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SPIE Professional October 2013

Adaptive lens

Adaptive microscope lens takes shape as commercial product

By Catherine Zandonella

image of TAG Lens, winner of 2013 Prism Award

On a late night in February 2011, two researchers at Princeton University (USA) packed a small object into a box and set it out for the morning mail. The engineers had spent four years developing a new type of microscope lens that focuses in response to sound waves. They were sending their invention to their first customer.

Two years and a lot of hard work later, their invention, the TAG Optics Lens 2.0, has a customer base spanning the globe, from Japan to Germany.

The lens has won numerous technology awards, including a 2013 Prism Award for Photonics Innovation in the category of optical components and an R&D Magazine “R&D 100 Award.” The National Science Foundation recently awarded TAG Optics a Small Business Innovation Research grant to further develop the technology for laser manufacturing and materials processing.

But the road from university laboratory to marketplace was not easy. The story of TAG Optics illustrates the roller coaster-style journey that new technologies — and their inventors — take as they embark on the path to commercialization. Its journey demonstrates the risks and rewards of entrepreneurship and how such experiences can help university professors become better teachers and mentors.


Craig Arnold, Christian Theriault and David Amrhein accept the 2013 Prism Award for Photonics Innovation for TAG Optics.

The idea for the TAG Lens began in 2005 when SPIE member Craig Arnold, then an assistant professor in mechanical and aerospace engineering at Princeton, offered undergraduate Adam Hopkins, also an SPIE member, an intriguing senior thesis project: to explore how sound can bend and shape a beam of light passing through a fluid. Arnold quickly saw the potential for a new type of microscope.

Hopkins completed his thesis and moved on to other projects at Princeton (earning his PhD in 2012), and Arnold continued the work with subsequent students. By 2007, Arnold and another graduate student, Euan McLeod, working with postdoctoral researcher Alexandre Mermillod-Blondin, had created a lens unlike any other: a tunable acoustic gradient index of refraction lens.

No moving parts in adaptive lens

The lens consisted of a clear silicone-based liquid trapped in a barrel-shaped housing containing a small speaker capable of blasting sound waves into the liquid. The sound waves created small changes in the density of the liquid, altering its index of refraction and thereby shaping light as it travels through the lens.

Most lenses, from the one found in the human eye to the ones found in microscopes and telescopes, use moving parts to adjust the focus.

“Our lens uses a fundamentally different technology,” Arnold explains. “There are no moving parts and thus it can focus at extremely high speeds in response to electronic signals.”

With the help of Princeton’s Office of Technology Licensing, Arnold applied for a patent for the invention in 2007, but he had little time to think about commercializing the lens while teaching, mentoring students, and conducting other research.

Creating TAG Optics

The lens remained a lab project until early 2010 when Arnold, recently tenured, began talking about commercializing the lens. The idea attracted the interest of a former Princeton student, Christian Theriault, who had studied molecular biology, materials science and engineering, engineering biology, and mechanical and aerospace engineering.

Theriault was eager to team up with Arnold and take on the challenge of converting a laboratory-grade gadget into an industrial high-precision lens that electronic device manufacturers and medical-imaging companies could use.

“I knew there was no other product like this on the market,” said Theriault, who, at 25 years old, was “at a point in life where I could take risks.”

Industry seemed eager for the lens as well, judging from the response to Theriault’s presentation about applications of the technology at an academia-industry partnership meeting in late 2010. “The next thing you know I got a call from someone asking, ‘Where can I buy your lens?’” Arnold said.

A few months later, in January 2011, Arnold and Theriault started TAG Optics Inc., taking part of its name from what they had devised, a "tunable acoustic gradient index of refraction lens." 

Tthe truly hard work thus began. Arnold was on sabbatical that semester, and the two worked around the clock to make a prototype lens.

By February, the two-person company was ready to ship its first unit. “I can still remember packing the first lens that we sent out,” Theriault said. “It was about 3 am. The package contained the lens and an instruction manual that was five lines of text.”

Just days later, Arnold and Theriault received an important lesson in product development when the customer called to ask: “How do you turn it on?”

Avoiding the innovator's ‘valley of death’

The customer’s question illustrates the divide between invention and product. Invention is creative and dynamic, while product development can seem mundane, according to Arnold. “As a university researcher, my job was to create fundamental knowledge and new technologies,” he said. “I didn’t think about the difficulty that people would have in operating the device.”

