PATENT DOCUMENT

Publication Number: US-8441450-B2
Application Number: US-24196708-A
Country: US
Kind Code: B2

Title: Movable track pad with added functionality

Abstract:
An input device is disclosed. The input device includes a movable touch-sensitive track pad capable of detecting an object in close proximity thereto so as to generate a tracking control signal. The input device also includes a movement indicator capable of detecting the movements of the movable track pad so as to generate one or more other control signals (e.g., button signals). The control signals can be used to perform actions in an electronic device operatively coupled to the input device.

Claims:
What is claimed is: 
     
       1. An input device, comprising: a frame;
 a touch sensitive track pad, the touch sensitive track pad providing a first type control signal when the touch sensitive track pad moves with respect to the frame, comprising: 
 an outer touch-sensitive track surface configured for tracking object movements relative to the track surface and providing a corresponding second type control signal independent of the first type control signal, 
 a stiffener disposed beneath the outer touch-sensitive track surface configured to stiffen the outer touch-sensitive track surface in order to facilitate providing the second type control signal by the outer touch-sensitive track surface; and 
 a flexure hinge independent of the stiffener and configured to pivotally connect the track pad to the frame to allow the movement of the track pad relative to the frame that provides the first type control signal independent of the second type control signal, wherein the flexure hinge is a resilient plate extending between the frame and only one side of the track pad, wherein the flexure hinge has one end connected to the one side of the track pad and an opposite, cantilevered end extending from the frame, wherein the flexure hinge constrains the track pad to move substantially about only one axis defined by the flexure hinge, wherein the flexure hinge is configured to allow displacement of the track pad from a neutral position to an active position when a force is applied to substantially any portion of the track surface, and to bias the track pad towards the neutral position from the active position. 
 
     
     
       2. The input device as recited in  claim 1 , wherein the flexure hinge comprises a plurality of flexure hinges having one end connected to the one side of the track pad and an opposite, cantilevered end extending from the frame. 
     
     
       3. The input device as recited in  claim 1 , wherein the first type control signal is a button signal and the second type control signal is a tracking signal. 
     
     
       4. The input device as recited in  claim 1 , wherein the cantilevered end is unitary with the frame. 
     
     
       5. The input device as recited in  claim 4 , wherein the cantilevered end is attached to the frame in an opening in the frame. 
     
     
       6. The input device as recited in  claim 1 , further comprising a movement indicator for sensing movement of the track pad, wherein the movement indicator is disposed on a bottom of the track pad at a side of the track pad opposite from the side to which is connected the flexure hinge, wherein the first type control signal is based on movements of the track pad sensed by the movement indicator. 
     
     
       7. The input device as recited in  claim 6 , wherein the movement indicator is a tactile switch which is depressed when the track pad is in the active position. 
     
     
       8. The input device as recited in  claim 1 , wherein the track pad includes a touch sensor arrangement comprising an electrical layer disposed between the outer touch-sensitive layer and the stiffener, the electrical layer configured to respond to object movements along the outer touch-sensitive track surface by providing the second type control signal. 
     
     
       9. The input device as recited in  claim 8 , wherein the touch sensor arrangement includes a capacitive sensor. 
     
     
       10. The input device as recited in  claim 9 , wherein the electrical layer is electrically connected to an integrated circuit configured to displace with the track pad between the neutral and the active positions. 
     
     
       11. The input device as recited in  claim 10 , wherein the electrical layer has a cantilevered end which forms the cantilevered end of the flexure hinge. 
     
     
       12. The input device as recited in  claim 10 , wherein the track surface is made of a dielectric material. 
     
     
       13. The input device as recited in  claim 12 , wherein the dielectric material is glass. 
     
     
       14. The input device as recited in  claim 10 , further comprising the stiffener is connected to the electrode layer. 
     
     
       15. The input device as recited in  claim 14 , wherein the stiffener has a cantilevered end which forms the cantilevered end of the flexure hinge. 
     
     
       16. The input device as recited in  claim 4 , wherein the frame has a shoulder configured to keep the track surface substantially flush with an adjacent surface of the frame when the track pad is at the neutral position. 
     
     
       17. The input device as recited in  claim 16 , further comprising a shock absorber connected to the shoulder. 
     
     
       18. The input device as recited in  claim 1 , wherein a distance between the neutral position and the active position is adjustable. 
     
     
       19. The input device as recited in  claim 13 , wherein the track pad is delineated into zones. 
     
     
       20. The input device as recited in  claim 19 , wherein the zones are user-selectable and include a track zone and a pick zone. 
     
     
       21. The input device as recited in  claim 19 , further comprising means for separating the zones. 
     
     
       22. The input device as recited in  claim 19 , wherein the means for separating the zones is formed by a textured glass surface with light emitting diode side lighting, infrared ink with light emitting diode side lighting, electroluminescence, magnetic ink, or two-tone rolling wire. 
     
