Inspection apparatus and inspection method for detecting abnormalities in optical elements of additive manufacturing equipment.

Abstract

The present invention relates to an inspection apparatus (5) and inspection method for investigating an optical element (6) for abnormalities (7) used in an additive manufacturing apparatus (1) for manufacturing three-dimensional workpieces. The optical element is positioned between the illumination source (10) and the illumination surface (4) of the illumination system (8) along an optical beam path formed in the illumination system. The illumination device (12) has at least one illumination source (13) configured to emit an illumination beam (14) that generates at least one illumination pattern (15) on the optical element. The detection device (16) detects the reflected beam, which includes at least a portion of the illumination beam reflected by the optical element. The control unit (18) is configured to make the illumination pattern on the optical element identifiable, temporarily stores detection data (20) including data from the detection device, and records the detection data while illuminating the optical element with different illumination patterns on the optical surface (11) of the optical element. Thus, abnormalities in the optical element are represented as optical abnormality features (21) in the detection data.

Description

Technical Field

[0001] The present invention relates to an inspection apparatus and an inspection method for inspecting an optical element regarding an abnormality of the optical element, which are used in an additive manufacturing apparatus for manufacturing a three-dimensional workpiece by irradiating a raw material powder layer on an irradiation surface with a processing beam emitted from an irradiation system. Here, the optical element is arranged along a beam path between an irradiation source of the irradiation system and the irradiation surface. The inspection apparatus includes a lighting device, a detection device, and a control unit. The lighting device includes at least one lighting source configured to emit a lighting beam that generates at least one lighting pattern on the optical element. The detection device is configured to detect a reflected beam including at least a part of the lighting beam reflected by the optical element. The control unit is configured to be able to specify the lighting pattern on the optical element by the control unit and temporarily store detection data including data from the detection device.

[0002] The inspection apparatus and the inspection method are for use, for example, in an additive manufacturing apparatus. The optical element is for use, for example, in an additive manufacturing apparatus. The additive manufacturing apparatus is for manufacturing a three-dimensional workpiece by irradiating a raw material powder layer on an irradiation surface with a processing beam emitted from an irradiation system, for example. The detection device is for detecting and / or generating detection data, for example. The control unit is for controlling the lighting device so that the lighting device generates at least one lighting pattern on the optical element, for example.

Background Art

[0003] Powder bed melting is an additive layering process capable of processing powdered raw materials, such as metals and / or ceramics, to form three-dimensional workpieces of complex shapes. For this purpose, a layer of raw material powder is applied to a carrier within an irradiation surface, and electromagnetic radiation (e.g., laser radiation or particle radiation) is selectively applied according to the desired shape of the workpiece to be manufactured. The electromagnetic radiation penetrating the powder layer generates heat, melting or sintering the raw material powder particles. Further layers of raw material powder are then applied to the already irradiated and solidified layer on the carrier, and this process is repeated until the workpiece reaches the desired shape and size. Powder bed melting may be used in the manufacture of high-quality parts for prototypes, tools, replacement parts, automotive structures or aircraft, or medical supplies. Selective laser melting, selective laser sintering, and electron beam melting are examples of powder bed melting methods.

[0004] Additive manufacturing apparatuses for producing one or more workpieces by the method described above are known from the prior art. For example, European Patent Publication No. 2961549 and European Patent Publication No. 2878402 describe additive manufacturing apparatuses for producing three-dimensional workpieces by selective laser melting technique. The system further includes an irradiation device comprising a radiation source (e.g., a laser source) and an optical system. The optical system selectively guides a processing beam generated by the radiation source onto a layer of raw material powder coated on a carrier, according to the shape of the workpiece to be produced. When a three-dimensional workpiece is produced by selectively irradiating the powder layer coated on the carrier, the powder particles are melted and / or sintered by the radiant energy introduced into the raw material powder.

[0005] Optical elements in the beam path of the irradiation system and / or optical system within the additive manufacturing apparatus described above are exposed to high laser power ranging from several hundred watts to several kilowatts. The processing beam emitted from the irradiation system, such as laser irradiation, is parallelized to a predetermined raw beam diameter by a collimation lens, deflected by a deflection mirror within the irradiation system, and focused by a focusing lens. A strong radiant intensity is generated at the location where the processing beam strikes each optical element. Radiant intensity represents the surface power density and is calculated as power per unit area. The higher the power per unit area, the stronger the intensity, and vice versa.

[0006] Examples of optical elements in the beam path of the additive manufacturing apparatus described above for additive manufacturing of three-dimensional workpieces may include protective screens, protective windows, optical coupling screens, optical coupling glass, optical coupling windows, beam incidence glass, lenses, or mirrors. Protective screens or protective glass serve to keep the optical elements placed within the irradiation system in a clean environment and protect them from processing by-products generated during the laser melting process, such as processing waste gases or powder sputtered particles. When the additive manufacturing apparatus is used in the intended manner, these optical elements are placed in the beam path of the processing beam and are exposed to the processing beam during the operation of the additive manufacturing apparatus.

[0007] Using optical elements free from defects is of particular importance. Hereinafter, defects are understood as, for example, dirt or contamination of the optical element, such as dust particles, lint, powder residue, or other deposits on the optical surface. In addition, defects are also understood as penetrations, recesses, bulges, damage, or irregularities on the inside or outside of the optical element. Careful installation of optical elements in a clean, dust-free environment is of particular importance. Foreign matter, such as dust particles or lint, enclosed within the installed irradiation system and / or optical system, can accumulate on the optical surface of the protective glass. When the optical element is exposed to laser power, the laser radiation is absorbed by the foreign matter, and in the worst case, both the defect and the optical element are heated, resulting in damage to the optical element. Furthermore, heating of the optical element can lead to the formation of so-called thermal lenses. Changes in the refractive index occurring within the material of the optical element may result in a shift in the focal position of the processing beam, and in the worst case, a change in the beam diameter of the processing beam within the irradiation surface, leading to a change in the radiation intensity within the irradiation surface, affecting the processing stability of the melting process.

