A method and system for in-situ monitoring of molten pool temperature field based on multi-view field imaging

Abstract

The present invention provides a method and system for in-situ monitoring of the molten pool temperature field based on multi-eye light field imaging. The present invention adopts a multi-eye light field camera system and obtains the temperature field of the molten pool by establishing a light field sub-aperture Bayer model. R 、 G 、 B The melt pool images of three channels are used to calibrate the relative spectral response of the light field camera and the ratio of the dual wavelength intensity in the coaxial temperature measurement system. R 、 G 、 B The melt pool temperature field was derived using dual-wavelength thermometry, combining two of the three channels' melt pool images with calibration parameters. A multi-wavelength field temperature measurement system was calibrated using a blackbody furnace, maintaining a monitored temperature field error below 3%. This method simplifies the monitoring process, improves temperature measurement accuracy, and boasts a wide temperature range and low complexity, enabling in-situ monitoring of high-temperature metal melt pools. It holds broad application prospects in additive manufacturing.

Description

Technical Field

[0001] The present invention relates to the field of industrial vision technology, and in particular to a method and system for in-situ monitoring of a molten pool temperature field based on multi-view field imaging. Background Art

[0002] Laser metal additive manufacturing (LAM) involves the use of high-energy-density lasers to continuously melt metal and stack it layer by layer to produce complex, high-density metal parts. This process has been applied in core fields such as aerospace. Key process variables in LAM, such as melt pool temperature, can be used to characterize part quality. However, due to the high and rapidly changing melt pool temperature, achieving high-precision melt pool temperature field monitoring for component performance control remains a key obstacle to the widespread application of metal AM technology. Therefore, research on in-situ monitoring technology for the melt pool temperature field during AM processes is an important approach to addressing this challenge.

[0003] Currently, the primary hardware used to monitor melt pool temperature includes commercial devices such as infrared cameras and photodiodes, as well as dual-wavelength temperature measurement systems based on single or dual cameras. Infrared temperature measurement devices require precise and repeated calibration to account for the constantly changing emissivity of the material. However, precise calibration of the material's emissivity is challenging due to variations in temperature or surface condition, making it particularly difficult to correlate the infrared signal with the precise temperature during phase transformations. Furthermore, for certain powders, such as Ti6AI4V alloy, the melt pool temperature can exceed 3000°C, significantly limiting the applicability of commercial equipment. While improvements have been made to dual-wavelength pyrometry methods, these methods typically employ dual or single cameras. Dual-camera dual-wavelength pyrometry is costly, complex, and lacks integration. While single-camera dual-wavelength pyrometry offers some cost savings, it, like dual-camera pyrometry, requires a beam splitter. The intensities of the two beams formed by a single wavelength entering the beam splitter must be precisely calibrated, and the use of the beam splitter requires precise matching of the dual-wavelength images. However, errors in beam splitter calibration and image matching can affect temperature measurement accuracy. The dual-wavelength high-temperature measurement method based on a color camera avoids the problems of beam splitter calibration and image matching. However, this method is based on the assumption that pixels in adjacent areas correspond to the same object point information, which brings large errors to the temperature measurement. Summary of the Invention

[0004] The present invention provides a method and system for in-situ monitoring of the molten pool temperature field based on multi-light field (LF) imaging, which is used to address the defects in the existing technology and achieve high-precision temperature measurement without considering the pixel matching problem of different bands.

[0005] In a first aspect, the present invention provides a method for in-situ monitoring of a molten pool temperature field based on multi-lens LF imaging, comprising:

[0006] Acquire multi-view LF signals of the melt pool;

[0007] According to the mapping relationship between the microlens unit and the Bayer pixel block of the LF camera, a Light Field Sub-aperture Bayer Model (LFSBM) is established, and the multi-view LF signal of the molten pool is input into the LFSBM to obtain the R 、 G 、 B Single-wavelength melt pool images of three channels;

[0008] According to the dual-wavelength temperature measurement theory, a blackbody furnace is used to calibrate the relative spectral response of the LF camera.

[0009] Depend on R 、 G 、 B The molten pool temperature field is obtained based on the dual-wavelength temperature measurement theory using any two single-wavelength molten pool images and relative spectral responsivities in the three channels.

