Injection-molded micro lenses: explained

micro lens examples

Today’s devices are reducing in size, and becoming more complex at the same time. For this reason, designers are rethinking older designs, removing the traditional copper wire for glass or plastic fiber. Micro lenses, lenslets, and lens arrays are making these new designs possible. Glass and plastic, or resin fiber is smaller, and at the same time has faster transmission times. In the constant fight to reduce size and weight, OEM engineers often ask, what is the smallest micro lens that can be made? The answer is 37µm, but more background is necessary to explain.

What are micro lenses used for? 

Precision micro lenses have numerous applications. Consider the enormous server farms being built today; they all use fiber and require optical connectors. Micro optics is a rapidly growing market with hundreds of millions of connectors being produced every year, and there’s always a focus to shrink the size of tech while increasing its efficiency. Consider supercomputers: Some can have 250,000 connectors in one machine.

Extremely small micro lenses
Extremely small stand-alone micro lens

Sensors are also a rapidly growing category, being used in more applications today than before. There are sensors being used in our lives at every turn: sensors monitor data in our cars, activate screens in our mobile phones, turn on and off appliances, and even monitor our vital signs inside our watches. Sensors monitor motion, environmental light changes, moisture and pressure and micro-lenses are a key component in their design.

Many medical applications like blood glucose monitors, endoscopes, and surgical devices require micro-lenses, and like consumer technology, these devices are also getting smaller every year. The quest to find lighter packages and better efficiency requires smaller and more precise micro lenses. This is why one frequent question we get is this: what is the smallest micro lens that can be made?

What is the smallest micro lens that can be made? 

The smallest micro lens that can be made is 37µm, that is, it has a base radius of 37µm. Clarification is needed to understand the full scope of this part. This particular refractive lens was for a multi-core fiber application with a total of five lenslets within a 250µm circle. Each lenslet within this component had a base radius of 37µm.

Stand-alone lenses are different. The smallest stand-alone micro mold lens that we’ve produced to date, is 600µm. This was created for an augmented reality (AR) device. We can’t disclose the nature of this project, but you can get a good example of a similar lens, albeit a bit larger, would look like in the photo to the right.

What do engineers need to know about micro molded lenses? 

Creating a micro-injected lens, just like any micro mold part, is just as much an art form as a science. Understanding where ejection pins will work best, what resin should be used, and gate location isn’t always obvious. Resin behaves in unexpected ways, at micro-levels. (This is why many resin manufacturers use our help to test their new resins.)

One material variation or measurement decision can completely change the plan of how a lens or lenslet is produced, so this is why it’s vital to engage early with a micro-molder that has a deep understanding of possibilities.

What can and cannot be produced isn’t obvious to engineers who don’t specialize in micro lenses, so getting the right expertise early can truly be the difference between staying within your budget and timeline. Creating micro lenses is a team sport. Understanding mechanical design, optical requirements, and material requirements ahead of time is critical to the successful completion of the project.

If you need some quick advice, reach out and ask for me. I’m happy to help.

Get a fast response from a micro mold engineer.

Rick Brown

Rick Brown is the senior sales engineer for optical molding at Accumold where he has made a significant impact on growing the optics business. His technical background involving optical injection molding spans 47 years, beginning in the late 70’s for Polaroid and Kodak. He enjoys working closely with his customers on design and implementation of their ideas from white board to production parts. 

micromolding components next to EU coins.

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