DE102016015843B3 - Beam power measurement with widening using a lens array - Google Patents

Abstract

Device for measuring power and/or energy of a laser beam (10), comprising a radiation sensor (40), an expansion device (30), and a holder (20), the radiation sensor (40) having a receiving surface (41) and for Generating an electrical signal (47) which depends on the power of the laser beam (10) or on the energy of the laser beam (10), the expansion device (30) and the radiation sensor (40) being at a distance (25) from one another are arranged on the mount (20) to form a propagating laser beam (11) between the expansion device (30) and the radiation sensor (40), the expansion device (30) being designed to increase an angular spectrum of the laser beam (10), wherein the expansion device (30) is a lens array, with a diameter of the propagated laser beam (11, 12) on the receiver surface (41) being larger than a diameter of the laser beam (10) in the area of the expansion device (30), the radiation sensor (40) comprising an absorption body (44) and a temperature sensor (46), the temperature sensor (46) being thermally coupled to the absorption body (44), and the receiver surface (41) of the radiation sensor (40) encloses at least 90% of a cross-sectional area of the propagated laser beam (11, 12).

Description

FIELD OF THE INVENTION

The invention relates to a method and a device for measuring the power or energy of a laser beam. The invention enables the direct measurement of laser radiation with a very high power density, for example focused laser beams in the area of the laser beam focus.

BACKGROUND OF THE INVENTION

Devices for measuring the energy or the power of a laser beam are known in large numbers and with different functional principles. One way to measure the power or energy of a laser beam is to use a photodiode. An example is the patent U.S. 3,687,558 A referenced, in which a laser power energy meter with a photodiode and an electronic circuit is disclosed. Devices of this type are particularly suitable for measuring low levels of radiation power. At higher power densities, a photodiode can quickly become saturated or even be destroyed.

In the case of higher beam powers, measurements are therefore usually made indirectly, ie the beam does not hit the detector directly or does not hit the detector with its entire cross-section. One possibility of indirect measurement is to first weaken the laser beam, as is the case, for example, in DE 100 12 536 A1 will be shown. In the device proposed there for measuring the intensity of a light beam, a light-receiving window and a device for scattering and attenuating the light are provided in front of the detector. Since the detector records only a small portion of the incident light, great effort is required to keep the sensitivity of the recorded value of the position and the angle of the light beam on the light-receiving window low. In addition, the weakened beam power is mainly converted into heat, which can affect the accuracy, since the sensitivity of semiconductor sensors is generally temperature-dependent, for example due to the temperature-dependent dark current.

From the patent U.S. 6,072,573 A a compact, portable laser measuring device with a photocell and a displaceable attenuator is known. The attenuator contains, for example, two diffuser disks and can be pushed in front of the photo cell of the measuring device to attenuate and expand the laser beam to be measured.

Another common method for indirect measurement is the decoupling of a small part of the beam for the measurement. A device of this type is in the DE 43 36 589 C1 shown. A laser power meter is disclosed there, in which a highly transmitting beam splitter reflects a fraction of the laser beam towards the sensor. The problem here is the dependency of the degree of reflection on the polarization and the angle of incidence of the laser beam, so that calibration and thus precise measurement are difficult. To solve the problem of polarization dependence is in a second embodiment of the DE 43 36 589 C1 proposed to arrange two beam splitters of the same specification one after the other, with the second deflection taking place in a plane perpendicular to the first deflection. However, the problem of angle dependency remains, which is why the device is only suitable for collimated radiation and must be precisely aligned.

A further developed device of a similar kind with several reflections in different planes is shown in DE 10 2012 106 779 B4 . In the optics for beam measurement disclosed there, three partially reflecting mirrors are used in order to compensate for the polarization dependency and additionally the angle dependency of the reflection, so that a measurement is also possible on divergent radiation. However, the device disclosed there is primarily intended for geometric beam measurement, ie for measuring intensity profiles and for determining beam parameters, and is less suitable for determining the overall power of a beam.

A measurement of the total radiant power with devices in which the beam is heavily attenuated is always limited in accuracy. On the one hand, a complex calibration is required, which limits the measurement accuracy, and on the other hand, even small parameter deviations in the elements involved can influence the attenuation factor and lead to significant changes in the sensitivity of the measuring device due to the high attenuation factor.

With regard to the accuracy that can be achieved, direct measurement methods can therefore be advantageous. High accuracies can be achieved with calorimetric methods, in which the laser radiation striking a detector is essentially converted into heat and the temperature changes, the temperature gradients that form, or the heat flows that are dissipated are measured. In principle, this means that very high power levels can also be measured if the detector is sufficiently cooled. For example, in the DE 10 2014 012 913 A1 an energy jet power measurement in which the energy radiation is collected by an absorber and the absorber is cooled by means of a stationary fluid flow. The jet power is determined from the temperature increase in the cooling fluid compared to a temperature increase in the fluid caused by electrical heating. It can be used to measure very high power, but the power must be distributed in the absorber to prevent local overheating and possible damage to the absorber. A measurement in the area of a beam focus is therefore not possible.

The pamphlet CN 1 03 389 157 A shows an absorber for a laser calorimeter. The absorber includes a beam expander with an array of reflective conical regions and an absorbing cavity. The laser beam is expanded by means of the reflecting conical partial surfaces before it hits the absorbing surfaces of the cavity. A cooling liquid flows through the jet-expanding cones and the outer periphery of the absorbing cavity.

The patent shows an example of a laser power meter with an air-cooled measuring head U.S. 5,678,924A . The probe includes a capture disk in thermal contact with a heat sink. When the catching disc is irradiated, a temperature gradient forms in the catching disc, which is determined using an arrangement of thermocouples. Due to the heat sink and the air cooling with fans, the measuring head arrangement is relatively large, so that it is difficult to use it where space is limited. When used in the area of a beam focus, the capture disc can locally overheat and become damaged.

Calorimetric measuring devices can be made much more compact if they work according to the ballistic principle. There is no active cooling and the measurement is limited to a short period of time. The energy or the power can be determined from the temperature increase of the collecting body or the absorber. the DE 102 53 905 A1 and the U.S. 7,077,564 B2 show typical representatives of such a type of measuring device. Since the beam hits the absorber directly, it is not possible to measure high-power laser radiation in the area of a beam focus, as the absorber can be damaged at certain points due to overheating.

In the case of the direct measurement of laser radiation with high power or high power density, there is therefore a fundamental problem that the device or the sensor can be damaged. With practically all known measuring devices, care must therefore be taken to ensure that the laser beam on the detector does not exceed a specific power density. To do this, the laser beam must have a certain minimum diameter, the size of which depends, among other things, on the damage threshold of the detector and the power of the laser beam. For this purpose, the measuring device is usually arranged in the divergent beam at a sufficiently large distance from a beam focus. This is often possible with measurements on experimental setups in a laboratory, or at least achievable by making partial changes to the setup.

An important application of laser power meters is to set up and periodically test or control the power or energy of a laser beam in laser material processing equipment. The power or energy of the beam at the processing location is of interest, where the beam is usually focused and therefore particularly high power densities occur. It is therefore not possible to measure at this point with commercially available measuring heads; other measuring positions, where the laser beam has grown to a sufficient diameter due to its divergence, are often not accessible in laser material processing systems.

