Abstract:
A user interface of a mobile device is provided for adjusting dynamically sizes of displayed items in response to a contactless movement of a user&#39;s finger relative to a display. In one aspect, sizes of a subgroup of items are enlarged when the finger is approaching but not yet touching the icons. It helps the user to make a more accurate selection. In another aspect, some contents of the next hierarchical level are displayed in accompanying with the enlarged size of at least one displayed item. Various embodiments are disclosed for a position sensing system including image, ultrasonic and thermal sensing systems for the mobile device.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    Not applicable. 
       BACKGROUND 
       [0002]    1. Field of Invention 
         [0003]    This invention relates generally to user interface. More specifically, the invention relates to system and method for adjusting dynamically sizes of displayed items of a mobile computing and communication device. 
         [0004]    2. Description of Prior Art 
         [0005]    Mobile computing and communication devices have gained significant popularity in recent years. Users are using the mobile device such as, for example, iPhone, iPod and iPad from Apple Inc, Cupertino, Calif., to enjoy media assets and to access the Internet services. Methods for a user&#39;s interfacing with the devices have been developed. Graphical User Interface (GUI) based on touch-sensitive display has been adopted widely in recent years. 
         [0006]    However, there is a problem associated with the use of GUI implemented with the touch-sensitive display. A user may not be able to align his or her finger to a displayed item when a size of the displayed item is small. It is not always possible to increase the size of the displayed item because a number of items need to be displayed on a display screen with a limited size. 
         [0007]    It is, therefore, desirable to have a method and system to adjust the size of the displayed item in a dynamic manner. For example, at least some of the displayed items are enlarged when a user&#39;s finger is moving towards the displayed but not yet touching the screen. 
       SUMMARY OF THE INVENTION 
       [0008]    It is an object of the present invention to providing a system and method for adjusting dynamically sizes of displayed items in response to a contactless movement of a user&#39;s finger. 
         [0009]    It is another object of the present invention to have a system and method providing a means of previewing contents of next hierarchical level with an enlarged displayed item in response to a contactless movement of a user&#39;s finger. 
         [0010]    It is yet another object of the present invention to have a position sensing system integrated with the electronic apparatus pertaining to determining a position of a user&#39;s finger relative to the display. 
         [0011]    It is yet another object of the present invention to have a position sensing system integrated with the electronic apparatus pertaining to determining an orientation of a user&#39;s finger relative to the display. 
         [0012]    In an exemplary case, the electronic apparatus is a mobile computing and communication device such as, for example, a mobile phone. 
         [0013]    In one aspect, the mobile phone comprises a processor, a touch-sensitive display, a position sensing system and a user interface. A shortest distance between a finger and the display and the orientation of the finger related to a two dimensional display plane can be determined dynamically by the processor through analyzing data collected by the position sensing system. A plurality of items is displayed on the display through the user interface. The displayed items may be user selectable icons. The displayed items may be organized in a hierarchical manner. 
         [0014]    If the measured shortest distance is less than a predetermined value, the processor of the mobile device selects a subgroup of displayed items to which the finger is pointed and redisplays selected items with larger sizes through the user interface. 
         [0015]    In one implementation, at least one of the enlarged displayed items is redisplayed with a part of contents from next hierarchical level. 
         [0016]    In another aspect, either one finger or two fingers may be used. The user interface will not respond to the contactless movement of the finger if one finger is used. The system will respond to the contactless movement of the fingers if two fingers are used. 
         [0017]    In one embodiment, the position sensing system comprises image sensors installed in selected positions of the mobile device. In one implementation, at least some of the image sensors are disposed beneath the display. The image sensors may also include infrared sensors. 
         [0018]    In another embodiment, the position sensing system comprises ultrasonic sensors installed in selected positions of the mobile device including positions beneath the display. 
         [0019]    In yet another embodiment, the position sensing system comprises temperature sensors installed in selected positions of the mobile device. In one implementation, substrate units including the temperature sensors are disposed beneath the display. Heat generated from mobile device will elevate the temperatures of the units to a level above an ambient temperature. The temperatures of the units depend on resistance of heat transfer above the units. A contactless movement of a finger modulates the resistance of heat transfer in a zone associated with the display. Local temperature of a subgroup of the units starts to increase when the finger is moving towards the subgroup of the units. 
