High-precision milling and grinding forming method of convex-concave double off-axis high-order aspherical mirror

Abstract

The application discloses a high-precision milling and grinding forming processing method for convex-concave double-off-axis high-order aspheric mirrors, and belongs to the field of optical manufacturing; before processing of a concave surface and a convex surface, two upper and lower plane references and an outer cylindrical surface reference are ground on a cylindrical blank of the convex-concave double-off-axis high-order aspheric mirror, so as to position the concave surface processing; after the concave surface processing is completed, a positioning groove is processed on the outer cylindrical surface to calibrate an off-axis direction; the convex surface is positioned by using the positioning groove, the plane reference and the outer cylindrical surface reference, so as to ensure consistency of positioning in each process. Meanwhile, the shape precision is ensured by reasonably planning a processing path and a processing removal amount of equipment. The application solves the problems of deviation of the face shape precision, center deviation, face inclination angle and off-axis direction in the existing processing method.

Description

Technical Field

[0001] This invention relates to the field of optical manufacturing, specifically to a high-precision milling and forming method for convex-concave dual off-axis high-order aspherical mirrors. Background Technology

[0002] With the development of optical systems, the design of optical aspherical mirrors has become more complex, and the requirements for surface shape accuracy, center offset, surface tilt angle, and off-axis deviation are becoming increasingly stringent. Convex-concave dual off-axis aspherical mirrors primarily achieve effective transmission of parallel light in the central region. The effective transmission of parallel light is mainly affected by center offset, surface tilt angle, and off-axis rotation angle deviation. In existing technologies, convex-concave dual off-axis aspherical mirrors involve multiple processing steps and repeated positioning and clamping, and the processing methods do not control the off-axis direction. Furthermore, the lack of a unified processing positioning benchmark for the concave and convex surfaces results in significant deviations in the surface shape accuracy, center offset, surface tilt angle, and off-axis direction of the two surfaces in high-order convex-concave dual off-axis aspherical mirrors, thus affecting the imaging of the entire optical system.

[0003] Therefore, there is a need to provide a high-precision milling and forming method for convex and concave dual off-axis high-order aspherical mirrors to solve the above problems. Summary of the Invention

[0004] The technical problem to be solved:

[0005] To overcome the shortcomings of existing technologies, this invention provides a high-precision milling and forming method for convex and concave double off-axis high-order aspherical mirrors. Before machining the concave surface, a planar reference and an outer cylindrical reference are machined on the blank to position the concave surface. After the concave surface is machined, a positioning groove is machined on the outer cylindrical surface to mark the off-axis direction. During the machining of the convex surface, the positioning groove, the planar reference, and the outer cylindrical reference are used for positioning to ensure the consistency of positioning in each process. At the same time, by rationally planning the equipment processing path and the amount of material removed, the surface shape accuracy is guaranteed, thus solving the problems of deviation in surface shape accuracy, center offset, surface tilt angle, and off-axis direction of convex and concave double surfaces in existing processing methods.

[0006] The technical solution of this invention is: a high-precision milling forming method for convex and concave dual off-axis high-order aspherical mirrors, comprising the following steps:

[0007] The blank of a cylindrical convex-concave double off-axis aspherical mirror is ground and machined with two planes and an outer cylindrical surface, so that the two planes become the first reference plane and the second reference plane, and the outer cylindrical surface becomes the outer cylindrical reference plane.

[0008] The first reference surface of the blank is bonded and fixed to the tooling with beeswax, and then the tooling is installed on the worktable of the milling equipment.

[0009] First, the milling machine probe is used to align and determine the coordinate system for blank machining. Then, the workpiece position compensation function of the milling machine is used to perform position alignment compensation on the blank machining coordinate system, with the second reference surface as the Z-axis reference and the outer cylindrical reference surface as the X and Y-axis references.

[0010] Based on the concave surface design of the convex-concave dual off-axis aspherical mirror, the concave surface roughing and semi-finishing are performed on the second reference surface of the blank by a milling machine using a diamond grinding wheel;

[0011] Measure the surface dimensions after semi-finishing of the concave surface to correct the finished dimensions of the concave surface. Use a resin grinding wheel to finish the concave surface shape. The finishing trajectory is to process from the outside to the inside, and then process from the inside to the outside with the same processing parameters until the concave surface is finished.

