A Method for Eliminating Projection Seams and Equalizing Energy of Large-Size High-Precision DLP Multi-Optical Machines

Abstract

The present invention relates to the field of photocuring 3D printing, and more specifically to a method for eliminating projection seams and equalizing energy of a large-size high-precision DLP multi-projector. The method includes the following steps: S1: Divide the splicing area and non-splicing area of the printed two-dimensional slice image; S2: Modulate the power of the DLP projectors to make the powers of multiple DLP projectors uniform; S3: Use the Poisson fusion algorithm to fuse the images in the splicing area of the two-dimensional slice image to generate a seamless two-dimensional slice image; S4: Transmit the generated seamless two-dimensional slice image to multiple DLP projectors for printing; It can improve the quality of the splicing area during the photocuring forming process of the DLP multi-projector and ensure the quality of photocuring 3D printing.

Description

Technical Field

[0001] The present invention relates to the field of light-curing 3D printing, and more specifically to a method for eliminating the projection seam and equalizing the energy of a large-size and high-precision DLP multi-projector. Background Art

[0002] The DLP-based 3D printing technology is a kind of light-curing additive manufacturing technology. A digital light processing projector is used as a light source to irradiate a photosensitive resin, causing it to undergo a photopolymerization reaction to form a cured layer, and then a 3D model is formed by stacking the cured layers. The light-curing area based on DLP is the entire projection plane, which can greatly reduce the manufacturing time of parts. However, increasing the area of the projection plane will inevitably reduce the forming accuracy. Therefore, the method of using multi-projector splicing has become the main means to achieve large-size and high-precision process indicators. In the research of multi-projector splicing, on the one hand, due to the discontinuous gray-scale gradient at the splicing area, there are stepped vertical axis patterns on the surface of the finished product; on the other hand, since the energy of the DLP projector projection follows a Gaussian distribution and is not uniform, the curing depth of the splicing area is inconsistent. Therefore, multi-projector projection seam elimination and energy equalization have become a research hotspot in recent years. Among them, using the edge fusion algorithm to optimize the splicing area and combining the Poisson fusion algorithm with the method of averaging the energy of multi-projector projection can better meet the process requirements. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for eliminating the projection seam and equalizing the energy of a large-size and high-precision DLP multi-projector, which can improve the quality of the splicing area during the light-curing forming process of the DLP multi-projector and ensure the quality of light-curing 3D printing.

[0004] The purpose of the present invention is achieved through the following technical solutions:

[0005] A method for eliminating the projection seam and equalizing the energy of a large-size and high-precision DLP multi-projector, the method comprising the following steps:

[0006] S1: Divide the splicing area and non-splicing area of the printed two-dimensional slice image;

[0007] S2: Modulate the power of the DLP projector to make the power of multiple DLP projectors uniform;

[0008] S3: Use the Poisson fusion algorithm to fuse the images in the splicing area of the two-dimensional slice image to generate a seamless two-dimensional slice image;

[0009] S4: Transmit the generated seamless two-dimensional slice image to multiple DLP projectors for printing;

[0010] In S1, the imported three-dimensional model is sliced using software to form two-dimensional slice images; the process of dividing the stitching area and non-stitching area of the two-dimensional slice images includes: calculating the size of the overlapping areas printed by multiple DLP light machines and calculating the width of the overlapping areas printed by multiple DLP light machines; the overlapping areas of multiple DLP light machines include multiple pixels. To ensure subsequent gradient change operations on pixel grayscales using the Poisson algorithm, the pixel selection range is between 15 and 20.

[0011] In S2, modulating the power of the DLP light machine includes the following steps:

[0012] S21: Divide the image projected by the DLP light machine into multiple image blocks;

[0013] S22: Use a light power meter to measure the light power values of the image blocks and calculate the relative ultraviolet light power values of each image block;

[0014] S23: Calculate the minimum light power value and the maximum light power value respectively according to the relationship between the grayscale value and the light power value;

[0015] S24: Calculate the grayscale values of each point based on the minimum light power value, generate a light power correction coefficient matrix, and restore the modulated image blocks into a complete image through a convolution interpolation algorithm;

[0016] In S3, by adjusting the relative positions of multiple DLP light machines, ensure the alignment of the corresponding pixel points projected by multiple DLP light machines; according to the width of the overlapping areas of multiple DLP light machines calculated in S1, use the Poisson fusion algorithm, guided by the internal gradient field of the original two-dimensional slice image, to solve the Poisson equation to achieve gradient continuity, thereby achieving seamless fusion of the stitching area;

[0017] In S4, transmit the generated seamless two-dimensional slice image to multiple DLP light machines to cure the photosensitive resin-ceramic slurry by ultraviolet light projection, complete the stitching printing, and after the stitching printing is formed, detect the consistency of the photocuring depth to determine whether to modulate the power of the DLP light machine again.

