阅读说明：本技术 变光阑数据处理方法 (Variable aperture data processing method ) 是由 朱鸣 吕帅 邵仁锦 朱鹏飞 浦东林 于 2020-04-23 设计创作，主要内容包括：本申请涉及一种变光阑数据处理方法,如下步骤：获取三维模型；沿三维模型的竖直方向将三维模型分切成M层；将分切后的每一层再沿竖直方向分切成N层,以获取若干层二维图像数据；将N层中的每层二维图像数据转换为单色位图并将其分割成若干等份单元格图像；每个单元格图像的宽度为UnitX,高度为UnitY；对N层中的若干等份单元格图像进行错位重组以形成若干个基础长条带图像数据；将M层中的若干个基础长条带图像数据拼接后形成新的长条带图像数据,并将新的长条带图像数据上载至成像设备进行逐条带扫描光刻；其中,M及N为正整数。本申请的方法在光刻胶曝光成三维模型的过程中,图形不受限,方向不受限,被打印的三维模型的形状也不受限,方便快捷。(The application relates to a variable aperture data processing method, which comprises the following steps: acquiring a three-dimensional model; cutting the three-dimensional model into M layers along the vertical direction of the three-dimensional model; cutting each layer into N layers along the vertical direction to obtain a plurality of layers of two-dimensional image data; converting two-dimensional image data of each layer in the N layers into a monochromatic bitmap and dividing the monochromatic bitmap into a plurality of unit cell images in equal parts; the width of each cell image is UnitX, and the height of each cell image is UnitY; carrying out dislocation recombination on a plurality of equal parts of cell images in the N layers to form a plurality of basic long strip image data; splicing a plurality of basic long strip image data in the M layer to form new long strip image data, and uploading the new long strip image data to imaging equipment to carry out scanning photoetching one by one; wherein M and N are positive integers. In the method, in the process of exposing the photoresist into the three-dimensional model, the graph is not limited, the direction is not limited, the shape of the printed three-dimensional model is not limited, and the method is convenient and quick.)

1. A method of telecentricity data processing, comprising the steps of:

acquiring a three-dimensional model, and determining the pixel resolution of a digital micromirror required by exposure;

cutting the three-dimensional model into M layers along the vertical direction of the three-dimensional model according to the height of the three-dimensional model;

cutting each of the M layers into N layers along the vertical direction of the three-dimensional model to obtain a plurality of layers of two-dimensional image data;

converting the two-dimensional image data of each layer in the N layers into monochromatic bitmaps, and dividing each monochromatic bitmap into a plurality of unit grid images in equal parts; the width of each cell image is UnitX, and the height of each cell image is UnitY;

carrying out dislocation recombination on a plurality of equal parts of the cell images in the N layers to form a plurality of basic long strip image data;

splicing a plurality of basic long strip image data in the M layers to form new long strip image data, and uploading the new long strip image data to imaging equipment to carry out scanning photoetching one by one;

wherein M and N are positive integers.

2. The method of claim 1, wherein the width UnitX of the cell image or the height UnitY of the cell image multiplied by M is not greater than the horizontal pixel resolution of the digital micromirror, and the height UnitY of the cell image or the width UnitX of the cell image multiplied by N is not greater than the vertical pixel resolution of the digital micromirror.

3. The method for telecentric data processing according to claim 1, wherein the step of converting the two-dimensional image data of each of the N layers into a monochrome bitmap is specifically:

performing pixelization filling on the two-dimensional image data by using a filling factor to form a monochrome bitmap; wherein, the filling factor is the number of pixels to be filled in unit millimeter distance.

4. The method for processing stop-variable data according to claim 1, wherein said "dividing each said monochrome bitmap into a plurality of equal parts of cell images" is specifically:

and based on the maximum width and the maximum length of the three-dimensional model, filling white into the monochrome bitmap of each layer by taking the monochrome bitmap of each layer as a center, and dividing the monochrome bitmap of each layer after white filling into a plurality of unit cell images in equal parts.

5. The method as claimed in claim 4, wherein if the maximum width value of the three-dimensional model cannot divide the width UnitX of the cell image and/or the maximum length value of the three-dimensional model cannot divide the height UnitY of the cell image, the monochrome bitmap is continuously filled with white until the maximum width value of the three-dimensional model can divide the width UnitX of the cell image and/or the maximum length value of the three-dimensional model can divide the height UnitY of the cell image.

