Calibration method

Abstract

The present application provides a correction method suitable for correcting the uniformity of a single-layer structure of a three-dimensional printed model, comprising the following steps: S11: Full-scale projection of the single-layer structure to print a single-layer model; S12: Collecting the curing depth of each pixel position of the single-layer model in the projection plane; S13: Adjusting the light intensity corresponding to each pixel position according to the consistency of the multiple curing depths until the consistency of the multiple curing depths reaches a preset convergence threshold. The correction method can realize the correction of the plane flatness and accuracy of the three-dimensional printing device by printing a layer of model, and the correction accuracy is high.

Description

Technical Field

[0001] The present application mainly relates to the field of three-dimensional printing, and in particular to a correction method. Background Art

[0002] At present, the molding methods of 3D printing technology are still evolving, and the materials used are also diverse. Among various molding methods, photocuring is a relatively mature method. Photocuring is a method that uses the principle that photocurable resin is cured after being irradiated with ultraviolet light to perform material cumulative molding. It has the characteristics of high molding accuracy, good surface finish, and high material utilization rate. However, during the printing process, the existing technology relies on CCD optical image detection, and its resolution is limited by the CCD camera. After correction, there are still fine stripes that are difficult to identify during correction. Especially when performing micro-nano printing, due to the small size of the micro-nano projection image, the transparent photosensitive resin material has a large transmission depth, and the transmission depth changes dramatically with the light intensity, the uniformity has a much higher impact on the print size than the traditional non-transparent photosensitive resin material. The accuracy of the existing CCD-based optical image correction is greatly affected by the uniformity and dynamic range of the CCD, and it is difficult to meet the 3D printing needs of ultra-precision transparent micro-nano photosensitive resin materials. Summary of the invention

[0003] The technical problem to be solved by the present application is to provide a three-dimensional printing correction method that meets the three-dimensional printing requirements of ultra-precision transparent micro-nano photosensitive resin materials.

[0004] In order to solve the above technical problems, the present application proposes a correction method, which is suitable for correcting the uniformity and consistency of a single-layer structure of a three-dimensional printed model. The correction method includes the following steps: S11: performing full-scale projection on the single-layer structure to print a single-layer model; S12: collecting the curing depth of each pixel position of the single-layer model in the projection plane; S13: adjusting the light intensity corresponding to each pixel position according to the consistency of multiple curing depths until the consistency of the multiple curing depths reaches a preset convergence threshold.

[0005] In one embodiment of the present application, adjusting the light intensity corresponding to each pixel position according to the consistency of the plurality of curing depths includes: adjusting the light intensity by a gradient descent method.

[0006] In one embodiment of the present application, performing full-area projection on the single-layer structure includes: performing full-area projection on the single-layer structure using a sub-pixel micro-scanning technology.

[0007] In an embodiment of the present application, the size of each pixel corresponding to the pixel position is less than or equal to 1 μm.

[0008] In one embodiment of the present application, the transmission depth of the printing material used to print the single-layer model is greater than or equal to 1 mm.

[0009] In one embodiment of the present application, collecting the solidification depth of each pixel position of the single-layer model in the projection plane includes: using a laser confocal microscope to perform three-dimensional modeling of the transmission depth of the single-layer model.

[0010] In one embodiment of the present application, it further includes: exposing on photographic paper according to the single-layer structure, and representing the light intensity by the grayscale of each pixel position in the photographic paper.

[0011] In an embodiment of the present application, the consistency of the multiple curing depths includes a standard deviation, a variance and / or a range of the multiple curing depths.

[0012] In one embodiment of the present application, the preset convergence threshold is less than or equal to 0.1 times the average value of the multiple solidification depths.

[0013] In one embodiment of the present application, determining whether the consistency of the multiple solidification depths reaches a preset convergence threshold includes: when 95% of the pixels in the projection plane have a solidification depth less than the preset convergence threshold and 99% of the pixels have a solidification depth less than twice the preset convergence threshold, the consistency of the multiple solidification depths reaches the preset convergence threshold.

