Abstract:
These needs, and others, are met by at least one embodiment of the disclosed invention which provides for a touch sensitive screen for an electronic device wherein there is a sparse pattern of sensors disposed within the active area and a dense pattern of sensors disposed within the viewing area. In this configuration, the pixels in the active area may have a larger aspect ratio and provide a more pleasing image while the dense sensors disposed within the viewing area provide more accurate touch sensitivity. Further, the software, or other electronics, used to create the image, may be structured to position menus or other selectable images adjacent to the viewing area. Similarly, certain images, such as icons, can be programmed to be displayed directly under the sensors in the active area. Generally, this configuration provides for the best of both worlds; a bright, clear image with some touch sensitivity in the active area and a sensitive sensor grid in the viewing area where there are no pixels.

Description:
BACKGROUND 
     1. Field 
     This invention relates to electrical devices having a touch sensitive screen and, more specifically, to an electronic device having a touch sensitive screen wherein the touch detectors are disposed in a sparse pattern over the screen active area and in a dense pattern over the viewing area of the screen. 
     2. Description of the Related Art 
     As is well known in the art, users may interact with software or similar constructs through a display screen, or simply “screen.” That is, the screen is structured to display images of various command and control functions which the user selects with an input device. For larger electronic devices, such as computers, the user typically utilizes a keyboard and/or mouse. For smaller electronic devices, such as, but not limited to, personal digital assistants or cellular telephones, control was originally limited to a keypad, as a mouse or similar device was not included. Similarly, electronic devices used in public areas, such as, but not limited to, automatic teller machines, also used simple keypads and did not include input devices such as a mouse or a full keyboard. 
     Users, however, desired the simplicity and ease of use associated with mouse or similar input devices. Thus, one improvement over a simple keypad was the use of a touch sensitive screen. One type of touch sensitive screen included sensors in a transparent layer above the screen. This type of device, however, increased the thickness of the screen and reduced the screen&#39;s optical performance. “In-glass” touch sensitive screens, however, typically included a plurality of sensors  1  disposed within the screen  2  as shown in  FIG. 1 . It is noted that the sensors are shown schematically and are typically not visible to the naked eye. The sensors, which were typically capacitive, mechanical, or optical sensors, provided a signal when actuated. The sensors are actuated when an object, typically a stylus or a finger, is positioned on, or immediately adjacent to, the screen. The sensors are coupled to a sensor output device which is further coupled to a control assembly. The sensor output device and/or control assembly are structured to interpret the sensor signals to determine the position on the screen over which the object is located. Thus, for example, an electronic device could display an image representing commands, such as icons or a menu, and a user could use a stylus or a finger to select the command simply by touching the portion of the screen displaying the icon of menu. Further, the sensors could also, typically, detect a “tap” which indicated when a selection had been made. 
     A screen  2 , such as, but not limited to, a liquid crystal display (LCD) panel  3 , is typically disposed in a frame or housing. The LCD panel utilizes a liquid crystal medium to produce an image formed from a number of small, illuminated points, or pixels, located on a grid. The pixels are spaced as closely together as possible so that the image does not include voids or dark areas. Further, the pixels have an “aspect ratio” that represents the size of the pixel. The screen or LCD panel has an active area that is structured to display images. Disposed about the active area is an inactive area. There are no pixels in the inactive area. Because it is desirable to not have the image abut the frame, a portion of the inactive area is visible to the user. This area is also called the “viewing area.” Beneath the frame is a hidden portion of the inactive area that the user cannot see or touch. 
     As shown in  FIG. 1 , the sensors were typically disposed in a generally constant pattern over the entire active area and viewing area. This pattern is, typically, a dense pattern as the higher the number of sensors, the more accurate the touch sensitivity of the screen. That is, if the sensors were disposed in a sparse pattern, the accuracy of the sensor grid would be reduced and, for example, the controlling software may not be able to accurately identify which icon of menu item the user selected. The use of a dense pattern, however, is a disadvantage as the sensors required space in the active area and, to provide that space, the pixels had to have a reduced aspect ratio. This is a further disadvantage as the software, or other electronics, used to create the image can be structured to limit the locations of the menus or icon to specific portions of the active area, such as an area adjacent to the viewing area. 