Lens arrays are known, for example, from optical arrangements for wavefront measurement. Lens arrays are used in wavefront sensors to divide a light beam into a number of partial apertures and to image the partial beams formed from the partial apertures onto a detector. The document CN 1 01 285 712 A discloses an example of such a wavefront measuring device with a microlens array, in which the partial beams generated by the microlens array are imaged onto a group of detectors by means of an enlarging optical adjustment system.

There is therefore a need for a simple, compact laser power measuring device which enables the direct and precise measurement of the power and/or the energy of a laser beam even in areas close to the beam focus.

BRIEF DESCRIPTION OF THE INVENTION

It is the object of this invention to provide a method and a device for determining the power and/or the energy of a laser beam which are also suitable for direct and precise measurements in the focus area of a laser beam.

To solve the problem, a device for measuring the power and/or the energy of a laser beam is proposed, which includes a radiation sensor, an expansion device, and a holder. In this case, the radiation sensor has a receiving surface and is designed to generate an electrical signal which is dependent on the power of the laser beam or on the energy of the laser beam. The radiation sensor includes an absorption body and a temperature sensor. The temperature sensor is thermally coupled to the absorption body. The expansion device and the radiation sensor are arranged at a distance from one another on the holder, so that the laser beam propagates between the expansion device and the radiation sensor. The expanding device is a lens array and is designed to increase the angular spectrum of the laser beam. A diameter of the propagated laser beam on the receiving surface of the radiation sensor is larger than a diameter of the laser beam in the area of the expansion device. Furthermore, the receiving area of the radiation sensor encloses at least 90% of the cross-sectional area of the propagated laser beam.

In one possible embodiment, the expansion device has a light-scattering structure or a light-diffracting structure.

In a further possible embodiment, the holder is designed as a housing which encloses the expansion device and the radiation sensor and has an opening towards the expansion device.

The radiation sensor can be designed to detect an intensity that varies locally within a cross section of the laser beam as an integral value.

A possible embodiment is also provided, in which the device contains a light sensor which is designed to detect a small proportion of the laser beam or a scattered light proportion of the laser beam.

In a further possible embodiment of the device, a collimation device can be arranged between the expansion device and the radiation sensor.

The collimation device can include a converging lens, an optic consisting of several lenses, a Fresnel lens, a gradient index lens, or a concave mirror.

In yet another possible embodiment of the device, a beam guidance device can be arranged between the expansion device and the radiation sensor.

The beam guidance device can be a light-guiding prism, an inner cylinder mirror, an inner cone mirror, or a kaleidoscope-like mirror arrangement.

To solve the problem, a method for measuring the power and/or the energy of a laser beam with the following method steps is also proposed. The angular spectrum of the laser beam is increased by means of an expansion device. The angle spectrum of the laser beam is increased by means of a lens array. The laser beam propagates from the expansion device to a radiation sensor with a receiving surface, the radiation sensor containing an absorption body and a temperature sensor, and the expansion device and the radiation sensor being arranged at a distance from one another on a holder. At least 90% of the cross-sectional area of the propagated laser beam is detected by the receiver surface of the radiation sensor, with a diameter of the propagated laser beam on the receiver surface being larger than a diameter of the laser beam in the area of the expansion device. At least 90% of the cross-sectional area of the laser beam is detected by the receiver surface of the radiation sensor by absorbing the majority of the laser beam impinging on the receiver surface by means of the absorption body. An electrical signal is generated by the radiation sensor depending on the power of the laser beam or on the energy of the laser beam. The generation of the electrical signal as a function of the power or the energy of the laser beam is carried out by the temperature sensor, which is thermally coupled to the absorption body.

In one possible method, an intensity that varies locally within a cross section of the laser beam is detected by the radiation sensor as an integral value.

In a further possible method, provision is made in an additional method step to determine an energy or a power of the laser beam from the difference in the temperatures of the absorption body after the end of the irradiation of the laser beam and before the start of the irradiation of the laser beam.

An additional method step can also be provided to detect a small portion of the laser beam or a scattered light portion of the laser beam by means of a light sensor.

A possible method is also provided, which includes the following further method steps. An energy of the laser beam is determined from the difference in the temperatures of the absorption body after the end of the irradiation of the laser beam and before the beginning of the irradiation of the laser beam. An irradiation duration of the laser beam is determined from the course of the signal from the light sensor. Finally, a power of the laser beam is determined by dividing the energy and the irradiation time.

In a further possible method, the laser beam can be propagated from the expansion device to the radiation sensor in two sections. The angular spectrum of the propagating laser beam is reduced between the two sections by means of a collimation device which is arranged between the expansion device and the radiation sensor.

A method is also provided in which the propagated laser beam is centered on the receiving surface of the radiation sensor by means of a beam guiding device which is arranged between the expanding device and the radiation sensor.

character list

• 1: Eine schematische Darstellung einer ersten Ausführungsform der Erfindung mit einer Aufweitungseinrichtung und einem Strahlungssensor.
• 2: Eine schematische Darstellung einer zweiten Ausführungsform der Erfindung mit einer Aufweitungseinrichtung, einer Kollimationseinrichtung und einem Strahlungssensor.
• 3: Eine schematische Darstellung eines nicht von der Erfindung umfassten Ausführungsbeispiels der ersten Ausführungsform, bei der die Aufweitungseinrichtung als Sammellinse ausgebildet ist.
• 4: Eine schematische Darstellung eines nicht von der Erfindung umfassten Ausführungsbeispiels der zweiten Ausführungsform, bei der die Aufweitungseinrichtung als Zerstreuungslinse ausgebildet ist, und die Kollimationseinrichtung als Sammellinse ausgebildet ist.
• 5: Eine Darstellung eines Ausführungsbeispiels der ersten Ausführungsform der Erfindung mit einem Linsenarray als Aufweitungseinrichtung. Der Strahlungssensor ist als Absorptionskörper mit einem Temperatursensor ausgeführt.
• 6: Eine Darstellung eines Ausführungsbeispiels der zweiten Ausführungsform der Erfindung, mit einem Linsenarray als Aufweitungseinrichtung und mit einem Hohlspiegel als Kollimationseinrichtung.
• 7: Eine Darstellung eines nicht von der Erfindung umfassten Ausführungsbeispiels mit einem Konvexspiegel als Aufweitungseinrichtung, mit einem Hohlspiegel als Kollimationseinrichtung, und mit einer als Gehäuse ausgebildeten Halterung.
• 8: Eine Darstellung eines nicht von der Erfindung umfassten Ausführungsbeispiels ähnlich der in 7 gezeigten Ausführungsform, wobei hier die Aufweitungseinrichtung als Facettenspiegel ausgebildet ist.
• 9: Eine Darstellung eines Ausführungsbeispiels der Erfindung als kompaktes Messgerät, bei dem die Halterung als Gehäuse ausgebildet ist und eine elektronische Recheneinheit sowie eine Schnittstelle in das Gehäuse integriert ist.
• 10: Eine Darstellung eines weiteren Ausführungsbeispiels der Erfindung als kompaktes Messgerät ähnlich der in 9 gezeigten Ausführungsform. Die Kollimationseinrichtung ist hier als Optik mit mehreren Sammellinsen ausgeführt. Die Aufweitungseinrichtung umfasst zur Erhöhung des Winkelspektrums der Strahlung eine lichtstreuende Struktur.
• 11a: Eine schematische Darstellung einer dritten Ausführungsform der Erfindung mit einer Aufweitungseinrichtung, einer Strahlführungseinrichtung und einem Strahlungssensor.
• 11b: Eine Darstellung einer dritten Ausführungsform der Erfindung wie in 11a, mit einem schräg einfallenden Laserstrahl, der von der Strahlführungseinrichtung auf den zentralen Bereich der Empfängerfläche des Strahlungssensors gelenkt wird.
• 12: Eine Darstellung eines weiteren Ausführungsbeispiels der dritten Ausführungsform der Erfindung, bei der die Strahlführungseinrichtung durch Umlenkung von Teilbereichen des propagierenden Laserstrahls das Winkelspektrum der Strahlung verringert.
• 13: Eine schematische Darstellung einer vierten Ausführungsform der Erfindung, bei der die Aufweitungseinrichtung gleichzeitig als Strahlführungseinrichtung und als Kollimationseinrichtung ausgebildet ist.
• 14: Eine Darstellung eines weiteren Ausführungsbeispiels der ersten Ausführungsform der Erfindung, bei der der Strahlungssensor einen Absorptionskörper in Form eines Hohlkörpers mit einer konischen Empfängerfläche umfasst.
• 15: Eine Darstellung eines anderen Ausführungsbeispiels der ersten Ausführungsform der Erfindung, bei der der Strahlungssensor einen Absorptionskörper in Form eines Hohlzylinders beinhaltet und ein Teil der Empfängerfläche reflektierend ausgestaltet ist.
• 16: Eine Darstellung noch eines weiteren Beispiels der ersten Ausführungsform der Erfindung, bei der der Strahlungssensor einen Absorptionskörper in Form eines Hohlzylinders beinhaltet, und bei dem der Strahlungssensor mit einer Kühleinrichtung ausgestattet ist.
• 17: Eine Darstellung eines weiteren Ausführungsbeispiels der zweiten Ausführungsform der Erfindung, bei dem der Strahlungssensor mit einer Kühleinrichtung ausgestattet ist.

