WO2022266693A1

WO2022266693A1 - Measuring unit for measuring a gaseous or solid material in a measurement volume

Info

Publication number: WO2022266693A1
Application number: PCT/AT2022/060219
Authority: WO
Inventors: Andreas Pein; Gerald Steiner; Mario ARAR
Original assignee: Avl List Gmbh
Priority date: 2021-06-25
Filing date: 2022-06-24
Publication date: 2022-12-29
Also published as: AT525195A1; AT525195B1

Abstract

According to the invention, for sensitive and flexible measurement of a gaseous or solid material in an exhaust gas cloud, a light beam (4) is reflected multiple times between two reflection units (3, 5) or the light beam (4) is reflected by a deflecting mirror (11) to form a return beam (14) and the return beam (14) performs a plurality of additional reflections between the reflection units (3, 5) and passes through the measurement volume (7) multiple times in the process, wherein the plurality n of reflections of the light beam (4) is adjusted by variation of the first angle (α) in order to set the plurality n of reflections between the first reflection unit (3) and the second reflection unit (5). After the reflections, the return beam (14) is sensed by the at least one detector (21), and a light property of the return beam (14) is measured, the light property characterizing the at least one gaseous or solid material.

Description

Measuring unit for measuring a gaseous or solid substance in one

measurement volume

The present invention relates to a measuring unit for measuring at least one gaseous or solid substance in at least one measuring volume at a stationary measuring point, with a first reflection unit having a first reflection plane and a second reflection unit having a second reflection plane being provided in the measurement unit, the first reflection unit and the second reflection unit is arranged at a distance from one another and with reflection planes facing one another, and the measurement volume is formed between the first reflection unit and the second reflection unit, a light emitter unit being provided in the measurement unit, which emits a light beam in the direction of the first reflection unit and in one of a normal onto the first reflection plane and/or from a first angle deviating from a normal to the second reflection plane, wherein the first reflection unit is designed to emit the light beam to the second mirror elution unit to reflect and the second mirroring unit is designed to reflect the light beam back to the first mirroring unit, so that the light beam travels back and forth in a plurality of reflections between the first mirroring unit and the second mirroring unit.

The invention also relates to a corresponding method for measuring at least one gaseous or solid substance in at least one measuring volume.

Emissions of 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 permissible 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, can This can also be attributed to a lack of knowledge regarding the (non) functionality of these components while driving.

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, takes place at a stationary measuring point and can, for example, be attached to advantageously pre-installed infrastructure such as toll booths, 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 schedule mandatory maintenance. However, when setting up the devices, you have to make sure that there is 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 on 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 realized, for example, via light scattering or by measuring the attenuation of the return beam 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. Differences in the operating temperature of an engine can also result in differences in the substances to be measured. A number of the cross-influences and inaccuracies mentioned above could be remedied by multiple measurements of substances in an exhaust gas cloud. It may be possible to measure an exhaust gas cloud several times in succession, or to measure an exhaust gas cloud at several points.

US 2002/010554 A1 discloses a system for measuring exhaust clouds from small vehicles such as motorbikes. The device contains a light source, a detector and a double mirror system, the beam path being fixed in the double mirror system. Since the light is reflected several times in the double mirror system and thus shines through the exhaust gas cloud several times, the sensitivity of the measurement can be increased. US Pat. No. 4,924,095 A also discloses a measurement of exhaust gas clouds using a double mirror system with a fixed beam path. In particular, low-emission vehicles can also be measured with such measuring arrangements. However, the beam paths are predetermined so that it is very difficult or impossible to react to changing requirements.

CN 208224072 U discloses a measurement setup which has a light emitter unit for emitting a light beam, the angle of which can be adjusted in relation to a reflection unit via the adjustment system. The light beam is captured and analyzed by a detector. The measurement setup contains two reflection units on the surface and one reflection unit on the remote sensing setup above the surface. Thus, there are at least three mirroring units in the disclosure. The number of reflections of the light beam is therefore determined in the measurement setup by the number of reflection units and cannot be changed.

CN 109211795 A shows a structure similar to CN 208224072 U but without an adjustment system. In the disclosure, the number of reflections can be changed manually.

The object of the present invention is therefore to provide a sensitive remote sensing measurement for substances in a measurement volume, which allows flexible adaptation to different applications and requirements of the sensitivity of the measurement.

This object is achieved according to the invention by a measuring unit mentioned at the outset in that at least one detector is provided in the measuring unit, which either detects the at least one light beam after the plurality of reflections as at least one return beam, or at least one deflection unit is provided, which detects the light beam after of the plurality of reflections in the opposite direction to the light beam to at least one return beam and the at least one return beam carries out a number of reflections between the first reflection unit and the second reflection unit and the at least one detector detects the at least one return beam according to the number of reflections that the first angle of at least one of the The light beam emitted by the light emitter unit can be adjusted and thus the plurality of reflections of the at least one light beam in the measurement volume between the first reflection unit and the second reflection unit can be adjusted and that the at least one detector is provided to measure a light property of the at least one return beam that characterizes the at least one gaseous or solid substance .

This is advantageous because the selection of the plurality of reflections can be used to influence the sensitivity of the measurement by varying the total passage distance of the light beam through an exhaust gas cloud in the measurement volume and adapting it to the application, in particular increasing or decreasing it. In this way, the measurement can, for example, be easily adapted to a specific emission source, for example a low-emission or high-emission emission source. The angle can thus be adjusted in such a way that the measurement volume is screened as often as possible in a low concentration range and less often in the high concentration range. The double mirror arrangement in combination with the adjustability of the angle thus allows an extension of the measuring range of the analytical method by varying the sensitivity.

For example, measuring the emissions from a motorcycle requires a much higher level of sensitivity compared to emissions from a truck. In addition, exhaust gas clouds with a very small extent can also be measured with it, since the reflections form a "light curtain" that covers the entire measurement volume. This enables the measuring unit according to the invention to be used flexibly in a wide variety of applications.

A light source is advantageously provided in the measuring unit, which generates a main primary beam from which the light emitter unit generates the light beam. In other words, a light source is provided that generates a main primary beam that is guided to the light emitter unit, where the light beam can be generated from the main primary beam. The light source can then be arranged anywhere in the measuring unit and could even be selected based on the application.

The arrangement of the at least one detector can be chosen very flexibly and independently of the rest of the measuring unit and can be arranged on the first reflection unit or on the second reflection unit or in the light emitter unit or locally separate from these units.

In a particularly compact and simple design, the at least one detector is built into a housing with the light source. In one variant of the invention, the first reflection plane of the first reflection unit and/or the second reflection plane of the second reflection unit is designed to be continuous and/or in one piece.

In a further variant of the invention, the first reflection unit is designed with a divided first reflection plane and/or the second reflection unit with a divided second reflection plane, with at least two reflections of the light beam or reflected beam being provided on a divided section of a divided first and/or second reflection plane. In other words, the first mirroring unit is designed with a first mirroring plane divided into two or more sections and/or the second mirroring unit is designed with a second mirroring plane divided into two or more sections, the mirroring planes or their sections being designed such that when used as intended at least two reflections of the light beam or return beam take place.

The first reflection plane of the first reflection unit and/or the second reflection plane of the second reflection unit are preferably arranged coplanar at least in sections.

