Abstract:
Pointing devices and related methods are disclosed that generally involve manipulation of a cursor or other user interface component based on inputs from a user. In one embodiment, an image sensor captures an image of the underside of a transparent contact surface and determines whether an object (e.g., a user&#39;s finger) is present in the image. Cursor movement information comprising direction and velocity components can be calculated from a single image by equating the size of a detected object with a desired velocity and by equating the position of the detected object relative to a fixed reference point with a desired direction. Thus, detection of user motion is not required, nor is comparison of successive image frames relative to a time reference. As a result, a device having few or no moving parts can be provided while at the same time permitting continuous cursor motion without repetitive swiping by a user.

Description:
FIELD 
       [0001]    The present invention relates to input devices for computer systems. More particularly, the invention relates to pressure and position sensing pointing devices and related methods. 
       BACKGROUND 
       [0002]    Many computer systems include an input device that allows physical actions of a user to be translated into manipulations of a graphical user interface of the computer system. For example, most desktop computers are configured with pointing device such as a mouse. When the mouse is moved relative to a fixed surface, movement of an on-screen cursor occurs in a direction and at a speed that corresponds to the physical movement of the mouse. 
         [0003]    While the basic mouse has enjoyed widespread adoption as an input device for desktop computers, it can be less practical for use with portable computer systems or systems that are situated in a cluttered work environment. A number of pointing devices have been developed for such systems, however each suffers from inherent drawbacks. 
         [0004]    A first type of pointing device involves a small joystick. The joystick includes a finger pad coupled to a small shaft that pivots relative to a fulcrum point. The direction in which the joystick is angled relative to the fulcrum point is used to determine a direction to move the on-screen cursor, and a force applied to the joystick is used to determine a speed at which to move the on-screen cursor. One advantage to this type of pointing device is that it can be positioned in proximity to a keyboard (e.g., in the center of a keyboard as in the case of a laptop computer). This allows a user to switch between using the keyboard and using the pointing device without having to move their hands from a “home” position. The moving parts involved in this type of pointing device are susceptible to failure however, particularly when a user applies excessive input force. In addition, dust, dirt, or oils can easily contaminate or otherwise disrupt the delicate parts of the pointing device. Further still, repeated application of excessive force to the pointing device to obtain fast cursor movement can lead to user pain and repetitive stress injuries. This type of pointing device can also suffer from cursor drift, and a user can find it difficult to reliably apply the correct amount of force. 
         [0005]    U.S. Pat. No. 5,764,219 to Rutledge et al. discloses exemplary signal processing that can be used with pointing devices of the first type. Input force applied to the joystick is related to a velocity of a cursor on a video screen according to a transfer function. The transfer function, shown in  FIG. 2  of the Rutledge patent, has a dead band between force thresholds F 0  and F 1 , a low plateau between force thresholds F 2  and F 3 , a parabolic-sigmoid between force thresholds F 3  and F 4 , and a high plateau between force thresholds F 4  and F 5 . 
         [0006]    A second type of pointing device involves an optical scanner that reads the swipe of a user&#39;s finger. While this type of pointing device generally does not have moving parts, it requires several swipe actions by the user when moving a cursor for a long distance, which is inefficient and can cause user discomfort, fatigue, or annoyance. This type of pointing device also usually requires movement of the user&#39;s hands from the home position, which is undesirable. 
         [0007]    U.S. Pat. No. 6,552,713 to Van Brocklin et al. discloses an exemplary pointing device of the second type. The Van Brocklin device uses a transparent curved surface and an optical sensor to detect movement of a user&#39;s finger. The optical sensor captures successive images of the curved surface and calculates the change in position of a user&#39;s finger between the successive images. This change in position is related to a time scale and used to generate direction and velocity data for moving a cursor. The device of Van Brocklin is thus analogous to the second type of pointing device described above, in that it relies on motion of a user&#39;s finger relative to a fixed surface to determine cursor speed and direction. 
         [0008]    Japanese Publication No. JP2003-216321 to Kato discloses a pointing device of the second type that is very similar to the device disclosed in Van Brocklin. A dome-shaped cover is provided over an image pickup element which captures a video signal of a user&#39;s finger moving across the dome-shaped cover. This movement detection is used to control movement of a cursor on a display. 
         [0009]    U.S. Pat. No. 6,057,540 to Gordon et al. discloses yet another pointing device of the second type in which a transparent stud is provided over an image sensor. Movement of a user&#39;s finger across a top surface of the stud is detected and translated into motion of a cursor. 
