Method and apparatus for calibrating exposure surface of optical system, calibration measurement method, computer device, and computer program

Abstract

The present application discloses an exposure surface calibration method and device of an optical system, a computer device, and a storage medium, the method including the steps of performing flat-field correction on an imaging module by a reference light source, acquiring a gradation distribution image generated by imaging the exposure surface of the optical system by the imaging module, dividing the gradation distribution image into a mesh image including a plurality of divided regions and calculating fitting gradation values ​​of each divided region, selecting the smallest fitting gradation value from all the calculated fitting gradation values ​​as a reference gradation value, calculating gradation compensation coefficients corresponding to other divided regions based on the reference gradation value to generate a digital mask, and performing mask compensation on the projection image from the optical system by the digital mask to obtain a printing image with a uniform irradiance value on the exposure surface. The present application can improve the calibration accuracy and calibration efficiency of the exposure surface of the optical system by acquiring the pixel level distribution of the exposure surface and performing corresponding compensation on the gradation value. The present application further discloses a calibration measurement method for 3D printing. The calibration measurement method for 3D printing can measure multiple parameters of the optical system to determine whether each parameter of the optical system meets the requirements during 3D printing, so as to generate a clear image that is completely similar to the object, thereby realizing more accurate and efficient 3D printing.

Description

[Technical field]

[0001] This application claims priority to a Chinese patent application filed with the State Intellectual Property Office of China on July 22, 2021, bearing application number 202110832043.6 and entitled "Method and apparatus, computer equipment and storage medium for calibrating exposure surface of optical system", the entire contents of which are incorporated herein by reference. The present application relates to the technical field of optical systems, and in particular to an exposure surface calibration method and apparatus for an optical system, a calibration measurement method, a computer device, and a storage medium. [Background technology]

[0002] 3D printing technology in related technology generally uses DLP and LCD technologies when realizing the surface printing process in the field of photocuring. DLP photocuring printers use high-resolution DLP devices and ultraviolet light sources to project the cross section of a three-dimensional model onto the worktable and photocures the liquid photopolymer layer by layer. LCD photocuring printers are similar to the above, except that they use an LCD display instead of a DLP projection system to display the cross section directly on the worktable. DLP and LCD both belong to printing surface exposure technologies, and in the case of 3D printing, the irradiance of each point in the exposure surface must be consistent. If the difference in irradiance in the exposure surface is too large, vertical streaks will appear on the surface of the printed finished product, or in the worst case, it will fall off the printing platform during printing, resulting in printing failure.

[0003] The light source calibration technology generally involves dividing the entire format of the printing area into multiple measurement points, measuring the irradiance of each point with an optical power meter, and obtaining the irradiance distribution data of each point. Then, the gradation compensation value of each point is calculated based on the data distribution, and the area of ​​each point is projected or displayed with the gradation calculated by the compensation value, thereby achieving the calibration of the uniformity of the entire exposure surface.

[0004] However, such a method has a large limitation. For example, the irradiance measurement of a point after the format division only indicates the irradiance of the point, which belongs to a discrete point value. However, if the discrete point value is used instead of the area distribution value of the corresponding divided surface, that is, the uniform distribution situation in the plane is represented by the discrete points, the distribution value between the discrete points is replaced by the value of these two points, which leads to a decrease in the calibration accuracy of the uniformity. In order to increase the accuracy, it is usually done by increasing the number of points divided into the format, but this leads to an increase in detection time and difficulty. In addition, with the long-term use of the printing device, the gradation compensation value after the previous calibration may change due to the deterioration or replacement of elements in the optical system, and it is necessary to continue the calibration of the uniformity of the printing area, which requires a lot of effort and time. Summary of the Invention [Problem to be solved by the invention]

[0005] The present application provides a method and apparatus for calibrating an exposure surface of an optical system, a computer device, and a storage medium for improving the calibration accuracy and calibration efficiency for the exposure surface of the optical system. [Means for solving the problem]

[0006] In a first aspect, the present application provides a method for calibrating an exposure plane of an optical system, the method comprising: performing flat-field correction on the imaging module using a reference light source; acquiring a gradation distribution image generated by imaging an exposure surface of an optical system by an imaging module; Dividing the gradation distribution image into a mesh image including a plurality of divided regions, and calculating a fitting gradation value for each divided region; selecting a predetermined fitting gradation value as a reference gradation value from all the calculated fitting gradation values, and calculating gradation compensation coefficients corresponding to the other divided regions based on the reference gradation value to generate a digital mask; and performing mask compensation on the projected image from the optical system with a digital mask to obtain a printed image with uniform irradiance values ​​on the exposed surface.

[0007] In a second aspect, the present application provides a calibration measurement method for 3D printing, the method comprising: calibrating an exposure surface of the optical system by the above-mentioned method for calibrating an exposure surface of the optical system; obtaining a first irradiance value corresponding to a white image and a second irradiance value corresponding to a black image, both of which are projected by a calibrated optical system; obtaining a static contrast of the optical system based on the first irradiance value and the second irradiance value; obtaining irradiance values ​​for each region of a checkerboard map, the checkerboard map being projected by a calibrated optical system; and processing the irradiance values ​​of each region with the ANSI contrast calculation method to obtain the dynamic contrast of the optical system.

[0008] In a third aspect, the present application provides a method for calibrating an exposure plane of an optical system, the method comprising: acquiring an image information distribution image generated by imaging an exposure surface of an optical system by an imaging module; A step of performing a division process on the image information distribution image and calculating a mapping image information value of each divided area; The method may also include a step of selecting a reference mapping image information value from each mapping image information value and calculating compensation parameters corresponding to other divided regions based on the reference mapping image information value, the compensation parameters being for performing mask compensation on a projected image from the optical system to obtain a printed image having a uniform irradiance value on the exposure surface.

[0009] In a fourth aspect, the present application provides an apparatus for calibrating an exposure plane of an optical system, the apparatus comprising: an image acquisition unit configured to acquire a gradation distribution image generated by imaging an exposure surface of the optical system by the imaging module; A fitting unit configured to divide the gradation distribution image into a mesh image including a plurality of divided regions and calculate a fitting gradation value of each divided region; A selection unit configured to select a minimum fitting gray scale value from all the calculated fitting gray scale values ​​as a reference gray scale value, and calculate gray scale compensation coefficients corresponding to other divided regions based on the reference gray scale value to generate a digital mask; and a mask compensation unit configured to perform mask compensation on the projected image from the optical system using a digital mask to obtain a printed image with uniform irradiance values ​​on the exposed surface.

[0010] In a fifth aspect, the present application provides a computer device including a memory, a processor, and a computer program stored in the memory and executable on the processor, the processor, when executing the computer program, realizing the exposure surface calibration method of the optical system and the calibration measurement method for 3D printing. In a sixth aspect, the present application provides a computer-readable storage medium having a computer program stored thereon, the computer program realizing, when executed by a processor, the exposure surface calibration method for the optical system and the calibration measurement method for 3D printing. In a seventh aspect, the present application provides a computer program product including a computer program, which, when executed by a processor, realises the exposure surface calibration method for an optical system and the calibration measurement method for 3D printing. Effect of the Invention

[0011] The present application provides an exposure surface calibration method and device for an optical system, a computer device, and a storage medium, the method including the steps of performing flat-field correction on an imaging module using a reference light source, obtaining a gradation distribution image generated by imaging the exposure surface of the optical system using the imaging module, dividing the gradation distribution image into a mesh image including a plurality of divided regions, calculating fitting gradation values ​​for each divided region, selecting the smallest fitting gradation value from all the calculated fitting gradation values ​​as a reference gradation value, calculating gradation compensation coefficients corresponding to other divided regions based on the reference gradation value to generate a digital mask, and performing mask compensation on the projection image from the optical system using the digital mask to obtain a printed image with a uniform irradiance value on the exposure surface. The present application obtains all pixel level distributions of the irradiance values ​​of the exposure surface, converts them into a low-density discrete distribution, and then performs corresponding compensation on the gradation values, thereby effectively improving the calibration accuracy and calibration efficiency of the exposure surface of the optical system. [Brief description of the drawings]