[0012] A positioning groove is machined on the outer cylindrical surface according to the off-axis deviation requirements; thus, a semi-finished convex-concave double off-axis aspherical mirror is obtained;

[0013] Remove the tooling and heat it to separate the tooling and semi-finished product;

[0014] Flip the semi-finished product over and fix the concave edge to the tooling with beeswax. Then, install the tooling on the milling machine's worktable again.

[0015] The coordinate system for semi-finished product processing is determined by aligning the probe of the milling equipment. The coordinate system position of the semi-finished product is then aligned and compensated using the outer cylindrical datum surface, the first datum surface, and the positioning groove as references.

[0016] Based on the convex surface design of the convex-concave dual off-axis aspherical mirror, roughing and semi-finishing of the convex surface are performed on the first reference surface using a diamond grinding wheel on a milling machine.

[0017] Measure the surface dimensions after semi-finishing of the convex surface to correct the finished dimensions of the convex surface. Use a resin grinding wheel to finish the convex surface shape. The finishing trajectory is to process from the outside to the inside, and then process from the inside to the outside with the same processing parameters until the convex surface is finished.

[0018] The product's external dimensions are processed using milling equipment, ultimately yielding a convex-concave double off-axis high-order aspherical mirror.

[0019] A further technical solution of the present invention is as follows: the method of grinding the reference surface on the blank is to use a surface grinding machine to grind one plane of the blank, and then use the ground plane as a reference to grind another plane to form two reference planes, namely the first reference plane and the second reference plane; using the ground reference plane as the positioning bottom surface, an optical laser centering edge grinding machine is used to center and grind the outer cylindrical surface of the blank to form an outer cylindrical reference surface.

[0020] A further technical solution of the present invention is: when grinding the two reference planes, the flatness of the two reference planes is guaranteed to be ≤3μm, and the parallelism of the first reference plane and the second reference plane is guaranteed to be ≤3μm; when grinding the outer cylindrical surface, the cylindricity of the outer cylindrical reference surface is guaranteed to be ≤3μm, and the perpendicularity of the outer cylindrical reference surface and the reference plane is guaranteed to be ≤3μm.

[0021] A further technical solution of the present invention is: during concave surface processing, a second reference surface with a certain radial width is retained at the edge of the concave surface to form an annular positioning platform for surface positioning when flipping the convex surface.

[0022] A further technical solution of the present invention is: the tooling includes a fixed base and a milling mounting plate, the upper end of the fixed base and the milling mounting plate are coaxially and detachably connected, and the lower end of the fixed plate is detachably connected to the worktable of the milling equipment; when the blank and the tooling are bonded, the milling mounting plate and the blank after grinding the reference surface are heated, and the reference plane of the blank and the upper surface of the milling mounting plate facing away from the fixed base are coaxially bonded and fixed by yellow wax.

[0023] A further technical solution of the present invention is: the heating temperature is the melting temperature of beeswax, the beeswax is applied to the upper surface of the milling mounting plate and the reference plane of the blank, the two are bonded together, and can be fixed after cooling, and can be separated after reheating.

[0024] A further technical solution of the present invention is: when performing position alignment compensation on the blank machining coordinate system, the flatness of the second reference surface of the blank after alignment is measured so that it is consistent with the flatness of the second reference surface after grinding in step 1; when performing position alignment compensation on the semi-finished product machining coordinate system, the flatness of the first reference surface of the semi-finished product after alignment is measured so that it is consistent with the flatness of the first reference surface after grinding in step 1.

[0025] A further technical solution of the present invention is: when the milling equipment probe is aligned, the reference surface of the blank or semi-finished product is manually marked with points by the probe provided with the equipment for rough positioning, and the machining coordinate system is initially determined. Then, the final machining coordinates are determined by the alignment and compensation of the machining coordinate system.

