Ultra-precision turning method for an optical micro-structured lens mold

Abstract

The present invention discloses an ultra-precision turning method for an optical micro-structure lens mold, belonging to the field of optical ultra-precision machining. Technical solution: The ultra-precision turning method includes a linear turning process and an arc tool retraction process. In the linear turning process, the traditional circumferential path is converted into a linear path, and the movement trajectory of the tool during turning is a straight line relative to the lens mold; the arc tool retraction process is a process in which the tool moves away from the lens mold by a certain distance along the axis where it is located and then returns to the initial tool contact point in an arc path in the reverse direction. In the arc path area, the tool trajectory is an arc, and the projections of the starting point and the ending point of the arc on the XOY plane coincide with the tool contact points at the edge of the linear path. The optical lens mold involved is placed off-axis in a fixed fixture, and the surface of the mold is provided with a micro-structured optical surface in the form of a linear array.

Description

Technical Field

[0001] The present invention belongs to the field of optical ultra-precision machining, and particularly relates to an ultra-precision turning method for an optical micro-structure lens mold. Background Art

[0002] Optical micro-structure design and manufacturing play an important role in fields such as multi-focus focusing of light beams, local shaping, and uniform illumination, and are one of the key technologies for the development of the optical industry towards integration, light weight, and high performance. Currently, optical micro-structure spectacle lenses designed based on the myopic defocus theory are the mainstream products for the correction and prevention of adolescent myopia. The optical molds used for the injection molding of these spectacle lenses usually have a spherical or aspherical surface as the base, and a certain array of micro-structures is provided on the surface. The micro-structures are generally spherical or aspherical with various diameters such as millimeters or micrometers. These curved surfaces focus light in front of or behind the human eye retina to achieve a defocus effect, thereby controlling the elongation of the eyeball. The existing ultra-precision turning technology is the main method for manufacturing optical molds, and the involved tool paths are basically spiral or circular. For example, the invention patent CN201810565011.2 discloses a "Tool Path Optimization Method for Slow Tool Servo Turning of Micro-Lens Arrays", which mainly optimizes the effective tool path area, but has little improvement for micro-structures with small diameters, high density, and linear arrays. Summary of the Invention

[0003] The purpose of the present invention is to provide an ultra-precision tool feeding method for an optical micro-structure lens mold with a linear array, which optimizes the tool path through two processes of combining linear turning and circular arc tool retraction, so that the tool is a straight line relative to the mold surface during turning, effectively reducing the response frequency of the lathe Z-axis when processing high-density and small-diameter linear array micro-structures with a traditional spiral path.

[0004] The technical solution for achieving the purpose of the present invention is as follows:

[0005] One is the design of the linear turning path. In the XOY plane, the traditional circular path is converted into a linear path, and the tool movement trajectory is a straight line relative to the lens mold. In the nth linear path Q ns Q ne the distance ρ between each tool contact point and the rotation center O point nt is defined as follows: (4)

[0006] (5)

[0007] n is the number of path circles, L is the off-axis distance between the mold center O1 and the rotation center O, the value range of L is 1.5r ≤ L ≤ R - r, R is the fixture radius, l is the spacing between adjacent paths, r is the mold radius, Q ns is the initial tool contact point, Qns is the end tool contact point, θ nt is the distance ρ nt is the angle with the X-axis, θ n1 is the distance ρ n1 (The initial tool contact point Q ns is the angle between the distance from the center of rotation O) and the X-axis;

[0008] Second, the design of the arc retraction path, that is, the tool moves a distance Δz along the Z direction from the end tool contact point Q ns to leave the lens mold and then returns to the initial tool contact point Q along an arc path ns The distance ρ of each point on the arc path from the center of rotation O in the XOY plane is defined as follows: ng Define as follows:

[0009] (6)

[0010] ρ n1 is the distance from the initial tool contact point Q ns to the center of rotation O, θ ng is the rotation angle of the arc path;

[0011] The lathe completes the mold turning along the cylindrical coordinate system composed of the linear feed axis X-axis, the rotary axis C-axis and the linear feed axis Z-axis along (ρ nt , θ nt , Z(ρ n1 , θ nt )); The Z(ρ n1 , θ nt ) is the sagittal height equation of the microstructured lens mold.

