Methods and systems for determining, by parallel interferometry, the positions of elements of an optical system in an assembly for processing or measuring an object, and the position of the object relative to the assembly.

Abstract

Methods and systems are described for determining the relative positions of elements of an optical system for processing or measuring an object along a predetermined measurement line associated with the system. These involve generating a measurement beam and a reference beam with low-coherence optical radiation, wherein the measurement beam and reference beam alternately or in combination comprise a main beam and a multiplexed supplementary beam. The measurement beam, guided toward an element of the optical system or toward an object and reflected back toward the object, is superimposed on the reference beam in a common incident region of the interferometric optical sensor apparatus. The positions or frequencies of the main interference fringe pattern and the supplementary interference fringe pattern are detected thereon, and based on these, the difference between (a) the position of an element of the optical system or the separation distance between the processing tool or measuring instrument and an object outside the system and (b) a nominal predetermined position or nominal separation distance is determined.

Description

Technical Field

[0001] The present invention generally relates to industrial processing or measurement methods for objects or materials, for example by means of tools, instruments or probes arranged at a predetermined separation distance or in contact with the object or material, such as in the control of laser processing of the material, for example for laser cutting, drilling or welding of the material, or for additive manufacturing of a predetermined structure of the material.

[0002] Specifically, the present invention relates to determining the relative positions of elements of an optical system or at least a portion of a reflective surface outside the optical system with respect to a corresponding predetermined reference for a processing or measuring assembly. Elements of the optical system are those positioned along the propagation direction of a laser beam from a processing assembly (such as the head of a laser processor) or along the propagation direction of optical measuring radiation in a measuring assembly of a machine tool. Their relative positions are determined by comparison with a predetermined reference element (such as one end of a radiation source, processing tool, or measuring instrument). At least a portion of the reflective surface outside the optical system of the processing or measuring assembly is, for example, the surface of an object undergoing processing or measurement, and its relative position is determined by comparison with a predetermined reference element (such as the end of an optical radiation source, processing tool, or measuring instrument used for processing or measurement that faces the object under operating conditions).

[0003] The present invention further relates to parallel measurement of the positions of multiple elements of an optical system or multiple reflective surfaces outside the system, or also to parallel measurement of the positions of elements of an optical system and reflective surfaces outside the system.

[0004] More specifically, the present invention relates to a method for determining the relative positions of elements of an optical system for processing or measuring an object along a predetermined measurement line associated with the system, as described in the preamble of claims 1 and 13.

[0005] According to another aspect, the present invention relates to a machine for laser processing of materials according to the preamble of claim 24.

[0006] The present invention also relates to a method for determining a separation distance between a processing tool or measuring instrument and at least a portion of a reflective surface of an external object along a predetermined measuring line associated with at least a proximal portion of the surface of the processing tool or measuring instrument relative to the object, as described in the preamble of claims 2 and 14.

[0007] According to another aspect, the present invention relates to a machine for laser processing of materials according to the preamble of claim 25.

[0008] According to another aspect, the present invention relates to a method for determining the positions of a plurality of elements in a system that at least partially reflect optical radiation, the system comprising a plurality of optical components of a component for processing or measuring, or comprising at least one optical element of a component for processing or measuring, and an object located outside the component and subjected to said processing or measuring, wherein the plurality of at least partially reflecting elements are arranged along a predetermined common measurement line, as described in the preamble of claim 23. Background Technology

[0009] In the following description and claims, the term "article" refers to the finished product or workpiece being processed. When applied to machine tools, and specifically to machines used for laser processing, the term "workpiece," and in a preferred embodiment, "metal workpiece," is used to indicate any given manufactured article, such as a sheet or elongated profile having a closed cross-section (e.g., a hollow circle, rectangle, or square) or an open cross-section (e.g., a flat section or an L, C, U, or other shaped section). In additive manufacturing, the term "material" or "precursor material" refers to a raw material, typically a powder, subjected to sintering or localized melting by a laser beam.

[0010] In the following description and claims, the term "material," and in the preferred embodiment, "metallic material," is used to refer to any given manufactured article, such as a sheet or elongated profile having a closed cross-section (e.g., a hollow circle, rectangle, or square) or an open cross-section (e.g., a flat section or a section of L, C, U, or other shapes). In additive manufacturing, the term material refers to a raw material, typically a powder, subjected to sintering or localized melting by a laser beam.

[0011] In industrial processes, handling tools are typically brought close to objects or materials for remote processing without contact, such as by emitting working fluids or radiation. It is also known that measuring instruments approach workpieces or materials being processed during the manufacturing process of a product or finished product in order to detect certain geometric features or physical properties during, during, or at the end of the manufacturing process.

[0012] As an example of industrial processing methods, laser radiation is used as a thermal tool in the laser processing of materials, particularly sheet and profile metals, for a wide variety of applications that depend on the parameters of the interaction between the laser beam and the part being processed, specifically the energy density of the laser beam per unit incident volume on the part and the range of the interaction time.

[0013] For example, tempering processes are achieved by directing a low energy density (approximately tens of watts per square millimeter of surface) onto a metal workpiece for a prolonged period (approximately several seconds), while photoablation processes are achieved by directing an increased energy density (approximately tens of megawatts per square millimeter of surface) onto the metal workpiece for approximately femtoseconds or picoseconds. Controlling these parameters within an intermediate range of increasing energy density and decreasing processing time allows for processes such as welding, cutting, drilling, engraving, and marking. These processes are performed by emitting a laser beam from a working head that operates at a distance from the workpiece being processed.

[0014] In many processes, including those involving drilling and cutting, an auxiliary gas flow is required in the processing area where the laser beam interacts with the material. This auxiliary gas flow serves a mechanical function of propelling the melt, a chemical function of assisting combustion, or a technical function of shielding the surrounding area of ​​the processing zone. The auxiliary gas flow is also injected by corresponding nozzles at a distance from the part being manufactured.

[0015] In additive manufacturing, the material can be supplied, for example, in the form of filaments or powder ejected from a nozzle, or alternatively, in the form of a powder bed, due to the auxiliary gas flow. The material is then melted by laser radiation, and a three-dimensional mold is obtained after the material itself re-solidifies.

[0016] In the field of laser processing of materials, laser cutting, drilling, and welding are processes that can be performed using the same machine capable of generating a high-power focused laser beam with a predetermined lateral power distribution in at least one working plane of the material, typically with a power density between 1 and 10,000 kW / mm². 2 The machine controls the direction and position of the laser beam along the material, and, if necessary, the direction of the auxiliary gas flow. The differences between the various types of treatments that can be performed on the material essentially boil down to the power of the laser beam used and the duration of interaction between the laser beam and the material being treated.

[0017] Figure 1 The image shows a machine tool working on a part being processed.

[0018] Figure 1 The diagram shows a machine tool, such as a machine tool for laser processing of parts or materials, with the working head 10 located at a distance d from the material WP being processed. Processing or measuring instruments are typically indicated by 12, such as tools for processing, nozzles for jetting working fluids, outputs for processing radiation (e.g., high-power laser radiation for quenching, welding, cutting, drilling, engraving, marking, photoablation, or sintering of materials), or measuring probes.

[0019] The processing or measuring instrument 12 may be considered as the distal end of the working head, serving as a reference for the entire machine, or as the proximal end of the part or material being processed, and these terms shall be used interchangeably in the specification.

[0020] In a machine used for laser processing, the processing radiation output or "beam output" is the part of the working head from which the laser beam is emitted into free space or propagates toward the material being processed outside the volume of the head, and the processing radiation output or "beam output" can be the terminal part of an optical focusing system or its protective structure, or it can also be the conical end of a nozzle that distributes an auxiliary gas flow for applications that require the supply of gas for processing.

[0021] A movable actuator device 14 is coupled to the working head 10. The movable actuator device 14 is controlled by the processing control unit ECU via a servo motor 16 to control the mechanical parameters of the processing (such as controlling the movement of the working head along the degrees of freedom allowed by a specific embodiment of the machine) so as to follow a programmed working trajectory T on the part or material, specifically, to move along the Z-axis to approach or move away from the part or material according to the movement of its profile or processing profile.

[0022] Figure 2 An example of a working head 10 for laser processing according to the prior art is illustrated. A tubular channel, designated 30, has a cylindrical or conical portion in which the laser beam is transmitted, indicated by B. The laser beam B, generated by an emission source (not shown), is transmitted to the working head via an optical path with multiple reflections in air or optical fiber, and strikes a reflective deflector element 32 in a collimated manner, which deflects its propagation optical axis in the direction of incidence on the part or material being processed. An optical focusing system 20, located between the reflective deflector element 32 and a downstream protective glass 34, shields the focusing system from any molten splashes, and includes a lens holder 36 for calibrating the lens positioning transversely to the beam propagation direction (XY axis) and in the beam propagation direction (Z axis), the lens holder 36 being coupled to a mechanical adjustment mechanism 38.

[0023] Although Figure 2 A diagram of a working head using a high-power laser beam is shown; however, for the purposes of this invention, the optical components or optical chains shown in the diagram can be considered to substantially correspond to the optical components of a measurement probe that operates by means of a beam of low-power optical radiation striking an object or material, and that the beam is reflected or scattered and processed from the object or material according to one of the methods of the prior art.

[0024] In industrial processes where instruments are brought close to an object or material being processed, the outcome of the processing or measurement depends on the correct distance between the instrument and the object or material. For example, in the laser processing of parts or materials, and specifically in the control of laser processing of metal parts for laser cutting, drilling, or welding, or in additive manufacturing of predetermined structures from powder precursor materials, it is important to maintain the processing instrument at a controlled distance from the part or material. In the same example, controlling the propagation direction or lateral distribution of the laser beam power (e.g., with regard to the controlled distribution of the auxiliary gas or according to the separation distance between the working head and the part or material, the working trajectory to be followed, and the type of processing performed) provides advantages to the process. For example, controlling the power distribution of the laser beam allows the power distribution to be positioned or extended relative to the separation distance between the working head and the part or material and the working trajectory. The same can be said of the case of irradiation by a beam used to measure the physical properties or dimensions of a part or material.

[0025] Clearly, the control of the distance between the processing or measuring instrument and the object or material being processed, as well as the propagation direction and lateral distribution of the optical processing or measuring beam (such as a laser beam), should be as precise and repeatable as possible to achieve efficient and accurate processing or accurate measurement. For this purpose, the movement of the working head and the position of its proximal end relative to the part or material (e.g., the position of the laser processing beam output, and the position of the auxiliary gas outlet nozzle in processing where this is required, or the position of the optical measuring beam relative to the part or material), particularly relative to the position of the beam's incident point on the material, must be controlled with extreme precision and in real time, based on the current processing conditions and the current position along the working trajectory. Otherwise, there is a risk of focusing the power of the processing laser beam into an undesirable working plane within the thickness of the part or material, and the risk of using excessive or insufficient auxiliary gas pressure (at the surface of the part or material). During measurement, there is a risk of failing to adequately focus the optical measuring radiation onto the object, resulting in measurements that do not reflect reality.

[0026] It is also necessary to control the position of the optical elements associated with the optical transmission path of the beam in the machine's processing or measuring head (positioned along, facing, or adjacent to the optical path) with extreme precision and in real time. Otherwise, for example in laser processing, there is a risk of focusing laser power into an undesirable working plane within the thickness of the material.

[0027] The position of the optical elements can vary depending on the current operating conditions of the machine (including the current temperature of the area through which the optical elements and the high-power laser processing beam pass, the pressure of the auxiliary gas applied to the optical elements opposite the auxiliary gas nozzle, and possible mechanical deformation of the optical elements (fiber optics, mirrors, lenses) associated with the beam transmission path), and also due to positioning errors of the components on the parts by the technician during installation, or design tolerances and undesirable gaps during assembly.

[0028] Variations in the position of optical elements relative to their intended nominal position may cause uncontrolled changes during the process or affect measurements in the process, such as measuring the separation distance between the working head and the part or material, or the position of the laser beam output and auxiliary gas outlet nozzle in processes where this is required.

[0029] For these reasons, in industrial processing, it is desirable to be able to accurately determine the separation distance between the working head or the proximal end of the working head relative to the part or material and the surface of the part or material itself, as well as the local position of the optical elements associated with the optical transmission path of the optical processing or measuring beam. Summary of the Invention

[0030] The object of this invention is to provide a method for effectively monitoring (optionally in real time) a process of handling or measuring parts or materials by means of an optical radiation beam.

[0031] Specifically, the object of the present invention is to provide a method for determining the relative positions of components of an optical system of a machine tool for processing or measuring parts or materials by means of an optical radiation beam, such that the method is accurate and robust.

[0032] Specifically, another object of the present invention is to provide an accurate and robust method for determining the separation distance between a measuring instrument of a processing tool or machine tool and the surface of an external object, the measuring instrument of which is used to process or measure parts or materials by means of an optical radiation beam.

[0033] Another object of the present invention is to provide a method for effectively monitoring (optionally, in real time) a process of handling or measuring a part or material by an optical radiation beam over a wide measurable distance without sacrificing measurement accuracy, determining the relative positions of elements of an optical system for handling or measuring an object, or the separation distance between a handling tool or measuring instrument and the surface of an external object.