6. The method of claim 1, wherein the de-interlacing rebinning is performed by:

each layer of the N layers of the monochrome bitmap includes XMax × YMax cells, where XMax is the maximum length of the monochrome bitmap or the filled maximum length/UnitX, and YMax is the maximum width of the monochrome bitmap or the filled maximum width/UnitY;

sequentially extracting the cells of the monochromatic bitmaps in the N layers to form a first long strip to an XMax long strip;

the M first long strips are transversely stitched to obtain first base long strip image data until the M XMax long strips are transversely stitched to obtain XMax base long strip image data.

7. The method as claimed in claim 6, wherein the steps of sequentially extracting the cells of the monochromatic bitmap in the N layers to form the first long stripe to the XMax long stripe are as follows:

sequentially extracting 1 st unit cell image of the 1 st column of each layer of the monochromatic bitmap from large to small according to the size of the N layers of the monochromatic bitmaps, splicing and overlapping along the longitudinal direction of the three-dimensional model, and sequentially extracting 2 nd unit cell image of the 1 st column of each layer of the monochromatic bitmaps on the basis, continuously splicing and overlapping along the longitudinal direction of the three-dimensional model until the YMax unit cells of the 1 st column are sequentially extracted, splicing and overlapping along the longitudinal direction of the three-dimensional model to form a first long strip;

and splicing and overlapping the cells of the residual XMax-1 columns of the monochromatic bitmaps in each layer in the N layers according to the method until the XMax long strip is obtained.

8. The telecentricity data processing method as claimed in claim 1, further comprising:

before acquiring the three-dimensional model data, coating photoresist with corresponding thickness on the substrate according to the depth requirement of the film microstructure to form a photoresist plate.

9. The telecentricity data processing method as recited in claim 8, further comprising:

and before uploading the new strip image data to the imaging equipment for scanning and photoetching one by one, setting the number of rolling pixels during photoetching and the step pitch of the imaging equipment.

Technical Field

The invention relates to a diaphragm-variable data processing method, belonging to the technical field of photoetching.

Background

Currently, the main technical means of micromachining include techniques such as precision diamond turning, 3D printing, and photolithography. Diamond turning is a preferred method for making tens of micron-sized, regularly arranged 3D topographic microstructures, a typical application of which is microprism films. The 3D printing technology can manufacture a complex 3D structure, but the resolution of the traditional galvanometer scanning 3D printing technology is tens of microns; the resolution ratio of DLP projection type 3D printing is 10-20 um; the two-photon 3D printing technology has submicron resolution, but belongs to a serial processing mode, and has extremely low efficiency.

Microlithography is still the mainstream technical means of modern micromachining and is the highest precision machining means which can be achieved so far. 2D projection lithography has been widely used in the field of microelectronics, and 3D topography lithography is currently in its primary stage without a mature solution, and the current progress is as follows:

the traditional mask alignment method is used for manufacturing a multi-step structure, the depth of the structure is controlled by combining ion etching, the technological process needs to be aligned for many times, the technological requirement is high, and continuous 3D shapes are difficult to process. A gray mask exposure method adopts the technical scheme that a half-tone mask (halftone) is manufactured, a transmission light field with gray distribution is generated after irradiation of a mercury lamp light source, and photosensitive is carried out on photoresist to form a 3D surface structure. However, such reticles are difficult to fabricate and very expensive. The moving mask exposure method can produce regular microlens arrays and other structures. Acousto-optic scanning direct writing (e.g., Heidelberg instrument μ PG101) uses single beam direct writing, which is inefficient and still suffers from pattern stitching problems. The electron beam gray level direct writing (Joel JBX9300, Vistec, germany, Leica VB6, japan) still has low preparation efficiency of devices facing larger breadth, is limited by the energy of the electron beam, has insufficient 3D topography depth control capability, and is suitable for preparing small-scale 3D topography microstructures. The digital gray scale photoetching technology is a micro-nano processing technology developed by combining a gray scale mask and a digital light processing technology, a DMD spatial light modulator is used as the digital mask, a relief microstructure with a continuous three-dimensional surface shape is processed by one-time exposure, a step splicing method is adopted for a graph larger than an exposure field, but the gray scale modulation capability of the digital gray scale photoetching technology is limited by the gray scale level of the DMD, step-shaped field splicing seams exist, and the surface shape quality of a 3D shape can be influenced by the uniformity of light intensity inside a light spot.

