DE102014226342B4 - Thermal camera - Google Patents

Abstract

Hand-held thermal imaging camera (10) for the contact-free measurement of a temperature of a measurement area (22, 22a, 22b) located on a surface, comprising at least • a detector device (32) consisting of at least one detection surface (36) with a plurality of pixels (40) for detection of thermal radiation emitted from the measuring area (22, 22a, 22b) and for generating detection signals based on a detected thermal radiation, • optics (26, 26 ') for imaging thermal radiation emitted from the measuring area (22, 22a, 22b) onto the Detection area (36) with illumination of a plurality of pixels (40), the size of the measuring area (22, 22a, 22b) being changeable using the optics (26, 26 '), and • an evaluation device (52) for receiving and evaluating detection signals of the detector device (32), each pixel (40) of the detector device (32) being connectable to the evaluation device (52) in terms of signal technology , wherein the evaluation device (52) carries out an evaluation of the temperature of the measuring area (22, 22a, 22b) based on detection signals of at least a plurality of illuminated pixels (40) of the detector device (32), characterized in that • the evaluation device (52) and / or the detector device (32) has a binning architecture (62) which provides a signaling combination of pixels (40), the evaluation device (52) and / or the detector device (32) being provided for a signaling combination of pixels ( 40) in order to increase the sensitivity to heat radiation as a function of an increasing reduction in the measurement range (22, 22a, 22b), the evaluation device (52) and / or the detector device (32) being provided with increasing reduction in the measurement range (22, 22a, 22b) summarize an increasing number of pixels (40) to increase the sensitivity to heat radiation in terms of signal technology s, wherein when setting the smallest possible measuring range (22, 22b), all pixels of the detector device are combined and a determined measurement result corresponds to an average temperature in the measuring range (22, 22b).

Description

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

State of the art

Devices and methods for the contact-free measurement of a surface temperature of a measuring range 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 heat insulation as part of thermal and / or cold insulation. Often, infrared thermometers are used to discover and localize heat sources and / or heat sinks, which have the advantage of contactless and fast measurement compared to conventional temperature measuring devices and can therefore be used in particular when 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. A surface temperature of the emitting body can be determined from a measured intensity of the emitted heat radiation by means of the temperature measuring device.

Infrared thermometers known in the prior art can essentially be distinguished in two embodiments. Devices of the first type, so-called spot thermometers, typically have an infrared sensor, a lens and a display. The combination, ie in particular the arrangement of the infrared sensor with the lens, specifies a typically conical, preferably small, measurement volume from which heat radiation is detected. If the devices of the first type are aligned with a surface of an object, the intersection of the measurement volume with the surface of the object forms a measurement area. Part of the heat radiation emanating from this measurement area is detected by the device of the first type, an average surface temperature in the measurement area being evaluated from the measured intensity of the heat radiation and output by means of the display. With the help of an additional laser device, which is oriented such that, for example, the center of the measuring area is marked by the laser beam during a measurement, the contactless temperature measurement can be correlated with the location of the measurement carried out. US 6,659,639 B2 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 camera working in the visual spectral range, allow an object to be examined to be measured in the infrared range of the radiation spectrum and on the screen as a two-dimensional, color-coded Output image of the item. Such a thermal imaging camera can be used to easily identify and localize heat sources and heat sinks using the color coding of the temperature data. US 2009/0302219 A1 and US 7,652,251 A1 describe devices and methods of this second type, in US 2009/0302219 A1 also with a zoom lens.

Out US 2013/0176386 A1 and WO 2005/032126 A1 A thermal imaging camera is also known, which has a binning architecture for the signal-related combination of pixels.

Disclosure of the invention

According to the invention, a hand-held thermal imaging camera is proposed for the contact-free measurement of a temperature of a measurement area located on a surface, the at least one detector device consisting of at least one detection area with a plurality of pixels for the detection of heat radiation emitted from the measurement area and for the generation of detection signals based on a detected heat radiation , an optical system for imaging heat radiation emitted from the measurement area onto the detection surface while illuminating a plurality of pixels, and an evaluation device for receiving and evaluating detection signals of the detector device, each pixel of the detector device being connectable to the evaluation device in terms of signals.

According to the invention, the thermal imaging camera is characterized in that a size of the measurement area can be changed using the optics, the evaluation device carries out an evaluation of the temperature of the measurement area based on detection signals of at least a plurality of illuminated pixels of the detector device, and the evaluation device and / or the detector device has a binning architecture which provides a signaling combination of pixels, in particular to increase the heat radiation sensitivity of the detector device.

“Thermal imager” refers to a device for the contact-free measurement of a temperature of a measurement area located on a surface with output of at least one item of information relating to the temperature, advantageously one or more temperature measurement values, particularly advantageously a thermal image composed of a plurality of temperature measurement values. In order to simplify the description, “evaluation of a temperature”, “determination of a temperature”, “temperature measurement value” or the like in each case means information relating to the temperature of the surface in the measurement area, advantageously one or more, in particular also averaged, temperature measurement values, particularly advantageously a thermal image composed of a large number of measured temperature values.

