A coating device and method for large aperture non-porous optical elements

Abstract

The application discloses a coating device for large-aperture non-porous optical elements, comprising a driving shaft, a driven shaft, a gear set, a magnetron sputtering source and a correction plate; the rotation of the driving shaft drives the rotation of the driven shaft and the revolution of the driven shaft around the axis of the driving shaft; the optical element is fixedly installed above the second gear, and the optical element moves synchronously with the driven shaft; the magnetron sputtering source is fixedly arranged above the optical element, and the correction plate is provided with an opening; the magnetron sputtering source coats the upper surface of the optical element through the correction plate. The application also discloses a coating method for large-aperture non-porous optical elements, wherein the size of the opening in each region of the correction plate is determined by setting a correction coefficient vector, a film thickness distribution curve is drawn according to the thickness values of each point of the film layer on the coating surface, and the optical element is coated by using the correction plate after the correction coefficient vector is continuously adjusted according to the film thickness distribution curve. The application realizes the coating of the center non-porous optical element and the adjustment of the film thickness uniformity.

Description

Technical Field

[0001] This invention relates to a coating apparatus and method for optical elements, belonging to the field of optical equipment technology, and can be applied to the field of thin film optical fabrication technology. Background Technology

[0002] For equipment such as large optical telescopes and large space remote sensing satellites, their optical systems are mostly reflective optical systems. In such systems, large-aperture optical elements are indispensable and important components. To meet the requirements of the optical system, it is usually necessary to coat the optical elements with a thin film.

[0003] Traditional optical systems use a coaxial three-mirror structure with a through-hole in the center of the primary mirror. For such optical elements, coating can be performed by rotating the optical element around its central axis. However, more and more optical systems now employ an off-axis three-mirror structure, where the primary mirror lacks a central through-hole. For these optical elements, coating cannot be performed by rotating them around their central axis because the thickness correction baffle cannot correct the thickness in the central region of the optical element. This results in a thicker film in the central region compared to other areas, ultimately reducing the overall surface accuracy of the mirror.

[0004] Therefore, a coating device is needed to solve the problem of coating optical elements without a central hole and to correct the uniformity of the film thickness. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned defects and provide a coating apparatus and method for large-aperture, holeless optical elements, solving the technical problem of uneven film thickness in centrally holeless optical elements. This invention achieves the adjustment of coating uniformity and film thickness for centrally holeless optical elements.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] A coating apparatus for a large-aperture, hole-free optical element includes a drive shaft, a driven shaft, a gear set, a magnetron sputtering source, and a correction plate.

[0008] The gear set includes a first gear and a second gear. The first gear is located on the upper end of the drive shaft, and the second gear is located on the upper end of the driven shaft. The first gear and the second gear mesh with each other. The rotation of the drive shaft drives the rotation of the driven shaft and its revolution around the axis of the drive shaft.

[0009] The optical element is fixedly mounted above the second gear, and the geometric center of the optical element is located on the axis of the driven shaft. The optical element moves synchronously with the driven shaft.

[0010] The magnetron sputtering source is positioned above the optical element and is fixed in place. A correction plate is installed between the magnetron sputtering source and the optical element. The correction plate has an opening, through which the magnetron sputtering source coats the upper surface of the optical element.

[0011] Furthermore, the coating apparatus for the aforementioned large-aperture, non-porous optical element also includes a support fixture.

[0012] The support fixture includes several support rods, the upper end of which is fixedly connected to the lower surface of the optical element, and the lower end of which is fixedly connected to the second gear.

[0013] The center of the support fixture is located on the axis of the driven shaft.

[0014] A coating method for large-aperture, hole-free optical elements, which corrects the uniformity of the coating thickness by adjusting the openings on a correction plate, includes:

[0015] S1 calculates the thickness distribution matrix T of the film layer on the coated surface without a correction plate;

[0016] S2 sets the correction coefficient vector C;

[0017] S3 multiplies the thickness distribution matrix T of the film layer on the coated surface without a correction plate with the correction coefficient vector C to obtain the correction value TC;

[0018] S4 divides the correction plate into m regions and determines the coordinates of the openings in each region based on the correction value TC; m > 1;

[0019] S5 calculates the thickness value of the film layer at each point on the coating surface under the opening coordinates of the correction plate in step S4;

[0020] S6 plots the film thickness distribution curve based on the thickness values ​​of each point on the coated surface;

[0021] S7 When the difference between the maximum and minimum values ​​of the film thickness distribution curve is greater than △T, return to step S2; when the difference between the maximum and minimum values ​​of the film thickness distribution curve is less than or equal to △T, allow the magnetron sputtering source to deposit a film on the upper surface of the optical element through a correction plate with an opening size obtained in step S4; △T is a threshold set according to the uniformity requirements of the film thickness.

[0022] The correction plate is the correction plate in the above-mentioned coating device for large-diameter, non-porous optical elements, and the coating surface is the upper surface of the optical element.

