Processing device and method for aspherical lens

Abstract

The application discloses a kind of processing device of aspheric lens, including left clamping piece and right clamping piece for clamping lens blank;It further includes cylindrical grinding wheel for lens blank preliminary processing, opening grinding wheel for precision polishing, cylindrical polishing head for polishing and magnetic flow grinding head for surface type finishing;In the process of precision polishing, polishing and surface type finishing, lens blank is clamped using clamping assembly, and clamping assembly includes jig, one end of jig is clamping end, its non-clamping end is connected with plane base, and the other end of plane base is connected with main shaft.The application also discloses a kind of processing method applied to the above-mentioned aspheric lens.The application adopts the control mode of measuring and correcting center deviation of aspheric curvature surface in time when processing aspheric curvature surface in different processing procedures, different steps, to ensure the independent rotation symmetry axis center deviation of single aspheric curvature surface, and then indirectly ensure the center deviation requirement of entire aspheric surface.

Description

Technical Field

[0001] This invention belongs to the field of optical lens processing technology, and in particular relates to an apparatus and method for processing aspherical lenses. Background Technology

[0002] Unlike ordinary spherical lenses, aspherical optical lenses cannot have their center offset corrected by optical edge grinding after the two optical surfaces are machined. Currently, for a product with two aspherical surfaces, each has its own independent and fixed axis of rotational symmetry. When machining aspherical surfaces, it is necessary to ensure the center offset of each surface's curvature and its axis of rotation. By obtaining the center offset of the independent axis of rotation in the machining process, the center offset of the two surfaces' curvature and the common axis of rotation can be obtained. At present, it is difficult to ensure that the axis of rotational symmetry of the aspherical surface has a high degree of coaxiality with the two surfaces' curvature during machining, resulting in low center offset accuracy for aspherical surfaces. Summary of the Invention

[0003] Purpose of the invention: The purpose of this invention is to provide a processing apparatus for aspherical lenses with high processing accuracy, and another purpose of this invention is to provide a processing method for aspherical lenses with high processing accuracy.

[0004] Technical solution: The aspherical lens processing device of the present invention includes a left clamping member and a right clamping member for clamping the lens blank; it also includes a cylindrical grinding wheel for preliminary processing of the lens blank, an open grinding wheel for precision grinding, a cylindrical polishing head for polishing, and a magnetic flow grinding head for surface finishing; in the processes of precision grinding, polishing, and surface finishing, the clamping assembly is used to clamp the lens blank. The clamping assembly includes a fixture, one end of which is a clamping end, and its non-clamping end is connected to a flat base. The other end of the flat base is connected to a spindle.

[0005] The center offset angle between the lens blank and the cylindrical grinding wheel during cylindrical section grinding is no greater than 0.5′.

[0006] This also includes a dial indicator for measurement.

[0007] This also includes a reflector center offset meter for measuring the eccentricity of curvature surfaces.

[0008] A method for manufacturing an aspherical lens includes the following steps:

[0009] Step 1: Based on the aspherical finished product drawing, determine the thickness H and diameter D of the lens blank;

[0010] Step 2: Cut the lens blank into radius (R) and use a cylindrical grinding wheel to perform preliminary processing on the lens blank;

[0011] Step 3: Place the pre-processed lens blank on the clamping assembly, measure it, and then bond the lens blank to the fixture of the clamping assembly.

[0012] Step 4: Tighten the lens blank and fixture onto the spindle of the precision grinding machine, and use an open grinding wheel for precision grinding to ensure that the center deviation of the lens blank is less than 0.25′.

[0013] Step 5: Polish the finely ground lens blank with a cylindrical polishing head until the eccentricity of the curvature surface measured by the reflection center eccentricity meter is less than 0.25 minutes, and mark the corresponding point on the cylindrical surface with the maximum direction on the cylindrical surface.

[0014] Step 6: Use a magnetohydrodynamic (MHD) grinding head to refine the surface of the polished lens blank. Adjust the position of the MHD grinding head to ensure that the eccentricity of the curvature surface is less than 0.25′.

[0015] Step 7: Remove the finished fixture containing the lens blank, soak it in solvent, and remove the lens; repeat the above steps for processing aspherical surfaces to process another aspherical surface.

[0016] Step 8: Adjust and test the parameters of the lens after processing.