         [0020]    In another implementation, each of the units further includes a heating element integrated with the temperature sensor in the same substrate. The heating element brings the temperature of the unit to a predetermined level above the ambient temperature through a thermal feedback loop. A power required to sustain the predetermined temperature is measured. The power is related to the resistance of heat transfer. A finger above the unit increases the resistance and results in less power to sustain the predetermined temperature. 
         [0021]    In another aspect of the present invention, a display can be configured as a three-dimensional (3D) touch-sensitive display with an array of temperature sensors and heating elements. The 3D touch-sensitive display not only senses a touching event but also senses contactless movement of the finger towards the display. The 3D touch-sensitive display comprises a display layer and a thermal resistance measurement layer. The thermal resistance measurement layer is disposed beneath the display layer. The thermal resistance measurement layer further comprises a plurality of thermally isolated units. Each of the units includes a heating element, a temperature sensor and thermal feedback loop, which sustains the temperature of the unit to a predetermined level above the ambient temperature. The power required to sustain the predetermined temperature level is a measurement of the resistance of heat transfer, which is further related to the contactless movement of the finger. The processor monitors power required from each of the units and determines position and orientation of the finger. The present inventive concept can be readily extended to multiple touches by multiple fingers. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]    For a more complete understanding of the present invention and its various embodiments, and the advantages thereof, reference is now made to the following description taken in conjunction with the accompanying drawings, in which: 
           [0023]      FIG. 1A  is a schematic diagram of an exemplary operation of user interface in response to changing of positions of a user&#39;s finger in accordance with a first embodiment; 
           [0024]      FIG. 1B  is a schematic functional block diagram of an exemplary mobile device; 
           [0025]      FIG. 2  is a flowchart illustrating an exemplary operation of user interface in response to changing of positions of a user&#39;s finger in accordance with the first embodiment; 
           [0026]      FIG. 3  is a schematic diagram of an exemplary operation of user interface in response to changing of positions of a user&#39;s finger in accordance with a second embodiment; 
           [0027]      FIG. 4  is a flowchart illustrating an exemplary operation of user interface in response to changing of positions of a user&#39;s finger in accordance with the second embodiment; 
           [0028]      FIGS. 5A-B  is a schematic diagram of an exemplary operation of user interface in response to changing of positions of a user&#39;s finger in accordance with a third embodiment; 
           [0029]      FIG. 6  is a flowchart illustrating an exemplary operation of user interface in response to changing of positions of a user&#39;s finger in accordance with the third embodiment; 
           [0030]      FIG. 7  is a flowchart illustrating an aspect of the user interface for all three embodiments; 
           [0031]      FIG. 8  is a schematic diagram of an exemplary position sensing system in accordance with a first embodiment, wherein image sensors are installed along a frame of the display; 
           [0032]      FIG. 9  is a schematic diagram of an exemplary position sensing system in accordance with the first embodiment, wherein image sensors are disposed beneath the display; 
           [0033]      FIG. 10  is a schematic diagram of an exemplary position sensing system in accordance with a second embodiment, wherein ultrasonic sensors are installed along a frame of the display; 
           [0034]      FIG. 11  is a schematic diagram of an exemplary position sensing system in accordance with the second embodiment, wherein ultrasonic sensors are disposed beneath the display; 
           [0035]      FIG. 12  is a schematic diagram of an exemplary position sensing system in accordance with a third embodiment, wherein a two dimensional temperature sensor array is disposed beneath the display; 
           [0036]      FIG. 13  is a flowchart illustrating an exemplary operation of the position sensing system in accordance with the third embodiment; 
           [0037]      FIG. 14  is a schematic diagram of an exemplary position sensing system in accordance with a forth embodiment, wherein a two dimensional temperature sensor array and a plurality of heating elements are disposed beneath the display; 
           [0038]      FIG. 15  is a schematic diagram of an exemplary thermal feedback loop pertaining to controlling temperature of a substrate unit to oscillate around a predetermined value; 
           [0039]      FIG. 16  is a flowchart illustrating an exemplary operation of the position sensing system in accordance with the forth embodiment; 
           [0040]      FIG. 17  is a schematic diagram of an exemplary thermal feedback loop. 