[0008] Another important measure of the reproducible and reliable operation of additive manufacturing equipment is the cleanliness of the optical elements that couple the laser beam into the processing chamber. These optical elements, often referred to as beam-entry glass, are positioned between the optical unit and the processing chamber or powder floor surface, or the irradiation surface, as viewed from the beam propagation direction. The beam-entry glass is positioned so that the first surface of the protective glass faces the irradiation surface and the second surface of the protective glass faces the irradiation system. Furthermore, the focal beam, i.e., the beam that converges in the beam propagation direction, generally passes through the beam-entry glass. The beam diameter of the laser beam incident on the first or second surface of the protective glass is smaller than the diameter of the raw beam emitting from the sighting lens. Therefore, the protective lens is exposed to a high-intensity laser beam on the first and / or second surfaces in the region of the incident point. To reduce the risk of thermal damage to the protective lens at this incident point, it must be confirmed that the protective lens is clean and free of defects prior to the commencement of construction work.

[0009] Depending on the surrounding conditions and the mounting position of the optical element, it may be difficult to confirm that there is an abnormality in the protective lens. The degree to which an abnormality is visible depends heavily on the lighting conditions and / or the lighting arrangement relative to the camera position. Here, lighting conditions such as lighting brightness, lighting color, lighting direction, ambient brightness, and direction of the lighting source, as well as the camera direction, play important roles. To detect one or more abnormalities in the optical element and / or the optical surface of the optical element, the lighting may be installed, for example, so that the surface is illuminated from as low an angle as possible in the lateral direction, and the light reflected by the abnormality of the object is detected as scattered light by the camera.

[0010] Manual detection is known, in which optical elements are inspected by illuminating them with a flashlight. In this method, visual inspection for the presence of abnormalities in protective glass is performed by manually illuminating the protective lens. Whether or not abnormalities in the optical elements and / or the optical surfaces of the optical elements are visible depends heavily on the lighting conditions. In the case of manual inspection, the results of the inspection also depend heavily on the person performing the inspection, and therefore, it is generally not possible to obtain reproducible results, for example, regarding the degree of contamination of the optical elements or the nature of the abnormalities, through manual inspection.

[0011] The favorable lighting conditions described above are generally not possible when inspecting optical elements located in hard-to-reach areas of the processing room and / or illumination system, because actual spatial conditions do not allow for such camera and / or lighting placement. [Overview of the project]

[0012] The object of the present invention is to provide an inspection apparatus and inspection method that can reproducibly detect abnormalities present in an optical element and / or on the optical surface of an optical element.

[0013] This objective is achieved by the present invention, which further configures the control unit to record detection data while illuminating the optical surface of the optical element with multiple different illumination patterns, and to represent any anomalies in the optical element as optical anomaly features in the detection data.

[0014] Detection data is recorded by the detection device while, for example, the optical surface of an optical element is illuminated by multiple different illumination patterns. For example, at any given time, only a single illumination pattern is emitted onto the optical surface. Thus, multiple different illumination patterns are emitted onto the optical surface, for example, sequentially or at different times. For example, multiple different illumination patterns may scan the optical surface area by area.

[0015] Optical anomaly features are recognized, for example, based on detection data. The detection data may include a representation of the optical anomaly feature, such as an image.

[0016] The detection device may be designed to detect the illumination beam in one or more of the aforementioned wavelength ranges. The detection device may have an optical sensor, image sensor, photodiode, etc., designed as a camera. The corresponding light sensor may be designed as, for example, a CCD sensor, CMOS sensor, etc., and may detect the illumination beam reflected by the optical element. The detection data detected by the detection device may be stored in the form of an image, photograph, or signal data.

[0017] At least one illuminating source of the lighting equipment may be designed as a light-emitting illuminating source such as a light-emitting diode (LED), laser diode, etc. Preferably, the illuminating source is designed to emit an illumination beam of light preferably in the visible wavelength range. However, alternatively, further wavelength ranges such as the infrared wavelength range or the ultraviolet wavelength range are also possible.

[0018] Furthermore, the lighting device preferably has a beam-shaping element for shaping the illumination beam emitted from the illumination source to form an illumination pattern. The illumination beam may be magnified, shaped, or focused by, for example, the beam-shaping element. The shape or size of the illumination pattern generated on the optical surface of the optical element can thus be adjusted in a particularly advantageous manner.

[0019] By generating different illumination patterns, the illumination beam is reflected, at least partially, by the region of the optical element illuminated by the illumination pattern, and detected by the detection device. For example, the illumination beam reflected by foreign matter such as dust particles or soot particles can be recognized as an optical anomaly feature, for example, in the form of a brightness difference in the detection data.

[0020] By generating multiple different illumination patterns, it becomes possible to illuminate optical elements from multiple, different directions. Furthermore, any anomalies in the optical elements illuminated by the illumination patterns are also illuminated by the illumination beam. By generating detection data with different illumination directions for each case, anomalies can be made visible by illuminating them with the selected illumination pattern, and the anomaly does not necessarily need to be reflected in further detection data. However, if the illumination equipment and / or inspection equipment are facing each other such that the reflected illumination beam overlaps with the optical anomaly feature, the anomaly may not be detected. In other words, this occurs when the reflected illumination beam stored in the detection equipment in the first illumination pattern overlaps in intensity with the intensity of the illumination beam reflected by the anomaly.

[0021] Therefore, an advantageous configuration of the invention is provided, in which the control unit is configured to decompose the detection data into individual selection data for each case and process only the selection data that contains the anomaly and is represented as an optical anomaly feature. The determination of the selection data that includes the anomaly as an optical anomaly feature may be performed by manually checking the detection data or the selection data. If the arrangement of the inspection device with respect to the optical element is known, the determination of the selection data is initially performed manually, and in repeated anomaly inspections, these selection data that include the anomaly as an optical anomaly feature become known. The determination of the selection data can thus be performed particularly simply and quickly.

