DETECTION UNIT FOR GAS SENSOR, GAS SENSOR, SYSTEM FOR DETECTING A PLURALITY OF DIFFERENT TARGET GASES, AND METHOD FOR DETECTING A TARGET GAS

Abstract

A detection unit for a gas sensor, having at least one gas-sensitive element (1) including at least one gas-sensitive material, the optical properties of which vary as a function of the contact with a target gas. The detection unit is configured for arrangement on a mobile evaluation unit (5) having an image acquisition unit (6), in order to form a gas sensor, and the detection unit has at least one optical lens (2), and the gas-sensitive element (1) and the optical lens (2) are arranged in such a way that the ambient light (U) that passes through the gas-sensitive element (1) can be imaged by the optical lens (2), in particular can be imaged onto the image acquisition unit (6) when the detection unit is arranged on the mobile evaluation unit (5).

Claims

1. A detection unit for a gas sensor, the detection unit comprising: at least one gas-sensitive element (1) comprising at least one gas-sensitive material, optical properties of which vary as a function of contact with a target gas, the detection unit is configured for removable arrangement on a mobile evaluation unit (5) comprising an image acquisition unit (6), in order to form a gas sensor, at least one optical lens (2), and the gas-sensitive element (1) and the optical lens (2) are arranged such that ambient light that passes through the gas-sensitive element (1) is adapted to be imaged by the optical lens (2) onto the image acquisition unit (6) when the detection unit is arranged on the mobile evaluation unit (5).

2. The detection unit as claimed in claim 1, wherein the detection unit comprises a plurality of the optical lenses (2) that are arranged in a lens matrix in order to image a two-dimensional region in a plurality of focusing beams, to image a plurality of focusing beams onto a plurality of differently positioned points of the image acquisition unit (6) when the detection unit is arranged on the mobile evaluation unit (5).

3. The detection unit as claimed in claim 1, further comprising at least one position mark in order to determine a position of the detection unit relative to the image acquisition unit (6) when the detection unit is arranged on the mobile evaluation unit (5), wherein the gas-sensitive element is configured as the position mark.

4. The detection unit as claimed in claim 1, further comprising: at least one identification mark in order to identify the detection unit by the image acquisition unit (6) when the detection unit is arranged on the mobile evaluation unit (5), wherein the gas-sensitive element is configured as the identification mark.

5. The detection unit as claimed in claim 1, further comprising at least one reference region that is not gas-sensitive for the target gas, which is arranged such that the ambient light that passes through the reference region is adapted to be imaged by the optical lens (2) or a further optical lens (2) of the detection unit, onto the image acquisition unit (6) when the detection unit is arranged on the mobile evaluation unit (5).

6. The detection unit as claimed in claim 1, further comprising a flexible film as the carrier substrate (4), and the gas-sensitive element (1) and the optical lens (2) are at least one of formed in the carrier substrate (4) or arranged on the carrier substrate (4).

7. The detection unit as claimed in claim 6, wherein the carrier substrate (4) comprises an adhesive layer in order to arrange the detection unit removably on the mobile evaluation unit (5).

8. A gas sensor, having the detection unit as claimed in claim 1 and a mobile evaluation unit (5) comprising an image acquisition unit (6), and the mobile evaluation unit (5) is configured as a cellphone or tablet computer.

9. A system for detecting a plurality of different target gases, having a plurality of the detection units as claimed in claim 1, each said detection unit being configured to detect a different target gas than the other detection units and comprising at least one of a different identification mark or different reference region than the other detection units, and a mobile evaluation unit (5) comprising an image acquisition unit (6), the mobile evaluation unit (5) being configured to identify the detection unit as a function of optical data of the at least one of the identification mark or of the reference region of the detection unit acquired by the image acquisition unit (6).

