Faster, Smaller Delay Lines Drive Oct Applications FurtherAndrew Robertson, Senior VP, Business Development and Systems Technology Group, 3 May 2017
Optical coherence tomography (OCT) celebrated its 25th anniversary as a non-invasive imaging technique in 2016. In the past twenty years its use in commercial ophthalmology, cardiology and dermatology has been established. OCT can be used to reveal in real time the details of eye diseases such as early-stage glaucoma and macular degeneration. It can be used to detect skin cancer or monitor heart surgery. Indeed as the efficiency and effectiveness of imaging improves, the market is set to grow. According to a recent market survey1, the optical coherence tomography (OCT) market is forecast to experience growth of 12% per year through 2020, when annual global sales should total at least $1.3 billion.
Key to the next generation of commercially available OCT workstations are several optical subs-systems, for which Gooch & Housego is the leading developer. One of these is the optical delay line, a critical sub-assembly within the OCT Optical Engine.
Besides the delay lines, G&H also supplies the necessary interferometers and spectrometers. In effect, we are a one-stop shop for three of the five main subsystems enabling systems providing the highest quality OCT scanning. Our knowledge and expertise in these fields means that, with the positive OCT market trends, we are well positioned to grow our business.
It is not uncommon for our OCT customers to come to us for all three sub-systems given the attractive combination of plug-and-play ease of operation, complementary designs and the competitive prices resulting from the economies of scale we achieve.
One of the most important features of our delay line is its speed of operation. Its market-leading performance – typically four times faster than any competing delay line – ensures rapid system optimization during OCT scan operation meaning that patient throughput can be maximized.
The delay line travel speed is specified up to 25 mm/s with a control accuracy of 5 µm and in practice our systems have been run at speeds approaching 80 mm/s in short bursts. The standard variant offers optical delay of up to 1200 ps in point-and-return configuration.
In practice, all of our customers to whom we have sold these delay lines have actually been able to run our devices significantly faster than we have actually specified.
Interestingly, during development we didn’t prioritize the delay line to be just fast; it was primarily designed to be compact and reliable. The major objective of the customer-led designs and our multiple revisions (there have been three iterations over the past two years) has been to achieve the smallest possible size – with the high operational speed being a bonus. Our delay lines’ high speed, in particular, is achieved by our optimized optomechanical design.
The size reduction that G&H achieves is important because as these OCT systems and procedures become more commonplace, there is an industry-wide drive to make OCT overall systems smaller and less bulky. In particular, OCT functionality is being added to existing imaging systems with the critical requirement that there is minimum increase in overall instrument size.
Other important aspects of the design and performance of the G&H delay lines are their accuracy, resolution and repeatability of function. Our small form factor (SFF) delay line has been developed for volume production line requirements. The unit is plug- and-play and can be controlled with a wide range of drivers.
The SFF delay line, which measures just 30 mm x 30 mm x 180 mm also features a built in attenuator, saving the cost and simplifying the design of the overall OCT system. This feature saves on extra components in the system and simplifies system integration and tuning of the output because the interferometer is already integrated. The standard product can be configured in either a fiber-to-fiber configuration or point-and-return, depending on the OCT system type.
New applications, New Markets
Although ophthalmology and biomedical applications continue to dominate the OCT landscape, anybody looking to develop a system for other emerging markets, such as electronics or materials analysis, will automatically look at the biomedical systems because of the relative maturity of this sector.
Our delay lines are built for OEM manufacturing which means we are able to make them to both our high specifications and in production volumes. For the marketplace this has two notable advantages: we can produce them economically and sell them at an attractive price; and because of our tradition of high quality, never-fail high-tech equipment manufacturing, they are reliably and consistently manufactured.
At the same time, we offer a range of models of delay lines with different specifications required by different parts of the OCT market with six variants based on the same platform. These deliver different wavelengths for different applications.
There are three key wavelengths, covering: ophthalmology for the retina at 850 nm; whole eye imaging at 1060 nm and body tissue analysis based on 1300 nm. The other design variations include: fiber in / fiber out; fiber in and retro-reflector so the emerging signal goes back into same fiber; and variable lengths and physical sizes and different connectors, as required.
So for OCT system developers, G&H offers a range of sector leading delay lines. These systems are more than simple components; they are versatile subsystems that can be specified to meet different needs; they are available in production volumes with the associated high-quality and low-cost benefits; they can easily be integrated – “plug and play” – with other key components from our portfolio. All in all, the best combination for both today’s and next-generation OCT systems for this exciting sector’s rapidly emerging new applications.
(1) Analysis by Research & Markets (Coffey, Valerie. 2016. Advanced OCT Making Waves in the Market. Optics & Photonics. September 2016.)