       
    
    
     DETAILED DESCRIPTION 
       [0041]    One or more specific embodiments of the present invention will be described below. These described embodiments are only exemplary of the present invention. Additionally, in an effort to provide a concise description of these exemplary embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefits of this disclosure. 
         [0042]      FIG. 1A  is a schematic diagram of an exemplary operation of user interface in accordance with a first embodiment. Mobile computing and communication device  102  is used exemplarily to illustrate present inventive concept. The present inventive concept can be applied to any electronic apparatus with a display. Mobile device  102  includes but is not limited to a smart phone, a tablet computer, a laptop computer, a handheld media player, a wearable computing and communication device and a game console. As shown in  FIG. 1B , mobile device  102  includes processor  103 , display  104 , position sensing system  105  and user interface  107 . Display  104  is a touch-sensitive display in an exemplary case. The present inventive concept is not limited to the touch-sensitive display. A plurality of displayed items  106  are displayed on display  104  through user interface  107 . For example, a plurality of user selectable icons I1-9 is displayed. A schematic illustration of finger  108  of a user is illustrated exemplarily in  FIG. 1A . The present inventive concept can be extended to any object such as, for example, a stylus. 
         [0043]    Position sensing system  105  detects a contactless movement of finger  108 . A shortest distance between finger  108  and display  104  can be determined by processor  103  through analyzing data collected by position sensing system  105 . Processor  103  can further determine orientation of finger  108  through analyzing the data collected by position sensing system  105 . 
         [0044]    As shown in  FIG. 1A , finger  108  in position 1 does not affect the displayed items when the shortest distance between finger  108  and display  104  is more than a predetermined threshold value. In an exemplary case, the predetermined value can be any value in a range of 1 mm to 20 mm. After finger  108  is moved to position 2, the shortest distance is less than the threshold value. In response to the contactless movement of finger  108 , user interface  107  executed by processor  103  redisplays a subgroup of displayed items  110  with larger size. Position sensing system  105  not only detects the shortest distance between finger  108  and the display  104 , but also determines the orientation of the finger. The subgroup of the displayed items  110  is selected based upon the orientation of finger  108 . 
         [0045]      FIG. 2  is a flowchart illustrating an exemplary operation of user interface in accordance with the first embodiment. Process  200  starts with step  202  that a plurality of items ( 106 ) is displayed on a first screen of display  104  of mobile device  102 . Displayed items  106  may be user selectable items. Displayed items may be icons displayed on a touch-sensitive display. Displayed items may include sub items and be organized in a hierarchical structure. If one of the displayed items  106  is selected by a user through a user input device of mobile device  102 , a plurality of sub items may be displayed in a new display screen. A hierarchical user interface may include multiple levels. Finger  108  is positioned at a first position above the first screen in step  204 . The shortest distance between finger  108  and display  104  is determined by processor  103  through position sensing system  105  in step  206 . Position sensing system  105  determines both the shortest distance and the orientation of finger  108 . In step  208 , processor  103  decides if the distance is less than the threshold value. If the decision is positive, processor  103  selects a subgroup  110  of displayed items  106  and redisplays the items from subgroup  110  with the larger size in step  210  through user interface  107 . 
         [0046]      FIG. 3  is a schematic illustration of the operation of user interface  107  in accordance with the second embodiment. The second embodiment is identical to the first one except that a part of contents in second hierarchical level is displayed in accompanying with redisplaying of at least one of the displayed items in subgroup  110 . In an exemplary illustration, an icon for calendar is redisplayed with a larger size after the processor determines that finger  108  is moving towards and is pointing approximately to the icon. The redisplayed icon includes an item in the calendar. In another exemplary case, an email icon may be redisplayed with a larger size including a few latest email titles. In yet another exemplary case, a weather forecast icon may be redisplayed with a larger size including a weather forecast for the current position of the mobile device. 
         [0047]      FIG. 4  is a flowchart illustrating an exemplary operation of user interface  107  in accordance with the second embodiment. The flowchart is similar to the flowchart for the first embodiment except that at least one of the redisplayed items in larger size includes at least a part of contents in the next hierarchical level in step  410 . 
