Method of repairing micromirrors in spatial light modulators

Abstract

Disclosed herein is method of operating a device that comprises an array of micromirrors. The method comprises a process usable for repairing stuck micromirrors of the micromirror array during the operation. The reparation process applies, at the ON state, two consecutive refresh voltages to the mirror plates of the micromirrors in the array with the pulses being separated in time longer than the characteristic oscillation time of the micromirrors. The reparation process can be applied independently to the micromirrors. Alternatively, the reparation process can be incorporated with a bias inversion process.

1 . An apparatus for use in operating a device comprising an array of micromirrors, each comprising a mirror plate and an addressing electrode, the apparatus comprising 
 first means for switching the micromirrors between an ON and OFF state;    second means for applying a number of refresh voltage pulses to the mirror plates so as to repair a stuck micromirror; and    wherein a ratio of the number of switches of the micromirrors between the ON and OFF states to the number of refresh voltage pulses is greater than 1.    
   
   
       2 . The apparatus of  claim 1 , wherein the first means for switching the micromirrors between the ON and OFF states further comprises: 
 means for applying a bias voltage to the mirror plates of the micromirrors and a set of voltages to the addressing electrodes, wherein the voltages on the addressing electrodes are determined according to a set of image data produced from an image using a pulse-width-modulation technique.    
   
   
       3 . The apparatus of  claim 2 , further comprising: 
 means for applying the bias voltage to the mirror plate and a voltage to the addressing electrode associated with said mirror plate such that the mirror plate is rotated to an ON state angle of 10° degrees or more from a non-deflected state, wherein the difference between said two voltages is 30 volts or more.    
   
   
       4 . The apparatus of  claim 3 , wherein the ON state angle is 12° degrees or more relative to the non-deflected state.  
   
   
       5 . The apparatus of  claim 3 , further comprising: means for adjusting at least one of the applied bias voltage and the voltage on the addressing electrode such that the voltage difference between the mirror plate and addressing electrode is 17 volts or less.  
   
   
       6 . The apparatus of  claim 3 , wherein the voltage on the addressing electrode changes 10 volts or more when the mirror plate switches between the ON and OFF states.  
   
   
       7 . The apparatus of  claim 6 , wherein the change of the voltage on the addressing electrode is from 13 to 25 volts when the mirror plate switches between the ON and OFF states.  
   
   
       8 . The apparatus of  claim 1 , wherein the second means for applying a set of refresh voltage pulses further comprises: 
 means for performing a reparation process that comprises first and second refresh voltage pulses for the micromirrors, wherein the first and second refresh voltage pulses are spaced in time longer than the intrinsic oscillation time of the micromirror.    
   
   
       9 . The apparatus of  claim 8 , wherein the reparation process further comprises: 
 means for adjusting the bias voltage and the voltages on the addressing electrodes such that the micromirrors are expected to be in the OFF state; and    means for applying the first and second refresh voltage pulses to repair a stuck micromirror in the ON state.    
   
   
       10 . The apparatus of  claim 8 , wherein the reparation process is performed at most once during each frame period of a sequence of frames.  
   
   
       11 . The apparatus of  claim 8 , wherein the reparation process is performed during selected frames of the sequence of frames.  
   
   
       12 . The apparatus of  claim 10 , wherein the reparation process is performed at the end of the frame period.  
   
   
       13 . The apparatus of  claim 8 , wherein the reparation process is performed during a spoke time period intervening two of a sequence of color field periods.  
   
   
       14 . The apparatus of  claim 13 , wherein the first and second refresh pulses of the reparation process have opposite polarities.  
   
   
       15 . The apparatus of  claim 14 , wherein the polarization of the first refresh voltage pulse is opposite to the polarity of the bias voltage.  
   
   
       16 . The apparatus of  claim 1 , wherein the mirror plate comprises a metallic reflecting layer and a non-metallic layer, and each mirror plate is attached to a deformable hinge that comprises an electric conductive layer and a non-metallic layer; and wherein the deformable hinge deforms under the refresh voltage pulses so as to produce a restoration energy when the mirror plate is at the OFF state.  
   
   
       17 . The apparatus of  claim 8 , further comprising: 
 means for changing the polarity of the bias voltage.    
   
   
       18 . The apparatus of  claim 17 , further comprising: 
 means for changing the bias voltage from first value to second value, wherein the micromirror is expected to be at the OFF state with the second value of the bias voltage;    means for maintaining the bias voltage at the second value for a transition time period where the mirror plates at the ON state are expected to be at the OFF state; and    means for performing the reparation process during said transition time period.    
   