     
       23. The input device as recited in  claim 13 , wherein the track surface is an active matrix display. 
     
     
       24. The input device as recited in  claim 23 , wherein the active matrix display includes electronic paper. 
     
     
       25. The input device as recited in  claim 1 , further comprising a magnet connected to the track pad to bias the track pad to the neutral position.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to track pads. More particularly, the present invention relates to track pads capable of relative movement in order to increase the functionality of the track pad. 
     2. Background Art 
     There exist today many styles of input devices for performing operations in a consumer electronic device. The operations generally correspond to moving a cursor and making selections on a display screen. By way of example, the input devices may include buttons, switches, keyboards, mice, trackballs, touch pads, joy sticks, touch screens and the like. Each of these devices has advantages and disadvantages that are taken into account when designing the consumer electronic device. In handheld computing devices, the input devices are generally selected from buttons and switches. Buttons and switches are generally mechanical in nature and provide limited control with regards to the movement of a cursor (or other selector) and making selections. For example, they are generally dedicated to moving the cursor in a specific direction (e.g., arrow keys) or to making specific selections (e.g., enter, delete, number, etc.). In the case of hand-held personal digital assistants (PDA), the input devices tend to utilize touch-sensitive display screens. When using a touch screen, a user makes a selection on the display screen by pointing directly to objects on the screen using a stylus or finger. 
     In portable computing devices such as laptop computers, the input devices are commonly track pads (also known as touch pads). With a track pad, the movement of an input pointer (i.e., cursor) corresponds to the relative movements of the user&#39;s finger (or stylus) as the finger is moved along a surface of the track pad. Track pads can also make a selection on the display screen when one or more taps are detected on the surface of the track pad. In some cases, any portion of the track pad may be tapped, and in other cases a dedicated portion of the track pad may be tapped. In stationary devices such as desktop computers, the input devices are generally selected from mice and trackballs. With a mouse, the movement of the input pointer corresponds to the relative movements of the mouse as the user moves the mouse along a surface. With a trackball, the movement of the input pointer corresponds to the relative movements of a ball as the user rotates the ball within a housing. Both mice and trackballs generally include one or more buttons for making selections on the display screen. 
     In addition to allowing input pointer movements and selections with respect to a graphical user interface, or GUI, presented on a display screen, the input devices may also allow a user to scroll across the display screen in the horizontal or vertical directions. For example, mice may include a scroll wheel that allows a user to simply roll the scroll wheel forward or backward to perform a scroll action. In addition, track pads may provide dedicated active areas that implement scrolling when the user passes his or her finger linearly across the active area in the x and y directions. Both devices may also implement scrolling via horizontal and vertical scroll bars as part of the GUI. Using this technique, scrolling is implemented by positioning the input pointer over the desired scroll bar, selecting the desired scroll bar, and moving the scroll bar by moving the mouse or finger in the y direction (forwards and backwards) for vertical scrolling or in the x direction (left and right) for horizontal scrolling. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention relates generally to a track pad capable of detecting an object in close proximity thereto. More particularly, the present invention relates to a track pad capable of moving in order to increase the functionality of the track pad. For example, the track pad may be depressible so as to provide additional button functionality. 
     The invention relates in one embodiment to an input device having a track pad and a track surface. A flexure hinge is operatively connected at one end of the track pad and is configured to allow displacement of the track pad from a neutral position to an activate position when a force is applied to substantially any portion of the track surface, while at the same time urging the track pad towards the neutral position from the activate position. The track pad generates a first control signal when the track pad is at the activate position and the track pad generates a second control signal when an object is moved relative to the track surface. 
     The invention relates in another embodiment to a computing system having a computing device capable of receiving, processing and outputting data and an input device configured to send data to the computing device in order to perform an action in the computing device. The input device has a depressible touch-sensitive track pad coupled to the computing device by a flexure hinge and is configured to generate tracking signals, and a movement indicator configured to generate a button signal when the track pad is depressed. 
     The invention relates in another embodiment to an input device having a capacitive touch sensitive track pad with an etched glass track surface. A flexure hinge is operatively connected at one end of the track pad and is configured to allow displacement of the track pad from a neutral position to an activate position when a force is applied to substantially any portion of the track surface, while at the same time urging the track pad towards the neutral position from the activate position. The track pad generates a button signal when the track pad is in the activate position and the track pad generates a tracking signal when an object is moved relative to the track surface. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES 
       The present invention is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements and in which: 
         FIG. 1  is a simplified diagram of a touch pad and display. 
         FIG. 2  is a perspective view of an input device, in accordance with one embodiment of the present invention. 
       FIGS.  3 A, 3 B, 3 C, and  3 D are simplified side views of an input device having a button touch pad, in accordance with one embodiment of the present invention. 
         FIG. 4  is simplified block diagram of an input device connected to a computing device, in accordance with one embodiment of the present invention. 
         FIG. 5  is a side view, in cross section, of an input device, in accordance with one embodiment of the present invention. 
         FIG. 6  is a another side view, in cross section, of the input device of  FIG. 5 . 
         FIG. 7  is a perspective view of an input device being used as a track pad in a laptop computer, in accordance with one embodiment of the present invention. 
         FIG. 8  is an exploded view of the input device of  FIG. 7 . 
         FIG. 9  is a side view, in cross section, of a stiffener. 
         FIG. 10  is a bottom view of a portion of the input device of  FIG. 7 . 
         FIG. 11  is a side view, in cross section of a portion of the input device of  FIG. 7 . 
         FIG. 12  is a side view, in cross section of a portion of the input device of  FIG. 7 . 
         FIG. 13  is a side view, in cross section of a portion of the input device of  FIG. 7 . 
         FIG. 14  is a side view, in cross section of a portion of the input device of  FIG. 7 . 
         FIG. 15  is a perspective diagram of a media player, in accordance with one embodiment of the present invention. 
         FIG. 16  is a perspective diagram of a mobile phone, in accordance with one embodiment of the present invention. 
         FIG. 17  is a perspective diagram of a desktop computer with a peripheral input device connected thereto, in accordance with one embodiment of the present invention. 
         FIG. 18  is a perspective diagram of a remote control utilizing an input device, in accordance with one embodiment of the present invention. 
         FIG. 19  is a simplified block diagram of a remote control, in accordance with one embodiment of the present invention. 
         FIGS. 20A ,  20 B,  20 C,  20 D,  20 E, and  20 F are top views of track pads having delineated zones, in accordance with one embodiment of the present invention. 
         FIG. 21  is a top view of a track pad having a full pixel display, in accordance with one embodiment of the present invention. 
         FIG. 22  is side view, in cross section of electronic ink, in accordance with one embodiment of the present invention. 
         FIG. 23  is a side view of a piece of glass, in accordance with one embodiment of the present invention. 
         FIG. 24A  is a side view of a piece of etched glass, in accordance with one embodiment of the present invention. 
         FIG. 24B  is a top magnified view of the piece of glass shown in  FIG. 24A . 
         FIG. 25  is a side view of a piece of etched glass, in accordance with one embodiment of the present invention. 
         FIG. 26  is a top view of the surface of the piece of glass shown in  FIG. 25 . 
         FIG. 27  is a graph of the peak-to-peak ratio of the glass surface shown in  FIGS. 25 and 26 . 
         FIG. 28  is a side view, in cross section of a portion of an input device, in accordance with one embodiment of the present invention. 
         FIG. 29  is a side view, in cross section of a portion of an input device, in accordance with one embodiment of the present invention. 
         FIG. 30  is a side view, in cross section of a portion of an input device, in accordance with one embodiment of the present invention. 
         FIG. 31  is a side view, in cross section of a portion of an input device, in accordance with one embodiment of the present invention. 
         FIG. 32  is a side view of an input device, in accordance with one embodiment of the present invention. 
         FIG. 33  is a bottom view of the input device of  FIG. 32 . 
         FIG. 34A  is a side view, in cross section, of an input device, in accordance with one embodiment of the present invention. 
         FIG. 34B  is a side view, in cross section, of an input device, in accordance with one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention will now be described in detail with reference to a few embodiments thereof as illustrated in the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art, that the present invention may be practiced without some or all of these specific details. In other instances, well known process steps have not been described in detail in order not to unnecessarily obscure the present invention. 
     With regards to track pads, mice and track balls, a Cartesian coordinate system is used to monitor the position of the finger, mouse and ball, respectively, as they are moved. The Cartesian coordinate system is generally defined as a two dimensional coordinate system (x, y) in which the coordinates of a point (e.g., position of finger, mouse or ball) are its distances from two intersecting, often perpendicular straight lines, the distance from each being measured along a straight line parallel to each other. For example, the x, y positions of the mouse, ball and finger may be monitored. The x, y positions are then used to correspondingly locate and move the input pointer on the display screen. 
     Track pads generally include one or more sensors for detecting the proximity of the finger thereto. By way of example, the sensors may be based on resistive sensing, surface acoustic wave sensing, pressure sensing, optical sensing, capacitive sensing and the like. The sensors are generally dispersed about the track pad with each sensor representing an x, y position. In most cases, the sensors are arranged in a grid of columns and rows. Distinct x and y position signals, which control the x, y movement of a pointer device on the display screen, are thus generated when a finger is moved across the grid of sensors within the track pad. For brevity sake, the remaining discussion will be held to the discussion of capacitive sensing technologies. It should be noted, however, that the other technologies have similar features. 
     Capacitive sensing surfaces generally contain several layers of material. For example, the capacitive sensing surface may include a protective/cosmetic shield (usually a dielectric material), one or more electrode layers and a circuit board. The protective shield typically covers the electrode layer(s), and the electrode layer(s) is generally disposed on a front side of the circuit board. The electrode layer and circuit board may be, for example, a printed circuit board (PCB). The protective shield is the part of the capacitive sensing surface that is touched by the user to implement cursor movements on a display screen. The electrode layer(s), on the other hand, is used to interpret the x, y position of the user&#39;s finger when the user&#39;s finger is resting or moving on the protective shield. The electrode layer (s) typically consists of a plurality of electrodes that are positioned in columns and rows so as to form a grid array. The columns and rows are generally based on the Cartesian coordinate system and thus the rows and columns correspond to the x and y directions. 
     The capacitive sensing surface may also include sensing electronics for detecting signals associated with the electrodes. For example, the sensing electronics may be adapted to detect the change in capacitance at each of the electrodes as the finger passes over the grid. The sensing electronics are generally located on the backside of the circuit board. By way of example, the sensing electronics may include an application specific integrated circuit (ASIC) that is configured to measure the amount of capacitance in each of the electrodes and to compute the position of finger movement based on the capacitance in each of the electrodes. The ASIC may also be configured to report this information to the computing device. 
     Referring to  FIG. 1 , a touch-sensitive track pad  10  will be described in greater detail. The track pad is generally a small (often rectangular) area that includes a protective/cosmetic shield  12  and a plurality of electrodes  14  disposed underneath the protective shield  12 . Electrodes  14  may be located on a circuit board, for example a printed circuit board (PCB). For ease of discussion, a portion of the protective shield  12  has been removed to show the electrodes  14 . Each of the electrodes  14  represents a different x, y position. In one configuration, as a finger  16  (or alternately a stylus, not shown) approaches the electrode grid  14 , a tiny capacitance forms between the finger  16  and the electrodes  14  proximate the finger  16 . The circuit board/sensing electronics (not shown) measures capacitance and produces an x, y input signal  18  corresponding to the active electrodes  14  which is sent to a host device  20  (e.g., a computing device) having a display screen  22 . The x, y input signal  18  is used to control the movement of a cursor  24  on a display screen  22 . As shown, the input pointer moves in a similar x, y direction as the detected x, y finger motion.  FIG. 2  is a simplified perspective view of an input device  30 , in accordance with one embodiment of the present invention. The input device  30  is generally configured to send information or data to an electronic device (not shown) in order to perform an action on a display screen (e.g., via a graphical user interface (GUI)). For example, moving an input pointer, making a selection, providing instructions, etc. The input device may interact with the electronic device through a wired (e.g., cable/connector) or wireless connection (e.g., IR, bluetooth, etc.). 
     The input device  30  may be a stand alone unit or it may be integrated into the electronic device. When in a stand alone unit, the input device typically has its own enclosure. When integrated with an electronic device, the input device typically uses the enclosure of the electronic device. In either case, the input device may be structurally coupled to the enclosure as for example through screws, snaps, retainers, adhesives and the like. In some cases, the input device may be removably coupled to the electronic device as for example through a docking station. The electronic device to which the input device is coupled may correspond to any consumer related electronic product. By way of example, the electronic device may correspond to a computer such as a desktop computer, laptop computer or PDA, a media player such as a music player, a communication device such as a cellular phone, another input device such as a keyboard, and the like. 