In summary, there is a significant gap between the current research situation of 3D topography lithography and the leading edge requirements, and therefore, the research of high-quality lithography technology capable of realizing any 3D topography becomes an important and urgent requirement for microlithography in the related field.

Disclosure of Invention

The invention aims to provide a diaphragm-variable data processing method, which is convenient and quick and is not limited by a figure and a scanning direction in the process of exposing a photoresist.

In order to achieve the purpose, the invention provides the following technical scheme: a method of telecentricity data processing, the method comprising the steps of:

acquiring a three-dimensional model, and determining the pixel resolution of a digital micromirror required by exposure;

cutting the three-dimensional model into M layers along the vertical direction of the three-dimensional model according to the height of the three-dimensional model;

cutting each of the M layers into N layers along the vertical direction of the three-dimensional model to obtain a plurality of layers of two-dimensional image data;

converting the two-dimensional image data of each layer in the N layers into monochromatic bitmaps, and dividing each monochromatic bitmap into a plurality of unit grid images in equal parts; the width of each cell image is UnitX, and the height of each cell image is UnitY;

carrying out dislocation recombination on a plurality of equal parts of the cell images in the N layers to form a plurality of basic long strip image data;

splicing a plurality of basic long strip image data in the M layers to form new long strip image data, and uploading the new long strip image data to imaging equipment to carry out scanning photoetching one by one;

wherein M and N are positive integers.

Further, the width unitex of the cell image or the height unitey of the cell image multiplied by M is not greater than the horizontal pixel resolution of the digital micromirror, and the height unitey of the cell image or the width unitex of the cell image multiplied by N is not greater than the vertical pixel resolution of the digital micromirror.

Further, the "converting the two-dimensional image data of each of the N layers into a monochrome bitmap" specifically includes:

performing pixelization filling on the two-dimensional image data by using a filling factor to form a monochrome bitmap; wherein, the filling factor is the number of pixels to be filled in unit millimeter distance.

Further, the "dividing each of the monochrome bitmaps into a plurality of equal parts of cell images" specifically includes:

and based on the maximum width and the maximum length of the three-dimensional model, filling white into the monochrome bitmap of each layer by taking the monochrome bitmap of each layer as a center, and dividing the monochrome bitmap of each layer after white filling into a plurality of unit cell images in equal parts.

Further, if the maximum width value of the three-dimensional model cannot divide the width unitex of the cell image and/or the maximum length value of the three-dimensional model cannot divide the height unitey of the cell image, the monochrome bitmap is filled in white continuously until the maximum width value of the three-dimensional model can divide the width unitex of the cell image and/or the maximum length value of the three-dimensional model can divide the height unitey of the cell image.

Further, the "dislocation recombination" is specifically:

each layer of the N layers of the monochrome bitmap includes XMax × YMax cells, where XMax is the maximum length of the monochrome bitmap or the filled maximum length/UnitX, and YMax is the maximum width of the monochrome bitmap or the filled maximum width/UnitY;

sequentially extracting the cells of the monochromatic bitmaps in the N layers to form a first long strip to an XMax long strip;

the M first long strips are transversely stitched to obtain first base long strip image data until the M XMax long strips are transversely stitched to obtain XMax base long strip image data.

Further, sequentially extracting the cells of the monochromatic bitmaps in the N layers to form a first long strip to an XMax long strip specifically includes:

sequentially extracting 1 st unit cell image of the 1 st column of each layer of the monochromatic bitmap from large to small according to the size of the N layers of the monochromatic bitmaps, splicing and overlapping along the longitudinal direction of the three-dimensional model, and sequentially extracting 2 nd unit cell image of the 1 st column of each layer of the monochromatic bitmaps on the basis, continuously splicing and overlapping along the longitudinal direction of the three-dimensional model until the YMax unit cells of the 1 st column are sequentially extracted, splicing and overlapping along the longitudinal direction of the three-dimensional model to form a first long strip;

and splicing and overlapping the cells of the residual XMax-1 columns of the monochromatic bitmaps in each layer in the N layers according to the method until the XMax long strip is obtained.

