Manufacturing of a microlens array mold by a two-step method combining microindentation and precision polishing

Area of Science:

• Materials Science and Engineering
• Optical Engineering
• Manufacturing Technology

Background:

• Conventional methods for microlens array mold fabrication, such as single-point diamond turning, can be costly and lack flexibility.
• There is a need for alternative, low-cost, and adaptable manufacturing techniques for producing spherical microlens array molds.

Purpose of the Study:

• To propose and demonstrate a novel two-step method for manufacturing microlens array molds.
• To evaluate the cost-effectiveness, flexibility, and performance of the proposed method compared to conventional approaches.
• To confirm the feasibility of fabricating hexagonal microlens array molds with specific parameters.

Main Methods:

• A two-step process combining microindentation using steel balls and precision polishing.
• Hexagonal arrangement of steel balls pressed into a mold surface to create microdimples.
• Removal of material pileups via precision polishing to achieve the desired mold surface.
• Replication of the microlens array mold onto poly(methyl methacrylate) substrates using precision compression molding.

Main Results:

• Demonstrated feasibility with a hexagonal microlens array mold with a 1.58 mm curvature radius.
• Optical surface profiler measurements confirmed improved hardness and surface quality within the microdimples compared to steel balls.
• Replicated polymer microlens arrays exhibited high fidelity, uniformity, and good surface roughness.

Conclusions:

• The proposed two-step method is a viable, low-cost alternative for fabricating microlens array molds.
• The method offers significant advantages in cost and flexibility for spherical microlens array mold fabrication.
• The technique is suitable for high-volume production of precise optical elements, including those for integrated light-emitting diodes.