[0010] According to the in-situ monitoring method of the molten pool temperature field based on multi-view field imaging provided by the present invention, LFSBM is established according to the mapping relationship between the microlens unit and the Bayer pixel block of the LF camera, and the multi-view light field signal of the molten pool is input into the LFSBM to obtain the temperature field including R 、 G 、 B Three-channel single-wavelength melt pool images, including:

[0011] In the sensor pixel array under the Bayer filter, a coordinate system is established with the upper left corner of the pixel array as the origin, and the distribution pattern of the pixel RGB channels is obtained:

[0012]

[0013] Where, ( u , v ) is the pixel position index, \ is the remainder operation, when the sensor pixel array is distributed as GRBG Mode, and the upper left corner starts at G and R , if the pixel row and column index ( u , v ) = (odd number, even number), the pixel at this position is the pixel brightness value corresponding to the red light filter, if ( u , v ) = (even number, odd number), which is the pixel brightness value corresponding to the blue light filter, otherwise it is the pixel brightness value corresponding to the green light filter;

[0014] Determine each microlens unit in the LF camera A Covering a macro image pixel block B,extract A Middle i Go to m Row, No. j Column to n Microlenses A ij , and the corresponding macro image B ij , extract the pixels of the same wavelength from each macro image and stitch them together to get a single-wavelength melt pool image:

[0015]

[0016] Where, I λ for λ Melt pool image at wavelength, m 、 n is the number of microlenses in rows and columns, P i,j ( λ )express i , j The pixel value at Represents a splicing operation;

[0017] The white image is calibrated by the LF camera tool to obtain the center coordinates of the microlens, and the center coordinates of the microlens are matched one by one with the filter values ​​in the filter distribution law to obtain the following R 、 B Centered on G The pixel value distribution information of the microlens center in four cases of two modes is shown in the figure.

[0018] According to the present invention, a method for in-situ monitoring of the molten pool temperature field based on multi-view field imaging is provided. According to the dual-wavelength temperature measurement theory, a blackbody furnace is used to calibrate the relative spectral responsivity of the LF camera, which includes:

[0019] The dual-wavelength temperature measurement formula is determined as:

[0020]

[0021] Where, T Indicates temperature, C 2 is a constant, λ is the wavelength, M1 and M2 are the grayscale values ​​of two different wavelengths detected by the camera, let k = Ln(r 2 / r 1 ) , r 1 and r 2 represents the relative spectral responsivity of the camera to two different wavelength beams;

[0022] use RB 、 RG 、 BG The channel combination is calibrated and analyzed using a blackbody furnace at a working distance of L The relative spectral responsivity of the LF camera is calibrated above. A neutral density filter is placed between the LF camera and the blackbody furnace to reduce the light intensity;

[0023] In temperature range T 1 to T 2 range, the blackbody furnace is calibrated from T 1 temperature starts, every Δ T Gradually increase to T 2 temperature, record the grayscale ratio of dual wavelength at different temperatures, according to the current temperature value T , calculation parameters k , and the relative spectral responsivity of the LF camera is determined by linear fitting combined with temperature.

[0024] Specifically, the temperature T The vertical axis is the relative spectral responsivity k As the horizontal axis, the linear regression is performed by the least square method to obtain the relative spectral response calibration result of the LF camera. T and k A quadratic linear relationship is established between them:

[0025]

[0026] in, S 、 U 、 E 、 W 、 F 、 Y 、 Q 、 H 、 D is a constant coefficient, given by T 1- T 2 temperature, which can be obtained by performing least squares linear regression on the blackbody furnace calibration results. k bg Indicates from B , G aisle, k rb Indicates from R , B aisle, k rg Indicates from R , G The channel uses the relative spectral responsivity derived from the dual-wavelength temperature measurement formula.

[0027] In a second aspect, the present invention also provides an integrated application of in-situ monitoring of the molten pool temperature field in laser metal additive manufacturing based on multi-view field imaging, comprising: a system and a coaxial system;

[0028] Applications of paraxial systems include Laser Directed Energy Deposition (LDED) equipment, and applications of coaxial systems include Laser Powder Bed Fusion (LPBF) equipment.