Further, the method further comprises:

before acquiring the three-dimensional model data, coating photoresist with corresponding thickness on the substrate according to the depth requirement of the film microstructure to form a photoresist plate.

Further, the method further comprises:

and before uploading the new strip image data to the imaging equipment for scanning and photoetching one by one, setting the number of rolling pixels during photoetching and the step pitch of the imaging equipment.

The invention has the beneficial effects that: according to the number of layers of the cutting and a plurality of equal-part cell images, dislocation recombination is carried out on the cell images to form a plurality of basic long strip image data, and the basic long strip image data are spliced to form new long strip image data, so that the long strip image data are not limited by figures and directions in the exposure process; by splicing the data in the X direction and the Y direction, the photoetching of the whole breadth can be completed only by one-time photoetching without repeated zeroing and repeated photoetching, so that the photoetching precision and efficiency are improved.

The foregoing description is only an overview of the technical solutions of the present invention, and in order to make the technical solutions of the present invention more clearly understood and to implement them in accordance with the contents of the description, the following detailed description is given with reference to the preferred embodiments of the present invention and the accompanying drawings.

Drawings

FIG. 1 is a flow chart of a method of diaphragm data processing according to the present invention.

Fig. 2 is a flowchart of the dislocation rearrangement of the cell image in fig. 1.

FIG. 3 is a flow chart of the process of FIG. 1 for dividing the monochrome bitmap into a plurality of equal parts of cell images.

Fig. 4 is a schematic view of the formation of four long strips in a1 of the pyramid of example 1.

Fig. 5 is a schematic view of the formation of four long strips in a2 of the rectangular pyramid in example 1.

Fig. 6 is a schematic view of the formation of four long strips in a3 of the pyramid of example 1.

Fig. 7 is a schematic illustration of the transverse splicing of the first strip in a1, a2, and A3.

Fig. 8 is a schematic diagram of the transverse splicing of the second strip in a1, a2, and A3.

Fig. 9 is a schematic illustration of the transverse splicing of the third strip in a1, a2, and A3.

Fig. 10 is a schematic illustration of the transverse splicing of the fourth strip in a1, a2, and A3.

Detailed Description

The following detailed description of embodiments of the present invention is provided in connection with the accompanying drawings and examples. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.

Referring to fig. 1, before the method for processing stop data according to a preferred embodiment of the present invention is implemented, a photoresist with a corresponding thickness is coated on a substrate according to the trench depth requirement of the microstructure to form a photoresist plate, and then the photoresist plate is exposed in an imaging apparatus.

The diaphragm data processing method comprises the following steps:

and acquiring a three-dimensional model, and determining the pixel resolution of the digital micromirror required by exposure. The three-dimensional topography data is generated by three-dimensional modeling software that can derive a common three-dimensional data format for computer analysis, such as: STL, 3DS, STP, IGS, OBJ, etc. Preferably, the three-dimensional topographical data is consistent with the dimensions of the film microstructure.

Cutting the three-dimensional model into M layers along the vertical direction of the three-dimensional model according to the height of the three-dimensional model; and cutting each layer of the M layers into N layers along the vertical direction of the three-dimensional model to obtain a plurality of layers of two-dimensional image data. The pixel resolution of the digital micromirror comprises a horizontal pixel resolution and a vertical pixel resolution, wherein the direction of the horizontal pixel resolution is parallel to the x axis of the three-dimensional coordinate system, and the direction of the vertical pixel resolution is parallel to the y axis of the three-dimensional coordinate system. Specifically, the three-dimensional model is cut into M layers along the vertical direction (i.e., Z axis) of the three-dimensional model, and then each of the M layers after cutting is cut into N layers along the vertical direction of the three-dimensional model again, where M and N are positive integers. In the present embodiment, the three-dimensional model is sliced into M layers in the longitudinal direction of the three-dimensional model, and each of the M layers is sliced into N layers in the longitudinal direction of the three-dimensional model. The three-dimensional model sets up the section interval according to the technology demand in the vertical direction, and the section interval can be equidistant, also can be non-equidistant, and is decided according to actual conditions, does not do the specific limitation here.

