Abstract:
A cursor control device, such as a trackball, controls the movement of a cursor on a computer display. An electromagnetically generated braking effect is applied to the trackball, which effect varies with the speed of the cursor to allow precise control of the cursor.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to a cursor control device for controlling the movement of a cursor on a computer display. More specifically, the invention is concerned with such a device that comprises a tracking element.  
         BACKGROUND OF THE INVENTION  
         [0002]    The immense rise in popularity of personal computers is in large part attributable to improvements in user-machine interfaces. More particularly, improvements in data input devices, such as the mouse and the trackball, have made communication with computers easy and convenient, thus increasing the usefulness of computers.  
           [0003]    As is well known, a mouse and a trackball are useful devices for positioning a cursor on a computer display. To quickly and efficiently input certain types of data or commands to a computer, the cursor is positioned on an appropriate spot on the display and then manipulated (“clicked”). It will readily be appreciated that the convenience and, thus, usefulness of the computer is promoted by facilitating rapid, yet precise, cursor placement.  
           [0004]    It happens, unfortunately, that rapid cursor positioning is more or less competitive with precise cursor positioning. This is because the faster the cursor moves across the screen, the less time the user has to react to stop the cursor when it arrives at the desired screen location. Stated differently, the user is provided with only one kind of feedback, namely, visual feedback, to aid the user in stopping a rapidly moving cursor, and visual feedback alone often is insufficient to promote both rapid and precise cursor placement.  
           [0005]    It has therefore been suggested to enhance both rapid and precise cursor placement by providing more than one kind of feedback to the user. More specifically, tactile feedback is used in conjunction with visual feedback to promote both rapid and precise cursor placement.  
           [0006]    Thus, U.S. Pat. No. 5,889,670 discloses a method and apparatus implementing a user interface device, such as a mouse or trackball, having electronically controllable tactile responsiveness which is flexibly programmable. Programmable force-position characteristics relate the tactile responsiveness of the interface device to the position of the cursor within a limited area or on the display screen. A force generated by a servo motor after converting a digital signal from a controller into an analog current signal is perceived as a resistance, tactile pressure or the lack thereof, or as a positive, assisted motion which is indicative of position on a screen display.  
           [0007]    In U.S. Pat. No. 5,973,670 there is disclosed a cursor on a graphics display controlled by a cursor control device including a tactile generator. The tactile generator is activated when the cursor is located at a graphics object that has been determined to be intersecting, and that has a size which bears a predetermined relationship to the speed of the cursor, provided an update time has elapsed since the time of the last tactile activation of the cursor control device.  
           [0008]    Though precise placement of the cursor has been enhanced by providing additional tactile feedback, there is still a need to improve cursor control devices comprising a tracking element. These devices are mainly operated with the user&#39;s fingertips, his thumb or the palm of his hand. When retracting the user&#39;s hand from the cursor control device, e.g., to input data via a keyboard, the device may easily slip due to the fact that the user&#39;s hand has no support or that the palm exhibits a certain suction effect.  
         SUMMARY OF THE INVENTION  
         [0009]    It is therefore an object of the present invention to provide a cursor control device for controlling the movement of a cursor on a computer display that avoids the above mentioned disadvantages.  
           [0010]    The present invention provides a cursor control device for controlling the movement of a cursor on a computer display, said cursor control device comprising: a tracking element; and a braking device operable to apply a braking force on said tracking element, said braking force being dependent on the speed of said cursor.  
           [0011]    The present invention also provides a method for controlling a cursor, said method comprising the steps of: displaying a cursor; moving the cursor in response to manipulation of a cursor control device comprising a tracking element; and generating a user-discernible braking force on said tracking element depending on the speed of said cursor.  
           [0012]    Advantageous embodiments of the invention are defined in the dependent claims.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    The invention will hereinafter be described in more detail in connection with the accompanying drawings, in which FIG. 1 schematically depicts an embodiment of an apparatus according to the invention;  
         [0014]    [0014]FIGS. 2A and 2B show the apparatus according to FIG. 1 in a non-activated and in an activated state;  
         [0015]    [0015]FIG. 3 schematically depicts a second embodiment of an apparatus according to the invention;  
         [0016]    [0016]FIGS. 4A and 4B show the apparatus according to FIG. 3 in a non-activated and in an activated state;  
         [0017]    [0017]FIG. 5 schematically depicts another embodiment of the present invention;  
         [0018]    [0018]FIG. 6 schematically shows still another embodiment of the invention; and  
         [0019]    FIGS.  7  to  9  are graphs showing the braking effect relative to the speed of the tracking element for several embodiments of the invention.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0020]    [0020]FIG. 1 schematically shows an embodiment of an apparatus according to the invention. The apparatus shown therein consists of two parts and functions like a loudspeaker.  