[0012] In order to more clearly describe the technical means in the embodiments of the present application, the drawings that need to be used in the description of the embodiments will be briefly described below. It is obvious that the drawings in the following description are only some embodiments of the present application, and those skilled in the art can derive other drawings based on these drawings without creative labor. [Figure 1] 1 is a schematic flowchart of a method for calibrating an exposure surface of an optical system according to an embodiment of the present application. [Diagram 2] 1 is a schematic flowchart of a method for calibrating an exposure surface of an optical system according to another embodiment of the present application. [Diagram 3] 4 is a schematic sub-flowchart of a method for calibrating an exposure surface of an optical system according to an embodiment of the present application. [Figure 4] 13 is another schematic flowchart of a method for calibrating an exposure surface of an optical system according to an embodiment of the present application. [Diagram 5] 1 is an exemplary schematic diagram of a method for calibrating an exposure surface of an optical system according to an embodiment of the present application; [Figure 6] FIG. 13 is another exemplary schematic diagram of a method for calibrating an exposure surface of an optical system according to an embodiment of the present application. [Figure 7] 1 is a schematic flowchart of a calibration measurement method for 3D printing according to an embodiment of the present application. [Figure 8] 1 is a schematic block diagram of an exposure surface calibration device for an optical system according to an embodiment of the present application. [Figure 9] FIG. 2 is a schematic sub-block diagram of an exposure surface calibration device for an optical system according to an embodiment of the present application. [Figure 10] FIG. 2 is another schematic block diagram of an exposure surface calibration device for an optical system according to an embodiment of the present application. [Figure 11] FIG. 1 is a schematic block diagram of an optical system according to an embodiment of the present application. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, the technical means in the embodiments of the present application will be described clearly and completely with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only some of the embodiments of the present application, and are not all of them, and all other embodiments that a person skilled in the art can obtain based on the embodiments of the present application without creative labor are all within the scope of protection of the present application. It will be understood that the terms "including" and "comprising", when used in this specification and the appended claims, specify the presence of stated features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or groups thereof.

[0014] It is also to be understood that the terminology used in the specification of this application is for the purpose of describing particular embodiments only, and is not intended to be limiting of the specification. As used in the specification and the appended claims, the singular forms "a," "one," and "the" are intended to include the plural forms as well, unless the context clearly dictates otherwise. It will be further understood that as used in the specification and appended claims, the term "and / or" refers to and includes any and all possible combinations of one or more of the associated listed items.

[0015] 1 is a schematic flow chart of a method for calibrating an exposure surface of an optical system according to an embodiment of the present invention. As shown in FIG. 1, the method specifically includes steps S101 to S105. In S101, flat-field correction is performed on the imaging module using a reference light source. In S102, a gradation distribution image is obtained by capturing an image of an exposure surface of an optical system by an imaging module.

[0016] In S103, the gradation distribution image is divided into a mesh image including a plurality of divided regions, and a fitting gradation value is calculated for each divided region. In S104, a predetermined fitting tone value is selected as a reference tone value from all the calculated fitting tone values, and tone compensation coefficients corresponding to the other divided regions are calculated based on the reference tone value, thereby generating a digital mask.

[0017] In S105, a digital mask is used to perform mask compensation on the projected image from the optical system to obtain a printed image having a uniform irradiance value on the exposed surface. The fitting tone value may be a value obtained by mapping the tone distribution in the region, and a predetermined fitting tone value may be selected as a reference tone value from all the fitting tone values ​​obtained by calculation, and the predetermined fitting tone value may be adjusted based on practical experience of the optical system, and if necessary, the predetermined fitting tone value may be any fitting tone value among all the fitting tone values ​​obtained by calculation. In some embodiments, the predetermined fitting tone value may be equal to the minimum fitting tone value x 50% + the maximum fitting tone value x 50%. In other embodiments, the predetermined fitting tone value may be equal to the minimum fitting tone value x 75% + the maximum fitting tone value x 25%. The predetermined fitting tone value may be set as the reference tone value using other values.

[0018] In some embodiments, the minimum fitting grayscale value may be selected as the reference grayscale value. When the minimum fitting grayscale value is selected as the reference grayscale value, the optical device projects at maximum brightness when performing the light uniformity calibration. On the other hand, when the minimum fitting grayscale value is not used as the reference grayscale value, the optical device needs to be calibrated with a lower brightness, so that the grayscale can be increased even at points below the reference value, and the grayscale calibration of the exposure surface is made uniform.

[0019] Hereinafter, an embodiment in which the minimum fitting gradation value is selected as the reference gradation value will be described in detail, and Fig. 2 is a schematic flowchart of an exposure surface calibration method for an optical system according to another embodiment of the present application. Specifically, the method may include steps S202 to S205. In S202, a gradation distribution image is obtained by capturing an image of an exposure surface of an optical system by an imaging module.

[0020] In S203, the gradation distribution image is divided into a mesh image including a plurality of divided regions, and a fitting gradation value is calculated for each divided region. In S204, the smallest fitting tone value from all the calculated fitting tone values ​​is selected as a reference tone value, and tone compensation coefficients corresponding to the other divided regions are calculated based on the reference tone value to generate a digital mask. In S205, a digital mask is used to perform mask compensation on the projected image from the optical system to obtain a printed image having a uniform irradiance value on the exposed surface.

[0021] In this embodiment, first, a projection image, which is a white image in the entire format, projected or displayed by an optical system using a light guide film on an exposure surface is received, and 2 n A white image of -1 gradation is set to be used, and an 8-bit image is set to be a white image of 255 gradations in 0 to 255 gradations as an example, and the pure white imaging surface seen from the back side of the light guide film is the printing surface of the printer. Next, an imaging module is placed directly above the light guide film to image the imaging surface to obtain an imaging surface, and each irradiance value on the exposure surface of the optical system is converted to a different gradation by the imaging module to obtain a corresponding gradation distribution image. Next, a digital mask is generated by dividing the gradation distribution image to calculate a fitting gradation value and obtaining a corresponding minimum fitting gradation value and gradation compensation coefficient. By compensating the projected image with the digital mask, uniform calibration for the exposure surface can be realized, and the finally obtained printed image has a uniform irradiance value. Note that the reference light source in this embodiment is a reference height uniform surface light source in the flat field correction technology, that is, before S202, a step S201 of performing flat field correction on the imaging module by the reference light source is further included.

[0022] In this embodiment, the entire pixel level distribution of the irradiance of the exposure surface is obtained and converted into a low-density discrete distribution, and then the corresponding compensation is made to the grayscale value, so that the calibration accuracy and calibration efficiency of the optical system for the exposure surface can be effectively improved. At the same time, the imaging module realizes non-contact overall measurement, avoiding multiple repeated operations and saving measurement time. In addition, the correction accuracy of this embodiment can be adjusted according to the actual situation by itself, and there is no need to add extra operation steps.

[0023] It should be noted that the irradiance value referred to in this application may be indicated by light intensity, which is another physical quantity, and the two may be converted into each other for use. In one embodiment, there is further provided a method for calibrating an exposure surface of an optical system, the method comprising: acquiring an image information distribution image generated by imaging an exposure surface of an optical system by an imaging module; performing a division process on the image information distribution image to calculate a mapping image information value for each divided area; The method includes a step of selecting a reference mapping image information value from each mapping image information value and calculating compensation parameters corresponding to other divided regions based on the reference mapping image information value, the compensation parameters being for performing mask compensation on a projected image from an optical system to obtain a printed image having a uniform irradiance value on an exposed surface.

[0024] The image information may be grayscale, brightness, and other similar physical quantities. The image information distribution image may be a grayscale information distribution image or a brightness information distribution image, etc. The compensation parameter may be a compensation coefficient or a compensation value, etc. The mapping image information value is obtained by mapping the grayscale distribution in the mesh, and can be obtained by a fitting or interpolation method. The fitting algorithm includes, but is not limited to, the least squares method, polynomial fitting, and cubic spline fitting.

[0025] Specifically, a digital mask is generated by the compensation parameter, and the digital mask is used to perform mask compensation on the projected image to obtain a printed image with a uniform irradiance value on the exposed surface. In one specific example, the method further includes a step of performing flat-field correction on the imaging module by a reference light source before the step of obtaining an image information distribution image generated by the imaging module capturing the exposed surface of the optical system.

