demultiplexer is also implemented at the same time. An optical demultiplexer is effectively the inverse of an optical multiplexer, connecting multiple inputs to one output. This allows multiple input beams in a demultiplexer to be switched to an output of the demultiplexer. Alternatively and if necessary, a

Multiplexer unit 2 and a demultiplexer unit can be implemented separately from one another.

The partial beams 3 generated by the multiplexer unit 2 are each routed via their own optical path 6, with each partial beam 3 preferably being assigned exactly one optical path 6 and the optical paths 6 of the individual partial beams 3 running separately from one another. An optical path 6 is designed, for example, as an optical waveguide or optical fiber of a specific length. However, an optical path 6 can also be designed as another suitable optical system, such as a mirror arrangement. Depending on the measurement task or application or requirement, a different number of partial beams 3 in the

measuring unit 1 according to the invention can be provided.

The partial beams 3 are coupled out at different points at the ends of the optical paths 6 facing away from the multiplexer unit 2 at decoupling units 21 and emitted in the direction of a reflection unit 7 with a reflection plane 7.1. The emitted partial beams 3 are thus spatially separated from one another, but the beam paths of the partial beams 3 can also cross between the decoupling unit 21 and the reflection unit 7 . A decoupling unit 21 essentially serves to emit the partial beams 3 guided in the optical paths 6 in the desired direction into the area between the decoupling units 21 and the reflection unit 7, in particular the measurement volume 9. The orientation of the partial beams 3 is irrelevant here. The partial beams 3 could therefore be radiated, for example, normally onto a surface 8 or also parallel to it or also at any angle to the surface 8 . The respective mirroring unit 7 is corresponding

to be arranged so that a partial beam is reflected on it.

The decoupling units 21 are spaced a first distance d from the

Reflection unit 7 arranged with the reflection plane 7.1.

The reflection unit 7 can consist of several individual mirrors or several separate reflection planes 7.1. Several mirroring units 7 are also fundamental

possible.

The distance d can be selected to suit the application. For example, can

the distance d depends on the vehicles passing through, but also on the direction

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be the measurement. For example, the distance d can be smaller when measuring parallel to surface 8 and larger when measuring normal to surface 8 . The distance d to the reflection plane of 7.1

Reflection unit 7 does not have to be the same for each decoupling unit 21 either.

This is between the decoupling units 21 and the mirroring unit 7

Measuring volume 9 formed.

In FIG. 1, the decoupling units 21 are arranged next to one another in a line, so that the individual partial beams 3 produce a light curtain of a certain width in the measurement volume 9 . In this way, in particular, exhaust gas clouds 5 of different sizes can be reliably detected in the measurement volume 9 . An area or even spatial distribution can also be achieved by a corresponding arrangement of the decoupling units 21

of the partial beams 3 can be realized.

For a two-dimensional distribution, for example, two groups of partial beams 3 with different orientations, preferably perpendicular to one another, could be generated, with all partial beams 3 being arranged in a common beam plane. There are thus two arrangements of decoupling units 21 with different orientations, with a reflection unit 7, 7' having a reflection plane 7.1, 7.1' being provided opposite each of the arrangements. This is shown, for example, in FIG. With such an arrangement, the two-dimensional distribution of a gaseous or solid substance in the measurement volume can be determined. If an exhaust gas cloud 5 moves in the measurement volume 9 (for example in a direction normal to the plane of the drawing in Fig. 2), then a three-dimensional distribution of a gaseous or solid substance in the measurement volume 9 could even be determined by sequential measurement

be reconstructed.

However, it is also possible to realize a spatial distribution of the partial beams 3 . For this purpose, the decoupling units 21 could, for example, also be arranged in a third dimension (in FIG. 1, for example, offset from one another in a direction normal to the plane of the drawing). In such an arrangement, for example

several arrangement levels as shown in Figure 2 can be provided one behind the other.

The individual partial beams 3 are directed to a reflection plane 7.1 of at least one associated reflection unit 7. The partial beams 3 penetrate the at least one measurement volume 9. The arrangement of the reflection unit 7 depends on the orientation of the partial beams 3, which are coupled out of the multiplexer unit 2. The reflection unit 7 can, for example, be parallel to the plane of the surface 8,

normal to the plane of surface 8, or at an angle to the plane of surface 8

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be arranged. In one possible embodiment, the mirroring unit 7 can also be installed in or

be arranged as part of a surface 8.