[0014] Compared with the prior art, the correction method provided by the present application collects the solidification depth of each pixel position of a single-layer model in the projection plane, and adjusts the light intensity corresponding to each pixel position according to the consistency of multiple solidification depths. It can realize the correction of the plane flatness and accuracy of the three-dimensional printing equipment by printing a layer of model. The correction accuracy is high and there are no fine stripes after correction, so that the three-dimensional printing device corrected by the method can achieve pixel-level resolution when performing three-dimensional printing. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The accompanying drawings are included to provide a further understanding of the present application. They are included and constitute a part of the present application. The accompanying drawings illustrate embodiments of the present application and together with the present specification serve to explain the principles of the present application. In the accompanying drawings:

[0016] Figure 1 is a flow chart of a calibration method according to an embodiment of the present application;

[0017] Figure 2 It is a schematic diagram of a three-dimensional printing correction device according to an embodiment of the present application. DETAILED DESCRIPTION

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for the description of the embodiments. Obviously, the drawings described below are only some examples or embodiments of the present application. For ordinary technicians in this field, the present application can also be applied to other similar scenarios based on these drawings without creative work. Unless it is obvious from the language environment or otherwise explained, the same reference numerals in the figures represent the same structure or operation.

[0019] As shown in this application, unless the context clearly indicates an exception, the words "a", "an", "an" and / or "the" do not refer to the singular, but also include the plural. Generally speaking, the terms "include" and "comprise" only indicate the inclusion of the steps and elements that have been clearly identified, and these steps and elements do not constitute an exclusive list, and the method or device may also include other steps or elements.

[0020] Unless otherwise specifically stated, the relative arrangement, numerical expressions and numerical values ​​of the parts and steps set forth in these embodiments do not limit the scope of the present application. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to those of ordinary skill in the relevant field may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be considered as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so that once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0021] In the description of the present application, it should be understood that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction, and therefore cannot be understood as limiting the scope of protection of the present application; the directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0022] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0023] Flowcharts are used in the present application to illustrate the operations performed by the system according to the embodiments of the present application. It should be understood that the preceding or following operations are not necessarily performed accurately in order. On the contrary, various steps may be processed in reverse order or simultaneously. At the same time, other operations may be added to these processes, or one or more operations may be removed from these processes.

[0024] Figure 1 is a flow chart of a calibration method according to an embodiment of the present application. Figure 1 As shown, the calibration method of this embodiment includes the following steps:

[0025] Step S11: Full-scale projection is performed on the single-layer structure to print out a single-layer model.

[0026] Step S12: collecting the solidification depth of each pixel position of the single-layer model in the projection plane;

[0027] Step S13: adjusting the light intensity corresponding to each pixel position according to the consistency of the multiple curing depths until the consistency of the multiple curing depths reaches a preset convergence threshold.

[0028] Figure 2 Schematic diagram of a three-dimensional printing correction device according to an embodiment of the present application. The three-dimensional printing correction device can be used to perform the correction method of the present application. Figure 2 The above steps S11 to S13 are described. However, the calibration method of the present application is not limited to Figure 2 The three-dimensional printing correction device shown is used to perform.

[0029] In step S11, the single-layer structure is a design structure, which can be a layer structure to be printed pre-designed by software and represented in the form of an image. The three-dimensional printing device projects the single-layer structure onto an imaging plane using a projection device according to the single-layer structure. Figure 2 As shown, a light source 21 and a projection plane S are shown. The full-frame projection in step S11 is full-frame exposure, that is, all positions in the X direction and the Y direction in the projection plane S are exposed, which is conducive to correcting all exposure points of the full frame in subsequent steps.

[0030] In one embodiment of the present application, performing full-area projection on the single-layer structure in step S11 includes performing full-area projection on the single-layer structure using a subpixel micro scanning technology (SMS, Subpixel Micro Scanning).

