DE102018210264A1 - Process for the contact-free determination of a temperature distribution as well as infrared measuring system - Google Patents

Abstract

The proposed method for the contact-free determination of a temperature distribution of a surface (22) is based on an infrared measuring system (10, 10a), the infrared measuring system (10, 10a) having at least one infrared detector array (36) with a plurality of measuring pixels ( 62), the measurement pixels (62) being sensitive to infrared radiation and each providing a measurement signal for determining a temperature measurement value T which is dependent on an intensity of the incident infrared radiation. According to the invention, a temperature measurement value T ^{i of} at least one measurement pixel i (62) of the plurality of measurement pixels (62) is corrected by a temperature measurement value component ΔT ⁱ caused by scattered radiation, which is calculated from temperature measurement values T ^j of measurement pixels j (62) to be taken into account in the correction ,
An infrared measuring system (10, 10a) operated with the method is also proposed.

Description

The invention relates to a method for the contact-free determination of a temperature distribution of a surface and a corresponding infrared measurement system.

State of the art

Devices and methods for the contact-free determination of a temperature of a surface, in particular for the contact-free determination of a temperature distribution of a surface, are known in the prior art and are used in a variety of ways, for example for checking the safety of electrical circuits, for troubleshooting in mechanical processes or for identifying inadequate thermal insulation in the context of Thermal and / or cold insulation. Infrared measuring systems have the advantage of contactless and fast measuring compared to conventional temperature measuring devices and can be used in particular if areas to be measured are difficult or impossible to access. The temperature measurement using an infrared-sensitive thermometer is based on the detection of thermal radiation, i.e. Infrared radiation, in particular in a wavelength range between 3 µm and 50 µm, which is emitted by each object with different intensity depending on its temperature, in particular its surface temperature (note: in this document, the terms "infrared radiation" and "heat radiation" are to be understood as synonymous ). A surface temperature of the emitting body can be determined from an intensity of the emitted thermal radiation measured by means of the infrared measuring system.

Infrared measuring systems in the form of so-called thermal imaging cameras typically have an infrared-sensitive image sensor, a lens system and a screen and, similar to a camera working in the visual spectral range, allow an object to be examined in the infrared range of the radiation spectrum and displayed on the screen as a two-dimensional, color-coded image of the Issue item. DE 102016218295 A1 and DE 102016211829 A1 describe devices and methods of these infrared measuring systems.

Infrared measuring systems each have a specific field of view, from which infrared radiation is imaged through a lens onto an infrared detector array of the infrared measuring system. Due to incomplete absorption of the infrared radiation on the image sensor, part of the infrared radiation is reflected several times within the housing. This effect can be observed for infrared radiation regardless of the angle of incidence from which the infrared radiation falls on the infrared detector array. Due to this multiple reflection, a certain measuring pixel of the infrared detector array not only absorbs infrared radiation, which is imaged directly by the lens onto this measuring pixel, but also scattered radiation. Consequently, the temperature of each measurement pixel determined by the infrared measurement system also depends on scattered radiation, so that there is a kind of “crosstalk” between measurement pixels. It is known from the prior art to coat any optical components such as lenses and infrared detector arrays of the infrared measuring system with an antireflection layer in order to reduce scattered radiation. It is also common to blacken the inside surfaces of the housing.

Disclosure of the invention

The proposed method for the contact-free determination of a temperature distribution of a surface is based on an infrared measuring system with at least one infrared detector array, which has a plurality of measuring pixels, the measuring pixels being sensitive to infrared radiation and in each case a measuring signal for determining an incident intensity Provide infrared radiation-dependent temperature measurement value T.

The infrared measuring system, in particular the hand-held thermal imaging camera, is set up to detect infrared radiation emitted from a measuring area on the surface, in particular without contact. The infrared measuring system is intended to output information relating to a temperature of the surface. This information can advantageously be implemented as one or more temperature specifications or as a temperature distribution, particularly advantageously as a thermal image composed of a plurality of temperature specifications determined in a spatially resolved manner.

The “measurement area” is understood to mean a geometrical, limited area which comprises a quantity of particles or areas of the object, the infrared radiation of which leaves the object in the direction of the infrared measurement system and is at least partially detected by it. Depending on the material of the object, in particular depending on the transparency of the object for infrared radiation, particles or areas that are located at different distances in the object can be detected by the infrared measuring system. In particular, in addition to a solid, “object” can also be understood to mean a fluid, in particular a liquid and a gas, the temperature of which can be measured in an analogous manner. To simplify the following description, “measuring range” is used in particular to denote the area on an object surface that essentially results from the intersection between a measuring volume. the volume from which the device according to the invention detects infrared radiation - and gives the surface of the object to be examined. Depending on the material properties of the object, this measuring range can also include infrared radiation from deeper layers of the object.

The infrared measuring system, in particular the hand-held thermal imaging camera, has at least one infrared detector array and an evaluation device. Furthermore, in one embodiment of the infrared measuring system, the infrared measuring system can have an optical system, in particular an imaging optical system. Optics are provided for projecting or projecting infrared radiation emitted from the measuring range in the infrared spectrum, preferably in the middle infrared spectrum in the wavelength range between 3 µm and 50 µm, onto a surface of the infrared detector array of the infrared measuring system arranged behind the optics from the point of view of the object focus. For this purpose, an optical system can have optical components which direct, conduct, concentrate and / or otherwise influence the spatial distribution, for example lenses, mirrors or the like.

In the following, “intended” is to be understood specifically as “programmed”, “designed”, “designed” and / or “equipped”. The fact that an object is “provided” for a specific function should in particular be understood to mean that the object fulfills and / or executes this specific function in at least one application and / or operating state or is designed to fulfill the function.

The infrared detector array is used to detect infrared radiation emitted from the measurement area and directed onto the surface of the infrared detector array. The infrared detector array has at least one detector array substrate and a plurality of measurement pixels. In one embodiment of the infrared measuring system, the infrared detector array is implemented, for example, as a silicon sensor chip which has silicon as the detector array substrate.

