LCD Light-Curing 3D Printing Uniform Light Optimization Compensation Device and Method

Abstract

The present invention mainly provides a device and three methods for uniform light optimization compensation in LCD light-curing 3D printing. The device includes: a control unit, an image capturing unit, an LCD screen, a light source, and a semi-transmissive unit; the semi-transmissive unit covers the backlight surface of the LCD screen; when the LCD screen is fully exposed, the light irradiated by the light source passes through the LCD screen and irradiates on the semi-transmissive unit to form a semi-transmissive image on its backlight surface; the control unit captures and obtains the initial gray values of the image pixels within the full screen range on the semi-transmissive image through the image capturing unit; the difference iteration value-taking compensation method, the minimum value sequential value-taking compensation method, and the digital rounding plus high-frequency value value-taking compensation method are respectively adopted to obtain the gray compensation difference value; and after obtaining the optimized gray values of the pixels in the gray mask slice of the pattern to be printed, uniform light curing printing can be realized; through the semi-transmissive unit, the image capturing unit of the present invention can directly obtain the gray values within the full screen range, can directly perform uniform light compensation on the full screen pixels, and has a better uniform light effect.

Description

Technical Field

[0001] This application relates to the field of 3D printing technology, and particularly to an LCD light-curing 3D printing uniform light optimization compensation device and method. Background Art

[0002] Currently, single light sources or matrix light sources are generally used in light-curing 3D printers. Due to the service life of the lamp beads themselves, manufacturing errors, limitations in the manufacturing precision of optical devices, and different losses of the LCD path energy values, when the ultraviolet light source penetrates the mask pixels to irradiate the photosensitive curing reaction material, the irradiation light energy values at each point on the plane are inconsistent, resulting in uneven exposure. Generally, there are problems such as high energy in the middle position and low energy around, or different energy values and uneven photosensitivity at each point on the plane where the photosensitive curing reaction material cures. This will cause uneven photosensitivity when generating a model with the photosensitive curing reaction material during LCD light-curing printing, an uneven printing surface, and an unsatisfactory printing effect. In response to this problem, after retrieval, in the background art invention patent solution that has been published, a patent for an LCD light-curing 3D printing uniform light optimization compensation device and method with the patent number 202010781266X has proposed a solution to this problem.

[0003] However, in the existing LCD light-curing 3D printing technology, when performing uniform light compensation, an ultraviolet light test instrument can only measure the projection energy values of LCD pixel points point by point. Since the ultraviolet light test instrument is generally large and complex in structure, it is not conducive to being installed on an LCD light-curing 3D printer to automatically collect the energy values of pixel points. And it is unrealistic to collect the energy values of all pixel points with a handheld instrument due to the excessive workload.

[0004] In addition, during LCD light-curing 3D printing, the irradiation light needs to penetrate the mask pixels to irradiate the photosensitive curing reaction material, and the irradiation energy value needs to exceed the minimum value for the photosensitive curing reaction material to undergo a curing reaction. If the irradiation intensity emitted by the light source is insufficient, the overall printing will fail, and the photosensitive material will also be insufficiently formed, resulting in waste. If the irradiation intensity emitted by the light source is too high, the LCD screen will be subjected to high temperatures for a long time, resulting in a shortened service life or damaged screen. Moreover, in the existing LCD light-curing 3D printing technology, the LCD needs to be baked at high intensity for a long time, so problems such as damaged and opaque LCD pixels, aging and poor light transmission of LCD pixels, large light path losses, or completely transparent damaged LCD pixels always occur. Therefore, in this case, the invention patent solution in the background technology is too simplistic and idealistic. It does not consider judging and adjusting the irradiation intensity of the light source, nor does it consider the situation of pixel defects (opaque or semi-transparent) during the use of the LCD. For example, when the solution method selects the energy reference value based on the minimum energy value, if there are damaged and opaque LCD pixels, the uniform light received by the photosensitive curing reaction material after gray value compensation will also be zero, and the printing will fail. If there are semi-transparent damaged LCD pixels, the uniform light received by the photosensitive curing reaction material after gray value compensation depends on the degree of damage of this semi-transparent pixel, which may reduce the overall light intensity of the photosensitive curing reaction material and lead to printing failure. Summary of the Invention

[0005] In view of the above defects or deficiencies in the background technology, the present invention mainly provides a device and three methods for uniform light optimization and compensation in LCD light-curing 3D printing. The device includes: a control unit, an image capture unit, an LCD screen, a light source, and a semi-transparent unit. The semi-transparent unit covers the backlight surface of the LCD screen. When the LCD screen is fully exposed, the irradiation light from the light source passes through the LCD screen and irradiates the semi-transparent unit to form a semi-transparent image on its backlight surface. The control unit obtains the initial gray value of the image pixels within the full screen range of the semi-transparent image through the image capture unit. After the present invention uses a semi-transparent unit such as soft light paper for soft light diffusion reflection, it can directly obtain the semi-transparent image and its pixel gray value within the full screen range of the LCE with the help of devices such as a camera, without the need to use an ultraviolet light test instrument to collect the light transmission energy value point by point, and can also avoid the overexposure problem of directly collecting the irradiation light with a camera.

[0006] In addition, in the three methods, the control unit captures the initial gray values of the image pixels within the full-screen range of the semi-transparent image through the image capture unit; the control unit inputs the gray mask slice image of the to-be-printed graphic through a removable storage device, network, or computer and obtains the mask gray values of each pixel in each gray mask slice; then, the difference iteration value compensation method, the minimum value sequential value compensation method, and the digital rounding plus high-frequency value compensation method are respectively used to obtain the gray compensation differences; then, the control unit subtracts the values in the gray compensation difference table from the mask gray values of each pixel point of each gray mask slice image to obtain the optimized gray values of each gray mask slice image, thereby realizing the light-curing light homogenization printing. Such a light homogenization optimization compensation method obtains gray values for all pixels of the semi-transparent image of the LCD full screen, performs gray compensation for all pixel points of the gray mask slice image within the full-screen range, and is easier to achieve absolute light homogenization of the LCD full screen under ideal conditions. Therefore, it is the best solution with the best light homogenization effect.

[0007] The specific solution is as follows:

[0008] An LCD light-curing 3D printing light homogenization optimization compensation device includes: a control unit, an image capture unit, an LCD screen, a light source, and a semi-transparent unit; the semi-transparent unit covers the backlight surface of the LCD screen; the irradiation light emitted by the light source passes through the LCD screen and irradiates the semi-transparent unit when the LCD screen is fully exposed, and uses the visible characteristics of the mixed UV ultraviolet light and visible light of the light source and the soft light diffused reflection characteristics of the semi-transparent unit to form a semi-transparent image on its backlight surface; the image capture unit uses its capture function to capture the semi-transparent image and send it to the control unit, and the control unit extracts the initial gray values of the image pixels within the full-screen range of the semi-transparent image; after obtaining the gray compensation differences of each pixel and the optimized gray values of each pixel in the gray mask slice of the to-be-printed graphic, light-curing printing with uniform light is realized.

