DE102014014501A1 - Flame detector, method for flame detection and filter array for a CMOS chip - Google Patents

Abstract

The invention relates to a flame detector 10 having at least one objective 11, a CMOS chip 30 and at least one color filter 20, wherein the color filter 20 is an array of a plurality of filter elements 21, 22, 23, wherein the plurality of filter elements 21, 22, 23 has a first group of filter elements 21 that are transmissive to a first wavelength range 40, the plurality of filter elements 21, 22, 23 having at least a second group of filter elements 22 that are transmissive to a second wavelength range 50, and wherein the first Wavelength range 40 is a wavelength range 40 in which both a flame F and a noise source S emit a significant amount of electromagnetic radiation and that the second wavelength range 50 is a wavelength range 50 in which only the noise source S or only the flame F is a significant amount of electromagnetic Emitted radiation.

Description

The present invention relates to a flame detector according to the preamble of claim 1, and a method for flame detection using such a detector and a filter array for a camera chip, preferably CMOS chip, which can be used for example in a flame detector according to the invention.

Flame detectors are well known and are used, for example, in fire alarm systems, such as for the detection of hydrocarbon-based fires in the field of petrochemical or similar industries. Typically, the resulting flame in a fire is optically detected and detected by a camera. The emitted by the flame, characteristic electromagnetic radiation is detected using an optical sensor and evaluated using a corresponding algorithm.

Important in such systems is that false alarms are avoided as much as possible. False alarms can be triggered in particular by radiation, which, although lying in a similar or the same wavelength range, as the radiation emanating from the flame to be detected, but does not originate from a flame, but from a source of interference. Such sources of interference may, for example, be located in the monitored area light or heat sources, but also for example sun and moon. To distinguish between radiation originating from such sources of interference (source of interfering radiation) and radiation originating from a real burning flame (flame radiation), it is possible to exploit the fact that the electromagnetic spectrum of these radiation sources overlaps in certain areas of the electromagnetic spectrum False alarm is possible - in certain other areas, however, significantly different. Such an overlap often occurs in the visible region of the electromagnetic spectrum, which is why video cameras in particular can be susceptible to corresponding false alarms.

US 2009/0315722 A1 sees in this context a system for detecting flames that has two cameras. The first camera detects an image in the spectrum of visible light, the second camera detects an image in the near IR spectrum. With the help of a processor you can switch between the different pictures. The images obtained from the different cameras can then be compared and evaluated using an algorithm.

Alternatively, other known flame detectors use systems that have only one camera lens, but two digital video sensors, preferably complementary metal oxide semiconductor chips (CMOS), each of which detects different wavelength ranges. In order to be able to evaluate corresponding electromagnetic radiation captured by the objective with both sensors, a beam splitter, which directs a first part of the radiation to the first chip and a second part of the radiation to the second chip, is arranged in the beam path behind the camera objective. Here, too, therefore, always two different image sensors are used, the data are then compared with each other.

This type of flame detection is relatively complex in relation and requires a very accurate adjustment of the sensors and the optical components.

Based on this, it is an object of the invention to overcome these and other disadvantages of the prior art and to provide an improved flame detector. This should be inexpensive and easy to manufacture. In particular, he should work as precisely and quickly as possible.

To solve this problem, the invention proposes a flame detector according to claim 1, and a method for flame detection according to claim 9 and a filter array for a CMOS chip according to claim 16 before. Embodiments are each the subject of the dependent claims.

• • wobei die Vielzahl von Filterelementen eine erste Gruppe von Filterelementen aufweist, die für einen ersten Wellenlängenbereich durchlässig sind,
• • wobei die Vielzahl von Filterelementen wenigstens eine zweite Gruppe von Filterelementen aufweist, die für einen zweiten Wellenlängenbereich durchlässig sind, und
• • wobei die Filterelemente des Arrays derart matrixförmig angeordnet sind, dass Filterelemente, die innerhalb der Reihen und Spalten der Matrix benachbart zueinander angeordnet sind, jeweils für unterschiedliche Wellenlängenbereiche durchlässig sind,

sieht die Erfindung vor, dass der erste Wellenlängenbereich ein Wellenlängenbereich ist, in welchem sowohl eine Flamme als auch eine Störquelle eine signifikante Menge elektromagnetischer Strahlung emittieren und dass der zweite Wellenlängenbereich eine Wellenlänge ist, in welchem nur die Störquelle oder nur die Flamme eine signifikante Menge elektromagnetischer Strahlung emittiert.In a flame detector having at least one lens, a CMOS chip and at least one color filter, wherein the CMOS chip is connected to an evaluation unit and has a plurality of pixel elements, wherein the color filter between the lens and the CMOS chip is arranged and an array is made of a plurality of filter elements, each filter element is associated with at least one pixel element of the CMOS chip such that between the pixel element and the lens exactly one filter element is arranged, and

• Wherein the plurality of filter elements comprises a first group of filter elements that are transmissive to a first wavelength range,
• Wherein the plurality of filter elements comprises at least a second group of filter elements which are transmissive to a second wavelength range, and
• Wherein the filter elements of the array are arranged in matrix form in such a way that filter elements which are arranged adjacent to one another within the rows and columns of the matrix are each permeable to different wavelength ranges,

the invention provides that the first wavelength range is a wavelength range in which both a flame and a source of interference emit a significant amount of electromagnetic radiation and that the second wavelength range is a wavelength in which only the source of interference or only the flame emits a significant amount of electromagnetic radiation.

In such a flame detector, by comparing image data obtained in a first wavelength range with image data obtained in a second wavelength range, it can be determined whether or not a particular electromagnetic signal is from a flame. In particular, image data derived from pixel elements associated with filter elements that are transparent to a first wavelength range may be compared to image data derived from pixel elements associated with filter elements that are transparent to a second wavelength range.

In a preferred embodiment, the flame detector has exactly one lens, but it is also conceivable that a plurality of lenses are arranged in the manner of an insect eye, so that each pixel element is associated with a lens. Furthermore, it is preferred if exactly one pixel element of the CMOS chip is assigned to each filter element.

Of particular advantage in any case is the matrix-shaped arrangement of the filter elements. As a result, pixel elements that provide information about the first wavelength range and pixel elements that provide information about the second wavelength range are at most one pixel element far apart. A matrix-like arrangement is usually a 2-dimensional arrangement (array) of rows and columns, wherein in each case arranged in the rows elements of adjacent rows are arranged below or above one another such that they form the columns. Such a matrix arrangement is typically indicated by the number of rows and columns in the notation (R × S), where R is the number of rows and S is the number of columns. In an arrangement according to the invention of the filter elements, the matrix is then constructed in such a way that filter elements succeed each other in a row as well as in a column and are transparent to different wavelength ranges.