         [0010]    A third type of pointing device involves a jog ball mounted within a recess and configured to rotate first and second orthogonal rollers when the ball is manipulated by a user. Like the joystick type pointing devices described above, this type of device includes moving parts and is susceptible to contamination from dirt or dust. Pointing devices of the third type can also be broken easily when excessive operating force is applied. 
         [0011]    In view of these and other shortcomings, a need exists for improved pointing devices. 
         [0012]    Each of the patents and publications discussed above are incorporated herein by reference in their entireties. 
       SUMMARY 
       [0013]    Pointing devices and related methods are disclosed that generally involve manipulation of a cursor or other user interface component based on inputs from a user. In one embodiment, an image sensor captures an image of the underside of a transparent contact surface and determines whether an object (e.g., a user&#39;s finger) is present in the image. Cursor movement information comprising direction and velocity components can be calculated from a single image by equating the size of a detected object with a desired velocity and by equating the position of the detected object relative to a fixed reference point with a desired direction. Thus, detection of user motion is not required, nor is comparison of successive image frames relative to a time reference. As a result, a device having few or no moving parts can be provided while at the same time permitting continuous cursor motion without repetitive swiping by a user. 
         [0014]    In one aspect of at least one embodiment of the invention, a pointing device for providing an output direction and an output velocity to computer system to control a user interface of the computer system is provided. The pointing device includes a contact surface mounted to a support and a camera positioned beneath the contact surface and configured to capture an image of a lower side of the contact surface and an object that is in contact with an upper side of the contact surface. The pointing device also includes a velocity calculation unit configured to calculate the output velocity based on a size of the object within the image, and a direction calculation unit configured to calculate the output direction based on a position of the object within the image. 
         [0015]    Related aspects of at least one embodiment of the invention provide a device, e.g., as described above, that includes a light source positioned beneath the contact surface and configured to illuminate the lower side of the contact surface. 
         [0016]    Related aspects of at least one embodiment of the invention provide a device, e.g., as described above, in which the contact surface comprises a frosted dome. 
         [0017]    Related aspects of at least one embodiment of the invention provide a device, e.g., as described above, in which the object comprises a finger of a user. 
         [0018]    Related aspects of at least one embodiment of the invention provide a device, e.g., as described above, that includes a protective cover mounted adjacent to the contact surface. 
         [0019]    Related aspects of at least one embodiment of the invention provide a device, e.g., as described above, in which the object comprises a portion of the protective cover. 
         [0020]    Related aspects of at least one embodiment of the invention provide a device, e.g., as described above, in which the velocity calculation unit calculates the output velocity as zero when the size of the object within the image is less than a first threshold value. 
         [0021]    Related aspects of at least one embodiment of the invention provide a device, e.g., as described above, in which the velocity calculation unit calculates the output velocity as being proportional to the size of the object within the image when the size of the object within the image is greater than the first threshold value and less than a second threshold value. 
         [0022]    Related aspects of at least one embodiment of the invention provide a device, e.g., as described above, in which the velocity calculation unit calculates the output velocity as being a fixed speed limit velocity when the size of the object within the image is greater than the second threshold value. 
         [0023]    Related aspects of at least one embodiment of the invention provide a device, e.g., as described above, in which the direction calculation unit calculates the output direction by comparing a position of a center point of the contact surface within the image to a position of a center point of the object within the image. 
         [0024]    Related aspects of at least one embodiment of the invention provide a device, e.g., as described above, that includes an output unit configured to output the output velocity and the output direction to the computer system. 
         [0025]    Related aspects of at least one embodiment of the invention provide a device, e.g., as described above, that includes a display unit and in which a cursor displayed on the display unit moves at a speed corresponding to the output velocity and in a direction corresponding to the output direction. 
         [0026]    Related aspects of at least one embodiment of the invention provide a device, e.g., as described above, in which the velocity calculation unit is configured to calculate the output velocity based on a single image and the direction calculation unit is configured to calculate the output direction based on the same single image. 
         [0027]    In another aspect of at least one embodiment of the invention, a method of calculating movement information for manipulating a graphical user interface is provided. The method includes obtaining a captured image of a bottom side of a contact surface and determining whether the captured image includes an image of an object in contact with a top side of the contact surface. The method also includes, if the captured image includes an image of an object in contact with the top side of the contact surface, calculating an output velocity based on a size of the object within the captured image and calculating an output direction based on a position of the object within the captured image. 
