Calibrating multiple laser beams for additive manufacturing

A method of aligning a first scanning optic associated with a first irradiation beam and a second scanning optic associated with a second irradiation beam during additive manufacturing of a target object, the method comprising:

• irradiating an object area of a layer of a powdered material provided on a building platform with at least one of the first irradiation beam or the second irradiation beam, wherein the object area is associated with a cross-section of the target object;
• irradiating a calibration area of the layer of the powdered material with at least one of the first irradiation beam and the second irradiation beam, wherein the calibration area is associated with a cross-section of a calibration object, thereby forming an intermediate top face of the calibration object, wherein the forming of the intermediate top face of the calibration object includes irradiating the calibration area in a plurality of portions, a first portion of the plurality of portions is irradiated by guiding at least one of the first irradiation beam or the second irradiation beam along scan vectors that run parallel to each other in a first orientation or deviate from running parallel by less than 10°;
• guiding the first irradiation beam with the first scanning optic over the intermediate top face so as to melt a first calibration pattern having a first geometrical feature into the intermediate top face;
• guiding the second irradiation beam with the second scanning optic over the intermediate top face so as to melt a second calibration pattern having a second geometrical feature into the intermediate top face;
• directing a first illuminating light beam onto the intermediate top face, wherein an incident direction of the first illuminating light beam has an azimuthal component in a range from 45° to 90° with respect to the first orientation of the scan vectors of the first portion;
• acquiring at least a first image of the intermediate top face including the first calibration pattern and the second calibration pattern while the first illuminating light beam is directed onto the intermediate top face;
• using at least the first image, identifying image points related to the first geometrical feature and the second geometrical feature;
• from the image points, deriving a spatial offset between positions of the first geometrical feature and the second geometrical feature within the layer of the powdered material;
• and
• aligning at least one of the first scanning optic or the second scanning optic taking into account the spatial offset,
• wherein a second portion of the plurality of portions is irradiated by guiding at least one of the first irradiation beam and the second irradiation beam along scan vectors that run parallel to each other in a second orientation or deviate from running parallel by less than 10°, the method further comprising:
• directing a second illuminating light beam onto the intermediate top face, wherein an incident direction of the second illumination light beam has an azimuthal component in a range from 45° to 90° with respect to the second orientation,
• acquiring a second image of the intermediate top face including the first calibration pattern and the second calibration pattern while the second illuminating light beam is directed onto the intermediate top face, and
• generating a superposition of the first image and the second image,
• wherein the identifying of the image points related to the first feature and the second feature is performed based on the superposition of the first image and the second image.

A method of aligning a first scanning optic associated with a first irradiation beam and a second scanning optic associated with a second irradiation beam during additive manufacturing of a target object, the method comprising:

• irradiating an object area of a layer of a powdered material provided on a building platform with at least one of the first irradiation beam or the second irradiation beam, wherein the object area is associated with a cross-section of the target object;
• irradiating a calibration area of the layer of the powdered material with at least one of the first irradiation beam and the second irradiation beam, wherein the calibration area is associated with a cross-section of a calibration object, thereby forming an intermediate top face of the calibration object, wherein the forming of the intermediate top face of the calibration object includes irradiating the calibration area in a plurality of portions, a first portion of the plurality of portions is irradiated by guiding at least one of the first irradiation beam or the second irradiation beam along scan vectors that run parallel to each other in a first orientation or deviate from running parallel by less than 10°;
• guiding the first irradiation beam with the first scanning optic over the intermediate top face so as to melt a first calibration pattern having a first geometrical feature into the intermediate top face;
• guiding the second irradiation beam with the second scanning optic over the intermediate top face so as to melt a second calibration pattern having a second geometrical feature into the intermediate top face;
• directing a first illuminating light beam onto the intermediate top face, wherein an incident direction of the first illuminating light beam has an azimuthal component in a range from 45° to 90° with respect to the first orientation of the scan vectors of the first portion;
• acquiring at least a first image of the intermediate top face including the first calibration pattern and the second calibration pattern while the first illuminating light beam is directed onto the intermediate top face;
• using at least the first image, identifying image points related to the first geometrical feature and the second geometrical feature;
• from the image points, deriving a spatial offset between positions of the first geometrical feature and the second geometrical feature within the layer of the powdered material;
• aligning at least one of the first scanning optic or the second scanning optic taking into account the spatial offset, and
• for each of the first calibration pattern and the second calibration pattern, melting a plurality of straight-line segments with a flat surface region,
• wherein, for each of the first calibration pattern and the second calibration pattern, at least one of the plurality of straight-line segments extends in the first portion and is oriented with respect to the scan vectors used for the first portion with a first intersecting angle in a range from 45° to 90°.