Inspection apparatus and inspection method for detecting anomalies of optical elements of an additive manufacturing device

Abstract

The invention relates to an inspection apparatus (5) and an inspection method for examining an optical element (6) with respect to an anomaly (7), for use in an additive manufacturing device (1) for manufacturing a three-dimensional workpiece. The optical element (6) is disposed along an optical beam path formed by the irradiation system (8), between an irradiation source (10) of the irradiation system (8) and the irradiation plane (4). An illumination device (12) has at least one illumination source (13), which is configured such that it emits illumination beams (14) that generate at least one illumination pattern (15) on the optical element (6). A sensing device (16) is configured such that it senses a reflected beam which comprises at least a part of the illumination beams (14) that is reflected by the optical element (6). A control unit (18) is configured such that the illumination pattern (15) on the optical element (6) can be specified and that the control unit temporarily stores sensing data (20) which comprises data from the sensing device (16). The control unit (18) is also configured such that the sensing data (20) is recorded during illumination of the optical element (6) with different illumination patterns on an optical surface (11) of the optical element (6). Thus, the anomaly (7) of the optical element (6) can be presented as an optical anomaly feature (21) in the sensing data (20).

Description

[0001] Inspection device and inspection method for detecting anomalies of optical elements of an additive manufacturing facility

[0002] The invention relates to an inspection device and an inspection method for inspecting an optical element for an anomaly of the optical element for use in an additive manufacturing device for producing a three-dimensional workpiece by irradiating raw material powder layers in an irradiation plane with a processing beam emitted by an irradiation system. The optical element is arranged along a beam path between an irradiation source of the irradiation system and the irradiation plane. The inspection device comprises an illumination device, a detection device, and a control unit. The illumination device comprises at least one illumination source configured to emit illumination beams that generate at least one illumination pattern on the optical element.The detection device is configured to detect a reflected beam comprising at least a portion of the illumination beams reflected by the optical element. The control unit is configured to predetermine the illumination pattern on the optical element and to temporarily store detection data comprising data from the detection device.

[0003] The inspection device and the inspection method are particularly designed for use in the additive manufacturing facility. The optical element is particularly designed for use in the additive manufacturing facility. The additive manufacturing facility is particularly designed for producing the three-dimensional workpiece by irradiating raw material powder layers in the irradiation plane with the processing beam emitted by the irradiation system. The detection device is particularly designed to detect and / or generate the detection data. The control unit is particularly designed to control the illumination device such that the illumination device generates the at least one illumination pattern on the optical element.

[0004] Powder bed fusion is an additive layering process with which powdered, particularly metallic and / or ceramic, raw materials can be processed into three-dimensional workpieces with complex shapes. A layer of raw material powder is applied to a carrier within an irradiation plane and, depending on the desired geometry, is irradiated with electromagnetic radiation (e.g., laser radiation or particle radiation) in a location-selective manner depending on the desired geometry of the workpiece to be produced. The electromagnetic radiation penetrating the powder layer heats and thus melts or sinters the raw material powder particles. Further layers of raw material powder are then successively applied to the already irradiated and solidified layer on the carrier until the workpiece has reached the desired shape and size.Powder bed fusion can be used for the production of prototypes, tools, spare parts, high-quality components for the automotive or aerospace industries, or for medical products. Examples of powder bed fusion processes include selective laser melting, selective laser sintering, and electron beam melting.

[0005] Additive manufacturing systems for producing one or more workpieces using the above-mentioned method are known from the prior art. For example, European patent applications EP 2 961 549 A1 and EP 2 878 402 A1 describe an additive manufacturing system for producing a three-dimensional workpiece using selective laser melting technology. Furthermore, the system comprises an irradiation system equipped with a radiation source, in particular a laser source, and an optical system. The optical system serves to selectively guide a processing beam generated by the radiation source over the raw material powder layers applied to the carrier, depending on the geometry of the workpiece to be produced.When constructing a three-dimensional workpiece by selectively irradiating the powder layers applied to the carrier, the radiation energy introduced into the raw material powder causes the powder particles to melt and / or sinter.

[0006] The optical elements in a beam path of an additive manufacturing facility described above within an irradiation system and / or optical system are exposed to high laser powers ranging from a few hundred watts to several kilowatts. The processing beam emerging from the irradiation system, e.g., laser radiation, is collimated to a specific raw beam diameter by collimating lenses, directed by deflecting mirrors within the irradiation system, and focused by focusing lenses. A high radiation intensity is generated at the point of impact of the processing beam on the respective optical elements. The radiation intensity describes a surface power density and is calculated as power per unit area. The greater the power for the same area, the greater the intensity, and vice versa.

[0007] Examples of optical elements in a beam path of the additive manufacturing equipment described above for the additive production of workpieces include protective screens, protective windows, coupling screens, coupling glasses, coupling windows, beam entry glasses, lenses, or mirrors. Protective screens or protective glasses generally serve to keep the optical elements arranged in the irradiation system in a clean environment and to protect them from process byproducts, such as process fumes or powder splash particles that arise during the beam melting process. When the additive manufacturing equipment is used as intended, these optical elements are arranged within the beam path of the processing beam and are exposed to the processing beam during operation of the additive manufacturing equipment.

[0008] It is particularly important to use optical elements that are free of anomalies. Anomalies include, for example, dirt or contamination on the optical element, such as dust particles, lint, gunk, or other deposits on the optical surface. Anomalies also include burns, depressions, elevations, damage, or irregularities inside or outside the optical element. It is particularly important to carefully install the optical elements in a clean and dust-free environment. Foreign bodies such as dust particles or lint, once incorporated into the installed irradiation system and / or optical system, can become deposited on the optical surface of the protective glass.If the optical element is exposed to laser power, the laser radiation can be absorbed by the foreign bodies. In the worst case, this can cause both the anomaly and the optical element to heat up, and the resulting thermal heating can destroy the optical element. Heating of the optical element can also cause a so-called thermal lens to form. The change in the refractive index within the material of the optical element can lead to a shift in the focus position of the processing beam. In the worst case, this can change the beam diameter of the processing beam within the irradiation plane, which leads to a change in the radiation intensity within the irradiation plane and affects the process stability of the melting process.

