United States Patent 6,245,590
Wine , et al. June 12, 2001
Frequency tunable resonant scanner and method of making
Abstract
A MEM s scanning device has a variable resonant frequency. In one embodiment, the MEMs device includes a torsion arm that supports an oscillatory body. In one embodiment, an array of removable masses are placed on an exposed portion of the oscillatory body and selectively removed to establish the resonant frequency. The material can be removed by laser ablation, etching, or other processing approaches. In another approach, a migratory material is placed on the torsion arm and selectively stimulated to migrate into the torsion arm, thereby changing the mechanical properties of the torsion arm. The changed mechanical properties in turn changes the resonant frequency of the torsion arm. In another approach, symmetricaly distributed masses are removed or added in response to a measured resonant frequency to tune the resonant frequency to a desired resonant frequency. A display apparatus includes the scanning device and the scanning device scans about two or more axes, typically in a raster pattern. Various approaches to controlling the frequency responses of the scanning device are described, including active control of MEMs scanners and passive frequency tuning.
Inventors: Wine; David W. (Seattle, WA); Helsel; Mark P. (Seattle, WA); Barger; Jon D. (Snohomish, WA); Tegreene; Clarence T. (Redmond, WA)
Assignee: Microvision Inc. (Bothell, WA)
United States Patent 6,243,186
Melville June 5, 2001
Position detection of mechanical resonant scanner mirror
Abstract
Two piezoelectric sensors are mounted on the back of a spring-plate of a mechanical resonance scanner on respective sides of a center line coinciding with an axis of rotation. As the scanner mirror rotates back and forth the two sensors are accelerated and decelerated at a 180.degree. phase difference. Each sensor's output voltage crosses a zero level when the acceleration is unchanging. A differential amplifier detects the zero crossings for motion along the axis of rotation. Common mode rejection eliminates the non-rotational accelerations associated with external vibrations and shocks, and prevents masking the mirror's zero-crossings.
Inventors: Melville; Charles D. (Issaquah, WA)
Assignee: University of Washington (Seattle, WA) |