[0029] According to an integrated application of an in-situ monitoring system for a molten pool temperature field based on multi-view field imaging provided by the present invention, the LDED equipment includes an LF camera, a neutral density filter and a laser processing system;

[0030] The laser emitted by the laser processing system melts the object to be processed to form a molten pool. The molten pool light signal reaches the LF camera through the neutral density filter. The LF camera transmits the molten pool image data formed by the molten pool light signal to the image processing system.

[0031] According to an integrated application of an in-situ monitoring system for the molten pool temperature field based on multi-view field imaging provided by the present invention, the LPBF equipment includes an LF camera, a neutral density filter, a dichroic mirror, a field lens, a galvanometer, a beam expander, and a laser processing system;

[0032] The laser emitted by the laser processing system passes through the beam expander, the dichroic mirror, the galvanometer, and the field mirror in sequence and reaches the surface of the object to be processed to form a molten pool;

[0033] The molten pool light signal passes through the field lens and the galvanometer to the dichroic mirror, and then passes through the neutral density filter to the LF camera. The LF camera transmits the molten pool image data formed by the molten pool light signal to the image processing system.

[0034] In a third aspect, the present invention also provides an electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the in-situ monitoring method of the molten pool temperature field based on multi-view field imaging as described above is implemented.

[0035] In a fourth aspect, the present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the in-situ monitoring method of the molten pool temperature field based on multi-view field imaging as described above.

[0036] In a fifth aspect, the present invention also provides a computer program product, comprising a computer program, which, when executed by a processor, implements any of the above-described methods for in-situ monitoring of the molten pool temperature field based on multi-view field imaging.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] 1) It greatly simplifies the monitoring process, requiring only a single calibration of the relative spectral responsivity, avoiding the image matching and split ratio calibration process of traditional dual-wavelength temperature measurement systems. This overcomes the difficulty of reduced temperature measurement accuracy caused by matching and calibration errors. At the same time, compared with traditional color camera temperature measurement technology, its multi-view information improves temperature measurement accuracy.

[0039] 2) High temperature measurement accuracy and low error. Verified by a blackbody furnace, the temperature field error, taking a 30×30 pixel image as an example, remains below 3%. The average error at the highest temperatures of 2973.15K, 3073.15K, and 3273.15K is 1.03%.

[0040] 3) Compared with existing temperature measurement methods, the method proposed in this paper has the advantages of wide temperature range and low complexity compared with traditional infrared cameras and new dual-wavelength measurement methods;

[0041] 4) The multi-eye temperature field in-situ monitoring technology using LF cameras has broad application prospects for in-situ monitoring of high-temperature metal molten pools during additive manufacturing. It can provide a wide temperature range, the system is compact and easy to integrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0043] Figure 1 Schematic diagram of the process of the in-situ monitoring method of the molten pool temperature field based on multi-lens LF imaging provided by the present invention;

[0044] Figure 2 This is a schematic diagram of the principle of an application of the paraxial system provided by the present invention, such as a multi-eye LF in-situ temperature field monitoring device in LDED equipment;

[0045] Figure 3 This is a schematic diagram of the principle of an application of the coaxial system provided by the present invention, such as a multi-eye LF in-situ monitoring device for temperature field in LPBF equipment;

[0046] Figure 4This is a schematic diagram of the multi-eye imaging principle of the LF camera provided by the present invention;

[0047] Figure 5 : This is a mapping relationship diagram of the Bayer matrix of the LF camera provided by the present invention;

[0048] Figure 6 Schematic diagram of the coordinates of the Bayer pixel block provided by the present invention;

[0049] Figure 7 These are the four mode distribution diagrams of the Bayer array provided by the present invention;

[0050] Figure 8 It is a pixel image extracted by the same filter provided by the present invention;

[0051] Figure 9 This is the relative spectral responsivity diagram of the LF camera calibrated with a blackbody furnace provided by the present invention;

[0052] Figure 10 This is a graph showing the temperature monitoring results of the TiAl4V alloy molten pool using the LPBF coaxial monitoring system provided by the present invention;

[0053] Figure 11 It is a structural schematic diagram of the electronic device provided by the present invention. DETAILED DESCRIPTION

[0054] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0055] In response to the problems existing in the prior art, the present invention proposes a new method for in-situ monitoring of the temperature field of the additive manufacturing melt pool using an LF camera multi-eye system.