[0009] Furthermore, the cleanliness of the optical element for coupling the laser radiation into the process chamber is an important criterion for the reproducible and safe operation of an additive manufacturing facility. Such an optical element, often referred to as a beam entrance glass, is typically located between the optical unit and the process chamber or the powder bed surface or the irradiation plane, as seen in the beam propagation direction. The beam entrance glass is positioned so that a first surface of the protective glass faces the irradiation plane and a second surface of the protective glass faces the irradiation system. Furthermore, a focused beam, i.e., a beam converging in the beam propagation direction, typically passes through the beam entrance glass.This means that the beam diameter of the laser beam impinging on the first surface or the second surface of the protective glass is smaller than the raw beam diameter emerging from the collimation optics. Thus, the protective glass on the first surface and / or the second surface in the area of ​​the impact point is exposed to a high intensity of laser radiation. To reduce the risk of thermal damage to the protective glass at this impact point, the protective glass must be ensured to be clean and free of anomalies before starting a construction job.

[0010] Depending on the ambient conditions and the installation location of the optical elements, it can be difficult to check the protective glass for any anomalies. The degree of visibility of the anomaly is highly dependent on the lighting situation and / or the lighting arrangement relative to the camera arrangement. In particular, the lighting conditions such as lighting brightness, lighting color, lighting direction, ambient brightness and the orientation of the lighting source and the orientation of the camera play a significant role. To detect one or more anomalies within the optical element and / or on the optical surface of the optical element, the lighting can, for example, be adjusted so that the surface is illuminated from the side at the shallowest possible angle, so that the light reflected by the object's anomalies is captured by the camera as scattered light.Manual detection methods for inspecting optical elements are known, in which the optical elements are illuminated with a flashlight. A visual inspection of the protective glass for the presence of an anomaly is performed by manually illuminating the protective glass. The visibility of an anomaly within the optical element and / or on the optical surface of the optical element is highly dependent on the lighting situation. Since the examination result of a manual inspection is therefore also highly dependent on the respective operator performing the inspection, a manual inspection generally does not provide a reproducible statement, for example, regarding the degree of contamination or the type of anomaly in the optical element.

[0011] An advantageous lighting situation as described above is generally not possible for the inspection of optical elements arranged in hard-to-access areas of the process chamber and / or the irradiation system, since the available space does not allow such a camera and / or lighting arrangement.

[0012] The object of the present invention is to provide an inspection device and an inspection method with which a reproducible detection of anomalies present within the optical element and / or on the optical surface of the optical element is possible.

[0013] This object is achieved according to the invention in that the control unit is further configured such that the detection data is recorded on an optical surface of the optical element when the optical element is illuminated with different illumination patterns, such that the anomaly of the optical element can be represented as an optical anomaly feature in the detection data. The detection data is recorded in particular by the detection device while the optical surface of the optical element is illuminated with the different illumination patterns. In this case, in particular only a single illumination pattern is radiated onto the optical surface at any one time. The different illumination patterns are therefore radiated onto the optical surface in particular sequentially or at different times. For example, the different illumination patterns can scan the optical surface section by section.The optical anomaly feature can be detected, in particular, based on the acquisition data. The acquisition data can include a representation, in particular an image, of the optical anomaly feature.

[0014] The detection device can be designed to detect the illumination rays in one or more of the aforementioned wavelength ranges. The detection device can comprise an optical sensor configured as a camera, image sensor, photodiode, etc. A corresponding optical sensor can be configured, for example, as a CCD sensor, a CMOS sensor, etc., with which the illumination rays reflected by the optical element can be detected. The detection data detected by the detection device can be stored in the form of an image, a photograph, or signal data.

[0015] The at least one illumination source of the illumination device can be configured as a light-emitting illumination source, such as a light-emitting diode (LED), a laser diode, etc. Preferably, the illumination source is configured to emit light in the visible wavelength range as illumination beams. Alternatively, other wavelength ranges, such as the infrared wavelength range or the ultraviolet wavelength range, are also conceivable.

[0016] Furthermore, it may be advantageous for the illumination device to have a beam-shaping element, by which the illumination beams emitted by the illumination source are shaped into the illumination pattern. The illumination beams can be expanded, rectified, or focused, for example, by the beam-shaping element. Thus, the shape or size of the illumination pattern generated on the optical surface of the optical element can be adjusted in a particularly advantageous manner.

[0017] By generating different illumination patterns, the illumination beams are at least partially reflected by the areas of the optical element illuminated by the illumination pattern, so that they are detected by the detection device. As an optical anomaly feature, the illumination beams reflected by foreign bodies, such as dust particles or soot particles, can then be identified as brightness differences in the detection data. By generating different illumination patterns, the optical element can be illuminated with several different illumination directions. This also illuminates the anomaly of the optical element illuminated by the illumination pattern with the illumination beams.By generating the acquisition data with different illumination directions, the anomaly can be made visible by illuminating the anomaly with selected illumination patterns, whereas the anomaly may not be representable in further acquisition data. The anomaly may not be representable in such cases if the illumination device and / or the acquisition device are aligned in such a way that the reflected illumination rays cause a reflection that overlays the optical anomaly features. In other words, this is the case if the reflected illumination rays recorded by the acquisition unit in a first illumination pattern overlay the intensity of the illumination rays reflected at the anomaly.

[0018] Therefore, in an advantageous embodiment of the invention, the control unit is configured such that it breaks down the detection data into individual selection data and further processes only those selection data in which the anomaly is contained and representable as an optical anomaly feature. The determination of selection data containing the anomaly as an optical anomaly feature can be carried out by manually checking the detection data or the selection data. With a known orientation of the inspection device relative to the optical element, the determination of the selection data can be carried out manually for the first time, and upon repeated inspection of the anomaly, the selection data containing the anomaly as an optical anomaly feature is known. The determination of the selection data can thus be carried out particularly easily and quickly.

[0019] Alternatively, the acquisition data can be evaluated to determine the selection data by evaluating brightness values, intensity values, and so on to determine whether they exceed a specific, definable brightness threshold, intensity threshold, and so on. For this purpose, it can optionally be provided that the acquisition data be evaluated with data processing and data evaluation programs or with image processing programs and / or image evaluation programs with regard to brightness values, intensity values, and so on. This allows for a computer-based and / or automated evaluation of the acquisition data before the selection data is determined. This enables a particularly simple and rapid determination of the optical anomaly characteristics.