The gap between innovation and product development has earned the nickname “the valley of death” because many new inventions fail to successfully transition from lab to marketplace. Often the problem is finding funding to support the essential steps of product development, such as building a sturdy housing so that the item will not break if dropped.

Early research on the TAG Lens had been funded by government research grants from the U.S. Air Force Office of Sponsored Research, but federal guidelines bar the use of these funds for product development. Sales of the first TAG lenses helped, but the team needed money to try new housing materials, new ways of sealing the device, and other improvements. “I said to Craig, we cannot sell a product that takes a PhD to operate,” Theriault said.

Just as lack of money started to become an issue, the new technology received a much-needed financial boost in spring 2011: It won first place and a $25,000 prize from Princeton’s Keller Center Innovation Forum, in which university-based teams compete for funds to support their business plans for technologies they’ve developed.

Throughout 2011, Arnold and Theriault worked long hours to improve the lens. Arnold focused on publishable research — such as extending the lens’s capabilities. Theriault worked on what he called “product-ization” — making sure that the lens could survive in the real world where items get dropped and temperatures change — in other words, non-laboratory conditions. They contracted with external vendors to make an aluminum housing and software to control the lens.

Another critical influx of money arrived in early 2012. The Princeton University IP Accelerator Fund, a program designed expressly to support development of early-stage products, awarded $100,000 to the project.

By spring 2012, the company launched the next iteration, the TAG Lens 2.0, which shipped with a “driving kit” consisting of software and electronic components to control the lens. And yes, the device featured an “on” switch.

Throughout 2012, customer orders arrived, primarily from electronics manufacturing companies in Japan, Germany, and the United Kingdom. “Our business became 24/7,” said Theriault, who serves as TAG Optics’ CEO. Arnold and Theriault talked by phone around midnight every night, discussing the orders and refinements to their technology.

To fill the orders, Theriault hand-assembled each lens, conducted quality control testing, and packed them for shipping. That summer, the team won the Siemens’ Technology to Business Center’s national business and innovation competition.

Optics entrepreneurs find niche microscope lens market

Today, Theriault holds in his hand an object roughly the size and shape of a spool of thread capped on either end by clear glass.

Because there are no moving parts, the lens can focus thousands of times faster than a conventional lens, Theriault said, through its entire range up to 700,000 times per second. The next fastest competitor lens can change focus only about 150 times per second. “We can quickly increase the depth of field, or focus through an object, to capture a three-dimensional picture in the time it takes to snap a photo,” Theriault said.

That speed has enabled the technology to fill a niche: that of high-precision manufacturing of electronic components for cellphones, handheld computers, and other technologies. The TAG Lens focuses laser light to etch circuit designs into silicon or other materials. The electronic controls direct the laser to fire at different focal points in the material with high precision and speed.


The TAG Lens has changed over time from the first prototype on left to today’s version at right.

Industrial manufacturing has commanded the majority of sales so far, but Arnold and Theriault are working on adapting the lens for use in imaging-related applications where the lens provides technological benefits for cancer diagnosis and quality control assessments. According to Theriault, the TAG Lens could become an integral tool in molecular biology research, where its speed will allow researchers to drastically reduce the time it takes to acquire images and produce 3D images.

Entrepreneurial — and educational — adventure

Since that long night in 2011 when Theriault and Arnold packed the first TAG Lens, the work has been hard but extremely rewarding, according to the two researchers. “Our motivation for these hours of long work came from the desire to see a worthwhile technology succeed and be translated into a commercial success,” Theriault said.

“As engineers, you want to make a difference,” added Arnold, who is now an associate professor, adviser to the SPIE Student Chapter at Princeton, and the chief technology consultant at TAG Optics.

Arnold said the experience has helped him become a better teacher and mentor. “I can now stand in front of my students and teach them from firsthand knowledge the steps involved in becoming an entrepreneur.”

–Catherine Zandonella is communications and outreach strategist at the Princeton University Office of the Dean for Research. This article, originally published on the Princeton website in July, is used with permission and was slightly edited for SPIE Professional.



Technology overview

TAG Optics’ patented technology uses piezoelectrics to generate sound in liquid, resulting in an index of refraction profile that behaves like a simple aspheric lens element.

However, unlike static devices that rely on the deformation of a surface or interface, the TAG Lens is more properly thought of as a tunable gradient-index (GRIN) device that does not require any redistribution of mass or liquid to change its optical properties.

The computer-controlled adaptive lens can scan a complete range of focal lengths in microseconds with little to no spherical aberration.


DOI: 10.1117/2.4201310.03

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