10. A method for detecting a target gas, comprising the method steps of: A. arranging the detection unit as claimed in claim 1 on a mobile evaluation unit (5) comprising an image acquisition unit (6); B. analyzing the ambient light that passes through the gas-sensitive element (1) of the detection unit by the image acquisition unit (6) in order to detect the target gas; and C. removing the detection unit from the mobile evaluation unit (5).

11. The method as claimed in claim 10, further comprising determining a position of the gas-sensitive element (1) relative to the image acquisition unit (6) in order to localize an analysis region of the image acquired by the image acquisition unit (6), on which the ambient light that passes through the gas-sensitive element (1) is incident, including determining the position of the gas-sensitive element (1) with the aid of one or more of the following features a circumferential edge of the gas-sensitive element (1), which has different optical properties than the gas-sensitive element (1); a position of a position mark of the detection unit; a position of a reference mark of the detection unit; a position of an identification mark of the detection unit.

12. The method as claimed in claim 10, wherein one said detection unit comprising a reference region that is not gas-sensitive for the target gas is used, and ambient light that passes through the reference region is analyzed by the image acquisition unit (6).

13. The method as claimed in claim 10, wherein one said detection unit comprising an identification mark is used, and the detection unit is identified by the image acquisition unit (6) and the identification mark and, as a function of the identification, one of several evaluation methods stored in the mobile evaluation unit is used for the analysis of the ambient light that passes through the gas-sensitive element (1).

14. The method as claimed in claim 10, further comprising carrying out a white balance of the image acquisition unit (6) between method steps A and B.

15. The method as claimed in claim 10, further comprising carrying out at least one self-test, in which at least one of the following checks is carried out, before method step B: A. comparing a shape of the gas-sensitive element with a predefined shape; B. comparing a predefined hue for the gas-sensitive element with a hue, detected by of the image acquisition unit, of the ambient light that has passed through the gas-sensitive element.

16. The detection unit as claimed in claim 5, wherein optical properties of the reference region correspond substantially to optical properties of the gas-sensitive element (1) in an absence of contact with the target gas.

17. The system of claim 9, wherein a plurality of evaluation methods are stored in a data memory of the mobile evaluation unit (5) and a selection of the evaluation method for detecting the target gas takes place as a function of the identification of the detection unit.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0085] Further advantageous features and configurations will be explained below with the aid of exemplary embodiments and the figures, in which:

[0086] FIG. 1 shows a sectional representation of a first exemplary embodiment of a detection unit according to the invention;

[0087] FIG. 2 shows a first exemplary embodiment of a gas sensor according to the invention comprising a detection unit according to FIG. 1;

[0088] FIG. 3 shows a second exemplary embodiment of a detection unit according to the invention;

[0089] FIG. 4 shows a second exemplary embodiment of a gas sensor according to the invention comprising a detection unit according to FIG. 3;

[0090] FIG. 5 shows a third exemplary embodiment of a detection unit according to the invention in a sectional representation;

[0091] FIG. 6 shows a plan view from the front of the third exemplary embodiment according to FIG. 5;

[0092] FIG. 7 shows a plan view from the rear of the third exemplary embodiment according to FIG. 5; and

[0093] FIG. 8 shows a further exemplary embodiment of a gas sensor according to the invention comprising a detection unit that has a gas-sensitive element configured as an identification and position mark.

DETAILED DESCRIPTION

[0094] All the figures show schematic representations that are not true to scale. Reference signs that are the same in the figures denote elements that are the same or have the same effect.

[0095] FIG. 1 shows a first exemplary embodiment of a detection unit according to the invention for a gas sensor.

[0096] The detection unit has a gas-sensitive element 1 comprising a gas-sensitive material. The gas-sensitive element is configured in a manner known per se as a gasochromic layer, so that the optical absorption properties vary as a function of the contact with a target gas. In the present case, the gas-sensitive material of the gas-sensitive element is formed as bromophenol blue in order to detect ammonia (NH.sub.3) as the target gas.

