METHOD AND DEVICE FOR THE DYNAMIC CHARACTERIZATION OF A RADIATION BEAM MOVING BETWEEN DIFFERENT POINTS

Abstract

The invention relates to a device for characterizing at least one light beam (7) comprising: - a support platform (1) having a plurality of measurement points, each measurement point being equipped with at least one sensor (4i) for measuring at least one energy and / or spatial and / or temporal parameter of a beam incident on said sensor and with slave digital means (6i) for processing and / or storing data from said sensor; - master digital means (6) for storing data from the sensors of the different measurement points; - a plurality of digital buses (8i), each connecting one of the slave digital means (6i) to the master digital means (6), the different digital buses being parallel to each other, the slave digital means (6i) being capable of, or programmed to, transmit measurement data from the sensors to the master digital means (6). Figure for the abstract: Figure 1

Description

Title of the invention: METHOD AND DEVICE DYNAMIC CHARACTERIZATION OF A RADIATION BEAM MOVING BETWEEN DIFFERENT POINTS TECHNICAL FIELD AND PREVIOUS ART

[0001] The invention relates to a method and device for the energy and spatial characterization of one or more laser beams.

[0002] Energy and spatial characterization techniques for laser beams in the literature generally consist of using a device capable of evaluating a beam coming from a stationary source over a restricted area of ​​space. In this regard, document FR 29735573 discloses a device for characterizing the energy flux emitted by a pulsed laser. The radiometer as presented comprises, among other things, a laser absorber, a target, a thermopile, and a photodiode. It allows the evaluation of several energy and time parameters (the average power P (W), the pulse width of the signal T (ms), the pulse frequency of the signal F (Hz), the average energy per pulse E (J)).

[0003] The device described in document FR 2974176, which allows the analysis the spatial distribution of intensity of a fixed laser source by means of an image sensor (CCD or CMOS), but which does not allow the evaluation of energy and time parameters such as the shape of the pulse as a function of time.

[0004] Document WO2021 / 250346 is also known, which allows for the spatial characterization of markings resulting from laser impacts at different focal points on a platform. Here, it is the "HAZ," or heat-affected zone, that is analyzed. The position of the mirrors and optics used to deflect the laser beam introduces different optical path lengths, which can lead to positioning errors relative to the theoretical values ​​and variations in the geometry and size of the focal spot on the target. To resolve this problem, this document describes an image comparison device comprising test markings and reference markings. Corrections are stored in memory and applied to the machine to adjust the optical path length to closely approximate the reference markings.This device does not allow for real-time measurement of laser parameters at a given point such as laser firing time, deposited energy, average power, spatial distribution of laser illumination, etc. actual dimensions of the laser spot outside the "HAZ" (heat-affected zone) at a given point and the speed of movement of the beam.

[0005] Thus, a more complete and real-time evaluation of a moving laser beam in certain industrial applications remains a technical problem, particularly in the case of successive additive manufacturing of serial parts. Indeed, for this type of application, it is necessary to ensure that the beam parameters are constant at every point in order to produce nearly identical parts.

[0006] The problem therefore arises of finding a new method and a new device for measuring in real time the energy and temporal parameters of radiation, for example a laser beam, moved, for example at high speed, at different points in two-dimensional space, for example on the surface of a build platform. This is particularly relevant in the case of additive manufacturing.

[0007] In particular, when the beam moves in real time between different points with a speed that can reach up to a few m / s, the measurement of the energy and time parameters of a radiation source is a complex metrology problem that is not solvable with current means: indeed, it is not conceivable to move one of the existing or previously presented means at the same speed as the beam to ensure its metrology.

[0008] Furthermore, another problem is to be able to control different sensors at the rate of movement of a radiation for example a laser beam, especially if this beam moves with a speed that can reach up to a few m / s. Description of the invention

[0009] The invention relates first to a device for characterizing at least one light beam comprising:

[0010] - a support platform comprising a plurality of measurement points, each point measurement being equipped with at least one sensor for measuring at least one energy and / or spatial and / or temporal parameter of a beam incident on said sensor and slave digital means for processing and / or storing data from said sensor;

[0011] - master digital means for storing sensor data different measurement points;

[0012] - a plurality of digital buses, each connecting one of the slave digital means to the master digital means, the different digital buses being parallel to each other, the slave digital means being capable of, or programmed to, transmit measurement data from the sensors to the master digital means.

