PATENT DOCUMENT

Publication Number: US-7663601-B1
Application Number: US-55115706-A
Country: US
Kind Code: B1

Title: Hybrid low power computer mouse

Abstract:
Operating a pointing device in a low power manner by receiving first tracking information from a first tracking device, de-activating the first tracking device when the accuracy of the first tracking information is determined to be inadequate, activating a second tracking device in order to acquire second tracking information when the first tracking device is deactivated, wherein the first tracking device is substantially lower power device that the second tracking device.

Claims:
1. A method for operating a pointing device in a low power manner, comprising:
 receiving first position tracking information from a first position tracking device; 
 de-activating the first position tracking device when the accuracy of the first position tracking information is determined to be inadequate; and 
 activating a second position tracking device in order to acquire second position tracking information when the first position tracking device is deactivated, wherein the first position tracking device is substantially lower power device than the second position tracking device. 
 
     
     
       2. A method as recited in  claim 1 , further comprising:
 de-activating the second position tracking device and activating the first position tracking device when the accuracy of the first position tracking information is determined to be adequate. 
 
     
     
       3. A method as recited in  claim 1 , wherein the first position tracking device is an accelerometer and wherein the second position tracking device is an optical tracking engine. 
     
     
       4. A method as recited in  claim 1 , wherein the pointing device further includes a surface sensor. 
     
     
       5. A method as recited in  claim 4  wherein the pointing device is a computer mouse. 
     
     
       6. A low power pointing device, comprising:
 a first position tracking device arranged to provide first position tracking information when the accuracy of the first position tracking device is adequate, otherwise the first position tracking device is not active; and 
 a second position tracking device that provides second position tracking information when the first position tracking device is not active, wherein the first position tracking device is substantially lower power device than the second position tracking device. 
 
     
     
       7. A low power pointing device as recited in  claim 6  wherein the second position tracking device is de-activated concurrently with the first position tracking device being activated when the accuracy of the first position tracking information is determined to be adequate. 
     
     
       8. A low power pointing device as recited in  claim 6 , wherein the first position tracking device is an accelerometer and wherein the second position tracking device is an optical tracking engine. 
     
     
       9. A low power pointing device as recited in  claim 8 , wherein the pointing device further includes a surface sensor. 
     
     
       10. A low power pointing device as recited in  claim 9  wherein the pointing device is a computer mouse. 
     
     
       11. A low power pointing device as recited in  claim 10 , wherein the accelerometer provides a measure of mouse acceleration and mouse velocity. 
     
     
       12. A low power pointing device as recited in  claim 11 , wherein the surface sensor is arranged to observe a number of surface quality parameters and determine, based upon the observed surface quality parameters, if the mouse is in physical contact with a suitable surface. 
     
     
       13. A low power pointing device as recited in  claim 12 , wherein when the surface sensor determines that the mouse in not in physical contact with a suitable surface, then the surface sensor causes the mouse to deactivate. 
     
     
       14. A low power pointing device as recited in  claim 13 , wherein when the optical tracking system is only providing the position tracking information, the accelerometer provides corresponding accelerometer based velocity values each of which are compared to each other to provide an error value. 
     
     
       15. A low power pointing device as recited in  claim 14 , wherein a number of error values are combined to form an accumulated error value. 
     
     
       16. A low power pointing device as recited in  claim 15 , wherein the accumulated error value is used to reset an offset value for the accelerometer. 
     
     
       17. A low power pointing device as recited in  claim 16 , wherein the reset offset value reduces the accumulated error thereby commensurable reducing positional error at the computer. 
     
     
       18. A low power pointing device as recited in  claim 10 , wherein the low power pointing device is in wireless communication with a computer. 
     
     
       19. A computer readable storage medium for storing computer code executable by a processor for operating a pointing device in a low power manner, comprising:
 computer code for receiving first position tracking information from a first position tracking device; 
 computer code for de-activating the first position tracking device when the accuracy of the first position tracking information is determined to be inadequate; and 
 computer code for activating a second position tracking device in order to acquire second position tracking information when the first position tracking device is deactivated, wherein the first position tracking device is substantially lower power device than the second position tracking device. 
 
