Measurement of molten pool position in additive manufacturing

Abstract

Multiple detectors are positioned along an inclined optical axis to receive optical radiation from the workpiece surface. Changes in the received optical power are used to estimate the workpiece surface position along the workpiece surface axis. The received optical power is radiable from the workpiece surface, and the estimated temperature of the workpiece surface is used to adjust the received optical power. One or two single-element detectors, or linear detectors, can be used. [Effect] The position of the focused spot generated from the optical power received in a linear detector can be used to evaluate the axial position on the workpiece surface.

Description

Technical Field

[0001] This disclosure relates to material deposition evaluation in additive manufacturing.

Background Art

[0002] One additive manufacturing system uses a laser processing beam to create a melt pool onto which additive material is directed. This deep material is incorporated into the melt pool and increases the height of the portion being formed. It is desirable to measure with respect to the portion height. Accordingly, an improved approach is needed.

Summary of the Invention

[0003] A typical apparatus includes a tracking optical system positioned along a tracking axis, the tracking optical system comprising at least one focusing element and at least one photodetector. The at least one focusing element is positioned to receive optical radiation from the molten pool and direct the received optical radiation toward the photodetector. The tracking axis is tilted with respect to the machining axis, and the photodetector includes at least one single-pixel photodetector or linear detector. The photodetector is connected to the photodetector and is operable to generate a tracking signal related to the position of the molten pool along the machining axis based on the received optical radiation directed toward the photodetector. In some examples, the tracking axis is tilted at least 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, or 90 degrees with respect to the machining axis. In a typical example, the optical system further comprises an aperture plate positioned to attenuate the received optical radiation toward the photodetector, and at least one optical element is a lens positioned to focus the optical radiation received from the molten pool adjacent to the aperture plate. Some typical examples define aperture plates, circular apertures, rectangular apertures, slits, or two or more aperture edges. In some cases, the aperture plate is positioned to block 20% to 80% of the optical radiation received from the focusing element, thereby causing a beam displacement in the opposite direction that generates an opposite change in the optical power received at the photodetector. In some examples, the processing beam source is operable to generate the processing beam, and the positioning element responds to a tracking signal to adjust the relative position of the molten pool with respect to the tracking axis. In some examples, the positioning element is a stage operable to adjust the position of the molten pool along the processing axis.

[0004] In an additional example, at least one detector of the tracking optical system includes a first detector and a second detector, and the photodetector is configured to be operable to generate corresponding first and second tracking signals related to the position of the molten pool along the machining axis, based on the portion of the received optical radiation. The first and second tracking signals are configured to have opposite slopes with respect to changes in the position of the molten pool along the machining axis. In a convenient example, the optical system further includes a first aperture plate and a second aperture plate, respectively, configured to attenuate the received optical radiation directed toward the first and second photodetectors. In some examples, at least one photodetector is a linear array, and the photodetector is connected to the photodetector and configured to be operable to generate tracking signals related to the position of the molten pool along the machining axis, based on the position from which the received optical radiation enters the photodetector. In some embodiments, the position of the molten pool along the machining axis is based on the centroid of the intensity pattern of the radiation entering the photodetector.

[0005] In some embodiments, a processing beam source is operable to generate a processing beam, and a positioning element responds to a tracking signal to adjust the relative position between the molten pool and the tracking axis. In a typical example, a beam splitter is positioned to direct first and second portions of the received radiation to corresponding first and second ranges of a linear detector array. According to some embodiments, the first and second portions of the received radiation are different spectral portions, and the beam splitter is a dichroic beam splitter that selectively directs the different spectral portions to corresponding first and second ranges of a linear detector array. In further examples, the beam splitter is positioned to direct first and second portions of the received radiation to corresponding first and second ranges of a linear detector array that move further away as the distance to the molten pool increases.

[0006] A typical system includes a machining beam source positioned such that a machining beam along the machining axis is directed towards a working area on the substrate, thereby focusing the machining beam onto the working area. An optical focus sensor is positioned to receive optical radiation from the working area in response to the machining beam along an axis inclined with respect to the machining axis, and to establish the position of the machining beam focus relative to the working area. The optical focus sensor includes at least one of a single-pixel detector and a linear detector positioned to receive the optical radiation.

[0007] The method involves receiving optical radiation from a work area of ​​a substrate along a tracking axis inclined with respect to a substrate axis perpendicular to the work area. The power of the optical radiation received from the work area and transmitted by an aperture placed along the tracking axis is measured. Based on the measured power, the displacement of the work area along the substrate axis is estimated. In some cases, the displacement of the work area is adjusted based on the displacement, or one or more processing conditions are modified. In a typical example, the optical radiation from the work area is generated by the irradiation of the work area with the processing beam, or is a portion of the tracer beam directed toward the work area. In further examples, the displacement of the work area is adjusted by moving the work area along the substrate axis, or by adjusting the processing beam directed toward the work area. In some examples, the optical radiation is related to the molten pool generated by the processing beam, such as blackbody radiation, or other radiation generated based on the temperature of the molten pool. In an additional example, the temperature of the molten pool is estimated, and based on the estimated temperature, the measured power is adjusted, where the displacement of the work area along the substrate axis is determined based on the adjusted and measured power. In other typical embodiments, power measurement involves measuring first and second powers of optical radiation received from a work area and transmitted by first and second apertures positioned along the tracking axis, where the displacement of the work area along the substrate axis is determined based on the first and second powers.

[0008] An additional typical method includes receiving optical radiation from the substrate work area along a tracking axis inclined with respect to the substrate axis perpendicular to the work area, and directing the received optical radiation to a linear detector. Based on the position where the received optical radiation enters the linear detector, the displacement of the work area along the substrate axis is determined, and the displacement of the work area or the processing conditions are adjusted.