[0009] Preferably, the semi-transparent unit is made of semi-transparent paper, or thin paper, or soft light paper, or soft light film, or soft light cloth, or soft light board, or sulfuric acid paper, or copy paper, or butter paper, or diffusion film, or matte film, or butterfly cloth, or heat-resistant film, or semi-transparent acrylic board;

[0010] Preferably, the light source is a UV point light source or a UV matrix light source;

[0011] Preferably, the number of photosensitive pixels of the image capture unit in the length and width directions is greater than or equal to the number of display pixels of the LCD screen in the length and width directions; the total number of photosensitive pixels of the image capture unit is greater than or equal to the number of display pixels of the LCD screen.

[0012] Method 1: An LCD light-curing 3D printing light homogenization optimization compensation method using the difference iteration value compensation method, including the following steps:

[0013] SA01. Turn on the LCD light-curing printer and cover the semi-transparent unit on the backlight side of the LCD screen so that the light source irradiates the entire LCD screen;

[0014] SA02. The control unit obtains the semi-transparent image displayed on the backlight side of the semi-transparent unit during the full-screen exposure of the LCD screen through the image capture unit and obtains the initial gray values of the image pixels within the full-screen range of the semi-transparent image;

[0015] SA03. The control unit determines whether the average gray value of all the initial gray values is lower than the preset threshold; if it is determined that the average gray value is lower than the preset threshold, proceed to step SA09; if it is determined that the average gray value is not lower than the preset threshold, proceed to step SA04;

[0016] SA04. The control unit inputs the gray mask slice image of the graphic to be printed through a removable storage device or network or computer and obtains the mask gray values of each pixel in each gray mask slice;

[0017] SA05. The control unit extracts the non-zero minimum value among the respective initial gray values as the Nth reference value, subtracts the Nth reference value from each of the initial gray values to obtain the Nth gray compensation difference for each pixel, and forms a gray compensation difference table;

[0018] SA06. The control unit subtracts the values in the gray compensation difference table from the mask gray values of each pixel point of each gray mask slice image to obtain the optimized gray values of each gray mask slice image and forms an optimized gray table;

[0019] SA07. The control unit determines whether each of the optimized gray values is greater than or equal to the preset value; if it is determined that there is a value less than the preset value among the optimized gray values, execute step SA10; if it is determined that all the values in the optimized gray table are greater than or equal to the preset value, proceed to step SA08;

[0020] SA08. The control unit performs light-curing printing on each slice mask image according to the obtained optimized gray values of each gray mask slice image, and then proceeds to execute step SA11;

[0021] SA09. Manually adjust or the control unit adjusts and enhances the irradiation intensity of the 3D printer light source to brighten the backlight side of the semi-transparent unit, and then proceeds to execute step SA02;

[0022] SA10. The control unit extracts the non-zero minimum value in the Nth gray compensation difference as the (N + 1)th reference value, subtracts the (N + 1)th reference value from each of the initial gray values to obtain the (N + 1)th gray compensation difference, and forms a gray compensation difference table, and then proceeds to execute step SA06;

[0023] SA11. The process ends.

[0024] Method 2: An LCD photocuring 3D printing uniform light optimization compensation method, which adopts the minimum value sequential value-taking compensation method, includes the following steps:

[0025] SB01: Turn on the LCD photocuring printer and cover the semi-transmissive unit on the backlight surface of the LCD screen so that the light source irradiates the entire LCD screen;

[0026] SB02: The control unit obtains the semi-transmissive image displayed on the backlight surface of the semi-transmissive unit during the full-screen exposure of the LCD screen through the image capture unit and obtains the initial gray values of the image pixels within the full-screen range of the semi-transmissive image;

[0027] SB03: The control unit determines whether the average gray value of all the initial gray values is lower than the preset threshold; if it is determined that the average gray value is lower than the preset threshold, then go to step SB09; if it is determined that the average gray value is not lower than the preset threshold, then go to step SB04;

[0028] SB04: The control unit inputs the gray mask slice image of the pattern to be printed through a removable storage device or network or computer and obtains the mask gray values of each pixel in each gray mask slice;

[0029] SB05: The control unit extracts the non-zero Nth smallest value among the respective initial gray values as the Nth reference value, and then subtracts the Nth reference value from each initial gray value to obtain the Nth gray compensation difference value and form a gray compensation difference table;

[0030] SB06: The control unit subtracts the values in the gray compensation difference table from the mask gray values of each pixel point of each gray mask slice image to obtain the optimized gray values of each gray mask slice image and form an optimized gray table;

[0031] SB07: The control unit determines whether each optimized gray value is greater than or equal to the preset value. If so, execute step SB10; if it is determined that all the values in the optimized gray table are greater than or equal to the preset value, then go to step SB08;

[0032] SB08: The control unit performs photocuring printing on each slice mask image according to the obtained optimized gray values of each gray mask slice image, and then enters step SB11;

[0033] SB09: Manually adjust or the control unit adjusts and enhances the irradiation intensity of the 3D printer light source to brighten the backlight surface of the semi-transmissive unit, and then enters step SB02;

[0034] SB10. The control unit extracts the non-zero (N + 1)-th smallest value among all the initial gray values as the (N + 1)-th reference value, then subtracts the (N + 1)-th reference value from each initial gray value to obtain the (N + 1)-th gray compensation difference value and forms a gray compensation difference value table, and then proceeds to execute step SB06;

[0035] SB11. The process ends.

[0036] Method 3: An LCD light-curing 3D printing uniform light optimization compensation method, adopting a digital rounding plus high-frequency value extraction compensation method, includes the following steps:

[0037] SC01. Turn on the LCD light-curing printer and cover the semi-transmissive unit on the backlight surface of the LCD screen so that the light source irradiates the entire LCD screen;

[0038] SC02. The control unit obtains the semi-transmissive image displayed on the backlight surface of the semi-transmissive unit during the full-screen exposure of the LCD screen through the image capture unit and obtains the initial gray values of the image pixels within the full-screen range of the semi-transmissive image;

[0039] SC03. The control unit determines whether the average gray value of all the initial gray values is lower than the preset threshold; if it is determined that the average gray value is lower than the preset threshold, then proceed to step SC09; if it is determined that the average gray value is not lower than the preset threshold, then proceed to step SC04;

[0040] SC04. The control unit inputs the gray mask slice image of the pattern to be printed through a removable storage device or network or computer and obtains the mask gray values of each pixel in each gray mask slice;

[0041] SC05. The control unit rounds each initial gray value and extracts the integer value with the most occurrences and larger value as the N-th reference value, then subtracts the N-th reference value from each initial gray value to obtain the N-th gray compensation difference value and forms a gray compensation difference value table;