In further embodiments, the first reflection plane of the first reflection unit and/or the second reflection plane of the second reflection unit are designed to be planar or curved or structured, at least in sections.

In order to easily increase the number of measuring points for measuring at least one gaseous or solid substance, according to one variant of the invention, a beam splitter is arranged in the light emitter unit, which splits the main primary beam into at least one light beam and at least one secondary primary beam, the at least one Light beam and the at least one secondary primary beam are oriented in different directions. The secondary primary beam can then be used to form a further measuring point or be fed to such a further measuring point.

For this purpose, a second light emitter unit and a second measurement volume are preferably provided in the measurement unit, with the second light emitter unit receiving the secondary primary beam and generating a second light beam from the secondary primary beam, which is sent through the second measurement volume to the detector or to a second detector. In a further variant of the invention, a third reflection unit with a third reflection plane is provided in the measuring unit, and the third reflection plane reflects the second light beam of the second light emitter unit as a second return beam and sends the second return beam to the detector or to the second detector. In a particularly advantageous embodiment, the second light emitter unit, like the at least one first light emitter unit, is designed as a double mirror with multiple reflections. In particular, a third reflection unit with a third reflection plane and a fourth reflection unit with a fourth reflection plane are provided in the measuring unit, the third reflection unit and the fourth reflection unit being arranged at a distance from one another and with reflection planes facing one another, and the second measurement volume between the third reflection unit and the second reflection unit, wherein the second light emitter unit emits the second light beam in the direction of the third reflection unit and at a second angle deviating from a normal to the third reflection plane, wherein the third reflection plane of the third reflection unit is configured to reflect the second light beam to the fourth reflection unit and the fourth reflection plane of the fourth reflection unit is designed to reflect the second light beam back to the third reflection unit, so that the second Li The light beam runs back and forth in a plurality of reflections between the third reflection unit and the fourth reflection unit, and that the detector or the second detector is provided to detect the second light beam as a second return beam after the plurality of reflections, or a second deflection unit is provided , which deflects the second light beam after the plurality of reflections in the opposite direction to the light beam to form a second return beam and the second return beam carries out a number of reflections between the third reflection unit and the fourth reflection unit and the detector or the second detector detects the at least one return beam according to the number detected by reflections.

In this case, the second angle of the second light beam is advantageously adjustable.

In a variant of the invention, the third reflection plane of the third reflection unit and/or the fourth reflection plane of the fourth reflection unit is designed to be continuous and/or in one piece.

In a further variant, the third reflection unit is designed with a divided third reflection plane and/or the fourth reflection unit with a divided fourth reflection plane, with at least two reflections of the light beam (4') or return beam being provided on a divided section of a divided third and/or fourth reflection plane are. In other words, the third mirroring unit is designed with a third mirroring plane divided into two or more sections and/or the fourth mirroring unit is designed with a fourth mirroring plane divided into two or more sections, the mirroring planes or their sections being designed such that when used as intended at least two reflections of the light beam or return beam take place. The third reflection plane of the third reflection unit and/or the fourth reflection plane of the fourth reflection unit are preferably arranged coplanar at least in sections.

In further embodiments, the third reflection plane of the third reflection unit and/or the fourth reflection plane of the fourth reflection unit are designed to be planar or curved or structured, at least in sections.

In a further variant of the invention, at least one modulation unit is provided in the measuring unit in order to split the at least one light beam and/or the second light beam and/or the at least one return beam and/or the main primary beam and/or a secondary primary beam 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. If the at least one light beam and/or the second light beam and/or the at least one return beam and/or the main primary beam and/or the secondary primary beam is divided into individual light packets by a modulation unit, the detection of the return beams in the detector can be simplified. If the light packets are additionally modulated with a time offset, the time-offset light packets can be detected by the detector, so that a time dimension can be determined. At least two packets of light are therefore preferably offset in time. For example, spatially resolved measurements can be carried out in a simple manner by means of a detector if it only ever receives one light packet at a time.

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 when an exhaust gas cloud is present in the measuring volume, with an evaluation unit being present to convert the images recorded with the imaging unit into an image of the at least one to reconstruct part of the exhaust gas cloud and to determine a total passage distance of the light beam and/or the return beam through the exhaust gas cloud in the measurement volume from the image of at least part of the exhaust gas cloud, with the at least one detector that detects the return beam detecting a decrease in intensity of the return beam on the basis of the at least a gaseous or solid substance is detected and the evaluation unit is provided to determine a concentration of the at least one gaseous or solid substance in the measurement volume from the decrease in intensity and the determined total passage distance. 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 majority of the cameras and/or the one or more lidar units are preferably in different positions arranged. 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 planes of the reflection units from dirt or damage, a protective film is advantageously arranged in an exchangeable manner over a reflection plane of a reflection unit. This means that necessary maintenance intervals can be reduced.

The object of the invention is also achieved by a method mentioned at the outset, in which a light beam is emitted by a light emitter unit in the direction of a first reflection plane of a first reflection unit and at a first angle deviating from a normal to the first reflection plane, the light beam being emitted from the first reflection unit is reflected to a second reflection unit at a distance with a second reflection plane and then the light beam is reflected from the second reflection unit back to the first reflection unit, and the light beam carries out a plurality of reflections in the measurement volume between the first reflection unit and the second reflection unit and thereby the measurement volume between the first Mirroring unit and the second mirroring unit penetrates multiple times. According to the invention, after the plurality of reflections, the light beam is detected by at least one detector as a return beam, or the light beam is reflected on a deflection mirror to form a return beam and the return beam carries out a number of reflections between the first reflection unit and the second reflection unit, penetrating the measurement volume several times and the The return beam is detected by the at least one detector according to the number of reflections, with the plurality of reflections of the light beam being adjusted by varying the first angle in order to set the plurality of reflections between the first reflection unit and the second reflection unit, with the at least one detector being used to at least one gaseous or solid substance characterizing light property of the return beam is measured.

The present invention is explained in more detail below with reference to FIGS. 1 to 7, which show advantageous configurations of the invention by way of example, schematically and not restrictively. while showing

1 shows the double mirror system according to the invention for remote sensing applications,

2 shows a possible embodiment in the form of a multiple measurement,

3a a modulation unit, 3b shows an intensity diagram of the light packets generated by the modulation unit according to FIG. 3a,

Fig.4. a concentration measurement with the double mirror system according to the invention,

Fig.5. a protective film unit for the mirroring unit,

6 shows an embodiment of a reflection unit with divided sections of the reflection plane and with curved reflection planes, and

7 shows an embodiment with arched reflection planes.

1 shows an embodiment of the invention. The measuring unit 1 is designed to measure a gaseous or solid substance in a measuring volume 7, which is emitted, for example, by a vehicle in a public space with an exhaust gas cloud 31. A wide variety of gaseous and solid (e.g. particles) components can occur in the measurement volume 7 . For example, an exhaust gas cloud 31 of a car can be present in the measurement volume 7 . The gaseous or solid substances in the measurement volume 7 can come from any type of emission source, for example on a surface 8 . The emission source can be a vehicle such as passenger cars (cars), trucks (trucks), but also a single-track vehicle such as a motorcycle, moped and the like that has an internal combustion engine. Emissions from another emission source, such as fuel cells, which as a rule only emit water vapor and no pollutants, can also be measured using such a measuring unit 1 . The detection of such emission sources 15 can be helpful, for example to determine the proportion of vehicles with low or high emission values in road traffic. The measurement can be carried out, for example, on a surface 8, for example a street, 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 7 and the measurement is carried out parallel to the surface 8, or that the measuring unit 1 is also built into the surface 8 itself. Combinations of measurements from several sides are also conceivable.