The “measuring area” is understood to mean a geometrically, locally limited area which comprises a quantity of particles of the object, the thermal radiation of which leaves the object in the direction of the thermal camera and is at least partially captured by the latter. Depending on the material of the object, in particular on the transparency of the object for infrared radiation, the thermal imager can detect particles that are located at different distances in the object. 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. In order to simplify the following description, “measuring area” is used in particular to denote the area 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 heat radiation - and a surface of the object to be examined. Depending on the material properties of the object, this measuring range can also include heat radiation from deeper layers of the object.

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 are provided to project thermal 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 detector device of the thermal imaging camera arranged behind the optics from the point of view of the object, preferably an image of the measuring range to project a surface of the detector device, particularly preferably to focus an image of the measurement area onto a surface of the detector device. 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. For this purpose, the optics advantageously have optical components that direct, direct, concentrate, and / or otherwise influence the spatial distribution, in particular, for example, lenses, Fresnel lenses, mirrors, gratings, light guides, prisms, diffractive elements or other optical components that appear sensible to a person skilled in the art Components by means of which the heat radiation can be projected onto the surface of the detector device. These components can preferably consist in particular of moisture-sensitive salts such as sodium chloride and silver salt or of single-crystalline semiconductor materials such as germanium or zinc selenide.

According to the invention, the thermal imaging camera is intended to be able to adjust a size of the measuring area located on a surface using the optics. A focal length of the optics of the thermal imaging camera can advantageously be changed, in particular zoomed, in such a way that the size of the measuring range can be adapted by adapting the image section imaged by means of the optics. This gives a user of the thermal imager the advantage of both being able to get an overview of a surface to be examined using a large measuring range and also 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 an optical system which advantageously allows different focal lengths to be set in steps or particularly advantageously also continuously. According to the changeable, in particular zoomable, optics changeable image of the heat radiation emitted from the measurement area onto the detector device, an illuminated area of the detection area of the detector device, in particular an infrared light spot generated on the detection area, can be used as a function of a distance between the object emitting the heat radiation and the thermal imager and the exact setting of the changeable optics can generally be changeable.

The detector device detects heat radiation emitted from the measurement area and projected onto the surface thereof by means of the imaging optics and generates a detection signal based on the detected intensity. The Detector device on a surface facing the optics on a two-dimensional detection surface, which consists of a plurality of matrix-like arranged pixels. Each of the pixels of the detector device can - provided lighting by means of thermal radiation - determine image information, in particular thermal radiation emitted from a solid angle of the measuring area, preferably an intensity of the thermal radiation emitted from a solid angle of the measuring area, and generate a detection signal therefrom, whereby the detection signal generated by each pixel can then be used to determine a temperature, can advantageously be forwarded to an evaluation device, can be evaluated particularly advantageously 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, an illumination of a plurality of pixels can advantageously be achieved with thermal radiation radiated from the measurement area. Depending on the distance between the thermal imaging camera and the object and 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 represents 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 μm and 50 μm, 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 impinging on the element. Examples of infrared light-sensitive elements include photodiodes, bolometers, pyroelectric sensors, PIN diodes, avalanche photo diodes (APD), (modulated) CCD chips and CMOS pixels, but other, also sensible to a person skilled in the art, for example on silicon sensors, can also be used , 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-sensitive elements. The number of the plurality of pixels arranged in a matrix-like manner, 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 multiplicity of pixels of the detector device can be connected to the evaluation device in terms of signal technology directly or indirectly via further intermediate components. In particular, an indirect signal connection of the pixels to the evaluation device can also be implemented via switching elements, for example multiplexers or other selection circuits, which are designed to selectively pass on detection signals of a plurality of 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 and evaluated by the latter independently of detection signals of other pixels.

The evaluation device for receiving and evaluating detection signals of the detector device is to be understood as a device which has at least one information input for accepting detection signals, an information processing unit for processing, in particular evaluating the assumed detection signals, and an information output for forwarding the processed and / or evaluated detection signals , The evaluation unit 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 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 can particularly preferably also be designed as a single component. The evaluation device is provided for receiving, evaluating, and evaluating detection signals generated by the detector device, in particular the detection signals generated by the detector device, in particular signal-connected, in particular connectable, pixels of the detector device, and evaluating the temperature of the detector device based on detection signals of at least a plurality of illuminated pixels Measuring range. The evaluation device is preferably provided to perform 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 a plurality of illuminated pixels of the detector device. The evaluated information, in particular a generated temperature measurement value and / or a thermal image, can be used by the evaluation device for further processing and / or Output can be provided 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 can have stored correction and / or calibration tables and / or routines for calibration, which make it possible to interpret and / or convert evaluation results and / or to inter- and / or extrapolate as well as the thermal imaging camera calibrate in particular with regard to a temperature value, in particular with regard to a measured temperature measurement value.