[0009] A detection device for detecting a molten pool generated by a processing beam comprises a first photodetector that is ejected from the molten pool and receives first radiation along a first axis, and a second photodetector that is ejected from the molten pool and receives second radiation along a second axis tilted with respect to the first axis. The first photodetector may include a first focusing optical system for focusing the first radiation and a first photodetector for photoelectric conversion of the focused first radiation. The first photodetector may include an aperture member that defines an aperture located at the focusing position of the first radiation by the first focusing optical system, and the first photodetector receives the first radiation passing through the aperture of the aperture member. The first photodetector may include a linear detector located at the focusing position of the first radiation by the first focusing optical system, and may include a photoelectric conversion element arranged in one dimension. In some examples, the first angle formed by the propagation axis of the processing beam and the first axis is greater than the second angle formed between the propagation axis of the processing beam and the second axis. In further examples, the second angle formed between the propagation axis of the processing beam and the second axis is different from the third angle formed between the propagation axis of the processing beam and the axis of specular reflection of the processing beam from the molten pool. In additional examples, the second angle formed between the propagation axis of the processing beam and the second axis is smaller than the third angle formed between the propagation axis of the processing beam and the axis of specular reflection of the processing beam from the molten pool. According to this disclosure, the second angle formed between the propagation axis of the processing beam and the second axis is larger than the third angle formed between the propagation axis of the processing beam and the axis of specular reflection of the processing beam from the molten pool. In typical examples, the second axis is slightly inclined from the propagation axis of the processing beam. The second axis may be substantially parallel to the propagation axis of the processing beam. In examples, a folding member is placed in the optical path of the processing beam and bends the second axis. The second radiation may be received by a second photodetector via the folding member.

[0010] In a further example, the detection device of claim 29 includes a controller, a first photodetector including a first photodetector for photoelectric conversion of first radiation, and a second photodetector including a second photodetector for photoelectric conversion of second radiation, wherein the controller calculates a first output from the first photodetector and a second output from the second photodetector. In some examples, the controller obtains dimensions of the molten pool based on the first and second outputs. The dimensions of the molten pool include at least one of the height of the molten pool and the size perpendicular to the height direction of the molten pool. In a further example, a processing device that processes a workpiece by forming a molten pool on the workpiece with a processing beam comprises a detection device. In some examples, a property modification device is positioned to modify the properties of the processing beam, such as beam shape, size, power, polarization state, propagation direction, or other properties, based on an output from the property modification device. A material supply device is positioned to supply one or more materials to the molten pool. The processing device may shape an object on the workpiece by supplying the materials to the molten pool.

[0011] The aforementioned and other features and advantages of this disclosure will become more apparent from the following detailed description, which will proceed with reference to the attached drawings. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 shows a typical additive manufacturing system (AMS) that includes an optical height sensor. [Figure 2A] Figure 2A shows a portion of the AMS including an optical height sensor and an optical molten pool temperature sensor. [Figure 2B] Figure 2B shows a typical beam splitter used in the optical height sensor shown in Figure 2A. [Figure 2C] Figure 2C is a graph showing the detected optical power as a function of aperture position for a typical optical height sensor shown in Figure 2A. [Figure 2D]Figure 2D shows a typical arrangement of the processing beam axis and the temperature sensor axis. [Figure 2E] Figure 2E shows a typical arrangement of the processing beam axis and the temperature sensor axis. [Figure 2F] Figure 2F shows a typical arrangement of the processing beam axis and the temperature sensor axis. [Figure 2G] Figure 2G shows a typical arrangement of the processing beam axis and the temperature sensor axis. [Figure 2H] Figure 2H shows a typical arrangement of the processing beam axis and the temperature sensor axis. [Figure 3A] Figure 3A shows a portion of the AMS that includes an optical height sensor, which includes dual photodetectors and their respective apertures. [Figure 3B] Figure 3B is a graph showing the detected optical power as a function of aperture position for each of the dual detectors of a typical optical height sensor shown in Figure 3A. [Figure 3C] Figure 3C is a graph showing the detected optical power as a function of aperture position for each of the dual detectors of a typical optical height sensor shown in Figure 3A. [Figure 4A] Figure 4A shows a portion of the AMS that includes an optical height sensor, which includes a linear detector array. [Figure 4B] Figure 4B shows the beam transmission on the linear detector array in Figure 4A as a function of height variation. [Figure 4C] Figure 4C shows a linear detector array and a cylindrical lens that increases the optical power to the linear detector array. [Figure 5A] Figure 5A shows a portion of the AMS that includes an optical height sensor, which includes a linear detector array positioned to receive dual detection beams. [Figure 5B] Figure 5B shows the position of the focus spot on the linear detector array in Figure 5A for two different heights. [Figure 5C] Figure 5C shows the optical power in the linear detector array shown in Figure 5A. [Figure 5D]FIG. 5D is a diagram showing the optical power in the linear detector array of FIG. 5A. [Figure 6A] FIG. 6A is a diagram showing a part of an AMS including an optical height sensor having a linear detector array arranged to receive a dual detection beam in an intersecting optical path. [Figure 6B] FIG. 6B is a diagram showing the positions of the focused spots on the linear detector array of FIG. 6A for different heights. [Figure 6C] FIG. 6C is a diagram showing the positions of the focused spots on the linear detector array of FIG. 6A for different heights. [Figure 6D] FIG. 6D is a diagram showing the optical power in the linear detector array of FIG. 6A for the focused spots shown in FIG. 6C. [Figure 7] FIG. 7 is a diagram showing a representative shaping method including the optical height sensor disclosed herein. [Figure 8] FIG. 8 is a diagram showing a calibration method for using on-axis and off-axis signal pixel photodetectors to measure the height of a molten pool. [Figure 8A] FIG. 8A is a diagram showing a calibration method for using on-axis and off-axis signal pixel photodetectors to measure the height of a molten pool. [Figure 8B] FIG. 8B is a diagram showing a calibration method for using on-axis and off-axis signal pixel photodetectors to measure the height of a molten pool. [Figure 8C] FIG. 8C is a diagram showing a calibration method for using on-axis and off-axis signal pixel photodetectors to measure the height of a molten pool. [Figure 9] FIG. 9 is a diagram showing an additional shaping method using the disclosed method and apparatus for height sensing. DETAILED DESCRIPTION OF THE INVENTION

[0013] As used in this application and claims, the singular forms “a,” “an,” and “the” include the plural form unless the context clearly indicates otherwise. In addition, the term “includes” means “comprises.” Furthermore, the term “coupled” does not exclude the presence of intermediate elements between the combined items.