[0042] SC06. The control unit subtracts the values in the gray compensation difference value table from the mask gray values of each pixel point of each gray mask slice image to obtain the optimized gray values of each gray mask slice image and forms an optimized gray value table;

[0043] SC07. The control unit determines whether all the optimized gray values are greater than or equal to the preset value; if it is determined that there is a value less than the preset value among the optimized gray values, then execute step SC10; if it is determined that all the values in the optimized gray value table are greater than or equal to the preset value, then proceed to step SC08;

[0044] SC08. The control unit performs light-curing printing on each slice mask image according to the obtained optimized gray values of each gray mask slice image, and then proceeds to execute step SC11;

[0045] SC09. Manually adjust or control the unit to adjust and enhance the irradiation intensity of the light source of the 3D printer to brighten the backlight surface of the semi-transparent unit, and then enter the execution step SC02;

[0046] SC10. The control unit rounds each initial gray value and extracts the integer value with the most and larger same values as the (N + 1)-th reference value. Then subtract the (N + 1)-th reference value from each initial gray value to obtain the (N + 1)-th gray compensation difference value and form a gray compensation difference value table, and then enter the execution step SC06;

[0047] SC11. The process ends.

[0048] Preferably, when calculating the difference value of the gray value, all negative numbers obtained in the difference value calculation are set to zero;

[0049] Compared with the prior art, the beneficial effects of the present invention are:

[0050] 1. A light homogenization optimization compensation device provided by the present invention utilizes the visible characteristics after mixing the UV ultraviolet light and visible light of the light source and the soft light diffuse reflection characteristics of the semi-transparent unit to form a semi-transparent image on the backlight surface of the semi-transparent unit, so that the state of whether the UV ultraviolet light of the light source is evenly distributed can be presented and directly captured by the image capturing unit;

[0051] 2. A light homogenization optimization compensation device provided by the present invention directly captures and obtains the semi-transparent image and its pixel gray value by using the image capturing unit. Compared with the prior art solution of directly collecting the light transmission energy value of the irradiation light point by point using an ultraviolet light testing instrument, the installation structure of the capturing device is simpler, which is more conducive to the installation and use of miniaturized devices, and there is no need to irradiate and take values point by point with an ultraviolet light tester one by one, so it is more convenient to use;

[0052] 3. A light homogenization optimization compensation device provided by the present invention utilizes the soft light diffuse reflection characteristics of a semi-transparent unit such as a soft light paper, and can directly obtain the semi-transparent image and its pixel gray value by means of a device such as a camera, avoiding the overexposure problem caused by the direct penetration of the irradiation light of the light source directly onto the imaging device when the imaging device directly takes a picture;

[0053] 4. A light homogenization optimization compensation device provided by the present invention utilizes the soft light diffuse reflection characteristics of a semi-transparent unit such as a soft light paper, and can directly obtain the semi-transparent image and its pixel gray value by means of a device such as a camera, avoiding the conversion process of converting the energy value measured by the ultraviolet light testing instrument into a gray value;

[0054] 5. The three light-averaging optimization compensation methods provided by the present invention utilize an image capture unit to directly obtain grayscale values ​​for all pixels of the semi-transparent image of the full-screen LCD, and perform grayscale compensation on all pixel points of the grayscale mask slice image within the full-screen range. Ideally, it is easier to achieve absolute light-averaging of the full-screen LCD, so it is the best light-averaging effect and also the quickest solution.

[0055] 6. The three light-averaging optimization compensation methods provided by the present invention can obtain very good light-averaging effect and improve printing accuracy without making any changes to the original structure of the LCD. When the LCD screen has opaque bad pixels causing the grayscale reference value to be too low, the three methods of the present invention can reselect the reference value through the judgment step to ensure that most of the pixels are evenly-averaged and the illumination intensity is sufficient to ensure successful 3D printing;

[0056] 7. In the three light-averaging optimization compensation methods provided by the present invention, the judgment process and adjustment process of the light source illumination intensity are added in step 3 of the three methods. When the illumination is insufficient, the illumination intensity is enhanced to provide sufficient illumination guarantee for the subsequent grayscale value compensation of grayscale mask slices and the final 3D light-curing printing.

[0057] 8. In the three light-average optimization compensation methods provided by the present invention, a judgment process for optimizing the grayscale value is added in step 7 of the three methods. When the selected reference value is too small, the grayscale value of the printed image will be excessively reduced, so that the light intensity through the LCD screen is insufficient, resulting in curing printing failure. The judgment step can be added to reselect until the reference value is appropriate, so that the photosensitive curing reaction material is uniformly irradiated during the final printing and the intensity is sufficient to ensure smooth printing.

[0058] 9. The light averaging optimization compensation method 1 provided by the present invention adopts a difference iterative value compensation method, and continuously selects a non-zero minimum value through an initial gray value difference table to select reference values ​​point by point from low to high in disguised form, until the selected value is appropriate and reasonable enough to compensate the gray value of the gray mask slice while ensuring sufficient printing illumination to achieve a light averaging effect for most pixel points;

[0059] 10. The light averaging optimization compensation method 2 provided by the present invention adopts the minimum value sequential value compensation method, and directly selects reference values ​​point by point from low to high by comparing and sorting the points, until the selected values ​​are appropriate and reasonable enough to compensate the grayscale value of the grayscale mask slice while ensuring sufficient printing illumination to achieve the light averaging effect of most pixel points;

[0060] 11. The uniform light optimization compensation method 3 provided by the present invention adopts a digital rounding plus high-frequency value extraction compensation method. By rounding the initial gray value, the repetition probability of each initial gray value is increased, and then the high-frequency value with the most repetitions is directly captured to compensate as much as possible for the difference in the initial gray values of each point. At the same time, when two or more high-frequency values appear, selecting the point with a higher value as the reference value is conducive to quickly finding a more reasonable reference value, ensuring sufficient printing light while compensating the gray value of the gray mask slice to achieve the uniform light effect for most pixel points. Description of the Drawings

[0061] Figure 1 It is a flowchart of the uniform light optimization compensation method 1 for LCD light-curing 3D printing of the present invention;

[0062] Figure 2 It is the first part of the uniform light calculation process of the uniform light optimization compensation method 1 for LCD light-curing 3D printing of the present invention;

[0063] Figure 3 It is the second part of the uniform light calculation process of the uniform light optimization compensation method 1 for LCD light-curing 3D printing of the present invention;

[0064] Figure 4 It is a flowchart of the uniform light optimization compensation method 2 for LCD light-curing 3D printing of the present invention;

[0065] Figure 5 It is the first part of the uniform light calculation process of the uniform light optimization compensation method 2 for LCD light-curing 3D printing of the present invention;

[0066] Figure 6 It is the second part of the uniform light calculation process of the uniform light optimization compensation method 2 for LCD light-curing 3D printing of the present invention;

[0067] Figure 7 It is a flowchart of the uniform light optimization compensation method 3 for LCD light-curing 3D printing of the present invention;

[0068] Figure 8 It is the uniform light calculation process of the uniform light optimization compensation method 3 for LCD light-curing 3D printing of the present invention;

[0069] Figure 9 It is the schematic diagram of the uniform light optimization compensation device for LCD light-curing 3D printing of the present invention;

[0070] Figure 10 It is the schematic diagram of the 3D printer for light-curing after the uniform light optimization compensation for LCD light-curing 3D printing of the present invention.