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

In this context, “binning architecture” means an architecture and / or a device which allows a signaling combination of at least two pixels, in particular of adjacent pixels, preferably of a predeterminable number. “Summarize signal technology” and “summarize signal technology” should in particular be understood to mean that at least two pixels, preferably also a plurality of pixels, are summarized in such a way in terms of signal technology, advantageously interconnected, particularly advantageously combined, that a single detection signal of the interconnected pixels is output. Alternatively, “signal-technical summary” can also be understood to mean that a plurality of detection signals, generated by a plurality of pixels, are combined to form a detection signal, advantageously interconnected, and combined particularly advantageously. The signal-technical summary can already be carried out by means of the detector device itself, for example advantageously when using CCD sensors, whereby the at least two, preferably the several pixels are combined to form a “pixel block”. Since the detection signals of individual pixels of the detector device can be passed on and / or evaluated independently of one another, the evaluation device can alternatively and / or additionally also be designed to provide a signaling summary of pixels of the detector device, in particular also of their detection signals. The combined detection signal generated can be interpreted as being from a virtual pixel, consisting of at least two or advantageously a plurality of pixels.

A signal-technical combination of pixels can take place in different ways, preferably as an analog addition of physical charge-contributing pixels or as a digital addition of digitized values. In particular, a signaling 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 areas consisting of at least two, advantageously consisting of a plurality of pixels, are combined or combined to form pixel blocks or virtual pixels in such a way that advantageously a higher signal sensitivity per pixel block or per virtual block Pixel of the detector device is reached and a signal-to-noise ratio of the respective pixel block or the virtual pixel is improved. With the aggregation of pixels, the resolution of the detector device, i.e. in particular also a resolution of a measured thermal image, reduced in accordance with the number of pixels combined.

In an advantageous embodiment of the hand-held thermal imaging camera, the evaluation device and / or the detector device is provided to carry out a signal-related combination of pixels to increase the sensitivity to thermal radiation as a function of the intensity of the thermal radiation radiated onto the detection surface.

Many light-sensitive elements, in particular infrared light-sensitive elements, deliver an electronic detection signal, in particular, depending on an incident light intensity. However, with low intensity of the incident light, high noise often limits the detection accuracy of the photosensitive element compared to 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 sensitivity to heat radiation as a function of the intensity of the heat radiation radiated onto the detection surface.

The combination of the pixels can be carried out in different ways, in particular based on different requirements for an evaluation and with regard to different goals. Several or all of the plurality of pixels can advantageously be combined to form one or more pixel blocks or one or more virtual ones Combine 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. The combination of a plurality of pixels can also be carried out selectively, for example in particular limited to pixels illuminated by radiated heat radiation and advantageously with the exclusion of non-illuminated pixels. As a result, the combination of pixels can be carried out in adaptation to a partial area of the detection area illuminated by radiated heat radiation, in particular to an infrared light spot located on the detection area, so that signal contributions from unilluminated pixels, in particular signal contributions which merely represent an undesirable background noise, from the determination of the temperature of the measuring area on the surface. This is particularly advantageous for edge areas of the illuminated detection area.

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

Furthermore, portions or the entirety of the pixels of the detection area, in particular also selectively selected pixels, can be combined in terms of signal technology with the aim of generating an average value, so that in each case 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 measurement values averaged over at least partial areas of the measuring range. By combining the entirety of the pixels, in particular a pixel block covering the entire detection area of the detector device or a virtual pixel is generated, the generated detection signal corresponding in particular to an averaging of the thermal radiation radiated onto the detection area. In this form of use, the thermal imaging camera 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, with a simultaneous improvement in a signal-to-noise ratio and increasing averaging of the individual detection signals of the pixels. Consequently, an interconnection of pixels can advantageously be carried out to increase the signal-to-noise ratio and / or to increase the averaging of the thermal radiation radiated onto the individual pixels, in particular as a function of the intensity of radiated thermal radiation.

In an advantageous embodiment of the hand-held thermal imaging camera, the evaluation device and / or the detector device is provided for signaling the increasing number of pixels to increase the sensitivity to heat radiation as the intensity of the heat radiation radiated onto the detection surface decreases.

With decreasing intensity of the thermal radiation radiated onto the detection surface, the signal-to-noise ratio of electronic sensors, in particular also infrared-light-sensitive sensors, typically decreases, so that the portion of the signal that is attributable to statistical noise from the sensor increases in relation to the signal that is actually of interest and to be measured, and the measurement result becomes increasingly imprecise. According to the invention, this loss of accuracy as a result of decreasing intensity of radiated heat radiation can be compensated for by combining an increasing number of pixels, so that measurement results of high accuracy are obtained despite decreasing radiated intensity.

With decreasing intensity of radiated heat radiation, a summary of an increasing number of pixels of illuminated partial areas of the detection area - advantageously those pixels that are covered by the light spot on the detection area - can be carried out. Signal contributions from non-illuminated pixels, in particular signal contributions that merely represent an undesirable background noise, are thus excluded from the determination of the temperature of the measuring area on the surface.