[0026] A further technical solution of the present invention is as follows: the roughing of the concave and convex surfaces is carried out using a 200# diamond sintered grinding wheel, and a allowance of 0.3mm is left after roughing. The semi-finishing of the concave and convex surfaces is carried out using a 400# diamond sintered grinding wheel, and a allowance of 0.008mm is left after semi-finishing.

[0027] A further technical solution of the present invention is that the finishing of the concave and convex surfaces is carried out using an 800# resin grinding wheel, and the grinding amount is 0.004mm when machining from the outside to the inside and from the inside to the outside.

[0028] The beneficial effects of this invention are:

[0029] This invention addresses the issues of surface accuracy, center deviation, surface tilt angle, and off-axis direction deviation in the machining process. During machining, two planar references and an outer cylindrical reference are machined on the off-axis aspherical mirror blank. These serve as references for subsequent machining. When machining the concave surface, the planar and outer cylindrical references are used for positioning, and a positioning groove is machined on the outer cylindrical surface under the same positioning condition. When machining the convex surface, the planar reference, outer cylindrical reference, and the position of the positioning groove are used as references, thus ensuring the consistency of references between each milling and forming process. This invention considers the off-axis direction during the process of unifying the positioning references. The off-axis direction is calibrated by milling the corresponding positioning groove length based on the off-axis direction deviation, ensuring the deviation of the off-axis direction angle on both the convex and concave surfaces. This method enables the convex and concave dual off-axis aspherical mirrors to maintain reference consistency during multiple positioning and clamping operations, ensuring accurate machining of surface accuracy, center deviation, and surface tilt angle, while also achieving high machining efficiency.

[0030] This invention uses the product's own reference for positioning, eliminating the need for additional special tooling for reference positioning, thus facilitating processing.

[0031] The method of the present invention further improves the surface accuracy by using the machining trajectory to alternate between the outside to the inside and the inside to the outside during the finishing process, thereby offsetting the error caused by tool wear during the machining process. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a flowchart of a high-precision milling forming method for a convex-concave double off-axis high-order aspherical mirror according to the present invention;

[0034] Figure 2 This is a rough drawing of the blank after grinding the reference surface;

[0035] Figure 3 This is a schematic diagram of the reference plane for grinding the convex and concave double off-axis aspherical mirror blank in this invention;

[0036] Figure 4 This is a schematic diagram of the reference cylindrical surface for grinding the convex-concave double off-axis aspherical mirror blank in this invention;

[0037] Figure 5 This is a schematic diagram showing the bonding of the blank and tooling after grinding the reference surface.

[0038] Figure 6 This is a schematic diagram showing the position of the positioning groove in the off-axis direction;

[0039] Figure 7 A schematic diagram of the machining trajectory during concave surface finishing;

[0040] Figure 8 A schematic diagram of the finished convex-concave double off-axis high-order aspherical mirror after milling and forming (concave side).

[0041] Figure 9 A schematic diagram of the finished convex-concave double off-axis high-order aspherical mirror after milling and forming (convex side).

[0042] Figure 10 This is a schematic diagram for calibrating the off-axis direction using a directional groove;

[0043] Figure 11 This is a diagram illustrating the center offset and surface tilt angles of a convex-concave double off-axis high-order aspherical mirror.

[0044] In the diagram: 1. Blank, 1-1. First reference surface, 1-2. Second reference surface, 1-3. Outer cylindrical reference surface, 2. Tooling, 2-1. Fixed seat, 2-2. Milling mounting plate, 3. Semi-finished product of convex-concave dual off-axis aspherical mirror, 3-1. Positioning groove, 3-2. Annular positioning stage, 4. Finished product of convex-concave dual off-axis aspherical mirror, 4-1. Concave surface, 4-2. Convex surface, 5. Milling cutter, 6. Grinding table of surface grinding machine, 6-1. Grinding layer, 7. Grinding agent, 8. Adhesive film of surface grinding machine, 9. Adhesive layer, 10. Grinding wheel of optical laser centering edge grinding machine, A. Convex mechanical shaft, B. Concave mechanical shaft, C. Virtual optical axis, D. Actual optical axis. Detailed Implementation

