A device for highly real-time monitoring of laser direct energy deposition additive manufacturing

Abstract

The present application relates to the field of laser direct energy deposition additive manufacturing equipment, and provides a laser direct energy deposition additive manufacturing forming height real-time monitoring device.The device comprises a machining laser focusing lens group for irradiating a collimated detection laser on a deposition forming molten pool surface, a double-telecentric imaging light path and a camera arranged obliquely for collecting a light spot, and an upper computer connected to the camera; wherein the collimated detection laser is arranged in parallel or coaxially coincides with a focusing machining laser used for laser direct energy deposition processing, and does not overlap in the wave band; the light spot is formed when the collimated detection laser irradiates on the deposition forming molten pool surface; the machining laser focusing lens group comprises a turning mirror and a first focusing lens group arranged in sequence along the light path; and the double-telecentric imaging light path comprises a second focusing lens group, a diaphragm and a third focusing lens group arranged in sequence along the light path.

Description

Technical Field

[0001] This invention relates to the field of laser direct energy deposition additive manufacturing equipment, and more particularly to a real-time monitoring device for the forming height of laser direct energy deposition additive manufacturing. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] Laser direct energy deposition (L-DED), also known as laser metal deposition (LMD), is an additive manufacturing technology characterized by high energy density, low heat input, and high forming efficiency. It is applicable to a wide range of metal powders or wires and is widely used in aerospace, automotive, and shipbuilding industries. However, due to the strong light radiation and high dynamics of the molten pool spot region during metal deposition, the problem of real-time acquisition of deposition height (i.e., the vertical distance between the molten pool surface and the reference plane of the laser processing head) has been difficult to solve satisfactorily. Real-time acquisition of deposition height is of paramount importance for both process research on laser metal deposition and closed-loop control of the additive manufacturing part forming process.

[0004] Currently available methods for height monitoring in laser metal deposition mainly include the following:

[0005] One approach is to use a line laser scanner. After completing one or more layers of deposition, the line laser scanner is used to scan the outline of the part during the laser-off interval to generate a point cloud image of the cross-sectional outline of the printed surface. This allows for high-precision modeling of the deposition process. However, this height monitoring method is not real-time. Instead, it requires a continuous pause in the laser metal deposition process. The scanning and data processing are completed during the pauses in the laser metal deposition. This results in a large amount of data processing, and the scanning process will inevitably affect the deposition efficiency and product quality.

[0006] Secondly, a rangefinder high dynamic range camera is used to take pictures of the deposition contour from the side of the deposition layer under the supplementary lighting of industrial searchlights. The deposition height can be obtained in real time through image processing. However, the height dimension error extracted from the contour is relatively large, especially when the deposition process is unstable or collapse occurs. In addition, this monitoring method is greatly limited by the shape of the additive manufacturing parts. When the shape of the parts is slightly complex and the detection light path is blocked, the deposition height cannot be monitored in real time.

[0007] Thirdly, drawing on the principle of optical triangulation, a collimated probe laser beam is used to illuminate the molten pool surface, and the corresponding molten pool surface height value is obtained through optical imaging processing. To achieve real-time synchronization between deposition height monitoring and the molten pool movement process, the collimated probe laser focusing spot typically requires an accuracy of tens of micrometers and must illuminate the molten pool surface without deviation. This usually requires the probe and imaging optical paths to be coaxially arranged with the main optical path of the processing laser. While this method can achieve real-time measurement of the deposition height, has good synchronization and high measurement accuracy, and is not limited by the geometry of additive manufacturing parts, when the main optical path structure of the laser metal deposition head is slightly complex or constrained by the mechanical dimensions of the processing head itself, it becomes difficult to coaxially arrange the probe and imaging optical paths within the optical path of the processing head. Summary of the Invention

[0008] To address the technical problems mentioned above, this invention provides a real-time monitoring device for the forming height of laser direct energy deposition additive manufacturing. This invention designs a scheme in which the collimating detection laser and the processing focusing laser are arranged coaxially, and the dual telecentric imaging optical paths are arranged at an angle relative to the main optical path. While satisfying the requirement for real-time synchronous monitoring of the height of the deposited molten pool, the geometry of the laser metal deposition processing head is not restricted.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] The first aspect of the present invention provides a real-time monitoring device for the forming height of laser direct energy deposition additive manufacturing.