     
     
       20. A computer readable storage medium for storing computer code executable by a processor as recited in  claim 19 , further comprising:
 computer code for de-activating the second position tracking device and activating the first position tracking device when the accuracy of the first position tracking information is determined to be adequate. 
 
     
     
       21. A computer readable storage medium for storing computer code executable by a processor as recited in  claim 19 , wherein the first position tracking device is an accelerometer and wherein the second position tracking device is an optical tracking engine. 
     
     
       22. A computer readable storage medium for storing computer code executable by a processor as recited in  claim 19 , wherein the pointing device further includes a surface sensor. 
     
     
       23. A method as recited in  claim 1 , wherein the first position tracking information and the second position tracking information are each used to generate coordinate data that is used to move an on-screen icon.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. patent application Ser. No. 10/605,042 filed Sep. 3, 2003, entitled “HYBRID LOW POWER COMPUTER MOUSE,” which is hereby incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     This invention relates generally to low power user input devices. More specifically, the invention describes an ultra low power computer mouse having an optical tracking engine and inertial tracking engine that cooperate to provide velocity data to a computing device. 
     2. Description of Related Art 
     A computer mouse is a small device that a computer user pushes across a desk surface in order to point to a place on a display screen and to select one or more actions to take from that position. The mouse first became a widely-used computer tool when Apple Computer Inc. of Cupertino Calif. made it a standard part of the Apple Macintosh line of computers. Until the late 1990&#39;s, most computer mice were opto-mechanical in nature that required a number of moving parts to work in tandem with some form of optical emitters/receiving device (such as an infrared LED/infrared sensor) to provide tracking information to a processor coupled thereto arranged to generate coordinate data that is used to move an on-screen icon (such as a pointer). Since this process is repeated hundreds of times a second, the motion perceived by a computer user is smooth and continuous. 
     The use of mechanical components in the computer mouse limited the use of the computer mouse. However, towards the end of the 1990s, Agilent Technologies developed and introduced a purely optical mouse that in its first incarnation used a tiny camera that took over 1500 images every second to provide the requisite tracking information enabling the optical mouse to operate on almost any surface. Typically, the optical mouse includes a small, light emitting diode (LED) that bounces a beam of light off of a surface onto which the mouse was placed to be received by a light sensor (typically a CMOS type sensor). The CMOS sensor, in turn, transmitted each of the images to a digital signal processor (DSP) for subsequent analysis. Such analysis includes detecting patterns in the images and how these patterns moved since most recent previous image. The observed change in patterns over a sequence of images provides the requisite input data for the DSP to determine how far the mouse has moved which is then provided to a processor that calculates the corresponding coordinates for a computing device coupled thereto. 
     Since it was now possible to use an optical mouse on most surfaces, a next step in the evolution of the computer mouse resulted in a wireless mouse connected to the computing device only by way of a wireless link. Such wireless links include those based upon the Bluetooth specification which is a computing and telecommunications industry specification that describes how mobile phones, computers, and personal digital assistants (PDAs) can easily interconnect with each other and with home and business phones and computers using a short-range wireless connection. 