[0045] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0046] An embodiment of the high-precision milling forming method for convex and concave dual off-axis high-order aspherical mirrors according to the present invention is shown in the flowchart below. Figure 1As shown. The main purpose of a double off-axis aspherical mirror is to achieve effective transmission of parallel light in the central region. However, the effective transmission of parallel light is primarily affected by deviations in the center offset, surface tilt angle, and off-axis rotation angle. To address the impact of these parameters on the effective transmission of parallel light in the central region of the double off-axis aspherical mirror, this invention establishes a unified machining datum during processing to control the deviations in the center offset, surface tilt angle, and off-axis rotation angle between the convex and concave aspherical surfaces. The off-axis direction is considered during the unification of the datum. The off-axis direction is calibrated by milling the corresponding tangential length of the positioning groove based on the off-axis direction deviation, ensuring the deviation of the off-axis direction angle on both the convex and concave surfaces. Furthermore, by planning the motion trajectory and removal amount of the CNC milling equipment during the finishing process, and utilizing the alternating finishing trajectory from the outside to the inside and from the inside to the outside, errors caused by tool wear during processing are offset, thus improving surface accuracy.

[0047] The processing method of this invention is described below with reference to a specific product example. Product information for the convex-concave dual off-axis high-order aspherical mirror is as follows:

[0048] The outer diameter of the blank is φ260mm, and the thickness is 30mm.

[0049] The major axis dimension of the ellipse after completion mm, minor axis dimension mm;

[0050] The equation of the concave off-axis aspherical surface is: +Ar 4 +Br 6 +Cr 8 +Dr 10 , c=1 / R, R=-530.64, A=1.9229e-10, B=8.03e-17, C=1.2e-23, D=0;

[0051] The equation of a convex off-axis aspherical surface is a parabola. c = 1 / R, R = -536.64 = K=-1.005, surface accuracy PV≤0.2λ, RMS≤0.02λ;

[0052] In the above formula, Z1 is the height of the vertex of the concave surface along the optical axis, Z2 is the height of the vertex of the convex surface along the optical axis; h is the radial distance from a point on the surface to the optical axis; c is the curvature at the vertex of the surface; R is the radius of curvature of the vertex; k is the quadratic surface coefficient; A, B, C and D are all higher-order coefficients used to compensate for aberrations.

[0053] The concave surface is 245.54 mm off-axis and has an inclination angle of 24.5101°.

[0054] The convex surface is 253.73 mm off-axis and has an inclination angle of 24.5101°.

[0055] Central deviation χ≤0.2';

[0056] The center thickness is 19.75 ± 0.1 mm.

[0057] Surface defect level B=V, where V represents level 5 standard.

[0058] The convex-concave double off-axis high-order aspherical mirrors described above are processed using the processing method of this invention, specifically including the following steps:

[0059] Step 1. Blank datum machining. Grind the upper and lower planes and the outer cylindrical surface of the cylindrical convex-concave double off-axis aspherical mirror blank 1. This grinds the two planes of blank 1 to form the first datum surface 1-1 and the second datum surface 1-2, and the outer cylindrical surface of blank 1 to form the outer cylindrical datum surface 1-3. The blank structure diagram after machining the datum surfaces is shown below. Figure 2 As shown. The two reference planes must meet the requirements for flatness and parallelism, and the outer cylindrical reference plane must meet the requirements for cylindricity and perpendicularity to the reference plane.

[0060] During the grinding of the reference surface, a surface grinder is used to first grind one plane of the blank 1, and then another plane is ground using the ground plane as a reference, forming two reference planes, namely the first reference plane 1-1 and the second reference plane 1-2; then, using either of the ground reference planes as the positioning bottom surface, an optical laser centering edge grinding machine is used to center and grind the outer cylindrical surface of the blank 1, forming the outer cylindrical reference surface 1-3. Specifically, as follows... Figure 3 As shown, during planar datum grinding, the blank 1 is bonded to the underside of the adhesive film 8 of the planar grinding machine via the adhesive layer 9. The grinding table 6 of the planar grinding machine has a grinding layer 6-1, and an abrasive 7 is placed between the grinding layer 6-1 and the lower surface of the blank 1. The grinding table 6 rotates, and the blank 1 revolves with the adhesive film 8 of the planar grinding machine. The upper and lower planes of the blank 1 are ground by the grinding layer 6-1 and the abrasive 7. When grinding the two datum planes, the flatness of the two datum planes is ensured to be ≤3μm, and the parallelism of the first datum plane 1-1 and the second datum plane 1-2 is ≤3μm. When grinding the outer cylindrical datum plane, as... Figure 4 As shown, using a pre-ground planar reference surface as the positioning base, the outer cylindrical surface of blank 1 is ground by the grinding wheel of an optical laser centering edge grinding machine to form outer cylindrical reference surfaces 1-3. During the grinding of the outer cylindrical surface, the cylindricity of the outer cylindrical reference surface is ensured to be ≤3μm, and the perpendicularity between the outer cylindrical reference surface and the reference plane is ≤3μm.