         [0028]    Related aspects of at least one embodiment of the invention provide a method, e.g., as described above, that includes moving an on-screen cursor at a speed corresponding to the output velocity and in a direction corresponding to the output direction. 
         [0029]    Related aspects of at least one embodiment of the invention provide a method, e.g., as described above, in which calculating the output direction comprises determining a center point of the object within the captured image, determining a center point of the captured image, and calculating a direction vector that extends between the two center points. 
         [0030]    Related aspects of at least one embodiment of the invention provide a method, e.g., as described above, in which calculating the output velocity comprises calculating an output velocity of zero when the size of the object within the captured image is less than a first threshold value. 
         [0031]    Related aspects of at least one embodiment of the invention provide a method, e.g., as described above, in which calculating the output velocity comprises calculating an output velocity proportional to the size of the object within the captured image when the size of the object within the captured image is greater than the first threshold value and less than a second threshold value. 
         [0032]    Related aspects of at least one embodiment of the invention provide a method, e.g., as described above, in which calculating the output velocity comprises calculating an output velocity as a fixed speed limit velocity when the size of the object within the captured image is greater than the second threshold value. 
         [0033]    Related aspects of at least one embodiment of the invention provide a method, e.g., as described above, in which the contact surface comprises a frosted dome. 
         [0034]    Related aspects of at least one embodiment of the invention provide a method, e.g., as described above, in which the object comprises a finger of a user. 
         [0035]    Related aspects of at least one embodiment of the invention provide a method, e.g., as described above, in which the object comprises a portion of a protective cover mounted adjacent to the contact surface. 
         [0036]    Related aspects of at least one embodiment of the invention provide a method, e.g., as described above, in which the output velocity and the output direction are calculated based on a single captured image. 
         [0037]    The present invention further provides devices, systems, and methods as claimed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0038]    The invention will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
           [0039]      FIG. 1  is a schematic diagram of one embodiment of a pointing device; 
           [0040]      FIG. 2  is a schematic diagram of an image captured by an imaging device of the pointing device of  FIG. 1 ; 
           [0041]      FIG. 3  is a schematic diagram of another embodiment of a pointing device having a protective cover; 
           [0042]      FIG. 4  is a schematic diagram of an image captured by an imaging device of the pointing device of  FIG. 3 ; 
           [0043]      FIG. 5  is a flow chart depicting the operation of a control circuit of one embodiment of a pointing device; 
           [0044]      FIG. 6  is a schematic diagram of one embodiment of a pointing device, an image captured by the pointing device when a user touches the pointing device, and the movement of a cursor of a computer system that results from the user touching the pointing device; 
           [0045]      FIG. 7A  is a schematic diagram of an image captured by a pointing device when a user applies a large amount of force; 
           [0046]      FIG. 7B  is a schematic diagram of an image captured by a pointing device when a user applies a medium amount of force; 
           [0047]      FIG. 7C  is a schematic diagram of an image captured by a pointing device when a user applies a small amount of force; and 
           [0048]      FIG. 8  is a schematic diagram of a transfer function used to relate a captured image to an output velocity. 
       
    
    
     DETAILED DESCRIPTION 
       [0049]    Certain exemplary embodiments will now be described to provide an overall understanding of the principles of the structure, function, manufacture, and use of the methods, systems, and devices disclosed herein. One or more examples of these embodiments are illustrated in the accompanying drawings. Those skilled in the art will understand that the methods, systems, and devices specifically described herein and illustrated in the accompanying drawings are non-limiting exemplary embodiments and that the scope of the present invention is defined solely by the claims. The features illustrated or described in connection with one exemplary embodiment may be combined with the features of other embodiments. Such modifications and variations are intended to be included within the scope of the present invention. 
         [0050]    The term “computer system” as used herein refers to any of a variety of digital data processing devices, including personal computers, desktop computers, laptop computers, tablet computers, server computers, storage devices, cell phones, PDAs, gaming systems, televisions, radios, portable music players, and the like. 
         [0051]      FIG. 1  illustrates one exemplary embodiment of a pointing device  10 . The pointing device  10  receives input from a user (e.g., when a user contacts the pointing device with their finger  12 ) and converts that input into direction and velocity information which can subsequently be used to control a computer system (e.g., to move a cursor shown on a display device of the computer system). The pointing device  10  generally includes a support  14 , a contact surface  16 , a light source  18 , an imaging device  20 , and a control circuit (not shown). 