     Although a wireless optical computer mouse provides great flexibility to the computer user, one weak point of currently configured wireless computer mice is the relatively short battery life due primarily to the large power consumption of the optical tracking engine and wireless link. For example, a Bluetooth wireless mouse with the industry standard optical tracking sensor (i.e., the Agilent 2030 manufactured by Agilent Inc of Palo Alto, Calif.) draws approximately 35 mA from the on-board batteries (usually standard AA batteries) when in the active mode while the associated Bluetooth/microprocessor chip draws on the average of 7 mA for a total of approximately 40 mA in active mode. A power consumption of this magnitude translates into approximately a 2 month battery life creating an inconvenience for the user not to mention the cost of replacing the batteries at such frequent intervals. One solution to the problem involves substituting rechargeable batteries but this, of course, necessitates the use of a recharging station. 
     Therefore, what is required is a low power tracking solution. One such low power tracking solution is a hybrid computer mouse having both a low power accelerometer used in combination with an optical tracking engine to provide velocity or relative positional data with low tracking errors over a wide range of use. 
     SUMMARY OF THE INVENTION 
     The invention described herein pertains to a wireless low power tracking device and methods of use thereof. In one embodiment, a method for operating a pointing device in a low power manner by receiving first tracking information from a first tracking device, de-activating the first tracking device when the accuracy of the first tracking information is determined to be inadequate, and activating a second tracking device in order to acquire second tracking information when the first tracking device is deactivated, wherein the first tracking device is substantially lower power device that the second tracking device. 
     In another embodiment, a low power pointing device includes a first tracking device arranged to provide first tracking information when the accuracy of the first tracking device is adequate, otherwise the first tracking device is not active, and a second tracking device that provides second tracking information when the first tracking device is not active, wherein the first tracking device is substantially lower power device that the second tracking device. 
     In yet another embodiment, computer program product for operating a pointing device in a low power manner. The computer program product includes computer code for receiving first tracking information from a first tracking device, computer code for de-activating the first tracking device when the accuracy of the first tracking information is determined to be inadequate, and computer code for activating a second tracking device in order to acquire second tracking information when the first tracking device is deactivated, wherein the first tracking device is substantially lower power device that the second tracking device. The computer code is then stored in a computer readable medium. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be better understood by reference to the following description taken in conjunction with the accompanying drawings. 
         FIG. 1  shows a block diagram of an exemplary wireless hybrid computer mouse in accordance with an embodiment of the invention. 
         FIG. 2  shows a functional block diagram of a representative microcontroller suitable for use in the computer mouse in accordance with an embodiment of the invention. 
         FIG. 3  is a graphical illustration of a representative operational cycle of the computer mouse in accordance with an embodiment of the invention. 
         FIG. 4  shows accumulated error in accordance with an embodiment of the invention. 
         FIG. 5  is a flowchart detailing a process for operation of a hybrid computer mouse having an accelerometer and an optical tracking engine that cooperate to provide tracking information to computer. 
         FIG. 6  illustrates a computer system employed to implement the invention. 
     