The measurement pixels are each arranged on a surface of the detector array substrate facing the object to be examined. The measurement pixels are sensitive to infrared radiation incident from the measurement area, each measurement pixel representing an element sensitive to infrared radiation. The measurement pixels are intended to detect radiation from the infrared range, in particular the middle infrared range in the wavelength range between 3 μm and 50 μm, and to convert it into a measurement signal, in particular an electrical measurement signal. Examples of elements sensitive to infrared radiation include photodiodes, bolometers, pyroelectric sensors, P / N diodes, PIN diodes, avalanche photo diodes (APD), (modulated) CCD chips and CMOS pixels, but others can also be useful to a person skilled in the art appearing, for example based on silicon sensors, indium gallium arsenide sensors, lead sulfide sensors, indium antimony sensors, cadmium mercury telluride sensors, gallium arsenide quantum well sensors, cadmium mercury telluride sensors or the like Infrared radiation sensitive elements can be understood. In one embodiment of the infrared measuring system, the measuring pixels are implemented as P / N diodes or thermodiodes. These measurement pixels each heat up as a result of the irradiation of infrared radiation, an electrical voltage of the measurement pixel changing due to the heating compared to a current flowing through the measurement pixel. As a result, the voltage drop across the respective measurement pixel changes. By measuring the measurement pixel voltage and / or the measurement pixel current, a measurement signal can be provided in this way that correlates with the radiated heat output of the infrared radiation on the respective measurement pixel. Thus, the measurement pixels each provide a measurement signal that is dependent on an intensity of the incident infrared radiation for determining a temperature measurement value T that is also dependent on the intensity of the incident infrared radiation. Each of the plurality of measurement pixels can be connected to the evaluation device of the infrared measurement system directly or indirectly via further intermediate components. In particular, an indirect signal-technical connection of the measurement pixels to the evaluation device can also be implemented via switching elements, for example multiplexers or other selection circuits, which are designed to selectively transmit measurement signals from a plurality of measurement pixels. In this way it can be achieved in particular that measurement signals of individual measurement pixels or a group of measurement pixels can be forwarded to the evaluation device independently of measurement signals of other measurement pixels and can be evaluated by the latter. In particular, it should be pointed out that the respective measurement signals of each measurement pixel are or can be provided independently of one another. Each measurement signal provided by a measurement pixel can or is passed on to the evaluation device of the infrared measurement system for determining a temperature measurement value T, from which it can be evaluated individually and / or in combination with other measurement signals of other measurement pixels. A plurality of temperature measurement values T can thus be determined using an (arbitrary) plurality of measurement pixels of the infrared detector array. In particular, image information for a thermal image can be determined in this way from infrared radiation emitted in each case by the object to be examined into a solid angle of the measuring range.

The evaluation device for receiving and evaluating measurement signals of the infrared detector array is to be understood as a device that has at least one information input for accepting measurement signals, an information processing unit for processing, in particular evaluating the accepted measurement signals, and an information output for forwarding the processed and / or evaluated Measurement signals, in particular the temperature measured values T, has. The evaluation device advantageously has components which comprise at least one processor, a memory and an operating program with evaluation and calculation routines. In particular, the electronic components of the evaluation device can be arranged on a circuit board (printed circuit board), preferably on a common circuit board with a control device of the infrared measuring system for controlling the infrared measuring system, and particularly preferably in the form of a microcontroller. Furthermore, the control device and the evaluation device can also be designed as a single component. The evaluation device is provided to receive and evaluate measurement signals provided by the infrared detector array, in particular from the measurement pixels of the infrared detector array that can be connected to the evaluation device by signaling technology, and to evaluate, based on measurement signals, at least a plurality of measurement pixels of the infrared detector array Temperature of the measuring range. In particular, the evaluation device is provided to carry out an evaluation of one or more temperature measurement values T based on measurement signals of at least one (any) plurality of measurement pixels of the infrared detector array. The evaluated temperature measured values T can be provided by the evaluation device for further processing and / or for output, in particular for output to a user of the infrared measuring system by means of an output device and / or for output to an external device by means of a data communication interface.

In one embodiment, the plurality of measurement pixels are arranged in a matrix-like manner on the surface of the detector array substrate. The number of measurement pixels is, for example, 80 × 80 pixels, preferably 360 × 240 pixels, particularly preferably 640 × 480 pixels. Any other values are conceivable. The number of measurement pixels defines the resolution of the infrared measurement system, i.e. in particular the resolution of a thermal image of an object to be examined, measured by means of the infrared measuring system.

Furthermore, the infrared measuring system has at least one energy supply device, for example a mains-independent battery. In one embodiment, the infrared measuring system can also have a data communication interface for transmitting data to an external data device or from an external data device.

The infrared measuring system described serves as the basis for the method described below for the contact-free determination of a temperature distribution of a surface. Using the approaches explained at the beginning for suppressing scattered radiation - application of anti-reflective layers and / or blackening of device components - scattered radiation cannot be completely avoided. Although typically a calibration of the infrared detector array is carried out when manufacturing an infrared measuring system, a measurement result, for example a thermal image, depends directly on the size (or distance) of the surface or objects to be measured due to the influence of scattered radiation. If objects with the same temperature but different sizes are measured with an infrared measuring system, slightly different temperature values of the objects are output, since in both measuring scenarios different amounts of scattered radiation fall on each individual measuring pixel.

According to the invention, a temperature measurement value T ^{i of} at least one measurement pixel i of the plurality of measurement pixels is corrected by a temperature measurement value component ΔT ⁱ caused by scattered radiation, which is calculated from temperature measurement values T ^j of measurement pixels j to be taken into account in the correction. In one embodiment of the method, the temperature measurement values T ^{i of} all measurement pixels i of the infrared detector array are corrected by a temperature measurement value component ΔT ⁱ caused by scattered radiation, the respective temperature measurement value component ΔT ⁱ each from temperature measurement values T ^j of measurement pixels to be taken into account in the correction j is calculated. The evaluation device is particularly intended to carry out the method according to the invention for the contact-free determination of a temperature distribution of a surface.