The partial beams 3 are reflected at the reflection plane 7.1 of the at least one reflection unit 7 as return beams 14 (in Fig. 1 and 2 only some return beams are provided with a reference number for reasons of clarity) in the direction of the measurement volume 9 and penetrate the measurement volume 9 a second Just.

The return rays 14 are then detected by at least one detector 11 .

The at least one detector 11 measures at least one light property of a reflected beam 14 detected thereby, which characterizes the gaseous or solid substance to be measured. For example, a light intensity or a wavelength or any other measurable light property can be measured as a light property. The gaseous or solid substance can then be inferred from the measured light property, for example the presence of the substance, a quantity or a concentration of the substance.

In the measuring unit 1 according to the invention, a partial beam 3 penetrates the at least one measuring volume 9 twice due to the reflection via the reflection unit 7, namely as a partial beam 3 and after reflection as a return beam 13, the light beam being influenced twice by the gaseous and/or solid substance in the measuring volume 9 becomes, resulting in an integral measurement. This can be reflected in the measurement in increased sensitivity and an improvement in the signal-to-noise ratio because larger

measurement signals are possible. A higher measurement quality can thus be achieved.

In one possible embodiment, the detector 11 measures the reduced light intensity of the detected return beam 14 due to the at least one gaseous or solid substance. The measured light intensity can be converted into an absorption of a gaseous substance, for example by means of a previously performed reference measurement unit in the detector 11, which in the absence of a substance in the measuring volume 9 is carried out. Such a reference measurement can also take place at regular intervals or as required. A weakening of the light intensity due to a solid substance, for example due to scattering, can also be detected in this way. However, there can also be a weakening of the light intensity of the detected return beam 14 in relation to the light intensity of the partial beam 3 or 3 belonging to the respective return beam 14

based on the primary beam 4 can be determined.

The detector 11 can be arranged in the measuring unit 1 at a suitable point and

a different number of detectors 11 can be provided.

For example, a separate detector 11 is provided for each return beam 14 . Such

Execution is shown in Fig.3. In this embodiment, a primary light beam 4 in the

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Multiplexer unit 2 introduced, and the multiplexer unit 2 divides the primary light beam 4 into a plurality n of partial beams 3 . The partial beams 3 are emitted in the direction of the reflection unit 7, penetrate the measurement volume 9, are reflected on the reflection unit 7, penetrate the measurement volume 9 a second time and run back to the multiplexer unit 2 as return beams 14. In the multiplexer unit 2 there are detectors 11 for each of the Reflectors 14 provided. This enables a very accurate, locally separate measurement of the gaseous or solid substances in the measurement volume 9 and

requires only one light source 12, which provides a primary light beam 4.

Alternatively, a detector 11 could also be provided for several or even for all return beams 14 . Such an embodiment is indicated in FIG. This can be implemented, for example, by designing the multiplexer unit 2 as a multiplexer and demultiplexer. In this case, the return beams 14 are guided via the primary optical path 10 to the detector 11 and detected therein. The reflections 14 can also have a

separate demultiplexer unit to the detector 11 are performed.

However, it is also conceivable that the partial beams 3 are not radiated normally onto the reflection plane 7.1, but rather at a certain angle, so that the reflected return beams 14 are then, preferably after passing through the measurement volume 9 again, directed to a suitably arranged detector 11 will. In this way, multiple return beams 14 can be detected with one detector 11 or else

each return beam 14 individually with its own detector 11.

In a particularly advantageous embodiment, at least two optical paths 6 have different optical path lengths. The partial beams 3 running over it are therefore radiated in the direction of the reflection unit 7 with a time offset due to the different optical propagation times. If the return beams 14 generated in this way are detected by the same detector 11, the return beams 14 also arrive at the detector 11 with a time offset due to the different optical propagation times, which enables a simple spatially resolved measurement with a common detector 11. In one possible embodiment, all optical paths 6 of the partial beams 3 have different optical path lengths, which means that all return beams 14 can be detected

a single detector 11 facilitated.