[0026] In one embodiment, step S201 includes: A reference light source projects an exposure surface having a uniform irradiance value based on a preset gray level value; An imaging module captures an image of an exposure surface of a reference light source to obtain a reference light source image; obtaining a grayscale output value of each pixel unit in the photosensitive chip according to the reference light source image, and comparing the grayscale output value of each pixel unit with the preset grayscale value of the reference light source to obtain a grayscale correction coefficient of each pixel unit; and performing flat-field correction on the imaging module based on the tone correction coefficient of each pixel unit.

[0027] In this embodiment, first, a grayscale value is set for a reference light source (i.e., a reference height uniform surface light source) to project an exposure surface with a uniform irradiance value. Then, the reference light source is imaged by the imaging module, so that each pixel unit in the photosensitive chip can simultaneously receive light rays of the same energy. Then, the flat-field correction of the imaging module is completed based on the output data of the photosensitive chip. Specifically, in this embodiment, the entire reference light source is imaged by the imaging module, that is, the uniform surface light source is larger than the imaging surface range of the imaging module, and thus the photosensitive chip in the imaging module is completely covered by the image surface collected by the imaging objective lens. Specifically, the preset grayscale value is 2 n It may be -1, and when using 8-bit image gradation, the preset gradation value is 255.

[0028] Due to the influence of the lens vignetting in the imaging module and the photosensitivity difference of the photosensitive chip in the camera, when the imaging module captures a reference height uniform surface light source, the brightness detected at the center and edge of the photosensitive chip is different, so that the captured image shows different gray scales. Flat-field correction is performed by comparing the gray scale value detected by the photosensitive chip with a known reference height uniform surface light source, and taking the gray scale of an 8-bit image as an example, the gray scale value of the reference light source is set to 255, and the gray scale compensation value of each pixel of the imaging module can be obtained. After correcting the module with the compensation value, the reference height uniform surface light source can be captured to obtain the actual distribution of the uniformity of the light source, thereby completing the flat-field correction of the imaging module.

[0029] Further, in one embodiment, the step of obtaining a reference light source image by the imaging module capturing an image of an exposure surface of the reference light source includes: Dividing an imaging surface of the imaging module into several imaging sub-areas based on the size of an exposure surface of a reference light source; A step of projecting a reference light source onto each imaging sub-region by moving the reference light source to obtain several reference light source sub-images corresponding to each imaging sub-region; stitching several reference light source sub-images to obtain a reference light source image.

[0030] In this preferred embodiment, the imaging surface of the imaging module is divided based on the exposure size of the reference light source, and the reference light source is then moved to project onto each divided imaging sub-area to obtain a corresponding reference light source sub-image. In this preferred embodiment, a small-area, highly uniform surface light source is used as the reference light source, and the length and width of the reference light source are set to 1 / p and 1 / q of the length and width of the imaging plane, respectively, and the imaging plane and the imaging plane are conjugate, that is, for the imaging plane divided into p*q regions, there are a corresponding number of p*q regions on the imaging plane that are one-to-one mapped, where p and q are both integers.

[0031] Based on the length and width of the reference light source, the reference light source is made to correspond to p*q regions on the image plane. The p*q regions are stitched into a uniform imaging plane for each region, and the uniform imaging plane completes the flat-field correction of the imaging module. As shown in Fig. 5 and Fig. 6, Fig. 6 is obtained from the conjugation of Fig. 5, when the reference light source is set in region 1, the corresponding imaging region is 1', and when the reference light source is moved to region 2, the corresponding imaging region is 2'. The same reference light source is moved for each region, and the reference light source images p*q regions correspondingly, and after stitching for each region, a uniform imaging plane covering the photosensitive chip can be generated on the imaging plane, and this imaging plane can complete the flat field correction of the imaging module.

[0032] An optical system is an imaging system that can produce a clear and perfectly similar image of an object. A beam in which all rays or their extensions intersect at a single point is called a concentric beam. After an incident concentric beam passes through an ideal optical system, the emitted beam is also necessarily a concentric beam. The intersection points of the incident concentric beam and the emitted concentric beam are called object point and image point, respectively. An ideal optical system has the following properties: 1. After all rays that intersect an object point pass through the optical system, all the emitted rays intersect an image point, and vice versa. These pairs of object point and image point that are interchangeable are called conjugate points. 2. Each straight line on the object side and each straight line on the corresponding image side are called conjugate lines, and the corresponding surfaces are called conjugate planes. 3. For any plane perpendicular to the optical axis, the conjugate plane is still perpendicular to the optical axis. 4. For a pair of conjugate planes perpendicular to the optical axis, the lateral magnification is a constant.

[0033] In an embodiment, as shown in FIG. 3, the method for calibrating the exposure surface of an optical system may further include steps S301 to S303. In S301, the amount of exposure of the imaging module is limited. In S302, the irradiance value of the exposure surface of the reference light source is adjusted, the corresponding gradation value is acquired by the imaging module, and a relationship curve between the gradation and the irradiance value is generated by fitting.

[0034] In S303, the gradation of the projected image from the optical system is read by the imaging module based on the relational curve, and the corresponding irradiance value is obtained. In this embodiment, in addition to calibrating the uniformity of the printing exposure surface of the printer, the irradiance of the optical system can be monitored to grasp the deterioration state of the optical system. Specifically, during flat-field correction, first, the hardware parameters of the projected image are set, and the hardware parameters may include the exposure amount of the 3D printer, the gain of the imaging module, and the image processing conditions. Next, the exposure amount of the imaging module is made constant, and the gradation peak of the projected image is doubled by the constant exposure amount. n Keep it below -1 (255 in an 8-bit image).

[0035] A gradation calibration is performed on the projected image with a certain exposure amount to obtain the coordinate points of the captured gradation corresponding to the irradiance value. Then, different irradiance values ​​can be measured by the irradiance value measuring device to adjust the irradiance value of the projected image, and the corresponding gradation value can be obtained by the imaging module. After multiple adjustments, the coordinate points of the irradiance value can be fitted based on the adjustment results (i.e., different irradiance values ​​and corresponding gradation values) to generate a relationship curve between the gradation and the irradiance value. Then, when the imaging module reads the gradation of the projected image with the same exposure amount, the corresponding irradiance value can be determined based on the relationship curve.

[0036] Further, the method for calibrating the exposure surface of the optical system includes: acquiring illumination control parameters of an optical system and corresponding image information; obtaining a first relationship between image information of the optical system and illumination data; The method may further include a step of obtaining a second relationship between the illumination control parameters of the optical system and the illumination data based on the first relationship, the illumination control parameters and corresponding image information, wherein the second relationship is used to adjust the illumination data in the 3D printing process.

[0037] The irradiation control parameters are for adjusting the irradiation data (e.g., the brightness of the irradiation, the optical power, etc.), and may be, for example, related parameters such as current, or may be, for example, input brightness, input voltage, input power, etc. The image information reflects the characteristics of the image and can be expressed in a matrix format, and may be, for example, related parameters such as grayscale, brightness, etc., and the grayscale may be the average grayscale value of all pixels in a certain area, or the median value, total value, etc. of all pixels in a certain area. The irradiation data indicates electromagnetic radiation related information of the projected image, and may be, for example, parameters such as irradiation intensity, light intensity, illuminance, or optical power.

[0038] In one example, the maximum projection area of ​​the reference light source is equal to or larger than the projection area of ​​the optical system to ensure that each divided region can find the position of the corresponding mapping relationship. In the following, taking the example of current as the irradiation control parameter and gradation as the image information, in order to obtain the irradiation control parameter of the optical system and the corresponding image information, it is possible to use a method in which each preset current value is input to the optical system, the gradation value of the projected image emitted by the optical system based on each preset current value is obtained, and the gradation value corresponding to each preset current value is obtained.

[0039] The step of acquiring a first relationship between the image information of the optical system and the illumination data may include a step of acquiring a third relationship between the image information of the reference light source and the image information of the optical system, and a fourth relationship between the image information of the reference light source and the illumination data of the reference light source, and a step of obtaining the first relationship based on at least the third relationship and the fourth relationship, wherein the third relationship satisfies that the image information of the reference light source and the image information of the optical system match or there is a variation between them.