    
    
     DETAILED DESCRIPTION OF SELECTED EMBODIMENTS 
     Reference will now be made in detail to a preferred embodiment of the invention. An example of the preferred embodiment is illustrated in the accompanying drawings. While the invention will be described in conjunction with a preferred embodiment, it will be understood that it is not intended to limit the invention to one preferred embodiment. To the contrary, it is intended to cover alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims. 
     Although typical accelerometers are low power, they are susceptible to large tracking errors due to drift and other sources of error due to, for example, surface irregularities. Such tracking errors can be substantial after a fairly short length of time (approximately 0.5 seconds in some cases) thereby limiting the usefulness of an inertial tracking engine based computer mouse. On the other hand, low power optical tracking engines (such as, for example, the Agilent 2030) have difficulty compensating for high acceleration therefore limiting their usefulness to low acceleration (typically on the order of 0.15 G) situations. 
     Attempts to implement a low power computer mouse using only a low power optical tracking engine are not practicable due to the large tracking errors introduced when the computer mouse is accelerated much beyond 0.15 G as well as low power being only “lower power” that still substantially reduces on-board battery life. This extremely small range of acceptable acceleration can be appreciated when normal hand motions can induce accelerations on the order to 3 G. On the other hand, attempting to implement a low power computer mouse using a conventional accelerometer is also impractical due to the large induced tracking errors after only a short time of use especially in low acceleration cases where the signal to noise (S/N) ratios can be quite low. 
     The inventive computer mouse solves these problems by combining both an optical tracking engine and an accelerometer into a hybrid low power computer mouse having low power consumption requirements and long battery life. Accordingly, in a particularly useful implementation, a wireless computer mouse having an accelerometer and an optical tracking engine cooperate with each other to provide the tracking information to a computer is described. In the described embodiment, the optical tracking engine is inactive while the accelerometer is always active so as to provide continuous dead reckoning tracking information. The dead reckoning tracking information is periodically calibrated using optical tracking information provided by the now activated optical tracking engine. 
     For those periods of time that a dead reckoning tracking error measurement (being a difference between the dead reckoning tracking information and the optical tracking information) is greater than a pre-determined threshold, the optical tracking engine remains active to provide the optical tracking information to the computer. During these periods of time, an accumulated error value is calculated based upon a comparison of the optical tracking information and the dead reckoning tracking information that is used to reset an offset value associated with the accelerometer. By resetting the offset value, the overall accumulated error between the inertial tracking engine and the optical tracking engine is reduced. 
     At any time, a surface sensor monitors a surface pressure and/or a surface quality to determine whether or not the computer mouse is in contact with a suitable surface. In those situations where the computer mouse in not in contact with a suitable surface, both the accelerometer and the optical tracking engine are deactivated until such time as the sensor has determined that the computer mouse has been placed back on a suitable surface. It is contemplated that the surface sensor can be either a mechanical type sensor, an electro-mechanical type sensor, or an optical type sensor any of which would be well suited for use with the computer mouse described herein. 
     The invention will now be described in terms of a representative wireless computer mouse that should not be construed to limit either the scope or intent of the invention. It should be noted as well that the invention, although described in terms of a computer mouse, can be well adapted to any input device for providing any form of absolute or relative tracking information to a computing device. 
     Accordingly,  FIG. 1  shows a representative computer mouse  100  in accordance with an embodiment of the invention. The mouse  100  includes an optical tracking engine  102  and an accelerometer  104  each of which is coupled to a microcontroller unit  106 . It should be noted that the accelerometer  104  and the optical tracking engine  102  can be of any appropriate type and/or manufacture. For example, the Agilent 2030 can be used for the optical tracking engine  102  whereas the Analog Devices ADXC202 manufactured by Agilent Inc. of can be used for the accelerometer. In the described embodiment, the microcontroller unit  106  is connected to or has incorporated therein, a wireless transmitter unit  108 . It should be noted that although the wireless transmitter unit  108  is configured as a Bluetooth based radio transmitter unit, any appropriate wireless transmitter can be used. 