In addition to use in the automobile industry, other applications in which exhaust gas clouds 31 with gaseous or solid substances are emitted as emissions are also conceivable, for example in the process industry. Here, for example, emissions can be measured in chimneys, which can have diameters of a few meters. The measurement volume 7 would be formed in the chimney.

The measuring unit 1 can, for example, also measure the measuring volume 7 at other locations away from a surface 8, which are arranged, for example, protruding from a surface or also recessed into a surface. It is conceivable that a measuring unit 1 measures an exhaust gas cloud from an aircraft during take-off or landing on a runway at an airport in a measuring volume. It is also conceivable that an exhaust gas cloud from a ship, for example in a harbor basin or in a lock, is measured. The invention is not limited to the applications mentioned above, but rather all possible uses that become apparent to a person skilled in the art are conceivable.

The exhaust gas cloud 31 in the measuring volume 7 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 from an industrial process, which is discharged at a chimney, for example.

The substances in the measuring volume 7 can be gaseous substances such as carbon dioxide (CO2), 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 particles in the measuring volume 7, such as soot particles. The substances and their concentrations in the measuring volume 7 are usually dependent on 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) or the type of industrial process. 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, different substances are emitted in different operating states (e.g. given by current speed and current torque).

According to the invention, these gaseous or solid substances in the measuring volume 7 are to be measured. "Measuring a substance" can mean detecting the presence of the substance in the measuring volume 7, but also measuring a quantity or concentration of the gaseous or solid substance in the measuring volume 7.

According to the invention, a light emitter unit 2 of the measuring unit 1 provides a light beam 4 with a predetermined light intensity. The light emitter unit 2 can generate the light beam 4 itself, for example by a light source 22 in the light emitter unit 2 (as in FIG. 1).

However, the light beam 4 can also be supplied to the light emitter unit 2 from the outside, for example from an external light source 22 (as in the embodiment according to FIG. 2). The light beam 4 can be fed to the light emitter unit 2, for example, via an optical system (eg with mirrors, prisms, etc.) or an optical waveguide. This can be advantageous if there are a plurality of light emitter units 2 in the measuring unit 1 . As a result, a single light source 22 can supply the plurality of light emitter units 2 with a light beam 4 . In this case, the light source 22 can generate a main primary beam 4.1 and send it to the light emitter unit 2, which transmits it receives and emits as a light beam 4. Under certain circumstances, the light emitter unit 2 can also change the main primary beam 4.1 before it is emitted as a light beam 4, for example with a monochromator.

The light emitter unit 2 can be mounted parallel to the plane of the surface 8, normal to the plane of the surface 8, or also at an angle to the plane of the surface 8. Depending on the measurement task, a person skilled in the art can suitably select the arrangement and orientation of the light emitter unit 2 .

The light emitter unit 2 can, for example, emit monochromatic light as the light beam 4, e.g. in the form of laser light, which has a defined wavelength with a predetermined light intensity. For example, 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 emitter unit 2 has a polychromatically emitting lamp, such as a lamp in the ultraviolet (UV) or also in the infrared range (IR). A monochromator in the light emitter unit 2 or at another suitable point of the device 1 is also conceivable in order to select wavelengths in a targeted manner. A monochromator can be, for example, a Bragg grating, a prism, a movable mirror or an optical filter.

The light emitter unit 2 is set up or provided to direct the light beam 4 to a first reflection unit 3 of the measuring unit 1 with a first reflection plane 3.1.

The first reflection plane 3.1 can be aligned parallel to the plane of the surface 8, normal to the plane of the surface 8, or also at a different angle to the plane of the surface 8, and also depending on the orientation of the light beam 4, which is emitted by the light emitter unit 2 , be arranged. In one possible configuration, the first reflection unit 3 can also be arranged or mounted in a surface 8, for example in a street.

A second reflection unit 5 with a second reflection plane 5.1 is provided in the measuring unit 1. The second reflection unit 5 is arranged at a distance d from the first reflection unit 3 such that the first reflection plane 3.1 and the second reflection plane 5.1 are arranged facing one another. The first reflection plane 3.1 and the second reflection plane 5.1 are preferably arranged running parallel. Particularly preferably, the first reflection plane 3.1 and the second reflection plane 5.1 are arranged running parallel and oriented in the same way. Oriented in the same way here means that a longitudinal axis of the first reflection plane 3.1 runs in the same direction as a longitudinal axis of the second reflection plane 5.1. The measurement volume 7 is formed between the first reflection unit 3 and the second reflection unit 5 .

The light emitter unit 2 emits the light beam 4 at a defined first angle a, which first angle a deviates from a normal to the first reflection plane 3.1 of the first reflection unit 3. The light beam 4 strikes the first reflection plane 3.1 and, due to the angle of incidence deviating from the normal, is reflected from the first reflection plane 3.1 of the first reflection unit 3 at an angle deviating from the normal to the first reflection plane 3.1 and to the second reflection plane 5.1 of the second reflection unit 5 steered. At the second reflection plane 5.1, the light beam 4 is reflected again to the first reflection plane 3.1. The light beam 4 thus runs back and forth between the first reflection plane 3.1 and the second reflection plane 5.1, for example along their longitudinal axes.

The first mirroring unit 3 and the second mirroring unit 5 are arranged and designed according to the invention in such a way that a plurality n>1 of reflections is carried out between the first mirroring unit 3 and the second mirroring unit 5, specifically between the first mirroring plane 3.1 and the second mirroring plane 5.1. This can be achieved in a simple manner if the reflection planes 3.1, 5.1 are arranged parallel to one another and the dimensions (e.g. width B and length L) of the reflection planes 3.1, 5.1 are sufficiently large. The longitudinal axes of the planes of reflection 3.1, 5.1 extend along the length L. A suitable arrangement and extent can be selected depending on the application and is within the skill of the person skilled in the art. The light beam 4 thus travels through the measurement volume 7 several times due to the multiple reflections at the reflection planes 3.1, 5.1. In other words, the light beam 4 wanders through the measuring volume 7 several times with a zigzag course due to the arrival in the first angle a, which differs from the normal to the first reflection plane 3.1.

The plurality n of the reflections is determined via the angle a of the light beam 4 that is set or can be set by the light emitter unit 2 . The more the first angle a approaches the normal to the first reflection plane 3.1, the more reflections are possible. The plurality n of reflections is in particular limited by the length L of the reflection planes 3.1, 5.1.

The first angle a can be adjusted with a positioning unit 27 in the light emitter unit 2 or can be adjusted by such a positioning unit 27 . Such a positioning unit 27 can be, for example, an xy galvanometer or also a mirror that can be adjusted with an actuator (a so-called digital mirror device). Depending on the expected exhaust gas cloud 31 in a measurement volume 7 and/or depending on the desired sensitivity of the measurement, the plurality n of the reflections can therefore be set variably. The plurality n of reflections then corresponds to a total optical passage distance x, which the light beam 4 travels through the measurement volume 7 with the plurality n of reflections. This is indicated in FIG. 1 with the individual passage distances xi to x _n , the total passage distance x being the sum of the individual passage distances xi to x _n . This is advantageous because the light beam 4 can thus pass through the measurement volume 7 several times, and a higher sensitivity of the measurement of a gaseous or solid substance in the measurement volume 7 can thus be achieved via the integral measurement. This can also be reflected in an improvement in the signal-to-noise ratio because larger measurement signals are possible. A higher measurement quality can thus be achieved.

