CN108176854A - The modification method that electron beam defocuses - Google Patents

Abstract

The invention belongs to the technical field of electron beam correction, and in particular relates to a method for correcting electron beam defocus, comprising the following steps: S1: establishing the scanning range of the electron beam and discretizing the scanning range into several array points; S2: establishing each array point S3: Establish the vector expression of the control parameter group of each array point; S4: Establish the control parameter group matrix of all array points according to each vector expression; S5: Treat the control parameters of each focal length value as a constant, Introduce the focal length compensation amount, and establish the ratio relationship equation between the focal length value and its corresponding control parameters according to the mathematical relationship; S6: determine each focal length compensation amount according to the ratio relationship equation; S7: combine the focal length compensation amount of each array point with The focal length values are superimposed to form the actual focal length value of the electron beam corresponding to each array point. In this way, the correction of the focal length value of the electron beam is realized, so that the focusing point of the electron beam always falls on the target point, and the precise focusing of the electron beam is realized.

Description

Correction Method of Electron Beam Defocus

technical field

The invention belongs to the technical field of electron beam correction, and in particular relates to a correction method for electron beam defocus.

Background technique

EBSM (Electron Beam Selective Metal Melting) is an additive manufacturing technology that uses electron beams as a heat source to manufacture three-dimensional metal parts layer by layer by selectively melting preset powder layers. In EBSM forming, the defocusing of the electron beam at a large deflection angle will seriously affect the accuracy of the formed part. The EBSM system uses a focusing coil to focus the electron beam. Therefore, the electron beam is focused when not deflected, but defocused when deflected by large angles.

In the prior art, most electron beam scanning systems use D/A converters to generate deflection signals. By changing the data sent to the converters, the path of the electron beam can be adjusted or programmed, so that the dispersion of the electron beam can be adjusted. The defocusing phenomenon has been corrected to a limited extent, but it still cannot solve the defocusing problem of the large deflection angle of the electron beam.

Contents of the invention

The purpose of the present invention is to provide a method for correcting defocusing of electron beams, aiming at solving the technical problem in the prior art that defocusing of electron beams tends to occur when the deflection angle is large.

In order to achieve the above object, the technical solution adopted by the present invention is: a method for correcting electron beam defocus, comprising the following steps,

S1: establishing the scanning range of the electron beam and discretizing the scanning range into several array points;

S2: Determine the focal length value and beam current value of the electron beam corresponding to each of the array points and establish the control parameters of each of the array points in combination with the X-axis coordinates of each of the array points and the Y-axis coordinates of each of the array points Group;

S3: establishing an expression of a vector corresponding to the control parameter group of each array point;

S4: According to the expression of the vector of each of the array points, establish a matrix of control parameter groups of all the array points;

S5: Treat the control parameters corresponding to the focal length values in each of the control parameter groups as constants, and introduce the focal length compensation amount of the focal length value when the electron beam is deflected, according to the focal length value The mathematical relationship between the control parameters corresponding to the focal length value, establishing a ratio relationship equation between each focal length compensation amount and each focal length value;

S6: Determine the mathematical value of each focal length compensation amount according to a ratio relationship equation between each focal length compensation amount and each focal length value;

S7: Superimpose the focus compensation amount of each array point and the focus value to form an actual focus value of the electron beam corresponding to each array point when deflected.

Further, the expression of the vector in the step S3 is:

V _i,j =[XYFI] _i,j (1)

Wherein, V _i,j represents the vector corresponding to each of the array points, X represents the control data of the X-axis coordinates corresponding to each of the array points, and Y represents the Y-axis coordinates corresponding to each of the array points F represents the control data of the focal length value corresponding to each of the array points, and I represents the control data of the beam current value of the electron beam corresponding to each of the array points.

