Method and apparatus for controlling workpiece processing by confocal distance measurement

Abstract

A method and an apparatus for controlled machining of a workpiece are described. According to the described method, a laser light beam is focused at a target point of a workpiece to be machined to produce a laser focus point. Furthermore, according to the described method, distance measurement data are acquired by means of an optical distance measuring device in order to determine a distance between the target point of the workpiece to be machined and a laser target optical unit. The method comprises positioning the workpiece to be machined relative to the laser focus point on the basis of the acquired distance measurement data. The distance measuring device is designed as an optical confocal distance measuring device having a measurement light source for producing measurement light and having a variable focus measurement light optical unit. The method comprises varying the focus of the variable focus measurement light optical unit over time in order to acquire distance measurement data at different focus values of the variable focus measurement light optical unit, laser light reflected by the workpiece and / or process light produced during machining of the workpiece being detectable.

Description

[0001] This disclosure relates to a method and apparatus for laser processing of a workpiece. Specifically, this disclosure relates to a method for laser processing a workpiece while simultaneously controlling the positioning of the workpiece to achieve precision laser processing.

[0002] Methods for machining workpieces using laser beams or laser beams are known. Apparatus for performing such methods is also known. However, precision machining of workpieces using laser beams requires accurate workpiece positioning or precise adjustment of the corresponding laser processing apparatus, which can only be performed using known methods and apparatus within a limited scope.

[0003] One objective of embodiments of this disclosure is to provide an improved method and apparatus for controlled laser processing of workpieces, characterized by high processing accuracy and simple apparatus design.

[0004] According to a first aspect, a method for controlled machining of a workpiece is provided to achieve this objective. The method includes focusing a laser beam or machining beam using laser aiming optics to generate a laser focal point at a target location on the workpiece to be machined. Specifically, the laser beam can be generated using solid-state lasers (e.g., YAG lasers or fiber lasers) and gas lasers (e.g., CO2 lasers) emitting in the near-infrared spectral range.

[0005] Specifically, the laser aiming optics can be configured as focusing and alignment optics that achieve target alignment and focusing of the laser beam. More specifically, the laser aiming optics can be configured as a laser beam scanner, particularly a galvanometer scanner, thereby enabling laser beam alignment using an electronically controlled mirror.

[0006] The method includes acquiring distance measurement data by means of an optical ranging device or optical sensor to determine the distance between the target position of the workpiece to be processed and the laser aiming optics, or the fixed reference point or reference plane of the laser aiming optics.

[0007] The method further includes processing a target location on the workpiece using a focused laser beam. Specifically, the processing may include laser welding, laser cutting, and / or other laser processing.

[0008] According to the method, the ranging device is configured as an optical confocal ranging device having a variable focal length optics or a variable focal length measuring optical optics, wherein the method includes changing the focal length of the variable focal length measuring optical optics over time to acquire distance measurement data at different focal length values ​​of the variable focal length measuring optical optics.

[0009] By varying the focal length of a variable-focal-length measuring optics over time—a focal length that can be changed between a minimum and a maximum focal length—the desired measurement range can be defined. Specifically, the measurement range can be defined or fixed such that, even in laser processing setups with large focal lengths or small numerical apertures, an optical confocal sensor can accurately determine the distance between the laser aiming optics and the target position of the workpiece. Using the determined distance measurement data, the workpiece can be processed in a controlled and precise manner.

[0010] Variable focal length measuring optics can also perform distance measurements using optical elements with little or no optical dispersion, making it possible for optical elements provided for laser beam guiding, especially those with little or no optical dispersion, to be used for beam guiding of measuring light.

[0011] The method may further include positioning the workpiece relative to the laser focus based on acquired distance measurement data. Positioning the workpiece may include changing the spatial position and / or spatial orientation of the workpiece or the entire laser processing apparatus. Alternatively or additionally, positioning may include refocusing the laser beam. Thus, if necessary, the workpiece can be repositioned or the laser can be readjusted to allow for precision machining of the workpiece.

[0012] The laser aiming optics of a laser processing apparatus can form part of the measuring light optics of a ranging device. Specifically, the measuring light can be coupled to the beam path of the laser beam in such a way that the measuring beam extends coaxially with the laser beam at least in a segment.

[0013] By using the laser aiming optics of a laser processing apparatus as the measuring optical optics of a ranging device, the number of optical components required to perform the method can be reduced, and thus the optical setup can be simplified. Therefore, specifically, the distance sensor can be easily integrated into existing laser processing systems.

[0014] At least some of the process steps can be performed or repeated at several target locations on the workpiece to be machined. By repeating the process steps at several locations, the positioning of the workpiece to be machined can be rechecked and, if necessary, corrected.

[0015] In some embodiments, acquiring distance measurement data includes acquiring the intensity of measurement light reflected from the workpiece, wherein the distance is determined based on the intensity of the measurement light reflected from the workpiece over time.

[0016] Specifically, by controlling the time variation of the focal length of the variable focal length measuring optics, the time point for intensity detection can be assigned to a specific focal length of the variable focal length measuring optics and thus to the position of the focal point of the measuring light. From this, the distance between the laser aiming optics and the target position can be inferred. This is because the intensity is maximum when the focal plane of the measuring light coincides with the surface of the workpiece or the device under test. In this case, due to the confocal light guidance of the ranging device at the aperture or optical coupling point arranged on the side of the photodetector, the measuring spot generated on the surface of the workpiece is imaged. The aperture or optical coupling point also acts as the light exit aperture of the measuring light source, allowing the photodetector to detect the maximum intensity.

[0017] Broadband infrared light, specifically near-infrared light, can be used as the measurement light. Specifically, near-infrared LEDs (light-emitting diodes) with peak wavelengths between 900 nm and 1000 nm, particularly between 940 nm and 960 nm, and spectral half-widths between 40 nm and 60 nm, particularly between 45 nm and 55 nm, can be used to generate the measurement light. The broadband nature of this LED measurement light is sufficient to avoid or reduce disturbances or speckle effects. On the other hand, the narrow band of this LED measurement light is sufficient to suppress or maintain low levels of unwanted dispersion effects, such as chromaticity focus shift or focus shift.

[0018] In addition, optical components of the laser processing apparatus, such as mirrors and / or lenses configured with laser aiming optics for the near-infrared spectral range, can be used for distance measurement using near-infrared measuring light.

[0019] The method may further include obtaining or detecting a laser beam. In this case, instead of a measuring light or in addition to a measuring light, a laser beam is detected, which is reflected from the workpiece and guided via an aperture to a detector of the ranging device by a laser aiming optics and a measuring light optics. In this method, the laser focus is mapped onto the aperture, the focal length of the variable focal length measuring optics varies in a controlled manner over time, and the focal length is detected when the intensity of the laser transmitted through the aperture becomes maximum, i.e., when the laser focus is clearly imaged onto the aperture. In this method, for example, in a first step, the laser can be focused onto the workpiece and the focal length of the variable focal length measuring optics can be determined at which the maximum intensity of the laser transmitted through the aperture occurs. When the laser focus is no longer on the workpiece, but above or below it, the position of the image point in the aperture plane also changes. Therefore, the maximum intensity occurs at different focal lengths of the variable focal length measuring optics. This effect can be used to detect changes in the laser focus position.

[0020] In some embodiments, the method may include simultaneously detecting both the measurement light and the laser beam. In this case, both the laser focus and the measurement spot are imaged onto the aperture, and the measurement light and a portion of the laser beam transmitted through the aperture are guided to the detector of the ranging device.

[0021] Depending on the distance between the laser focus and the workpiece surface, as well as the color error of the optical components, the focal length at which the measurement spot is clearly imaged on the aperture can be different from the focal length at which the laser focus is clearly imaged on the aperture.