         [0052]    The support  14  can be the outer case of a standalone peripheral component, or can be part of the computer system to which the pointing device  10  is coupled. For example, the support  14  can be the base surface of a laptop keyboard or the front surface of a cell phone. Thus, the pointing device  10  can be positioned in any of a variety of locations to optimize user convenience and comfort. In one embodiment, the pointing device  10  is embedded in a laptop keyboard, adjacent to the home keys. The pointing device  10  can also be situated above or below the keyboard of a laptop computer. 
         [0053]    The contact surface  16  is fixedly coupled to the support  14  such that relative motion between the contact surface  16  and the support  14  is prevented. In the illustrated embodiment, the contact surface  16  is in the form of a spherical dome, however the contact surface  16  does not necessarily need to be spherical or dome-shaped. Rather, the contact surface  16  can have any of a variety of shapes, such as rectangular or cylindrical. The contact surface  16  can be completely transparent or clear, or can be frosted, tinted, or smoked such that it is translucent. The degree of translucency can be selected based on a variety of factors, such as ambient lighting conditions in which the pointing device  10  will typically be used, the sensitivity of the image sensor  20 , and/or the intensity of the light source  18 . The contact surface  16  is preferably formed from plastic, but can also be formed from other transparent or translucent materials, such as glass. 
         [0054]    The imaging device  20  is positioned beneath the contact surface  16  and is configured to capture an image of the underside of the contact surface  16 . The imaging device  20  can include any of a variety of image sensors (e.g., CCD or CMOS image sensors) and can include one or more lenses or filters for tailoring the exposure, field of view, and other parameters associated with image capture. Images captured by the imaging device  20  can be converted into a digital signal for processing by the control circuit, as explained below. 
         [0055]    The light source  18  is also positioned beneath the contact surface  16  and is configured to illuminate the underside thereof. The light source  18  can include one or more discrete sources, such as light-emitting diodes or incandescent bulbs, and can emit light of any of a variety of colors such as white, red, green, and/or blue. 
         [0056]    The light source  18  and the imaging device  20  can optionally be coupled to a printed circuit board or other substrate for supplying power and control signals thereto and for coupling the light source  18  and the imaging device  20  to the control circuit. 
         [0057]    When a user places their finger  12  on the contact surface  16 , light emitted by the light source  18  reflects off of the user&#39;s finger  12  and is captured by the imaging device  20 . As shown in  FIG. 2 , an image  22  of the contact surface  16  and of the user&#39;s finger  12  can then be generated by the imaging device  20  for subsequent processing by the control circuit, as explained below. 
         [0058]    As shown in  FIG. 3 , the pointing device  10  can also include a protective cover  24  disposed over the contact surface  16 . The protective cover  24  can be particularly suitable for use in dirty environments, since it can prevent the contact surface  16  from becoming stained or soiled, which can alter the images detected by the imaging device  20  and can lead to processing errors. The protective cover  24  can be sized and shaped to generally conform to the size and shape of the contact surface  16 . Preferably, the protective cover  24  includes a sidewall portion  26  that is effective to support the protective cover  24  above the contact surface  16  with a small clearance space  28  therebetween. The clearance space  28  can advantageously prevent inadvertent actuation of the pointing device  10 , e.g., when a user makes incidental contact with the cover  24  while typing, since a threshold amount of force is necessary to deform the cover  24  through the clearance space  28  and into contact with the contact surface  16 . 
         [0059]    The underside of the cover  24  can be corrugated or jagged, e.g., such that is has a plurality of surface features  30  formed thereon, such that the user&#39;s pushing force is distributed appropriately and the cover&#39;s appearance in a captured image mimics that of a human finger. In particular, the surface features  30  can prevent the cover  24  from “smearing” against the contact surface  16 , and can thus ensure that the area of the protective cover  24  seen by the imaging device  20  generally approximates the area of the user&#39;s finger. Preferably, the protective cover  24  is formed from a rubber or rubber-like material such as silicone, though any of a variety of other materials can also be used, such as plastic. 
         [0060]    When the protective cover  24  is provided and a user applies pressure to the protective cover  24 , a portion of the protective cover  24  beneath the user&#39;s finger  12  is pressed against the contact surface  16  and appears in captured images as a finger image. The contact area between the cover  24  and the contact surface  16  increases with pushing force, as is the case when a human finger  12  is used directly on the contact surface  16  as in  FIG. 1 . Light emitted by the light source  18  is reflected off of the portion of the protective cover  24  that is pressed against the contact surface  16 , and the reflected light is captured by the imaging device  20  to produce an image  32  as shown in  FIG. 4 , in which a contact region  34  of the protective cover  24  is clearly identifiable. The image  32  can subsequently be processed by the control circuit, as explained below. 