   
       19 . The apparatus of  claim 8 , wherein the reparation process lasts for a time period of 10 microseconds or less.  
   
   
       20 . The apparatus of  claim 8 , wherein the reparation process lasts for a time period of 1 microsecond or less.  
   
   
       21 . A projection system, comprising: 
 a light course producing illumination light;    a spatial light modulator for modulating the illumination light, comprising an array of micromirrors each comprising a deflectable mirror plate and an addressing electrode;    a controller in connection with the spatial light modulator, comprising the apparatus of  claim 1;  and    a display target on which the modulated light from the spatial light modulator is projected.    
   
   
       22 . An apparatus for use in operating a device comprising an array of micromirrors each comprising a deflectable mirror plate and an addressing electrode, the apparatus comprising: 
 first means for applying a bias voltage to the mirror plates and a set of voltages to the addressing electrodes during a sequence of color field periods; and    second means for applying a refresh voltage pulse to the mirror plates during a spoke period intervening two adjacent color field periods.    
   
   
       23 . The apparatus of  claim 22 , further comprising: 
 means for applying the bias voltage to the mirror plate and a voltage to the addressing electrode associated with said mirror plate such that the mirror plate is rotated to an ON state angle of 10° degrees or more from a non-deflected state, wherein the difference between said two voltages is 30 volts or more.    
   
   
       24 . The apparatus of  claim 23 , wherein the ON state angle is 12° degrees or more relative to the non-deflected state.  
   
   
       25 . The apparatus of  claim 23 , further comprising: means for adjusting at least one of the applied bias voltage and the voltage on the addressing electrode such that the voltage difference between the mirror plate and addressing electrode is 17 volts or less.  
   
   
       26 . The apparatus of  claim 25 , wherein the voltage on the addressing electrode changes 10 volts or more when the mirror plate switches between the ON and OFF states.  
   
   
       27 . The apparatus of  claim 26 , wherein the change of the voltage on the addressing electrode is from 13 to 25 volts when the mirror plate switches between the ON and OFF states.  
   
   
       28 . The apparatus of  claim 22 , further comprising: 
 means for performing a reparation process that comprises the first and a second refresh voltage following the first voltage pulses for the micromirrors, wherein the first and second refresh voltage pulses are spaced in time longer than the intrinsic oscillation time of the micromirror.    
   
   
       29 . The apparatus of  claim 28 , wherein the reparation process further comprises: 
 means for adjusting the bias voltage and the voltages on the addressing electrodes such that the micromirrors are expected to be in the OFF state; and    means for applying the first and second refresh voltage pulses to repair a stuck micromirror in the ON state.    
   
   
       30 . The apparatus of  claim 29 , wherein the reparation process is performed at most once during each frame period of a sequence of frames.  
   
   
       31 . The apparatus of  claim 28 , wherein the reparation process is performed during selected frames of the sequence of frames.  
   
   
       32 . The apparatus of  claim 30 , wherein the reparation process is performed at the end of the frame period.  
   
   
       33 . The apparatus of  claim 28 , wherein the reparation process is performed during a spoke time period intervening two of a sequence of color field periods.  
   
   
       34 . The apparatus of  claim 23 , wherein the first and second refresh pulses of the reparation process have opposite polarities.  
   
   
       35 . The apparatus of  claim 24 , wherein the polarization of the first refresh voltage pulse is opposite to the polarity of the bias voltage.  
   
   
       36 . The apparatus of  claim 22 , wherein the mirror plate comprises a metallic reflecting layer and a non-metallic layer, and each mirror plate is attached to a deformable hinge that comprises an electric conductive layer and a non-metallic layer; and wherein the deformable hinge deforms under the refresh voltage pulses so as to produce a restoration energy when the mirror plate is at the OFF state.  
   
   
       37 . The apparatus of  claim 28 , further comprising: 
 means for changing the polarity of the bias voltage.    
   
   
       38 . The apparatus of  claim 27 , further comprising: 
 means for changing the bias voltage from first value to second value, wherein the micromirror is expected to be at the OFF state with the second value of the bias voltage;    means for maintaining the bias voltage at the second value for a transition time period where the mirror plates at the ON state are expected to be at the OFF state; and    means for performing the reparation process during said transition time period.    
   
   
       39 . The apparatus of  claim 28 , wherein the reparation process lasts for a time period of 1 microsecond or less.  
   