         [0021]    The upper part consists of a cylinder  10 , a first iron core  12 , a pin  14  and a coil  16 . The cylinder  10  is preferably made of aluminum or synthetic material. The coil  16  is wound around the cylinder  10 , the first iron core  12  functions as a support for the cylinder  10  and as a magnetic core for the attraction of a tracking element of the cursor control device. The pin  14  is made of brass or synthetic material, i.e., it should be of nonmagnetic material and is connected with the first iron core  12 . The first iron core  12  is thereby movably connected with the cylinder  10 .  
         [0022]    The lower part consists of a pot-like element  18 , preferably made of alumina or synthetic material, carrying a felt ring  20  at its upper surface. The felt ring may be provided with an additional specific amount of rubber. At its inner lower surface  22  the pot-like element  18  is provided with a second iron core  24  fixedly connected thereto and having an opening  26  in the middle thereof. The pot-like element  18  is, in turn, provided with an opening which is arranged coaxially to the opening  26 , and a plate  28  is arranged at its outer bottom surface  30 .  
         [0023]    The pin  14  is inserted into the opening  26  of the second iron core  24  and passed through the coaxially arranged opening in the bottom portion of the pot-like element  18 , where it is connected to the plate  28 .  
         [0024]    Thus, the second iron core  24  is slidably arranged around the pin  14  so that it may move up and down along the pin  14 . The length of the pin  14  is dimensioned such that the distance between the lower surface of the first iron core  12  and the upper surface of the plate  28  is greater than the thickness of the second iron core  24 .  
         [0025]    The tracking element  32 , having an iron shell, is arranged on top of the pot-like element  18  and is carried by the housing of the device (not shown), thereby not touching the pot-like element  18  in quiescent condition.  
         [0026]    When the tracking element  32  is started to move slowly, the coil  16  will be energized.  
         [0027]    The second iron core  24  is drawn up in the direction of the first iron core  12 . Since the pot-like element  18  is fixedly connected to the second iron core  24 , it will be drawn up as well. At the same time, the tracking element  32  is drawn in the direction of the second iron core  24 , thus bringing the apparatus in an activated state (FIG. 2B). The felt ring  20  will touch the surface of the tracking element  32  thus producing a braking effect on the tracking element.  
         [0028]    The braking effect can be released by de-energizing the coil, e.g., by a mouse click or the like.  
         [0029]    When accelerating the movement of the tracking element  32 , a point will be reached where a magnetic force will no longer exist. At this point, the second iron core  24  will no longer be attracted by the first iron core  12 , and the pot-like element  18  will return into its non-activated state (FIG. 2A). Accordingly, the braking effect will cease and the brake will be released.  
         [0030]    Since the iron cores  12 ,  24  have small dimensions, lying in the millimeter range, the pot-like element  18  can be adjusted to different sizes of tracking elements, i.e., smaller or greater pot-like elements  18  can be used. The ratio of dimensions between pot-like element and tracking element thereby is about 1:3.  
         [0031]    Providing the felt ring  20  with an additional amount of rubber will increase its resisting force, but not the braking force. Using a “harder” brake covering, i.e., a mixture of felt and rubber, or cork or the like, will need to employ a pulsing brake mechanism. This will be described with respect to FIG. 9 later.  
         [0032]    [0032]FIG. 3 schematically depicts a second embodiment of an apparatus according to the invention. In this embodiment, the tracking element  32  is held in a depression  34  present in the housing  36  of the device by means of ball bearings  38 . Within the housing  36 , a cylinder  40 , preferably made of synthetic material, is arranged below the tracking element  32 . Inside the cylinder  40 , there is mounted a coil  42 . The upper end of the cylinder  40  carries a mat  44  being comprised of a fleece, cork, rubber or the like, the lower end of the cylinder  40  has the form of a round plate  46  which will serve as a stopper, what will be described in more detail below. The coil  42  is inserted into a magnetic ring  48 , and a spring  50  is arranged between the ring  48  and the plate  46 . The magnetic ring  48  is secured to the housing  36  and the coil  42  rests on the bottom of the housing  36 .  