[0013] The slave digital means may be capable of processing and / or storing data from the sensors of the support platform. They may be programmed to transmit this data to the master digital means, the latter then being able to store it and possibly transmit it to an external intelligence (for example a PC) via an appropriate digital interface (for example of type RS232, or RS422, or USB, or IEEE, or parallel, or by wireless transmission, etc.), so as to allow for example its exploitation and / or its traceability over time.

[0014] The master digital means may also be capable of processing and storing part of the data from the sensors implanted in the support platform according to the electrical connections made.

[0015] The different digital buses can be galvanically isolated using independent analog ground power supplies.

[0016] Data transmission via the buses can be optocoupled: thus, this transmission can be electrical, then optical, then electrical again, the buses being optocoupled to the slave and master digital means. The master digital means can enable the control of different sensors at the rate of movement of a radiation source, for example a laser beam, particularly if this source moves at a speed that can reach, for example, a few m / s.

[0017] Thus, a measurement command can be pre-programmed in the master digital means and stored according to the predefined position of the beam on the sensors. However, the invention also has the advantage of being able to operate according to a random sequence, since each sensor associated with slave digital means (for example, a microcontroller) can, depending on the electrical connections made, automatically detect the presence of the beam and / or trigger its measurement sequence autonomously. The application settings will define the chosen strategy according to the need.

[0018] Each sensor in a device according to the invention can provide information independent of that provided by the other sensors. The different sensors are independent of each other, without mutual interference, and the data provided by each sensor is therefore not influenced by the data provided by the other sensors. The architecture with buses connected in parallel between master and slave digital means contributes to this independence and allows for data transfer without interaction or mutual interference and EMC-type immunity to the environment. Galvanic isolation of each sensor can also contribute to the aforementioned independence.

[0019] At least one sensor at at least one measurement point may include a sensor for measuring at least one energy parameter, for example energy and / or the average power of a beam, comprising at least one radiometer, for example a calorimeter, or a power meter, or a wattmeter, or a joule meter. For example, said sensor comprises at least one thermocouple and / or a thermopile and / or a thermistor and / or a platinum resistance probe and / or a pyroelectric probe and / or a photoconductive sensor, and / or a photodiode.

[0020] At least one sensor at at least one measurement point may include a sensor for measuring at least one geometric parameter of a beam, for example the spatial distribution of the illuminance EZ(X,Y) (W / m2) of a light beam in a plane perpendicular to its direction of propagation and / or its diameter at the measurement point and / or its focusing caustic. This sensor includes, for example, at least one CMOS or CCD sensor.

[0021] At least one sensor at at least one measurement point may include a sensor for measuring at least one temporal parameter of a beam pulse, for example, a rising edge, or a falling edge, or a rising edge and a falling edge, or the temporal shape of said pulse. This sensor includes, for example, at least one photodiode or a fast pyroelectric sensor with a response time not exceeding Ips. The rising and / or falling edges of the temporal signal delivered by the sensor may be detected by the master digital means (for example, via an interrupt input) or by the slave digital means (for example, again via an interrupt input) or by the master and slave digital means simultaneously (depending on the connections made) in order to deduce their duration.

[0022] The master digital means, for example their so-called "interrupt" inputs, can be used for time-stamping the measurements taken on the different sensors, for example in order to deduce the speed of movement of the beam between each sensor.

[0023] In a device according to the invention, the digital master means, or slave means, or master and slave means simultaneously, can be programmed to trigger a measurement by at least one sensor of a corresponding measurement point when a light beam incident on the measurement point is detected.

[0024] A device according to the invention may further include means for powering each of the sensors. These power supply means may be integrated with the master digital means, for example in the form of an electronic board.

[0025] At least one measurement point may include means for absorbing a light beam incident on the measurement point.