[0071] Reference Numeral Description:

[0072] Control unit 1; Image capturing unit 2; LCD screen 3; Light source 4; Semi-translucent unit 5; Storage liquid tank 6; Bottom film of the liquid storage tank 61; Photosensitive curing reaction material 7; Curing forming part pallet 8. Detailed implementation mode

[0073] The following further describes the embodiments of the present invention with reference to the accompanying drawings.

[0074] Currently, LCD light-curing 3D printers usually adopt single light sources or matrix light sources. Due to the service life of the lamp beads themselves, manufacturing errors, limitations in the manufacturing precision of optical devices, and different losses of the LCD path energy value, when the ultraviolet light source penetrates the mask pixels to irradiate the photosensitive curing reaction material, the irradiation light energy values at each point on the plane are inconsistent, resulting in uneven exposure. And when there are dead pixels on the LCD screen, if the pre-stored gray value of the LCD screen is too small or the irradiation intensity of the light source is insufficient, there will also be problems of printing failure. In addition, in the background technology, the method of measuring the projection energy values of each pixel point on the screen during full-screen exposure of the LCD screen point by point with an ultraviolet light test instrument and then performing light equalization processing is too laborious and unrealistic to implement. In view of these problems, the present invention discloses a device and three methods for light equalization optimization compensation in LCD light-curing 3D printing.

[0075] It should be particularly noted that since the value range of the gray value is 0 - 255; and the light source energy value range is wider, such as 0 μW / cm2 - 2550 μW / cm2. In order to facilitate unifying the gray value and the energy value into the same numerical range for expounding the light equalization principle and expressing the calculation process, in the subsequent tables, it is assumed that the minimum energy value emitted by the light source is 0 μW / cm2 and the maximum is 255 μW / cm2; the corresponding relationship formula between the energy value and the gray value can be: Y i j = kX i j + b for calculation; where, Y ij is the energy value of the pixel point at the i-th row and j-th column on the LCD screen obtained by the energy acquisition unit during full-screen exposure of the LCD; X i j is the gray value of the energy value of the pixel point at the i-th row and j-th column on the LCD screen during full-screen exposure of the LCD; the k and b are empirical value constants or actual deduced values obtained through calculation; the maximum value of the energy value corresponds to the maximum value of the gray value 255, and the minimum value of the energy value corresponds to the minimum value of the gray value 0. Substituting these into the relationship formula Y ij = kX ij + b to calculate the deduced values of k and b; and in the light equalization principle and calculation under the method of the present invention, the whole process only involves the calculation and processing of the image gray value, and does not involve the conversion process between the light source energy value and the image gray value.

[0076] Figure 1This is the flowchart of the light homogenization optimization compensation method 1 for LCD light-curing 3D printing of the present invention. The process steps are as shown in the figure. It adopts the difference iteration value-taking compensation method. The value of N in steps 5 and 10 in the figure takes values of 1, 2, 3 to N.

[0077] Figure 2 This is the space 1 of the light homogenization calculation process of the light homogenization optimization compensation method 1 for LCD light-curing 3D printing of the present invention. Since the space for the operation display process is too long, it is divided into two parts, space 1 and space 2. The calculation process mainly describes the value-taking and calculation comparison process when the method 1 adopts the difference iteration value-taking compensation method. The 4*4 grids in each table represent the corresponding positions of 16 arbitrary pixel points on the LCD screen, on the semi-transparent image within the full screen range, and on the gray mask slice image. As shown in the figure, Table 1-1 shows that in the ideal state, the light source provides sufficient and uniform illumination light, so that the 16 pixel points receive uniform illumination intensity. Table 1-2 shows that in the ideal state, there are no dead pixels on the LCD screen and the light transmission loss in the light transmission path of each pixel point is the same. Table 1-3 shows that if the semi-transparent unit material used is ideal, the soft light effect is relatively uniform. Therefore, in this link, the energy loss of the illumination light passing through each pixel point is also uniform. If the gray mask slice image is not loaded at this time, then a semi-transparent image with sufficient energy and uniform brightness as shown in Table 1-4 will surely be formed at the corresponding positions of the 16 pixel points on the backlight side of the semi-transparent unit, and the brightness of each pixel point is also uniform.

[0078] Table 2-1 shows that in general actual situations, the light source emits uneven illumination light with sufficient energy. The illumination light energy in the middle position of the light source is sufficient, while the illumination light energy at the edge position is relatively weak. Table 2-2 shows that there is energy value loss when the illumination light penetrates the LCD screen. The position of the number 125 represents an aging pixel point with weak light transmission ability, resulting in a relatively high light energy loss. The position of the number 0 represents that this pixel point is completely light-transmissive. Table 2-3 shows that the LCD screen loads the mask image of the printed slice. According to the calibration value that the gray mask slice of the LCD is fully light-transmissive and all are 0, it can be known that the gray values at the corresponding 16 pixel points of the printed slice mask image should all be 255 to achieve full light transmission, because the gray value 255 represents white and the gray value 0 represents black. Table 2-4 shows the energy value of the illumination light received at the corresponding positions of the fixed pixel points when the photosensitive curing material uses photosensitive resin. From the uneven values in the table, it can be analyzed that if the light homogenization optimization compensation is not carried out on the LCD light-curing printing device, then the photosensitive resin will surely receive uneven illumination in the end, resulting in a poor printing effect.

[0079] Table 3-1 shows that when using a weak light source with a low light energy value, the light source may be high in the middle and low around, or the lamp beads may have low light emission due to aging, resulting in uneven illumination; Table 3-2 shows that there will be energy losses such as scattering and heating when the illuminating light emitted by the light source penetrates the LCD screen. The position of the number 0 indicates that this is a dead pixel on an LCD pixel, which is completely transparent and cannot load and store the original color of the image; the position of the number 125 indicates that this is an aging point on an LCD pixel, with low light transmission ability and large light loss; if this point is a dead pixel, it should be represented by 255 to indicate complete light impermeability. At this time, if the method of taking the minimum value once for gray compensation printing in the background technology is still used, due to improper value taking, the photosensitive energy of the photosensitive resin will be all zero in the end, resulting in printing failure; Table 3-3 shows that the semi-transmissive unit used has relatively uniform soft light effect, so the energy loss of the illuminating light passing through in this link is also uniform; if the gray mask slice image is not loaded at this time, then an image with low energy and uneven brightness as shown in Table 3-4 will inevitably be formed on the backlight surface of the semi-transmissive unit, and the brightness of each pixel is also uneven; it can be seen from these four tables that when the emitted light of the light source is weak, the energy and brightness of the image formed on the backlight surface of the semi-transmissive unit are both low. If the gray mask slice image is loaded for photocuring printing after removing the semi-transmissive unit under this light source irradiation intensity, the light required for photosensitive forming is insufficient and the printing will inevitably fail; therefore, it is necessary to adjust the light source to increase the irradiation intensity of the illuminating light.