The invention is illustrated in more detail using the following figures, without being restricted to the embodiments and examples shown. Rather, embodiments are also provided in which several features shown in different figures can be combined. It shows:

• 1 : A schematic representation of a first embodiment of the invention with an expansion device and a radiation sensor.
• 2 : A schematic representation of a second embodiment of the invention with an expansion device, a collimation device and a radiation sensor.
• 3 1: A schematic representation of an exemplary embodiment of the first embodiment not covered by the invention, in which the widening device is designed as a converging lens.
• 4 1: A schematic representation of an exemplary embodiment of the second embodiment not covered by the invention, in which the expansion device is designed as a diverging lens and the collimation device is designed as a converging lens.
• 5 : A representation of an embodiment of the first embodiment of the invention with a lens array as expansion device. The radiation sensor is designed as an absorption body with a temperature sensor.
• 6 : A representation of an exemplary embodiment of the second embodiment of the invention, with a lens array as expansion device and with a concave mirror as collimation device.
• 7 1: A representation of an exemplary embodiment not covered by the invention, with a convex mirror as the expansion device, with a concave mirror as the collimation device, and with a holder designed as a housing.
• 8th : An illustration of an embodiment not covered by the invention similar to that in FIG 7 embodiment shown, in which case the expansion device is designed as a facet mirror.
• 9 : A representation of an embodiment of the invention as a compact measuring device, in which the holder is designed as a housing and an electronic processing unit and an interface are integrated into the housing.
• 10 : A representation of a further embodiment of the invention as a compact measuring device similar to that in 9 embodiment shown. The collimation device is designed here as an optic with several converging lenses. The expansion device includes a light-scattering structure to increase the angular spectrum of the radiation.
• 11a : A schematic representation of a third embodiment of the invention with an expansion device, a beam guiding device and a radiation sensor.
• 11b : An illustration of a third embodiment of the invention as in FIG 11a , with an obliquely incident laser beam, which is directed by the beam guidance device onto the central area of the receiving surface of the radiation sensor.
• 12 1: An illustration of a further exemplary embodiment of the third embodiment of the invention, in which the beam guiding device reduces the angular spectrum of the radiation by deflecting partial areas of the propagating laser beam.
• 13 1: A schematic representation of a fourth embodiment of the invention, in which the expansion device is designed simultaneously as a beam guiding device and as a collimation device.
• 14 1: An illustration of a further exemplary embodiment of the first embodiment of the invention, in which the radiation sensor comprises an absorption body in the form of a hollow body with a conical receiver surface.
• 15 1: An illustration of another exemplary embodiment of the first embodiment of the invention, in which the radiation sensor contains an absorption body in the form of a hollow cylinder and part of the receiver surface is designed to be reflective.
• 16 : An illustration of still another example of the first embodiment of the invention, in which the radiation sensor includes an absorption body in the form of a hollow cylinder, and in which the radiation sensor is equipped with a cooling device.
• 17 1: An illustration of a further exemplary embodiment of the second embodiment of the invention, in which the radiation sensor is equipped with a cooling device.

DETAILED DESCRIPTION OF THE FIGURES

1 shows a first possible embodiment of the invention in a schematic representation. A radiation sensor 40 with a receiver surface 41 is provided for measuring the energy or the power of a laser beam 10 . An expansion device 30 is arranged at a distance 25 in front of the radiation sensor 40 . The expansion device 30 and the radiation sensor 40 are attached to a holder 20 . The expansion device 30 increases the angular spectrum of the laser beam 10. After passing the expansion device 30, the laser beam 11 propagates with an increasing beam cross section and hits the receiver surface 41 of the radiation sensor 40 with a diameter 14. The receiver surface 41 covers at least 90% of the cross section of the propagated laser beam 11 The diameter 14 of the laser beam 11 on the receiver surface 41 is larger than the diameter 13 of the laser beam 10 in the area of the expansion device 30. Without the expansion device 30, the laser beam 16 would not increase in cross section and would therefore have a very small diameter in the area of the radiation sensor 40 Have diameter 17. The radiation sensor 40 generates an electrical signal 47 which is dependent on the energy or the power of the laser beam 10 or the propagated laser beam 11 .

In 2 a second possible embodiment of the invention is shown schematically. This embodiment includes all of the elements and features of 1 shown first embodiment. In the second embodiment, a collimation device 36 is additionally provided, which is arranged between the widening device 30 and the radiation sensor 40 . The collimation device 36 is also fastened to the holder 20 . The expansion device 30 and the collimation device 36 are at a distance 26 from one another. The collimation device 36 and the radiation sensor 40 are arranged at a distance 27 from one another. The collimation device 36 reduces the angular spectrum of the propagated laser beam 11. The laser beam 12 propagates further and hits the receiving surface 41 of the radiation sensor 40. The functioning of the device corresponds to that in the rest 1 shown first embodiment.

3 shows an embodiment not covered by the invention 1 shown first embodiment. In this example, the expansion device 30 is designed as a converging lens with a very short focal length. The laser beam 10 is focused by the converging lens and, after focusing, propagates with a greatly increasing cross section. The propagated laser beam 11 hits the receiving surface 41 of the radiation sensor 40 with a large diameter 14.