[0026] The invention also relates to a system comprising a device according to the invention and means for moving a beam emitted by a radiation source relative to the support platform. These means for moving a beam are, for example, part of a machine to be characterized. They include, for example, means Optical means, including, for example, focusing devices, such as a flat-field focusing device, and / or one or more mirrors, such as galvanometer mirrors. These means allow the beam to be directed to each of the different measurement points, preferably at an angle perpendicular or nearly perpendicular to the surface of the platform. In one embodiment, these optical means include a galvanometer mirror system and / or a flat-field focusing device.

[0027] A device or system according to the invention may include means for visualizing the path of the beam between the different measurement points and / or values ​​of one or more of the measurement(s) made at each of these points, for example the pulse duration and / or the beam energy and / or the beam power and / or at least one geometric parameter, for example the spatial distribution of the illuminance EZ (X,Y) (W / m2) of the light beam in a plane perpendicular to its direction of propagation and / or its diameter at the measurement point and / or its focusing caustic and / or, for example on the line which connects 2 successive points, the duration of movement of the beam between 2 points and / or the distance between these 2 points and / or the resulting speed of movement.

[0028] The invention also relates to a method for characterizing at least one light beam emitted by a radiation source, for example implementing a device as described above and in the present application, comprising:

[0029] a) - direct the light beam successively towards a plurality of measurement points on the device,

[0030] b) - measure at each of said measurement points, using at least one measurement sensor, at least one energy and / or spatial and / or temporal parameter of the incident beam;

[0031] c) - transmit data from said measurements to the master digital means via one or more of the digital buses.

[0032] Such a process may include processing and / or storing at least part of the data measured by the digital means used for processing and / or storing data from said measurement points.

[0033] Such a method may include identification by the master digital means of the presence of radiation on at least one of the sensors, and then sending by these master digital means a request to transmit data to said slave digital means. However, depending on the electrical connections made, such a method may also include identification by the slave digital means of the presence of radiation on at least one of the sensors, a presence which may also be automatically transmitted to the master digital means for time stamping, and then sending the measurement data to the master digital means.

[0034] A method according to the invention may include:

[0035] - an identification by master and / or slave digital means of presence of radiation on at least one of the sensors;

[0036] - then sending, via these master digital means, a request for transmission of data to said digital slave means;

[0037] - then sending the measurement data from the slave digital means to the means digital masters. A method according to the invention may include a display on visualization means of the path of the beam between the different measurement points and / or of the values ​​of one or more of the measurement(s) made at each of these points, for example the pulse duration and / or the beam energy and / or the beam power and / or at least one geometric parameter, for example the spatial distribution of the illuminance EZ (X,Y) (W / m2) of the light beam in a plane perpendicular to its direction of propagation and / or its diameter at the measurement point and / or its focusing caustic and / or, for example on the line which connects 2 successive points, the time of movement of the beam between 2 points and / or the distance between these 2 points and / or the resulting speed of movement.

[0038] In a method according to the invention:

[0039] - the light beam can be moved relative to the platform at a speed between between Imm / s and 10 m / s;

[0040] - and / or the light beam may be a laser beam. BRIEF DESCRIPTION OF THE FIGURES

[0041] - [Fig.1] represents an example of an embodiment of a system according to the invention;

[0042] - [Fig.2], [Fig.3] and [Fig.4] represent examples of components, comprising including an absorber, which can be used as part of a system according to the invention;

[0043] - [Fig.5] represents an example of displaying measurement points and measurements carried out at each of these points and between them.

[0044] DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

[0045] Fig. 1 represents a first example of an embodiment of a system 10 according to the invention.

[0046] A platform or support 2 comprises a plurality of N measurement points 4b 4;... 4N (i= 1, .. .N) distributed for example in the form of a matrix on the surface of this platform. Each measurement point is associated with coordinates (X^Y;), (i=1.. .N).

[0047] A beam 7 of pulsed or continuous radiation is emitted, for example by a laser source 14.

[0048] The beam emitted by the laser source can be moved by the optical and / or digital elements of the machine with which it is interfaced: the beam can therefore be moved from a measurement point (Xi, Yi) to a neighboring point (Xi+i, Yi+i) on the platform (the two beams 7, 7i of [Fig. 1] thus represent the same beam 7 moved to two points of different measurements, and measured at 2 different times). Optical means 12, including for example a galvanometric mirror system 12' and a so-called flat field focusing optic, allow the beam 7 to be directed towards each of the different measurement points at an incidence perpendicular or almost perpendicular to the surface of the plate 2.