     There is, therefore, a need for a touch sensitive screen for an electronic device that has a reduced number of sensors in the active area. 
     There is a further need for a touch sensitive screen for an electronic device that has a sparse pattern of sensors in the active area and a dense pattern of sensors in the viewing area. 
     SUMMARY OF THE INVENTION 
     These needs, and others, are met by at least one embodiment of the disclosed invention which provides for a touch sensitive screen for an electronic device wherein there is a sparse pattern of sensors disposed within the active area and a dense pattern of sensors disposed within the viewing area. In this configuration, the pixels in the active area may have a larger aspect ratio and provide a more pleasing image while the dense sensors disposed within the viewing area provide more accurate touch sensitivity. Further, the software, or other electronics, used to create the image, may be structured to position menus or other selectable images adjacent to the viewing area. Similarly, certain images, such as icons, can be programmed to be displayed directly under the sensors in the active area. Generally, this configuration provides for the best of both worlds; a bright, clear image with some touch sensitivity in the active area and a sensitive sensor grid in the viewing area where there are no pixels. Further, in use, the user&#39;s finger or stylus is disposed generally to the side of the menu as opposed to blocking the menu from view. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of a prior art touch sensitive screen having sensors disposed in a constant pattern. 
         FIG. 2  is a schematic, exploded view of an electronic device. 
         FIG. 3  is a schematic view of a touch sensitive screen having sensors disposed in a sparse pattern in the active area and in a dense pattern in the viewing area. 
         FIG. 4  is a schematic view of a touch sensitive screen having sensors disposed in a sparse pattern in the active area and in a dense pattern in the viewing area, and further showing how the displayed image corresponds to the placement of the sensors. 
         FIG. 5  is a schematic view of a touch sensitive screen having sensors generally disposed in a sparse pattern in the active area, in a dense pattern in the viewing area, and having a limited area of dense sensors in the active area. 
         FIG. 6  is a schematic view of a touch sensitive screen having sensors disposed in a sparse pattern in the active area and in an alternate dense pattern in the viewing area. 
         FIG. 7  is a schematic view of a touch sensitive screen having sensors disposed in a sparse pattern in the active area and in an alternate dense pattern in the viewing area. 
     
    
    
     Similar numerals refer to similar parts throughout the specification. 
     DESCRIPTION 
     As used herein, “touch sensitive” means structured to detect contact or near contact. 
     As used herein, “coupled” means a link between two or more elements, whether direct or indirect, so long as a link occurs. 
     As used herein, “directly coupled” means that two elements are directly in contact with each other. 
     As used herein, an “aspect ratio” it the ratio of a pixel&#39;s height divided by the pixel&#39;s width. 
     As shown in  FIG. 2 , an electronic device  10 , herein represented by a handheld personal digital assistant, includes a housing  12 , a control assembly  14 , and a display assembly  16 . As is known, the control assembly  14  includes a processor  18 , memory  20 , as well as other components, such as, but not limited to, a circuit board (not shown), structured to link the processor  18 , memory  20 , and display assembly  16 . The control assembly  14  further includes a set of instructions, such as, but not limited to, software, structured to perform various functions including creating images on the display assembly  16  and receiving input from the user. Thus, the control assembly  14  is structured to provide a video input to the display assembly  16  input/output assembly  30  (described below) and to receive sensor output from a sensor assembly  70  ( FIG. 3 .). 
     The display assembly  16  includes an input/output assembly  30  and an LCD panel  32 . The display assembly input/output assembly  30  is structured to receive a video input from the control assembly  14  and to produce an image on the LCD panel  32 . The LCD panel  32  includes a lower substrate  40  and an upper substrate  42  disposed in a close, but spaced, relationship. The LCD panel  32  also includes a liquid crystal layer  44  disposed between the lower and upper substrates  40 ,  42 . Upon application of an electrical charge, the liquid crystal molecules of the liquid crystal layer  44  are structured to align in a generally perpendicular direction with respect to the substrates  40 ,  42 . The lower substrate  40  has a lower, outer surface  46  and an upper, inner surface  48 . The upper substrate  42  has a lower, inner surface  50  and an upper, outer surface  52 . The lower substrate upper, inner surface  48  has a first electrode  54 , also called the pixel electrode, applied thereto. The upper substrate lower, inner surface  50  has a second electrode  56 , also called the common electrode, applied thereto. 