         [0048]      FIGS. 5A-B  is a schematic diagram of user interface  107  in accordance with a third embodiment. User interface  107  in the third embodiment provides flexibility for a user to select or not to select a function of enlarging a subgroup of displayed item  110  when the user&#39;s finger is approaching the items. In  FIG. 5A , user interface  107  does not respond to the contactless movement of finger  108  if only one finger is positioned. In  FIG. 5B , user interface  107  responds to the contactless movement of finger  108  and redisplays the subgroup of displayed items  110  with larger sizes if two fingers are positioned. 
         [0049]    In yet another embodiment, the subgroup of displayed items  110  is redisplayed with larger sizes if two fingers are presented, wherein at least one item from the subgroup is redisplayed with a part of contents from the next hierarchical level. 
         [0050]      FIG. 6  is a flowchart illustrating an exemplary operation of user interface  107  in accordance with the third embodiment. Process  600  starts with step  602  that a plurality of items ( 106 ) is displayed on a first screen of display  104  of mobile device  102 . One or two fingers  108  are positioned at a first position above the first screen in step  604 . The shortest distance between finger (s)  108  and display  104  is determined by processor  103  through position sensing system  105  in step  606 . Processor  103  determines both the shortest distance and the orientation of finger  108  based on the data collected by position sensing system  105 . According to the third embodiment, position sensing system  105  further determines if one or two fingers are presented. In step  608 , processor  103  decides if the shortest distance between finger  108  and display  104  is less than the threshold value and also decides if one or two fingers are positioned. If the decision is positive, processor  103  selects a subgroup  110  of displayed item  106  and redisplays the subgroup items with the larger size in step  610  through user interface  107 . 
         [0051]      FIG. 7  is a flowchart illustrating one aspect of user interface  107  for all of the three embodiments. Process  700  starts with step  702  that finger  108  is positioned in a distance less than the threshold value. The subgroup of displayed items  110  is redisplayed in step  704  with larger sizes. Subsequently, the user moves finger  108  away to have the shortest distance more than the threshold value in step  706 . In response to the contactless movement of finger  108 , displayed items  106  are redisplayed with normal sizes in step  708 . 
         [0052]      FIG. 8  is a schematic diagram of an exemplary position sensing system  105  in accordance with a first embodiment. Mobile device  102  includes a house, a front surface and a back surface. In one aspect as shown in  802 , mobile device  102  includes a display  104  in a rectangular shape on the front surface in an exemplary case. Image sensors  112  are disposed in selected positions of the front surface along a frame of display  104 . Image sensors  112  may be sensors for visible lights. Image sensor  112  may also be sensors for invisible lights such as, for example, for infrared radiations. Image sensors  112  may even be a combination of sensors for measuring both visible lights and the infrared radiations. In one implementation, each of four image sensors is disposed approximately at a middle point of each of the sides of the rectangular display. Each of the sensors  112  takes photos of the finger  108  from different angles when the finger is approaching display  104  as shown in  804  and  806 . The photos are transmitted to processor  103  for analyzing. Processor  103  determines the shortest distance between finger  108  and display  104  through analyzing data collected by image sensors  112 . Processor  103  further determines orientation of finger  108  based on the data. A control signal is generated when the distance between finger  108  and display  104  is less than the threshold value. The control signal can be used to redisplay a subgroup of displayed items with larger size through user interface  107 . 
         [0053]    More or less image sensors may be disposed at different positions in the front surface of mobile device  102 . 
         [0054]    In another aspect of the first embodiment of position sensing system  105  as shown in  FIG. 9 , image sensors are disposed underneath display  104 . In an exemplary case, the image sensors are configured as a two dimensional array. 
         [0055]    In yet another aspect, image sensors  112  may be disposed beneath display  104  and also in the positions outside the display area. 
