Abstract:
In one embodiment, a touch detection system and method is achieved having high resolution by forming an integrated array of alternating emitters and detectors. Using integration techniques, the detectors can be made much larger than the emitters while the gaps between the emitters and detectors are maintained relatively small. Thus, high resolution is achieved without dramatically increasing the number of emitter/detector pairs. In one embodiment each array is positioned on an edge of a display such that the emitter of one array is lined up (on axis with) a detector of an opposing display. In one embodiment, the touch detection system and method operates to detect the amplitude of signals arriving from opposing arrays so as to precisely determine the location of a touched position. Off-axis scanning can be employed to increase sensitivity.

Description:
TECHNICAL FIELD  
       [0001]     This disclosure is related to optical touch position systems and more particularly to such systems using interleaved emitters and detectors and using full amplitude signal detection and processing.  
       BACKGROUND  
       [0002]     Infrared optical touch panels can be found in a variety of systems, most notably on 10″ to 15″ LCD display systems such as ATM terminals, vending machines, and kiosk terminals. By surrounding the LCD with infrared emitters paired with corresponding detectors across the LCD display, the touch panels are able to respond to contact with the screen. Such a response is accomplished by scanning each of the infrared emitters sequentially to determine whether the infrared signal received by the corresponding detector has been “blocked”. When a blocked signal is found, a “touch” is sensed and the position of the touch is calculated based on the “blocked” detector.  
         [0003]     For large LCD display systems, such as the ones discussed above, it is easy to place numerous emitter/detector pairs around the system as the size of the emitters and detectors are not a major constraint on such relatively large display systems. The numerous pairings produce a relatively sensitive screen and enables the user to make contact in many areas of the screen.  
         [0004]     However, coupled with the growth in the market for portable devices is the demand for infrared displays on these devices. It has become increasingly marketable to include highly-sensitive infrared displays on cellular phones, personal digital assistants (PDAs), calculators, and the like. By including infrared displays on these systems, manufacturers are able to replace traditional key pads and further decrease the size of these devices.  
         [0005]     As a result of the decrease in size of these portable devices, it has become a major technical challenge to implement highly-accurate infrared optical touch panels in such a limited space. As the space available to mount these infrared systems onto the portable devices has decreased considerably, manufacturers desire to keep the width and thickness of the infrared system on these devices minimal. To accomplish this goal, the size of the emitter/detector pairs must be designed in very low profile to fit the dimensions of these compact systems.  
         [0006]     The use of infrared panels on portable devices is further constrained by the need for accuracy and sensitivity. Thus, such devices must be able to support use of a stylus having a relatively fine point as well as handwriting recognition. This in turn increases the need for a high-resolution, high-sensitivity display. Accordingly, such a system must either include a large number of emitter/detector pairs, thus increasing the overall size and bulk of the device, or employ an algorithm and alternate design for the emitter/detector pairing to produce a high-resolution, highly-sensitive infrared panel that is relatively compact in size.  
       BRIEF SUMMARY  
       [0007]     A touch detection system and method is accomplished by surrounding an LCD display with integrated arrays of alternating emitters and detectors. By integrating the arrays into one unit, the size of the detectors can be much greater than that of the emitters and the space between each emitter and its adjacent detector can be reduced to a relatively small amount. In one embodiment, a touch detection system and method is achieved having high resolution by forming an integrated array of alternating emitters and detectors. Using integration techniques, the detectors can be made much larger than the emitters while the gaps between the emitters and detectors are maintained relatively small. Thus, high resolution is achieved without dramatically increasing the number of emitter/detector pairs. In one embodiment each array is positioned on an edge of a display such that the emitter of one array is lined up (on axis with) a detector of an opposing display. In one embodiment, the touch detection system and method operates to detect the amplitude of signals arriving from opposing arrays so as to precisely determine the location of a touched position. Off-axis scanning can be employed to increase sensitivity. By lining up emitters on one edge of the display with a corresponding detector on an array across the display, a greater percentage of the display screen is covered by infrared signals, thus increasing the sensitivity and resolution of the touch detection system.  