[0023] Furthermore, in step S1, the method for calculating the thickness distribution matrix T of the film layer on the coated surface without a correction plate includes:

[0024] S1.1 Establish a coordinate system OXYZ; the origin of the coordinate system OXYZ is the intersection of the plane containing the sputtering surface of the magnetron sputtering source and the axis of the active shaft, the X-axis points from the origin to the center of the sputtering surface, the Z-axis points from the origin upward along the axis of the active shaft, and the Y-axis conforms to the right-hand rule;

[0025] S1.2 Based on the coordinate system OXYZ, calculate the film thickness t produced by the sputtering of the area element dσ of the magnetron sputtering source onto the area element ds of any point on the coating surface. ds ;

[0026] S1.3 Establish the length r of the line connecting dσ and ds, and the expression for the coordinates of ds with respect to the sputtering time t;

[0027] S1.4 According to t ds The length r of the line connecting dσ and ds with respect to sputtering time t, and the coordinates of ds with respect to sputtering time t, are used to determine the film thickness T sputtered by the entire sputtering surface onto ds within sputtering time t. ds ;

[0028] S1.5 divides the coated surface into m rings of different radii from the center point to the edge, and assumes that the coated surfaces at the same radius have the same thickness. T ds Convert to a column matrix containing m distinct elements;

[0029] S1.6 Normalize each element in the column matrix to obtain the thickness distribution matrix T of the film layer on the coating surface without a correction plate.

[0030] Furthermore, in step S1.2, the film thickness t generated by sputtering the area element dσ of the magnetron sputtering source onto the area element ds of any point on the coating surface is... ds for:

[0031]

[0032] in, θ is the angle between the line connecting dσ and ds and the normal to the sputtering surface; θ is the angle between the line connecting dσ and ds and the normal to the coating surface; n is the divergence characteristic constant of the magnetron sputtering source;

[0033] in, h is the distance between the sputtering surface of the magnetron sputtering source and the coating surface of the optical element;

[0034] In step S1.3:

[0035] The coordinates of ds are (x s ,y s ,-h);

[0036] x s =R·cos(ω·t)+ρ·cos(K·ω·t);

[0037] y s =R·sin(ω·t)-ρ·sin(K·ω·t);

[0038] r = [(x t -xs ) 2 +(y t -y s ) 2 +h 2 ] 1 / 2 ;

[0039] Where R is the distance between the driving and driven axes, K is the ratio of the rotational angular velocities of the driven and driving axes, ω is the rotational angular velocity of the driving axis, t is the sputtering time, ρ is the distance between any point on the coating surface and the center point of the coating surface, and the coordinates of dσ are (x... t ,y t ,0).

[0040] Furthermore, in step S1.4,

[0041]

[0042] Where, x t-min The minimum value of the X-coordinate of the sputtering surface, x t-max The maximum value of the X-coordinate of the sputtering surface, y t-min The minimum value of the Y-coordinate of the sputtering surface, y t-max This represents the maximum value of the Y-coordinate of the sputtering surface.

[0043] Furthermore, in step S1.5, T ds Convert to a column matrix containing m distinct elements:

[0044] T ds =[T ds (1); T ds (2); T ds (3); ...; T ds (m-1),T ds (m)];

[0045] Among them, T ds (1) is the film thickness at the position ρ = 0 on the coating surface, i.e., the film thickness at the center point, T. ds (m) represents the film thickness at the edge of the coating surface, and the width of the ring represented by each point is the radius of the optical element divided by m. In this invention, the radius of the optical element is preferably 2000 mm.

[0046] In step S1.6, the thickness distribution matrix T of the film layer on the coated surface without the correction plate is obtained as follows:

[0047] That is, T = [T1; T2; T3; ... T m-1 ;T m ].

[0048] Furthermore, let Cp be the correction coefficient vector C set in step S2 during the p-th execution, where p = 1, 2, 3, ..., Cp = [C p,1 C p,2 C p,3 ;...C p,m-1 C p,m ];

[0049] In step S3, the correction value TCp obtained from the p-th execution of step S3 is [TC p,1 ;TC p,2 ;TC p,3 ;...TC p,m-1 ;TC p,m ];

[0050] In step S4, let the correction plate be rectangular, and the coordinates of the correction range of the correction plate be (x... t-max -x t-min )×(y t-max -y t-min (This coordinate system coincides with the coordinate system of the magnetron sputtering surface). The correction plate is divided into m regions along the X-axis. The coordinates of the two ends of the i-th region along the X-axis are: x t-min +[(x t-max -x t-min )×(i-1))] / (m-1) and x t-min +[(x t-max -x t-min )×i) / (m-1);

[0051] Open the i-th region, with the opening located at x-axis coordinate x. t-min +[(x t-max -x t-min At point (i-1) / (m-1), the opening coordinate of the Y-axis is ±[(y t-max -y t-min )*TCp(min)] / [TC p,i +TCp(min)]; at the x-axis coordinate x t-min +[(x t-max -x t-min At position )*i] / (m-1), the opening coordinate of the Y-axis is ±[(y t-max -y t-min )*TCp(min)] / [TC p,i+1 +TCp(min)], that is, the coordinates of the four vertices of the opening are (x1, y1), (x2, y2), (x1, y3), (x2, y4):

[0052]

[0053]

[0054]

[0055]

[0056] Where TCp(min) is the non-zero minimum value in the correction value TCp vector.