[0056] Figure 1 FIG. 1 is a flow chart of an in-situ monitoring method for a molten pool temperature field based on multi-view field imaging according to an embodiment of the present invention. Figure 1 Shown, including:

[0057] Step 100: Acquire multi-view LF signals of the molten pool;

[0058] Step 200: According to the mapping relationship between the micro-lens unit and the Bayer pixel block of the LF camera, an LFSBM is established, and the multi-view LF signal of the molten pool is input into the LFSBM to obtain the image containing R 、 G 、 B Single-wavelength melt pool images of three channels;

[0059] Step 300: Calibrate the relative spectral responsivity of the LF camera using a blackbody furnace according to dual-wavelength temperature measurement theory;

[0060] Step 400: R 、 G 、 B The molten pool temperature field is obtained based on the dual-wavelength temperature measurement theory using any two single-wavelength molten pool images and relative spectral responsivities in the three channels.

[0061] Specifically, the monitoring system proposed in the embodiment of the present invention includes the application of a metal additive manufacturing system and a multi-eye LF temperature monitoring system, including a paraxial and coaxial system. The multi-eye LF temperature monitoring system includes an LF camera, a neutral density filter, and an image processing system. The present invention adopts an LF camera multi-eye system to obtain the temperature of the metal additive manufacturing system by establishing LFSBM. R 、 G 、 B The three-channel melt pool image is used to calibrate the relative spectral response of the LF camera. R 、 G 、 B The melt pool temperature field was derived using dual-wavelength thermometry, combining two of the three channels' melt pool images with calibration parameters. The LF light field temperature measurement system was calibrated using a blackbody furnace, maintaining a monitored temperature field error below 3%. This method simplifies the monitoring process, improves temperature measurement accuracy, and boasts a wide temperature range and low complexity, enabling in-situ monitoring of high-temperature metal melt pools. It holds broad application prospects in additive manufacturing.

[0062] like Figure 2 and Figure 3 As shown, the present invention utilizes an LF camera to construct an in-situ monitoring system. Applications of the rangefinder system include laser directed energy deposition processes, and applications of the coaxial system include laser powder bed fusion processes. The in-situ monitoring system includes an LF camera, a neutral density filter, a dichroic mirror for coaxial systems such as LPBF processes, a field lens, a galvanometer, a beam expander, an image processing system, and a laser processing system. For rangefinder systems such as LDED processes, the molten pool light signal directly passes through the neutral density filter to the LF camera, and the LF camera transmits the molten pool image data to the image processing system; for coaxial systems such as LPBF processes, the molten pool light signal passes through the field lens, the galvanometer to the dichroic mirror, and then through the neutral density filter to the LF camera. The LF camera transmits the multi-view LF signal of the molten pool to the image processing system. The neutral density filter is used to adjust the light intensity to prevent the camera from overexposure.

[0063] The in-situ monitoring method of the melt pool temperature field in the metal additive manufacturing process based on multi-lens LF imaging based on the above system includes the following steps:

[0064] Step 1: Establishment of LFSBM. By analyzing the mapping relationship between the microlens unit and the Bayer pixel block of the LF camera, LFSBM is established to obtain R 、 G 、 B Melt pool images of three channels at a single wavelength.

[0065] Preferably, in step 1, LFSBM specifically obtains the microlens center coordinates by calibrating the white image, matches it with the color filter array, determines the pixel value distribution under different Bayer patterns, and thus obtains single-wavelength images of the molten pool in different channels.

[0066] The dual-wavelength temperature measurement formula is as follows:

[0067] (1)

[0068] Where, T Indicates temperature, C 2 is a constant, λ is the wavelength, M is the grayscale value detected by the camera, let k = Ln ( r 2 / r 1), r 1 and r 2 represents the relative spectral responsivity of the camera to light beams of different wavelengths.