[0031] The higher the printing precision in ordinary 3D printing technology, the slower the printing speed. Sub-pixel micro-scanning technology uses liquid crystal projection technology and involves an array image source. The liquid crystal panel contains many pixels, each of which can individually control the polarization direction of polarized light. In conjunction with the polarizers on both sides of the liquid crystal panel, it can control whether the light of a certain pixel passes through. For sub-pixel micro-scanning technology, please refer to the Chinese patent with publication number CN104669619A. All the contents of this patent can be used to illustrate the sub-pixel micro-scanning technology in this application. Sub-pixel micro-scanning technology can obtain a light spot with a minimum diameter of up to 500nm. The printing accuracy is improved by controlling the position and brightness of the light spot, and no splicing is required.

[0032] like Figure 2 As shown, the projection plane S may be the projection plane after passing through the liquid crystal panel. The projection plane S is a specific layer at a certain height in the Z direction (vertical direction). Printing material is arranged below the projection plane S, and the image of the single-layer structure is fully projected onto the projection plane S, so that the printing material is irradiated and exposed. The light-curing printing material is cured by light to form a single-layer model. Figure 2 The area 20 in the figure represents the projection area corresponding to the single-layer structure. Figure 2 The illustration is only an example, used to distinguish the projection plane S from the area 20. Full-scale projection means that the area 20 is equal to or almost equal to the entire projection plane S, that is, covers the entire projection plane S. Therefore, the entire projection plane S can be corrected.

[0033] refer to Figure 2As shown, the upper right corner of area 20 is partially enlarged and shown, and the enlarged area includes a plurality of small squares arranged in a matrix, and each small square corresponds to a pixel on the liquid crystal panel. It should be noted that the entire area 20 is composed of a plurality of small squares, that is, it includes a plurality of pixels, and each pixel has a pixel position. It can be understood that the more pixels there are and the higher the density, the higher the printing accuracy, and the higher the correction accuracy of the correction method of the present application.

[0034] In step S11, the single-layer model obtained by printing refers to a model obtained by exposing the printing material according to the image indicated by the single-layer structure, such as a thin sheet. For a complex three-dimensional model, its three-dimensional structure is divided into multiple layers, and the three-dimensional printing device prints layer by layer according to the multi-layer image. The single-layer structure can be the first layer in the multi-layer projection image. In some embodiments, the single-layer structure includes a complete plane structure, that is, in theory, the single-layer model obtained according to the single-layer structure should be a thin plate with a thickness of one layer, and its area is equal to the area of ​​the projection plane S.

[0035] In some embodiments, after step S11, the single-layer model may be further solidified and cleaned. Further solidification may be, for example, using other means to further solidify the single-layer model that is already solid to strengthen its shape. The cleaning method may be, for example, ultrasonic cleaning.

[0036] The pixel position on the single-layer model corresponds to each pixel position in the projection plane S. At each pixel position, the photocurable material has a certain depth after printing, that is, the curing depth. For a single-layer model, the curing depth at a certain pixel position can be understood as the thickness of the sheet at the pixel position. Due to equipment reasons, the curing depths at different pixel positions may be different.

[0037] In a preferred embodiment of the present application, the size of the pixel is less than or equal to 1 μm. A smaller pixel size is beneficial to improving the correction accuracy and model accuracy.

[0038] In step S12, collecting multiple solidification depths of each pixel position of the single-layer model in the projection plane can be achieved in a variety of ways. In a preferred embodiment of the present application, a laser confocal microscope can be used to perform three-dimensional modeling of the transmission depth of the single-layer model, thereby collecting multiple solidification depths of each pixel position of the single-layer model in the projection plane, and this method has high accuracy.

[0039] In some embodiments, adjusting the light intensity corresponding to each pixel position according to the consistency of multiple solidification depths in step S13 includes: adjusting the light intensity by gradient descent method. Specifically, when collecting multiple solidification depths of each pixel position of the single-layer model in the projection plane S for the first time, the consistency of the multiple solidification depths obtained may be relatively poor. Assuming that the light intensity of each pixel irradiated by the current light source 21 is x, the light intensity is first adjusted by gradient descent method at this time, and step S12 is executed again after adjustment, and multiple solidification depths of each pixel position adjusted at this time are collected again, and their consistency is calculated. It can be understood that it is usually difficult to complete the correction with a single or a few adjustments, so it is necessary to repeat the above steps, collect again after each adjustment, calculate the consistency and decide whether it needs to be adjusted again, until the consistency of the collected multiple solidification depths reaches the preset convergence threshold, then the correction is considered to be completed.

