The steady state response motion of a base excited cantilever beam with circular cross-section excited by a unidirectional displacement will fall along a straight line. However, achieving straight-line motion with a real cantilever beam of circular cross-section is difficult to accomplish. This is due to the fact that nonlinear effects, small deviations from circularity, asymmetric boundary conditions, and actuator cross coupling can induce whirling. The vast majority of previous work on cantilever beam whirling has focused on the effects of system nonlinearities. We show that whirling is a much broader problem in the design of resonant beam scanners in that the onset of whirling does not depend on large amplitude of motion. Rather, whirling is the norm in real systems due to small system asymmetries and actuator cross coupling. It is therefore necessary to control the growth of the whirling motion when a unidirectional beam motion is desired. We have developed a novel technique to identify the two eigen directions of the beam. Base excitation generated by virtual electrodes along these orthogonal eigen axes of the cantilever beam system generates tip vibration without whirl. This leads to accurate open loop control of the motion of the beam through the combined actuation of two pairs of orthogonally placed actuator electrodes.

A new and miniature imaging device is being developed to allow flexible endoscopy in regions of the body that are difficult to reach. The scanning fiber endoscope employs a single scanning optical fiber to illuminate a target area, while backscattered light is detected one pixel at a time to build a complete image. During each imaging cycle the fiber is driven outward in a spiral pattern from its resting state at the image center to the outer fringe of the image. At this point, the fiber is quickly driven back to its initial position before acquiring a subsequent frame. This work shortens the time between successive images to achieve higher overall frame rates by applying a carefully timed input, which counteracts the tip motion of the scanning fiber, quickly forcing the scanning fiber to the image center. This input is called motion braking and is a square wave function dependent upon the damped natural frequency of the scanning fiber and the instantaneous tip displacement and velocity. Imaging efficiency of the scanning fiber endoscope was increased from 75–89% with this implementation.

Advances in mobile devices have enabled internet access and viewing of images and video, but small screens constrain the experience. We have developed a novel scanning fiber optical projector that is 1.07 mm in diameter and 13 mm long, and can project images at up to a 100° throw angle. IntroductionThe increasing computational power and connectivity of mobile devices, such as cell phones, video iPods, and PDAs, have enabled mobile internet access and playback of large images and video. However, the usefulness of such capabilities is limited by small screens. A compact projector unit as a display for a mobile device can increase effective screen size without significantly increasing the size and weight of the devicehowever, it is nontrivial to create a sufficiently compact and lightweight optical projection engine.Projectors using LCD panels as imaging elements are reasonably low cost, but are not energy efficient. To create dark pixels in the projected image, LCD panels block a portion of the light energy generated by the source from reaching the screen, so dark images require as much energy to project as bright images, placing an additional drain on the limited battery capacity of mobile devices. Furthermore, the maximum resolution of the projector is constrained by the size of the LCD panel and the attainable pixel pitch. In order to increase resolution, the dimensions of the LCD panel in the mobile device must be increased proportionately.Holographic projectors can provide the advantage of lowered power consumption, as the majority of the light generated by the laser sources reaches the screen [1]. However, holographic image generation requires complex processing, placing high computational demands on mobile devices with small, lowvoltage processors, and the resolution of the projected image is also ultimately dependent on the size and pixel pitch of the spatial light modulator used to generate the holographic image.In contrast, scanned beam displays sweep a single pixel serially across a surface to form an image, and an increase in image resolution does not require an increase in the size of the components in the device. Instead, their resolution is governed primarily by the number of scan lines-dependent, in turn, on the frequency of the optical scanner-and the speed at which the light source can be luminance-modulated. In addition, such displays are energy efficient, as less power is required to display darker pixels. Scanned beam projection displays using miniature scanning mirrors and modulatable laser sources have been developed [2-3].The compactness of such projectors is limited by the physical arrangement necessary to guide light from the source(s) at an appropriate reflection angle for the scanning mirror to create a useable image.We have developed a novel light-scanning engine that uses a vibrating optical fiber to scan light in two axes. Rather than reflecting light from a scanning element, the light is deflected directly as it emerges from being transmitted along the optical fiber, enabling a reduc...

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In order to develop a one-millimeter outside diameter endoscope we have moved away from using a bundle of optical fibers that are an integral part of current endoscopes. To achieve the field of view and the resolution requirements in spite of the small diameter we are using a single optical fiber that acts as a scanning source. Photo detectors positioned along the side of the scanning fiber detect the backscattered light and software then reconstructs the image on a monitor. The single optical fiber moves in a spiral scan pattern that is produced using a four quadrant piezoelectric tube as the actuator. The optical fiber is fed through the center of the piezoelectric tube and glued into place.