DE102014226342A1 - Thermal camera - Google Patents

Abstract

The invention relates to a handheld thermal imaging camera (10) for non - contact measurement of a temperature of a measuring area (22, 22a, 22b) located on a surface, comprising at least one detector device (32) comprising at least one detection area (36) with a multiplicity of pixels (40 ) for detecting heat radiation emitted from the measuring region (22, 22a, 22b) and for generating detection signals based on a detected thermal radiation, an optical system (26, 26 ') for imaging thermal radiation emitted from the measuring region (22, 22a, 22b) on the detection surface (36) under illumination of a plurality of pixels (40), and an evaluation device (52) for receiving and evaluating detection signals of the detector device (32), each pixel (40) of the detector device (32) with the evaluation device (52 ) is technically connectable. According to the invention, the thermal imaging camera (10) is characterized in that a size of the measuring area (22, 22a, 22b) can be changed using the optics (26, 26 '), the evaluation device (52) being based on detection signals of at least one plurality of illuminated pixels (40 ) of the detector device (32) carries out an evaluation of the temperature of the measuring region (22, 22a, 22b) and the evaluation device (52) and / or the detector device (32) has a binning architecture (62) which comprises a signal-technical summary of pixels ( 40), in particular for increasing the thermal radiation sensitivity of the detector device (32), provides.

Description

The invention relates to a device and a method for non-contact measurement of a temperature of a measurement area located on a surface.

State of the art

Devices and methods for non-contact measurement of a surface temperature of a measuring range are known in the art and are used in a variety of applications, for example for the safety inspection of electrical circuits, for troubleshooting in machine processes or for the identification of insufficient heat insulation in the context of thermal and / or cold insulation. Infrared thermometers are often used to detect and localize heat sources and / or heat sinks, which have the advantage of non-contact and rapid measurement compared to conventional temperature measuring devices and thus can be used especially when areas to be measured are difficult or impossible to access. The temperature measurement by means of an infrared-sensitive thermometer is based on the detection of thermal radiation, i. Infrared radiation, in particular in a wavelength range between 3 microns and 50 microns, which is emitted by each object depending on its temperature, in particular its surface temperature, with different intensity. From a measured intensity of the emitted heat radiation by means of the temperature measuring device, a surface temperature of the emitting body can be determined.

Infrared thermometers known in the prior art can essentially be distinguished in two embodiments. Devices of the first kind, so-called spot thermometers, typically comprise an infrared sensor, a lens and a display. The combination, ie in particular the arrangement of the infrared sensor with the lens, provides a typically conical, preferably small measuring volume, from which heat radiation is detected. When the devices of the first kind are aligned with a surface of an object, the intersection of the measurement volume with the surface of the article forms a measurement area. A portion of the thermal radiation emanating from this measuring range is detected by the device of the first type, wherein from the measured intensity of the heat radiation an average surface temperature in the measuring range is evaluated and output by means of the display. With the aid of an additional laser device, which is aligned such that, for example, the center of the measuring range is marked during a measurement by the laser beam, the contactless temperature measurement can be correlated with the location of the measurement made. US 6,659,639 A1 and US 2009/0304042 A1 describe devices and methods of a measuring device of this type.

Infrared thermometers of a second type, so-called thermal imaging cameras, typically have an infrared-sensitive image sensor, a lens system and a screen and, similar to a working in the visual spectral range camera, to measure an object to be examined in the infrared region of the radiation spectrum and on the screen as a two-dimensional to output a color-coded image of the object. By means of such a thermal imaging camera, heat sources and heat sinks can be easily identified and localized on the basis of the color coding of the temperature data. US 2009/0302219 A1 and US Pat. No. 7,652,251 A1 describe devices and methods of this second type.

Disclosure of the invention

According to the invention, a hand-held thermal imaging camera is proposed for the non-contact measurement of a temperature of a measuring area located on a surface, comprising at least one detector device comprising at least one detection surface with a plurality of pixels for detecting thermal radiation radiated from the measuring area and for generating detection signals based on a detected thermal radiation , An optics for imaging radiated from the measuring range thermal radiation on the detection surface under illumination of a plurality of pixels, and an evaluation device for receiving and evaluating detection signals of the detector device, each pixel of the detector device with the evaluation device is signal-technically connectable.

According to the invention, the thermal imaging camera is characterized in that a size of the measuring range can be changed using the optics, the evaluation device performs an evaluation of the temperature of the measuring range based on detection signals of at least one plurality of illuminated pixels of the detector device and the evaluation device and / or the detector device a binning architecture which provides a signal-technical summary of pixels, in particular for increasing the thermal radiation sensitivity of the detector device.

"Thermal imaging camera" refers to a device for non-contact measurement of a temperature of a measuring area located on a surface with output of at least one temperature information, advantageously one or more temperature readings, particularly advantageously one of a plurality of Temperature readings composite thermal image. For the purpose of simplifying the description, the term "evaluating a temperature", "determining a temperature", "temperature measured value" or the like refers in each case to information relating to the temperature of the surface in the measuring range, advantageously one or more, in particular also averaged, temperature measured values advantageously a composite of a plurality of temperature measurements thermal image.

The "measuring range" is understood to mean a geometrically, locally limited area which comprises a quantity of particles of the object whose heat radiation leaves the object in the direction of the thermal camera and is at least partially detected by it. Depending on the material of the article, in particular depending on the transparency of the article for infrared radiation, particles can be detected by the thermal imaging camera, which are located at different distances in the object. In particular, by "object" in addition to a solid also a fluid, in particular a liquid and a gas can be understood, the temperature of which can be measured in an analogous manner. To simplify the following description, the term "measuring range" particularly identifies the region on an object surface, which essentially results from the intersection between a measuring volume-the volume from which the device according to the invention detects thermal radiation-and a surface of the object to be examined. Depending on the material property of the article, however, this measuring region may also comprise heat radiation from deeper layers of the article.

According to the invention, the thermal imaging camera has at least one detector device, an optical system, in particular an imaging optical system, and an evaluation device.