[0022] Alternatively, the evaluation of the detected data for determining the selected data may be performed by evaluating whether the luminance values, intensity values, etc., exceed predetermined luminance thresholds, intensity thresholds, etc. For this purpose, the evaluation of the detected data for luminance values, intensity values, etc., may be provided using a data processing and data evaluation program, and / or an image processing program and / or an image evaluation program. Computer-based and / or automated evaluation of the detected data may be performed before determining the selected data. This allows for the simple and rapid determination of optical anomaly features.

[0023] If the placement and orientation of the lighting equipment relative to the detection equipment are known and fixed, preferred selection data representing anomalies can be predetermined after manual and / or automatic evaluation of the detected values. According to the selected orientation, only the area of ​​the optical surface illuminated by the lighting pattern is relevant to the selection data. Therefore, it may also be provided that only a portion of the optical surface, for example, the area of ​​the optical surface illuminated by the lighting pattern, is recorded by the detection equipment. This enables particularly time-saving recording and resource-saving temporary storage of the detected data.

[0024] In an example of detection data recorded as multiple whole images, the whole image is decomposed into multiple sub-regions for each case, and the location and size of the sub-regions are selected to include illumination conditions that are unfavorable to evaluation, such as interference reflections overlapping with optical anomalous features. Furthermore, the sub-regions may contain optical anomalous features and be further processed to evaluate contamination of the optical elements.

[0025] For example, each time the detection device is irradiated with an illumination pattern having an optical surface, it may record an image of the entire optical surface and save this image. Each image may be decomposed into partial regions corresponding to the selection data. The partial regions may be selected according to each illumination pattern. For example, each image may be decomposed into one or more first partial regions and one or more second partial regions, and a certain illumination pattern is seen in each first partial region and not seen in each second partial region. In this case, it is conceivable to further process only the first partial regions, for example, only the first partial regions capable of recognizing optical anomaly features. For example, all the first partial regions may be combined to form an overall image, and all the optical anomaly features may be identified based on this overall image.

[0026] An advantageous implementation of the inventive concept is provided, which is further configured such that the control unit combines the selection data to form an evaluation data set in order to obtain an overall overview of the anomalies to be inspected on the optical surface of the optical element. The entire optical surface of the optical element is observable as an anomaly as an optical anomaly feature and is represented in the evaluation data set. A plurality of partial regions including the optical anomaly features are combined to form an overall evaluation image, and an overall image of the optical surface including the anomalies present in the optical element and / or the optical surface of the optical element is generated.

[0027] The evaluation of the optical anomaly for determining the degree of contamination of the optical element is performed in subsequent evaluation steps such that the optical anomaly features are evaluated regarding the size of the optical anomaly features, the number of optical anomaly features per unit area, and the nature of the optical anomaly features. This may be done using known image processing methods and programs.

[0028] Each illumination pattern may be designed so as not to cover the entire optical surface. Different illumination patterns, for example, have different regions of the optical surface covered by the illumination pattern.

[0029] According to the present invention, in order to illuminate an optical element particularly advantageously, an illumination beam may be provided that generates an illumination pattern such that at least a portion of the optical surface of the optical element is illuminated. By illuminating the optical surface in a certain portion, it becomes possible to avoid interference reflection that may occur when the illumination beam is reflected by the unilluminated portion of the optical surface. When the arrangement of the lighting device with respect to the optical surface is previously known, the area of the optical surface illuminated by the illumination pattern can be determined in advance. Furthermore, since the arrangement of the detection device with respect to the optical surface is known, the evaluation of the detection data can be performed such that only the illuminated area is evaluated. Thus, the evaluation of the optical surface for optical anomaly features can be performed in a particularly simple manner.

[0030] By illuminating only a certain area of the optical surface, the amount of light emitted by the illumination beam, that is, the amount of light emitted by the illumination beam onto the optical surface, can be reduced. As a result, the amount of light reflected by the optical surface or transmitted through the optical element is also similarly reduced. The amount of light in the environment of the optical element that is to be investigated as a result of reflection and / or transmission at the optical surface is also advantageously reduced. For example, interference reflection caused by the illumination beam reflected by the wall of the processing chamber or an element of the optical system arranged on the rear side of the irradiation system and / or the optical element that transmits can be reduced in this way. An optical surface without anomalies can be detected as a dark optical surface in the detection data. Anomaly existing in the illuminated area of the optical surface is thus particularly well represented as an optical anomaly feature.

[0031] According to the present invention, in order to design the lighting device particularly simply and cheaply, it is provided that the entire optical surface of the optical element is illuminated by the illumination beam emitted by the lighting device. Thereby, the complicated orientation of the lighting device with respect to the optical element is omitted, and the inspection device can be installed particularly simply and quickly.

[0032] An advantageous implementation of the inventive concept provides that the entire optical surface of an optical element can be detected by the detection device. This ensures that even the edges of the optical element, where abnormalities may exist, can be reliably detected. Furthermore, complex orientation of the detection device relative to the region of the optical surface illuminated by the illumination pattern is eliminated.

[0033] Irradiation systems, including optical elements, are generally installed in a clean and pure environment, ensuring that no abnormalities are introduced into the system during installation. In addition, the illumination system is nearly hermetically sealed to protect the interior from the intrusion of dust particles from the surrounding atmosphere, for example. The optical surfaces of optical elements facing the illumination system are, for structural reasons, no longer accessible from the outside and are therefore less susceptible to abnormalities than the optical surfaces of optical elements further away from the illumination system.

[0034] For example, according to the present invention, an inspection apparatus is provided in which the lighting equipment and the detection equipment are arranged on the same side of the optical element. This is because, depending on the structural shape of the additive manufacturing apparatus and the arrangement of the optical element in the illumination system, access to the optical element in the additive manufacturing apparatus is often difficult, and in some cases impossible, and may only be accessible from the optical surface of the optical element away from the illumination system.

[0035] For example, the optical surfaces of optical elements such as beam-injector glass that guides the processing beam into the processing chamber are exposed to the risk of abnormalities caused by processing by-products formed during the melting process, such as exhaust gas, agitated particles, or soot products. Therefore, in a particularly advantageous configuration of the inspection apparatus, it is provided that the inspection apparatus is positioned on the side facing the optical surface of the optical element or the optical surface opposite to the irradiation system.

