METHOD AND DEVICE FOR 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 plate (1) comprising a plurality of measurement points, each measurement point being provided 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 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 OF DYNAMIC CHARACTERIZATION OF A RADIATION BEAM SE MOVING BETWEEN DIFFERENT POINTS TECHNICAL FIELD AND PRIOR ART

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

[0002] The techniques for energetic and spatial characterization of 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 makes it possible to evaluate several energy and time parameters (the average power P(W), the value of the pulse width of the signal T(ms), the frequency of the pulses of the signal F(Hz), the average energy per pulse E(J)).

[0003] We also know the device of document FR 2974176 which makes it possible to analyze 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 temporal parameters such as the shape of the pulse as a function of time.

[0004] Document WO2021 / 250346 is also known, which makes it possible to carry out a spatial characterization of the markings resulting from laser impacts at different focusing points on a plate. Here, it is the "ZAT", or zone thermally affected by the beam, which is analyzed. The position of the mirrors and optics used to deflect the laser beam introduces different lengths of optical paths followed by the beam, which results in a possible positioning error relative to the theory and variations in the geometry and dimension of the focusing spot on the target. To solve this problem, this document describes an image comparison device comprising, on the one hand, test markings and, on the other hand, reference markings. Corrections are stored in memory and applied to the machine to correct the length of the optical path so as to get as close as possible to the reference markings.This device does not allow 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 beam movement speed.

[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 parts in series. Indeed, for this type of application, we seek to ensure that the beam parameters are constant at all points in order to produce almost identical parts.

[0006] The problem therefore arises of finding a new method and a new device making it possible to measure in real time the energy and time parameters of radiation, for example of the laser beam type, moved, for example at high speed, at different points in two-dimensional space, for example on the surface of a manufacturing plate. This is the case in particular in the case of the manufacturing of parts by additive technique.

[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 soluble with current means: in fact it is not possible 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 being able to ensure the control of different sensors at the rate of movement of a radiation, for example a laser beam, in particular if this beam moves at a speed which can reach up to a few m / s. Statement of the invention

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

[0010] - a support plate comprising a plurality of measuring points, each point measuring device being provided 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 digital slave means for processing and / or storing data from said sensor;

[0011] - master digital means for storing data from the sensors of the different measuring 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 on the support plate. They may be programmed to transmit this data to the master digital means, the latter then being capable of storing it and possibly transmitting it to an external intelligence (for example a PC) via a suitable digital interface (for example of the RS232, or RS422, or USB, or IEEE, or parallel, or by wireless transmission, etc.) type, so as to allow for example their exploitation and / or their traceability over time.

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

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

[0016] The transmission of data by the buses can be optocoupled: thus, this transmission can be of the electrical type, then optical, then again electrical, the buses being optocoupled to the slave digital means and to the master digital means. The master digital means can make it possible to ensure the control of different sensors at the rate of movement of a radiation source, for example a laser beam, in particular if this source moves with a speed which can reach for example up to a few m / s.

[0017] Thus a measurement order can be preprogrammed in the master digital means and memorized according to the predefined position of the beam on the sensors. But the invention also has the advantage of being able to operate according to a random sequence, because each sensor associated with slave digital means (for example a microcontroller) can be capable, depending on the electrical connections made, of automatically detecting the presence of the beam and / or of triggering its measurement sequence autonomously. It is the configuration of the application which will define the strategy chosen according to the need.

[0018] Each of the sensors of a device according to the invention can deliver information independent of that delivered by the other sensors. The different sensors are independent of each other, without mutual interference between them, 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 data transfer without interaction or mutual disturbance and EMC type immunity from the environment. Galvanic isolation of each of the sensors can also contribute to the independence mentioned above.

[0019] At least one sensor of at least one measuring point may comprise a sensor for measuring at least one energy parameter, for example the 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 of at least one measuring point may comprise a sensor for measuring at least one geometric parameter of a beam, for example the spatial distribution of the illumination EZ(X,Y) (W / m2) of a light beam in a plane perpendicular to its direction of propagation and / or its diameter at the measuring point and / or its focusing caustic. This sensor comprises for example at least one CMOS or CCD sensor.

[0021] At least one sensor of at least one measuring point may comprise a sensor for measuring at least one temporal parameter of a pulse of a beam, 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 comprises for example at least one photodiode or a fast pyroelectric sensor, with a response time at most equal to 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 by an interrupt input) or by the slave digital means (for example again by an interrupt input) or by the master and slave digital means simultaneously (depending on the connections made) to deduce the duration therefrom.