[0061] Step 2. Blank clamping and fixing. Install the blank with the machined reference surface onto the machining equipment. First, fix the first reference surface 1-1 and tooling 2 by bonding with beeswax. Then, install tooling 2 on the milling machine's worktable.

[0062] Specifically, such as Figure 5 As shown, based on the blank dimensions after grinding the reference surface in step 1 (in this embodiment, the center thickness of blank 1 after grinding the reference surface is 29.96mm, and the outer diameter is φ259.85mm), a corresponding machining fixture 2 is designed. Fixture 2 is used to connect blank 1 and machining equipment. Fixture 2 includes a fixed base 2-1 and a milling mounting plate 2-2. The upper end of the fixed base 2-1 and the milling mounting plate 2-2 are coaxially and detachably connected, and the lower end of the fixed plate 2-2 is detachably connected to the worktable of the milling equipment. The lower surface of the milling mounting plate 2-2 is connected to the fixed plate 2-2, and its upper surface is used to bond and fix blank 1. The dimensions of the milling mounting plate 2-2 are adapted to the dimensions of blank 1, and the diameter of the milling mounting plate 2-2 is smaller than the outer diameter of the blank. The fixed base 2-2 serves to connect the milling mounting plate 2-2 and the milling equipment. When bonding blank 1 and tooling 2, first clean the upper surface of the milling mounting plate 2-2 and the outer surface of blank 1 after grinding the reference surface. Then, place the milling mounting plate 2-2 and blank 1 on a hot plate and heat them to the melting temperature of beeswax. Apply beeswax to the upper surface of the milling mounting plate 2-2 and the first reference surface 1-1 of blank 1. Coaxially bond the first reference surface 1-1 of blank 1 to the upper surface of the milling mounting plate 2-2. After natural cooling, a fixed connection is achieved. Then, install the milling mounting plate 2-2 on the fixed base 2-1. The lower end of the fixed base 2-1 and the worktable of the milling equipment are detachably connected by bolts. This completes the installation of the blank onto the milling equipment.

[0063] Step 3. Blank Position Compensation and Alignment Before Concave Surface Machining. First, the blank's second datum surface 1-2 and outer cylindrical datum surface 1-3 are manually marked with the milling machine's built-in probe for rough positioning, initially determining the blank's machining coordinate system. Then, using the milling machine's workpiece position compensation function, the second datum surface 1-2 is used as the Z-axis datum, and the outer cylindrical datum surface 1-3 is used as the X and Y-axis datums to perform position alignment compensation on the blank's machining coordinate system. The flatness of the second datum surface 1-2 after alignment is measured using a plane measurement program. The measurement result is the same as the flatness result of the second datum surface 1-2 after grinding, determining the final machining coordinates, and concave surface machining can then proceed. In this embodiment, the flatness of the second datum surface 1-2 after alignment is measured to be 0.0025μm, and the cylindricity of the outer cylindrical datum surface 1-3 is 0.0018μm, both within the required range, using the milling machine's plane measurement program.