[0036] According to the present invention, it is also possible and selectively provided that the optical beam path forms the optical axis, and the optical path of the illumination beam is positioned at an angle with respect to the optical axis of the inspection device. The illumination beam is intentionally directed to a predetermined area of ​​the optical surface in a particularly simple manner, and the illumination pattern is incident on the optical surface according to the inclined arrangement.

[0037] According to the present invention, it is also advantageous and optional that at least one illuminator be offset perpendicular to the optical axis, where the distance between the at least one illuminator and the optical axis may be adjusted according to a set inclination of the illuminator, and / or according to a selected working distance, and / or according to the existing spatial conditions. Particularly advantageous illumination of the optical element can thus be created.

[0038] An advantageous configuration of the invention provides that illumination beams are activated individually and isolated for each case, such that their illumination attributes, such as intensity and / or wavelength, differ from one another. Here, the illumination attributes are advantageously adjusted according to the assumed back reflection of the reflected illumination beam. The characteristics and degree of back reflection can vary according to the reflective or transmission properties of the optical element. Thus, by adapting the intensity and wavelength, illumination conditions with less interference can be established.

[0039] Lighting equipment may be activated such that the lighting attributes of the lighting beam differ among two or more lighting patterns.

[0040] The size of the range of selected data to be further processed may be set or influenced by the configured illumination attributes, such as the intensity of the illumination beam. If the intensity of the illumination beam is set low, back reflection in a particular area will be reduced, and anomalies may be represented as anomaly features, potentially increasing the size of selected data to be further processed.

[0041] Differences in the wavelength of illumination beams can be advantageously used to detect and distinguish different types of anomalies from one another. For example, illumination beams reflected by foreign matter such as dust residue, agitated particles, or soot particles can be recognized as optical anomaly features in the form of differences in brightness in the detection data.

[0042] When using multiple illuminators, the variations in the illumination attributes of each illuminator may be set separately from one another in order to obtain the desired effect on generating the largest possible selection data.

[0043] Depending on the configuration of the optical element, illuminating the optical surface with different illumination patterns can be advantageous. Here, the illumination pattern may, on the one hand, be adapted to the shape of the optical element. According to the present invention, the illumination pattern can be provided to be point-shaped, strip-shaped, or tile-shaped, which is advantageous and selective. This allows certain areas or parts of the optical element to be illuminated depending on its shape. With strip-shaped illumination, certain parts of the optical element are illuminated, and anomalies in the optical element are preferably contained in the illuminated areas, which are further processed as selective data to become a selective dataset. In addition, on optical surfaces that are only partially illuminated by the illumination pattern, anomalies can be represented with a high contrast ratio.

[0044] An advantageous implementation of the inventive concept is provided in which the inspection device has at least one mount on which lighting equipment and sensing equipment can be mounted. Due to the predetermined position and arrangement of the mount, lighting equipment and sensing equipment can be easily and quickly mounted within the inspection device. The mount may be designed as a housing that at least partially encloses the lighting equipment and sensing equipment. Optical elements enclosed by the housing are protected.

[0045] Inspections of optical elements used within additive manufacturing equipment may be performed at different times during the installation and / or operation of the equipment. The timing and necessity of the inspections will be determined based on the type of optical element being inspected. For example, protective glass in an illumination system may be inspected for abnormalities after the protective glass has been installed in the illumination system. This ensures that the optical elements to be installed in the illumination system are free from abnormalities before the illumination system is installed in the optical carrier or the additive manufacturing equipment and access to the optical elements is restricted. Depending on accessibility, inspections may be performed after the installation in the additive manufacturing equipment is complete.

[0046] The beam-injection glass, positioned in the processing chamber cover, is typically inspected before the start of a construction job and / or each time it is cleaned to monitor cleaning operations. According to the present invention, to inspect the beam-injection glass, an inspection device is positioned between the beam-injection glass and the irradiation surface within the processing chamber. Here, the processing chamber housing may be designed with a receiver or receiving recess in which the inspection device is at least partially positioned, and the inspection device is positioned outside the deflection region of the deflected processing beam. Here, the inspection device is positioned next to the optical element facing the irradiation surface. The optical surface, which is exposed to the risk of increased contamination by processing by-products generated during the melting process, can be inspected. In addition, by integrating the inspection device within the processing chamber, the inspection of the beam-injection glass can be performed during a construction job. For this purpose, the inspection operation is preferably performed during the coating operation of the raw material powder layer, when the irradiation system is inactive, allowing the beam-injection glass to be inspected without interrupting the construction job.

[0047] According to the present invention, the inspection device may be designed as a portable inspection device that can be detachably combined with an additive manufacturing apparatus and / or illumination system. The inspection device may be designed to be located in the beam path of one or more illumination systems, below the beam-injection glass in the processing chamber. When the inspection device is positioned in this manner, it is necessary that the inspection device can be removed from the beam path after the inspection of the optical elements is completed. For this purpose, according to the present invention, an advantageous configuration of the inspection device is provided in which the mount has means for fixing the mount to the additive manufacturing apparatus and / or illumination system for detachability. Suitable fixing means are detachable fixing means such as screws, tightening levers, fasteners, bolts, and magnetic fixing means. For example, the inspection device may be designed to be detachably fixed to a carrier below the beam-injection glass in the area of ​​the illumination surface within the processing chamber of the additive manufacturing apparatus. The area of ​​the illumination surface is generally easily accessible and reachable, and mounting and removal of the inspection device at a position within the illumination surface is possible in a simple manner.

[0048] The receiving device is preferably designed to be in contact with the corresponding receiving device of the additive manufacturing apparatus and / or irradiation system. Centering or orientation of the inspection device may be performed via known orientation means such as a center pin, bolt, sleeve, pin, or ring. The inspection device is thus positioned in a predetermined position relative to the optical element and subsequently removably fixed in place by fixing means.

[0049] The fixing means may preferably be designed so that the inspection device is oriented in a predetermined position relative to the optical element and fixed in the desired position and / or arrangement. This thus enables rapid and repeatable introduction and orientation of the inspection device to and / or within the optical element in the processing chamber.