[0049] Preferably, the distribution or arrangement of these different measurement points on the platform 2 is identical or similar to that of the working points of a manufacturing or processing machine. An example of such a machine is an additive manufacturing machine, for example by melting metal powder, or filament (PET: Polyethylene terephthalate glycol) or resin, using a beam that emits radiation which travels, for example at high speed, according to said distribution of working points.

[0050] Each measurement point (Xi,Yi) comprises at least one sensor 4; which will allow the measurement of a characteristic of a beam of radiation incident on this sensor. Such a sensor can, for example, be combined with, or associated with, a thermal and / or optical sensor, as explained later.

[0051] By way of example, each sensor 4 allows for the measurement of an energy parameter (energy E and / or average power P) of the incident beam: it may, in particular, be or include a radiometer, for example a calorimeter, or a power meter, or a wattmeter, or a joule meter. It is, for example (non-exhaustive list): a thermocouple, or a thermopile, or a thermistor, or a platinum resistance probe, or a pyroelectric probe, or a photoconductive sensor, or a photodiode.

[0052] Alternatively, or in combination with either of the preceding sensors, one or more sensors may include a camera with a CMOS or CCD sensor. This type of CMOS or CCD sensor makes it possible to obtain information concerning the geometric parameters of the incident beam, for example:

[0053] - the spatial distribution of the illuminance EZ(X,Y) (W / m2) of a light beam in a section (X,Y), X and Y defining a plane perpendicular to its propagation in Z (axis of propagation of the beam);

[0054] - and / or its diameter at the measurement point;

[0055] - and / or on the focusing caustic (evolution of the characteristic diameter 2RZ (X,Y) illuminated by the beam following its propagation in Z on either side of the focal plane, X and Y being defined above.

[0056] Alternatively, or in combination with either of the preceding sensors, one or more sensors may include optical means for detecting at least one temporal parameter of a beam pulse, for example a photodiode with a response time, for example 50 ns or less. Such means allow to detect, for example, a rising and / or falling edge of a radiation pulse and / or the width of such a pulse. Alternatively, it is possible to implement an algorithm, for example, an algorithm embedded with a slow-response thermal sensor that processes the growth of a signal resulting from the absorption of a beam. For example, if two measurement points each have such optical or algorithmic means, it is possible to calculate the time elapsed between two beam pulses to determine the beam's velocity between these same two points and / or the time between successive beam pulses and / or the width of each beam pulse.

[0057] One or more measurement point(s) may be equipped with different sensors, for example a calorimeter-type sensor at one point and a CMOS sensor at another point, each point also being equipped with optical means for detecting at least one time parameter of the incident beam.

[0058] Each sensor can be connected to an independent power supply, for example, provided by one or more batteries.... This power supply can be centralized (using the means 6 described below) or not. It is preferably independent of the 3D printing machine and therefore does not require connection to it or modification to pass through the protective casing for a mains power cable, which makes it possible to consider using the instrument array in any machine.

[0059] Each measurement point can be equipped with means 20 for capturing the radiation from a radiation source; these means are hereinafter referred to as "absorbers." Examples of absorber implementations will be given below. The associated optical absorption techniques and geometries can be varied: flat disk or flat disk with concentric grooves, or cone, or semi-reflective cone combined with a cylinder, etc., each of these elements preferably being coated with a layer that absorbs optically for the wavelength of the beam.

[0060] The entire device can be placed, for example, under a hood (not shown in the figures) which can be fitted with a door giving access to the various sensors and means implemented on the support 2. By implementing an independent power supply for each sensor, as explained above, there is no need for connection to an external power supply, which would require passing through the possible protective hood for the passage of a mains power cable.

[0061] The entire device, in particular the instrument matrix, is autonomous in its operation: it does not require any connection or synchronization with a manufacturing or processing machine as mentioned above.

[0062] As explained later, the entire device is equipped with electronic means, analog and / or digital, which will allow the signals to be processed representative data from the different sensors, which will for example be formatted and / or filtered and / or converted digitally and / or stored.