[0017] In step 1, the thickness H of the lens blank is determined to be the sum of the allowance for the opening radius on both sides, the allowance for fine grinding on both sides, and the allowance for polishing on both sides. The maximum contour radii R1 and R2 of the aspherical surface are calculated to ensure the edge grinding threshold. Secondary optimization is performed on the maximum contour radii R1 and R2, based on the height loss formula. Where h is the height loss and R is the radius. The diameter is given, and the thickness of the blank is increased by the difference in height between the two curvatures to determine the final thickness H of the blank.

[0018] The step 1, determining the diameter D of the lens blank, includes calculating the linear value C of the center offset caused by the processing of the lens blank based on the radius R, where C = 0.291(n-1)*L. ’ *X / 1000, where n represents the transmittance of the lens, L ’ Let X be the focal length at the top of the image, and R be the center offset caused by the opening R machining, in minutes. According to Δt=C*D / R, the linear value is converted into edge thickness difference, and the outer diameter machining allowance of the blank is calculated based on the edge thickness difference of the lens: Δt=|ΔD(ΔD+D)(R1+R2-d) / 2R1*R2| is the outer diameter machining allowance, d is the distance between the two convex surfaces of the lens, that is, the blank thickness H. Based on the diameter of the lens and the outer diameter machining allowance, the outer diameter dimension of the blank is determined to be D+ΔD+2f, where f is the edge effect error value when the aspherical surface is polished.

[0019] When the lens blank and fixture are connected to any spindle, a dial indicator must be used to check the machining parameters of the lens blank to ensure that the diameter difference in the reverse direction of the cylindrical surface is less than 0.0005mm and the roundness runout is less than 0.0001mm.

[0020] In step 8, the adjustment of the lens after processing includes adjusting the reflective eccentricity of any side of the lens to be less than 0.25′, and the maximum eccentricity to be less than 0.5′.

[0021] The marginal effect error value f ranges from 1 mm to 3 mm.

[0022] Beneficial effects: Compared with the prior art, the present invention has the following significant advancements: The present invention determines the size of the lens blank to be processed based on the size of the target aspherical lens, uses the cylindrical surface of the lens blank as the processing reference, and then completes the processing of the aspherical surfaces on both sides. The aspherical surface processing process includes grinding, polishing, and surface refinement. Before each processing step, the size error and radial runout of the cylindrical surface are radially detected. During the processing of the aspherical curvature surface in the above steps, the center deviation is measured and corrected in a timely manner, thereby ensuring the center deviation of the independent rotational symmetry axis of a single aspherical surface, and thus ensuring the center deviation of the entire aspherical surface. The accuracy of the processed product is significantly improved. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of an aspherical lens;

[0024] Figure 2 This is a schematic diagram of the initial processing stage of the processing equipment.

[0025] Figure 3 This is a schematic diagram showing the measurement after the initial processing by the processing device.

[0026] Figure 4 A schematic diagram of a machining device using an open-face grinding wheel;

[0027] Figure 5 This is a schematic diagram of the polishing process using a processing device.

[0028] Figure 6 This is a schematic diagram of a machining device using a magnetorheological grinding head.

[0029] Figure 7 A schematic diagram for measuring reflection eccentricity in a processing device. Detailed Implementation

[0030] like Figures 1-7As shown, the aspherical lens processing apparatus of the present invention includes a left clamping member 6 and a right clamping member 5 for clamping the lens blank 1; it also includes a cylindrical grinding wheel 4 for preliminary processing of the lens blank 1, an open grinding wheel 12 for precision grinding, a cylindrical polishing head 14 for polishing, and a magnetohydrodynamic grinding head 15 for surface finishing; in the processes of precision grinding, polishing, and surface finishing, the clamping assembly is used to clamp the lens blank 1. The clamping assembly includes a fixture 9, one end of which is a clamping end, and its non-clamping end is connected to a flat base 11. The other end of the flat base 11 is connected to a spindle. When the cylindrical section of the lens blank 1 is being ground, the center offset angle 7 between it and the cylindrical grinding wheel 4 is no greater than 0.5′. The apparatus also includes a dial indicator 8 for measurement and a reflection center offset meter 13 for measuring the eccentricity of the curvature surface.