[0097] Examples of alternative configurations with alternative dyes and the target gases that can be detected with them are given in the aforementioned Table 1.

[0098] The detection unit comprises an optical lens 2 configured as a converging lens, which is arranged on an optically transparent lens carrier element 3. The optical lens and the lens carrier element 3 are formed in the present case from polymers.

[0099] The gas-sensitive element 3 is arranged on the lens carrier element 3.

[0100] The detection unit is configured for removable arrangement on a mobile evaluation unit comprising an image acquisition unit, in order to form a gas sensor.

[0101] For this purpose, the detection unit according to the first exemplary embodiment comprises a carrier substrate 4 configured as a flexible film, which is optically transparent and is formed from polymers.

[0102] The gas-sensitive element 1 and the optical lens 2 are arranged in such a way that the ambient light that passes through the gas-sensitive element 1 is focused by means of the optical lens 2.

[0103] FIG. 1 schematically represents a subregion of a mobile evaluation unit 5, which in the present case is configured as a cellphone, comprising an image acquisition unit.

[0104] By means of the carrier substrate 4, the detection unit is arranged on the mobile evaluation unit so that the ambient light that passes through the gas-sensitive element 1 can be imaged by means of the optical lens 2 onto the image acquisition unit of the mobile evaluation unit 5, as explained in more detail below in FIG. 2.

[0105] Because of the low weight of the detection unit, there is already a sufficient grip on the mobile evaluation unit by the air pressure of the surroundings.

[0106] In one development of the first exemplary embodiment, the carrier substrate 4 is configured as an adhesion film in order to achieve a better grip.

[0107] In an alternative development, the carrier substrate 4 has in the present case an adhesive layer based on rubber on the side facing away from the optical lens 2 in order to arrange the detection unit removably on the mobile evaluation unit. In an alternative configuration, the adhesive layer is one or adhesive layers based on acrylate. The use of other adhesive layers also lies within the scope of the invention.

[0108] FIG. 2 represents an exemplary embodiment of a gas sensor according to the invention. The gas sensor has the detection unit shown in FIG. 1 according to the first exemplary embodiment and a mobile evaluation unit comprising an image acquisition unit, which in the present case is configured as a cellphone. In an alternative configuration, the mobile evaluation unit is configured as a tablet computer.

[0109] The image acquisition unit 6 of the mobile evaluation unit 5 comprises a first camera shown at the top in FIG. 2 and an underlying second camera for the usual color spectrum in the visible range for taking photographs. The detection unit in the present case is arranged on one of the two cameras, in the present case on the lower camera of the image acquisition unit 6 of the mobile evaluation unit 5, in order to detect a color change of the gas-sensitive element 1 of the detection unit by means of this camera.

[0110] The edges of the lens carrier element 3 are represented by dashes.

[0111] The ambient light passes through both the gas-sensitive element 1 and the region enclosing the gas-sensitive element 1, and is focused by means of the optical lens 2 onto the image acquisition unit 6 of the mobile evaluation unit 5 so that the gas-sensitive element is imaged onto the image acquisition unit 6.

[0112] The mobile evaluation unit 5 comprises a computing unit and a data memory unit. An evaluation program is stored in the data memory unit in order to analyze the image data of the image acquisition unit 6 by means of the computer unit.

[0113] Even if there is no contact between a target gas and the gas-sensitive element 1, the position of the gas-sensitive element can be ascertained by means of analyzing the position-resolved image data of the image acquisition unit 6, since the gas-sensitive element has an absorption and therefore a characteristic color even in the absence of contact with the target gas and can therefore be localized in the image data of the image acquisition unit 6, for example by filtering over pixels with the corresponding color values.

[0114] During the evaluation, a localization of those pixels which acquire ambient light that passes through the gas-sensitive element initially takes place as described above.

[0115] Since the gas-sensitive material used and its optical properties are known, a color spectrum that corresponds to the color of the gas-sensitive element upon contact with the target gas is furthermore predefined in the evaluation program.