If the multiplexer unit 2 is designed as a “Fiber Optic Switching Network” and the primary beam 4 is divided into at least two partial beams 3 one after the other, this also allows a detector 11 for the at least two partial beams 3 to be added in a simple manner

use, because even then only one return beam 14 arrives at the detector 11.

4 shows a further advantageous embodiment of the measuring unit 1 according to the invention.

According to the invention, the multiplexer unit 2 receives a primary light beam 4 and divides it into

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a plurality of partial beams 3. At least one partial beam 3 of the plurality of partial beams 3 is directed to at least one deflection unit 13, which in this case represents the decoupling unit 21. In one possible embodiment, a plurality of partial beams 3 can be directed to a deflection unit 13, but a plurality of deflection units 13, for example one deflection unit 13 per partial beam 3, can also be present. For this purpose, the deflection unit 13 contains, for example, a mirror or another suitable optical system or device, which deflects the partial beam 3 and directs it in the direction of an associated reflection unit 7 with a reflection plane 7.1. In this embodiment, a dedicated reflection unit 7 is preferably provided for each partial beam 3 deflected in a deflection unit 13 . The deflected partial beams 3 are then reflected at the respective associated reflection unit 7 and are then (as described above) as return beams 14 (only one of them is labeled in FIG. 4) for at least

sent to a detector 11 (not shown in Figure 4).

It is also conceivable that at least one detector 11 is arranged on a deflection unit 13 . This embodiment is advantageous in order to enable a large number of parallel measurements. As shown in FIG. 4, the deflection units 13 can be arranged next to one another on or at a certain distance above a surface 8, here a multi-lane road. However, the deflection units 13 can also be arranged one behind the other on or at a certain distance above a surface 8 . One behind the other means offset along a direction of travel when it is the

Surface 8 is a road.

In a possible embodiment according to FIG. 4, at least two partial beams 3 are radiated and used as described in FIGS. For these partial beams 3 would then be

no deflection unit 13 available.

It is thus possible for a person skilled in the art to implement several separately designed measurement volumes 9 in a simple manner. This allows a measurement architecture to be implemented that

a specific measurement task and measurement requirement is necessary.

In a variant that is not shown, a deflection unit 13 can also be used in order to implement a multiple passage through the measurement volume 9 . In this embodiment, a further reflection unit with a reflection plane is arranged opposite and at a distance from the reflection plane 7.1 of the reflection unit 7 assigned to the deflection unit 13. The partial beam 3 is radiated by the deflection unit 13 onto the reflection plane 7.1 at an angle that deviates from the normal to the reflection plane 7.1. The partial beam 3 is reflected at the reflection plane 7.1 in the direction of the further reflection plane and at this again in the direction of the

Mirror plane 7.1 reflected back. So that the partial beam runs in a plurality of

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Reflections back and forth between the reflection planes, which increases the number of passages through the measurement volume 9 . The return beam 14 can also be sent back to the associated detector 11 in a number of reflections between the reflection planes. A higher sensitivity of the measurement is thus achieved due to the multiple passages of the light through the measurement volume 9 . In such an embodiment, the angle of the partial beam can also be adjustable, for example with a suitable

Positioning optics to specify the number of passages through the measurement volume 9.

In a further advantageous embodiment of the invention, also not shown in the figures, the multiplexer unit 2 is pivotable. This can be done, for example, via a rotatable axis that makes the multiplexer unit 2 rotatable. The multiplexer unit 2 can preferably be pivoted about an axis which is normal to the reflection plane 7.1 and/or normal to a surface 8. Thus, in an embodiment according to Figure 4, the partial beams 3, for example, to different

Deflection units 13 are directed in order to be able to measure at different points.

Provision can also be made for the entire measuring unit 1 to be pivotable. In this case, for example, the multiplexer unit 2 and the plurality of deflection units 13 are fixed to the measuring unit 1 and the entire measuring unit 1 can be pivoted about an axis mentioned above. The measuring unit 1 can then change between different lanes of a road, for example, or it can start from different lanes

several consecutive measurements on a lane are changed.