[0050] During illumination of the optical element under two or more lighting patterns, for example, all (e.g., directly following each other), the lighting and sensing devices may be positioned in the same orientation relative to the optical element. At least the lighting and sensing devices may be fixed in position relative to the optical element during the recording of sensing data based on at least two lighting patterns.

[0051] In a typical configuration, the inspection device is designed such that each illumination beam forms an illumination pattern, and the illumination beam is reflected by an optical element, such as an optical surface illuminated by the illumination pattern, and reaches the detection device, and the optical element is designed to have an incident angle that falls within a predetermined incident angle range, and / or a reflected angle that falls within a predetermined reflection angle range. These angle ranges may be the same or different. Each angle range is between a minimum angle and a maximum angle, where 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 interval between the minimum angle and the maximum angle may be 5°, 10°, 15°, 20°, or 25°.

[0052] It is also conceivable that the illumination device and the detection device are moved (for example, together) relative to the optical element, such that each illumination beam has an incident angle that falls within a predetermined incident angle range, or / or that the illumination beam reflected by the optical element has a reflection angle that falls within a predetermined reflection angle range. For this purpose, the illumination device and the detection device may be arranged in a common movable holding device within the processing chamber. The holding device may be designed to positionally orient, for example, the illumination device and the detection device to multiple predetermined positions (for example, relative to the optical element). For example, at a first of these predetermined positions, the illumination device and the detection device may emit a first illumination pattern onto the optical element to record corresponding detection data, and after moving (for example, manually) to a second of these predetermined positions, they may emit a second illumination pattern onto the optical element to record corresponding detection data again. Here, the illumination device may be activated in the same way at both predetermined positions, i.e., emitting the same light pattern, but the areas covered by the illumination beam may differ due to the different positions.

[0053] It is also conceivable that the illuminating equipment be moved relative to the detection equipment (for example, between illumination of the optical element with two consecutive illumination patterns) to ensure that each illumination beam has an incident angle that falls within a predetermined incident angle range, and / or a reflection angle that falls within a predetermined reflection angle range. For this purpose, the illuminating equipment and / or the detection equipment may be mounted on movable positioning devices within the processing chamber. Each positioning device may be designed to positionally oriented, for example, the illuminating equipment or the detection equipment to a plurality of predetermined positions (for example, relative to the optical element). For example, at a first of these predetermined positions, the inspection device may emit a first illumination pattern onto the optical element and record the corresponding detection data, and after moving (for example, manually) to a second of these predetermined positions, it may emit a second illumination pattern onto the optical element and again record the corresponding detection data. Here, the illuminating equipment may be activated in the same way at both predetermined positions, i.e., emitting the same light pattern, but the areas covered by the illumination beams may differ due to the different positions.

[0054] It is also conceivable that an inspection device may be used to inspect one or more first optical elements (e.g., protective glass) at a first position among predetermined locations, and that the inspection device may be moved to a second position among predetermined locations, for example by a holding device, for inspecting one or more second optical elements (e.g., another protective glass). Depending on the embodiment, the lighting device and the detection device may be repositioned together or individually. Repositioning ensures that a desired angular range is maintained. If the angular range is the same for each detection of detection data (e.g., image recording), this makes it easier to compare selected data (e.g., subregions of different images).

[0055] In a typical embodiment, the inspection device is housed in a construction cylinder designed to be connected to a processing chamber. In addition to the inspection device, other measuring instruments and / or maintenance equipment may be housed in the same construction cylinder. For example, the inspection device may be positioned on a mounting plate that is axially removable within the construction cylinder (e.g., together with other measuring instruments and / or maintenance equipment). After the construction cylinder is connected to the processing chamber, the mounting plate is displaced by the drive system of the additive manufacturing device in a direction toward the processing chamber until, for example, the mounting plate rests on the illumination surface. The method described herein is performed by the inspection device positioned in the processing chamber. The construction plate may then be returned, i.e., moved away from the processing chamber, for example, downward. The inspection device thus leaves the processing chamber and returns to the construction cylinder. The construction cylinder housing the inspection device may be removed and replaced with a construction cylinder designed for three-dimensional workpiece manufacturing. This has the effect of eliminating the need to manually bring the inspection device into the processing chamber and eliminating the need to provide a loading hatch in the processing chamber that is sized to accommodate the manual introduction of the inspection device into the processing chamber.

[0056] The objective described at the beginning can also be achieved by inspection methods for visual representation beyond what is present on the optical surface of an optical element. The inspection method is provided for use in additive manufacturing equipment that manufactures three-dimensional workpieces by irradiating a layer of raw material powder coated on an illumination surface with a processing beam emitted from an illumination system, and the optical element is positioned between the illumination source of the illumination system and the illumination surface, along the optical beam path formed by the illumination system. The inspection method includes the following steps: (i) illuminating the optical element to generate an illumination pattern on the optical surface of the optical element; (ii) simultaneously with the illumination, detecting the reflected beam, the reflected beam including at least a portion of the illumination beam reflected by the optical element; (iii) the illumination pattern on the optical element (6) may be predefined; and (iv) detection data, including data from a detection device, is temporarily stored. While the optical element is illuminated with multiple different illumination patterns on the optical surface of the optical element, the detection data is recorded, and any abnormalities in the optical element are represented in the detection data as optical anomaly features.

[0057] According to the method of the present invention, abnormalities contained in and / or on the optical surface of an optical element can be detected. The inspection method is preferably performed before the additive manufacturing apparatus starts manufacturing a build job. In this way, the beam injection glass of the processing chamber or multiple beam injection glasses can be checked individually or sequentially for the presence of abnormalities.

[0058] According to the advantageous configuration of the present invention, the detection data is decomposed into individual selected data for each case, and only the selected data in which the anomaly is included as an optical anomaly feature is further processed.

[0059] According to the present invention, selected data can be combined to form an evaluation dataset, and optical anomaly features of anomalies present within and / or on the optical surface of the optical element can also be evaluated from the evaluation dataset and are provided selectively.