[0040] Specifically, the third relationship can be obtained by obtaining a fifth relationship between the gradation of the optical system and the irradiation data, and a sixth relationship between the gradation of the reference light source and the irradiation data, and obtaining the third relationship between the gradation of the reference light source and the gradation of the optical system based on the fifth relationship and the sixth relationship. The fourth relationship may be in the form of a mapping table or a fitting curve, and is not particularly limited here. Taking the gradation value as an example of image information, the irradiation data of the exposure surface of the reference light source is adjusted, and under each irradiation data, the imaging module obtains the corresponding gradation value, that is, the imaging module obtains any irradiation data and the gradation value corresponding to the irradiation data, thereby generating the relationship between the gradation value of the reference light source and the irradiation data. It should be noted that the first relationship can be obtained based on the relationship between the initial irradiation control parameters of the optical system and the irradiation data as well as the third relationship and the fourth relationship. Furthermore, the first relationship can also be obtained based on the relationship between other parameters of the optical system.

[0041] In one embodiment, the image information of the reference light source and the image information of the optical system are found to be consistent, so that the image information and illumination data of the optical system can be obtained based on the third relationship between the image information of the reference light source and the image information of the optical system and the fourth relationship between the image information of the reference light source and the illumination data of the reference light source. In another embodiment, there is a variation between the image information of the reference light source and the image information of the optical system. The variation can be obtained by obtaining a relationship between the grayscale of the optical system and the illumination data and a relationship between the grayscale of the reference light source and the illumination data, and then obtaining a seventh relationship between the grayscale of the reference light source and the grayscale of the optical system based on the above two relationships. The first relationship can be obtained based on the seventh relationship, the third relationship, and the fourth relationship. In order to further explain the above exposure surface calibration method, the following takes as an example that the image information is grayscale and the exposure control parameter is current.

[0042] 1) The image information of the reference light source and the image information of the optical system can be recognized as being identical. Adjust the irradiance value of the exposure surface of the reference light source, and obtain the corresponding grayscale value by the imaging module; Generate an eighth relationship between the tone values ​​and the irradiance values ​​of the reference light source based on the irradiance values ​​and the corresponding tone values; Each preset current value is input to the optical system, and the gradation value of the projected image generated by the optical system based on each preset current value is obtained, thereby obtaining the gradation value corresponding to each preset current value. The illumination data of the exposure surface of the reference light source is adjusted, and the corresponding gradation value is obtained by the imaging module. Using the eighth relation, process the corresponding gray scale values ​​to obtain irradiation data corresponding to each preset current value; Each preset current value and the projection data corresponding to each preset current value are processed to obtain a ninth relationship between the current value of the optical system and the projection data, and the ninth relationship is used to adjust the projection data during 3D printing. Here, the illumination data may be one of illumination intensity, power, light intensity and other related values.

[0043] Specifically, the illumination data of the exposure surface of the reference light source is adjusted, and the imaging module obtains the corresponding grayscale value under each illumination data, that is, the imaging module obtains any illumination data and the grayscale value corresponding to the illumination data, thereby generating the eighth relationship between the grayscale value and the illumination data. Here, the eighth relationship may be in the form of a mapping table or a fitting curve, and is not particularly limited here. The illumination data and the corresponding grayscale value can be fitted by any fitting algorithm in the field, such as the least squares method, the polynomial fitting algorithm, and the cubic spline fitting algorithm. Each preset current value is input to the optical system, and the preset current value can be determined based on the optical system. In this technical solution, the current value sent to the optical system is controlled by the host computer, and the magnitude of the current affects the illumination data and grayscale of the projection image. Since the optical system projects the projection images with different grayscale values ​​under each preset current value, the imaging module can read the grayscale to obtain the grayscale value of the projection image projected by the optical system under each preset current value. Based on the eighth relationship between the grayscale value and the irradiation data, the irradiation data corresponding to each preset current value can be obtained. The ninth relationship may be in the form of a mapping table or in the form of a fitting curve, and is not particularly limited here. The manner of processing each preset current value and the irradiation data corresponding to each preset current value can be determined based on the form of the ninth relationship. In one embodiment, the fitting algorithm fits the preset current value and the corresponding irradiation data, and a fitting curve relationship between the preset current value and the irradiation data can be obtained. After obtaining the ninth relationship, 3D printing can be performed according to the ninth relationship, in which case the calibration of the irradiation data of the optical system is completed. In one embodiment, the method further includes a step of limiting the exposure amount of the imaging module before adjusting the irradiation data of the exposure surface of the reference light source.

[0044] In addition, in 3D printing, the illumination data required for the image of each layer may be different. Therefore, during printing, the illumination data needs to be changed as necessary. As the years of use of the optical system increase, the illumination data of its projected image changes with the same current, so it is necessary to calibrate the illumination data for the optical system. In the prior art, illumination data is usually collected manually for each point using an optical power meter. When large-format printing is required, it is necessary to sample the illumination data for a long time, and it is necessary to use an optical power meter that is not only inefficient but also expensive. In the present application, the optical system can be calibrated automatically and quickly without the need for an optical power meter by calibrating the optical uniformity and the illumination data for the optical system, and at the same time, labor costs are saved.

[0045] 2) There may be variation between the image information of the reference light source and the image information of the optical system. Obtaining a tenth relationship between the gradation of the optical system and the illumination data, and an eleventh relationship between the gradation of the reference light source and the illumination data; Obtain a twelfth relationship between the gradation of the reference light source and the gradation of the optical system based on the tenth relationship and the eleventh relationship; inputting each preset current value into the optical system, and reading the gradation of the projected image generated by the optical system based on each preset current value, thereby obtaining a gradation value corresponding to each preset current value; 12. Processing each corresponding grayscale value using the twelfth relation to obtain the compensation grayscale value of the reference light source; 10. Processing each compensation gray level value using the tenth relation to obtain illumination data corresponding to each preset current value; Each preset current value and the corresponding projection data are processed to obtain a thirteenth relationship between the current value of the optical system and the projection data, and the thirteenth relationship is used to adjust the projection data during 3D printing.

[0046] Here, the illumination data may be one of illumination intensity, power, and other related values. Specifically, the tenth relationship and the eleventh relationship may be measured in advance and stored in a storage unit, and may be directly called up when needed, or may be obtained in a manner similar to that of obtaining the eighth relationship. Taking the tenth relationship as an example of a fitting curve relationship, the grayscale value and irradiation data of the optical system are measured before shipment of the optical system, stored in a storage unit, and the grayscale value and irradiation data are fitted by a fitting algorithm to obtain the tenth relationship. After the tenth relationship and the eleventh relationship are determined, the relationship between the grayscale value of the reference light source and the grayscale value of the optical system can be obtained. Since the optical system projects a projection image with different grayscale values ​​under each preset current value, the grayscale can be read by the imaging module, thereby obtaining the grayscale value of the projection image projected by the optical system under each preset current value. Since the optical system projects a projection image with different grayscale values ​​under each preset current value, the grayscale can be read by the imaging module, thereby obtaining the corresponding grayscale value in the optical system. According to the 12th relationship and the grayscale value corresponding to the optical system, the compensation grayscale value in the reference light source can be obtained, and further, the irradiation data corresponding to each preset current value can be determined according to the 11th relationship. Thus, the irradiation data corresponding to each preset current value can be obtained. According to the irradiation data corresponding to each preset current value, the 13th relationship can be obtained. Note that the 10th relationship, the 11th relationship, the 12th relationship, and the 13th relationship can all be in the form of a mapping table or a fitting curve relationship. After the 6th relationship is obtained, 3D printing can be performed according to the 6th relationship, and in this case, the calibration of the irradiation data of the optical system is completed. The above method can solve the grayscale difference between the reference light source and the optical system in the unified irradiation data by obtaining the grayscale relationship between the reference light source and the optical system, and further improve the accuracy of the calibration of the irradiation data.

[0047] In a preferred embodiment, steps S301 and S302 can be performed during flat-field correction. In one embodiment, step S202 includes: A step of adjusting the exposure amount of the imaging module so that the captured gradation distribution image has a maximum gradation value or less, the maximum gradation value being 2 n -1, n is the number of bits in the image, and the maximum grayscale value in an 8-bit image may include steps of 255.

[0048] In this embodiment, the imaging surface is imaged by the imaging module after flat-field correction, and the exposure of the imaging module is adjusted to make the gradation value of the entire imaged imaging surface below the maximum gradation value (when the gradation displayed in the gradation image is 0 to 255, the maximum gradation value is 255), thereby obtaining the actual uniformity distribution of the imaging surface, i.e., a gradation distribution image of the corresponding pixel level.

