Abstract:
A light control module appropriate for an optical pointing device. The light control module comprises a processing unit outputting a first signal and a second signal, a photo sensor unit executing a capture operation according to an impulse of the first signal, and a light emitting unit executing a light emitting operation according to an impulse of the second signal, wherein when a frequency value of the first signal is less than a first preset value, at least one impulse is inserted between two successive impulses of the second signal for adjusting a frequency value of the second signal such that an equivalent frequency value corresponding to any two successive impulses of the second signal is greater than a second preset value, thus rendering flickers of the light emitting unit imperceptible.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a light control module and method thereof, and in particular to a light control module and method appropriate for an optical pointing device.  
         [0003]     2. Description of the Related Art  
         [0004]     A mouse is a commonly used input device. A wheel mouse processes a displacement signal, a button signal, and an interface signal and communicates with a computer via an interface using the mechanical structure of its wheel and a micro-controller chip. An optical mouse replaces the mechanical structure of the wheel mouse with a complementary metal oxide semiconductor (CMOS) photo sensor chip capable of optical navigation. The CMOS photo sensor senses a series of continuous images of an operating surface. The displacement of the optical mouse can be determined by processing the images.  
         [0005]     Typically, an optical mouse requires an auxiliary light source, such as a Light Emitting Diode (LED), supplying sufficient brightness for CMOS photo sensor operation. The LED flashes each time the CMOS photo sensor captures an image. Therefore, the auxiliary light source must provide sufficient and continuous brightness when the CMOS photo sensor captures a series of continuous images of the operating surface.  
         [0006]     In practice, the auxiliary light source operates in accordance with a capture frequency of the CMOS photo sensor, to reduce power consumption and extend life. Thus, the auxiliary light source turns on when the CMOS photo sensor captures an image and turns off when the CMOS photo sensor is idle. When the auxiliary light source operates in accordance with a very low frequency CMOS photo sensor, flickers generated thereby are apparent and may cause discomfort for a user.  
         [0007]      FIG. 1   a  is a diagram of the conventional optical mouse  1 .  FIG. 1   b  is a diagram of the under side of the optical mouse  1  in  FIG. 1   a . As shown in  FIG. 1   b , the optical mouse  1  has a photo sensor area  2  on the under side thereof for placement on an operating surface, such as a desktop. The photo sensor determines a displacement of the optical mouse  1  on the operating surface.  FIG. 2  is a diagram showing operation of the photo sensor area  2  of the conventional optical mouse  1 . As shown in  FIG. 2 , the optical mouse  1  comprises a photo sensor  3  and a light emitting diode (LED)  4 . When the optical mouse  1  is moved on the operating surface  6 , the LED  4  emits a beam  5  which is reflected by the operating surface  6  to the photo sensor  3 , thus improving brightness for the photo sensor  3 .  
         [0008]     Typically, the LED  4  operates in coordination with the photo sensor  3 . Thus, the LED emits light each time the photo sensor  3  executes a capture operation. When the optical mouse  1  is in a normal mode, for example being moved, the photo sensor  3  and the LED  4  both operate at a high frequency of 1500 Hz. When the optical mouse is in a standby mode, however, for example, when idle for some duration, the photo sensor  3  operates at a capture frequency of 30 Hz to reduce power consumption. Accordingly, the LED  4  also operates at a light emitting frequency of 30 Hz.  
         [0009]     Typically, flickers from a light source are imperceptible when the frequency of the light source is greater than 60 Hz. However, as described above, when the conventional optical mouse  1  is in the standby mode, the photo sensor operates at the capture frequency of 30 Hz, and the LED  4  operates at the light emitting frequency of 30 Hz accordingly. Therefore, flickers from the LED  4  are apparent and may cause discomfort for a user.  
       SUMMARY OF THE INVENTION  
       [0010]     Accordingly, an object of the present invention is to provide a light control module appropriate for an optical pointing device. When a photo sensor unit of the optical pointing device operates at a low frequency, the frequency of a light emitting unit of the optical pointing device can be adjusted accordingly, thus avoiding perceptible flickers, reducing power consumption, and prolonging life of the light emitting unit.  