The optics is provided to project heat radiation emitted from the measuring region 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 thermal imaging camera's detector device, which is arranged behind the optics, preferably an image of the measuring region to project a surface of the detector device, particularly preferably to focus an image of the measuring area on a surface of the detector device. The term "provided" is to be understood in the following to mean specifically "programmed", "designed", "designed" and / or "equipped". By "providing" an object for a particular function, it should be understood, in particular, that the object fulfills and / or executes this particular function in at least one application and / or operating state or is designed to perform the function. For this purpose, the optics advantageous heat radiation directing, conducting, bundling and / or otherwise in the spatial propagation influencing optical components, in particular for example lenses, Fresnel lenses, mirrors, grids, light guides, prisms, diffractive elements or other, one skilled in the reasonable appearing optical Components by means of which the heat radiation can be projected onto the surface of the detector device. These components may preferably consist in particular of moisture-sensitive salts such as, for example, sodium chloride and silver salt or of monocrystalline semiconductor materials such as, for example, germanium or zinc selenide.

According to the invention, the thermal imaging camera is provided to adjust a size of the measuring area located on a surface using the optics changeable. Advantageously, a focal length of the optics of the thermal imaging camera can be set in such a variable, in particular zoomable, that an adaptation of the size of the measuring range is possible via an adaptation of the image section imaged by means of the optics. This gives a user of the thermal imaging camera the advantage of both gaining an overview of a surface to be examined using a large measuring range and of examining details of the surface to be examined using a small measuring range. Such a change in the size of the measuring range can be realized in different ways, preferably for example by means of optics, which advantageously allows adjustment of different focal lengths in stages or particularly advantageously also steplessly. In accordance with the variable, in particular zoomable, optically changeable mapping of the heat radiation emitted from the measuring area to the detector device, an illuminated area of the detection area of the detector device, in particular an infrared spot generated on the detection area, depending on a distance between the object emitting the heat radiation and The thermal imaging camera as well as the exact setting of the changeable optics in general be changeable.

The detector device detects thermal radiation emitted from the measuring area and projected onto the surface thereof by means of the imaging optics and generates a detection signal on the basis of the detected intensity. For this purpose, the detector device on a surface facing the optics on a two-dimensional detection surface, which consists of a plurality of matrix-like pixels arranged. Each of the pixels of the detector device can - provided lighting by means of thermal radiation - image information, in particular one of a solid angle of the measuring range emitted heat radiation, preferably an intensity radiated onto the pixel of the thermal radiation emitted from a solid angle of the measuring range, and generate a detection signal therefrom, wherein the detection signal generated by each pixel can subsequently be used to determine a temperature, can advantageously be forwarded to an evaluation device, can be evaluated particularly advantageous by the evaluation device individually and / or in combination with other pixels of the plurality of pixels of the detector device.

By means of the imaging optics of the thermal imaging camera, in particular by means of the zoomable optics, it is advantageously possible to achieve illumination of a plurality of pixels with thermal radiation emitted from the measurement area. Depending on the distance between the thermal imaging camera and the object and depending on the setting of the size of the measuring area located on its surface, a different number of pixels of the detector device can be illuminated.

Each pixel of the detector device is a radiation-sensitive, in particular infrared-sensitive, element and is intended to detect radiation from the infrared range, in particular the middle infrared range in the wavelength range between 3 .mu.m and 50 .mu.m, and to convert it into a signal, in particular an electrical detection signal. Typically, the detection signals generated by such radiation-sensitive elements are dependent on a heat radiation intensity incident on the element. Examples of elements sensitive to infrared light include photodiodes, bolometers, pyroelectric sensors, PIN diodes, avalanche photodiodes (APD), (modulated) CCD chips and CMOS pixels, but it is also possible for other, for example on silicon sensors, to make sense to a person skilled in the art , 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 based infrared photosensitive elements. The number of the plurality of matrix-like arranged pixels, for example in particular 80 × 80 pixels, preferably 360 × 240 pixels, particularly preferably 640 × 480 pixels, defines the resolution of the thermal imaging camera, in particular the resolution of a thermal image measured by means of the thermal imaging camera.

According to the invention, each of the plurality of pixels of the detector device can be connected to the evaluation device directly or indirectly via further intermediate components by signal technology. In particular, an indirect signal connection of the pixels with the evaluation device can also be realized via switching elements, for example multiplexers or other selection circuits, which are designed to selectively forward detection signals of several pixels. In this way it can be achieved, in particular, that detection signals of individual pixels or a group of pixels can be forwarded to the evaluation device independently of detection signals of other pixels and evaluated by the latter.

The evaluation device for receiving and evaluating detection signals of the detector device should be understood to mean a device which has at least one information input for accepting detection signals, an information processing unit for processing, in particular evaluation of the assumed detection signals, and an information output for passing on the processed and / or evaluated detection signals , Advantageously, the evaluation unit 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 printed circuit board (printed circuit board), preferably on a common board with a control device of the thermal imaging camera for controlling the thermal imaging camera, and particularly preferably in the form of a microcontroller. Furthermore, the control device and the evaluation device may be particularly preferably designed as a single component. The evaluation device is provided for receiving and evaluating detection signals generated by the detector device, in particular detection signals generated by the evaluation device, in particular connectable pixels of the detector device, and evaluating the temperature of the detector based on detection signals of at least one plurality of illuminated pixels of the detector device Measuring range. Preferably, the evaluation device is provided for carrying out an evaluation of one or more temperature measurement values, in particular also averaged temperature measurement values, particularly preferably a thermal image, based on detection signals of at least one plurality of illuminated pixels of the detector device. The evaluated information, in particular a generated temperature measured value and / or a thermal image, can be provided by the evaluation device for further processing and / or output to a user of the thermal imaging camera by means of an output device and / or an external device by means of a data communication interface.

Furthermore, the evaluation and / or the control device stored correction and / or calibration tables and / or routines for Have calibration that allow interpretation and / or to re-calculate evaluation results and / or to interpolate and / or extrapolate and to calibrate the thermal imager in particular with respect to a temperature value, in particular with respect to a measured temperature reading.