[0034] Another object of the present invention is to provide a method capable of compensating for any measurement disturbances in the relative position of optical elements or the separation distance between a processing tool or measuring instrument and the surface of an external object.

[0035] Another object of the present invention is to provide a method that enables multiple measurements of the relative position of an optical element or the separation distance between a processing tool or measuring instrument and the surface of an external object in a shorter time.

[0036] Another object of the present invention is to provide a method for the above-mentioned purpose, which is applicable to a machine for laser processing of parts or materials.

[0037] According to the invention, these objectives are achieved by means of a method for determining the relative positions of elements of an optical system of an assembly (having the features presented in claim 1) and a method for determining the separation distance between a processing tool or measuring instrument and at least a portion of the reflective surface of an external object along a predetermined measuring line (having the features presented in claim 2), the assembly being used to process or measure an object along a predetermined measuring line associated with the system, the method, the predetermined measuring line being associated with at least one proximal portion of the tool or instrument relative to the surface of the object.

[0038] Another subject of the invention is a method for determining the relative positions of elements of an optical system of an assembly (having the features presented in claim 13), and a method for determining the separation distance between a processing tool or measuring instrument and at least a portion of the reflective surface of an external object along a predetermined measuring line (having the features presented in claim 14), the assembly being used to process or measure an object along a predetermined measuring line associated with the system, the predetermined measuring line being associated with at least one proximal portion of the surface of the tool or instrument relative to the object.

[0039] The specific embodiments are the subject of the dependent claims, and their contents should be understood as an integral part of this specification.

[0040] Another subject of the invention is a machine for laser-processing materials according to claims 24 and 25.

[0041] In short, this invention is an application based on the principle of optical interferometry.

[0042] The term "optical interferometry" refers to various techniques that utilize the interference phenomenon between an optical measurement beam and an optical reference beam, which, when overlapped, generates interference fringes. The theory of optical interferometry in coherent light is well-known and has been applied in relative comparisons of distances; however, it cannot provide definitive information about the absolute measurement of said distance after, for example, a temporary interruption of the optical signal.

[0043] This invention is inspired by the consideration that absolute distance measurement can be optically achieved by employing low-coherence interferometry. Low-coherence interferometry is a simple technique for measuring the distance between a probe and an objective lens with high precision, based on a comparison of the travel distance of an optical measurement beam propagating from a source to a detection component and emitted from the probe and reflected back from the target along this path, and an optical reference beam propagating from the source to the detection component via a reference path, tuned to the measurement path under nominally known distance conditions between the probe and the target.

[0044] In low-coherence interferometry, the optical measurement beam and reference beam are generated by low-coherence sources (such as LEDs or superluminescent diodes), and interference fringes between the beams appear only under corresponding conditions between corresponding optical paths (or optical path lengths), i.e., when the length of the measurement path corresponds to the length of the reference path within a range of coherence lengths. The optical path is defined as the sum of the products of the geometric lengths and the corresponding refractive indices between each segment traveling along the entire optical path. Knowing the length of the reference path, the length of the measurement path can be obtained by detecting the presence of the envelope of the interference fringes, which has a resolution on the order of the coherence length, which is on the order of micrometers (between 5 μm and 100 μm).

[0045] This technique is particularly robust to optical noise because light from other sources or from the laser processing itself is incoherently added to the interferometric measurement signal without altering the interference fringe pattern. The application of the measurement is localized at the point where the optical measurement beam is guided, independent of the surrounding morphology. This further allows for absolutely precise distance measurements in a distribution substantially coaxial with the laser processing.

[0046] Various techniques are known for detecting interference fringe patterns in the time, frequency, and spatial domains, respectively. Advantageously, techniques for detecting interference fringe patterns in both the spatial and frequency domains appear to be more promising and efficient in terms of operational flexibility compared to detection in the time domain.

[0047] In low-coherence interferometry with time-domain detection, interference fringe patterns are detected by photodiodes or photodiode arrays, or by an analog acquisition screen, thereby varying the length of the reference path until a correspondence is achieved between the lengths of the reference path and the measurement path, except for tolerances on the order of coherence length. In this case, the limitation on the interval of available measurements is due to the change in the length of the reference path, for example, accomplished by translating a back-reflecting element positioned along the path, with spatial intervals between translations of the back-reflecting element of the reference path ranging from a few micrometers to a few millimeters, and this wide translation range comes at the cost of actuation speed or operational complexity.

[0048] Even though time-domain detection techniques are relatively easy to implement and allow for readily establishing a correspondence between the absolute optical lengths of the measurement path and the reference path, they remain poorly suited for real-time measurement applications implemented in industrial processes. In fact, for dynamic measurements, the length of the reference path needs to be continuously modulated to find conditions corresponding to the length of the current measurement path that determines the appearance of the interference fringe pattern. This can be achieved using various types of control devices, including refractive index modulators or fast mechanical actuators, such as piezoelectric actuators; however, these types of devices are quite expensive and very precise because they require actuation speeds much higher than the sampling rate used for measuring distances, typically greater than kHz, conditions that are often difficult to obtain (especially over large displacements).

[0049] Different detection techniques are based on the Fourier transform relationship between the spectral density function and the cross-correlation between the measurement beam and the reference beam. This Fourier transform relationship allows for the extraction of differential measurements of distance in real space from the wavelength spectral profiles of the two interfering beams. In this way, mechanical actuators are not required to align the length of the reference path with the length of the measurement path. The spectral distribution of the interfering beams can be projected onto a linear sensor device (such as a camera) by using a diffraction grating and a downstream focusing lens to perform single spectral acquisition of the overlapping measurement and reference beams. The spectra of the two interfering beams exhibit periodic modulation, and the periodicity (frequency) of this modulation in the wavelength space varies with the difference between the optical lengths of the measurement and reference paths. Algorithms for calculating the Fourier transform (such as the FFT algorithm) are applied to extract measurements of signal intensity peaks related to the difference between the optical paths in real space.

[0050] In contrast to low-coherence interferometry techniques in the time domain, where the length of the reference path is scanned temporally and information comparing the length of the measurement path to the length of the reference path is encoded in the wavelength space in the frequency domain, low-coherence interferometry techniques with detection in the spatial domain combine the aforementioned two techniques and make it possible to directly visualize measurement results in real space, enabling rapid acquisition using economical devices such as image sensors, e.g., linear sensors.

[0051] In a typical embodiment of a low-coherence interferometry system with detection in the frequency domain, the measurement beam and the reference beam overlap collinearly along the same incident direction toward a wavelength-dispersive optical device, such as a diffraction grating, a refractive prism, or a similar optical element for detecting the spectrum, capable of separating the frequency components of the entire beam obtained from the overlap of the measurement beam and the reference beam in the common incident region of the optical interferometry sensor device. In this configuration, the spectra (interference fringe patterns) of the two interfering beams exhibit periodic modulation, and the fringe pattern undergoes periodic changes in the spatial dimension of the wavelength as the spatial variation of the optical measurement path relative to the optical reference path is altered. Its extension in the frequency domain is determined by the coherence length of the low-coherence optical radiation. Therefore, the frequency of the interference fringe pattern between the measurement beam and the reference beam can be detected by processing the signal output from the sensor device to extract a measurement of the difference between the length of the optical measurement path and the length of the optical reference path.

[0052] In a typical embodiment of a low-coherence interferometry system with detection in the spatial domain, the measurement beam and reference beam are overlapped and strike the surface of a sensor device from different directions, and the surface of the sensor device can directly detect the interference fringe pattern resulting from this overlap. In this configuration, the spatial variation of the optical measurement path relative to the optical reference path is directly visualized on the sensor device due to the mutual tilt angle of the two beams. Therefore, the measurement of the difference between the length of the optical measurement path and the length of the optical reference path can be extracted by simply detecting the position of the interference fringe pattern on the sensor device; the extension of the interference fringe pattern in the linear dimension of the sensor device is on the order of the coherence length of the optical radiation of the beam.

[0053] In low-coherence interferometry techniques with detection in the spatial domain, the length of the optical path of each beam obliquely striking the common incident region of a sensor device varies as a linear function of its position along the illumination axis of the sensor device. Therefore, the difference between the optical measurement path and the reference path also varies as a linear function. Corresponding to the condition that the optical lengths of the measurement path and the reference path are equal within the coherence length of the optical radiation, interference fringe patterns appear in specific linear intervals of the image acquired by the sensor device, while in other areas of the sensor device, the beams overlap in an incoherent manner. The corresponding length of the measurement path can be extracted by detecting the position of the envelope of the interference fringe pattern along the linear extension of the sensor device.

[0054] This measurement is limited only by conditions in which the envelope of the interference fringe pattern is established within the illumination area of ​​the sensor device or within the sensitive area of ​​the photodetector device implementing the sensor device. The measurement interval is determined by the tilt of the beam in the incident region, or even better by the incident angle between the beams, and, given equal tilt of the beams, by the minimum value between the number of photodetectors or the number of photodetector areas (also represented as pixels of the sensor device) illuminated by overlapping beams and the total number of photodetectors in the sensor device or the minimum number of areas (pixels) that need to be illuminated to demodulate the interference fringe pattern relative to the total number of areas (pixels) available on the sensor device. Under common conditions, using sensor devices comprising thousands of photodetectors, measurement intervals of a fraction of a millimeter can be obtained before the aliasing effect of the interference fringes appears. However, the inventors have shown that the presence of the aliasing effect of the interference fringe pattern is not limited to measurement but can even be used to increase the interval of measurable distances. In fact, this undersampling is reflected in the efficient demodulation of the fringe pattern at low spatial frequencies, which is similarly achieved directly at the level of the photodetectors of the interferometric sensor device without the need for additional components.

[0055] Advantageously, the use of interferometric techniques with detection in the spatial domain enables accurate distance measurements to be performed using a static system with optical measurement and reference paths, and for each individual acquisition or sampling of the spatial distribution of optical radiation from the overlapping measurement and reference beams striking the sensor device. To achieve this type of system, all that is required is: standard optical components, and a simple computational algorithm for processing the signals emitted by the sensor device that is not starved of computational resources.

[0056] Applying the foregoing considerations to machine tools (such as those used for laser processing of materials, particularly for laser cutting, drilling, or welding, or for manufacturing three-dimensional structures via laser additive manufacturing) is achieved by providing an interferometric measurement system comprising an optical measurement path and an optical reference path arranged along a measurement line or direction, the optical measurement path being at least partially integrated into the machine's working head, and the optical reference path being associated with the optical measurement path, which may also be integrated into or located outside the working head. The optical measurement path is reflected or scattered by the back-reflecting surface of an optical element associated with the optical transmission path of the machine tool's processing optical radiation (e.g., the optical transmission path of a laser beam), or by the surface of an object outside the machine (e.g., the part or material being processed).

[0057] The implementation of an additional optical measurement path or reference path multiplexed with the main optical measurement path or reference path allows for an extension of the measurable distance range or compensation for the main measurement affected by disturbances with additional calibration measurements. In particular, in the case of machines used for laser processing of parts or materials, the implementation of an additional optical measurement path or reference path multiplexed with the main optical measurement path or reference path allows for an extension of the range of measurable separation distances, or compensation for the measurement of the separation distance between the working head and the surface of the part or material, which is affected by disturbances caused by variations in at least one physical parameter of the transmission device in which the optical measurement path runs.

[0058] More generally, the term "optical element associated with an optical transmission path that processes optical radiation" refers to an element of an optical element system arranged along a predetermined measurement line associated with the system. Attached Figure Description

[0059] Further features and advantages of the invention will be explained in more detail in the following detailed description of an embodiment given by way of non-limiting example, with reference to the accompanying drawings, in which:

[0060] Figure 1 An exemplary illustration shows the working head of a machine tool and the corresponding control device near a part being processed according to the prior art;

[0061] Figure 2 An exemplary illustration of the working head of a laser machine according to the prior art is shown;

[0062] Figure 3a The configuration of a low-coherence interferometry system with detection in the frequency domain is schematically shown;

[0063] Figure 3b The interference fringe pattern F is shown on the illumination axis of a sensor device positioned before wavelength dispersion;

[0064] Figure 3c The relationship between the frequency of the interference fringes and the difference in optical length between the measurement path and the reference path is shown.

[0065] Figure 4a The configuration of a low-coherence linear interferometry system with detection in the spatial domain is schematically shown;

[0066] Figure 4b The diagram schematically illustrates the variation of the lengths of the optical measurement path and the reference path relative to the relative incident point on the illumination axis of the sensor device with respect to the interference fringe pattern.

[0067] Figure 4cThe diagram schematically illustrates the variation in the difference between the lengths of the optical measurement path and the reference path relative to the relative incident point on the illumination axis of the sensor device (top figure), and the positioning of the interference fringe pattern on the illumination axis of the sensor device under the condition that the optical lengths of the measurement path and the reference path are equal (bottom figure).

[0068] Figure 5 An exemplary illustration is shown of a system for determining the separation distance between the working head of a machine used for laser processing of a material and the surface of the material;

[0069] Figures 6a to 6e This is a schematic diagram of different possible combinations of the main optical measurement path, the supplementary optical measurement path, the main optical reference path, and the supplementary optical reference path.