In this context, a multiplicity of filter elements is typically understood to mean a number of two or preferably more than two filter elements. A group of filter elements is a selection of a plurality of filter elements from this plurality of filter elements, wherein the selected filter elements have identical properties. The filter elements of a group are arranged in the matrix so that they are adjacent to each other if at all then only in the diagonal direction and that within a row and within a column always only filter elements of different groups adjacent to each other.

The objective can be adjustable in such a way that the image which is imaged on the CMOS chip has a certain blurring, namely such that two pixel elements lying adjacent to one another are illuminated almost identically. The lens of the flame detector is preferably a wide-angle lens, i. H. It is preferably an objective whose angle of view is greater than 30 °, more preferably greater than 50 °.

Under an almost identical exposure is understood in this context that, in principle, although existing differences in the exposure of spatially juxtaposed pixels due to the blur of the optics are no longer resolvable. The information obtained from such neighboring pixel elements is therefore based on identical electromagnetic radiation and differs only in that the spectrum of this radiation is limited by the respectively arranged between the pixel element and the lens filter elements in different ways. A pixel element in the sense of the present invention is typically understood to mean the smallest individually evaluable area unit of the CMOS chip. The connection of the CMOS chip to the evaluation unit is preferably designed such that the evaluation unit can specifically assign the information sent to individual pixel elements. It is particularly advantageous if the CMOS chip is an active sensor (APS sensor, active pixel sensor). In such an active sensor, each pixel element has its own amplifier circuit for signal readout.

A filter element which is permeable to a certain wavelength range may be, for example, a color foil, a gel element or the like. It is characterized in that selectively only electromagnetic radiation of one or more specific wavelengths can pass through the filter element (is transmitted). Electromagnetic radiation of other wavelengths is typically absorbed or reflected by such a filter element. Filter elements which are permeable to different wavelength ranges may be permeable to electromagnetic radiation of completely or partially overlapping wavelength ranges. For example, it is conceivable that a first filter element transmits radiation, for example in the range from 380 to 780 nm, while a second filter element transmits radiation for example, in the range of 430 to 490 nm. The filter elements of different groups can also be transparent for radiation of complementary wavelength ranges or else for radiation of non-overlapping wavelength ranges.

It is particularly advantageous if the first group of filter elements is transparent to a wavelength range in which both a flame and a source of interference emit a significant amount of electromagnetic radiation, and if the second group of filter elements is transparent to a wavelength range in which only the flame or only the source of interference emits a significant amount of electromagnetic radiation. A significant amount of electromagnetic radiation is a quantity of electromagnetic radiation that can be detected by a pixel element without the presence of the filter element arranged between the pixel element and the objective and that has a certain characteristic intensity.

In a first preferred embodiment, it is provided that the flame detector is a first group of filter elements, which is permeable to electromagnetic radiation in a first wavelength range, and a group of filter elements, which is transparent to electromagnetic radiation in a second wavelength range, wherein the first Wavelength range is a wavelength range in which both a flame and a source of interference emit a significant amount of electromagnetic radiation and wherein the second wavelength range is a wavelength in which only the source of interference emits a significant amount of electromagnetic radiation.

While the source of interference emits radiation both in the first wavelength range and in the second wavelength range, the flame is therefore only visible in the first wavelength range for the CMOS chip. If the electromagnetic radiation incident on the chip by the objective comes from a source of interference, both those pixel elements which are provided with a filter element which is permeable to the first wavelength range and those pixel elements which are provided with a filter element are exposed, which is permeable to the second wavelength range. On the other hand, if the electromagnetic radiation originates from a flame, only those pixel elements are exposed which are provided with a filter element which is transparent to the first wavelength range.

If a correspondingly conducted information from the CMOS chip to the evaluation unit is therefore present both in the first wavelength range and in the second wavelength range, the electromagnetic radiation captured by the objective in all likelihood originates from a source of interference and no alarm is triggered. However, if the information is present only in one of the two wavelength ranges, in particular in the first wavelength range, then there is a flame and an alarm must be triggered. False alarms, which could be triggered by electromagnetic radiation from sources of interference, are effectively avoidable in this way.

In a second preferred embodiment, it may alternatively be provided that the flame detector comprises a first group of filter elements that is permeable to electromagnetic radiation in a first wavelength range, and a group of filter elements that is permeable to electromagnetic radiation in a second wavelength range, wherein the first wavelength range is a wavelength range in which both a flame and a noise source emit a significant amount of electromagnetic radiation, and wherein the second wavelength range is a wavelength in which only the flame emits a significant amount of electromagnetic radiation.

The following applies here: If an information transmitted by the CMOS chip to the evaluation unit is present both in the first wavelength range and in the second wavelength range, then the electromagnetic radiation captured by the objective in all likelihood comes from a flame and an alarm is triggered. However, if the information is present only in one of the two wavelength ranges, in particular in the first wavelength range, then there is no flame and the triggering of the alarm has to be omitted. False alarms, which could be triggered by electromagnetic radiation from sources of interference, are effectively preventable in this way, too.

In each case, it is particularly advantageous if the flame detector in each embodiment only has a single sensor, namely only a single CMOS chip. All image data can be obtained with this one CMOS chip at the same time. In other words, thanks to the present invention, with only one lens and one CMOS chip, an image can be simultaneously acquired in several relevant wavelength ranges and analyzed by comparison. Typically usable CMOS chips can detect a spectral range of about 350 nm to about 1000 nm.

Such a spectral range encompasses both the visible light range and parts of the UV radiation and the near infrared range. In this area emit both conventional artificial and natural light sources corresponding electromagnetic radiation and flames, which arise for example in the combustion of hydrocarbons. Such flames may be of interest, in particular in the field of petrochemistry but also in oil production, since they may be at least partially invisible to the human eye, but nevertheless constitute a natural source of danger.

