Abstract:
An optically addressed photo luminescent display having a printed bar code pixel identifier on an internal side for providing feedback of scanning beam to pixel registration.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application relates to co-pending application entitled “OPTICALLY ADDRESSED DIRECT VIEW PHOTO-LUMINESCENT DISPLAY” by the same inventor, assigned to the same assignee, and filed on even date herewith, which application is incorporated herein in its entirety by this reference. 
     1. Field of the Invention 
     The present invention generally relates to displays, and more particularly relates to optically addressed displays, and even more particularly relates to methods and systems for registering an optical beam used to address pixels in a display. 
     2. Background of the Invention 
     For many years, avionics engineers have endeavored to improve the image quality of displays used in aircraft cockpits. In today&#39;s air transport jetliners, it is becoming increasingly desirable to have displays which are simultaneously viewable by several members of the flight crew (cross-cockpit viewing). This is often a significant challenge for liquid crystal displays, which often have viewing angle limitations. Also, these cockpits frequently experience very high ambient light conditions which increase the brightness requirements for cockpit displays. One display type that has been proposed to address these requirements is the optically addressed direct view photo luminescent display. 
     While the direct view phosphor panel associated with these displays provides excellent viewing angle and brightness characteristics, they do have several drawbacks. At least one of these is that improper coloration and other problems can occur, if the display is excited by a scanned beam of light, because it is often difficult to obtain and maintain proper registration between the scanning beam and the display pixels. 
     Consequently, there exists a need for improved methods and systems for improving display quality in optically addressed displays in an efficient manner. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a system and method for improving display quality in optically addressed displays in an efficient manner. 
     It is a feature of the present invention to include a bar coded beam registration scheme. 
     It is an advantage of the present invention to achieve improved efficiency in registering a scanning light beam with discrete pixels in the display. 
     The present invention is an apparatus and method for improving the quality of optically addressed displays, designed to satisfy the aforementioned needs, provide the previously stated objects, include the above-listed features, and achieve the already articulated advantages. The present invention is carried out in a “misregistration-less” manner in a sense that the misregistration of a scanning light beam with respect to individual display pixels has been greatly reduced. 
     Accordingly, the present invention is a system and method for improving the quality of optically addressed displays which include a bar coding disposed on a backside of a display surface and a detector and feedback mechanism for registering a scanning optical beam. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention may be more fully understood by reading the following description referred embodiments of the invention, in conjunction with the appended drawings wherein: 
     FIG. 1 is a simplified partial cross-section view of a system of the present invention. 
    
    
     DETAILED DESCRIPTION 
     Now referring to the drawings wherein like numerals refer to like matter throughout, and more specifically referring to FIG. 1, there is shown a system of the present invention generally designated  100 , which includes a display panel  102 . Also shown in FIG. 1 is scanning light beam  104  which is emitted from light beam source  105 , which can be a laser light source or a UV LED and optics, such as is commercially available from Nichia Chemical Industries, LTD. of Tokushima, Japan. The spectral frequency of scanning light beam  104  is a matter of designer&#39;s choice and should be matched to a particular type(s) of phosphors used. It should also be noted here that the present bar coding registration scheme, while described herein as being used with a direct view phosphor display, could be used for other displays as well. The direct view phosphor display is, however, believed to be the preferred display. Scanning light beam  104  is preferably scanned using known techniques for scanning beams in optically addressed displays, such as x-y mirrors or acousto-optical modulators. Other means of optically addressing a display panel could be employed as well. 
     The purpose of display  100  is to provide a high quality image to viewer  106 . To assure that the display being presented resembles the intended image, the primary novel feature of the present invention is that it includes a “scanning or addressing beam to pixel” or pixel group registration scheme, which includes a registration feedback photodetector  110 , which detects light from scanning light beam  104  (or other type of addressing optical beam) which, during the excitation process, is reflected off an array of registration bar codes  122  disposed in the display panel  102 . The spectral reflectance of the registration bar codes  122  is a matter of designer&#39;s choice and should be matched to spectral frequency of scanning light beam  104 . The level of specular and diffuse reflectance is also a matter of designer&#39;s choice. The diffuse reflectance should be large enough (greater than 10%) to produce a detectable signal at the registration feedback photodetector  110 . Registration bar codes  122  provide uniquely identifiable reflections from individual pixels or display areas. These uniquely identifiable reflections are captured by registration feedback photodetector  110  and provided to display driving computer  108 , where it is used to feed back information relating to the registration of scanning light beam  104 . These registration bar codes  122  can be minute bar codes which are thin films or other matter printed on the back of phosphor panel  124 . It is believed that registration bar codes  122  are preferably made of reflective material; however, it is possible that the registration bar codes  122  can be an absorptive material, and the reflections of the array of registration bar codes  122  are identified by the lack of reflection from a particular location. Various methods of creating and arranging registration bar codes  122  could be used, depending upon the particular requirements of any application. Whether an individual pixel or merely a display segment is used for registration is a matter of designer&#39;s choice as well. 
     In some applications, it may be preferred to include a lens (refractive or diffractive)  120  which refracts/diffracts the scanning light beam  104 , so that it is more collimated as it passes through registration bar codes  122  and the phosphor panel  124 . 
     Phosphor panel  124  may, in a preferred embodiment, be a broad spectrum producing molecularly aligned non-pixelated phosphor material used in conjunction with a pixelated color filter  126 . Pixelated color filter  126  may be a filter of the type which is well known in the art of LCDs. If attenuation of the scanning light beam  104  is desired, which may be the case for UV light, a dielectric UV blocking element  128  can be disposed between the phosphor panel  124  and the viewer  106 . This dielectric UV blocking element  128  can be an optical bandstop filter or a frequency dependent reflector, both of which are well known in the art. Other well-known means for reducing emission of excitation radiation could be used as well. 
     In some applications where brightness is critical, it may be desirable to provide a multi-color pixelated phosphor panel  124  which has individual color emissive elements which are individually addressed by the scanning light beam  104 . This would eliminate the need for pixelated color filter  126  and its associated brightness attenuation. 
     Throughout this description, reference is made to avionics, because it is believed that the beneficial aspects of the present invention would be most readily apparent when used in an aviation environment; however, it should be understood that the present invention is not intended to be limited to use in such an environment and should be hereby construed to include other non-avionics displays as well. 
     It is thought that the method and apparatus of the present invention will be understood from the foregoing description and that it will be apparent that various changes may be made in the form, construct steps, and arrangement of the parts and steps thereof, without departing from the spirit and scope of the invention or sacrificing all of their material advantages. The form herein described is merely a preferred exemplary embodiment thereof.