According to the invention, the evaluation device and / or the detector device to a binning architecture, which enables a signal-technical summary of pixels of the detector device to increase the heat radiation sensitivity of the detector device.

In this case, "binning architecture" means an architecture and / or a device which permits a signal-technical combination of at least two pixels, in particular of adjacent pixels, preferably of pixels of a predefinable number. By "summarize signal technology" and "signal-technical summary" is to be understood in particular that at least two pixels, preferably summarized in terms of signal technology, advantageous interconnected, particularly advantageous combined that a single detection signal of the interconnected pixels is output. Alternatively, "signal-technical summary" can also be understood as meaning that a plurality of detection signals, generated by a plurality of pixels, combined to form a detection signal, advantageously interconnected, are combined particularly advantageously. The signal-technical summary can already be done by means of the detector device itself, for example, advantageously when using CCD sensors possible, in which way the at least two, preferably the plurality of pixels are combined to form a "pixel block". Since the detection signals of individual pixels of the detector device can be passed on independently and / or evaluated, the evaluation device can alternatively and / or additionally be designed to provide a signal-technical summary of pixels of the detector device, in particular also of its detection signals. In this case, the generated combined detection signal can be interpreted by a virtual pixel consisting of at least two or advantageously several pixels.

A signal-technical summary of pixels can take place in different ways, preferably as an analogue addition of physical charge-contributing pixels or as a digital addition of digitized values. In particular, a signal-based combination of detection signals of a plurality of pixels can advantageously be implemented by means of a combiner, for example using an OR gate.

According to the invention, it can be realized in this way that regions consisting of at least two, advantageously consisting of a plurality of pixels, are combined or combined in a signal-technically manner into pixel blocks or virtual pixels, that advantageously have a higher signal sensitivity per pixel block or per virtual one Pixel of the detector device is achieved and improves a signal-to-noise ratio of the respective pixel block or the virtual pixel. With the aggregation of pixels, the resolution of the detector device, i. in particular, a resolution of a measured thermal image, corresponding to the number of combined pixels reduced.

In an advantageous embodiment of the hand-held thermal imaging camera, the evaluation device and / or the detector device is provided to perform a signal-technical summary of pixels to increase the heat radiation sensitivity as a function of the intensity of radiated heat radiation on the detection surface.

Many photosensitive elements, in particular elements sensitive to infrared light, deliver, in particular, an electronic detection signal depending on an incident light intensity. However, with low intensity of the incident light, high noise often limits the detection accuracy of the photosensitive member as compared with the actually detectable intensity. This is often the case in particular with electronic sensors. According to the invention, this noise signal superimposed on the generated detection signal can be effectively and advantageously reduced by combining pixels to increase the thermal radiation sensitivity as a function of the intensity of the thermal radiation radiated onto the detection surface.

The summary of the pixels can be carried out in different ways, in particular based on different requirements for an evaluation and with respect to different goals. Advantageously, in each case several or even the entirety of the multiplicity of pixels can be combined to form one or more pixel blocks or one or more virtual pixels, so that the detection signal generated by each pixel block or virtual pixel is improved, preferably optimized with regard to its signal-to-noise ratio , Particularly advantageously, the combination of a plurality of pixels can also be selective, for example, in particular limited to pixels illuminated by radiated heat radiation and advantageously to the exclusion of unilluminated pixels. This can be used to customize the aggregation of pixels a sub-area of the detection surface illuminated by irradiated heat radiation, in particular to an infrared spot located on the detection surface, so that signal contributions of non-illuminated pixels, in particular signal contributions, which represent only unwanted background noise, are determined from the determination of the temperature of the measurement area on the Surface are excluded. This is particularly advantageous for edge regions of the illuminated detection surface.

For example, in one embodiment of the thermal imaging camera according to the invention, the detector device and / or the evaluation device may be designed to first determine in a preliminary measurement using a threshold which pixels of the detection surface actually detect heat radiation and which pixels only detect background radiation in the form of noise. Furthermore, it is also possible to determine the intensity of the thermal radiation detected with each pixel. Subsequently, only the detection signals of the pixels illuminated by the heat radiation can be used for the actual measurement of the temperature, which are advantageously combined selectively based in particular on the previously determined intensity for reducing the statistical noise.

Furthermore, portions or the entirety of the pixels of the detection surface, in particular also selectively selected pixels, can be signal-technically combined with the aim of producing an average, so that detection signals averaged over the combined pixels, in particular a detection signal averaged over the entirety of the pixels, are output. This is useful, for example, if there is an interest in temperature measured values which are averaged over at least partial regions of the measuring region. By combining the entirety of the pixels, a pixel block or a virtual pixel covering the entire detection surface of the detector device is generated in particular, wherein the generated detection signal corresponds in particular to an averaging of the thermal radiation radiated onto the detection surface. In this embodiment, the thermal imager according to the invention has the functionality of a spot thermometer.

As a result of an increasing combination of pixels, the spatial resolution of the detector device is increasingly reduced, while at the same time improving a signal-to-noise ratio and increasing the averaging of the individual detection signals of the pixels. Consequently, an interconnection of pixels can advantageously be carried out for increasing the signal-to-noise ratio and / or for averaging the heat radiation radiated onto the individual pixels, in particular as a function of the intensity of radiated heat radiation.

In an advantageous embodiment of the hand-held thermal imaging camera, the evaluation device and / or the detector device is provided to summarize an increasing number of pixels to increase the heat radiation sensitivity with decreasing intensity of the irradiated on the detection surface heat radiation signal technology.

As the intensity of the thermal radiation radiated onto the detection surface decreases, the signal-to-noise ratio of electronic sensors, in particular infrared-sensitive sensors, typically decreases, so that the signal component due to statistical noise of the sensor increases in relation to the actual signal of interest and to be measured the measurement result becomes increasingly inaccurate. According to the invention, this loss of accuracy due to decreasing intensity of radiated heat radiation can be compensated by combining an increasing number of pixels, so that measurement results of high accuracy are obtained despite decreasing incident intensity.