In a preferred embodiment, it is advantageous if the first wavelength range extends from 900 ± 10 nm to 1000 ± 10 nm, preferably from 920 ± 10 nm to 960 ± 10 nm, most preferably from 940 ± 10 nm to 960 ± 10 In particular, hydrocarbon flames typically have a local maximum intensity in the wavelength range around about 950 nm, but emit relatively little visible light radiation at about 400 nm. However, most sources of interference emit corresponding noise both in this range and in visible light Radiation. A pixel element associated with a filter element which is transparent to that region thus recognizes both the source of interference and the flame. In this wavelength range, the radiation of the sun is relatively low, so that another advantage of this embodiment is that the potential glare of the camera by the sun is relatively low.

Alternatively, the first wavelength range can also be transmissive to radiation in the UV range, namely, for example, for wavelengths in the range from 50 ± 10 nm to 380 ± 10 nm, preferably from 200 ± 10 nm to 380 ± 10 nm, particularly preferably from 200 ± 10 nm to 280 ± 10 nm. This is favorable, for example, if flames with a characteristic emission in the UV range, for example hydrogen flames, are to be detected with the aid of the flame detector according to the invention.

It is also conceivable that the first wavelength range comprises two subregions in which the filter is permeable. For example, it is conceivable that a filter element which is permeable to the first wavelength range, both for radiation in the near infrared region and for radiation in the range of the near UV range is transparent, but not for radiation in the range of visible light. The first wavelength range may include radiation in the range of less than 380 nm and greater than 780 nm, preferably radiation in the range of 50 ± 10 nm to 380 ± 10 nm and in the range of 900 ± 10 nm to 1000 ± 10 nm. In this Fall can with the help of the flame detector according to the invention both flames with an emission in the IR range, such as. B. hydrocarbon flames, as well as flames with an emission in the UV range, such. B. hydrogen flames monitored and detected.

It can be seen that in this context it is in any case favorable if the second wavelength range extends from 300 ± 10 nm to 580 ± 10 nm, preferably from 350 ± 10 nm to 490 ± 10 nm, very particularly preferably from 380 ± 10 nm 450 ± 10 nm. In this wavelength range, there is typically a significant emission of artificial light sources, as well as of the sun and moon, whereas hydrocarbon flames appear dark in this wavelength range.

In a particularly preferred embodiment, it is therefore provided that the first wavelength range is a wavelength range in which both a flame and a source of interference emit a significant amount of electromagnetic radiation, namely a wavelength range extending from 900 ± 10 nm to 1000 ± 10 nm , preferably from 920 ± 10 nm to 960 ± 10 nm, most preferably from 940 ± 10 nm to 960 ± 10 nm, and / or a wavelength range extending from 50 ± 10 nm to 380 ± 10 nm, preferably 200 ± 10 nm to 380 ± 10 nm, more preferably from 200 ± 10 nm to 280 ± 10 nm, and that the second wavelength range is a wavelength in which only the noise source emits a significant amount of electromagnetic radiation, namely a wavelength range different from 300 ± 10 nm to 580 ± 10 nm, preferably from 350 ± 10 nm to 490 ± 10 nm, most preferably from 380 ± 10 nm to 450 ± 10 nm.

For the effective evaluation of the information obtained by the CMOS chip, it is favorable if the filter elements are each arranged in sections of four filter elements, each section having at most two filter elements which are permeable to the same wavelength range. These departments can then repeat identically along the entire filter array. The color filter can therefore consist of a repetitive pattern of four filter elements. It is conceivable that the four filter elements of each section are arranged in the form of a (2 × 2) matrix, each row and each row of the (2 × 2) matrix each having a filter element which is transparent to the first wavelength range, and a filter element permeable to the second wavelength range. In such an arrangement, in the direction of the rows of the matrix as well as in the direction of the columns of the matrix, two pixel elements are always adjacent to each other, to each of which a filter element of different groups is assigned. The evaluation unit can in each case compare the information obtained from these adjacent pixel elements. In this way, a pixel-perfect comparison of the entire CMOS Chip captured image quickly and easily possible. The pixel elements to be compared with each other, to each of which a filter element which is permeable to the first wavelength range, or a filter element which is permeable to the second wavelength range, are in each case along the rows or columns of the (2 × 2) matrix arranged next to each other.

In a further embodiment, it is provided that the plurality of filter elements has a third group of filter elements that are transparent to a third wavelength range. For example, it is conceivable that the first wavelength range covers the range of 900 to 1000 nm, the second wavelength range the range of 380 to 780 nm and the third wavelength range the range of 50 to 380 nm. In this way, with the aid of the pixel elements, which filter elements are assigned to the third group, radiation in the UV range recognizable. Of course, it is also conceivable that the first and / or the second wavelength range corresponds to one of the wavelength ranges described above. It is thus conceivable that with the aid of the flame detector according to the invention it can be distinguished whether an invisible flame emits radiation in the near-IR range or in the UV range.

Alternatively, it is also conceivable that the first wavelength range includes that IR range in which hydrocarbon flames have a characteristic emission maximum, the second wavelength range comprises the range around 400 nm, in which an emission maximum of artificial and / or natural light sources lies, and the third wavelength range full range of the visible spectrum in which video pictures are typically recorded for black and white videos.

The latter is particularly advantageous if not only a flame detection with the help of the flame detector is to be performed, but at the same time the video surveillance of the desired area is desired. This can be advantageous for clarifying the cause or closer circumstances of a detected flame, for example. It may be possible to clarify more precise circumstances of a flame outbreak in a potentially explosive area by means of video surveillance of an area, without it being necessary to send personnel to this area. It can be seen that it can be particularly favorable if the third wavelength range comprises the range of the visible light. In further embodiments, it is conceivable that four or more groups of filter elements are present, which are permeable to different wavelength ranges.

Even with a flame detector having three different groups of filter elements, it is favorable if the filter elements are arranged in a repetitive pattern. In particular, it will be appreciated that it is beneficial if the filter elements are each arranged in divisions of four filter elements, each section each comprising a filter element permeable to the first wavelength range, a filter element permeable to the second wavelength range, and two filter elements which are transparent to the third wavelength range. Again, it is advantageous if each adjacent filter elements are transparent to different wavelengths. Thus, it will be appreciated that it is advantageous if the four filter elements of each compartment are arranged in the form of a (2 × 2) matrix, each line and row of the (2 × 2) matrix each having a first filter element and a second filter element wherein the first filter element is either a filter element that is transmissive to the first wavelength range, or a filter element that is transmissive to the second wavelength range, and wherein the second filter element is a filter element that is transmissive to the third wavelength range. The pixel elements to be compared with each other, to each of which a filter element which is permeable to the first wavelength range, or a filter element which is permeable to the second wavelength range, are thus arranged along the diagonal of the (2 × 2) matrix.

