Patent Publication Number: US-11385069-B2

Title: Optical navigation device and optical navigation method

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an optical navigation device and an optical navigation method, and particularly relates to an optical navigation device and an optical navigation method which can adjust the motion report to have a fixed report size. 
     2. Description of the Prior Art 
     An optical navigation device such as an optical mouse always needs to report motions thereof to a host device via a USB device, such that the host device can determine a location of the optical navigation device based on the motions. However, a sensor report rate of the conventional optical navigation device may be asynchronous with a USB report rate thereof. Such situation may cause some problems. 
       FIG. 1  is a schematic diagram illustrating a conventional motion report operation of an optical navigation device. As illustrated in  FIG. 1 , an image sensor of the conventional optical navigation device may sense a plurality of image frames SF 1 -SF 7 . Also, the USB device of the conventional optical navigation device reports USB reports Ur 1 , Ur 2  and Ur 3  to the host every fixed time interval. The USB report may indicate a motion which is calculated based on at least one of the image frames SF 1 -SF 7 . 
     However, since the sensor report rate (e.g. a frame rate of the image sensor) is asynchronous with a USB report rate (i.e. a frequency that the USB device reports motions), each USB report may have different data sizes. That is, the USB report may correspond to data in different time intervals. As shown in  FIG. 1 , the motion indicated by the USB report Ur 1  is 0 since the motion could not be calculated based on only one image frame SF 1 . Also, the USB report Ur 2  indicates motion  1 , which is calculated based on image frames SF 1 , SF 2 , SF 3  and SF 4 . Further, the USB report Ur 3  indicates motion  2 , which is calculated based on image frames SF 4 , SF 5  and SF 6 . Accordingly, the USB reports Ur 2  and Ur 3  correspond to image frames in different time intervals thus have different report sizes, which may cause some bad user experiences. For example, the user may feel a speed of the icon controlled by the optical navigation device is non-constant since the USB reports Ur 2  and Ur 3  have different report sizes. 
     SUMMARY OF THE INVENTION 
     Therefore, one objective of the present invention is to provide an optical navigation system which can scale motion reports to correspond to a fixed time interval. 
     Another objective of the present invention is to provide an optical navigation method which can scale motion reports to correspond to a fixed time interval. 
     One objective of the present invention is to provide an optical navigation system comprising a control circuit and an optical navigation device. The optical navigation device comprises: an image sensor, configured to generate a plurality of image frames; and a motion reporting device, configured to report a first motion of the optical navigation device to the control circuit at a first time after a reference time, and configured to report a second motion to the control circuit at a second time after the first time. The first motion and the second motion are calculated according to the image frames. The control circuit calculates a first scaled motion according to the first motion, the second motion, a first time difference between the first time and the reference time, and a second time difference between the first time and the second time. 
     Another objective of the present invention is to provide an optical navigation method applied to an optical navigation device. The optical navigation method comprises: (a) generating a plurality of image frames by an image sensor; (b) reporting a first motion of an optical navigation device to a control circuit at a first time after a reference time, and reporting a second motion to the control circuit at a second time after the first time, wherein the first motion and the second motion are calculated according to the image frames; (c) calculating a first scaled motion according to the first motion, the second motion, a first time difference between the first time and the reference time, and a second time difference between the first time and the second time by the control circuit; and (d) determining a location of the optical navigation device according to the first scaled motion. 
     In view of above-mentioned embodiments, the motion reports can be scaled to correspond to a fixed time interval. Thus the issues for a conventional motion reporting operation can be improved. 
     These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram illustrating a conventional motion report operation of an optical navigation device. 
         FIG. 2  is a block diagram illustrating an optical navigation device according to one embodiment of the present invention. 
         FIG. 3  and  FIG. 4  are schematic diagrams illustrating motion report operations of an optical navigation device according to different embodiments of the present invention. 
         FIG. 5  is a flow chart illustrating an optical navigation method according to one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     In following descriptions, several embodiments are provided to explain the concept of the present invention. Please note, each component or step in following embodiments can be implemented by hardware (e.g. a circuit or a device) or by firmware (e.g. a processor installed with at least one program). Further, each component in following embodiments can be separated to more components or be integrated to fewer components. Besides, the terms “first”, “second”, “third” in following descriptions are only for defining different components or parameters, but do not mean the sequence thereof. 
       FIG. 2  is a block diagram illustrating an optical navigation device  200  according to one embodiment of the present invention. Besides,  FIG. 3  and  FIG. 4  are schematic diagrams illustrating motion report operations of the optical navigation device  200  according to different embodiments of the present invention. Please refer to  FIG. 2  and  FIG. 3  together, and refer to  FIG. 2  and  FIG. 4  together, to understand the concepts of the present invention for more clarity. 
     Please first refer to  FIG. 2  and  FIG. 3  together. As illustrated in  FIG. 2 , the optical navigation device  200  comprises an image sensor  201  and a motion reporting device  203 . The optical navigation device  200  can be an optical mouse, but not limited. The image sensor  201  is configured to generate a plurality of image frames SF 1  . . . SF 7 . The motion reporting device  203 , which can be but not limited to a USB device, is configured to report a first motion M 1  of the optical navigation device  200  to a control circuit  205  in a host device  207  at a first time T 1  after a reference time Tr, and is configured to report a second motion M 2  of the optical navigation device  200  to the control circuit  205  at a second time T 2  after the first time T 1 . After that, a first scaled motion MS 1  is calculated by the control circuit  205  based on the first motion M 1  and the second motion M 2 . The host device  207  can be a computer which is connected to the optical navigation device wiredly or wirelessly. 
     The first motion M 1  and the second motion M 2  are calculated according to at least one of the image frames SF 1  . . . SF 7 . In the embodiment of  FIG. 3 , the motion M 1  is calculated based on image frames SF 2 -SF 4 , and the motion M 2  is calculated based on image frames SF 4 -SF 5 . Further, the first scaled motion MS 1  is calculated according to the first motion M 1 , the second motion M 2 , a first time difference TD 1  between the first time T 1  and the reference time Tr, and a second time difference TD 2  between the first time T 1  and the second time T 2 . In one embodiment, the first scaled motion MS 1  is calculated by an equation of 
                 (       M   ⁢   1     +     M   ⁢   2       )     ×       T   ⁢   D   ⁢   1         T   ⁢   D   ⁢   1     +     T   ⁢   D   ⁢   2           ,         
but not limited.
 