Preferably, with decreasing intensity of radiated heat radiation, a summary of an increasing number of pixels of illuminated subregions of the detection surface-advantageously of those pixels which are covered by the light spot on the detection surface-can be carried out. Thus, signal contributions from non-illuminated pixels, particularly signal contributions, which are merely unwanted background noise, are excluded from the determination of the temperature of the measurement area on the surface.

Particularly advantageous is the combination of an increasing number of pixels correlated with a decrease in intensity of the radiated heat radiation on the detection surface due to an increasing reduction of the measuring range. If the measuring range is reduced by means of the optics, ie zoomed in particular by means of the optics, typically less heat radiation from the reduced measuring range is imaged onto the detector device. Consequently, the radiated intensity also decreases. A decrease in the measurement accuracy with increasing reduction of the measuring range on the surface can thus be counteracted according to the invention by combining an increasing number of pixels, so that measurement results of high accuracy can be obtained despite decreasing incident intensity. By the aggregation of pixels of increasing number the spatial resolution of the Detector device, however, so that the reduced, in particular zoomed, measuring range can be measured only with a smaller number of separately resolvable pixels. Since an average, non-spatially resolved temperature in the sense of a point measurement is typically of interest in the case of a greatly reduced measuring range (compare functionality and application of the spot thermometer), the evaluation device and / or the detector device can be particularly advantageously provided with decreasing intensity radiated heat radiation increasingly pool more pixels, until finally, advantageously, when setting the smallest possible measurement range, the summary of all pixels of the detector device is performed and the determined measurement result of a mean temperature in the measurement area on the surface corresponds. In this way, a stepless transition from a particular high-resolution thermal imaging camera to a point-measuring spot thermometer can be realized, so that in principle two different functionalities - camera and spot meter - are combined in one device.

In an advantageous embodiment of the handheld thermal imaging camera, the evaluation device and / or the detector device has a variable binning architecture, which in particular allows a signal-technical combination of pixels of different numbers.

By carrying out the binning architecture as a variable binning architecture, it is advantageously possible to combine any pixels of the detector device, in particular pixels of any rows and / or columns of the detector device, by signal technology, in particular to combine them. Furthermore, it is also possible to provide a signal-technical summary of pixels in different ways, in particular using differently operating combiners. For example, it is possible to switch between analogous summary by physical charge addition and digital summarization by addition of digitized values.

In an advantageous embodiment of the hand-held thermal imaging camera, the evaluation device and / or the detector device has a symmetrical binning architecture.

By "symmetrical binning architecture" is to be understood in particular that the pixels of the detector device can be summarized in a symmetrical, in particular point and / or mirror-symmetric way. In particular, it can be provided, for example, that pixels which each have an identical distance to the geometric center of the detection surface can be combined in essentially annular structures. Advantageously, a combination of pixels can also take place in each case point-symmetrically to the geometric center of the detection surface, so that, for example, a summary of two first pixel point symmetrical with respect to the geometric center of the detection surface to a summary of two other pixels. In this way, the symmetrical binning architecture of the evaluation device and / or the detector device allows the realization of a particularly simple and economically advantageous variable binning architecture.

In an advantageous embodiment of the handheld thermal imaging camera, the size of the measuring range can be changed using the optics in at least two stages.

According to the invention, the thermal imaging camera is provided to adjust a size of the measurement area located on the surface using the optics changeable. In particular, changeable optics have the advantage that a user of the thermal imager can both gain an overview of a surface to be examined using a large measurement range and also examine details of the object's surface to be examined using a small measurement range. A change in the size of the measuring range can be realized cost-effectively and particularly economically by means of optics having different and variable, in particular fixed, focal lengths in at least two stages, advantageously in several stages. These can be realized, for example, by interchangeable, exchangeable optical components which can be folded in and out of the optical path, advantageously by means for switching between optical paths, in particular mirrors, prisms or the like.

Particularly advantageously, the at least two stages can be selected such that in a first stage the measuring range is preferably realized large, while in the second stage the measuring range is preferably realized small. In this way, at least two different sizes of the measuring range can be provided, which are preferably significantly different from one another, so that advantageously at least two-stage, simple and rapid change of the size of the measuring range can be realized by means of the optics.

In an advantageous embodiment of the hand-held thermal imaging camera, the size of the measuring range is infinitely variable using the optics.

Advantageously, it can be achieved in this way that the size of the measuring range can be arbitrarily varied between a maximum and a minimum size, which are given by the optics, respectively. In particular, a measuring range can thus advantageously be adapted to a surface area of the object of interest to the operator of the thermal imaging camera, so that the temperature measured by means of the thermal imaging camera also advantageously relates only to the region of interest actually on the surface.

Preferably, a continuously variable optics can be realized by using lens means which, in particular arranged movably relative to one another, are suitable for changing the size of the measuring range. In a preferred embodiment of the thermal imager, the lens means comprise at least one adjustable lens system for changing the size of the measuring area. An adjustable lens system may include, inter alia, one or more lenses suitable for thermal radiation, i. Radiation in the mid-infrared range, are permeable and serve to direct infrared radiation from the measuring range to the detection surface of the detector device, in particular to project. Such an adjustable lens system advantageously allows the size of the measuring range to be set quickly, reliably, defined and infinitely variable according to the invention.

In an advantageous embodiment of the hand-held thermal imager, the evaluation device and / or the detector device has a calibration device for calibrating the evaluation device and / or the detector device, which is provided for the evaluation device or the detector device based on stored information and / or measured information, in particular to calibrate based on a measured temperature T in a measuring range _C.

The evaluation device and / or the detector device can be advantageously provided to interpret and / or convert interpolation and / or interpolation and / or extrapolation and to calibrate the thermal imager, in particular with regard to a temperature value, in particular with respect to a measured temperature measurement value T _C. In addition to the calibration on the basis of a temperature measurement value T _C , calibration can also be carried out by means of stored correction and / or calibration tables and / or calibration values and / or calibration routines.