[0049] In another embodiment, Step S202 of acquiring a gradation distribution image generated by imaging an exposure surface of an optical system by an imaging module includes: acquiring a first gradation distribution image and a second gradation distribution image, the first gradation distribution image being obtained by capturing a first image projected by the optical system, the second gradation distribution image being obtained by capturing a second image projected by the optical system, a first gradation region in the first image corresponding to a second gradation region in the second image, and the second gradation region in the first image corresponding to the first gradation region in the second image; and processing the first greyscale distribution image and the second greyscale distribution image to obtain a greyscale distribution image.

[0050] Here, the first gradation area and the second gradation area correspond in gradation, and taking an 8-bit image as an example, the first gradation area may be a white area (i.e., 255 gradations) and the second gradation area may be a black area (i.e., 0 gradations). Specifically, a white area in the first image corresponds to a black area in the second image, i.e., if an arbitrary position in the first image is a white area, the corresponding position in the second image is a black area. A black area in the first image corresponds to a white area in the second image, i.e., if an arbitrary position in the first image is a black area, the corresponding position in the second image is a white area. The first image is captured by the imaging module to obtain a first gradation distribution image, and the second image is captured by the imaging module to obtain a second gradation distribution image. By superimposing the first gradation distribution image and the second gradation distribution image, a gradation distribution image generated by capturing an exposure surface of the optical system is obtained.

[0051] The above method obtains a first gradation distribution image and a second gradation distribution image by two image projections, thereby making it possible to reduce the gradation difference between the center and edges and improve the accuracy of the gradation values ​​in the gradation distribution image. The first gradation region in the first image and the second gradation region in the first image are spaced apart, and the first gradation region in the second image and the third gradation region in the second image are spaced apart. 2 The second gradation area in the image is provided at an interval, the first gradation area in the first image is circular or square, and the first gradation area in the second image is circular or square, i.e., the first image and the second image may be checkerboard-shaped or may be a uniformly distributed dot pattern. For example, the first image and the second image are dot patterns, the first image may include a plurality of light-projection areas, and the light-projection areas may be lattices of the same size. Each dot may be provided within the light-projection area, and the diameter of the dot may be preset. If there is a white dot in any of the light-projection areas in the first image, the white dot will not be present in the area adjacent to that light-projection area. On the other hand, if there is no white dot in any of the light-projection areas in the second image, the white dot will be present in the area adjacent to that light-projection area. The image obtained by superimposing the first image and the second image is an image in which each light-projection area has a white dot.

[0052] In one embodiment, the lens of the imaging module is further provided with an optical filter for filtering the influence of ambient light on the imaging module. In one embodiment, the fitting gray scale value of each divided region is calculated by a fitting algorithm, which is a least squares method, a polynomial fitting algorithm, or a cubic spline fitting algorithm.

[0053] In this embodiment, when calculating the fitting tone value of each divided region by a fitting algorithm, the least squares method, a polynomial fitting algorithm, or a cubic spline fitting algorithm may be used, or other fitting algorithms may be used. When dividing a gradation distribution image into a mesh image including a plurality of divided regions, specifically, it is possible to divide it into m rows and n columns to form an m*n mesh distribution.

[0054] In one embodiment, as shown in FIG. 4, step S204 may include steps S401 to S403. In S401, all fitting gradation values ​​are sorted according to the order of the corresponding divided regions. 11 , P 12 , ……, P mn Then, the number of items is m*n.

[0055]

number

[0056] The gradation array is obtained. In the S402, gradation array to the minimum value P min Select as the minimum fitting grayscale value, and perform normalized ratio calculations between the minimum fitting grayscale value and other data in the grayscale array to obtain a ratio matrix. In S403, the ratios included in the ratio matrix are taken as corresponding tone compensation coefficients, and then the required image tone value is multiplied by each ratio in the ratio matrix to obtain the corresponding digital mask.

[0057] In this embodiment, the minimum fitting tone value in the mesh image is selected as the reference, and the tone compensation coefficient can be obtained by comparing with other fitting tone values. The tone compensation coefficient in the mesh image can be configured as a digital mask, and then, after performing mask compensation of the digital mask for each projected image, a printed image with a uniform irradiance value on the exposure surface can be obtained. Specifically, the fitting grayscale value of the first mesh in the mesh image is P 11 Similarly, the fitting tone value of the last mesh is P mn Let the number of items be m*n.

[0058]

number

[0059] The minimum value P min Select the minimum value P min Calculate the normalized ratio for other fitting tone values ​​in the tone array

[0060]

number

[0061] to generate a corresponding ratio matrix, and the ratio in the ratio matrix is ​​the compensation coefficient. The required image gray scale value is the gray scale value of the image that the user wants to project, and if the required predetermined image gray scale value is a, a can be multiplied by the ratio matrix to obtain the digital mask.

[0062] In another embodiment of the present application, a calibration measurement method for 3D printing is further provided. In addition to calibrating the exposure surface of the optical system through the exposure surface calibration method of the optical system according to some embodiments of the present application, the calibration measurement method further includes multiple measurement steps, and measures multiple parameters of the optical system, so that each parameter of the optical system can be determined to meet the requirements during 3D printing, so that a clear image that is completely similar to the object can be generated, and more accurate and efficient 3D printing can be realized.

[0063] Hereinafter, detailed description will be given with reference to FIG. 7, which is a schematic flowchart of a calibration measurement method for 3D printing according to an embodiment of the present application. The calibration measurement method for 3D printing may include a step of calibrating the exposure surface of an optical system by an exposure surface calibration method 100 of an optical system according to some embodiments of the present invention, and steps S701 to S705 of the calibration measurement method as follows. Since the exposure surface calibration method 100 of an optical system according to some embodiments of the present invention has been described in detail with reference to FIGS. 1 to 6, the description will be omitted here for brevity. Hereinafter, steps S701 to S705 of the calibration measurement method will be described in detail.

[0064] In S701, the static contrast and dynamic contrast of the optical system are measured, that is, the irradiance value of each sampling point in the contrast image is extracted by the above-mentioned irradiance value measurement method, and the calculated values ​​are output based on the static contrast and dynamic contrast calculation method. In S702, the clarity of the optical system is measured, that is, the camera module captures the resolution test image displayed by the exposure system, and calculates the required spatial resolution value by CTF and MTF image algorithm to judge the clarity of the exposure system. Focus feedback can also be provided for the exposure lens with a motorized focusing system.

[0065] In S703, it is detected whether there is dirt on the optical equipment. That is, the camera module extracts the gradation distribution of the exposed surface in the above steps, and based on the gradation continuity distribution, if the gradation of a certain area suddenly changes and is lower than a preset threshold, it is determined that the area is dirty. In S704, the size of the exposure surface image is measured. The camera module is calibrated with different heights, and based on the principle that the magnification ratio of different object distances is constant, the size and relative distribution of various images of the exposure surface can be tested. It should be noted that the order of steps S701 to S705 is merely exemplary, and these steps may be performed in different orders to achieve measurement of various parameters, and the present application is not limited thereto.

[0066] Specifically, in step S701, the step of measuring the static contrast and the dynamic contrast of the optical system includes the steps of obtaining a first irradiance value corresponding to a white image and a second irradiance value corresponding to a black image, where both the white image and the black image are projected and obtained by the calibrated optical system; obtaining a static contrast of the optical system based on the first irradiance value and the second irradiance value; obtaining irradiance values ​​for each region of a checkerboard map, the checkerboard map being obtained by projecting the checkerboard map using a calibrated optical system; and processing the irradiance values ​​of each region with the ANSI contrast calculation method to obtain the dynamic contrast of the optical system.

[0067] In some embodiments, the static contrast can be measured based on the exposure surface calibration technique of the present application, which specifically includes the following steps: First, receive a projected image, which is a white image in the entire format, projected or displayed by an optical system using a light guide film on the exposure surface; nA white image of -1 gradation can be set to be used, and a pure white image of 255 gradations from 0 to 255 gradations can be set to be used, taking an 8-bit image as an example. The irradiance value measuring device of the optical system is used to measure the irradiance value of the pure white image to obtain a first irradiance value. Then, a projected image, the entire format of which is a pure black image, which is projected or displayed by the optical system using a light guiding film on the exposure surface, is received, and a pure black image of 0 gradation is set to be used. The irradiance value measuring device of the optical system is used to measure the irradiance value of the pure black image to obtain a second irradiance value. Then, a static contrast of the optical system is calculated based on the ratio between the first irradiance value and the second irradiance value by a contrast measuring device.