[0070] Figures 7a-7d This is a schematic diagram illustrating the application of the present invention;

[0071] Figure 8a It is a diagram showing the positioning of a main signal indicating the location of an interference fringe pattern along the illumination axis of a sensor device as a function of the separation distance between the working head and the material; and a corresponding additional multiplexed signal indicating the positioning of a corresponding additional interference fringe pattern along the illumination axis of the sensor device caused by travel along an additional optical measurement path or reference path having a geometric length different from that of the main optical measurement path or reference path, the corresponding additional multiplexed signal including at least one portion back-reflected at the surface of the inserted optical element along the optical path of the working laser beam;

[0072] Figure 8b An exemplary calibration curve representing the signal peak of the principal interference fringe pattern as a function of the separation distance between the working head and the material; and

[0073] Figure 8c A series of illustrations are shown to represent the measurements performed during the cutting process. Detailed Implementation

[0074] The existing technology has already been described. Figure 1 and Figure 2 And their contents are understood to be those claimed herein, since they are common to the implementation of machine tools controlled to carry out the methods taught according to the present invention.

[0075] Figure 3aThe Michelson configuration of a low-coherence interferometry system for detection in the frequency domain is schematically illustrated. A collimated beam of optical measurement radiation, denoted M, from the objective lens T, and a collimated beam of the same optical reference radiation, denoted R, from the reference reflecting element RM, both originate from source L, strike the diffraction grating G in an overlapping manner, and the spectral distribution of the interfering beams extends from here through a focusing lens to the common incident region C of the sensor device S, thus forming an interference fringe pattern F, as shown below. Figure 3b As shown in the image.

[0076] The sensor device S includes, for example, an arrangement of photodetectors along at least one illumination axis (x-axis in the figure) of the incident region. The arrangement of the photodetectors is linear or two-dimensional, preferably linear. The illumination axis of the incident region is determined by the intersection line of a plane defined by the incident angles of the measurement beam M and the reference beam R with the sensing surface of the sensor device.

[0077] Figure 3c The image shows the processed results of the interference fringe pattern acquired by the photodetector, where the spectrum of the interference beam has been changed from... Figure 3b The signal intensity distribution is extracted, and the frequency of the fringes has been determined by the FFT algorithm, as is known, depending on the phase difference of the interference beam, or the corresponding difference Δp in the optical lengths of the measurement path and the reference path.

[0078] Figure 4a The configuration of a low-coherence interferometric measurement system with linear spatial detection is schematically illustrated. A collimated beam of optical measurement radiation, denoted as M, and a collimated beam of the same optical reference radiation, denoted as R, overlap and strike a common incident region C of a sensor device S at a predetermined incident angle α, where they form an interference fringe pattern F, the extension of which in the common incident region is on the order of the coherence length of the optical radiation. The widths of the collimated beams of the optical radiation and the optical reference radiation are preferably such that they substantially illuminate the entire sensor device. To increase the intensity and contrast of the detected signal, the beams can be focused onto the sensor, for example, by means of a cylindrical focusing lens, in a direction perpendicular to the illumination axis.

[0079] The sensor device S includes, for example, an arrangement of photodetectors along at least one illumination axis (x-axis in the figure) of the incident region. The arrangement of the photodetectors is linear or two-dimensional, preferably linear. The illumination axis of the incident region is determined by the intersection line of the plane defined by the incident angles of the measurement beam M and the reference beam R with the sensing surface of the sensor device.

[0080] exist Figure 4bThe diagram schematically illustrates the variation of the length p of the optical measurement path and reference path, in a typical case of a symmetrical arrangement of two beams incident on a sensor device, referencing the initial incident wavefronts of the corresponding measurement and reference beams on the common incident region of the sensor device S. The horizontal axis represents the position, or x-coordinate, along the illumination axis of the photodetector arrangement. p1 represents the additional length of the first optical path (e.g., the optical measurement path of the optical radiation measurement beam M) relative to the wavefront of the measurement beam M at the first end of the common incident region C, x1 (the origin of the measurement axis). p2 represents the additional length of the second optical path (e.g., the optical reference path of the optical radiation reference beam R) relative to the wavefront of the reference beam R at the second end of the common incident region x2, opposite the first end. Δp represents the difference p1-p2 between the additional lengths of the two paths, which is zero at the midpoint of the photodetector arrangement, and the value Δp from the end x1 of the common incident region. x1 The value Δp changes to the value at x2 of the common incident region. x2 .

[0081] exist Figure 4c In the middle, the above figure shows the corresponding Figure 4b The figure below shows the curve Δp, and the figure below also shows the position of the interference fringe pattern F on the illumination axis (x) of the sensor device S, obtained under the condition that the optical lengths of the measurement path and the reference path are equal. The envelope of the interference fringe pattern F is shown by the dashed line, and in the figure above, the peak coordinates of the envelope are x. p The corresponding difference Δp between the additional lengths of the paths of the optical measurement beam and the reference beam. p Related.

[0082] The following notes apply to determining the relative positions of optical elements using interferometry techniques that are detected in the spatial domain.

[0083] By P M and P R The measurement path and reference path are indicated, and their total length can be expressed as P. M =P1+p1 and P R = P2 + p2, where P1 is the optical length of the optical measurement path from the low-coherence optical radiation source to the first wavefront impacting the sensor device, and P2 is the optical reference path from the same low-coherence optical radiation source to the first wavefront impacting the sensor device, preferably constant. P1 can be considered to include P... nom +d, where P nomP1 is the nominal length of the optical path, comprising a first segment between the low-coherence optical radiation source and the predetermined back-reflecting surface of the optical element, and a second segment between the back-reflecting surface and the sensor device S. The position of the optical element is determined according to its predetermined nominal position, and each segment has a corresponding predetermined and invariant geometric length. d represents the positional offset of the optical element relative to its nominal position. P2 is the optical length of the optical reference path, which is equal to the optical length P of the optical measurement path under nominal operating conditions where the optical element is located in its predetermined nominal position. nom .

[0084] The optical length difference between the optical measurement path and the optical reference path is mathematically expressed as:

[0085] P M -P R

[0086] Interference fringes appear when the value is zero, or:

[0087] P M -P R =0

[0088] This relationship can be decomposed into:

[0089] P1 + p1 - (P2 + p2) = 0

[0090] It can also be written as:

[0091] P nom +d+p1-P2-p2=0

[0092] Therefore, we can conclude that:

[0093] P nom +d-P2+Δp=0

[0094] P nom +dP nom +Δp=0

[0095] Δp=-d

[0096] That is, the current position of the optical element is equal to the difference between the additional length of the optical measurement path and the optical reference path.

[0097] Therefore, the current local position of an optical element relative to its nominal local position, determined by the difference in optical length between the optical measurement path and the optical reference path, can be expressed as the difference between the additional lengths of the optical measurement path and the optical reference path, and thus can be expressed as the displacement of the interference fringe pattern along the illumination axis x of the sensor device S relative to the nominal position (e.g., the mid-plane of the sensor device S itself).

[0098] The following notes apply to determining the separation distance between a processing tool or measuring instrument and the surface of an external object using interferometry techniques that are detected in the spatial domain.

[0099] By P M and P R The measurement path and reference path are indicated, and their total length can be expressed as P. M =P1+p1 and P R = P2 + p2, where P1 is the optical length of the optical measurement path from the low-coherence optical radiation source to the first wavefront impacting the sensor device, and P2 is the optical reference path from the same low-coherence optical radiation source to the first wavefront impacting the sensor device, preferably constant. P1 can be considered to include P... head +D standoff , where P head It is the length of the optical path upstream and within the working head, including a first segment contained between the low-coherence optical radiation source and the end of the processing tool or measuring instrument carried by the working head, adjacent to the part or material WP being processed (e.g., the output of a laser beam), and a second segment contained between the proximal end of the processing tool or measuring instrument (e.g., the output of a laser beam) and the sensor device S, these segments having corresponding predetermined and constant geometric lengths, and D standoff P2 is the free air separation distance between the end of the processing tool or measuring instrument near the part or material being processed (WP) and the surface of the material. P2 is the optical length of the optical reference path; under nominal operating conditions, P2 is equal to the optical length of the optical measurement path, hereinafter referred to as P1. nom The distance between the end of the processing tool or measuring instrument (such as the output of a laser beam) and the surface of the part or material WP corresponds to a predetermined nominal separation distance D. standoff_nom .

[0100] The optical length difference between the optical measurement path and the optical reference path is mathematically expressed as:

[0101] P M -P R

[0102] Interference fringes appear when the value is zero, or:

[0103] P M -P R =0

[0104] This relationship can be decomposed into:

[0105] P1 + p1 - (P2 + p2) = 0

[0106] It can also be written as:

[0107] P head +D standoff +p1-P2-p2=0

[0108] Therefore, we can conclude that:

[0109] P head +D standoff -P² + Δp = 0

[0110] P head +D standoff -P1 nom +Δp=0

[0111] P head +D standoff -P head -D standoff_nom +Δp=0

[0112] Δp=D standoff_nom -D standoff

[0113] That is, (a) the current separation distance D between the end of the processing tool or measuring instrument and the surface of the material in the processing area. standoff (b) Nominal separation distance D standoff_nom The difference between them is equal to the difference between the additional lengths of the optical measurement path and the optical reference path.

[0114] Therefore, the difference between the current separation distance between the end of the processing tool or measuring instrument and the surface of the part or material WP and the nominal separation distance determined by the optical length difference between the optical measurement path and the optical reference path can be expressed as the difference between the additional lengths of the optical measurement path and the optical reference path, and thus can be expressed as the displacement of the interference fringe pattern along the illumination axis x of the sensor device S relative to the nominal position (e.g., the mid-plane of the sensor device S itself), or the displacement of the frequency of the interference fringe pattern relative to the predetermined nominal position in the domain of the Fourier transform of the spectrum displaying the interference fringes.

[0115] It should be noted that in laser cutting or drilling applications involving an auxiliary gas flow, the end of the working head adjacent to the part or material being processed is typically the terminal portion of the auxiliary gas nozzle, while in welding or additive manufacturing applications where no gas is supplied, the end of the working head adjacent to the material being processed is typically the output of the working laser beam.

[0116] In the application of this invention, the length of the optical reference path is established such that it corresponds to the length of the optical measurement path at a predetermined nominal separation distance between the processing tool or measuring instrument and the surface of the part or material in the processing area; and the difference between (a) the current separation distance between the processing tool or measuring instrument and the surface of the material in the processing area and (b) the predetermined nominal separation distance is generated by the length difference between the optical measurement path and the optical reference path, which can be expressed as a function of the position of the interference fringe pattern along the illumination axis of the incident region of the sensor device S. Advantageously, the intermediate position of the interference fringe pattern along the illumination axis corresponds to the predetermined nominal separation distance. Alternatively, the extreme position of the interference fringe pattern along the illumination axis can correspond to the zero nominal separation distance between the nozzle and the material being processed, equivalent to the contact between the nozzle constituting the proximal end of the head and the material, and the separation distance between the nozzle and the material can only be increased such that the interference fringe pattern moves only toward the opposite end of the illumination axis. Similarly, by using an interferometric technique having the ability to detect the interference fringe pattern in the frequency domain, the predetermined nominal separation distance corresponds to the intermediate or extreme position of the peak of the interferometric signal in the space of the Fourier transform of the spectrum presenting the interference fringes.

[0117] See Figure 4c The image below shows the position x of the interference fringe pattern along the illumination axis. p It is the inherent position of the envelope of the optical radiation intensity of the interference fringe pattern, and this inherent position of the envelope of the optical radiation intensity of the interference fringe pattern is, for example, the position of the peak value or the position of the maximum intensity of the envelope of optical radiation, or the average of the positions of the photodetectors weighted by the optical intensity of the fringe envelope.

[0118] The detection of the fringe envelope can be accomplished using demodulation techniques of the optical intensity distribution, for example, by using a passband spatial filter, or sequential high-pass and low-pass filters, to reveal only the signal components corresponding to the spatial frequencies of the interference fringes. For example, in the first stage of data processing of the optical intensity, the optical intensity detected by the sensor array is integrated along a direction perpendicular to the development direction of the interference fringes, for example, by integrating the columns of the sensor array, which are oriented to receive vertically aligned interference fringe patterns (this operation is unnecessary if the sensor arrangement is a linear arrangement of photodetectors (the beam is focused onto the photodetector by means of a cylindrical lens)). The signal generated by the photodetector is then normalized relative to a background signal (e.g., a background signal extracted from an image lacking interference fringes). Then, for example, a high-pass spatial filter is applied at 1 / 5 of the spatial frequency of the photodetector to remove the baseline and preserve the interference fringe pattern. Since a signal oscillating around zero is obtained in this way, the absolute value is extracted from this signal, and then a low-pass spatial filter is applied, for example, at 1 / 25 of the spatial frequency of the photodetector, to extract the envelope of the interference fringe pattern. The location of the interference fringe pattern can be obtained by detecting the position of the envelope of the fringe pattern and finding the maximum value, or by comparing the envelope with a predetermined model function (e.g., a Gaussian function) and extracting the peak value from the model function.

[0119] Figure 5 A diagram is shown of a system according to a presently preferred embodiment for determining the separation distance between the working head 10 of a machine for laser processing of a part or material WP and the surface of the part or material itself.