[0014] The systems, apparatus, and methods described herein should not be construed as limiting. Rather, this disclosure covers all novel and non-obvious features and aspects of the various disclosed embodiments, both individually and in various combinations and subcombinations of each other. The disclosed systems, methods, and apparatus are not limited to any particular aspects or features or combinations thereof, and the disclosed systems, methods, and apparatus do not require the existence of any one or more particular interests or the solution of any problem. The operating theory is provided for the sake of explanation, but the disclosed systems, methods, and apparatus are not limited to such operating theory.

[0015] Some of the operations of the disclosed methods are described in a particular order for convenience, but it should be understood that the method of this description is inclusive of reordering unless required by the specific wording set forth below. For example, operations described consecutively may, in some cases, be reordered or performed simultaneously. Furthermore, for simplicity, the accompanying drawings may not show the various techniques by which the disclosed systems, methods, and apparatus may be used in conjunction with other systems, methods, and apparatus. In addition, the description may sometimes use terms such as “produce” and “provide” to describe the disclosed methods. These terms are high-level abstractions of the actual operations performed. The actual operations corresponding to these terms may vary depending on the particular implementation and will be readily recognizable to those skilled in the art.

[0016] For convenience in the following explanation, the terms “light” and “optical radiation” refer to propagating electromagnetic waves in the wavelength range of 300 nm to 10 μm, although other wavelengths may also be used. This radiation is referred to here as propagating within one or more “beams” typically based on optical radiation, generated by lasers such as laser diodes and other light sources, or emitted from molten pools or other heat sources. The beams may have a spatial extent associated with one or more laser transverse modes and may be substantially collimated.

[0017] For convenience, a beam is described as propagating along one or more axes. Such axes are generally based on one or more line segments, and thereafter, the axes may include several noncollinear portions as axes that are bent, folded, or otherwise respond to mirrors, prisms, lenses, and other optical elements. The term “lens” is used here to refer to a single refractive optical element (singlet), or a composite lens containing one or more singlets, doublets, or other composite lenses. In some examples, the beam is shaped or directed by a refractive optical element, while in others, a reflective optical element such as a mirror is used, or a combination of refractive and reflective elements is used. Such optical systems may be called refractive, reflective, and reflective-refracting, respectively. Other types of refractive, reflective, diffracting, holographic, and other optical elements may be used as convenient. In some examples, a beam splitter, such as a cubic beam splitter, is used to separate the input beam into a transmitted beam and a reflected beam, but a plate or other beam splitter may be used. In this context, angles less than 0.5, 1, 2, 5, 10, or 20 degrees are referred to as slight angles, and axes of angles less than 0.5, 1, 2, 5, 10, or 20 degrees are referred to as substantially parallel.

[0018] The examples are described using the XYZ coordinate system and generally describe methods and apparatus for height adjustment or the Z-axis. In most examples, thermally induced radiation (such as blackbody radiation) is used to estimate the change in height, but a dedicated optical beam or processing beam section may be used. A single-element photodetector (also called a single-pixel photodetector) or linear detector is convenient, however, an imaging array detector may be used, although it may be unnecessarily complex and expensive compared to a single-element or linear detector. An axis inclined with respect to the work surface normal is sometimes referred to as a tracking axis or simply an inclined axis. The processing beam can also be transmitted to axes with slight inclination, but it should be clear which axis is intended in the description. The work surface position may be measured with respect to the surface normal or the processing beam axis, and generally, height is preferably measured with respect to the surface normal, but in any case, such position measurement is referred to as height measurement. The work surface or molten pool axis is an axis perpendicular to the work surface or molten pool and is typically slightly different from the processing axis. "Photodetector" refers to an electronic system capable of operating to generate either a digital or analog output in response to optical power detected by one or more photodetectors, and may include processing to compensate for substrate temperature or other processing. Such processing may also be performed by additional processing hardware or processor-executable instructions.

[0019] Typical additive manufacturing systems Referring to Figure 1, a typical additive manufacturing system 100 includes a laser optical system 102 positioned such that the processing beam is aligned with an axis 104 that is inclined at an angle α with respect to an axis 106 perpendicular to the target area 107 on the substrate 108. For convenience, a typical XYZ coordinate system 101 is shown. The xyz axis stage 105 is coupled to the laser optical system 102 to adjust the processing beam focus size or focus position. The processing beam is generally directed towards the target area 107 to be melted, and for this reason, the target area is referred to here as the molten pool. In a typical AMS application, the processing beam provides sufficient power to generate the molten pool. The substrate 108 is held by the XYZ stage 109. During processing, the movements of the stages 105 and 109 may be adjusted so that they move simultaneously or continuously. In other examples, the stage 105 or the XYZ stage 109 may be a 5-axis or 6-axis stage system. A portion of the manufacturing process may be moved relative to the processing head, or the processing head may be moved relative to the portion, or both may be moved relative to each other. In the following, a Z-sensor is used to determine the processing beam.

[0020] Nozzles 110 and 112 are connected to a material supply 114 by supply lines 111 and 113, respectively, and are capable of supplying material to the molten pool 107 to manufacture the intended portion. The nozzles 110 and 112 and the substrate material 108 are placed in a chamber 134 connected to a reservoir 136 containing an inert gas such as nitrogen, so that processing can be carried out in a suitable atmosphere.

[0021] During processing, material from nozzles 110 and 112 is added to the molten pool 107, changing the Z position of the molten pool 107. This height change can be measured by a Z sensor 122 positioned to receive optical synchrotron radiation (and typically blackbody synchrotron radiation, or other thermal synchrotron radiation emitted in response to the processing beam) along an axis 120 tilted at an angle Θ with respect to axis 106, where Θ is generally greater than 5, 10, 15, 20, 25, 30, 40, 45, or 50 degrees. In other examples, an additional optical source may be provided, with a beam directed onto the molten pool 107, and a portion of this beam used by the Z sensor 122. The optical radiation received by the Z sensor 122 may be visible or infrared radiation, or radiation in other spectral ranges. Visible and infrared radiation are convenient because inexpensive detectors in these spectral ranges are available. Alternatively, a reflected or scattered portion of the processing beam may be used by the Z sensor 122. In some cases, a portion of the processing beam may be used. The optical power emitted from the molten pool 107 depends on the temperature of the molten pool, and typically, the amount of optical radiation measured by the Z sensor 122 is adjusted based on the temperature of the molten pool when determining the height of the molten pool. The Z sensor 122 may be fixed to the xyz stage 123 to allow positioning along and around the axis 120. Alternatively, the laser optics 102 and the Z sensor may be coupled to a common xyz stage. The Z sensor 122 is coupled to a controller 130, which may adjust processing conditions such as the processing beam focus, substrate position, or material flow rate or processing beam power. The controller 130 is connected to a database 132 containing part specifications used in the fabrication process, and to valves 111A, 113A capable of controlling the material flow to the molten pool 107.