4 shows an embodiment not covered by the invention 2 second embodiment shown. In this example, the expander 30 is implemented as a diverging lens with a very short focal length. The collimation device 36 is designed as a converging lens.

In 5 is an inventive embodiment of in 1 shown first embodiment shown. According to the invention, the expansion device 30 is designed as a lens array. As shown in the drawing, the individual lenses of the lens array can have a convex shape. Furthermore, the 5 an example of the embodiment of the radiation sensor 40. The radiation sensor 40 here includes an absorption body 44 and a temperature sensor 46, which is thermally coupled to the absorption body 44. The receiving surface 41 is a surface of the absorption body 44 and has the highest possible degree of absorption. When the laser beam 10, 11 strikes, the beam power is essentially converted into heat, so that the temperature of the absorption body 44 rises. The temperature of the absorption body 44 is detected by the temperature sensor 46 . The temperature sensor 46 generates the electrical signal 47.

An embodiment of the second embodiment of the invention is in 6 shown. Similar to in 5 the expansion device 30 is designed according to the invention as a lens array. The second embodiment also has a collimation device 36 on. In this example, the collimation device 36 is designed as a concave mirror.

the 7 shows an embodiment not covered by the invention. As in 6 the collimation device 36 is designed as a concave mirror. The expansion device 30 is a convex mirror in this example. The mount 20 is designed as a housing which encloses the expansion device 30 , the collimation device 36 and the radiation sensor 40 . The housing has an opening towards the expansion device 30 through which the laser beam 10 can impinge on the expansion device 30 .

Another embodiment not covered by the invention is 8th shown. This example is similar to the one in 7 shown example up to the expansion device 30, which is not a convex mirror in this example, but a facet mirror. The individual facets of the facet mirror can have a convex shape.

9 shows schematically an embodiment of the second embodiment of the invention as an independent measuring device. According to the invention, the expansion device 30 is designed as a lens array. The individual lenses of the lens array can, as in 9 indicated to have a concave shape. The collimation device 36 is designed as a converging lens. As in the embodiment of 5 contains the radiation sensor 40 an absorption body 44 and a temperature sensor 46, which is thermally coupled to the absorption body 44 to detect the temperature of the radiation sensor 40. A second temperature sensor 48 is provided, which detects a second temperature in the vicinity of the radiation sensor 40. For this purpose, the second temperature sensor 48 can be thermally coupled to the housing. Furthermore, a light sensor 56 is provided, which registers a fraction of the laser beam 10, 11, 12 directed onto the radiation sensor 40. In the exemplary embodiment shown, the light sensor 56 is arranged laterally between the collimation device 36 and the radiation sensor 40 so that at least part of the receiving surface 41 of the radiation sensor 40 lies in the geometric-optical detection range of the light sensor 56 . The light sensor 56 is thus able to detect scattered light, which is generated to a small extent on the receiving surface 41 . The signals from the temperature sensor 46, the second temperature sensor 48 and the light sensor 56 are registered and processed by an electronic processing unit 60. The data calculated by the electronic processing unit 60 such as the power and/or the energy of the laser beam 10 are made available via an interface 62 . The holder 20 is designed here as a housing which contains the expansion device 30 , the collimation device 36 , the radiation sensor 40 , the second temperature sensor 48 , the light sensor 56 , the electronic processing unit 60 and the interface 62 . The housing has an opening through which the laser beam 10 can fall onto the expansion device 30 .

In 10 a further exemplary embodiment is shown as an independent measuring device. In contrast to, for example, from 9 In this example, the expansion device 30 has a light-scattering structure 31 to increase the angular spectrum of the laser beam 10. The collimation device 36 is designed as an optical system consisting of two converging lenses 37.

the 11a and 11b show a third possible embodiment of the invention in a schematic representation. This embodiment includes all elements of 1 shown first embodiment. In the third embodiment, a beam guidance device 33 is additionally provided, which is arranged between the expansion device 30 and the radiation sensor 40 . The beam guidance device 33 can be a prism, for example, on the side surfaces of which portions of the propagating laser beam 11 can be deflected by total reflection. In the exemplary embodiment shown, the beam guiding device 33 is dimensioned such that the beam guiding device 33 is ineffective when the laser beam 10 is aligned axially, as in FIG 11a shown. If the laser beam is irradiated at an angle, i.e. the laser beam 10 has an angle to the optical axis 39 of the device, as in 11b shown, then a partial area of the propagating laser beam 11 is deflected in the direction of the receiving surface 41 of the radiation sensor 40 . The laser beam 11 is thus centered on the receiver surface 41 by means of the beam guidance device 33 . The functioning of the device otherwise corresponds to that in 1 shown first embodiment.

In 12 another example of the third embodiment is shown schematically. In this exemplary embodiment, the beam guidance device 33 is dimensioned such that lateral areas of the propagating laser beam 11 are deflected at large angles to the beam axis by reflection on the side surfaces of the beam guidance device 33 .

13 shows a fourth possible embodiment of the invention in a schematic representation. In this embodiment, the widening device 30 integrates several functions in one component. In the example shown, the expansion device 30 has a light-scattering structure 31 on the front surface or on the beam entrance surface surface of expansion device 30. Light-scattering structure 31 causes the angular spectrum of laser beam 10 to be increased. The side surfaces of expansion device 30 are inclined and/or curved, so that the radiation components of propagating laser beam 11 reflected on the side surfaces reach receiver surface 41 of the radiation sensor 40 are deflected and the angle of the deflected radiation components is reduced to the beam axis. Thus, in this embodiment, the expansion device 30 simultaneously fulfills the function as a beam guidance device and at least partially as a collimation device. The functioning of the device otherwise corresponds to that in 1 shown first embodiment.

In 14 a further exemplary embodiment of the first embodiment is shown schematically. In this example, the radiation sensor 40 includes an absorption body 44 and a temperature sensor 46 that is thermally coupled to the absorption body 44 . The absorption body 44 is designed as a cavity absorber, in this example as a hollow cone or inner cone, with which the receiving area 41 is enlarged and the cross section of the propagated laser beam 11 is distributed over a larger area. Furthermore, a light sensor 56 is provided, which receives a portion of the laser beam 11 partially scattered on the receiver surface 41 . The signals from the temperature sensor 46 and from the light sensor 56 are recorded and processed in the electronic processing unit. An interface 62 is provided for exchanging data with an external display unit or device.

15 Fig. 12 shows still another embodiment of the first embodiment. Similar to in 14 the absorption body 44 is designed as a cavity absorber, in this example as a hollow cylinder. A portion 42 of the receiver surface 41, here the base of the hollow cylinder, is designed to be reflective or partially reflective. As a result, the radiation impinging in this area is guided to the cylindrical side surfaces. For this purpose, the base of the hollow cylinder is provided with a flat cone shape. Instead of an interface, a display device 64 is provided in this example, by means of which the data determined by the electronic processing unit 60 can be displayed.