         [0033]    When the tracking element  32  is started to move slowly, the coil  42  will be energized, the cylinder  40  will be moved in the direction of the tracking element  32  against the tension of the spring  50 . The mat  44  will be pressed against the tracking element  32  thus creating a braking effect. As has already been mentioned above, the round plate  46  will thereby act as a stopper, limiting the movement of the cylinder  40  by abutting to the magnetic ring  48 . As already discussed in view of the first embodiment, the braking force will cease when the tracking element is accelerated beyond a certain velocity where no magnetic force will be present any more. The cylinder  40  will, under the tension of spring  50 , return into its non-activated position.  
         [0034]    [0034]FIGS. 4A and 4B show the apparatus according to the second embodiment in its non-activated and activated state.  
         [0035]    In FIGS. 5 and 6, there are shown still other embodiments of the arrangement shown in FIG. 3. FIG. 5 shows that three coils are arranged one beside the other on the side of the tracking element  32  being arranged within the depression  34 . The advantage of such an arrangement is that the tracking element  32  can project far beyond half of the housing  36 , without a risk that the tracking element  32  falls out of the depression when it is stopped. FIG. 6 depicts four coils according to the one presented in FIG. 3, which are arranged around the tracking element  32  at an angle of 90°, respectively.  
         [0036]    FIGS.  7  to  9  are graphs showing the braking effect relative to the speed of the tracking element for several embodiments of the invention.  
         [0037]    When looking at FIG. 7, two different behaviors are shown. The upper curve I describes the case that the tracking element is moved very quickly. In this case no braking effect occurs since the coil will not be energized due to the quick movement of the tracking element.  
         [0038]    However, in case the tracking element is moved slowly, the coil will be energized and the braking effect will occur after a slight delay (point B in FIG. 7). Due to the braking effect, the speed of the tracking element will decrease to a nearly constant value (curve II in FIG. 7). The braking effect will continue until it will be stopped by the user by releasing the brake with a mouse click or the like (point C in FIG. 7). The hatched part in FIG. 7 illustrates the time the braking effect is present.  
         [0039]    [0039]FIG. 8 depicts a typical graph when drawing with the apparatus according to the invention. First, the tracking element is moved quickly until the target is nearly reached (point N in FIG. 8). Here, the speed of the tracking element is reduced until the exact position of the tracking element is reached (point E in FIG. 8). At this point, the braking effect starts (again with a slight delay, as shown in curve B in FIG. 8). Again, the braking effect will continue until it will be stopped by the user by releasing the brake with a mouse click or the like (point C in FIG. 8).  
         [0040]    In FIG. 9 there is shown the pulsed braking effect already mentioned above. The continuous line in this figure represents the speed of the tracking element, whereas the broken line represents the braking force. When using a “harder” brake covering like a mixture of felt and rubber, the braking force comes in by pulses, or, with other words, the tracking element moves jerkily. Each time such a pulse occurs, the speed of the tracking element slightly decreases, what is shown by the depressions of the continuous line.  
         [0041]    Again, the braking force can be stopped by the user releasing the brake with a mouse click or the like (point C in FIG. 9).  
         [0042]    Thus, there are two categories of braking forces. The constant breaking force, using a felt ring as the brake, can ideally be used when drawing freely with the tracking element. Furthermore, it can be used for a linear control of, e.g., film editing machines.  
         [0043]    The pulsed breaking force, achieved by using a brake material formed, e.g., by a mixture of felt and rubber, represents a stronger brake and may be used, e.g., for drawing applications like connection schemes or construction programs, which require a certain scanning.  
         [0044]    There are also applications which need a constant and precise control. In this case a light sensor, e.g., an IR sensor, may be integrated into the apparatus, so that it can be detected when a user&#39;s hand approaches the tracking element, and the braking effect may thus be started before the user touches the tracking element.  
         [0045]    The present invention provides a self-applying brake for a tracking element without the necessity of applying a counter pressure. Thus, the tracking element of a cursor control device that controls the movement of a cursor on a computer display can be precisely controlled in the area of lower velocities and stopped. This may be especially advantageous when drawing freely using such a cursor control device.