     As shown in  FIG. 2 , the input device  30  includes a frame  32  (or support structure) and a track pad  34 . The frame  32  provides a structure for supporting the components of the input device. The frame  32  in the form of a housing may also enclose or contain the components of the input device. The components, which include the track pad  34 , may correspond to electrical, optical and/or mechanical components for operating the input device  30 . 
     Track pad  34  provides an intuitive interface configured to provide one or more control functions for controlling various applications associated with the electronic device to which it is attached. By way of example, the touch initiated control function may be used to move an object or perform an action on the display screen or to make selections or issue commands associated with operating the electronic device. In order to implement the touch initiated control function, the track pad  34  may be arranged to receive input from a finger (or object) moving across the surface of the track pad  34  (e.g., linearly, radially, angular, etc.), from a finger holding a particular position on the track pad  34  and/or by a finger tapping on a particular position of the track pad  34 . As should be appreciated, the touch pad  34  provides easy one-handed operation, i.e., lets a user interact with the electronic device with one or more fingers. 
     The track pad  34  may be widely varied. For example, the touch pad  34  may be a conventional track pad based on the Cartesian coordinate system, or the track pad  34  may be a touch pad based on a polar coordinate system. An example of a touch pad based on polar coordinates may be found in U.S. Pat. No. 7,046,230 to Zadesky et al., entitled “TOUCH PAD FOR HANDHELD DEVICE”, filed Jul. 1, 2002, which is herein incorporated in its entirety by reference thereto. 
     The track pad  34  may be used in a relative or absolute mode. In absolute mode, the track pad  34  reports the absolute coordinates of where it is being touched. For example x, y in the case of the Cartesian coordinate system or (r, θ) in the case of the polar coordinate system. In relative mode, the track pad  34  reports the direction and/or distance of change. For example, left/right, up/down, and the like. In most cases, the signals produced by the track pad  34  direct motion on the display screen in a direction similar to the direction of the finger as it is moved across the surface of the track pad  34 . 
     The shape of the track pad  34  may be widely varied. For example, the track pad  34  may be circular, oval, square, rectangular, triangular, and the like. In general, the outer perimeter of the track pad  34  defines the working boundary of the track pad  34 . In the illustrated embodiment, the track pad is rectangular. Rectangular track pads are common on laptop computers. 
     The track pad  34 , which generally takes the form of a rigid planar platform, includes a touchable outer track surface  36  for receiving a finger (or object) for manipulation of the track pad. Although not shown in  FIG. 2 , beneath the touchable outer track surface  36  is a sensor arrangement that is sensitive to such things as the pressure and/or motion of a finger thereon. The sensor arrangement typically includes a plurality of sensors that are configured to activate as the finger sits on, taps on or passes over them. In the simplest case, an electrical signal is produced each time the finger is positioned over a sensor. The number of signals in a given time frame may indicate location, direction, speed, and acceleration of the finger on the track pad  34 , i.e., the more signals, the more the user moved his finger. In most cases, the signals are monitored by an electronic interface that converts the number, combination and frequency of the signals into location, direction, speed and acceleration information. This information may then be used by the electronic device to perform the desired control function on the display screen. The sensor arrangement may be widely varied. By way of example, the sensors may be based on resistive sensing, surface acoustic wave sensing, pressure sensing (e.g., strain gauge), infra red sensing, optical sensing, dispersive signal technology, acoustic pulse recognition, capacitive sensing and the like. 
     In the illustrated embodiment, the track pad  34  is based on capacitive sensing. A capacitively-based track pad is arranged to detect changes in capacitance as the user moves an object such as a finger around the track pad. In most cases, the capacitive track pad includes a protective shield, one or more electrode layers, a circuit board and associated electronics including an application specific integrated circuit (ASIC). The protective shield is placed over the electrodes; the electrodes are mounted on the top surface of the circuit board; and the ASIC is mounted on the bottom surface of the circuit board. The protective shield serves to protect the underlayers and to provide a surface for allowing a finger to slide thereon. The surface is generally smooth so that the finger does not stick to it when moved. The protective shield also provides an insulating layer between the finger and the electrode layers. The electrode layer includes a plurality of spatially distinct electrodes. Any suitable number of electrodes may be used. In most cases, it would be desirable to increase the number of electrodes so as to provide higher resolution, i.e., more information can be used for things such as acceleration. 
     Capacitive sensing works according to the principals of capacitance. As should be appreciated, whenever two electrically conductive members come close to one another without actually touching, their electric fields interact to form capacitance. In the configuration discussed above, the first electrically conductive member is one or more of the electrodes and the second electrically conductive member is, for example, the finger of the user. Accordingly, as the finger approaches the touch pad, a tiny capacitance forms between the finger and the electrodes in close proximity to the finger. The capacitance in each of the electrodes is measured by an ASIC located on the bottom (or backside) of the circuit board. By detecting changes in capacitance at each of the electrodes, the ASIC can determine the location, direction, speed and acceleration of the finger as it is moved across the touch pad. The ASIC can also report this information in a form that can be used by the electronic device. 
     In accordance with one embodiment, track pad  34  is movable relative to frame  32  so as to initiate another set of signals (other than just tracking signals). By way of example, track pad  34  in the form of the rigid planar platform may rotate, pivot, slide, translate, flex and/or the like relative to frame  32 . Track pad  34  may be coupled to frame  32  and/or it may be movably restrained by frame  32 . By way of example, track pad  34  may be coupled to frame  32  through screws, axels, pin joints, slider joints, ball and socket joints, flexure joints, magnets, cushions and/or the like. Track pad  34  may also float within a space of the frame (e.g., gimbal). It should be noted that the input device  30  may additionally include a combination of joints such as a pivot/translating joint, pivot/flexure joint, pivot/ball and socket joint, translating/flexure joint, and the like to increase the range of motion (e.g., increase the degree of freedom). When moved, touch pad  34  is configured to actuate a circuit that generates one or more signals. The circuit generally includes one or more movement indicators such as switches, sensors, encoders, and the like. An example of a gimbaled track pad may be found in patent application Ser. No. 10/643,256, entitled, “MOVABLE TOUCH PAD WITH ADDED FUNCTIONALITY,” filed Aug. 18, 2003, which is herein incorporated in its entirety by reference thereto. 
     In the illustrated embodiment, track pad  34  takes the form of a depressible button that performs a “picking” action. That is, a portion of the entire track pad  34  acts like a single or multiple button such that one or more additional button functions may be implemented by pressing on track pad  34  rather than tapping on the track pad or using a separate button/separate zone. As shown in  FIGS. 3A and 3B , according to one embodiment of the invention, track pad  34  is capable of moving between an upright (or neutral) position ( FIG. 3A ) and a depressed (or activate) position ( FIG. 3B ) when a force from a finger  38 , palm, hand, or other object is applied to the track pad  34 . The force should not be so small as to allow for accidental activation of the button signal, but not so large as to cause user discomfort by requiring undue pressure. Track pad  34  is typically biased in the upright position as for example through a flexure hinge, a spring member, or magnets. Track pad  34  moves to the activate position when the bias is overcome by an object pressing on track pad  34 . As shown in  FIG. 3C , the track pad  34  may be pivoted at one end such that the activate position is slightly inclined with respect to the neutral position. When the finger (or other object) is removed from track pad  34 , the biasing member urges it back towards the neutral position. A shim, shock absorber, upstop or other structure (not shown) may prevent track pad  34  from overshooting the neutral position as it returns. For example, a portion of frame  32  may extend outwardly above a portion of track pad  34  so as to stop track pad  34  at the neutral position. In this way, the track surface can be kept flush with frame  32  if desired. For example, in laptop computers or handheld media devices, it may be desirable to have the track pad flush with the housing of the computer or device. 
     As shown in  FIG. 3A , in the upright/neutral position, track pad  34  generates tracking signals when an object such as a user&#39;s finger is moved over the top surface of the touch pad in the x,y plane. Although  FIG. 3A  depicts the neutral position as being upright, the neutral position may be situated at any orientation. As shown in  FIG. 3B , in the depressed position (z direction), track pad  34  generates one or more button signals. The button signals may be used for various functionalities including but not limited to making selections or issuing commands associated with operating an electronic device. By way of example, in the case of a music player, the button functions may be associated with opening a menu, playing a song, fast forwarding a song, seeking through a menu and the like. In the case of a laptop computer, the button functions can be associated with opening a menu, selecting text, selecting an icon, and the like. As shown in  FIG. 3D , input device  30  may be arranged to provide both the tracking signals and the button signal at the same time, i.e., simultaneously depressing the touch pad  34  in the z direction while moving tangentially along the track surface (i.e. in the x, y directions). In other cases, input device  30  may be arranged to only provide a button signal when touch pad  34  is depressed and a tracking signal when the touch pad  34  is upright. 
     To elaborate, track pad  34  is configured to actuate one or more movement indicators, which are capable of generating the button signal when track pad  34  is moved to the activate position. The movement indicators are typically located within frame  32  and may be coupled to track pad  34  and/or frame  32 . The movement indicators may be any combination of switches and sensors. Switches are generally configured to provide pulsed or binary data such as activate (on) or deactivate (off). By way of example, an underside portion of track pad  34  may be configured to contact or engage (and thus activate) a switch when the user presses on track pad  34 . The sensors, on the other hand, are generally configured to provide continuous or analog data. By way of example, the sensor may be configured to measure the position or the amount of tilt of touch pad  34  relative to the frame when a user presses on the track pad  34 . Any suitable mechanical, electrical and/or optical switch or sensor may be used. For example, tact switches, force sensitive resistors, pressure sensors, proximity sensors and the like may be used. 
     Track pads  10  and  30  shown in  FIGS. 1-3  may, in some embodiments, be multi-touch trackpads. Multi-touch consists of a touch surface (screen, table, wall, etc.) or touchpad, as well as software that recognizes multiple simultaneous touch points, as opposed to the standard touchscreen (e.g., computer touchpad, ATM), which recognizes only one touch point. This effect is achieved through a variety of means, including but not limited to: capacitive sensing, resistive sensing, surface acoustic wave sensing, heat, finger pressure, high capture rate cameras, infrared light, optic capture, tuned electromagnetic induction, and shadow capture. An example of a multi-touch mobile phone is the iPhone produced by Apple Inc. of Cupertino, Calif. An example of a multi-touch media device is the iPod Touch produced by Apple Inc. Examples of laptop computers having multi-touch track pads are the MacBook Air and MacBook Pro produced by Apple Inc. All of the input devices described herein may employ multi-touch technology in some embodiments; alternatively the input devices described herein may employ single touch track pads. 
       FIG. 4  is a simplified block diagram of a computing system  39 , in accordance with one embodiment of the present invention. The computing system generally includes an input device  40  operatively connected to a computing device  42 . By way of example, the input device  40  may generally correspond to the input device  30  shown in  FIGS. 2 and 3 , and the computing device  42  may correspond to a laptop computer, desktop computer, PDA, media player, mobile phone, smart phone, video game or the like. As shown, input device  40  includes a depressible track pad  44  and one or more movement indicators  46 . Track pad  44  is configured to generate tracking signals and movement indicator  46  is configured to generate a button signal when the track pad  44  is depressed. Although track pad  44  may be widely varied, in this embodiment, track pad  44  includes capacitance sensors  48  and a control system  50  for acquiring the position signals from sensors  48  and supplying the signals to computing device  42 . Control system  50  may include an application specific integrated circuit (ASIC) that is configured to monitor the signals from sensors  48 , to compute the location (Cartesian or angular), direction, speed and acceleration of the monitored signals and to report this information to a processor of computing device  42 . Movement indicator  46  may also be widely varied. In this embodiment, however, movement indicator  46  takes the form of a switch that generates a button signal when track pad  44  is depressed. Switch  46  may correspond to a mechanical, electrical or optical style switch. In one particular implementation, switch  46  is a mechanical style switch that includes a protruding actuator  52  that may be pushed by track pad  44  to generate the button signal. By way of example, the switch may be a tact switch or tactile dome. 
     Both track pad  44  and switch  46  are operatively coupled to computing device  42  through a communication interface  54 . The communication interface provides a connection point for direct or indirect connection between the input device and the electronic device. Communication interface  54  may be wired (wires, cables, connectors) or wireless (e.g., transmitter/receiver). 
     Computing device  42  generally includes a processor  55  (e.g., CPU or microprocessor) configured to execute instructions and to carry out operations associated with the computing device  42 . For example, using instructions retrieved for example from memory, the processor may control the reception and manipulation of input and output data between components of the computing device  42 . In most cases, processor  55  executes instruction under the control of an operating system or other software. Processor  55  can be a single-chip processor or can be implemented with multiple components. 