• a. Belichtung der Pixelelemente des CMOS-Chip mit einer vorgegebener Belichtungszeit und Analogverstärkung,
• b. Erfassen der Bildinformationen aller Pixelelemente des CMOS-Chips mit Hilfe der Auswerteeinheit,
• c. Vergleich der Bildinformationen derjenigen Pixelelemente, denen ein Filterelement zugeordnet ist, das für den ersten Wellenlängenbereich durchlässig ist, mit den Bildinformationen derjenigen Pixelelemente, denen ein Filterelement zugeordnet ist, das für den zweiten Wellenlängenbereich durchlässig ist, mit Hilfe der Auswerteeinheit.

In another aspect, the present invention provides a method of flame detection using a previously described flame detector, the method comprising the steps of:

• a. Exposure of the pixel elements of the CMOS chip with a given exposure time and analog gain,
• b. Acquiring the image information of all pixel elements of the CMOS chip with the aid of the evaluation unit,
• c. Comparison of the image information of those pixel elements, which is associated with a filter element which is transparent to the first wavelength range, with the image information of those pixel elements, which is associated with a filter element which is transparent to the second wavelength range, with the aid of the evaluation.

Upon exposure of the pixel elements in step a, the electromagnetic radiation captured by the lens of the flame detector is passed through the color filter to the CMOS chip. However, in each case only that radiation can pass through the individual filter elements of the color filter, for which the respective filter element is permeable. As a result, the pixel elements arranged in the beam path behind the filter elements are only exposed if the respective one Filter element is permeable to the radiation captured by the lens.

In step b, the information of all pixel elements is then read out. It is advantageous if the CMOS chip is an active sensor, as already described above. In this case, each pixel element forwards corresponding information about the received radiation intensity to the evaluation unit.

In order to determine whether a signal captured by the lens originates from a flame or from a source of interference, the information transmitted by the individual pixel elements to the evaluation unit is finally evaluated in step c. In each case, the information of adjacent pixel elements, to each of which different filter elements are assigned, is preferably compared.

• • mit einer ersten Gruppe von Filterelemente, die für elektromagnetische Strahlung in einem ersten Wellenlängenbereich durchlässig ist, und
• • einer Gruppe von Filterelementen, die für elektromagnetische Strahlung in einem zweiten Wellenlängenbereich durchlässig ist,
• • wobei der erste Wellenlängenbereich ein Wellenlängenbereich ist, in welchem sowohl eine Flamme als auch eine Störquelle eine signifikante Menge elektromagnetischer Strahlung emittieren und wobei der zweite Wellenlängenbereich eine Wellenlänge ist, in welchem nur die Störquelle eine signifikante Menge elektromagnetischer Strahlung emittiert,

so wird ein Alarm dann ausgelöst, wenn nur diejenigen Pixelelemente belichtet wurden, denen ein Filterelement zugeordnet ist, das für Strahlung im ersten Wellenlängenbereich durchlässig ist, nicht jedoch diejenigen Pixelelemente, denen ein Filterelement zugeordnet ist das für Strahlung im zweiten Wellenlängenbereich durchlässig ist.Based on this comparison, it is decided with the aid of an evaluation algorithm whether an alarm is to be triggered or not. For example, the flame detector is a flame detector

• With a first group of filter elements which is permeable to electromagnetic radiation in a first wavelength range, and
• A group of filter elements permeable to electromagnetic radiation in a second wavelength range,
• Wherein the first wavelength range is a wavelength range in which both a flame and a source of interference emit a significant amount of electromagnetic radiation and wherein the second wavelength range is a wavelength in which only the source of interference emits a significant amount of electromagnetic radiation,

Thus, an alarm is triggered when only those pixel elements were exposed, which is associated with a filter element which is transparent to radiation in the first wavelength range, but not those pixel elements, which is associated with a filter element which is transparent to radiation in the second wavelength range.

• • mit einer ersten Gruppe von Filterelemente, die für elektromagnetische Strahlung in einem ersten Wellenlängenbereich durchlässig ist, und
• • einer Gruppe von Filterelementen, die für elektromagnetische Strahlung in einem zweiten Wellenlängenbereich durchlässig ist,
• • wobei der erste Wellenlängenbereich ein Wellenlängenbereich ist, in welchem sowohl eine Flamme als auch eine Störquelle eine signifikante Menge elektromagnetischer Strahlung emittieren und wobei der zweite Wellenlängenbereich eine Wellenlänge ist, in welchem nur die Flamme eine signifikante Menge elektromagnetischer Strahlung emittiert,

so wird ein Alarm dann ausgelöst, wenn sowohl diejenigen Pixelelemente belichtet wurden, denen eine Filterelement aus der ersten Gruppe zugeordnet ist, als auch diejenigen Pixelelemente, denen ein Filterelement aus der zweiten Gruppe zugeordnet ist.If the flame detector is a flame detector,

• With a first group of filter elements which is permeable to electromagnetic radiation in a first wavelength range, and
• A group of filter elements permeable to electromagnetic radiation in a second wavelength range,
• Wherein the first wavelength range is a wavelength range in which both a flame and a source of interference emit a significant amount of electromagnetic radiation, and wherein the second wavelength range is a wavelength in which only the flame emits a significant amount of electromagnetic radiation,

Thus, an alarm is triggered when both those pixel elements were exposed to which a filter element from the first group is assigned, and those pixel elements to which a filter element from the second group is assigned.

The comparison of the image information is preferably carried out with the aid of a corresponding algorithm stored in the evaluation unit. Different comparison modes are conceivable. In a preferred embodiment, it is provided that the comparison of the image information in step c. by subtracting the image information of the pixel elements associated with a filter element that is transparent to the first wavelength range from the image information of the pixel elements associated with a filter element that is transparent to the second wavelength range, or vice versa.

In any case, it is advantageous if in each case the image information within a division of pixel elements are compared with one another. This is particularly advantageous in view of the invention almost identical exposure of the pixel elements of a department, as described above.

In terms of reliable comparability, it can be seen that it is also advantageous if the exposure in step a. for all pixel elements with a constant exposure time. Moreover, it is advantageous in this context if the analog gain is constant for all pixel elements to which a filter element which is permeable for the first or the second wavelength range is constant.