In particular for the absolute determination of temperature measured values, a calibration of the thermal imaging camera, in particular a calibration of the evaluation and / or the detector device, can be provided. For example, a calibration measurement, by means of which a temperature measurement value T _C in a set measurement range, in particular in a measurement range of relatively small size, is determined as the basis for establishing an absolute temperature scale and thus for calibrating the thermal imaging camera. All subsequent measurements, in particular also measurements using other measuring ranges, in particular also using measuring ranges of a different size, are then evaluated in relation to this calibration measurement. Thus, for example, a temperature measurement value T _C , which was determined in a small measuring range, preferably in the smallest adjustable measuring range of the thermal imaging camera, serve as the basis for a calibration of the thermal imaging camera for all subsequent measurements, which in particular can include all sizes of the measuring range. Preferably, an averaged, preferably particularly accurate, measured value which has been determined in the smallest adjustable measuring range of the thermal imaging camera is suitable for the calibration.

Thus, a measurement result which is obtained using a measuring range of small size, ie in particular a temperature reading which is as accurate as possible, can be used particularly advantageously for the calibrated, in particular optimized, evaluation of detection signals which are measured using measuring ranges, in particular of a different size. In this context, "optimized evaluation" should be understood in particular to mean that the temperature measurement underlying the calibration is used to influence, advantageously improve and / or optimize at least one evaluation routine and / or an evaluation process of the evaluation device, and to calibrate it particularly advantageously to allow improved and / or more accurate evaluations of subsequent detection signals.

In an advantageous embodiment of the handheld thermal imaging camera, the calibration device is provided to calibrate the evaluation device and / or the detector device based on a detection of background radiation.

In this way, it can advantageously be achieved that a background noise superimposed on a detection signal, in particular that portion of the detection signal which is due to a detection of background radiation, can be eliminated from the measured detection signal. Consequently, thus a significant increase in accuracy of the thermal imager can be achieved, which has a positive effect especially in the measurement of relatively low temperatures. In a particularly simple embodiment of the functionality of the calibration device, for example, a calibration signal with closed optics (for example, using a Lens cap) are determined on the basis of a noise generated by background radiation, which is then subtracted in the evaluation of all subsequent temperature measurements, the calibration signal from the measured detection signals.

In an advantageous embodiment of the handheld thermal imaging camera, an output device, in particular a display and / or a wireless data communication interface, is provided for outputting a temperature measurement.

An output device of the thermal imaging camera may preferably be provided in the form of a data communication interface and / or a screen. Preferably, a data communication interface uses a standardized communication protocol for transmitting electronic, in particular digital data to, in particular, external devices. For this purpose, the data communication interface can advantageously have a wireless interface, in particular, for example, a WLAN, Bluetooth, infrared, NFC, RFID interface or another wireless interface that appears appropriate to a person skilled in the art. Alternatively, the data communication interface can also have a wired adapter, for example a USB or micro USB adapter. A screen, in particular a display, can be provided to display the evaluated information relating to a temperature of a measuring area located on a surface, preferably also a thermal image, and thus to output it directly to an operator of the thermal imager. By way of example, a display may be configured as a liquid crystal, thin film transistor, surface conduction electron emitter, plasma, light emitting diode or field emission screen. Particularly advantageously, a touch display can be used, by means of which in addition to the output of information also inputs by an operator of the thermal imager are possible.

In an advantageous embodiment of the hand-held thermal imaging camera, a camera operating in the visual spectrum is provided to record a visual image of the measuring area that can be output together with the temperature measurement.

By means of a camera operating in the visual spectrum, preferably by means of a visual image sensor for detecting a visible, in particular visual, radiation of an image area, advantageously a camera image based on detected visible radiation can be generated. The visual image area preferably comprises the measuring area of the thermal camera at least partially, particularly preferably completely. As an image sensor devices come into question that detect visible radiation between 380 nm and 780 nm wavelength and create a camera image. The camera image can in particular be designed as an electronic image signal. Examples of an image sensor according to the invention include CCD image sensors or CMOS image sensors. In the context of the present application, an image area is understood to be the quantity of particles from which visible radiation emanates which the image sensor detects.

Particularly advantageously, the evaluation and / or the control device can create an image and output by means of an output device. Particularly preferably, the visual image can be output together with the temperature measurement. In this way, according to the invention, it can be achieved that a user of the thermal imaging camera does not have to switch between the thermal imaging camera and the measurement area located on the object during the measurement because the screen is advantageous both for sighting the measurement area and for reading the measurement area determined temperature can be used. As a result, the user can concentrate particularly advantageously on an exact alignment of the thermal imaging camera, in particular also on an exact setting of the size of the measuring range, and on the reading of the measured data.

In an advantageous embodiment of the hand-held thermal imaging camera, the visual image can be at least partially superimposed or superimposed with the temperature measurement.

Particularly advantageously, the evaluation and / or the control device can output a visual image together with a temperature measurement, in particular together with a temperature measurement value and / or together with a measured thermal image. In this case, an output common image can be generated at least partially by superimposing, superimposing, trimming at least one part of the camera image with at least one information generated by the thermal imager, in particular a measured temperature of a measuring area located on a surface, preferably with at least a part of a generated thermal image ,

In this way, an advantageously intuitive and easily interpretable representation of both the measurement results and the visual images can be realized.

In an advantageous embodiment of the hand-held thermal imaging camera, a projection module is provided which serves to generate a visible marking of the measuring area. In particular, the projection module has a Light source in the visible region of the radiation spectrum, preferably a collimated light beam generating light diode or laser diode, which is suitable for generating a light mark on the surface of the object. Furthermore, further means for beam shaping may be provided, for example collimator lens, mirrors, prisms or the like. Preferably, a light pattern can also be generated from the essentially collimated light beam by means of the projection module, so that patterns, for example in the form of a polygon, cross or a conic section, in particular a circle, can be projected onto the surface. This embodiment has the advantage that the measuring range can be assigned to a location on the surface of the object even without viewing a screen, and in particular also indicates its extent, so that a very fast orientation of the thermal imaging camera to an object to be examined and adjustment can be particularly advantageous the desired size of the measuring range is possible by the user.