[0022] The processing beam is transmitted to the molten pool 107 via a beam splitter 121 positioned to receive optical radiation from the molten pool 107 and direct the optical radiation towards a temperature sensor (T sensor) 126. Typically, the T sensor 126, Z sensor 122, and laser optics 102 are positionable on a common xyz stage. The beam splitter 121 typically includes a portion for transmitting the processing beam and a portion for reflecting the optical radiation from the molten pool 107. Other beam splitters, such as neutral or dichroic beam splitters, may be used, in which case the processing beam is reflected to the substrate 108 by the beam splitter, and the temperature sensor 126 receives the optical radiation transmitted by the beam splitter. In yet another example, no beam splitter is used, and the optical paths to the laser optics 102 and the temperature sensor 126 do not overlap. The optical radiation emitted from the molten pool 107 is based on the molten pool temperature, and the received optical power can be used to evaluate the molten pool temperature. The temperature output of the temperature sensor 126 can be used in conjunction with the Z sensor 122 to compensate for the dependence of the optical power at the Z sensor 122 on the molten pool temperature. In an alternative embodiment, the Z sensor 122 may be rotated to measure the position of the molten pool 107 along the X, Y, or other axes, or one or more additional sensors providing multiple sensors may be arranged in different configurations and may provide different position information, enabling compensation for position or other dependencies. For example, the Z sensor 122 may be positioned to measure the position of the molten pool 107 along the X and Y axes.

[0023] Typical single-detector Z sensor Figure 2A shows the AMS200 and typical Z-sensor 203 and T-sensor 201. The XYZ coordinate system 291 is used for convenience. Referring to Figure 2A, the processing beam 202 is directed towards the lens 206 along the inclination axis 204 and then directed towards the surface 211 of the molten pool on the substrate 210 via the beam splitter 208. As shown in Figure 2B, the beam splitter 208 is positioned along an axis 209 inclined with respect to the X and Y axes of the coordinate system 291 and includes an aperture 208A through which the processing beam 202 is transmitted. Because the beam splitter 208 is tilted, the aperture 208A is elongated to provide a nearly circular effective aperture in a plane perpendicular to the axis 204 for the transmission of the processing beam 202. The radiation emitted from the molten pool is directed along the axis 240 to the beam splitter 208 and to a T-sensor 201 which includes a lens 242 that focuses the radiation emitted to the detector 246 through the aperture defined in the aperture plate 244. The detector 246 generates an output signal related to the molten pool temperature.

[0024] The Z sensor 203 is positioned along the tilt axis 216 and includes a lens 220 that directs radiation 214 emitted from the surface 211 toward an aperture 222 defined within the aperture plate 224. The radiation emitted from the surface 211 is focused to a first position 217. The detector 230 is optically positioned behind the aperture plate 224 and generates a Z signal that can be used to determine the Z-axis position of the surface 211. During machining, the surface 211 is constructed to become surface 211' with a displacement Δz relative to surface 211. The radiation emitted from surface 211' then propagates along axis 232 to a second focal point 233 that is displaced from the first focal point 217. Because the first focal point 217 and the second focal point 233 are displaced, the received radiation may be attenuated differently in the aperture plate 224, thereby causing the detector 230 to generate different output signals that may be related to the Z-axis displacement, such as ΔZ.

[0025] The position of aperture 222 along axis 236 may be selected to produce appropriate Z-dependent attenuation. As shown in Figure 2C, the aperture may be at 250, centered relative to the beam focus of the molten pool radiation. Additional Z displacement in either direction reduces the received optical power. However, if the aperture is positioned, for example at 252, to block a portion of the focused beam, and a +Z-axis displacement increases the received beam power and a -Z displacement decreases the received power, the processing beam or substrate stage control can be adjusted in an appropriate direction.

[0026] In the exemplary configuration shown in Figure 2A, the processing beam 202 is directed toward the surface 211 at a small angle of incidence, generating a specular reflected beam 203 that propagates along axis 205, which lies between axis 204 and axis 240 associated with the T sensor 201. Other configurations may be used, and axis 240 does not need to be perpendicular to the surfaces 211, 211'. For example, referring to Figure 2D, the processing beam 202A may be directed toward the surface 211 along axis 204A to generate a specular reflected beam 203A that propagates along axis 205A, which is at a larger angle than axis 240. In another example shown in Figure 2E, the processing beam 202B may be directed toward the surface 211 along axis 204B to generate a specular reflected beam 202B that propagates along axis 205B, whose angle is opposite to axis 240.

[0027] The axis arrangements shown in Figures 2A and 2E-2F are shown in Figures 2F-2H, where the optical elements are omitted for convenience. In Figure 2F, the processing beam 272 is incident along axis 274, and the reflected portion of the processing beam 273 is reflected along axis 275, which is perpendicular to the perpendicular 270 to the surface 271. The temperature sensor is positioned to receive radiation along axis 277, which is at an angle to the perpendicular 270 that is greater than the angle of axis 275. In Figure 2G, the processing beam 282 is incident along axis 284, and the reflected portion of the processing beam 283 is reflected along axis 285, which is perpendicular to the perpendicular 280 to the surface 271. The temperature sensor is positioned to receive radiation along axis 287, which is at an angle to the perpendicular 280 that is less than the angle of axis 285, and therefore lies between the perpendicular 280 and axis 285. In Figure 2H, the processing beam 292 is incident along axis 294, and the reflected portion of the processing beam 293 is reflected along axis 295, which is indicated by perpendicular 290 to the surface 271. The temperature sensor is positioned to receive radiation along axis 297, which is at an angle to perpendicular 290 that is smaller than the angle of axis 294, and therefore located between perpendicular 290 and axis 294. None of the above axes need to be perpendicular to the surface 271.