[0022] Specifically, the method may include positioning the workpiece to be processed relative to the laser focus based on a determined difference between the two focal lengths of the measured spot or laser focus clearly imaged on the aperture.

[0023] Changing the focal length of a variable focal length measuring optics over time can involve tuning, specifically periodically tuning the focal length of the variable focal length measuring optics to detect distance measurement data at different focal lengths of the optics. When tuning the focal length, the focal length range of the variable focal length measuring optics between the minimum and maximum focal lengths is covered, allowing the focal point of the measuring optics to scan the entire measurement range of the optical sensor. By cyclically tuning the focal length of the variable focal length measuring optics, the evaluation of the detected distance measurement data can be synchronized with the time-varying focal length, thereby facilitating the explicit and reliable assignment of the detected measurement data to the distance to be determined. The distance value or distance to the surface of the workpiece to be measured can be determined based on the focal length variation of the measuring light in one cycle or in one measurement cycle, specifically a single distance value or distance.

[0024] In some embodiments, the focal point of the measurement beam is located on the surface of the object to be measured or the workpiece to be processed at two different times within the cycle, such that the reflection of the measurement spot on the surface of the workpiece is clearly imaged onto the fiber end or optical coupling point, resulting in the photodetector detecting a maximum light intensity. The distance to the workpiece can be determined from the time when the maximum light intensity detected by the photodetector is observed by means of a predetermined relationship or some other relationship, which can be determined by a calibration measurement between the cycle time and the position of the focal point of the measurement beam.

[0025] The method may further include performing calibration measurements to determine the relationship between cycle time and distance. The relationship between cycle time and distance determined by the calibration measurements can improve the reliability and accuracy of the evaluation of distance measurement data, allowing the distance to be determined to be calculated explicitly and reliably from the time of the maximum intensity in the cycle.

[0026] Calibration measurements can specifically involve detecting reflections from concave and convex lenses downstream of a variable focal length optics at different cycle times. These lenses include concave and convex surfaces. Specifically, the lenses can be arranged such that, when the variable focal length optics is tuned, light reflected from the concave surface and light reflected from the convex surface are alternately focused at the optical coupling point, each resulting in a measurable intensity peak of the light fed into the fiber. The temporal positions of these peaks within the tuning cycle correspond to the well-defined focal length of the variable focal length optics, allowing for precise calibration of the variable focal length optics or ranging device based on the temporal positions of these intensity peaks or calibration peaks.

[0027] In some embodiments, calibration measurements include measuring a two-dimensional grid of the lateral position of a scanner or laser aiming optics. Distance measurement data acquired on the two-dimensional grid can then be used to calibrate the ranging device.

[0028] The method may further include calibration measurements to determine the distance at which the laser is optimally focused on the workpiece.

[0029] When machining a workpiece, the machining laser can generate process light in the visible and infrared light ranges. Specifically, during laser machining of the workpiece, process light can appear in a spectral range outside the laser's spectral distribution. The appearance of process light is coupled to the laser intensity at the workpiece irradiation point. When the laser operates at low power, process light appears only when the workpiece is exactly within the laser's focal plane.

[0030] To determine the focal plane of the laser, the distance between the laser focus and the workpiece is changed. This can be done, for example, by positioning the workpiece or by focusing the laser beam using focusing optics.

[0031] The presence of process light is recorded by a detector. The detection of process light indicates that the laser beam is sufficiently focused on the workpiece to generate the process light. Based on the detected process light, it can also be determined that the laser beam is optimally focused on the workpiece. If this is the case, the corresponding distance value can be determined by measuring the distance with a measuring light.

[0032] In an alternative embodiment, instead of operating the laser at a constant power, the laser power is varied. Specifically, the laser power can be continuously increased from a low value, and a critical power at which the process light first appears can be determined.

[0033] This step can be repeated for different distances between the workpiece and the laser focus. The characteristic of focusing the laser on the workpiece at the distance that allows for the best possible focusing is based on assuming a minimum critical power.

[0034] Distance measurement data can be acquired at measurement points at several locations or at the target location. In this context, arranging measurement points at the target location means that the measurement points can be located within, at, or around the target location. By acquiring distance measurement data at several measurement points at the target location, the sensitivity to measurement errors can be reduced through averaging. Acquiring distance measurement data at several measurement points also reduces the influence of speckle on the measurement results. This is because the local intensity fluctuations of light reflected back from the workpiece due to speckle can be averaged by measuring at several measurement points.

[0035] Specifically, distance measurement data can be acquired sequentially or temporarily at several measurement points within a measurement cycle. During the measurement cycle, distance measurement data can thus be acquired from different measurement points, allowing the average distance to be determined quickly and with minimal computational effort.

[0036] In some embodiments, distance measurement data is acquired at multiple locations along a scan path at the target location. Specifically, the scan path can be selected such that the distance measurement data acquired along the scan path can be used to infer the target distance.

[0037] The shape of the scanning path can be a circle surrounding the target location of the workpiece. Specifically, the measurement circle can include a path radius equivalent to the laser point. Distance measurement data acquired along the measurement circle generates a database, which efficiently reduces measurement errors through averaging.

[0038] The scanning path can be a spiral centered on the target location of the workpiece. Specifically, the center of the spiral can coincide with the target location. Due to the spiral scanning path, distance measurement data can be acquired from particularly large surfaces, thereby enhancing the averaging effect and reducing the sensitivity of the measurement to interference.

[0039] In some implementation schemes, distance measurement data is acquired at several measurement points, specifically within a measurement cycle, substantially simultaneously, wherein the distance is determined based on physical average distance measurement data.

[0040] The physical averaging of distance measurement data, specifically, means that distance determination is not performed individually for each measurement point; for example, an average distance value is formed from the determined distances. Physical averaging means that all distance measurement data recorded at several measurement points at the target location, specifically the intensity measurement data of the measurement light reflected back from the workpiece, are included in the distance determination at the target location, so that a single distance value is determined for all measurement points.

[0041] Because of physical averaging, specifically, all distance measurement data recorded at different measurement points at the target location can be evaluated together in a single evaluation step, making it possible to determine distance values ​​in a fast and simple manner.

[0042] The measurement light can be split into multiple portions using at least one perforated mask with multiple apertures (specifically, in the form of confocal apertures) to simultaneously acquire distance measurement data at several measurement points. With at least one perforated mask, the portions of measurement light required to acquire distance measurement data at several measurement points can therefore be generated in a simple manner.

[0043] A portion of the measurement light can be detected using a common photodetector. Using the common photodetector for all portions of the measurement light simplifies the acquisition of distance measurement data from several measurement points. Simultaneously with acquiring the portion of the measurement light using the common photodetector, a physical average of the distance measurement data or light intensity is performed. This is because the common photodetector cannot distinguish light reflected from different measurement points. Therefore, the averaging of the distance measurement data is performed automatically without requiring computational steps.

[0044] According to the second aspect, an apparatus for controlled machining of workpieces is proposed.

[0045] The device includes a laser source for generating a laser beam for machining or laser processing a workpiece. Specifically, solid-state lasers (such as YAG lasers or fiber lasers) emitting in the near-infrared spectral range and gas lasers, such as CO2 lasers, can be used to generate the laser beam.

[0046] The apparatus further includes laser aiming optics for focusing a laser beam onto a laser focal point at a target location on the workpiece. Specifically, the laser aiming optics can be configured as focusing and alignment optics that achieve target alignment and focusing of the laser beam. More specifically, the laser aiming optics can be configured as a laser beam scanner, particularly a galvanometer scanner, wherein laser beam alignment can be performed by means of an electro-optic mirror.

[0047] The apparatus further includes: a ranging device for determining the distance between the target position of the workpiece to be processed and the laser aiming optics based on distance measurement data acquired by the ranging device; and a positioning device for positioning the workpiece to be processed relative to the laser focus, and / or for refocusing the laser based on the detected distance measurement data.