[0012] In the above technical solution: The maximum value of the angle θ n1 (i.e., the turning angle range of the tool) does not exceed 70 degrees, and the distance ΔZ moved during the retraction process only needs to exceed the edge sagittal height point on the same path by 50 um, that is:

[0013] ΔZ = 0.05 + Z(ρ n1 , θ n1 ) (7)

[0014] The above description is only an overview of the method of the present invention. In order to be able to understand the technical means of the present invention more clearly, it can be implemented according to the content of the specification. And in order to make the above and other objects, features and advantages of the present invention more obvious and understandable, the following specific preferred embodiments are given and described in detail in conjunction with the accompanying drawings as follows. Description of the Drawings

[0015] Figure 1 is a schematic diagram of a linear array microstructured lens mold

[0016] Figure 2 It is a schematic diagram of the turning path design method;

[0017] Figure 3 It is a schematic diagram of the ultra-precision turning process;

[0018] Figure 4 It is a complete tool path; Specific implementation mode

[0019] The technical solution of the present invention will be further elaborated below in conjunction with the accompanying drawings and embodiments.

[0020] Refer to the attached Figure 1 , the diameter of the linear array micro-structure lens mold to be processed is 76 mm, the base is a spherical surface with a radius of curvature of 224 mm, and linear micro-structures are uniformly distributed on the base surface with a spacing of 2 mm in the X direction and 1.5 mm in the Y direction. The morphology of each micro-structure is an ellipse with a major axis of 1 mm and a minor axis of 0.5 mm.

[0021] Refer to the attached Figure 2 and the attached Figure 3 , according to the parameters of the linear array micro-structure lens mold, design the ultra-precision turning path. Among them, the diameter of the fixed fixture is 230 mm, the distance L between the mold center and the fixture center is 75 mm, the total number of path circles n = 15200, the adjacent path interval is l = 0.005 mm, and the distance ρ between each tool contact point and the rotation center O point in the 7600th linear path nt is as follows:

[0022] (8)

[0023] At this time, the distance ρ between each point on the circular arc path and the rotation center O point in the XOY plane ng is as follows:

[0024] (9)

[0025] where θ nt The sampling interval is 0.004°. Before ultra-precision turning, the same weight needs to be placed at the position symmetric to the mold on the fixture to reduce the dynamic balance error.

[0026] The attached Figure 4 is the cylindrical coordinate system (ρ nt , θ nt , Z(ρ n1 , θ nt((The tool path under)) enables the lathe tool to complete the mold turning along this tool path. Since the tool is in a straight line relative to the mold surface during turning, which is consistent with the linear array, compared with the traditional helical machining method, the number of responses of the tool's Z-axis during one machining cycle is reduced during linear turning, and the completed microstructure profile is clearer and more complete. The use of an arc path for tool withdrawal not only optimizes the ineffective path of the entire tool path, but also enables the tool to smoothly transition to the next turning path, reducing the following error of the spindle and improving the turning accuracy.

Claims

1. An ultra-precision turning method for an optical microstructure lens mold, characterized in that : Relates to an ultra-precision linear turning feed method for an optical micro-structure lens mold; the ultra-precision linear turning feed method includes two processes, one is the linear turning process, and the other is the arc retraction process; The described linear turning process converts the traditional circular path into a linear path in the XOY plane. The tool motion trajectory is a straight line relative to the lens mold. In the nth linear path Q ns Q ne the distances from each tool contact point to the rotation center O point ρ nt are defined as follows: (1) (2) n is the number of path circles, L is the off-axis distance between the die center O1 and the rotation center O, and the value range of L is 1.2 r ≤ L ≤ R - r , R is the fixture radius, l is the spacing between adjacent paths, r is the die radius, Q ns is the initial tool contact point, Q ns is the end tool contact point, θ nt is the distance ρ nt with the X-axis angle, θ n1 is the distance ρ n1 (the distance between the initial tool contact point Q ns and the rotation center O) with the X-axis angle; The described circular arc retraction process, that is, the tool moves a distance Δz along the Z direction to leave the lens mold from the end tool contact point Q ns and then returns to the initial tool contact point Q along a circular arc path ns after leaving the lens mold; the distance between each point on the circular arc path and the rotation center O point in the XOY plane ρ ng is defined as follows: (3) ρ n1 is the initial tool contact point Q ns the distance from the center of rotation O, θ ng is the arc path rotation angle; The lathe completes the turning of the mold in the cylindrical coordinate system composed of the linear feed axis X-axis, the rotary axis C-axis, and the linear feed axis Z-axis along ( ρ nt , θ nt , Z ( ρ n1 , θ nt )); the Z ( ρ n1 , θ nt ) is the equation of the sagittal height of the microstructure lens mold.

2. The ultra-precision turning method of an optical microstructure lens mold according to claim 1, characterized in that : The optical micro-structure lens mold is a type of optical spectacle lens mold with a spherical surface as the base and micro-structures in the form of a linear array on the surface; the micro-structures are aspherical surfaces with various diameters of 0.4 to 1.0 mm, and this surface focuses light in front of or behind the human eye retina to achieve a defocus effect.

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