[0060] A system including optical elements and inspection equipment is also provided. An additive manufacturing apparatus for producing a three-dimensional workpiece by irradiating a raw material powder layer with a processing beam is also provided, and the apparatus includes optical elements and inspection equipment.

[0061] The objective described at the beginning is an additive manufacturing apparatus for manufacturing a three-dimensional workpiece by irradiating a raw material powder layer with a processing beam, which can also be achieved by an additive manufacturing apparatus comprising an inspection device as described in any one of claims 1 to 13. The inspection device is preferably moved to the beam path before the start of the construction process and is preferably designed so that the inspection device according to the present invention is performed. Once the inspection method is complete, the inspection device is moved again and positioned outside the beam path of the processing beam so that there are no obstructions in the beam path of the processing beam and the processing beam strikes the raw material powder layer coated on the irradiation surface without obstruction.

[0062] A more preferred configuration of the invention will be described with reference to a typical embodiment shown in the following drawings. [Brief explanation of the drawing]

[0063] [Figure 1] Figure 1 is a schematic diagram showing the details of an additive manufacturing apparatus with inspection equipment located in the processing chamber. [Figure 1A] Figure 1A is a schematic diagram showing details of a modified version of the additive manufacturing apparatus shown in Figure 1, which has a holding device for (re)positioning of the inspection device. [Figure 2] Figure 2 is a schematic diagram of detection data recorded by the inspection device while the beam injection glass is illuminated with different lighting patterns. [Figure 3] Figure 3 is a schematic diagram of the evaluation dataset of coupled selected data for illuminated beam injection glass. [Figure 4] Figure 4 is a schematic diagram showing the first irradiation state of an inspection device for inspecting the protective glass of an irradiation system. [Figure 5] Figure 5 is a schematic diagram showing the second irradiation status of an inspection device used to inspect the protective glass of an irradiation system. [Figure 6] Figure 6 is a schematic diagram of the detection data recorded by the inspection device while the protective glass is illuminated by all light sources. [Figure 7] Figure 7 is a schematic diagram of the evaluation dataset of combined selection data for illuminated protective glass. [Modes for carrying out the invention]

[0064] Figure 1 is a schematic diagram showing the details of an additive manufacturing apparatus 1 having an inspection device 5 located inside a processing chamber 2. The inspection device 5 is positioned on the carrier 3 of the additive manufacturing apparatus 1 within the irradiation surface 4.

[0065] Carrier 3 may be a construction plate that is detachably mounted on the construction cylinder and connectable to the processing chamber 2. It is also conceivable that the inspection device 5 be housed inside the construction cylinder so that it can be mounted into the processing chamber 2 from below after the construction cylinder is connected.

[0066] The inspection device 5 is placed in the processing chamber 2 to investigate one or more abnormalities 7 of the optical element 6, in this embodiment, the beam incidence glass 6a. The beam incidence glass 6a is placed in the optical beam path formed by the irradiation system 8 between the irradiation source 10 of the irradiation system 8 and the irradiation surface 4. The beam incidence glass 6a is oriented such that its first optical surface 11a faces the irradiation surface and its second optical surface 11b faces the irradiation system 8. The illumination equipment 12 of the inspection device 5 has an illumination source 13 configured to emit an illumination beam 14 to generate an illumination pattern 15 on the optical element 6. In a typical embodiment shown in Figure 1, the illumination source 13 is designed as a video projector, which can generate an illumination beam 14 with a predefined illumination pattern 15 that illuminates the beam incidence glass 6a with a portion of the first optical surface 11a. The detection device 16 of the inspection device 15 is configured to detect a reflected illumination beam 17 that includes at least a portion of the illumination beam 14 reflected by the optical element 6. The control unit 18 of the inspection device 5 is configured so that the illumination beam 14 is directed toward the optical surface 11 and generates an illumination pattern 15 on the optical surface 11 of the optical element 6. The detection device 16 has a camera 19 and records the first optical surface 11a of the optical element 6 to generate detection data 20. The control unit 18 is configured to temporarily store the detection data 20, including the data from the detection device 16. Recording is performed for each illumination pattern 15 and temporarily stored.

[0067] Figure 2 is a schematic diagram of the detection data 20 in the form of individual images, recorded by the inspection device 5. The detection data 20 is generated while the beam incidence glass 6a is illuminated with different illumination patterns. Each of the illumination patterns 15 constitutes a strip-shaped illumination pattern 15, and the width of the strip is reduced in each of the records represented by individual images (a) to (h). By reducing the 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 by illuminating only a part of the optical surface 11, the detection device 16 can record the interference-free optical surface 11 in the detection data 20. Thus, because there is a large difference in brightness between the brightness of the reflected illumination beam 17 due to the anomaly 7 and the brightness of the reflected illumination beam 17 due to the clean area of ​​the optical surface 11, the anomaly 7 is represented on the optical surface 11 that is only partially illuminated by the illumination pattern 15.

[0068] It is preferable that the incident angle and reflection angle of the illumination beam radiated onto the optical element and detected by the detection device fall within a predetermined angular range (for example, between 0° and 20°, respectively) at each detection step, i.e., for each illumination pattern. In this case, the intensity of the reflected illumination beam received by the detection device is also within a preferred range.

[0069] If the position of the inspection device 5 in the processing chamber 2 is fixed, as long as this situation is maintained, only a portion of the optical surface 11 will be illuminated by the illumination pattern, and the reflected light will be detected. However, in order to inspect the entire optical surface 11, the position of the inspection device 5 in the processing chamber 2 may be deflected.

[0070] For example, as shown in Figure 1A, the inspection device 5 is positioned on a holding device 31 that defines a number of predetermined positions for the inspection device 5, and allows the inspection device 5 to be repositioned between these positions manually or by motor drive. The holding device 31 is positioned on a carrier 3. For example, the holding device 31 comprises a fixing part that is fixed to the carrier 3, and a holding part connected thereto that supports the inspection device 5 so that it can move between predetermined positions (for example, by rotation and / or transiently). For example, after inspecting a region of an optical element, the inspection device may be moved in the X direction and / or rotated around a vertical axis to inspect other regions of the optical element that are far apart in the X direction by illumination and detection.