An exemplary embodiment of the first embodiment, which is also suitable for continuously measuring the power of the laser beam 10, is in 16 shown. The radiation sensor 40 is constructed in a manner similar to that in FIG 15 shown example. A cooling device 70 is provided to dissipate the heat absorbed by the absorption body 44 . A coolant 77 is introduced into the cooling device 70 via a coolant inlet 72 , flows through the absorption body 44 of the radiation sensor 40 and is discharged via a coolant outlet 74 . The coolant 77 is passed through pipes, bores or channels in the absorption body 44 and absorbs the heat of the absorption body 44 . The temperature sensor 46 coupled to the absorption body 44 is arranged downstream with respect to the coolant flow direction, where the heated coolant leaves the absorption body 44 and thus registers the temperature of the heated coolant. The second temperature sensor 48 is arranged upstream before the coolant is conducted into the absorption body 44, and thus registers the flow temperature of the coolant 77. The flow rate of the coolant 77 can be determined using a flow sensor, not shown. The power of the laser beam 10 is determined from the difference between the temperatures measured by the temperature sensors 46 and 48 and the flow rate.

17 Fig. 12 shows an embodiment of continuous measurement of the second embodiment. The cooling device 70 corresponds to that in FIG 16 shown example. Instead of a cavity absorber as in the 16 a simple flat absorption body 44 is provided here. As a result, the absorption body 44 has a low thermal mass, as a result of which the response time of the temperature change, ie the signal from the temperature sensor 46, is reduced. The temperature sensor 46 of the radiation sensor 40 is arranged downstream at the coolant outlet of the absorption body 44, and the second temperature sensor 48 is arranged upstream in front of the absorption body. For optimal absorption of the radiation on the receiver surface 41, a collimation device 36 is provided in front of the radiation sensor 40, by means of which the angular spectrum of the propagated laser beam 11 is reduced. In this example, the collimation device 36 is a converging lens, which collimates the propagating laser beam 11 , so that the laser beam 12 , which propagates further, strikes the receiving surface 41 essentially approximately perpendicularly. In order to expand the laser beam 10, the angular spectrum of the laser beam 10 has previously been enlarged by means of the expansion device 30. The signals from the temperature sensors 46 and 48 are recorded and processed by the electronic processing unit 60 . The calculated data are transmitted to an external device via an interface 62 .

DETAILED DESCRIPTION OF THE INVENTION

A solution to the problem of providing a simple method and a compact device for the direct and precise measurement of the power and/or the energy of a laser beam, which also enables a measurement in areas close to the beam focus, is to be specified.

In order to solve the task, a device is proposed which contains a holder 20, an expansion device 30 and a radiation sensor 40 with a receiver surface 41. The expansion device 30 and the radiation sensor 40 are arranged at a distance 25 from one another by means of the holder 20 . The device is intended to capture a laser beam 10 . The laser beam 10 first hits the expansion device 30. The laser beam 10 has a diameter 13 in the area of the expansion device 30. The expansion device 30 enlarges the angular spectrum of the laser beam 10. The term angular spectrum means the distribution width of the angles of all partial beams of the laser beam to the beam axis . After the angle spectrum has been increased by the expansion device 30, the laser beam 10 propagates between the expansion device 30 and the radiation sensor 40, shown in this area with the reference number 11, with an increasing beam cross section. The propagated laser beam 11 hits the receiving surface 41 of the radiation sensor 40. The laser beam 11 has a diameter 14 on the receiving surface 41. The diameter 14 on the receiving surface 41 is larger than the diameter 13 of the laser beam 10 in the area of the expansion device 30. The receiving surface 41 of the radiation sensor 40 encloses at least 90% of the cross-sectional area of the propagated laser beam 11. With a round beam cross-section of the laser beam 10, 11, the diameter of the receiver surface 41 is greater than or at least equal to 0.95 times the diameter 14 of the propagated laser beam 11. Furthermore the propagated laser beam 11 is accordingly centered on the receiver surface 41 in such a way that at most 10% of the cross-sectional area of the laser beam 11 lies outside of the receiver surface 41 . The radiation sensor 40 generates an electrical signal 47 which is dependent on the power or the energy of the laser beam 10, 11. The power or energy value of the laser beam 10, 11 is determined from the electrical signal 47.

The laser beam 10 can be focused and the device according to the invention can be positioned in the area of the focus of the laser beam 10 . The laser beam 10 can have a very small diameter 17 in the area of the focus if the laser beam 10 propagates unhindered, ie without an expansion device. The virtual propagation of the laser beam 10 without an expansion device 30 is, for example, in FIG 1 shown as dashed lines with reference number 16 . The diameter 17 in the focal area can be, for example, of the order of 0.1 mm and the power of the laser beam 10 can be 1 kW, for example. The power density is then on the order of about 10 MW/cm ² . With such power densities, practically all non-transparent materials are immediately melted or pierced. No detector of any kind can withstand such power densities. The widening device 30 is therefore arranged at a distance 25 in front of the radiation sensor 40 . The expansion device 30 enlarges the angular spectrum of the laser beam 10, that is, the width of the distribution of the angles of all partial beams of the laser beam 11 to the beam axis is larger after passing the expansion device 30. For example, a collimated beam has an angular spectrum of almost zero, or well under 1°. A laser beam focused by processing optics typically has an angular spectrum of a few degrees. The expansion device 30 can be designed, for example, to increase the angular spectrum by +/-5°, ie to a width of the distribution of 10°, and the distance 25 between the expansion device 30 and the radiation sensor 40 can be 50 mm, for example. The beam diameter 14 on the receiver surface is then just under 9 mm and the power density at 1 kW is less than 2 kW/cm ² . Compared to the above example of the beam in the focus area without increasing the angular spectrum, the power density is reduced by almost 4 powers of ten. The reduced power density can be processed by many detectors without damage, at least for a short time.

In one possible embodiment, it is provided that the distance 25 between the expansion device 30 and the radiation sensor 40 is in a range of 10 mm to 200 mm. The distance 25 can in particular be 20 mm to 100 mm.

The increase in the angle spectrum by the expansion device 30 can be in a range from +/-1° to +/-50°. The increase in the angle spectrum can in particular be in the range from +/-2° to +/-30°.

The expansion device 30 can be designed in various ways. The angle spectrum can be increased by refraction, reflection, diffraction or scattering. It is not necessary that an intensity distribution, a beam profile, or a beam parameter product of the Laser beam 10 is preserved, only the total power or total energy integrated over the cross section of the beam must essentially be preserved. All embodiments of the expansion device 30 have in common that the laser beam 10 passes through the expansion device 30 with almost no attenuation. The degree of absorption of the expander 30 is less than one percent. If the expansion device 30 is a transmitting optical component, then the transmittance is greater than 90%, preferably greater than 99%. For this purpose, the beam entry and exit surfaces of the expansion device 30 can be provided with an anti-reflective coating. If the expander 30 is a reflective optical component, then the reflectivity is greater than 99%.

In an embodiment not covered by the invention, the expansion device 30 can be an optical lens. The focal length of the optical lens is a fraction of the distance 25 between the expansion device 30 and the radiation sensor 40. It is envisaged that the amount of the focal length of the optical lens is at most 1/3 of the distance 25. The optical lens can be a concave lens or a convex lens, ie a negative lens or a positive lens. The advantage of a diverging lens is that with the same focal length of the lens, the distance 25 can be selected to be somewhat shorter in order to achieve an equally enlarged beam diameter 14 on the receiver surface 41 . An example of an embodiment of the widening device 30 as a converging lens is shown in FIG 3 , while in 4 a negative lens is shown as expansion device 30 .