[0057] Furthermore, the method for step S5 is as follows:

[0058] S5.1 Under the opening coordinates of the correction plate in step S4, obtain the thickness of the coating surface sputtered by the magnetron sputtering source through the i-th region of the correction plate to any point on the coating surface.

[0059]

[0060] in,

[0061] X left =x1,X right = x2;

[0062] S5.2 The thicknesses sputtered from m regions at any point on the coating surface are summed to obtain the thickness values ​​of the film layer at each point on the coating surface:

[0063]

[0064] Furthermore, the film thickness distribution curve is plotted with ρ as the abscissa;

[0065] When step S2 is executed for the second time or more, a correction coefficient vector C is set according to the film thickness distribution curve. Specifically, according to the film thickness distribution curve, the larger the film thickness at a certain position, the larger the element corresponding to that position in the correction coefficient vector C.

[0066] Compared with the prior art, the present invention has the following advantages:

[0067] (1) The present invention provides a magnetron sputtering evaporation coating device, which realizes the coating of central non-porous optical elements and the adjustment of film thickness uniformity;

[0068] (2) The device of the present invention has a simple structure and avoids the instability of the mechanism caused by the movement of the target material;

[0069] (3) This invention provides a basis for adjusting the uniformity of film thickness by designing the movement mode of optical element coating process;

[0070] (4) The present invention provides a method for calculating the film thickness distribution on the coating surface and a method for designing a correction baffle. The correction baffle is placed below the sputtering surface and closely attached to the sputtering surface, which can block excess coating material and achieve equal film thickness on the coating surface as much as possible. Attached Figure Description

[0071] Figure 1 This is a three-dimensional view of the structural arrangement of the coating device for the large-aperture, hole-free optical element of the present invention.

[0072] Figure 2 This is a top view of the coating device for the large-aperture, hole-free optical element of the present invention.

[0073] Figure 3 This is a schematic diagram of the coating device for the large-aperture, hole-free optical element of the present invention from the main view direction.

[0074] Figure 4 This is a schematic diagram showing the angles and parameters of the coating device for the large-aperture, holeless optical element of the present invention.

[0075] Figure 5 This is the film thickness distribution pattern obtained without a correction plate in an embodiment of the present invention;

[0076] Figure 6 This is the thickness distribution of the film obtained after adding the correction plate in an embodiment of the present invention;

[0077] Figure 7 This represents the ideal film thickness distribution ultimately obtained in the embodiments of the present invention;

[0078] Figure 8 This is a schematic diagram of the final film thickness uniformity correction plate in an embodiment of the present invention;

[0079] In the figure, 1-drive shaft, 2-driven shaft, 3-gear set, 4-support fixture, 5-optical element, 6-coating surface, 7-magnetron sputtering source, 8-sputtering surface. Detailed Implementation

[0080] The features and advantages of the present invention will become clearer and more apparent from the following detailed description.

[0081] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments. Although various aspects of embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless specifically indicated otherwise.

[0082] This invention provides a magnetron sputtering coating apparatus, which can be used to coat optical elements with a diameter of 2-4m and no central hole. This invention also provides a method for correcting film thickness uniformity. By calculating the shape of the correction baffle, it is placed at the lower part of the magnetron sputtering source to block excess material, thereby ensuring that the film deposited at any point on the substrate has equal thickness.

[0083] In a preferred embodiment, the present invention provides a magnetron sputtering coating apparatus, comprising: a drive shaft arranged at the center of a vacuum chamber, a driven shaft cooperating with the drive shaft, a support fixture on the upper part of the driven shaft, an optical element placed on the support fixture (in the present invention, the coating surface of the optical element is a plane mirror), a magnetron sputtering source above the optical element, the magnetron sputtering source being rectangular in shape, and a film thickness correction plate below the magnetron sputtering source.

[0084] Furthermore, the driving shaft and the driven shaft are engaged by gears. When the driving shaft rotates at a certain angular velocity, the driven shaft will also rotate at a fixed angular velocity.

[0085] Furthermore, the central axis of the optical element coincides with the center of the support fixture, and the two are tightly connected together with no relative movement between them.

[0086] Furthermore, the film thickness correction plate is located directly below the magnetron sputtering source, with a distance of only a few millimeters from the source. In subsequent calculations, for the sake of simplification, it is assumed that the two are tightly attached to each other.

[0087] During the coating process, the magnetron sputtering source sputters thin film particles downwards, which then adhere to the mirror surface of the optical element.

[0088] To adjust film thickness uniformity using a film thickness correction plate, the coating apparatus performs the following movements: Driven by the drive shaft, the driven shaft rotates around the drive shaft, causing the optical elements to also move. The center point revolves around the center of the drive shaft; other points move in planetary orbits, that is, they revolve around the center of the drive shaft and rotate around the center of the mirror surface. In this way, every point on the mirror surface is in relative motion, and the film thickness correction plate does not constantly obstruct the center point. Therefore, the film thickness correction plate can be used to correct film thickness uniformity.