[0063] According to an advantageous embodiment, each sensor is associated with, or equipped with, means for the temporal detection of radiation, for example a laser beam, to initiate one or more measurements of one or more temporal characteristic(s) of the beam; this avoids synchronization with other elements or sensors of the machine. Such detection means:

[0064] - include, for example, at least one fast detector (e.g., photodiode, or pyroelectric device, etc...) which can be connected to an input, for example the "interrupt" input, of a microcontroller, which is scanned at a high frequency;

[0065] - and / or implement an algorithm, for example an embedded algorithm, which deals with the growth of a signal resulting from the absorption of a beam.

[0066] Each sensor can be calibrated against the same reference using the same range of radiation parameters, for example power and / or energy and / or diameter and / or beam illumination distribution; such calibration makes it possible to compare the results obtained at different points of the platform and thus to determine the stability of the parameters of the beam used, over time and / or during beam movements.

[0067] The calibration of the sensor matrix can be implemented for example using a digital table adjustable in position (X,Y) which includes means for moving the sensor tray 2 relative to a fixed beam, for example a laser beam.

[0068] Or, a beam, for example a laser, is transported by optical fiber with a focusing head associated with a 3-axis rectangular gantry, which allows the beam to be moved vertically on the matrix 2 of sensors without risking deformation of this beam by a difference in optical path length.

[0069] These different calibration solutions make it possible to have a beam that is stable in energy and geometry regardless of the position of the sensor of the matrix to be calibrated.

[0070] As illustrated in [Fig. 1], each measurement point can be associated with electronic means 6; (i= 1, .. .N) for processing (shaping and / or filtering and / or digital conversion) and / or storing data measured by the sensor(s) of that same measurement point, these means comprising, for example, as explained above, a microcontroller and / or an FPGA to ensure the aforementioned functions of saving and / or transmitting data; for example, such individual means 6; implement digital slave means made with a microcontroller, for example of type HCS12, which has an external 16-bit bus to exploit the analog signals from the sensors converted digitally and which makes it possible to obtain the energies deposited at different points of the support by the beam.

[0071] The central means 6 implement master digital means made with a microcontroller, for example of type HCS12, which has n (for example n= 8) interrupt inputs PTO to PT(nl) which receive signals from a fast detector in order for example to timestamp the sequence of laser shots and to measure their durations.

[0072] Each of the individual means 6 (means “slave”) is connected to the central digital means 6 (means “master”) by a digital bus 8 (i= 1, ...N), each bus being arranged in parallel with the other buses, between a measurement point i and the digital means 6: for example the master and slave digital buses can be connected with the CAN bus of the HCS12 microcontrollers.

[0073] The central digital means 6 can therefore retrieve and save all the measurements taken by the different sensors.

[0074] The power supply means, for example one or more batteries, can be integrated with the central digital means 6. The power supply means can be partially localized with the individual digital means 6, by means of converters or voltage references which allow decoupling of the analog electrical grounds associated with each of the sensors to ensure galvanic isolation.

[0075] As can be understood from the explanations above, each sensor in the matrix delivers information independent of that delivered by the other sensors in the matrix. The data provided by each sensor is therefore not influenced by the data provided by the other sensors, and there is no mutual interference between the different sensors. Furthermore, the architecture with buses 8 connected in parallel to the means 6 reinforces this independence and allows for good data transfer and good immunity without EMC interference related to the environment for digital transmission between each of the "slave" means 6 and the "master" means 6. In particular, high-speed digital CAN buses can be chosen as they are well-suited to the invention; moreover, these buses can be optocoupled to guarantee their independence.

[0076] Each of the electronic means 6; (i= 1, .. .N) comprises, for example, an electronic processing and / or storage board. These means 6; comprise, for example, a microcontroller, for example of type HCS12, referred to as the "slave" microcontroller (see example already given above), associated with filtering and / or amplification and / or digitization means (circuits).

[0077] In the case of radiometers that transmit data such as energy and / or exposure time and / or power, the microcontroller is equipped with RAM and / or flash memory. In the case of a beam illumination distribution sensor, more sophisticated means can be implemented, for example, a card-type sensor. acquisition (FPGA) which has enough memory to store images of distributions obtained for example using CMOS or CCD sensors.