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

[0023] In a device according to the invention, the master, or slave or master and slave digital means 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 comprise means for supplying power to each of the sensors. These supply means may be integrated with the master digital means, for example in the form of an electronic card.

[0025] At least one measuring point may comprise means for absorbing a light beam incident on the measuring 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 plate. These moving means are, for example, part of a characterizing machine. They comprise, for example, means optical means, comprising for example focusing means, for example called flat field, and / or one or more mirror(s), for example of the galvanometric type. These means make it possible to direct the beam towards each of the different measuring points, preferably at an incidence perpendicular or almost perpendicular to the surface of the plate. According to one embodiment, these optical means comprise a galvanometric mirror system and / or flat field focusing optics.

[0027] A device or system according to the invention may comprise means for displaying the path of the beam between the different measurement points and / or 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 illumination 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) - directing the light beam successively towards a plurality of measuring points of the device,

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

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

[0032] Such a method may comprise processing and / or storing at least part of the data measured by the slave digital means for processing and / or storing data from said measuring 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, then sending by these master digital means of a request for transmission of data to said slave digital means. But 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, presence which may also be transmitted automatically to the master digital means for time-stamping, then sending the measurement data to the master digital means.

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

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

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

[0037] - then sending the measurement data from the slave digital means to the means master digital. A method according to the invention may comprise a display on visualization means of the path of the beam between the different measurement points and / or 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 illumination 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.

[0038] In a method according to the invention:

[0039] - the light beam can be moved relative to the plate at a speed of between between 1 mm / s and 10 m / s;

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

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

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

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

[0044] DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

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

[0046] A plate or support 2 comprises a plurality of N measuring points 4b 4;... 4N (i= 1, .. .N) distributed for example in the form of a matrix on the surface of this plate. Each measuring point is associated with coordinates (X^Y;), (i=l.. .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 measuring point (X;,Y;) to a neighboring point (Xi+i,Yi+i) of the plate (the 2 beams 7, 7i of [Fig.l] thus represent the same beam 7 moved to 2 points different measurement points, and measured at 2 different times). Optical means 12, comprising for example a galvanometric mirror system 12' and a so-called flat-field focusing optic, make it possible to direct the beam 7 towards each of the different measurement points following an incidence perpendicular or almost perpendicular to the surface of the plate 2.

[0049] Preferably, the distribution or distribution of these different measurement points on the plate 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 which emits radiation which moves, for example at high speed, according to said distribution of the working points.

[0050] Each measuring point (Xi,Yi) comprises at least one sensor 4; which will make it possible to measure 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 below.

[0051] By way of example, each sensor 4; makes it possible to measure an energy parameter (energy E and / or average power P) of the incident beam: it may in particular be or comprise a radiometer, for example a calorimeter, or a power meter, or a Wattmeter, or a Joule meter. It is, for example (non-limiting 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 one or other of the preceding sensors, one or more sensors may comprise a CMOS or CCD sensor camera. 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 illumination 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 measuring 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 focusing plane, X and Y being defined above.

[0056] Alternatively, or in combination with one or other of the preceding sensors, one or more sensors may comprise optical means for detecting at least one temporal parameter of a pulse of a beam, for example a photodiode with a response time, for example 50 ns or less. Such means allow to detect for example a rising edge and / or a 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 embedded algorithm with a slow-response thermal sensor which processes the growth of a signal resulting from the absorption of a beam. For example, if 2 measurement points each comprise such optical or algorithmic means, it is possible to calculate the time elapsing between 2 pulses of the beam to determine the speed of movement of the latter between these same 2 points and / or the time between successive pulses of the beam and / or the width of each pulse of the beam.

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

[0058] Each sensor can be connected to an autonomous power supply, for example implemented by one or more battery(ies).... This power supply can be centralized (with 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 arrangement to pass through the protective cover for the passage of a mains power cable, which makes it possible to envisage the use of the instrument matrix in any machine.

[0059] Each measuring point can be provided with means 20 for capturing the radiation from a radiation source, these means are subsequently referred to as "absorbers". Examples of embodiments of absorbers will be given below. The associated optical absorption techniques and geometries can be diverse: flat disc or flat disc or with concentric grooves, or cone, or semi-reflecting cone combined with a cylinder, etc., each of these elements preferably being coated with an optically absorbing layer for the wavelength of the beam.

[0060] The entire device can be placed for example under a cover (not shown in the figures) which can be provided with a door giving access to the various sensors and means implemented on the support 2. By implementing an autonomous electrical 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 cover 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 below, the entire device is equipped with electronic, analog and / or digital means, which will make it possible to process the signals representative from the different sensors, which will for example be formatted and / or filtered and / or digitally converted and / or stored.