[0120] In the figure, 100 represents a low-coherence optical radiation source, preferably a linearly polarized light source, such as an LED or light-emitting diode, for example, an LED or light-emitting diode operating in the wavelength range of visible or near-infrared light. Optical radiation emitted by source 100 downstream of a suitable optical isolator 120 is injected into an optical waveguide (e.g., fiber 140) and carried to a beamsplitter 160, which is capable of generating light in the optical measurement path P. M The optical measurement radiation beam M and the optical reference path P of the upper route. R The optical reference radiation beam R of the upper route.

[0121] Optical measurement path P M and optical reference path P R These are guiding paths, and they include optical guides (e.g., optical fibers) capable of maintaining the constant polarization of the beam along the entire path.

[0122] As described above, optical measurement path P MThe part or material is brought to the machine's working head 10 for laser processing, and the optical measurement path P M The measuring beam M travels from the working head 10 toward the impacting part or material being processed. The output cross-section of the measuring beam M corresponds to the cross-section of the measuring head used to measure the distance from the material, such as the orifice of a nozzle used to distribute auxiliary gas flow or the output of a laser beam.

[0123] On the other hand, optical reference path P R The light is brought to the back-reflecting element 180, preferably through the insertion of the optical density filter 200, the dispersion-compensating optical element 220, the λ / 4 plate 240, and the focusing lens 260. The optical reflecting element 180 is arranged along an optical reference path such that the optical length of this path from the beam splitter 160 to the reflecting optical element 180 corresponds to the optical length of the optical measurement path from the beam splitter 160 to the (reflective) surface of the part or material WP being processed under operating conditions, wherein said surface is located at a predetermined nominal separation distance D from the working head. standoff_nom The predetermined nominal separation distance D from the end of a nearby part or material (such as the orifice of an auxiliary gas nozzle or the beam output) of the working head. standoff_nom Place.

[0124] Optical measurement path and reference path P M P R The optical radiation travels along these paths in two directions, returning to the beam splitter 160 after reflection at the surface of the part or material WP being processed and at the reflecting optical element 180, respectively. In the optical reference path P... R In the process, the linear polarization of the reference beam R, determined by the dual channels of the λ / 4 plate 240, is rotated by 90°, thus presenting a linear polarization orthogonal to the linear polarization of the measurement beam M. The beam splitter 160 therefore recombines the optical measurement beam and the optical reference beam, and routes the overlapping optical measurement beam and optical reference beam along the optical detection path P (shared by the segments of the optical measurement path and the optical reference path). D Route towards sensor device S.

[0125] Both the optical measurement beam and the reference beam are obtained through a cylindrical focusing lens 280, which focuses and collimates the beam along a single direction (specifically, a direction orthogonal to the illumination axis of the sensor device) for the purpose of concentrating the signal along this axis, thus optimizing the illumination of the photodetector. The optical measurement beam and the reference beam then reach a polarization beam splitter 300, which separates the optical measurement beam M and the optical reference beam R based on their polarizations. A first portion of the beam is routed toward a first reflecting element M1, and a second portion is routed toward a second reflecting element M2, in the latter case, through an inserted λ / 2 plate 320 capable of restoring the original polarization. Due to this configuration, the first reflecting element M1 and the second reflecting element M2 guide the optical measurement beam and the optical reference beam toward the sensor device S at an incident angle α, respectively, more precisely toward the common incident area of ​​the sensor device. In one embodiment of the system, the incident angle α can be advantageously controlled within a predetermined range, wherein the reflecting elements M1 and M2 can be translated along the propagation axis of the respective beam and rotated about an axis perpendicular to the incident plane (the position indicated by the dashed line in the figure).

[0126] Of course, in one embodiment based on interferometry techniques that detect interference fringe patterns in the frequency domain, the optical detection path P D It does not involve a further separation of the measurement beam and the reference beam, but rather includes, according to Figure 4a The spectrometer with the architecture described in the document.

[0127] As described above, the sensor device S includes a plurality of photodetector devices, each of which is capable of emitting a corresponding signal representing the intensity of the optical impact thereon, and the aggregate of these signals is transmitted to a processing device 350 adapted to identify an interference fringe pattern F, which is established in the common incident region C of the sensor device by acquiring the total incident light power of the overlapping optical measurement beam and the optical reference beam.

[0128] Preferably, the optical measurement path and the optical reference path include corresponding optical elements, and specifically, the optical reference path includes a back-reflecting element whose optical scattering and reflection characteristics correspond as much as possible to the optical scattering and reflection characteristics of the surface of the part or material inserted in the optical measurement path. Optionally, an optical attenuator device may be provided, which is capable of balancing the intensity of the optical reference radiation reflected by the back-reflecting element relative to the intensity of the optical measurement radiation reflected by the part or material being processed.

[0129] Falling within the scope of this invention Figure 5 The system can be summarized at least as follows.

[0130] A system for determining the relative positions of elements of an optical system for processing or measuring an object along a predetermined measurement line associated with the system, the system comprising:

[0131] - A device for generating a beam of light for low-coherence optical measurement radiation;

[0132] - A device for propagating a measurement beam, capable of directing the measurement beam along a measurement line toward the element, and capable of directing a measurement beam reflected or scattered by the back-reflecting surface of the element toward an interferometric optical sensor device, the measurement beam striking the back-reflecting surface in a manner that is at least partially back-reflected, wherein the measurement beam travels from a corresponding source to the sensor device along an optical measurement path, the optical measurement path comprising: a first segment contained between the source and the back-reflecting surface of the element, and a second segment contained between the back-reflecting surface of the element and the sensor device, the first segment and the second segment having corresponding predetermined nominal geometric lengths when the element is located in a predetermined nominal position corresponding to predetermined operating conditions of the system;

[0133] - A means for generating the corresponding beam of the low-coherence optical reference radiation;

[0134] - A means for propagating a reference beam, the means being capable of orienting the reference beam toward a sensor device, wherein the reference beam comprises a main reference beam generated by traveling along a main optical reference path or optical path, and at least one additional multiplexed reference beam; the optical length of the main optical reference path is equal to the optical length of the optical measurement path under nominal operating conditions where the position of the element is a predetermined nominal position; the at least one additional multiplexed reference beam is generated by traveling along an additional optical reference path, the additional optical reference path having a geometric length different from that of the main optical reference path under operating conditions where the position of the element is a predetermined modified position;

[0135] The means for propagating the measurement beam and the means for propagating the reference beam are adapted to make the measurement beam and the reference beam overlap along a predetermined illumination axis at least in the common incident area of ​​the sensor device.

[0136] - A detector device arranged along the illumination axis in a common incident region, capable of detecting the position of the main interference fringe pattern between the measurement beam and the main reference beam, and the position of the additional interference fringe pattern between the measurement beam and the additional reference beam, wherein the extension of the interference fringe pattern along the illumination axis corresponds to the coherence length of the low-coherence optical radiation, and the additional interference fringe pattern has (i) a peak or maximum intensity of the envelope of optical radiation that is different from the peak or maximum intensity of the envelope of optical radiation of the main interference fringe pattern, or (ii) an inherent position of the envelope of the intensity of optical radiation of the main interference fringe pattern, or (iii) a spatial frequency that is different from the spatial frequency of the main interference fringe pattern.

[0137] Alternatively,

[0138] - A detector arrangement in the common incident region, capable of detecting the frequency of the fringe pattern in the wavelength spectrum and the frequency of the additional interference fringe pattern between the measurement beam and the additional reference beam, the fringe pattern being obtained from the principal interference between the measurement beam and the principal reference beam by the wavelength dispersion of the beams, the extension of the fringe pattern in the frequency domain being determined by the coherence length of the low-coherence optical radiation, and the additional interference fringe pattern (i) having a frequency different from the frequency of the principal interference fringe pattern, or (ii) being determined by the overlap of the measurement beam and the additional reference beam in a region of the common region different from the overlap region of the measurement beam and the principal reference beam; and

[0139] - A processing apparatus adapted to determine, respectively, an optical length difference between an optical measurement path and an optical reference path or an additional optical reference path based on the position of the interference fringe pattern or an additional interference fringe pattern along the illumination axis of the incident region, or the frequency of the interference fringe pattern or the additional interference fringe pattern in the frequency domain, the optical length difference indicating (a) the difference between the current position of the element and (b) a predetermined nominal position or a predetermined modified nominal position of the element along the axis of the measurement beam.

[0140] Alternatively or in combination, a system for determining the relative positions of elements of an optical system for processing or measuring an object along a predetermined measurement line associated with the system, the system comprising:

[0141] - A device for generating a beam of light for low-coherence optical measurement radiation;

[0142] - A device for propagating a measurement beam, capable of directing the measurement beam along a measurement line toward the element, and capable of directing a measurement beam reflected or scattered by a back-reflecting surface of the element toward an interferometric optical sensor device, the measurement beam striking the back-reflecting surface in a manner at least partially back-reflected, wherein the measurement beam travels from a corresponding source to the sensor device along an optical measurement path comprising: a first segment contained between the source and the back-reflecting surface of the element, and a second segment contained between the back-reflecting surface of the element and the sensor device, the first segment and the second segment having corresponding predetermined nominal geometric lengths when the element is located in a predetermined nominal position corresponding to a predetermined operating state of the system, and the measurement beam comprising a main measurement beam and an additional multiplexed measurement beam; the main measurement beam is generated by travel along the main optical measurement path, wherein the main optical measurement path travels along the measurement line through each optical element inserted upstream of the element; the additional multiplexed measurement beam is generated by travel along an additional optical measurement path having a geometric length different from that of the main optical measurement path;

[0143] - A means for generating the corresponding beam of the low-coherence optical reference radiation;

[0144] - A device for propagating a reference beam, which is capable of directing the reference beam toward a sensor device, wherein the reference beam travels along an optical reference path, and under nominal operating conditions where the position of the element is a predetermined nominal position, the optical length of the optical reference path is equal to the optical length of the main optical measurement path.

[0145] The means for propagating the measurement beam and the means for propagating the reference beam are both adapted to make the measurement beam and the reference beam overlap along a predetermined illumination axis, at least in a common incident region of the sensor device;

[0146] - A detector device arranged along the illumination axis in a common incident region, capable of detecting the position of the main interference fringe pattern between the main measurement beam and the reference beam, and the position of the additional interference fringe pattern between the additional measurement beam and the reference beam, wherein the extension of the interference fringe pattern along the illumination axis corresponds to the coherence length of the low-coherence optical radiation, and the additional interference fringe pattern has (i) a peak or maximum intensity of the envelope of optical radiation that is different from the peak or maximum intensity of the envelope of optical radiation of the main interference fringe pattern, or (ii) an inherent position of the envelope of intensity of optical radiation that is different from the inherent position of the envelope of intensity of optical radiation of the main interference fringe pattern, or (iii) a spatial frequency that is different from the spatial frequency of the main interference fringe pattern;

[0147] Alternatively,

[0148] - A detector arrangement in the common incident region, capable of detecting the frequency of the fringe pattern in the wavelength spectrum and the frequency of the additional interference fringe pattern between the additional measurement beam and the reference beam, the fringe pattern being obtained from the principal interference between the principal measurement beam and the reference beam by the wavelength dispersion of the beams, the extension of the fringe pattern in the frequency domain being determined by the coherence length of the low-coherence optical radiation, and the additional interference fringe pattern (i) having a frequency different from the frequency of the principal interference fringe pattern, or (ii) being determined by the overlap of the additional measurement beam and the reference beam in a region of the common region that is different from the overlap region of the principal measurement beam and the reference beam; and

[0149] - A processing apparatus adapted to determine, based on the position of the interference fringe pattern or the additional interference fringe pattern along the illumination line axis of the incident region, or the frequency of the interference fringe pattern or the additional interference fringe pattern in the frequency domain, the optical length difference between the optical measurement path or the additional optical measurement path and the optical reference path, the optical length difference indicating the difference between (a) the current position of the element and (b) a predetermined nominal position of the element along the axis of the measurement beam.

[0150] A system for determining a separation distance between a processing tool or measuring instrument and at least a partial reflective surface of an external object along predetermined measuring lines associated with at least one proximal portion of the surface of the tool or instrument relative to an object, the system comprising:

[0151] - A device for generating a beam of light for low-coherence optical measurement radiation;

[0152] - A device for propagating a measurement beam, capable of directing the measurement beam toward the surface of an object through a proximal portion of a tool or instrument, and capable of directing a measurement beam reflected or scattered by the surface of the object through the proximal portion of the tool or instrument toward an interferometric optical sensor device, wherein the measurement beam travels along an optical measurement path from a corresponding source to the sensor device, the optical measurement path comprising a first segment between the source and the proximal portion of the tool or instrument and a second segment between the proximal portion of the tool or instrument and the sensor device, the first segment and the second segment having corresponding predetermined and constant geometric lengths;

[0153] - A means for generating the corresponding beam of the low-coherence optical reference radiation;

[0154] - A device for propagating a reference beam, the device being capable of orienting the reference beam toward a sensor device, wherein the reference beam includes a main reference beam and at least one additional multiplexed reference beam, the main reference beam being generated by travel along a main optical reference path, the optical length of the main optical reference path being equal to the optical length of the optical measurement path under nominal operating conditions where the distance between the proximal portion of the tool or instrument and the surface of the object corresponds to a predetermined nominal separation distance; the at least one additional multiplexed reference beam being generated by travel along an additional optical reference path, the additional optical reference path having a geometric length different from that of the main optical reference path under operating conditions where the distance between the proximal portion of the tool or instrument and the surface of the object corresponds to a predetermined modified separation distance;

[0155] The means for propagating the measurement beam and the means for propagating the reference beam are adapted to make the measurement beam and the reference beam overlap along a predetermined illumination axis, at least in a common incident region of the sensor device;

[0156] - A detector device arranged along the illumination axis in a common incident region, capable of detecting the position of the main interference fringe pattern between the measurement beam and the main reference beam, and the position of the additional interference fringe pattern between the measurement beam and the additional reference beam, wherein the extension of the interference fringe pattern along the illumination axis corresponds to the coherence length of the low-coherence optical radiation, and the additional interference fringe pattern has (i) a peak or maximum intensity of the envelope of optical radiation different from that of the main interference fringe pattern, or (ii) an inherent position of the envelope of optical radiation intensity different from that of the main interference fringe pattern, or (iii) a spatial frequency different from that of the main interference fringe pattern.