[0028] Typical dual-detector Z sensors Referring to Figure 3A, a typical dual-detector Z-sensor 300 includes a lens 302 positioned to direct radiation emitted from region 304 of the substrate 306 towards the inclined plate 308. The XYZ coordinate system 301 is used for convenience. A beam splitter 310 directs the focused portion of the emitted radiation to apertures 312, 313 defined on aperture plates 316, 317 and to detectors 320, 321. The beam splitter 310 may be a neutral beam splitter or a dichroic beam splitter. A dichroic beam splitter may generate different spectral portions that can be measured and compared to evaluate the substrate temperature. As shown in Figures 3B-3C, apertures 312, 313 may be positioned to be associated with inclinations of different signs with respect to Z-axis displacement. The inclined plate 308 may be adjusted to appropriately position or “bias” the beam to each aperture. Referring to Figure 3A, radiation emitted from region 304 is incident near the edges of aperture plates 316 and 317 in a direction along axis 340, thereby attenuating the emitted radiation to bias positions such as 350 and 351 in Figures 3B-3C. When region 304 is displaced as region 304', the emitted radiation is focused along axis 342, closer to the center of aperture 312 and closer to the edge of aperture 313, thereby increasing the power detected in relation to aperture 312 and decreasing the power detected in relation to aperture 313, as shown in Figures 3B-3C, respectively. Rotation of the inclined plate 308 displaces axes 340 and 342, thereby adjusting the attenuation of the beam propagating along these axes to apertures 312 and 313. For example, rotation may be applied to attenuate by 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or other numerical values ​​in the range of 0-100%. When a beam is incident on an aperture and initially placed at the center of the aperture, subsequent changes in the Z position reduce the beam power received by the associated detector, but generally, no indicator of the direction of the Z change is provided.For example, due to the appropriate rotation of the inclined plate 308, the position change in the +Z direction may be related to an increase in the beam power received by the detector 320, and the position change in the -Z direction may be related to a decrease in the beam power received by the detector 320. Therefore, the change in the beam power received may be related to both the magnitude and direction of the Z-axis position change of region 304 of the substrate 306.

[0029] In this example, the optical power received from the molten pool depends on the temperature of the molten pool, but the optical power in detectors 320 and 321 are proportional, so that a ratio or other combination may be used to reduce or eliminate the temperature dependence in the Z-sensor optical power, and a separate temperature sensor is not required. In this and other examples, the Z-sensor includes a circular or elliptical aperture, but instead, a slit, an opaque or reflective spot, a rectangle, other curved or polygonal shapes, or the detector size itself may be used. The dimensions of apertures 312 and 313 along axes 315 and 319 are selected based on the beam dimensions to provide beam attenuation selected as a function of the Z-axis displacement of region 304, respectively.

[0030] Typical Linear Detector Z Sensor Referring to Figure 4A, a typical Z-sensor 400 includes a linear detector 402 positioned along a tilt axis 414 to receive optical radiation from the surface 404 of the molten pool on the substrate 405. The linear detector 402 is typically a unitary linear photodiode array, such as a self-scanning diode array containing photodiodes arranged along axis 403, but other linear arrays, such as two or more discrete photodiodes, may be used. As shown, as the surface 404 of the molten pool grows along axis 405 by a quantity ΔZ to become a displaced surface 404', the beam from the molten pool surface (i.e., 404 or 404' formed by the lens 411) that initially propagates along the tilt axis 414 propagates along the tilt axis 416. However, depending on the configuration of the lens 411 and any associated optical system, the displaced axis may be either above or below the initial axis at the linear detector 402. The linear detector 402 is connected to a processor 410 that can be operated to determine the molten pool temperature and the displacement in the Z-axis direction. The Z-axis controller 412 is connected to the processor 402 and, further, to the substrate stage, the processing beam optics, or both, to adjust the Z-axis position as needed. In Figure 4A, radiation emitted from surface 404 is focused along the tilt axis 414 toward the focus spot 450, while radiation emitted from the displaced surface 404' is directed toward the focus spot 452 along axis 416, generating a displaced focus spot in the linear detector 402. As shown, a +Z displacement of the molten pool surface generates a downward shift of the focus spot 450, although in other examples, an upward shift may be generated.

[0031] For example, referring to Figure 4B, along axis 414, the focus spot 450 generated in the linear detector 402 is located within the active region 451 of the linear detector 402. Along axis 416, the focused spot 452 generated in the linear detector 402 is located within the active region 451 and is displaced along axis 454 of the linear detector. Therefore, the displacement of the molten pool results in the displacement of the focus spots 450 and 452, and the position of the focused spots indicates the Z position. With linear sensors, it is not necessary to accurately measure power, and the detector elements can be saturated. The beam center on the linear detector can be found by identifying the edge position of the detector element having a linear or other response, or the center of the saturated spot.

[0032] Figure 4C shows a typical linear sensor assembly 460, which includes a linear sensor 462 and a cylindrical lens 464 positioned to increase the optical power supplied to the linear sensor 462.

[0033] Typical dual-beam linear detector Z sensor Referring to Figure 5A, a typical dual-beam linear detector Z sensor 500 is similar to the Z sensor in Figure 4A, but includes a beam splitter 550 and an inclined plate 552. The beam splitter 550 directs the first and second beam portions from the work surface 506 along their respective axial portions 502, 503 to mirrors, prisms, or other reflectors 560, 562, thereby causing the first and second beam portions to enter different areas of the linear detector 556. The beam portions are generally focused to generate first and second beam spots in the linear detector 556. If the work surface 506 is displaced by ΔZ, indicated as the work surface 506', the beam portions are directed along the axial portions 512, 513 and focused as first and second spots, respectively, displaced relative to the beam spot associated with the previous position of the work surface. The inclined plate 552 may be rotated to select the appropriate location for the beam spot.