[0080] From a series of tables from Table 4-1 to Table 10-4, the whole process of calculation and comparison of the uniform light optimization compensation method 1 in this application can be clearly understood. Table 4-1 shows that the light source emits uneven illuminating light with sufficient energy at the pixel point; Table 4-2 shows that there is energy value loss at the pixel point when the illuminating light penetrates the LCD screen; Table 4-3 shows that the semi-transmissive unit uniformly loses the energy of the illuminating light; Table 4-4 shows that the image capturing unit obtains an image on the backlight surface of the semi-transmissive unit, in which the brightness of each pixel in the semi-transmissive image is sufficient but uneven, and the gray values of each pixel are also uneven.

[0081] In Table 5-1 are the initial gray values of the pixel points in the semi-transmissive image obtained by the image capturing unit described in Table 4-4; Table 5-2 shows that the non-zero minimum value 85 is extracted for the first time from the above values. The reason for extracting the non-zero minimum value is also to exclude the reference selection of completely light-impermeable dead pixels. Therefore, the initial gray values obtained by the image capturing unit need to be uniformly subtracted by this reference value, thereby obtaining the first gray compensation difference value in Table 5-4.

[0082] Figure 3This is the light - averaging calculation process of the light - averaging optimization compensation method 1 for LCD light - curing 3D printing in the present invention, with a length of 2. The calculation process mainly describes the value - taking and calculation comparison process when the method 1 adopts the difference iteration value - taking compensation method. The 4*4 grid in each table represents the positions corresponding to 16 arbitrary pixel points. As shown in the figure, in Table 6 - 1, the gray - scale values of the pixel points of the gray - scale mask slice are all 255. The first gray - scale compensation difference in Table 6 - 2 is the first gray - scale compensation difference obtained in Table 5 - 4. Subtracting the values in Table 6 - 2 from the corresponding values in Table 6 - 1 can obtain the first - optimized gray - scale value of the gray - scale mask slice in Table 6 - 3. This gray - scale value is the mask pixel gray - scale value of each pixel point in the LCD mask link, that is, the first gray - scale value of each pixel point of the gray - scale mask slice loaded into the LCD screen during LCD light - curing printing. Next, after light - averaging optimization compensation, the photosensitive resin photosensitive energy value is calculated to verify whether the photosensitivity of the photosensitive resin is uniform. Through the inverse calculation of the gray - scale value and the pixel light - shielding ability, subtracting the values in Table 6 - 3 from the slice gray - scale value 255, the LCD image pixel light - loss energy value in Table 6 - 4 is obtained.

[0083] Subtracting the energy value loss when the incident light penetrates the LCD screen in Table 7 - 2 and the energy value shielded by the gray - scale mask loaded in the LCD in Table 7 - 3 (which is the value in Table 6 - 4) from the energy value emitted by the light source with uneven illumination but sufficient energy in Table 7 - 1, the photosensitive resin photosensitive energy value in Table 7 - 4 can be obtained. It can be seen from Table 7 - 4 that each point on the photosensitive plane of the photosensitive resin is uniformly photosensitive when illuminated. In particular, it can be known that when performing light - averaging optimization compensation for LCD light - curing 3D printing, the uniformity value and photosensitive irradiation intensity of the photosensitive curing reaction material in the end are determined by the sum of the reference value 80 selected in Table 5 - 3 and the light - energy shielding of the semi - transparent unit in Table 4 - 3 to the incident light. Therefore, when selecting the reference value in step 4 of the three methods in the present invention, the influence of zero value needs to be excluded. And if the selected reference value is too small, it will also lead to insufficient printing light energy. Therefore, in step 7 of the three methods in the present invention, the optimized gray - scale value of the final gray - scale mask slice image also needs to be selected, and then the reference value is re - selected. For example, assuming that the preset value in step 7 of method 1 is 200, and there are values less than 200 in Table 6 - 3, then it is necessary to enter step 11 to re - select the reference value to obtain the gray - scale compensation difference. In the background technology, when directly selecting the minimum value, if there are light - - impermeable bad points on the LCD screen, then its reference value must be zero, which will lead to too low optimized gray - scale value of the gray - scale mask slice image, resulting in the photosensitive resin receiving light energy value being all 25 in the end, causing insufficient light energy and printing failure.

[0084] Tables 8-1 to 8-4 show that in the previous steps, if the selected value of the reference value 85 is not appropriate, the value needs to be reselected. Therefore, in the first gray-scale compensation difference between Table 8-1 and Table 5-4, the non-zero minimum value 80 is selected again as the second reference value 80. Then, the first gray-scale compensation difference is subtracted by the second reference value 80 to obtain the second gray-scale compensation difference in Table 8-4, and the negative numbers generated are directly set to zero. This is to avoid the second optimized gray value of the gray mask obtained later exceeding the physical range of the maximum gray value of 255. Specifically, repeatedly selecting the non-zero minimum value in each gray-scale compensation difference is actually the difference iteration value compensation method. It is equivalent to gradually excluding the minimum value one by one in a column of gradually increasing values and selecting values step by step upward. Eventually, a reference value that can make the printing light energy sufficient and uniform can always be found, so as to obtain the optimized gray value of the gray mask required.

[0085] Table 9-1 shows the gray values of the pixel points corresponding to the gray mask slices of the image to be printed. The gray value 255 represents full light transmission; subtracting the second gray-scale compensation difference in Table 9-2 from Table 9-1 can obtain the optimized gray values of the pixel points of the second gray mask slice in Table 9-3, and uniform light printing under sufficient light energy can be achieved. Table 9-4 is obtained by subtracting each value in Table 9-3 from 255, and it represents the light shielding energy value brought by the LCD loading the pixel gray value of the gray mask slice to shield the irradiated light.

[0086] In the arithmetic expressions composed of Tables 10-1, 2, and 3, substituting the LCD gray mask light shielding energy value in Table 9-4 can obtain the photosensitive value received by the photosensitive resin in Table 10-4. This is a verification process. It can be seen that after the second production value selection and compensation, the photosensitive energy value of the photosensitive resin has increased significantly compared with Table 7-4.

[0087] Figure 4 This is the flowchart of the uniform light optimization compensation method 2 for LCD photocuring 3D printing of the present invention. The process of the method steps is as shown in the figure. It adopts the minimum value sequential value compensation method, and the value of N in steps 5 and 10 in the figure is 1, 2, 3 to N.