[0157] Or alternative

[0158] - A detector arrangement in the common incident region, capable of detecting the frequency of the fringe pattern in the wavelength spectrum and the frequency of the additional interference fringe pattern between the measurement beam and the additional reference beam, the fringe pattern being obtained from the principal interference between the measurement beam and the principal reference beam through the wavelength dispersion of the beams, the extension of the fringe pattern in the frequency domain being determined by the coherence length of the low-coherence optical radiation, and the additional interference fringe pattern (i) having a frequency different from the frequency of the principal interference fringe pattern, or (ii) being determined by the overlap of the measurement beam and the additional reference beam in a region of the common region different from the overlap region of the measurement beam and the principal reference beam; and

[0159] - A processing device adapted to determine, based on the position of the interference fringe pattern or the additional interference fringe pattern along the illumination axis of the incident region, or the frequency of the interference fringe pattern or the additional interference fringe pattern in the frequency domain, the optical length difference between the optical measurement path and the optical reference path or the additional optical reference path, respectively indicating (a) the difference between the current separation distance between the proximal portion of the tool or instrument and the surface of the object and (b) a predetermined nominal separation distance or a predetermined modification interval distance.

[0160] Alternatively or in combination, a system for determining a separation distance between a processing tool or measuring instrument and at least a partial reflective surface of an external object along predetermined measuring lines respectively associated with at least one proximal portion of the surface of the tool or instrument relative to an object, the system comprising:

[0161] - A device for generating a beam of light for low-coherence optical measurement radiation;

[0162] - A device for propagating a measurement beam, capable of directing the measurement beam toward the surface of an object through a proximal portion of a tool or instrument, and capable of directing a measurement beam reflected or scattered by the surface of the object through the proximal portion of the tool or instrument toward an interferometric optical sensor device, wherein the measurement beam travels along an optical measurement path from a corresponding source to the sensor device, the optical measurement path comprising: a first segment contained between the source and the proximal portion of the tool or instrument, and a second segment contained between the proximal portion of the tool or instrument and the sensor device, the first segment and the second segment having corresponding predetermined and constant geometric lengths; the measurement beam comprising a main measurement beam and an additional multiplexed measurement beam, the main measurement beam being generated by travel along the main optical measurement path, wherein the main optical measurement path travels along the measurement line through each optical element inserted upstream of the tool or instrument; the additional multiplexed measurement beam being generated by travel along an additional optical measurement path having a geometric length different from that of the main optical measurement path;

[0163] - A means for generating the corresponding beam of the low-coherence optical reference radiation;

[0164] - A device for propagating a reference beam, which is capable of directing the reference beam toward a sensor device, wherein the reference beam travels on an optical reference path, and in nominal operating conditions where the distance between the proximal portion of the tool or instrument and the surface of the object corresponds to a predetermined nominal separation distance, the optical length of the optical reference path is equal to the optical length of the main optical measurement path.

[0165] The means for propagating the measurement beam and the means for propagating the reference beam are adapted to make the measurement beam and the reference beam overlap along a predetermined illumination axis, at least in a common incident region of the sensor device;

[0166] - A detector device arranged along the illumination axis in a common incident region, capable of detecting the position of the main interference fringe pattern between the main measurement beam and the reference beam, and the position of the additional interference fringe pattern between the additional measurement beam and the reference beam, wherein the extension of the interference fringe pattern along the illumination axis corresponds to the coherence length of the low-coherence optical radiation, and the additional interference fringe pattern has (i) a peak or maximum intensity of the envelope of optical radiation different from that of the main interference fringe pattern, or (ii) an inherent position of the envelope of optical radiation intensity different from that of the main interference fringe pattern, or (iii) a spatial frequency different from that of the main interference fringe pattern.

[0167] Or alternative

[0168] - A detector apparatus arranged in a common incident region, capable of detecting the frequency of the fringe pattern in the wavelength spectrum and the frequency of the additional interference fringe pattern between the additional measurement beam and the reference beam, the fringe pattern being obtained from the principal interference between the principal measurement beam and the reference beam by the wavelength dispersion of the beams, the extension of the fringe pattern in the frequency domain being determined by the coherence length of the low-coherence optical radiation, and the additional interference fringe pattern (i) having a frequency different from the frequency of the principal interference fringe pattern, or (ii) being determined by the overlap of the additional measurement beam and the reference beam in a region of the common region that is different from the overlap region of the principal measurement beam and the reference beam; and

[0169] - A processing device adapted to determine, based on the position of the interference fringe pattern or the additional interference fringe pattern along the illumination axis of the incident region, or the frequency of the interference fringe pattern or the additional interference fringe pattern in the frequency domain, the optical length difference between the optical measurement path or the additional optical measurement path and the optical reference path, the optical length difference indicating the difference between (a) the current separation distance between the proximal portion of the tool or instrument and the surface of the object and (b) a predetermined nominal separation distance.

[0170] With the help of Figure 5 The system or equivalent system implements a method for determining the relative position of at least one optical element, and implements a method for determining the separation distance between a processing tool or measuring instrument and the surface of a part or material WP at a processing area defined by a predetermined working trajectory T followed by a laser processing beam emitted from the head.

[0171] This method involves generating a beam M of low-coherence principal optical measurement radiation associated with at least a proximal portion of a processing tool or measuring instrument of a system, optical element, or external object. If the spatial orientation of the beam changes along its path, the beam M travels along a measurement direction (or more generally, a measurement line). The beam (e.g., within the working head 10 of a machine tool) is directed toward an element of the system or toward a surface of an object outside the tool or instrument, and the beam is reflected or scattered by a back-reflecting surface of the element or by a surface of the external object. The beam strikes the back-reflecting surface of the element or the surface of the external object in a manner that is at least partially back-reflected. Optionally, the beam passes through a proximal portion of the processing tool or measuring instrument toward a sensor device S.

[0172] The main beam M for optical measurement radiation specifically travels from source 100 to sensor device S along an optical measurement path, which includes two segments with corresponding predetermined and unchanging nominal geometric lengths. When the relative positions of the elements of the optical system are determined, these two segments have corresponding predetermined and unchanging nominal geometric lengths when the element is located in a predetermined nominal position corresponding to predetermined operating conditions of the system.

[0173] When determining the relative positions of the optical system components within the working head, the two sections respectively include: a first section included between the source and the back-reflecting surface of the component, and a second section included between the back-reflecting surface of the component and the sensor device S.

[0174] In determining the separation distance between the processing tool or measuring instrument and the surface of an external object, the two sections respectively include a first section and a second section, the first section being included between the source 100 and the portion of the processing tool or measuring instrument near the part or material WP, and the second section being included between the portion near the part or material WP and the sensor device S.

[0175] The low-coherence optical radiation master reference beam R is generated from the same source 100 and is also directed toward the sensor device S. The master reference beam R is along the reference optical path P. R Ascending, referencing optical path P R The optical length is equal to the optical measurement path P under nominal operating conditions. M The optical length, under the nominal operating conditions, is the position of the optical system element at a predetermined nominal position or the distance between the proximal portion of the processing tool or measuring instrument and the surface of the part or material WP corresponding to a predetermined nominal separation distance.

[0176] The measuring beam M and the reference beam R overlap in the common incident area C of the sensor device S along a predetermined illumination axis.

[0177] Using an interferometric technique that detects interference fringe patterns in the spatial domain, the position of the interference fringe pattern F between the measurement beam M and the reference beam R along the illumination axis in the common incident region C is detected by the processing device 350, and as described above, this makes it possible to determine the optical measurement path P. M With optical reference path P R The optical length difference between (a) the current position of the optical element and (b) the predetermined nominal position, or the difference between the current separation distance between the proximal portion of the processing tool or measuring instrument and the surface of the object and (b) the predetermined nominal separation distance.

[0178] Using an interferometric technique that detects interference fringe patterns in the frequency domain, the frequency of the interference fringe pattern F between the measurement beam M and the reference beam R (which is obtained by wavelength dispersion of those beams along the illumination axis in the common incident region C) is detected by the processing device 350, and as described above, this makes it possible to determine the optical measurement path P. M With optical reference path P R The optical length difference between (a) the current position of the element and (b) a predetermined nominal position, or the difference between (a) the current separation distance between the proximal portion of the processing tool or measuring instrument and the surface of the object and (b) a predetermined nominal separation distance.

[0179] To increase the interval between the difference between the length of the measurement path and the reference path, which can be measured by the techniques described in this invention, or to obtain supplementary measurements of a reference stable and undisturbed optical element in parallel (which supplementary measurements can be used to compensate for the main measurement), according to the invention, under operating conditions where the position of the element in the optical system is a predetermined modified position, or under operating conditions where the distance between the proximal portion of the processing tool or the measuring instrument and the surface of the object corresponds to a predetermined modified separation distance, at least one additional optical measurement path having a geometric length different from the geometric length of the main optical measurement path and / or at least one optical reference path having a predetermined geometric length different from the geometric length of the main optical reference path are utilized.

[0180] In one embodiment, such as Figure 6a As shown, the additional optical measurement path P' M Included in optical element OE M At least one portion of the surface of the optical element OE reflects backwards. MInserted upstream of the element C being measured (an element of the optical system inside the working head or the surface of the object being processed or measured) along the measurement line; for example, along the optical path of the processing laser beam or optical radiation measurement beam relative to the main optical measurement path P. M The optical path is inserted into the optical element, with transmission through each optical element (not shown), which is inserted upstream of the element C being measured.

[0181] In alternative embodiments, such as Figure 6b As shown, the additional optical measurement path P' M Including along the main measurement beam P M Optical element OE inserted along the optical path M At least one back reflection inside.

[0182] In alternative implementations, such as Figure 6c As shown, the additional optical measurement path P' M Including relative to the main optical measurement path P M A deflection of a path segment, for example, by inserting a line from the main optical measurement path P. M Optical element BS1 for partially extracting the measurement beam M and optical element P for reintroducing the extracted measurement beam M into the main optical measurement path. M The additional beam is obtained by using optical element BS2, and the optical element BS1 used for partially extracting the beam is, for example, a beam-splitting optical device or prism capable of continuously controlling the optical length of the deflection path segment. Extraction of the additional beam can be achieved by splitting the main beam into several parts, subdividing the intensity into several beams, or by utilizing different optical properties (e.g., by separating components with different polarizations). Alternatively, beam splitting can occur in front of the sensor device without further recombination.

[0183] Main optical measurement path P M and additional optical measurement path P' M At least one segment overlaps and collinearly impacts the common incident area of ​​the sensor device S, and may impact different corresponding areas of the incident area.

[0184] In one embodiment, such as Figure 6d As shown, the additional optical reference path P' R Included along the master optical reference path P R Inserted optical element OE R At least a portion of the surface reflects backwards. In alternative embodiments, such as... Figure 6e As shown, the additional optical reference path P' R Included along the master optical reference path P R Inserted optical element OER At least one internal back reflection at the location.

[0185] In alternative embodiments, such as Figure 6f As shown, the additional optical reference path P' R Including relative to the master optical reference path P R A path segment of deflection, for example, by inserting a segment from the master optical reference path P. R Optical element BS1 for partially extracting the reference beam R and optical element P for reintroducing the extracted reference beam R into the main optical reference path. R The optical element BS2 is used to obtain the additional beam; the optical element BS1 used for partially extracting the beam is, for example, a beam-splitting optical device or prism capable of continuously controlling the optical length of the deflection path segment. The extraction of the additional beam can be achieved by splitting the main beam into several parts, subdividing the intensity into several beams, or by utilizing different optical properties (e.g., by separating components with different polarizations).

[0186] Main optical reference path P R and additional optical reference path P' R At least one segment overlaps and collinearly impacts the common incident area of ​​the sensor device S, and may impact different corresponding areas of the incident area.

[0187] Those skilled in the art will understand that the above teachings (refer to the optical measurement path and the optical reference path, respectively) can be combined into a possible embodiment.