[0089] To achieve the adjustment of the mirror film thickness using a film thickness correction plate, the thickness distribution of the thin film on the optical element must first be calculated without using the film thickness correction plate. This includes the following steps:

[0090] S1: Establish a rectangular coordinate system in the vacuum chamber, with the height direction as the Z direction and the sputtering surface of the magnetron sputtering target as the Z=0 direction. The coordinate system conforms to the right-hand rule.

[0091] S2: The distance between the sputtering surface of the magnetron sputtering source and the coating surface of the optical element is h, and the coordinates of the sputtering surface of the magnetron sputtering source are (x...).t ,y t The coordinates of the optical element's coating surface are (x, 0), s ,y s The area element of any point on the coated surface is called ds, and the area element of the magnetron sputtering surface is called dσ. Then the thickness produced by dσ sputtering on ds is:

[0092]

[0093] in, Let be the angle between the line connecting dσ and ds and the normal to the sputtering surface;

[0094] θ is the angle between the line connecting dσ and ds and the normal to the coated surface;

[0095] r is the length of the line connecting dσ and ds;

[0096] n is the divergence characteristic constant of the magnetron sputtering source, which is determined experimentally;

[0097] in,

[0098] S3: Let the area of ​​the entire sputtering surface be D, and the sputtering time be t. Then, the thickness of the film sputtered by the entire sputtering surface at point ds on the coating surface within time t is:

[0099]

[0100] When t is large, it is assumed that the coating surfaces at the same radius have the same thickness. Therefore, it is only necessary to find the thickness of a certain point at several different radii to represent the film thickness at that radius.

[0101] S4: Using the thickness at the center point of the coating surface as the reference thickness, divide the thickness at other radii by the reference thickness to obtain the relative film thickness with the center point thickness as 1.

[0102] S5: Design a film thickness correction plate based on the relative thickness. The film thickness correction plate can block the sputtering width at different locations on the sputtering surface. No blocking is applied at locations with the smallest relative film thickness; at other locations, the width of the sputtering surface is blocked proportionally according to the relative film thickness.

[0103] S6: After designing the film thickness correction plate, place it below the sputtering surface, and then further fine-tune the shape of the correction plate based on experimental data.

[0104] The following is in conjunction with the appendix Figure 1-7 Further explanation of the technical solution of the present invention:

[0105] like Figure 1As shown, this invention provides a coating apparatus for depositing a center-hole-free optical element 5. The apparatus includes a drive shaft 1, a driven shaft 2, a gear set 3, a magnetron sputtering source 7, and a correction plate. Optionally, it also includes a support fixture 4. The drive shaft 1 and the driven shaft 2 mesh with each other via the gear set 3. The center of the optical element 5 is located on the axis of the driven shaft 2. The distance R between the axis of the driven shaft 2 and the axis of the drive shaft 1 is used to sputter thin film material. The sputtering surface 8 is the lower surface of the magnetron sputtering source 7. The thin film material is sputtered onto the coating surface 6 to form a thin film. The coating surface 6 is the upper surface of the optical element 5. The distance h between the sputtering surface 8 and the coating surface 6 is used to form a thin film. During coating, the drive shaft 1 rotates at a constant angular velocity, and the driven shaft, driven by the drive shaft, also rotates at a certain speed. The optical element 5 revolves and rotates around the center of the drive shaft, ensuring that every point on the coating surface 6 is in motion. Specifically, the center point of the coating surface 6 undergoes circular motion, while other points undergo planetary motion. This avoids the problem of fixed points on the coating surface 6 preventing the film thickness from being corrected by a film thickness correction plate. In this invention, the length of the magnetron sputtering source 7 is close to the radius of the optical element 5, i.e., the length of the magnetron sputtering source 7 is 90%-110% of the radius of the optical element 5, and the width of the magnetron sputtering source 7 is between 150mm and 200mm. The distance between the drive shaft and the driven shaft is between 450mm and 900mm, and the distance between the magnetron sputtering surface and the coating surface 6 is between 100mm and 200mm. At the start of coating, the relative positions of the magnetron sputtering source and the optical element are fixed. The magnetron sputtering source has coordinates (500, 2500) in the X-axis direction and (-90, 90) in the Y-axis direction; the center of the optical element has two-dimensional coordinates (800, 0) at the start of coating.