[0088] Figure 5This is the light - equalizing calculation process section 1 of the light - equalizing optimization compensation method 2 for LCD light - curing 3D printing in the present invention. The calculation process mainly describes the value - taking and calculation comparison process when method 2 adopts the minimum - value sequential - value - taking compensation method. Since the operation display process is too long, it is divided into two parts, section 1 and section 2. The 4*4 grids in each table represent the corresponding positions of 16 arbitrary pixel points on the LCD screen, on the semi - transparent image within the full screen range, and on the grayscale mask slice image. As shown in the figure, Table 11 - 1 represents the uneven illumination light with sufficient energy emitted by the light source; Table 11 - 2 represents the energy value loss when the illumination light penetrates the LCD screen; Table 11 - 3 represents that no grayscale mask slice image is loaded, so there is no light - energy loss; Table 11 - 4 represents the initial grayscale values of the pixel points in the semi - transparent image obtained by the image capture unit.

[0089] Tables 12 - 1, 2, and 3 represent selecting the non - zero minimum value from the photosensitive energy values obtained from the image capture unit as the first reference value, and then obtaining the first grayscale compensation difference value in Table 12 - 4.

[0090] Tables 13 - 1, 2, and 3 represent obtaining the first - optimized grayscale value of the grayscale mask in Table 13 - 3 according to the grayscale values of the grayscale mask slices in Table 13 - 1 and the grayscale - mask slice grayscale compensation difference value in Table 13 - 2. The grayscale - mask slice grayscale compensation difference value in Table 13 - 2 is the first grayscale compensation difference value in Table 12 - 4. Assume that the preset value in step 7 of method 2 is 220. If there are values less than 220 in Table 16 - 3, then it is necessary to enter step 11 to re - select the reference value to obtain the difference value. Table 13 - 4 is obtained by subtracting each value in Table 13 - 3 from 255, and it represents the energy value loss caused by the LCD loading the grayscale mask slice pixel grayscale to block the illumination light.

[0091] In the operation formula composed of Tables 14 - 1, 2, and 3, substituting the energy value loss of the LCD grayscale mask in Table 13 - 4, the photosensitive value received by the photosensitive resin in Table 14 - 4 can be obtained. It can be seen from the table that the illumination light is uniform, but it may be on the low side. This is a verification process.

[0092] Tables 15 - 1 and 2 represent re - extracting the second minimum value on the basis of excluding the previous minimum value, that is, extracting the reference value in ascending order from small to large. After obtaining the second reference value in Table 15 - 3, subtracting each value in Table 15 - 1 from the second reference value to obtain the second grayscale compensation difference value in Table 15 - 4, and directly setting the negative numbers generated to zero. This is to prevent the second - optimized grayscale value of the grayscale mask obtained later from exceeding the physical range of the maximum grayscale value of 255.

[0093] Figure 6This is the light intensity calculation process section 2 of the light intensity optimization compensation method for LCD light-curing 3D printing in the present invention. The calculation process mainly describes the value selection and calculation comparison process when Method 2 adopts the minimum value sequential value selection compensation method. The 4*4 grids in each table represent the positions corresponding to 16 arbitrary pixel points. As shown in the figure, Table 16-1 represents the gray-scale mask slice pixel gray-scale values of the image to be printed, and the gray-scale value of 255 represents full light transmission; subtracting the second gray-scale compensation difference in Table 16-2 from Table 16-1 can obtain the optimized gray-scale values of the second gray-scale mask slice in Table 16-3. Assuming that the preset value in step 7 of Method 2 is 220, and there are values less than 220 in Table 16-3, then it is necessary to enter step 11 to reselect the reference value to obtain the difference. Table 16-4 is obtained by subtracting the values in Table 16-3 from 255, and it represents the light shielding energy value brought by the LCD loading the gray-scale mask slice pixel gray-scale to block the irradiated light.

[0094] In the arithmetic expressions composed of Tables 17-1, 2, and 3, substituting the LCD gray-scale mask light shielding energy values in Table 16-4 can obtain the photosensitive values received by the photosensitive resin in Table 17-4. This is a verification process. From this, it can be seen that after the second production value selection and compensation, the photosensitive energy value of the photosensitive resin has increased significantly compared to Table 14-4.

[0095] After the above two selections of reference values and light intensity compensation, if the technician sets the preset value in step 7 to 220, and there are values less than 220 in Table 16-3, then it is necessary to enter step 11 to reselect the reference value to obtain the difference and perform the third light intensity compensation optimization.

[0096] Tables 18-1 and 2 represent re-extracting the third minimum value on the basis of excluding the previous minimum value, that is, sequentially extracting the reference values from small to large. After obtaining the third reference value in Table 18-3, subtracting the values in Table 18-1 from the third reference value to obtain the third gray-scale compensation difference in Table 18-4, and directly setting the generated negative numbers to zero. This is to prevent the third optimized gray-scale value of the gray-scale mask from exceeding the physical range of the maximum gray-scale value of 255 in the subsequent process.

[0097] Table 19-1 represents the gray-scale mask slice pixel gray-scale values of the image to be printed, and the gray-scale value of 255 represents full light transmission; subtracting the third gray-scale compensation difference in Table 19-2 from Table 19-1 can obtain the optimized gray-scale values of the third gray-scale mask slice in Table 19-3. According to step 7 of Method 2, assuming that the preset value in step 7 is 220, then all the values in Table 19-3 are greater than 220, and uniform light printing under sufficient light energy can be achieved. Table 19-4 is obtained by subtracting the values in Table 19-3 from 255, and it represents the light shielding energy value brought by the LCD loading the gray-scale mask slice pixel gray-scale to block the irradiated light.

[0098] In the arithmetic expressions composed of Tables 20-1, 20-2, and 20-3, substituting the LCD grayscale mask loss energy values in Table 19-4 can obtain the photosensitive values received by the photosensitive resin in Table 20-4. This is a verification process. From this, it can be known that after the third production value selection and compensation, the photosensitive energy value of the photosensitive resin has increased significantly compared to Table 17-4. However, in terms of the light homogenization effect, the pursuit of absolute light homogenization is abandoned. But in actual 3D light-curing printing, as long as the printing irradiation is sufficient and the light of each pixel on the irradiated plane of the photosensitive resin meets most of the balance, in fact, the negative impact on the actual printing effect is not significant.

[0099] Specifically, gradually selecting the non-zero minimum value from low to high in the photosensitive energy value of the image capture unit as the reference value is actually using the minimum value sequential value-taking compensation method. It is equivalent to gradually excluding the minimum value one by one in a column of gradually increasing values and selecting values step by step upward. Eventually, a reference value that can make the final printing light energy sufficient and uniform can always be found, so as to obtain the optimized grayscale value of the grayscale mask required.

[0100] Figure 7 This is the flowchart of the light homogenization optimization compensation method 3 for LCD light-curing 3D printing of the present invention. The process of the method steps is as shown in the figure. It uses the digital rounding plus high-frequency value value-taking compensation method. The value of N in steps 5 and 10 in the figure is 1, 2, 3 to N.