[0064] Step 4. Roughing and Semi-finishing of the Concave Surface. Based on the concave surface dimensions of the convex-concave dual-off-axis aspherical mirror model, the machining path is planned using the CAM software of the milling equipment, and the concave surface is roughed and semi-finished by the milling equipment. During roughing, a 200# diamond sintered grinding wheel is used to roughen the concave surface shape on the second reference surface 1-2 of the blank. The concave surface shape is located at the center of the second reference surface 1-2, and a certain radial width of the second reference surface 1-2 is reserved at the edge of the concave surface to form an annular positioning platform 3-2 for surface positioning when turning over to machine the convex surface, so as to retain the positioning reference of the second reference surface 1-2. After the roughing is completed, a 0.3mm allowance is left for semi-finishing. After the roughing is completed, a 400# diamond sintered grinding wheel is used to semi-finish the concave surface shape, leaving a 0.008mm allowance after semi-finishing.

[0065] Step 5. Finish machining the concave surface and machining the positioning groove. Using the in-machine measurement system of the milling machine, accurately measure the surface dimensions of the concave surface after semi-finishing. Based on the measured dimensions, correct the final dimensions required for finishing the concave surface. Plan the machining path using the CAM software of the milling machine. The milling machine uses an 800# resin grinding wheel to finish the concave surface. The finishing path involves machining once from the outside in, and then once from the inside out using the same machining parameters, completing the concave surface machining. Figure 7 As shown, Figure 7 This is a schematic diagram of the machining trajectory during the finishing of the concave surface. When the milling cutter 5 of the milling equipment processes the surface from the outside in and from the inside out, the grinding depth is 0.004 mm. By alternating between outside-in and inside-out milling under the same processing parameters, errors caused by tool wear during the machining process are offset. After the concave surface is machined, without changing the clamping position, a positioning groove 3-1 is machined on the outer cylindrical surface of the blank 1 according to the off-axis deviation requirement. The off-axis direction is calibrated by the tangential length of the positioning groove 3-1. At this point, the semi-finished product 3 of the convex-concave double off-axis aspherical mirror is obtained, with the concave surface and positioning groove 3-1 already machined on the semi-finished product 3.

[0066] Step 6. Flip and Fix the Semi-finished Product. After completing Step 5, remove the milling mounting plate 2-2 and heat it on a hot plate until the beeswax melts, separating the milling mounting plate 2-2 from the semi-finished product 3 of the convex-concave dual off-axis aspherical mirror. Then flip the semi-finished product 3 over and fix the annular positioning platform 3-2 on the concave edge of the semi-finished product to the upper surface of the milling mounting plate 2-2 with beeswax. After the beeswax cools and solidifies, fix the upper end of the milling mounting plate 2-2 and the fixing plate 2-2 again, so that the first reference surface 1-1 previously bonded to the milling mounting plate 2-2 is on top, and the second reference surface 1-2 is fixed to the milling mounting plate 2-2. During this process, the fixing seat 2-1 is installed on the milling equipment worktable without being removed.

[0067] Step 7. Position Compensation and Alignment of Semi-finished Product Before Convex Surface Machining. First, use the probe built into the milling machine to manually mark points on the first datum surface 1-1 and the outer cylindrical datum surface 1-3 for rough positioning, initially determining the coordinate system for semi-finished product machining. Then, using the workpiece position compensation function of the milling machine, with the first datum surface 1-1 as the Z-axis datum and the outer cylindrical datum surface 1-3 as the X and Y-axis datums, perform position alignment compensation on the coordinate system for semi-finished product machining. Measure the flatness of the first datum surface 1-1 after alignment using a plane measurement program, ensuring that the measurement result is the same as the flatness result of the first datum surface 1-1 after grinding, and determine the final machining coordinates, then proceed with convex surface machining.

[0068] Step 8. Roughing and Semi-finishing of the Convex Surface. Based on the convex surface design of the convex-concave dual-off-axis aspherical mirror model, the machining path is planned using the CAM software of the milling equipment. The milling equipment uses a diamond grinding wheel to perform roughing and semi-finishing of the convex surface on the first reference surface 1-1. During roughing, a 200# diamond sintered grinding wheel is used to roughen the convex surface shape on the first reference surface 1-1 of the blank. After roughing, a semi-finishing allowance of 0.3mm is left. After roughing, a 400# diamond sintered grinding wheel is used to semi-finish the convex surface shape, leaving a semi-finishing allowance of 0.008mm.