Referring to fig. 3, the two-dimensional image data of each of the N layers is converted into a monochrome bitmap, and each monochrome bitmap is divided into a plurality of unit cell images in equal parts. The width of each cell image is UnitX, and the height of each cell image is UnitY. As stated above, UnitX times M is not greater than the horizontal pixel resolution of the DMDM, and UnitY times N is not greater than the vertical pixel resolution of the DMDM. Converting each layer of two-dimensional image data into a monochrome bitmap specifically comprises the following steps: performing pixelization filling on the two-dimensional image data by using a filling factor to form a monochrome bitmap; the fill factor is the number of pixels that need to be filled per millimeter distance. During segmentation, the maximum width and the maximum length of the three-dimensional model are taken as the basis, the monochrome bitmap of each layer is taken as the center and is filled with white, and then the monochrome bitmap of each layer after white filling is segmented into a plurality of unit cell images in equal parts according to the pixel resolution of the digital micromirror. And if the maximum width value of the three-dimensional model cannot divide the width UnitX of the cells and/or the maximum length value of the three-dimensional model cannot divide the height UnitY of the cells, filling white into the monochrome bitmap continuously until the maximum width value of the three-dimensional model can divide the width UnitX of the cells and/or the maximum length value can divide the height UnitY of the cells. In this embodiment, the width direction of the three-dimensional model is the X-axis direction in the three-dimensional model, and the length direction of the three-dimensional model is the Y-axis direction in the three-dimensional model.

And carrying out dislocation recombination on a plurality of equal parts of the cell images in the N layers to form a plurality of basic long-strip image data, and splicing the plurality of basic long-strip image data in the M layers to form new long-strip image data.

Referring to fig. 2, the "dislocation recombination" specifically includes: each layer of the N layers of the monochrome bitmap includes XMax × YMax cells, where XMax is the maximum length of the monochrome bitmap or the filled maximum length/UnitX, and YMax is the maximum width of the monochrome bitmap or the filled maximum width/UnitY; sequentially extracting the cells of the monochromatic bitmaps in the N layers to form a first long strip to an XMax long strip; the M first long strips are transversely stitched to obtain first base long strip image data until the M XMax long strips are transversely stitched to obtain XMax base long strip image data.

Specifically, the method for sequentially extracting the cells of the monochromatic bitmaps in the N layers to form the first long stripe to the XMax long stripe specifically includes:

sequentially extracting 1 st unit cell image of the 1 st column of each layer of the monochromatic bitmap from large to small according to the size of the N layers of the monochromatic bitmaps, splicing and overlapping along the longitudinal direction of the three-dimensional model, and sequentially extracting 2 nd unit cell image of the 1 st column of each layer of the monochromatic bitmaps on the basis, continuously splicing and overlapping along the longitudinal direction of the three-dimensional model until the YMax unit cells of the 1 st column are sequentially extracted, splicing and overlapping along the longitudinal direction of the three-dimensional model to form a first long strip; and splicing and overlapping the cells of the residual XMax-1 columns of the monochromatic bitmaps in each layer in the N layers according to the method until the XMax long strip is obtained.

And uploading the new strip image data to an imaging device for scanning photoetching strip by strip.

Before uploading new strip image data to the imaging equipment for scanning photoetching one by one, the number of rolling pixels and the step pitch of the imaging equipment during photoetching are set.

The present invention will be described in detail with reference to an embodiment in which the horizontal pixel resolution of the digital micromirror is 1920, the vertical pixel resolution of the digital micromirror is 1080, and the three-dimensional model is a rectangular pyramid.

Example 1:

referring to fig. 4 to 6, a rectangular pyramid model is obtained, and the rectangular pyramid model is vertically divided into 12 parts, wherein the rectangular pyramid model is first horizontally divided into 3 equal parts of two-dimensional image data along the vertical direction, and the parts are represented as being vertically equal in height. The 3 equal parts of two-dimensional image data are respectively numbered as a1, a2, A3, wherein A3 has a maximum length and a maximum width, and then each of the 3 equal parts of two-dimensional image data is longitudinally divided into 4 equal parts of two-dimensional image data in the vertical direction.