[0031] The specific processing method includes the following steps: First, based on the aspherical finished product drawing, determine the thickness H of the lens blank 1, which is the allowance for the radius of the two sides + the allowance for the fine grinding of the two sides + the allowance for the polishing of the two sides. Calculate the maximum contour radii R1 and R2 of the aspherical surface, and simultaneously, based on the edge grinding threshold: To facilitate machining and improve the centering accuracy of edge grinding, the maximum contours R1 and R2 are optimized a second time. Specifically, the closer the R value is to a hemisphere, the better for centering. This is based on the height loss formula. Where h is the height loss and R is the radius. Given the diameter, the blank thickness is increased by the difference in height between the two curvatures, determining the final blank thickness H; based on the opening radius R, the linear value C is calculated for the center offset generated during lens processing, C = 0.291(n-1)*L'*X / 1000, where n represents the lens transmittance, L... ’Let X be the focal length at the top of the image, and X be the center offset caused by the R machining process, in minutes. The center offset is 10 minutes. Then, according to Δt = C*D / R2, the linear value is converted into the edge thickness difference, and the outer diameter machining allowance of the blank is calculated based on the edge thickness difference of the lens: Δt = |ΔD(ΔD+D)(R1+R2-d) / 2R1*R2| is the outer diameter machining allowance, and d is the distance between the two convex surfaces of the lens; that is, the blank thickness H. Based on the diameter of the lens and the outer diameter machining allowance, the outer diameter of the blank is determined to be D+ΔD. At the same time, the edge effect error value f during aspherical polishing must be considered, that is, the surface shape is not good at a certain distance from the edge. This is an inherent processing defect of aspherical small grinding head polishing. In this embodiment, f is taken as 2mm. The blank tilt must also be considered because the blank... The radial offset caused by the tilt of the cylindrical surface is c = tanY*L, where Y represents the tilt angle of the blank surface relative to the axis. It is controlled within 1 minute. When the lens edge thickness L is short, the value is very small, so the influence of radial offset is ignored. However, when the lens edge thickness is long, even if the tilt angle is small, the resulting radial offset will be large, which will cause the cylindrical surface of the lens to deviate along the length direction. When performing center offset correction, because the radial offset is large, the outer diameter of the outer cylindrical surface of the lens cannot be ground, which leads to the incompleteness of the outer cylindrical surface and affects the accuracy reference of the cylindrical surface during subsequent processing. Since the outer diameter allowance of aspherical surfaces is large, it can generally be ignored. At this time, the blank diameter is D = D1 + ΔD1 + 2f, f = 2mm, and the thickness is H. The blank size is determined at this time.

[0032] Lens opening radius (R): Using a traditional opening radius machine, the lens is opened to the required thickness and curvature, especially ensuring that the critical parameter of lens eccentricity is <10. ′ To prevent excessive eccentricity, which would make edge grinding more difficult.

[0033] The lens blank 1 is placed between the left clamping part 6 and the right clamping part 5 of the edging machine and clamped, ensuring that the center deviation is 0.5 points. The corresponding lens edge thickness difference is less than 0.01mm. During subsequent measurements, the accuracy of the lens edge thickness difference is adjusted. At the same time, the rotating shaft 3 used to fix the cylindrical grinding wheel 4 and the clamping part 2 are adjusted to ensure that the tolerance of the large and small ends of the cylindrical surface is 0.0005mm and the roundness is less than 0.0001mm. This ensures the high accuracy of the cylindrical surface reference of the lens blank 1 and ensures that the influence of the lens center deviation caused by the measurement error itself is minimal. The outer diameter is machined to the required outer diameter D of the lens blank 1.

[0034] Screw the flat base 11 onto the bonding machine, place the lens blank 1 into the groove end of the fixture 9, and adjust the relative positions of 9 and 11 to be centered and aligned. Tighten the screw 10 appropriately, then move the fixture 9 and the lens blank 1, and use the measurement reference of the curvature surface of the lens blank 1 until the error of the dial indicator 8 on the cylindrical surface of the lens blank 1 in the opposite direction of the diameter is less than 0.0005, and the runout in the roundness direction is less than 0.0001. The lens blank 1 bonded to the fixture must be rotated at least once. Then, use high-strength adhesive to connect the lens. The adhesive will gradually harden over time. Remove the overall fixture 9 that connects the lens.

