Molded polymer optics are a rapidly developing technology that is increasingly being used in complex applications.[1] Due to technological advances in the production process of molded polymer (also called plastic) optics, fast reproduction of optical components with a broad range of shapes and microstructures is possible. This can offer a significant advantage over glass optics because it allows for a more sophisticated design (e.g., aspheric optical surfaces are produced as easily as spherical surfaces) and the ability to include mounting and alignment features.
Free-form optics are an example of an optical element that can be produced at a lower cost than glass. Furthermore, a diverse set of applications becomes possible, offering greater options for optics design.
Both polymer and glass have unique traits and advantages that make them valuable in optical solutions. The properties of glass are different from that of molded polymer optics. Compared to polymers, glass is generally harder, more durable, and remains stable in moist and high-temperature environments compared to polymers. However, it is 2.5 – 4 times heavier than polymer (plastic) materials, which offer design freedoms that are difficult to achieve with glass for technical and economic reasons.
Manufacturing Molded Polymer Optics vs. Glass Optics
The manufacturing processes of polymer and glass optics are entirely different. Various mold techniques produce precision polymer optics, including injection and compression molding. Traditional manufacturing of glass optics, on the other hand, involves casting, grinding, and polishing processes.
Molded polymer optics have unique processing, quality, and economic advantages, which we’ll explore in more detail below.
Polymer Optics Offer Greater Design Complexity
Producing sophisticated shapes, apart from curved or flat surfaces, is challenging and uneconomical with glass, due to the need to cast, cut, grind, and polish.
Comparatively, using polymers offers easier manufacturing and better economics when creating intricate forms like diffractive and aspheric surfaces. The ability to create complex designs in an economical way makes it possible to utilize polymers for broader optical applications.
Plastic Optics are Lightweight
Compared to glass, polymer materials are lightweight. This is particularly significant for eyeglasses lenses, illumination optics such as flashlights, and head-worn systems such as AR/VR and HUDs (head-up displays).
Large Volume Production Flexibility and Reduced Manufacturing Costs
Molding methods for polymers enable high-volume production while maintaining low unit costs. Though glass optics may attain relatively high-volume manufacturing, comparable cost reductions are challenging to achieve. This is because glass processing is inherently time-consuming, labor-intensive, and demands a high amount of per unit energy.
Structural Mounting
When creating a complex optical product, individual components must be mounted and aligned. Glass requires a mechanical mounting system, while polymer optics from a mold can provide elements that include mounting features with high reproducibility.
Consistent Quality with Molded Polymer Optics
Polymer optics products are produced with consistent quality since they are all derived from the same mold. However, similar to other material processing techniques, the specific conditions for polymer processing are critical, requiring them to be optimized and controlled. It is critical to work with an optical molder, as the tolerances for optical elements are much tighter than those for non-optical plastic products.
Micro-structured surfaces can be produced in polymer optics. This allows for the combination of light-shaping features (e.g., diffusers, beam splitters) and conventional elements (lenses).
Sophisticated molding techniques are the key to making all this possible. For example, diffractive optical elements such as microlens arrays [2] and prism arrays [3] are the microstructures used in polymer optical applications like solar panel concentration structures [4], beam design homogenization, measuring systems, sensors [5], and more.
For the optical engineer, the refractive index and the Abbe number are the most significant material characteristics of polymer optics.[1] The refractive index can be a limiting issue since no material with high refractive index is available in comparison to glass optics. The most commonly used injection-molded optics materials are:
- Polycarbonate (PC)
- Acrylic (PMMA)
- Cyclic olefin copolymers (COCs)
- Cyclic olefin polymers (COPs)
The choice of an appropriate material depends upon the application. Each of these materials has its own technological features (water absorption, internal stress, environmental resistance, intrinsic birefringence).
The market value of molded polymer optics is increasing with the development of innovative technologies. However, research on making polymer optics scratch resistant, chemical resistant, having an increased range of available refractive indices, and more sustainable in a high-temperature environment is ongoing.
Get Started with Molded Plastic Optics with AOS
Apollo Optical Systems (AOS) focuses on developing customized solutions for consumer, commercial, solid-state (LED) lighting, medical, and automotive markets to implement innovative technologies. Contact us for more details.
Sources:
- https://www.spiedigitallibrary.org/conference-proceedings-of-spie/7424/74240Q/Optical-and mechanical-design-advantages-using-polymer-optics/10.1117/12.832319.full?SSO=1
- https://link.springer.com/article/10.1007%2Fs00542-004-0387-2
- https://www.spiedigitallibrary.org/conference-proceedings-of-spie/1806/0000/Micro-optical-setup-with-microlenses-and-microprisms-based-on-refractive/10.1117/12.147834.full
- https://www.osapublishing.org/oe/fulltext.cfm?uri=oe-18-2-1122&id=194406
- https://iopscience.iop.org/article/10.1088/0957-0233/20/7/077002