[0048] The device further includes an evaluation control unit configured to evaluate the acquired distance measurement data and control the positioning device based on the acquired distance measurement data.

[0049] The ranging device is configured as an optical confocal ranging device, which has a measuring light source for generating measuring light and a variable focal length measuring light optics, such that the focal length of the variable focal length measuring light optics can vary over time to acquire distance measurement data at different focal length values ​​of the variable focal length measuring light optics.

[0050] By changing the focal length of the variable focal length measuring optical device over time, the effective measurement range of the ranging device can be increased. This allows for the precise determination of the distance between the laser aiming optics and the target position of the workpiece to be processed using an optical confocal sensor, even in laser processing devices with large focal lengths or small numerical apertures.

[0051] Variable focal length measuring optics can also perform distance measurements using optical elements with no or only low optical dispersion, making the optical elements required for laser beam guiding, especially those with no or low optical dispersion, also suitable for beam guiding of the measuring light.

[0052] The measuring optical components of the ranging device may include at least a portion of the laser aiming optical components.

[0053] By using laser aiming optics as the measuring optical optics in a ranging device, the number of required optical components can be reduced, or the device structure can be significantly simplified. Therefore, the distance sensor can also be easily integrated into existing laser processing systems.

[0054] The ranging device may include a photodetector for detecting the intensity of measuring light reflected back from the workpiece and configured in such a way that the distance can be determined based on the detected intensity of the measuring light reflected back from the workpiece over time.

[0055] Specifically, as the focal length of the variable focal length measuring optics changes over a controlled time, the time point of intensity detection can be assigned to a specific focal length of the variable focal length measuring optics and thus to a specific distance, from which the distance between the laser aiming optics and the target position can be inferred.

[0056] Broadband infrared light sources, specifically those emitting light in the near-infrared spectral range, can be used as measurement light sources. Specifically, near-infrared LEDs with a peak wavelength of approximately 950 nm and a spectral half-width of approximately 50 nm can be used to generate the measurement light. The broadband nature of this LED measurement light is sufficient to avoid or reduce perturbation interference or speckle effects. On the other hand, the narrow band of this LED measurement light is sufficient to suppress or maintain low levels of undesirable dispersion effects, such as chromaticity focus shift.

[0057] The variable focal length measuring optics can be configured to be tunable, specifically, cyclically tunable. When the focal length is tuned, the focal length range of the variable focal length measuring optics, covering both the minimum and maximum focal lengths, ensures that the focal point of the measuring optics covers the entire measurement range of the optical sensor, for example, + / - 7 mm. By cyclically tuning the focal length of the variable focal length measuring optics, the evaluation can be synchronized with the time-varying focal length, in a way that allows the recorded measurement data to be explicitly and reliably assigned to the distance to be determined.

[0058] Specifically, the variable focal length optics can be arranged in the diverging section of the imaging system of the rangefinder. The diverging section is part of the imaging system of the rangefinder, in which the measuring optical optics form a diverging measuring beam. In the diverging section of the imaging system, the variable focal length measuring optics can be positioned in a way that allows for optimal utilization of the free aperture of the variable focal length optics.

[0059] Variable focal length measuring optics can include variable focal length lenses. Specifically, a variable focal length lens allows for a simple change in the focal length of the measuring optics. The free aperture of the variable focal length lens can be between 1 and 10 mm, specifically between 2 and 6 mm in diameter. Specifically, the variable focal length lens can be positioned near the optical coupling point or near the end of the optical fiber from which the measuring light diverges.

[0060] In some embodiments, the apparatus includes at least one perforated mask having multiple holes for splitting measurement light into multiple portions of measurement light. Distance measurement data can be acquired simultaneously at several measurement points using these portions of measurement light.

[0061] In one embodiment, the apparatus includes an optical fiber having optical coupling points for coupling in and out of measurement light, wherein at least one perforated mask is arranged at the optical coupling point. This arrangement of the perforated mask is suitable for apparatuses with fiber optic couplers, wherein the optical coupling point is configured to couple out light generated by a measurement light source and to couple in measurement light reflected back from a workpiece to be processed. In this case, distance measurement data can be acquired at different measurement points in a simple manner using a single perforated mask.

[0062] Specifically, the perforation mask can be placed directly on the optical coupling point or on the end of the optical fiber. Placing the perforation mask on the optical coupling point allows for the efficient use of the perforation mask by capturing virtually all the measurement light emanating from the optical coupling point.

[0063] The optical coupling point or end of the optical fiber and the perforation mask can be sized such that the perforation mask is essentially completely illuminated. This means that the area of ​​the perforation mask can be used particularly effectively.

[0064] In some embodiments, the apparatus includes a first optical fiber having a light emitting end and a second optical fiber having a light entering end, wherein a first perforated mask is disposed at the light emitting end and a second perforated mask is disposed at the light entering end. This arrangement of the perforated masks is suitable for an apparatus having a beam splitter configured to couple measurement light generated by a measurement light source to an imaging system of the ranging device and to couple measurement light reflected back from a workpiece to be processed.

[0065] Two perforated masks can be positioned in such a way that the holes of the two perforated masks are confocally aligned in pairs. Due to the confocal alignment of the holes of the two perforated masks, a portion of the measurement beam generated by the hole of the first perforated mask is bound to the corresponding hole of the second perforated mask, thereby minimizing the optical loss caused by the perforated masks.

[0066] Instead of using individual optical fibers, fiber bundles can be used to generate a large number of partial measurement beams for recording distance measurement data at different measurement points. Fiber bundles already provide a large number of partial measurement beams, eliminating the need for perforated masks. Fiber bundles used to split the measurement beams into partial measurement beams can be used in both devices with fiber couplers and devices with beam splitters. By using fiber bundles, the structure and operation of the device can be simplified.

[0067] In some embodiments, the apparatus includes a camera that can be configured to visually inspect the machining position of a workpiece before, during, and / or after machining.

[0068] In some embodiments, the apparatus includes a detector configured to detect the presence of process light, wherein the process light is outside the spectral distribution of the laser. The apparatus may include a second detector configured to detect the presence of the process light, specifically another photodetector.

[0069] The embodiments are explained in more detail below with reference to the accompanying drawings, wherein the same reference numerals are used to denote the same or equivalent components.

[0070] Figure 1 An apparatus for controlled machining of a workpiece according to an embodiment is illustrated schematically.

[0071] Figure 2 Explanation of the perforated mask according to the embodiment,

[0072] Figure 3 Description of a perforated mask according to another embodiment,

[0073] Figure 4 A schematic side view illustrating the concave and convex lenses according to an embodiment is shown.

[0074] Figure 5 illustrate Figure 4 A schematic top view of a concave and convex lens.

[0075] Figure 6 The possible beam paths in a section of the ranging device according to an embodiment are illustrated schematically.

[0076] Figure 7 Illustrative explanation based on Figure 6 Another possible beam path in the segment,

[0077] Figure 8 Illustrative explanation based on Figure 6 Another possible beam path in the segment,

[0078] Figure 9 This illustrates how the intensity of light reflected from the concave and convex lenses changes over time.

[0079] Figure 10 An apparatus for controlled machining of a workpiece according to another embodiment is illustrated schematically.

[0080] Figure 11 A flowchart illustrating a method for controlled machining of a workpiece according to an embodiment, and

[0081] Figure 12 An apparatus for controlled machining of a workpiece according to another embodiment is illustrated schematically.

[0082] Figure 1 An apparatus for controlled machining of a workpiece according to an embodiment is schematically illustrated. The apparatus 1 includes a laser source 2 for generating a laser beam 3 for machining a workpiece 4. Furthermore, the apparatus 1 includes a laser aiming optics 5 for aiming or selectively focusing the laser beam 3 onto a focal point F at a target position 6 on the workpiece 4.

