Abstract:
A method of and system for providing user input to a computer, or the like, having a display by detecting a change in fingerprint pattern of a user. The system controls the position of a pointer on a display by detecting motion of ridges and pores of a fingerprint of a user and moving the pointer on the display according to detected motion of the ridges and pores of the fingerprint. The system captures successive images of the fingerprint ridges and pores and detects motion of the ridges and pores based upon the captured successive images.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to methods of and systems for providing user input to user interfaces for computers and the like, and more particularly to a semiconductor capacitive user input device and method for controlling the position of a cursor or pointer on a display. 
     DESCRIPTION OF THE PRIOR ART 
     Pointing devices are commonly used in conjunction with computers to control the movement of graphical cursors on a display screen and to select objects and operate controls displayed on the screen. For desktop computers and workstations, the most commonly used pointing device is a mouse. As is well known, a mouse is moved over a flat surface to control the position of the pointer on the display screen. A mouse includes one or more buttons that may be pressed or clicked to perform operations on objects and controls displayed on the screen. 
     Recently, small laptop and notebook computers have become very popular. Laptop and notebook computers may be used in conjunction with a docking station so that a standard keyboard, mouse, and CRT display may be used for the user interface. However, laptop and notebook computers are designed to be used while traveling and away from the office or home. In such remote locations, the user does not always have available a flat surface upon which to use a mouse. Accordingly, laptop and notebook computers typically have a built-in pointing device, such as a track ball, touch pad or a pressure-actuated pointing device, such as the IBM TrackPoint (TM) device. 
     In addition to computers, certain television and set top box systems include a graphical user interface for enabling a user to input information to the system and change or control system settings. The user input device for such systems is typically a hand-held infrared keypad controller. Such controllers may include devices similar to those used in laptop and notebook computers to control the position of a pointer on the television screen. 
     Track balls, touch pads, and pressure-actuated pointing devices have certain drawbacks. For example, while track balls are compact, they require considerable finger movement to produce large cursor displacements at low velocities. In addition, track balls are mechanical devices that may not be well suited for operation in dirty environments. A touch pad comprises a rectangular surface that is mapped to correspond to a display screen. By touching a location on the touch pad, the user causes the computer to move the pointer to the corresponding location on the screen. Since a typical touch pad is substantially smaller than the screen, accurate positioning of the pointer can be difficult. In order to be usable, a touch pad must be large enough to permit the user to position the pointer accurately. The large size of touch pads makes them difficult or impossible to use in a hand held device such as a television remote control. 
     Pressure-actuated pointing devices include strain gages or transducers that detect the direction and magnitude of the force of a user&#39;s finger on the device. The pointer is moved in a direction corresponding to the direction of the force and at a speed corresponding to the magnitude of the force. Certain individuals have trouble using pressure-actuated pointing devices to position the pointer accurately on the screen. One source of trouble is inertia, whereby the pointer continues to move after the user releases the pressure on the device. 
     It is an object of the present invention to provide a low-cost, small-sized, non-mechanical pointer position controlling device that overcomes the shortcomings of the prior art. 
     SUMMARY OF THE INVENTION 
     The present invention provides a method of and system for providing user input to a computer, or the like, having a display by detecting a change in fingerprint pattern of a user. In one of it aspects, the present invention provides a method of and system for controlling the X-Y position of a pointer on a display by detecting motion of ridges and pores of a fingerprint of a user and moving the pointer on the display according to detected motion of the ridges and pores of the fingerprint. In another of its aspects, the present invention provides Z axis input, such as button clicks, by detecting a widening of fingerprint ridges caused by increased pressure on a detector surface, or by detecting the lifting or the placement of the finger from or on the detector surface. 
     The method and system of the present invention captures successive images of the fingerprint ridges and pores and detects motion in or changes of the ridges and pores based upon the captured successive images. The method and system of the present invention captures the successive images by scanning an array of sensors, each of the sensors being smaller than the width of an individual ridge of a fingerprint. Preferably, the array of sensors is smaller than the pad of a finger of a user. In the preferred embodiment, each sensor of the array of sensors includes a capacitive element and the system captures the successive images by detecting changes in capacitance of the capacitive elements. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram of a system according to the present invention. 
     FIG. 2 is a block diagram of a sensor array according to the present invention. 