In a further embodiment, a plurality of multiplexer units 2 is also provided in the measuring unit. For example, a beam splitter unit can be provided to split a primary light beam 4 into several light beams and to direct them to a plurality of multiplexer units 2, which can then be designed according to the invention as described above in order to detect a gaseous or solid substance in different measurement volumes 9. It may thus be possible to

spatially resolved measurement of different measurement volumes 9 to perform.

In a further embodiment, at least one modulation unit 27 is provided in a measuring unit 1 according to the invention (indicated in Fig. 3) in order to split the primary light beam 4 and/or at least one partial beam 3 (as in Fig. 3) and/or at least one return beam 14 into individual split light packets. The division into individual light packets has the effect that the return beams 14 detected by a detector 11 are also divided into light packets. The light packets have a predetermined time length and are separated in time. In the simplest embodiment, such a modulation unit 27 can be a light chopper

be that generates defined light packets. Such light choppers can, for example

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be rotating discs, mirrors, corner mirrors or prisms. Also electro-optical

Modulators as a modulation unit, such as Mach-Zehnder interferometers, are conceivable.

The division into light packets can be advantageous in order to simplify or facilitate the detection of a plurality of return beams 14 with a detector 11, in particular when this is the case

it is ensured that the light packets arrive at the detector 11 with a time offset.

This can also be advantageous in order to send light packets of different wavelengths to a multiplexer unit 2 and thus enable a spectroscopic measurement. In this case, the primary light beam 4 would be divided into light packets. This can be done, for example, in different light packets one after the other, and thus a spectroscopic spatially resolved measurement of different gaseous or solid substances in

the measuring unit 1 allows.

Fig. 5 shows a further advantageous embodiment of the invention for the precise measurement of the concentration of a gaseous or solid substance in a measuring volume 9 with a measuring unit 1 according to the invention. In order to determine a concentration c of a substance more precisely, knowledge of the actual passage distance x of the light through the den volume containing gaseous or solid substances (e.g. an exhaust gas cloud 5) in the measuring volume 9 and the absorption 1-(l/lo), referred to as A for short, or transmission 1/lo of a specific wavelength is required. The measurement of a substance is frequency-dependent and should therefore take place at, or at least close to, the absorption maximum in order to obtain a reliable result. For example, CO, has characteristic vibrational modes at a wavenumber (reciprocal wavelength) of 1388 cm' (asymmetric stretch mode) and at 667 cm (bending mode). According to Lambert-Beer's law, the absorption A depends on the passage distance x, the concentration c and an absorption coefficient k (as a known material parameter).

the formula

In Lak*xke.

An absorption A can be determined using a detector 11 . However, the passage distance x is dependent on the expansion of the exhaust gas cloud 5 in the measurement volume 9 and is

usually not known.

In this embodiment, an imaging unit 29 is provided in the measuring unit 1 to record the passage distance x, in order to record at least part of the measuring volume 9 from different directions (e.g. angles w, β). The imaging unit 29 generates images of the measurement volume 9 from different directions in one

Evaluation unit 15 are processed. The evaluation unit 15 can now from the received

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Reconstruct images from different directions, part of an image of an exhaust gas cloud 5 in the measurement volume 9 . From the image of the part of the exhaust gas cloud 5, the passage distance x, as the sum of all passages of a partial beam 3 and the associated reflected return beam 14, through the exhaust gas cloud 5 can be determined. For example, the known dimensions of the measurement volume 9 can be used to calculate the dimensions of at least part of the exhaust gas cloud 5 in the measurement volume 9 and thus the passage distance x of a specific partial jet 3 and/or return jet 14

will.

For this purpose, a 2D projection of the exhaust gas cloud 5 in the plane of the partial beam 3 and/or the return beam 14 can be generated from the images and the passage distance x of the partial beam 3 and/or the return beam 14 can thus be determined directly. In one possible embodiment, the evaluation unit 15 creates a spatial reconstruction of the exhaust gas cloud 5. This reconstruction can also be dependent on a running variable, such as time, for example. For example, a time-dependent expansion

an exhaust gas cloud 5 can be determined.

