Vortex Surface Ridges Reduce Stray Light in Metal Mold Machining
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Solution Overview
Problem
Manufacturing of vortex lenses using metal molds results in circular or spiral processing marks at the center of the vortex surface, leading to stray light generation due to concentrated stress during machining, which cannot form the desired ring-shaped intensity distribution.
Innovation Solution
A light flux controlling member with a vortex surface featuring a continuous or stepwise spiral shape and radially disposed ridges or grooves around the center, where the height decreases toward the center, formed using a shaping metal mold with a complementary vortex shaping surface, processed through radial cutting to minimize processing marks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the vortex surface is formed by cutting in concentric circles around the center of the spiral, then the vortex lens can be manufactured using conventional machining methods, but circular processing marks are formed at the center and outer periphery portions of the vortex surface, leading to stray light generation
Solution Approach 1:
The vortex surface is divided into multiple regions: a central region without processing marks, an intermediate region with reduced processing marks, and an outer region with controlled processing marks. This segmentation is achieved by controlling the cutting depth and path to create ridges with decreasing heights toward the center, effectively isolating the harmful processing marks from the optical path.
Solution Approach 2:
The processing marks that would normally cause stray light are converted into beneficial ridges with specific height profiles. These ridges, formed by controlled machining, actually reduce stray light by creating a gradual transition zone that directs light away from the optical axis while maintaining the vortex phase modulation function.
2Shape
If the center of the vortex forming surface is machined, then the vortex shape is formed, but stress is concentrated resulting in formation of large spiral-shaped processing marks (crush) in the center
Solution Approach 1:
Different regions of the vortex surface are given different machining qualities: the outer regions receive full-depth cutting to form the vortex shape, while the central region receives reduced or no cutting to avoid stress concentration. This creates ridges with spatially varying heights that eliminate processing marks at the critical center location while maintaining the overall vortex structure.
3Ease of manufacture
If the center of the vortex surface is made flat to avoid processing marks, then processing simplicity is improved, but high intensity light passes through the flat part and the desired ring-shaped intensity distribution cannot be formed
Solution Approach 1:
Instead of a static flat center, the solution implements a dynamic gradient structure where ridge heights continuously decrease toward the center. This creates a transitional zone that naturally guides light intensity distribution, allowing the center to remain structurally simple while optically functional, as the gradual height reduction automatically produces the desired ring-shaped intensity pattern.
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 solution effectively suppresses stray light generation at the center of the vortex surface, enabling the formation of a ring-shaped intensity distribution and improving the optical performance by reducing processing marks and stress concentrations.
Implementation Method 1
A vortex lens (vortex phase plate) is an optical element (light flux control member) with a surface (vortex surface) having a continuous or stepwise spiral shape. When light with a Gaussian distribution with a high intensity at the center portion is passed through a vortex lens, it is converted into light with a ring-shaped intensity distribution, with a marked decrease in intensity at the center portion.
Implementation Method 2
a plurality of ridges radially disposed around a center of a spiral in the vortex surface... When the light converted into a ring-shaped intensity distribution by the vortex lens is injected into the multimode fiber, the light can be suppressed from directly entering the center portion of the core
Data Source
AI summary
A light flux controlling member includes: a vortex surface having a continuous or stepwise spiral shape; and a plurality of ridges radially disposed around a center of a spiral in the vortex surface. The height of the plurality of ridges decreases toward the center.