[0188] Elements of the optical chain (such as in) Figures 6a-6f The combination of the main measuring beam (illustrated in the example) and the additional measuring beam and reference beam reflected from the surface of an object outside it makes parallel readings possible, and therefore the invention can be used in many applications, including Figures 7a-7d The application is illustrated in the diagram.

[0189] Figure 7a This illustrates an application of measuring the separation distance between a laser beam processing tool and the surface of the part WP being processed, performed simultaneously with determining the position of an optical element OE inserted along the propagation direction of the laser beam.

[0190] In this application, an optical element OE inserted along the propagation direction of a laser beam and onto the surface of the part WP being processed constitutes a plurality of elements in a system that at least partially reflects optical radiation. The system includes at least one optical element of a processing or measuring component and an object outside the at least one optical element undergoing the processing or measurement. The plurality of at least partially reflecting elements are arranged along a predetermined common measurement line. The method involves the following steps:

[0191] - Generate a measurement beam with low coherence optical radiation, guide the measurement beam along a measurement line toward multiple elements of the system, guide the measurement beam reflected or scattered by the back-reflecting surface of each element toward the interferometric optical sensor device, the measurement beam strikes the back-reflecting surface of each element in a manner that is at least partially back-reflected, wherein the measurement beam travels from a corresponding source to the interferometric optical sensor device along an optical measurement path; the optical measurement path includes: a first segment contained between the source and the back-reflecting surface of each element, and a second segment contained between the back-reflecting surface of each element and the interferometric sensor device; the first segment and the second segment have corresponding predetermined nominal geometric lengths when each element finds itself in a corresponding predetermined nominal position corresponding to predetermined operating conditions of the system; and the measurement beam includes a first measurement beam and a second multiplexed measurement beam, the first measurement beam being generated by the first optical measurement path as it travels along the measurement line by reflection from the first element, the second multiplexed measurement beam being generated by the second optical measurement path as it travels along the measurement line by reflection from the second element, the second optical measurement path having a larger geometric length that is different from the geometric length of the first optical measurement path; and

[0192] - Generate a corresponding reference beam with low coherence optical radiation and guide the reference beam toward the interferometric measurement optical sensor device, wherein the reference beam includes a first reference beam and a second multiplexed reference beam, the first reference beam being generated by the travel of a first optical reference path, the optical length of which is equal to the optical length of a first optical measurement path under nominal operating conditions, the position of the first element being a corresponding predetermined nominal position; the second multiplexed reference beam being generated by the travel of a second optical reference path, the second optical reference path having a geometric length different from that of the first optical reference path under operating conditions where the position of the second element is a corresponding predetermined nominal position.

[0193] Along a predetermined illumination axis, in at least one common incident region of the interferometric optical sensor device, a first measurement beam and a second measurement beam are respectively superimposed on a first reference beam and a second reference beam.

[0194] Along the illumination axis in the common incident region, the positions of a first interference fringe pattern between a first measuring beam and a first reference beam and a second interference fringe pattern between the second measuring beam and a second reference beam are detected. The second interference fringe pattern has (i) a peak or maximum intensity of an envelope of optical radiation different from the peak or maximum intensity of the envelope of optical radiation of the first interference fringe pattern, or (ii) an inherent position of an envelope of intensity of optical radiation different from the inherent position of the envelope of intensity of optical radiation of the first interference fringe pattern, or (iii) a spatial frequency different from the spatial frequency of the first interference fringe pattern. Alternatively, in the common incident region, the frequency of the first fringe pattern obtained by interference between the first measuring beam and the first reference beam or by wavelength dispersion of the beams is detected in the wavelength spectrum, and the frequency of the second interference fringe pattern between the second measuring beam and the second reference beam is detected, the second interference fringe pattern having (i) a frequency different from the frequency of the first interference fringe pattern, or (ii) determined by the overlap of the second measuring beam and the reference beam in a region of the common region different from the overlap region of the first measuring beam and the reference beam.

[0195] Finally, the optical length difference between the first optical measurement path and the first optical reference path is determined based on either the position of the first interference fringe pattern along the illumination axis of the incident region or the frequency of the first interference fringe pattern in the frequency domain. This optical length difference indicates the difference between (a) the current position of the first element and (b) a predetermined nominal position of the first element along the axis of the measurement beam. Simultaneously, the optical length difference between the second optical measurement path and the second optical reference path is also determined based on either the position of the second interference fringe pattern along the illumination axis of the incident region or the frequency of the second interference fringe pattern in the frequency domain. This optical length difference indicates the difference between (a) the current position of the second element and (b) a predetermined nominal position of the second element along the axis of the measurement beam.

[0196] Figure 7b An application is shown for measuring the separation distance between a laser beam processing tool and the surface of a part WP being processed. This application uses a multiplexed reference beam with intervals corresponding to different operational separation distances to measure this distance over a wide range of or non-intersecting measurement intervals.

[0197] Figure 7c An application for measuring the separation distance between a laser beam processing tool and the surface of a workpiece WP being processed is shown. This application utilizes a calibration beam to provide compensation for the distance measurement, which is derived from disturbances introduced by the effects of pressure, temperature, or mechanical deformation of the transmission device at the nozzle N, acting on the path common to the calibration beam itself (as an example, the disturbance along a segment of the measurement path is denoted as P).

[0198] Figure 7d An application is shown for measuring the separation distance between a laser beam processing tool and the surface of a part WP being processed. This is achieved by compensating for disturbances along the optical measurement path (for example, disturbances along a segment of the measurement path are denoted as P), through the influence of an additional pressure chamber N' positioned along an optical reference path (e.g., connected to the nozzle chamber to present the same pressure) on the auxiliary gas pressure at the nozzle N. Figure 7c As shown in the image.

[0199] This method can be implemented in real time during the processing, for example, to describe the state of the optical elements of the working head or to determine the separation distance between the working head and the current processing area on the material, and the method can also be implemented before or after the processing, for example, to describe the part being processed or the processing that has been performed.

[0200] The following describes a specific application example.

[0201] In a machine used for laser cutting, drilling, or welding materials, or for manufacturing three-dimensional structures via laser additive manufacturing, the machine includes a working head having nozzles for distributing auxiliary gas flows to determine the separation distance between the working head of the machine for laser processing and the surface of the part or material being processed. A measuring beam striking a sensor device S includes a main measuring beam and at least one additional multiplexed measuring beam. The main measuring beam is generated by a main optical measuring path traveling along the optical path of the processing laser beam, with reflections and transmissions from the surface of the part or material in the processing area, through each optical element inserted along the optical path of the processing laser beam. The at least one additional multiplexed measuring beam is generated by an additional optical measuring path traveling with reflections from the surface of the part or material being processed, the additional optical measuring path having a geometric length greater than the geometric length of the main optical measuring path, for example, because it includes at least one portion of the surface of the optical element inserted along the optical path of the processing laser beam that is back-reflected.

[0202] In this embodiment, the method described in this invention is based on the detection of the position of an additional interference fringe pattern in the common incident region C of the sensor device S, the position being determined by the interference between the additional measurement beam and the reference beam. In interferometric techniques that detect interference fringe patterns in the spatial domain, the additional interference fringe pattern exhibits, for example, (i) a peak or maximum intensity of the optical radiation envelope of the main interference fringe pattern between the main measurement beam and the reference beam that is different from (e.g., less than) the peak or maximum intensity of the optical radiation envelope of the main interference fringe pattern; or (ii) when the additional interference fringe pattern and the main interference fringe pattern appear simultaneously, the additional interference fringe pattern exhibits an inherent position of the optical radiation intensity envelope of the main interference fringe pattern that is different from the inherent position of the optical radiation intensity envelope of the main interference fringe pattern; or (iii) when the additional measurement beam strikes the sensor device at an angle different from the incident angle of the main measurement beam, the additional interference fringe pattern exhibits a spatial frequency different from the spatial frequency of the main interference fringe pattern.

[0203] Figure 8a This diagram illustrates the signal output by the photodetector along the illumination axis (vertical axis) of the sensor device S, representing the intensity of the envelope of the interference fringe pattern formed in the common incident region. Specifically, the diagram shows the interferometric measurement signal varying according to the separation distance (horizontal axis) between the working head and the material surface, and thus the spatial position of the interference fringe pattern along the illumination axis (vertical axis). For example, such a diagram can be generated during the calibration phase by providing a fixed-length optical reference path and continuously varying the relative position between the working head and the material surface (i.e., the separation distance between the working head and the material surface) along the Z-axis, and treating the readings of the interferometric measurement signal as a function of discrete predetermined values ​​of the separation distance.

[0204] like Figure 8b As shown in the figure, it can be noted that, under aliasing conditions, the strong interferometric measurement signal and the translational movement of the interference fringe pattern within an interval of approximately 2 mm (corresponding to approximately 1500 pixels) are acquired according to the approximately linear variation of the signal peak indicating the interference fringe pattern. Sensitivity can be defined as the separation distance corresponding to the pixel size of the photodetector or incident region, in this case 1.5 μm / pixel. The translational movement of the envelope of the interference fringe pattern along the entire illumination axis of the sensor device allows determination of the separation distance between the working head and the surface of the material from approximately 0.25 mm to approximately 2 mm.

[0205] The surrounding area shows a corresponding additional multiplexed signal indicating the position of a corresponding additional interference fringe pattern produced by the travel of a corresponding additional optical measurement path along the illumination axis of the sensor device. This additional optical measurement path has a geometric length different from that of the main optical measurement path. The corresponding additional multiplexed signal includes at least a portion of back-reflection at the surface of an optical element inserted along the optical path of the processed laser beam.

[0206] In cases where several different operating intervals are not aligned or overlapped on the sensor device, but are sufficiently separated to alternately display the corresponding interference fringes, the selection of the interference fringe pattern is automatic by realizing the separation distance between the working head and the material, in which only one of the main measuring beam or the supplementary measuring beam enters and interferes with the reference beam, so as to produce an interference fringe pattern on the surface of the sensor device S.

[0207] Under the aforementioned conditions, based on the position of the additional interference fringe pattern along the illumination axis of the incident region, an optical length difference is determined between the additional optical measurement path and the optical reference path, which represents the difference between (i) the current separation distance between the working head and the surface of the material in the processing area and (ii) a predetermined nominal separation distance.

[0208] As from Figure 8a As can be seen, by relying on the signal indicating the main interference fringe pattern read in the first interval and the signal indicating the additional interference fringe pattern read in the second interval, the sensor device S with a smaller extension (such as half the extension used for the measurement in question) of the illumination axis will still allow the detection of the separation distance between the working head and the surface of the material in the same value range of 0.25-2 mm, thereby obtaining a significant increase in the measurement range based on the illumination characteristics of the sensor device.

[0209] Figure 8c A series of illustrations are shown to represent measurements performed during a laser cutting process. In this example, the laser cutting process is the cutting of a 40mm square notch on one side of a 3mm thick flat stainless steel sheet, during which the working head operates at a nominal distance from the sheet that varies between 0.9 and 1mm.

[0210] The figure above illustrates the time progression of a series of processing parameters. Specifically, it is determined by V. x and V y The indicated curve represents the rate of translational movement of the cutting head along the orthogonal x and y directions in the cutting plane, denoted by P. L The indicated curve represents the optical intensity of the processed laser beam, curve P rThe figure represents the auxiliary gas pressure. The middle figure illustrates the process of measuring the actual separation distance between the working head and the part, as measured by low-coherence optical interferometry. The lower figure shows the corresponding interference fringes obtained in the spatial domain using detection techniques. These fringes are visible in the main (lower) image with greater intensity and in the supplementary (upper) signal with less intensity, mimicking the process of the main curve at a constant distance. The supplementary image is generated by internal or multiple back reflections induced by the surface of the optical chain inserted along the measurement path, determining the supplementary measurement beam multiplexed with the main beam.

[0211] In different embodiments, the reference beam striking the sensor device S includes a main reference beam and at least one additional multiplexed reference beam; the main reference beam is generated by the travel of a main optical reference path, and the at least one additional multiplexed reference beam is generated by the travel of an additional optical reference path having a geometric length different from that of the main optical reference path.

[0212] In this embodiment, the method discussed in the present invention is based on the detection of the position of an additional interference fringe pattern in the common incident region of the sensor device S, which is determined by the interference between the measurement beam and the additional reference beam.

[0213] In the same case, the additional interference fringe pattern exhibits, for example, (i) a peak or maximum intensity of the envelope of optical radiation different from (e.g. less than) that of the main interference fringe pattern between the measuring beam and the main reference beam, or (ii) when the additional interference fringe pattern appears simultaneously with the main interference fringe pattern, the additional interference fringe pattern exhibits an inherent position of the envelope of optical radiation intensity different from that of the main interference fringe pattern, or (iii) when the additional reference beam strikes the sensor device at an angle different from the incident angle of the main reference beam, the additional interference fringe pattern exhibits a spatial frequency different from that of the main interference fringe pattern.

[0214] When several different operating intervals are not aligned or overlapped on the sensor device, but are sufficiently separated to alternately display the corresponding interference fringes, the interference fringe pattern is selected by choosing this additional reference path.

[0215] Under the aforementioned conditions, based on the position of the additional interference fringe pattern along the illumination axis of the incident region, an optical length difference is determined between the optical measurement path and the additional optical reference path, which indicates the difference between (i) the current separation distance between the working head and the surface of the material in the processing area and (ii) a predetermined nominal separation distance.