In one possible embodiment, the evaluation unit 15 receives data about the outside temperature and humidity. Depending on the outside temperature and humidity, there may be differences in the evaluation and reconstruction of an exhaust gas cloud 5. For example, temperature differences in summer between the environment and the exhaust cloud are less pronounced than in winter. This can lead to the passage distance x showing seasonal differences. In order to avoid this source of error, a correction factor for the calculation of the reconstruction depending on the outside temperature and air humidity can be provided. The evaluation unit 15 can thus carry out a reliable calculation independently of the conditions of the passage section x

execute.

The evaluation unit 15, usually a computer with the appropriate evaluation software, can also receive data on the absorption A from at least one detector 11, and use the passage distance x, which was reconstructed from part of an image of the exhaust gas cloud 5, to calculate the concentration c of a gaseous or solid substance according to Lambert-Beer's law. In one possible embodiment, multiple data on the absorption A are also used to calculate a spatial distribution of the concentration c im

To calculate measuring volume 9 .

The imaging unit 29 can be implemented in the form of several cameras 16 (as shown in FIG. 5). Also an embodiment of the imaging unit 29 with one or more

Lidar units, one or more radar units or combinations of such units

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or with cameras is conceivable. In addition, there can be other versions of an imaging unit 29

give.

In an embodiment with cameras 16, these are installed at different locations in order to record a measurement volume 9 from different directions w, ß. The cameras 16 can be arranged on a multiplexer unit 2 and/or a deflection unit 13, for example. The cameras 16 can also be installed on a separate device, or they can use existing infrastructure in the area of the measuring unit 1, such as bridges, houses, street lamps or the like. If necessary, the cameras 16 can also be arranged in such a way that they record, for example, several measurement volumes 9 simultaneously

be able. In this way, the number of cameras 16 can be kept low.

The cameras 16 can record images of the measurement volume 9 and thus also record an exhaust gas cloud 5 present in the measurement volume 9 . However, it is also possible for the cameras 16 to additionally record metadata about a vehicle, such as its size, type or license plate number. When using cameras 16 as an image unit 29, for example, image processing software can be used to the exhaust cloud 5 or

to reconstruct part of it.

The cameras 16 can be infrared cameras, for example, which record thermal images of the exhaust gas cloud present in the measurement volume 9 . In this way, the heat distribution in the exhaust gas cloud can also be recorded, which can have an influence on the substances or the absorption coefficient k. Due to the temperature differences, convection and diffusion phenomena can occur, which cause substances to be distributed over time. Individual concentrations c of substances can also depend on the temperature, since some reactions only take place at higher temperatures. It can happen that different exhaust gas clouds 5 from emission sources located one behind the other or next to one another, such as vehicles, mix. Then the measurement can be adjusted accordingly, e.g

by positioning or aligning a camera 16.

However, the cameras 16 can also work, for example, in the ultraviolet (UV) or visible (VIS) range, or in both ranges (UV/VIS cameras). UV or VIS is higher energy radiation than IR and excites electron transitions in molecules and

can be more advantageous for the measurement.

In one possible embodiment, the cameras 16 are designed partially or completely as multispectral and hyperspectral cameras. Instead of the classic simple recording in a simple spectral range, a large number of spectral bands are used

used. This can be advantageous in order to achieve significantly higher color quality and

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See color differences as each pixel already contains a full spectrum of colors.

Such a camera 16 can function, for example, with the snapshot mosaic technique.

A lidar unit is based on a laser, for example a YAG laser with a wavelength of 1064 nm or 532 nm, or similar designs that the person skilled in the art deems appropriate. IR lasers can also be used, although adequate shielding may be necessary to avoid eye damage. A lidar unit in the UV or NIR (near infrared) range can be used, for example, to measure gaseous or solid substances directly. Lidar is known to be able to detect, for example, carbon dioxide (CO2), sulfur dioxide (SO2) and methane (CHa) from atmospheric measurements. This can be used, for example, to carry out rough estimates of substances or to add redundant measurements to the measurement according to the invention

receive.