In a preferred embodiment, all of the plurality n of reflections take place between continuous, one-piece reflection planes 3.1, 5.1, as can be seen, for example, in FIGS. In one variant of the invention, at least one of the reflection planes 3.1, 5.1 is divided, i.e. not continuously in one piece, but the light beam 4 or the return beam 14 is reflected at least twice at each divided section of a divided reflection plane 3.1, 5.1 at each angle a. Each divided section of a divided reflection plane 3.1, 5.1 must therefore have a corresponding length so that the at least two reflections are possible. In other words, each reflection plane 3.1, 5.1 is made in one piece or from two or more sections, with at least two or more reflections of the plurality n of reflections taking place on each reflection plane 3.1, 5.1 or each section of a reflection plane 3.1, 5.1 when the measuring unit is used as intended .

The reflection planes 3.1, 5.1 do not necessarily have to be coplanar, as for example in FIG. 1, but can also be arranged at a certain angle to one another, at least in sections, in order to achieve an additional directivity of the reflection direction. This also applies in the same way to a divided section of a mirroring plane 3.1, 5.1 designed to be divided.

A reflection plane 3.1, 5.1 is not necessarily designed to be planar, but can also be curved, at least in sections, in order to influence the reflection behavior in a targeted manner. For example, a reflection plane 3.1, 5.1, or a section thereof, can be concave, convex, spherical or else structured, at least in sections.

This also applies in the same way to a split section of a split reflection plane 3.1, 5.1. For example, FIG. 6 shows a first reflection unit 3 with a divided reflection plane 3.1, which consists of two divided sections 3.1a, 3.1b. The two divided sections 3.1a, 3.1b form concave mirror elements, for example in the form of inwardly curved concave mirrors in the form of a paraboloid of revolution. The second reflection unit 5 has a continuous, one-piece reflection plane 5.1. The second reflection plane 5.1 is also designed as a concave mirror element, for example in the form of an inwardly curved concave mirror in the form of a paraboloid of revolution. In this embodiment, the radii of curvature of the sections 3.1a, 3.1b of the first reflection plane 3.1 and the second reflection plane 5.1 are preferably the same. In this embodiment, the multiple reflections on the sections 3.1a, 3.1b of the first reflection plane 3.1 each take place at the same point. The distance between the reflection planes 3.1 (3.1a, 3.1b), 5.1 preferably corresponds to the radius of curvature of the curved reflection plane 5.1. The angle a and thus the number of reflections can take place, for example, with a positioning unit 27 (not shown in FIG. 6) by adjusting the orientation (eg a tilting angle) of the sections 3.1a, 3.1b of the first reflection plane 3.1.

In the embodiment according to FIG. 7, reflective units 3, 5 are provided with continuous, one-piece reflective planes 3.1, 5.1, with the reflective planes 3.1,

5.1 spherical (spherical surface) are formed. A spherical reflection plane 3.1, 5.1 is easier to manufacture. The light beam 4 can, for example, as shown in FIG. 7, be coupled in and/or out through a hole in one of the reflection planes 3.1, 5.1, but could also be coupled in and/or out from the side. The angle a and thus the number of reflections can be adjusted with a positioning unit 27 (not shown in FIG. 7), for example by adjusting the distance between the two reflection planes 3.1, 5.1.

A detector 21 is also arranged in the measuring unit 1 . The detector 21 measures at least one light property of a light beam detected with it, 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.

After the last of the plurality n of reflections, the light beam 4 emerging between the first reflection unit 3 and the second reflection unit 5 can be directed as a return beam 14 to the detector 21 and detected by the detector 21 (as in the embodiment according to FIG of the return beam 14 to measure. For this purpose, the detector 21 at a suitable location on the first reflection unit 3 or the second mirroring unit 5 can be arranged. However, the detector 21 can also be arranged at another suitable location and the return beam 14 can be guided to the detector 21 either directly or via an optical system (for example a mirror system or an optical waveguide). However, a deflection unit 11 (eg a deflection mirror) can also be arranged on the first reflection unit 3 or the second reflection unit 5 in order to direct the light beam 4 as a return beam 14 to a detector 12, either directly or via an optical system.

However, provision can also be made for the light beam 4 to be deflected back in the direction of the light emitter unit 2 after the plurality n reflections and to be deflected further there in the direction of the detector 21 , with the detector 21 also being able to be arranged in the light emitter unit 2 . This can be done, for example, via a deflection unit 11 that is arranged in the measuring unit 1 at the opposite end of the light emitter unit 2 . The deflection unit 11 is preferably designed in such a way that an incoming light beam 4 is reflected in the opposite direction to its direction of incidence. The orientation of the beam reflected by the deflection unit 11 thus coincides with the incident light beam 4, but is oriented in the opposite direction. In this embodiment, the reflection at the deflection unit 11 produces a return beam 14 which preferably takes the same optical path as the light beam 4 back to the light emitter unit 2 .

The return beam 14 thus also travels back and forth in a number m>1 of reflections between the first reflection unit 3 and the second reflection unit. However, it is entirely conceivable that the number m of reflections of the return beam 14 and the plurality n of reflections of the light beam 4 are different.

The deflection unit 11 can also be variable in order to adjust the number of reflections of the return beam 14, also depending on the first angle a of the light beam 4. Provision can also be made for a plurality of deflection units 11 to be provided in the measuring unit 1. Depending on the number n of reflections of the light beam 2, another deflection mirror 11 can be selected for reflection, which is suitable.

A plurality of detectors 21 can also be provided. Each detector 21 can be arranged to match a specific first angle a of the light beam 4 . Each detector 21 is thus assigned to a specific first angle a. A multiplicity of different light beams 4 adjusted via the first winding a can thus be detected via a multiplicity of detectors 21, with a different multiplicity n of reflections being carried out.

It is also conceivable that the light emitter unit 2 simultaneously emits a plurality of light beams 4 with different first angles a, which are reflected in a plurality n of reflections between the first reflection unit 3 or the second reflection unit 5 walking back and forth. For this purpose, several positioning units 27 can be provided in the light emitter unit 2 or one positioning unit 27 that switches between the different first angles a. In the latter case, the light beams 4 would be emitted in the form of individual light packets. The multiple light beams 4 also generate multiple return beams 14 which, as described above, can be directed to different detectors 21 or to the same detector 21 and can be detected there.

These multiple light beams 4 can be generated with an optical multiplexer unit, for example. The multiplexer unit can be designed, for example, as an electrical or electro-optical circuit, which splits the light beam 4 (alternatively and equivalently also the main primary beam 4.1 or a secondary primary beam 12) into a plurality of individual light beams. A light beam 4 is thus multiplied with the multiplexer unit.

In an advantageous embodiment of the invention, the at least one detector 21 can measure the reduced light intensity of the at least one detected return beam 14 due to the at least one gaseous or solid substance and convert it into an absorption of a gaseous substance, for example by means of a previously performed reference measurement in detector 21, which is carried out in the absence of a substance in the measuring volume 7. 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, a weakening of the light intensity of the detected return beam 14 in relation to the light intensity of the light beam 4 emitted by the light emitter unit 2 can also be determined.