“Temperature measurement value T ^{i of} at least one measurement pixel i of the plurality of measurement pixels” is to be understood in particular to mean that measurement signals are initially provided for a measurement pixel i (in principle any) and passed on to the evaluation device. The evaluation device evaluates a pixel-dependent temperature measurement value T ⁱ for the corresponding measurement pixel ⁱ . “Pixel-dependent” means in particular that the respective temperature measured value T ⁱ with index “i” is uniquely assigned or can be assigned to a specific pixel “i”. Corresponding temperature measured values T ⁱ can, in one embodiment of the method, be the temperature of the surface to be examined characteristic values, for example in degrees Celsius (° C) or Kelvin (K) or the like, can be realized. A correspondingly determined temperature measurement value T ⁱ is composed of a temperature measurement value component which is based on infrared radiation emitted directly by the emitting object - and which reaches the measurement pixel i without scattering, and a temperature measurement value component ΔT ⁱ which is based on Scattered radiation can be returned.

The correction of the temperature measurement value T ^{i of} at least one measurement pixel i of the plurality of measurement pixels by such a temperature measurement value component ΔT ⁱ caused by scattered radiation is calculated according to the invention using temperature measurement values T ^j of measurement pixels j to be taken into account in the correction. This teaching is based on the knowledge that a distribution of scattered radiation can be simulated and / or calculated approximately by determining temperature measurement values T ^j of measurement pixels j to be taken into account in the correction. In particular, it was recognized that the scattered radiation incident on a measurement pixel i typically originates from a certain angular range, which can be characterized by a reception cone, in the tip of which the measurement pixel i lies. The scattered radiation emitted in this receiving cone can be simulated and / or calculated according to the invention by determining temperature measurement values T ^j of measurement pixels j to be taken into account in the correction. The temperature measurement value component ΔT ^{i is} calculated on the basis of temperature measurement values T ^j , which are determined in particular for adjacent measurement pixels j of the measurement pixel i to be taken into account.

It should be pointed out that “measurement pixels j to be taken into account” can in principle be arbitrarily chosen, the number of measurement pixels to be taken into account does not necessarily have to correspond to the totality of the measurement pixels available. Therefore, the amount of pixels evaluated can be smaller than the total amount of measurement pixels available on the infrared detector array. In one embodiment of the method, the measurement pixels j to be taken into account in the correction are selected as the (entire) plurality of measurement pixels of the infrared detector array. A proportion of scattered radiation which is generated or caused by the measurement pixel i itself is taken into account. A particularly precise calculation of the temperature measurement component ΔT ⁱ is thus possible. In an alternative embodiment of the method, the measurement pixels j to be taken into account in the correction are selected as the plurality of measurement pixels of the infrared detector array, but with the exception of the measurement pixel i itself.

In another alternative embodiment of the method, the measurement pixels j to be taken into account in the correction are selected in accordance with a symmetrical arrangement of the measurement pixels j on the infrared detector array. A “symmetrical arrangement” is to be understood in particular to mean that the measurement pixels j to be taken into account are arranged in a symmetrical, in particular point and / or mirror symmetry, manner with respect to the measurement pixel i. In particular, it can be provided, for example, that measurement pixels j, each of which have an identical geometric distance d ^ij from measurement pixel i and are therefore present in essentially ring-shaped structures, are taken into account for the calculation in a combined or averaged manner (ie measurement pixels j that are in a circular ring with a determined Distance d ^ij to the measuring pixel i are identical, contribute to the scattered radiation on the measuring pixel i). As an alternative or in addition, measurement pixels j of a restricted angular range - for example of 90 ° or 45 ° or the like - of an otherwise essentially rotationally symmetrical arrangement can be taken into account for the calculation, the symmetrical components that are not calculated being recorded multiplicatively during the calculation multiplication by "4" if a 90 ° segment is taken into account. In this way, symmetry considerations can be included which reduce the computing effort of the evaluation device required to calculate the temperature measured value component ΔT ⁱ . Consequently, a particularly simple and quick calculation can be implemented in this way, and furthermore, a requirement for the evaluation device with regard to its computing power can be kept particularly low and costs can thus be saved.

Correcting a temperature measurement value T ^{i of} a measurement pixel i by a pixel-associated temperature measurement value component ΔT ⁱ denotes a correction which is or can be applied for each measurement pixel i of the plurality of measurement pixels for which temperature measurement values T ^{i have been} determined. This can be done particularly characterized in an embodiment of the method that is added to a to a respective measuring pixels i detected temperature measurement value T ⁱ a for this measurement pixel i calculated temperature reading component .DELTA.T ^i, ie T ⁱ _corr = T ⁱ + .DELTA.T ^i. In this way, a temperature measurement value (namely T ⁱ _corr ) which is independent of scatter radiation can advantageously be obtained. The present invention thus improves the accuracy of the infrared measuring system and can also better display an output thermal image due to the improved temperature information.

berechnet, wobei C ein konstanter Korrekturfaktor ist und n die Anzahl der zu berücksichtigenden Messpixel j. Insbesondere kann auf diese Weise ein besonders einfaches Berechnungsverfahren angegeben werden, bei dem unter Verwendung der Temperaturmesswerte T^j von zu berücksichtigenden Messpixeln j eine durchschnittliche Temperatur der Temperaturverteilung ermittelt werden, mit der anschließend die vorhandene Streustrahlung für jedes zu korrigierende Messpixel i abgeschätzt wird. Dabei wird ein Temperaturmesswert Tⁱ eines Messpixels i unter Berücksichtigung des ermittelten Durchschnittswerts wie folgt korrigiert:

• - Weisen berücksichtigte Messpixel j einen gemittelten Temperaturmesswert auf, der dem Temperaturmesswert Tⁱ entspricht, so wird im Wesentlichen keine Korrektur durchgeführt, da die Temperaturmesswert-Komponente ΔTⁱ klein ist (im Wesentlichen gleich Null ist);
• - Weisen berücksichtigte Messpixel j einen gemittelten Temperaturmesswert auf, der kleiner ist als der Temperaturmesswert Tⁱ, so wird eine positive Temperaturmesswert-Komponente ΔTⁱ erhalten und der von Streustrahlung unabhängige Temperaturmesswert Tⁱ _corr wird größer als Tⁱ;
• - Weisen berücksichtigte Messpixel j einen gemittelten Temperaturmesswert auf, der größer ist als der Temperaturmesswert Tⁱ, so wird eine negative Temperaturmesswert-Komponente ΔTⁱ erhalten und der von Streustrahlung unabhängige Temperaturmesswert Tⁱ _corr wird kleiner als Tⁱ.