As described above, the two-dimensional image data of 4 equal parts in a1 are a1, a2, A3 and a4, respectively, a1, a2, A3 and a4 are filled with a1, a2, A3 and a4 as centers to be converted into monochrome bitmaps, the monochrome bitmaps of a1, a2, A3 and a4 are respectively filled with white based on the maximum length and the maximum width in A3, the image sizes of the a1, a2, A3 and a4 after the white filling are equal, wherein the shaded parts are the original sizes of a1, a2, A3 and a 4. Then, the widths of the white-filled a1, a2, a3 and a4 are divided by the width UnitX of the cell image, respectively, and the lengths of the white-filled a1, a2, a3 and a4 are divided by the height UnitY of the cell image, respectively, and if the lengths and/or widths of the a1, a2, a3 and a4 cannot be evenly divided by the height UnitY of the cell image and/or the width UnitX of the cell image, the white filling is continued so that the lengths and/or widths of the a1, a2, a3 and a4 are exactly evenly divided (i.e., increased by one). In the present embodiment, a1, a2, a3 and a4 are equally divided into 16 cell images, wherein the shaded portions are the original partial areas of a1, a2, a3 and a 4. Then 16 cell images in a1 are labeled jx-y, and a2, a3, a4 are labeled the same way as a1, then 16 cell images in a2 are labeled kx-y; the 16 cell images in a3 are labeled mx-y; the 16 cell images in a4 are labeled nx-y. Wherein, the value range of x is 1-4, the value range of y is 1-4, and x and y are both positive integers. Accordingly, the four divided parts of the two-dimensional image data a2 is divided into b1, b2, b3 and b4, and the four divided parts of the two-dimensional image data A3 is divided into c1, c2, c3 and c 4. The reference numbers of the cells in b1, b2, b3, b4, c1, c2, c3 and c4 are the same as those of the cells in a1, a2, a3 and a 4.

Referring to fig. 7 to 10, according to the size of the two-dimensional image data of a1, a2, a3 and a4, sequentially extracting n1-1 in a4, m1-1 in a3, k1-1 in a2, j1-1 in a1, n1-2 … in a4, m1-2 in a3, k1-2 in a2, j1-2 in a1 and … from a 464 from large to small in the longitudinal direction until n1-4 in a4, m1-4 in a3, k1-4 in a2 and j1-4 in a1 are misaligned and superposed in the longitudinal direction to form a first long stripe; taking n2-1 in a4, m2-1 in a3, k2-1 in a2, j2-1 in a1, n2-2 in a4, m2-2 in a3, k2-2 in a2 and j2-2 … in a1 to perform dislocation and superposition on n2-4 in a4, m2-4 in a3, k2-4 in a2 and j2-4 in a1 along the longitudinal direction to form a second long strip; taking n3-1 in a4, m3-1 in a3, k3-1 in a2, j3-1 in a1, n3-2 in a4, m3-2 in a3, k3-2 in a2 and j3-2 … in a1 to perform dislocation and superposition on n3-4 in a4, m3-4 in a3, k3-4 in a2 and j3-4 in a1 along the longitudinal direction to form a third long strip; and taking n4-1 in a4, m4-1 in a3, k4-1 in a2, j4-1 in a1, n4-2 in a4, m4-2 in a3, k4-2 in a2 and j4-2 … in a1, and carrying out dislocation and superposition on n4-4 in a4, m4-4 in a3, k4-4 in a2 and j4-4 in a1 along the longitudinal direction to form a fourth long strip. A2 and A3 were used to obtain the first to fourth long bands in the same manner as described above.

Then, the first strips in a1, a2 and A3 are spliced in the transverse direction of the three-dimensional model to obtain first basic long-strip image data, the second strips in a1, a2 and A3 are spliced in the transverse direction of the three-dimensional model to obtain second basic long-strip image data, the third strips in a1, a2 and A3 are spliced in the transverse direction of the three-dimensional model to obtain third basic long-strip image data, and the fourth strips in a1, a2 and A3 are spliced in the transverse direction of the three-dimensional model to obtain fourth basic long-strip image data.

In summary, the following steps: according to the number of layers of the cutting and a plurality of equal-part cell images, dislocation recombination is carried out on the cell images to form a plurality of basic long strip image data, and the basic long strip image data are spliced to form new long strip image data, so that the long strip image data are not limited by figures and directions in the exposure process; by splicing the data in the X direction and the Y direction, the photoetching of the whole breadth can be completed only by one-time photoetching without repeated zeroing and repeated photoetching, so that the photoetching precision and efficiency are improved.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.