Further, the expression of the matrix in the step S4 is:

M=V _n×m ＝[XYFI] _n×m (2)

Wherein, M represents the matrix formed by all the control parameter groups, n represents the number of rows of the matrix, m represents the number of columns of the matrix, V _{i, j} represent the vectors corresponding to each of the array points, X Represents the control data of the X-axis coordinates corresponding to each of the array points, Y represents the control data of the Y-axis coordinates corresponding to each of the array points, F represents the control of the focal length value corresponding to each of the array points data, and I represents the control data of the beam current value of the electron beam corresponding to each of the array points.

Further, the ratio relationship equation between each focal length compensation amount and each focal length value in the step S5 is:

Wherein, Δf represents the focal length compensation amount, f represents the focal length value, x represents the X-axis coordinate, and y represents the Y-axis coordinate.

Further, a mathematical change is performed on the ratio relational equation between each focal length compensation amount and each focal length value in the step S5, and the first ratio of each focal length compensation amount to each focal length value is obtained. A simplified equation:

Wherein, Δf represents the focal length compensation amount, f represents the focal length value, x represents the X-axis coordinate, and y represents the Y-axis coordinate.

Further, according to the mathematical relationship between the focal length value of the electron beam corresponding to each of the array points and the control data corresponding to each of the focal length values, the calculation of each of the focal length compensation amounts and each of the focal length values is simplified. The second simplified equation of the ratio relationship equation:

Wherein, ΔF represents the control data compensation amount of the focal length value, f represents the focal length value, and F represents the control data of the focal length value corresponding to each of the array points.

Further, the first simplified equation and the second simplified equation are combined to establish a system of equations.

Further, according to the simultaneous solution of the equations, the solution formula of the control data compensation value of the focal length value is obtained:

Wherein, K _ΔF is a proportional coefficient, ΔF represents the control data compensation amount of the focal length value, f represents the focal length value, F represents the control data of the focal length value corresponding to each of the array points, and x represents the X axis Coordinate, y represents the Y-axis coordinate.

Further, the scanning area is determined, and the control data sets of the four corner points of the scanning area are determined, and the control data sets of the four corner points are substituted into the solution formula to obtain the four corner points The proportional coefficient of the four corner points is averaged to obtain the average proportional coefficient.

Further, substituting the average proportional coefficient value into the solution formula to obtain the control data compensation amount of the focal length value corresponding to each of the array points, and substituting the control data compensation amount of each focal length value into the In the first simplified equation, each of the focal length compensation amounts is obtained.

Beneficial effects of the present invention: The focus correction method for electron beam defocus of the present invention can refine the scanning range of the electron beam to each point by discretizing the scanning range of the electron beam into several array points, and The defocusing behavior of the electron beam is analyzed specifically for each point. By determining the focal length and beam current value of the electron beam corresponding to each array point and combining the X-axis coordinates and Y-axis coordinates of each array point to establish a control parameter group for each array point, the electron beam scanning information of each array point can be digitized , which is convenient for correcting the defocus of the electron beam through mathematical methods in the later stage. By vectorizing the control parameter groups of each array point and putting each vector into a matrix, a database of the control parameter groups of each array point is formed, which is convenient for later retrieval of the control parameters of each array point. Since the control parameters of the focal length value corresponding to each array point are regarded as constants and the concept of the focal length compensation amount of the focal length value is introduced, it is possible to establish each focal length compensation amount and The ratio relationship equation of each focal length value. The focal length compensation amount of the focal length value corresponding to each array point can be obtained through the ratio relationship equation, and then the focal length compensation amount and each focal length value are superimposed, and the electron beam corresponding to each array point when deflected is obtained. In this way, the correction of the focal length value of the electron beam corresponding to each array point is realized, so that when the electron beam is deflected at a large angle, the focus point of the electron beam no longer falls above the target point, but falls on the In this way, the precise focusing of the electron beam at large deflection angles is realized.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the accompanying drawings that need to be used in the descriptions of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only of the present invention. For some embodiments, those of ordinary skill in the art can also obtain other drawings based on these drawings without paying creative efforts.

FIG. 1 is a flow chart of steps of a method for correcting electron beam defocus provided by an embodiment of the present invention.