[0101] Figure 8 This is the light homogenization calculation process of the light homogenization optimization compensation method 3 for LCD light-curing 3D printing of the present invention. The calculation process mainly describes the value-taking and calculation comparison process when the method 3 uses the digital rounding plus high-frequency value value-taking compensation method. The 4*4 grids in each table represent the corresponding positions of 16 arbitrary pixel points corresponding to each other on the LCD screen, on the semi-transparent image within the full screen range, and on the grayscale mask slice image. As shown in the figure, Table 21-1 represents the non-uniform irradiation light with sufficient energy emitted by the light source; Table 21-2 represents the energy value loss when the irradiation light penetrates the LCD screen; Table 24-6 represents that no grayscale mask slice image is loaded, so there is no light energy loss; Table 21-4 represents the initial grayscale value of the pixel points in the semi-transparent image obtained by the image capture unit.

[0102] Tables 22-1 and 22-2 indicate that the initial grayscale values obtained by the image capture unit need to be rounded first. Since the original captured photosensitive initial grayscale values in Table 22-1 always contain non-integers, if no rounding process is performed, when selecting the reference value according to the same-value frequency in the subsequent Table 22-3 step, the values are scattered and it is not easy to extract the number with the highest same-value frequency. Moreover, the data processing process will also consume too much computing power of the control unit. After rounding, the integer initial grayscale values in Table 22-2 are obtained. Specifically, as shown in Table 22-3, when selecting the integer value with the most same values, there are two groups of integer values with the most same values. At this time, it is necessary to select the larger integer value as the reference value from the two groups of integer values. Then, the first reference value of the initial grayscale value in Table 22-4 is obtained.

[0103] Tables 23-1, 23-2, and 23-3 indicate that based on the initial grayscale values of the pixel points in Table 23-1 and the first reference value selected in Table 22-4, the first grayscale compensation difference in Table 23-3 is obtained. And for the negative numbers generated, they are directly set to zero to obtain the first grayscale compensation difference in Table 23-4. This is to prevent the first optimized grayscale value of the grayscale mask obtained later from exceeding the physical range of the maximum grayscale value of 255.

[0104] Table 24-1 represents the grayscale values of the pixel points of the grayscale mask slice of the image to be printed. The grayscale value of 255 represents full light transmission. By subtracting the first grayscale compensation difference in Table 24-2 from Table 24-1, the first optimized grayscale value of the grayscale mask slice in Table 24-3 can be obtained. Thus, uniform light printing under sufficient light energy can be achieved. Table 24-4 is obtained by subtracting each value in Table 24-3 from 255, and it represents the light shielding energy value brought by the LCD loading the grayscale mask slice pixel grayscale to block the irradiated light.

[0105] In the arithmetic expressions composed of Tables 25-1, 25-2, and 25-3, substituting the light shielding energy value of the LCD grayscale mask in Table 24-4, the photosensitive value received by the photosensitive resin in Table 25-4 can be obtained. This is a verification process. From this, it can be known that after the first production value selection and compensation, the energy of the photosensitive resin's photosensitive energy value is sufficient. However, the degree of uniform light is not absolutely uniform. In terms of the uniform light effect, the pursuit of absolute uniform light is abandoned. But in actual 3D light-curing printing, as long as the printing irradiation is sufficient and the light of each pixel on the irradiated plane of the photosensitive resin satisfies most of the balance, in fact, the negative impact on the actual printing effect is not significant.

[0106] Specifically, when Method 3 rounds the initial grayscale values, it increases the collision probability of each value and the probability of the same value. It is equivalent to directly grabbing a maximum distribution interval to select a maximum probability distribution value, and then performing uniform light optimization compensation on this basis. In fact, it is the method of digital rounding plus high-frequency value extraction compensation; at the same time, to avoid multiple high-probability numbers with the same probability appearing simultaneously, a larger or smaller reference value needs to be selected. A larger value means more sufficient light source illumination. Therefore, in this method, in Steps 4 and 11, the method of rounding and extracting the largest integer value with the most same values is used as the reference value; if the selected reference value is not appropriate, it is necessary to reselect the second-largest integer value with the most same values as the reference value, that is, select the second-largest integer value with the most same values as the reference value; finally, a reference value that can make the printing light energy sufficient and uniform in the final printing can always be found, so as to obtain the optimized grayscale value of the grayscale mask required.

[0107] Figure 9 This is the schematic diagram of the uniform light optimization compensation device for LCD light-curing 3D printing of the present invention. As shown in the figure, a uniform light optimization compensation device for LCD light-curing 3D printing includes: a control unit 1, an image capturing unit 2, an LCD screen 3, a light source 4, and a semi-transmissive unit 5; the semi-transmissive unit 5 covers the backlight surface of the LCD screen 3; the irradiation light emitted by the light source 4 is fully exposed on the LCD screen 3 and passes through the LCD screen 3 to irradiate on the semi-transmissive unit 5, and a semi-transmissive image is formed on its backlight surface by using the visible characteristics of the mixed UV ultraviolet light and visible light of the light source 4 and the soft light diffuse reflection characteristics of the semi-transmissive unit 5; the image capturing unit 2 uses its capturing function to capture and obtain the semi-transmissive image and send it to the control unit 1, and the control unit 1 extracts the initial grayscale values of the image pixels within the full screen range of the semi-transmissive image; after obtaining the grayscale compensation difference of each pixel and the optimized grayscale value of each pixel in the grayscale mask slice of the pattern to be printed, uniform light curing printing is realized.

[0108] Figure 10This is the schematic diagram of the light-curing 3D printer after the uniform light optimization compensation of the LCD light-curing 3D printing of the present invention. As shown in the figure, the technical solution of the light-curing 3D printer includes: a control unit 1, an LCD screen 3, a light source 4, a storage tank 6, a bottom film 61 of the storage tank, a photosensitive curing reaction material 7, and a curing forming part pallet 8. The control unit 1 enables the LCD screen 3 to load the grayscale mask slice image of the pattern to be printed. After the grayscale value is uniformly light-optimized and compensated, it is used for selective mask light transmission. The photosensitive curing reaction material 7 is stored in the storage tank 6. Among them, the photosensitive curing reaction material 7 generally uses photosensitive resin. The bottom of the storage tank 6 is a light-transmissive bottom film 61 of the liquid tank, which is used for irradiating light transmission. The light source 4 generally uses a UVLED point light source or a UVLED matrix light source to emit 405 nm ultraviolet light to irradiate the photosensitive curing reaction material 7 through the grayscale mask of the LCD screen 3 for curing printing. The curing forming part pallet 8 is used to attach the coagulated glue after curing during the curing reaction process and continuously lift and grow it until the 3D printing is completed.