[0083] The apparatus 1 includes a ranging device 7 for determining the distance between a target position 6 of the workpiece 4 to be processed and a laser aiming optics 5. The ranging device 7 is configured as an optical confocal ranging device and includes a measuring light source 8 for generating measuring light and a photodetector 9 for detecting the measuring light reflected from the workpiece 4. In this embodiment, the ranging device 7 has a distance measuring range H of + / - 7 mm around the zero plane O.

[0084] The measurement light source 8 is connected to the first optical fiber 10 at the first connection point 11 of the fiber coupler 12, which is in the form of a Y-coupler. The photodetector 9 is connected to the second optical fiber 13 at the second connection point 14 of the fiber coupler 12. A third optical fiber 16, having a first end, is connected to the third connection point 15 of the fiber coupler 12, wherein the second end of the third optical fiber 16 is formed as an optical coupling point 17 for coupling in and out of the measurement light. In this embodiment, the first optical fiber 10, the second optical fiber 13, and the third optical fiber 16 are configured as a multimode optical fiber capable of transmitting broadband light in the near-infrared spectral range.

[0085] A collimating lens 18 is positioned downstream of the optical coupling point 17, with a variable focal length lens 19 positioned between the optical coupling point 17 and the collimating lens 18. The optical coupling point 17 is configured such that the measurement light exits from the optical coupling point 17 in a divergent manner, thus creating a region between the optical coupling point 17 and the collimating lens 18. In this embodiment, the variable focal length lens 19 is an electrically controllable variable focal length lens EL-03-10 from Optotune.

[0086] A first deflector 30 is arranged in the beam path of the laser beam 3 to couple the measurement light to the beam path of the laser beam 3 and the laser aiming optics 5, respectively, and to decouple the measurement light. The deflector 30 may be configured in such a way that the measurement light can, specifically, propagate coaxially to the laser beam 3 along the common optical axis A of the measurement light and the laser beam in the beam path of the laser beam.

[0087] The device 1 further includes a second deflector plate 31, which is located in the beam path of the laser beam between the first deflector plate 30 and the laser aiming optics 5. The camera 32 is optically connected to the laser aiming optics 5 via a second collimating lens 33 and the second deflector plate 31, in such a way that the processing position of the workpiece can be visually inspected using the camera 32. The deflector plates 30 and 31 are configured to be transparent or partially transparent to the laser, such that the beam path of the laser beam is not interfered with by the deflector plates 30 and 31 or is only slightly interfered with by them.

[0088] In some embodiments, the light for camera 32 is redirected between laser 2 and deflector 30 via deflector 31. By branching the camera light between laser and deflector 30, distance measurements via deflector 31 for the branched camera light are unaffected.

[0089] exist Figure 1 In the arrangement described herein, the laser beam 3 is coupled to the laser aiming optics 5 via deflection plate 30 or deflection plate 31, and thus transmissively. In an alternative embodiment, the laser beam 3 is coupled to the laser aiming optics 5 by reflection or by means of a laser beam mirror.

[0090] Specifically, the laser beam can be coupled to the optical system of device 1 in a reflective manner, either transversely or perpendicularly to the common optical axis A. In this arrangement, for example, the laser 2 will be arranged in place of the camera 32 and collimating lens 33, and the laser beam mirror will be arranged in place of the deflector 31. A laser beam mirror that is at least partially transparent to the measurement light can be used as the laser beam mirror. Other configurations of the beam path are also possible, in which the principles described herein can be implemented. In a non-limiting embodiment, the measurement light is coupled coaxially or along the common optical axis A to the beam path of the laser beam.

[0091] In some embodiments of the laser aiming optics 5, the focusing lens 50 is located downstream of the mirror pair 51, such that the laser beam 3 is first aligned through the mirror pair 51 before it can be focused at the target location by the focusing lens 50.

[0092] according to Figure 1 The apparatus 1 of the embodiment further includes an evaluation control unit 40. The evaluation control unit 40 includes: an evaluation unit 41 for evaluating detected distance measurement data; a lens control unit 42 for controlling the focal length of the variable focal length lens 19; and a positioning control unit 43 for positioning the workpiece to be processed relative to the laser focus. The evaluation unit 41 is connected to the output of the photodetector 9 via a signal line 44. The lens control unit 42 is connected to the control port of the variable focal length lens 19 via a lens control line 45. The positioning unit 43 is connected to the positioner 47 via a positioning control line 46 to position the workpiece 4 to be processed.

[0093] The laser source used in this embodiment is a YAG laser that generates light radiation in the wavelength range between 1030 nm and 1070 nm.

[0094] Other solid-state lasers, especially those emitting in the near-infrared spectral range, or gas lasers such as CO2 lasers, can also be used as laser sources. Lasers emitting in the near-infrared spectral range are well-suited for materials processing because they can provide power in the kW range and the high power optical radiation density required for materials processing. Device 1 further includes: a laser power control configured to control the power of laser 2; and a laser focusing control comprising controllable focusing optics arranged in the laser beam path and configured to control laser focusing. For simplicity, in Figure 1 The laser power control and laser focusing control are not shown.

[0095] The measurement light source used in this embodiment is a broadband near-infrared LED with a peak wavelength of approximately 950 nm and a spectral half-width of approximately 50 nm. The broadband nature of this LED measurement light is sufficient to avoid or reduce disturbances or speckle effects. On the other hand, the narrow band of this LED measurement light is sufficient to suppress or maintain low levels of unwanted dispersion effects, such as chromaticity focus shift.

[0096] exist Figure 1 In this embodiment, the laser aiming optics 5 or scanner includes a focusing lens 50 and a pair of controllable mirrors 51 for guiding focused radiation to a target position 6 of the workpiece 4 to be processed and, if necessary, for moving along with the focused laser beam on the processing area of ​​the workpiece 4. Specifically, the pair of mirrors 51 can be configured as a pair of galvanometers that can be electrically controlled in a simple manner.

[0097] The focusing lens 50 has a focal length of approximately 180 mm. The diameter of the laser beam 3 is approximately 10 mm before entering the laser aiming optics 5. The laser aiming optics 5 is sized such that the laser beam 3 can handle a processing area of ​​approximately 80 mm x 80 mm.

[0098] In some embodiments, the laser aiming optics 5 is configured as a telecentric laser aiming optics. The telecentric configuration of the laser aiming optics enables the processing of the workpiece at different distances from the device using a laser beam.

[0099] Specifically, the positioner 47 can be configured to position and / or orient the workpiece 4 to be processed relative to the laser beam focus, and, more specifically, may include one or more actuators, which can be controlled by one or more control signals from the positioning control unit 46 to position or orient the workpiece 4 to be processed. The possibility of orienting the workpiece is... Figure 1 The coordinate axes are used to symbolically represent this.

[0100] In some embodiments, such as in Figure 1 In the example described herein, device 1 includes a perforated mask 60 or aperture arranged in the beam path of ranging device 7. The perforated mask 60 includes elements that can be described below. Figure 2 and 3 Multiple holes 61 are clearly visible. A perforated mask 60 is located between the optical coupling point 17 and the variable focal length lens 19, causing the measurement light to be split into multiple parts by the perforated mask 60 for simultaneously acquiring distance measurement data at multiple locations on the surface of the workpiece 4. Figure 1 In the embodiment described herein, the perforation mask is placed directly on the end of the optical fiber that serves as the optical coupling point 17, such that the end of the optical fiber also serves as a support for the perforation mask 60.

[0101] In some embodiments, the optical fiber with the perforated mask placed at its end has backlight sufficient to substantially completely illuminate the perforated mask 60 and capture backlight reflected off substantially all the holes 61 of the perforated mask 60.