Detailed ways

Embodiments of the present invention are described in detail below, examples of which are shown in the drawings, wherein the same or similar reference numerals designate the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to FIG. 1 are exemplary and are intended to explain the present invention, but should not be construed as limiting the present invention.

In describing the present invention, it should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", The orientation or positional relationship indicated by "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than Nothing indicating or implying that a referenced device or element must have a particular orientation, be constructed, and operate in a particular orientation should therefore not be construed as limiting the invention.

In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be interpreted as indicating or implying relative importance or implicitly specifying the quantity of indicated technical features. Thus, a feature defined as "first" and "second" may explicitly or implicitly include one or more of these features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

In the present invention, unless otherwise clearly specified and limited, terms such as "installation", "connection", "connection" and "fixation" should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection , or integrated; it can be mechanically connected or electrically connected; it can be directly connected or indirectly connected through an intermediary, and it can be the internal communication of two components or the interaction relationship between two components. Those of ordinary skill in the art can understand the specific meanings of the above terms in the present invention according to specific situations.

As shown in FIG. 1, a method for correcting electron beam defocus provided by an embodiment of the present invention includes the following steps,

S1: Establish the scanning range of the electron beam and discretize the scanning range into several array points;

S2: Determine the focal length value and beam current value of the electron beam corresponding to each array point, and combine the X-axis coordinates of each array point and the Y-axis coordinates of each array point to establish a control parameter group for each array point;

S3: Establish the expression of the vector corresponding to the control parameter group of each array point;

S4: Establish a matrix of control parameter groups for all array points according to the expression of the vector of each array point;

S5: Treat the control parameters corresponding to the focal length values in each control parameter group as constants, and introduce the focal length compensation amount of the focal length value when the electron beam is deflected, according to the mathematics of the focal length value and the control parameter corresponding to the focal length value relationship, and establish the ratio relationship equation between each focal length compensation amount and each focal length value;

S6: Determine the mathematical value of each focal length compensation amount according to the ratio relationship equation between each focal length compensation amount and each focal length value;

S7: superimpose the focal length compensation amount of each array point and the focal length value to form the actual focal length value of the electron beam corresponding to each array point when deflected.

The electron beam defocus correction method provided by the embodiment of the present invention discretizes the scanning range of the electron beam into several array points, so that the scanning range of the electron beam can be refined to each point, and for each point Specifically analyze the defocusing behavior of the electron beam. By determining the focal length and beam current value of the electron beam corresponding to each array point and combining the X-axis coordinates and Y-axis coordinates of each array point to establish a control parameter group for each array point, the electron beam scanning information of each array point can be digitized , which is convenient for correcting the defocus of the electron beam through mathematical methods in the later stage. By vectorizing the control parameter groups of each array point and putting each vector into a matrix, a database of the control parameter groups of each array point is formed, which is convenient for later retrieval of the control parameters of each array point. Since the control parameters of the focal length value corresponding to each array point are regarded as constants and the concept of the focal length compensation amount of the focal length value is introduced, it is possible to establish each focal length compensation amount and The ratio relationship equation of each focal length value. The focal length compensation amount of the focal length value corresponding to each array point can be obtained through the ratio relationship equation, and then the focal length compensation amount and each focal length value are superimposed, and the electron beam corresponding to each array point when deflected is obtained. In this way, the correction of the focal length value of the electron beam corresponding to each array point is realized, so that when the electron beam is deflected at a large angle, the focus point of the electron beam no longer falls above the target point, but falls on the At the target point, the precise focusing of the electron beam at a large deflection angle is realized, so that the focusing value of the electron beam is no longer constant, and the precise control of the focal length of the electron beam within the scanning range is realized, avoiding the electron beam Defocus occurs in the state of large deflection angle, which significantly improves the forming quality of the workpiece and makes the electron beam scanning system easy to control.

In this embodiment, the expression of the vector in step S3 is:

V _i,j =[XYFI] _i,j (1)

Among them, V _{i, j} represents the vector corresponding to each array point, X represents the control data of the X-axis coordinates corresponding to each array point, Y represents the control data of the Y-axis coordinates corresponding to each array point, and F represents the focal length corresponding to each array point I represents the control data of the beam current value of the electron beam corresponding to each array point.