It is also possible for the evaluation to be carried out on at least one detector 21 as a function of the wavelength, so that a spectroscopic evaluation of a number of gaseous or solid substances can be implemented. This is advantageous if a number of gaseous or solid substances are to be measured simultaneously.

2 shows an advantageous embodiment of the invention. In this embodiment, a light source 22 and a detector 21 are formed outside the light emitting unit 2 and both are housed in a common housing. The light source 22 emits a main primary beam 4.1 which is directed to the light emitter unit 2. FIG. This can take place via a light transport unit, such as an optical waveguide or a mirror system or another optical system. However, the light source 22 can also be arranged in the light emitter unit 2 and generate the main primary beam 4.1. The second reflection unit 5 with the second reflection plane 5.1, which faces the first reflection plane 3.1, is arranged at a first distance di from the reflection unit 3 with the first reflection plane 3.1. The distance di can be selected based on the application, for example depending on the vehicles driving through, but also on the direction of measurement. For example, the distance di can be smaller when measuring parallel to surface 8 and larger when measuring normal to surface 8 .

A beam splitter 9 is arranged in the light emitter unit 2 . The main primary beam 4.1 is split by the beam splitter 9 into a light beam 4 and at least one secondary primary beam 12, which continue in different directions. For this purpose, a double mirror or another suitable optical system or device can be provided in the beam splitter 9, which divides the light intensity of the main primary beam 4.1 into a light intensity of the light beam 4 and the at least one secondary primary beam 12. Preferably, the light intensity of the main primary beam 4.1 is divided equally between the light intensity of the secondary primary beam 12 and the light beam 4.

As described above, the light beam 4 is reflected multiple times according to the invention between the first reflection plane 3.1 of the first reflection unit 3 and between the second reflection plane 5.1 of the second reflection unit 5 with the plurality n of reflections. In this configuration, the light beam 4 is reflected at a first deflection unit 11 and deflected back to the light emitter unit 2 as a return beam 14 . In the embodiment shown, the plurality n of the reflections of the light beam 2 is equal to the plurality m of reflections of the return beam 14. The light emitter unit 2 forwards the return beam 14 to the detector 21, for example via the same light transport unit with which the main primary beam 4.1 is guided into the light emitter unit 2 will. However, it is also conceivable for the return beam 14 to be detected, as described above, with a detector 21 arranged elsewhere in the measuring unit 1 .

The at least one secondary primary beam 12 can be directed to at least one additional, second light emitter unit 2' (as in FIG. 2). For this purpose, the secondary primary beam 12 can essentially retain the direction of the main primary beam 4.1 or, in contrast, can also be deflected, for example by 90° as in FIG. In the exemplary embodiment shown, however, the main primary beam 4.1 and the deflected secondary primary beam 12 run in the same plane, which does not have to be the case in all variants.

In the second light emitter unit 2′, the secondary primary beam 12 can be deflected into a further, second light beam 4′, if required, at a beam deflection unit 10 which is arranged in the at least one second light emitter unit 2′ in the exemplary embodiment shown. This deflection can also be used to set a second angle a′ of the second light beam 4′, with which it is oriented with respect to a third reflection plane 3.1′ and/or a fourth reflection plane 5.1′. However, a differently designed positioning optics unit can also be provided in the second light emitter unit 2' in order to position the second light beam 4' at the desired second angle a'. send out. The second light emitter unit 2' can be designed like the first light emitter unit 2 described above, with the angles a, a' of the light beams 4, 4' not having to be the same. These statements can be used analogously for the second light emitter unit 2'.

The second light beam 4' is thus reflected multiple times between a double mirror system with a third reflection unit 3' and a fourth reflection unit 5' with corresponding reflection planes 3.1', 5.1', as described above, and the plurality n'>1 of the reflections (those not must agree with the above-mentioned plurality n) can be controlled or set via the preferably adjustable second angle a'. The distance d2 between the third reflection unit 3' and a fourth reflection unit 5' of the second light emitter unit 2' does not have to be the same as the distance di in the first light emitter unit 2. There is thus a gap between the third reflection unit 3' and the fourth reflection unit 5' another, second measurement volume 7'. For this purpose, the additional light beam 4' is reflected multiple times at the third reflection plane 3.1' of the third reflection unit 3' and between the fourth reflection plane 5.1' of the fourth reflection unit 5'. A deflection unit 11' can also be provided to reflect the second light beam 4' as a return beam 14' and to reflect the second return beam with a number m'>1 of reflections (which does not have to match the number m mentioned above) in the direction of the second light emitting unit 2'. In the embodiment shown according to FIG. 2, the plurality n' of reflections of the second light beam 4' is different from the plurality m' of reflections of the second return beam 14'. At the end of the reflections, the resulting return beam 14' can be detected with a second detector 21', for example in the second light emitter unit 2' or at another suitable location. However, it would also be conceivable to direct the second return beam 14' back to the detector 21, for example via the beam deflection unit 10 and the beam splitter 9.

Instead of a second light emitter unit 2' designed as described above, however, a differently designed measuring arrangement with a measuring volume 7' for measuring a gaseous or solid substance in the measuring volume 7' could also be provided. In a simple configuration, the second light emitter unit 2' generates the second light beam 4', which, however, is guided only once through the measurement volume 7' to a detector 21. However, the second light beam 4' emitted by the second light emitter unit 2' could also be reflected at a third reflection unit 3' and guided to a detector 21 as a return beam 14'. The return beam can be passed through the measuring volume 7' a second time.

The above statements on the continuous one-piece nature and the shape of the surface of a reflection plane 3.1, 5.1 also apply in an analogous manner to the third Reflection level 3.1 ^c and fourth reflection level 5.1 ', and also for each additional reflection level.

In the embodiment of FIG. 2, the two light emitter units 2, 2' are arranged one behind the other on a surface 8, for example in the direction of travel of a street. In this way, for example, the course over time of an exhaust gas cloud 31, 31' from a single emission source, such as a vehicle, can be determined. In a further embodiment, not shown, the light emitter units 2, 2' are arranged next to one another. In this way, different surfaces 8, such as multi-lane roads, can be measured at the same time. For this purpose, the secondary primary beam 12 can be directed in a suitable manner from the light emitter unit 2 to the further light emitter unit 2'.

Further possible and advantageous embodiments of a measuring unit 1 or a light emitter unit 2, 2' are described below.

The measuring point, in particular the measuring volume 7, is stationary during the measurement with the measuring unit 1; a stationary measurement is thus implemented with the measuring unit 1 at a specific stationary measuring point. The exhaust gas cloud 31 can thus move or change relative to the measurement volume 7 during the measurement, but the measurement unit 1, specifically the individual units of the measurement unit 1, remain stationary at the measurement point. In particular, the at least one light emitter unit 2, 2', the positioning unit 27, the reflection units 3, 5, 3', 5' with the reflection planes 3.1, 5.1, 3.1', 5.1' and the at least one detector 21, 21' remain during the measurement fixed. If there are other units in the measuring unit 1, such as a multiplexer unit, a beam deflection unit 10, a beam splitter 9, a deflection unit 11, a modulation unit 16, an image unit 29, etc., these are also stationary during the measurement.