[0018] The beneficial effects of the present invention are:

[0019] The method for eliminating seams and equalizing energy provided by the present invention uses the Poisson fusion algorithm to fuse the images to be stitched while retaining the gradient information of the image before stitching. This method can achieve continuity in the image gradient domain and meet the seamless fusion at the stitching of large-size and high-precision forming;

[0020] At the same time, combined with ultraviolet light power modulation, it ensures that the distribution of light power values in the stitching area and non-stitching area is basically the same, making the distribution of light power values of the complete image after stitching uniform and meeting the requirements of the forming process. Brief Description of the Drawings

[0021] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0022] Figure 1 It is a flow chart of a method for eliminating projection seams and equalizing energy of large-size and high-precision DLP multi-light machines of the present invention;

[0023] Figure 2 It is a flow chart of power modulation of a DLP single-light machine of the present invention;

[0024] Figure 3 It is a flow chart of the splicing process of DLP multi-light machines of the present invention. Specific implementation manners

[0025] The present invention will be further described in detail below in conjunction with the accompanying drawings.

[0026] As Figures 1 to 3 shown, in order to achieve the technical effect of "improving the quality of the splicing area during the light curing forming process of DLP multi-light machines and ensuring the quality of light curing 3D printing", the steps and functions of a method for eliminating projection seams and equalizing energy of large-size and high-precision DLP multi-light machines will be described in detail below;

[0027] As Figure 1 shown, a method for eliminating projection seams and equalizing energy of large-size and high-precision DLP multi-light machines includes the following steps:

[0028] Step S1: Import a three-dimensional model, obtain a two-dimensional slice image by using software, and divide the splicing area and the non-splicing area. Among them, it is necessary to calculate the size of the overlapping area of multiple DLP light machines and the width of the overlapping area of multiple light machines. Among them, the overlapping area of DLP light machines includes multiple pixels. In order to ensure subsequent gradient change operations on pixel grayscales using the Poisson algorithm, the pixel selection range should be between 15 and 20;

[0029] Step S2: Perform power modulation on a single DLP light machine to make its power uniform. As Figure 2As shown, the DLP projection image is divided into multiple image blocks. The optical power meter is used to measure the optical power values of the image blocks, and the relative ultraviolet optical power values of each image block are calculated. According to the relationship between the gray value and the optical power value, the minimum optical power value and the maximum optical power value are calculated respectively. Based on the minimum optical power value, the gray values of each point are calculated to generate an optical power correction coefficient matrix. The modulated image blocks are restored to a complete image through a convolution interpolation algorithm. Among them, when using the optical power meter to measure the optical power values of the image blocks, since measuring the power value of each pixel will greatly increase the measurement difficulty and complexity, the image is processed in blocks, and further measuring the power values of the image blocks can effectively reduce the measurement and correction difficulties. At the same time, according to the relationship between the gray value and the optical power value, the gray values of each point are calculated based on the minimum optical power value, which better avoids the influence of the optical power distribution caused by the Gaussian distribution. This DLP optical engine power equalization method effectively reduces the influence of uneven curing depth caused by the Gaussian distribution, and at the same time ensures the accuracy requirements of power equalization, laying an important foundation for eliminating the seams in the subsequent splicing of the DLP optical engine projection area.

[0030] Step S3: Use the Poisson fusion algorithm to fuse the splicing area images of the two-dimensional slice images to generate a seamless two-dimensional slice image. Since the image may have a decrease in forming accuracy due to geometric distortion during the projection process, it is of great significance to calibrate the splicing positions of multiple DLP optical engines. Specifically, as Figure 3 shown, the CMOS is used to monitor the projection position of the optical engine in real time. By adjusting the relative positions of the DLP optical engines, the alignment of the corresponding pixel points projected by multiple DLP optical engines is ensured, and at the same time, optical calibration is performed to eliminate the influence of optical distortion. According to the width of the overlapping area of multiple DLP optical engines calculated in Step S1, using the Poisson fusion algorithm, guided by the internal gradient field of the slice image to be spliced, the Poisson equation is solved to achieve gradient continuity, so as to achieve seamless fusion of the splicing area. Compared with the existing technology, the method of using Poisson fusion avoids a large amount of calculations on the size of the splicing area during the large-format splicing process, and at the same time avoids the complex implementation of the Alpha-Matting method. The method of Poisson fusion is guided by the gradient field of the source image block, and smoothly diffuses the difference between the target scene and the source image on the fusion boundary into the fusion image block. The process of selecting the fusion area is relatively simple, and the seam elimination effect is better.

