Optical coherence tomography (OCT) provides non-invasive cross-sectional imaging capability and
high resolution, but it has very limited applications inside human body because of the stringent size
requirements for accessing the internal organs. Micro-Electro-Mechanical Systems (MEMS) is an
emerging technology that can make devices with small size and fast speed. This paper reports the
design optimization of a MEMS mirror-based miniature OCT probe. The probe consists of three main
parts: a GRIN lens module (1.3 mm in diameter), a MEMS mirror (1.7 mm x 1.55 mm), and a stainless
steel mount. A special assembly holder is designed for easy placement of parts and accurate optical
alignment and real-time monitoring of optical alignment and electrical characteristics is also used to the
assembly process. Code V is used for the optical design and analysis. Simulation shows that the
changes of the spot size and focal length are within the acceptable range when the distance between the
optical fiber and the GRIN lens varies less than 0.1 mm. The fiber may tilt as much as 2.5 degrees
without any considerable change of the spot size and working distance. The maximum tolerance to the
lateral shift between the fiber and GRIN lens is about 0.1 mm.
We present the design and experimental results of a new MEMS-based endoscopic optical coherence tomography (OCT) probe. The uniqueness of this miniature OCT imaging probe is a two-axis MEMS mirror with through-silicon vias (TSVs) for interconnecting. The TSV interconnection enables ultracompact probe design, successfully reducing the probe size to only 2.6 mm in diameter. The MEMS mirror is actuated by an electrothermal actuator that is capable of scanning ±16° at only 3.6 V DC. Two-dimensional and three-dimensional OCT images of microspheres embedded in PDMS and acute rat brain tissue have been obtained with this miniature probe in a time-domain OCT system.
KEYWORDS: Optical coherence tomography, Microelectromechanical systems, Mirrors, Actuators, Doppler tomography, In vivo imaging, 3D image processing, Endoscopy, Ear, Cancer
Most cancers occur inside human body, so endoscopic high-resolution imaging modalities are required for early cancer
detection and surgical removal. This paper reports in vivo endoscopic 3D imaging based on optical coherence
tomography (OCT). Endoscopic imaging is enabled by integrating rapid-scanning MEMS mirror into a miniature
imaging probe. The MEMS mirror has an aperture size of 1 mm by 1 mm and a chip size of 2 mm by 2 mm. The optical
scan angle exceeds ±25 V at 6 Vdc, and thus large, constant-velocity, linear scan can be realized. The outer diameter of
the probe is only 5 mm. The axial resolution is about 10 μm and the imaging speed is 2.5 frames per second. Doppler
OCT imaging has also been demonstrated.
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