If not only the occurrence of a flame is to be monitored with the aid of the flame detector, but at the same time a video surveillance of the observed area is to take place, it is favorable if the color filter of the flame detector has a third group of filter elements. This third group of filter elements, for example, can be transmissive to radiation in the visible light range. The pixel elements associated with these filter elements can thus provide a black and white image of the observed area. This black and white image can be used for normal video surveillance of the area. In order to ensure a consistent quality of the video signal and to achieve a certain independence from the possibly fluctuating light conditions within the area, it may be advantageous to the analog gain for these pixel elements depending on the variable actual lighting conditions. Thus, it will be appreciated that it is beneficial if the analog gain is variable for all pixel elements associated with a filter element that is transparent to the third wavelength range.

In a further aspect, the invention also relates to a filter array for a CMOS chip. In such a filter array for a CMOS chip, the filter array having a first plurality of filter elements that are transparent to a first wavelength range, and at least one second plurality of filter elements that are transparent to a second wavelength range, wherein the filter elements arranged in a matrix are that on the sides of each filter element always adjoin only filter elements at least one other wavelength range, the invention provides that the first wavelength range is a wavelength range in which both a flame and a source of interference emit a significant amount of electromagnetic radiation and that the second Wavelength range is a wavelength in which only the source of interference emits a significant amount of electromagnetic radiation. As described above, such a filter array can be used as a component in a flame detector according to the invention. However, the use of such filter arrays is by no means limited to video cameras or the like, but also in photo cameras, screens or the like conceivable. With the help of such a filter array is distinguishable in particular, whether some electromagnetic radiation originates from an artificial or natural light source or a flame. For this purpose, it is particularly advantageous if the first wavelength range extends from 900 ± 10 nm to 1000 ± 10 nm, preferably from 920 ± 10 nm to 960 ± 10 nm, very particularly preferably from 940 ± 10 nm to 960 ± 10 nm and / or that the second wavelength range extends from 300 ± 10 nm to 580 ± 10 nm, preferably from 350 ± 10 nm to 490 ± 10 nm, most preferably from 380 ± 10 nm to 450 ± 10 nm.

In a further embodiment, it is also advantageous if the filter array has a third plurality of filter elements that are transparent to visible light, preferably for light of the wavelength of 300 ± 10 nm to 850 ± 10 nm, particularly preferably for light of the wavelength of 380 ± 10 nm to 780 ± 10 nm.

If the filter array has only two groups of different filter elements, then it is favorable if the filter elements are each arranged in sections of four filter elements, each section having at most two filter elements which are permeable to the same wavelength range, the four filter elements of each section in Are arranged in a (2 × 2) matrix, each row and each row of the (2 × 2) matrix each having a filter element that is transparent to the first wavelength range, and a filter element that is transparent to the second wavelength range, having.

On the other hand, if the filter array has more than two groups of different filter elements, it is favorable if the filter elements are arranged in each case in sections of four filter elements, each section having at most two filter elements which are permeable to the same wavelength range, the four filter elements each Division are arranged in the form of a (2 × 2) matrix, each row and each row of the (2 × 2) matrix each having a first filter element and a second filter element, wherein the first filter element either a filter element, which for the first Wavelength range is permeable, or a filter element which is permeable to the second wavelength range, and wherein the second filter element is a filter element which is transparent to the third wavelength range. Overall, special advantages and refinements of the filter array according to the invention are also evident from the above-described description of the flame detector according to the invention, which has such a filter array.

Further features, details and advantages of the invention will become apparent from the wording of the claims, as well as from the following description of embodiments with reference to the drawings.

Show it:

1 a schematic representation of a flame detector according to the invention with a filter array according to the invention

2 a schematic overview of the wavelength ranges in the electromagnetic spectrum, for which various filter elements of the filter array according to the invention can be permeable, as well as the intensity of interference sources and flames in these areas,

3 a schematic representation of a filter array according to the invention

4 a schematic representation of an alternative filter array according to the invention

5 a schematic representation of the sequence of a method according to the invention for flame detection.

The in 1 schematically shown flame detector 10 has a lens 11 , a color filter 20 , a CMOS chip 30 and an evaluation unit 12 , The objective 11 , the color filter 20 and the CMOS chip 30 can be arranged in a (not shown), for example, explosion-proof housing.

The color filter 20 consists of a variety of filter elements 21 . 22 , The filter elements 21 . 22 form several groups, each for radiation in different wavelength ranges 40 . 50 are permeable. A first group consists of filter elements 21 which is permeable to both radiation originating from a source of disturbance S and to radiation originating from a flame F. These filter elements 21 are therefore for radiation in a first wavelength range 40 permeable. A second group consists of filter elements 22 , which is permeable only to radiation originating from a source of interference S. These filter elements 22 are therefore for radiation in a second wavelength range 50 permeable.

One recognizes in 1 further, that the CMOS chip consists of a multitude of pixel elements 31 consists. Every pixel element 31 is exactly one filter element 21 . 22 assigned. The filter element 21 . 22 is in each case between the pixel element 31 and the lens 11 arranged. The one from the lens 11 Captured electromagnetic radiation can only then to the respective pixel element 31 arrive when the associated filter element 21 . 22 is permeable to this radiation. Every pixel element 31 is about a connection 13 with the evaluation unit 12 connected. About this connection 13 receives the evaluation unit 12 Information about whether and to what extent each pixel element 31 is exposed.

Those pixel elements 31 to which a filter elements 21 from the first group, are exposed both by radiation originating from a source of interference S and by radiation originating from a flame F. pixel elements 31 to which a filter element 21 is assigned from the first group, are therefore of radiation in the first wavelength range 40 exposed.

Those pixel elements 31 to which a filter element 22 is assigned from the second group, are exposed only by radiation originating from the source of interference S. pixel elements 31 to which a filter element 22 from the second group, are therefore of radiation in the second wavelength range 50 exposed.

In a preferred embodiment, the wavelength ranges are 40 . 50 in which the filter elements 21 . 22 are permeable, as in the 2 represented diagram selected. The wavelength in nm is plotted on the x-axis of the diagram. On the y-axis is the intensity of a noise source S or a flame F - in this case a butane flame - and the sensitivity E of the CMOS chip 30 represented as a relative value between 0 and 1.