     Computing device  42  also includes an input/output (I/O) controller  56  that is operatively coupled to processor  54 . I/O controller  56  may be integrated with processor  54  or it may be a separate component, as shown. I/O controller  56  is generally configured to control interactions with one or more I/O devices that can be coupled to computing device  42 , for example, input device  40 . I/O controller  56  generally operates by exchanging data between computing device  42  and I/O devices that desire to communicate with computing device  42 . 
     Computing device  42  also includes a display controller  58  that is operatively coupled to processor  54 . Display controller  58  may be integrated with processor  54  or it may be a separate component, as shown. Display controller  58  is configured to process display commands to produce text and graphics on a display screen  60 . By way of example, display screen  60  may be a monochrome display, color graphics adapter (CGA) display, enhanced graphics adapter (EGA) display, variable-graphics-array (VGA) display, super VGA display, liquid crystal display (LCD) (e.g., active matrix, passive matrix and the like), cathode ray tube (CRT), plasma displays, backlit light-emitting diode (LED) LCD displays, or the like. 
     In one embodiment (not shown), track pad  44  can comprise a glass surface functioning not only as a touch-sensitive surface, but also as a display screen; in this case display screen  60  shown in  FIG. 4  would be integrated with the glass surface of the track pad  44 . This could be useful in computing devices (e.g., media players or mobile phones) having touch sensitive displays. An example of a media player having a touch sensitive display is the iPod Touch produced by Apple Inc. of Cupertino Calif. An example of a mobile phone having a touch sensitive display is the iPhone produced by Apple Inc. of Cupertino Calif. 
     In most cases, processor  54  together with an operating system operates to execute computer code and produce and use data. The computer code and data may reside within a program storage area  62  that is operatively coupled to processor  54 . Program storage area  62  generally provides a place to hold data that is being used by computing device  42 . By way of example, the program storage area may include Read-Only Memory (ROM), Random-Access Memory (RAM), hard disk drive and/or the like. The computer code and data could also reside on a removable program medium and loaded or installed onto the computing device when needed. In one embodiment, program storage area  62  is configured to store information for controlling how the tracking and button signals generated by input device  40  are used by computing device  42 . 
       FIG. 5  shows one embodiment of an input device, generally shown at  70 , comprising a track pad  72  connected to a frame  76 . Frame  76  may be a housing for a stand alone input device, or it may be a casing for another device which incorporates track pad  72 , for example a laptop computer, desktop computer, hand held media device, PDA, mobile phone, smart phone, etc. Track pad  72  includes various layers including an outer touch-sensitive track surface  74  for tracking finger movements. Track surface  74  may also provide a low friction cosmetic surface. In one embodiment, track pad  72  is based on capacitive sensing; therefore, it includes an electrode layer  80 , which, for example, may be implemented on a PCB. In the case of capacitive sensing, track surface  74  is a dielectric material. A stiffener  84  is located below electrode layer  80 . Stiffener  84  is shown in  FIG. 5  and  FIG. 6 , but in some embodiments may be omitted. Stiffener  84  may be used to compensate for the inherent flexibility of electrode layer  80 . Electrode layer  80  responds to finger movements along track surface  74  by sending signals to sensor  82 . In the case of capacitive sensing, electrode layer  80  registers changes in capacitance based on finger movements and sensor  82  is a capacitive sensor. In this way, track pad  72  incorporates a touch sensor arrangement. Sensor  82  is shown disposed on the bottom of electrode layer  80 , but it may be located elsewhere in other embodiments. If, as in the illustrated embodiment, sensor  82  is located on a movable part of track pad  72 , the input device may incorporate a flexible electrical connection (not shown) capable of moving with the system. 
     A movement indicator  78  is disposed on the bottom of track pad  72 . Movement indicator  78  may be widely varied, however, in this embodiment it takes the form of a mechanical switch, which is typically disposed between the track pad  72  and the frame  76 . In other embodiments, movement indicator  78  may be a sensor, for example an electrical sensor. Movement indicator  78  may be attached to frame  76  or to track pad  72 . In the illustrated embodiment, movement indicator  78  is attached to the bottom side of electrode layer  80 . By way of example, if electrode layer  80  is located on a PCB, movement indicator  78  may be located on the bottom of the PCB. In another example, movement indicator  78  may tack the form of a tact switch and more particularly, may be an SMT dome switch (dome switch packaged for SMT). 
     Track pad  72  is shown in its neutral position in  FIG. 5 , where movement sensor  78  is not in contact with frame  76 . When a user applies a downward pressure to track surface  74 , track pad  72  may move downward causing movement sensor  78  to register this change in position. In the illustrated embodiment, movement sensor  78  (a tact switch) would contact either frame  76 , or in this case set screw  88 . Set screw  88  may be manually adjusted to alter the distance between the neutral and activate positions. In one embodiment (not shown), set screw  88  may directly abut movement sensor  78  in the neutral position, such that there is no slack or pre-travel in the system. A flexure hinge  86  connects track pad  72  with frame  76 . Flexure hinge  86  is a resilient material that flexes when a force is applied, but exerts a restoring force so as to urge track pad  72  back towards the neutral position. In one embodiment, flexure hinge  86  may be thin spring steel. 
     As shown in  FIG. 6 , flexure hinge  86  will flex when a user pushes down on track surface  74 . Flexure  86  also urges track pad  72  towards its neutral position, which in the illustrated embodiment shown in  FIG. 5  is horizontal. In this way, a user can press down virtually anywhere on track surface  74  and cause a “pick,” meaning that movement indicator  78  will register this depression. This is in contrast to prior track pads which incorporate separate track zones and pick zones. Being able to pick anywhere on track surface  74  will provide the user with a more intuitive and pleasurable interface. For example, a user may be able to generate tracking and button signals with a single finger without ever having to remove the finger from track surface  74 . In contrast, a user operating a track pad with separate track and pick zones may, for example, use a right hand for tracking and a left hand for picking, or a forefinger for tracking and a thumb for picking. 
     A shoulder  90 , which may be an extension of frame  76  or a discreet member, blocks track pad  72  from traveling past its neutral position by contacting a part of track pad  72 , for example stiffener  84 . In this way, track surface  74  may be kept substantially flush with a top surface of frame  76 . There may be a shock absorber or upstop (not shown) incorporated in conjunction with shoulder  90  to cushion contact between track pad  72  and shoulder  90 . 
     As should be appreciated, the pick generated by pressing on track surface  74  may include selecting an item on the screen, opening a file or document, executing instructions, starting a program, viewing a menu, and/or the like. The button functions may also include functions that make it easier to navigate through the electronic system, as for example, zoom, scroll, open different menus, home the input pointer, perform keyboard related actions such as enter, delete, insert, page up/down, and the like. 
     Flexure hinge  86  allows for a movable track pad in the minimum vertical space possible. Minimum vertical space is achieved because flexure hinge  86  is thin and is generally situated parallel to a bottom layer of track pad  72 , consequently, flexure hinge  86  does not appreciably add to the thickness of track pad  72 . Therefore, this arrangement is feasible for use in ultrathin laptop computers (or other ultrathin devices). In such ultrathin laptop computer applications, vertical space is extremely limited. In the past, the size of electrical components was often the limiting feature as to how small electrical devices could be made. Today, electrical components are increasingly miniaturized, meaning that mechanical components (e.g., movable track pads) may now be the critical size-limiting components. With this understanding, it is easy to appreciate why linear-actuation (e.g., supporting a movable track pad by coil springs or the like) is not ideal in some applications. Furthermore, using springs may add unnecessary complexity (increased part count, higher cost, higher failure rates, etc. . . . ) to the manufacturing process. Another disadvantage of springs is that in some embodiments springs may mask or compromise the tactile switch force profile. In contrast, flexure  86  can deliver a substantially consistent feel across track surface  74 , and give the user a more faithful representation of the tactile switch force profile. 
     Referring now to  FIG. 6 , according to one embodiment of the present invention, when a user presses on track surface  74  of track pad  72 , track pad  72  pivots downwardly and activates switch  78  disposed underneath. When activated, switch  78  generates button signals that may be used by an electronic device connected to input device  70 . Flexure  86  can constrain track pad  72  to move substantially about only one axis. This can be accomplished by, for example, using multiple flexures arranged along an axis on one side of track pad  72 , such as the rear side. Furthermore, if track pad  72  is made stiff (for example, by inclusion of stiffener  84  if necessary), a leveling architecture is achieved. The coupling of a stiff track pad  72  to flexure hinge  86  allows track pad  72  to remain level when articulated off-center. 
       FIG. 7  and  FIG. 8  show an input device  100 , in accordance with one embodiment of the present invention.  FIG. 7  is a perspective view of an input device  100  shown in use with a laptop computer.  FIG. 8  is an exploded perspective view of a disassembled track pad  101  used in input device  100 . 
     Input device, shown generally at  100  in  FIG. 7  is a depressible touch-sensitive track pad  101  disposed in a laptop computer frame  104 . As installed in computer frame  104 , the only portion of input device  100  visible to the user is track surface  102 , which may be flush with computer frame  104 . In the illustrated embodiment, track surface  102  is glass. Glass provides a dielectric, low-friction, durable, cosmetic surface. In one embodiment, track surface  102  is made of slightly frosted glass. In other embodiments, track surface  102  may be ceramic, plastic, or the like. If input device  100  is based on capacitive sensing, track surface  102  must be a dielectric material. The front end (i.e., nearest the user) of track surface  102  has a mid point  201  and a corner  203 . Track surface  102  moves approximately 0.2 mm when picked at the mid point of the extreme front end  201 . Due to the leveling architecture and stiffness of the illustrated embodiment, track surface  102  moves only approximately 0.4 mm when picked in the extreme left or right corner of the front end  203 , making input device  100  suitable for use with ultrathin laptops or other ultrathin applications where a depressible track pad is desirable. 
     As best seen in  FIG. 8 , immediately below glass  102  is a layer of ink  106 . Ink  106  is for cosmetic purposes, and may be color-matched to the color of computer frame  104 . Alternatively, ink  106  may be a different color than computer frame  104 , for example, a different shade of a similar color or a contrasting color. A layer of pressure-sensitive adhesive (PSA)  108  attaches glass  102  to the top surface of PCB  110 . A second layer of PSA  112  attaches the bottom surface of PCB  110  to the top surface of stiffener  114 . 
     In the illustrated embodiment, PSA layers  110  and  112  are shown as sheets shaped to match with the adjacent layers  106 ,  110 , and  114 . Modifications can be made, for example cutting holes in layers  110  and  112  to accommodate rigid posts or epoxy glue or the like in order to control shear between adjacent layers. Alternatively, PSA layers  110  and  112  can be cut back at their perimeters in order to make room for an entire perimeter of glue. These modifications may strengthen the bond between adjacent layers when subjected to high shear loads. PSA is described herein by way of example; other means of attaching layers could be used, for example, double-sided tape, glue, or cement. 
     PCBs generally have some inherent flex to them, which stiffener  114  substantially corrects for in order to add rigidity to track pad  101 . Stiffener  114  may have cutouts  116   a  to selectively reduce its weight, and or to selectively adjust its stiffness. Other cutouts, for example  118   a , not only serve to reduce weight (or to modulate stiffness) but also to allow electrical contact between PCB  110  and sensors incorporated on flex  120 , as will be discussed below. Overlying PSA layer  112  has corresponding cutouts  116   b  and  118   b.    
     In general, stiffener  114  should be stiff, light (i.e., low density), and thin enough for use in space-sensitive applications (e.g., ultrathin laptops, media devices, mobile phones, smart phones or the like). An ideal stiffener would be very stiff, very light, while at the same time very stiff. However, these three qualities (stiffness, light weight, thin) can be considered as tradeoffs; for example, there is generally a tradeoff between stiffness and weight for a given material. In the illustrated embodiment, stiffener  114  is made of steel. Steel is a compromise material because it is moderately heavy, but is very stiff. Because of its high stiffness, a stiffener  114  constructed of steel can be made relatively thin. Other metals may be used, for example, aluminum or titanium. Titanium is very light but may be more expensive than steel. 
     In other embodiments clad stiffeners may be used, in particular clad metallic stiffeners formed from various metals or other materials. An exemplary clad metallic stiffener  115  is shown in  FIG. 9  consisting of, for example, an aluminum core  117  surrounded by an upper steel layer  119  and a lower steel layer  121 . Steel has a higher elastic modulus (also known as modulus of elasticity) than inner core  117  of aluminum. An elastic modulus is the mathematical description of an object or substance&#39;s tendency to be deformed elastically (i.e., non-permanently) when a force is applied to it. A material with a higher elastic modulus (e.g., steel) is stiffer than a material with a lower elastic modulus (e.g. aluminum). This is important because, under certain conditions, the deflection of a stiffener is inversely proportional to the product of the elastic modulus and the second moment of area. This means that a stiffener made exclusively of aluminum of the same size and shape as stiffener  115 , which has an aluminum core and steel outer layers, would be lighter but would not be as stiff. 
     The clad effect (i.e., increasing stiffness by using high modulus materials as outer layers on a lightweight core) is similar to what happens with I-beams in constructing buildings; but in I-beams the second moment of area is adjusted instead of the elastic modulus. This is why beams with higher area moments of inertia, such as I-beams, are so often seen in building construction as opposed to other beams with the same area. 
     In other embodiments, stiffeners can be made of any suitable structural material, including but not limited to glass, ceramics, tungsten carbide, carbon fiber composites, and metal matrix composites. Such structural materials are very light and thin, making them desirable for use as stiffeners in thin, lightweight portable electronic devices. 