[0068] In some embodiments, the dynamic contrast can be measured based on the exposure surface calibration technique of the present application, specifically including the following steps: First, receive a checkerboard map projected or displayed by an optical system using a light guiding film on the exposure surface, and use an irradiance value measuring device of the optical system to sequentially measure the irradiance value at each point of the checkerboard map to obtain the irradiance value at each point of the checkerboard map. Then, calculate the dynamic contrast value of the optical system according to the ANSI contrast calculation method by the contrast measuring device. In this embodiment, the irradiance value is measured by a machine vision method.

[0069] In some embodiments, the irradiance value is obtained based on the exposure surface calibration technique of the present application, specifically including the following steps: First, perform grayscale calibration on the projected image with a certain exposure amount to obtain the coordinate points of the image grayscale corresponding to the irradiance value, and after the output irradiance value of the irradiation device is changed, measure different irradiance values ​​by the irradiance value measurement device, and then obtain the grayscale value of the image by the imaging module, fit the coordinate points after measuring the different irradiance values ​​multiple times, and generate a grayscale / irradiance value curve based on the fitted coordinate points. Therefore, when the imaging module reads the grayscale of the projected image with the same exposure amount, the grayscale value can be converted into the corresponding irradiance value.

[0070] In step S702, the step of measuring the clarity of the projected image specifically includes the steps of controlling the calibrated optical system to project an image at a preset position on the projection format, the image including at least one sagittal line and at least one meridian line; obtaining an actual tone distribution curve of the projected image, and confirming a CTF value or an MTF value corresponding to each preset position based on the actual tone distribution curve and the preset tone distribution curve; and determining the clarity of the optical system based on the CTF value or the MTF value corresponding to each preset position.

[0071] Here, the preset positions may include one center position and four corner positions of the projection format. The CTF (Contrast Transfer Function) value can be calculated by a means commonly used in the art. The MTF (Modulation Transfer Function) value can also be calculated by a means commonly used in the art.

[0072] Specifically, the step of determining the clarity of the optical system based on the CTF value or MTF value corresponding to each preset position includes a step of determining that the clarity of the optical system is unacceptable if any of the CTF values ​​is less than a first set value or any of the MTF values ​​is less than a second set value. The clarity is determined based on the CTF value, and if the calculated CTF value is less than a set value, the point is determined to be unclear. The clarity can also be determined based on the MTF value, and if the calculated MTF value is less than a set value, the point is determined to be unclear. If there is an unclear point, the clarity of the lens of the optical instrument is considered to be low. Furthermore, when there are multiple sagittal lines and multiple meridian lines, the pitch between the sagittal lines may be N pixels and is used to determine whether the meridian direction is blurred. The pitch between the meridian lines may be N pixels, etc. and is used to determine whether the sagittal direction is blurred. The width of the line may be N pixels, where N is a positive integer.

[0073] In step S703, the step of detecting whether the optical equipment is dirty specifically includes a step of determining that the optical equipment is dirty if the value of any point on the actual tone distribution curve is lower than a lower limit value and / or if the actual tone distribution curve has a steep curve. In some embodiments, the optical system according to the present application detects contamination by the following steps: By setting a lower limit of the tone distribution, the tone distribution of the optical device generally changes continuously in one format. If the actual tone is lower than the lower limit and / or there is an abrupt change in the actual tone distribution curve of the optical device, contamination is considered to be present.

[0074] In step S704, the step of measuring the size of the object includes, specifically, a step of calibrating the size corresponding to each pixel on the imaging surface of the camera module and determining the size of the object based on the number of pixels occupied by the side length of the object; and / or The method includes a step of acquiring the size of the imaging surface of the camera module, and determining the size of the subject based on the ratio of the side length of the subject to the imaging surface.

[0075] Specifically, the size measuring device of the optical system according to the present application measures the size in the following manner. In some embodiments, the size corresponding to each pixel on the imaging surface of the camera is calibrated in advance, and then the size of the object is determined by the size measuring device of the optical system based on the number of pixels occupied by the side length of the subject on the camera. In some other embodiments, the size of the imaging surface of the camera is acquired, and the size of the object is determined by the size measuring device of the optical system based on the ratio of the side length of the subject to the imaging surface.

[0076] In some embodiments, the optical system according to the present application needs to use different camera modules for different detection items. The optical system according to the present application can realize automatic detection by selecting a corresponding camera module for different detection items and executing a corresponding detection process. That is, the optical system determines a current detection item, selects a corresponding camera module based on the current detection item, and then executes the above steps S701 to S704.

[0077] FIG. 8 is a schematic block diagram of an exposure surface calibration device 800 for an optical system according to the present embodiment. The device 800 includes: an image acquisition unit 802 configured to acquire a tone distribution image generated by imaging an exposure surface of the optical system by the imaging module; a fitting unit 803 configured to divide the gray scale distribution image into a mesh image including a plurality of divided regions and calculate a fitting gray scale value of each divided region; A selection unit 804 configured to select a minimum fitting gray scale value from all the calculated fitting gray scale values ​​as a reference gray scale value, and calculate gray scale compensation coefficients corresponding to other divided regions according to the reference gray scale value to generate a digital mask; and a mask compensation unit 805 configured to perform mask compensation on the projected image from the optical system using a digital mask to obtain a printed image with a uniform irradiance value on the exposed surface.

[0078] In one embodiment, the apparatus 800 further comprises a flat-field correction unit 801 configured to perform a flat-field correction on the imaging module with a reference light source. In one embodiment, the flat-field correction unit 801 comprises: a projection unit configured to project an exposure surface having a uniform irradiance value based on a preset grayscale value by a reference light source; an exposure surface imaging unit configured such that an imaging module images an exposure surface of the reference light source to obtain a reference light source image; A data acquisition unit configured to acquire a grayscale output value of each pixel unit in the photosensitive chip according to a reference light source image, and compare the grayscale output value of each pixel unit with a preset grayscale value of the reference light source to obtain a grayscale correction coefficient of each pixel unit; and a coefficient correction unit configured to perform flat-field correction on the imaging module based on the tone correction coefficient of each pixel unit.

[0079] In one embodiment, the exposure surface imaging unit comprises: an imaging surface division unit configured to divide an imaging surface of the imaging module into several imaging sub-areas according to a size of an exposure surface of a reference light source; a moving projection unit configured to project a reference light source onto each imaging sub-area by the reference light source to obtain several reference light source sub-images corresponding to each imaging sub-area; and an image stitching unit configured to stitch several reference light source sub-images to obtain a reference light source image.

[0080] In one embodiment, as shown in FIG. 9, the exposure surface calibration device 800 of the optical system further includes: A limiting unit 901 configured to limit the exposure amount of the imaging module; A curve generating unit 902 configured to adjust the irradiance value of the exposure surface of the reference light source, obtain the corresponding grayscale value by the imaging module, and fit and generate a relationship curve between the grayscale and the irradiance value; The imaging module further includes a gradation reading unit 903 configured to read the gradation of the projected image from the optical system based on the relationship curve, and obtain a corresponding irradiance value.

[0081] In one embodiment, the image acquisition unit 802 includes: The imaging device may further include an adjustment unit configured to adjust the exposure of the imaging module so that the captured tone distribution image has a maximum tone value or less. In one embodiment, the fitting gray scale value of each divided region is calculated by a fitting algorithm, which is a least squares method, a polynomial fitting algorithm, or a cubic spline fitting algorithm.

[0082] In one embodiment, as shown in FIG. 10, the selection unit 804 includes: All fitting tone values ​​are sorted according to the order of the corresponding division regions. 11 , P 12 , ……, P mn Then, the number of items is m*n.

[0083]

number

[0084] A region labeling unit 1001 configured to obtain a gray scale arrangement of Minimum value P from the gradation array min a calculation unit 1002 configured to select as the minimum fitting grayscale value, and perform a normalization ratio calculation on the minimum fitting grayscale value and other data in the grayscale array to obtain a ratio matrix; and a multiplication unit 1003 configured to take the ratios included in the ratio matrix as corresponding tone compensation coefficients, and then multiply a preset image tone value by each ratio in the ratio matrix to obtain a corresponding digital mask.