[0040] It should be noted that the curing depth can also be used to reflect the light intensity at a certain pixel position. The curing depth at each pixel position is obtained using a laser confocal microscope, and the result has a high accuracy. Using this curing depth to reflect the light intensity at the pixel position has a high sensitivity.

[0041] In some embodiments, adjusting the light intensity using the gradient descent method includes: adjusting the light intensity corresponding to each pixel position.

[0042] The gradient descent method can be expressed by the following formula (1):

[0043] x'←x-α▽f(x); (1)

[0044] Where x is the light intensity, f(x) is the theoretical transmission depth, α is the drop rate, and x' is the adjusted light intensity. By deriving from Beer's law, we can get f(x)=A·ln(x)+B. Where A and B are constants related to the material. x' is usually 0.001-0.3. After calculating the consistency of the curing depth, if the consistency does not meet the standard, the light intensity at the relevant pixel position is adjusted to the adjusted light intensity x' according to formula (1).

[0045] In some embodiments, the light intensity is adjusted by the gradient descent method including: increasing the light intensity corresponding to the pixel position with a smaller curing depth, and / or decreasing the light intensity corresponding to the pixel position with a larger curing depth. According to these embodiments, there is no need to reprint the single-layer structure, but adjustments are made based on the original single-layer structure, and finally a single-layer model with good consistency in curing depth is obtained. At the same time, the three-dimensional printing device will record the adjustment history of each light intensity, and finally obtain a high-precision exposure parameter corresponding to the full-width.

[0046] In some other embodiments of the present application, the correction method further includes: exposing on photographic paper according to the single-layer structure, and representing the light intensity at the corresponding position by the grayscale of each pixel position in the photographic paper. In some embodiments, the photographic paper uses a photosensitive material. According to these embodiments, the light source 21 directly exposes the image of the single-layer structure on the photographic paper, that is, the image of the single-layer structure is projected on the photographic paper, and the photographic paper is fixed to obtain a photograph. Since the photographic paper is opaque, a black-and-white or color photograph with a pattern on a white background can be obtained. Taking a black-and-white photograph as an example, the grayscale of each pixel position in the photographic paper is obtained, and then the grayscale is used to represent the light intensity of the pixel.

[0047] In some embodiments, after obtaining the photo, the digital information of the image on the photo is obtained by, for example, a scanner, and then the grayscale corresponding to each pixel position on the image is calculated by software. It can be understood that by projecting on photographic paper, no printed material is needed.

[0048] In one embodiment of the present application, the consistency of multiple curing depths includes the standard deviation, variance and / or range of multiple curing depths. It is understandable that the larger the standard deviation, variance and / or range, the worse the consistency of multiple curing depths and the lower the printing accuracy. Further, the preset convergence threshold can be adjusted by the staff according to the actual needs of printing accuracy. In a preferred embodiment, the preset convergence threshold can be determined based on the average value of multiple curing depths. Specifically, in one embodiment, the preset convergence threshold is less than or equal to 0.1 times the average value of multiple curing depths.

[0049] Furthermore, the consistency of multiple solidification depths can be judged in a graded manner, specifically: when 95% of the pixels in the projection plane have a solidification depth less than a convergence threshold and 99% of the pixels have a solidification depth less than twice the convergence threshold, the consistency of multiple solidification depths reaches a preset convergence threshold. By performing the graded judgment, the correction speed can be accelerated and convergence can be achieved earlier.

[0050] According to the correction method of the present application, the uniformity of the single-layer structure of the 3D printing model can be corrected, and then the 3D printing device can be corrected. With this correction method, only one single-layer structure is needed to complete the correction of the 3D printing device. After the correction is completed, the light intensity adjustment parameters corresponding to each pixel are saved. In the subsequent formal 3D printing, the saved light intensity adjustment parameters are called to obtain a 3D printing model with high fixed depth consistency.