     PCB  110  includes an electrode layer (not shown) on the top surface and a movement sensor  126  on the bottom surface. In the illustrated embodiment, movement sensor  126  is a mechanical switch (see  FIGS. 8 and 11 ). Movement sensor  126  may be widely varied. Generally, tact switches may be used. More particularly, it may be a bare, packaged or encased metal dome switch. When a user presses down on track surface  102 , flexure hinge  122  allows for displacement of track pad  101 , thereby allowing movement sensor  126  to contact set screw  128 . Since switch  126  is electrically connected to other parts of the system (e.g., it is mounted on PCB  110 ), a pick signal will be registered and processed each time the user presses down sufficiently far to actuate sensor  126 . 
     Set screw  128  can be adjusted to increase or completely eliminate any offset displacement from movement sensor  126  in the neutral position. As shown in  FIG. 11 , there may be a small offset between movement sensor  126  and set screw  128  in the neutral position. In another embodiment (not shown), set screw  128  may directly abut switch  126  in the neutral position. 
     Flexure  122  will now be discussed with reference to  FIGS. 8 ,  10 , and  12 . In the illustrated embodiment, two flexures  122  are attached along a side of track pad  101  opposite sensor  126 . This arrangement constrains track pad  101  to move generally as a pivot about an axis defined by the location of the flexures  122 . The physical separation of the flexures  122  help to establish a leveling architecture. However, some amount of twist about a perpendicular axis (e.g., an axis on the midline of the track surface and perpendicular to the axis defined by the location of flexures  122 ) will also be possible if a user presses down on track surface  102  off center. This twist is partly from inherent flexibility in track pad  101  (even if stiffener  114  is used) and partly from variable bending of flexures  122 . This twist could be at least partially compensated by, for example, a more robust stiffener and/or using more or stiffer flexures. As previously mentioned, in the illustrated embodiment, track surface  102  moves approximately 0.4 mm when pressed off center (e.g., at corner  203  in  FIG. 7 ) and only approximately 0.2 mm when pressed on its centerline (e.g., at  201  in  FIG. 7 ). This extremely small amount of twist does not degrade the performance of track pad  101 . 
     Flexure  122  has a top flexure portion  130  and a bottom flexure stiffener portion  132 . Flexure portion  130  may be made of a thin resilient material, for example thin spring steel. When a flexible component is subject to bending stress, an instability can occur that manifests itself as a buckling. To relieve this instability, flexure members  130  have slots  134 , generally oriented substantially parallel to the axis about which they are most likely to be bent. Flexure stiffeners  132  stiffen flexures  122  in the area where they are attached to frame  104 . In the illustrated embodiment, each flexure  122  has three fasteners  136  which thread through holes  136   a  in flexure member  130  and holes  136   b  in stiffener  114 . In the illustrated embodiment, each flexure  122  also has two more rear fasteners  138  which thread through holes  138   a  in flexure  122  and  138   b  in frame  104  to secure flexures  122  to frame  104 . While three fasteners  136  and two rear fasteners  138  are shown, the type and number of fasteners can be varied. 
     As shown in  FIGS. 8 and 13 , two upstops  140  are positioned above extensions  146  of stiffener  114  and below an extension or shoulder of frame  104 . This arrangement prevents track pad  101  from overshooting the neutral position after a depression cycle, maintaining track surface  102  substantially flush with a surface of frame  104 . PSA  144  can be used to attach upstop  140  to frame  104 . Alternatively, PSA  144  can be used to attach upstop  140  to stiffener  114 . After a depression cycle, flexures  122  urge track pad  101  back towards the neutral position. In the illustrated embodiment, extensions  146  of stiffener  114  come into contact with upstop  140 , which is positioned underneath frame  104 . Upstop  140  acts as a mild shock absorber, preventing stiffener  114  from actually contacting frame  104 , which may be substantially rigid. Suitable materials for upstop  140  include plastic, foam, rubber, biaxially-oriented polyethylene terephthalate (boPET) polyester film, which is known by the trade mark Mylar®, and the like. By absorbing the impact between stiffener  114  and frame  104  when the track pad  101  rebounds to neutral, Upstop  140  can selectively dampen undesirable acoustic noise after a depression cycle. Upstop  140  serves the dual function of shock absorption and limiting an upper range of motion of track pad  101  to coincide with the neutral position, which may be substantially flush with frame  104 . While two upstops  140  are shown, more or fewer may be used. 
     Flex  120  can best be seen in  FIGS. 8 and 14 . Since track pad  101  is movable, flex  120  must be able to travel with track pad  101  as it moves. This is accomplished by providing a flexible electrical connection  150 , which runs between a computer connection  152  configured to communicate with the electronic device in which input device  100  is housed in, for example a laptop computer, and a sensor connection  154  configured to communicate with PCB  110 . Integrated circuits  156  are located on the top surface of flex  120 . Integrated circuits  156  receive and process data from the electrode layer on PCB  110  to form the heart of a capacitive sensor, providing functions such as reading when a user&#39;s finger, for example, is in contact with track surface  102 , and for determining finger movement. A PCB-based sensor is discussed by way of example, and not by way of limitation. Non-PCB sensors such as stamped sheetmetal, flex circuits (e.g., polyimide), conductive ink printed on substrates, e.g., polyethylene terephthalate (PET) substrates, indium tin oxide (ITO) on glass, and the like can also be used in the present invention. A cosmetic label  124  covers flex  120  from below. The assembled input device  100  is seen from below in  FIG. 10 . 
     Although not shown, input device  100  may be back lit. For example, PCB  110  can be populated with light emitting diodes (LEDs) on either side to enable a user to more easily see input device  100  in low light. 
     The input devices described herein may be integrated into an electronic device or they may be separate stand alone devices. One example of an input device integrated into a laptop computer is shown in  FIG. 7  and previously discussed;  FIG. 15  shows an input device  200  integrated into a media player  202  while  FIG. 16  shows an input device  207  integrated into a mobile phone.  FIGS. 17 and 18 , on the other hand, show some implementations of input device  200  as a stand alone unit. In  FIG. 17 , input device  200  is a peripheral device that is connected to a desktop computer  206 . In  FIG. 18 , the input device  200  is a remote control that wirelessly connects to a docking station  208  with a media player  210  docked therein. It should be noted, however, that remote control  200  can also be configured to interact with media player  210  (or other electronic device) directly thereby eliminating the need for a docking station. An example of a docking station for a media player with which the present invention may be used can be found in U.S. patent application Ser. No. 10/423,490, “MEDIA PLAYER SYSTEM,” filed Apr. 25, 2003, which is herein incorporated in its entirety by reference thereto. It should be noted that these particular embodiments are not a limitation and that many other devices and configurations may be used. 
     Referring to  FIG. 15 , the media player  202  will be discussed in greater detail. The term “media player” generally refers to computing devices that are dedicated to processing media such as audio, video or other images, as for example, music players, game players, video players, video recorders, cameras, and the like. In some cases, the media players contain single functionality (e.g., a media player dedicated to playing music) and in other cases the media players contain multiple functionality (e.g., a media player that plays music, displays video, stores pictures and the like). In either case, these devices are generally portable so as to allow a user to listen to music, play games or video, record video or take pictures wherever the user travels. 
     In one embodiment, the media player is a handheld device that is sized for placement into a pocket of the user. By being pocket sized, the user does not have to directly carry the device and therefore the device can be taken almost anywhere the user travels (e.g., the user is not limited by carrying a large, bulky and often heavy device, as in a laptop or notebook computer). For example, in the case of a music player, a user may use the device while working out at the gym. In case of a camera, a user may use the device while mountain climbing. In the case of a game player, the user can use the device while traveling in a car. Furthermore, the device may be operated by the users hands, no reference surface such as a desktop is needed. In the illustrated embodiment, the media player  202  is a pocket sized hand held MP3 music player that allows a user to store a large collection of music (e.g., in some cases up to 40,000 CD-quality songs). By way of example, the MP3 music player may correspond to one of the iPod family of MP3 players manufactured by Apple Inc. of Cupertino, Calif. Although used primarily for storing and playing music and/or video, the MP3 music player shown herein may also include additional functionality such as storing a calendar and phone lists, storing and playing games, storing photos and the like. In fact, in some cases, it may act as a highly transportable storage device. 
     As shown in  FIG. 15 , the media player  202  includes a housing  222  that encloses internally various electrical components (including integrated circuit chips and other circuitry) to provide computing operations for the media player  202 . In addition, the housing  222  may also define the shape or form of the media player  202 . That is, the contour of the housing  222  may embody the outward physical appearance of the media player  202 . The integrated circuit chips and other circuitry contained within the housing  222  may include a microprocessor (e.g., CPU), memory (e.g., ROM, RAM), a power supply (e.g., battery), a circuit board, a hard drive, other memory (e.g., flash) and/or various input/output (I/O) support circuitry. The electrical components may also include components for inputting or outputting music or sound such as a microphone, amplifier and a digital signal processor (DSP). The electrical components may also include components for capturing images such as image sensors (e.g., charge coupled device (CCD) or complimentary oxide semiconductor (CMOS)) or optics (e.g., lenses, splitters, filters). 
     In the illustrated embodiment, the media player  202  includes a hard drive thereby giving the media player massive storage capacity. For example, a 160 GB hard drive can store up to 40,000 songs, approximately 200 hours of video, or up to 25,000 photos. In contrast, flash-based media players on average store up to 128 MB, or about two hours, of music. The hard drive capacity may be widely varied (e.g., 8, 16, 80, 160 GB, etc.). In addition to the hard drive, the media player  202  shown herein also includes a battery such as a rechargeable lithium ion battery. These type of batteries are capable of offering about 30 hours of continuous music playtime to the media player or 5 hours of video playtime. 
     The media player  202  also includes a display screen  224  and related circuitry. The display screen  224  is used to display a graphical user interface as well as other information to the user e.g., text, objects, graphics). By way of example, the display screen  224  may be a liquid crystal display (LCD). In one particular embodiment, the display screen corresponds to a 320-by-240-pixel high-resolution display LCD display, with LED backlight to give clear visibility in daylight as well as low-light conditions. As shown, the display screen  224  is visible to a user of the media player  202  through an opening  225  in the housing  222 , and through a transparent wall  226  that is disposed in front of the opening  225 . Although transparent, the transparent wall  226  may be considered part of the housing  222  since it helps to define the shape or form of the media player  202 . 
     The media player  202  also includes the touch pad  200  such as any of those previously described. The touch pad  200  generally consists of a touchable outer surface  231  for receiving a finger for manipulation on the touch pad  230 . In the illustrated embodiment, touch pad  200  is circular, but its shape can be widely varied, e.g., rectangular, square, etc. Although not shown in  FIG. 15 , beneath the touchable outer surface  231  is a sensor arrangement. The sensor arrangement includes a plurality of sensors that are configured to activate as the finger sits on, taps on or passes over them. In the simplest case, an electrical signal is produced each time the finger is positioned over a sensor. The number of signals in a given time frame may indicate location, direction, speed and acceleration of the finger on the touch pad, i.e., the more signals, the more the user moved his or her finger. In most cases, the signals are monitored by an electronic interface that converts the number, combination and frequency of the signals into location, direction, speed and acceleration information. This information may then be used by the media player  202  to perform the desired control function on the display screen  224 . For example, a user may easily scroll through a list of songs by swirling the finger around the touch pad  200 . 
     In addition to above, the touch pad may also include a movable button configured to provide one or more dedicated control functions for making selections or issuing commands associated with operating the media player  202 . By way of example, in the case of an MP3 music player, the button functions may be associated with opening a menu, playing a song, fast forwarding a song, seeking through a menu, making selections and the like. In most cases, the button functions are implemented via a mechanical clicking action. 
     The position of the touch pad  200  relative to the housing  222  may be widely varied. For example, the touch pad  200  may be placed at any external surface (e.g., top, side, front, or back) of the housing  222  that is accessible to a user during manipulation of the media player  202 . In most cases, the touch sensitive surface  231  of the touch pad  200  is completely exposed to the user. In the illustrated embodiment, the touch pad  200  is located in a lower, front area of the housing  222 . Furthermore, the touch pad  230  may be recessed below, level with, or extend above the surface of the housing  222 . In the illustrated embodiment, the touch sensitive surface  231  of the touch pad  200  is substantially flush with the external surface of the housing  222 . 
     The shape of touch pad  200  may also be widely varied. Although shown as circular, the touch pad may also be annular, rectangular, triangular, and the like. 
     Media player  202  may also include a hold switch  234 . The hold switch  234  is configured to activate or deactivate the touch pad and/or buttons associated therewith. This is generally done to prevent unwanted commands by the touch pad and/or buttons, as for example, when the media player is stored inside a user&#39;s pocket. When deactivated, signals from the buttons and/or touch pad are not sent or are disregarded by the media player. When activated, signals from the buttons and/or touch pad are sent and therefore received and processed by the media player. 
     Moreover, the media player  202  may also include one or more headphone jacks  236  and one or more data ports  238 . The headphone jack  236  is capable of receiving a headphone connector associated with headphones configured for listening to sound being outputted by the media device  202 . The data port  238 , on the other hand, is capable of receiving a data connector/cable assembly configured for transmitting and receiving data to and from a host device such as a general purpose computer (e.g., desktop computer, portable computer). By way of example, the data port  238  may be used to upload or down load audio, video and other images to and from the media device  202 . For example, the data port may be used to download songs and play lists, audio books, ebooks, photos, and the like into the storage mechanism of the media player. 