     A surface detector  110  continuously monitors a number of surface related parameters in order to assure that the computer mouse  100  is in physical contact with a suitable surface. By suitable surface it is meant a surface that is free, or mostly free, of substantial surface irregularities, substantially planar, and substantially parallel to the local surface of the earth. In some embodiments, the computer mouse  100  includes (but not shown in  FIG. 1 ) an acceleration monitor that is used to determine that the computer mouse  100  is in an inertial reference frame (i.e., not accelerated) such that in an non-inertial reference frame (such as a moving vehicle), the computer mouse  100  accommodates for the externally applied acceleration that is independent of the computer mouse acceleration generated by a computer user. 
     In the described embodiment, whenever the mouse  100  is determined to be on a suitable surface, the accelerometer  104  is in an active state thereby providing a stream of acceleration (dv/dt) data to the microcontroller  106 . It should be noted at this point, that since the accelerometer  104  provides tracking information in the form of acceleration (in Cartesian coordinates, d 2 Y/dX 2 ), an integration operation is performed on the acceleration data that converts the acceleration data to velocity data (dY/dX) appropriate for use as the dead reckoning tracking information. In those situations where the mouse  100  has either just been placed on a suitable surface or is restarting from a stopped position or is being powered up, the optical tracking engine  102  is activated in order to provide a calibration datum used to calibrate the dead reckoning tracking information provided by the accelerometer  104 . 
     Using both the optical tracking datum and the associated dead reckoning tracking information, the microcontroller  106  determines if the optical tracking engine  102  remains active in order to provide the appropriate tracking information to the computer  112  by way of the wireless transmitter  108 . It should be noted that the tracking information provided to the computer  112  is in fact velocity data (which can be in units of counts, or dots, moved per report that can be approximately 8 msec) which ultimately undergoes an integration operation at the computer  112  from velocity to position before being used to place a cursor  114  on an associated display screen  116 . 
     In the described embodiment, the determination of the source of tracking information sent to the computer  112  is based upon a dead reckoning tracking error value E calculated by comparing the optical tracking datum and the associated dead reckoning tracking information at a particular point in time. If the dead reckoning tracking error value E is greater than a pre-determined error threshold E thresh , then the microcontroller  106  directs the optical tracking engine  102  to 1) remain active using a duty cycle signal S provided thereto and 2) to provide the relevant tracking information to the computer  112 . It should be remembered that even though the accelerometer  104  is not providing the tracking information to the computer  112 , the accelerometer  104  is nonetheless still active and providing dead reckoning data at periodic intervals. In this way, the accelerometer  106  is always ready to take over from the optical tracking engine  102  when directed by the microcontroller  106 . 
     Whenever the optical tracking engine  102  is active, the microcontroller  106  determines the dead reckoning tracking error value E for each of a number of periodic intervals. These periodic intervals may be based upon the report rate of the accelerometer  104  to provide valid dead reckoning tracking information and the processing specs of the microcontroller and typically is on the order of 10 msecs. In the described embodiment, the dead reckoning tracking error E is used to reset an offset value G associated with the accelerometer  104 . As well known in the art, the offset value G for an accelerometer is that value representative of a bias value around which the particular accelerometer operates. Thereby, resetting the offset value G provides a simple way of compensating the output of the accelerometer in order to account for systemic errors that may adversely affect the accuracy of the accelerometers readings. Such systematic errors are typically related to process variations in the manufacture of the accelerometer itself as well as to the differences with mounting in the mouse chassis. 
     One error is referred to as accumulated error resulting from the differences in velocities observed by the accelerometer and the optical tracking engine for the same mouse motion. This difference in velocity measurement is due, in part, to the fact that the accelerometer and the optical tracking engines react very differently to the same external conditions, such as high/low acceleration, surface quality, etc. This error is present at one degree or another for each velocity data point provided by both the accelerometer and the optical tracking engine. 
     Accordingly, since the tracking information provided by to the computer  112  is integrated in order to arrive at a coordinate value (i.e., X, Y), any associated dead reckoning tracking error will also be integrated potentially resulting in substantial error in placement of the cursor  114 . Therefore, it is important to reduce the accumulated tracking error as much as possible. In one embodiment, the tracking error for each interval is calculated and used to reset the offset value G for the accelerometer  104  having the effect of reducing the accumulated tracking error by “closing the gap” between the dead reckoning tracking information and the optical tracking information resulting in a commensurate reduction in any positional error in placement of the cursor  114 . 