In one embodiment of the method, the temperature measured value component .DELTA.T ⁱ via the relationship $\mathrm{\Delta }{T}^i=\left(T^i-\left({\displaystyle {\Sigma }_{j=1}^n{T}^j}\right)\text{/}n\right)\cdot C$

calculated, where C is a constant correction factor and n is the number of measurement pixels to be considered j. In particular, a particularly simple calculation method can be specified in this way, in which an average temperature of the temperature distribution is determined using the temperature measurement values T ^j of measurement pixels j to be taken into account, with which the existing scattered radiation is then estimated for each measurement pixel i to be corrected. A temperature measurement value T ^{i of} a measurement pixel i is corrected as follows, taking into account the determined average value:

• - If the measured pixels j have an averaged temperature measured value that corresponds to the temperature measured value T ⁱ , then essentially no correction is carried out, since the temperature measured value component ΔT ^{i is} small (essentially equal to zero);
• - If measured pixels j have an averaged temperature measurement value that is smaller than the temperature measurement value T ⁱ , a positive temperature measurement value component ΔT ^{i is} obtained and the temperature measurement _value T ⁱ _corr , which is independent of scattered radiation, becomes greater than T ⁱ ;
• - If measured pixels j have an averaged temperature measured value that is greater than the temperature measured value T ⁱ , a negative temperature measured value component ΔT ^{i is} obtained and the temperature measured _value T ⁱ _corr , which is independent of scattered radiation, becomes smaller than T ⁱ .

berechnet werden, wobei C^ij jeweils ein von einem zu berücksichtigenden Messpixel j abhängiger, insbesondere vom Abstand d^ij abhängiger, Korrekturfaktor ist. Derart kann eine von einem jeweiligen, insbesondere benachbarten, Messpixel j auf ein jeweiliges Messpixel i einfallende Streustrahlung gezielt berechnet und somit bei der Korrektur berücksichtigt werden.In one embodiment of the method, the temperature measurement value component ΔT ⁱ is calculated from temperature measurement values T ^j of measurement pixels j to be taken into account in the correction and their distance d ^{ij from} the measurement pixel i. In this way, the temperature measured value component ΔT ⁱ can be determined much more precisely. In an exemplary embodiment of the method, the temperature measured value component ΔT ^{i can be} related $\mathrm{\Delta }{T}^i={\displaystyle {\Sigma }_{j=1}^n\left(T^i-T^j\right)\cdot C^{ij}}$

are calculated, where C ^{ij is in} each case a correction factor dependent on a measurement pixel j to be taken into account, in particular dependent on the distance d ^ij . In this way, a scattered radiation incident from a respective, in particular adjacent, measurement pixel j onto a respective measurement pixel i can be specifically calculated and thus taken into account in the correction.

In one embodiment of the method, the correction factor C ^{ij is determined} from an assignment stored internally in the device, which specifies for each measurement pixel j to be taken into account a proportion of scattered radiation which acts on the measurement pixel j from a measurement pixel i. The assignment therefore specifies from which directions - ie from which neighboring measurement pixels j - in principle how much scattered radiation is received on a measurement pixel i. The stored assignment can be implemented, for example, in the form of a table, a function, a matrix or the like. In particular, this assignment is determined during a factory calibration of the infrared measuring system and stored, in particular stored, in the infrared measuring system. In particular, the evaluation device of the infrared measurement system has the assignment for each measurement pixel combination i, j (ie C ^ij for all i, j) of the infrared detector array. These can advantageously be retrievable from a memory of the evaluation device for each measurement pixel i, j of the infrared detector array, with an unambiguous assignment of scattered radiation components to the corresponding measurement pixel combinations i, j being ensured. In one embodiment of the infrared measuring system, the assignment is stored in the form of a table.

For example, a method for determining a calibration function or an assignment of an infrared measurement system can be specified, in which at least one temperature measurement value T ⁱ of a temperature distribution of a first surface of known temperature is determined by means of at least one measurement pixel i by means of the infrared measurement system in a first method step, and in further method steps, at least further temperature measured values T ⁱ from a temperature distribution of at least one further, reduced-area surface of the same known temperature, in particular with the interposition of an aperture partially covering the first surface, are determined by means of the at least one measurement pixel i. In this way, a large surface of known temperature is placed in front of the infrared measuring system. This thermal source (or sink) can then be at least partially covered by an aperture. With increasing aperture, that is, with increasing "visible" surface is of, increasing by means of a measurement pixel i calculated temperature value T ⁱ as the additionally received scattered radiation is also increased with increasing aperture. A dependency arises which saturates with increasing aperture, ie if the aperture is opened further, the temperature value T i determined by means of the measurement pixel ⁱ does not increase any further. Subsequently, in a further method step, the temperature measurement values determined by the measurement pixel i are plotted depending on the size of the surface (or equivalently depending on the aperture opening). With the exception of a scaling factor, this application also corresponds to an application as a function of the size of the light spot on the infrared detector array, since the object that is getting smaller (getting smaller Aperture) emitted and infrared radiation incident on the infrared detector array generates a smaller and smaller illuminated light spot on the infrared detector array. Using this application, it can now be determined in a further method step how much stray radiation from an adjacent measurement pixel j is incident on the measurement pixel i in question. The further a measurement pixel j is from the measurement pixel i, the less scattered radiation it receives. The light spot size can be parameterized as a function of the light spot radius, which in turn can be expressed in units of measuring pixel distances. Consequently, the plot - apart from a scaling factor - also corresponds to a plot depending on the distance d ^ij . The derivation of the application results in the increase in radiation incident on a measurement pixel i as a function of an enlargement of the aperture or the size of the light spot or the distance d ^ij . Consequently, the dependence of the scattered radiation on the distance d ^ij can be determined in this way and the correction factors C ^ij can be determined. In one exemplary embodiment, the application is approximated by a “crosstalk function” of the form a · ln x + b, where x corresponds to the aperture or the size of the light spot or the distance d ^ij . The derivation is then given by a / x.