     The data port  238  may be widely varied. For example, the data port may be a PS/2 port, a serial port, a parallel port, a USB port, a Firewire port and/or the like. In some cases, the data port  238  may be a radio frequency (RF) link or optical infrared (IR) link to eliminate the need for a cable. Although not shown in  FIG. 12 , the media player  202  may also include a power port that receives a power connector/cable assembly configured for delivering powering to the media player  202 . In some cases, the data port  238  may serve as both a data and power port. In the illustrated embodiment, the data port  238  is a Firewire port having both data and power capabilities. 
     Although only one data port is shown, it should be noted that this is not a limitation and that multiple data ports may be incorporated into the media player. In a similar vein, the data port may include multiple data functionality, i.e., integrating the functionality of multiple data ports into a single data port. Furthermore, it should be noted that the position of the hold switch, headphone jack and data port on the housing may be widely varied. That is, they are not limited to the positions shown in  FIG. 15 . They may be positioned almost anywhere on the housing (e.g., front, back, sides, top, bottom), or even be absent in some embodiments. For example, the data port may be positioned on the bottom surface of the housing rather than the top surface as shown. 
     Referring back  FIG. 16 , mobile phone  207  will be discussed in greater detail. Phone  207  may be a smart phone. Mobile phone  207  comprises a frame  209  and a touch sensitive screen  211 . Touch-sensitive screen  211 , which may be a multi-touch screen, similar to that used on the iPhone produced by Apple Inc. of Cupertino, Calif. can be made clickable by allowing it to displace relative to frame  209  when pressed on. In this way a button functionality like the previously described depressible input devices of the present invention can be incorporated to phone  207 . In some embodiments, tactile and/or aural feedback may be incorporated with the button function. For example, pressing down on screen  211  not only activates some function, but may also produce an audible clicking sound. The clicking sound may be mechanically produced (for example by the mechanical switch itself) and/or may be electrically produced (for example through a speaker which is activated whenever the user presses down far enough). Moreover, tactile feedback can be generated, for example the mechanical feedback generated by positively clicking a mechanical switch or a vibration which is triggered whenever a pick is detected. Although specifically discussed with reference to mobile phone  207 , tactile and/or aural feedback may be incorporated with the button function of any embodiment discussed herein (e.g., laptop track pad, media player track pad or screen, remote control track pad, etc. . . . ) 
     In another embodiment (not shown) a mobile phone can incorporate a non-touch sensitive screen (i.e., a traditional screen) in conjunction with a touch-sensitive, depressible track pad, such as the track pads previously described herein. In this embodiment, the screen functions as the display, while the track pad can, for example, move a cursor on the display and also incorporate a button function. In other words, a depressible track pad can be used on a mobile phone in conjunction with a separate screen instead of depressing the screen itself, as was the case with the embodiment discussed in reference to  FIG. 16 . 
     Turning to  FIG. 19 , a simplified block diagram of a remote control  280  incorporating an input device  282  therein, in accordance with another embodiment of the present invention is shown. By way of example, input device  282  may correspond to any of the previously described input devices of the present invention. Input device  282  includes a touch pad  284  and switch  286 . Touch pad  284  and switch  286  are operatively coupled to a wireless transmitter  288 , configured to transmit information over a wireless communication link so that an electronic device having receiving capabilities may receive the information over the wireless communication link. The wireless transmitter  288  may be widely varied. For example, it may be based on wireless technologies such as FM, RF, Bluetooth, 802.11 UWB (ultra wide band), infrared (IR), magnetic link (induction) and/or the like. In the illustrated embodiment, the wireless transmitter  288  is based on IR. IR generally refers wireless technologies that convey data through infrared radiation. As such, the wireless transmitter  288  generally includes an IR controller  290 . The IR controller  290  takes the information reported from the touch pad  284  and switches  286  and converts this information into infrared radiation as for example using a light emitting diode  292 . 
     As previously noted, the track surface of the present invention may be made of glass. Besides providing a low friction, durable, cosmetic surface, glass provides for options that opaque surfaces (e.g., plastic, ceramic, and the like) do not provide. For example, in one embodiment, track pad  101  can be delineated into separate zones, using, for example, lights, textured glass, or combinations thereof. Each zone can have a different function. For example, one zone may be a track zone (which may move a cursor) while another zone may be a pick zone (which may be depressible to activate a button function.) 
       FIGS. 20   a - 20   e  show exemplary delineation options for track pad  300 .  FIG. 20   a  shows transparent or semi-transparent track pad  300  made of glass with a single zone  302 , i.e., the entire track surface is depressible to activate a button function.  FIG. 20   b  shows track pad  300  with an upper track surface  304  and a single pick zone  306 . The line  308  which separates track surface  304  from pick zone  306  can be created by a textured glass surface with LED side lighting, IR ink with LED side lighting, electro-luminescence, magnetic ink, two-tone rolling wire, or the like.  FIG. 20   c  shows an alternate embodiment having two pick zones  310  and  312 . These zones can be associated with separate button functions, for example “left click” and “right click.”  FIG. 20   d  shows two track zones that are left-biased, i.e., left pick zone  314  is larger than right pick zone  316 .  FIG. 20   e  shows two track zones that are right-biased, i.e. left pick zone  318  is smaller than right pick zone  320 .  FIG. 20   f  shows three pick zones  322 . The delineation options shown in  FIG. 20  are given by way of example, and not by way of limitation. 
     In one embodiment, track and pick zones can be user-selectable. For example, the user can turn off the delineation line(s), such that the track pad is like that shown in  FIG. 20   a  corresponding to a track pad that can be picked anywhere on its track surface, which now functions similar to the embodiment shown in  FIG. 7 . If the user later desires a more traditional track pad having left and right pick zones, he can configure the track pad to appear as shown in  FIG. 20   c , with a corresponding change in functionality of the track pad. 
     As shown in  FIG. 21 , in addition to displaying delineation lines on the track pad, a track pad  324  with a glass (or otherwise transparent or semi-transparent) track surface  326  can even function as a full pixel display. In one embodiment, track surface  326  can be an active matrix display, for example using electronic paper/electronic ink, LCD, thin film transistor liquid crystal display (TFT-LCD), etc. 
     E ink® is the trade mark for one type of electronic paper developed by E Ink Corporation of Cambridge, Mass. The principal components of E ink® are millions of tiny microcapsules  327 , about the diameter of a human hair. In one embodiment, shown in  FIG. 22 , each microcapsule contains positively charged white particles  328  and negatively charged black particles  330  suspended in a clear fluid  332 . When a negative electric field  334  is applied, the white particles move to the top of the microcapsule to become visible to the reader. This makes the surface appear white at that spot. At the same time, an opposite electric field  336  pulls the black particles to the bottom of the microcapsules where they are hidden. By reversing this process, the black particles appear at the top of the capsule, which now makes the surface appear dark at that spot. The top  338  and/or bottom  340  electrodes are transparent so that a user can see the colored particles. 
     To form an E Ink® electronic display, the ink is printed onto a sheet of plastic film that is laminated to a layer of circuitry. The circuitry forms a pattern of pixels that can then be controlled by a display driver. These microcapsules are suspended in a liquid “carrier medium” allowing them to be printed using existing screen printing processes onto virtually any surface, including glass, plastic, fabric and even paper. An exemplary E ink® display was unveiled in February 2004 by Polymer Vision Ltd. This display is an organics-based quarter VGA (QVGA) (i.e., 320×240 pixels) active matrix display with a diagonal of five inches, a resolution of 85 dpi and a bending radius of 2 cm. The display combined a 25 micron thick active-matrix back pane containing the polymer electronics-based pixel driving, with a 200 micron front plane of reflective E Ink®. 
     As discussed, a glass surface can be used as a track surface in some embodiments of the present invention. Ideally, such a glass surface should have a low coefficient of friction, should be clean with high clarity, should not readily pick up smudges, readily scratch, or be abrasive to skin, and finally should be mechanically robust in order to survive thousands of cycles of track pad depressions. 
     One disadvantage of conventional glass structures is that they do not have all of these attributes simultaneously, e.g., conventional glass may be very clear, but it has a high coefficient of friction. Low friction is important in track pads (e.g., track pads on laptop computers) because overcoming excessive frictional forces between the glass and a user&#39;s finger, for example, can cause user discomfort or could cause inadvertent picks in the case of a depressible track pad. The preferred glass surface is one that is silky-smooth and highly optically clear. 
     There are various known methods to treat glass including, for example, blasting, laser etching, honing, and chemical etching. These conventional methods are normally applied to a piece of raw glass. The surface of raw glass may appear smooth to the naked eye, but its smoothness actually increases the coefficient of friction because the finger (or other surface) is in direct contact with glass over a large percentage of surface area. To correct for this, treatments (etching, etc.) are sometimes applied to smooth surface  344  in order to decrease friction or change the optical properties of the glass. Etching glass produces microscopic bumps or peaks which reduces the smoothness of the raw glass; this lowers the coefficient of friction by reducing the surface area that a finger is in contact with the glass. In other words, a finger rubbed across a piece of etched glass will have to overcome frictional forces associated with directly contacting the bumps or peaks on the etched glass surface, but the finger will experience greatly reduced friction in areas between the bumps or peaks, which is essentially just air. 
     Producing a final piece of treated glass (e.g., for use in an LCD) is commonly been done in one step. For example, the raw glass is chemically etched. However, this single-step method does not yield a glass surface that has all of the desirable attributes mentioned above. For example, the glass surface may have lower friction, but is often associated with decreased clarity or decreased smudge resistance. Efforts to process the glass in multiple steps (e.g., mechanical abrasion followed by chemical post-processing) has also not been previously successful; the glass surfaces produced in multiple steps suffer the same disadvantages as those produced in a single step. 
     In the present invention, raw glass may be processed in a two step method to produce a much improved glass. 
     In the first step, a piece of raw glass  342  is processed mechanically or chemically to create a “seed surface” with a fine pitch. Tailoring the seed surface to have a very fine pitch (i.e., a very rough surface) would enable a subsequent liquid-polishing (i.e., in the second step) so as to produce a final glass surface having all of the desirable attributes. The seed surface is best seen in  FIG. 24A  where the processed glass has a bumpy surface  346  characterized by a peak-to-peak ratio  348  and an amplitude  350 . This is the seed surface. A fine pitch seed surface, such as  346 , will have a very low transmittance (ratio of transmitted to incident light), on the order of 30%. 
     The first step of processing the glass may be performed using chemical etching, for example using ammonium BiFlouride cream mixed with an inert carrier. This chemical etching cream is applied to the surface and left there for a period of time, for example 30 minutes.  FIG. 24B  shows the seed surface  346  at the conclusion of the first step. The seed surface is shown at 1,000 magnification. The scale at the bottom of  FIG. 24B  is scaled to 10 μm. 
     In the second step, the seed surface is exposed to a hydrofluoric acid (HF) solution incorporating a secondary acid. This is a wet application, meaning that HF could be sprayed onto the seed surface, or the seed surface could be dipped into HF. In one embodiment, the solution consists of HF and hydrocholoric acid, i.e., HF+HCl. In another embodiment, the solution consists of HF and sufluric acid, i.e., HF+H 2 SO 4 . In either of these embodiments, the acid solution may be mixed with water. The higher the concentration of HF the faster the process will occur, but the net result will be the same. In one embodiment, the solution may consist of approximately 5% HF with approximately 10% HCl and approximately 85% H 2 O. The primary acid is HF, while the secondary acid (HCl or H 2 SO 4 ) functions to remove residuals from the glass surface to let the HF react with the glass. The HF reacts with seed surface  346  produced during the first step and changes its topography, which in turn changes the relevant properties of the glass (e.g., transmittance, coefficient of friction). The resulting final glass surface  356  is shown in  FIG. 25 . Surface  356  has an amplitude  352  roughly equal to amplitude  350  of the seed surface, but a peak-to-peak ratio  354  that is roughly an order of magnitude larger (e.g., eight to twelve times) than the peak-to-peak ratio  348  of seed surface  346 . Testing has shown that the amplitude is not significantly correlated to the relevant glass properties; the peak-to-peak ratio is the dominant characteristic. In other words, varying the amplitude of the final glass surface did not affect the relevant glass properties, while independently varying the peak-to-peak ratio drastically affected the relevant properties. 
     When seen from above, as in  FIG. 26 , which is magnified 1000 times, the final surface  356  has a matrix of divots  358 , resembling a metal surface that has been randomly struck by a ball peen hammer. The resulting glass has all of the desirable attributes (low friction, clear, durability, smudge-resistant, etc. . . . ), and has an appearance that is “lively” and “sparkly.” The transmittance of this glass is on the order of 90%. 
     The final surface  356  is a low friction surface. The coefficient of friction, μ, of a surface is the ratio of a normal force, F N , from an object on that surface to the frictional force, F F , that must be overcome in order to move the object relative to the surface, i.e., 
             μ   =         F   N       F   f       .           
The frictional force is further classified into static and dynamic friction. Static friction, F S , is the force that must be overcome when two objects are not moving relative to each other, while dynamic friction, F D , is the frictional force between two objects in relative motion. Static friction is typically higher than dynamic friction, i.e., it normally takes a larger force to get an object moving relative to another surface when they were initially stationary, but a smaller force to keep the object in motion. The coefficients of static μ S  and dynamic μ D  friction are therefore defined as:
 