The combination of an increasing number of pixels is particularly advantageously correlated with a decrease in the intensity of the thermal radiation radiated onto the detection surface as a result of an increasing reduction in the measurement range. If the measuring range is reduced by means of the optics, ie zoomed in particular by means of the optics, less heat radiation from the reduced measuring range is typically imaged onto the detector device. As a result, it also drops radiated intensity. A decrease in the measuring accuracy with increasing reduction of the measuring area 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 irradiated intensity. By combining pixels of increasing numbers, however, the spatial resolution of the detector device decreases, so that the reduced, in particular zoomed, measuring range can only be measured with a smaller number of separately resolvable pixels. Since, in the case of a greatly reduced measuring range, an averaged, non-spatially resolved temperature in the sense of a point measurement is of interest - compare functionality and application of the spot thermometer - the evaluation device and / or the detector device can be provided particularly advantageously with decreasing intensity of the radiate more and more pixels until finally, advantageously when setting the smallest possible measuring range, the combination of all pixels of the detector device is carried out and the determined measurement result corresponds to an average temperature in the measuring range on the surface. In this way, a stepless transition from an in particular high-resolution thermal imager to a spot thermometer that measures points can be realized, so that in principle two different functionalities - camera and spot measuring device - are combined in one device.

In an advantageous embodiment of the hand-held 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 executing the binning architecture as a variable binning architecture, it is advantageously possible to combine, in particular, combine any pixels of the detector device, in particular pixels of any rows and / or columns of the detector device. Furthermore, a signal-technical combination of pixels can also be provided in different ways, in particular using combiners working differently. For example, it is possible to switch between analog summary by physical charge addition and digital summary by adding 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.

“Symmetrical binning architecture” is to be understood in particular to mean that the pixels of the detector device can be combined in a symmetrical, in particular point and / or mirror symmetrical manner. In particular, it can be provided, for example, that pixels, which are each at an identical distance from the geometric center of the detection surface, can be combined in essentially ring-shaped structures. Pixels can advantageously also be combined in a point-symmetrical manner with respect to the geometric center of the detection area, so that, for example, two first pixels are combined in a point-symmetrical manner with respect to the geometric center of the detection area to form a combination of two further pixels. In this way, the symmetrical binning architecture of the evaluation device and / or the detector device allows the implementation of a particularly simple and economically advantageous variable binning architecture.

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

According to the invention, the thermal imaging camera is provided so that the size of the measuring area on the surface can be changed using the optics. In particular, a changeable optic is associated with the advantage that a user of the thermal imager can both get an overview of a surface to be examined using a large measuring range and can examine details of the surface of the object to be examined using a small measuring range. A change in the size of the measuring range can be realized in a cost-saving and particularly economical manner by means of an optical system which has different and changeable, in particular fixed, focal lengths in at least two stages, advantageously in several stages. These can be implemented, for example, by means of optical components which can be moved relative to one another, can be exchanged, and can be folded in and out of the optical path, advantageously by means of switching between optical paths, in particular mirrors, prisms or the like.

The at least two stages can be selected particularly advantageously such that in a first stage the measuring range is preferably implemented in a large manner, while in the second stage the measuring range is preferably implemented in a small manner. In this way, at least two different sizes of the measuring range can be provided, which preferably differ significantly from one another, so that at least one advantageously differs by means of the optics realizes two-stage, simple and fast change of the size of the measuring range.

In an advantageous embodiment of the hand-held thermal imaging camera, the size of the measuring range can be changed continuously using the optics.

It can advantageously be achieved in this way that the size of the measuring range can be varied as desired between a maximum and a minimum size, which are respectively predetermined by the optics. In particular, a measuring area can thus advantageously be adapted to a surface area of the object that is of interest to the operator of the thermal imaging camera, so that the temperature measured by means of the thermal imaging camera likewise advantageously relates only to the area of the surface that is actually of interest.

An infinitely variable optic can preferably be implemented using lens means which, in particular arranged movably with respect to one another, are suitable for changing the size of the measuring range. In a preferred embodiment of the thermal imaging camera, the lens means have at least one adjustable lens system for changing the size of the measuring range. For this purpose, an adjustable lens system can have, among other things, one or more lenses which are suitable for heat radiation, i.e. Radiation in the mid-infrared range are transparent and serve to direct infrared radiation from the measuring range onto the detection surface of the detector device, in particular to project it. Such an adjustable lens system advantageously allows the size of the measuring range to be set quickly, reliably, in a defined manner and according to the invention, continuously.

In an advantageous embodiment of the hand-held thermal imaging camera, 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 based on a temperature T _C measured in a measuring range.

The evaluation device and / or the detector device can advantageously be provided for interpreting and / or converting and / or interpolating and / or extrapolating evaluation results and for calibrating the thermal imaging camera in particular with regard to a temperature value, in particular with regard to a measured temperature measurement value T _C. In addition to calibration on the basis of a temperature measurement value T _C , calibration can also be carried out using stored correction and / or calibration tables and / or calibration values and / or routines for calibration.