The measuring unit 1 according to the invention is therefore in particular not a measuring unit that is installed in a moving vehicle for measuring exhaust gas and moves with the vehicle during the measurement.

However, the measuring unit 1 is only necessarily arranged in a stationary position during the measurement. The measuring unit 1 or parts thereof can also be moved between two measurements. In the course of remote sensing measurements, it may be necessary, for example, for the measuring unit 1 to switch between different measuring points, for example in order to use it to record a larger number of vehicles driving in a larger area (eg a city). In this context, provision can also be made for the measuring unit 1 to be partially or completely mounted on a trailer in order to be able to change the measuring unit 1 between the measuring points in a mobile manner. The main part of the measuring unit 1, in particular a light emitter unit 2, the positioning unit 27, the second Reflection units 5 with the second reflection plane 5.1 and the at least one detector 21 can be pre-assembled on an extendable frame on the trailer. Parts of the measuring unit 1 that can be attached to the measuring point, such as the first reflection unit 3 with the first reflection plane 3.1, are then arranged in a suitable manner at the measuring point. During the measurement, however, all units are stationary again.

In a further embodiment, a light beam 4, 4' or a main primary beam 4.1 or a secondary primary beam 12 or a return beam 14, 14' can be guided via a modulation unit 16, as shown in FIG. A modulation unit 16 is advantageously used for each light beam 4, 4' in the device 1.

The at least one modulation unit 16 causes the light beam 4, 4' or a main primary beam 4.1 or a secondary primary beam 12 or a return beam 14, 14 to be divided into individual light packets 17, if necessary also with different light intensities I. The light packets 17 have a predetermined time length and are separated in time. In the simplest embodiment, such a modulation unit 16 can be a light chopper that generates defined light packets 17 . Such light choppers can be, for example, rotating discs, mirrors, corner mirrors or prisms. Electro-optical modulators as modulation unit 16, such as Mach-Zehnder interferometers, are also conceivable.

The division by means of a modulation unit 16 has the effect that the return beams 14', 14' detected by a detector 21 are also divided into light packets 17, 17'. The division into individual light packets 17, 17' is advantageously carried out in such a way that the light packets 17, 17' arriving in the detector 21 arrive with a time offset. This makes it easy to measure different return beams 14, 14' in one detector 21.

For example, in a device as in FIG. 2, both the first light beam 4 and the second light beam 4' can each be divided into light packets 17, 17' with a modulation unit 16. The modulation by means of a first modulation unit 16 of the first light beam 4 can take place with a time delay to the modulation by means of a second modulation unit 16 of the second light beam 4'. The reflected light packets 17, 17' of the respective return beam 14, 14' thus arrive at a detector 21 with a time offset relative to one another. A spatially resolved measurement using a single detector 5 can thus be made possible in a simple manner.

In a further embodiment of the invention, the light emitter unit 2, 2' is designed to be pivotable about an axis. The axis can be normal to a first or third reflection plane 3.1, 3.T or normal to a surface on which the measuring unit 1 is arranged. For this purpose it can be provided that the entire measuring unit 1 is pivotable. In this case, for example, the light emitter units 2, 2' are fixed to the measuring unit 1 and the entire measuring unit 1 can be pivoted about the axis mentioned. The entire measuring unit 1 can then, for example, change between different lanes of a multi-lane road as required.

Fig. 4 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 7, 7' 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 total passage distance x (again as the sum of the individual passage distances of the light beam 4, 4') and the absorption 1-(l/lo), referred to as A for short, or transmission l/lo of a specific wavelength is required. The measurement of a substance is frequency-dependent and should therefore take place at the absorption maximum, or at least close to it, in order to obtain a reliable result. For example, CO2 has characteristic vibrational modes at a wave number (reciprocal wavelength) of 1388 cm ^-1 (asymmetric stretch mode) and at 667 cm ^-1 (bending mode). According to Lambert-Beer's law, the absorption A depends on the total penetration distance x, the concentration c and an absorption coefficient k (as a known material parameter). This relationship can be determined using the formula

be expressed. An absorption A can be determined via a detector 21 in the measuring unit 1 . The total passage distance x depends on the extent of an exhaust gas cloud 31, 3T in the measurement volume 7, 7' and is usually not known.

In order to record the total passage distance x, an imaging unit 29 is provided in the measuring unit 1 according to the invention in order to record at least part of the measuring volume 7, 7' from different directions (e.g. angles w, ß). The imaging unit 29 generates images of the measurement volume 7, 7' from different directions, which are processed in an evaluation unit 13. The evaluation unit 13 can now reconstruct part of an image of an exhaust gas cloud 31, 3T in the measurement volume 7, 7' from the images obtained from different directions. The total passage distance x (or the individual passage distances) of a light beam 4, 4′ through the exhaust gas cloud 31, 3T can be determined from the image of the part of the exhaust gas cloud 31, 3T. For example, based on the known dimensions of the measuring volume 7, 7', the dimensions of at least part of the exhaust gas cloud 31, 3T in the measuring volume 7, 7' and thus the total passage distance x (or the individual passage distances) can be back-calculated.

For this purpose, a 2D projection of the exhaust gas cloud 31, 3T in the plane of the light beam 4, 4' and/or the return beam 14, 14' can be generated from the images and the total passage distance x (or the individual passage distances) can be determined directly. In one possible embodiment, the evaluation unit 13 can perform a spatial reconstruction the exhaust gas cloud 31, 31 'create. This reconstruction can, for example, also be dependent on a running variable such as time. For example, a time-dependent expansion of an exhaust gas cloud 31, 31' can be determined.

In a further embodiment, the evaluation unit 13 can receive data on the outside temperature and air humidity. Depending on the outside temperature and humidity, there may be differences in the evaluation and reconstruction of an exhaust gas cloud 31, 31'. For example, temperature differences in summer between the environment and the exhaust cloud are less pronounced than in winter. This can lead to the total 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 13 can thus carry out a reliable calculation independently of the conditions of the total passage distance x.

The evaluation unit 13, usually a computer with the appropriate evaluation software, can also receive data on the absorption A from at least one detector 21, and use the total passage distance x, which was reconstructed from part of an image of the exhaust gas cloud 31, 3T, to calculate the concentration c of a substance to be calculated according to Lambert-Beer's law. In a further embodiment, multiple data on absorption A can also be used to calculate a spatial distribution of the concentration c in a measurement volume 7, 7'.

The imaging unit 29 can be implemented in the form of several cameras 23 (as shown in FIG. 4). An embodiment of the imaging unit 29 with one or more lidar units, one or more radar units or combinations of such units or with cameras 23 is also conceivable. In addition, other versions of an imaging unit 29 are also possible.

In an embodiment with cameras 23, these are installed at different locations in order to record a measurement volume 7, 7' from different directions w, ß. The cameras 23 can be arranged, for example, on a light emitter unit 2, 2'. The cameras 23 can also be installed on a separate device or use existing infrastructure in the area of the device 1 such as bridges, houses, street lamps or the like. With a plurality of light emitter units 2, 2', the cameras 23 can also be arranged in such a way that they can, for example, record a plurality of measurement volumes 7, 7' at the same time. In this way, the total number of cameras 23 required can be kept low.