         [0056]      FIG. 10  is a schematic diagram of an exemplary position sensing system  105  in accordance with a second embodiment. In one implementation as shown in  1002 , a plurality of ultrasonic sensors  114  are disposed in selected positions outside the display area. In one aspect, three sensors are installed as shown in  FIG. 10  in an exemplary manner. The ultrasonic sensor  114  further comprises a sound generating unit  116  and a sound receiving unit  117 . Ultrasonic sensors  116  generate high frequency sound wave through sound generating units  116  and receive the sound wave reflected from finger  108  by sound receiving units  117 . Received signals are analyzed by processor  103 . The position and orientation of finger  108  can be determined by performing a triangulation by the processor. When a user moves finger  108  as shown in  1002  and  1006 , a three dimensional image can be reconstructed by processor  103  based upon received sound signals. A control signal is generated if the distance between finger  108  and display  104  is less than the threshold value. More than three ultrasonic sensors may be used to improve accuracy of the measurement. 
         [0057]    In another implementation, sound generating unit  116  and sound receiving unit  117  may be disposed in different locations. Sound receiving units may also be used as conventional microphones for mobile device  102 . 
         [0058]      FIG. 11  is a schematic diagram of an exemplary position sensing system  105  in accordance with another implementation of the second embodiment, wherein ultrasonic sensors  116  are disposed beneath display  104  as shown in  1102 . The contactless movement of finger  108  as shown in  1104  and  1106  can be tracked by processor  103  through position sensing system  105 . A control signal is generated if the distance between finger  108  and display  104  is less than the threshold value. Three ultrasonic sensors are depicted in  FIG. 11 . More or less ultrasonic sensors may be used. Ultrasonic sensors may be arranged in a two-dimensional array. Ultrasonic sensors can also be disposed beneath display  104  and also be disposed outside the display area in the front surface of mobile device  102 . 
         [0059]      FIG. 12  is a schematic diagram of an exemplary position sensing system  105  in accordance with a third embodiment. An array of temperature sensor  118  as shown exemplarily in  1202  is disposed beneath display  102 . Temperature sensors  118  measures temperature distribution or map in a plane beneath display  104 . Each of temperature sensors is disposed in a substrate unit. The substrate units are disposed underneath display  104 . The operations of mobile device  102  generate heat, which is called self heating in this disclosure. The temperature sensors measure the temperature of each of the substrate units. The measured temperatures form a temperature map overlapping the display plane. The temperature map is measured according to a predetermined frequency and is transmitted to processor  103  in real time base. The self heating leads to the measured temperatures at levels higher than an ambient temperature. The heat is transferred to the ambient through display  104 . Each of the substrate units is associated with a resistance of heat transfer. The resistance is affected by an object in the heat transfer path and also by the distance of the object to the substrate unit. If the path of the heat transfer is blocked by finger  108 , temperatures measured in a zone underneath finger  108  are higher than the temperature measured in a zone without finger  108  above it. As shown in  1204  and  1206 , moving finger  108  from position 1 to position 2 creates a temperature map having a zone beneath finger  108  with higher temperatures. 
         [0060]    In one implementation, a two dimensional temperature sensor array  118  is placed in a substrate in a form of a sheet which can be placed beneath the display plane. Each of the sensors can be accessed by the processor through an address decoder and a bit line and a word line. The temperature sensors may be silicon based sensors manufactured by a semiconductor manufacturing process. The temperature sensors may also be thin film based sensors manufactured by a thin film process. The word and the bit lines can also be formed by the thin film process. 
         [0061]      FIG. 13  is a flowchart illustrating an exemplary operation of position sensing system  105  in accordance with the third embodiment. Process  1300  starts with step  1302  that the temperature map of a plane beneath display  104  is determined by temperature sensors in arrayl  18  in accordance with a predetermined frequency. Measured temperature maps are transmitted to processor  103  in step  1304 . The received temperature maps are analyzed by processor  103  in step  1306 . Processor  103  decides in step  1308  if the heat transfer paths are blocked by finger  108  that leads to increasing in temperatures in a zone of substrate beneath finger  108 . If the result is positive, a control signal is generated by processor  103  in step  1310 . Otherwise, processor  103  will continue to analyze received temperature maps until an event of blocking the heat transfer path by finger  108  is detected. 