[0069] Step 9. Convex Surface Finishing. Using the in-machine measurement system of the milling machine, accurately measure the surface dimensions of the convex surface after semi-finishing. Based on the measured dimensions of the semi-finished surface, correct the finished dimensions required for the convex surface finishing. Plan the machining path using the CAM software of the milling machine. The milling machine uses an 800# resin grinding wheel to finish the concave surface. The finishing path is to machine once from the outside to the inside, and then once from the inside to the outside with the same machining parameters. The grinding amount is 0.004mm for both the outside-to-inside and inside-to-outside machining. By alternating between outside-to-inside and inside-to-outside machining with the same machining parameters, the error caused by tool wear is eliminated.

[0070] Step 10. Machining the outer dimensions based on the product model. Based on the 3D model dimensions of the convex-concave double off-axis high-order aspherical mirror, the machining path is generated using the CNC milling CAM software of the milling equipment. The outer dimensions are then machined by the milling equipment. The final machining ellipse dimensions are φ227.43mm for the major axis and φ207.96mm for the minor axis. After machining, the product is separated from the milling mounting plate 2-2 by heating, finally obtaining the finished convex-concave double off-axis high-order aspherical mirror. The finished product image is shown below. Figure 8 , Figure 9 As shown, Figure 8 Concave surface 4-1 is shown. Figure 9 Convex surface 4-2 is shown.

[0071] Center offset refers to the deviation in the X and Y directions between the theoretical position of an off-axis aspherical lens in its parent mirror's aspherical coordinate system and its actual position after machining and assembly. Plane tilt angle refers to the angular deviation between the normal to the curved surface of the off-axis aspherical lens and the system's mechanical reference axis. For a more intuitive understanding of the center offset and plane tilt angle of convex-concave double off-axis high-order aspherical lenses, please refer to... Figure 10 and Figure 11 .

[0072] like Figure 10 As shown in the figure, b1 represents the orientation groove deviation, and a1 represents the off-axis angle variation. This invention calibrates the off-axis direction by milling the corresponding positioning groove 3-1 tangential length according to the off-axis direction deviation requirement, thus ensuring the deviation of the off-axis direction angle on both the convex and concave sides. Figure 11 As shown in the figure, A is the convex mechanical axis, B is the concave mechanical axis, C is the virtual optical axis, D is the actual optical axis, Δa is the surface tilt angle of the concave surface, Δb is the surface tilt angle of the convex surface, Δx1 is the center offset of the convex surface, and Δx2 is the center offset of the concave surface. Through this invention, the consistency of the reference between each process is maintained during the processing. Combined with the reasonable arrangement of the motion trajectory of the finishing process, the accuracy of the surface shape, center offset and surface tilt angle are guaranteed, and the out-of-tolerance is avoided.

[0073] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for high-precision milling and forming of a convex-concave dual-off-axis high-order aspherical mirror, characterized in that, Includes the following steps: The blank of a cylindrical convex-concave double off-axis aspherical mirror is ground and machined with two planes and an outer cylindrical surface, so that the two planes become the first reference plane and the second reference plane, and the outer cylindrical surface becomes the outer cylindrical reference plane. The first reference surface of the blank and the tooling are bonded and fixed with beeswax, and then the tooling is installed on the worktable of the milling equipment. First, the milling machine probe is used to align and determine the coordinate system for blank machining. Then, the workpiece position compensation function of the milling machine is used to perform position alignment compensation on the blank machining coordinate system, with the second reference surface as the Z-axis reference and the outer cylindrical reference surface as the X and Y-axis references. Based on the concave surface design of the convex-concave dual off-axis aspherical mirror, the concave surface roughing and semi-finishing are performed on the second reference surface of the blank by a milling machine using a diamond grinding wheel; Measure the surface dimensions after semi-finishing of the concave surface to correct the finished dimensions of the concave surface. Use a resin grinding wheel to finish the concave surface shape. The finishing trajectory is to process from the outside to the inside, and then process from the inside to the outside with the same processing parameters until the concave surface is finished. A positioning groove is machined on the outer cylindrical surface according to the off-axis deviation requirements; thus, a semi-finished convex-concave double off-axis aspherical mirror is obtained; Remove the tooling and heat it to separate the tooling and semi-finished product; Flip the semi-finished product over and fix the concave edge and tooling together with beeswax. Then, install the tooling onto the milling machine's worktable again. The coordinate system for semi-finished product processing is determined by aligning the probe of the milling equipment. The coordinate system position of the semi-finished product is then aligned and compensated using the outer cylindrical datum surface, the first datum surface, and the positioning groove as references. Based on the convex surface design of the convex-concave dual off-axis aspherical mirror, roughing and semi-finishing of the convex surface are performed on the first reference surface using a diamond grinding wheel on a milling machine. Measure the surface dimensions after semi-finishing of the convex surface to correct the finished dimensions of the convex surface. Use a resin grinding wheel to finish the convex surface shape. The finishing trajectory is to process from the outside to the inside, and then process from the inside to the outside with the same processing parameters until the convex surface is finished. The product's external dimensions are processed using milling equipment, ultimately yielding a convex-concave double off-axis high-order aspherical mirror.