According to the invention, the expansion device 30 is a lens array or a microlens array, ie the expansion device 30 comprises a plurality of individual lens elements arranged next to one another. The special feature of using a lens array as an expansion device 30 is that an increase in the angular spectrum can be achieved, the angular distribution width of which is not dependent on the diameter 13 of the laser beam 10 in the area of the expansion device 30 if the lateral dimensions of the individual lens elements of the lens array can be chosen small enough. In order to achieve this, the lateral dimensions or the width of the individual lens elements can be chosen to be smaller than or at most equal to the diameter 13 of the laser beam 10 in the area of the expansion device 30 . The width of the individual lens elements can be in the range from 0.1 mm to 5 mm, for example. The magnitude of the focal length of the individual lens elements can be in the range from 0.3 mm to 20 mm. The ratio of the magnitude of the focal length of the individual lens elements to the width of the individual lens elements can be in the range from 2 to 30, for example. The individual lens elements of the lens array can have a positive or a negative refractive power, ie the surfaces of the individual lens elements can be convex or concave. Embodiments of a convex lens array are in the 5 and 6 shown, while the expansion device 30 in FIGS 9 and 14 until 17 is designed as a concave lens array.

The expansion device 30 can also have a light-scattering structure 31 . The light-scattering structure 31 scatters the radiation of the laser beam 10 in the forward direction and in a limited angular range. The light-scattering structure 31 can be designed, for example, as an interface of an optically transparent material with a roughness or waviness. At the unevenness of the rough or wavy interface, the radiation is deflected into different angles by refraction. The light-scattering structure 31 can also be a structure with a locally varying refractive index, for example.

The enlargement of the angular spectrum by the expansion device 30 can also be achieved by means of diffraction. For this purpose, the expansion device 30 can have a light-diffracting structure. The light-diffracting structure can be applied to an interface of the expander 30 by lithographic methods, for example.

Various detectors can be used as the radiation sensor 40 . The radiation sensor 40 has a receiving surface 41. The receiving surface 41 is large enough for the entire beam cross section of the laser beam 10, 11, 12 or at least 90% of the cross-sectional area of the laser beam to be detected by the receiving surface 41. Within the cross section of the laser beam, the intensity of the radiation is usually location-dependent. Many laser beams have an approximately Gaussian intensity distribution. The intensity distribution in the propagating laser beam 11 can be changed by the expansion device 30 . The radiation sensor 40 detects the entire or at least almost the entire cross-section of the beam and therefore generates a signal value which corresponds to the integral value of the intensity distribution. The integral value of the intensity distribution is the intensity of the laser beam 10, 11, 12 integrated over the receiver surface. The signal value is therefore dependent on the total power or the total energy of the laser beam. The signal value is output as an electrical signal 47 .

According to the invention, the radiation sensor 40 is designed as a calorimetric sensor. To the radiation sensor 40 includes an absorption body 44 and a temperature sensor 46. The temperature sensor 46 is thermally coupled to the absorption body 44 in order to detect the temperature of the absorption body 44. In this case, the receiving surface 41 is a surface of the absorption body 44. The receiving surface 41 has a high degree of absorption. For this purpose, the receiver surface can have a black or absorbing coating. The receiver surface 41 can also have a structure, for example a groove pattern. The laser beam 10, 11, 12 striking the receiver surface 41 is for the most part absorbed and converted into heat. This increases the temperature of the absorption body 44, which is registered by the temperature sensor 46. The temperature sensor 46 generates the electrical signal 47. The radiation sensor 40 or the absorption body 44 is thermally insulated on the holder 20 or in the holder 20 designed as a housing. For this purpose, the holding elements, which are connected to the radiation sensor 40 or the absorption body 44, are made, for example, from a material with low thermal conductivity. The thermally insulated attachment reduces uncontrolled heat flows from the absorption body 44 into the environment, which can reduce the accuracy of the measurement.

For many detectors, the magnitude of the signal generated is dependent to a small extent on the beam position on the detector and the angle of incidence of the beam on the detector. In order to achieve high measurement accuracy, it is important to ensure that the beam hits the detector as axially symmetrically or centrally as possible, and that the angle of incidence deviates as little as possible from perpendicular incidence.

To further improve the measurement accuracy, a collimation device 36 is therefore arranged in a further possible embodiment of the invention between the expansion device 30 and the radiation sensor 40, as shown in FIG 2 shown schematically. The collimation device 36 is arranged at a distance 26 from the expansion device 30 . The collimation device 36 reduces the angular spectrum of the propagating laser beam 11, which was previously enlarged by the expansion device 30. This ensures that the angles of all partial beams of the laser beam to the beam axis are as small as possible after passing through the collimation device 36 . The after the collimation device 36 propagating laser beam, as in the 2 shown in this area with the reference numeral 12, so keeps its cross-section or diameter approximately the same, that is, the diameter of the laser beam 11 in the area of the collimation device 36 is approximately the same as the diameter 14 of the laser beam 11, 12 on the receiver surface 41. The partial beams of the laser beam 12 propagating after the collimation device 36 therefore strike the receiver surface 41 of the radiation sensor 40 approximately perpendicularly.

The collimation device 36 can be, for example, a converging lens or convex lens, a Fresnel lens, a gradient index lens, an optic consisting of several lenses, or a concave mirror. The collimation device has a positive focal length f _K . In a possible embodiment of the invention, the focal length of the collimation device 36 can be greater than or equal to the distance 26 between the expansion device 30 and the collimation device 36, i.e.: $${\text{f}}_{\text{K}}\ge {\text{i.e}}_{\text{AK}}$$

In this case, f _K is the focal length of the collimation device 36, and d _AK is the distance 26 between the expansion device 30 and the collimation device 36. It should be noted that the distance d _AK 26 is defined from the expansion device 30 to the main plane (or main surface) of the collimation device 36

Furthermore, the focal length f _K of the collimation device 36 can be less than or equal to the following value: $${\text{f}}_{\text{K}}\le {\text{i.e}}_{\text{AK}}{\varnothing }_{\text{SE}}/\left({\varnothing }_{\text{SE}}-{\varnothing }_{\text{SA}}\right)$$

Here, Ø _SA is the diameter 13 of the laser beam 10 in the area of the expansion device 30, and Ø _SE is the diameter of the laser beam 11, 12 on the receiver surface 41 or in the area of the collimation device 36.

the 4 and 9 show examples with a converging lens as collimation device 36. In 10 an optical system consisting of two converging lenses 37 is shown as a collimation device 36 . the 6 , 7 and 8th show an example of a concave mirror as collimation device 36.

In a further possible embodiment of the invention, a beam guidance device 33 is provided, which is arranged between the expansion device 30 and the radiation sensor 40 . The impact position of the beam spot on the receiver surface 41 can be optimized by means of the beam guiding device 33 in that the beam guiding device 33 keeps the laser beam 11 within a desired cross section.