[0020] With a known and fixed arrangement and orientation of the illumination device relative to the detection device, it is possible, after manual and / or automated evaluation of the detection values, to predetermine the selection data suitable for displaying the anomaly. Depending on the selected orientation, only the areas of the optical surface illuminated with the illumination pattern are relevant as selection data. Therefore, it can optionally be provided that only a partial area of ​​the optical surface, for example, the area of ​​the optical surface illuminated with the illumination pattern, is recorded with the detection device. This enables particularly time-saving recording and resource-efficient intermediate storage of the detection data.

[0021] In the example of acquisition data recorded as multiple complete images, each complete image is divided into several sub-sections. The position and size of the sub-sections are selected so that they either contain an unfavorable lighting condition for analysis, such as a disturbing reflection that overlays the optical anomaly feature. Additional sub-sections may contain the optical anomaly feature and can be further processed to assess contamination of the optical element.

[0022] For example, the detection device can capture an image of the entire optical surface at each time the optical surface is irradiated with an illumination pattern and save this image. Each image can then be broken down into respective subsections, which then correspond to the selection data. The subsections can be selected depending on the respective illumination pattern. For example, each image is broken down into one or more first subsections and one or more second subsections, with an illumination pattern being visible in each first subsection, but not in any of the second subsections. It is then conceivable to further process only the first subsections, in particular only those of the first subsections in which an optical anomaly feature is recognizable.For example, all of the first partial sections can be combined to form an overall image, and all of the optical anomaly features can be identified based on the overall image. In order to obtain an overall overview of the anomalies of the optical surface of the optical element to be inspected, an advantageous implementation of the inventive concept provides that the control unit is further configured to combine the selection data into an evaluation data set. The evaluation data set thus shows the entire optical surface of the optical element, in which the anomaly is visibly represented as an optical anomaly feature. The multiple partial sections containing the optical anomaly feature are combined to form an overall evaluation image, thereby generating an overall image of the optical surface with the anomalies present within the optical element and / or on the optical surface of the optical element.

[0023] An evaluation of the optical anomaly to determine the degree of contamination of the optical element can be carried out in subsequent evaluation steps such that the optical anomaly feature is evaluated with regard to the size of the optical anomaly feature, the number of optical anomaly features per unit area, and the type of optical anomaly feature. This can be done using known image processing methods and programs.

[0024] Each illumination pattern can be designed so that it does not cover the entire optical surface. The different illumination patterns differ particularly in the areas of the optical surface covered by the illumination patterns.

[0025] In order to achieve particularly advantageous illumination of the optical element, the invention can provide for the illumination beams to generate an illumination pattern with which the optical surface of the optical element is illuminated at least in sections. By illuminating the optical surface in sections, it is possible to avoid illumination beams being reflected from the non-illuminated areas of the optical surface, which would cause disruptive reflection. With a previously known arrangement of the illumination device relative to the optical surface, the area of ​​the optical surface illuminated by the illumination pattern can be predetermined. By means of an additional known arrangement of the detection device relative to the optical surface, the detection data can be evaluated in such a way that only the illuminated areas are evaluated.This allows for particularly simple evaluation of the optical surface with regard to the optical anomaly feature. By illuminating only sections of the optical surface, the amount of light emitted by the illumination beams onto the optical surface can be reduced. As a result, the amount of light reflected at the optical surface or transmitted through the optical element is also reduced. Advantageously, this also reduces the amount of light in the vicinity of the optical element under investigation due to reflection and / or transmission at the optical element.This allows for the reduction of disruptive reflections caused by reflected illumination beams, for example, on a process chamber wall or on an element of the irradiation system and / or optical system arranged in the background of the transparent optical element. An optical surface that contains no anomalies can be recorded as a dark optical surface in the acquisition data. An existing anomaly in the illuminated area of ​​the optical surface can thus be particularly well represented as an optical anomaly feature.

[0026] In order to design the illumination device in a particularly simple and cost-effective manner, the invention provides for the optical surface of the optical element to be fully illuminated by the illumination beams emitted by the illumination device. This eliminates the need for complex alignment of the illumination device relative to the optical element, allowing the inspection device to be installed particularly quickly and easily.

[0027] According to an advantageous implementation of the inventive concept, the detection device completely detects the optical surface of the optical element. This ensures that even edge areas of the optical element, where anomalies may be present, are reliably detected. This eliminates the need for complex alignment of the detection device to the areas of the optical surface illuminated by the illumination pattern.

[0028] The irradiation system containing the optical elements is typically assembled under clean and pure conditions, ensuring that no anomalies are trapped inside the irradiation system during assembly. Furthermore, the irradiation system is usually sealed gas-tight to protect the interior of the irradiation system from the ingress of, for example, dust particles from the ambient atmosphere. Due to its design, the optical surface of the optical element facing the irradiation system is generally no longer accessible from the outside and is therefore less exposed to the risk of an anomaly than the optical surface of the optical element facing away from the irradiation system.

[0029] For example, the invention provides for the inspection device to be designed such that the illumination device and the detection device are arranged on the same side of the optical element. Depending on the design of the additive manufacturing device and the arrangement of the optical elements within the irradiation system, access to the optical elements within an additive manufacturing device is often difficult or sometimes impossible, and in the exemplary case, only possible from an optical surface of the optical element facing away from the irradiation system.

[0030] In particular, the optical surface of an optical element, such as the beam entry glass for introducing the processing beam into the interior of the process chamber, is exposed to the risk of anomalies due to the process byproducts generated during the melting process, such as fumes, powder turbulence, or soot formation. Thus, in a particularly advantageous embodiment of the inspection device, it is arranged on the side of the optical element, the optical surface facing the irradiation plane or opposite the irradiation system.

[0031] It is also possible, and optionally provided according to the invention, for the optical beam path to form an optical axis, with an optical path of the illumination beams being arranged at an incline to the optical axis of the inspection device. This allows the illumination beams to be directed particularly easily into specific areas of the optical surface, so that the illumination pattern impinges on the optical surface depending on the inclined arrangement.