[0116] By means of the evaluation program, whether a color change takes place in the predefined spectrum at the pixels of the image acquisition unit 6 that are assigned to the gas-sensitive element is then repeatedly checked. If there is a color change, a warning message that the target gas has been detected is emitted to the user on a display unit of the mobile evaluation unit 5, which is arranged on the opposite side of the mobile evaluation unit 5 from the image acquisition unit 6.

[0117] In an alternative configuration, the light intensity is used by means of the evaluation program and the image acquisition unit 6 only as an indicator in order to detect a variation of the optical properties of the gas-sensitive element and therefore a presence of the target gas. With such an evaluation, the risk exists that a variation of the intensity of the ambient light leads to an erroneous detection. In one development of the exemplary embodiment, the intensity of the ambient light acquired by means of the image acquisition unit 6, which does not pass through the gas-sensitive element, is therefore additionally acquired and a ratio is formed, in the present case as the quotient of this reference intensity to the light intensity of the ambient light that passes through the gas-sensitive element. Erroneous detections in the event of a varying intensity of the ambient light may be avoided by taking this reference intensity into account.

[0118] In a variant of the exemplary embodiment represented in FIG. 1, several gas-sensitive elements are arranged on the upper-lying side of the lens carrier element 3 in FIG. 1, in particular a matrix comprising a multiplicity of gas-sensitive elements, in the present case a 55 matrix therefore comprising a total of 25 gas-sensitive elements, is preferably formed. The gas-sensitive elements have different gas-sensitive materials than one another, so that detection of a multiplicity of target gases is possible.

[0119] FIG. 3 shows a second exemplary embodiment of a detection unit according to the invention in a sectional representation. FIG. 4 shows a second exemplary embodiment of a gas sensor according to the invention comprising a detection unit according to FIG. 3. The two exemplary embodiments of a detection unit and gas sensor are constructed in substantially the same way as the first exemplary embodiments according to FIGS. 1 and 2. In order to avoid repetitions, the essential differences will be discussed below.

[0120] The detection unit according to the second exemplary embodiment has in total nine gas-sensitive elements comprising different gas-sensitive materials, so that 9 different target gases can be detected. The nine gas-sensitive elements are arranged in a square 33 matrix on the lens carrier element 3. In the sectional representation according to FIG. 3, therefore, 3 gas-sensitive elements can be seen, the gas-sensitive element lying on the right being denoted by way of example with the reference sign 1. In a variant of the second exemplary embodiment, it comprises only 3 different gas-sensitive materials, 3 gas-sensitive elements in each case comprising the same gas-sensitive material. In this variant, 3 different target gases can therefore be detected and there is furthermore a redundancy in the measurements, so that the measurement accuracy is improved.

[0121] In the plan view from above shown in FIG. 4, likewise as in FIG. 2, a border of the lens carrier element 3 is represented by a dashed line. The 9 gas-sensitive elements are characterized by different hatchings. The 9 gas-sensitive elements are arranged at a distance from one another so that ambient light passing through the detection unit between the gas-sensitive elements is not absorbed, or is absorbed only to a small extent, and is not modified in its spectrum.

[0122] The rectangular grid formed by the distances between the gas-sensitive elements can therefore be detected by means of the image sensor 6a of the image acquisition unit 6. The position of the detection unit relative to the mobile evaluation unit 5 can be deduced with the aid of the location of the rectangular grid. In particular, whether all 9 fields of the rectangular grid are acquired by means of the image acquisition unit 6 is checked. If this is not the case, an error message is emitted to the user via the optical display of the mobile evaluation unit 5 so that they can position the detection unit correctly.

[0123] FIG. 5 shows a third exemplary embodiment of a detection unit according to the invention in a sectional representation. The detection unit comprises a matrix of in total 49 detection fields, which are arranged in a square 77 matrix. Each detection field comprises 9 gas-sensitive elements, which are arranged in a square 33 matrix as described in the 2.sup.nd exemplary embodiment with reference to FIGS. 3 and 4.