[0011] A real-time monitoring device for the forming height of laser direct energy deposition additive manufacturing includes: a processing laser focusing lens group for irradiating the surface of the deposited molten pool with a collimating probe laser; a dual telecentric imaging optical path and camera arranged at an angle for collecting the light spot; and a host computer connected to the camera; wherein the collimating probe laser and the focusing processing laser used for laser direct energy deposition are arranged parallel or coaxially and coincidentally, and do not overlap in the wavelength band; the light spot is formed when the collimating probe laser irradiates the surface of the deposited molten pool;

[0012] The processing laser focusing lens group includes a deflecting mirror and a first focusing lens group arranged sequentially along the optical path;

[0013] The dual telecentric imaging optical path includes a second focusing lens group, an aperture stop, and a third focusing lens group arranged sequentially along the optical path;

[0014] The host computer analyzes the deviation between the light spot and the deposition point at the reference position based on image processing to obtain the distance between the surface of the deposited molten pool and the processing head, so as to monitor the forming height.

[0015] Furthermore, the dual telecentric imaging optical path also includes a bandpass filter and a narrowband filter. The narrowband filter is disposed between the camera and the third focusing lens group, and the bandpass filter is disposed in front of the second focusing lens group, between the second focusing lens group and the aperture stop, or between the aperture stop and the third focusing lens group.

[0016] Furthermore, the cutoff wavelength of the bandpass filter is less than the wavelength of the focused laser used in laser direct energy deposition (LDED) processing, and the transmission wavelength range covers the wavelength range of the collimated probe laser; the center wavelength of the narrowband filter is equal to the center wavelength of the collimated probe laser, and the filter bandwidth range is 1 ± 0.2 nm.

[0017] Furthermore, the vertical distance between the focal plane of the second focusing lens group and the surface of the deposited molten pool is f1±10mm, and the distance between the aperture and the focal plane of the second focusing lens group is f1; the distance between the focal plane of the third focusing lens group and the aperture is f2, and the distance between the camera and the focal plane of the third focusing lens group is f2±10mm; where f1 is the focal length of the second focusing lens group and f2 is the focal length of the third focusing lens group.

[0018] Furthermore, the tilt angle α between the optical axis of the dual telecentric imaging optical path and the optical axis of the processing laser focusing lens group ranges from 30° to 60°. The processing laser focusing lens group is also used to focus the processing laser for transmitting or reflecting direct energy deposition processing.

[0019] Furthermore, when a lens is used in the processing laser focusing lens assembly, the transmittance of the lens through collimating the detected laser is not less than 50%.

[0020] Furthermore, when a reflector is used in the processing laser focusing lens assembly, the reflectivity of the reflector through collimating the detected laser is not less than 50%.

[0021] Furthermore, the lateral distance between the optical axis of the collimating detection laser and the optical axis of the processing laser focusing lens group is 0–30 mm.

[0022] Furthermore, there is no beam combining mirror group or there is a beam combining mirror group between the deflecting mirror and the first focusing mirror group. The beam combining mirror group includes: a first deflecting plane mirror, a beam combining prism mirror and a second deflecting plane mirror arranged in sequence according to the optical path.

[0023] Furthermore, the aperture has a circular hole at its center with a diameter of 0.5 to 1.5 mm.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] This invention designs a real-time monitoring device for the forming height in laser direct energy deposition (LDD) additive manufacturing by combining a parallel or overlapping collimated probe laser with a side-axis tilted imaging optical path. Based on practical problems, it solves the difficulty of integrating the imaging optical path into the LDD processing optical path due to the limitations imposed by the imaging optical path structure on the focal length of the focusing lens and the position of optical components. Simultaneously, it simplifies the structure of the optical path system. This design allows for better understanding and control of the process, improving the dimensional accuracy of the deposited form.