     In those situations, where the observed dead reckoning tracking error is less than the dead reckoning tracking error threshold E thresh , the microcontroller  106  adjusts the duty cycle signal S to as to deactivate the optical tracking engine  102 . In this way, the tracking information provided to the computer  112  is formed of only the dead reckoning tracking information provided by the accelerometer  104 . In this way, by turning off the high power consumption optical tracking engine  102 , the power consumed by the computer mouse  100  is substantially reduced. It should be noted, however, that since the accelerometer  104  is susceptible to any number of sources of error (some of which are described above), at periodic calibration intervals, the microcontroller  106  adjusts the duty cycle signal S in such a way that the optical tracking engine  102  is activated for a period of time sufficient to provide a calibration datum. This calibration datum is then used to calibrate associated dead reckoning tracking information associated of the same time interval. Again, the results of this comparison will determine whether or not the computer mouse  100  remains in hybrid mode (i.e., with only the accelerometer  104  providing the tracking information to the computer  112 ) or reverts to an optical tracking active mode whereby the tracking information is provided solely by the optical tracking engine  102  with the concomitant increase in power consumption. 
     It should be noted, that at any time the surface sensor  110  has determined that the mouse  100  is not in physical contact with a suitable surface, the mouse  100  ceases sending tracking information to the computer  112  until such time as the mouse  100  has been placed back on a suitable surface. In some cases (though not shown in  FIG. 1 ), a tilt sensor can be incorporated into the mouse  100  to monitor the tilt of the mouse  100 . Since any tilting of the mouse  100  from vertical can substantially affect the accuracy of the accelerometer  104 , the tilt monitor provides real time feedback that can be used to modify the accelerometer  104  operation. It is contemplated that in one implementation, a series of contact sensitive feet placed between a surface and the mouse  100  can be use as such a tilt monitor. By measuring and comparing signals from each of the feet, the microcontroller  106  can determine relative tilt angle, if the mouse is on a valid surface, and adjust the signals from the accelerometer  104  accordingly. 
       FIG. 2  shows a functional block diagram of a representative microcontroller  200  suitable for use in the computer mouse  100  in accordance with an embodiment of the invention. It should be noted that the microcontroller  200  is merely an example of any of a number of possible implementations that could be used for the computer mouse  100  and should not be construed as limiting either the intent or scope of the invention. Accordingly, the microcontroller  200  includes a dead reckoning tracking error generator  202  coupled to the optical tracking engine  102  and an integrator  204  arranged to receive output data directly from the accelerometer  104  (as acceleration data). 
     As mentioned above, since the accelerometer  104  directly generates acceleration data, the acceleration data must be integrated to acceleration velocity data (i.e., dead reckoning tracking information) in order to be compared the velocity data provided by the optical tracking engine  102  (i.e., optical tracking information). Therefore, once the acceleration data has been appropriately integrated to form the dead reckoning tracking information, the dead reckoning tracking information error generator  202  determines the dead reckoning tracking information error E by comparing the optical tracking information provided by the optical tracking engine  102  and the dead reckoning tracking information provided the by accelerometer  104  (by way of the integrator  204 ) for each of a number of time intervals. In the case where the dead reckoning tracking information error E is less than a pre-determined threshold E threshold , the dead reckoning tracking error generator  202  adjusts the duty cycle signal S to de-activate the optical tracking engine  102  such that the only source of tracking information provided to the computer  112  is from the accelerometer  104 . By de-activating the optical tracking engine  102 , the overall power consumption of the computer mouse  100  is greatly reduced thereby providing a commensurate increase in probable battery life for battery powered computer mice. 
     However, in those cases where the dead reckoning tracking error E is greater than the threshold E threshold , then the dead reckoning tracking error generator  202  adjusts the duty cycle signal S to activate the optical tracking engine  102  in such a way that the only source of tracking information to the computer  112  is that provided by the optical tracking engine  102 . In this mode, however, at each time interval, the dead reckoning tracking error generator  202  compares the optical tracking datum to an associated dead reckoning tracking datum in order to ascertain a corresponding dead reckoning tracking information error E for each interval to form the accumulated tracking error discussed above that is used to update the accelerometer offset value G in order to reduce accumulated positional error of the cursor  114 . 