A calibration of the thermal imaging camera, in particular a calibration of the evaluation and / or the detector device, can be provided in particular for the absolute determination of temperature measurement values. For example, a calibration measurement, by means of which a temperature measurement value T _{C is determined} in a set measurement range, in particular in a measurement range of relatively small size, can serve 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 measurement ranges, in particular also using measurement ranges of a different size, are then evaluated in relation to this calibration measurement. Thus, for example, a temperature measured value T _C , which was determined in a small measuring range, preferably in the smallest adjustable measuring range of the thermal imaging camera, can 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. Averaged, preferably particularly accurate, measured value, which was determined in the smallest adjustable measuring range of the thermal imager, is preferably suitable for calibration.

A measurement result that is obtained using a measurement area of small size, that is, in particular a temperature measurement value that is as accurate as possible, can thus be used particularly advantageously for the calibrated, in particular optimized, evaluation of detection signals that are measured using measurement areas, in particular of different sizes. In this context, “optimized evaluation” should be understood in particular to mean that the temperature measurement on which the calibration is based is used to influence at least one evaluation routine and / or one evaluation process of the evaluation device, advantageously to improve and / or optimize it, to calibrate particularly advantageously and thus enable improved and / or more precise evaluations of subsequent detection signals.

In an advantageous embodiment of the hand-held thermal imaging camera, the calibration device is provided for calibrating 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 that relates to a Detection of background radiation is due, from which the measured detection signal can be eliminated. Consequently, a significant increase in the accuracy of the thermal imager can be achieved, which has a positive effect, in particular when measuring 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 cover) can be determined on the basis of a noise signal generated by background radiation, the calibration signal then being subtracted from the measured detection signals when evaluating all subsequent temperature measurement values.

In an advantageous embodiment of the hand-held 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 imager can preferably be provided in the form of a data communication interface and / or a screen. A data communication interface preferably 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 measurement area located on a surface, preferably also a thermal image, and thus to output it directly to an operator of the thermal imaging camera. For example, a display can be configured as a liquid crystal, thin film transistor, surface conduction electron emitter, plasma, light emitting diode or field emission screen. A touch display can be used particularly advantageously by means of which inputs by an operator of the thermal imaging camera are possible in addition to the output of the information.

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 range, which can be output together with the temperature measurement.

A camera image based on detected visible radiation can advantageously be generated by means of a camera operating in the visual spectrum, preferably by means of a visual image sensor for detecting visible, in particular visual, radiation from an image area. The visual image area preferably includes the measurement area of the thermal camera at least partially, particularly preferably completely. Devices that can detect visible radiation between a wavelength of 380 nm and 780 nm and use them to create a camera image can be used as the image sensor. 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. An image area in the sense of the present application is understood to mean the amount of particles from which visible radiation originates, which the image sensor detects.

The evaluation and / or control device can particularly advantageously create an image and output it by means of an output device. The visual image can particularly preferably be output together with the temperature measurement. In this way, it can be achieved according to the invention 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, since the screen is advantageous both for sighting the measurement area and for reading the area determined temperature can be used. As a result, the user can particularly advantageously concentrate on precisely aligning the thermal imager, in particular also on precisely setting the size of the measurement area, and on reading the measurement data.

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

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. An output common image can be generated at least partially by superimposing, fading, cropping at least a part of the camera image with at least one item of information generated by the thermal imaging camera, in particular a measured temperature of a measuring area located on a surface, preferably with at least 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. The projection module in particular has a light source in the visible region of the radiation spectrum, preferably a light diode or laser diode generating a collimated light beam, which is suitable for generating a light marking on the surface of the object. Furthermore, further means for beam shaping can be provided, for example a collimator lens, mirror, prisms or the like. The projection module can preferably also be used to generate a light pattern from the essentially collimated light beam, so that patterns, for example in the form of a polygon, cross or conic section, in particular a circle, can be projected onto the surface. This embodiment is associated with the advantage that the measuring area can be assigned to a location on the surface of the object even without viewing a screen, in particular also its extent can be recognized, so that it is particularly advantageous to align the thermal imager very quickly to an object to be examined and setting the desired size of the measuring range is possible by the user.

According to the invention, a method for non-contact measurement of a temperature of a measurement area located on a surface, in particular a method for operating a hand-held thermal imaging camera according to the invention, is proposed, wherein pixels of a detector device of the thermal imaging camera are used to increase a sensitivity to thermal radiation of the detector device as a function of an intensity of radiated heat radiation Binning architecture of the detector device and / or an evaluation device can be combined in terms of signal technology, and at least the temperature of the measurement area is evaluated based on detection signals of at least a plurality of illuminated pixels of the detector device.

