Resonant beam scanner with raster pinch compensation

Abstract

A MEMs 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, symmetrically 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.

1. A resonant beam scanning system, comprising:
 A beam generator operable to produce an electromagnetic beam,  
 a first mechanically resonant beam director operable to scan the electromagnetic beam sinusoidally across a first axis at a first resonant frequency,  
 a second beam director operable to simultaneously scan the electromagnetic beam in a second axis at a second frequency,  
 a third mechanically resonant beam director operable to simultaneously scan the electromagnetic beam in the second axis, and  
 control electronics circuit coupled to the three beam directors, the control electronics circuit operable to provide a signal to the third beam director comprised of a primary frequency and at least one higher order harmonic frequency.  
 
     
     
       2. The resonant beam scanning system of  claim 1 :
 wherein the first and second beam directors are mechanically combined as a scan plate and gimbal ring.  
 
     
     
       3. The resonant beam scanning system of  claim 2 :
 Wherein all three beam directors are mechanically combined as a scan plate and nested gimbal rings.  
 
     
     
       4. The resonant beam scanning system of  claim 1 :
 wherein the beam directors include at least one mirror positioned to receive the electromagnetic beam.  
 
     
     
       5. The resonant beam scanning system of  claim 1 :
 wherein the beam generator is mounted on at least one of the beam directors.  
 
     
     
       6. The resonant beam scanning system of  claim 1 :
 wherein the electromagnetic beam is a beam of light.  
 
     
     
       7. The resonant beam scanning system of  claim 6 :
 wherein the beam of light includes red light.  
 
     
     
       8. The resonant beam scanning system of  claim 6 :
 wherein the beam of light includes infrared light.  
 
     
     
       9. The resonant beam scanning system of  claim 6 :
 wherein the beam of light includes ultraviolet light.  
 
     
     
       10. The resonant beam scanning system of  claim 1 
 wherein the primary frequency is substantially equal to the resonant frequency of the third beam director, and  
 the at least one higher order harmonic frequency includes at least one odd harmonic.  
 
     
     
       11. The resonant beam scanning system of  claim 10 :
 wherein the at least one odd harmonic includes the third harmonic.  
 
     
     
       12. The resonant beam scanning system of  claim 1 :
 wherein the second beam director is operable to scan the electromagnetic beam in substantially a sawtooth pattern.  
 
     
     
       13. The resonant beam scanning system of  claim 12 :
 wherein the third beam director is operable to scan the electromagnetic beam in substantially a sawtooth pattern.  
 
     
     
       14. A method of driving a MEMS scanning system, comprising the steps of:
 generating first and second respective periodic signals for driving first and second scanners;  
 generating a third periodic signal comprising a primary frequency and at least one odd harmonic for driving a scanner; and  
 transmitting the first, second and third respective signals to a MEMS scanning system.  
 
     
     
       15. The method of driving a MEMS scanning system of  claim 14 , wherein:
 the first periodic signal is a sinusoidal waveform; and  
 the primary frequency of the third signal is equal to twice the frequency of the first periodic signal.  
 
     
     
       16. The method of driving a MEMS scanning system of  claim 15 , wherein:
 the first periodic signal has a frequency substantially equal to a horizontal scan frequency.  
 
     
     
       17. The method of driving a MEMS scanning system of  claim 14 :
 wherein the second periodic signal has a frequency substantially equal to a frame rate.  
 
     
     
       18. The method of driving a MEMS scanning system of  claim 17 :
 wherein the second periodic signal is a sawtooth waveform.