     The first and second electrodes  54 ,  56  form a grid that defines the aperture size of the pixels. The display assembly input/output assembly  30  selectively controls the location of the charge applied to the first electrode  54  thereby forming images on the LCD panel  32 . Typically, the display assembly input/output assembly  30  includes a programmable logic circuit, or integrated circuit, structured to apply a charge to the proper pixels. 
     The LCD panel  32  only creates an image in the area defined by the overlap of the first and second electrodes  54 ,  56 . The LCD panel  32  has a greater area than the first and second electrodes  54 ,  56 , however. As shown in  FIG. 3 , the area wherein an image is created is the active area  60  of the LCD panel  32 . Immediately adjacent to, and surrounding, the active area  60  is an inactive area  62  wherein there are no pixels and no image is created. This area is called the viewing area  64 . Typically, the perimeter of the inactive area  62  is disposed below the electronic device housing  12  and cannot be seen or touched by the user during normal operation. 
     The electronic device  10  ( FIG. 2 ) also includes a sensor assembly  70  ( FIG. 3 ) having an output device  72  and a plurality of detectors  74 . As noted above, the detectors  74  are shown schematically and are typically too small to be seen by the naked eye. Each detector  74  is in electrical communication with the output device  72 . Each detector  74  creates an output signal when actuated. The detectors  74  are disposed in a pattern, discussed below, and are structured to detect an external object immediately adjacent to, or touching, the LCD panel  32 . The external object is typically a stylus or the user&#39;s finger (not shown). The output device  72  and/or the control assembly  14  are structured to receive the detector signals and convert the signals to data representing the location of the external object relative to the LCD panel  32 . The detectors  74  are typically capacitive detectors  74 A, optical detectors  74 B, or mechanical detectors  74 C. Typically, capacitive detectors  74 A are structured to detect a change in capacitance caused by the electrical field of the external object or a change in capacitance caused by the compression of the capacitive detector  74 A. Optical detectors  74 B are structured to detect a reflection of light, e.g., light created by the LCD panel  32 . Mechanical detectors  74 C include a charged grid with columns disposed on one side of the LCD panel  32  and a corresponding grid without columns on the opposing side of the LCD panel  32 . When the LCD panel  32  is compressed, i.e. as a result of being touched by the user, the columns at the area of compression contact the opposing grid thereby completing a circuit. Capacitive detectors  74 A may be disposed upon the lower substrate upper, inner surface  48  or upon the upper substrate upper, outer surface  52 . The detectors  74 , although small, require space and any pixel adjacent to a detector  74  will have a reduced size, or aperture, to accommodate the adjacent detector  74 . 
     The detectors  74  are disposed in a pattern, preferably in lines wherein multiple lines form a grid. The pattern has at least a first portion  80  and a second portion  82 . Detectors  74  in the first portion  80  are disposed over the active area  60 . Because the active area  60  also includes the pixels that form the image, the detectors  74  in the first portion  80  are disposed in a sparse pattern so that fewer pixels will have a reduced aspect ratio. Preferably, the spacing of detectors  74  in the first portion  80  is between about 1.0 mm and 10.0 mm between the detectors  74 , and more preferably about 3.0 mm between the detectors  74 . Conversely, detectors  74  in the second portion  82  are disposed over the viewing area  64 . Because the image is not created in the viewing area  64 , and therefore there are no pixels to be adversely affected, the detectors  74  in the second portion  82  are disposed in a dense pattern. Preferably, the density of detectors  74  in the second portion  82  is between about 0.5 mm and 6.0 mm between the detectors, and more preferably about 1.0 mm between the detectors. 