The method according to the invention can advantageously enable a user of the thermal imaging camera to carry out precise temperature measurements in measuring ranges of different sizes, which can be adjusted in stages, preferably continuously, by means of an optical system of the thermal imaging camera. In this way, a user of the thermal imager can, for example, determine temperatures in large measurement ranges as part of an overview measurement, or specifically examine temperatures in a measurement range of reduced size, preferably selectively, by setting a small measurement range. While when using a small measuring range, an object has to be scanned in a targeted manner in order to locate a heat source or heat sink, the measurement result obtained can advantageously be regarded as particularly accurate and as being determined on a locally limited measuring range. On the other hand, the use of a large measuring range enables a quick 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 of temperature measurement data, preferably a thermal image, output on a display of the thermal imaging camera, warm and / or cold surfaces instantly recognize.

In particular, a user of the thermal imaging camera can set a measuring range particularly small by means of the optics of the thermal imaging camera, i.e. Zoom in on a detail of the object to be examined in order to determine a temperature measurement value in a measurement range that is as precise and locally as possible. According to the invention, the heat radiation radiated with decreasing intensity, in particular also with decreasing size of the set measurement range, allows an increasing number of pixels of the detector device to be carried out using a binning architecture of the detector device and / or of the evaluation device, an increase in the signal-to-noise ratio which counteracted also with decreasing intensity of radiated heat radiation.

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 einer erfindungsgemäßen Wärmebildkamera in einer perspektivischen, schematischen Darstellung,
• 2 eine perspektivische, schematische Schnittdarstellung einer Ausführungsform einer erfindungsgemäßen Wärmebildkamera,
• 3a/b eine schematische Darstellung zweier möglicher Strahlengänge von Wärmestrahlung in je einer Ausführungsform der Optik der erfindungsgemäßen Wärmebildkamera, in (a) unter Realisierung eines großen Messbereichs und in (b) unter Realisierung eines kleinen Messbereichs,
• 4 eine schematische Darstellung einer Detektorvorrichtung, bestehend aus einer eine Vielzahl von Pixeln aufweisenden Detektionsfläche und einer Binning-Architektur

Show it:

• 1 An embodiment of a thermal imaging camera according to the invention in a perspective, schematic representation,
• 2 2 shows a perspective, schematic sectional illustration 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 imaging camera according to the invention, in (a) realizing a large measuring range and (b) realizing a small measuring range,
• 4 is a schematic representation of a detector device consisting of a detection surface having a plurality of pixels 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 reflects the internal structure of the thermal imager. The thermal imaging camera 10 includes a housing 12 with one handle 14 , With the handle 14 can the thermal imager 10 are comfortably held in one hand while in use. The housing 12 the thermal imager 10 also points to a user while using the thermal imager 10 facing side an output device in the form of a touch display 16 as well as controls 18 for user input and control of the thermal imager 10 on. On the side of the housing facing away from a user 12 is an entrance opening 20 in the housing 12 provided by the radiated from an object, in particular from a measuring range 22 (see 3 ) thermal radiation emitted on a surface of the object into the thermal imager 10 can occur. Immediately behind the entrance opening 20 is located in a light tube that reduces stray light 24 a lens system 26 ' as optics 26 , consisting of two separate pairs of lenses 28 , which is the entrance opening 20 averted pair of lenses 28b via a sliding device 30 in position with respect to that of the entry opening 20 facing pair of lenses 28a can be moved, in particular can be moved continuously. The lens pairs 28 , in particular the encompassed lenses, are transparent to radiation in the mid-infrared range and are used primarily for imaging, in particular projection, preferably focusing, of thermal radiation onto the detector device 32 , Both pairs of lenses 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 between the pair of lenses is also 28b to the detector device 32 adjustable.

The detector device 32 captures heat radiation from the infrared radiation spectrum, starting from the measurement range 22 on a surface to be examined in a conical shape into the inlet opening 20 the thermal imager 10 enters and by means of a lens system 26 ' on the detector device 32 , especially one of the entry opening 20 facing detection area 36 (see. 3 ) of the detector device 32 illuminating a plurality of pixels 40 (see. 4 ) is mapped. 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 conical detection area 38 can be determined by the position of the lens pair 28b of the adjustable lens system 26 , especially the distance between the pair of lenses 28b to the detector device 32 and the pair of lenses 28a , change. Accordingly, the size of the measuring range 22 about the adjustment of the sliding device 30 of 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 area 36 with a variety of pixels 40 (see. 4 ), especially with 640 × 480 infrared-sensitive pixels 40 , intended. Every pixel 40 generates an electrical detection signal based on a detected heat 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 camera working in the visual spectrum 42 provided by means of a visual image of the measurement area 22 is recorded, which is output together with the temperature measurement, in particular is at least partially superimposed or output with the temperature measurement. The camera 42 is implemented in the illustrated embodiment as a CCD image sensor. Furthermore, a further lens system (not shown in more detail), in particular a variable lens system, can be used in order to use the camera 42 considered image section at least partially overlapping with the measurement area 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 store, which can be designed as a rechargeable battery or batteries, for example.