[0026] This invention designs a scheme in which the collimating detection laser and the processing focusing laser are arranged coaxially, and the dual telecentric imaging optical paths are arranged at an angle relative to the main optical path. This scheme allows for real-time synchronous monitoring of the molten pool height during deposition, while the geometry of the laser metal deposition head remains unrestricted. This invention is adaptable to conventional lateral coaxial powder-feed laser metal deposition heads, lateral wire-feed (or powder-feed) laser cladding heads, and various annular laser metal deposition heads with in-center wire-feed (or powder-feed) optical paths. It solves the problems of these types of heads, where the focusing lens group and other units typically have central openings and relatively complex structures, and are often limited by the size of the focusing lens group and other optical path structures, making it difficult to meet the geometric constraints between imaging units in the dual telecentric imaging optical path. Furthermore, this invention offers high measurement accuracy, and the height monitoring range fully meets the requirements of actual industrial measurement and control. Attached Figure Description

[0027] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0028] Figure 1 This is a structural diagram of the laser direct energy deposition additive manufacturing forming height real-time monitoring device shown in Embodiment 1 of the present invention;

[0029] Figure 2 This is a structural diagram of the beam combining and focusing lens assembly after coupling the processing laser of the processing head with the collimating detection laser for monitoring the forming height, as shown in Embodiment 2 of the present invention;

[0030] Figure 3 This is a structural diagram of the beam combining mirror assembly shown in Embodiment 2 of the present invention;

[0031] Among them, 1. Collimating detection laser, 2. Deflecting mirror, 3. Collimating processing laser optical axis, 4. Collimating detection laser optical axis, 5. First focusing lens group, 6. Plane corresponding to the actual molten pool surface, 7. Reference molten pool surface (i.e., the position of 0 point of deposition height), 8. Camera, 9. Narrowband filter, 10. Third focusing lens group, 11. Aperture, 12. Double telecentric optical path optical axis, 13. Second focusing lens group, 14. Bandpass filter, 201. Collimating detection laser, 202. Deflecting mirror, 203. Collimating processing ring laser, 204. Feed tube (processing optical axis is coaxial with it), 205. Beam combining mirror group, 206. First focusing lens group, 207. Reference molten pool surface (i.e., the position of 0 point of deposition height), 501. First folding plane mirror, 502. Beam combining prism mirror, 503. Second folding plane mirror. Detailed Implementation

[0032] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0033] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0034] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0035] Example 1

[0036] This embodiment provides a real-time monitoring device for the forming height of laser direct energy deposition additive manufacturing, comprising: a processing laser focusing lens group for irradiating the surface of the deposited molten pool with a collimating probe laser, a dual telecentric imaging optical path and camera 8 arranged at an angle for collecting the light spot, and a host computer connected to the camera 8; wherein, the collimating probe laser and the focusing laser used for laser direct energy deposition processing are arranged parallel or coincidentally (the two optical axes can coincide, i.e., coaxial, or they can not coincide but the two axes are parallel), and do not overlap in the wavelength band; the light spot is formed when the collimating probe laser irradiates the surface of the deposited molten pool;

[0037] The processing laser focusing lens group includes a deflecting mirror 2 and a first focusing lens group 5 arranged sequentially along the optical path;

[0038] The dual telecentric imaging optical path includes a second focusing lens group 13, an aperture stop 11, and a third focusing lens group 10 arranged sequentially along the optical path;

[0039] The host computer calculates the deviation between the light spot and the deposition point at the reference position through image processing, and obtains the distance between the surface of the deposited molten pool and the processing head, so as to monitor the forming height.

[0040] The dual telecentric imaging optical path also includes a bandpass filter 14 and a narrowband filter 9.

[0041] This embodiment mainly focuses on a lateral coaxial powder-feeding ring-shaped laser metal deposition head. The key technical features of this embodiment are as follows:

[0042] like Figure 1 As shown, 1 is the collimating detection laser, 2 is the deflecting mirror, 3 is the collimating processing laser optical axis, 4 is the collimating detection laser optical axis, 5 is the first focusing lens group, 6 is the plane corresponding to the actual molten pool surface, 7 is the reference molten pool surface (i.e., the position of 0 point of deposition height), 8 is the camera, 9 is the narrowband filter, 10 is the third focusing lens group, 11 is the aperture stop, 12 is the optical axis of the dual telecentric optical path, 13 is the second focusing lens group, and 14 is the bandpass filter. The bandpass filter 14 and the narrowband filter 9 are fixed in front of the camera 8, with the bandpass filter 14 fixed in front of the narrowband filter 9.