     FIG. 3 illustrates the physical structure of the individual sensor cells and their electrical operation according to the present invention. 
     FIGS. 4A and 4B comprise a pictorial illustration of the operation of a system according to the present invention to control the X-Y position of a pointer. 
     FIG. 5 is a pictorial illustration of the operation of a system according to one embodiment of the present invention to control the Z position of a pointer. 
     FIG. 6 is a pictorial illustration of the operation of a system according to an alternative embodiment of the present invention to control the Z position of a pointer. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings, and first to FIG. 1, a system according to the present invention is designated generally by the numeral  11 . System  11  includes a display  13 , which includes a screen  15 . A pointer  17  is shown displayed on screen  15 . System  11  includes a pointer controller  25  that controls the position of pointer  17  on screen  15 . Display  13  may be, for example, a standard CRT computer monitor or television. Alternatively, screen  13  may operate on any of several non-CRT technologies used in laptop and notebook computers. 
     System  11  includes a user input device  19 . In FIG. 1, user input device is represented generally as a rectangle. The specific form of user input device  19  is determined by the configuration. For example, user input device may be integrated into the body of a laptop or notebook computer, or it may be part of a hand held infrared remote control device. 
     User input device  19  includes a sensing element  21 . As will be described in detail hereinafter, sensing element  21  senses movement of a user&#39;s thumb or finger, shown in phantom and designated by the numeral  23 , to control the X-Y position of pointer  17  on screen  15 . Sensing element  21  may also sense changes of finger pressure on sensing element, by detecting changes in width of fingerprint ridges, or the placing or lifting of the finger on sensing element  21 , to control the Z position of pointer  17  or to input button inputs to processor As shown in FIG. 1, sensing element  21  is substantially smaller than the pad portion of finger  23 . 
     The direction and speed of movement of the finger  23  over sensing element  21  is output to a pointer controller  25 . Pointer controller  25  receives output from user input device  19 , preferably as X-Y and Z position changes, and produces an output to control the position of pointer  17  on screen  15 . 
     Referring now to FIG. 2, there is shown a block diagram of user input device  19 . User input device  19  is preferably integrated into a single chip, and it includes an array  27  of cells  29 . For purposes of illustration, array  27  is shown comprising nine cells  29 . In an actual device, more than nine cells would be included. Each cell  29  is smaller than the width of a fingerprint ridge and enough cells  29  are included in array  27  so that several ridges and pores may be detected. In the preferred embodiment, cells  29  are on a pitch of 50 μm, which corresponds to a resolution of about 508 dpi. 
     Device  19  includes a horizontal scanning stage  31  and a vertical scanning stage  33 . Scanning stages  31  and  33  enable one cell  29  at the time according to a predetermined scanning pattern. In the preferred embodiment, each cell  29  is scanned once each millisecond to produce a frame rate of 1,000 frames per second. 
     Input device  19  includes a power supply and scan control unit  35 . Power supply and scan control unit  35  supplies a reference voltage to each cell  29  of array  27 . Power supply and scan control  35  also operate scanning stages  31  and  33  to produce the desired scanning of cells  29 . 
     An A/D converter  37  is connected to receive the output of each cell  29  of array  27 . The output of A/D converter  37  is connected to output logic  39 . Output logic  39  processes the output of buffer  37  to capture successive images of a portion of the fingerprint of the user. Output logic  39  compares successive images to detect movement of the fingerprint. If output logic  39  detects movement, output logic  39  computes the displacement of the fingerprint ridges and pores in the X and Y directions over the scanning period, which in the preferred embodiment is one millisecond, and outputs X and Y displacement signals to pointer controller  25  of FIG.  1 . If output logic  39  detects a widening or flattening of the fingerprint ridges, which indicates an increase in pressure of the user&#39;s finger, or the lifting of the finger from sensing element  21 , output logic  39  outputs a Z displacement signal, which pointer controller  25  may interpret as a button press or click. 