The proposed method can be carried out individually for each infrared measurement system produced and thus an individual assignment for each infrared measurement system can be determined and stored in each case. As an alternative, this method can also be carried out for a specific type of infrared measuring system manufactured and thus an individual assignment for a “device series” can be determined and stored in the infrared measuring systems of the series.

In one embodiment of the method according to the invention, the temperature measurement value T ^{i of} at least one measurement pixel i of the plurality of measurement pixels is repeated at time intervals, in particular regularly, preferably continuously or quasi-continuously, corrected. It should be pointed out that this correction is carried out during use of the infrared measuring system by a user and not during a calibration that is still taking place in the factory. By means of the correction repeated at intervals, it can be realized that the temperature, in particular a thermal image, given to a user of the infrared measuring system, is also repeated, corrected for the scattered radiation. Advantageously, the evaluation device is provided for a regular, in particular a continuous or quasi-continuous, determination of the temperature measured value components .DELTA.T ⁱ , and thus a regular, in particular a continuous or quasi-continuous, correction of the determined temperature by a high processing rate of the temperature measured values. especially the thermal image. “Quasi-continuous” is to be understood in particular to mean that the repetitive correction takes an internal processing time by the evaluation device through to the finished correction of the temperature measured _values T ⁱ _corr of less than 10 seconds, preferably less than 5 seconds, particularly preferably less than 1 Second. In this way, the user is given the impression that the temperature determined for the examined surface, in particular the thermal image, is corrected immediately, preferably in real time and continuously.

drawings

The invention is explained in more detail in the following description with reference to exemplary embodiments shown in the drawings. The drawing, the description and the claims contain numerous features in combination. The person skilled in the art will expediently also consider the features individually and combine them into useful further combinations. The same reference symbols in the figures denote the same elements.

• 1 eine Ausführungsform eines erfindungsgemäßen Infrarot-Messsystems in einer perspektivischen Frontansicht,
• 2 eine Ausführungsform eines erfindungsgemäßen Infrarot-Messsystems in einer perspektivischen Rückansicht,
• 3 eine perspektivische, schematische Rückansicht des erfindungsgemäßen Infrarot-Messsystems vor einem zu vermessenden Gegenstand,
• 4 eine schematische Darstellung einer Ausführungsform der zur Ausführung des erfindungsgemäßen Verfahrens erforderlichen und sinnvollen Komponenten des erfindungsmäßen Infrarot-Messsystems,
• 5 eine schematische Aufsicht auf eine Ausführungsform eines Infrarot- Detektorarrays,
• 6 eine Ausführungsform des erfindungsgemäßen Verfahrens in einem Verfahrensdiagramm.

Show it:

• 1 an embodiment of an infrared measuring system according to the invention in a perspective front view,
• 2 an embodiment of an infrared measuring system according to the invention in a perspective rear view,
• 3 2 shows a perspective, schematic rear view of the infrared measuring system according to the invention in front of an object to be measured,
• 4 1 shows a schematic representation of an embodiment of the components of the infrared measuring system according to the invention that are necessary and useful for carrying out the method according to the invention,
• 5 1 shows a schematic top view of an embodiment of an infrared detector array,
• 6 an embodiment of the method according to the invention in a process diagram.

Description of the embodiments

The following is an infrared measuring system according to the invention 10 in the form of a hand-held thermal imaging camera 10a presented. 1 and 2 show an exemplary embodiment of this thermal imager 10a in a perspective front view or in a perspective rear view. The thermal imaging camera 10a includes a housing 12 with one handle 14 , With the handle 14 can the thermal imager 10a are comfortably held in one hand while in use. The housing 12 the thermal imager 10a also points to a user while using the thermal imager 10a facing side 16 an output device in the form of a touch-sensitive screen 18 as well as controls 20 for user input and control of the thermal imager 10a on. In particular, the thermal imaging camera 10a a trigger 20a with which a user can determine the temperature distribution of a surface without contact 22 of an object 24 can trigger.

On the side facing away from a user 26 of the housing 12 is an entrance opening 28 in the housing 12 provided by the of the subject 24 broadcast, especially in one measuring range 30 (see 3 dashed solid angle) from a surface 22 of the object 24 emitted, infrared radiation in the thermal imager 10a can occur. Immediately behind the entrance opening 28 is located in a light tube that reduces stray light 32 a lens system 34 as optics. The lens system 34 is permeable to radiation in the middle infrared range and is used to focus thermal radiation on an infrared detector array 36 (see in particular explanations for 5 ) of the thermal imager 10a ,

On a user while using the thermal imager 10a opposite side 26 of the housing 12 is in one embodiment of the thermal imager 10a also a camera working in the visual spectrum 38 provided by means of a visual image of the measurement area 30 is recordable. This visual image can be combined with a thermal image generated from a temperature measurement initiated by the user 40 are output, in particular at least partially with the thermal image 40 overlaid or faded out. The camera 38 can be implemented, for example, as a CCD image sensor.

On the bottom of the thermal imager 10a has the handle 14 a recording 42 to accommodate an energy store 44 on, which can be implemented, for example, in the form of a rechargeable battery or in the form of batteries.

The thermal imaging camera 10a serves a thermal image 40 of an object to be examined 24 record like this in 3 is shown schematically. After turning on the thermal imager 10a detects the thermal imager 10a in the measuring range 30 from the surface 22 of the object 24 radiated heat radiation without contact. The one from the thermal imager 10a The temperature determined characterizes the temperature of the surface 22 and is to be understood in this exemplary embodiment as a temperature distribution, for example in the form of a spatially resolved thermal image 40 to the user of the thermal imager 10a is issued. As a result of activating the trigger 20a by the user of the thermal imager 10a In this exemplary embodiment, a temperature distribution corrected by temperature measurement value components ΔT ⁱ caused by scattered radiation, in particular a thermal image corrected by temperature measurement value components ΔT ⁱ caused by scattered radiation 40 , generated on the screen 18 output and saved.