The sensitivity range of the CMOS chip shown by way of example 30 ie the wavelength range of the electromagnetic spectrum in which the pixel elements 31 of the CMOS chip 30 can be basically exposed by electromagnetic radiation, extends from about 380 nm to about 1100 nm. The lower limit 41 a first wavelength range 40 is about 930 nm. The upper limit 42 this wavelength range 40 is about 970 nm. It can be seen that in this area both a source of interference S and a butane flame F emit electromagnetic radiation. A first group of filter elements 21 , for example, the in 1 or the 3 and 4 shown first group of filter elements 21 , is for radiation in this first wavelength range 40 permeable. In particular, this first group of filter elements 21 for radiation in a wavelength range 40 from 940 ± 10 nm to 960 ± 10 nm in which both a noise source S and a flame F emit a significant amount of electromagnetic radiation.

The lower limit 51 a second wavelength range 50 lies, how to get in 2 detects, at about 380 ± 10 nm. The upper limit 52 this second wavelength range 50 is about 450 ± 10 nm. In this second wavelength range 50 The noise source S emits a significant amount of electromagnetic radiation, while the flame F emits no radiation. For radiation in this wavelength range 50 is a second group of filter elements 22 permeable, for example, the in 1 or the 3 and 4 shown second group of filter elements 22 , The second group of filter elements 22 is insofar for radiation in a wavelength range 50 from about 380 ± 10 nm to about 450 ± 10 nm, in which only the source of interference S emits a significant amount of electromagnetic radiation.

A third in 2 exemplary shown wavelength range 60 includes the range of visible light. This area is particularly useful, in addition to distinguishing between a possible flame and a source of interference, a live video image of one using the flame detector 10 to gain control over the monitored area. The lower limit 61 this wavelength range 60 is about 380 ± 10 nm. The upper limit of this wavelength range 60 is about 780 ± 10 nm. Especially in the 4 shown embodiment of a color filter 20 , is a third group of filter elements 23 for this wavelength range 60 permeable.

One recognizes in 2 that the wavelength ranges 40 . 50 . 60 both overlapping and not overlapping each other can be formed.

In the following description of various arrangements of filter elements according to the invention filter arrays (color filter) now denote both the reference numerals 71 . 72 . 73 and 74 as well as the reference numerals 21 . 22 and 23 the filter elements of the color filter 20 , In this case, the reference numerals relate 71 . 72 . 73 . 74 each on the position of the respective filter element 21 . 22 . 23 in the color filter 20 , The reference numerals 21 . 22 and 23 By contrast, they refer to the group from which the respective filter element is selected and therefore to the wavelength range in which the filter element transmits radiation. As a filter element 21 . 71 is therefore a filter element with regard to its arrangement in the filter matrix 71 and with respect to the group from which it is selected is a filter element 21 ie, for example, a filter element 21 that for the first wavelength range 40 is permeable. Purely physically, however, it is one and the same component of the filter.

In a particularly simple embodiment, the color filter 20 (Filter array) only two groups of filter elements 21 . 22 on. These are as in 3 recognizable, arranged as an array in the form of a matrix with rows M and columns N. Four filter elements each 71 . 72 . 73 . 74 form a department 70 , The filter elements 71 . 72 . 73 . 74 a department 70 are either from the first group of filter elements 21 or from the second group of filter elements 22 selected. Every department 70 has two filter elements 71 . 74 from the first group of filter elements 21 and two filter elements 72 . 73 from the second group of filter elements 22 on. The four filter elements 71 . 72 . 73 . 74 are in turn arranged in two rows M and two columns N in such a way that within each row and column always one filter element 71 . 74 that is from the first group of filter elements 21 is selected, and a filter element 72 . 73 that is from the second group of filter elements 22 is selected exists. In a row M adjacent filter elements 71 . 72 or in a column N adjacent filter elements 71 . 73 a department 70 belong therefore always to different groups of filter elements 21 . 22 , This means that the filter elements so adjacent 71 . 72 respectively. 71 . 73 always for radiation in different wavelength ranges 40 . 50 are permeable. Two filter elements each 21 . 71 . 74 are here for the first wavelength range 40 permeable, in which - as in 2 both the flame F and the source of interference S emit electromagnetic radiation. The two other filter elements 22 . 72 . 73 are for the second wavelength range 50 permeable, in which - as well as in 2 shown - only the source of interference S emits radiation. In every department 70 are therefore two filter elements 21 . 71 . 74 present, with the help of the downstream pixel elements 31 a radiation typical for a flame F is detectable. Furthermore, in each case two filter elements 21 . 71 . 74 present, with the help of the downstream pixel elements 31 It is distinguishable whether this detected radiation actually comes from a flame F or from a source of interference S.

In another, in 4 illustrated, embodiment of a color filter according to the invention 20 (Filter array) the array comprises three different groups of filter elements 21 . 22 . 23 , Again, the filter elements selected from the different groups are 21 . 22 . 23 in departments 70 arranged, each with four filter elements 71 . 72 . 73 . 74 exhibit. In each department is at least one of the filter elements 71 . 72 . 73 . 74 a filter element 21 selected from the first group for the first wavelength range 40 is permeable. Next is at least one of the filter elements 71 . 72 . 73 . 74 a filter element 22 selected from the second group and for the second wavelength range 50 is permeable. It can be seen that in each row M and each column N of this arrangement of filter elements 71 . 72 . 73 . 74 respectively. 21 . 22 . 23 at least one filter element 23 . 72 . 73 which is selected from the third group and for a third wavelength range 60 is permeable. This third wavelength range 60 can be like in 2 shown to include radiation in the visible light range, so that these filter elements 23 . 72 . 73 can be used to obtain a live video image, while at the same time the other filter elements 21 . 22 . 71 . 74 every department 70 for detecting a flame F and distinguishing the flame F of a source of interference S can be used.

Both with a flame detector 10 who has a color filter 20 according to the in 3 has shown embodiment variant, as well as a flame detector 10 who has a color filter 20 according to the in 4 having shown variant, can, with the aid of in 5 shown method, whether one of the lens 11 captured electromagnetic signal from a flame F or a source of interference S comes. In such a method, in a first step a. the CMOS chip 30 with the lens 11 exposed electromagnetic radiation. The exposure takes place with a predetermined exposure time. For each pixel element 31 In addition, the analog gain is specified for each exposure. Is the color filter 20 a filter array whose filter elements 21 . 22 as in 3 shown, are selected from two groups, so is the Analog gain at each exposure for all pixel elements 31 constant. Is the color filter 20 however, a filter array, with filter elements 21 . 22 . 23 that like in 4 shown to come from three different groups, with a group of filter elements 23 is used to obtain a live video image, so is the analog gain for the pixel elements 31 that the filter elements 21 . 22 associated with the first and second groups, constant at each exposure. For the pixel elements used to obtain the live video image 31 that the filter elements 23 are assigned to the third group, the analog gain can be variable.