     In one embodiment, the second time T 2  is after the first time T 1  for a predetermined time interval. However, the second time T 2  can also be the same as a time that a next sensor report occurs following the first time T 1 , for example, a time of the image frame SF 5  in  FIG. 3 . In one embodiment, the motion reporting operation at the first time T 1  is triggered by the control circuit  205  in the host device  207 . Such operation can clear an interrupt generated by a previous sensor report thus the control circuit  205  can know the exact moment when the next sensor report occurs (e.g. a time of the image frame SF_ 5 ). Also, in one embodiment, the motion reporting device  203  is triggered by the image sensor  201  to report the second motion M 2  at the second time T 2 . In such case, the image sensor  201  transmits an interrupt to the control circuit  205 , and the control circuit  205  reads the second motion M 2  corresponding to the interrupt. 
     Furthermore, in one embodiment, the reference time Tr is a time at which the motion reporting device  200  reports a third motion of the optical navigation device  200  to the host device  207 . In the embodiment of  FIG. 3 , the third motion is 0 since only one image frame exists before the reference time Tr. 
     Please refer to  FIG. 2  and  FIG. 4  together. In the embodiment of  FIG. 4 , the motion reporting device  200  reports a fourth motion M 4  of the optical navigation device  200  to the control circuit  205  at a fourth time T 4  after the second time T 2 , and reports a fifth motion M 5  of the optical navigation device  200  to the control circuit  205  at a fifth time T 5  after the second time T 4 . After that, a second scaled motion MS 2  is calculated by the control circuit  205  based on the fourth motion M 4  and the fifth motion M 5 . 
     The fourth motion M 4  and the fifth motion M 5  are calculated according to at least one of the image frames SF 1 -SF 7 . Specifically, the fourth motion M 4  is calculated based on the image frames SF 5 , SF 6 , and the fifth motion M 5  is calculated based on the image frames SF 6 , SF 7 . The second scaled motion MS 2  is calculated according to the fourth motion M 4 , the fifth motion M 5 , a third time difference TD 3  between the first time T 1  and the fourth time T 4 , a fourth time difference TD 4  between the fourth time T 4  and the fifth time T 5 , and a remainder motion Mr calculated by the control circuit  205 . The remainder motion Mr is calculated based on a difference between the first scaled motion MS 1  and a sum of the first motion M 1 , the second motion M 2 . That is, the remainder motion Mr is the motion included in the sum of the first motion M 1 , the second motion M 2  but not included in the first scaled motion MS 1 . In one embodiment, the second scaled motion MS 2  is calculated by an equation of 
     