[0034] Figure 5B shows the active region 570 of the linear detector 556, showing the first and second beam spots 572, 573 associated with the work surface 506, and the first and second beam spots 574, 575 associated with the work surface 506'. Figures 5C-5D show the beam spot intensity as it corresponds to its position on the active region 570. Figure 5C corresponds to the work surface 506, and Figure 5D corresponds to the work surface 506'. As shown, in the configuration of Figure 5A, the beam spots move away as the work surface rises.

[0035] The beam splitter 550 may be a dichroic beam splitter, thereby associating beam spots such as beam spots 572 and 573 with different spectral portions of the beam from the work surface 506. Differences in power or spot shape using the spectral portions allow for estimation of the work surface temperature.

[0036] Typical dual-beam linear detector Z sensor with intersecting beams Referring to Figure 6A, a typical dual-beam linear detector Z sensor 600 is similar to the Z sensor in Figure 5A and includes a beam splitter 650 and an inclined plate 652. The beam splitter 650 directs the first and second beam portions from the work surface 606 along their respective axial portions 602, 603 to mirrors, prisms, or other reflectors 660, 662, thereby causing the first and second beam portions to be incident on different regions of the linear detector 656. The beam portions are generally focused to generate first and second beam spots in the linear detector 656. If the work surface 606 is displaced by ΔZ, indicated as the work surface 606', the beam portions are directed along the axial portions 612, 613 and focused as first and second spots, respectively, displaced relative to the beam spot associated with the previous position of the work surface. The inclined plate 652 may be rotated to select the appropriate location for the beam spot. In contrast to Figure 5A, the propagation axes related to the beam spot in the beam partial cross-section and linear detector converge as the working surface height increases, as shown in Figures 6B-6C.

[0037] Figure 6B shows the active region 670 of the linear detector 656, which includes first and second beam spots 672, 673 associated with the work surface 606, and first and second beam spots 674, 675 associated with the work surface 606'. In a further example shown in Figure 6C, the active region 670 receives first and second beam spots 672, 673 associated with the work surface 606, and first and second beam spots 678, 679 associated with the work surface 606'. In this example, the first and second beam spots 678, 679 are in contact and beginning to overlap. A typical power distribution in the linear detector 656 is shown in Figure 6D.

[0038] Typical Z-sensing methods Referring to Figure 7, a typical method 700 includes, in 702, receiving optical radiation from the work surface along the tilt axis. The optical radiation may be radiation emitted from the molten pool, a portion of the processing beam, or a dedicated Z-sensing beam. For example, thermal radiation emitted by the molten pool, scattered or reflected portions of the processing beam, or scattered or reflected portions of a Z-axis analysis beam from a dedicated Z-axis source may be used. To accommodate different sensing configurations, in 704, a detector or sensor type is selected. If a single-element photodetector is used, in 706, the optical power transmitted by an aperture located around the tilt axis is measured, and in 708, if necessary, the measured power is corrected for the molten pool temperature. In 710, the Z position is determined, and in 712, the Z position of the substrate or the processing beam focus may be adjusted, or other processing conditions may be applied based on the determined Z position.

[0039] When a dual single-element detector is used, at 714, the optical power transmitted by each aperture located around the tilt axis is measured, and at 716, the power ratio is obtained. At 710, the Z position is determined, and at 712, the Z axis or machining adjustment is performed. When a linear detector is used, at 720, the beam position on the linear detector is measured, at 710, the Z position is determined, and at 712, it is adjusted. In some cases, the measured Z position is used to interrupt or accelerate material deposition at one or more positions by controlling the machining beam diameter, the optical power of the machining beam, or the material flow, and the Z position does not need to be adjusted.

[0040] Typical Z calibration Signals from on-axis and off-axis detectors may be used to determine the height using a lookup table or other approach. Referring to Figure 8-8C, a typical method 800 includes a calibration method 801A and a height measurement method 801B. In 802, signals from on-axis and off-axis detectors (VON and VOFF, respectively) are measured as a function of molten pool temperature for several heights Z. The resulting data appear to resemble curves 851-853 shown in Figure 8A for three heights Z1-Z3. For the data at each height Z, in 804, the slope (Cl) and intercept (C2) of a linear fit for VOFF are calculated as a function of VON. The slope and intercept differ for each height Z, so Cl=C1(Z) and C2=C2(Z). In 806, a linear fit of C2(Z) is performed as a function of C1(Z) with slope C3 and intercept C4. Figure 8B shows a typical graph of C2(Z) as a function of C1(Z) as measurement 861 along a linear fit 862. In 808, C1(Z) fits a Gaussian distribution shown as curve 871 in Figure 8C. Similarly, C2(Z) fits a Gaussian distribution as curve 872 in Figure 8C, but only one of C1(Z) or C2(Z) is needed. In 808, this fit is inverted to find Z=F(C1), where F is the reciprocal of the Gaussian distribution. That is, C1(Z) fits a Gaussian distribution as C1(Z)=Aexp[-aZ2], where A and a are fitting constants and Z=[In(A / Cl) / a]¹ / ². C3, C4 and F (fitting constants A, a) are stored for use in measurement. Representative measurement data is shown in graphs in Figures 8A-8C. These graphs are for illustrative purposes only, and it is not necessary to perform the required calibration steps.

[0041] Once calibration method 801A is complete, height measurement can be performed as shown in method 801B. In 820, the off-axis and on-axis signals are measured at each detector, and in 822, Cl is calculated as Cl = (VOFF - C4) / (VON + C3), where C3 and C4 are determined in advance during calibration. For Cl, in 824, the height may be found as Z = F(C1), where F is determined in advance during calibration.

[0042] Typical molding methods Referring to Figure 9, a typical method 900 includes selecting or generating an appropriate part design in 901 and preparing a substrate in 902. In 903, additive manufacturing is used to fabricate the part according to the design, while measuring the height using one or more optical beams propagating along one or more axes inclined with respect to the substrate surface, or a working area such as a molten pool on the substrate. Based on the measured height, the height or fabrication parameters may be adjusted. In 904, the fabricated part is post-processed as necessary, for example, by polishing or smoothing the surface, or by removing excess material added by the fabrication process. In 906, the part is inspected before shipping.

[0043] The processing beam from the AMS may include a laser beam, synchrotron radiation, X-ray beam, electron beam, ion beam, or other beam. The operator may use only one of the dual detectors as needed. For example, the user may switch between the two detectors to observe the molten pool using only the on-axis detector and the off-axis detector.