The cameras 23 can record images of the measurement volume 7, 7' and thus also record an exhaust gas cloud 31, 3T present in the measurement volume 7, 7'. However, it is also possible for the cameras 23 to additionally record metadata about a vehicle, such as Size, type or even the license plate number. When cameras 23 are used as the image unit 29, suitable image processing software can be used, for example, in order to reconstruct the exhaust gas cloud 31, 3T or a part thereof.

The cameras 23 can be infrared cameras, for example, which record thermal images of the exhaust gas cloud present in the measurement volume 7 , 7 . In this way, the heat distribution in the exhaust gas cloud 31, 3T 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 also happen that different exhaust gas clouds 31, 3T from emission sources located one behind the other or next to one another, such as vehicles, mix. The measurement can then be adjusted accordingly, for example via the positioning optics unit described above or via an adjusted positioning or alignment of one or more cameras 23.

However, the cameras 23 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 stimulates electron transitions in molecules and can be more advantageous for the measurement.

In one possible embodiment, the cameras 23 can be designed as multispectral and hyperspectral cameras. Instead of the classic simple recording in a simple spectral range, a large number of spectral bands are used. This can be advantageous for recognizing a significantly higher color quality and color differences, since each pixel already contains a complete color spectrum. Such a camera 23 can function with the snapshot mosaic technique, for example.

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 (CH ₄ ) from atmospheric measurements. This can be used, for example, to carry out rough estimates of substances or to obtain redundant measurements for the measurement according to the invention. 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 31, 31'. The at least one lidar unit can be used to image different exhaust gas clouds 31, 31' in a measurement volume 7, 7 or also different exhaust gas clouds 31, 31' in different measurement volumes 7, 7. For this purpose, the lidar unit scans the environment and depending on the reflection time of the emitted Laser pulses can be used to generate images of the environment.

A combination of lidar units and cameras 23 is also conceivable as the imaging unit 29 . In this way, for example, gaseous substances can be measured via a lidar unit, while solid substances in the exhaust gas cloud 31, 31' are detected via the measuring unit 1 according to the invention. In this way, a representative measurement of the concentration of several critical substances in the exhaust gas cloud 31, 31' can take place.

A possible embodiment for protecting a first or third reflection unit 3, 3' is a protective film unit 24, which is shown in FIG. This serves to arrange a protective film 25 over a reflection unit 3, 3', in particular over a reflection plane 3.1, 3.V of a reflection unit 3, 3', in order to protect it from dirt or damage (e.g. from scratches). The protective film 25 is of course designed to be sufficiently transparent. A dirty protective film 25 can be replaced with a clean protective film 25 if necessary. A possible embodiment of a protective film unit 24 according to FIG. 5 consists of a first roll 20 on which clean protective film 25 is wound.

Clean protective film 25 can be unwound from this first roll 20 and arranged over a reflection unit 3, 3'. A second roll 21 can be provided, onto which the soiled protective film 25 can be wound. When used as intended, clean protective film is unwound from the first roll 20 as required and dirty protective film is wound up from the second roll 21 at the same time. The reflection unit 3, 3' is arranged below the surface 8 in this possible embodiment. The unwound protective film 25 is arranged over the reflection unit 3, 3' in order to protect the reflection unit 3, 3' from dirt or damage. For reasons of stability, a mechanical protection 26 can also be provided between the reflection unit 3, 3' and the protective film 25, which, however, should enable sufficient optical transparency. One of the two rollers 20, 21 can be driven in order to bring about a further movement of the protective film 25 over the reflection unit 3, 3' 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 with a detector 21 detected return beam 14, 14 '. The automation unit can then automatically control the driven roller 20, 21 in order to move the protective film 25 further. In this way, the soiled protective film 25 above the reflection unit 3, 3' can be easily and if necessary replaced by a clean one. This can be advantageous if the reflection unit 3, 3' is generally exposed to a high level of contamination.

A heating device, for example an electric heater, can also be integrated in the protective film unit 24, preferably in the mechanical protection 26. The heating device can prevent the optical system of the measuring unit 1 from being damaged when it is wet, e.g. in rain, fog or snow the formation of ice or puddles on the surface of the protective film 25 is impaired.

Furthermore, it can also be provided that a camera recording is also carried out in the area of the measuring unit 1 for the measurements described above. This means that license plates or other characteristics of vehicles can be recorded in compliance with data protection regulations. This allows vehicle owners to be notified if a vehicle exhibits gaseous or solid substances in the form of exhaust emissions outside of standard reference values.

Claims

patent claims

1. Measuring unit for measuring at least one gaseous or solid substance in at least one measuring volume (7) at a stationary measuring point, in the measuring unit

(1) a first reflection unit (3) with a first reflection plane (3.1) and a second reflection unit (5) with a second reflection plane (5.1) are provided, the first reflection unit (3) and the second reflection unit (5) being at a distance from one another and are arranged with mutually facing reflection planes (3.1, 5.1), and the measurement volume (7) is formed between the first reflection unit (3) and the second reflection unit (5), wherein the measurement unit (1) has a light emitter unit

(2) is provided which emits at least one light beam (4) in the direction of the first reflection unit (3) and at a first angle (a) deviating from a normal to the first reflection plane (3.1) and/or from a normal to the second reflection plane. radiates, the first reflection plane (3.1) of the first reflection unit

(3) is designed to reflect the light beam (4) to the second reflection unit (5) and the second reflection plane (5.1) of the second reflection unit (5) is designed to reflect the light beam (4) back to the first reflection unit (3), so the light beam

(4) runs back and forth in a plurality n of reflections between the first reflection unit (3) and the second reflection unit (5), with at least one detector (21) being provided in the measuring unit (1), which detects either the at least one light beam (4) detected as at least one return beam (14) after the plurality n of reflections, or at least one deflection unit (11) is provided which directs the light beam (4) after the plurality n of reflections in the opposite direction to the light beam (4) at least a return beam (14) and the at least one return beam (14) carries out a number m of reflections between the first reflection unit (3) and the second reflection unit (5) and the at least one detector (21) deflects the at least one return beam (14) after the Number m of reflections recorded, characterized in that the first angle (a) of the at least one light beam (4) emitted by the light emitter unit (2) can be adjusted and thus the plurality (n) of R reflections of the at least one light beam (4) in the measuring volume (7) between the first reflection unit (3) and the second reflection unit (5) can be adjusted and that the at least one detector (21) is provided, a light property characterizing the at least one gaseous or solid substance of the to measure at least one return beam (14).

2. Measuring unit according to claim 1, characterized in that in the measuring unit (1) a light source (22) is provided which generates a main primary beam (4.1) from which the light emitter unit (2) generates the light beam (4).

3. Measuring unit according to claim 1 or 2, characterized in that the at least one detector (21) is arranged on the first reflection unit (3) or on the second reflection unit (5) or in the light emitter unit (2) or locally separate from these units . 4. Measuring unit according to claim 2, characterized in that the at least one

Detector (21) with the light source (22) is installed in a housing.

5. Measuring unit according to one of claims 1 to 4, characterized in that the first reflection plane (3.1) of the first reflection unit (3) and/or the second reflection plane (5.1) of the second reflection unit (5) is designed to be continuous and/or in one piece.

6. Measuring unit according to one of claims 1 to 4, characterized in that the first reflection unit (3) is designed with a divided first reflection plane (3.1) and/or the second reflection unit (5) with a divided second reflection plane (5.1), wherein at least two reflections of the light beam (4) or return beam (14) are provided on a divided section of a divided first and/or second reflection plane (3.1, 5.1).