[0124] The third exemplary embodiment shown in FIG. 5 therefore has a large number of gas-sensitive elements, there being a high redundancy of the detection for each of the 9 target gases since 49 detection units are respectively arranged on the lens carrier element 3 for each of the 9 target gases.

[0125] In contrast to the 1.sup.st and 2.sup.nd exemplary embodiments of a detection unit, the detection unit represented in FIG. 5 comprises a plurality of optical lenses, which are formed from the material of the lens carrier element 3 and are arranged as hemispherical projections on the opposite side of the lens carrier element 3 from the gas-sensitive elements. By way of example, the optical lens lying on the right in FIG. 5 is denoted by the reference sign 2. One optical lens is formed for each detection field, so that the optical lenses are correspondingly also arranged in a square 77 matrix.

[0126] The optical lenses 2 comprise an adhesive layer in order to arrange the detection unit on the mobile evaluation unit 5. For illustration, FIG. 5 represents a partial detail of the image acquisition unit 6 of the mobile evaluation unit 5. In the present case, the mobile evaluation unit 5 is configured as a tablet computer.

[0127] FIG. 6 represents a plan view of the detection unit shown in FIG. 5, the detection fields arranged in the 77 matrix being represented schematically as squares. The detection field at the top left is shown with a detail enlargement, the individual gas-sensitive elements, which are arranged in a 33 matrix, being visible in the detail enlargement.

[0128] FIG. 7 shows a plan view of the rear side of the detection unit shown in FIG. 5, the optical converging lenses, which are arranged in a 77 matrix, respectively being schematically represented as circles.

[0129] FIG. 8 represents a further exemplary embodiment of a gas sensor according to the invention comprising a further exemplary embodiment of a detection unit according to the invention. The structure is substantially the same as the structure shown in FIG. 2, with a mobile evaluation unit 5 that comprises the image acquisition unit 6, on which the detection unit comprising a carrier substrate 4 and a lens carrier element 3, denoted by dashed lines, and a gas-sensitive element 1 are arranged.

[0130] An essential difference from the first exemplary embodiment represented in FIGS. 1 and 2 is that the gas-sensitive element 1 is configured as a geometrical figure and therefore constitutes both a position mark and an identification mark.

[0131] The gas-sensitive element comprises a plurality of angular elements. The position of the angle elements is acquired by means of the image sensor so that the position and rotation of the gas-sensitive element relative to the image sensor can be acquired. Furthermore, the detection unit can be distinguished from other detection units that comprise a gas-sensitive element, the shape and/or individual elements of which are configured differently than that shown in FIG. 8. The user can therefore be provided with a plurality of detection units which comprise different gas-sensitive dyes and are therefore suitable for the detection of different target gases.

[0132] The detection unit is identified with the aid of the shape of the gas-sensitive element, so that the evaluation takes place specifically for the gas-sensitive element applied on the mobile evaluation unit, and the target gas detected by this gas-sensitive detection unit can be displayed in plain text to the user on an optical display of the mobile evaluation unit 5.

[0133] The gaps between the angular elements of the gas-sensitive element are optically transparent for light in the visible range, so that the intensity of the ambient light can be measured by means of the pixels of the image sensor of the image acquisition unit 6 which acquire ambient light that passes through these gaps, and a fluctuation in the intensity of the ambient light can be taken into account as described above by forming the quotient during the evaluation.

LIST OF REFERENCE SIGNS

[0134] 1 gas-sensitive element [0135] 2 optical lens [0136] 3 lens carrier element [0137] 4 carrier substrate [0138] 5 mobile evaluation unit [0139] 6 image acquisition unit [0140] 6a image sensor [0141] 7 adhesive element [0142] U ambient light