In 4 are required to carry out the method according to the invention (cf. in particular 6 ) necessary or helpful components of the thermal imaging camera according to the invention 10a shown schematically. These components are inside the case 12 the thermal imager 10a housed as electrical components and interconnected. The components essentially comprise the infrared detector array 36 , a control device 48 , an evaluation device 50 , a data communication interface 52 , a power supply device 54 , as well as a data storage 56 ,

The infrared detector array 36 the thermal imager 10a has at least a plurality of measurement pixels 62 on, which are intended to provide heat radiation from the infrared radiation spectrum in the measurement range 30 based on the surface to be examined 22 of the object 24 into the entrance opening 28 the thermal imager 10a occurs (cf. 3 ), capture. The in the entry opening 28 heat radiation entering is by means of the lens system 34 on the infrared detector array 36 under illumination of at least a plurality of measurement pixels 62 focused (not shown here).

Each measurement pixel i 62 is provided to provide an electrical measurement signal U ⁱ , for example a potential, at its output, with the radiated heat output of the infrared radiation P ⁱ onto the measurement pixel 62 correlated. These pixel-dependent measurement signals U ⁱ are used individually or in combination with other measurement signals from other measurement pixels 62 first to the control device 48 of the infrared measuring system 10 output and from this to the evaluation device 50 of the infrared measuring system 10 forwarded.

The control device 48 of the infrared measuring system 10 represents in particular a device that has at least one control electronics and means for communication with the other components of the thermal imager 10a includes, in particular means for controlling and regulating the thermal imager 10a , The control device 48 is about that provided the thermal imager 10a to control and enable their operation. This is the control device 48 with the other components of the infrared measuring device 10 , especially the infrared detector array 36 (via a circuit), the evaluation device 50 , the data communication interface 52 , the power supply device 54 , the data storage 56 , but also the controls 20 , 20a and the touch-sensitive screen 18 connected by signaling.

The power supply device 54 in 4 is preferred by the in 1 and 2 energy storage shown 44 realized.

The evaluation device 50 is used to receive and evaluate measurement signals from the infrared detector array 36 , ie the pixel-associated measurement signals U ^{i of} the measurement pixels i 62 , The evaluation device 50 has a plurality of functional blocks 60a - 60d which are used for information processing, in particular the evaluation of the assumed measurement signals. The evaluation device 50 also has a processor, a memory and an operating program with evaluation and calculation routines (not shown in each case). The evaluation device 50 is provided by the infrared detector array 36 Provided measurement signals, in particular from measurement pixels i 62 provided measurement signals U ⁱ to receive and evaluate (function block 60a ). In this way, temperature measurement values T ^{i of} at least one measurement pixel i 62 , preferably a plurality of measurement pixels i 62 , certainly.

The evaluated temperature measured values T ⁱ can be obtained from the evaluation device 50 for further processing of the control device 48 to be provided. Furthermore, the evaluation device 50 provided for a temperature measurement value T ^{i of} at least one measurement pixel i 62 the plurality of measurement pixels 62 to correct a temperature measurement component ΔT ⁱ caused by scattered radiation. The temperature measured value component ΔT ⁱ is also from the evaluation device 50 , from temperature measurement values T ^j of measurement pixels j to be taken into account in the correction 62 calculated. The function block performs this correction 60c by. The evaluation of the measurement pixel components ΔT ⁱ associated with the measurement pixel is carried out by the function block 60b , The process steps through the functional blocks 60a - 60d are fulfilled or processed in connection with the 6 described.

Overall, the thermal imager 10a , in particular their evaluation device 50 , provided for this purpose, based on measurement signals of at least a plurality of measurement pixels j 62 , ie in particular based on temperature measured values T, a correction of a thermal image 40 of the measuring range 30 perform, the thermal image 40 with respect to a pixel-associated scattered radiation component, the temperature measured value component ΔT ⁱ , is corrected.

The from the evaluation device 50 evaluated temperature measuring values T ^i, the pixel corresponding temperature measurement value components .DELTA.T ^i, the associated pixel by the temperature measurement value components .DELTA.T ⁱ corrected temperature values T ⁱ _corr and _corr from these corrected temperature values T ⁱ composite thermal images, particularly the output level thermal image 40 , are in this embodiment of the infrared measuring system 10 from the evaluation device 50 for further processing of the control device 48 provided. Such an output can be given to a user of the thermal imager 10a using the screen 18 the output device. Alternatively or additionally, the output to an external data device (not shown in more detail) such as, for example, a smartphone, a computer or the like using the data communication interface 52 respectively. The data communication interface 52 is executed in the illustrated embodiment as a WLAN and / or Bluetooth interface. There is also an output to the data store 56 for storing the determined data and thermal images 40 conceivable.

5 shows a schematic plan view of an embodiment of the infrared detector array 36 the thermal imaging camera according to the invention 10a from the direction of the incoming measuring radiation. Every measurement pixel 62 is represented here simply as a square. The majority of measurement pixels is an example 62 Matrix-like in the form of an array 68 on the surface 70 of the infrared detector array 36 arranged. The number of measurement pixels 62 is 42 × 32 in this exemplary embodiment. Any other values are conceivable.

The method according to the invention is described below with reference to 6 explained.

In 6 A method diagram is shown, which is an embodiment of the method according to the invention for the contact-free determination of the temperature of the surface 22 , in particular for the contact-free determination of a thermal image 40 the surface 22 , reproduces. The method is intended to be used by an infrared measuring system 10 , especially a thermal imaging camera 10a to be operated as it is in connection with the 1 to 5 was introduced.