After the exposure is in a next step b by the evaluation unit 12 the information captures what quality and what quantity of electromagnetic radiation from the pixel elements 31 was measured. It will be within each department 70 at least that information is simultaneously detected, that of those pixel elements 31 delivered, which are arranged in the same column. This type of reading, in a more general understanding of the term, also serves as simultaneous capture of the image information of all pixel elements 31 designated.

Subsequently, according to step c of the method, that of each adjacent pixel elements 31 obtained information compared with each other. The comparison of the data is carried out in a preferred embodiment by subtracting the information to be compared with each other. Alternatively, the comparison of the data can also be done by thresholding. However, other algorithmic methods are also conceivable. On the basis of this comparison, question d can be answered as to whether the radiation originates from a flame F or an interference source S. Is the flame detector 10 while a flame detector 10 in which the filter elements 21 the first group for radiation in a first wavelength range 40 are permeable, in which both the flame F and the source of interference S emits radiation, and in which the filter elements 22 the second group for radiation in a second wavelength range 50 permeable, in which only the interference source S emits radiation, the answer to the question d is as follows: Deliver only the pixel elements 31 to which a filter element 21 The first group is assigned a signal but not the pixel elements 31 to which a filter element 22 is associated with the second group, then the detected radiation comes from a flame F. As a result, the process continues with step d.1 and an alarm is triggered.

On the other hand, they deliver both the pixel elements 31 to which a filter element 21 the first group is assigned, as well as the pixel elements 31 to which a filter element 22 is associated with the second group, a signal, then the detected radiation comes from a source of interference S. As a result, the process continues with step d.2 and no alarm is triggered.

The invention is not limited to one of the above-described embodiments, but can be modified in many ways.

So can the filter elements 21 be transparent in a variant embodiment for a wavelength range in which both the source of interference S and the flame F emits a significant amount of electromagnetic radiation, while the filter elements 22 are transmissive to a wavelength range in which only the flame F emits a significant amount of electromagnetic radiation.

The triggering of an alarm according to step d.1 of the method according to the invention then takes place in a flame detector having such an alternative filter array, in the case when both the pixel elements 31 to which a filter element 21 the first group is assigned, as well as the pixel elements 31 to which a filter element 22 the second group is assigned to provide a signal.

It is also conceivable that the color filter 20 more than three groups of filter elements 21 . 22 . 23 having. It is also a complementary training of different wavelength ranges 40 . 50 . 60 imaginable.

All of the claims, the description and the drawings resulting features and advantages, including design details, spatial arrangements and method steps may be essential to the invention both in itself and in a variety of combinations.

LIST OF REFERENCE NUMBERS

F

flame

S

interference source

M

line

N

column

e

Sensitivity CMOS sensor

10

flame detector

11

lens

12

evaluation

13

connection

20

Color filter / filter array

21

filter element

22

filter element

23

filter element

30

CMOS chip

31

pixel element

40

Wavelength range

41

lower limit

42

upper limit

50

Wavelength range

51

lower limit

52

upper limit

60

Wavelength range

61

lower limit

62

upper limit

70

Department

71

filter element

72

filter element

73

filter element

74

filter element

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 2009/0315722 A1 [0004]

Claims (20)