[0085] As described above, the optical system according to the present application is an imaging system that can generate a clear and perfectly similar image of an object. In some embodiments, the optical system according to the present application may further include one or more additional devices that perform multiple measurement steps, and by measuring multiple parameters of the optical system, it can be determined that each parameter of the optical system meets the requirements during 3D printing, so that a clear and perfectly similar image of an object can be generated, and more accurate and efficient 3D printing can be achieved.

[0086] Hereinafter, a detailed description will be given with reference to FIG. 11. FIG. 11 is a schematic block diagram of an optical system according to an embodiment of the present application. The optical system 1100 includes, in addition to the exposure surface calibration device 800 shown in FIG. 8, A contrast measurement device 1101 configured to measure the static and dynamic contrast of an optical system; a clarity measuring device 1102 configured to measure the clarity of the projected image; A dirt measuring device 1103 configured to detect whether the optical instrument is dirty or not; and a size measuring device 1104 configured to measure the size of the object.

[0087] The optical system according to the present application can perform static contrast and dynamic contrast measurements on the optical system by using the contrast measurement device 1101 . The contrast measurement device 1101 may be configured to obtain a first irradiance value corresponding to a white image and a second irradiance value corresponding to a black image, where both the white image and the black image are projected by a calibrated optical system, and obtain a static contrast of the optical system based on the first irradiance value and the second irradiance value, and obtain an irradiance value of each region in a checkerboard map, where the checkerboard map is projected by the calibrated optical system, and process the irradiance value of each region using an ANSI contrast calculation method to obtain a dynamic contrast of the optical system.

[0088] In some embodiments, the optical system of the present application further comprises a clarity measuring device 1102 for measuring the clarity of the optical system. The clarity measurement device 1102 may be configured to control the calibrated optical system to project an image at a preset position on a projection format, the image including at least one sagittal line and at least one meridian line, obtain an actual tone distribution curve of the projected image, check a CTF value corresponding to each preset position based on the actual tone distribution curve and the preset tone distribution curve, and determine the clarity of the optical system based on the CTF value corresponding to each preset position. If any CTF value is less than a preset value, determine that the clarity of the optical system is unacceptable.

[0089] In some embodiments, the optical system according to the present application further comprises a dirt measuring device 1103, which can detect whether the optical instrument is dirty or not. The contamination measurement device 1103 is configured to determine that the optical system is contaminated if the value of any point on the actual tone distribution curve is below a lower limit and / or if the actual tone distribution curve has a steep curve.

[0090] In some embodiments, the optical system of the present application further comprises a size measuring device 1104, which can measure the size of an object to achieve more accurate 3D printing. The size measurement device 1104 is configured to calibrate the size corresponding to each pixel on the imaging surface of the camera module and determine the size of the subject based on the number of pixels occupied by the side length of the subject, and / or to obtain the size of the imaging surface of the camera module and determine the size of the subject based on the proportion of the side length of the subject that occupies the imaging surface.

[0091] In some embodiments, the optical system according to the present application performs different detection items by contrast measuring device 1101, clarity measuring device 1102, dirt measuring device 1103, and / or size measuring device 1104. Different detection items require different camera modules to be used. The optical system according to the present application can realize automatic detection by selecting corresponding camera modules for different detection items and performing corresponding detection processes.

[0092] Since the device part embodiment and the method part embodiment correspond to each other, the device part embodiment can refer to the description of the method part embodiment and the description thereof will be omitted here. The embodiments of the present application further provide a computer-readable storage medium having a computer program stored thereon, which can realize the steps according to the above embodiments when the computer program is executed. The storage medium may include various media capable of storing program code, such as a USB flash drive, a portable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk, or an optical disk.

[0093] The embodiments of the present application further provide a computer device including a memory and a processor, the memory storing a computer program, and the processor calling the computer program in the memory can realize the steps of the above embodiments. Of course, the computer device may further include various network interfaces, power supplies, and other components.

[0094] The optical system according to the present application is preferably an optical system of a 3D printer, an optical device including DLP (Digital Light Processing), or an optical device including LCD (Liquid Crystal Display), or an optical device including LCOS (Liquid Crystal on Silicon), or an optical device including OLED (Organic Light-Emitting Diode), Micro-LED, Mini-LED, liquid crystal projection, or the like.

[0095] In this specification, each embodiment is described using a progressive method, and the differences between each embodiment are described with emphasis on the differences from other embodiments, and the same or similar parts between each embodiment may be referred to each other. The systems disclosed in the embodiments are briefly described because they correspond to the method parts disclosed in the embodiments, and the relevant parts may be referred to the description of the method parts. It should be noted that those skilled in the art may make some improvements and modifications to this application without departing from the principles of this application, and these improvements and modifications are also included in the scope of the claims of this application.

[0096] It should be noted that, in this specification, relational terms such as first and second, etc., distinguish one entity or operation from another without requiring or implying that any such actual relationship or order exists between those entities or operations. And, the terms "comprise", "comprises", or any other variation thereof, cover a non-exclusive inclusion such that a process, method, article, or device that includes a set of elements includes not only those elements, but also other elements not expressly listed, or includes the inherent elements of such process, method, article, or device. Absent more limitations, an element qualified by the phrase "comprises a" does not exclude the presence of other identical elements in the process, method, article, or device that includes the element. [Industrial Applicability]

[0097] The present application provides an exposure surface calibration method and device for an optical system, a computer device, and a storage medium, the method including the steps of performing flat-field correction on an imaging module using a reference light source, acquiring a gradation distribution image generated by imaging the exposure surface of the optical system using the imaging module, dividing the gradation distribution image into a mesh image including a plurality of divided regions and calculating fitting gradation values ​​for each divided region, selecting the smallest fitting gradation value from all the calculated fitting gradation values ​​as a reference gradation value, and calculating gradation compensation coefficients corresponding to the other divided regions based on the reference gradation value to generate a digital mask, and performing mask compensation on the projection image from the optical system using the digital mask to obtain a printing image with a uniform irradiance value on the exposure surface. The present application can improve the calibration accuracy and calibration efficiency of the exposure surface of the optical system by acquiring the pixel level distribution of the exposure surface and performing corresponding compensation on the gradation value. The present application further discloses a calibration measurement method for 3D printing. The calibration measurement method for 3D printing measures multiple parameters of the optical system, so that each parameter of the optical system can be determined to meet the requirements during 3D printing, thereby generating a clear and completely similar image of the object, thereby realizing more accurate and efficient 3D printing.

[0098] It is also understood that the method and apparatus for calibrating the exposure surface of an optical system, the calibration measurement method, the computer equipment, and the storage medium according to the present application are reproducible and can be used for various industrial applications. For example, the method and apparatus for calibrating the exposure surface of an optical system, the calibration measurement method, the computer equipment, and the storage medium according to the present application can be applied to the technical field of optical systems.

Claims

1. performing flat-field correction on the imaging module using a reference light source; acquiring a gradation distribution image generated by imaging an exposure surface of an optical system by an imaging module; Dividing the gradation distribution image into a mesh image including a plurality of divided regions, and calculating a fitting gradation value for each divided region; selecting a predetermined fitting gradation value as a reference gradation value from all the calculated fitting gradation values, and calculating gradation compensation coefficients corresponding to the other divided regions based on the reference gradation value to generate a digital mask; and performing mask compensation on the projected image from the optical system using the digital mask to obtain a printed image having a uniform irradiance value on the exposed surface. the step of selecting a predetermined fitting gradation value as a reference gradation value from all the fitting gradation values ​​obtained by calculation includes a step of selecting a minimum fitting gradation value as a reference gradation value from all the fitting gradation values ​​obtained by calculation; the step of selecting the smallest fitting gradation value from all the calculated fitting gradation values ​​as a reference gradation value, and calculating gradation compensation coefficients corresponding to the other divided regions based on the reference gradation value to generate a digital mask; All fitting gradation values ​​are sequentially labeled as P 11 , P 12 , . . . , P mn according to the order of the corresponding divided regions, and a set of fitting gradation values ​​is obtained in which the number of items is m*n. [0010] obtaining a gray scale array of selecting a minimum value P min from the grayscale array as a minimum fitting grayscale value, and performing a normalized ratio calculation on the minimum fitting grayscale value and other data in the grayscale array to obtain a ratio matrix; a step of determining the ratios contained in the ratio matrix as corresponding tone compensation coefficients, and then multiplying a required image tone value by each ratio in the ratio matrix to obtain a corresponding digital mask.