7. Measuring unit according to one of claims 1 to 6, characterized in that the first reflection plane (3.1) of the first reflection unit (3) and/or the second reflection plane (5.1) of the second reflection unit (5) are arranged coplanar at least in sections.

8. Measuring unit according to one of claims 1 to 6, characterized in that the first reflection plane (3.1) of the first reflection unit (3) and/or the second reflection plane (5.1) of the second reflection unit (5) is at least partially planar or curved or structured are.

9. Measuring unit according to one of Claims 2 to 8, characterized in that a beam splitter (9) is arranged in the light emitter unit (2) and divides the main primary beam (4.1) into at least one light beam (4) and at least one secondary primary beam (12). divided, wherein the at least one light beam (4) and the at least one secondary primary beam (12) are oriented in different directions.

10. Measuring unit according to Claim 9, characterized in that a second light emitter unit (2') and a second measuring volume (7') are provided in the measuring unit (1), the second light emitter unit (2') receiving the secondary primary beam (12) and a second light beam (4') is generated from the secondary primary beam (12) and is sent through the second measurement volume (7') to the detector (21) or to a second detector (21').

11. Measuring unit according to claim 10, characterized in that a third reflection unit (3) with a third reflection plane (3.1') is provided in the measurement unit (1), and the third reflection plane (3.1') transmits the second light beam (4'). second light emitter unit (2') as a second return beam (14') and sends the second return beam (14') to the detector (21) or to the second detector (21').

12. Measuring unit according to claim 10 or 11, characterized in that in the measuring unit (1) there is a third reflection unit (3') with a third reflection plane (3.1') and a fourth reflection unit (5') with a fourth reflection plane (5.1'). are provided, the third reflection unit (3) and the fourth reflection unit (5') being arranged at a distance from one another and with reflection planes (3.1', 5.1') facing one another, and the second measurement volume (7') between the third reflection unit (3' ) and the second reflection unit (5'), the second light emitter unit (2') sending the second light beam (4) in the direction of the third reflection unit (3') and in a direction that deviates from a normal to the third reflection plane (3.1'). second angle (a '), wherein the third reflection plane (3.1 ') of the third reflection unit (3') is designed to reflect the second light beam (4 ') to the fourth reflection unit (5') and the fourth reflection plane (5.1 ') of the fourth reflection unit (5) is designed to reflect the second light beam (4') back to the third reflection unit (3), so that the second light beam (4') in a plurality n of reflections between the third reflection unit (3') and the fourth reflection unit (5'), and that the detector (21) or the second detector (21') is provided, the second light beam (4) after the plurality n of reflections as the second return beam (14'), or a second deflection unit (11') is provided, which deflects the second light beam (4') after the plurality n of reflections in the opposite direction to the light beam (4') to a second return beam (14'). and the second return beam (14') carries out a number m of reflections between the third reflection unit (3') and the fourth reflection unit (5') and the detector (21) or the second detector (21') the at least one return beam (14' ) after the number m of reflections detected.

13. Measuring unit according to claim 12, characterized in that the second angle (a') of the second light beam (4) is adjustable.

14. Measuring unit according to one of claims 11 to 13, characterized in that the third reflection plane (3.1') of the third reflection unit (3') and/or the fourth reflection plane (5.1') of the fourth reflection unit (5') is continuous and/or is formed in one piece.

15. Measuring unit according to one of claims 11 to 13, characterized in that the third reflection unit (3') with a divided third reflection plane (3.1') and/or the fourth reflection unit (5') with a divided fourth reflection plane (5.1') is designed, at least two reflections of the light beam (4') or return beam (14') being provided on a divided section of a divided third and/or fourth reflection plane (3.1', 5.1').

16. Measuring unit according to one of claims 11 to 15, characterized in that the third reflection plane (3.1') of the third reflection unit (3') and/or the fourth reflection plane (5.1') of the fourth reflection unit (5') are arranged coplanar at least in sections are.

17. Measuring unit according to one of Claims 1 to 6, characterized in that the third reflection plane (3.1') of the third reflection unit (3') and/or the fourth reflection plane (5.1') of the fourth reflection unit (5') is at least partially planar or are curved or structured.

18. Measuring unit according to one of Claims 1 to 13, characterized in that at least one modulation unit (16) is provided in the measuring unit (1) in order to modulate the at least one light beam (4) and/or the second light beam (4') and/or or dividing the at least one return beam (14) and/or the main primary beam (4.1) and/or a secondary primary beam (12) into individual light packets (17).

19. Measuring unit according to claim 18, characterized in that at least two light packets (17) are offset in time.

20. Measuring unit according to one of Claims 1 to 19, characterized in that at least one imaging unit (29) is provided in the measuring unit (1) in order to, if an exhaust gas cloud (31, 31') is present in the measuring volume (7, 7'), at least recording part of the exhaust gas cloud (31, 3T) from different directions, with an evaluation unit (13) being present in order to reconstruct the images recorded with the imaging unit (29) into an image of at least part of the exhaust gas cloud (31, 3T) and from the image of at least part of the exhaust gas cloud (31, 3T), a total passage distance (x) of the at least one light beam (4), the second light beam (4') and/or the return beam (T, 14') through the exhaust gas cloud (31 , 3T) in the measurement volume (7, 7'), wherein the at least one detector (21) that detects the return beam (14, 14') detects a decrease in intensity of the return beam (14, 14') due to the at least one gaseous or solid substance detected and the evaluation unit (13) provision is made for determining a concentration (c) of the at least one gaseous or solid substance in the measuring volume (7, 7') from the decrease in intensity and the determined total passage distance (x).

21. Device according to one of Claims 1 to 20, characterized in that a protective film (25) is arranged in an exchangeable manner over a reflection plane (3.1, 3.1') of a reflection unit (3, 3').

22. Method for measuring at least one gaseous or solid substance in at least one measuring volume (7) at a stationary measuring point, a light beam (4) passing through a light emitter unit (2) in the direction of a first reflection plane (3.1) of a first reflection unit (3) and is emitted at a first angle (a) deviating from a normal to the first reflection plane, the light beam (4) being reflected from the first reflection unit (3) to a spaced-apart second reflection unit (5) with a second reflection plane (5.1) and thereafter the light beam (4) is reflected from the second mirroring unit (5) back to the first mirroring unit (3), and the light beam (4) carries out a plurality n of reflections between the first mirroring unit (3) and the second mirroring unit (5) and thereby the measurement volume (7) penetrates multiple times between the first reflection unit (3) and the second reflection unit (5), the light beam (4) after the plurality n of reflections is detected by at least one detector (21) as a return beam (14) or the light beam (4) is reflected at a deflection mirror (11) to form a return beam (14) and the return beam (14) has a number of reflections between the first reflection unit (3) and the second reflection unit (5) and thereby penetrating the measurement volume (7) several times and the return beam (14) after the number m of reflections is detected by the at least one detector (21), characterized that the plurality n of reflections of the light beam (4) is adjusted by varying the first angle (a) in order to set the plurality n of reflections in the measurement volume (7) between the first reflection unit (3) and the second reflection unit (5) and that with the at least one detector (21) measures a light property of the return beam (14) that characterizes the at least one gaseous or solid substance.