         [0008]     In one embodiment a change in amplitude of the optic signal is detected yielding, a greater degree of accuracy can be achieved when calculating the position of an object in contact with the display screen.  
         [0009]     The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized that such equivalent constructions do not depart from the invention as set forth in the appended claims. The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present invention. 
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0010]      FIGS. 1 and 2  show prior art touch screen system;  
         [0011]      FIG. 3  shows one embodiment of a high resolution touch screen;  
         [0012]      FIG. 4A  illustrates how coordinates of a “touch” can be determined for a relatively large stylus;  
         [0013]      FIG. 4B  illustrates how coordinates of a “touch” can be determined for a small stylus; and  
         [0014]      FIG. 5  illustrates the logic controlling one embodiment of the system. 
     
    
     DETAILED DESCRIPTION  
       [0015]      FIG. 1  depicts one prior art optical touch system. On the vertical axis, emitters are placed on the left side of display  10 , while corresponding detectors are placed on the opposite edge of the display, thus forming emitter/detector pairings  001 - 007  along the vertical (y) axis. Note that each pair (such as pair  001 ) includes an emitter (such as emitter E 001 ) and a detector (such as detector D 001 ). The same pairings occur on the horizontal axis of display  10 , with emitters placed at the top of display  10  and corresponding detectors located at the bottom of the display, forming emitter/detector pairings  011 - 016  along the horizontal (x) axis. Under the prior art, when contact  130  is sensed, the system scans the y-coordinate by activating emitter/detector pairs  001 - 007  sequentially. Thus, beginning with emitter/detector pair E 001  and D 001 , the system determines whether the infrared signal between the emitter and corresponding detector has been blocked. This process occurs until the system activates emitter E 003  and detector D 003 , and recognizes that the signal between emitter E 003  and detector D 003  has been interrupted. Thus, the y-coordinate of contact  130  is known. The system then scans the x-axis by sequentially activating emitter/detector pairs  011 - 016  to determine where the infrared signal has been blocked. Upon activating emitter E 015 , the system recognizes that the signal to detector D 015  has been blocked, and the x-coordinate of contact  130  is thus known. As both the horizontal and vertical axis have been scanned, the position of contact  130  is now known. In actual practice, several beams would be interrupted (unless the stylus was very small) and the position would be determined by averaging the x position and then the y position.  
         [0016]     The conventional touch screen system works relatively well when large objects make contact with a particular position on the screen and completely block the infrared signals produced by two intersecting emitter/detector pairings. However, a number of problems arise under the prior art. As depicted in  FIG. 1 , the resolution of the display screen is limited by the density of the emitter/detector pairs. Since the emitted infrared signal from an emitter is conical in shape it tends to “fan” out as it traverses the panel and thus a signal from one detector would fall upon not only the diode directly opposite, but on adjacent diodes as well. This will cause cross-talk and by enabling the emitter/diode pairs sequentially such cross-talk is reduced. Because the signal is a conical beam the area that can be detected is limited by the width of the detecting diode. This, as will be noted below, allows “holes” in the coverage for touches having small size and results in areas of display  10  that are not covered by an infrared signal. For example, if contact occurs precisely at position  101 ,  110 ,  120 ,  130 , or  140 , blockage of intersecting signals is recognized and the exact location of contact can be determined. However, if contact occurs at positions  105 ,  115 ,  125 , or  135 , upon sequential activation of the emitter/detector pairs on both the vertical and horizontal axis, the signal is not blocked, and contact is not registered. Using the conventional method, contact is detected on less than 50% of the screen and blind spots, such as blind spot  100 , result. This will cause serious problems when the stylus size is small because the stylus cannot block any beam if the stylus is touching areas such as  100 ,  105 ,  115 ,  125  or  135 .  