[0071] Moving the inspection device 5 is beneficial, for example, in the case of wide-range optical elements or when inspecting multiple optical elements that are spaced apart from each other. For this reason, the additive manufacturing device 1 may be equipped with, for example, multiple beam-injection glasses 6a. Figure 1A shows an example of two beam-injection glasses 6a, in which inspection may be performed after the inspection device 5 has been (re)positioned accordingly. The manufacturing device 1 may be equipped with other beam-injection glasses 6a or other optical elements, in which case inspection may be performed after the inspection device 5 has been (re)positioned accordingly. If the optical surfaces 11 to be inspected are sufficiently close to each other, repositioning of the inspection device 5 between inspections of individual optical surfaces 11 may not be necessary, for example, if the desired angular range can be maintained even if the inspection device 5 is in the same position.

[0072] Figure 3 is a schematic diagram of an evaluation dataset 22 generated from combined selected data 23 of the illuminated beam-incident glass 6a. The optical surface 11 of the beam-incident glass 6a is partially illuminated in time by a strip-shaped illumination pattern 15, and the illuminated optical surface 11 is recorded by a detection device 16. After each recording, the strip-shaped illumination pattern 15 is offset in the offset direction 24 shown in the figure, perpendicular to the strip-shaped illumination pattern 15, preferably by the width of the strip of the illumination pattern 15, and subsequent recording of the optical surface 11 is performed. In a modified example, the inspection device 5 may be designed so that the strip-shaped illumination pattern 15 is continuously guided over the optical surface 11, and recording of the optical surface 11 is performed at time intervals corresponding to the movement speed of the illumination pattern. In each recording, a portion of the optical surface 11 of the beam-incident glass 6a is illuminated, and the entire area of ​​the optical surface 11 is continuously recorded. In Figure 3, the control unit 18 (not shown) is configured to decompose the detection data 20 into individual selection data 23 and further process the selection data 23 in which the anomaly 7 is included as an optical anomaly feature 21. In this embodiment, the selection data 23 corresponding to the illuminated area of ​​the optical surface 11 is further processed.

[0073] Figure 4 is a schematic diagram showing the first irradiation state of the inspection device 5 for inspecting the optical element 6, which is configured as protective glass 6b, of the irradiation system 8. The protective glass 6b shown in Figure 4 shields the interior of the irradiation system 8 from the ambient atmosphere. For this purpose, the inspection device 5 is inserted into the insertion hole of the irradiation system 8, into which the fiber end of an irradiation source 10 (not shown in Figure 4) is inserted when the irradiation system 8 is used as intended. The illumination equipment 12, as also shown in the AA cross-sectional view in Figure 4, in this example has eight illumination sources 13 arranged in a circle coaxial with the vertical axis 25 of the inspection device 5. The camera 19 of the detection equipment 16 is positioned in the center on the vertical axis 26 of the hole and is directed to detect the first optical surface 11a of the protective glass 6b. When the inspection device 5 is used as intended, the vertical axis 25 of the inspection device 5 and the vertical axis 26 of the hole coincide. In the insertion hole, the ratio of hole length to hole diameter is large, and the hole diameter mainly corresponds to several millimeters or several centimeters. Therefore, illumination of the protective glass 6b located at the rear of the insertion hole is only possible by the illumination beam 14 incident almost perpendicularly on the first optical surface 11a. Illumination from the side is advantageous but not possible.

[0074] The inspection device 5 shown in Figure 4 represents a first illumination condition in which the individual illumination sources 13 of the first illumination source group 27a of the lighting equipment 12, for example, two illumination sources 13 that are close to each other, are switched on during the first recording. The illumination sources 13 of the second illumination source group 27b, the third illumination source group 27c, and the fourth illumination source group 27d are switched off. At this time, the optical surface 11 is illuminated by the illumination sources 13 of the first illumination source group 27a, and anomalies 7 present in the first illumination area 28a become visible, while anomalies 7 present in the second illumination area 27b are not shown by interference reflection 29.

[0075] In order to represent anomaly 7 that is not shown in the detection data 20 in the first illumination condition, the first optical surface 11a is illuminated in the second illumination condition shown in Figure 5. For this purpose, the illumination source 13 of the second illumination source group 27b is 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. At this time, the optical surface 11 is illuminated by the illumination source 13 of the first illumination source group 27b, and anomaly 7 present in the second illumination area 28b becomes visible, while anomaly 7 present in the first illumination area 28a is not shown by interference reflection 29. Subsequently, the illumination sources 13 of the third illumination source group 27c and the fourth illumination source group 27d are switched on to generate the third and fourth illumination conditions, and in each case, detection data 20 (not shown in Figures 4 and 5) of the optical surface 11 is recorded.

[0076] Figure 6 is a schematic diagram of the detection data 20 performed by the inspection device 5 shown in Figures 4 and 5 while illuminating the protective glass 6b. All illumination sources 13 of the illumination source group 27 are switched on, and the area is illuminated by a total of eight illumination sources 13. In this case, the illumination devices 12 and / or detection devices 16 are aligned with each other so that multiple reflections 29 overlapping the optical anomaly feature 21 are produced by the reflected illumination beam 17, and therefore the anomaly 7 present on the optical surface 11 is not represented.