The at least one lidar unit can move in at least one axis and record images of the environment and the existing exhaust gas clouds 5 . The at least one lidar unit can be used to image different exhaust gas clouds 5 in a measurement volume 9 or different exhaust gas clouds 5 in different measurement volumes 9. For this purpose, the lidar unit scans the environment and, depending on the reflection time of the emitted laser pulse, images of the environment can be generated

be generated.

A combination of lidar units and cameras 16 is also conceivable as the image unit 29 . In this way, for example, gaseous substances can be measured via a lidar unit, while solid substances in the exhaust gas cloud 5 can be detected via the measuring unit 1 according to the invention. In this way, a representative concentration measurement of several critical

Substances of the exhaust cloud 5 take place.

A further embodiment for protecting a reflection unit 7 includes a protective film unit 24, which is shown in FIG. This serves to arrange a protective film 23 over a reflection unit 7 in order to protect it from dirt or damage (e.g. from scratches). The protective film 23 is of course designed to be sufficiently transparent. A dirty protective film 23 can be replaced with a clean protective film 23 if necessary. A possible embodiment of a protective film unit 24 according to FIG. 6 consists of a first roll 20 on which clean protective film 23 is wound. Clean protective film 23 can be unwound from this first roll 20 and arranged over a reflection unit 7 . A second roll 21 can be provided, onto which the soiled protective film 23 can be wound. When used as intended, as required

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Protective film wound up from the second roll 21. The reflection unit 7 is arranged below the surface 8 in this embodiment. The unwound protective film 23 is arranged over the reflection unit 7 in order to protect the reflection unit 7 from dirt or damage. For reasons of stability, a mechanical protection 22 can also be provided between the reflection unit 7 and the protective film 23, which, however, should enable sufficient optical transparency. One of the two rollers 20, 21 can be driven in order to cause the protective film 23 to move further over the reflection unit 7 as required. An automation unit which controls the drive of the driven roller 20, 21 can also be provided for this purpose. Advantageously, the rollers 20, 21 can be driven when the value falls below a limit value, for example a loss of light intensity of a return beam 14 detected by a detector 11. The automation unit can then automatically control the driven rollers 20, 21 in order to move the protective film 23 on. In this way, the soiled protective film 23 above the reflection unit 7 can be easily and if necessary replaced by an unpolluted one. This can be beneficial if the

Reflection unit 7 is generally exposed to high pollution.

Claims (15)