     Array  27  must be a sufficient size to capture a partial image containing several fingerprint ridges and pores. As the finger is moved over array  27 , user input device  19  detects, either directly or indirectly, the relative motion of the finger surface. In direct detection, user input device  19  contains motion-detection circuitry that allows it to output directly the relative motion direction and speed of the finger surface. In indirect detection, relative motion between frames is calculated explicitly with a simple correlation algorithm running in a standard digital controller. The higher the frame rates supported by user input device  19 , the less motion there will be between frames, even at maximum finger motion speeds, and the easier the task of the correlation algorithm for computing relative motion. At a frame rate of 1,000 frames per second, acceptable results can be achieved using a square array of sensors about five millimeters on a side. 
     Referring now to FIG. 3, there is illustrated the structure and operation of a cell  29  according to the present invention. The preferred cell of the present invention is of the type disclosed in Tartagni, U.S. patent application Ser. No. 08/799,543, filed Feb. 13, 1997, entitled Capacitive Distance Sensor, the disclosure of which is incorporated herein by reference. Each cell  29  includes a first conductor plate  47  and a second conductor plate  49  supported on a semiconductor substrate, which is preferably a conventional silicon substrate that may have a conventional shallow epitaxial layer defining an upper surface region thereof. The top surface of the substrate includes an insulating layer  41 . Insulating layer  41  is preferably an oxide layer, which may be a conventional thermally grown silicon dioxide layer. Conductor plates  47  and  49  are covered by a protective coating  51  of a hard material. Protective coating  51  protects sensor  29  from abrasion, contamination, and electrostatic discharge. 
     Each cell  29  includes a high gain inverting amplifier  53 . The input of inverter  53  is connected to a reference voltage source V REF  through an input capacitor  54 . The output of inverter  53  is connected to an output V OUT . The input of inverter  53  is also connected to conductor plate  47  and the output of inverter  53  is also connected to conductor plate  49 , thereby creating a charge integrator whose feedback capacitance is the effective capacitance between conductor plates  47  and  49 . 
     When a finger  23  is placed on the surface of protective layer  51 , the surface of the skin over each sensor acts as a third capacitor plate separated from adjacent conductor plates  47  and  49  by a dielectric layer that includes protective coating  51  and a variable thickness of air. Because fingerprint valleys or pores will be farther from conductor plates  47  and  49  than finger ridges  57 , sensors  29  beneath valleys or pores will have more distance between their conductor plates  47  and  49  and the skin surface than sensors under ridges. The thickness of this dielectric layer will modulate the capacitance coupling between plates  47  and  49  of each cell  29 . Accordingly, sensors  29  under valleys or pores will exhibit a different effective capacitance than sensors  29  under ridges. As shown in FIG. 3, the effective capacitance of sensor  29   a  is different from the effective capacitance of sensor  29   b.    
     Sensors  29  work in two phases. During the first phase, the charge integrator is reset with a switch  59  by shorting the input and output of inserter  53 . This causes inverter  53  to settle at its logical threshold. During the second phase a fixed charge is input to charge integrator, causing an output voltage swing inversely proportional to the feedback capacitance, which is the effective capacitance between conductor plates  47  and  49 . For a fixed amount of input charge, the output of inverter  53  will range between two extremes depending on the effective feedback capacitance value. The first extreme is a saturated voltage level if the effective feedback capacitance is very small. The second extreme is a voltage close to the logical threshold, which is the reset value, when the effective feedback capacitance is large. Since the distance between the skin and the sensor changes the effective feedback capacitance of the charge integrator, the output of sensor  29   a  under ridge  57  will be different from the output of sensor  29   b  under valley  55 . 
     The operation of the system of the present invention to control the X-Y position of pointer  17  on screen  15  is illustrated with respect to FIGS. 4A and 4B, which illustrate the movement of pointer  17  on screen  15  responsive to successive captured images of a portion of a user&#39;s fingerprint. In FIG. 4A, an image of a portion of a user&#39;s fingerprint is captured by sensing element  21  at an initial time T 0  is represented by the numeral  61 . In FIG. 4B, pointer  17  is positioned at an initial position at time T 0 . As the finger is moved over sensing element  21 , output logic  39  of FIG. 2 detects a change in position of the dark ridges and/or pores, which are light areas within the dark ridges, and computes displacement the X and Y directions of the ridges or pores over the scanning period and outputs X and Y displacement signals to move pointer  17 , as indicated by arrows in FIG.  4 B. For example, image  62  of FIG. 4A captured at time T 1  shows the ridges and pores displaced a distance X 1  in the X direction and a distance 0 in the Y direction. Correspondingly, pointer  17  moves to the right in FIG.  4 B. Similarly, image  63  of FIG. 4A shows the image of the ridges and pores captured at a later time T 2 , wherein the image is displaced a distance X 2  in the X direction and a distance  0  in the Y direction. The further movement of the finger causes a corresponding further movement of pointer  17  in the direction of the right arrow of FIG.  4 B. 