         [0017]      FIG. 1  also depicts one attempt by the prior art to increase the density of infrared signals as shown, additional emitters are positioned between the existing emitters E 001  to E 007 . However, simply inserting additional emitters, such as additional emitter E 002 . 5  does not work because there is not sufficient room to insert matching diodes between diode D 002  and D 003 . In order to make room for additional detectors (thereby increasing sensitivity), the size of each detector would have to be made smaller with the result that the sensitivity of the detectors actually decreases (less volume upon which light can fall) on thus the power of each emitter must be increased to maintain sensitivity.  
         [0018]     Other problems also arise when an object only partially blocks an infrared signal. For example, contact-area  160 , while interrupting x-axis emitter/detector pair  012  fails to interrupt any cross-signal produced by any emitter/detector pair on the y-axis, and contact-area  170  only partially interrupts a signal between emitter/detector pairs  004  and  012 . In the case where only one signal is partially or fully blocked, only one coordinate can be obtained and the system must employ alternative methods to determine the second coordinate of the object. Off-axis sweeping has been suggested as a possible remedy to this problem. However, if off-axis sweeping is to be done, the system would require higher speed processing capabilities and more complicated algorithms for mapping from a non-uniform (cross-axis) grid to a uniform one.  
         [0019]     As depicted in  FIG. 2 , attempts have been made to alternate emitters and detectors around a display such as display  20 , in an effort to ameliorate the density issues noted with respect to  FIG. 1 . In this configuration, emitter  201  is situated adjacent to detector  202 , which is situated adjacent emitter  203 , etc. On the opposite side of display  20 , detector  210  receives a signal from emitter  201 , emitter  211  produces a signal received by detector  202 , etc. Although an improvement over the conventional touch-screen method, this alternating scheme still results in less than 50% of display  20  being covered by infrared signals.  
         [0020]      FIG. 3  depicts one embodiment of a high resolution touch screen. Along each horizontal and vertical axis, emitters and diodes are alternated and integrated into arrays. In these arrays, the emitter size is fairly small and the detector diameter is fairly large. By increasing the proportional size of a detector relative to its corresponding emitter, the sensitivity of the sensor is maintained and thus less power consumption is required by the emitter. Additionally, the gaps between emitters and detectors are kept as small as possible (on the order of 1 mm, thus increasing the number of emitters and detectors that can be inserted around the display system in a given area a typical detector would be at least 3 times the size of an emitter. As a result of the interleaving configuration with such a small gap size and emitter/detector ratio to length, the overall sensitivity of the system to contact is increased due to greater signal coverage.  
         [0021]     By constructing these arrays using integrated circuit technology, the arrays can be positioned around the four edges of display  30  and can have a height of 0.4 mm with a width of 0.4 mm. This results in an emitter on one-axis aligned with a detector on the same axis across display  30 . For example, the array comprising the left y-axis is arranged such that emitter E 301  is placed directly adjacent to detector D 302 . Located directly across display  30  on the right y-axis are corresponding detector D 301  and emitter E 302 . The same pairing occurs on the horizontal axis—emitter E 314  at the top display  30  is paired with detector D 314  at the bottom of display  30  and emitter D 324  at the top display  30  is paired with detector D 324  at the bottom of display  30 .  
         [0022]     As shown in  FIG. 4A  for a relatively large stylus, when an object  410  comes into contact with display  40 , the system performs on-axis x and y direction sweeping to provide the coarse position (Xi, Yi) and size information of the stylus. This coarse information is (X 1 , X 2 ; Y 1 , Y 2 ), where X 1  and X 2  (X 2 &gt;=X 1 ) are the starting and ending coarse coordinates in the X direction, while Y 1  and Y 2  (Y 2 &gt;=Y 1 ) are the starting and ending coarse coordinates in the y-direction. The detected amplitudes at X 1 , X 2 , Y 1 , Y 2  is more than or equal to zero (partially or completely blocked), while the amplitudes of those between them are zero (completely blocked).  