[0032] Advantageously, the invention also optionally provides for the at least one illumination source to be arranged offset perpendicularly to the optical axis. The distance between the at least one illumination source and the optical axis can be adjusted according to a set inclination of the illumination source and / or according to the selected working distance and / or according to the existing space conditions. This allows for particularly advantageous illumination of the optical element.

[0033] In an advantageous embodiment of the invention, the illumination beams can be individually and separately controlled in terms of their lighting properties, such as their intensity and / or wavelength. The lighting properties can advantageously be adjusted depending on the expected back reflections of the reflected illumination beams. The intensity and degree of the back reflections can vary depending on the reflection properties or transmission properties of the optical element. Accordingly, a lighting situation with minimal disruptive reflections can be achieved by adjusting the intensity and / or wavelength.

[0034] The illumination device can be controlled so that the illumination properties of the illumination beams differ between two or more of the illumination patterns.

[0035] Depending on the set lighting properties, such as the intensity of the illumination beams, the size of the area of ​​the selection data that is further processed can be adjusted or influenced. A set low intensity of the illumination beams can accordingly lead to low back reflection in certain areas, thus increasing the size of the selection data in which the anomaly can be represented as an optical anomaly feature and which is further processed.

[0036] Varying the wavelength of the illumination beams can be advantageously used to detect and differentiate between different types of anomalies. This allows anomalies on the optical element, such as smoke, spatter particles, soot, and so on, to be detected.

[0037] Advantageously, when using multiple illumination sources, a variation of the illumination properties of each individual illumination source can be adjusted separately in order to promote the desired effect with regard to generating the largest possible selection data.

[0038] Depending on the design of the optical element, it can be advantageous to illuminate the optical surface with different illumination patterns. On the one hand, the illumination pattern can be adapted to the shape of the optical element. Advantageously, the invention optionally provides for the illumination pattern to be point-shaped, strip-shaped, or tile-shaped. Thus, an optical element can be illuminated in regions or sections depending on its shape. Strip-shaped illumination illuminates the optical element in sections, so that the anomalies of the optical element are preferably contained in the illuminated regions, and these are further processed as selection data to form a selection data set. In addition, the anomaly can be displayed with a high contrast ratio on an optical surface that is only partially illuminated by the illumination pattern.

[0039] In an advantageous implementation of the inventive concept, the inspection device comprises at least one receiving element to which the illumination device and the detection device can be secured. Predetermined positions and configurations of the receiving elements allow for simple and rapid installation of the illumination device and the detection device within the inspection device. The receiving element can also be designed as a housing that at least partially surrounds the illumination device and the detection device. This provides protection for the optical elements enclosed by the housing.

[0040] An inspection of the optical elements used in an additive manufacturing facility can be performed at various times during assembly and / or operation of the additive manufacturing facility. The timing and necessity of the inspection depend on the type of optical element to be examined. For example, protective glasses of an irradiation system are inspected for the presence of anomalies after the protective glasses have been installed in the irradiation system. This can ensure that the optical elements installed in the irradiation system are free of anomalies before the irradiation system is installed on an optics carrier or before it is incorporated into the additive manufacturing facility, which restricts accessibility to the optical elements. Depending on accessibility, an inspection can also be performed after assembly in the additive manufacturing facility has been completed.

[0041] The beam entry glasses arranged in the process chamber ceiling are generally cleaned before the start of a construction job and / or after each cleaning of the beam entry glasses to monitor the cleaning process. To inspect the beam entry glasses, the invention can provide for the inspection device to be arranged within the process chamber in an area between the beam entry glasses and the irradiation plane. The process chamber housing could be designed such that a receptacle or a receptacle recess is provided in which the inspection device can be arranged at least in part, so that the inspection device is arranged outside the deflection areas of the deflected processing beams. The inspection device is arranged on the side of the optical element facing the irradiation plane.This allows for inspection of the optical surface, which is exposed to an increased risk of contamination from the byproducts generated during the melting process. Furthermore, by integrating the inspection device within the process chamber, the beam entry lenses can be inspected during a build job. For this purpose, the inspection process can advantageously be performed during the application of a raw material powder layer, during which the irradiation system is switched off, allowing the beam entry lenses to be inspected without pausing the build job.

[0042] Optionally, the inspection device according to the invention can also be designed as a portable inspection device that can be detachably arranged with the additive manufacturing device and / or the irradiation system. The inspection device can be designed such that it can be arranged within the process chamber at a position below the beam entry glasses and within the beam path of the one or more irradiation systems. Such an arrangement of the inspection device requires that the inspection device can be removed from the beam path again after the inspection of the optical elements. For this purpose, an advantageous embodiment of the inspection device according to the invention provides that the receiving element has a fixing means with which the receiving element can be detachably fixed to the additive manufacturing device and / or to the irradiation system.Detachable fastening devices, such as screws, clamping levers, clamps, bolts, or magnetic fasteners, can be used as fastening devices. For example, the inspection device can be designed such that it can be detachably secured to the carrier within the process chamber of the additive manufacturing device in the area of ​​the irradiation plane and below the beam entry glasses. The area of ​​the irradiation plane is generally easily accessible and reachable, allowing manual assembly and disassembly of the inspection device at a position within the irradiation plane. Advantageously, the receiving element is designed such that it can be brought into contact with a corresponding receiving element of the additive manufacturing device and / or the irradiation system.Centering or alignment of the inspection device can be achieved using known alignment means, such as centering pins, bolts, sleeves, mandrels, or rings. Thus, the inspection device can be moved into a predetermined position relative to the optical element in order to releasably secure the inspection device in the predetermined position using the fastening means.

[0043] Advantageously, the fixing means can optionally be configured such that the inspection device can be aligned in the predetermined position relative to the optical element and can be locked in a desired position and / or orientation. This enables rapid and reproducible insertion and alignment of the inspection device relative to the optical element within the process chamber and / or within the optical element.

[0044] The illumination device and the detection device can be positioned in the same pose relative to the optical element during irradiation of the optical element with two or more, in particular all, (e.g., immediately consecutive) illumination patterns. Thus, at least the illumination device and the detection device can be fixed in position relative to the optical element when recording detection data based on at least two illumination patterns.