Flame detector ( 10 ) with at least one lens ( 11 ), a CMOS chip ( 30 ) and at least one color filter ( 20 ), where the CMOS chip ( 30 ) with an evaluation unit ( 12 ) and a plurality of pixel elements ( 31 ), wherein the color filter ( 20 ) between the lens ( 11 ) and the CMOS chip ( 30 ) and an array of a plurality of filter elements ( 21 . 22 . 23 ), each filter element ( 21 . 22 . 23 ) at least one pixel element ( 31 ) of the CMOS chip ( 30 ) is assigned such that between the pixel element ( 31 ) and the lens ( 11 ) exactly one filter element ( 21 . 22 ), and wherein the plurality of filter elements ( 21 . 22 . 23 ) a first group of filter elements ( 21 ), which for a first wavelength range ( 40 ) are permeable, wherein the plurality of filter elements ( 21 . 22 . 23 ) at least a second group of filter elements ( 22 ), which for a second wavelength range ( 50 ) are permeable, and wherein the filter elements ( 21 . 22 ) of the array are arranged in matrix form such that adjacent filter elements ( 21 . 22 ) in each case for different wavelength ranges ( 40 . 50 ) are permeable, characterized in that the first wavelength range ( 40 ) a wavelength range ( 40 ) in which both a flame (F) and a source of interference (S) emit a significant amount of electromagnetic radiation and that the second wavelength range ( 50 ) a wavelength range ( 50 ) in which only the source of interference (S) or only the flame (F) emits a significant amount of electromagnetic radiation. Flame detector according to claim 1, characterized in that the first wavelength range ( 40 ) extends from 900 ± 10 nm to 1000 ± 10 nm, preferably from 920 ± 10 nm to 960 ± 10 nm, most preferably from 940 ± 10 nm to 960 ± 10 nm. Flame detector according to one of claims 1 or 2, characterized in that the second wavelength range ( 50 ) extends from 300 ± 10 nm to 580 ± 10 nm, preferably from 350 ± 10 nm to 490 ± 10 nm, most preferably from 380 ± 10 nm to 450 ± 10 nm. Flame detector according to one of the preceding claims, characterized in that the filter elements ( 21 . 22 ) in each case in departments ( 70 ) of four filter elements ( 71 . 72 . 73 . 74 ), each department ( 70 ) highest two filter elements ( 21 . 22 ), which for the same wavelength range ( 40 . 50 ) are permeable. Flame detector according to one of the preceding claims, characterized in that the four filter elements ( 71 . 72 . 73 . 74 ) of each department ( 70 ) are arranged in the form of a (2 × 2) matrix, each row and each row of the (2 × 2) matrix each having a filter element ( 21 . 71 . 74 ), which for the first wavelength range ( 40 ) is permeable, and a filter element ( 22 . 72 . 73 ), which for the second wavelength range ( 50 ) is permeable. Flame detector according to one of the preceding claims, characterized in that the plurality of filter elements ( 21 . 22 . 23 ) a third group of filter elements ( 23 ), which for a third wavelength range ( 60 ) are permeable. Flame detector according to one of the preceding claims, characterized in that the third wavelength range ( 60 ) includes the range of visible light. Flame detector according to one of the preceding claims, characterized in that the filter elements ( 21 . 22 . 23 ) in each case in sections of four filter elements ( 71 . 72 . 73 . 74 ) are arranged, each department each having a filter element ( 21 . 71 ), which for the first wavelength range ( 40 ) is permeable, a filter element ( 22 . 74 ), which for the second wavelength range ( 50 ) is permeable, and two filter elements ( 23 . 72 . 73 ) for the third wavelength range ( 60 ) are permeable. Flame detector according to one of the preceding claims, characterized in that the four filter elements ( 71 . 72 . 73 . 74 ) of each department ( 70 ) are arranged in the form of a (2 × 2) matrix, each row and each row of the (2 × 2) matrix each having a first filter element ( 21 . 22 . 71 . 74 ) and a second filter element ( 23 . 72 . 73 ), wherein the first filter element ( 21 . 22 . 71 . 74 ) either a filter element ( 21 . 71 ), which for the first wavelength range ( 40 ) is permeable, or a filter element ( 22 . 74 ), which for the second wavelength range ( 50 ) is permeable, and wherein the second filter element ( 23 . 72 . 73 ) a filter element ( 23 ), that for the third wavelength range ( 60 ) is permeable. A method of flame detection using a flame detector according to any one of claims 1 to 9, said method comprising the steps of: a. Exposure of pixel elements ( 31 ) of the CMOS chip ( 30 ) with a given exposure time and analog gain, b. Capturing the image information of all pixel elements ( 31 ) of the CMOS chip with the aid of the evaluation unit ( 12 c. Comparison of the image information of those pixel elements ( 31 ), to which a filter element ( 21 ) assigned to the first wavelength range ( 40 ) is transparent, with the image information of those pixel elements ( 31 ), to which a filter element ( 22 ) assigned to the second wavelength range ( 50 ) is permeable, with the aid of the evaluation unit ( 12 ). A method according to claim 10, characterized in that the comparison of the image information in step c. by subtracting the image information of the pixel elements ( 31 ), to which a filter element ( 21 ) associated with the first wavelength range ( 40 ) is permeable to the image information of the pixel elements ( 31 ), to which a filter element ( 22 ) assigned to the second wavelength range ( 50 ) is permeable, or vice versa. Method according to one of the preceding claims, characterized in that in each case the image information within a department ( 70 ) of pixel elements ( 31 ) are compared. Method according to one of the preceding claims, characterized in that the exposure in step a. for all pixel elements ( 31 ) with a constant exposure time. Method according to one of the preceding claims, characterized in that the analog gain for all pixel elements ( 31 ), to which a filter element ( 21 . 22 ) for the first or the second wavelength range ( 40 . 50 ) is permeable, constant. Method according to one of the preceding claims, characterized in that the analog gain for all pixel elements ( 31 ), to which a filter element ( 23 ) associated with the third wavelength range ( 60 ) is permeable. Filter array ( 20 ) for a CMOS chip ( 30 ) where the filter array ( 20 ) a first plurality of filter elements ( 21 ) for a first wavelength range ( 40 ) are permeable, and at least one second plurality of filter elements ( 22 ), which for a second wavelength range ( 50 ) are permeable, the filter elements ( 21 . 22 ) of the array are arranged in matrix form such that on the sides of each filter element ( 21 . 22 ) always only filter elements ( 21 . 22 ) at least one respective other wavelength range ( 40 . 50 ), characterized in that the first wavelength range ( 40 ) is a wavelength range in which both a flame (F) and a source of interference ( 5 ) emit a significant amount of electromagnetic radiation and that the second wavelength range ( 50 ) is a wavelength in which only the source of interference ( 5 ) or only the flame (F) emits a significant amount of electromagnetic radiation. Filter array according to claim 16, characterized in that the first wavelength range ( 40 ) from 900 ± 10 nm to 1000 ± 10 nm, preferably from 920 ± 10 nm to 960 ± 10 nm, very particularly preferably from 940 ± 10 nm to 960 ± 10 nm and / or that the second wavelength range ( 50 ) extends from 300 ± 10 nm to 580 ± 10 nm, preferably from 350 ± 10 nm to 490 ± 10 nm, most preferably from 380 ± 10 nm to 450 ± 10 nm. Filter array according to one of the preceding claims, characterized in that the filter array ( 20 ) a third plurality of filter elements ( 23 ) which are transparent to visible light, preferably for light of the wavelength of 300 ± 10 nm to 850 ± 10 nm, more preferably for light of the wavelength of 380 ± 10 nm to 780 ± 10 nm. Filter array according to one of the preceding claims, characterized in that the filter elements ( 21 . 22 ) in each case in departments ( 70 ) of four filter elements ( 71 . 72 . 73 . 74 ), each department ( 70 ) highest two filter elements ( 71 . 72 . 73 . 74 . 21 . 22 ), which for the same wavelength range ( 40 . 50 ) are permeable, the four filter elements ( 71 . 72 . 73 . 74 ) of each department ( 70 ) are arranged in the form of a (2 × 2) matrix, each row and each row of the (2 × 2) matrix each having a filter element ( 21 ), which for the first wavelength range ( 40 ) is permeable, and a filter element ( 22 ), which for the second wavelength range ( 50 ) is permeable. Filter array according to one of the preceding claims, characterized in that the filter elements ( 20 ) in each case in departments ( 70 ) of four filter elements ( 71 . 72 . 73 . 74 ), each department ( 70 ) highest two filter elements ( 71 . 72 . 73 . 74 . 21 . 22 . 23 ), which for the same wavelength range ( 40 . 50 . 60 ) are permeable, the four filter elements ( 71 . 72 . 73 . 74 ) of each department ( 70 ) are arranged in the form of a (2 × 2) matrix, each row and each row of the (2 × 2) matrix each having a first filter element ( 21 . 22 ) and a second filter element ( 23 ), wherein the first filter element ( 21 . 22 ) either a filter element ( 21 ), which for the first wavelength range ( 40 ) is permeable, or a filter element ( 22 ), which for the second wavelength range ( 50 ) is permeable, and wherein the second filter element ( 23 ) a filter element ( 23 ), that for the third wavelength range ( 60 ) is permeable.

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