         [0023]     As depicted in  FIG. 4A , the emitter and detector pairs on the x axis are labeled EX 00 , DX 00 , EX 01 , DX 01  to EX 13 , DX 13  and on the Y axis, EY 00 , DY 00  to EY 21 , DY 21 . The coarse X coordinates are defined from 0 to 13 Y from 0 to 21. Note that any number of pairs can be used on the X or Y axis. The panel is divided so that the fine x coordinates are from 0 to 50 and the fine y coordinates are from 0 to 96. For different panel sizes and the ratio of emitter to detector pairs and gap size, the fine coordinate dividing may be different. Slight approximation is needed for establishing the coordinate dividing.  
         [0024]     The controller will activate the emitter/detector pairs simultaneously in any sequence. One example would be to scan X 00 , X 02 , X 04 , . . . X 20 , X 01 , X 03 , . . . X 21 , Y 00 , Y 02 , Y 04 , . . . Y 24 , Y 01 , Y 03 , . . . Y 25  sequentially. Another example would be to scan X 00 , X 01 , X 02 , . . . X 21 , Y 00 , Y 01 , Y 02 , . . . Y 25  sequentially. The coarse coordinates and the detected signal amplitudes are recorded for those blocked (completely or partially) pairs. The starting and ending of the x coarse coordinates are denoted as X 1  and X 2 , and those of y coarse coordinates Y 1  and Y 2 . The signals amplitudes of these four detectors are AX 1 , AX 2 , AY 1 , AY 2 . For example, if stylus position  410  is shown as in  FIG. 4A , X 1 =7, X 2 =10, Y 1 =7, Y 2 =10, AX 1 =10%, AX 2 =60%, AY 1 =70%, AY 2 =70%. Ne Nd and Ng are denoted as the number of fine grids of the emitter, detector and gap. Nx and Ny are denoted as the maximum of coarse X and Y coordinate. In the example, Ne=1, Nd=5, Ng=1, NX=13, NY=21. AX and AY are denoted as the amplitude of each detector without any portion of the signal being blocked. For simplicity of explanation, assume AX and AY to be 1. The above information will be used to calculate the fine starting and ending x and y coordinates following the algorithm shown below. The method utilizes similitude triangular relationships between the un-blocked detector width (proportional) to the signal amplitude and the blocked beam width in the stylus position. The geometric gravity center of the stylus expressed in coarse coordinate (X 1 +X 2 )/2, (Y 1 +Y 2 )/2 and NX, NY will be involved in the calculation.  
         [0025]     The following is one embodiment of an  
                                   //algorithm to map the starting and ending detector&#39;s coarse coordinate       (X1, X2, Y1, Y2) + amplitude (AX1, AX2, AY1, AY2) to fine coordinate       (xx1, xx2, yy1, yy2).       //determine xx1         if (X1%2==1) { //if starting X coordiante is on top, which is the case         here           xx1=int (X1*(Ne+Nd+Ng*2)/2.0−(1.0/2.0−        AX1/AX)*Nd*(Y1+Y2)/2.0/NY);         }         else { // if starting X coordinate is on bottom           xx1=int (X1*(Ne+Nd+Ng*2)/2.0−(1.0/2.0−AX1/AX)*Nd*(1.0−        (Y1+Y2)/2.0/NY));         }         //determine xx2         if (X2%2==1) { //if ending X coordinate is on top           xx2=int (X2*(Ne+Nd+Ng*2)/2.0+(1.0/2.0−        AX2/AX)*Nd*(Y1+Y2)/2.0/NY);         }         else { //if ending X coordinate is on bottom, which is the case         here           xx2= int (X2*(Ne+Nd+Ng*2)/2.0+(1.0/2.0−AX2/AX)*Nd*(1.0−        (Y1+Y2)/2.0/NY));         }         //determine yy1         if (Y1%2==1) { //if starting Y coordinate is in right, which is the case         here           yy1=int (Y1*(Ne+Nd+Ng*2)/2.0−(1.0/2.0−AY1/AY)*Nd*(1.0−        (X1+X2)/2.0/NX));         }         else { //if starting Y coordinate is in left           yy1=int (Y1*(Ne+Nd+Ng*2)/2.0−(1.0/2.0−        AY1/AY)*Nd*(X1+X2)/2.0/NX);         }         //determine yy2         if (Y2%2==1) { //if ending Y coordinate is in right           yy2=int (Y2*(Ne+Nd+Ng*2)/2.0+(1.0/2.0−AY2/AY)*Nd*(1.0−        (X1+X2)/2.0/NX));         }         else { //if ending Y coordinate is in left, which is the case here           yy2=int (Y2*(Ne+Nd+Ng*2)/2.0+(1.0/2.0−        AY2/AY)*Nd*(X1+X2)/2.0/NX);         }                  
 