[0045] In an exemplary embodiment, the inspection device is designed such that each illumination beam forming an illumination pattern, which is reflected by the optical element, in particular by the optical surface irradiated with the illumination pattern, and reaches the detection device, has an angle of incidence at the optical element that lies within a predetermined angle of incidence range and / or has a reflection angle that lies within a predetermined angle of reflection. The two angle ranges can be identical or different. Each angle range can lie between a minimum angle and a maximum angle, wherein the minimum angle is, for example, 15°, 10°, 5°, 4°, 3°, 2°, 1° or 0.5° and / or the maximum angle is, for example, 50°, 45°, 40°, 35°, 30°, 25°, 20°, 15°, 10°, 5°, 4°, 3°, 2° or 1°. The difference between minimum angle and maximum angle can be 5°, 10°, 15°, 20° or 25°.It is conceivable that the illumination device and the detection device are moved (e.g. jointly) relative to the optical element (e.g. between irradiating the optical element with two successive irradiation patterns) to ensure that the illumination beams each have an angle of incidence that lies within the predetermined angle of incidence range and / or that the illumination beams reflected at the optical element have a reflection angle that lies within the predetermined angle of reflection range. For this purpose, the illumination device and the detection device can be arranged in the process chamber on a common movable holding device. The holding device can in particular be designed to align the illumination device and the detection device with precise positioning in several predefined positions (e.g. relative to the optical element).For example, the illumination device and the detection device can emit a first irradiation pattern onto the optical element in a first of these predefined positions and record corresponding detection data. After a (e.g., manual) transfer to a second of these predefined positions, they can emit a second irradiation pattern onto the optical element and, in turn, record corresponding detection data. It is conceivable that the illumination device is controlled in the same way in both predefined positions, i.e., emits the same light pattern, whereby the areas of the optical surface covered by the illumination beams differ due to the difference in position.

[0046] It is also conceivable for the illumination device to be moved relative to the detection device (e.g., between irradiating the optical element with two consecutive irradiation patterns) to ensure that the illumination beams each have an angle of incidence that lies within the predetermined angle of incidence range and / or a reflection angle that lies within the predetermined angle of reflection range. For this purpose, the illumination device and / or the detection device can each be arranged on a movable positioning device in the process chamber. The respective positioning device can, in particular, be designed to precisely align the illumination device or the detection device in several predefined positions (e.g., relative to the optical element).For example, the inspection device can emit a first irradiation pattern onto the optical element in a first of these predefined positions and record corresponding detection data. After a (e.g., manual) transfer to a second of these predefined positions, the inspection device can emit a second irradiation pattern onto the optical element and, in turn, record corresponding detection data. It is conceivable that the illumination device is controlled in the same way in both predefined positions, thus emitting the same light pattern. Due to the difference in the position of the inspection device, the areas of the optical surface covered by the illumination beams then differ.

[0047] It is of course also conceivable to use the inspection device in a first of the predefined positions to inspect one or more first optical elements (e.g. protective glasses), and to move the inspection device to a second of the predefined positions to inspect one or more second optical elements (e.g. further protective glasses), in particular using the holding device. Depending on the embodiment, the illumination device and the detection device can be repositioned together or separately. The repositioning can in turn ensure that the desired angular ranges are maintained. If the angular ranges are the same for each acquisition of the acquisition data (e.g. image recording), this makes the comparison of selection data (e.g. partial areas of different images) easier.

[0048] In an exemplary embodiment, the inspection device is stored in a construction cylinder which is designed to be coupled to the process chamber. In addition to the inspection device, other measuring devices and / or maintenance devices can also be stored in the same construction cylinder. In particular, the inspection device (e.g. together with the further measuring devices and / or maintenance devices) can be arranged on a mounting plate which is mounted axially displaceably in the construction cylinder. After the construction cylinder has been coupled to the process chamber, the mounting plate can be displaced in the direction of the process chamber by a drive system of the additive manufacturing device, for example until the mounting plate lies in the irradiation plane. The method described herein can then be carried out with the inspection device positioned in this way in the process chamber.The build plate can then be moved back, away from the process chamber, specifically downwards. This moves the inspection device from the process chamber back into the build cylinder. The build cylinder, with the inspection device inside, can then be detached and replaced with a build cylinder designed for the production of a three-dimensional workpiece. This approach has the advantage that the inspection device does not have to be manually brought into the process chamber, and the process chamber does not require a correspondingly large loading hatch for manual insertion of the inspection device.

[0049] The aforementioned problem is also solved by an inspection method for the visual representation of anomalies present on an optical surface of an optical element. The inspection method is intended for use in an additive manufacturing facility for producing a three-dimensional workpiece by irradiating layers of raw material powder applied within an irradiation plane with a processing beam emitted by an irradiation system. The optical element is arranged along an optical beam path formed by the irradiation system between an irradiation source of the irradiation system and the irradiation plane.The inspection method comprises the following steps: (i) illuminating the optical element to generate an illumination pattern on the optical surface of the optical element, wherein, in parallel with the illumination step (ii), a reflected beam is detected, which comprises at least a portion of the illumination beams reflected by the optical element, wherein (iii) the illumination pattern on the optical element is predeterminable, and (iv) acquisition data, which comprises data from the acquisition device, are temporarily stored. The acquisition data are recorded upon illumination of the optical element with mutually different illumination patterns on an optical surface of the optical element, such that the anomaly of the optical element can be represented as an optical anomaly feature in the acquisition data.

[0050] The method according to the invention can detect the anomaly contained in the optical element and / or on the optical surface of the optical element. The inspection method is preferably carried out before the additive manufacturing facility starts producing a build job. This allows the one or more beam entry glasses of the process chamber to be inspected individually or sequentially for the presence of an anomaly.

[0051] In an advantageous embodiment of the invention, the detection data is broken down into individual selection data, and only those selection data containing the anomaly as an optical anomaly feature are further processed. Furthermore, it is possible and optionally provided according to the invention for the selection data to be combined into an evaluation data set, so that the optical anomaly feature of the anomaly present within the optical element and / or on the optical surface of the optical element can be evaluated from the evaluation data set.