The beam guidance device 33 can be designed, for example, as a light-guiding prism, ie as a prism made of a transparent material. The prism has a beam entrance surface, a jet exit surface, and side surfaces. Partial beams of the laser beam 11, which have a very large angle to the axis, are reflected on the side surfaces of the prism and are thus deflected in the direction of the central region of the radiation sensor 40. The reflection at the side surfaces of the prism can take place by total internal reflection. The side surfaces of the prism can also be mirrored. The beam guiding device 33 can also be a kaleidoscope-like arrangement of mirrors. the 11a , 11 b and 12 12 show exemplary embodiments of the invention with a beam guiding device 33. The shape of the beam guiding device 33 can be, for example, a cylindrical or conical rod, or a rod with a triangular, quadrangular, pentagonal, hexagonal or octagonal cross-sectional area. The side surfaces can be inclined to the axis, that is, the cross section of the jet exit surface can be larger than the cross section of the jet entry surface. Due to the inclination of the side surfaces, the angle to the axis of partial beams of the laser beam 11, which are reflected on the side surfaces, is reduced. The beam guidance device 33 can thus bring about a reduction in the angular spectrum of the laser beam 11 in a similar way to the collimation device 36. The reduction of the angular spectrum by the beam guidance device can be optimized by the side surfaces being inclined and also having a curvature, as is the case, for example, in 13 is shown.

In 13 a further embodiment of the invention is shown, in which the expansion device 30 and the beam guidance device 33 are integrated into one component. For this purpose, the entry surface of the beam guidance device 33 can be designed as an expansion device 30 . The entry surface can, for example, be concavely curved, have a surface with lens facets arranged as an array, or have a light-scattering structure 31 .

• - Die Erfindung ermöglicht die direkte Messung der Leistung oder der Energie eines Laserstrahls ohne Strahl-Abschwächung und kann dadurch eine hohe Genauigkeit erreichen.
• - Die Leistungs- und/oder Energie-Dichte der Strahlung auf dem Strahlungssensor ist wesentlich reduziert.
• - Die Erfindung ermöglicht Messungen im Fokus-Bereich eines fokussierten Laserstrahls und hat dadurch einen wesentlich größeren Anwendungsbereich als konventionelle Messgeräte, weil konventionelle Messgeräte weit außerhalb des Fokus-Bereichs positioniert werden müssen, um Beschädigungen des Detektors zu vermeiden.
• - Der Auftreffwinkel der Strahlung auf der Empfängerfläche des Strahlungssensors kann unabhängig vom Eintrittswinkel des Laserstrahls annähernd konstant und nahe am senkrechten Einfall gehalten werden, wodurch besonders genaue und reproduzierbare Messungen ermöglicht werden.
• - Die Auftreffposition des Strahlquerschnitts auf der Empfängerfläche des Strahlungssensors kann unabhängig vom Eintrittswinkel und von der Eintrittsposition des Laserstrahls in einem engen Bereich und nahe am Zentrum des Strahlungssensors gehalten werden, wodurch Genauigkeit und Reproduzierbarkeit der Messungen weiter gesteigert werden können.
• - Die erfindungsgemäße Vorrichtung kann sehr kompakt aufgebaut werden.

The invention has numerous advantages over the prior art:

• - The invention enables the direct measurement of the power or energy of a laser beam without beam attenuation and can thereby achieve high accuracy.
• - The power and/or energy density of the radiation on the radiation sensor is significantly reduced.
• - The invention enables measurements in the focus area of a focused laser beam and thus has a much larger area of application than conventional measuring devices, because conventional measuring devices must be positioned far outside the focus area in order to avoid damage to the detector.
• - The angle of incidence of the radiation on the receiver surface of the radiation sensor can be kept almost constant and close to vertical incidence, regardless of the angle of incidence of the laser beam, which enables particularly precise and reproducible measurements.
• - The impact position of the beam cross-section on the receiving surface of the radiation sensor can be kept in a narrow range and close to the center of the radiation sensor, regardless of the angle of incidence and the entry position of the laser beam, which can further increase the accuracy and reproducibility of the measurements.
• - The device according to the invention can be very compact.

The invention can advantageously be further developed in a wide variety of ways in accordance with the further listed embodiments and the further listed features, without departing from the scope and the object of the invention. Further embodiments of the invention are provided by different combinations of the features described, even if not every possible embodiment is described or illustrated in figures.

In the case of an embodiment of the radiation sensor 40 as a calorimetric sensor, the absorption body 44 can be designed in the most varied of ways. The absorption body can be a cavity absorber, for example. The cavity can be shaped in different ways. The absorption body 44 can be conical or cone-shaped, as in 14 shown. The absorption body 44 can also have a concave receiver surface.

The absorption body 44 can also be a hollow cylinder open on one side, as in FIGS 15 and 16 shown. It can be provided that the radiation is mainly absorbed on the cylindrical inner surfaces of a hollow cylinder. For this purpose, a partial area 42 of the receiver surface 41 can be designed to be reflective. The reflective partial area 42 can be in the area of the base area or floor area of the hollow cylinder. The area of the base or bottom surface of the hollow cylinder can have the shape of a flat cone in order to reflect the radiation impinging there towards the cylindrical inner surface.

The radiation sensor 40 designed as a calorimetric sensor can also be equipped with a cooling device 70 . At the refrigerator A coolant 77 is supplied to device 70 through a coolant inlet 72 and discharged through a coolant outlet 74 . Between the coolant inlet 72 and the coolant outlet 74 the coolant 77 is conducted through a system of pipes, bores, channels or other cavities which are at least partially in thermal contact with the absorption body 44 or lead through the absorption body 44 . The coolant 77 thus absorbs the heat of the absorption body 44 and dissipates it. The temperature sensor 46 is arranged at a point where the coolant 77 is discharged from the absorption body 44 and thus registers the temperature of the heated coolant.

The invention may further include a second temperature sensor 48 . The second temperature sensor 48 is arranged in the vicinity of the radiation sensor 40 and is not thermally coupled to the absorption body 44 . The second temperature sensor 48 thus detects a second temperature in the vicinity of the radiation sensor 40 or the absorption body 44. The second temperature sensor 48 can be attached to the holder 20 or on or in the holder 20 designed as a housing, as in FIG 9 shown. By detecting the second temperature, the increase in temperature of the absorption body 44, from which the power or the energy of the laser beam is calculated, can be determined more precisely. In addition, by detecting the second temperature, the size of the uncontrolled heat flows of the absorption body 44 into the environment can be estimated and the accuracy of the calculation of the power or the energy of the laser beam can thus be improved.

If the radiation sensor 40 is equipped with a cooling device 70, then the second temperature sensor 48 can be arranged at a point in the coolant supply before the coolant is introduced into the absorption body 44. The second temperature sensor 48 thus detects the base temperature or flow temperature of the coolant 77. From the temperature difference between the temperature sensor 46 and the second temperature sensor 48, the heat dissipated and thus the power of the laser beam 10, 11, 12 can be determined. Corresponding exemplary embodiments show the 16 and 17 .

The device according to the invention can also be equipped with a light sensor 56 . The light sensor 56 is designed to detect a small portion of the radiation formed by the laser beam 10 , 11 , 12 . The small proportion of radiation can be, for example, scattered light 19 that is generated to a small extent on the receiving surface 41 of the radiation sensor 40 when the laser beam 10 , 11 , 12 strikes the receiving surface 41 . The light sensor 56 can be arranged in such a way that the receiving surface 41 lies at least partially in the geometric-optical light detection range of the light sensor 56 . For this purpose, the light sensor 56 can be fastened, for example, to the holder 20 or in the housing in the area between the expansion device 30 and the radiation sensor 40 .