According to the invention, a method is also proposed for non-contact measurement of a temperature of a measurement area located on a surface, in particular a method for operating a handheld thermal imaging camera according to the invention, wherein pixels of a thermal imaging camera detector device increase thermal radiation sensitivity of the detector device as a function of an intensity of radiated heat radiation using a Binning architecture of the detector device and / or an evaluation device are summarized by signal technology, and at least the temperature of the measuring range based on detection signals of at least one plurality of illuminated pixels of the detector device is evaluated.

Advantageously, the method according to the invention enables a user of the thermal imaging camera to perform precise temperature measurements in measuring ranges of different sizes, which can be set in steps, preferably steplessly, by means of optics of the thermal imaging camera. In this way, a user of the thermal imager can, for example, determine temperatures in large measuring ranges within the scope of an overview measurement, or specifically investigate temperatures in a measuring range of reduced size, preferably at points, by setting a small measuring range. While, when using a small measuring range, an object has to be traversed in order to locate a heat source or heat sink, the measurement result obtained can advantageously be regarded as being particularly accurate and determined as being of a locally limited measuring range. On the other hand, the use of a large measuring range allows a rapid and intuitive determination of temperature profiles, in particular using a thermal image generated from the temperature measurement, so that in particular on the basis of a color coding issued on a display of the thermal imager temperature measurement data, preferably a thermal image, warm and / or cold surfaces instantly recognize.

In particular, a user of the thermal imaging camera can set a measuring range very small by means of the optics of the thermal imaging camera, i. Zoom to a detail of the object to be examined in order to determine a temperature reading in a very precise and locally very limited range. According to the invention allows the irradiated with decreasing intensity heat radiation, especially so with decreasing size of the set measuring range, carried out signal-technical summary of an increasing number of pixels of the detector device using a binning architecture of the detector device and / or the evaluation device an increase in the signal-to-noise ratio, the also with decreasing intensity radiated heat radiation takes place to counteract.

drawings

The invention is explained in more detail in the following description with reference to exemplary embodiments illustrated 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 meaningful further combinations. Like reference numerals in the figures indicate like elements.

Show it:

1 an embodiment of a thermal imaging camera according to the invention in a perspective, schematic representation,

2 a perspective, schematic sectional view of an embodiment of a thermal imaging camera according to the invention,

3a / b is a schematic representation of two possible beam paths of thermal radiation in one embodiment of the optics of the thermal imager according to the invention, in (a) with realization of a large measuring range and in (b) with realization of a small measuring range,

4 a schematic representation of a detector device, consisting of a one Variety of pixels having detection surface and a binning architecture

Description of the embodiments

1 and 2 show an exemplary embodiment of a thermal imaging camera according to the invention 10 in a perspective overall view or in a sectional view, which reproduces the internal structure of the thermal imaging camera. The thermal imager 10 includes a housing 12 with a handle 14 , With the handle 14 can the thermal imager 10 be conveniently held in one hand during use. The housing 12 the thermal imager 10 also indicates a user while using the thermal imager 10 side facing an output device in the form of a touch display 16 as well as operating elements 18 for user input and control of the thermal imager 10 on. On the side facing away from a user of the housing 12 is an entrance opening 20 in the case 12 provided by the radiated from an object, in particular from a measuring range 22 (see 3 ) radiated on a surface of the object, heat radiation in the thermal imaging camera 10 can occur. Immediately behind the entrance opening 20 is located in a stray light-reducing light tube 24 a lens system 26 ' as optics 26 consisting of two separate lens pairs 28 , Wherein the entrance opening 20 remote lens pair 28b via a sliding device 30 in its position with respect to the inlet 20 facing lens pair 28a can be moved, in particular, can be moved continuously. The lens pairs 28 , in particular the lenses included, are transparent to radiation in the mid-infrared range and serve primarily for imaging, in particular projection, preferably focusing, of thermal radiation on the detector device 32 , Both lens pairs 28 as well as the entrance opening 20 are collinear along an axis 34 with the detector device 32 the thermal imager 10 arranged. In particular, the distance of the lens pair is also 28b to the detector device 32 adjustable.

The detector device 32 detects heat radiation from the infrared radiation spectrum, which starts from the measuring range 22 on a surface to be examined conical in the inlet opening 20 the thermal imager 10 enters and by lens system 26 ' on the detector device 32 , in particular to one of the inlet opening 20 facing detection surface 36 (see. 3 ) of the detector device 32 under illumination of a plurality of pixels 40 (see. 4 ) is displayed. An axis of symmetry of the conical detection area is preferred 38 the thermal imager 10 also along the axis 34 aligned. The opening angle of the cone-shaped detection area 38 can be over the position of the lens pair 28b the adjustable lens system 26 , in particular about the distance of the lens pair 28b to the detector device 32 and the lens pair 28a , change. Accordingly, the size of the measuring range 22 about the adjustment of the pusher 30 the adjustable lens system 26 to be changed.

The detector device 32 is in the illustrated embodiment as a two-dimensional detector array, consisting of a detection surface 36 with a variety of pixels 40 (see. 4 ), in particular with 640 × 480 infrared photosensitive pixels 40 , intended. Every pixel 40 generates an electrical detection signal based on a detected thermal radiation, preferably as a function of a detected intensity of radiated heat radiation.

On the one user while using the thermal imager 10 opposite side of the housing 12 is still a working in the visual spectrum camera 42 provided by means of a visual image of the measuring range 22 is recorded, which is output together with the temperature measurement, in particular at least partially superimposed with the temperature measurement or blended output. The camera 42 is realized in the illustrated embodiment as a CCD image sensor. Furthermore, another lens system (not shown in detail), in particular a variable lens system, can be used to control the camera 42 considered image section at least partially overlapping with the measuring range 22 the thermal imager 10 to realize.

On the bottom of the thermal imager 10 has the handle 14 a recording 46 for receiving an energy storage device, which can be embodied by way of example as a rechargeable accumulator or batteries.