     
       
         
           
             
               μ 
               S 
             
             = 
             
               
                 
                   
                     F 
                     N 
                   
                   
                     F 
                     S 
                   
                 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 and 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 
                   μ 
                   D 
                 
               
               = 
               
                 
                   
                     F 
                     N 
                   
                   
                     F 
                     D 
                   
                 
                 . 
               
             
           
         
       
     
     To demonstrate the frictional qualities of surfaces like final surface  356 , a 1-inch diameter neoprene disk with a roughened surface using 320-grit sandpaper was loaded with a normal force and pulled along various samples of surfaces like  356 . Tests were performed on various samples, and the neoprene disk was either pulled at 50 mm/min or 500 mm/min, and was loaded at either 71.4 grams or 295.9 grams. The surface was lubricated with squalene during some tests and not lubricated during the other tests. Table 1 summarizes the testing data: 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Friction Data 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                   
                 FN 
                   
                 Test 1 
                 Test 2 
                 Test 3 
                   
                 Standard 
                   
                 Standard 
               
               
                 Sample 
                 (grams) 
                 Lubrication 
                 (grams) 
                 (grams) 
                 (grams) 
                 μ D   
                 deviation 
                 μ S /μ D   
                 deviation 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 1 
                 71.4 
                 Yes 
                 32.37 
                 33.27 
                 32.41 
                 0.46 
                 0.01 
                 1.07 
                 0.01 
               
               
                 1 
                 295.9 
                 Yes 
                 106.46 
                 105.85 
                 111.39 
                 0.36 
                 0.01 
                 1.04 
                 0.01 
               
               
                 1 
                 71.4 
                 Yes 
                 38.58 
                 37.35 
                 39.07 
                 0.54 
                 0.01 
                 1.16 
                 0.06 
               
               
                 1 
                 295.9 
                 Yes 
                 115.5 
                 115.63 
                 116.35 
                 0.39 
                 0.00 
                 1.08 
                 0.03 
               
               
                 1 
                 71.4 
                 No 
                 77.77 
                 78.17 
                 76.58 
                 1.09 
                 0.01 
                 1.03 
                 0.00 
               
               
                 1 
                 295.9 
                 No 
                 284.24 
                 268.88 
                 260.79 
                 0.92 
                 0.04 
                   
                   
               
               
                 1 
                 71.4 
                 No 
                 58.9 
                 58.68 
                 56.4 
                 0.81 
                 0.02 
                 1.31 
                 0.04 
               
               
                 1 
                 295.9 
                 No 
                 250.52 
                 246.24 
                 244.39 
                 0.83 
                 0.01 
                 1.09 
                 0.05 
               
               
                 2 
                 71.4 
                 Yes 
                 25.3 
                 24.65 
                 25.25 
                 0.35 
                 0.01 
                 1.13 
                 0.08 
               
               
                 2 
                 295.9 
                 Yes 
                 81.75 
                 81.83 
                 83.2 
                 0.28 
                 0.00 
                 1.10 
                 0.02 
               
               
                 2 
                 71.4 
                 Yes 
                 40.35 
                 37.02 
                 35.47 
                 0.53 
                 0.03 
                 1.15 
                 0.02 
               
               
                 2 
                 295.9 
                 Yes 
                 111.77 
                 112.91 
                 110.12 
                 0.38 
                 0.00 
                 1.05 
                 0.01 
               
               
                 2 
                 71.4 
                 No 
                 94.67 
                 92.67 
                 87.71 
                 1.28 
                 0.05 
                 1.05 
                 0.02 
               
               
                 2 
                 295.9 
                 No 
                 n/a 
                 n/a 
                 n/a 
                 n/a 
                 n/a 
                 n/a 
                 n/a 
               
               
                 2 
                 71.4 
                 No 
                 81.52 
                 81.89 
                 80.82 
                 1.14 
                 0.01 
                 1.21 
                 0.04 
               
               
                 2 
                 295.9 
                 No 
                 341.19 
                 332.56 
                 324.6 
                 1.12 
                 0.03 
                 1.06 
                 0.01 
               
               
                 3 
                 71.4 
                 Yes 
                 24 
                 24.58 
                 25.08 
                 0.34 
                 0.01 
                 1.07 
                 0.02 
               
               
                 3 
                 295.9 
                 Yes 
                 78.22 
                 78.63 
                 78.78 
                 0.27 
                 0.00 
                 1.04 
                 0.02 
               
               
                 3 
                 71.4 
                 Yes 
                 33.49 
                 34.48 
                 36.04 
                 0.49 
                 0.02 
                 1.10 
                 0.01 
               
               
                 3 
                 295.9 
                 Yes 
                 102.95 
                 102.49 
                 103.29 
                 0.35 
                 0.00 
                 1.03 
                 0.00 
               
               
                 3 
                 71.4 
                 No 
                 82.32 
                 90.8 
                 85.67 
                 1.21 
                 0.06 
                 1.18 
                 0.09 
               
               
                 3 
                 295.9 
                 No 
                 n/a 
                 n/a 
                 n/a 
                 n/a 
                 n/a 
                 n/a 
                 n/a 
               
               
                 3 
                 71.4 
                 No 
                 101 
                 98.1 
                 96.93 
                 1.38 
                 0.03 
                 1.10 
                 0.01 
               
               
                 3 
                 295.9 
                 No 
                 371.08 
                 368.13 
                 365.01 
                 1.24 
                 0.01 
                 1.01 
                 0.00 
               
               
                   
               
            
           
         
       
     
