Reflective microelectrical mechanical structure (MEMS) optical modulator and optical display system

Abstract

A MEMS optical display system includes an illumination source for providing illumination light, a collimating lens for receiving the illumination light and forming from it collimated illumination light, and a microlens array having an array of lenslets for receiving the illumination light from the collimating lens. The converging microlens array directs the illumination light through an array of pixel apertures in an aperture plate to a microelectrical mechanical reflector array positioned opposite the aperture plate. The microelectrical mechanical reflector array includes an array of microelectrical mechanical actuators that support reflectors in alignment with the array of pixel apertures and selectively orients the reflectors to direct the illumination light back through the pixel apertures (to form part of a display image) or against the aperture plate (to be blocked). The illumination light passing back through the pixel apertures passes through the microlens array and a beamsplitter to a display screen.

1 . A microelectrical mechanical device comprising: 
 (a) a substrate;    (b) an arm having a first end anchored to the substrate and a free end extending over the substrate, the arm having a bottom surface facing the substrate and a top surface opposite the bottom surface;    (c) a reflector extending over the top surface of the free end of the arm;    (d) an electrostatic activation electrode supported by the substrate and facing the bottom surface of the arm, the electrode, when activated by a first voltage, providing an electrical force sufficient to move the free end of the arm; and    (e) an electrostatic lock, supported by the substrate and facing the bottom surface of the arm, the lock, when activated by a second voltage, providing an electrical force sufficient to hold the free end of the arm in position.    
   
   
       2 . The microelectrical device of  claim 1 , wherein the lock is supported by the substrate beneath the free end of the arm.  
   
   
       3 . The microelectrical device of  claim 1 , wherein the arm is formed of a bimorph material, the material having a relaxed state.  
   
   
       4 . The microelectrical device of  claim 3 , wherein the arm flexes away from the substrate in the relaxed state.  
   
   
       5 . A method comprising: 
 a) providing a microelectrical mechanical device having a substrate, an arm having a first end anchored to the substrate and a free end extending over the substrate, the arm having a bottom surface facing the substrate and a top surface opposite the bottom surface, a reflector extending over the top surface of the free end of the arm, an electrostatic activation electrode supported by the substrate and facing the bottom surface of the arm, and an electrostatic lock supported by the substrate and facing the bottom surface of the arm;    b) activating the electrode with a first voltage for providing an electrical force sufficient to move the free end of the arm; and    c) activating the electrostatic lock with a second voltage for providing an electrical force sufficient to hold the free end of the arm in position, the second voltage being different from the first voltage.    
   
   
       6 . The method of  claim 5 , wherein the lock is supported by the substrate beneath the free end of the arm.  
   
   
       7 . The method of  claim 5 , wherein the arm is formed of a bimorph material, the material having a relaxed state.  
   
   
       8 . The method of  claim 7 , wherein the arm flexes away from the substrate in the relaxed state.  
   
   
       9 . The method of  claim 5 , wherein the arm includes at least one flex score extending across at least a portion of a width of the arm.  
   
   
       10 . The method of  claim 9 , wherein the free end of the arm proximate the reflector is free of the at least one flex score.  
   
   
       11 . The method of  claim 5 , wherein the microelectrical mechanical device further includes at least one standoff dimple, the dimple spacing the free end of the arm away from the substrate.  
   
   
       12 . The method of  claim 5 , wherein the first voltage is greater than the second voltage.  
   
   
       13 . A device comprising: 
 (a) a plurality of microelectrical mechanical reflectors in an array having a plurality of rows and columns, each microelectrical mechanical reflector having a substrate, a reflector element supported by the substrate, and an electrostatic activation electrode supported by the substrate proximate the reflector element;    (b) at least one row electrode coupling at least one row of microelectrical mechanical reflectors to a row driver for delivering a first row voltage to each reflector element in the at least one row of microelectrical mechanical reflectors, the first row voltage being insufficient to activate a reflector element;    (c) at least one column electrode coupling at least one column of microelectrical mechanical reflectors to a column driver for delivering a first column voltage to each reflector element in the at least one column of microelectrical mechanical reflectors, the first column voltage being insufficient to activate a reflector element, the combination of the first row voltage and the first column voltage being sufficient to activate a reflector element at an intersection of the at least one row and the at least one column of microelectrical mechanical reflectors.    
   
   
       14 . The device of  claim 13 , wherein each microelectrical mechanical reflector further includes a memory electrode, the at least one row electrode for delivering a second row voltage to each memory electrode in the at least one row, and the at least one column electrode for delivering a second column voltage to each reflector element in the at least one column, the combination of the second row voltage and the second column voltage being sufficient to maintain activation of the reflector element at the intersection.  
   
   
       15 . The device of  claim 14 , wherein the combination of the second row voltage and the second column voltage is less than the combination of the first row voltage and the first column voltage.  
   
   
       16 . The device of  claim 13 , wherein the arm includes at least one flex score extending across at least a portion of a width of the arm.  
   
   
       17 . The device of  claim 13 , further comprising at least one stand-off dimple, the dimple spacing the free end of the arm away from the substrate.  
   
   
       18 . The device of  claim 13 , wherein the arm is formed of a bimorph material, the material having a relaxed state.  
   
   
       19 . The device of  claim 18 , wherein the arm flexes away from the substrate in the relaxed state.