         [0011]     The present invention provides a light control module, appropriate for an optical pointing device, comprising a processing unit outputting a first signal and a second signal, a photo sensor unit executing a capture operation according to an impulse of the first signal, and a light emitting unit emitting light according to an impulse of the second signal, wherein when a frequency value of the first signal is less than a first preset value, at least one impulse is inserted between two successive impulses of the second signal for adjusting a frequency value of the second signal such that an equivalent frequency value corresponding to any two successive impulses of the second signal is greater than a second preset value, thus preventing the light emitting unit from flickering.  
         [0012]     The present invention also provides a light control method comprising the steps of outputting a first signal and a second signal, executing a capture operation according to an impulse of the first signal, executing a light emitting operation according to an impulse of the second signal, determining whether a frequency value of the first signal is less than a first preset value, and if so, inserting at least one impulse between two successive impulses of the second signal for adjusting a frequency value of the second signal such that an equivalent frequency value corresponding to any two successive impulses of the second signal is greater than a second preset value, thus preventing the light emitting unit from flickering.  
         [0013]     A detailed description is given in the following embodiments with reference to the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     The present invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:  
         [0015]      FIG. 1   a  is a diagram of the conventional optical mouse.  
         [0016]      FIG. 1   b  is a diagram of the under side of the optical mouse in  FIG. 1   a.    
         [0017]      FIG. 2  is a diagram showing operations in the photo sensing area of the conventional optical mouse.  
         [0018]      FIG. 3  is a schematic diagram of circuits of the light control module of the optical mouse of the present invention.  
         [0019]      FIG. 4  is a wave diagram showing the impulses according to which the photo sensor unit and the light emitting unit (Light Emitting Diode, LED) work when the photo sensor unit of the optical mouse of the present invention operates at a low frequency in a low power mode.  
         [0020]      FIG. 5  is a process chart of the light control method of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
     First Embodiment  
       [0021]      FIG. 3  is a schematic diagram of circuits of the light control module of the optical mouse of the present invention. The optical mouse comprises a processing unit  501 , a photo sensor unit  504 , and a light emitting unit  505 . The light emitting unit  505  is an LED. The processing unit  501  comprises a counter  502  and a controller  503 . The counter  502  sequentially generates counting numbers T for transmission to the controller  503 . The counting numbers T are increased from 0 to 3000 by increments of 1 in one second for use as a time division standard.  
         [0022]     The controller  503  generates a capture signal F 41  and a light emitting signal F 42  according to two selected sets of counting numbers respectively. The capture signal F 41  and the light emitting signal F 42  are output to the photo sensor unit  504  and the light-emitting unit  505  respectively. When a counting number presently generated by the counter  502  belongs to the selected set of counting numbers, the controller  503  outputs one impulse. The photo sensor unit  504  executes at least one capture operation according to the impulse of the capture signal F 41 . Similarly, the light emitting unit  505  executes a light emitting operation according to the impulse of the light emitting signal F 42 . Because the light emitting unit  505  operates in coordination with the photo sensor unit  504 , the selected set of counting numbers for the light emitting signal F 42  must comprise all numbers in the selected set of counting numbers for the capture signal F 41 , such that the light emitting unit  505  executes the light emitting operation each time when the photo sensor unit  504  executes the capture operation.  
         [0023]     When the optical mouse is in a normal mode, for example being moved, the two selected sets of counting numbers comprise the same numbers. Thus, the capture signal F 41  and the light emitting signal F 42  have the same frequency value. Therefore, it is guaranteed that the light emitting unit  505  executes the light emitting operation each time when the photo sensor unit  504  executes the capture operation. In this embodiment, the counting numbers T are increased from 0 to 3000 by increments of 1 in one second. Each selected set of counting numbers is determined by selecting all multiples of 2, so the photo sensor unit  504  and the light emitting unit  505  both operate at a high frequency of 1500 Hz  FIG. 4  is a wave diagram showing the impulses according to which the photo sensor unit  504  and the light emitting unit (Light Emitting Diode, LED)  505  work when the photo sensor unit  504  of the optical mouse of the present invention operates at a low frequency in a low power mode. When the optical mouse is in a standby mode, for example, when idle for some duration, the two selected sets of counting numbers comprise different numbers. The selected set of counting numbers for the capture signal F 41  is determined so as to decrease the frequency of the capture signal F 41  to be 30 Hz for reducing power consumption.  