The signal from the light sensor 56 is approximately proportional to the power of the incident laser beam 10. A photodiode, for example, can be used as the light sensor 56. A photodiode has a very short signal rise time and thus supplies signals with a very high temporal resolution. The start and end of a pulse or an irradiation period of the laser beam 10 can be registered very precisely on the basis of the signal from the light sensor 56 . The power of the laser beam 10 can thus be determined with even greater accuracy.

The device can be equipped with an electronic computing unit 60 . The electronic processing unit 60 processes the electrical signal 47 of the radiation sensor 40. The electronic processing unit can optionally also process the signals of the second temperature sensor 48 and the light sensor 56, if these are provided. The processing of the signals can include, for example, the A/D conversion and storage of the signals and/or the calculation of the power or the energy of the laser beam 10 .

The device can also be equipped with a display device 64 . The calculated data, ie the power or the energy of the laser beam 10, can be displayed by means of the display device.

The device can also be equipped with an interface 62 . The calculated data, for example the power or the energy of the laser beam, or the recorded signals can be transmitted to an external device by means of the interface 62 . Control commands can also be exchanged between the device and an external device via the interface 62 . Interface 62 may be an electrical interface with a connector, such as a USB interface. The interface 62 can also be a wireless interface that enables data transmission using radio signals, for example a so-called Bluetooth interface.

Reference List

10

laser beam

11

propagating laser beam with increased angle spectrum

12

propagating laser beam with reduced angular spectrum

13

Diameter of the laser beam in the area of the expansion device

14

Diameter of the laser beam on the receiver surface

16

virtual path of the laser beam without expansion device

17

Diameter of the virtual laser beam without expansion device

19

scattered light

20

bracket

25

Distance between expansion device and radiation sensor

26

Distance between expander and collimator

27

Distance between collimation device and radiation sensor

30

expansion device

31

light-diffusing structure

33

beam guiding device

36

collimation device

37

converging lens

39

Optical axis of expansion device and radiation sensor

40

radiation sensor

41

receiver surface

42

part of the receiver surface

44

absorption body

46

temperature sensor

47

electrical signal

48

second temperature sensor

56

light sensor

60

electronic computing unit

62

interface

64

display device

70

cooling device

72

coolant inlet

74

coolant outlet

77

coolant

Claims (15)

Device for measuring power and/or energy of a laser beam (10), comprising a radiation sensor (40), an expansion device (30), and a holder (20), the radiation sensor (40) having a receiver surface (41) and for Generating an electrical signal (47) which depends on the power of the laser beam (10) or on the energy of the laser beam (10), the expansion device (30) and the radiation sensor (40) being at a distance (25) from one another are arranged on the mount (20) to form a propagating laser beam (11) between the expansion device (30) and the radiation sensor (40), the expansion device (30) being designed to increase an angular spectrum of the laser beam (10), wherein the expansion device (30) is a lens array, with a diameter of the propagated laser beam (11, 12) on the receiver surface (41) being larger than a diameter of the laser beam (10) in the area of the expansion device (30), the radiation sensor (40) comprising an absorption body (44) and a temperature sensor (46), the temperature sensor (46) being thermally coupled to the absorption body (44), and the receiver surface (41) of the radiation sensor (40) encloses at least 90% of a cross-sectional area of the propagated laser beam (11, 12). device after claim 1 , wherein the holder (20) is designed as a housing which encloses the expansion device (30) and the radiation sensor (40) and has an opening towards the expansion device (30). Device according to one of Claims 1 or 2 , wherein the radiation sensor (40) is designed to detect an intensity that varies locally within a cross section of the laser beam (10) as an integral value. Device according to one of Claims 1 until 3 , further comprising a light sensor (56), which is designed to detect a small portion of the laser beam (10, 11, 12) or a scattered light portion of the laser beam (10, 11, 12). Device according to one of Claims 1 until 4 , A collimation device (36) being arranged between the expansion device (30) and the radiation sensor (40). device after claim 5 , Wherein the collimation device (36) comprises a converging lens, an optic consisting of several lenses, a Fres nel lens, a gradient index lens, or a concave mirror. Device according to one of Claims 1 until 6 , A beam guiding device (33) being arranged between the expanding device (30) and the radiation sensor (40). device after claim 7 , wherein the beam guiding device (33) is a light-guiding prism, an inner cylinder mirror, an inner cone mirror, or a kaleidoscope-like mirror arrangement. Method for measuring a power and/or an energy of a laser beam (10), comprising the following method steps: - increasing an angular spectrum of the laser beam (10) by means of an expansion device (30), the increasing of the angular spectrum of the laser beam (10) taking place by means of a lens array, - Propagation of the laser beam (10) from the expansion device (30) to a radiation sensor (40) with a receiving surface (41), the expansion device (30) and the radiation sensor (40) being at a distance (25) from one another on a holder (20 ) are arranged, wherein the radiation sensor (40) comprises an absorption body (44) and a temperature sensor (46), - Detection of at least 90% of a cross-sectional area of the propagated laser beam (11, 12) by means of the receiver surface (41) of the radiation sensor (40), a diameter of the propagated laser beam (11, 12) on the receiver surface (41) being larger than a diameter of the laser beam (10) in the area of the expansion device (30), with at least 90% of the cross-sectional area of the laser beam (11, 12) being detected by means of the receiver surface (41) of the radiation sensor (40) by absorbing the majority of the light on the receiver surface (41) incident laser beam (11, 12) by means of the absorption body (44), - Generating an electrical signal (47) by means of the radiation sensor (40) as a function of the power of the laser beam (10) or of the energy of the laser beam (10), wherein the generation of the electrical signal (47) as a function of the power or of the energy of the laser beam (10) takes place through the temperature sensor (46), which is thermally coupled to the absorption body (44). procedure after claim 9 , wherein an intensity that varies locally within a cross section of the laser beam (10) is detected by the radiation sensor (40) as an integral value. procedure after claim 9 , further comprising the method step: - determining the energy or the power of the laser beam (10) from a difference in temperatures of the absorption body (44) after the end of irradiation of the laser beam (10) and before the start of irradiation of the laser beam (10). Procedure according to one of claims 9 until 11 , further comprising the method step: - detecting a small portion of the laser beam (10, 11, 12) or a scattered light portion of the laser beam (10, 11, 12) by means of a light sensor (56). procedure after claim 12 , further comprising the method steps: - determining the energy of the laser beam (10) from the difference in the temperatures of the absorption body (44) after the end of the irradiation of the laser beam (10) and before the beginning of the irradiation of the laser beam (10), - determining an irradiation duration of the Laser beam (10) from a course of a signal from the light sensor (56), - determining a power of the laser beam (10) by dividing the energy and the irradiation time. Procedure according to one of claims 9 until 13 , wherein the propagation of the laser beam (10) from the expansion device (30) to the radiation sensor (40) takes place in two sections and between the two sections the angular spectrum of the propagating laser beam (11) is reduced by means of a collimation device (36) which is located between the expansion device (30) and the radiation sensor (40) is arranged. Procedure according to one of claims 9 until 14 , further comprising the method step: - centering the propagated laser beam (11, 12) on the receiver surface (41) of the radiation sensor (40) by means of a beam guiding device (33) which is arranged between the expansion device (30) and the radiation sensor (40).

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