Polishing Tool Spherical Zone Shape for Optical Surface Accuracy
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Solution Overview
Problem
Conventional polishing methods for optical elements, such as lenses, often result in surface distortion due to uneven peripheral velocities across the polishing surface, leading to reduced shape accuracy.
Innovation Solution
A polishing method utilizing a polishing tool with a spherical zone shape and a concentric hole, where the polishing surface has a smaller peripheral velocity ratio and a ring width coefficient greater than or equal to 0.9, to minimize surface distortion and enhance accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional polishing tool with constant radius of curvature is used, then the polishing process is simple, but surface distortion occurs due to uneven peripheral velocities
Solution Approach 1:
The polishing tool surface is designed with a spherical zone shape instead of a constant radius of curvature. The radius of curvature varies in the radial direction, being smaller near the outer peripheral portion and larger near the inner peripheral portion. This curvature variation compensates for the uneven peripheral velocities, reducing surface distortion while maintaining manufacturing feasibility.
Solution Approach 2:
Different regions of the polishing tool surface have different radii of curvature tailored to their specific functional requirements. The outer peripheral portion with smaller radius addresses the higher linear velocity zone, while the inner peripheral portion with larger radius addresses the lower linear velocity zone, creating localized optimization across the surface.
2Manufacturing precision
If the polishing surface covers the entire workpiece diameter, then productivity is high, but surface distortion increases due to velocity variation
Solution Approach 1:
The polishing tool surface is segmented into different radial zones, each with optimized radius of curvature. The spherical zone shape divides the surface into an outer peripheral portion and an inner peripheral portion, allowing independent optimization of each zone to address velocity variation while maintaining overall polishing coverage.
Solution Approach 2:
The radius of curvature parameter is varied radially across the polishing surface. By making the radius smaller at the outer periphery and larger at the inner periphery, the tool compensates for the velocity distribution, maintaining surface accuracy across the full polishing area without sacrificing productivity.
3Productivity
If the polishing tool rotates at high speed to increase productivity, then polishing efficiency improves, but surface distortion worsens due to centrifugal effects and velocity variation
Solution Approach 1:
The spherical zone shape with radially varying curvature is specifically designed to counteract the effects of high-speed rotation. The smaller radius at the outer periphery and larger radius at the inner periphery create a velocity compensation effect that maintains surface accuracy even at high polishing speeds.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method effectively suppresses surface distortion and improves the surface accuracy of optical elements by maintaining a controlled peripheral velocity ratio and ring width coefficient, while maintaining workability and cost-effectiveness.
Implementation Method 1
polishing is performed by sliding a polishing tool and a workpiece against each other
Implementation Method 2
abrasive grains for polishing, interposed at an interface between the polishing tool and the workpiece, are used for polishing
Implementation Method 3
swinging the polishing tool at a constant swing width with respect to a reference point while rotating the polishing tool around the rotation axis
Data Source
AI summary
A polishing method comprising: arranging a polishing tool and a workpiece on lower and upper shaft sides of a polishing device, respectively, the polishing tool including: a polishing surface having a spherical zone shape; and a hole that is provided inside the polishing surface and concentric with an outer edge of the polishing surface around a rotation axis on a projection plane orthogonal to the rotation axis, a ratio of an outer diameter of the polishing surface to an inner diameter of the polishing surface being greater than 1.0 and 6.0 or less; and swinging the polishing tool relative to a reference point while rotating the polishing tool around the rotation axis. The reference point is positioned where a straight line, which passes through a center of the workpiece and intersects with the rotation axis, passes through a center of a spherical zone of the polishing surface in width direction.