[0043] In one embodiment of the present invention, the narrowband filter 9 can be arranged between the camera 8 and the third focusing lens group 10, and the bandpass filter 14 can be arranged in front of the second focusing lens group 13. The cutoff wavelength of the bandpass filter 14 is less than the wavelength of the focusing laser used in laser direct energy deposition (LDED) processing, and the transmission wavelength range covers the wavelength range of the collimating probe laser; the center wavelength of the narrowband filter 9 is equal to the center wavelength of the collimating probe laser, and the filtering bandwidth range is 1 ± 0.2 nm.

[0044] In another embodiment of the present invention, the narrowband filter 9 can be arranged between the camera 8 and the third focusing lens group 10, and the bandpass filter 14 can be arranged between the second focusing lens group 13 and the aperture stop 11. The cutoff wavelength of the bandpass filter 14 is less than the wavelength of the focusing laser used in laser direct energy deposition (LDED) processing, and the transmission wavelength range covers the wavelength range of the collimating probe laser; the center wavelength of the narrowband filter 9 is equal to the center wavelength of the collimating probe laser, and the filtering bandwidth range is 1 ± 0.2 nm.

[0045] In another embodiment of the present invention, the narrowband filter 9 can be arranged between the camera 8 and the third focusing lens group 10, and the bandpass filter 14 can be arranged between the aperture stop 11 and the third focusing lens group 10. The cutoff wavelength of the bandpass filter 14 is less than the wavelength of the focusing laser used in laser direct energy deposition (LDED) processing, and the transmission wavelength range covers the wavelength range of the collimating probe laser; the center wavelength of the narrowband filter 9 is equal to the center wavelength of the collimating probe laser, and the filtering bandwidth range is 1 ± 0.2 nm.

[0046] The above three schemes are only for illustrating three implementation schemes of the present invention. As for the positional relationship between the bandpass filter 14 and the narrowband filter 9 and the second focusing lens group 13, the third focusing lens group 10 and the aperture 11, there are no requirements and they can be flexibly selected. The present invention does not limit them here.

[0047] In some embodiments, the vertical distance between the focal plane of the second focusing lens group 13 and the surface of the deposited molten pool is f1 ± 10 mm; the distance between the aperture 11 and the focal plane of the second focusing lens group 13 is f1; the distance between the focal plane of the third focusing lens group 10 and the aperture 11 is f2; the distance between the camera 8 and the focal plane of the third focusing lens group 10 is f2 ± 10 mm; the tilt angle α of the optical axis of the dual telecentric imaging optical path relative to the optical axis of the processing laser focusing lens group ranges from 30° to 60°; wherein, f1 is the focal length of the second focusing lens group 13, and f2 is the focal length of the third focusing lens group 10. Based on this, we can conclude that:

[0048]

[0049] Wherein, d1 represents the distance between the principal ray of the actual probe light reflected back to the dual telecentric imaging optical path (and before it has passed through the second focusing lens group 13) from the focused spot on the surface of the molten pool and the optical axis of the dual telecentric imaging optical path, and d2 represents the distance between the principal ray of the actual probe light reflected back to the dual telecentric imaging optical path from the focused spot on the surface of the molten pool and when it reaches the camera 8 and the optical axis of the dual telecentric imaging optical path.

[0050] In some embodiments, the diameter of the collimating probe laser ranges from 1 to 5 mm, and the lateral distance between the optical axis of the collimating probe laser and the optical axis of the processing laser focusing lens group is 0 to 30 mm (when it is equal to 0, it is coaxial arrangement; when it is not equal to 0, it is parallel arrangement); the intersection of the optical axis of the dual telecentric imaging optical path and the reference molten pool surface 7 falls within the molten pool, and the distance from the edge of the molten pool ranges from ±2 mm.

[0051] In some embodiments, the wavelength range of the focused laser used in laser direct energy deposition processing does not overlap with that of the collimating probe laser. The wavelength of the collimating probe laser is in the visible light band, and the wavelength range of the collimating probe laser varies within ±1 nm of its main wavelength. The collimating probe laser power (i.e., the power of the rake laser) reaching the surface of the molten pool ranges from 1 to 10 mW.

[0052] In one embodiment of the present invention, the aperture 11 has a circular hole at its center, the diameter of which ranges from [missing information]. The thickness of the aperture is 0.1 to 1 mm.