       
         
           
             
               
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     Please refer to  FIG. 4  again. The operations of the embodiment illustrated in  FIG. 4  can be illustrated as: The motion reporting device  203  reports a first motion M 1  at the first time T 1  and reports a second motion M 2  at the second time T 2  to the control circuit  205 . After that, the first scaled motion MS 1  between the reference time Tr and the first time T 1  is acquired by the control circuit  205  based on the above-mentioned steps. Additionally, the motion reporting device  203  reports a fourth motion M 4  at the fourth time T 4  and reports a fifth motion M 5  at the fifth time T 5  to the control circuit  205 . After that, the second scaled motion MS 2  between the first time T 1  and the fourth time T 4  is acquired based on the above-mentioned steps. If the reference time Tr is a time that the motion reporting device  203  triggered by the control circuit  205  to report a motion, a time interval between the reference time Tr, the first time T 1 , and a time interval between the first time T 1 , the fourth time T 4  are the same. Accordingly, each motion report MP 2 , MP 3  which respectively indicates the first scaled motion MS 1  and the second scaled motion MS 2  can have the same report sizes. 
     Please note, in the above-mentioned embodiments, the first scaled motion M 1 , the second scaled motion M 2  and the remainder motion Mr are calculated by the control circuit  205  in the host device  207 . However, the first scaled motion M 1 , the second scaled motion M 2  and the remainder motion Mr can be calculated by a control circuit provided in the optical navigation device  200 . In such case, the optical navigation device  200  reports the first motion M 1 , the second motion M 2 , the fourth motion M 4 , the fifth motion M 5  to the control circuit located therein. 
     In such case, the control circuit in the optical navigation device  200  calculates the first motion M 1  at the first time T 1  and calculates the second motion M 2  at the first time T 2  in the embodiments of  FIG. 3  and  FIG. 4 . Further, the control circuit in the optical navigation device  200  calculates the first scaled motion MS 1  via above-mentioned steps. Also, the control circuit in the optical navigation device  200  calculates the fourth motion M 4  at the fourth time T 4  and calculates the fifth motion M 5  at the fifth time T 5  in the embodiment of  FIG. 4 . Further, the control circuit in the optical navigation device  200  calculates the second scaled motion MS 2  via above-mentioned steps. Besides, the optical navigation device  200  reports first scaled motion MS 1  and the second scaled motion MS 2  to the host device  207  respectively at the second time T 2  and the fifth time T 5 . Therefore, the control circuit in the host device  207  or in the optical navigation device  200  can be regarded as an optical navigation system. Such variations should also fall in the scope of the present invention. 
     After the scaled motions are acquired, the host device  207  can determine a location of the optical navigation device  200  based on the scaled motions rather than the original first motion M 1 , the second motion M 2 , the third motion M 3  and the fourth motion M 4 . 
     In view of above-mentioned embodiments, an optical navigation method applied to an optical navigation device can be acquired.  FIG. 5  is a flow chart illustrating an optical navigation method according to one embodiment of the present invention, which comprises: 
     Step  501   
     Generate a plurality of image frames (e.g. SF 1 -SF 7  in  FIG. 3 ) by an image sensor. 
     Step  503   
     Report a first motion (e.g. M 1  in  FIG. 3 ) of an optical navigation device to a control circuit at a first time after a reference time, and report a second motion (e.g. M 2  in  FIG. 3 ) to the control circuit at a second time after the first time, wherein the first motion and the second motion are calculated according to the image frames. 
     Step  505   
     Calculate a first scaled motion (e.g. MS 1  in  FIG. 3 ) according to the first motion, the second motion, a first time difference between the first time and the reference time, and a second time difference between the first time and the second time by the control circuit. 
     Step  507   
     Determine a location of the optical navigation device according to the first scaled motion. 
     Other steps can be acquired in view of above-mentioned disclosure, thus are omitted for brevity here. 
     In view of above-mentioned embodiments, the motion reports can be scaled to correspond to a fixed time interval. Thus the issues for a conventional motion reporting operation can be improved. 
     Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.