[0035] Tighten the integral fixture 9 with the lens blank 1 attached to it onto the spindle of the precision grinding machine. Adjust the position of the fixture 9 and the flat base 11. Ensure that the error of the large and small heads of the dial indicator 8 on the cylindrical surface of the lens blank 1 is less than 0.0005 in the cylindrical direction and the runout in the roundness direction is less than 0.0001. Rotate the lens blank 1 attached to the fixture at least once. Adjust the edge angle of the open grinding wheel 12. Compile the equation for the aspherical surface. Start the machine to begin precision grinding and control the machining allowance reserved for subsequent processes. At this time, adjust the position of the grinding head to ensure that the center deviation of the lens is less than 0.25 points.

[0036] Take out the finely ground lens blank 1 along with the integral fixture 9. Tighten the integral fixture 9, which has the lens blank 1 attached, onto the main shaft of the polishing machine. Adjust the positions of fixtures 9 and 11. Ensure that the error of the large and small heads of the dial indicator 8, which is placed on the cylindrical surface of the lens blank 1, is less than 0.0005 in the cylindrical direction and the runout in the roundness direction is less than 0.0001. Rotate the lens blank 1 attached to the fixture at least one revolution. Adjust the edge angle of the polishing head 14. Compile the equation for the aspherical surface. Start the machine to begin polishing and control the machining allowance reserved for subsequent processes. At this time, adjust the position of the polishing head. Use a reflection center offset instrument to measure the curvature surface eccentricity, which is less than 0.25 points. Using the contact point of the dial indicator 8 on the cylindrical surface of the lens blank 1, mark the corresponding point on the cylindrical surface where the eccentricity is less than 0.25 points. This will help determine the maximum deviation direction of the center offset when processing the other side and the impact on the center offset of the entire lens.

[0037] Tighten the integral fixture with the lens blank 1 attached to the machine spindle. Adjust the position of the fixture 9 and the flat base 11. Use a dial indicator 8 to measure the diameter error of the cylindrical surface of the lens blank 1; the error should be less than 0.0005 mm, and the radial runout should be less than 0.0001 mm. Rotate the lens blank 1 at least one revolution. Use magnetorheological finishing to refine the surface shape. At this time, adjust the position of the magnetorheological grinding head and use a reflection center offset instrument to measure the eccentricity of the curvature surface; the eccentricity should be less than 0.25. ′ Take out the complete fixture of the processed lens blank 1, soak it in a special solvent, and then take out the lens blank 1.

[0038] Repeat the above processing steps to process the aspherical surface on the other side. During polishing with the small grinding head, the position of the direction of maximum eccentricity deviation of aspherical surface 1 is aligned with or opposite to the previous cylindrical surface mark, and its reflection eccentricity direction is opposite by 0.25. ′ The same is 0.25 ′ +0.25 ′ =0.5 ′ Remove the pre-processed lens blank 1 from the overall fixture, soak it in a special solvent, and then remove the lens blank 1. Use a grinding machine to process the lens blank 1, and adjust the eccentricity of one reflective surface to less than 0.25. ′ Therefore, its maximum eccentricity is less than 0.25. ′ The outer diameter is machined to the required outer diameter, while ensuring the required coaxiality of the lens and the required parameters such as the diameter of the cylindrical section.