[0109] The above embodiments only describe the preferred embodiments of the present invention and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solution of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. An LCD light-curing 3D printing light homogenization optimization compensation method, characterized in that It includes the following steps: SA01. Turn on the LCD light-curing printer and cover the semi-transparent unit on the backlight side of the LCD screen so that the light source irradiates the entire LCD screen; SA02. The control unit obtains the semi-transparent image displayed on the backlight side of the semi-transparent unit during the full-screen exposure of the LCD screen through the image capture unit and obtains the initial gray values of the image pixels within the full-screen range of the semi-transparent image; SA03. The control unit determines whether the average gray value of all the initial gray values is lower than the preset threshold; if it is determined that the average gray value is lower than the preset threshold, step SA09 is performed; if it is determined that the average gray value is not lower than the preset threshold, step SA04 is performed; SA04. The control unit inputs the gray mask slice image of the graphic to be printed through a removable storage device or network or computer and obtains the mask gray values of each pixel in each gray mask slice; SA05. The control unit extracts the non-zero minimum value among the respective initial gray values as the Nth reference value, subtracts the Nth reference value from each of the initial gray values to obtain the Nth gray compensation difference for each pixel, and forms a gray compensation difference table; SA06. The control unit subtracts the respective values in the gray compensation difference table from the mask gray values of each pixel point of each gray mask slice image to obtain the optimized gray values of each gray mask slice image and forms an optimized gray table; SA07. The control unit determines whether each of the optimized gray values is greater than or equal to the preset value; if it is determined that there is a value less than the preset value among the optimized gray values, step SA10 is executed; if it is determined that the values in the optimized gray table are all greater than or equal to the preset value, step SA08 is performed; SA08. The control unit performs light-curing printing on each slice mask image according to the obtained optimized gray values of each gray mask slice image, and then proceeds to execute step SA11; SA09. Manually adjust or the control unit adjusts to enhance the light irradiation intensity of the 3D printer to brighten the backlight side of the semi-transparent unit, and then proceeds to execute step SA02; SA10. The control unit extracts the non-zero minimum value in the Nth gray compensation difference as the (N + 1)th reference value, subtracts the (N + 1)th reference value from each of the initial gray values to obtain the (N + 1)th gray compensation difference, and forms a gray compensation difference table, and then proceeds to execute step SA06; SA11. The process ends.

2. An LCD light-curing 3D printing light homogenization optimization and compensation method, characterized in that It includes the following steps: SB01. Turn on the LCD light-curing printer and cover the semi-transparent unit on the backlight side of the LCD screen so that the light source irradiates the entire LCD screen; SB02. The control unit obtains the semi-transparent image displayed on the backlight side of the semi-transparent unit during the full-screen exposure of the LCD screen through the image capture unit and obtains the initial gray values of the image pixels within the full-screen range of the semi-transparent image; SB03. The control unit determines whether the average gray value of all the initial gray values is lower than the preset threshold; if it is determined that the average gray value is lower than the preset threshold, step SB09 is performed; if it is determined that the average gray value is not lower than the preset threshold, step SB04 is performed; SB04. The control unit inputs the gray mask slice image of the graphic to be printed through a removable storage device or network or computer and obtains the mask gray values of each pixel in each gray mask slice; SB05. The control unit extracts the non-zero Nth smallest value from each initial gray value as the Nth reference value, then subtracts the Nth reference value from each initial gray value to obtain the Nth gray compensation difference value and forms a gray compensation difference value table. SB06. The control unit subtracts the mask gray value of each pixel point in each gray mask slice image from the values in the gray compensation difference value table respectively to obtain the optimized gray value of each gray mask slice image and forms an optimized gray value table. SB07. The control unit determines whether each optimized gray value is greater than or equal to a preset value. If so, it executes step SB10. If it is determined that each value in the optimized gray value table is greater than or equal to the preset value, then step SB08 is performed. SB08. The control unit performs stereolithography printing on each slice mask image according to the optimized gray value of each gray mask slice image obtained, and then enters and executes step SB11. SB09. Manually adjust or the control unit adjusts to increase the illumination intensity of the 3D printer light source to brighten the backlight surface of the semi-transmissive unit, and then enters and executes step SB02. SB10. The control unit extracts the non-zero (N + 1)th smallest value from each initial gray value as the (N + 1)th reference value, then subtracts the (N + 1)th reference value from each initial gray value to obtain the (N + 1)th gray compensation difference value and forms a gray compensation difference value table, and then enters and executes step SB06. SB11. The process ends.

3. An LCD light-curing 3D printing light homogenization optimization compensation method, characterized in that, It includes the following steps: SC01. Turn on the LCD stereolithography printer and cover the semi-transmissive unit on the backlight surface of the LCD screen so that the light source irradiates the entire LCD screen. SC02. The control unit obtains the semi-transmissive image displayed on the backlight surface of the semi-transmissive unit during the full-screen exposure of the LCD screen through the image capturing unit and obtains the initial gray value of the image pixels within the full-screen range of the semi-transmissive image. SC03. The control unit determines whether the average gray value of all initial gray values is lower than a preset threshold. If it is determined that the average gray value is lower than the preset threshold, then step SC09 is performed. If it is determined that the average gray value is not lower than the preset threshold, then step SC04 is performed. SC04. The control unit inputs the gray mask slice images of the graphics to be printed through a removable storage device or network or computer and obtains the mask gray value of each pixel in each gray mask slice. SC05. The control unit rounds each initial gray value and extracts the integer value with the most same and larger values as the Nth reference value, then subtracts the Nth reference value from each initial gray value to obtain the Nth gray compensation difference value and forms a gray compensation difference value table. SC06. The control unit subtracts the mask gray value of each pixel point in each gray mask slice image from the values in the gray compensation difference value table respectively to obtain the optimized gray value of each gray mask slice image and forms an optimized gray value table. SC07. The control unit determines whether each optimized gray value is greater than or equal to a preset value. If it is determined that there is a value less than the preset value among each optimized gray value, then step SC10 is executed. If it is determined that each value in the optimized gray value table is greater than or equal to the preset value, then step SC08 is performed. SC08. The control unit optimizes the gray values according to each obtained gray mask slice image and performs photocuring printing on each slice mask image, and then proceeds to execution step SC11; SC09. Manually adjust or the control unit adjusts to increase the illumination intensity of the 3D printer light source to brighten the backlight surface of the semi-transparent unit, and then proceeds to execution step SC02; SC10. The control unit rounds each initial gray value and extracts the integer value with the most and larger same values as the (N + 1)-th reference value, then subtracts the (N + 1)-th reference value from each initial gray value to obtain the (N + 1)-th gray compensation difference value and forms a gray compensation difference value table, and then proceeds to execution step SC06; SC11. The process ends.

4. The LCD light-curing 3D printing uniform light optimization compensation method according to any one of claims 1-3, characterized in that When calculating the difference value of the gray value, all negative numbers obtained in the difference value calculation are set to zero.

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