       FIG. 3  is a graphical illustration of a representative operational cycle  300  of the computer mouse  100  in accordance with an embodiment of the invention. For ease of discussion, the cycle  300  is illustrated using an XY graph having an X axis representing a time dimension (t) and a Y axis representing Velocity (V). For the remainder of this discussion, both the dead reckoning tracking information and the optical tracking information will be described in terms of accelerometer velocity Vacc and optical velocity Vopt. 
     Therefore, at an initial time interval, the optical tracking engine  102  is active and provides the optical velocity Vopt 1  while the accelerometer  104  and integrator  204  provides the accelerometer velocity Vacc 1 . It should be noted that this initial time interval is representative of those situations where the computer mouse  100  is restarting from a stopped or otherwise inactive state. Such states can be due to the mouse  100  being powered up for the first time, being replaced upon a suitable surface after having been lifted off the surface, etc. Therefore, in order to provide an initial calibration point, the optical tracking engine  102  is activated. The initial calibration point (in this case, Vopt 1 ) is used to compare to the accelerometer velocity Vacc 1  and based upon this comparison, the optical tracking engine  102  is either de-activated (as in this example) or remains active. 
     In order to maintain close correlation between the accelerometer  104  and the optical tracking engine  102 , a calibration operation is performed at regular intervals, referred to as a calibration interval. A typical calibration interval is approximately 80 ms during which the accelerometer  104  is calibrated against the optical tracking engine  102 . In the situation shown in  FIG. 3 , the initial calibration indicates that the accelerometer  104  and the optical tracking engine  102  produce velocity values that are within an acceptable range. Accordingly, the computer mouse  100  is in the hybrid mode where the optical tracking engine  102  is deactivated and the accelerometer  104  is sending the appropriate tracking information to the computer  112 . At a next calibration point C 1 , the optical tracking engine  102  is activated just prior to the calibration point C 1  (in order for the optical tracking engine  102  to produce valid velocity data). A calibration check between the accelerometer  104  and the optical tracking engine  102  indicates a difference in the two velocities of such a magnitude that the optical tracking engine  102  takes over sending the tracking information to the computer  112  in place of the accelerometer  104 . It should be noted, however, that for each of a number of intervals, a comparison between the accelerometer  104  and the optical tracking engine  102  is performed until such time as the measured error between the two velocities is deemed acceptable. Once the error is deemed acceptable, the computer mouse  100  is returned to hybrid mode by de-activating the optical tracking engine  102  such that the accelerometer  104  only provides the tracking information to the computer  112 . 
     Also shown in  FIG. 3  is a representative duty cycle signal S illustrating the adaptive nature of the inventive computer mouse  112 . It should also be noted, that whenever a calibration operation is performed, the optical tracking engine  102  must be activated in order to provide the appropriate calibration velocity for an amount of time required for the optical tracking engine  102  to provide valid data. 
     Referring to  FIG. 4 , the source of accumulated error as the result of a summation (or integration) of the individual error points is illustrated. For example, errors e 1 , e 2 , and e 3  are summed during a subsequent integration operation used to transform the velocity data to position data by the computer  112 . Therefore, reducing the gap between the accelerometer velocity curve  402  and the optical tracking engine velocity curve  404 , the accumulated error is also reduced. This reduction in accumulated error has the beneficial effect of reducing positional error experienced by the cursor  114 . 
       FIG. 5  is a flowchart detailing a process  500  for operation of a hybrid computer mouse having an accelerometer and an optical tracking engine that cooperate to provide tracking information to computer. It should be noted that although not specifically shown in  FIG. 5 , a surface sensor is continuously monitoring various parameters referred to collectively as surface quality to assure that the computer mouse remains in physical contact with a suitable surface. Therefore, if at anytime the surface sensor determines that the computer mouse is not in physical contact with a suitable surface, the tracking data becomes zero until such time as it is again placed upon a suitable surface. 
     Accordingly, the process  500  begins at  502  by activating the accelerometer. It should be noted that the accelerometer remains active at all times except for those periods of time when the mouse is not active. At  504 , the accelerometer generates a velocity value. It should be noted, that the process  500  is predicated upon the assumption that the computer mouse has already been initialized in that the accelerometer has been calibrated to the optical tracking engine and is therefore not explicitly shown. Nonetheless, it should be understood that the initialization process is performed whenever the mouse is restarted, powered up, or replaced upon a suitable surface. At  506 , a determination is made whether or not the accelerometer requires calibration. Typically, this determination is based upon specific calibration intervals that are based upon any number of factors that include specific accelerometer manufacturer and model, environmental factors such as observed surface quality, etc. 