         [0026]     As shown in  FIG. 4B , when the stylus, such as stylus  400 , is small it might be located within a beam. In this case, X 1 =X 2  and/or Y 1 =Y 2 . In this case, off-axis sweeping is needed to acquire the fine coordinates. For example, as shown in  FIG. 4B , for the initial scanning we obtain the coarse coordinates Y 1 =Y 2 =3. By activating the nearby LED E 402  and then sequentially activating the detectors on the opposite side, the blocked area in the right side frame can be determined. Again using similitude relationship between the two triangles, we can obtain accurate information of the y coordinates. Note that the selection of activated LED is based on the position (coarse coordinates) of the stylus. For example, if the stylus is located in the first quadrant of the panel, then the LED to determine the fine y coordinate should be the one on the left and directly above the coarse coordinate; while the LED to determine the fine x coordinate should be on the top and directly to the left of the coarse coordinate. The principle is to “project” the small value of width to the frame so as to “amplify” it.  
         [0027]     Upon calculation of the coordinates of a touched position, the system is then able to utilize the precise coordinates of contact to accomplish a myriad of activities, including, but not limited to, handwriting analysis, invocation of various applications, name-recognition dialing, memo functions, and changes in user preferences.  
         [0028]      FIG. 5  illustrates the logic controlling one embodiment of the system. Display  50  is connected to controller  51  by cable  52 , which typically would be a wireline connection, such as a flexible PCB, but could, if desired, be wireless. Controller  51  would typically also be formed as part of display  50 , perhaps on the back thereof, or in a separate control unit attached nearby. Within controller  51  reader multiplexer  507  is syncronized with driver multiplexer  502  so that driver multiplexer turns on an emitter, such as emitter E 313 , and multiplexer  507  turns on diode D 313 , which is matched to emitter E 313 . For off-axis sweeping, one emitter is enabled and the photodiodes on the opposite side of frame are also enabled sequentially, because they are sharing the same amplifier/filter/ADC circuits. For on-axis screening, all other diodes are switched to ground to avoid cross-talk. This then allows for sequential enablement of the diode-emitter pairs around periphery of the device for on-axis screening. For off-axis screening, one emitter is enabled all of the diodes along the opposite edge are enabled in sequence. This allows for detection of a small stylus. Reader multiplexer  507  is connected to amplifier/filter  506 , which is in turn connected to Analog-to-Digital Converter (ADC)  505 . The ADC  505 , memory/software  501 , and Driver/Multiplexer  502  and Reader Multiplexer  507  all feed into Microcontroller  504 . Software in memory  501  can control microcontroller  504 , if desired, note that control  51  can, if desired, be one or more ASICS. In one embodiment, microcontroller  504  is connected to a host computer, such as computer  503 , which can be in the same physical location, as would occur for a cellular phone or PDA, or can be remote and accessed wirelessly for other types of touch screens.  
         [0029]     Use of an array of alternating emitters and detectors on integrated circuits solves a number of problems present in the prior art. First, there are fewer “blind spots” on the display screen. By alternating emitters and diodes, decreasing the gaps between the two, and increasing the size of the detectors, the current system is able to significantly increase the density of the infrared signals over the prior art without significantly increasing the emitter/diode pairs. This increase in density allows for use of a smaller stylus and better coordinate mapping. Second, instead of determining the coordinates of a touch by detecting whether a beam has been blocked, the present system arguments its detection by also determining coordinates by determining a change in amplitude of the infrared signal and also by off-axis screening.  
         [0030]     Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, compositions of matter, means, methods and steps described in the specification. As one will readily appreciate from the disclosure, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.