2. The processing method according to claim 1, characterized in that, The method for grinding the reference surface on the blank is as follows: use a surface grinder to grind one plane of the blank, and then use the ground plane as a reference to grind another plane to form two reference planes, namely the first reference plane and the second reference plane; use the ground reference plane as the positioning bottom surface, and use an optical laser centering edge grinding machine to center and grind the outer cylindrical surface of the blank to form the outer cylindrical reference surface.

3. The processing method according to claim 2, characterized in that, When grinding two reference planes, ensure that the flatness of the two reference planes is ≤3μm and the parallelism of the first reference plane and the second reference plane is ≤3μm; when grinding the outer cylindrical surface, ensure that the cylindricity of the outer cylindrical reference surface is ≤3μm and the perpendicularity of the outer cylindrical reference surface and the reference plane is ≤3μm.

4. The processing method according to claim 1, characterized in that, When machining a concave surface, a second reference surface with a certain radial width is retained at the edge of the concave surface to form an annular positioning platform, which is used for surface positioning when machining a convex surface.

5. The processing method according to claim 1, characterized in that, The tooling includes a fixed base and a milling mounting plate. The upper end of the fixed base and the milling mounting plate are coaxially and detachably connected, and the lower end of the fixed plate is detachably connected to the worktable of the milling equipment. When bonding the blank and the tooling, the milling mounting plate and the blank after grinding the reference surface are heated, and the reference plane of the blank and the upper surface of the milling mounting plate facing away from the fixed base are coaxially bonded and fixed by using beeswax.

6. The processing method according to claim 5, characterized in that, The heating temperature is the melting temperature of beeswax. Apply beeswax to the upper surface of the milling mounting plate and the reference plane of the blank, and bond the two together. After cooling, it can be fixed. It can be separated after reheating.

7. The processing method according to claim 1, characterized in that, When performing position alignment compensation on the blank machining coordinate system, the flatness of the second reference surface of the blank after alignment is measured to ensure that it is consistent with the flatness of the second reference surface after grinding in step 1; when performing position alignment compensation on the semi-finished product machining coordinate system, the flatness of the first reference surface of the semi-finished product after alignment is measured to ensure that it is consistent with the flatness of the first reference surface after grinding in step 1.

8. The processing method according to claim 1, characterized in that, When aligning the milling machine probe, the reference surface of the blank or semi-finished product is manually marked with points by the probe provided with the machine for rough positioning, and the machining coordinate system is initially determined. Then, the final machining coordinates are determined by aligning and compensating the machining coordinate system.

9. The processing method according to claim 1, characterized in that, The roughing of both the concave and convex surfaces is performed using a 200# diamond sintered grinding wheel, with a allowance of 0.3mm after roughing. The semi-finishing of both the concave and convex surfaces is performed using a 400# diamond sintered grinding wheel, with a allowance of 0.008mm after semi-finishing.

10. The processing method according to claim 1, characterized in that, The finishing of both the concave and convex surfaces is performed using an 800# resin grinding wheel. When machining from the outside in and from the inside out, the grinding amount is 0.004 mm.

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