[0069] The principle of multi-camera imaging is as follows:

[0070] like Figure 4 As shown in Figure 2, the LF camera captures light from object points at different angles through a microlens array and images them at different positions on the sensor, such as Figure 4 As shown in the red box, object points at different angles pass through different microlens units and are imaged to different pixel positions under the microlens units on the sensor, thereby retaining the target point. P Angle information.

[0071] Typically, a color camera is equipped with R 、 G 、 B The filter is used to capture the original Bayer format image and obtain the common color image through the post interpolation algorithm. To obtain images of different wavelengths, the LF camera used in the present invention has a built-in R 、 G 、 B Filter. GRBG " format image as an example, such as Figure 5 The LFSBM shown in Figure 1 shows that each microlens unit A Overlay a block of pixels called a macro image B . SelectA Middle i Go to m Row, No. j Column to n The microlenses of the column are analyzed. A ij Indicates the i Success j A column of microlenses corresponds to the macro image it covers B ij , the wavelength distribution of each macro image pixel is different and unknown.

[0072] Furthermore, in order to obtain the RGB channel distribution of each pixel under the macro image, a coordinate system is established in the sensor pixel array under the Bayer filter with the upper left corner of the pixel array as the origin. In the pixel coordinate system, it is assumed that the pixels are GRBG Format distribution, get the distribution law of pixel RGB channels:

[0073] (2)

[0074] Where, ( u , v ) is the pixel position index, \ is the remainder operation, if the sensor pixel distribution is GRBG Mode, and the upper left corner starts at G and R , when the pixel row and column index ( u , v ) = (odd, even), the pixel at this position is the pixel brightness value corresponding to the red light filter. When ( u , v ) = (even, odd), it is the pixel brightness value corresponding to the blue light filter, otherwise it is the pixel brightness value corresponding to the green light filter;

[0075] Since the temperature of the molten pool is consistent under different viewing angles, in order to obtain the image of the scene under the same filter, based on the fact that each macro image represents the information of the same object point at different viewing angles, the same wavelength pixels are sequentially spliced ​​from each macro image to obtain images of different wavelengths. Therefore, it can be defined as:

[0076] (3)

[0077] Where, I λ is the image at wavelength λ, m 、 n is the number of microlenses in rows and columns, P i,j ( λ )express i , j The pixel value at Represents a splicing operation.

[0078] The white image is calibrated by the LF camera tool to obtain the center coordinates of the microlens, and the center coordinates of the microlens are matched one by one with the filter values ​​in the filter distribution law to obtain the following R 、 B Centered on G The pixel value distribution information of the microlens center in four cases with two modes in the center.

[0079] like Figure 7 As shown, the four modes are R Central RGGB distribution (mode 1), with B Central BGGR distribution (mode 2), with G Central GRBG distribution (mode 3), and G Central GBRG Distribution (Mode 4). The present invention uses numbers to mark 25 viewing angles on each distribution mode. To distinguish different distribution modes, each mode number has a different color. Modes 1-4 are represented by white, black, yellow, and gray respectively. Figure 8 is a single wavelength image extracted by the same filter. R 1 means at position ( i , j )、( i , j +1), ( i +1, j )and( i +1, j +1) is the concatenation of pixels with indices 13, 7, 12, and 8 in the macro image. R 2- R 4. B 1- B 4. G 1- G 4 The same logic applies. Finally, we can get R 、 G 、 B Single wavelength melt pool image.

[0080] Step 2: Calibrate the relative spectral responsivity of the LF camera. Based on the dual-wavelength temperature measurement theory, a blackbody furnace is used to calibrate the relative spectral responsivity of the LF camera.

[0081] Preferably, in step 2, a specific temperature range of the blackbody furnace is selected for calibration and verification. By recording the grayscale ratio of the dual wavelengths at different temperatures, the parameters in formula (1) are obtained. k , and the relative spectral responsivity of the LF camera is determined by linear fitting combined with temperature.