         [0061]    The control circuit is implemented in hardware and/or software and is configured to process images captured by the imaging device  20  and to calculate velocity and direction parameters therefrom. Thus, the control circuit generally includes a direction calculation unit and a velocity calculation unit. In one embodiment, the control circuit comprises an ASIC, a processor, a memory, and/or a set of logic devices that generate an output signal which can be transmitted to the computer system. The output signal conveys information indicative of the direction in which a cursor should be moved and/or the velocity at which the cursor should be moved. In an alternative embodiment, the control circuit comprises a software-implemented pointing device driver that is executed on the computer system. Images captured by the imaging device  20  are processed by the pointing device driver and used to determine direction and velocity information for an on-screen cursor. 
         [0062]    One exemplary method of operation of the control circuit is illustrated schematically in the flow chart of  FIG. 5 . While various methods disclosed herein are shown in relation to a flowchart or flowcharts, it should be noted that any ordering of method steps implied by such flowcharts or the description thereof is not to be construed as limiting the method to performing the steps in that order. Rather, the various steps of each of the methods disclosed herein can be performed in any of a variety of sequences. In addition, as the illustrated flowcharts are merely exemplary embodiments, various other methods that include additional steps or include fewer steps than illustrated are also within the scope of the present invention. 
         [0063]    In step S 100 , the control circuit receives an image of the contact surface  16  captured by the imaging device  20 . A variety of preliminary image processing routines can be executed on the captured image at this time to prepare the image for processing by the control circuit. Such routines can include brightness and contrast adjustments, color balancing, cropping, rotating, resizing, etc. 
         [0064]    In step S 102 , the control circuit determines whether or not an object (e.g., a user&#39;s finger  12  or a portion  34  of the protective cover  24 ) is detected in the captured image. This can be accomplished using any of a variety of techniques known in the art, such as comparing luminous intensity values for one or more pixels in the captured image to a predetermined threshold value. 
         [0065]    If the control circuit determines in step S 102  that no object is present in the captured image, processing returns to step S 100  and a new image is received by the control circuit. In this situation, no velocity or direction information is output from the control circuit and, accordingly, the cursor whose movement is controlled by the pointing device  10  remains stationary, as would be the case if a traditional computer mouse were held stationary on a desk. 
         [0066]    If the control circuit determines in step S 102  that an object is present in the captured image, processing proceeds to step S 104  in which the position of the detected object is determined. In one embodiment, the “position” of the detected object is the 2D pixel coordinates of the geometric center of the detected object. 
         [0067]    In step S 106 , an output direction is calculated by comparing the position of the detected object to a fixed reference point on the contact surface  16  (e.g., the center of the contact surface  16 ). 
         [0068]    When operating a pointing device, a user generally places their finger on a side of the device opposite from the desired direction of movement and applies a force in the desired direction of movement. Thus, in one embodiment, a directional component of a cursor movement vector can be determined by connecting the center point of the detected object to the center point of the contact surface, e.g., by adding or subtracting the pixel coordinates of the respective points. As shown in  FIG. 6 , a user can place their finger  12  on a portion of the protective cover  24  that is above and to the right of the center point  36  of the contact surface  16 . By connecting the center point  38  of the touched area  34  to the center point  36  of the contact surface  16  in a captured image  40 , a direction arrow  42  extending down and to the left is obtained. Direction information corresponding to the obtained direction arrow  42  can then be output to a computer system  44  to cause movement of an on-screen cursor  46  in a direction  48  corresponding to the direction of the direction arrow  42  (down and to the left in this example). Accordingly, in this embodiment, an on-screen cursor  46  is moved up when a user places their finger  12  below the center  36  of the contact surface  16  and is moved down when a user places their finger above the center of the contact surface. Similarly, the on-screen cursor  46  is moved right when a user places their finger  12  to the left of the center  36  of the contact surface  16  and is moved left when a user places their finger to the right of the center of the contact surface. 
         [0069]    In step S 108 , the size of the detected object is determined, for example by calculating the pixel area of the detected object as a percentage of the overall area of the captured image. The pixel area can be the total number of pixels having a luminous intensity that exceeds a certain threshold value, or can be calculated from an approximated outline of the detected object. 
