Feature Of The Week 9/11/11: Researchers at University of Florida Probe Into Miniature MEMs for OCT Imaging
Researchers at the University of Florida, let by Dr. Huikai Xie, have been active for many years in developing advanced optical scanning technology using MEMS technology. Such technology is important for OCT and other optical imaging modalities. Below is a summary of some of their recent work.
Endoscopic optical coherence tomography (OCT) imaging is very useful since it can replace risky, painful and time-consuming biopsy. However Endoscopic OCT is also very challenging, because fast lateral optical scan must be realized in a small imaging probe that must be able to fit into the small biopsy channel of endoscopes. MEMS technology is a promising solution to this problem due to its small size, fast speed, ease of integration and low cost. Electrothermal MEMS mirrors are especially suitable for endoscopic imaging applications, because of their large optical aperture, large scan angle, high fill factor and low driving voltage.
In this study, a series of electrothermal MEMS mirror-based OCT probes are discussed. The first generation probe is based on a lateral-shift-free large-vertical-displacement MEMS mirror design. The mirror plate is 1mm × 1mm sitting on top of a mirror base of 2mm × 2mm, resulting in a large fill-factor of 25%. The mirror scans up to ±30° optical angle when driven at 5.5V. This first generation probe is made of stainless steel, and its diameter is 5mm and it has a working distance of 1.5mm in air. Electrical connection is first made through wire bonding to the mirror pads and then with conductive glue to the PCB pads, which lead to the driving signal. Real time imaging capability of the probe has been demonstrated in a time-domain OCT system.
The second generation MEMS-OCT probe employed a folded-dual-S-shaped-bimorph hidden actuator MEMS mirror design. By hiding the actuators under the mirror plate, the fill factor was increased to 32%; with the same mirror aperture of 1mm × 1mm, the mirror footprint was decreased to 1.55mm × 1.7mm, which enables further probe miniaturization. Up to ±23° optical scan angle was obtained at 4.8V. The probe diameter was reduced to 2.5mm. Probe packaging was made easy by employing a flexible PCB with matching pattern to the mirror pads. Electrical connection was made by flip chip bonding the MEMS mirror to the PCB, so no wire bonding process was necessary. Real time imaging results were also demonstrated.
For more information click Here. Courtesy Jingjin Sun and Huikai Xie.