[0078] Thus, each sensor of each measurement point can be associated with electronic means specific to the measurement point considered, which strengthens the independence of the measurements made with the sensor(s) of this measurement point with respect to the sensors of neighboring measurement points.

[0079] These electronic means 6; (i= 1, .. .N) include, for example:

[0080] - one or more input port(s) for the signals from the associated sensor(s);

[0081] - and / or have a digital interface, for example of type RS232, RS422, RS485, USB, Ethernet, CAN, etc. which allows it to transmit its measurement results, via the communication bus 8, to central digital means which can save all the measurements taken in anticipation of future use;

[0082] - at least one memory, for example a non-volatile flash memory, for to store the measurement results obtained by the associated sensor(s).

[0083] According to one embodiment, the slave digital means can be programmed to trigger a measurement by at least one sensor at a corresponding measurement point when a light beam incident on the measurement point is detected. The central (or "master") digital means 6 comprise, for example, an electronic board equipped with input port(s) to receive signals from the sensors at the various measurement points. These means include, for example, a microcontroller, for example of the HCS12 type, referred to as the "master" (see example already given above), comprising means (circuits) for processing and / or storing the received signals. For example, these means 6 are designed to:

[0084] - receive a signal from each sensor when it receives a radiation, this signal indicating the presence of a beam;

[0085] - trigger and initiate energy and / or beam characteristic measurements and / or beam duration on each sensor;

[0086] - to store the data received from the signals received from the different sensors;

[0087] - optionally timestamp the measurements taken by the sensors using a clock of the matrix, for example to deduce the beam movement velocities between 2 points of the matrix.

[0088] The central digital means 6 can be integrated with power supply means 32, for example at least one rechargeable battery and means for generating, from the voltage supplied by these power supply means, a supply voltage for each of the electronic means 6; (i = 1, ... N). According to one embodiment, this battery comprises N (for example N = 10) accumulators (for example, each with a capacity of 1.2 V) connected in series. The voltage delivered by this battery is Converted using linear regulators (for example, three of them) to provide a voltage (for example, +5V), which can be regulated (for example, to better than 1%) and thus be well-suited for low-noise, high-resolution measurements. This voltage powers the various electronic components, for example, via DC voltage converters with decoupled analog ground, which provides galvanic isolation that complies with the EMC requirements of the entire system.

[0089] According to one embodiment, as illustrated in Figures 1-4, one or more measuring points (X, Yi), (i=l.. .N) may be equipped(s):

[0090] - of an absorber 20, for example made of copper, conical in shape to absorb a beam received after multiple reflections; such an absorber preferably has an internal conical shape with an apex angle for example equal to 45°; it absorbs the beam after a certain number n (for example n= 180° / 45°= 4) successive reflections, so as to minimize the dependence of its absorption factor on the diameter of the incident beam which can vary depending on the depth of field used;

[0091] - of a thermal sensor, for example a Peltier element 22, which will transmit and to dissipate the heat resulting from the absorption of the beam and which will deliver an electrical voltage proportional to the energy deposited; the absorber 20 can be fixed to this element using a thermally conductive adhesive 21 on an input face of this Peltier element; the reference 34 in [Fig.3] designates 2 electrical connections (ground + signal) of the sensor implemented;

[0092] - of 24 fast optical detection means (for example a time-detection photodiode) (with a response time of 50 ns or less) to detect the arrival and presence of an incident beam; these means 24 deliver a pulsed signal representative of the temporal shape of the beam at the point considered. In one embodiment, these means 24 are mounted on an electronic board 28 with a reverse-current photodiode assembly with a fixed gain resistor. The signal delivered by these means can be formatted, for example, in TTL 0-5V format to be directly connected to the interrupt inputs of master and / or slave microcontrollers, depending on the electrical connections made; for example, in the embodiment described above, a hole, for example with a diameter of 0.5 mm, can be made in the bottom of the absorber, perpendicular to its extension direction, to allow a few photons to escape, which will be detected by the fast detection means.

[0093] A signal from the optical fast detection means 24 can be transmitted to the "master" means 6, which can measure the duration of this signal, for example using an internal clock called a "timer," between a trigger on a rising edge and a trigger on a falling edge. This duration can be stored in a memory of the means 6. The latter can therefore time-stamp the signals corresponding to the beams with the internal clock and possibly extract the time elapsed between 2 consecutive measurement points and / or the speed of movement of the beam between these points.