Specifically, by establishing the vector of the control data of each array point, the relevant information data of each array point: X-axis coordinate, Y-axis coordinate, focal length value and beam intensity can be vectorized, and then the method of matrix theory can be used , retrieve and analyze the above information data of each array point. Of course, other mathematical methods may also be used to organize the above-mentioned information data of each array point, which is not limited in this embodiment.

In this embodiment, the expression of the matrix in step S4 is:

M=V _n×m ＝[XYFI] _n×m (2)

Among them, M represents the matrix formed by all control parameter groups, n represents the number of rows of the matrix, m represents the number of columns of the matrix, V _{i, j} represents the vector corresponding to each array point, and X represents the X-axis coordinate corresponding to each array point Control data, Y represents the control data of the Y-axis coordinates corresponding to each array point, F represents the control data of the focal length value corresponding to each array point, and I represents the control data of the beam current value of the electron beam corresponding to each array point.

Specifically, by matrixing the vectors of the relevant information data of all array points, the process of extracting and invoking the relevant information data of each array point is significantly optimized, so that the computer can call the correlation of each array point in the matrix through mathematical software. Information data, and then realize the data processing of the computer, so that the manual workload is significantly reduced, and it is possible to discretize the electron beam scanning area into tens of thousands or even more array points. In this way, the more array points in the scanning area, the more accurate the correction of the defocus of the electron beam in the state of large deflection angle will be.

Further, the scanning range is specifically: 120 mm×120 mm, and the number of array points within the scanning range is 361,201, that is, there are 361,201 array points evenly distributed in the square area. Specifically in the matrix, the number of rows of the matrix is 601, and the number of columns of the matrix is also 601. At the same time, the vertical and lateral intervals between two adjacent array points are both 0.2 mm, and the diameter of the electron beam is 0.4 mm. In this way, the electron beam can cover each array point in the scanning area without missing any array point in the scanning area, thereby ensuring that the data of each array point in the scanning area is valid and significantly improving the accuracy of the electron beam. Accuracy of defocus correction at high beam deflection angles.

In this embodiment, the ratio relationship equation between each focal length compensation amount and each focal length value in step S5 is:

Among them, Δf represents the focal length compensation amount, f represents the focal length value, x represents the X-axis coordinate, and y represents the Y-axis coordinate.

Specifically, by constructing the above-mentioned ratio relationship equations between each focal length compensation amount and each focal length value, the focal length compensation amount corresponding to each array point can be obtained, so that it is possible to determine the The corresponding actual focal length value of the electron beam makes the focus point of the electron beam accurately fall on the target point, thereby realizing precise focusing of the electron beam in a state of large deflection angle.

Preferably, the above-mentioned ratio relationship equation can be further optimized to obtain the intermediate simplified equation of the above-mentioned ratio relationship equation:

In this way, the intermediate simplified equation is obtained by simplifying the above ratio relationship equation, which simplifies the calculation of the focal length compensation amount and improves the accuracy of the calculation of the focal length compensation amount.

In this embodiment, mathematical changes are made to the ratio relational equations of each focal length compensation amount and each focal length value in step S5, and the first simplified equation of the ratio of each focal length compensation amount to each focal length value is obtained:

Among them, Δf represents the focal length compensation amount, f represents the focal length value, x represents the X-axis coordinate, and y represents the Y-axis coordinate.

Specifically, the first simplified equation is further simplified on the basis of the above-mentioned intermediate simplified equation, and the mathematical relationship between the focal length compensation amount and the focal length value can be intuitively obtained through the above formula, that is, the focal length compensation amount of each array point is equal to The ratio of the sum of the square of the X-axis coordinate value and the square of the Y-axis coordinate value of each array point to twice the focal length value. Therefore, the value of the focal length compensation amount corresponding to each array point can be simply calculated through the above formula.