On a system board 48 , in particular a printed circuit board, are the electrical components of the thermal imager 10 connected. Are 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 that has at least one control electronics and means for communication with the other components of the thermal imager 10 includes, in particular means for controlling and regulating the thermal imager 10 , The control device 50 is provided 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 evaluation device 52 , the controls 18 , the touch display 16 as well as the data communication interface 54 connected by signaling. The evaluation device 52 is used to receive and evaluate detection signals from the detector device 32 , where each pixel 40 the detector device 32 with the evaluation device 52 is connectable in terms of signaling. The control device 50 and / or the evaluation device 52 and / or the detector device 32 also includes a calibration device (not shown in detail) by means of which the evaluation device 52 and / or the detector device 32 can be calibrated based on stored information, in particular using calibration values and / or tables, and / or measured information, in particular based on a temperature T _C measured in a measuring range.

It is also on the system board 48 a data communication interface 54 , in particular a WLAN and / or Bluetooth interface, which is provided for outputting a temperature measurement to an external device. Other sensors can also be used 56 in, on or on the housing 12 the thermal imager 10 be accommodated, the extended functionality of the thermal imager 10 serve. For example, in one embodiment of the thermal imaging camera according to the invention 10 further sensor 56 can be provided from a group of sensors, which includes at least induction, capacitance, ultrasound, temperature, humidity, radiation, inclination, angle, magnetic field, acceleration and rotation rate sensitive sensors.

One by an operator of the thermal imager 10 Easily accessible and operable switch 58 is used to trigger a temperature measurement.

In the representation in 3 are the components of optics 26 the one out 1 and 2 known embodiment of the thermal imaging camera according to the invention 10 to recognize, including in particular the detector device 32 with detection area 36 , Light tube 24 , Lens system 26 ' consisting of one of the entry opening 20 facing pair of lenses 28a , one of the entry openings 20 facing, steplessly movable pair of lenses 28b , as well as the entrance opening 20 , Furthermore, there are two exemplary optical beam paths 60 shown over which a measuring range 22 , here using the example of the lettering "ABCDE", on the detection surface 36 is mapped. 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 detection area 38a the optics 26 the thermal imaging camera according to the beam path 60a on the detection surface 36 displayed. Here is the pair of lenses 28b exemplary at a relatively large distance from 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 the beam path 60b on the detection surface 36 displayed. In this embodiment, the pair of lenses is located 28b at a relatively short distance from the detector device 32 ,

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

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

The detection area 36 the detector device 32 has, for example, 6 × 6 × 9 = 324 infrared light-sensitive pixels 40 on, a majority of which by radiated heat radiation, which is a light spot 64 on the detection surface 36 generated, illuminated. Every pixel 40 is via electrical interconnection either directly or via intermediate electrical components, in particular for example multiplexers, 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, via a combining function, preferably an OR gate, to summarize in terms of signal technology, in particular to interconnect, in particular to combine. As a result, detection signals of various infrared light sensitive pixels 40 accepted and 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 signaling summary advantageously allows an increase in the sensitivity to heat radiation of the detector device 32 , since, as a result of the interconnection, a noise, in particular statistical noise, superimposed on the detection signal can be reduced.

Pixels are particularly advantageous 40 summarize variable in terms of number and geometry in terms of signals. Examples are in 4a nine pixels each 40 with a combiner 66 connected, indicated by a signal connection 72 one as a pixel block 74 summarized plurality of nine pixels 40 to a combiner 66 ,

For reasons of clarity, such a signaling interconnection is only for four pixel blocks 74 shown as an example.

According to the invention, the variable signal-technical combination of pixels 40 the detector device 32 can be achieved depending on the intensity of the detection area 36 radiated heat radiation a different number of pixels 40 is summarized. Preference is given to the detection area decreasing in intensity 36 radiated heat radiation an increasing number of pixels 40 summarized in terms of signal technology to increase the sensitivity to heat radiation.

Furthermore, the detector device allows 32 , especially 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 area is advantageous 76 defines the preferably illuminated pixels by radiated heat radiation 40 comprises, on the basis of which an evaluation of the temperature is to be carried out. In 4a are those from the spot of light 64 covered pixels 40 about 14 Pixel blocks 74 signaling via combiners 66 with the evaluation device 52 connected. This 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 attributable to non-illuminated pixels 40 , is excluded from the evaluation. The active detection area is particularly advantageous 76 for all measurements, especially for all set sizes of the measuring range 22 , optimally to the size of the light spot actually depicted 64 in the detection area 36 adjusted, ie minimized accordingly. In this way, the detection signals from only those individual infrared light-sensitive pixels are targeted 40 evaluated that actually receive heat radiation. This enables the active detection area 76 are reduced and the noise contribution from background radiation is minimized, which is synonymous with an improvement in the signal-to-noise ratio. The determination of pixels 40 that actually receive heat radiation can be obtained, for example, as part of a preliminary measurement and subsequent comparison of measured detection signals with a threshold value and / or calibration values of the thermal imaging camera 10 respectively.