       FIG. 27  shows the peak-to-peak ratio produced in the second step of the glass treatment process as a function of time. The peak-to-peak ratio rapidly increases before a critical time Tcrit  360 , at which point it proceeds basically asymptotically. This is important in manufacturing the glass because the process window of the second step is very large. In other words, the second step chemical treatment process is not time sensitive; the treatment can be applied and left on the glass for either a shorter time (near Tcrit  360 ) or for a much longer time to still get a relatively constant peak-to-peak ratio. This means that the time does not have to be carefully controlled; therefore, defective parts that would have needed to be scrapped if the peak-to-peak ratio were incorrect are reduced or eliminated. While the peak-to-peak ratio stays substantially constant in the asymptotic part of the peak-to-peak curve, the overall thickness of the glass is constantly decreasing during this process because the HF thins the glass. 
     In an alternate process, the first step can employ a mechanical treatment in lieu of the chemical treatment described above. For example, the glass can be treated with a fine grit (e.g., cerium oxide) and then mechanically honed. In some cases though, this may create micro fractures and/or give the final glass a lower four-point bending strength. As noted, the glass should be robust in order to survive thousands of pick cycles when used with a track pad; therefore, a chemical treatment, as described above, may be preferred to mechanical honing. 
     The two-step process of the present invention can be performed on a large sheet of glass, which is then subsequently cut into the desired shape, such as a rectangle. Alternatively, the raw glass can be cut into the desired shape first, and then treated. Cutting the glass into smaller shapes can introduce imperfections into the glass (e.g., small chips) which the chemical treatment can subsequently mask; therefore, in some embodiments it is desirable to cut the raw glass before treating it. 
     As shown in  FIG. 28 , PCB  110  can serve as the flexure hinge in an alternate embodiment. This has the advantage of requiring fewer parts. In this embodiment, track surface  102  and stiffener  114  surround PCB  110  except for a cantilevered portion  105  attached to computer frame  104 . In this way, a gap  106  is formed which serves as the flexure hinge. When a user presses down on track surface  102 , the track pad will pivot about  106  as cantilevered PCB  110  flexes in the area of  106 . When pressure from the user is relieved, PCB  110  will urge the track pad back to the neutral position, which in the illustrated embodiment is shown as horizontal. In another embodiment (not shown), gap  106  may be eliminated. 
       FIG. 29  shows another embodiment where a flexure hinge is made entirely from stiffener  114 . In this embodiment, stiffener  114  has a cantilevered end  107  that is thinner than the main body of stiffener  114 . End  107  is attached to computer frame  104  in an opening  109  in frame  104 . When a user presses down on track surface  102 , the track pad will pivot as end  107  flexes along gap  106 . When pressure from the user is relieved, end  107  of stiffener  114  will urge the track pad back to the neutral position, which in the illustrated embodiment is shown as horizontal. 
       FIG. 30  shows a flexure hinge made from a clad stiffener  123 . Like clad stiffener  115  described above with reference to  FIG. 9 , clad stiffener  123  has, for example, and aluminum core  125  surrounded by an upper steel layer  127  and a lower steel layer  129 . However, unlike clad stiffener  115 , upper layer  127  has a cantilever extension  131  which is attached to computer frame  104  in an opening  109  in frame  104 . When a user presses down on track surface  102 , the track pad will pivot as extension  131  flexes along gap  106 . When pressure from the user is relieved, extension  131  will urge the track pad back to the neutral position, which in the illustrated embodiment is shown as horizontal. Instead of upper layer  127  having a cantilevered extension  131 , core  125  or lower steel layer  129  may have a cantilever extension (not shown) to connect to frame  104  and act as a flexure hinge. Materials other than aluminum and steel may be used in a clad stiffener, provided they are stiff (i.e., high elastic modulus), thin, and are low density (i.e., lightweight). 
     Turning now to  FIG. 31 , another embodiment is shown in which stiffener  133  is unitary with computer frame  104 . When a user presses down on track surface  102 , the track pad will pivot as stiffener  133  flexes. When pressure from the user is relieved, stiffener  133  will urge the track pad back to the neutral position, which in the illustrated embodiment is shown as horizontal. In this embodiment, stiffener  133  and housing may be made of aluminum, for example. 
     Another input device  135  according to the present invention is shown in  FIGS. 32 and 33 . In this embodiment, input device  135  has a track surface  137 , an electrode (or PCB) layer  139 , and a stiffener  141 . Stiffener  141  partially extends into a cavity  143  of computer frame  145 . A trap  147  is attached to the underside of frame  145 . Trap  147  has an X-Y alignment post  151  which extends into a notch  153  in stiffener  141 . X-Y alignment post  151  fits inside of notch  153  and prevents stiffener  141  from moving in its own plane. Offset  155  extends along the front edge or pivot edge  157  of trap  147  and an area  159  between notch  153  and the maximum thickness of stiffener  141 . When a user presses down on track surface  137 , stiffener  141  rotates about pivot edge  157 . The presence of offset  155  and stiffener thickness transition  159  enables one-way rotation downward of input device  135 . One-way rotation is desirable to retain input device  135  inside of frame  145  and to keep track surface  137  flush to the outside of frame  145  in the nominal state as represented in  FIG. 32 . 
     As can be appreciated, all of the various flexure hinges described herein do not appreciably add to the thickness of the depressible track pads. Therefore, any of the flexure hinges of the present invention are particularly suitable for use in ultrathin applications (laptops, media devices, mobile phones, game players, etc.) 
     In the various track pads discussed above, inherent flexibility of various flexure hinges serves to urge the track pads back to their neutral positions whenever the user is not depressing the track pad to activate the button function. In other words, the track pads discussed above are biased to the neutral position by way of inherent flexibility. It is possible to use magnetic forces to bias a track pad to the neutral position. Magnetic force can be the sole biasing mechanism, or it can enhance existing biasing due to inherent flexibility. In other words, magnets can be used on any of the previously discussed input devices to supplement the bias provided from the various flexure hinges discussed. 
     In the various track pads discussed above, a mechanical dome switch serves as the primary restorative member to urge the track pads back to their neutral positions whenever the user is not depressing the track pad to activate the button function. Inherent flexibility in the various flexure hinges described above also urges the track pads back to their neutral positions. The mechanical dome is also responsible for providing tactile feedback to a user for a pick event. It is possible to use magnetic forces to bias a track pad to the neutral position and or to provide tactile feedback to the user. Magnetic force can be the sole biasing and tactile mechanism, or it can enhance existing biasing and tactile feel due to the mechanical dome switch and inherent flexibility from flexure hinges. In other words, magnets can be used on any of the previously discussed input devices to supplement the bias and tactile feel to the neutral position. 
     Turning to  FIG. 34   a , an input device  161  using magnetic forces is shown. Input device  161  has a track pad  163  having a track surface  165 . Like the other track pads discussed herein, track pad  163  has a sensor arrangement to detect and process finger movements on track surface  165 . For example, track pad  163  may employ capacitive sensing. To this end, track pad  163  has an electrode layer  167  (which may be on a PCB) for capacitive sensing. In the illustrated embodiment, track pad  163  has a pick zone  169  which is separated from track surface  165 . In this case, a user moves his finger relative to track surface  165  in order to perform tracking operations (e.g., move a cursor) but depresses pick zone  169  in order to activate a button functionality. 
     Input device  161  is shown in the neutral position in  FIG. 34   a . Magnetic attractive forces between magnet  179  and flange  177  biases the pick zone  169  to the neutral position and allows for movement to an activate position (to activate a button function) whenever a user depresses pick zone  169 . Button assembly  171  consists of a leveling plate  173 , flexure attachment  175 , flange  177  and pick zone  169 . Leveling plate  173  is composed of a relatively stiff material, for example, steel, which is also optimally thin and lightweight. Leveling plate  173  is connected to track pad  163  by flexure attachment  175 , which may be, for example, a thin piece of steel attached with screws. Flexure attachment  175  is capable of bending, similar to flexure hinge  122  discussed in relation to  FIGS. 8 ,  10 , and  12 . In another implementation, flexure attachment  175  can be a pivot pin assembly. When depressed at pick zone  169 , button assembly  171  hinges or pivots at flexure attachment  175  causing a movement sensor (not shown) to activate. The movement sensor may be capacitive, proximity, Hall-effect, optical, mechanical membrane or a plurality of sensors. Input device  161  is shown in the activate position in  FIG. 34   b.    
     Magnet  179  may be positioned anywhere, but in the illustrated embodiment, flange  177  is located on an end of leveling plate  173  and is situated directly below magnet  179  which is opposite the pivot point defined by flexure attachment  175 . Flange  177  may be a ferrous metal or other material capable of being attracted magnetically. Magnet  179  may be, for example, a permanent magnet, or electromagnet. In the illustrated embodiment magnet  179  is fixedly connected to the housing (not shown) of input device  161 . In another embodiment,  179  may be fixed to the housing (not shown) of an electronic device in which input device  161  is incorporated. In this case, magnet  179  would not move, but flange  177  would move with leveling plate  173  when the magnetic force attraction between magnet  179  and flange  177  is overcome by the user depressing pick zone  169 . In another embodiment (not shown) the magnet may move with leveling plate  173  while the metal portion stays fixed; in other words, magnet  179  and flange  177  can be the reverse of what is shown in  FIG. 34 . In such an embodiment, flange  177  may be a separate component from or it may integral with the housing (not shown). The magnetic force between magnet  179  and flange  177  can be controlled to obtain the desired click feel, for example by using a stronger or weaker permanent magnet, by varying the size or separation of magnet  179  and or flange  177 , or by using an adjustable electromagnet. 
     Although input device  161  is shown in  FIG. 34  as having a track surface  165  that is separate from a pick zone  169 , magnetic biasing can be used on a track pad having a depressible track surface, such as those described above. In other words, magnets can be used to bias depressible track pads to their neutral position. For example, magnets can be used with track pad  100  shown in  FIG. 7 , or with the various flexure hinges shown in  FIGS. 28-32 . 
     While this invention has been described in terms of several embodiments, there are alterations, permutations, and equivalents, which fall within the scope of this invention. It should also be noted that there are many alternative ways of implementing the methods and apparatuses of the present invention. It is therefore intended that the following appended claims be interpreted as including all such alterations, permutations, and equivalents as fall within the true spirit and scope of the present invention.

Metadata:
Filing Date: 20080930
Publication Date: 20130514
Grant Date: 20130514
Priority Date: 20080930
Inventors: DEGNER BRETT WILLIAM
KESSLER PATRICK
LIGTENBERG CHRIS A.
WILSON, JR. THOMAS W.
ANDRE BARTLEY K.
CASEBOLT MATTHEW P.
Assignee: APPLE INC
CPC Classifications: [{"code": "H01H25/041", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/169", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/03547", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/0446", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/041", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0446", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F1/169", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/0446", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F1/169", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F2203/04105", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/03547", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01H25/041", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F2203/04105", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F2203/04105", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/042", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/03547", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/042", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 42056883