[0094] Furthermore, the detection of a rising edge by means 6 allows a signal to be transmitted to the sensor(s) at the corresponding measurement point to trigger a measurement, for example of energy, preferably proportional to the peak signal delivered by the sensor. The data corresponding to this measurement can be stored by means 6 and / or transmitted to means 6 via bus 8.

[0095] As shown in [Fig. 1], the sensor matrix can be connected to interface means 10, for example a computer or microcomputer via a serial link, for example of type RS232 or RS232 / USB or USB, or via a parallel link. An interface allows communication with the means 6 for:

[0096] - retrieve the time measurements;

[0097] - and / or ask it to communicate via bus 8; coupled with means 6; « "slave" to retrieve energy measurement data. All the data resulting from the measurements carried out, durations of radiation pulses and / or energies and possibly those derived from them (average powers and / or speeds of movement) can be stored and / or displayed on visualization devices;

[0098] - and / or configure the application, for example the associated calibration coefficients to the various sensors, and / or the firing sequences, etc...

[0099] Visualization means 11 allow the display of measurement results performed according to the invention: such an example of results is illustrated in [Fig. 5]. These means can also provide the functions of a debugging, control, storage, and parameterization interface.

[0100] The platform 2 according to the invention is placed in the 3D printing machine, with the door closed, without being connected to it, and in place of the platform on which the parts to be printed are built. As explained above, the radiation source emits the beam, for example, the laser beam, which is moved between different measurement points. The beam is detected at the different measurement points, and the measurement data can be saved in the means 6. The platform 2 is then removed from the machine and can be connected to external means 10, which retrieve the measurement data and save it, optionally display it, and / or process it, for example, compare it: [Fig. 5] shows an example of results obtained with 2 sensors for each measurement point (a photodiode and a Peltier element) which make it possible to obtain the pulse duration T, the measured energy E, and the resulting power (P=E / T).For example, we see that the beam has moved from points 3 to 4 where the results of the measurements are indicated for each of the points: pulse duration, energy and power and, on the line which connects 2 points. The following are indicated for successive points: the beam travel time, the distance between the two points, and the resulting speed of movement. The broken line represents the beam's path between the different points: 3 to 4, 4 to 2, 2 to 1, etc., 6 to 7, and 7 to 8. The results of [Fig. 5] can be displayed on screen 11.

[0101] The invention relates in particular to the characterization of one or more laser beams used for manufacturing identical parts in a machine known as a "laser melting machine," also called a "3D printer": on a build platform, a network or matrix of parts as identical as possible can be manufactured by an additive manufacturing process that uses the laser beam(s). These beam(s) melt metal powder, a filament (PET), or a resin by moving very rapidly at different points on the build platform. The machine in question can use:

[0102] - a single beam, which is guided by optical means 12 (see [Fig. 1] and (description above);

[0103] - or several independent beams carried by optical fiber and possessing their own fast focusing and deflection optics, positioned at different points on motorized or non-motorized axes to share the scanning area in (X,Y).

[0104] In all cases, the aim is to ensure that the energy and spatial parameters of the laser beam or beams used conform to the parameters programmed by the machine and remain stable and repeatable at every point on the platform, in order to manufacture a network of perfectly conforming parts. The invention makes it possible to perform these checks.

[0105] The invention allows in particular the characterization of one or more beam(s), for example laser(s), by the measurement of one or more of its energy parameters (the power P(W) and / or the measured energy E(J): W=E / t) and / or one or more of its temporal and / or geometric and / or spatial parameters.

[0106] The speed of movement of the beam from one measurement point to another on the platform can also be evaluated: this speed, if it does not constitute a characteristic of the beam itself, can constitute additional information concerning the control of the proper functioning of the machine over time.

[0107] Beam characteristic data can therefore be collected, for example one or more of the following characteristics:

[0108] - the pulse width (for example between 0.1 ms and 100 ms);

[0109] - the energy of each pulse (for example between 100 mJ and 100 J);

[0110] - the power of each pulse (for example between 1 W and 1000 W;

[0111] - the delay between pulses (for example between 1 ms and 1 s;

[0112] - the speed of movement from one measurement point to another (for example, including between 1 mm / s and a few m / s, for example 10 m / s.