     The control assembly  14  is structured to create the image and define the boundaries of selectable portions of the image on the active area  60  of the LCD panel  32 . For example, and as shown in  FIG. 4 , the control assembly  14  will, for example, create the image of a pull-down menu  90  or a selectable icon  92  ( FIG. 3 ) on specific portions of the active area  60  of the LCD panel  32 . The control assembly  14  is further structured to relate specific detectors  74  to the specific portions of the active area  60  of the LCD panel  32 . Thus, when the control assembly  14  detects the actuation of a specific detector  74  adjacent to a specific image, e.g. an icon  92 , the control assembly  14  will perform the command related to that icon  92 , e.g. opening the calendar program. 
     As shown in  FIGS. 3 and 4 , in one embodiment the detectors  74  in the first portion  80  are disposed in a loose grid and detectors  74  in the second portion  82  are disposed in a dense line extending adjacent to the right-hand side and the bottom side of the active area  60 . When the detectors  74  are disposed in this pattern, the control assembly  14  is, preferably, structured to create interactive images having multiple selections, such as, but not limited to, pull-down menus  90  along the right side of the active area  60 . Conversely, other interactive images, such as, but not limited to, icons  92  or, as shown, selectable dates  94  on a calendar ( FIG. 4 ), are created in the first portion  80  and are created so that each interactive image is located adjacent to a limited number of detectors  74 . In this configuration a user may, for example, select a date by touching the desired date. As there is, preferably, only one detector  74  within the image of the date, the output device  72  and/or the control assembly  14  will be able to identify which date is being selected. The user may then, for example, open a pull down menu  90 . As the pull-down menu  90  has multiple selections, i.e. menu items, located very close to each other, the user moves the external object along the right side of the active area  60  wherein the detectors  74  in the second portion  82  are disposed in a dense pattern. Because the detectors  74  in the second portion  82  are disposed in a dense pattern, the control assembly  14  will be able to more accurately identify which of the closely disposed menu items is being selected. 
     As shown in  FIG. 5 , in another embodiment the pattern of detectors  74  has a first portion  80 , a second portion  82 , and a third portion  84 . The first portion  80  and second portion  82  are substantially similar to the embodiment described above. The third portion  84  is an area of detectors  74  disposed in a dense pattern and located within the active area  60 . In this configuration, the third portion  84  is structured to support a virtual control device  100 , such as a virtual roller wheel  102  or similar device. The image quality in the third portion  84  is adversely affected for the reasons set forth above. However, the third portion  84  is, preferably, a relatively small area compared to the entire active area  60 . Preferably, the density of detectors  74  in the third portion  84  is between about 0.05 mm and 3.0 mm between the detectors, and more preferably about 0.1 mm between the detectors. Further, because the third portion  84  is a dedicated area for the virtual roller wheel  102 , it is acceptable to have a reduced pixel density with larger pixels. Since the pixel size would be very large, the aspect ratio could be significantly higher, e.g., about 65 to 98. These pixels would be special function pixels, such as pixels to light up the roller wheel  102  area and other features to highlight the roller wheel  102 . 
     As shown in  FIGS. 3-5 , the detectors  74  in the second portion  82  are shown as being in a single straight line. The invention, however, is not so limited. For example, as shown in  FIG. 6 , the detectors  74  in the second portion  82  may be disposed in a dense but alternating pattern having two generally parallel lines of detectors  74 . Further, as described above and as shown in  FIGS. 3-5 , the detectors  74  in the second portion  82  are disposed in a dense line extending adjacent to the right-hand side and the bottom side of the active area  60 . Again, the invention is not so limited and, as shown in  FIG. 7 , the detectors  74  may be disposed on any portion of the viewing area  64  such as, but not limited to, along the left-hand side for use with interactive images that are displayed along the left side of the active area  60 . Further, sensors  74  may be disposed along both the left-hand side and the right-hand side so that the user may use either hand, or both hands, to operate the electronic device  10 . 
     While specific embodiments of the disclosed and claimed concept have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the disclosed and claimed concept which is to be given the full breadth of the claims appended and any and all equivalents thereof.