What Are the Manufacturing Technologies of Aspheric Lenses?

Precision Glass Molding for Manufacturing Aspheric Lenses

Precision glass molding is a manufacturing technology that heats an optical glass core to high temperatures to give its surface sufficient plasticity. It is then molded through an aspheric mold, gradually cooled to room temperature, and the optical glass core maintains the molded shape. Creating the mold has a high initial startup cost because it must be precisely made from highly durable materials that maintain a smooth surface and account for any potential shrinkage of the glass core in order to produce the desired aspheric molded shape. However, once the mold is complete, the marginal cost of manufacturing each lens is lower than that of standard manufacturing technology, making it particularly suitable for high-volume production settings.

Precision Polishing for Manufacturing Aspheric Lenses

For many years, aspheric lenses required individual grinding and polishing when being machined. Although the step-by-step process for manufacturing custom aspheric lenses has not changed significantly, major advancements in manufacturing technology have improved the achievable maximum precision. Most notably, computer-controlled precision polishing can automatically adjust tool dwell parameters to polish high points that require more polishing. If high polishing quality is needed, magneto-rheological finishing (MRF) technology can be used to perfect the surface. Compared to standard polishing techniques, MRF technology can precisely control the removal position while maintaining a high removal rate, thus achieving high-performance polishing in a shorter time. Other manufacturing techniques generally require a specific mold where each lens has its unique mold, but polishing uses standard tools, making it the primary choice for prototype manufacturing andlow-volumeproduction applications.

Computer-Controlled Polishing

Magneto-Rheological Finishing(MRF)

Hybrid Molding for Manufacturing Aspheric Lenses

Hybrid molding uses a standard spherical surface, such as that of an achromatic lens, as a base. By including a thin layer of photosensitive polymer in the aspheric mold, the spherical surface is cast into the mold, ultimately producing an aspheric surface. This technology uses a diamond-ground aspheric mold and a glass achromatic lens (though other types of single and double lenses can also be used). The photosensitive polymer is injected into the aspheric mold, which then casts the spherical surface. Finally, this technique produces an aspheric achromatic lens by compressing at room temperature and UV curing the two surfaces. The optical properties of this lens combine the optical properties exhibited by its individual components: achromatism and spherical aberration correction. The image below shows the manufacturing process of hybrid lenses. Hybrid molding is very suitable for high-precision, high-volume applications. Besides requiring extremely high performance, the cost savings from high-volume production can offset the high initial tool costs.

Hybrid Molding Technology

Plastic Molding for Aspheric Lenses

In addition to the glass manufacturing technologies mentioned above, there is also a unique plastic manufacturing technology. Plastic molding involves injecting molten plastic into an aspheric mold. Compared to glass, plastic has poorer thermal stability and compressive strength, requiring special treatment to achieve equivalent aspheric lenses. However, the advantages of plastic include being lightweight, easy to shape, and can be integrated with a fixture to produce a single module. Although the selection of optically qualified plastics is limited, plastic aspheric lenses are low-cost and lightweight, making them a design choice for certain applications.