[0063] According to an advantageous embodiment, each sensor is associated with, or provided with, means for temporal detection of radiation, for example a laser beam, to initialize 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] - comprise for example at least one fast detector (for example: 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 relative to the same reference using the same range of radiation parameters, for example power and / or energy and / or diameter and / or illumination distribution of the beam; such calibration makes it possible to compare the results obtained at different points on the plate and therefore to decide on the stability of the parameters of the beam used, over time and / or during movements of the beam.

[0067] The calibration of the sensor matrix can be implemented for example using a digital table adjustable in position (X,Y) which comprises means for moving the sensor plate 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 makes it possible to move the beam vertically on the matrix 2 of sensors without risking deforming 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 terms of energy and geometry regardless of the position of the sensor of the matrix to be calibrated.

[0070] As illustrated in [Fig. 1], each measuring 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 this same measuring point, these means comprising for example, as explained above, a microcontroller and / or an FPGA to ensure the functions mentioned above of saving and / or transmitting data; for example, such individual means 6; implement slave digital means produced with a microcontroller, for example of the HCS12 type, which has a 16-bit external bus for exploiting the analog signals of the digitally converted sensors 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 produced with a microcontroller, for example of the HCS12 type, which has n (for example n= 8) interrupt inputs PTO to PT(nl) which receive the signals from a fast detector in order, for example, to time-stamp the sequence of laser shots and measure their durations.

[0072] Each of the individual means 6 (“slave” means) is connected to the central digital means 6 (“master” means) by a digital bus 8 (i= 1, ...N), each bus being arranged in parallel with the other buses, between a measuring 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 recover and save all of the measurements made by the different sensors.

[0074] The power supply means, for example one or more batteries, can be embedded with the central digital means 6. The power supply means can be partially located 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 understood from the above explanations, each of the sensors of the matrix delivers information independent of that delivered by the other sensors of 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. In addition, the architecture with buses 8; connected in parallel to the means 6 reinforces this independence and allows good data transfer and good immunity without EMC type disturbance linked to the environment for the digital transmission between each of the “slave” means 6; and the “master” means 6. In particular, fast digital buses of the CAN type can be chosen because 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 card. These means 6; comprise for example a microcontroller, for example of the HCS12 type, called “slave” (see example already given above), associated with filtering and / or amplification and / or digitization means (circuits).

[0077] In the case of radiometers which transmit data such as energy and / or exposure time and / or power, the microcontroller is provided with RAM and / or flash memory(ies). In the case of a beam illumination distribution sensor, more elaborate means can be implemented, for example of the card type. 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 measuring point can be associated with electronic means specific to the measuring point considered, which reinforces the independence of the measurements made with the sensor(s) of this measuring point in relation to the sensors of the neighboring measuring points.

[0079] These electronic means 6; (i= 1, .. .N) comprise 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 the RS232, RS422 type, 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 preparation for future use;

[0082] - at least one memory, for example a non-volatile flash memory, for store the results of measurements made 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 of a corresponding measuring point when a light beam incident on the measuring point is detected. The central (or “master”) digital means 6 comprise, for example, an electronic card, provided with input port(s) for receiving the signals coming from the sensors of the different measuring points. These means comprise, for example, a microcontroller, for example of the HCS12 type, called “master” (see example already given above), comprising means (circuits) for processing and / or storing the signals received. 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 and / or beam duration measurements on each sensor;

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

[0087] - Optionally timestamp the measurements made by the sensors of the matrix, for example to deduce the beam displacement speeds 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 1.2V) connected in series. The voltage delivered by this battery is converted using linear regulators (e.g. 3 in number) to provide a voltage (e.g. +5V), which can be regulated (e.g. to better than 1%) and thus be well suited to high-resolution low-noise measurements. This voltage supplies the various electronic means 6;, for example via direct current voltage converters, with decoupled analog ground which allows galvanic isolation respecting the EMC of the assembly.

[0089] According to one embodiment, as illustrated in figures 1 - 4, one or more measuring points (X;,Yi), (i=l.. .N) can be provided with:

[0090] - an absorber 20, for example made of copper, of conical shape to absorb a beam received after multi-reflections; such an absorber preferably has a conical internal 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] - a thermal sensor, for example a Peltier element 22, which will transmit and evacuate 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 glue 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 optical means of rapid detection (for example a time photodiode response time of 50ns or less) to detect the arrival and presence of an incident beam; these means 24 deliver a pulse signal representative of the temporal shape of the beam at the point considered. In an exemplary embodiment, these means 24 are installed on an electronic card 28 with a reverse current photodiode assembly with fixed gain resistance. The signal delivered by these means can be shaped, for example in TTL 0-5V format to be directly connected to the interrupt inputs of the 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 0.5mm, can be made at the bottom of the absorber, perpendicular to the direction of extension thereof, to allow a few photons to escape which will be detected by the fast detection means.