[0052] A system is further provided, which comprises the optical element and the inspection device. An additive manufacturing device for producing a three-dimensional workpiece by irradiating raw material powder layers with a processing beam is also provided, which device comprises the optical element and the inspection device.

[0053] The object posed at the outset is also achieved by an additive manufacturing device for producing a three-dimensional workpiece by irradiating raw material powder layers with a processing beam, wherein the additive manufacturing device comprises an inspection device according to one of claims 1 to 13. The inspection device is advantageously designed such that it is moved into the beam path before the start of the construction process, so that the inspection method according to the invention can be carried out. After completion of the inspection method, the inspection device is moved again and arranged outside the beam path of the processing beam, so that the beam path of the processing beam is cleared and the processing beam can impinge unhindered on the raw material powder layer applied in the irradiation plane.

[0054] Further advantageous embodiments of the invention are explained with reference to exemplary embodiments illustrated in the drawings. They show:

[0055] Fig. 1 is a schematic representation of a section of an additive manufacturing facility with the inspection device arranged within the process chamber,

[0056] Fig. 1a is a schematic representation of a section of a variant of the additive manufacturing device from Fig. 1 with a holding device for (re-)positioning the inspection device, Fig. 2 is a schematic representation of detection data recorded with the inspection device when illuminating the beam entry glass with different illumination patterns,

[0057] Fig. 3 is a schematic representation of an evaluation data set from combined selection data of the illuminated beam entry glass,

[0058] Fig. 4 is a schematic representation of the inspection device for inspecting the protective glass of an irradiation system in a first illumination situation,

[0059] Fig. 5 is a schematic representation of the inspection device for inspecting the protective glass of an irradiation system in a second illumination situation,

[0060] Fig. 6 is a schematic representation of detection data recorded with the inspection device when the protective glass is illuminated with all illumination sources and

[0061] Fig. 7 is a schematic representation of an evaluation data set from combined selection data of the illuminated protective glass.

[0062] Fig. 1 shows a schematic representation of a section of an additive manufacturing device 1 with an inspection device 5 arranged within a process chamber 2 and on a carrier 3 of the additive manufacturing device 1 within an irradiation plane 4.

[0063] The carrier 3 can be a build plate that is movably mounted in a build cylinder that can be coupled to the process chamber 2. It is therefore conceivable to store the inspection device 5 in a build cylinder in order to insert it into the process chamber 2 from below after coupling this build cylinder.

[0064] The inspection device 5 is arranged within the process chamber 2 for examining an optical element 6, which in the present case is designed as a beam entry glass 6a, with regard to one or more anomalies 7 of the optical element 6. The beam entry glass 6a is arranged in an optical beam path 9 formed by an irradiation system 8 between an irradiation source 10 of an irradiation system 8 and the irradiation plane 4. The beam entry glass 6a is aligned such that a first optical surface 11a of the beam entry glass 6a points in the direction of the irradiation plane 4 and a second optical surface 11b of the beam entry glass 6a points in the direction of the irradiation system 8. An illumination device 12 of the inspection device 5 has an illumination source 13 configured to emit illumination beams 14 that generate an illumination pattern 15 on the optical element 6. In the embodiment shown in Fig.In the embodiment shown in Figure 1, the illumination source 13 is designed as a video projector, with which the illumination beams 14 can be generated in a predeterminable illumination pattern 15, which illuminates the beam entry glass 6a on the first optical surface 11a in sections. A detection device 16 of the inspection device 5 is configured to detect a reflected illumination beam 17, which comprises at least a portion of the illumination beams 14 that is reflected by the optical element 6. A control unit 18 of the inspection device 5 is configured such that the illumination beams 14 are directed onto the optical surface 11 and the illumination pattern 15 is generated on the optical surface 11 of the optical element 6. The detection device 16 has a camera 19, which records the first optical surface 11a of the optical element 6 and generates detection data 20.The control unit 18 is configured to temporarily store the detection data 20, which includes data from the detection device 16. A recording of each illumination pattern 15 is taken and temporarily stored.

[0065] Fig. 2 shows a schematic representation of acquisition data 20 recorded with the inspection device 5 in the form of individual images. The acquisition data 20 were generated by illuminating the beam entry glass 6a with various illumination patterns 15. The illumination pattern 15 represents a strip-shaped illumination pattern 15, the strip width of which is reduced in each of the images shown in individual images (a) to (h). By reducing the strip width of the illumination pattern 15, the visibility of the anomaly 7, which can be represented as an optical anomaly feature 21, on the first optical surface 11a is increased. This is because only sectionally illuminating the optical surface 11 enables an interference-free recording of the optical surface 11 in the acquisition data 20 recorded by the acquisition device 16.Thus, on an optical surface 11 only partially illuminated by the illumination pattern 15, the anomaly 7 can be represented by the large brightness differences between the brightness of illumination rays 17 reflected by an anomaly 7 compared to the brightness of illumination rays 17 reflected from a clean area of ​​the optical surface 11. It can be advantageous if the angles of incidence and reflection of the illumination rays emitted onto the optical element and detected by the detection device lie within predetermined angular ranges (e.g., between 0° and 20° in each case) for each detection step, i.e., for each illumination pattern. In this case, the intensity of the reflected illumination rays received by the detection device can also lie within a preferred range.

[0066] It is possible that a fixed positioning of the inspection device 5 in the process chamber 2 while maintaining these conditions may result in only a portion of the optical surface 11 being illuminated by an illumination pattern and its reflected light being detected. To still enable a complete inspection of the optical surface 11, the position of the inspection device 5 in the process chamber 2 can be changed.

[0067] For example, the inspection device 5, as shown in Fig. 1A, is arranged on a holding device 31, which defines a plurality of predetermined positions of the inspection device 5, between which the inspection device 5 can be repositioned manually or by motor. The holding device 31 can be arranged on the carrier 3. For example, the holding device 31 comprises a fastening section fastened to the carrier 3 and a holding section movably coupled thereto between the predetermined positions (e.g., rotationally and / or translationally) and carrying the inspection device 5. For example, after inspecting a region of an optical element, the inspection device can be offset in the x-direction and / or rotated about a vertical axis in order to inspect the illumination and detection of another region of the optical element spaced apart in the x-direction.