[0044] Given the many possible embodiments to which the principles of the disclosed technology may be applied, it should be recognized that the illustrated embodiments are merely preferred examples of the invention and should not be construed as limiting the scope of this disclosure. I claim as my invention all that is contained in the scope and spirit of the appended claims, all novel and non-obvious features, and all combinations of the disclosed features.

[0045] Innovative features The innovative features described herein include, but are not limited to, the following: [A1] A tracking optical system positioned along a tracking axis and having at least one focusing element and at least one photodetector, wherein the at least one focusing element is positioned to receive optical radiation from the molten pool and direct the received optical radiation toward the photodetector, the tracking axis is inclined with respect to the machining axis, and the photodetector includes at least one single-pixel photodetector or a linear detector. A photodetector connected to the photodetector and operable to generate a tracking signal associated with the position of the molten pool along the machining axis or the molten pool axis perpendicular to the molten pool, based on the received optical radiation directed toward the photodetector, A device equipped with the following features. [A2] The tracking axis is inclined at least 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, or 90 degrees relative to the machining axis or the molten pool axis. The apparatus described in A1. [A3] The optical system further comprises an aperture plate positioned to attenuate the received optical radiation directed toward the photodetector. The apparatus described in either A1 or A2. [A4] The at least one optical element is a lens positioned to focus the received optical radiation from the molten pool adjacent to the aperture plate. The apparatus described in any of A1 to A3. [A5] The aperture plate defines a circular aperture, a rectangular aperture, a slit, or two or more aperture edges. The apparatus described in any of A1 to A4. [A6] The aperture plate is a slit or is defined by two or more aperture edges. The apparatus described in any of A1 to A5. [A7] The aperture plate is positioned to block 20% to 80% of the received optical radiation from the focusing element, thereby causing the beam displacement in the opposite direction to generate the opposite change in the received optical power. The apparatus described in any of A1 to A6. [A8] The system further comprises a processing beam source operable to generate the processing beam, and a positioning element that responds to the tracking signal to adjust the relative position between the molten pool and the tracking axis. The apparatus described in any of A1 to A7. [A9] The positioning element is a stage that can operate to adjust the position of the molten pool along the machining axis or the molten pool axis. The apparatus described in any of A1 to A8. [A10] At least one detector of the tracking optical system includes a first detector and a second detector, wherein the detector is configured to operate to generate corresponding first and second tracking signals relating to the position of the molten pool along the machining axis based on a portion so of the received optical radiation, wherein the first and second tracking signals have opposite inclinations with respect to changes in the position of the molten pool along the machining axis or the molten pool axis. The apparatus described in any of A1 to A9. [A11] The optical system further comprises a first aperture plate and a second aperture plate, respectively, which are positioned to attenuate the received optical radiation directed toward the first detector and the second detector. The apparatus described in any of A1 to A10. [A12] The at least one photodetector is a linear detector array. The apparatus described in any of A1 to A11. [A13] The light receiver is connected to the photodetector and is operable to generate the tracking signal associated with the position of the molten pool along the machining axis, based on the position where the received optical radiation enters the photodetector. The apparatus described in any of A1 to A12. [A14] The position of the molten pool along the processing axis or the molten pool axis is based on the centroid of the intensity pattern of the radiation intensity relative to the photodetector. The apparatus described in any of A1 to A13. [A15] The system further comprises a processing beam source operable to generate the processing beam, and a positioning element that responds to the tracking signal to adjust the relative position between the molten pool and the tracking axis. The apparatus described in any of A1 to A14. [A16] The array further comprises beam splitters arranged to direct the first and second portions of the received optical radiation to corresponding first and second ranges of the linear detector array. The apparatus described in any of A1 to A15. [A17] The first and second portions of the received optical radiation are different spectral portions, and the beam splitter is a dichroic beam splitter that selectively directs the different spectral portions to the corresponding first and second ranges of the linear detector array. The apparatus described in any of A1 to A16. [A18] The beam splitter is positioned such that the first and second portions of the received optical radiation are directed to corresponding first and second ranges of the linear detector array, having a separation that increases with increasing distance to the molten pool. The apparatus described in any of A1 to A17. [A19] The optical radiation received from the molten pool is one or more thermal radiation emitted from the molten pool in response to the processing beam, a portion of the processing beam, or a portion of the analytical beam from the analytical beam source. The apparatus described in any of A1 to A18. [B1] A machining beam source is positioned such that a machining beam along the machining axis is directed towards the work area of ​​the substrate, thereby focusing the machining beam onto the work area. An optical focus sensor is positioned to receive optical radiation from the work area in response to the machining beam along an axis inclined with respect to the machining axis, Equipped with, The optical focus sensor includes at least one of a single-pixel detector and a linear detector, which are arranged to receive the optical radiation. system. [C1] Receiving optical radiation from the work area of ​​the substrate along a tracking axis that is inclined with respect to the substrate axis perpendicular to the work area, The power of the optical radiation received from the work area and transmitted by an aperture positioned along the tracking axis is measured. Based on the measured power, the displacement of the work area along the substrate axis is determined, Based on the determined displacement, adjust at least one machining parameter, A method that includes this. [C2] The machining parameter is the position of the work area. The method described in C1. [C3] The optical radiation from the work area is generated by the irradiation of the work area by the processing beam, or is a portion of the tracer beam directed toward the work area. The method described in either C1 or C2. [C4] The displacement of the work area is adjusted by moving the work area along the substrate axis, or by adjusting the processing beam directed toward the work area. The method described in any of C1 to C3. [C5] The optical radiation is related to the molten pool generated by the processing beam. The method described in any of C1 to C4. [C6] The optical radiation is thermal radiation associated with the melting pool. The method described in any of C1 to C5. [C7] To estimate the temperature of the melting pool, Based on the estimated temperature, the measured power is adjusted, It further includes, The displacement of the work area along the substrate axis is determined based on the adjusted measured power. The method described in any of C1 to C6. [C8] Measuring the power includes measuring the first and second powers of the optical radiation received from the work area and transmitted through the first and second apertures, wherein the displacement of the work area along the substrate axis is determined based on the first and second powers. The method described in any of C1 to C7. [D1] Receiving optical radiation from the work area of ​​the substrate along a tracking axis that is inclined with respect to the substrate axis perpendicular to the work area, The received optical radiation is directed towards a linear detector, Based on the position at which the received optical radiation enters the linear detector, the displacement of the work area along the substrate axis is determined, Based on the determined displacement, adjust at least one machining parameter, A method that includes this. [D2] The machining parameter is the displacement of the work area. The method described in D1. [D3] The optical radiation received from the work area is one or more thermal radiation emitted from the substrate, a portion of the processing beam directed toward the substrate, or a portion of the analysis beam directed toward the substrate from the analysis beam source. The method described in either D1 or D2. [E1] A detection device for detecting a molten pool generated by a processing beam, A first photodetector is ejected from the molten pool and receives first radiation along the first axis, A second photodetector that receives a second radiation emitted from the molten pool and along a second axis tilted with respect to the first axis, A detection device equipped with the following features. [E2] The first light-receiving device includes a first focusing optical system for focusing the first radiation and a first photodetector for photoelectric conversion of the focused first radiation. The detection device described in E1. [E3] The first light receiving device includes an aperture member that defines an aperture positioned at the focal point of the first radiation by the first focusing optical system, and the first photodetector receives the first radiation passing through the aperture member. A detection device as described in either E1 or E2. [E4] The first photodetector includes a linear detector positioned at the focal point of the first radiation by the first focusing optical system, and also includes a photoelectric conversion element arranged in one dimension. A detection device as described in any of E1 to E3. [E5] The first angle formed by the propagation axis of the processing beam and the first axis is greater than the second angle formed between the propagation axis of the processing beam and the second axis. A detection device as described in any of E1 to E4. [E6] The second angle formed between the propagation axis of the processing beam and the second axis is different from the third angle formed between the propagation axis of the processing beam and the axis of specular reflection of the processing beam from the molten pool. A detection device as described in any of E1 to E5. [E7] The second angle formed between the propagation axis of the processing beam and the second axis is smaller than the third angle formed between the propagation axis of the processing beam and the axis of specular reflection of the processing beam from the molten pool. A detection device as described in any of E1 to E6. [E8] The second angle formed between the propagation axis of the processing beam and the second axis is greater than the third angle formed between the propagation axis of the processing beam and the axis of specular reflection of the processing beam from the molten pool. A detection device as described in any of E1 to E7. [E9] The second axis is slightly inclined from the propagation axis of the processing beam. A detection device as described in any of E1 to E8. [E10] The second axis is substantially parallel to the propagation axis of the processing beam. A detection device as described in any of E1 to E9. [E11] The system further comprises a folding member positioned in the optical path of the processing beam and bending the second axis. A detection device as described in any of E1 to E10. [E12] The second radiation is received by the second photodetector via the folding member. A detection device as described in any of E1 to E11. [E13] Equipped with an additional controller, The first photodetector includes a first photodetector that converts the first radiation into photoelectricity, the second photodetector includes a second photodetector that converts the second radiation into photoelectricity, and the controller calculates a first output from the first photodetector and a second output from the second photodetector. A detection device as described in any of E1 to E12. [E14] The controller obtains the dimensions of the melt pool based on the first and second outputs. A detection device as described in any of E1 to E13. [E15] The dimensions of the melting pool include at least one of the height of the melting pool and the size of the melting pool. A detection device as described in any of E1 to E14. [E16] The dimensions of the melt pool include at least one transverse dimension of the melt pool. A detection device as described in any of E1 to E15. [F1] A processing device that processes a workpiece by forming a molten pool on the workpiece with a processing beam, The detection device is provided as described in any of E1 to E16. Processing device. [F2] The system further comprises a characteristic changing device that modifies the characteristics of the processing beam based on the output from the characteristic changing device. The processing device described in F1. [F3] The system further comprises a material supply device for supplying material to the aforementioned melting pool. A processing device as described in either F1 or F2. [F4] The processing device forms an object on the workpiece by supplying the material to the molten pool. A processing device as described in F1 to F3.