         [0062]      FIG. 14  is a schematic diagram of an exemplary position sensing system  105  in accordance with a forth embodiment. In one aspect as shown in  1402 , a substrate sheet is disposed beneath display  104 . The substrate sheet includes a plurality of units. Each of the units includes one of temperature sensors  118  and one of heating elements  120 . In one implementation, the heating element is placed next to the temperature sensor in each of the units. In another implementation, the heating element and the temperature sensor can be integrated in a single substrate unit. The substrate unit may be a chip. The heating element  120  and the temperature sensor  118  can be disposed in a microstructure of the chip manufactured by a micromachining technology. Heating elements  120  include but are not limited to heating resistors and heating transistors. Each of the substrate units is thermally isolated. The temperature sensors  118  and the heating elements  120  can be connected to processor  103  through a bit/word line structure. 
         [0063]    In accordance with the forth embodiment, each of the heating elements  120  sets the temperature measured by each of the temperature sensors  118  to a predetermined value above the ambient temperature. Power for each of the heating elements required to sustain the predetermined value is measured and is transmitted to processor  103 . Heat is transferred to the ambient through display  104 . If the heat transfer in a zone associated with a zone in the display plane is blocked by an object such as, for example, finger  108 , the power required to sustain the predetermined value is reduced. By measuring power required to sustain the predetermined temperature, the object moving from position 1 in  1404  to position 2 in  1406  can be detected. Thermal feedback loops can be used to control the temperature of each unit to oscillate around the predetermined value within a small range. 
         [0064]      FIG. 15  is a schematic diagram of an exemplary thermal feedback loop  121  pertaining to controlling temperature of a substrate unit to oscillate around a predetermined value. Such an implementation is known from an article by Pan (the present inventor) and Huijsing in Electronic Letters 24 (1988), 542-543. This circuit is theoretically appropriate for measuring physical quantities such as resistance of thermal transfer, speed of flow, pressure, IR-radiation, or effective value of electrical voltage or current (RMS), the influence of the quantity grated integrated circuit (chip) to its environment being determined in these cases. In these measurements, a signal conversion takes place twice: from physical (resistance of thermal transfer path, speed of flow, pressure, IR-radiation or RMS value) to the thermal domain, and from the thermal to the electrical domain. 
         [0065]    This known semiconductor circuit theoretically consists of a heating element, integrated in the circuit, and a temperature sensor. The power dissipated in the heating element is measured with the help of an integrated amplifier unit, an amplifier with a positive feedback loop being used, because of which the temperature oscillates around a constant value with small amplitude. In the known circuit the temperature will oscillate in a natural way because of the existence of a finite transfer time of the heating element and the temperature sensor with a high amplifier-factor. 
         [0066]    As shown in  FIG. 15 , thermal feedback loop  121  includes temperature sensor  118  and heating element  120 . Temperature sensor  118  and heating element  120  are disposed close to each other. Temperature sensor  118  and heating element  120  can also be integrated into a single substrate. The heat may also be generated from self heating  122  resulting from operations of mobile device  102 . Thermal feedback loop  121  further comprises power supply  124  and power modulator  126 . Power modulator  126  converts an incoming power into a desired form such as, for example, into a Pulse Width Modulation (PWM) or a bit stream form. Temperature sensor  118  measures temperature of the unit. Temperature sensor  118  is coupled to power modulator  126  that adjusts its output based upon the measured temperature. Temperature sensor  118  may be a diode or a transistor. Temperature sensor  118  may also be a resistor such as, for example, a poly-crystalline silicon resistor or a resistor formed by a diffused layer in a typical integrated circuit process. 
         [0067]      FIG. 16  is a flowchart illustrating an exemplary operation of position sensing system  105  in accordance with the forth embodiment. Process  1600  starts with step  1602  that mobile device  102  is switched on. Temperatures of all units are brought up to the predetermined level through thermal feedback loop  121  comprising temperature sensor  118  and heating element  120 . The temperatures are measured according to a predetermined frequency in step  1604 . Powers required to sustain the elevated temperatures are measured and are transmitted to processor  103  in step  1606 . Powers required to sustain the predetermined temperature in each of the units are analyzed by processor  103  in step  1608 . Processor  103  decides in step  1610  if finger  108  has been placed above a zone of display  104  to block the heat transfer path. If the result is positive, a control signal is generated by the processor in step  1612 . 