2. The step of acquiring a gradation distribution image generated by imaging an exposure surface of an optical system by an imaging module includes: acquiring a first gradation distribution image and a second gradation distribution image, the first gradation distribution image being obtained by capturing a first image projected by the optical system, the second gradation distribution image being obtained by capturing a second image projected by the optical system, a first gradation region in the first image corresponding to a second gradation region in the second image, and the second gradation region in the first image corresponding to the first gradation region in the second image; 2. The method of claim 1, further comprising the step of: processing the first tone distribution image and the second tone distribution image to obtain the tone distribution image.

3. 3. The method of calibrating an exposure surface of an optical system as described in claim 2, characterized in that a first gradation area in the first image and a second gradation area in the first image are spaced apart, a first gradation area in the second image and a second gradation area in the second image are spaced apart, the first gradation area in the first image is circular or rectangular, and the first gradation area in the second image is circular or rectangular.

4. 4. The method of calibrating an exposure surface of an optical system according to claim 3, wherein the first gradation region is a white region, and the second gradation region is a black region.

5. 2. The method for calibrating an exposure surface of an optical system according to claim 1, further comprising providing an optical filter to a lens of the imaging module.

6. The step of performing flat-field correction on the imaging module using a reference light source includes: a reference light source projecting an exposure surface having a uniform irradiance value; An imaging module captures an image of an exposure surface of a reference light source to obtain a reference light source image; obtaining a grayscale output value of each pixel unit on the photosensitive chip according to the reference light source image, and comparing the grayscale output value of each pixel unit with a preset grayscale value of the reference light source to obtain a grayscale correction coefficient of each pixel unit; 6. The method for calibrating an exposure plane of an optical system according to claim 1, further comprising the step of: performing flat-field correction on the imaging module based on the gradation correction coefficient of each pixel unit.

7. The step of obtaining a reference light source image by the imaging module capturing an image of an exposure surface of the reference light source includes: Dividing an imaging surface of the imaging module into several imaging sub-areas based on the size of an exposure surface of a reference light source; A step of projecting a reference light source onto each imaging sub-area by moving the reference light source to obtain several reference light source sub-images corresponding to each imaging sub-area; and stitching the several reference light source sub-images to obtain the reference light source image.

8. limiting the exposure of the imaging module; adjusting the irradiance value of the exposure surface of the reference light source, and acquiring the corresponding grayscale value by the imaging module, thereby fitting and generating a relationship curve between the grayscale and the irradiance value; The exposure surface calibration method for an optical system according to any one of claims 1 to 5, further comprising a step of reading the gradation of a projected image from the optical system by an imaging module based on the relationship curve, and obtaining a corresponding irradiance value.

9. acquiring illumination control parameters of an optical system and corresponding image information; obtaining a first relationship between image information of the optical system and illumination data; 6. The method for calibrating an exposure plane of an optical system according to claim 1, further comprising: obtaining a second relationship between an irradiation control parameter of the optical system and irradiation data based on the first relationship, the irradiation control parameter and the corresponding image information, the second relationship being used to adjust irradiation data in a 3D printing process.

10. The step of obtaining a first relationship between image information of the optical system and illumination data includes: obtaining a third relationship between image information of the reference light source and image information of the optical system, and a fourth relationship between the image information of the reference light source and illumination data of the reference light source; obtaining the first relationship based on at least the third relationship and the fourth relationship; 10. The method of calibrating an exposure surface of an optical system according to claim 9, wherein the third relationship satisfies that the image information of the reference light source and the image information of the optical system match or there is a variation between them.

11. The step of acquiring a gradation distribution image generated by imaging an exposure surface of an optical system by an imaging module includes: The method for calibrating an exposure plane of an optical system according to any one of claims 1 to 5, further comprising a step of adjusting the exposure amount of the imaging module so that the captured gradation distribution image is equal to or less than the maximum gradation value.

12. 6. A method for calibrating an exposure surface of an optical system according to claim 1, further comprising: calculating a fitting gradation value of each divided region using a fitting algorithm, the fitting algorithm being a least squares method, a polynomial fitting algorithm, or a cubic spline fitting algorithm.

13. calibrating an optical system by the method for calibrating an exposure surface of an optical system according to claim 1; obtaining a first irradiance value corresponding to a white image and a second irradiance value corresponding to a black image, the white image and the black image both being obtained by projecting using a calibrated optical system; obtaining a static contrast of the optical system based on the first irradiance value and the second irradiance value; obtaining irradiance values ​​for each region of a checkerboard map, the checkerboard map being obtained by projecting the checkerboard map using a calibrated optical system; and processing the irradiance values ​​of each of the regions with an ANSI contrast calculation method to obtain a dynamic contrast of the optical system.

14. The calibration measurement method includes: controlling the calibrated optical system to project an image at a predefined location on a projection format, the image including at least one sagittal line and at least one meridian line; obtaining an actual tone distribution curve of a projected image, and determining a CTF value or an MTF value corresponding to each of the preset positions based on the actual tone distribution curve and the preset tone distribution curve; The calibration measurement method for 3D printing of claim 13, further comprising a step of determining clarity of the optical system based on the CTF or MTF values ​​corresponding to each of the pre-defined positions.

15. determining the clarity of the optical system based on the CTF or MTF values ​​corresponding to each of the preset positions, 15. The calibration measurement method for 3D printing of claim 14, further comprising a step of determining that the clarity of the optical system fails if any of the CTF values ​​are less than a first set value or any of the MTF values ​​are less than a second set value.

16. The calibration measurement method includes:

15. The calibration measurement method for 3D printing of claim 14, further comprising the step of determining that the optical system is contaminated if the value of any point on the actual tone distribution curve is below a lower limit value and / or if the actual tone distribution curve has a steep curve.

17. The calibration measurement method includes: Calibrating the size of each pixel on the imaging surface of the camera module and determining the size of the object based on the number of pixels that the side length of the object occupies; and / or The calibration measurement method for 3D printing according to any one of claims 13 to 15, further comprising a step of acquiring the size of the imaging surface of the camera module and determining the size of the subject based on the proportion of the side length of the subject that occupies the imaging surface.

18. The calibration measurement method for 3D printing according to any one of claims 13 to 15, further comprising a step of determining a current detection item and selecting a corresponding camera module based on the current detection item.

19. an image acquisition unit configured to acquire a gradation distribution image generated by imaging an exposure surface of the optical system by the imaging module; a fitting unit configured to divide the gradation distribution image into a mesh image including a plurality of divided regions and calculate a fitting gradation value of each divided region; a selection unit configured to select a predetermined fitting gray scale value as a reference gray scale value from all the calculated fitting gray scale values, and calculate gray scale compensation coefficients corresponding to other divided regions based on the reference gray scale value to generate a digital mask; a mask compensation unit configured to perform mask compensation on a projected image from an optical system using the digital mask to obtain a printed image having a uniform irradiance value on an exposure surface; The selection unit is further configured to select a minimum fitting gray scale value as a reference gray scale value from all the calculated fitting gray scale values; The selection unit further comprises: All fitting gradation values ​​are sequentially labeled as P 11 , P 12 , . . . , P mn according to the order of the corresponding divided regions, and a set of fitting gradation values ​​is obtained in which the number of items is m*n. [0025] A region labeling unit configured to obtain a gray scale arrangement of a calculation unit configured to select a minimum value P min from the grayscale array as a minimum fitting grayscale value, and perform a normalized ratio calculation on the minimum fitting grayscale value and other data in the grayscale array to obtain a ratio matrix; and a multiplication unit configured to set the ratios included in the ratio matrix as corresponding tone compensation coefficients, and then multiply a required image tone value by each ratio in the ratio matrix to obtain a corresponding digital mask.

20. The exposure plane calibration apparatus for an optical system according to claim 19 , further comprising a flat-field correction unit configured to perform flat-field correction on the imaging module using a reference light source.

21. A computer device including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the computer program, realizes the exposure surface calibration method for an optical system described in any one of claims 1 to 5 and the calibration measurement method for 3D printing described in claim 13. The computer device.

22. A computer program comprising: A computer program causing a processor to execute the exposure surface calibration method for an optical system according to any one of claims 1 to 5 and the calibration measurement method for 3D printing according to claim 13.

Images