[0082] According to formula (1), based on the single wavelength sub-aperture image outlined in step 1, ( R 1, B 1) ( R 1, G 1), ( B 1, G 1) Channel combination for calibration analysis. Use a blackbody furnace at a working distance of L The relative spectral responsivity of the LF camera is calibrated above. A neutral density filter is placed between the LF camera and the blackbody furnace to reduce the light intensity. T 1 to T 2. The blackbody furnace is calibrated from T 1 temperature starts, every Δ P Gradually increase to T 2 temperature. Through this process, record the grayscale ratio of dual wavelength at different temperatures. According to the current temperature value T , calculate the parameters in formula (1) k , and the relative spectral responsivity of the LF camera is determined by linear fitting combined with temperature.

[0083] Furthermore, the relative spectral responsivity is calibrated as follows: T 1- T 2 temperature range calibration results as an example, taking the temperature T The vertical axis is the relative spectral responsivity k The horizontal axis is the linear regression method of least squares to obtain the relative spectral response calibration result of the LF camera. k bg Indicates from B , G aisle, k rb Indicates from R , B aisle, k rg Indicates from R , G The channel ratio is derived using formula (1). By linear regression, T and k A quadratic linear relationship is established between them:

[0084] (4)

[0085] In the formula S 、 U 、 E 、 W 、 F 、 Y 、 Q 、 H 、D is a constant coefficient, given by T 1- T 2 temperature, which can be obtained by performing least squares linear regression on the blackbody furnace calibration results. T I =1273.15K, T When 2=2893.15K, the relative spectral responsivity of the LF camera calibrated by a blackbody furnace is as follows: Figure 9 The root mean square errors of the temperature fitting are 76.34K, 62.24K, and 78.66K respectively.

[0086] Step 3: Get the molten pool temperature field. R 、 G 、 B The dual-wavelength images and relative spectral responsivity of the centers of two of the three channels are used to obtain the melt pool temperature field based on the dual-wavelength temperature measurement theory.

[0087] In particular, taking the LPBF coaxial monitoring system as an example, the present invention monitors the Ti6Al4V alloy molten pool. R 、 G 、 B The molten pool images of the three channels are combined with the LF camera after calibration of the blackbody furnace, and the molten pool temperature field is derived using the dual-wavelength temperature measurement method. The temperature field distribution is shown as follows: Figure 10 shown.

[0088] Figure 11 An example of a physical structure diagram of an electronic device is shown below. Figure 11 As shown, the electronic device may include: a processor 1110, a communication interface 1120, a memory 1130 and a communication bus 1140, wherein the processor 1110, the communication interface 1120 and the memory 1130 communicate with each other via the communication bus 1140. The processor 1110 may call the logic instructions in the memory 1130 to execute the in-situ monitoring method of the molten pool temperature field based on multi-lens LF imaging, the method comprising: obtaining a multi-view LF signal of the molten pool; establishing an LFSBM according to the mapping relationship between the microlens unit of the LF camera and the Bayer pixel block, inputting the multi-view LF signal of the molten pool into the LFSBM, and obtaining a molten pool temperature field in-situ monitoring method based on the multi-lens LF imaging; R 、 G 、 B Sub-aperture images of three channels and single-wavelength melt pool images; According to the dual-wavelength temperature measurement theory, a blackbody furnace is used to calibrate the relative spectral response of the LF camera. R 、 G 、 BThe molten pool temperature field is obtained based on the dual-wavelength temperature measurement theory using any two single-wavelength molten pool images and relative spectral responsivities in the three channels.

[0089] Furthermore, the logic instructions in the aforementioned memory 1130 can be implemented as software functional units and, when sold or used as independent products, can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the portion that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product, stored in a storage medium, includes instructions for enabling a computer device (which can be a personal computer, server, or network device, etc.) to perform all or part of the steps of the methods described in various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as a USB flash drive, a mobile hard drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0090] On the other hand, the present invention also provides a computer program product, which includes a computer program. The computer program can be stored on a non-transitory computer-readable storage medium. When the computer program is executed by a processor, the computer can execute the in-situ monitoring method of the molten pool temperature field based on multi-eye LF imaging provided by the above methods, the method comprising: obtaining a multi-view LF signal of the molten pool; establishing an LFSBM according to the mapping relationship between the microlens unit and the Bayer pixel block of the LF camera, inputting the multi-view LF signal of the molten pool into the LFSBM, and obtaining a molten pool temperature field in-situ monitoring method based on multi-eye LF imaging; R 、 G 、 B Sub-aperture images of three channels and single-wavelength melt pool images; According to the dual-wavelength temperature measurement theory, a blackbody furnace is used to calibrate the relative spectral response of the LF camera. R 、 G 、 B The molten pool temperature field is obtained based on the dual-wavelength temperature measurement theory using any two single-wavelength molten pool images and relative spectral responsivities in the three channels.

