This review paper describes the applications of dental optical coherence tomography (OCT) in oral tissue images, caries, periodontal disease and oral cancer. The background of OCT, including basic theory, system setup, light sources, spatial resolution and system limitations, is provided. The comparisons between OCT and other clinical oral diagnostic methods are also discussed.

Due to the advancement of microoptoelectromechanical systems and microelectromechanical systems (MEMS) technologies, novel display architectures have emerged. One of the most successful and well-known examples is the Digital Micromirror Device from Texas Instruments, a 2-D array of bistable MEMS mirrors, which function as spatial light modulators for the projection display. This concept of employing an array of modulators is also seen in the grating light valve and the interferometric modulator display, where the modulation mechanism is based on optical diffraction and interference, respectively. Along with this trend comes the laser scanning display, which requires a single scanning device with a large scan angle and a high scan frequency. A special example in this category is the retinal scanning display, which is a head-up wearable module that laser-scans the image directly onto the retina. MEMS technologies are also found in other display-related research, such as stereoscopic (3-D) displays and plastic thin-film displays.

In this paper, we report on a MEMS-based two-axis optical scanner array with a high fill factor (>96%), large mechanical scan angles (/spl plusmn/4.4/spl deg/ and /spl plusmn/3.4/spl deg/), and high resonant frequencies (20.7 kHz). The devices are fabricated using SUMMiT-V, a five-layer surface-micromachining process. High fill factor, which is important for 1/spl times/N/sup 2/ wavelength-selective switches (WSSs), is achieved by employing crossbar torsion springs underneath the mirror, eliminating the need for gimbal structures. The proposed mirror structure can be readily extended to two-dimensional (2-D) array for adaptive optics applications. In addition to two-axis rotation, piston motion with a stroke of 0.8 /spl mu/m is also achieved. [1496].

We present a high-port-count (scalable to 1 times 32) wavelength-selective switch (WSS) using a large scan-angle, high fill-factor, two-axis analog micromirror array in conjunction with a densely packed two-dimensional array of fiber collimators. A partially populated (1 times 9) WSS exhibits a fiber-to-fiber insertion loss of 5.57 plusmn 1.4 dB and an extinction ratio of 51 plusmn 11 dB. The channel spacing is 100 GHz

A new high-port-count wavelength-selective switch (WSS) has been realized using two cross-scanning one-axis analog micromirror arrays in a 4-f optical system. The number of output ports is increased from N to N/sup 2/, where N is the maximum linear port count limited by optical diffraction. Using surface-micromachined micromirrors with hidden vertical comb drives, large scan angles (>/spl plusmn/5/spl deg/ mechanical), low drive voltages (7 V), and high fill factors (> 96.25%) are achieved for both scanning mirrors. Experimental results for WSS are demonstrated using both two-dimensional (2-D) array of discrete collimators and monolithic 2-D collimator array. A fiber-to-fiber insertion loss ranging from 6 to 18 dB and a switching time of <700 /spl mu/s have been achieved.