Development of a Web-Based e-Portal for Freeform Surfaced Lens Design and Manufacturing and Its Implementation Perspectives

At a Glance

Metadata	Details
Publication Date	2025-01-16
Journal	Machines
Authors	Shangkuan Liu, Kai Cheng, N. Dianat
Institutions	Brunel University of London
Citations	1
Analysis	Full AI Review Included

Executive Summary

This research details the development and validation of a web-based e-portal designed to streamline the personalized design and manufacturing of freeform surfaced varifocal lenses.

Core Innovation: The e-portal integrates lens design (using Winthrop’s model), surface modeling, ultraprecision toolpath generation, and virtual optical performance assessment into a single, highly responsive digital platform (Shiny/R-script).
Manufacturing Integration: The system generates a surface point cloud file directly from the prescription, which is essential for deterministic manufacturing processes like Single-Point Diamond Turning (SPDT) in Fast Tool Servo (FTS) mode.
Quality Assurance (Virtual): Optical performance is validated using COMSOL Multiphysics ray tracing simulations, adhering to ISO 8980-1 standards, ensuring quality is assessed in the ‘earlier digital’ stage.
Performance Validation: Ray tracing demonstrated significant optical improvement, reducing the Root Mean Square (RMS) radius of the rays from 1.82 x 10⁴ µm (before optics) to 5.79 x 10³ µm (after passing through the lens).
Customization Accuracy: The case study confirmed the designed surface achieved an equivalent spherical power in the near-vision zone (12.2 D) that matched the customer’s specified prescription (12.048 D) within a tolerance of less than 0.08 D.
Agility and Transparency: The platform is specifically engineered for personalized mass customization, offering users real-time visualization (2D contour plots, 3D topography) and transparent tracking of the design and manufacturing process.

Technical Specifications

Parameter	Value	Unit	Context
Case Study Sphere Power (SPH)	12.048	Diopter (D)	Customer Prescription Input
Case Study Addition Power (ADD)	2.0	Diopter (D)	Customer Prescription Input
Resulting Near-Vision Power	12.2	Diopter (D)	Designed optical surface output
Mean Optical Power Difference	1.8	Diopter (D)	Difference between near and far vision zones
Lens Material (Case Study)	Polycarbonate (PC) (C₁₆H₁₄O₃)_n	N/A	Selected material for simulation
Refractive Index (n)	1.5848	N/A	Polycarbonate value used in simulation
Abbe Number (V_d)	27.86	N/A	Polycarbonate value used in simulation
Standard Radiation Wavelength (λ)	550	nm	Ray tracing simulation setup
Calculated Center Thickness (CT)	1.1265	mm	Based on D, h, and n
Lens Blank Radius (h)	30	cm	Simulation setup parameter
RMS Radius (Ray Creation)	1.82 x 10⁴	µm	Ray distribution before passing through optics
RMS Radius (Image Plane)	5.79 x 10³	µm	Ray distribution result after passing through optics
Light Source to Optics Distance	50	mm	Ray tracing setup (ISO 8980-1 reference)
Optics to Image Plane Distance	80	mm	Ray tracing setup (Freeze wall distance)
Machining Tool Edge Radius	0.35	mm	SPDT experimental setup
Machining Tool Included Angle	60	degrees	Polycrystalline diamond tools used in SPDT

Key Methodologies

The integrated design and validation process relies on a structured, multi-module workflow:

Data Acquisition and Specification:
- Customer prescriptions (optical parameters: SPH, CYL, ADD) and geometric parameters (Corridor Length, Far-Zone Distance) are imported via the Shiny e-portal.
- Lens material is selected from a reference table, defining critical properties like refractive index (n) and Abbe number (V_d).
Computational Surface Modeling:
- The varifocal freeform surface is generated using Winthrop’s model functions, which define the meridional power law via an eighth-order polynomial power law.
- The platform calculates the bipolar progressive surface z(x,y) using R-Script language, ensuring the progressive corridor is accurately constructed.
Visualization and Data Export:
- The resulting surface is visualized in real-time via the portal using 2D contour plots (mean surface power distribution) and 3D topography models (Z point cloud distribution).
- The surface geometry is exported as a data point cloud file, serving as the input for manufacturing and simulation.
Virtual Optical Assessment (COMSOL Multiphysics):
- The surface data point cloud is imported into COMSOL Multiphysics 6.0 via the COMSOL API. Linear interpolation is used to generate the surface mesh, minimizing precision loss.
- A 3D spherical meniscus lens model is constructed, applying the freeform surface to the concave side and incorporating the selected material properties (n=1.5848 for PC).
- The ray tracing simulation environment is configured based on ISO 8980-1 standards, defining the light source, diaphragm, and image plane distances (50 mm and 80 mm, respectively).
- Simulation results (2D spot diagrams) are analyzed to validate optical performance, focal points, and aberration reduction.
Manufacturing Preparation:
- The validated surface point cloud file is prepared for export to the ultraprecision machining system (UPL250 machine), enabling deterministic manufacturing via SPDT/FTS.

Commercial Applications

Industry/Sector	Specific Application or Product	Technical Value Proposition
Ophthalmic Optics	High-Precision Progressive Addition Lenses (PALs) and Multifocal Contact Lenses.	Enables personalized mass customization, allowing local laboratories to deliver lenses tailored precisely to the wearer’s unique visual requirements and frame geometry.
Precision Optics Manufacturing	Production of Freeform Optics for Imaging Systems, Sensors, and Displays.	Provides a seamless digital workflow from design to manufacturing, ensuring high surface quality and minimizing defects caused by misalignment between design specifications and machine constraints.
E-Manufacturing / Digital Supply Chain	Agile, Web-Based Production Order Management and Service Delivery.	Facilitates real-time communication and data exchange among designers, manufacturers, and customers, enhancing responsiveness and reducing delivery time for complex, customized products.
Tooling and Machining	Optimization of Single-Point Diamond Turning (SPDT) Toolpaths.	Generates validated surface point cloud data that directly informs the Fast Tool Servo (FTS) toolpath, crucial for achieving nanometric surface roughness and high accuracy in ultraprecision machining.

View Original Abstract

In modern freeform surfaced optics manufacturing, ultraprecision machining through single-point diamond turning (SPDT) plays a crucial role due to its ability to meet the high accuracy demands of optical design and stringent surface quality requirements of the final optic. The process involves meticulous steps, including optic surface modeling and analysis, optic design, machining toolpath generation, and manufacturing. This paper presents an integrated approach to customized precision design and the manufacturing of freeform surfaced varifocal lenses through a web-based e-portal. The approach implements an e-portal-driven manufacturing system that seamlessly integrates lens design, modeling and analysis, toolpath generation for ultraprecision machining, mass personalized customization, and service delivery. The e-portal is specifically designed to meet the stringent demands of personalized mass customization, and to offer a highly interactive and transparent experience for the lens users. By using Shiny and R-script programming for platform development and combining COMSOL Multiphysics for the ray tracing simulation, the e-portal leverages open-source technologies to provide manufacturing service agility, responsiveness, and accessibility. Furthermore, the integration of R-script and Shiny programming allows for advanced interactive information processing, which also enables the e-portal-driven manufacturing system to be well suited for personalized complex products such as freeform surfaced lenses.

Tech Support

Original Source

DOI: https://doi.org/10.3390/machines13010059

References

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