In this embodiment, according to the mathematical relationship between the focal length value of the electron beam corresponding to each array point and the control data corresponding to each focal length value, the second simplified equation of the ratio relationship equation between each focal length compensation amount and each focal length value is simplified:

Wherein, ΔF represents the control data compensation amount of the focal length value, f represents the focal length value, and F represents the control data of the focal length value corresponding to each array point.

Specifically, the mathematical relationship between the focal length value of the electron beam corresponding to each array point and the control data corresponding to each focal length value is:

In this way, by introducing the concept of the control data compensation amount of the focal length value, and combining the mathematical relationship between the focal length value of the electron beam and the control data corresponding to each focal length value, the above-mentioned second simplified equation can be obtained, thus the control of the focal length value A mathematical relationship is established between the data compensation amount and the compensation amount of the focal length value. In this way, the computer can first call the control parameter groups of each array point in the above-mentioned matrix through the mathematical software, and then calculate the control data compensation amount of the focal length value according to each control parameter group, so that the compensation amount of the focal length value can be obtained through the focal length The control data compensation amount of the value is associated with the matrix formed by the control parameter groups of each array point, and finally the compensation amount of the focal length value is obtained through the mathematical software installed in the computer.

In this embodiment, the first simplified equation and the second simplified equation are combined to establish a system of equations, and according to the system of equations, the solution formula of the control data compensation value of the focal length value is obtained:

Among them, K _ΔF is a proportional coefficient, ΔF represents the control data compensation amount of the focal length value, f represents the focal length value, F represents the control data of the focal length value corresponding to each array point, x represents the X-axis coordinate, and y represents the Y-axis coordinate.

Specifically, by combining the first simplified equation and the second simplified equation, the control data compensation amount of the focal length value of each array point can be related to the X-axis coordinate, Y-axis coordinate and proportional coefficient of each array point. In this way, the calculation of the compensation amount of the control data for the focal length value of each array point can be realized.

In this embodiment, the scanning area is determined, and the control data sets of the four corner points of the scanning area are determined, and the control data sets of the four corner points are substituted into the solution formula to obtain the proportional coefficients of the four corner points, and the four The average of the proportional coefficients of the corner points is obtained to obtain the average proportional coefficient.

Specifically, it can be obtained from the above solution formula that the proportional coefficient is equal to the ratio of the negative number of the control parameter value of the focal length of the electron beam to four times the square of the focal length value. In this way, the scale coefficient of each array point can be obtained. By substituting the control data groups of the four corner points into the solution formula, the proportional coefficients of the four corner points are obtained, and the average proportional coefficients of the four corner points are obtained to obtain the average proportional coefficient. In this way, the average proportional coefficient can be obtained more accurately by taking the proportional coefficients of a limited number of array points, and there is no need to calculate the proportional coefficient of each array point, thereby significantly saving the calculation workload. Of course, according to the actual situation, more array points may also be used for calculating the average proportional coefficient, which is not limited in this embodiment.

In this embodiment, the average proportional coefficient value is substituted into the solution formula to obtain the control data compensation amount of the focal length value corresponding to each array point, and the control data compensation amount of each focal length value is substituted into the first simplified equation to obtain each Amount of focus compensation.

Specifically, after obtaining the average proportional coefficient and the control data compensation amount of the focal length value corresponding to each array point through the above solution formula, it is only necessary to substitute the control data compensation amount of the focal length value corresponding to each array point into the first simplified equation Solve the focal length compensation amount of each array point. Finally, the correction of the focal length value of the electron beam corresponding to each array point is realized.

The above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention. Inside.