[0216] Advantageously, the technique discussed in this invention makes it possible to determine, for example, the perturbation of the current optical length of at least a portion of the optical measurement path relative to the current optical length of the corresponding portion of the optical reference path, and to calibrate the value determined by the perturbation for the separation distance between the working head and the surface of the material. The perturbation arises, for example, due to a change in at least one physical parameter of the transmission device through which the optical measurement path extends.

[0217] For these purposes, the measurement beam striking the sensor device S includes at least one additional calibration measurement beam generated by the travel of an additional calibration optical measurement path, wherein the measurement beam is reflected or scattered by at least one back-reflecting surface of a static optical element inserted along the optical measurement path, and the reference beam striking the sensor device S includes a corresponding additional calibration reference beam generated by the travel of an additional calibration optical reference path, wherein the optical length of the additional calibration optical reference path is equal to the optical length of the calibration optical measurement path under nominal calibration operating conditions where the geometry and refractive index of the transmission device of the calibration optical measurement path are equal to the geometry and refractive index of the transmission device of the calibration optical reference path within a given tolerance range. The static optical element may be, for example, a component of an optical focusing system for a laser beam.

[0218] Determining the perturbation of at least a portion of the current optical length of the optical measurement path includes the following operations:

[0219] - Along the illumination axis, the calibration measurement beam and the calibration reference beam are overlapped in the common incident area of ​​the sensor device S;

[0220] - Using an interferometric technique with detection in the frequency domain, detect the position of the interference fringe pattern between the calibration measurement beam and the calibration reference beam along the illumination axis in a common incident region, or detect the frequency of the interference fringe pattern between the calibration measurement beam and the calibration reference beam; and - determine the optical length difference between the calibration optical measurement path and the calibration optical reference path based on the position of the interference fringe pattern along the illumination axis of the incident region or the frequency of the interference fringe pattern in the frequency domain, the optical length difference indicating (a) the difference between the geometric length of the calibration optical measurement path and the geometric length of the calibration optical reference path, and / or (b) the difference between the refractive index of the calibration optical measurement path and the refractive index of the calibration optical reference path. The optical length difference between the calibration optical measurement path and the calibration optical reference path indicates the interference of the current optical length of at least a portion of the optical measurement path.

[0221] When the location of the interference fringe pattern is detected, the predetermined reference position of the interference fringe pattern (corresponding to the condition that the optical length of the calibration optical measurement path and the optical length of the reference path are equal) can be used as an indication rather than a limiting example, and is the middle or extreme position along the illumination axis of the photodetector.

[0222] When the frequency of the interference fringe pattern is detected, the predetermined reference position of the interference fringe pattern (corresponding to the condition that the optical length of the calibration optical measurement path and the optical length of the reference path are equal) can be used as an indicative rather than limiting example only, according to known techniques for detection in the spectral or Fourier domain, and is the intermediate frequency in the space of the Fourier transform.

[0223] By carefully and accurately determining the separation distance between the working head and the material surface in the processing zone (whether it is the current processing zone or the calibration processing zone), for example by acting on a motion actuator device for controlling the movement of the working head along the Z-axis, the control unit of the machine used for laser processing can, in response to the calibration or control of the processing distance or other processing parameters, move closer to or further away from the material according to the results of interferometry measurements. This is particularly useful, for example, in improving the efficiency of cutting processes.

[0224] It should be noted that the implementations of this invention presented in the foregoing discussion are purely exemplary and not intended to limit the nature of the invention. Those skilled in the art can readily implement the invention in different embodiments, but these embodiments do not depart from the principles set forth herein and therefore fall within the scope of this patent.

[0225] This is merely a non-limiting example, and is particularly applicable to wavelengths using low-coherence optical radiation that are different from those mentioned, or have the same wavelengths as those mentioned. Figure 5 The possibilities for optical measurement and reference paths for those different inserted optical elements are shown.

[0226] Of course, while maintaining the principles of the invention, the implementation methods and particular forms of implementation can vary widely with respect to what has been described and shown, and are provided as non-limiting examples only, without departing from the scope of protection of the invention as defined by the appended claims.

Claims

1. A method for determining the relative positions of elements of an optical system for processing or measuring an object along a predetermined measurement line associated with the system, characterized in that, The method includes the following steps: A measurement beam with low coherence optical radiation is generated, and the measurement beam is guided along the measurement line toward the element. The measurement beam, reflected or diffused by the back-reflecting surface of the element, is also guided toward an optical interferometric sensor device. The measurement beam strikes the back-reflecting surface in a manner that is at least partially back-reflected. The measurement beam travels from a corresponding source to the optical interferometric sensor device along a measurement optical path, which includes a first portion between the source and the back-reflecting surface of the element, and a second portion between the back-reflecting surface of the element and the interferometric sensor device. The first and second portions have corresponding predetermined nominal geometric lengths when the element is in a predetermined nominal position corresponding to predetermined operating conditions of the system. The process involves generating a corresponding reference beam of low-coherence optical radiation and guiding the reference beam toward the optical interferometric measurement sensor device. The reference beam includes a main reference beam and at least one additional multiplexed reference beam. The main reference beam is generated by the travel of a main reference optical path, which, under nominal operating conditions where the element is at the predetermined nominal position, has an optical length equal to the optical length of the measurement optical path. The at least one additional multiplexed reference beam is generated by the travel of an additional reference optical path, which, under operating conditions where the element is at a predetermined modified position, has a geometric length different from that of the main reference optical path. The measurement beam and the reference beam are superimposed on at least the common incident area of ​​the optical interferometric measurement sensor device along a predetermined illumination axis; The positions of the primary interference fringe pattern between the measurement beam and the primary reference beam, and the positions of the secondary interference fringe patterns between the measurement beam and the secondary reference beam, are detected along the illumination axis in the common incident region. The extension of the interference fringe pattern along the illumination axis corresponds to the coherence length of the low-coherence optical radiation. The secondary interference fringe patterns have (i) a peak or maximum intensity of the optical radiation envelope that differs from the peak or maximum intensity of the optical radiation envelope of the primary interference fringe pattern, or (ii) an inherent position of the intensity envelope of the optical radiation that is offset from the inherent position of the intensity envelope of the optical radiation of the primary interference fringe pattern, or (iii) a spatial frequency that differs from the spatial frequency of the primary interference fringe pattern; or The frequency of the fringe pattern in the wavelength spectrum and the frequency of the additional interference fringe pattern between the measurement beam and the additional reference beam are detected in the common incident region. The fringe pattern is obtained from the principal interference between the measurement beam and the main reference beam by the wavelength dispersion of the beam. The extension of the fringe pattern in the frequency domain is determined by the coherence length of the low-coherence optical radiation. The additional interference fringe pattern (i) has a frequency different from the frequency of the main interference fringe pattern, or (ii) is determined by the overlap of the measurement beam and the additional reference beam in a region of the common incident region that is different from the overlap region of the measurement beam and the main reference beam. The optical length difference between the measurement optical path and the reference optical path or the additional reference optical path is determined based on the position of the interference fringe pattern or the additional interference fringe pattern along the illumination axis of the incident region, or the frequency of the interference fringe pattern or the additional interference fringe pattern in the frequency domain. The optical length difference indicates the difference between (a) the current position of the element and (b) the predetermined nominal position or the predetermined modified position of the element along the axis of the measurement beam.

2. The method according to claim 1, wherein, The primary reference optical path and the secondary reference optical path overlap at least partially and collinearly strike the common incident area of ​​the optical interferometry sensor device.

3. The method according to claim 1, wherein, The primary reference optical path and the secondary reference optical path collide on corresponding different areas of the common incident region of the optical interferometry sensor device.

4. The method according to claim 1, wherein, The optical interferometric measurement sensor device includes an arrangement of photodetectors along the illumination axis, and the arrangement of the photodetectors is a linear arrangement of photodetectors.

5. The method according to claim 1, wherein, The optical interferometric measurement sensor device includes an arrangement of photodetectors along the illumination axis, and the arrangement of the photodetectors is a two-dimensional arrangement of photodetectors.

6. A method for determining a separation distance between a working tool or measuring instrument and at least a portion of a reflective surface of an object outside the working tool or measuring instrument along predetermined measuring lines, the predetermined measuring lines being associated with at least proximal portions of the instrument and the surface of the tool relative to the object, characterized in that, The method includes the following steps: A measurement beam with low coherence optical radiation is generated; the measurement beam is guided toward the surface of the object through the proximal portion of the tool or instrument; and the measurement beam, reflected or diffused from the surface of the object, is guided through the proximal portion of the tool or instrument toward an optical interferometric sensor device, wherein the measurement beam travels along a measurement optical path from a corresponding source to the optical interferometric sensor device, the measurement optical path comprising a first portion between the source and the proximal portion of the tool or instrument and a second portion between the proximal portion of the tool or instrument and the interferometric sensor device, the first portion and the second portion having corresponding predetermined and constant geometric lengths. The process involves generating a corresponding reference beam of low-coherence optical radiation and guiding the reference beam toward the optical interferometric measurement sensor device. The reference beam includes a main reference beam and at least one additional multiplexed reference beam. The main reference beam is generated by the travel of a main reference optical path, and under nominal operating conditions where the distance between the proximal portion of the tool or instrument and the surface of the object corresponds to a predetermined nominal separation distance, the main reference optical path has an optical length equal to the optical length of the measurement optical path. The at least one additional multiplexed reference beam is generated by the travel of an additional reference optical path, and under operating conditions where the distance between the proximal portion of the tool or instrument and the surface of the object corresponds to a predetermined modified separation distance, the additional reference optical path has a geometric length different from the geometric length of the main reference optical path. The measurement beam and the reference beam are superimposed on at least the common incident area of ​​the optical interferometric measurement sensor device along a predetermined illumination axis; The positions of the primary interference fringe pattern between the measurement beam and the primary reference beam, and the positions of the secondary interference fringe pattern between the measurement beam and the secondary reference beam, are detected along the illumination axis in the common incident region. The extension of the interference fringe pattern along the illumination axis corresponds to the coherence length of the low-coherence optical radiation. The secondary interference fringe pattern has (i) a peak or maximum intensity of the optical radiation envelope that differs from the peak or maximum intensity of the optical radiation envelope of the primary interference fringe pattern, or (ii) an inherent position of the intensity envelope of the optical radiation that is offset from the inherent position of the intensity envelope of the optical radiation of the primary interference fringe pattern, or (iii) a spatial frequency that differs from the spatial frequency of the primary interference fringe pattern; or The frequency of the fringe pattern in the wavelength spectrum and the frequency of the additional interference fringe pattern between the measurement beam and the additional reference beam are detected in the common incident region. The fringe pattern is obtained from the principal interference between the measurement beam and the main reference beam by the wavelength dispersion of the beam. The extension of the fringe pattern in the frequency domain is determined by the coherence length of the low-coherence optical radiation. The additional interference fringe pattern (i) has a frequency different from the frequency of the main interference fringe pattern, or (ii) is determined by the overlap of the measurement beam and the additional reference beam in a region of the common incident region that is different from the overlap region of the measurement beam and the main reference beam. The optical length difference between the measuring optical path and the reference optical path or the additional reference optical path is determined based on the position of the interference fringe pattern or the additional interference fringe pattern along the illumination axis of the incident region, or the frequency of the interference fringe pattern or the additional interference fringe pattern in the frequency domain. The optical length difference indicates the difference between (a) the current separation distance between the proximal portion of the tool or instrument and the surface of the object and (b) a predetermined nominal separation distance or a predetermined modified separation distance.

7. The method according to claim 6, wherein, The primary reference optical path and the secondary reference optical path overlap at least partially and collinearly strike the common incident area of ​​the optical interferometry sensor device.

8. The method according to claim 7, wherein, The additional reference optical path includes at least a partial back reflection at the surface of an optical element inserted along the optical path of the main reference beam.

9. The method according to claim 7, wherein, The additional reference optical path includes at least back reflections within an optical element inserted along the optical path of the main reference beam.

10. The method according to claim 7, wherein, The additional reference optical path includes a portion of the path that is deflected relative to the optical path of the main reference beam.

11. The method according to claim 10, wherein, The deflection path portion is obtained by inserting optical elements for partially extracting the reference beam from the optical path of the main reference beam and optical elements for reintroducing the extracted reference beam into the optical path of the main reference beam.

12. The method according to claim 11, wherein, The optical element used for partial beam extraction is a beam splitting device.

13. The method according to claim 11, wherein, The optical element used for partial beam extraction is a prism adapted to continuously control the optical length of the deflection path portion.

14. The method according to claim 6, wherein, The primary reference optical path and the secondary reference optical path collide on corresponding different areas of the common incident region of the optical interferometry sensor device.

15. The method according to claim 6, wherein, The optical interferometric measurement sensor device includes an arrangement of photodetectors along the illumination axis, and the arrangement of the photodetectors is a linear arrangement of photodetectors.

16. The method according to claim 6, wherein, The optical interferometric measurement sensor device includes an arrangement of photodetectors along the illumination axis, and the arrangement of the photodetectors is a two-dimensional arrangement of photodetectors.