[0106] First, calculate the thickness distribution of the coating layer on the coated surface without a correction plate, including the following steps:

[0107] S1: Establish a rectangular coordinate system inside the vacuum chamber, as follows: Figure 2 and Figure 3 As shown, the center of the active axis is the Z-axis, and the plane containing the X-axis coincides with the sputtering surface;

[0108] S2: As Figure 4 The distance between the sputtering surface of the magnetron sputtering source and the coating surface of the optical element is h; for example Figure 2 The coordinates of the sputtering surface of the magnetron sputtering source are (x t ,y t The centerline of the magnetron sputtering source in the width direction coincides with the X-axis; the coordinates of the optical element coating surface are (x, 0), s ,y s The area element of any point on the coated surface is called ds, and the area element of the magnetron sputtering surface is called dσ. Then the thickness produced by dσ sputtering on ds is:

[0109]

[0110] in, Let be the angle between the line connecting dσ and ds and the normal to the sputtering surface;

[0111] θ is the angle between the line connecting dσ and ds and the normal to the coated surface;

[0112] r is the length of the line connecting dσ and ds;

[0113] n is the divergence characteristic constant of the magnetron sputtering source, which is determined experimentally;

[0114] in,

[0115] S3: Based on the characteristics of Earth's rotation and Figure 5 When the optical element rotates, the coordinates of the coated surface and r are:

[0116] x s =R·cos(ω·t)+ρ·cos(K·ω·t);

[0117] y s =R·sin(ω·t)-ρ·sin(K·ω·t);

[0118] r = [(x t -x s ) 2 +(y t -y s ) 2 +h 2 ] 1 / 2 ;

[0119] in:

[0120] K is the ratio of the angular velocity of the driven shaft to that of the driving shaft;

[0121] ω is the angular velocity of the driving shaft;

[0122] ρ is the distance from any point on the coating surface to the center of the coating surface, i.e., the radius at different positions;

[0123] t is the sputtering time;

[0124] S4: Let the area of ​​the entire sputtering surface be D, and the sputtering time be t. Then the thickness of the film sputtered by the entire sputtering surface at point ds on the coating surface within time t is:

[0125]

[0126] Furthermore, the formula can be expanded as follows:

[0127]

[0128]

[0129] x t-min Minimum X-coordinate of the sputtering surface;

[0130] x t-max : Maximum value of the X coordinate of the sputtering surface;

[0131] y t-min Minimum value of the Y-coordinate of the sputtering surface;

[0132] y t-max : Maximum value of the Y-coordinate of the sputtering surface.

[0133] S5: When t is large, it is assumed that the coating surface at the same radius has the same thickness. Therefore, the thickness of the coating surface at several different radii ρ from the center to the edge can represent the film thickness at that radius position.

[0134] S6: T ds Normalization is performed. Let the mirror surface of the optical element be divided into m rings of different radii from its center point to its edge, then T... ds There are m distinct elements, which form a column matrix T. ds =[T ds (1); T ds (2); T ds (3); ...; T ds (m-1),T ds (m)];T ds (1) is the film thickness at the location when ρ = 0, T ds (m) represents the film thickness at the edge of the optical element, denoted by T. ds (1) The film thickness is a unit film thickness, T ds Divide all elements by T ds (1), T is about to be ds Normalization was performed. The normalized film thickness distribution matrix is ​​named T:

[0135] That is, T = [T1; T2; T3; ... T m-1 ;T m ].

[0136] After obtaining the film thickness distribution data, the shape of the correction plate can be designed using this data to ensure a uniform film thickness distribution across the entire surface of the optical element. This includes the following steps:

[0137] S1: The normalized film thickness distribution T has been obtained through the above steps. Let the correction coefficient vector be C1, C1 = [C 1,1 C 1,2 C1,3 ;...C 1,m-1 C 1,m ]; 1 represents the first revision;

[0138] S2: Multiply the film thickness distribution T by the corresponding elements of the correction coefficient vector to obtain the correction value TC1, TC1 = [TC 1,1 ;TC 1,2 ;TC 1,3 ;...TC 1,m-1 ;TC 1,m ];

[0139] S3: The initial shape of the film thickness correction plate is a solid rectangular thin metal plate, and the size of its correction area is (x t-max -x t-min )×(y t-max -y t-min That is, the coordinates and size of the sputtering surface are the same as those of the magnetron sputtering source;

[0140] S4: Divide the film thickness correction plate into m equal regions along the x-axis. The coordinates of the two ends of the i-th region are: x t-min +[(x t-max -x t-min )*(i-1)] / (m-1) and x t-min +[(x t-max -x t-min )*i] / (m-1);

[0141] S5: Open the i-th region along the y-axis. During the first correction, the opening width coordinates are as follows: (x-axis coordinate is x...) t-min +[(x t-max -x t-min At point (i-1) / (m-1), the opening coordinate of the Y-axis is ±[(y t-max -y t-min )*TC1(min)] / [TC 1,i +TC1(min)];At the X-axis coordinate x t-min +[(x t-max -x t-min At position )*i] / (m-1), the opening coordinate of the Y-axis is ±[(y t-max -y t-min )*TC1(min)] / [TC 1,i+1 +TC1(min)], where TC1(min) is the non-zero minimum value in the correction value TC1 vector.

[0142] The coordinates of the four corners of the opening are as follows:

[0143]

[0144]

[0145]

[0146]

[0147] S6: Integrating the opening region yields the thickness of the sputtered material from the magnetron sputtering source after passing through the i-th region of the correction plate onto a point on the optical element mirror.