     As another example, image  64  of FIG. 4A captured at time T 1  shows the ridges and pores displaced a distance X 1  in the X direction and a distance Y 1  in the Y direction. Correspondingly, pointer  17  moves up and to the right on screen  15  in FIG.  4 B. Similarly, image  65  of FIG. 4A shows the image of the ridges and pores captured at a later time T 2 , wherein the image is displaced a distance X 2  in the X direction and a distance X 2  in the Y direction. The further movement of the finger causes a corresponding further movement of pointer  17  in the direction of the up and right diagonal arrow of FIG.  4 B. 
     It will be recognized that the present invention detects motion of the finger in all X-Y directions, as shown by the remaining images of FIG. 4A, and that such detected motion causes corresponding movement of pointer  17 , as indicated by the arrows of FIG.  4 B. Those skilled in the art will recognize that motion in all directions, and not just the forty-five degree directions in the examples of FIGS. 4A and 4B, may be detected. The high resolution provided by the detector of the present invention enables the motion of pores to be detected. The ability to detect pores makes it possible to detect motion in a direction generally parallel to the ridges. 
     The operation of the system of the present invention to control the Z position of pointer  17  on screen  15  or to perform button clicks is illustrated with respect to FIGS. 5 and 6, which illustrate the change in width of fingerprint ridges responsive increased pressure of a user&#39;s finger on sensing element  21 . In FIG. 5, an image of a portion of a user&#39;s fingerprint is captured by sensing element  21  at a time T 0 . Image  71  shows narrow ridges, which indicates a light touch on sensing element  21 . An image  72  of the user&#39;s fingerprint captured by sensing element  21  at a later time T 1  shows the ridges and pores is not displaced, but the ridges are wider than those of image  71 . Similarly, an image  73  of the user&#39;s fingerprint captured by sensing element  21  at a still later time T 2  shows the ridges and pores again not displaced, but the ridges are even wider than those of image  72 . Images  72  and  73  indicate an increase in finger pressure on sensing element  21 . Similarly, images  74  and  75 , which are captured at later times T 3  and T 4 , respectively, indicate a decrease in finger pressure on sensing element  21 . If the system senses the widened and narrowing of the ridges within a predetermined time period, i.e. T 4  minus T 0  is less than a preselected value, the system outputs a mouse button click, which is interpreted in the manner well known to those skilled in the art to make user selections and the like. 
     In FIG. 6 there is shown an alternative embodiment of the Z control of the present invention. An image  77  of a portion of a user&#39;s fingerprint is captured by sensing element  21  at a time T 0 . Image  77  shows fairly wide ridges, which indicates a medium touch on sensing element  21 . An image  78  of the user&#39;s fingerprint captured by sensing element  21  at a later time T 1  shows the ridges and pores is not displaced, but the ridges are narrower than those of image  77 , which indicates a lessening of finger pressure on sensing element  21 . An image  79 , captured by sensing element  21  at a still later time T 2  is blank, which indicates that the user&#39;s finger has been lifted from sensing element  21 . Images  80  and  81 , which are captured at later times T 3  and T 4 , respectively, indicate a return of the user&#39;s finger pressure on sensing element  21 . If the system senses the lifting and return of the ridges within a predetermined time period, i.e. T 4  minus T 0  is less than a preselected value, the system outputs a mouse button click. 
     From the foregoing, it may be seen that the present invention is well adapted to overcome the shortcomings of the prior art. The pointer position control device of the present invention is non-mechanical and, therefore, not subject to breakage or mechanical failure. The device of the present invention is small in size, and it may be fabricated on a single integrated circuit chip. The devices small size makes its cost very low compared to devices of the prior art. 
     Although the present invention has been illustrated and described with respect to a presently preferred embodiment, it is to be understood that various changes, substitutions and alterations can be made therein without departing from the spirit and scope of the invention as defined by the appended claims.