[0068] Relocating the inspection device 5 is particularly advantageous for large-area optical elements or when inspecting multiple optical elements arranged at a distance. For example, the additive manufacturing device 1 can comprise multiple beam entry glasses 6a. Fig. 1A shows two beam entry glasses 6a as an example, which can be inspected after appropriate (re)positioning of the inspection device 5. It is understood that the manufacturing device 1 can comprise additional beam entry glasses 6a or other optical elements, which can then be inspected, in particular after appropriate (re)positioning of the inspection device 5.If the optical surfaces 11 to be inspected are close enough to each other, then repositioning of the inspection device 5 between the inspection of the individual optical surfaces 11 may not be necessary, in particular if the desired angular ranges can be maintained even with the position of the inspection device 5 remaining the same.

[0069] Fig. 3 shows a schematic representation of the evaluation data set 22, which was generated by combining selection data 23 of the illuminated beam entry glass 6a. The optical surface 11 of the beam entry glass 6a was illuminated section by section and sequentially with a striped illumination pattern 15, and the illuminated optical surface 11 was recorded with the recording device 16. After each recording, the striped illumination pattern 15 is offset perpendicular to the striped illumination pattern 15 by a distance of preferably the stripe width of the illumination pattern 15 in the indicated offset direction 24 in order to take another recording of the optical surface 11.In an alternative embodiment, the inspection device 5 can optionally be configured such that the strip-shaped illumination pattern 15 is continuously guided over the optical surface 11, and a recording of the optical surface 11 is performed at time intervals depending on the movement speed of the illumination pattern 15. Thus, the optical surface 11 of the beam entry glass 6a is illuminated sectionally in each recording and successively recorded in all areas of the optical surface 11. The control unit 18 (not shown in Fig. 3) is configured to break down the acquisition data 20 into individual selection data 23 and to further process those selection data 23 in which the anomaly 7 is contained as an optical anomaly feature 21. In the present case, those selection data 23 that correspond to the illuminated area of ​​the optical surface 11 are further processed.

[0070] Fig. 4 shows a schematic representation of the inspection device 5 for inspecting an optical element 6, which is designed as a protective glass 6b, of an irradiation system 8 in a first illumination situation. The protective glass 6b shown in Fig. 4 serves to shield an interior of the irradiation system 8 from an ambient atmosphere. For this purpose, the inspection device 5 is inserted into an insertion bore of the irradiation system 8, into which bore a fiber end of the irradiation source 10, which is not shown in Fig. 4, is inserted when the irradiation system 8 is used as intended. The illumination device 12, which is additionally shown in Fig. 4 in a sectional view AA, has a total of eight illumination sources 13 in this example, arranged in a circle and coaxial with a longitudinal axis 25 of the inspection device 5.The camera 19 of the detection device 16 is arranged centrally on a bore longitudinal axis 26 and is aligned such that it detects the first optical surface 11a of the protective glass 6b. When the inspection device 5 is used as intended, the longitudinal axis 25 of the inspection device 5 and the bore longitudinal axis 26 are identical. Since the insertion bore has a large ratio between a bore length and a bore diameter, and the bore diameter usually corresponds to a few millimeters or a few centimeters, illumination of the protective glass 6b, which is arranged set back within the insertion bore, is only possible with illumination beams 14 incident almost perpendicularly on the first optical surface 11a. Advantageous lateral illumination is not possible.

[0071] The inspection device 5 shown in Fig. 4 is depicted in a first illumination situation, in which individual illumination sources 13 of a first illumination source group 27a, for example, two adjacent illumination sources 13, of the illumination device 12 are switched on during a first exposure. Illumination sources 13 of a second illumination source group 27b, third illumination source group 27c, and fourth illumination source group 27d are switched off. The optical surface 11 is illuminated by the illumination sources 13 of the first illumination source group 27a, so that an anomaly 7 present in a first illumination region 28a can be made visible, whereas an anomaly 7 present in a second illumination region 28b cannot be displayed due to interfering reflections 29.

[0072] In order to be able to display the anomaly 7 in the acquisition data 20 that could not be displayed in the first lighting situation, the first optical surface 11a is illuminated in a second lighting situation shown in Fig. 5. For this purpose, illumination sources 13 of a second illumination source group 27b are switched on, and the illumination sources 13 of the first illumination source group 27a, the third illumination source group 27c, and the fourth illumination source group 27d are switched off. The optical surface 11 is illuminated by the illumination sources 13 of the first illumination source group 27b, so that the anomaly 7 present in the second illumination region 28b can be made visible, whereas the anomaly 7 present in the first illumination region 28a cannot be displayed due to interfering reflections 29.Subsequently, a third illumination situation and a fourth illumination situation are generated by switching on the illumination sources 13 of the third illumination source group 27c and the fourth illumination source group 27d, respectively, and detection data 20 of the optical surface 11 are recorded, which is not shown in Figs. 4 and 5.

[0073] Fig. 6 shows a schematic representation of the acquisition data 20, which was obtained with the inspection device 5 shown in Fig. 4 and Fig. 5 when the protective glass 6b was illuminated. The illumination sources 13 of all illumination source groups 27 are switched on, corresponding to illumination with a total of eight illumination sources 13. The anomaly 7 present on the optical surface 11 cannot be displayed in this case, since the illumination device 12 and / or the acquisition device 16 are aligned with one another in such a way that the reflected illumination beams 17 produce several reflections 29 superimposed on the optical anomaly features 21.