Claims

1. A light source that irradiates a processing beam and forms a molten pool in the workpiece with the processing beam, A material supply device that supplies molding material to the melting pool and deposits it onto the object to be molded, In addition, A photodetector that receives radiation ejected from the molten pool and having temperature-dependent optical power, A detector for measuring the output related to the temperature of the melt pool, Equipped with, Based on the output of the light receiving device and the output of the detector, information regarding the height of the molten pool is detected. Additive molding device.

2. The light-receiving device includes a focusing optical system for focusing the radiation and a photodetector for converting the focused radiation into photoelectric energy. The additive molding apparatus according to claim 1.

3. The light receiving device includes an aperture member that defines an aperture positioned at the focusing position of the radiation by the focusing optical system, and the photodetector receives the radiation passing through the aperture member. The additive molding apparatus according to claim 2.

4. The photodetector includes a linear detector positioned at the point of focus of the radiation by the focusing optical system, and also includes a photoelectric conversion element arranged in one dimension. The additive molding apparatus according to claim 2.

5. Equipped with an additional controller, The light receiving device includes a photodetector that converts the radiation into photoelectric energy. The controller compensates for the dependence of the output detected by the photodetector on the temperature of the molten pool based on the output of the detector, and calculates information regarding the height of the molten pool. The additive molding apparatus according to any one of claims 1 to 4.

6. The detector measures an output relating to the temperature of the molten pool based on the radiation from the molten pool. The additive molding apparatus according to any one of claims 1 to 5.

7. A processing device that processes a workpiece by forming a molten pool on the workpiece with a processing beam, The addition molding apparatus is provided according to any one of claims 1 to 6. Processing device.

8. The processing device creates an object on the workpiece by supplying the molding material to the molten pool. The processing device according to claim 7.

9. A processing beam is irradiated to form a molten pool in the workpiece. A material supply device that supplies molding material to the melting pool and deposits it onto the object to be molded, In addition, A photodetector that receives radiation ejected from the molten pool and having temperature-dependent optical power, A detector for measuring the output related to the temperature of the melt pool, Equipped with, Based on the output of the light receiving device and the output of the detector, information regarding the height of the molten pool is detected. Additive molding device.

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