Abstract
Optical microendoscopy enabled by a microelectromechanical system (MEMS) scanning mirror offers great potential for in vivo diagnosis of early cancer inside the human body. However, an additional beam folding mirror is needed for a MEMS mirror to perform forward-view scanning, which drastically increases the diameter of the resultant MEMS endoscopic probe. This paper presents a new monolithic two-axis forward-view optical scanner that is composed of an electrothermally driven MEMS mirror and a beam folding mirror both vertically standing and integrated on a silicon substrate. The mirror plates of the two mirrors are parallel to each other with a small distance of 0.6 mm. The laser beam can be incident first on the MEMS mirror and then on the beam folding mirror, both at 45°. The MEMS scanner has been successfully fabricated. The measured optical scan angles of the MEMS mirror were 10.3° for the x axis and 10.2° for the y axis operated under only 3 V. The measured tip-tilt resonant frequencies of the MEMS mirror were 1590 Hz and 1850 Hz, respectively. With this compact MEMS design, a forward-view scanning endoscopic probe with an outer diameter as small as 2.5 mm can be made, which will enable such imaging probes to enter the subsegmental bronchi of an adult patient.
Highlights
Squamous dysplasia of the lung (SD) has been widely considered as a pre-invasive lesion leading to lung squamous cell carcinoma (SCC) [1]
Optical coherence tomography (OCT) has emerged as such an imaging technique [8,9,10,11,12] optical coherence tomography (OCT) typically employs near infrared light that is radiation-free and safe
Through a simple geometric calculation, we found that the height and width of this scanning module were 1.4 mm and 2 mm, respectively
Summary
Squamous dysplasia of the lung (SD) has been widely considered as a pre-invasive lesion leading to lung squamous cell carcinoma (SCC) [1]. TThhee ssttrruuccttuurree ooff aa ssiiddee--vviieeww MMEEMMSS ssccaannnniinngg pprroobbee iiss iilllluussttrraatteedd iinn FFiigguurree 22aa,, wwhheerree aann ooppttiiccaall bbeeaamm ccoommiinngg ffrroomm aann ooppttiiccaall fifibbeerr rreeaacchheedd tthhee MMEEMMSS mmiirrrroorr ppllaattee tthhaatt bboouunncceedd ooffff tthhee ooppttiiccaall bbeeaamm ttoowwaarrddss tthhee ssiiddee ooff tthhee ttuubbee. It was very challenging to make a forward-view MEMS endoscopic probe with an outer diameter (OD) smaller than 5.0 mm based on the design shown in Figure 2b [22]. By using the vertical MEMS dual-mirror design shown, the probe OD could be reduced by about one half. The probe consisted of a single-mode fiber, a graded-index (GRIN) lens and a vertical MEMS dual-mirror chip. The SiOB based vertical MEMS dual-mirror was the enabling component and is the focus of this paper that will be discussed in detail in the two sections
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