[0074] Fig. 7 shows a schematic representation of the selection data 23 of the protective glass 6b combined to form an evaluation data set 22. The acquisition data 20 of the protective glass 6b were generated when the protective glass 6b was illuminated by the four different lighting situations described above. The control unit 18, not shown in Fig. 7, is configured to break down the acquisition data 20 into individual selection data 23 and to further process only those selection data 23 in which the anomaly 7 is contained as an optical anomaly feature 21. In the present case, an overall image of the optical surface 11 of the protective glass 6b is broken down into a plurality of partial sections 30, wherein the position and size of the partial sections 30 are selected such that they do not contain an illumination condition that is unfavorable for the evaluation, such as an interfering reflection 29 that overlays the optical anomaly feature 21.In the present case, the overall image has been divided into four partial sections 30, each representing a quadrant of the overall image. Those partial sections 30 containing an interfering reflection 29 are disregarded. The selection data 23 are combined to form an evaluation data set 22, in which the entire optical surface 11 is represented and on which the optical anomaly features 21 are visible. The optical anomaly features 21 can then be evaluated using image evaluation programs in order to assess the degree of contamination of the protective glass 6b, for example, by determining the size of the optical anomaly feature 21, by determining the number of optical anomaly features 21 per unit area, and / or by determining the type of the optical anomaly feature 21.

[0075] In the illustrations of Figures 1 to 7, only individual elements of several similar types are identified by way of example with a reference symbol.

Claims

P A T E N T A N S P R Ü C H E 1. Inspection device (5) for examining an optical element (6) with regard to an anomaly (7) of the optical element (6) for use in an additive manufacturing device (1) for producing a three-dimensional workpiece by irradiating raw material powder layers applied within an irradiation plane (4) with a processing beam emitted by an irradiation system (8), wherein the optical element (6) is arranged along an optical beam path formed by the irradiation system (8) between an irradiation source (10) of the irradiation system (8) and the irradiation plane (4), wherein the inspection device (5) has an illumination device (12), a detection device (16), and a control unit (18), wherein the illumination device (12) has at least one illumination source (13) configured to emit illumination beams (14),which generate at least one illumination pattern (15) on the optical element (6), wherein the detection device (16) is configured to detect a reflected beam comprising at least a portion of the illumination beams (14) reflected by the optical element (6), wherein the control unit (18) is configured to predetermine the illumination pattern (15) on the optical element (6) by the control unit (18), and wherein the control unit (18) is configured to temporarily store detection data (20) comprising data from the detection device (16), characterized in that the control unit (18) is further configured to record the detection data (20) on an optical surface (11) of the optical element (6) when the optical element (6) is illuminated with different illumination patterns,so that the anomaly (7) of the optical element (6) can be represented as an optical anomaly feature (21) in the acquisition data (20).

2. Inspection device (5) according to claim 1, characterized in that the control unit (18) is configured such that it breaks down the detection data (20) into individual selection data (23) and further processes only those selection data (23) in which the anomaly (7) is contained as an optical anomaly feature (21).

3. Inspection device (5) according to claim 2, characterized in that the control unit (18) is configured to combine the selection data (23) into an evaluation data set (22) so that the optical anomaly feature (21) of the anomaly (7) present within the optical element (6) and / or on the optical surface (11) of the optical element (6) can be evaluated from the evaluation data set (22).

4. Inspection device (5) according to one of the preceding claims, characterized in that the optical surface (11) of the optical element (6) is illuminated at least in sections by the illumination beams (14).

5. Inspection device (5) according to one of the preceding claims, characterized in that the optical surface (11) of the optical element (6) is completely illuminated by the illumination beams (14).

6. Inspection device (5) according to one of the preceding claims, characterized in that the optical surface (11) of the optical element (6) is completely detected by the detection device (16).

7. Inspection device (5) according to one of the preceding claims, characterized in that the illumination device (12) and the detection device are arranged on the same side of the optical element (6).

8. Inspection device (5) according to one of the preceding claims, characterized in that the optical beam path (9) forms an optical axis, wherein an optical path of the illumination beams (14) is arranged inclined to the optical axis of the inspection device (5).

9. Inspection device (5) according to one of the preceding claims, characterized in that the illumination beams (14) can be controlled in an individually and separately variable manner in terms of illumination properties, such as their intensity and / or their wavelength.

10. Inspection device (5) as dependent on claim 8, characterized in that the at least one illumination source (13) is arranged offset perpendicular to the optical axis.

11. Inspection device (5) according to one of the preceding claims, characterized in that the illumination pattern (15) is point-shaped, strip-shaped or tile-shaped.

12. Inspection device (5) according to one of the preceding claims, characterized in that the inspection device (5) has at least one receiving element to which the lighting device (12) and the detection device (16) can be fixed.

13. Inspection device (5) according to claim 12, characterized in that the receiving element has a fixing means with which the receiving element can be releasably fixed to the additive manufacturing device (1) and / or to the irradiation system (8).

14. Inspection method for examining an optical element (6) with regard to an anomaly (7) of the optical element (6) for use in an additive manufacturing device (1) for producing a three-dimensional workpiece by irradiating raw material powder layers applied within an irradiation plane (4) with a processing beam emitted by an irradiation system (8), wherein the optical element (6) is arranged along an optical beam path formed by the irradiation system (8) between an irradiation source (10) of the irradiation system (8) and the irradiation plane (4), wherein the inspection method comprises the following steps: i) illuminating the optical element (6) to generate an illumination pattern (15) on the optical surface (11) of the optical element (6), wherein, in temporally parallel fashion to the illumination step ii), a reflected beam comprising at least a portion of the illumination beams (14) is detected,which is reflected by the optical element (6), wherein iii) the illumination pattern (15) on the optical element (6) can be predetermined, and wherein iv) detection data (20) comprising data from the detection device (16) are temporarily stored, characterized in that the detection data (20) when the optical element (6) is illuminated with mutually different illumination patterns on an optical surface (11) of the, optical element (6) are recorded so that the anomaly (7) of the optical element (6) can be represented as an optical anomaly feature (21) in the acquisition data (20).

15. Inspection method according to claim 14, characterized in that the detection data (20) are each broken down into individual selection data (23) and only those selection data (23) are further processed in which the anomaly (7) is contained as an optical anomaly feature (21).

16. Inspection method according to claim 15, characterized in that the selection data (23) are combined to form an evaluation data set (22), so that the optical anomaly feature (21) of the anomaly (7) present within the optical element (6) and / or on the optical surface (11) of the optical element (6) can be evaluated from the evaluation data set (22).

17. Additive manufacturing device (1) for producing a three-dimensional Workpiece by irradiating raw material powder layers with a processing beam, comprising an inspection device (5) according to one of claims 1 to 13.

Images