Claims (10)

1. A correction method for electron beam defocus, characterized in that: comprise the steps: S1: establishing the scanning range of the electron beam and discretizing the scanning range into several array points; S2: Determine the focal length value and beam current value of the electron beam corresponding to each of the array points and establish the control parameters of each of the array points in combination with the X-axis coordinates of each of the array points and the Y-axis coordinates of each of the array points Group; S3: establishing an expression of a vector corresponding to the control parameter group of each array point; S4: Establish a matrix of control parameter groups of all array points according to the expression of the vector of each array point; S5: Treat the control parameters corresponding to the focal length values in each of the control parameter groups as constants, and introduce the focal length compensation amount of the focal length value when the electron beam is deflected, according to the focal length value Establishing a ratio relationship equation between each of the focal length compensation amounts and each of the focal length values based on the mathematical relationship with the control parameters corresponding to the focal length values; S6: Determine the mathematical value of each focal length compensation amount according to a ratio relationship equation between each focal length compensation amount and each focal length value; S7: Superimpose the focus compensation amount of each array point and the focus value to form an actual focus value of the electron beam corresponding to each array point when deflected. 2. The correction method for electron beam defocus according to claim 1, characterized in that: in the step S3, the expression of the vector is: V _i,j =[XYFI] _i,j (1) Wherein, V _i,j represents the vector corresponding to each of the array points, X represents the control data of the X-axis coordinates corresponding to each of the array points, and Y represents the Y-axis coordinates corresponding to each of the array points F represents the control data of the focal length value corresponding to each of the array points, and I represents the control data of the beam current value of the electron beam corresponding to each of the array points. 3. The correction method for electron beam defocus according to claim 2, characterized in that: in the step S4, the expression of the matrix is: M=V _n×m ＝[XYFI] _n×m (2) Wherein, M represents the matrix formed by all the control parameter groups, n represents the number of rows of the matrix, m represents the number of columns of the matrix, V _{i, j} represent the vectors corresponding to each of the array points, X Represents the control data of the X-axis coordinates corresponding to each of the array points, Y represents the control data of the Y-axis coordinates corresponding to each of the array points, F represents the control of the focal length value corresponding to each of the array points data, and I represents the control data of the beam current value of the electron beam corresponding to each of the array points. 4. The correction method for electron beam defocus according to claim 1, characterized in that: in the step S5, the ratio relationship equation between each of the focal length compensation amounts and each of the focal length values is: Wherein, Δf represents the focal length compensation amount, f represents the focal length value, x represents the X-axis coordinate, and y represents the Y-axis coordinate. 5. The method for correcting electron beam defocus according to claim 4, characterized in that: mathematically changing the ratio relational equation between each of the focal length compensation amounts and each of the focal length values in the step S5, And obtain the first simplified equation of the ratio of each described focal length compensation amount and each described focal length value: Wherein, Δf represents the focal length compensation amount, f represents the focal length value, x represents the X-axis coordinate, and y represents the Y-axis coordinate. 6. The method for correcting electron beam defocus according to claim 5, characterized in that: according to the mathematical relationship between the focal length value of the electron beam corresponding to each of the array points and the control data corresponding to each of the focal length values , to simplify the second simplified equation of the ratio relationship equation between each of the focal length compensation amounts and each of the focal length values: Wherein, ΔF represents the control data compensation amount of the focal length value, f represents the focal length value, and F represents the control data of the focal length value corresponding to each of the array points. 7. The method for correcting electron beam defocus according to claim 6, characterized in that: the first simplified equation and the second simplified equation are combined to establish an equation system. 8. The correction method for electron beam defocus according to claim 7, characterized in that: according to the simultaneous solution of the equations, the solution formula of the control data compensation value of the focal length value is obtained: Wherein, K _ΔF is a proportional coefficient, ΔF represents the control data compensation amount of the focal length value, f represents the focal length value, F represents the control data of the focal length value corresponding to each of the array points, and x represents the X axis Coordinate, y represents the Y-axis coordinate. 9. The correction method for electron beam defocus according to claim 8, characterized in that: determine the scan area, and determine the control data sets of four corner points of the scan area, four corner points Substituting the control data set into the solution formula to obtain the proportional coefficients of the four corner points, and taking the average value of the proportional coefficients of the four corner points to obtain the average proportional coefficient. 10. The correction method for electron beam defocus according to claim 9, characterized in that: the average proportional coefficient value is substituted into the solution formula to obtain the control data of the focal length value corresponding to each of the array points compensation amount, and substitute the control data compensation amount of each focal length value into the first simplified equation to obtain each focal length compensation amount.