[0148]

[0149] In the above formula, X left =x1,X right = x2;

[0150] S7: By summing the film thicknesses of m regions, we can obtain the thickness value of a point on the mirror surface by the magnetron sputtering source after adding the film thickness correction plate.

[0151]

[0152] Here, mask1 represents the first correction;

[0153] S8: According to T mask1 The calculation formula calculates the film thickness distribution at different radii and plots the film thickness distribution curve. The film thickness distribution results are observed, and the correction coefficient is adjusted according to the film thickness distribution results. The correction is continuously adjusted (i.e., the correction coefficient vector is set to C2 next time, and the correction value TC2 is obtained...) until a satisfactory film thickness uniformity result is obtained.

[0154] Example:

[0155] Here is a detailed explanation using a specific example:

[0156] like Figure 1-4 In this example:

[0157] The distance between the driving shaft and the driven shaft is R = 800 mm;

[0158] The distance h between the sputtering surface and the coating surface is 150 mm;

[0159] The angular velocity ω of the drive shaft is π / 3;

[0160] The ratio K of the angular velocities of the driven shaft and the driving shaft is 37 / 110;

[0161] The sputtering time t is 300 seconds;

[0162] The divergence characteristic constant of the magnetron sputtering source is n = 4;

[0163] The radius of the coated surface is 2000 mm;

[0164] If 41 radii are selected on the coating surface, ranging from 0 mm to 2000 mm with an interval of 50 mm, then ρ = [0; 50; 100; 150; ...; 1950; 2000];

[0165] The coordinates of the sputtering surface are:

[0166] x t-min :500;

[0167] x t-max 2500;

[0168] y t-min -90;

[0169] y t-max :90;

[0170] Calculate using the formula:

[0171]

[0172] According to the formula, the relative film thickness from the center (0mm) to the edge (2000mm) can be calculated:

[0173] T=[1;1.001;1.0016;0.9915;0.9817;0.9398;0.8875;…;0.3097;0.2951;0.2826;0.2653];

[0174] The film thickness distribution follows a pattern where it is thickest at the center and thinnest at the edges. The film thickness distribution pattern is as follows: Figure 5 As shown;

[0175] The relative film thickness is multiplied by a correction coefficient vector, which is set according to the rule that the larger the relative film thickness, the larger the correction vector. After multiplying, the correction value TC1 is:

[0176] TC1=[1.1;1.1011;1.10176;1.09065;1.08581;…;0;0.2653];

[0177] Among them, 0.2653 is the minimum non-zero value in the correction value TC1 vector;

[0178] Using the formula, the entire target material can be divided into 40 regions, each 50mm in length, with the starting coordinates of its opening in the X direction as follows:

[0179] [(500,550); (550,600); (600,650); ...; (2400,2450); (2450,2500)];

[0180] Simultaneously, the coordinate values ​​of the sputtering width (i.e., the opening width in the Y direction) of each region can be calculated using the formula. The coordinate values ​​of the starting point of the sputtering width of each region are:

[0181] [(-17.48,17.48); (-17.47,17.47); (-17.46,17.46); ...; (-90,90)];

[0182] The openings in each region of the correction plate are trapezoidal in shape, and the X-coordinates of the trapezoidal openings are the same as the X-coordinates of each region, such as... Figure 8 As shown.

[0183] By substituting the above data into the formula, the thickness distribution of the film layer after the correction plate is applied can be obtained, and the result is as follows: Figure 6 As shown.

[0184] Based on the correction results, the correction coefficient is adjusted and the correction is continued until the ideal film thickness distribution is finally obtained, such as... Figure 7 As shown.

[0185] Based on the final data results, a film thickness correction plate is made and placed below the sputtering surface.

