Patent Application
20080122997
The present invention relates to a liquid crystal display (LCD) panel for use with pen tablet applications, and more particularly, to equipping the LCD panel with a sensor for detecting a location designated by a pen shaped device.
There are various types of user interfaces for liquid crystal display (LCD) based applications. For example, some LCD devices allow users to interact via keyboard or touchscreen. However, many types of LCD devices utilize pen tablet applications to receive user input. Pen tablet applications are intuitive. Also, pen-based interfaces are particularly useful for smaller, more portable LCD devices, e.g., personal digital assistants (PDAs).
The configuration of a typical LCD panel will now be explained with reference to
Furthermore, a series of electrodes (not shown) are positioned across the LC layer 20. Particularly, by selectively applying voltages across the liquid crystal molecules in the LC layer 20, these molecules are made to “twist” in such a manner as to allow light to pass through. Thus, the electrodes (not shown) drive the LC layer 20 to display certain images by controlling the passage of light therethrough.
Generally, previous attempts to utilize a pen tablet application in conjunction with an LCD panel (backlit or reflective-type) require additional panels or layers to be added to the LCD device 1. For example, in an existing type of pen tablet application, an additional printed circuit board (PCB) provides coiled antennae beneath the LCD screen, in order to create an alternating magnetic field around the LCD screen. Movement of the pen device (stylus) across the LCD screen is sensed using the alternating magnetic field from the PCB board. However, such use of additional layers to the LCD device is disadvantageous, because it introduces unwanted interactions and noise in the LCD device, decreases brightness, increases the complexity of the resultant device, and reduces overall system reliability.
Exemplary embodiments of the present invention are directed to a liquid crystal display (LCD) device, which is adapted for applications utilizing a stylus or pen shaped input device. Particularly, the tip of the input device includes a light emitter, and a light sensor is built within the LCD device to sense the light rays emitted by the input device. Thus, as the input device is being used to designate a particular location on the display surface (e.g., by touching the display surface with the input device), the LCD device senses light rays from the input device transmitting through the liquid crystal (LC) layer. Based on this sensing operation, the LCD device is capable of determining the location on the display surface being designated by the input device.
According to an aspect of the present invention, the LC layer may be controlled in such a way as to help track down the location being designated by the stylus or pen shaped input device. For instance, after the presence of the input device is initially detected, the LC layer may be controlled to selectively provide one or more translucent regions or “openings,” while the remainder of the LC layer is in a default state of opacity. Thus, by manipulating (i.e., changing the position, size, and/or number of) these translucent openings, and simultaneously monitoring the status of the light sensing device, the location of the tip of the input device may be narrowed down to a desired level of precision.
For instance, it is possible to control the LC layer to cause a translucent opening to scan the display surface in search for the location being designated by the input device. By taking measurements with the light sensor at each scan interval, the designated location would correspond the scan location of the translucent opening that maximizes the measured intensity.
Alternatively, the LC layer may be controlled according to a process where search areas are recursively defined within the LC layer. As each new search area is defined, the search area may cycle through a series of states in which the translucent region becomes successively smaller. By cycling through each search area through these states, the designated location is tracked down to a smaller region within the search area, and this smaller region is defined as the next search area for the next iteration of the recursive process.
According to another aspect of the invention, the LCD device may be designed to operate according to two distinct interleaved modes. These modes may include an image display mode during which the LC layer is controlled to display images on the display surface, and a “pen tablet” mode during which the LC layer is controlled (as described above) to facilitate detection of the location being designated by the stylus or pen shaped input device.
Further aspects in the scope of applicability of the present invention will become apparent from the detailed description provided below. However, it should be understood that the detailed description and the specific embodiments therein, while disclosing exemplary embodiments of the invention, as provided for purposes of illustration only.
A more complete understanding of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings, which are given by way of illustration only and, thus, are not limitative of the present invention. In these drawings, similar elements are referred to using similar reference numbers, wherein:
In order to allow users to interface with a liquid crystal display (LCD) device, the present invention utilizes a stylus or pen shaped input device, which is configured to emit light from one end (i.e., its “tip”), and a light sensing device within the stack of LCD layers for sensing the light emitted by the input device. Based on the operation of the light sensing device, the LCD device is capable of determining the location of the tip of the input device, as it touches (or nearly touches) the display surface. Thus, the LCD device is capable of determining a particular location being designated by the user via the input device.