[0051] The penetration depth of light in different materials may be different. In one embodiment provided in the present application, the penetration depth of the printing material used to print a single-layer model is greater than or equal to 1 mm, preferably a photosensitive resin, and the curing process is performed by a single light source 21 through a glass sheet (not shown in the figure), wherein the light emitted by the light source 21 is parallel light. In this embodiment, the glass sheet is used as a reference plane, which itself has a relatively flat surface. Other light-transmitting materials with a flat surface can also be used as a reference plane. The printing material is arranged under the glass sheet so that a layer of material after curing adheres to the lower surface of the glass sheet. The light emitted by the light source 21 can be approximately parallel light or parallel light, which can prevent the light of adjacent pixels from interfering with each other.

[0052] Compared with the prior art, the correction method provided in the present application adjusts the consistency of the curing depth of each pixel in the plane of the single-layer model through the gradient descent method, so as to achieve pixel-level resolution and high correction accuracy. After correction, there are no fine stripes in the whole format, so that the final molded parts have higher consistency in full-format dimensional accuracy, match the actual printing material, and have good printing uniformity.

[0053] The present application uses specific words to describe the embodiments of the present application. For example, "one embodiment", "an embodiment", and / or "some embodiments" refer to a certain feature, structure or characteristic related to at least one embodiment of the present application. Therefore, it should be emphasized and noted that "one embodiment" or "an embodiment" or "an alternative embodiment" mentioned twice or multiple times in different positions in this specification does not necessarily refer to the same embodiment. In addition, some features, structures or characteristics in one or more embodiments of the present application can be appropriately combined.

[0054] Some aspects of the present application may be performed entirely by hardware, entirely by software (including firmware, resident software, microcode, etc.), or by a combination of hardware and software. The above hardware or software may be referred to as "data blocks", "modules", "engines", "units", "components" or "systems". The processor may be one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DAPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, or combinations thereof. In addition, various aspects of the present application may be represented as computer products located in one or more computer-readable media, which include computer-readable program codes. For example, computer-readable media may include, but are not limited to, magnetic storage devices (e.g., hard disks, floppy disks, tapes ...), optical disks (e.g., compact disks CDs, digital versatile disks DVDs ...), smart cards, and flash memory devices (e.g., cards, sticks, key drives ...).

[0055] A computer-readable medium may include a propagated data signal containing computer program code, such as in baseband or as part of a carrier wave. The propagated signal may have a variety of manifestations, including electromagnetic, optical, etc., or a suitable combination. A computer-readable medium may be any computer-readable medium other than a computer-readable storage medium, which may be connected to an instruction execution system, device or apparatus to communicate, propagate or transmit a program for use. The program code on the computer-readable medium may be propagated via any suitable medium, including radio, cable, fiber optic cable, radio frequency signal, or similar medium, or any combination of the above mediums.

[0056] Similarly, it should be noted that in order to simplify the description of the disclosure of this application and thus help understand one or more embodiments of the invention, in the above description of the embodiments of this application, multiple features are sometimes combined into one embodiment, figure or description thereof. However, this disclosure method does not mean that the features required by the object of this application are more than the features mentioned in the application. In fact, the features of the embodiment are less than all the features of the single embodiment disclosed above.

[0057] In some embodiments, the numbers describing the number of components and attributes are used. It should be understood that such numbers used for the description of the embodiments are modified by the modifiers "about", "approximately" or "substantially" in some examples. Unless otherwise specified, "about", "approximately" or "substantially" indicate that the numbers allow a change of ±20%. Accordingly, in some embodiments, the numerical parameters used in the full text are approximate values, which can be changed according to the required characteristics of individual embodiments. In some embodiments, the numerical parameters should consider the specified significant digits and adopt the method of general digit retention. Although the numerical domains and parameters used to confirm the breadth of the range in some embodiments of the present application are approximate values, in specific embodiments, the setting of such numerical values ​​is as accurate as possible within the feasible range.