[0186] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

[0187] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A coating apparatus for a large-aperture, hole-free optical element, characterized in that, It includes a drive shaft (1), a driven shaft (2), a gear set (3), a magnetron sputtering source (7), and a correction plate; The gear set (3) includes a first gear and a second gear. The first gear is located on the upper end of the drive shaft (1), and the second gear is located on the upper end of the driven shaft (2). The first gear and the second gear mesh with each other. The rotation of the drive shaft (1) drives the rotation of the driven shaft (2) and its revolution around the axis of the drive shaft (1). The optical element (5) is fixedly installed above the second gear, and the geometric center of the optical element is located on the axis of the driven shaft (2). The optical element moves synchronously with the driven shaft (2). The magnetron sputtering source (7) is located above the optical element (5) and its position is fixed. The correction plate is installed between the magnetron sputtering source (7) and the optical element (5). The correction plate has an opening, and the magnetron sputtering source (7) coats the upper surface of the optical element (5) through the correction plate. The uniformity of the coating thickness is corrected by adjusting the openings on the correction plate. Specific methods include: S1 calculates the thickness distribution matrix T of the film layer on the coated surface without a correction plate; S2 sets the correction coefficient vector C; S3 multiplies the thickness distribution matrix T of the film layer on the coated surface without a correction plate with the correction coefficient vector C to obtain the correction value TC; S4 divides the correction plate into m regions and determines the coordinates of the openings in each region based on the correction value TC; m > 1; S5 calculates the thickness value of the film layer at each point on the coating surface under the opening coordinates of the correction plate in step S4; S6 plots the film thickness distribution curve based on the thickness values ​​of each point on the coated surface; S7 When the difference between the maximum and minimum values ​​of the film thickness distribution curve is greater than △T, return to step S2; when the difference between the maximum and minimum values ​​of the film thickness distribution curve is less than or equal to △T, the magnetron sputtering source (7) is used to deposit a film on the upper surface of the optical element (5) through a correction plate with the opening size obtained in step S4; △T is a threshold set according to the uniformity requirements of the film thickness. The correction plate is a correction plate in a coating device for a large-diameter, non-porous optical element, and the coating surface is the upper surface of the optical element (5). In step S1, the method for calculating the thickness distribution matrix T of the film layer on the coated surface without a correction plate includes: S1.1 Establish a coordinate system OXYZ; the origin of the coordinate system OXYZ is the intersection of the plane where the sputtering surface of the magnetron sputtering source (7) is located and the axis of the active axis (1). The X-axis points from the origin to the center of the sputtering surface, the Z-axis points from the origin upward along the axis of the active axis (1), and the Y-axis conforms to the right-hand rule. S1.2 Based on the coordinate system OXYZ, the thickness t of the film generated by the sputtering of the magnetron sputtering source (7) sputtering surface area element dσ on any point of the coating surface area element ds is calculated. ds ; S1.3 Establish the length r of the line connecting dσ and ds, and the expression for the coordinates of ds with respect to the sputtering time t; S1.4 According to t ds The length r of the line connecting dσ and ds with respect to sputtering time t, and the coordinates of ds with respect to sputtering time t, are used to determine the film thickness T sputtered by the entire sputtering surface onto ds within sputtering time t. ds ; S1.5 divides the coated surface into m rings of different radii from the center point to the edge, and assumes that the coated surface at the same radius has the same thickness. T ds Convert to a column matrix containing m distinct elements; S1.6 Normalize each element in the column matrix to obtain the thickness distribution matrix T of the film layer on the coating surface without a correction plate; Let Cp be the correction coefficient vector C set in step S2 during the p-th execution, where p = 1, 2, 3, ... Cp=[C p,1 ;C p,2 ;C p,3 ;…C p,m-1 ;C p,m ]; In step S3, the correction value obtained from the p-th execution of step S3 is... TCp=[TC p,1 TC p,2 TC p,3 TC p,m-1 TC p,m ]; In step S4, let the correction plate be rectangular, and the coordinates of the correction range of the correction plate be (x... t-max -x t-min )×(y t-max -y t-min Divide the correction plate into m equal regions along the X-axis. The coordinates of the two ends of the i-th region along the X-axis are: x t-min +[(x t-max -x t-min )×(i-1))] / (m-1) and x t-min +[(x t-max -x t-min )×i) / (m-1); The i-th region is opened up, and the coordinates of the four vertices of the opening are (x1, y1), (x2, y2), (x1, y3), and (x2, y4). Where TCp(min) is the non-zero minimum value in the correction value TCp vector; The diameter of large-aperture, holeless optical elements is 2–4 m; In step S1.6, the thickness distribution matrix T of the film layer on the coated surface without the correction plate is obtained as follows:

2. The coating apparatus for a large-aperture, hole-free optical element according to claim 1, characterized in that, It also includes supporting fixtures (4); The support fixture (4) includes several support rods, the upper end of which is fixedly connected to the lower surface of the optical element (5), and the lower end of which is fixedly connected to the second gear. The center of the support fixture (4) is located on the axis of the driven shaft (2).