[0091] On the other hand, the present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which is implemented when the computer program is executed by a processor to perform the in-situ monitoring method of the molten pool temperature field based on multi-view LF imaging provided by the above methods, the method comprising: obtaining a multi-view LF signal of the molten pool; establishing an LFSBM according to the mapping relationship between the microlens unit and the Bayer pixel block of the LF camera, inputting the multi-view LF signal of the molten pool into the LFSBM, and obtaining a molten pool temperature field monitoring ... R 、 G 、 BSub-aperture images of three channels and single-wavelength melt pool images; According to the dual-wavelength temperature measurement theory, a blackbody furnace is used to calibrate the relative spectral response of the LF camera. R 、 G 、 B The molten pool temperature field is obtained based on the dual-wavelength temperature measurement theory using any two single-wavelength molten pool images and relative spectral responsivities in the three channels.

[0092] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, i.e., they may be located in one location or distributed across multiple network units. Some or all of the modules may be selected based on actual needs to achieve the objectives of the present embodiment. Persons of ordinary skill in the art will be able to understand and implement the present invention without inventive effort.

[0093] Through the above description of the embodiments, those skilled in the art will clearly understand that each embodiment can be implemented using software plus a necessary general-purpose hardware platform, or of course, hardware. Based on this understanding, the essence of the above technical solution, or the portion that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a magnetic disk, or an optical disk, and includes a number of instructions for causing a computer device (such as a personal computer, server, or network device) to execute the methods described in each embodiment or certain portions of the embodiments.

[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for in-situ monitoring of molten pool temperature field based on multi-view field imaging, characterized in that: include: Acquire multi-view light field LF signals of the molten pool; According to the mapping relationship between the microlens unit and the Bayer pixel block of the LF camera, a light field sub-aperture Bayer model LFSBM is established, and the multi-view light field LF signal of the molten pool is input into the LFSBM to obtain the R 、 G 、 B Sub-aperture images of three channels and single-wavelength melt pool images, including: In the sensor pixel array under the Bayer filter, a pixel coordinate system is established with the upper left corner of the pixel array as the origin, and the pixel RGB channel distribution law is obtained: Where, ( u , v ) is the pixel position index, \ is the remainder operation, if the sensor pixel array is distributed as GRBG Mode, and the upper left corner starts at G and R , when the pixel row and column index ( u , v ) = (odd, even), the pixel at this position is the pixel brightness value corresponding to the red light filter. When ( u , v ) = (even, odd), it is the pixel brightness value corresponding to the blue light filter, otherwise it is the pixel brightness value corresponding to the green light filter; Determine each microlens unit in the LF camera A Covering a macro image pixel block B ,extract A Middle i Go to m Row, No. j Column to n Microlenses A ij , and the corresponding macro image B ij , extract pixels of the same wavelength from each macro image and sequentially stitch them together to obtain images of different wavelengths: Where, I λ is the image at wavelength λ, m 、 n is the number of microlenses in rows and columns, P i,j ( λ )express i , j The pixel value at Represents a splicing operation; The white image is calibrated by the LF camera tool to obtain the center coordinates of the microlens, and the center coordinates of the microlens are matched one by one with the filter values ​​in the filter distribution law to obtain the following R 、 B Centered on G The pixel value distribution information of the microlens center in four cases of two modes is shown in the figure. According to the dual-wavelength temperature measurement theory, a blackbody furnace is used to calibrate the relative spectral responsivity of the LF camera; Depend on R 、 G 、 B The molten pool temperature field is obtained based on the dual-wavelength temperature measurement theory using any two single-wavelength molten pool images and relative spectral responsivities in the three channels.