Furthermore, at least one light sensing device 80 is implemented within the LCD stack, behind the LC layer 20. A key feature of this particular embodiment is that the light sensing device(s) 80 is implemented behind the LC layer 20. Otherwise, the positioning of the light sensing device 80 and other elements in
As shown in
For example, the user may simulate handwriting or drawing movements on the display surface, using the input device 200, in order to continuously designate locations on the display surface. The LCD device 100 is capable of tracking the continuous movement of the input device 200 while it is touching the screen. Further, the LCD device 100 may be configured to illuminate pixels corresponding to this movement, thereby displaying the symbols or pictures drawn by the user. Thus, the LCD device 100 may operate as a type of pen tablet for the user's notes, pictures, symbols, etc.
Thus, as a matter of convenience, the operation of the LCD device 100 in detecting the location(s) designated by the user, via the input device 200, will be referred to as a “pen tablet” mode of operation. However, the use of this term is not limiting. For example, while operating in the pen tablet mode, the LCD device 100 may merely allow the user to designate singular locations on the display surface with the input device 200, e.g., pointing to checkboxes in order to choose from a plurality of menu choices.
Operative principles of the LCD device 100 will now be described. To describe general principles of operation, reference will be made to
According to an exemplary embodiment, the LCD device 100 may be configured for dual modes of operation, where the pen tablet mode is interleaved with a normal image display mode. Thus, the total system cycle time for the device 100 may be split into two distinct time periods: (1) a normal LCD frame period and (2) a pen tablet period.
During the normal LCD frame period (image display mode), the LCD device 100 operates to actively display an image, e.g., according to conventional techniques. Thus, during this period, the LC layer controller 92 may use conventional processes or programming for controlling the LC layer 20 to display a desired image. Also, if the LCD device 100 is backlit, the backlight source 50 is in normal operation during this period.
On the other hand, during the pen tablet period (pen tablet mode), the LCD device 100 detects whether the input device 200 is currently being used to designate a location and, if so, which location is currently being designed. Thus, during the pen tablet period, the LC layer controller 92 controls the LC layer 20 to facilitate such detection, according to principles to be described below. During this period, the position determining unit 94 and light sensing device 80 are also operative, as will be described in more detail below. Also, during the pen tablet period, any backlight source(s) 50 may be turned off to make it easier for the light sensing device 80 to sense light being emitted through the LC layer 20 from the emitter 210 of the input device 200.
It should be noted that, depending on the processing speed of the LCD device 100, the pen tablet periods may be much smaller than the LCD frame periods. Thus, a majority of the system cycle time in the LCD device 100 will be devoted to the normal image display mode. As another design consideration, the rate of interleaving between pen tablet periods and LCD frame periods should be relatively high. For example, it is contemplated that the pen tablet periods could be interleaved with the LCD frame periods at a rate of 60, 90, or 120 Hz (however, other interleaving rates could also be used).
According to an exemplary embodiment, in order to initially detect the presence of the input device 200 at the display surface during a particular pen tablet period, an operative portion of the LC layer 20 may be made translucent (i.e., optically transparent), while all other portions of the LC layer are made opaque. If the input device 200 was not detected during the preceding pen tablet period, the operative portion for the current period may be defined as corresponding to all areas of the display surface that could potentially be designated by the input device 200. However, if the input device 200 was detected during the preceding pen tablet period, the operative portion for the current period may be defined as a particular window or region surrounding the previously designated location, thus allowing the emitter 210 to be more rapidly detected/located.
As the operative portion is made translucent during the initial stage of the pen tablet period, a sensing operation is performed by the light sensing device 80 to detect whether the input device 200 is at the display surface. For example, to perform this detection, an intensity measurement may be obtained from the light sensing device 80 and compared to a threshold. If the threshold is met or exceeded, further operations may be performed by the LCD device 100 to determine the designated location, i.e., the location on the display surface where the emitter 210 is currently located.