3. A coating method for a large-aperture, hole-free optical element, characterized in that, The uniformity of the coating thickness is corrected by adjusting the openings on the correction plate, including: S1 calculates the thickness distribution matrix T of the film layer on the coated surface without a correction plate; S2 sets the correction coefficient vector C; S3 multiplies the thickness distribution matrix T of the film layer on the coated surface without a correction plate with the correction coefficient vector C to obtain the correction value TC; S4 divides the correction plate into m regions and determines the coordinates of the openings in each region based on the correction value TC; m > 1; S5 calculates the thickness value of the film layer at each point on the coating surface under the opening coordinates of the correction plate in step S4; S6 plots the film thickness distribution curve based on the thickness values ​​of each point on the coated surface; S7 When the difference between the maximum and minimum values ​​of the film thickness distribution curve is greater than △T, return to step S2; when the difference between the maximum and minimum values ​​of the film thickness distribution curve is less than or equal to △T, the magnetron sputtering source (7) is used to deposit a film on the upper surface of the optical element (5) through a correction plate with the opening size obtained in step S4; △T is a threshold set according to the uniformity requirements of the film thickness. The correction plate is the correction plate in the coating device for a large-diameter non-porous optical element according to claim 1, and the coating surface is the upper surface of the optical element (5). In step S1, the method for calculating the thickness distribution matrix T of the film layer on the coated surface without a correction plate includes: S1.1 Establish a coordinate system OXYZ; the origin of the coordinate system OXYZ is the intersection of the plane where the sputtering surface of the magnetron sputtering source (7) is located and the axis of the active axis (1). The X-axis points from the origin to the center of the sputtering surface, the Z-axis points from the origin upward along the axis of the active axis (1), and the Y-axis conforms to the right-hand rule. S1.2 Based on the coordinate system OXYZ, the thickness t of the film generated by the sputtering of the magnetron sputtering source (7) sputtering surface area element dσ on any point of the coating surface area element ds is calculated. ds ; S1.3 Establish the length r of the line connecting dσ and ds, and the expression for the coordinates of ds with respect to the sputtering time t; S1.4 According to t ds The length r of the line connecting dσ and ds with respect to sputtering time t, and the coordinates of ds with respect to sputtering time t, are used to determine the film thickness T sputtered by the entire sputtering surface onto ds within sputtering time t. ds ; S1.5 divides the coated surface into m rings of different radii from the center point to the edge, and assumes that the coated surface at the same radius has the same thickness. T ds Convert to a column matrix containing m distinct elements; S1.6 Normalize each element in the column matrix to obtain the thickness distribution matrix T of the film layer on the coating surface without a correction plate; Let Cp be the correction coefficient vector C set in step S2 during the p-th execution, where p = 1, 2, 3, ... Cp=[C p,1 ;C p,2 ;C p,3 ;…C p,m-1 ;C p,m ]; In step S3, the correction value obtained from the p-th execution of step S3 is... TCp=[TC p,1 TC p,2 TC p,3 TC p,m-1 TC p,m ]; In step S4, let the correction plate be rectangular, and the coordinates of the correction range of the correction plate be (x... t-max -x t-min )×(y t-max -y t-min Divide the correction plate into m equal regions along the X-axis. The coordinates of the two ends of the i-th region along the X-axis are: x t-min +[(x t-max -x t-min )×(i-1))] / (m-1) and x t-min +[(x t-max -x t-min )×i) / (m-1); The i-th region is opened up, and the coordinates of the four vertices of the opening are (x1, y1), (x2, y2), (x1, y3), and (x2, y4). Where TCp(min) is the non-zero minimum value in the correction value TCp vector.

4. The coating method for a large-aperture, hole-free optical element according to claim 3, characterized in that, In step S1.2, the film thickness t generated by the sputtering surface area element dσ of the magnetron sputtering source (7) sputtering the area element ds at any point on the coating surface is... ds for: in, θ is the angle between the line connecting dσ and ds and the normal to the sputtering surface; θ is the angle between the line connecting dσ and ds and the normal to the coating surface; n is the divergence characteristic constant of the magnetron sputtering source (7); in, h is the distance between the sputtering surface of the magnetron sputtering source and the coating surface of the optical element; In step S1.3: The coordinates of ds are (x s ,y s ,-h); x s =R·cos(ω·t)+ρ·cos(K·ω·t); y s =R·sin(ω·t)-ρ·sin(K·ω·t); r=[(x t -x s ) 2 +(y t -y s ) 2 +h 2 ] 1 / 2 ; Where R is the distance between the driving shaft (1) and the driven shaft (2), K is the ratio of the rotation angular velocities of the driven shaft (2) and the driving shaft (1), ω is the rotation angular velocity of the driving shaft (1), t is the sputtering time, ρ is the distance between any point on the coating surface and the center point of the coating surface, and the coordinates of dσ are (x t ,y t ,0).

5. The coating method for a large-aperture, hole-free optical element according to claim 4, characterized in that, In step S1.4, Where, x t-min The minimum value of the X-coordinate of the sputtering surface, x t-max The maximum value of the X-coordinate of the sputtering surface, y t-min The minimum value of the Y-coordinate of the sputtering surface, y t-max This represents the maximum value of the Y-coordinate of the sputtering surface.

6. The coating method for a large-aperture, hole-free optical element according to claim 5, characterized in that, In step S1.5, T ds Convert to a column matrix containing m distinct elements: T ds =[T ds (1);T ds (2);T ds (3);…;T ds (m-1),T ds (m)]; Among them, T ds (1) T is the film thickness at the position ρ = 0 on the coating surface. ds (m) represents the film thickness at the edge of the coated surface.

7. The coating method for a large-aperture, hole-free optical element according to claim 6, characterized in that, The method for step S5 is as follows: S5.1 Under the opening coordinates of the correction plate in step S4, the thickness of the coating surface sputtered by the magnetron sputtering source (7) through the i-th region of the correction plate to any point is obtained. in, S5.2 The thicknesses sputtered from m regions at any point on the coating surface are summed to obtain the thickness values ​​of the film layer at each point on the coating surface:

8. The coating method for a large-aperture, hole-free optical element according to claim 7, characterized in that, The film thickness distribution curve is plotted with ρ as the abscissa; When step S2 is executed for the second time or more, a correction coefficient vector C is set according to the film thickness distribution curve. Specifically, according to the film thickness distribution curve, the larger the film thickness at a certain position, the larger the element corresponding to that position in the correction coefficient vector C.

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