[0102] In some embodiments, instead of the optical fiber 16 having a perforated mask 60, a coupling to and Figure 1 The fiber bundle is similar to that of an optical fiber coupler.

[0103] In some embodiments, for example Figure 1 In the example described herein, the apparatus 1 for controlled machining of a workpiece includes a concave-convex lens 80 located between a variable focal length lens 19 and a collimating lens 18.

[0104] The concave-convex lens 80 includes a substantially spherical concave surface 81 and a substantially spherical convex surface 82. The concave surface 81 or concave side of the concave-convex lens 80 faces the variable focal length lens 19, and the convex surface 82 or convex side of the concave-convex lens 80 faces the collimating lens 18. In the illustrated embodiment, the concave-convex lens 80 includes a central circular aperture 83.

[0105] In the operation of device 1, a portion of the light generated in the measurement light source 8 is guided through the first fiber 10 to the optical coupling point 17 via the fiber coupler 12 and the third fiber 16. The measurement light diverges from the optical coupling point 17, then passes through the variable focal length lens 19 and the collimating lens 18, and is coupled to the beam path of the laser beam 3 via the deflection plate 30. The measurement light coupled to the beam path of the laser beam 3 can then pass through the laser aiming optics 5 and reach the workpiece 4 to be processed.

[0106] When the measuring light reaches workpiece 4, a portion of the measuring light can be reflected back and reach the third optical fiber 16 via the laser aiming optics 5, collimating lens 18, variable focal length lens 19, and optical coupling point 17. Therefore, a portion of the measuring light is redirected at fiber coupler 12 via the second optical fiber 13 to photodetector 9. Photodetector 9 supplies a measuring signal to evaluation unit 41 via signal line 44 for evaluation. Evaluation unit 41 is configured to evaluate the intensity of the light detected by photodetector 9 over time. Evaluation unit 41 is also configured to deduce the distance between the target position of the workpiece and the laser aiming optics from the intensity development over time.

[0107] Specifically, the variable focal length lens 19 can be cyclically controlled such that the refractive power of the variable focal length lens is tuned by, for example, + / -13 diopters, thereby shifting the focal point of the measurement light along the optical axis by approximately + / -7 mm. At two different times within the cycle, the focal point of the measurement beam is on the surface of the object to be measured or the workpiece to be processed, such that the reflection of the measurement spot on the surface of the workpiece is clearly imaged onto the fiber end or optical coupling point 17, resulting in the photodetector detecting the light intensity at its maximum value.

[0108] The distance to the workpiece can be determined by means of a predetermined relationship or some other relationship based on the time it takes to observe the maximum intensity value of the light detected by the photodetector, which can be determined by a calibration measurement between the cycle time and the position of the focal point of the measuring light.

[0109] Specifically, the calibration measurements used to determine the relationship between the cycle time points and the distance to the surface of the workpiece to be processed may have been performed in advance or before laser processing. The calibration measurements can be performed via a two-dimensional grid of the lateral position of the scanner or laser aiming optics. Using the determined relationship, the distance to the surface or the distance between the laser aiming optics 5 and the target position 6 of the workpiece to be processed can then be determined from the time point of maximum intensity in the cycle.

[0110] The cyclic change or adjustment of the focal length of the variable focal length lens 19 is... Figure 1 The relationship between the cyclic focal length variation of the variable focal length lens 19 and the occurrence of the maximum intensity is symbolically represented by a sawtooth curve in the lens control unit 42. Figure 1 The dashed line is used to schematically illustrate the relationship between the sawtooth curve of the lens control unit 42 and the intensity curve with time coordinate t shown in the evaluation unit 41.

[0111] The measurement light, separated by the perforated mask 60, enables simultaneous acquisition of distance measurement data at multiple locations on the surface of the workpiece 4. Specifically, the measurement light reflected from the workpiece also passes through the holes 61 of the perforated mask 60 via coupling point 17 into the optical fiber 16, allowing it to be detected by the photodetector 9. The light intensity detected by the photodetector 9 corresponds to the total intensity of the light reflected from all measurement points collected through all holes 61 of the perforated mask 60, resulting in a physical average of the intensity differences between the light reflected from different points due to the optical arrangement. The physical average of the different light intensities detected by the different holes 61 of the perforated mask 60 significantly simplifies the evaluation of the measurement data, as distance determination does not necessarily have to be performed individually for each location. Instead, for all locations generated by the perforated mask 60, the distance may have already been determined using the physically averaged distance measurement data, specifically the intensity data.

[0112] Due to the arrangement of the concave and convex lenses 80, the light reflected from the surfaces 81 and 82 of the concave and convex lenses 80 can enter the optical fiber 16 via the optical coupling point 17 and can be detected by the photodetector 9.

[0113] Specifically, when light rays emitted from the variable focal length lens 19 strike one of the two surfaces 81 and 82 of the concave-convex lens 80 perpendicularly, the maximum proportion of light from the corresponding surface 81 or 82 of the concave-convex lens 80 is reflected back into the optical fiber 16 by the variable focal length lens 19. This beam configuration can therefore be detected by the corresponding intensity peaks of the reflected light, each of the two surfaces 81 and 82 of the concave-convex lens 80 causing its own intensity peak.

[0114] In some embodiments, the concave and convex lenses are sized such that peaks appear at the beginning and end of repetitive time cycles during the tuning of the variable focal length lens 19. The position of each of the two peaks always corresponds to a constant value of the focal length of the variable focal length lens 19 and therefore to the same distance. The relationship between the peaks and the distance value can change over time due to temperature variations. The tunable lens has a significant effect such that the relationship between the control value of the variable focal length lens 19 and the focal length can change with temperature variations. Since the intensity peaks caused by the concave and convex lenses 80 each appear at the same focal length of the variable focal length lens 19, the relationship between the variable focal length lens 19 and the time process and distance can be precisely calibrated based on these peaks. This is because the concave and convex lenses 80 have negligible temperature dependence compared to the variable focal length lens 19.

[0115] Through the circular aperture 83 at the center of the concave-convex lens 80, the measuring light passes through the lens 80 undisturbed, allowing only peripheral rays to be reflected back by the lens 80. By selecting the lens area or aperture size, the intensity of the reflection can be adjusted so that the intensity of the light reflected from the concave-convex lens 80 is high enough to serve as a calibration signal, but not so high that the reflection from the lens obstructs the corresponding measuring signal or intensity signal of the measuring light reflected from the object to be processed. In some embodiments, the aperture 83 is sized such that the majority of the measuring light passes through the aperture 83 of the concave-convex lens 80 without reflection.

[0116] In some embodiments, an aperture is arranged downstream of a concave-convex lens 80, which is configured to allow an inner portion of the measuring light beam to pass through and to cut off an outer portion of the measuring light beam. In this way, specifically, the beam affected by the concave-convex lens 80 can be excluded from the measurement.

[0117] In some embodiments, the concave-convex lens 80 does not have a hole, and the concave-convex lens 80 includes a coating on at least one of two surfaces 81, 82. The corresponding thickness or reflectivity of the coating can be selected such that the measurement signal is not masked by the reflective components of the concave-convex lens. In some embodiments, the concave-convex lens 80 includes an anti-reflection coating, and the reflective components of the anti-reflection coating are less than 4% within the wavelength range of the measurement light.

[0118] In some embodiments, the concave-convex lens 80 includes both a circular hole 83 and a coating, and the size calibration of the circular hole 83 and the thickness of the coating can be selected to obtain a sufficiently strong calibration signal without masking or overly affecting the measurement signal.

[0119] Figure 2 Illustrate a perforated mask according to an embodiment.

