Printed Optics Usher in New Era of Manufacturing

Jyrki Saarinen, University of Eastern Finland, and Richard Van De Vrie, Luxexcel

Additive manufacturing techniques are set to revolutionize fabrication and integration of optical products for a variety of applications, from lighting to imaging and beyond.

Additive manufacturing techniques are creating a new awakening in optics and photonics, and two factors that will expand this reawakening are digital computing and a new fabrication method for functional optics.

Industry experts have a clear vision of 3-D printing’s role in the optical market. They also have a clear picture of the main challenges that optics faces in the lighting industry. When designers can control light output and tailor it to every specific application or project, they will save energy and create far less light pollution.

Optics, like many other sectors before additive manufacturing, has suffered from long prototyping times and a lack of cost-effective manufacturing methods for low and even medium volumes. Customers know and accept that customization costs significantly more, if it is even available.

But a market exists, even without any reasonable supply. For example, smartphone consumers are ready to pay quite a lot of money (relative to the phone itself) to make their phones look unique. However, several gadgets have not been commercialized because of the entrance barrier of initial investments. Additive manufacturing is changing these paradigms. Printoptical technology makes this available to optics, too.

Additive manufacturing will likely become the leading fabrication method for prototyping and one of the leading methods for low-volume optics. Customers then will decide with their wallets how important a role customization will play in products supplied in medium or large volumes. The market also will depend on progress in materials, processes and equipment; and also on whether and when additive manufacturing will enter into various application areas and markets, including imaging.

Additive manufacturing for lighting

The lighting industry uses lenses or reflectors to manage light output. A lens is needed to distribute the light from a source to the required place. Mass-fabrication processes for lenses require expensive molds, and lenses must be ordered in volume. Customized optics for a project or application simply are not affordable. This means that lighting manufacturers are torn, because investing in optics and molds is expensive, and LED light sources improve so rapidly that lighting collections have to be updated regularly. This leads to high financial write-offs – and mountains of wasted lenses, molds or other components. To avoid this, manufacturers often use standard available lenses, but these do not provide adequate control of lighting, energy waste or light pollution.

Market growth is strong for LED lighting products, but it is challenging to make a profit as a manufacturer. In most cases, the development period from idea to product launch takes more than a year. LED lenses are often the most time-consuming part of the product development process. It can be highly frustrating to start selling a product and then have customers call for an update of the light output, while in the meantime, competitors have developed LED chips with better performance specifications. This cycle is happening continuously.

A solution would be a flexible optics manufacturing process that enables the production of customized lenses. This was attempted back in 2008, but products made using the 3-D printing processes of the time needed a lot of postprocessing. Also, printing layer by layer could not achieve the smooth surface necessary for functional optics.

Adapted faster wide-format printers seemed to be the answer. Some basic research led to the development of a solid process with fully dedicated digital printers to make optics in the additive way. This digital process was called printoptical technology. In this process, individual droplets of a UV-curable material are jetted by specialized piezoelectric printheads staging a “fluent dynamic dance of droplets” – a unique method of jetting, flowing and merging droplets before curing. The in-house-developed printer software and algorithms control very precise digital printer platforms to allow the printing of optical components. Once the CAD file is uploaded, the software decides which droplet is being used as a building block and which one is used to flow, creating a perfectly smooth surface. The patented process is easy and scalable, and the printed products are smooth enough that they do not require postprocessing.

A patented CAD-based process is easy and scalable, and produces printed optics smooth enough that they do not need postprocessing. Images courtesy of LUXeXceL.

To digitize optics manufacturing for many optical industries and products, an essential focus is on 3-D printing functional optics for LED lighting and various other nonimaging applications. The fabrication process develops best through close cooperation with specialized companies and universities to create more and better printing materials and coatings, to improve the CAD rendering for printing files, and to develop an online platform with many design tools. Optics design and order platforms such as Shapeways or i.materialise enable clients to order customized optical components easily.

The process has advanced to the point that CAD files can be uploaded online, and customers will get their finished parts delivered in a few days – in the required volume. To demonstrate the printing speed, we can look at an example lens of 3-cm diameter and 0.5-cm height; the new printer will be able to print 400 to 500 of these lenses per hour. And all of those lenses are ready to go without any postprocessing. This easily makes the process scalable.

Because of this, digital manufacturing will drive the lighting industry to tailor every fixture for improved light output while reducing energy consumption and global light pollution.

The process is useful for nonlighting applications, as well: LUXeXceL has even successfully 3-D-printed a functional pair of eyeglasses as proof of concept. The disruptive advantages of just scanning the eye and directly printing spectacle lenses are clear. It could even be done at the supermarket while the customer shops. But every application is different, and the additive printing process of various functional optical parts might require a different approach – perhaps even mechanical or software changes to the printer. Ophthalmic-quality lenses need special attention to surface roughness, optical homogeneity and transmittance. The newly developed printing platform is expected to make steps toward better imaging quality, and several major companies in the eyewear space have shown interest in collaborating on 3-D printing of glasses.

LUXeXceL and other companies are working closely with the University of Eastern Finland to support the progress on a project sponsored by the European Union and TEKES (Finnish Funding Agency for Technology and Innovation)to refine 3-D printing in photonics applications and to help create new optical functions and products.

Looking ahead

Experimental results – for example, work toward a master’s thesis at UEF – have already proved that the surface roughness and quality needed for imaging optics are very close. All applications and markets that today are addressed by conventional optics, including both imaging and nonimaging applications, will also be addressed by additive manufacturing within the next two to four years. Market penetration may not occur that quickly, however, in every optics market. The optics industry is conservative – no wonder, when optical technology goes back 2700 years. Fortunately, 3-D printing is getting a lot of publicity these days, and hopefully innovative engineers and visionary optical designers will see the benefits soon.

Additive manufacturing has shown that it can revolutionize mechanical supportive structures: Novel optical lattice and hollow structures, never before producible with any conventional technology, will introduce new levels of rigidity, mechanical resistance and weight savings. These structures will open new possibilities for making integrated optical systems. Lenses could even be designed and manufactured inside lenses. Optical designers must think out of the box. Not only do outer surfaces of optical components have optical functions, but every single position inside an optical component can also have its own optical function.

In less than 10 years, we will see new types of optics not described in textbooks today.

Additive manufacturing will also boost the development of free-form optics, with free-form surfaces made layer by layer from micron-scale building blocks, rather than by optimizing kinematics in ultraprecision diamond turning machines.

The combination of various additive manufacturing methods and/or materials can also lead to interesting solutions in optomechanics. For example, optics and holders can be printed in one shot, avoiding slow and expensive optomechanical assembly. And mechanics can even be built inside optics. For example, three-dimensional apertures are as easy to make as simple holes in metal plates. And this technology already exists, as with LUXeXceL’s Royal Eyeware.

In optoelectronics, combining additive manufacturing of optics with printed electronics or ink-jet-printed quantum dots will open novel solutions for optics with fully embedded electronics or light sources and displays, respectively. Ink-jet printing of functional materials, together with the availability of fully transparent optical materials and optical-quality surfaces, will also introduce novel applications in bioprinting.

Meet the authors

Professor Jyrki Saarinen of the University of Eastern Finland is the founder of Heptagon and executive director of the European Optical Society; email: jyrki.saarinen@uef.fi. Richard van de Vrie is a lighting and 3-D printing industry entrepreneur and founder of LUX- eXceL; email: richard.vandevrie@luxexcel.com.