   
       40 . An apparatus for use in operating a device comprising an array of micromirrors each comprising a deflectable mirror plate and an addressing electrode, the apparatus comprising: 
 first means switching the micromirrors between an ON and OFF states with first bias voltage and a set of voltages on the addressing electrodes; and    second means for applying first and second refresh voltage pulses to the micromirrors, wherein the first and second refresh voltage pulses are spaced in time longer than the intrinsic oscillation time of the micromirrors.    
   
   
       41 . The apparatus of  claim 40 , wherein the first means for switching the micromirrors between the ON and OFF states further comprises: 
 means for applying a bias voltage to the mirror plates of the micromirrors and a set of voltages to the addressing electrodes, wherein the voltages on the addressing electrodes are determined according to a set of image data produced from an image using a pulse-width-modulation technique.    
   
   
       42 . The apparatus of  claim 41 , further comprising: 
 means for applying the bias voltage to the mirror plate and a voltage to the addressing electrode associated with said mirror plate such that the mirror plate is rotated to an ON state angle of 10° degrees or more from a non-deflected state, wherein the difference between said two voltages is 30 volts or more.    
   
   
       43 . The apparatus of  claim 42 , wherein the ON state angle is 12° degrees or more relative to the non-deflected state.  
   
   
       44 . The apparatus of  claim 42 , further comprising: means for adjusting at least one of the applied bias voltage and the voltage on the addressing electrode such that the voltage difference between the mirror plate and addressing electrode is 17 volts or less.  
   
   
       45 . The apparatus of  claim 42 , wherein the voltage on the addressing electrode changes 10 volts or more when the mirror plate switches between the ON and OFF states.  
   
   
       46 . The apparatus of  claim 45 , wherein the change of the voltage on the addressing electrode is from 13 to 25 volts when the mirror plate switches between the ON and OFF states.  
   
   
       47 . The apparatus of  claim 40 , wherein the means for applying a set of refresh voltage pulses further comprises: 
 means for performing a reparation process that comprises first and second refresh voltage pulses for the micromirrors, wherein the first and second refresh voltage pulses are spaced in time longer than the intrinsic oscillation time of the micromirror.    
   
   
       48 . The apparatus of  claim 47 , wherein the reparation process further comprises: 
 means for adjusting the bias voltage and the voltages on the addressing electrodes such that the micromirrors are expected to be in the OFF state; and    means for applying the first and second refresh voltage pulses to repair a stuck micromirror in the ON state.    
   
   
       49 . The apparatus of  claim 47 , wherein the reparation process is performed at most once during each frame period of a sequence of frames.  
   
   
       50 . The apparatus of  claim 47 , wherein the reparation process is performed during selected frames of the sequence of frames.  
   
   
       51 . The apparatus of  claim 49 , wherein the reparation process is performed at the end of the frame period.  
   
   
       52 . The apparatus of  claim 47 , wherein the reparation process is performed during a spoke time period intervening two of a sequence of color field periods.  
   
   
       53 . The apparatus of  claim 52 , wherein the first and second refresh pulses of the reparation process have opposite polarities.  
   
   
       54 . The apparatus of  claim 53 , wherein the polarization of the first refresh voltage pulse is opposite to the polarity of the bias voltage.  
   
   
       55 . The apparatus of  claim 47 , wherein the mirror plate comprises a metallic reflecting layer and a non-metallic layer, and each mirror plate is attached to a deformable hinge that comprises an electric conductive layer and a non-metallic layer; and wherein the deformable hinge deforms under the refresh voltage pulses so as to produce a restoration energy when the mirror plate is at the OFF state.  
   
   
       56 . The apparatus of  claim 47 , further comprising: 
 means for changing the polarity of the bias voltage.    
   
   
       57 . The apparatus of  claim 56 , further comprising: 
 means for changing the bias voltage from first value to second value, wherein the micromirror is expected to be at the OFF state with the second value of the bias voltage;    means for maintaining the bias voltage at the second value for a transition time period where the mirror plates at the ON state are expected to be at the OFF states; and    means for performing the reparation process during said transition time period.    
   
   
       58 . The apparatus of  claim 47 , wherein the reparation process lasts for a time period of 1 microsecond or less.  
   
   
       59 . A projection system, comprising: 
 a light source providing illumination light;    a spatial light modulator for modulating the illumination light, comprising an array of micromirrors each comprising a deflectable mirror plate and an addressing electrode;    a controller in communication with the micromirrors, comprising: 
 first means switching the micromirrors between an ON and OFF states with first bias voltage and a set of voltages on the addressing electrodes; and  
 second means for applying first and second refresh voltage pulses to the micromirrors, wherein the first and second refresh voltage pulses are spaced in time longer than the intrinsic oscillation time of the micromirrors; and  
   a display target.    
   