[0120] Figure 2 The perforated mask 60 is in the form of substantially rectangular pores and includes a plurality of circular holes 61. In this embodiment, the circular holes 61 are substantially evenly distributed on the entire surface of the pores in a hexagonal grid. The distribution of the holes 61 in the hexagonal grid achieves a high density of holes, so that the measurement light can be divided into multiple parts by the perforated mask to obtain distance measurement data at multiple measurement points. At the same time, for a given density, when a hexagonal grid is selected, the distance between adjacent holes is the largest, so that the crosstalk between the holes is minimized.

[0121] Figure 3 Illustrate a perforated mask according to another embodiment.

[0122] Figure 3 The perforated mask 60 is similar to the perforated mask 60 in the form of pores and includes a plurality of holes 61. Compared with the perforated mask 60 in Figure 2 The holes 61 of the perforated mask 60 in Figure 2 are rectangular and are substantially evenly distributed on the entire surface of the pores in a checkerboard pattern. Figure 3 The filling degree of the perforated mask in

[0123] Figure 2 and 3 The perforated mask 60 illustrated in is preferably between about 30% and 70%, specifically about 50%, such that about 50% of the light incident on the perforated mask passes through the perforated mask.

[0124] As an alternative to the embodiments illustrated in Figure 2 and 3 The perforated mask can also be substantially circular. The circular perforated mask is particularly suitable for being precisely placed at the end of an optical fiber having a circular cross-section.

[0125] Figure 4 Illustrate a schematic side view of a concave-convex lens according to an embodiment.

[0126] If possible Figure 4 As clearly seen in the view, the concave-convex lens 80 includes a substantially spherical concave surface 81 and a substantially spherical convex surface 82. In the illustrated embodiment, the concave-convex lens 80 includes a central circular aperture 83.

[0127] Figure 5 illustrate Figure 4 A schematic top view of a concave and convex lens.

[0128] exist Figure 5 In the top view, the circular aperture 83 of the concave-convex lens 80 can be seen particularly clearly. As mentioned above... Figure 1 The specification states that the concave-convex lens 80 can have different shapes. Specifically, at least one of the two surfaces 81, 82 may include a coating. Furthermore, the size of the circular aperture 83 and / or the thickness or reflectivity of the coating can be selected such that the back reflections at the surfaces 81, 82 of the concave-convex lens 80 produce a calibration peak of sufficient intensity without obscuring the measurement signal or impairing the distance measurement.

[0129] Figure 6 Possible beam paths in a section of the ranging device according to an embodiment are illustrated schematically.

[0130] Figure 6 The sections described herein include Figure 1 The coupling point 17 of the variable focal length lens 19, the concave-convex lens 80 and the optical fiber 13 described herein.

[0131] The long arrow pointing away from the optical coupling point 17 indicates the measurement beam emitted from the optical coupling point 17, which is radiated through the variable focal length lens 19 and also partially through the concave-convex lens 80. The arrows returning from the concave-convex lens 80 to the optical coupling point 17 indicate the light rays reflected from the concave surface 81 or the convex surface 82, respectively. Due to the substantially spherical curvature of surfaces 81 and 82, the reflected light rays are bound to the respective focal points.

[0132] exist Figure 6 In the case described, the light reflected from the concave surface 81 of the concave-convex lens 80 is focused at the light exit surface of the light coupling point 17, while the light reflected back from the convex surface 82 of the concave-convex lens 80 has a focal point higher than the light entry surface or the light coupling point 17. The described beam path can, specifically, appear at a specific focal length of the variable focal length lens 19.

[0133] Figure 7 Illustrative explanation based on Figure 6 Another possible beam path in the segment.

[0134] Figure 7The beam path basically corresponds to Figure 6 The beam path described in [the document]. (And / or] Figure 6 Compared to the situation described in the previous section, the variable focal length lens 19 has a different focal length value, so that neither of the two reflected beams is bound to the optical coupling point 17.

[0135] Figure 8 Illustrative explanation based on Figure 6 Another possible beam path in the segment.

[0136] When the light reflected from 82 of the concave-convex lens 80 is focused at the light exit surface of the light coupling point 17, and the focal point of the light reflected from the concave surface 81 of the concave-convex lens 80 is lower than the focal point from the light input surface or the light coupling point 17, Figure 8 The beam path described corresponds to the focal length of the variable focal length lens 19.

[0137] exist Figure 6 , 7 The possible ray configurations of the measuring light shown in Figure 8 illustrate the operation of the concave-convex lens 80. For example, when the variable focal length lens 19 is cyclically tuned, the focal length will periodically cycle through all values ​​between the minimum and maximum focal lengths, and in doing so, Figure 6 , 7 The light configuration described in section 8 can occur periodically. When the light beams reflected back by the concave-convex lens 80 are not focused at the optical coupling point 17, Figure 7 The beam configuration described herein, or similar beam configurations, can appear in various settings of the variable focal length lens 19. Conversely, Figure 6 and 8 The beam configuration described herein can occur only at very specific focal length values ​​of the variable focal length lens 19. Because the light reflected from surfaces 81 and 82 of the concave-convex lens 80 is focused at the optical coupling point 17 of the fiber 13, a greater proportion of the light reflected from the concave-convex lens 80 is coupled to the optical coupling point 17 of the fiber 13 compared to other cases. Figure 6 and 8 The optical coupling point in the beam configuration described herein. This increase in the amount of coupled light can be detected by a corresponding increase in light intensity detected by a photodetector. The corresponding intensity peak can be detected by a photodetector, for example, by... Figure 1 The photodetector 9 in the arrangement detects and uses it as a calibration peak for calibrating the ranging device 7. Specifically, the time position of the corresponding intensity peak can be used to infer the corresponding focal length of the variable focal length lens 19 or the corresponding measurement distance of the ranging device 7.

[0138] Figure 6 , 7The section described in section 8 does not have the perforated mask 60. Therefore, when the perforated mask 60 is used to split the measurement light into several parts and to obtain distance measurement data from different positions, such as those arranged between the coupling point 17 and the variable focal length lens 19, Figure 6 , 7 The above explanation regarding the operation of the concave and convex lens 80 in section 8 also applies.

[0139] Figure 9 This illustrates how the intensity of light reflected from the concave and convex lenses changes over time.

[0140] Specifically Figure 9 illustrate Figure 6 , 7 The time dependence of the measured light intensity in the arrangement described in section 8, wherein the intensity of a portion of the light reflected back by the concave-convex lens 80 and the workpiece 4 is measured during the tuning cycle, the light being coupled to the optical fiber 16. Here, the tuning cycle corresponds to the progression from the minimum drive value to the maximum drive value, and vice versa. Time t and intensity I in Figure 9 The values ​​are expressed in arbitrary units. For certain time values, the time dependence of intensity I(t) shows different intensity peaks or calibration peaks. Specifically, curve I(t) includes a left peak (a), a right peak (c), and a slightly wider intermediate peak (m). When the reflection from the concave surface 81 of the concave-convex lens 80 is focused at the optical coupling point 17 of the optical fiber 16 and thus enters the optical fiber 16 in a focused manner, the left peak (a) corresponds to... Figure 6 The beam configuration described herein. Between the two peaks (a) and (c), when the optical coupling point 17 is located between the two focal points of the light reflected from the concave surface 81 and the convex surface 82 of the concave-convex lens 80, a beam configuration occurs. Figure 7 The beam configuration described herein. In this case, reflections from the concave surface 81 and the convex surface 82 cannot be properly coupled to the fiber 16. In this interval, a peak (m) appears, which originates from the light reflected from the workpiece 4 and allows for the determination of the distance to the workpiece 4 (measurement peak). When the reflection from the convex surface 82 of the concave-convex lens enters the fiber 16 in a bundled manner at the optical coupling point 17, the right peak (c) corresponds to Figure 8 The beam configurations described herein. Specifically, the peaks (a) and (c) at the beginning and end of the depicted cycle, respectively, each have well-defined temporal positions, allowing them to serve as the basis for precise calibration of the rangefinder. Based on the characteristic processes of the intensity curves, peaks (a) and (c) can be easily identified and assigned to the corresponding beam configurations.