2. The method for in-situ monitoring of the molten pool temperature field based on multi-view field imaging according to claim 1 is characterized in that: According to the dual-wavelength temperature measurement theory, a blackbody furnace is used to calibrate the relative spectral responsivity of the LF camera, including: The dual-wavelength temperature measurement formula is determined as: Where, T Indicates temperature, C 2 is a constant, and For two different wavelengths, M 1 and M 2 is the grayscale value of two different wavelengths detected by the camera, let k = Ln(r 2 / r 1 ) , r 1 and r 2 represents the relative spectral responsivity of the camera to two different wavelength beams; use RB 、 RG 、 BG The channel combination is calibrated and analyzed using a blackbody furnace at a working distance of L The relative spectral responsivity of the LF camera is calibrated above. A neutral density filter is placed between the LF camera and the blackbody furnace to reduce the light intensity; In temperature range T 1 to T 2 range, the blackbody furnace is calibrated from T 1 temperature starts, every Δ T Gradually increase to T 2 temperature, record the grayscale ratio of dual wavelength at different temperatures, according to the current temperature value T , calculation parameters k , and the relative spectral responsivity of the LF camera is determined by linear fitting combined with temperature.

3. The in-situ monitoring method of the molten pool temperature field based on multi-view field imaging according to claim 2 is characterized in that: Based on the dual-wavelength temperature measurement theory, a blackbody furnace is used to calibrate the relative spectral responsivity of the LF camera, which also includes: By temperature T The vertical axis is the relative spectral responsivity k As the horizontal axis, the linear regression is performed by the least square method to obtain the relative spectral response calibration result of the LF camera. T and k A quadratic linear relationship is established between them: in, S 、 U 、 E 、 W 、 F 、 Y 、 Q 、 H 、 D is a constant coefficient, given by T 1- T 2 Temperature is determined by the least squares linear regression obtained through the blackbody furnace calibration results. k bg Indicates from B , G aisle, k rb Indicates from R , B aisle, k rg Indicates from R , G The channels use the ratio derived from the dual-wavelength thermometry formula.

4. A molten pool temperature field in-situ monitoring system based on multi-view field imaging, comprising an image processing system for executing the molten pool temperature field in-situ monitoring method based on multi-view field imaging according to any one of claims 1 to 3, characterized in that: include: Rangefinder and coaxial systems; The applications of paraxial systems include laser directed energy deposition (LDED) equipment, and the applications of coaxial systems include laser powder bed fusion (LPBF) equipment.

5. The in-situ monitoring system for molten pool temperature field based on multi-view field imaging according to claim 4 is characterized in that: LDED equipment includes LF cameras, neutral density filters, and laser processing systems; The laser emitted by the laser processing system melts the object to be processed to form a molten pool. The molten pool light signal reaches the LF camera through the neutral density filter. The LF camera transmits the molten pool image data formed by the molten pool light signal to the image processing system.

6. The molten pool temperature field in-situ monitoring system based on multi-view field imaging according to claim 4 is characterized in that: LPBF equipment includes LF cameras, neutral density filters, dichroic mirrors, field lenses, galvanometers, beam expanders, and laser processing systems; The laser emitted by the laser processing system passes through the beam expander, the dichroic mirror, the galvanometer, and the field mirror in sequence and reaches the surface of the object to be processed to melt and form a molten pool; The molten pool light signal passes through the field lens and the galvanometer to the dichroic mirror, and then passes through the neutral density filter to the LF camera. The LF camera transmits the molten pool image data formed by the molten pool light signal to the image processing system.

7. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the program, the in-situ monitoring method of the molten pool temperature field based on multi-view field imaging as described in any one of claims 1 to 3 is implemented.

8. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the in-situ monitoring method of the molten pool temperature field based on multi-view field imaging as described in any one of claims 1 to 3 is implemented.

9. A computer program product comprising a computer program, characterized in that When the computer program is executed by a processor, the in-situ monitoring method of the molten pool temperature field based on multi-view field imaging as described in any one of claims 1 to 3 is implemented.

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