     If it is determined that the accelerometer does not require calibration, then the current accelerometer velocity value is sent to the computer at  508  and a new accelerometer velocity value is generated by the accelerometer at  510  after which control is again passed to  506  for a determination of calibration. If it is determined that calibration is required, then the optical tracking engine is activated at  512 . Once the optical tracking engine is activated, an optical tracking engine velocity value is generated at  514  providing a calibration datum to be used to calibrate the accelerometer velocity value. At  516 , the current accelerometer velocity value is compared to the optical tracking velocity value and if at  518  the comparison is determined to be valid the optical tracking engine is deactivated at  520 . By the comparison being valid it is meant that the difference between the two velocity values are within a pre-selected range indicating that the accelerometer and the optical tracking engine agree to within acceptable limits. 
     If, on the other hand, the comparison is not valid, then the optical tracking engine remains active and the current optical tracking engine velocity value is sent to the computer at  522  and a new optical tracking velocity value is provided at  516 . Therefore, the optical tracking engine remains active until such time as the comparison is valid at which time the optical tracking engine is turned off allowing only the accelerometer to provide the tracking information to the computer. 
       FIG. 6  illustrates a computer system  900  employed to implement the invention. The computer system  900  or, more specifically, CPU  902 , may be arranged to support a virtual machine, as will be appreciated by those skilled in the art. As is well known in the art, ROM acts to transfer data and instructions uni-directionally to the CPU  902 , while RAM is used typically to transfer data and instructions in a bi-directional manner. CPU  902  may generally include any number of processors. Both primary storage devices  904 ,  906  may include any suitable computer-readable media. A secondary storage medium  908 , which is typically a mass memory device, is also coupled bi-directionally to CPU  902  and provides additional data storage capacity. The mass memory device  908  is a computer-readable medium that may be used to store programs including computer code, data, and the like. Typically, mass memory device  908  is a storage medium such as a hard disk or a tape which generally slower than primary storage devices  904 ,  906 . Mass memory storage device  908  may take the form of a magnetic or paper tape reader or some other well-known device. It will be appreciated that the information retained within the mass memory device  908 , may, in appropriate cases, be incorporated in standard fashion as part of RAM  906  as virtual memory. A specific primary storage device  904  such as a CD-ROM may also pass data uni-directionally to the CPU  902 . 
     CPU  902  are also coupled to one or more input/output devices  910  that may include, but are not limited to, devices such as video monitors, track balls, mice, keyboards, microphones, touch-sensitive displays, transducer card readers, magnetic or paper tape readers, tablets, styluses, voice or handwriting recognizers, or other well-known input devices such as, of course, other computers. Finally, CPU  902  optionally may be coupled to a computer or telecommunications network, e.g., an Internet network or an intranet network, using a network connection as shown generally at  912 . In some embodiments of the present invention, computer code is tangibly embodied in a computer readable medium. The claims shall not be interpreted to cover an intangible medium such as a carrier wave. 
     The many features and advantages of the present invention are apparent from the written description and, thus, it is intended by the appended claims to cover all such features and advantages of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, the invention should not be limited to the exact construction and operation as illustrated and described. Hence, all suitable modifications and equivalents may be resorted to as falling within the scope of the invention. 
     While this invention has been described in terms of a preferred embodiment, there are alterations, permutations, and equivalents that fall within the scope of this invention. It should also be noted that there are many alternative ways of implementing both the process and apparatus of the present invention. It is therefore intended that the invention 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: 20061019
Publication Date: 20100216
Grant Date: 20100216
Priority Date: 20030903
Inventors: HOTELLING STEVE
STRICKON JOSHUA
HUPPI BRIAN
KRAH CHRISTOPH
Assignee: APPLE INC
CPC Classifications: [{"code": "G06F1/3215", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0317", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/3215", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/3259", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/038", "inventive": true, "first": true, "tree": "[]"}, {"code": "Y02D10/00", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y02D10/00", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/03543", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/038", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/03543", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0317", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/3259", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 37569473