[0141] Figure 10 An apparatus for controlled machining of a workpiece according to another embodiment is illustrated schematically. Figure 10 Device 1 basically corresponds to Figure 1 The apparatus 1 described herein, but instead of an optical fiber coupler, includes a beam splitter 90 configured to couple measurement light through the light exit end 91 of the first optical fiber 10 and to couple measurement light reflected back from the workpiece 4. The measurement light coupled through the beam splitter 90 can be coupled to the light entry end 92 of the second optical fiber 13 for detection by a photodetector. The light exit end 91 of the first optical fiber 10 and the light entry end 92 of the second optical fiber 13 are confocally arranged. By using the beam splitter, the interference stray light effect that occurs in the optical fiber coupler can be avoided. In some embodiments, the beam splitter 90 is configured as a beam splitter cube. The beam splitter cube is robust and has low scattering loss.

[0142] In some embodiments, the device 1 having a beam splitter 90 includes at least one perforated mask.

[0143] exist Figure 10 In the example described herein, device 1 includes two substantially identically formed perforated masks 60, one perforated mask 60 being connected downstream of the light emitting end 91 of the first optical fiber 10 and the second perforated mask 60 being connected upstream of the light entering end 92 of the second optical fiber 13. The perforated masks 60 are disposed directly at the optical fiber ends of the first optical fiber 10 and the second optical fiber 13.

[0144] The perforated mask 60 can be similar to that in Figure 1 , 2 The perforated masks described in section 3 and above. The perforated masks 60 are arranged and aligned such that the holes 61 (not shown) of the two perforated masks 60 are confocally aligned with each other.

[0145] Figure 11 A flowchart illustrating a method for controlled machining of a workpiece according to an embodiment.

[0146] The method 100 for controlled machining of a workpiece includes several steps, which may be performed in different orders and repeated when necessary. This can be achieved, for example, by means of... Figure 1 The method is performed by device 2.

[0147] In step 110, the laser beam is focused to create a laser focal point at the target location on the workpiece to be processed. Specifically, the focusing of the laser beam can be performed by a laser aiming optics to specifically focus the laser beam at the target location on the workpiece to be processed. The focusing of the laser beam in step 110 can, specifically, be performed at low laser power, such that no material processing or only slight material processing is performed on the workpiece 4 in step 110. The laser beam can also be focused by means of, for example, an auxiliary laser focusing device, the beam of which is coupled collinearly to the beam path of the laser beam, for example, via a deflector plate. A galvanometer scanner with two rotatable galvanometers can be used as a laser aiming optics or scanner.

[0148] In step 120, optical distance measurement data is acquired using an optical ranging device to determine the distance between the target position of the workpiece to be processed and the laser aiming optics or a reference point or reference plane of the laser aiming optics. The ranging device can be configured as an optical confocal ranging device having a measurement source for generating measurement light, specifically broadband measurement light in the near-infrared spectral range, and having a variable focal length measurement light optics, specifically a variable focal length lens. The method may include changing the focal length of the variable focal length measurement light optics over time to acquire distance measurement data at different focal length values ​​of the variable focal length measurement light optics.

[0149] The acquisition of distance measurement data may specifically include the acquisition of the intensity of the measuring light reflected back from the workpiece, so that the distance is determined based on the intensity, specifically based on the intensity of the measuring light reflected back from the workpiece over time.

[0150] In step 130, the workpiece to be processed is positioned relative to the laser focus based on the acquired distance measurement data. In some embodiments, the laser is refocused as an alternative to or supplement to positioning the workpiece.

[0151] In step 140, a focused laser beam is used to process the target position of the workpiece to be processed.

[0152] In some embodiments, changing the focal length of the variable focal length measuring optics over time includes tuning, specifically cyclically tuning the focal length of the variable focal length measuring optics to acquire distance measurement data at different focal lengths of the variable focal length measuring optics.

[0153] Specifically, variable focal length optical elements can be used, specifically variable focal length lenses, to perform the focal length change of variable focal length measurement optics.

[0154] The measurement cycle can typically last 25 ms. During the measurement cycle, the optical power of the variable focal length lens can be tuned, for example, within a range of + / -13 diopters, wherein the focus of the measurement light can be shifted axially or along the optical axis of the measurement light optics by approximately + / -7 mm.

[0155] By using the known relationship between cycle time and the position of the focus, the distance to the workpiece to be processed can be determined using the maximum intensity.

[0156] In order to determine the relationship between cycle time and distance, in some embodiments, calibration measurements are performed specifically before laser processing.

[0157] Figure 12 An apparatus for controlled machining of a workpiece according to another embodiment is illustrated schematically. Figure 12 Device 1 basically corresponds to Figure 10 The apparatus described herein, however, further includes a photodetector 161 by which the process light generated by the laser 2 used to process the workpiece can be detected.

[0158] In addition, according to Figure 12 The device 1 includes a filter 162 with wavelength-dependent reflectivity, which is configured to reflect process light within a specific spectral range but not laser light. Additionally, the filter 162 is configured to transmit substantially all measurement light, such that the measurement is unaffected by the filter.

[0159] The process light generated by laser 2 during workpiece processing reaches filter 162 via laser aiming optics 5 and measuring optics. It is reflected by filter 162 and guided to beam splitter 90, which in turn reflects the process light and guides it to photodetector 161. Due to the reflective properties of filter 162, laser light reflected or scattered by workpiece 4 and returning to filter 162 via laser aiming optics 5 is not guided to photodetector 161.

[0160] Process light is detected when the distance at which the laser is optimally focused on the workpiece is determined. When the light source 8 used for measuring light is disconnected, this ensures that neither the measuring light nor the laser is detected by the photodetector 161 and is not misinterpreted as process light.

[0161] In some embodiments, photodetector 161 only checks for the presence of process light but does not provide location information about the location where the process light is initiated. For this reason, the process light does not need to be focused on photodetector 161. This, in turn, facilitates structural implementation because the precise position of photodetector 161 is not critical, and therefore, adjustment of the photodetector is unnecessary.

[0162] As Figure 12In an alternative to the embodiment described herein, the perforated mask 60 may have a partially reflective layer, such that the perforated mask 60 acts as a reflective filter that reflects only the process light, but not the laser and measurement light. In this embodiment, the additional component in the form of filter 162 can thus be omitted.

[0163] In some embodiments, the process light is detected by photodetector 9. In this embodiment, filter 162 is capable of transmitting both process light and measurement light, but not laser light. When the measurement light source 8 is disconnected, photodetector 9 can therefore be used to detect the process light.

[0164] Although at least one exemplary embodiment has been shown in the foregoing description, various changes and modifications can be made. The foregoing embodiments are merely examples and are not intended to limit the scope, applicability, or configuration of this disclosure in any way. Rather, the foregoing description provides a plan for those skilled in the art to implement at least one exemplary embodiment, wherein many changes can be made to the function and arrangement of the elements described in the exemplary embodiments without departing from the scope of protection of the appended claims and their legal equivalents.