On a system board 48 , in particular a printed circuit board, are the electrical components of the thermal imager 10 connected. Also on the system board 48 a control device 50 and an evaluation device 52 accommodated. The control device 50 represents in particular a device which comprises at least one control electronics and means for communication with the other components of the thermal imaging camera 10 includes, in particular means for controlling and regulating the thermal imaging camera 10 , The control device 50 is intended to use the thermal imager 10 to control and enable their operation. This is the control device 50 with the other components of the measuring device, in particular the detector device 32 , the evaluator 52 , the controls 18 , the touch display 16 as well as the data communication interface 54 signally connected. The evaluation device 52 serves to receive and evaluate detection signals of the detector device 32 where each pixel 40 the detector device 32 with the evaluation device 52 can be connected by signal technology. The control device 50 and / or the evaluation device 52 and / or the detector device 32 moreover comprises a calibration device (not shown in detail), by means of which the evaluation device 52 and / or the detector device 32 based on stored information, in particular using calibration values and / or tables, and / or measured information, in particular based on a temperature measured in a measuring range T _C , can be calibrated.

Further, on the system board 48 a data communication interface 54 , In particular a WLAN and / or Bluetooth interface housed, which is provided for outputting a temperature measurement to an external device. Also, other sensors 56 in, on or on the case 12 the thermal imager 10 be housed, the extended functionality of the thermal imager 10 serve. For example, in one embodiment of the thermal imaging camera according to the invention 10 additional sensor 56 be provided from a group of sensors that includes at least induction, capacitance, ultrasound, temperature, humidity, radiation, inclination, angle, magnetic field, acceleration and rotational rate sensitive sensors.

One by an operator of the thermal imager 10 easy to reach and operate switch 58 serves to trigger a temperature measurement.

In the illustration in 3 are the components of optics 26 the out 1 and 2 known embodiment of the thermal imaging camera according to the invention 10 to detect, in particular comprising the detector device 32 with detection surface 36 , Light tube 24 , Lens system 26 ' consisting of one of the inlet opening 20 facing lens pair 28a , one of the inlet opening 20 facing away, continuously movable lens pair 28b , as well as the entrance opening 20 , Furthermore, two exemplary optical beam paths 60 represented, over which a measuring range 22 , here by the example of the lettering "ABCDE" on the detection surface 36 is shown. In particular, in 3a in a first arrangement of the lens system 26 a large measuring range 22a , ie the entire lettering "ABCDE", as a result of a large coverage area 38a the optics 26 the thermal imaging camera according to beam path 60a on the detection surface 36 displayed. This is the lens pair 28b exemplary in a relatively large distance to the detector device 32 ,

In contrast, in 3b in a second arrangement of the lens system 26 a small measuring range 22b , ie only a section "C" of the lettering "ABCDE", as a result of a small detection area 38b the optics 26 the thermal imager 10 according to beam path 60b on the detection surface 36 displayed. In this embodiment, the lens pair is located 28b at a relatively small distance to the detector device 32 ,

Between the two exemplary beam paths shown 60 In particular, it can be varied steplessly by the pair of lenses 28b by sliding device 30 is changed in his position. The size of the measuring range can be particularly easily and quickly achieved in this way 22 vary on the subject in particular continuously.

According to the invention, the evaluation device 52 and / or the detector device 32 a binning architecture 62 on, which is a signal summary of pixels 40 in particular for increasing the thermal radiation sensitivity of the detector device 32 , allows. In 4 is a detector device according to the invention 32 shown in an exemplary embodiment, such a binning architecture 62 as well as a variety of pixels 40 having detection surface 36 includes.

The detection area 36 the detector device 32 exemplifies 6x6x9 = 324 infrared photosensitive pixels 40 on, of which a majority by radiated heat radiation, the light spot 64 on the detection surface 36 be generated, illuminated. Every pixel 40 is via electrical interconnection either directly or via intermediate electrical components, in particular, for example, multiplexer, with a combiner 66 connected. There is a combiner 66 provided via an entrance 68 incoming detection signals, in particular from different pixels 40 come together via a Kombinierfunktion, preferably an OR gate, signal technology, in particular interconnect, in particular to combine. As a result, detection signals of various infrared photosensitive pixels become 40 accepted and sent to an exit 70 of the combiner 66 as a combined, in particular combined, detection signal of the corresponding pixels 40 output. The exit 70 of the combiner 66 is also signal technology with the evaluation device 52 the thermal imager 10 connected.

The signal-technical summary advantageously allows an increase in the thermal radiation sensitivity of the detector device 32 , as a result of Zusammenschalts a the Detection signal superimposed, in particular statistical, noise can be reduced.

Particularly advantageous are pixels 40 variable in terms of number and geometry summarize signal technology. Exemplary are in 4a nine pixels each 40 with a combiner 66 connected, indicated by a signaling connection 72 one as a pixel block 74 combined plurality of nine pixels 40 to a combiner 66 ,

Such a signaling connection is, for reasons of clarity, only four pixel blocks 74 exemplified.

According to the invention, by means of the variable signal technology summary of pixels 40 the detector device 32 be achieved that, depending on the intensity of the detection surface 36 radiated heat radiation a different number of pixels 40 is summarized. Preference is given to the detection surface with decreasing intensity 36 radiated heat radiation an increasing number of pixels 40 summarized by signal technology to increase the heat radiation sensitivity.

Furthermore, the detector device allows 32 , in particular using the binning architecture 62 , Detection signals of only those pixels 40 to the evaluation device 52 forward, which are actually illuminated by radiated heat radiation, ie in particular by the light spot 64 are covered. In this way, an active detection surface becomes advantageous 76 defined, preferably by irradiated heat radiation illuminated pixels 40 includes, based on which an evaluation of the temperature is to be performed. In 4a are those of the light spot 64 covered pixels 40 above 14 Pixel blocks 74 Signaling about combiners 66 with the evaluation device 52 connected. This so defined active detection area 76 is represented by a patterned surface. pixel 40 that are not part of the active detection area 76 are not taken into account in the evaluation of detection signals, so that advantageously a comparatively high noise component attributed to non-illuminated pixels 40 , is excluded from the evaluation. Particularly advantageous is the active detection surface 76 for all measurements, in particular for all set values of the measuring range 22 , optimally to the size of the actually pictured light spot 64 in the detection area 36 adapted, ie minimized accordingly. In this way, the detection signals of exclusively those individual infrared photosensitive pixels are targeted 40 evaluated that actually receive heat radiation. As a result, the active detection area 76 reduces and the noise contribution of background radiation is minimized, which is equivalent to an improvement of the signal-to-noise ratio. The determination of pixels 40 , which actually receive heat radiation, for example, in the context of a pre-measurement and subsequent comparison of measured detection signals with a threshold value and / or calibration values of the thermal imager 10 respectively.