[0053] As an embodiment of the present invention, the camera 8 is an area scan camera or a line scan camera, the detector of the camera is a CCD or CMOS detector, and the applicable image signal acquisition frequency of the camera is 30Hz to 50KHz. When a line scan camera is used, the detector line array, the collimating detection laser optical axis, and the optical axis of the dual telecentric optical path system of the line scan camera are all on the same plane.

[0054] As an embodiment of the present invention, the processing laser focusing lens group is a lens or a reflector. In addition to transmitting or reflecting the focusing laser used in laser direct energy deposition processing, the lens or reflector can also collimate and detect the laser. When a lens is used, the transmittance of the lens through collimated laser detection is not less than 50%; when a reflector is used, the reflectance of the reflector through collimated laser detection is not less than 50%.

[0055] In this embodiment, the light reflected from the collimated detection laser focusing spot, which is parallel to the optical axis of the dual telecentric imaging optical path, can reach the dual telecentric imaging optical path without obstruction.

[0056] Example 2

[0057] This embodiment provides a real-time monitoring device for the forming height of laser direct energy deposition additive manufacturing, comprising: an annular processing laser beam combiner-focusing lens group for irradiating the surface of the deposited molten pool with a collimating probe laser; a dual telecentric imaging optical path and camera 8 arranged at an angle for collecting the light spot; and a host computer connected to the camera 8; wherein the collimating probe laser and the beam combiner-focusing laser used for laser direct energy deposition processing are arranged in parallel (because there is a hole in the center of the beam combiner-focusing lens group, the optical axes of the collimating probe laser and the beam combiner-focusing laser usually cannot coincide), and do not overlap in the wavelength band; the light spot is formed when the collimating probe laser irradiates the surface of the deposited molten pool;

[0058] like Figure 2 As shown, the processing laser focusing lens group includes a deflecting mirror 202, a beam combining mirror group 205 and a first focusing mirror group 206 arranged sequentially along the optical path;

[0059] The function of the deflector 202 is to deflect the ring laser with a gap in the middle by 90 degrees and to allow the feed tube assembly to be arranged in the center of the ring laser without blocking the light.

[0060] The function of the beam combining mirror group 205 is to combine the ring lasers with gaps in the middle after being folded at 90 degrees, so as to form a ring laser without gaps in the middle.

[0061] The function of the first focusing lens group 206 is to focus the gapless ring laser into a high-energy spot with a spot diameter of 1 to 4 mm;

[0062] The dual telecentric imaging optical path includes a second focusing lens group 13, an aperture stop 11, and a third focusing lens group 10 arranged sequentially along the optical path;

[0063] The host computer calculates the deviation between the light spot and the deposition point at the reference position through image processing, and obtains the distance between the surface of the deposited molten pool and the processing head, so as to monitor the forming height.

[0064] The dual telecentric imaging optical path also includes a bandpass filter 14 and a narrowband filter 9.

[0065] The difference between this embodiment and Embodiment 1 is that this embodiment targets a ring-shaped laser metal deposition head with coaxial powder (or wire) feeding at the center. The lens of its processing laser focusing lens group has a central opening, and it also includes a beam combiner, a deflector, and other structures (all with a central opening). Therefore, the optical axes of the collimating probe laser and the processing laser cannot coincide; they must be parallel and separated by a certain distance. This ensures that the collimated probe laser passes entirely through the processing laser focusing lens group of the processing head, and the collimated probe laser beam converges unobstructed onto the surface of the molten pool, forming a bright spot of approximately 200µm. Figure 3 As shown, after the collimated probe laser passes through the deflecting mirror 202, it is reflected by the folding plane mirrors 501 and 503 and the beam combining prism mirror 502, and then enters the first focusing mirror group 206 and converges onto the surface of the molten pool.