[0077] Figure 7 is a schematic diagram of the selection data for the protective glass 6b, which has been combined to form an evaluation dataset 22. The detection data 20 for the protective glass 6b is generated while the protective glass 6b is illuminated under the different lighting conditions described above. The control unit 18 (not shown in Figure 7) is configured to decompose the detection data 20 into individual selection data 23 for each case and to process only the selection data 23 in which the anomaly 7 is included as an optical anomaly feature 21. In this case, the overall image of the optical surface 11 of the protective glass 6b is decomposed into multiple sub-regions 30 for each case, and the position and size of the sub-regions 30 are selected so as not to include lighting conditions that are unfavorable for evaluation, such as interference reflections 29 that overlap with the optical anomaly feature 21. In this case, the overall image is divided into four sub-regions 30, each constituting a quadrant of the overall image. These sub-regions 30 containing disruptive reflections 29 are ignored. The selection data 23 are combined to form an evaluation dataset 22, which represents the entire optical surface 11 and makes the optical anomaly feature 21 visible. Next, in order to determine the degree of contamination of the protective glass 6b, the optical anomaly features 21 may be evaluated by an image evaluation program, for example, by identifying the size of the optical anomaly features 21, identifying the number of optical anomaly features 21 per unit area, and / or identifying the nature of the optical anomaly features 21.

[0078] In Figures 1 through 7, only some of several elements of the same type are shown by symbols as examples.

Claims

1. An inspection device (5) for investigating an optical element (6) with respect to an abnormality (7) of the optical element (6) used in an additive manufacturing apparatus (1) that manufactures a three-dimensional workpiece by irradiating a processing beam emitted from an irradiation system (8) onto a raw material powder layer coated on an irradiation surface (4), wherein the optical element (6) is arranged between the irradiation source (10) of the irradiation system (8) and the irradiation surface (4), along the optical beam path formed by the irradiation system (8), and the inspection device (5) comprises an illumination device (12), a detection device (16), and a control unit (18). The lighting device (12) has at least one lighting source (13) configured to emit a lighting beam (14) that generates at least one lighting pattern (15) on the optical element (6), The detection device (16) is configured to detect a reflected beam that includes at least a portion of the illumination beam (14) reflected by the optical element (6), The control unit (18) is configured such that the illumination pattern (15) on the optical element (6) can be identified by the control unit (18). The control unit (18) is configured to temporarily store detection data (20) including data from the detection device (16), The control unit (18) is further configured such that the detection data (20) is recorded while the optical surface (11) of the optical element (6) is illuminated with a plurality of different illumination patterns, and the abnormality (7) of the optical element (6) is represented as an optical abnormality feature (21) in the detection data (20). Inspection device (5).

2. The inspection apparatus (5) according to claim 1, wherein the control unit (18) is configured to decompose the detection data (20) into individual selection data (23) for each case, and to process only the selection data (23) in which the anomaly (7) is included as an optical anomaly feature (21).

3. The inspection apparatus (5) according to claim 2, wherein the control unit (18) combines the selected data (23) to form an evaluation dataset (22), and the optical anomaly features (21) of the anomaly (7) present in the optical element (6) and / or on the optical surface (11) of the optical element (6) can be evaluated from the evaluation dataset (22).

4. The inspection apparatus (5) according to any one of claims 1 to 3, wherein at least a portion of the optical surface (11) of the optical element (6) is illuminated by the illumination beam (14).

5. The inspection apparatus (5) according to any one of claims 1 to 4, wherein the optical surface (11) of the optical element (6) is illuminated entirely by the illumination beam (14).

6. The inspection device (5) according to any one of claims 1 to 5, wherein the optical surface (11) of the optical element (6) is detected in its entirety by the detection device (16).

7. The inspection apparatus (5) according to any one of claims 1 to 6, wherein the lighting device (12) and the detection device are arranged on the same side of the optical element (6).

8. The inspection apparatus (5) according to any one of claims 1 to 7, wherein the optical beam path (9) forms an optical axis, and the optical path of the illumination beam (14) is arranged at an angle with respect to the optical axis of the inspection apparatus (5).

9. The inspection apparatus (5) according to any one of claims 1 to 8, wherein the illumination beams (14) are activated individually and isolated for each case, such that their illumination attributes, such as intensity and / or wavelength, differ from one another.

10. The inspection apparatus (5) according to claim 8, wherein at least one of the illumination sources (13) is offset perpendicularly with respect to the optical axis.

11. The inspection apparatus (5) according to any one of claims 1 to 10, wherein the lighting pattern (15) is in the shape of points, strips, or tiles.

12. The inspection device (5) according to any one of claims 1 to 11, having at least one mounting bracket to which the lighting device (12) and the detection device (16) can be attached.

13. The inspection apparatus (5) according to claim 12, wherein the receiving device has mounting means for detachably attaching it to the additive manufacturing apparatus (1) and / or the irradiation system (8).

14. An inspection method for investigating an optical element (6) with respect to an abnormality (7) of the optical element (6) used in an additive manufacturing apparatus (1) that manufactures a three-dimensional workpiece by irradiating a processing beam emitted from an irradiation system (8) onto a raw material powder layer coated on an irradiation surface (4), wherein the optical element (6) is arranged between the irradiation source (10) of the irradiation system (8) and the irradiation surface (4), along the optical beam path formed by the irradiation system (8), i) Illuminate the optical element (6) to generate an illumination pattern (15) on the optical surface (11) of the optical element (6), ii) Simultaneously with the illumination, the reflected beam is detected, wherein the reflected beam includes at least a portion of the illumination beam (14) reflected by the optical element (6). iii) The illumination pattern (15) on the optical element (6) may be predetermined. iv) The detection data (20), including the data from the detection device (16), is temporarily stored. This includes, While the optical element (6) is illuminated by a plurality of different illumination patterns on its optical surface (11), the detection data (20) is recorded, and the abnormality (7) of the optical element (6) is further configured to be represented in the detection data (20) as an optical anomaly feature (21). Testing method.

15. The inspection method according to claim 14, wherein the detection data (20) is broken down into individual selected data (23) for each case, and only the selected data (23) in which the anomaly (7) is included as an optical anomaly feature (21) is further processed.

16. The inspection method according to claim 15, wherein the selected data (23) is combined to form an evaluation dataset (22), and the optical anomaly features (21) of an anomaly (7) present in the optical element (6) and / or on the optical surface (11) of the optical element (6) can be evaluated from the evaluation dataset (22).

17. Additive manufacturing apparatus (1) comprising an inspection apparatus (5) according to any one of claims 1 to 13, wherein a processing beam is irradiated onto a raw material powder layer to manufacture a three-dimensional workpiece.

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