Claims

Demands

1. A device for characterizing at least one light beam (7) comprising: - a support platform (1) having a plurality of measurement points, each measurement point being equipped with at least one sensor (4j) for measuring at least one energy and / or spatial and / or temporal parameter of a beam incident on said sensor and of digital slave means (6;) for processing and / or storing data from said sensor; - digital master means (6) for storing data from the sensors of the different measurement points; - a plurality of digital buses (8i), each connecting one of the digital slave means (6;) to the digital master means (6), the different digital buses being parallel to each other, the digital slave means (6i) being capable of, or programmed to, transmit measurement data from the sensors to the digital master means (6).

2. Device according to claim 1, at least one sensor (4;) being a sensor for measuring at least one energy parameter, for example the average energy and / or power of a beam, comprising at least one radiometer, for example a calorimeter, or a power meter, or a wattmeter, or a joule meter.

3. Device according to claim 1, said sensor (4;) comprising at least one thermocouple and / or one thermopile and / or one thermistor and / or one platinum resistance probe and / or one pyroelectric probe and / or one photoconductive sensor, and / or one photodiode.

4. Device according to any one of claims 1 to 3, at least one sensor (4;) being a sensor for measuring at least one geometric parameter, for example the spatial distribution of the illuminance EZ(X,Y) of a light beam in a plane perpendicular to its direction of propagation and / or its diameter at the point of measurement and / or its focusing caustic.

5. Device according to claim 4, said sensor (4;) comprising at least one CMOS or CCD sensor.

6. A device according to any one of claims 1 to 5, wherein at least one sensor (4j) is a sensor for measuring at least one parameter temporal of a beam pulse, for example a rising edge, or a falling edge, or a rising edge and a falling edge, or the temporal shape of said pulse.

7. Device according to claim 6, said sensor (4;) comprising at least one photodiode (26) or a fast pyroelectric sensor, with a response time of less than Ips.

8. Device according to any one of claims 1 to 7, the master digital means (6) and / or the slave digital means (6i) being programmed to trigger a measurement by the sensor (4i) of the corresponding measurement point when a light beam incident on the measurement point is detected.

9. A device according to any one of claims 1 to 8, further comprising means (11) for visualizing the path of the beam (7) between the different measurement points and / or values ​​of one or more of the measurement(s) made at each of these points, for example the pulse duration and / or the beam energy and / or the beam power and / or at least one geometric parameter, for example the spatial distribution of the illuminance EZ (X,Y) (W / m2) of the light beam in a plane perpendicular to its direction of propagation and / or its diameter at the measurement point and / or its focusing caustic and / or, for example on the line which connects 2 successive points, the time of movement of the beam between 2 points and / or the distance between these 2 points and / or the speed of movement of the beam.

10. System for the characterization of at least one light beam comprising a device according to any one of claims 1 to 9, and further comprising means for moving, relative to the support plate (1), the light beam (7) emitted by a radiation source.

11. System according to claim 10, the means of displacement, relative to the support plate (1), of the light beam (7) comprising optical means (12).

12. System according to claim 11, optical means (12) comprising focusing means, for example flat field, and / or one or more mirror(s), for example galvanometric type(s).

13. A method for characterizing at least one light beam (7) emitted by a radiation source, employing a device according to any one of claims 1 to 9 or a system according to any one of claims 10 to 12, this method comprising: a) - direct the light beam (7) successively towards a plurality of measurement points of the device; b) - measure at each of said measurement points, using at least one measurement sensor (4;), at least one energy and / or spatial and / or temporal parameter of the incident beam; c) - transmit data from said measurements to the master digital means (6) via one or more of the digital buses (8i).

14. Method according to claim 13, comprising processing and / or storing at least a portion of the data measured by the digital slave means (6;) for processing and / or storing data from said measurement points.

15. A method according to claim 13 or 14, comprising: - identification by master (6) and / or slave (6i) digital means of the presence of radiation on at least one of the sensors; - then sending by these master digital means (6) a request to transmit data to said slave digital means (6); - then sending the measurement data from the digital slave means (6;) to the digital master means (6).

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