Starting from the in 3 shown measurement scenario is a user of the thermal imager 10a on an investigation of the temperature distribution of the surface 22 of an object 24 Interested. The user sets up to measure the surface 22 the thermal imager 10a on the object to be examined 24 , Meanwhile, the thermal imager captures 10a with the infrared detector array 36 continuous infrared radiation from the measuring range 30 and continuously shows an uncorrected thermal image 40 on the screen 18 on. In a first step 200 the user actuates the trigger 20a the thermal imager 10a and thereby manually initiates a sequence of the following process steps 202 to 210 , In an alternative exemplary embodiment of the method (not shown in more detail here), this initiation can also be automated, in particular repeated at intervals or quasi-continuously, that is to say without actuation of the trigger 20a (see arrow 212 ).

The control device then conducts 48 that at the time of initiation from the infrared detector array 36 provided measurement signals U to the evaluation device 50 further. In process step 202 determines the evaluation device 50 the pixel-dependent temperature measurement values T of a plurality of measurement pixels 62 from their measurement signals U. These temperature measurement values T are the temperature measurement values T ⁱ to be corrected in this exemplary embodiment by the method according to the invention and at the same time the temperature measurement values T ^{j to} be used for calculating the respective temperature measurement value component ΔT ⁱ . The temperature measurement values T are determined from the measurement signals in the function block 60a the evaluation device 50 , see. 4 , The function block changes 60a the respective measurement signals U into temperature measurement values T um. These temperature measured values T serve to generate a thermal image 40 of the object to be examined 24 , Each temperature measurement value T ^{i determined} for each measurement pixel i is composed of a temperature measurement value component which is based on directly received infrared radiation and a temperature measurement value component ΔT ⁱ which can be attributed to scattered radiation. The aim of the further method is to subject these temperature measurement values T to a correction with regard to the temperature measurement value component ΔT ⁱ caused by scattered radiation.

berechnet, wobei C ein konstanter Korrekturfaktor ist und n die Anzahl der zu berücksichtigenden Messpixel j. In diesem Ausführungsbeispiel mit 42 × 32 Pixel ergibt sich folglich $\mathrm{\Delta }{T}^i=\left(T^i-\left({\displaystyle {\sum }_{j=1}^{n1805}{T}^j}\right)\text{/}1805\right)\cdot C$

für i = 1...1806. In einem alternativen Verfahrensschritt 204b wird die Temperaturmesswert-Komponente ΔTⁱ über den Zusammenhang $\mathrm{\Delta }{T}^i={\displaystyle {\sum }_{j=1}^n\left(T^i-T^j\right)\cdot C^{ij}}$

berechnet, wobei C^ij jeweils ein von einem zu berücksichtigenden Messpixel j abhängiger, insbesondere vom Abstand d^ij abhängiger, Korrekturfaktor ist. In diesem Ausführungsbeispiel ergibt sich folglich wiederum $\mathrm{\Delta }{T}^i={\displaystyle {\sum }_{j=1}^{n1805}\left(T^i-T^j\right)\cdot C^{ij}}$

für i = 1...1806. Dabei lädt die Auswertevorrichtung 50 aus dem Datenspeicher 56 des Infrarot-Messsystems 10 für jede der Kombinationen i,j einen Wert C^ij ab. Mittels dieser Korrekturfaktoren C^ij ermittelt die Auswertevorrichtung 50 für jedes zu berücksichtigende Messpixel j einen Anteil an Streustrahlung, die von diesem Messpixel j auf ein jeweiliges Messpixel i wirkt. Die Korrekturfaktoren C^ij sind in diesem Ausführungsbeispiel in Form einer Tabelle geräteintern abgespeichert, wobei eine eindeutige Identifikation der i,j-Kombination beispielhaft jeweils über eine Zeilen- und Spaltennummer gewährleistet ist. Die Tabelle bildet somit eine Zuordnung, die für jedes zu berücksichtigende Messpixel j einen Anteil an Streustrahlung spezifiziert, die vom Messpixel j auf ein Messpixel i wirkt. Insbesondere wurde diese Zuordnung bei einer Werkskalibrierung des Infrarot-Messsystems 10 ermittelt und im Infrarot-Messsystem 10 hinterlegt. Die Entscheidung, welcher der beiden beschriebenen Zusammenhänge verwendet wird, kann entweder durch einen Benutzer wählbar sein oder durch das Infrarot-Messsystem 10 vorgegeben sein. Der Verfahrensschritt 204 wird in dem Funktionsblock 60b der Auswertevorrichtung 50, vgl. 4, durchgeführt.The method according to the invention can be carried out with the temperature measurement values T now available. For at least one measurement pixel i 62 , preferably for all measurement pixels i 62 , for which temperature measurement values T ⁱ are available, temperature measurement value components ΔT ⁱ are now calculated [Note: in order to avoid confusion in the following with the figures, the reference symbol “ 62 “Omitted to the measuring pixels). In the present exemplary embodiment with 1806 measurement pixels i there are 1806 temperature measured values T ⁱ , i = 1 ... 1806. In this exemplary embodiment, the measurement pixels j to be taken into account in the correction are selected as the plurality of measurement pixels of the infrared detector array with the exception of the respective measurement pixel i itself, ie information from all adjacent measurement pixels j (ie j ≠ i) is taken into account for calculating the scattered radiation , Consequently, in principle 1806 temperature measured value components ΔT ⁱ can be calculated using 1805 (taken into account) temperature measured values T ^j . For example, ΔT ¹ for measurement pixels 1 using measurement pixels j = 2 ... 1806, ΔT ² for measurement pixels 2 using measurement pixels j = 1, 3 ... 1806, ΔT ³ for measurement pixels 3 using measurement pixels j = 1, 2, 4 ... 1806, ..., ΔT ¹⁸⁰⁶ for measurement pixels 1806 using measurement pixels j = 1 ... 1805. In process step 204 this pixel-associated temperature measurement component ΔT ^{i is} calculated on the basis of the temperature measurement values T ^j . The calculation can be carried out in different ways. In the process diagram shown, two options are provided, implemented as process steps 204a respectively. 204b , In process step 204a the temperature measured value component ΔT ⁱ via the relationship $\mathrm{\Delta }{T}^i=\left(T^i-\left({\displaystyle {\Sigma }_{j=1}^n{T}^j}\right)\text{/}n\right)\cdot C$