In 4b are further examples of binning patterns of a signaling combination of pixels 40 shown. During a periodic summary of pixels 40 in 2 × 2 pixel blocks each (left, compare also 3 × 3 pixel blocks in 4a) enables a particularly homogeneous and therefore particularly quick and easy evaluation, an improved adaptation to light spots to be measured can be achieved by means of more complex binning patterns (right) 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 edge areas of the light spot 64 , in particular corresponding to the edge areas of the measuring area 22 , decreases.

Claims (11)

Hand-held thermal imaging camera (10) for the contact-free measurement of a temperature of a measurement area (22, 22a, 22b) located on a surface, comprising at least • a detector device (32) consisting of at least one detection surface (36) with a plurality of pixels (40) for detection of thermal radiation emitted from the measuring area (22, 22a, 22b) and for generating detection signals based on a detected thermal radiation, • optics (26, 26 ') for imaging thermal radiation emitted from the measuring area (22, 22a, 22b) onto the Detection area (36) with illumination of a plurality of pixels (40), the size of the measuring area (22, 22a, 22b) being changeable using the optics (26, 26 '), and • an evaluation device (52) for receiving and evaluating detection signals of the detector device (32), each pixel (40) of the detector device (32) being connectable to the evaluation device (52) in terms of signal technology The evaluation device (52) is based on detection signals of at least a plurality of illuminated pixels (40) of the detector device (32) Temperature of the measuring area (22, 22a, 22b), characterized in that • the evaluation device (52) and / or the detector device (32) has a binning architecture (62) which provides a signaling combination of pixels (40), The evaluation device (52) and / or the detector device (32) is provided to carry out a signaling combination of pixels (40) to increase the sensitivity to heat radiation as a function of an increasing reduction in the measuring range (22, 22a, 22b), the evaluation device ( 52) and / or the detector device (32) is provided to combine an increasing number of pixels (40) for increasing the sensitivity to heat radiation as the measurement area (22, 22a, 22b) becomes smaller, whereby when setting a smallest possible measurement range (22 , 22b) all the pixels of the detector device are combined and a determined knife result of an average temperature in the measuring range (22, 22b). Hand-held thermal imaging camera (10) Claim 1 , characterized in that the evaluation device (52) and / or the detector device (32) has a variable binning architecture (62), which in particular allows a signaling combination of pixels (40) of different numbers. Hand-held thermal imager (10) according to one of the Claims 1 - 2 , characterized in that the evaluation device (52) and / or the detector device (32) has a symmetrical binning architecture (62). Hand-held thermal imager (10) according to one of the Claims 1 - 3 , characterized in that the size of the measuring range (22, 22a, 22b) can be changed in at least two stages using the optics (26, 26 '). Hand-held thermal imager (10) according to one of the Claims 1 - 4 , characterized in that the size of the measuring range (22, 22a, 22b) can be changed continuously using the optics (26, 26 '). Hand-held thermal imager (10) according to one of the Claims 1 - 5 , characterized in that the evaluation device (52) and / or the detector device (32) has a calibration device for calibrating the evaluation device (52) and / or the detector device (32), which is provided for the evaluation device (52) and / or calibrate the detector device (32) based on stored information and / or measured information, in particular based on a temperature T _C measured in a measuring range (22, 22a, 22b). Hand-held thermal imaging camera (10) Claim 6 , characterized in that the calibration device is provided to calibrate the evaluation device (52) and / or the detector device (32) based on a detection of background radiation. Hand-held thermal imager (10) according to one of the Claims 1 - 7 , 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. Hand-held thermal imager (10) according to one of the Claims 1 - 8th , characterized in that a camera (42) operating in the visual spectrum is provided to record a visual image of the measuring area (22, 22a, 22b), which can be output together with the temperature measurement. Hand-held thermal imaging camera (10) Claim 9 , characterized in that the visual image can be at least partially superimposed or output with the temperature measurement. Method for the contact-free measurement of a temperature of a measuring area (22, 22a, 22b) located on a surface, in particular method for operating a hand-held thermal imaging camera (10) according to one of the Claims 1 - 10 , wherein • pixels (40) of a detector device (32) of the thermal imaging camera (10) for increasing a thermal radiation sensitivity of the detector device (32) as a function of an increasing reduction in the measuring range (22, 22a, 22b) using a binning architecture (62) Detector device (32) and / or an evaluation device (52) are combined in terms of signal technology, and at least the temperature of the measuring area (22, 22a, 22b) is evaluated based on detection signals of at least a plurality of illuminated pixels (40) of the detector device (32), • wherein as the measuring range (22, 22a, 22b) becomes smaller, an increasing number of pixels (40) are combined in terms of signal technology to increase the sensitivity to heat radiation, • whereby when setting the smallest possible measuring range (22, 22b) all pixels of the detector device are combined and a determined one Measurement result of an average temperature in the measuring range (22, 22b).

Images