patent claims 1. Measuring unit (1) for measuring at least one gaseous or solid substance in at least one measuring volume (9), characterized in that a multiplexer unit (2) and a light source (12) are provided in the measuring unit (1), the light source being 5th (12) generates a primary light beam (4) and sends it to the multiplexer unit (2) and the Multiplexer unit (2) generates a plurality of partial beams (3) from the primary light beam (4) in that the multiplexer unit (2) is designed to direct the partial beams (3) to different locations via an optical path (6) and a decoupling unit (21). a reflection plane (7.1) to emit at least one reflection unit (7), wherein the 10 decoupling units (21) are arranged at a distance from the reflection unit (7) and the at least one measuring volume (9) is arranged between the decoupling units (21) and the reflection unit (7), that the at least one reflection unit (7) is provided, the partial beams (3) to reflect after their passage through the measurement volume (9) as return rays (14) in the direction of the measurement volume (9), that at least one 15 detector (11) is provided, which detects the return rays (14) after they have passed through the measurement volume (9) and that the at least one detector (11) is provided, a light property characterizing the at least one gaseous or solid substance to measure at least one detected return beam (14). 2. Measuring unit according to claim 1, characterized in that a partial light intensity 20 (I) of each sub-beam (3) is equal to a primary light intensity (I„) of the primary light beam (4) or a sum of the sub-light intensities (I+) of each sub-beam (3) is equal to a primary light intensity (Ip) of the primary light beam (4). 3. Measuring unit according to claim 1 or 2, characterized in that the at least one reflection unit (7) has at least two partial beams (3) of the plurality of partial beams (3) 25 reflected as at least two return beams (14) to a detector (11). 4. Measuring unit according to claim 1 or 2, characterized in that the at least one reflection unit (7) reflects each partial beam (3) as a return beam (14) to a respective detector (11). 5. Measuring unit according to one of claims 1 to 4, characterized in that at least two radiated partial beams (3) of the plurality of partial beams (3) have different directions and the at least two partial beams (3) of different directions each have a reflection unit (7, 7°) are directed with a reflection plane (7.1, 7.1'), and the respective reflection unit (7, 7°) reflects the respective incident partial beam (3) as a return beam (14) to the at least one detector (11) 35. -21 15 20 25 30 35 AV-4264AT 6. Measuring unit according to claim 5, characterized in that two groups of partial beams (3) are provided and the partial beams (3) of a first group penetrate the measurement volume (9) in a different direction than the partial beams (3) a second group. 7. Measuring unit according to one of Claims 1 to 6, characterized in that at least two optical paths (6) have different optical path lengths and the partial beams (3) of the plurality of partial beams (3) running over these at least two optical paths (6) are based on of the different optical path lengths after passing through the measuring volume (9), the reflection at the at least one reflection unit (7) and passing through the measuring volume (9) as reflected rays (14) with a time offset (14). arrive at the at least one detector (11). 8. Measuring unit according to claim 7, characterized in that all optical paths (6) have different optical path lengths. 9. Measuring unit according to claim one of claims 1 to 8, characterized in that the measuring unit (1) is designed to project at least one partial beam (3) in one of a normal to the reflection plane of the at least one reflection unit (7) radiate at different angles. 10. Measuring unit according to Claims 1 to 9, characterized in that the multiplexer unit (2) is designed to direct a number of partial beams (3) to at least one deflection unit (13), the at least one deflection unit (13) being provided, the number of partial beams (3) increases in the direction of the at least one reflection unit (7). direct and the mirroring unit (7) reflects the partial beams (3) as return beams (14). 11. Measuring unit according to claims 1 to 10, characterized in that the multiplexer unit (2) is designed to be pivotable about an axis, the axis normal to the reflection plane (7.1) of the at least one reflection unit (7) or normal to a Surface (8) on which the measuring unit (1) is arranged, is arranged to run. 12. Measuring unit according to one of Claims 1 to 11, characterized in that a modulation unit (27) is provided in the measuring unit (1) in order to modulate the primary beam (4) and/or at least two partial beams (3) and/or at least two return beams (14) in split individual light packages. 13. Measuring unit according to Claims 1 to 12, characterized in that at least one imaging unit (29) is provided in the measuring unit (1) in order to display at least part of the exhaust gas cloud (5) when an exhaust gas cloud (5) is present in the measuring volume (9). to be recorded from different directions, with an evaluation unit (15) being present, to select the multiple images recorded with the imaging unit (29). 23 1317 15 20 AV-4264AT different directions to an image of at least one part of the exhaust gas cloud (5) and to reconstruct a passage path (x) of at least one partial jet (3) of the plurality of partial jets (3) from the image of at least one part of the exhaust gas cloud (5) and/or of the return beam (14) through the exhaust gas cloud (5) in the measurement volume (9), the at least one detector (11) that detects the return beam (14) detecting a decrease in intensity of the return beam (14) due to the at least one gaseous or solid Substance detected and the evaluation unit (15) is provided, from the decrease in intensity and the determined passage distance (x) a concentration (c) of to determine at least one gaseous or solid substance in the measuring volume (9). 14. Device according to one of claims 1 to 13, characterized in that a Protective film (23) is arranged interchangeably over the mirroring unit (7). 15. Method for measuring at least one gaseous or solid substance in at least one measuring volume (9), wherein a primary light beam (4) generated by a light source (12) is divided into a plurality of partial beams (3) in a multiplexer unit (2), wherein the partial beams (3) are each radiated via an optical path (6) and a decoupling unit (21) to different points of a reflection plane (7.1) of a reflection unit (7), and the partial beams (3) thereby penetrate the measurement volume (9), which between the decoupling units (21) and the reflecting unit (7), the partial beams (3) being reflected at the reflecting unit (7) as return beams (14) and the return beams (14) penetrating the measurement volume (9) a second time and wherein the return rays (14) are detected with at least one detector (11) and with the at least one detector (11) a light characterizing the gaseous or solid substance property of at least one detected return beam (14) measured will. 24 131°