[0066] according to Figure 2 The optical path structure is arranged such that the first focusing lens group 206 of the annular laser metal deposition head, which feeds powder or wire coaxially in the center, adopts a plano-convex focusing lens with a central opening. The focal length is 150mm, and the processing laser wavelength is 1070±10nm; the collimating detection laser wavelength is 532±1nm, the collimated laser diameter is 3.5mm, and the power is 3.5mW. The collimated 532nm collimated detection laser 201 is incident at 45° onto the deflector 202, and after being reflected by the beam combiner group 205, it enters the plano-convex focusing lens 206. The optical axis (blue dashed line) of the collimated processing ring laser 203 is parallel to the optical axis (red dashed line) of the collimated detection laser 201, and the two optical axes are 25mm apart. Because the deflector 202 can reflect the 1070±10nm processing laser, and has a transmittance of up to 95% for the 532±1nm laser, the collimated detection laser, after being refracted by the deflector 202, is again incident at 45° onto the beam combiner group 205. Among these, as... Figure 3As shown, the beam combining mirror group 205 includes: a first folding plane mirror 501, a beam combining prism mirror 502, and a second folding plane mirror 503 arranged sequentially according to the optical path. This beam combining mirror group has extremely high reflectivity for both 1070±10nm and 532±1nm lasers. Therefore, after the collimating detection laser is reflected twice by the beam combining mirror group, it is perpendicularly incident on the plano-convex focusing lens and finally focused on the surface of the molten pool without obstruction. The surface of the molten pool with a vertical distance of 100mm from the focal plane of the plano-convex focusing lens is used as the reference plane (i.e., the theoretical minimum spot of the processing laser, which is also the deposition height of 0 at this time).

[0067] The diameter of the molten pool deposition spot is 3 mm; the optical axis of the dual telecentric optical path is tilted at a 45° angle to the optical axis of the collimating probe laser 201; the second focusing lens group 13 adopts a plano-convex focusing lens with a diameter of 12.7 mm and a focal length of 100 mm; the bandpass filter 14 is located in front of the second focusing lens group 13 at an appropriate position, with a diameter of 12.7 mm, a center wavelength of 1000 nm, a transmission band of 465-985 nm, a cutoff band of 1035-1400 nm, an aperture of 1 mm, and a thickness of 0.5 mm; the third focusing lens group 10 adopts a plano-convex focusing lens with a diameter of 12.7 mm and a focal length of 75 mm; the narrowband filter 9 is located behind the third focusing lens group 10 at an appropriate position, with a diameter of 12.7 mm, a wavelength of 532±1 nm, and a minimum transmittance of 40%; the 500,000-pixel CMOS area array camera includes a 4.8 μm pixel detector, a camera resolution of 808*608, and an acquisition frame rate of 116 fps. The reference molten pool plane 207 is located 150 mm from the focal plane of the processing laser focusing lens group (i.e., the theoretical minimum spot size of the processing laser). The intersection of the optical axis of the dual telecentric optical path and the principal ray of the collimated detection laser is located on the reference molten pool plane 207. Based on the selection constraints such as the molten pool deposition spot diameter of 3 mm, the position of the intersection of the two optical axes, the diameter of the second focusing lens group, and the camera resolution of 808*608, with the reference molten pool plane as the deposition height reference 0 point, the detectable deposition height range is no more than ±9 mm.

[0068] In some embodiments, a 4096-pixel monochrome CMOS industrial linear scan camera with a 7µm pixel detector can be used, resulting in a camera resolution of 4096*2 and a maximum acquisition frame rate of 14kHz. The intersection of the optical axis of the dual telecentric optical path and the collimated detection laser optical axis is located on the reference molten pool plane. Based on the above parameters, with the reference molten pool plane as the zero point of the deposition height reference, the detectable deposition height range is no more than ±4mm, meeting the needs of practical industrial applications.

[0069] Furthermore, in another embodiment of this invention, the narrowband filter 9 can be arranged between the camera 8 and the third focusing lens group 10, and the bandpass filter 14 can be arranged between the second focusing lens group 13 and the aperture stop 11. The cutoff wavelength of the bandpass filter 14 is less than the wavelength of the focusing laser used in laser direct energy deposition (LDED) processing, and the transmission wavelength range covers the wavelength range of the collimating probe laser; the center wavelength of the narrowband filter 9 is equal to the center wavelength of the collimating probe laser, and the filtering bandwidth range is 1 ± 0.2 nm.

[0070] In another embodiment of this invention, the narrowband filter 9 can be arranged between the camera 8 and the third focusing lens group 10, and the bandpass filter 14 can be arranged between the aperture stop 11 and the third focusing lens group 10. The cutoff wavelength of the bandpass filter 14 is less than the wavelength of the focusing laser used in laser direct energy deposition (LDED) processing, and the transmission wavelength range covers the wavelength range of the collimating probe laser; the center wavelength of the narrowband filter 9 is equal to the center wavelength of the collimating probe laser, and the filtering bandwidth range is 1 ± 0.2 nm.