[0031] Step S4: Transmit the generated seamless two-dimensional slice image to multiple DLP optical engines to cure the ultraviolet light projection of the photosensitive resin-ceramic slurry to complete the splicing printing. After the splicing printing is formed, the consistency of the photocuring depth is detected to judge whether to perform DLP optical engine power modulation again, and the splicing printing is performed according to the result.

[0032] In particular, at this time, by detecting whether the curing depth is consistent, it is determined whether to further use power modulation to further optimize the forming quality at the splicing point. If optimization is required, the process is the same as that described in step S2 above and will not be elaborated here. Finally, the process requirement standard is required to be met.

[0033] In this article, specific examples are used to elaborate on the principles and implementation manners of the present invention. The descriptions of the above embodiments are only used to help understand the method and its core idea of the present invention. At the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A large-size, high-precision DLP multi-optical projection seam elimination and energy equalization method, characterized by: The method comprises the following steps: S1: Divide the stitching area and non-stitching area of ​​the printed two-dimensional slice image; S2: modulate the power of the DLP optical machine to make the power of multiple DLP optical machines uniform; S3: fusing the stitching area images of the two-dimensional slice images to generate a seamless two-dimensional slice image; S4: transmitting the generated seamless two-dimensional slice image to multiple DLP optical machines for printing; In the above S1, the process of dividing the stitching area and the non-stitching area of ​​the two-dimensional slice image includes: calculating the size of the overlapping area of ​​the multiple DLP optical machine printing and calculating the width of the overlapping area of ​​the multiple DLP optical machine printing; In S3, the splicing area images of the two-dimensional slice images are fused using a Poisson fusion algorithm; In S3, the relative positions of the multiple DLP optical machines are adjusted to ensure alignment of corresponding pixel points projected by the multiple DLP optical machines; According to the widths of the overlapping areas of the multiple DLP optical machines calculated in S1, the Poisson fusion algorithm is used to solve the Poisson equation to achieve gradient continuity with the internal gradient field of the original two-dimensional slice image as a guide, thereby achieving seamless fusion of the splicing area.

2. According to claim 1, a large-size high-precision DLP multi-optical projection seam elimination and energy equalization method is characterized by: In S1, the imported three-dimensional model is sliced ​​to form a two-dimensional slice image.

3. The method for eliminating seams and equalizing energy for large-size, high-precision DLP multi-optical projection according to claim 1, characterized in that: The overlapping area of ​​multiple DLP optical machines includes multiple pixels, and the pixel selection range is between 15-20.

4. The method for eliminating seams and equalizing energy for large-size, high-precision DLP multi-optical projection according to claim 1, characterized in that: In S2, modulating the power of the DLP optical engine includes the following steps: S21: dividing the image projected by the DLP optical machine into a plurality of image blocks; S22: using an optical power meter to measure the optical power value of the image block, and calculating the relative ultraviolet light power value of each image block; S23: Calculate the minimum optical power value and the maximum optical power value respectively according to the relationship between the gray value and the optical power value; S24: Calculate the gray value of each point according to the minimum optical power value, generate an optical power correction coefficient matrix, and restore the modulated image block to a complete image through a convolution interpolation algorithm.

5. The method for eliminating seams and equalizing energy for large-size, high-precision DLP multi-optical projection according to claim 1, characterized in that: In the above S4, the generated seamless two-dimensional slice image is transmitted to a plurality of DLP optical machines, so that the ultraviolet light is projected to solidify the photosensitive resin-ceramic slurry, thereby completing the splicing printing.

6. The method for eliminating seams and equalizing energy of large-size, high-precision DLP multi-optical projection according to claim 5, characterized in that: After the splicing and printing, the consistency of the light curing depth is detected to determine whether to perform DLP optical machine power modulation again.

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