17. A method for determining the relative positions of elements of an optical system for processing or measuring an object along a predetermined measurement line associated with the system, characterized in that, The method includes the following steps: A measurement beam with low coherence optical radiation is generated, the measurement beam is guided along the measurement line toward the element, and the measurement beam reflected or diffused by the back-reflecting surface of the element is guided toward the optical interferometric sensor device. The measurement beam strikes the back-reflecting surface in a manner that is at least partially back-reflected. The measurement beam travels from a corresponding source to the optical interferometric sensor device along a measurement optical path, the measurement optical path comprising: a first portion between the source and the back-reflecting surface of the element, and a second portion between the back-reflecting surface of the element and the interferometric sensor device. The first portion and the second portion have corresponding predetermined nominal geometric lengths when the element is in a predetermined nominal position corresponding to predetermined operating conditions of the system. The measurement beam comprises a main measurement beam and an additional multiplexed measurement beam. The main measurement beam is generated by the travel of the main measurement optical path, which travels along the measurement line through each optical element inserted upstream of the element. The additional multiplexed measurement beam is generated by the travel of the additional measurement optical path, which has a geometric length different from that of the main measurement optical path. Generate a corresponding reference beam of the low-coherence optical radiation, and guide the reference beam toward the optical interferometric measurement sensor device, wherein the reference beam travels in a reference optical path, and under nominal operating conditions where the position of the element is a predetermined nominal position, the reference optical path has an optical length equal to the optical length of the main measurement optical path; Along a predetermined illumination axis, the measurement beam and the reference beam are superimposed on at least one common incident area of ​​the optical interferometric measurement sensor device; The positions of the main interference fringe pattern between the main measurement beam and the reference beam, and the positions of the additional interference fringe patterns between the additional multiplexed measurement beam and the reference beam, are detected along the illumination axis in the common incident region; wherein the extension of the interference fringe pattern along the illumination axis corresponds to the coherence length of the low-coherence optical radiation, and the additional interference fringe pattern has (i) a peak or maximum intensity of the optical radiation envelope that is different from the peak or maximum intensity of the optical radiation envelope of the main interference fringe pattern, or (ii) an inherent position of the intensity envelope of the optical radiation that is offset from the inherent position of the intensity envelope of the optical radiation of the main interference fringe pattern, or (iii) a spatial frequency that is different from the spatial frequency of the main interference fringe pattern, or The frequency of the fringe pattern in the wavelength spectrum and the frequency of the additional interference fringe pattern between the additional multiplexed measurement beam and the reference beam are detected in the common incident region. The fringe pattern is obtained from the principal interference between the main measurement beam and the reference beam by the wavelength dispersion of the beam. The extension of the fringe pattern in the frequency domain is determined by the coherence length of the low-coherence optical radiation. The additional interference fringe pattern (i) has a frequency different from the frequency of the main interference fringe pattern, or (ii) is determined by the overlap of the additional multiplexed measurement beam and the reference beam in a region of the common incident region that is different from the overlap region of the main measurement beam and the reference beam. The optical length difference between the measurement optical path or the additional measurement optical path and the reference optical path is determined based on the position of the interference fringe pattern or the additional interference fringe pattern along the illumination axis of the incident region, or the frequency of the interference fringe pattern or the additional interference fringe pattern in the frequency domain. The optical length difference indicates the difference between (a) the current position of the element and (b) a predetermined nominal position of the element along the axis of the measurement beam.

18. The method according to claim 17, wherein, The main measurement optical path and the additional measurement optical path overlap at least partially and collinearly impact the common incident area of ​​the optical interferometric measurement sensor device.

19. The method of claim 17, wherein, The main measurement optical path and the additional measurement optical path collide on corresponding different areas of the common incident area of ​​the optical interferometry sensor device.

20. A method for determining a separation distance between a working tool or measuring instrument and at least a portion of a reflective surface of an object outside the working tool or measuring instrument along predetermined measuring lines, the predetermined measuring lines being associated with at least proximal portions of the instrument and the surface of the tool relative to the object, characterized in that, The method includes the following steps: A measurement beam with low coherence optical radiation is generated and guided toward the surface of the object through the proximal portion of the tool or instrument; and the measurement beam reflected or diffused from the surface of the object is guided through the proximal portion of the tool or instrument toward an optical interferometric sensor device, wherein the measurement beam travels from a corresponding source to the optical interferometric sensor device along a measurement optical path, the measurement optical path including a first portion between the source and the proximal portion of the tool or instrument and a second portion between the proximal portion of the tool or instrument and the interferometric sensor device, the first portion and the second portion having corresponding predetermined and constant geometric lengths, the measurement beam including a main measurement beam and an additional multiplexed measurement beam, the main measurement beam being generated by the travel of the main measurement optical path, the main measurement optical path being transmitted along the measurement line through each optical element inserted upstream of the tool or instrument, the additional multiplexed measurement beam being generated by the travel of the additional measurement optical path, the additional measurement optical path having a geometric length different from that of the main measurement optical path; Generate a corresponding reference beam of the low-coherence optical radiation, and guide the reference beam toward the optical interferometric measurement sensor device, wherein the reference beam travels in a reference optical path, and the reference optical path has an optical length equal to the optical length of the main measurement optical path under nominal operating conditions where the distance between the proximal portion of the tool or instrument and the surface of the object corresponds to a predetermined nominal separation distance; Along a predetermined illumination axis, the measurement beam and the reference beam are superimposed on at least one common incident area of ​​the optical interferometric measurement sensor device; The positions of the main interference fringe pattern between the main measurement beam and the reference beam, and the positions of the additional interference fringe patterns between the additional multiplexed measurement beam and the reference beam, are detected along the illumination axis in the common incident region; wherein the extension of the interference fringe pattern along the illumination axis corresponds to the coherence length of the low-coherence optical radiation, and the additional interference fringe pattern has (i) a peak or maximum intensity of the optical radiation envelope that is different from the peak or maximum intensity of the optical radiation envelope of the main interference fringe pattern, or (ii) an inherent position of the intensity envelope of the optical radiation that is offset from the inherent position of the intensity envelope of the optical radiation of the main interference fringe pattern, or (iii) a spatial frequency that is different from the spatial frequency of the main interference fringe pattern, or The frequency of the fringe pattern in the wavelength spectrum and the frequency of the additional interference fringe pattern between the additional multiplexed measurement beam and the reference beam are detected in the common incident region. The fringe pattern is obtained from the principal interference between the main measurement beam and the reference beam by the wavelength dispersion of the beam. The extension of the fringe pattern in the frequency domain is determined by the coherence length of the low-coherence optical radiation. The additional interference fringe pattern (i) has a frequency different from that of the main interference fringe pattern, or (ii) is determined by the overlap of the additional multiplexed measurement beam and the reference beam in a region of the common incident region that is different from the overlap region of the main measurement beam and the reference beam. The optical length difference between the measuring optical path or the additional measuring optical path and the reference optical path is determined based on the position of the interference fringe pattern or the additional interference fringe pattern along the illumination axis of the incident region, or the frequency of the interference fringe pattern or the additional interference fringe pattern in the frequency domain. The optical length difference indicates the difference between (a) the current separation distance between the proximal portion of the tool or instrument and the surface of the object and (b) the predetermined nominal separation distance.

21. The method according to claim 20, wherein, The main measurement optical path and the additional measurement optical path overlap at least partially and collinearly impact the common incident area of ​​the optical interferometric measurement sensor device.

22. The method according to claim 21, wherein, The additional measurement optical path includes at least a partial back reflection at the surface of an optical element inserted along the optical path of the main measurement beam.

23. The method according to claim 21, wherein, The additional measurement optical path includes at least back reflection within an optical element inserted along the optical path of the main measurement beam.

24. The method according to claim 21, wherein, The additional measurement optical path includes a portion of the path that is deflected from the optical path of the main measurement beam.

25. The method according to claim 24, wherein, The deflection path portion is obtained by inserting an optical element for partially extracting the measurement beam from the optical path of the main measurement beam and an optical element for reintroducing the extracted measurement beam into the optical path of the main measurement beam.

26. The method of claim 25, wherein, The optical element used for partial beam extraction is a beam splitting device.

27. The method according to claim 25, wherein, The optical element used for partial beam extraction is a prism adapted to continuously control the optical length of the deflection path portion.

28. The method according to claim 20, wherein, The main measurement optical path and the additional measurement optical path collide on corresponding different areas of the common incident area of ​​the optical interferometry sensor device.

29. A method for determining the positions of a plurality of elements that at least partially reflect optical radiation in a system, said system comprising a plurality of optical components of a processing or measuring assembly, or said system comprising at least one optical element of the processing or measuring assembly and an object external to said processing or measuring assembly and subjected to said processing or measurement, wherein, The plurality of at least partially reflective elements are arranged along a predetermined common measurement line, characterized in that the method includes the following steps: A measurement beam with low coherence optical radiation is generated, and the measurement beam is guided along the measurement line toward a plurality of elements of the system. The measurement beam, reflected or diffused from the back-reflecting surface of each element, is guided toward an optical interferometric sensor device. The measurement beam strikes the back-reflecting surface in a manner that is at least partially back-reflected. The measurement beam travels from a corresponding source to the optical interferometric sensor device along a measurement optical path, which includes a first portion between the source and the back-reflecting surface of each element, and a second portion between the back-reflecting surface of each element and the interferometric sensor device. The first and second portions have corresponding predetermined nominal geometric lengths when each element is in a corresponding predetermined nominal position corresponding to predetermined operating conditions of the system. The measurement beam includes a first measurement beam and a second multiplexed measurement beam. The first measurement beam is generated by the first measurement optical path traveling along the measurement line with reflection from a first element. The second multiplexed measurement beam is generated by the second measurement optical path traveling along the measurement line with reflection from a second element. The second measurement optical path has a geometric length different from that of the first measurement optical path. The process involves generating a corresponding reference beam of low-coherence optical radiation and guiding the reference beam toward the optical interferometric measurement sensor device. The reference beam includes a first reference beam and a second multiplexed reference beam. The first reference beam is generated by the travel of a first reference optical path, which, under nominal operating conditions where the position of the first element is a corresponding predetermined nominal position, has an optical length equal to the optical length of the first measurement optical path. The second multiplexed reference beam is generated by the travel of a second reference optical path, which, under operating conditions where the position of the second element is a corresponding predetermined nominal position, has a geometric length different from the geometric length of the first reference optical path. Along a predetermined illumination axis, the first measurement beam and the second multiplexed measurement beam are respectively superimposed on the first reference beam and the second multiplexed reference beam on at least one common incident area of ​​the optical interferometric measurement sensor device; The positions of a first interference fringe pattern between the first measurement beam and the first reference beam, and a second interference fringe pattern between the second multiplexed measurement beam and the second multiplexed reference beam, are detected along the illumination axis in the common incident region; wherein the extension of the interference fringe pattern along the illumination axis corresponds to the coherence length of the low-coherence optical radiation; the second interference fringe pattern has (i) a peak or maximum intensity of an optical radiation envelope different from the peak or maximum intensity of the optical radiation envelope of the first interference fringe pattern, or (ii) an inherent position of the intensity envelope of the optical radiation offset from the inherent position of the intensity envelope of the optical radiation of the first interference fringe pattern, or (iii) a spatial frequency different from the spatial frequency of the first interference fringe pattern, or The frequency of a first fringe pattern in the wavelength spectrum and the frequency of a second interference fringe pattern between the second multiplexed measurement beam and the second multiplexed reference beam are detected in the common incident region. The first fringe pattern is obtained from the interference between the first measurement beam and the first reference beam by the wavelength dispersion of the beams. The extension of the first fringe pattern in the frequency domain is determined by the coherence length of the low-coherence optical radiation. The second interference fringe pattern (i) has a frequency different from that of the first interference fringe pattern, or (ii) is determined by the overlap of the second multiplexed measurement beam and the reference beam in a region of the common incident region that is different from the overlap region of the first measurement beam and the reference beam. Sure: (i) Determine the optical length difference between the first measuring optical path and the first reference optical path based on either the position of the first interference fringe pattern along the illumination axis of the incident region or the frequency of the first interference fringe pattern in the frequency domain, wherein the optical length difference indicates (a) the difference between the current position of the first element and (b) a predetermined nominal position of the first element along the axis of the measuring beam; and (ii) Determine the optical length difference between the second measuring optical path and the second reference optical path based on the position of the second interference fringe pattern along the illumination axis of the incident region or the frequency of the second interference fringe pattern in the frequency domain, the optical length difference indicating (a) the difference between the current position of the second element and (b) a predetermined nominal position of the second element along the axis of the measuring beam.

30. A machine for laser processing of materials, the machine operating by means of a processing laser beam guided along an optical path for transmitting the laser beam, the machine comprising an optical system, characterized in that, The machine includes a system for determining the relative positions of the elements of the optical system, the system being arranged to perform the method according to claim 1 or 17.

31. A machine for laser processing of materials, the machine operating by means of a processing laser beam guided along an optical path for transmitting the laser beam, the machine comprising processing tools or measuring instruments, characterized in that, The machine includes a system for determining a separation distance between the processing tool or the measuring instrument and at least a portion of the reflective surface of an object outside the processing tool or the measuring instrument, the system being arranged to perform the method according to claim 6 or 20.

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