[0071] The above three schemes are only for illustrating three implementation schemes of the present invention. As for the positional relationship between the bandpass filter 14 and the narrowband filter 9 and the second focusing lens group 13, the third focusing lens group 10 and the aperture 11, there are no requirements and they can be flexibly selected. The present invention does not limit them here.

[0072] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A real-time monitoring device for the forming height in laser direct energy deposition additive manufacturing, characterized in that, include: A processing laser focusing lens assembly for irradiating the surface of a deposited molten pool with a collimating probe laser, a dual telecentric imaging optical path and camera arranged at an angle for acquiring the light spot, and a host computer connected to the camera; wherein, the collimating probe laser and the focusing processing laser used for laser direct energy deposition are arranged parallel or coaxially and coincidentally, and do not overlap in the wavelength band; the diameter of the collimating probe laser is in the range of 1~5mm, and the lateral distance between the optical axis of the collimating probe laser and the optical axis of the processing laser focusing lens assembly is 0~30mm; the light spot is formed when the collimating probe laser irradiates the surface of the deposited molten pool; The processing laser focusing lens group includes a deflecting mirror and a first focusing lens group arranged sequentially along the optical path; There is no beam combining mirror group or there is a beam combining mirror group between the deflecting mirror and the first focusing mirror group. The beam combining mirror group includes: a first deflecting plane mirror, a beam combining prism mirror and a second deflecting plane mirror arranged in sequence according to the optical path. The dual telecentric imaging optical path includes a second focusing lens group, an aperture stop, and a third focusing lens group arranged sequentially along the optical path; The host computer analyzes the deviation between the light spot and the deposition point at the reference position based on image processing to obtain the distance between the surface of the deposited molten pool and the processing head, so as to monitor the forming height in real time.

2. The real-time monitoring device for the forming height of laser direct energy deposition additive manufacturing according to claim 1, characterized in that, The dual telecentric imaging optical path also includes a bandpass filter and a narrowband filter. The narrowband filter is disposed between the camera and the third focusing lens group, and the bandpass filter is disposed in front of the second focusing lens group, between the second focusing lens group and the aperture stop, or between the aperture stop and the third focusing lens group.

3. The real-time monitoring device for the forming height of laser direct energy deposition additive manufacturing according to claim 2, characterized in that, The cutoff wavelength of the bandpass filter is less than the wavelength of the focused laser used in laser direct energy deposition (LDED) processing, and the transmission wavelength range covers the wavelength range of the collimated probe laser; the center wavelength of the narrowband filter is equal to the center wavelength of the collimated probe laser, and the filter bandwidth range is 1 ± 0.2 nm.

4. The real-time monitoring device for the forming height of laser direct energy deposition additive manufacturing according to claim 1, characterized in that, The vertical distance between the focal plane of the second focusing lens group and the surface of the deposited molten pool is f1±10mm, and the distance between the aperture and the focal plane of the second focusing lens group is f1; the distance between the focal plane of the third focusing lens group and the aperture is f2, and the distance between the camera and the focal plane of the third focusing lens group is f2±10mm; where f1 is the focal length of the second focusing lens group and f2 is the focal length of the third focusing lens group.

5. The real-time monitoring device for the forming height of laser direct energy deposition additive manufacturing according to claim 1, characterized in that, The tilt angle α between the optical axis of the dual telecentric imaging optical path and the optical axis of the processing laser focusing lens group ranges from 30°. o ~60 o The processing laser focusing lens group is also used for focusing processing lasers in direct energy deposition processing of transmitted or reflected lasers.

6. The real-time monitoring device for laser direct energy deposition additive manufacturing forming height according to claim 5, characterized in that, When a lens is used in the processing laser focusing lens assembly, the transmittance of the lens through collimating the detected laser is not less than 50%.

7. The real-time monitoring device for laser direct energy deposition additive manufacturing forming height according to claim 5, characterized in that, When a reflector is used in the processing laser focusing lens assembly, the reflectivity of the reflector for collimating and detecting the laser is not less than 50%.

8. The real-time monitoring device for forming height in laser direct energy deposition additive manufacturing according to claim 1, characterized in that, The aperture has a circular hole at its center with a diameter of 0.5~1.5mm.

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