         [0070]    When operating a pointing device, a user generally applies more force to the pointing device when a higher velocity of cursor movement is desired. In other words, a user will generally push harder to make the cursor move faster. Due to the compliant nature of human fingers, the contact area between a finger and a surface against which it is pressed increases in proportion to the amount of force applied. This effect is increased when the surface is dome-shaped, as in the case of the contact surface  16  of the pointing device  10  of  FIG. 1 . 
         [0071]    Accordingly, in step S 110 , the control circuit can calculate a velocity component of a cursor movement vector based on the size of the detected object. As shown in  FIG. 7A , a relatively large finger image  50  is observed when a user applies a relatively large force to the contact surface  16 . As shown in  FIG. 7B , a mid-sized finger image  52  is observed when the same user applies a medium force to the contact surface  16 . A relatively small finger image  54  is observed when the same user applies a relatively small force to the contact surface  16 , as shown in  FIG. 7C . The same relationship holds true in embodiments in which the pointing device  10  includes a protective cover  24 , as shown in  FIG. 8 . As shown, application of a relatively small force to the cover  24  results in a relatively small detected object  56 , application of a medium force to the protective cover  24  results in a medium-sized detected object  58 , and application of a relatively large force to the protective cover  24  results in a relative large detected object  60 . 
         [0072]    In one embodiment, a transfer function can be used as shown in  FIG. 8  to equate the area of the detected object to a desired velocity. When the area is below a first size threshold T 1  (e.g., in the case of the detected object  56 ), the calculated velocity is zero. This “dead band” of the transfer function prevents cursor movement when a user is merely resting their finger on the pointing device  10  or when the user makes inadvertent, incidental contact with the pointing device  10 . When the area exceeds the first size threshold T 1  and is below a second size threshold T 2  (e.g., in the case of the detected object  58 ), the velocity is calculated to increase linearly with the size of the area. Finally, when the area is above the second size threshold T 2  (e.g., in the case of the detected object  60 ), the velocity is calculated as a fixed “speed limit” velocity, regardless of the area size. It will be appreciated that the various size thresholds, speed limit value, and other transfer function parameters can be user-configurable, e.g., via a pointing device driver and associated user interface executed on the computer system. Any of a variety of other transfer functions having any number of thresholds can also be used without departing from the scope of the present invention. 
         [0073]    In some embodiments, the control circuit can also assess captured images for the size of surface features  30  of the protective cover  24 . As shown in  FIG. 8 , when the protective cover  24  includes a plurality of concentric annular protrusions  30 , the protrusions  30  appear as lines in images captured by the imaging device  20 . The thickness of these lines increases with input force, and therefore the desired velocity can be calculated based on the thickness of the lines. For example, the lines corresponding to the protrusions  30  in the detected object  56  are relatively thin, whereas the lines in the detected object  58  are somewhat thicker and the lines in the detected object  60  are very thick, to the point where they appear to be touching. Assessing the apparent thickness of the surface features  30  can in some cases provide more accurate velocity information than simply assessing the outline size of the detected object. In other words, in certain instances, such as when a user has relatively large fingers, it can be desirable to calculate the velocity based on deformation of the cover&#39;s surface features  30 , either alone or in combination with the outline size of the detected object, rather than based on outline size alone. 
         [0074]    In step S 112 , the direction and velocity information can be output to the computer system, e.g., to control movement of an on-screen cursor. 
         [0075]    The pointing device  10  thus uses a captured image to generate a movement vector having a direction determined by the position of an object within the image and a magnitude (velocity) determined by the size of the object or the size of surface features of the object. By determining velocity and direction information in this way, there is no need to compare successive image frames and perform complex time scale comparisons. In addition, the user is not required to make repeated swiping motions to move long distances, as they can simply hold their finger stationary, apply pressure, and thereby effect continuous cursor movement. User convenience is thus improved and user fatigue prevented. Furthermore, the pointing device can have few or no moving parts and is not susceptible to contamination from dust or other debris. 
         [0076]    Although the invention has been described by reference to specific embodiments, it should be understood that numerous changes may be made within the spirit and scope of the inventive concepts described. For example, the image sensor can be replaced with any of a variety of systems for detecting the size and position of an object relative to a detection region, such as an RF imaging system, a capacitive system, a thermal system, and the like. Any of the methods or devices disclosed herein can be implemented in part or in full in software, which can be stored as an executable program on a non-transitory computer-readable storage medium. Accordingly, it is intended that the invention not be limited to the described embodiments, but that it have the full scope defined by the language of the following claims.