According to an exemplary embodiment, the input device 200 may be designed to emit modulated light. Thus, the light sensing device 80 may be configured to demodulate and measure such light. For example, the emitter 210 may comprise a light-emitting diode (LED), or other type of light source, configured to emit modulated light. In order to more easily discriminate the emitted light from other light (e.g., backlight or ambient light), the emitter 210 may emit infrared (IR) light, and the light sensing device 80 may include an IR light sensor.
During the pen tablet period, if the emitter 210 of input device 200 is detected at the display surface, the LC layer 20 may further be controlled in order to determine the location being designated by the input device 200. To make this determination, the LC layer 20 may be divided into opaque and translucent regions.
As particularly illustrated in
Accordingly, as shown in
This concept of utilizing a translucent region 25 in an otherwise opaque LC layer 20 may be implemented in different ways. To illustrate this, two alternative embodiments will be described below.
In one particular exemplary embodiment, during each pen tablet period, a small translucent region 25 may be provided to scan the LC layer 20 in search for the designated location. In this embodiment, the translucent region 25 may be referred to as a translucent “opening” because its size is relatively small. Specifically, the size of the translucent opening 25 corresponds to the desired precision for determining the designated location. For instance, the translucent opening 25 may be the size of a single pixel, or on the order of a few pixels, for pen tablet applications requiring precise tracking of input device 200.
In this embodiment, during each pen tablet period, the translucent opening 25 may scan the operative portion of the LC layer 20 according to a particular scanning pattern. Examples of such scanning patterns are illustrated in
For an embodiment utilizing a scanning translucent opening 25, it is possible to begin each pen tablet period by first making the operative portion of LC layer 20 translucent in order to sense whether or not the input device 200 is present at the display surface. If the light sensing device 80 detects the presence of input device 200 during this initial stage, the LCD device 100 may proceed to scan the translucent opening 25 to determine the designated location. However, it is not absolutely necessary to perform this initial detection stage during each pen tablet period. Another possibility would be to start scanning the translucent opening 25 at the beginning of each pen tablet period.
As described above, according to one exemplary embodiment, a translucent opening 25 may scan the LC layer 20 to search for the location designated by the user via the input device 200. However, there are other ways to determine the designated location.
For instance, according to an alternative exemplary embodiment, the LC layer 20 may be controlled through successive stages to narrow down the designated location to a particular search area. Furthermore, after a new search area is designated in such a manner, the process may be recursively applied to the new search area in order to further track down the designated location.
At the beginning of a pen tablet period, the operative portion of the LC layer 20 may be logically divided into four quadrants (I-IV). As described above, the operative portion of the LC layer 20 may correspond to all areas of the display surface that could potentially be designated by the input device 200. However, if a designated location was found during the preceding pen tablet period, the operative portion may correspond to a particular region or window that is centered upon the previously found designated location.
Referring again to
As shown in
Thus, in the First Stage, it is determined whether the light sensing device 80 still senses the presence of the emitter 210 when only two of the quadrants are translucent, in order to narrow down the operative portion to “candidate quadrants,” i.e., quadrants that could possibly contain the designated location. Particularly, if the emitter 210 is still sensed during the First Stage (as would be the case in
After the First Stage,
This process may then be recursively applied to the new designated search area 28. Accordingly, the process illustrated in
Particularly,
As shown in
In the exemplary embodiment described above in connection with
For example, assume that the location of the emitter 210 on the display surface (i.e., the location being designated via input device 200) is to be determined within an M-by-M pixel block of accuracy. Further, assume that the display surface is defined by 2n such pixel blocks along the horizontal axis and 2n such pixel blocks along the vertical axis. For the pen tablet period in which the input device 200 is initially detected, it would take at most 2n+1 steps to determine the designated location on the display surface. Thus, if the designated location is to be determined within one pixel, in a 60 Hz LCD device 100 with a display surface covering 1024-by-1024 pixels, it should take at most 0.3 seconds (31 pen tablet periods) to find the designated location within the desired precision.
Exemplary embodiments having been described above, it should be noted that such descriptions are provided for illustration only and, thus, are not meant to limit the present invention as defined by the claims below. Any variations or modifications of these embodiments, which do not depart from the spirit and scope of the present invention, are intended to be included within the scope of the claimed invention.