         [0068]    The present inventive concept based upon the forth embodiment of the position sensing system  105  can be generalized to provide a novel three-dimensional touch-sensitive display. The display can sense contactless movement of finger  108  in additional to sensing an event of touching of the display by finger  108 . 
         [0069]    In one aspect of the present invention, display  104  can be configured as a three-dimensional (3D) touch-sensitive display with an array of temperature sensors  118  and heating elements  120 . The 3D touch-sensitive display  104  not only senses a touching event but also senses contactless movement of finger  108  towards display  104 . The 3D touch-sensitive display  104  comprises a display layer and a thermal resistance measurement layer. In one implementation, the thermal resistance measurement layer is disposed beneath the display layer. The thermal resistance measurement layer further comprises a plurality of thermally isolated units. Each of the units includes one of the temperature sensors  118 , one of the heating elements  120  and other components required for thermal feedback loop  121  as shown in  FIG. 15 . Thermal feedback loop  121  sustains the temperature of the unit to a predetermined level above the ambient temperature. The power required to sustain the predetermined temperature level is a measurement of the resistance of the heat transfer, which is further related to the contactless movement of finger  108 . Processor  103  monitors power required from each of the units and determines position and orientation of finger  108 . Finger  108  starts to affect a heat transfer path when the finger is within a predetermined distance of the display  104 . The power required to sustain the temperatures of some of the units, therefore, starts to drop because of slower heat transferring from the units to the ambient. 
         [0070]    In another implementation, the thermal resistance measurement layer is merged with the display layer. Temperature sensors  118 , heating elements  120  and some of other components in thermal feedback loops  121  are manufactured based upon at least a part of process flows formed the display layer. 
         [0071]    If mobile device  102  is a wearable device, the size of its display  104  is relatively small. A chip including temperature sensors  118 , heating elements  120  and the other components in thermal feedback loops  121  can be disposed beneath display  104 . The size of the chip is approximately equal to the size of display  104 . The chip may be thinned down before attaching to the display layer. In one implementation, the chip is manufactured by an integrated circuit process flow. In one aspect, the chip may be made by a Silicon-On-Insulator (SOI) substrate to achieve thermal isolation among the units. 
         [0072]    The system may also include an ambient temperature sensor for measuring the ambient temperature. In one implementation, the ambient temperature sensor is thermal isolated from the substrate unit and the rest of the mobile device. The measured ambient temperature is transmitted to each of the units by processor  103  to set the predetermined temperature level. 
         [0073]    The present inventive concept can be readily extended to multiple touches by multiple fingers. 
         [0074]      FIG. 17  shows an exemplary implementation of the thermal feedback principle as mentioned above to measure if the heat transfer path is blocked. A thermal feedback loop in accordance with one implementation includes a DC power source  1702 , DC to PWM converter  1703  and power to heat converter  1704 . The thermal feedback loop further comprises self heating  1706  generated from operations of mobile device  102 . Power to heat converter  1704  further includes a heating element. The heating element may be a heating resistor in an exemplary case. The heating element may also be an active component. Power to heat converter  1704  may be a part of an integrated circuit or a chip. 
         [0075]    Temperature sensor  1708  in the same integrated circuit is used to measure the temperature of the integrated circuit (chip). According to one implementation of the present invention, the heating element and temperature sensor may be disposed in a microstructure such as a membrane or a cantilever beam, manufactured by a micromachining technology. 
         [0076]    Output of temperature sensor  1708  is coupled to one input of comparator  1710 . Reference generated by controller  1714  is coupled to another input of comparator  1710 . Output of comparator  1710 , which is a PWM signal, is coupled to DC to PWM converter  1703 . As soon as the measured temperature by temperature sensor  1708  exceeds a predetermined value, set by the reference, the output of the comparator switches off DC power source  1702 . As a result, power to heat converter  1704  does not receive any power and the output of temperature sensor  1708  starts to drop. As soon as the output is below the reference, the output of comparator  1710  switches on DC power source to power to heat converter  1704 . The temperature of the chip or the microstructure will oscillate around a small value. The power required to maintain the predetermined value of the temperature is determined by the reference and also by a resistance of heat transfer from the unit to the ambient. In one aspect, the reference is determined by the ambient temperature measured by ambient temperature sensor  1716 .