In 4b are further examples of binning patterns of a signal aggregation of pixels 40 shown. While a periodic summary of pixels 40 in each case 2 × 2 pixel blocks (left, also compare 3 × 3 pixel blocks in 4a ) allows a particularly homogeneous and thus particularly fast and simple evaluation, by means of complex binning patterns (right) an improved adaptation to be measured light spots 64 respectively. For example, a fine resolution in the center of the light spot can be particularly advantageous 64 , corresponding to a fine resolution in the center of the measuring range 22 , can be achieved while the resolution to the peripheral areas of the light spot 64 , in particular corresponding to the edge regions of the measuring range 22 , decreases.

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 6659639 A1 [0003]
• US 2009/0304042 A1 [0003]
• US 2009/0302219 A1 [0004]
• US 7652251 A1 [0004]

Claims (13)

Handheld thermal imaging camera ( 10 ) for non-contact measurement of a temperature of a measurement area located on a surface ( 22 . 22a . 22b ), comprising at least one detector device ( 32 ) consisting of at least one detection surface ( 36 ) with a plurality of pixels ( 40 ) for the detection of out of the measuring range ( 22 . 22a . 22b ) radiated heat radiation and for generating detection signals based on a detected heat radiation, • an optic ( 26 . 26 ' ) for mapping from the measuring range ( 22 . 22a . 22b ) radiated heat radiation on the detection surface ( 36 ) illuminating a plurality of pixels ( 40 ), and • an evaluation device ( 52 ) for receiving and evaluating detection signals of the detector device ( 32 ), each pixel ( 40 ) of the detector device ( 32 ) with the evaluation device ( 52 ) is signal-technically connectable, characterized in that • a size of the measuring range ( 22 . 22a . 22b ) using the optics ( 26 . 26 ' ), • the evaluation device ( 52 ) based on detection signals of at least a plurality of illuminated pixels ( 40 ) of the detector device ( 32 ) an evaluation of the temperature of the measuring range ( 22 . 22a . 22b ) and • the evaluation device ( 52 ) and / or the detector device ( 32 ) a binning architecture ( 62 ), which comprises a signal-technical summary of pixels ( 40 ), in particular for increasing the heat radiation sensitivity of the detector device ( 32 ). Handheld thermal imaging camera ( 10 ) according to claim 1, characterized in that the evaluation device ( 52 ) and / or the detector device ( 32 ) is intended to provide a signal summary of pixels ( 40 ) for increasing the thermal radiation sensitivity as a function of the intensity of the detection surface ( 36 ) radiated heat radiation to perform. Handheld thermal imaging camera ( 10 ) according to any one of claims 1-2, characterized in that the evaluation device ( 52 ) and / or the detector device ( 32 ) is provided with decreasing intensity of the on the detection surface ( 36 ) radiated heat radiation an increasing number of pixels ( 40 ) to increase the heat radiation sensitivity signal technology summarized. Handheld thermal imaging camera ( 10 ) According to any one of claims 1-3, characterized in that the evaluation device ( 52 ) and / or the detector device ( 32 ) a variable binning architecture ( 62 ), in particular a signal-technical summary of pixels ( 40 ) of different numbers allowed. Handheld thermal imaging camera ( 10 ) according to one of claims 1-4, characterized in that the evaluation device ( 52 ) and / or the detector device ( 32 ) a symmetric binning architecture ( 62 ) having. Handheld thermal imaging camera ( 10 ) according to any one of claims 1-5, characterized in that the size of the measuring range ( 22 . 22a . 22b ) using the optics ( 26 . 26 ' ) is variable in at least two stages. Handheld thermal imaging camera ( 10 ) according to any one of claims 1-6, characterized in that the size of the measuring range ( 22 . 22a . 22b ) using the optics ( 26 . 26 ' ) is infinitely variable. Handheld thermal imaging camera ( 10 ) according to any one of claims 1-7, characterized in that the evaluation device ( 52 ) and / or the detector device ( 32 ) a calibration device for calibrating the evaluation device ( 52 ) and / or the detector device ( 32 ), which is provided to the evaluation device ( 52 ) or the detector device ( 32 ) based on stored information and / or measured information, in particular based on a in a measuring range ( 22 . 22a . 22b ) measured temperature T _C , to calibrate. Handheld thermal imaging camera ( 10 ) according to claim 8, characterized in that the calibration device is provided to the evaluation device ( 52 ) and / or the detector device ( 32 ) to calibrate based on detection of background radiation. Handheld thermal imaging camera ( 10 ) according to any one of claims 1-9, characterized in that an output device, in particular a display ( 16 ) and / or a wireless data communication interface ( 54 ), is provided for outputting a temperature measurement. Handheld thermal imaging camera ( 10 ) according to any one of claims 1-10, characterized in that a working in the visual spectrum camera ( 42 ), a visual image of the measuring range ( 22 . 22a . 22b ), which can be output together with the temperature measurement. Handheld thermal imaging camera ( 10 ) according to claim 11, characterized in that the visual image at least partially with the Temperature measurement can be superimposed or blended output. Method for non-contact measurement of a temperature of a measuring area located on a surface ( 22 . 22a . 22b ), in particular method for operating a hand-held thermal imaging camera ( 10 ) according to any one of claims 1-12, characterized in that 40 ) a detector device ( 32 ) of the thermal imager ( 10 ) for increasing a thermal radiation sensitivity of the detector device ( 32 ) as a function of an intensity of radiated heat radiation using a binning architecture ( 62 ) of the detector device ( 32 ) and / or an evaluation device ( 52 ) are summarized by signal technology, and • at least the temperature of the measuring range ( 22 . 22a . 22b ) based on detection signals of at least a plurality of illuminated pixels ( 40 ) of the detector device ( 32 ) is evaluated.

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