Privacy-enhanced display device

Abstract

A method displays an image only to an authorized user by generating a mask image from a data image. The data and mask image are then displayed periodically in an alternating manner on a display device by a select signal. The opening end shutting of an optical shutter device is synchronized to the displaying of the selected images so that only the data image is perceived by the authorized user viewing the display device through the optical shutter device, and a gray image is perceived by an unauthorized user viewing the data and mask images directly.

1. A method for displaying an a data image only to an authorized user, comprising:
 generating a data image; 
 generating a mask image, from pixels of the data image, wherein the mask image is a negation of the pixels of the data image; 
 generating automatically a select signal with a controller; 
 selecting alternately the data image or the mask image according to the select signal; and 
 sequentially displaying the selected images on a display device to merge the data image and the mask image into a perceived continuous image to provide a perceived gray image to an unauthorized user while displaying the data image only to an authorized user. 
 
     
     
       2. The method of  claim 1  further comprising:
 opening an optical shutter device, according to the select signal, when the data image is displayed; 
 shutting the optical shutter device, according to the select signal, when the mask image is displayed so that only the data image is perceived by the authorized user viewing the display device through the optical shutter device, and the gray image is perceived by the unauthorized user viewing the data and mask images directly, the opening and shutting synchronized in phase and frequency to the select signal. 
 
     
     
       3. The method of  claim 2  wherein the optical shutter device includes a polarizing lens on either side of a ferroelectric liquid crystal polarization rotator. 
     
     
       4. The method of  claim 2  further comprising:
 synchronizing the displaying, and the opening and shutting by a wire link. 
 
     
     
       5. The method of  claim 2  further comprising:
 synchronizing the displaying, and the opening and shutting by a wireless link. 
 
     
     
       6. The method of  claim 5  wherein the synchronization is according to a phase of the select signal. 
     
     
       7. The method of  claim 2  further comprising:
 generating a first random select signal to select the displayed images; 
 generating a second random select signal to open and shut the optical shutter device; and 
 synchronizing the second random select signal to the first random select signal. 
 
     
     
       8. The method of  claim 1  wherein each image is a color image, and the negation is done independently for each color channel of the color image. 
     
     
       9. The method of  claim 8  further comprising:
 gamma-correcting each color channel after the negation. 
 
     
     
       10. The method of  claim 8  wherein each input pixel of each color image has an intensity in a range from 0 to 255, and each output pixel is determined by:
   output=255((input/255) 1/γ )+0.5. 
 
     
     
       11. The method of  claim 1  wherein the select signal is generated by a clock, and further comprising: alternately selecting the data and mask images according to clock cycles. 
     
     
       12. The method of  claim 1  wherein the select signal is generated by a random generator of the controller. 
     
     
       13. The method of  claim 12  wherein the displayed images occur in pairs so that each pair includes a first image and a second image in a random order. 
     
     
       14. The method of  claim 12  wherein the random generator operates according to an internal seed value and a real-time supplied value. 
     
     
       15. The method of  claim 1  wherein each the data image includes a plurality of pixels, and further comprising:
 negating each pixel of the data image serially to generate each corresponding pixel of the mask image; and 
 serially selecting each pixel of the data image or the mask image according to a the select signal; and 
 sequentially displaying the selected pixels on a the display device. 
 
     
     
       16. The method of  claim 15  further comprising:
 opening an optical shutter device when the selected pixel of the data image is displayed; 
 shutting the optical shutter device when the selected pixel of the mask image is displayed so that only the data image is perceived by the authorized user viewing the display device through the optical shutter device, and a gray image is perceived by the unauthorized user viewing the data and mask images directly, the opening and shutting synchronized in phase and frequency to the select signal. 
 
     
     
       17. The method of  claim 16  wherein the select signal is generated by a clock, and further comprising:
 alternately selecting the pixel from the data image and the pixel from the mask images image according to clock cycles of the controller. 
 
     
     
       18. The method of  claim 1  wherein the select signal is generated by a random generator of the controller. 
     
     
       19. The method of  claim 1  wherein a plurality of data images are provided in a video, and each data image is sequentially negated to produce the corresponding mask image. 
     
     
       20. An apparatus for displaying an a data image only to an authorized user, comprising:
 a video camera generating a data image; 
 an inverter for generating a mask image from pixels of the data image, wherein the mask image is a negation of the pixels of the data image; 
 a controller generating automatically a select signal for selecting alternately the data image or the mask image; and 
 a display device for sequentially displaying selected images as a merged perceived continuous image on a the display device to produce provide a perceived gray image and to an unauthorized user while displaying the data image only to an authorized user. 
 
     
     
       21. The apparatus of  claim 20  further comprising:
 an optical shutter device that is opened when the data image is displayed and closed when the mask image is displayed so that only the data image is perceived by the authorized user viewing the display device through the optical shutter device, and a gray image is perceived by the unauthorized user viewing the data and mask images directly, the opening and shutting of the optical shutter device synchronized in phase and frequency to the select signal. 
 
     
     
       22. The apparatus of  claim 20  wherein the data and mask images are selected periodically by the automatically generated select signal. 
     
     
       23. The apparatus of  claim 20  wherein the data and mask images are selected randomly. 
     
     
       24. The apparatus of  claim 20  wherein each image includes a plurality of pixels, and wherein each pixel of the data image is negated serially. 
     
     
       25. The apparatus of claim 20 further comprising a video camera operable to generate the data image.  
     
     
       26. A method for displaying a data image only to an authorized user, comprising:
 emitting a backlight through at least one polarizer and an optical rotator element to project said data image outwardly from a display; and   automatically controlling a modulation of an angle of polarization of the projected data image by controlling said optical rotator element, wherein a substantially uniformly solid color is perceived when viewing the projected data image with an unaided eye and wherein the projected data image is viewable through an optical shutter modulated substantially synchronously with the modulation of the angle of polarization of the projected data image.    
     
     
       27. The method as recited in claim 26 wherein the automatically controlling a modulation of the angle of polarization is performed at least in part by the optical rotator element offsetting a polarization angle by substantially 45°.  
     
     
       28. The method as recited in claim 26 wherein the automatically controlling a modulation of the angle of polarization is random.  
     
     
       29. An apparatus for displaying a data image only to an authorized user, comprising:
 a backlight;   an optical rotator element disposed in front of a polarizer, the optical rotator element modulating an angle of polarization of the data image;   the polarizer positioned between said backlight and said optical rotator element, such that light from the backlight passes through the polarizer and the optical rotator element to project the data image outwardly; and   a controller configured to automatically control the modulation of the angle of polarization by the optical rotator element such that a substantially uniformly solid color is perceived by an unaided eye.    
     
     
       30. The apparatus as recited in claim 29, further comprising:
 an optical shutter device comprising a second optical rotator element;   a second polarizer disposed proximate said second optical rotator element; and   a second controller configured to automatically control a modulation of the angle of polarization by the second optical rotator element, such that said data image is viewable through said optical shutter device.    
     
     
       31. The apparatus as recited in claim 30 wherein the second controller controls the modulation of the angle of polarization to offset the angle of polarization by substantially 45°.  
     
     
       32. The apparatus as recited in claim 30 wherein the modulation is random.  
     
     
       33. The method as recited in claim 26 wherein the uniformly solid color is white.