   
       60 . An apparatus for use in operating a device comprising an array of micromirrors each comprising a deflectable mirror plate and an addressing electrode, the apparatus comprising: 
 first means for switching the micromirrors between an ON and OFF states with first bias voltage and a set of voltages on the addressing electrodes;    second means for adjusting the bias voltages and the voltages on the addressing electrodes such that the micromirrors of the array are expected to be in the OFF state; and    third means for applying first refresh voltage pulse to the micromirrors of the array so as to repair a stuck micromirror in the ON state.    
   
   
       61 . The apparatus of  claim 60 , wherein the first means for switching the micromirrors between the ON and OFF states further comprises: 
 means for applying a bias voltage to the mirror plates of the micromirrors and a set of voltages to the addressing electrodes, wherein the voltages on the addressing electrodes are determined according to a set of image data produced from an image using a pulse-width-modulation technique.    
   
   
       62 . The apparatus of  claim 61 , further comprising: 
 means for applying the bias voltage to the mirror plate and a voltage to the addressing electrode associated with said mirror plate such that the mirror plate is rotated to an ON state angle of 10° degrees or more from a non-deflected state, wherein the difference between said two voltages is 30 volts or more.    
   
   
       63 . The apparatus of  claim 62 , wherein the ON state angle is 12° degrees or more relative to the non-deflected state.  
   
   
       64 . The apparatus of  claim 62 , further comprising: means for adjusting at least one of the applied bias voltage and the voltage on the addressing electrode such that the voltage difference between the mirror plate and addressing electrode is 17 volts or less.  
   
   
       65 . The apparatus of  claim 64 , wherein the voltage on the addressing electrode changes 10 volts or more when the mirror plate switches between the ON and OFF states.  
   
   
       66 . The apparatus of  claim 65 , wherein the change of the voltage on the addressing electrode is from 13 to 25 volts when the mirror plate switches between the ON and OFF states.  
   
   
       67 . The apparatus of  claim 60 , wherein the means for applying a set of refresh voltage pulses further comprises: 
 means for performing a reparation process that comprises first and second refresh voltage pulses for the micromirrors, wherein the first and second refresh voltage pulses are spaced in time longer than the intrinsic oscillation time of the micromirror.    
   
   
       68 . The apparatus of  claim 67 , wherein the reparation process is performed at most once during each frame period of a sequence of frames.  
   
   
       69 . The apparatus of  claim 67 , wherein the reparation process is performed during selected frames of the sequence of frames.  
   
   
       70 . The apparatus of  claim 60 , wherein the reparation process is performed at the end of the frame period.  
   
   
       71 . The apparatus of  claim 67 , wherein the reparation process is performed during a spoke time period intervening two of a sequence of color field periods.  
   
   
       72 . The apparatus of  claim 71 , wherein the first and second refresh pulses of the reparation process have opposite polarities.  
   
   
       73 . The apparatus of  claim 72 , wherein the polarization of the first refresh voltage pulse is opposite to the polarity of the bias voltage.  
   
   
       74 . The apparatus of  claim 70 , wherein the mirror plate comprises a metallic reflecting layer and a non-metallic layer, and each mirror plate is attached to a deformable hinge that comprises an electric conductive layer and a non-metallic layer; and wherein the deformable hinge deforms under the refresh voltage pulses so as to produce a restoration energy when the mirror plate is at the OFF state.  
   
   
       75 . The apparatus of  claim 77 , further comprising: 
 means for changing the polarity of the bias voltage.    
   
   
       76 . The apparatus of  claim 75 , further comprising: 
 means for changing the bias voltage from first value to second value, wherein the micromirror is expected to be at the OFF state with the second value of the bias voltage;    means for maintaining the bias voltage at the second value for a transition time period where the mirror plates at the ON state are expected to be at the OFF state; and    means for performing the reparation process during said transition time period.    
   
   
       77 . The apparatus of  claim 76 , wherein the reparation process lasts for a time period of 10 microseconds or less.  
   
   
       78 . The apparatus of  claim 76 , wherein the reparation process lasts for a time period of 1 microsecond or less.  
   
   
       79 . A computer readable medium comprising computer executable instructions for performing the method of  claim 1 .  
   
   
       80 . A computer readable medium comprising computer executable instructions for performing the method of  claim 21 .  
   
   
       81 . A computer readable medium comprising computer executable instructions for performing the method of  claim 40 .  
   
   
       82 . A computer readable medium comprising computer executable instructions for performing the method of  claim 60.