Abstract-A resonant piezoelectric scanner is developed for high-resolution laser-scanning displays. A novel actuation scheme combines the principle of mechanical amplification with lead zirconate titanate (PZT) thin-film actuation. Sinusoidal actuation with 24 V at the mechanical resonance frequency of 40 kHz provides an optical scan angle of 38.5• for the 1.4-mm-wide mirror. This scanner is a significant step toward achieving full-highdefinition resolution (1920 × 1080 pixels) in mobile laser projectors without the use of vacuum packaging. The reported piezoscanner requires no bulky components and consumes < 30-mW power at maximum deflection, thus providing significant power and size advantages, compared with reported electromagnetic and electrostatic scanners. Interferometry measurements show that the dynamic deformation is at acceptable levels for a large fraction of the mirror and can be improved further for diffraction-limited performance at full resolution. A design variation with a segmented electrode pair illustrated that reliable angle sensing can be achieved with PZT for closed-loop control of the scanner.[ 2012-0116]Index Terms-High-frequency laser beam scanning, lead zirconate titanate (PZT) thin-film-actuated, microelectromechanical systems (MEMS), MEMS mirror, resonant scanner.
A comb-actuated torsional microscanner is developed for high-resolution laser-scanning display systems. Typical torsional comb-drive scanners have fingers placed around the perimeter of the scanning mirror. In contrast, the structure in this paper uses cascaded frames, where the comb fingers are placed on an outer drive frame, and the motion is transferred to the inner mirror frame with a mechanical gain. The structure works only in resonant mode without requiring any offset in the comb fingers, keeping the silicon-on-insulator-based process quite simple. The design intent is to improve actuator efficiency by removing the high-drag fingers from the high-velocity scanning mirror. Placing them on the lower velocity drive frame reduces their contribution to the damping torque. Furthermore, placement on the drive frame allows an increase of the number of fingers and their capacity to impart torque. The microscanner exhibits a parametric response, and as such, the maximum deflection is found when actuated at twice its natural frequency. Analytical formulas are given for the coupled-mode equations and frame deflections. A simple formula is derived for the mechanical-gain factor. For a 1-mm × 1.5-mm oblong scanning mirror, a 76 • total optical scan angle is achieved at 21.8 kHz with 196-V peak-to-peak excitation voltages.[2009-0304]
A novel MEMS actuation technique has been developed for scanned beam display and imaging applications that allows driving a two-axes scanning mirror to wide angles at high frequency. This actuation technique delivers sufficient torque to allow non-resonant operation as low as DC in the slow-scan axis while at the same time allowing one-atmosphere operation even at fast-scan axis frequencies great enough to support SXGA resolutions. Several display and imaging products have been developed employing this new MEMS actuation technique.Exceptionally good displays can be made by scanning laser beams much the same way a CRT scans electron beams. The display applications can be as diverse as an automotive head up display, where the laser beams are scanned onto the inside of the car's windshield to be reflected into the driver's eyes, and a head-worn display where the light beams are scanned directly over the viewer's vision.For high performance displays the design challenges for a MEMS scanner are great. The scanner represents the system's limiting aperture so it must be of sufficient size; it must remain flat to fractions of a wavelength so as to not distort the beam's wave front; it must scan fast enough to handle the many millions of pixels written every second; and it must scan in two axes over significant angles in order to "paint" a wide angle, two-dimensional image. Using the new actuation method described, several MEMS scanner designs have been fabricated which meet the requirements of a variety of display and imaging applications.
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