Abstract:
A display system reduces latent image formation by shifting an image between a first position and a second position, displaced only a few pixels from the first position. Preferably, the image is displayed briefly simultaneously at the first and second positions and then displayed only in the second position for a second predetermined time period.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates generally to a display system and a method for reducing latent images in displays, particularly electro-luminescent displays (ELDs), VFDs, FEDs or CRTs, and assuring that the emissive elements of the display “age” more evenly.  
           [0002]    The effect of uneven aging of the emissive elements in displays, particularly ELDs displays, is well known. Pixels which are activated more than others will “age” sooner than others. As a result, a “latent” image formed by the “aged” pixels will become visible on the display.  
           [0003]    It is known to dim the screen after a period of inactivity by the user, indicated by a lack of input on a user-input device. Alternatively, “screen savers” display moving or changing images which more evenly age the pixels; however, none of these techniques is implemented during use. There may be portions of the display which remain activated for extended periods of time while sufficient activity is occurring in other portions of the screen to prevent the screensaver from activating or the screen to dim.  
           [0004]    High resolution reconfigurable displays are being used more frequently in vehicles. Latent images in these displays is a particular problem, since long periods of time without input from a user-input device are not unusual and do not normally mean that the screen can be dimmed or that a “screen saver” can replace the information being displayed. For example, a display which includes vehicle gages, such as the vehicle speedometer, might operate continuously for hours without a user input, but the information must be displayed constantly. Therefore, the known techniques for reducing latent images are inapplicable.  
         SUMMARY OF THE INVENTION  
         [0005]    The present invention provides a display system and method for reducing the latent image caused by uneven aging of the emissive elements in a display. Generally, the display system displays an image at a first position for a first predetermined time period. The display system then displays the image at a second position only a few pixels displaced from the first position for a second predetermined period of time. Preferably, the image is displayed in the first and second positions simultaneously briefly, and then only in the second position. This reduces the noticeability of the transition of the image from the first position to the second position. In the second position, different pixels will be activated, thus more evenly aging pixels on the screen. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]    The above, as well as other advantages of the present invention, will become readily apparent to those skilled in the art from the following detailed description of a preferred embodiment when considered in the light of the accompanying drawings in which:  
         [0007]    [0007]FIG. 1 is a schematic of the display system of the present invention;  
         [0008]    [0008]FIG. 2 is the display system of FIG. 1, with the image displayed simultaneously in the first and second positions; and  
         [0009]    [0009]FIG. 3 is the display system of FIG. 1 with the image displayed in the second position only.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0010]    A display system  20  of the present invention is shown schematically in FIG. 1. The display system  20  includes a display  22 , such as an ELD, VFD, FED or CRT, having a matrix of pixels  23 , as is generally known. The illumination of the pixels  23  in display  22  is controlled by a display controller  24  having a memory  25 , such as VRAM. It should be recognized that the exact configuration and software of the display controller  24  will depend upon the type of display  22 . The display controller  24  is preferably appropriate to the technology used by the display  22 , again, preferably ELD.  
         [0011]    The display controller  24  drives the display  22  to illuminate a plurality of pixels in a manner generally known according to a video source  26 , which may be a CPU. Based upon the information from the video source  26  stored in the memory  25 , the display controller  24  causes a plurality of pixels to be illuminated on display  22 , forming an image  30  in a first position  32   a  on the display  22 . Although for exemplary purposes, the image  30  is shown as text, it should be recognized that the image  30  could be any image on display  22 , and is preferably the entire image on display  22 , including any icons, text or other images.  
         [0012]    After a first predetermined time period, such as two minutes (or which may be user-defined through software) the display controller  24 , via its software, displays the image  30  in a second position  32   b , while simultaneously displaying the image  30  in the first position  32   a , such as is shown in FIG. 2. This is preferably accomplished by the software in the display controller  24 , without actually changing the content of memory  25 . Preferably, the second position  32   b  is displaced by only a single row and/or single column of pixels from the first position  32   a . For illustrative purposes, the second position  32   b  is shown in FIG. 2 displaced diagonally, as shown, from the first position  32   a . The image  30  is displayed simultaneously in the first and second positions  32   a,b  for an interim period, which is preferably approximately 0.1 seconds. Preferably, the intensities of the image  30  in the first position  32   a  is shifted during the interim period to the image  30  in the second position  32   b . For example, the intensity of image  30  at the first position  32   a  is preferably decreased proportionally as the intensity of the image  30  at the second position  32   b  is increased. The change in intensity for the images  30   a,b  is preferably linear over the interim period. In this manner, the total intensity of the display  22  is not altered and the change from the first position  32   a  to the second position  32   b  is not noticeable.  
         [0013]    After the interim period, the intensity of the image  30  in the first position  32   a  is zero, leaving only the second image  30   b  in the second position  32   b , as shown in FIG. 3. In this manner, different pixels  23  in display  22  are activated, while the user has not perceived that the image  30  has been moved. It is recognized that some of the same pixels activated by the image  30   a  in the first position  32   a  will remain activated by the image  30  in the second position  32   b . Therefore, it may be desirable to continue shifting the image  30  to a third position, preferably also downwardly to the right in the same manner as described with respect to FIGS.  1 - 3 . Subsequently, the image may be shifted in a similar manner in other directions, such as to the left and/or upward, until the image  30  eventually returns to the first position  32   a.    
         [0014]    The total number of pixels by which image  30  is ultimately displaced from the first position  32   a  will depend upon the number of pixels in display  22 , and possibly, the content of image  30 . However, preferably for a standard display of 640 by 480 pixels, the third position is displaced three pixels to the right and two pixels downward from the first position  32   a . Preferably, the display  22  has more pixels than the image  30  displayed so that there is room to move the image  30  without cutting part of it off.  
         [0015]    In accordance with the provisions of the patent statutes and jurisprudence, exemplary configurations described above are considered to represent a preferred embodiment of the invention. However, it should be noted that the invention can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.