Claims

1. A method for processing an aspherical lens, characterized in that: The method is carried out using the following apparatus, which includes a left clamping member (6) and a right clamping member (5) for clamping the lens blank (1); it also includes a cylindrical grinding wheel (4) for preliminary processing of the lens blank (1), an open grinding wheel (12) for precision grinding, a cylindrical polishing head (14) for polishing, and a magnetic flow grinding head (15) for surface finishing; in the process of precision grinding, polishing and surface finishing, the clamping assembly is used to clamp the lens blank (1), the clamping assembly includes a fixture (9), one end of the fixture (9) is the clamping end, its non-clamping end is connected to the flat base (11), and the other end of the flat base (11) is connected to the spindle; the cylindrical surface of the lens blank is used as the processing reference and then the aspherical surfaces on both sides are processed. The above processing method specifically includes the following steps: Step 1: Based on the aspherical finished product drawing, determine the thickness H and diameter D of the lens blank (1); Step 2: Open the lens blank (1) by cutting the lens radius and use a cylindrical grinding wheel (4) to perform preliminary processing on the lens blank (1); Step 3: Place the pre-processed lens blank (1) on the clamping assembly, measure it, and then bond the lens blank (1) to the fixture (9) of the clamping assembly; Step 4: Tighten the lens blank (1) and fixture (9) onto the spindle of the precision grinding machine, and use an open grinding wheel (12) for precision grinding to ensure that the center deviation of the lens blank (1) is less than 0.25′. Step 5: Polish the finely ground lens blank (1) with a cylindrical polishing head (14) until the eccentricity of the curvature surface measured by the reflection center eccentricity meter (13) is less than 0.25′, and mark the corresponding point on the cylindrical surface where the maximum direction of the eccentricity is less than 0.25′. Step 6: Use a magnetohydrodynamic grinding head (15) to refine the surface of the polished lens blank (1). Adjust the position of the magnetohydrodynamic grinding head (15) to ensure that the eccentricity of the curvature surface is less than 0.25′. Step 7: Take out the jig (9) containing the processed lens blank (1), soak it in solvent, and take out the lens; repeat the above steps for processing aspherical surfaces to process another aspherical surface; Step 8: Adjust and test the parameters of the lens after processing.

2. The method for processing an aspherical lens according to claim 1, characterized in that, The center offset angle (7) between the lens blank (1) and the cylindrical grinding wheel (4) during cylindrical section grinding is not greater than 0.5′.

3. The method for processing an aspherical lens according to claim 1, characterized in that, It also includes a dial indicator (8) for measurement.

4. The method for processing an aspherical lens according to claim 1, characterized in that, It also includes a reflective center eccentricity meter (13) for measuring the eccentricity of curvature surfaces.

5. The method for processing an aspherical lens according to claim 1, characterized in that, Step 1 determines the thickness H of the lens blank (1) as the sum of the allowance for the opening radius on both sides, the allowance for fine grinding on both sides, and the allowance for polishing on both sides. The maximum contour radii R1 and R2 of the aspherical surface are calculated to ensure the edge grinding threshold: Z = Ø1 / 4R1 + Ø2 / 4R2 > 0.

15. Secondary optimization is performed on the maximum contour radii R1 and R2, according to the height loss formula h = R - (R 2 -(Ø / 2) 2 ) 1 / 2 Where h is the height loss, R is the radius, Ø is the diameter, and the increase in blank thickness is the difference in height loss between the two curvatures, thus determining the final thickness H of the blank.

6. The method for processing an aspherical lens according to claim 1, characterized in that, The step 1, determining the diameter D of the lens blank (1), includes calculating the linear value C of the center offset generated during the processing of the lens blank (1) based on the radius R, where C = 0.291(n-1)*L. ’ *X / 1000, where n represents the transmittance of the lens, L ’ Let X be the focal length at the top of the image, and R be the center offset caused by the opening R machining, in minutes. According to Δt=C*D / R, the linear value is converted into edge thickness difference, and the outer diameter machining allowance of the blank is calculated based on the edge thickness difference of the lens. Δt=|ΔD(ΔD+D)(R1+R2-d) / 2R1*R2|, where ΔD is the outer diameter machining allowance, d is the distance between the two convex surfaces of the lens, i.e. the blank thickness H. Based on the diameter of the lens and the outer diameter machining allowance, the outer diameter of the blank is determined to be D+ΔD+2f, where f is the edge effect error value when polishing aspherical surfaces.

7. The method for processing an aspherical lens according to claim 1, characterized in that, When the lens blank (1) and the fixture (9) are connected to any spindle, a dial indicator (8) must be used to check the processing parameters of the lens blank (1) to ensure that the diameter of its cylindrical surface is less than 0.0005mm in the opposite direction and the roundness runout is less than 0.0001mm.

8. The method for processing an aspherical lens according to claim 1, characterized in that, The adjustment of the lens after processing in step 8 includes adjusting the reflective eccentricity of any side of the lens to be less than 0.25′, and the maximum eccentricity to be less than 0.5′.

9. The method for processing an aspherical lens according to claim 6, characterized in that, The marginal effect error value f ranges from 1 mm to 3 mm.

Images