[0093] A signal from the fast optical 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 elapsing between 2 consecutive measurement points and / or the speed of movement of the beam between these points.

[0094] In addition, the detection of a rising edge by the means 6 makes it possible to transmit to the sensor(s) of the corresponding measuring point a signal 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 the means 6; and / or transmitted to the means 6 by the bus(es) 8;.

[0095] As shown in [Fig.l], the sensor matrix can be connected to means 10 forming an interface, for example a computer or microcomputer via a serial link, for example of the RS232 or RS232 / USB or USB type, or via a parallel link. An interface makes it possible to communicate with the means 6 for:

[0096] - recover the time measurements;

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

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

[0099] Visualization means 11 make it possible to display results of measurements carried out according to the invention: such an example of results is illustrated in [Fig.5]. These means can also provide the function of debugging, control, storage, and parameterization interface.

[0100] The plate 2 according to the invention is placed in the 3D printing machine, with the door closed, without connection with it, and in place of the plate 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 measuring points. The beam is detected at the different measuring points, and the measurement data can be saved in the means 6. The plate 2 is then removed from the machine, and can be connected to the external means 10 which recover the measurement data and save them, possibly display them, and / or process them, for example compare them: [Fig.5] represents an example of results obtained with 2 sensors for each measuring point (a photodiode and a Peltier element) which make it possible to obtain the duration of the pulse 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 measurement results are indicated for each point: pulse duration, energy and power and, on the line which connects 2 points. successive points are indicated: the duration of the beam movement, the distance between the 2 points and the resulting speed of movement. The broken line represents the path of the beam 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 applies in particular to the characterization of one or more laser beam(s) used for the manufacture of identical parts in a so-called "laser fusion" machine, also called a "3D Printer": on a plate, it is thus possible to manufacture a network or a matrix of parts as identical as possible, by an additive manufacturing process which uses the or one of the laser beam(s). The latter melts metal powder, or a filament (PET) or a resin, by moving very quickly at different points on the plate. The machine in question can use:

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

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

[0104] In all cases, it is sought to ensure that the energy and spatial parameters of the laser beam or beams used are consistent with the parameters programmed by the machine and remain stable and repeatable at any point on the plate, in order to be able to manufacture a network of parts that are all consistent. The invention makes it possible to carry out 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 measuring point to another on the plate 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 correct functioning of the machine over time.

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

[0108] - the width of the pulses (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 the pulses (for example between 1 ms and 1 s;

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

Claims

Claims

1. Device for characterizing at least one light beam (7) comprising: - a support plate (1) comprising a plurality of measurement points, each measurement point being provided 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 slave digital means (6;) 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 (6;) 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).

2. Device according to claim 1, at least one sensor (4;) being a sensor for measuring at least one energy parameter, for example the 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.

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 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 illumination EZ(X,Y) 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.

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

6. Device according to one of claims 1 to 5, at least one sensor (4j) being a sensor for measuring at least one parameter temporal shape of a pulse of a beam, 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 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 measuring point when a light beam incident on the measuring point is detected.

9. Device according to one of claims 1 to 8, further comprising means (11) for displaying the path of the beam (7) between the different measurement points and / or the values ​​of one or more of the measurements 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 illumination 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 speed of movement of the beam.

10. System for characterizing at least one light beam comprising a device according to 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 for moving, relative to the support plate (1), the light beam (7) comprising optical means (12).

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

13. Method for characterizing at least one light beam (7) emitted by a radiation source, implementing a device according to one of claims 1 to 9 or a system according to one of claims 10 to 12, this method comprising: a) - directing the light beam (7) successively towards a plurality of measuring points of the device; b) - measuring at each of said measuring points, using at least one measuring sensor (4;), at least one energy and / or spatial and / or temporal parameter of the incident beam; c) - transmitting 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 part of the measured data by the digital slave means (6;) for processing and / or storing data from said measuring points.

15. A method according to claim 13 or 14, comprising: - identification by the 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 for data transmission to said slave digital means (6;); - then sending the measurement data from the slave digital means (6;) to the master digital means (6).

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