[0058] Although the present application has been described with reference to the current specific embodiments, ordinary technicians in this technical field should recognize that the above embodiments are only used to illustrate the present application, and various equivalent changes or substitutions may be made without departing from the spirit of the present application. Therefore, as long as the changes and modifications to the above embodiments are within the essential spirit of the present application, they will fall within the scope of the present application.

Claims

1. A correction method, suitable for correcting the uniformity of a single-layer structure of a three-dimensional printed model, characterized in that: The calibration method comprises the following steps: S11: Perform full-scale projection on the single-layer structure to print out a single-layer model, wherein the full-scale projection on the single-layer structure includes: performing full-scale projection on the single-layer structure using a sub-pixel micro-scanning technology, wherein an imaging system using the sub-pixel micro-scanning technology includes: a light source that emits a light beam; a liquid crystal panel that is located on the light output path of the light source, and the liquid crystal panel includes a plurality of pixels; a first polarized light splitting prism that is disposed on the light incident side of the liquid crystal panel; a projection lens that is disposed between the liquid crystal panel and the surface of the photosensitive material and is located between the image of the light source and the surface of the photosensitive material, and projects the image of the light beam onto the surface of the photosensitive material; a polarizer or a second polarizer A light beam splitter prism, wherein the polarizer is disposed between the projection lens and the surface of the photosensitive material, and a second polarized light beam splitter prism is disposed on the light-exiting side of the liquid crystal panel. The polarizer or the second polarized light beam splitter prism and the first polarized light beam splitter prism cooperate with the liquid crystal panel to block a portion of the light beam to form a light beam image; a focusing lens array is disposed on the light-incident side of the liquid crystal panel, and each focusing lens of the focusing lens array corresponds to each pixel of the liquid crystal panel. Each focusing lens can converge the light beam irradiated to the corresponding pixel, so that the light beam can pass through the light-transmitting area of ​​the pixel as much as possible, and form an image on the light-exiting side of the liquid crystal panel, and the size of the image is smaller than the size of the light-transmitting area of ​​the corresponding pixel; S12: collecting the solidification depth of each pixel position of the single-layer model in the projection plane; S13: adjusting the light intensity corresponding to each pixel position according to the consistency of the multiple curing depths until the consistency of the multiple curing depths reaches a preset convergence threshold, wherein judging whether the consistency of the multiple curing depths reaches the preset convergence threshold includes: when 95% of the pixels in the projection plane have a curing depth less than the preset convergence threshold and 99% of the pixels have a curing depth less than twice the preset convergence threshold, the consistency of the multiple curing depths reaches the preset convergence threshold, and adjusting the light intensity corresponding to each pixel position according to the consistency of the multiple curing depths includes: adjusting the light intensity by a gradient descent method, including using the following formula to represent the gradient descent method: x'←x-α▽f(x); Wherein, x is the light intensity, f(x) is the theoretical transmission depth, α is the drop rate, and x' is the adjusted light intensity; wherein the liquid crystal panel is divided into a plurality of liquid crystal units filled with liquid crystal, and adjusting the light intensity corresponding to each pixel position includes: controlling the arrangement direction of the liquid crystal molecules of each liquid crystal unit to control the brightness of light passing through the liquid crystal unit.

2. The calibration method according to claim 1, characterized in that: The size of each pixel corresponding to the pixel position is less than or equal to 1 μm.

3. The calibration method according to claim 1, characterized in that: The transmission depth of the printing material used to print a single-layer model is greater than or equal to 1 mm.

4. The calibration method according to claim 1, wherein: Collecting the solidification depth of each pixel position of the single-layer model in the projection plane includes: using a laser confocal microscope to perform three-dimensional modeling on the transmission depth of the single-layer model.

5. The calibration method according to claim 1, wherein: Also includes: Exposure is performed on photographic paper according to the single-layer structure, and the light intensity is represented by the grayscale of each pixel position in the photographic paper.

6. The calibration method according to claim 1, wherein: The consistency of the plurality of cure depths may include a standard deviation, a variance, and / or a range of the plurality of cure depths.

7. The calibration method according to claim 1, characterized in that: The preset convergence threshold is less than or equal to 0.1 times an average value of the plurality of solidification depths.

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