calculated, where C is a constant correction factor and n is the number of measurement pixels to be considered j. This results in this embodiment with 42 × 32 pixels $\mathrm{\Delta }{T}^i=\left(T^i-\left({\displaystyle {\Sigma }_{j=1}^{n1805}{T}^j}\right)\text{/}1805\right)\cdot C$

for i = 1 ... 1806. In an alternative process step 204b the temperature measured value component ΔT ⁱ via the relationship $\mathrm{\Delta }{T}^i={\displaystyle {\Sigma }_{j=1}^n\left(T^i-T^j\right)\cdot C^{ij}}$

calculated, where C ^{ij is in} each case a correction factor dependent on a measurement pixel j to be taken into account, in particular dependent on the distance d ^ij . In this exemplary embodiment, this again results $\mathrm{\Delta }{T}^i={\displaystyle {\Sigma }_{j=1}^{n1805}\left(T^i-T^j\right)\cdot C^{ij}}$

for i = 1 ... 1806. The evaluation device loads 50 from the data store 56 of the infrared measuring system 10 a value C ^ij for each of the combinations i, j. The evaluation device uses these correction factors C ^ij 50 for each measurement pixel j to be taken into account, a proportion of scattered radiation which acts from this measurement pixel j on a respective measurement pixel i. In this exemplary embodiment, the correction factors C ^ij are stored internally in the form of a table, with a unique identification of the i, j combination being ensured, for example, in each case by means of a row and column number. The table thus forms an assignment which specifies for each measurement pixel j to be taken into account a proportion of scattered radiation which acts from the measurement pixel j on a measurement pixel i. In particular, this assignment was made at a Factory calibration of the infrared measuring system 10 determined and in the infrared measuring system 10 deposited. The decision as to which of the two described relationships is used can be either user-selectable or the infrared measurement system 10 be given. The procedural step 204 is in the function block 60b the evaluation device 50 , see. 4 , carried out.

Finally, a respective temperature measurement value T ^{i of} a measurement pixel ^{i is} corrected by the pixel-associated temperature measurement value component ΔT ⁱ , which was calculated in advance. This is realized in that to a pixel i to a respective measurement determined temperature measuring value T ⁱ is calculated for this pixel i measuring temperature reading component .DELTA.T ⁱ in step 206 is added, ie T ⁱ _corr = T ⁱ + ΔT ^{i is} calculated. The implementation of the procedural step 206 takes place in function block 60c the evaluation device 50 , see. 4 ,

With function block 60d the evaluation device 50 , see. 4 , in process step 208 the corrected temperature measured values T ⁱ _corr are smoothed (homogenized).

Finally, in process step 210 the corrected and possibly homogenized thermal image 40 using the screen 18 to the user of the thermal imager 10a output.

According to arrow 212 the method can run repeatedly, in particular in an exemplary embodiment in which the method without actuating a trigger 20a repeated at intervals, in particular regularly, preferably continuously or quasi-continuously.

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included 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.

Patent literature cited

• DE 102016218295 A1 [0003]
• DE 102016211829 A1 [0003]

Claims (10)

Method for the contact-free determination of a temperature distribution of a surface (22) by means of an infrared measuring system (10, 10a), the infrared measuring system (10, 10a) having at least one infrared detector array (36) with a plurality of measuring pixels (62), wherein the measurement pixels (62) are sensitive to infrared radiation and each provide a measurement signal for determining a temperature measurement value T dependent on an intensity of the incident infrared radiation, characterized in that a temperature measurement value T ^{i of} at least one measurement pixel i (62) of the plurality of measurement pixels (62) is corrected by a temperature measurement value component ΔT ⁱ caused by scattered radiation, which is calculated from temperature measurement values T ^j of measurement pixels j (62) to be taken into account in the correction. Procedure according to Claim 1 , characterized in that the measurement pixels j (62) to be taken into account in the correction are selected as the plurality of measurement pixels (62) of the infrared detector array (36). Procedure according to Claim 1 , characterized in that the measurement pixels j (62) to be taken into account in the correction are selected as the plurality of measurement pixels (62) of the infrared detector array (36) without the measurement pixel i (62). Procedure according to Claim 1 , characterized in that the measurement pixels j (62) to be taken into account in the correction are selected in accordance with a symmetrical arrangement of the measurement pixels j (62) on the infrared detector array (36). Procedure according to one of the Claims 1 - 4 , characterized in that the temperature measured value component ΔT ⁱ via the relationship $\mathrm{\Delta }{T}^i=\left(T^i-\left({\displaystyle {\Sigma }_{j=1}^n{T}^j}\right)\text{/}n\right)\cdot C$

is calculated, where C is a constant correction factor. Procedure according to one of the Claims 1 - 4 , characterized in that the temperature measurement component ΔT ^{i is} calculated from temperature measurement values T ^j of measurement pixels j (62) to be taken into account in the correction and their distance d ^{ij from} the measurement pixel i (62). Procedure according to Claim 6 , characterized in that the temperature measured value component ΔT ⁱ via the relationship $\mathrm{\Delta }{T}^i={\displaystyle {\Sigma }_{j=1}^n\left(T^i-T^j\right)\cdot C^{ij}}$

is calculated, where C ^{ij is in} each case a correction factor which is dependent on a measurement pixel j (62) to be taken into account, in particular on the distance d ^ij . Procedure according to Claim 7 , characterized in that the correction factor C ^{ij is determined} from an assignment stored in the device, which specifies for each measurement pixel j (62) to be taken into account a proportion of scattered radiation which acts on the measurement pixel i (62) from the measurement pixel j (62). Method according to one of the preceding claims, characterized in that the temperature measurement value T ^{i of} at least one measurement pixel i (62) of the plurality of measurement pixels (62) is repeated at time intervals, in particular regularly, preferably continuously or quasi-continuously, is corrected. Infrared measuring system (10, 10a), in particular hand-held thermal imaging camera (10a), for the contact-free determination of a temperature distribution of a surface (22), characterized by an evaluation device (50) which is set up to carry out the method according to one of the preceding claims.

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