[0165] Reference Symbol List

[0166] 1 device

[0167] 2. Laser

[0168] 3. Laser beam

[0169] 4. Workpiece

[0170] 5. Laser aiming optics

[0171] 6. Target location

[0172] 7. Distance measuring device

[0173] 8. Measuring light source

[0174] 9. Photodetector

[0175] 10 First Fiber Optic

[0176] 11 First Connection Point

[0177] 12 Fiber Optic Couplers

[0178] 13 Second optical fiber

[0179] 14 Second Connection Point

[0180] 15 Third Connection Point

[0181] 16 Third optical fiber

[0182] 17 Optical coupling points

[0183] 18 Collimating Lenses

[0184] 19. Variable focal length lens

[0185] 30 Deflection plate

[0186] 31 Deflection plate

[0187] 32 cameras

[0188] 33 Collimating Lens

[0189] 40 Evaluation Control Unit

[0190] 41 Evaluation Unit

[0191] 42 Lens Control Unit

[0192] 43 Positioning Control Unit

[0193] 44 signal lines

[0194] 45 Lens control line

[0195] 46 Positioning control lines

[0196] 47 Positioning device

[0197] 50 Focusing Lens

[0198] 51. Mirrors

[0199] 60 Perforated Mask

[0200] 61 holes

[0201] 80 Concave-convex lens

[0202] 81 Concave surface

[0203] 82 Convex Surface

[0204] 83 Circular Holes

[0205] 90 beam splitter

[0206] 91 End of the first optical fiber

[0207] 92 End of the second optical fiber

[0208] 100 methods

[0209] 110 Focus

[0210] 120 Acquire distance measurement data

[0211] 130 Positioning

[0212] 140 processing

[0213] 161 Photodetector

[0214] 162 Filter

[0215] A optical axis

[0216] F Focus

[0217] H Measurement range

[0218] O Zero plane

[0219] T time coordinate

[0220] X, Y, Z spatial coordinates

Claims

1. A method for controlled machining of a workpiece, the method comprising: - By means of a laser aiming optics (5), the laser beam (3) is focused to generate a laser focus (F) at the target position (6) of the workpiece (4) to be processed. -Distance measurement data is acquired by means of an optical ranging device (7) to determine the distance between the target position (6) of the workpiece (4) to be processed and the laser aiming optics (5), and - The focused laser beam (3) is used to process the target position (6) of the workpiece (4) to be processed. Its features The ranging device (7) is configured as an optical confocal ranging device having a measuring light source (8) for generating measuring light and having a variable focal length measuring light optics (19), wherein the method includes changing the focal length of the variable focal length measuring light optics (19) over time to acquire distance measurement data at different focal length values ​​of the variable focal length measuring light optics (19), and wherein process light generated during the processing of the workpiece (4) is detected by a photodetector (161), wherein the variable focal length measuring light optics (19) includes a variable focal length lens (19).

2. The method according to claim 1, wherein the distance between the laser focus (F) and the workpiece (4) is variable, and the presence of process light is recorded according to the distance between the laser focus (F) and the workpiece (4), wherein the distance is determined by means of the ranging device (7).

3. The method according to any one of claims 1 or 2, wherein the power of the laser beam (3) is varied, and a critical power is determined for the first appearance of the process light.

4. The method according to claim 3, wherein the power of the laser beam (3) varies with different distances between the workpiece (4) and the laser focus (F), and for each distance, the critical power is determined at the first appearance of the process light.

5. The method according to any one of claims 1 or 2, wherein the method further comprises positioning the workpiece (4) relative to the laser focus (F) based on the acquired distance measurement data.

6. The method according to any one of claims 1 or 2, wherein acquiring distance measurement data includes detecting the intensity of measurement light reflected from the workpiece (4), and wherein the distance is determined based on the intensity of the measurement light reflected from the workpiece (4) over time.

7. The method according to any one of claims 1 or 2, wherein changing the focal length of the variable focal length measuring optical optics (19) over time includes tuning the focal length of the variable focal length measuring optical optics (19) to acquire the distance measurement data at different focal lengths of the variable focal length measuring optical optics (19).

8. The method of claim 7, wherein the method further comprises performing a calibration measurement to determine a relationship between cycle time and distance, wherein the calibration measurement comprises detecting reflections from a concave-convex lens (80) disposed downstream of the variable focal length measuring optical device (19).

9. The method according to any one of claims 1 or 2, wherein the acquisition of the distance measurement data is performed at several measurement points at the target location (6).

10. The method of claim 9, wherein the acquisition of the distance measurement data at a plurality of measurement points is performed sequentially within a measurement cycle, wherein the measurement points are arranged along the scanning path at the target location (6).

11. The method according to claim 10, wherein the shape of the scanning path is a circle surrounding the target position (6) of the workpiece (4) to be processed or a spiral centered on the target position (6) of the workpiece (4).

12. The method of claim 9, wherein the acquisition of the distance measurement data at a plurality of measurement points is performed substantially simultaneously, and wherein the determination of the distance is based on physical average distance measurement data.

13. The method according to claim 12, wherein the measurement light is split into multiple measurement light portions by means of at least one perforated mask (60) having a plurality of holes (61) to simultaneously acquire the distance measurement data at a plurality of measurement points.

14. The method of claim 13, wherein the portion of the measurement light is simultaneously detected using a shared photodetector.

15. An apparatus for controlled machining of a workpiece, the apparatus comprising: - A laser source (2), which is used to generate a laser beam (3) for processing the workpiece (4) to be processed. - A laser aiming optics (5) for focusing the laser beam (3) onto a laser focal point (F) at a target position (6) on the workpiece (4). - A ranging device (7) for determining the distance between the target position (6) of the workpiece (4) to be processed and the laser aiming optics (5) based on distance measurement data acquired by the ranging device (7). - Positioning device (47), which is used to position the workpiece to be processed relative to the laser focus (F), and - An evaluation control unit (40) configured to evaluate the acquired distance measurement data and control the positioning device (47) based on the acquired distance measurement data. Its features The ranging device (7) is configured as an optical confocal ranging device having a measuring light source (8) for generating measuring light and having a variable focal length measuring light optics, in such a way that the focal length of the variable focal length measuring light optics can change over time so as to acquire the distance measurement data at different focal length values ​​of the variable focal length measuring light optics, wherein the process light generated during the processing of the workpiece (4) can be detected by a photodetector (161), wherein the variable focal length measuring light optics (19) includes a variable focal length lens (19).

16. The apparatus of claim 15, wherein the ranging device (7) includes a first photodetector (9) for detecting the intensity of the measuring light reflected from the workpiece (4), and is configured in such a way that the distance can be determined based on the detected intensity of the measuring light reflected from the workpiece (4) over time.

17. The apparatus of claim 15, wherein the apparatus includes a filter (162) having wavelength-dependent reflectivity, the filter being configured to reflect process light in a specific spectral range while transmitting substantially all of the measurement light.

18. The apparatus of claim 15, wherein the measuring light source (8) is capable of being turned on and off, and the first photodetector (9) is configured to detect the presence of process light when the measuring light source is turned off.

19. The apparatus of claim 15, wherein the measuring light source (8) is configured as a broadband infrared light source.

20. The apparatus of claim 15, wherein the focal length of the variable focal length measuring optical device (19) is tunable.

21. The apparatus according to claim 15, wherein the variable focal length measuring optical optics (19) is arranged in the divergence portion of the imaging system of the ranging device (7).

22. The apparatus of claim 15, wherein the apparatus (1) comprises at least one perforated mask (60) having a plurality of holes (61) for splitting the measurement light into a plurality of portions of measurement light.

23. The apparatus of claim 22, wherein the apparatus (1) comprises an optical fiber (16) having an optical coupling point (17) for coupling into and out of the measurement light, and wherein the at least one perforated mask (60) is disposed at the optical coupling point (17).

24. The apparatus of claim 23, wherein the perforated mask (60) has a partially reflective layer such that the perforated mask (60) acts as a reflective filter that reflects only the process light, but not the laser light and the measurement light.

25. The apparatus according to any one of claims 23 or 24, wherein the apparatus comprises a first optical fiber (10) having a light emitting end (91) and a second optical fiber (13) having a light entering end (92), and wherein a first perforation mask (60) is disposed at the light emitting end (91) and a second perforation mask (60) is disposed at the light entering end (92).

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