         [0024]     As shown by the upper wave in  FIG. 4 , the counting numbers T corresponding to the capture signal F 41  are t 41  ( 100 ), t 42  ( 120 ), t 43  ( 200 ), and t 44  ( 220 ). As described above, the light emitting unit  505  must operate in coordination with the photo sensor unit  504 , thus the counting numbers T corresponding to the capture signal F 41 , t 41 , t 42 , t 43 , and t 44 , are also used to generate the light emitting signal F 42 . For convenience, counting numbers t 41 , t 42 , t 43 , and t 44  are referred to hereinafter as original counting numbers for the light emitting signal F 42 .  
         [0025]     When the controller  503  detects that the frequency of the capture signal F 41  is less than a first preset value of 60 Hz, the controller  503  inserts two impulses P 51  and P 52  between two successive impulses P 421  and P 422  of the light emitting signal F 42 . In practice, this is done by evenly or randomly selecting some numbers between two successive original counting numbers as new counting numbers for the light emitting signal F 42 . Thus, the equivalent frequency corresponding to any two successive impulses of an updated light emitting signal F 42  generated by the controller  503  according to updated counting numbers is greater than a second preset value of 60 Hz, which is an acceptable flicker rate.  
         [0026]     In this embodiment as shown by the lower wave in  FIG. 4 , t 51  ( 133 ), t 52  ( 143 ), t 53  ( 166 ), and t 54  ( 176 ) are the new counting numbers selected by the controller  503  corresponding to the two inserted impulses P 51  and P 52 . Thus, the frequency of the updated light emitting signal F 42  generated by the controller  503  according to the updated counting numbers is increased to 90 Hz. Additionally, the equivalent frequency corresponding to any two successive impulses of the updated light emitting signal F 42  is 90 Hz, greater than the second preset value, 60 Hz.  
         [0027]     The photo sensor unit  504  executes the capture operation according to the impulses P 411  and P 412  of the capture signal F 41  as shown in the upper wave in  FIG. 4 . Similarly, the light emitting unit  505  executes the light emitting operation according to the impulses P 421 , P 51 , P 52 , and P 422  of the light emitting signal F 42  as shown by the lower wave in  FIG. 4 . In the upper wave, when the counting number presently generated by the counter  502  is t 41  ( 100 ) or t 43  ( 200 ), the voltage level of the capture signal F 41  switches from LOW to HIGH, and the photo sensor unit  504  executes at least one capture operation. When the counting number presently generated by the counter  502  is t 42  ( 120 ) or t 44  ( 220 ), the voltage level of the capture signal F 41  switches from HIGH to LOW, and the photo sensor unit  504  stops the capture operation. Similarly, in the lower wave, when the counting number presently generated by the counter  502  is t 41  ( 100 ), t 51  ( 133 ), t 53  ( 166 ), or t 43  ( 200 ), the voltage level of the light emitting signal F 42  switches from LOW to HIGH, and the light emitting unit  505  executes at least one light emitting operation. When the counting number presently generated by the counter  502  is t 42  ( 120 ), t 52  ( 143 ), t 54  ( 176 ), or t 44  ( 220 ), the voltage level of the light emitting signal F 42  switches from HIGH to LOW, and the light emitting unit  505  stops the light emitting operation.  
       Second Embodiment  
       [0028]      FIG. 5  is a process chart of the light control method of the present invention. For simplicity, description of  FIGS. 3 and 4  of the first embodiment are omitted. The optical mouse comprises a processing unit  501 , a photo sensor unit  504 , and a light emitting unit  505 . The light emitting unit  505  is an LED. The processing unit  501  comprises a counter  502  and a controller  503 .  
         [0029]     In step S 1 , the counter  502  sequentially generates counting numbers T for transmission to the controller  503 . The counting numbers T are increased from 0 to 3000 by increments of 1 in one second for use as a time division standard. In step S 2 , the controller  503  generates a capture signal F 41  and a light emitting signal F 42  according to two selected sets of counting numbers respectively. The capture signal F 41  and the light emitting signal F 42  are output to the photo sensor unit  504  and the light emitting unit  505  respectively. When a counting number presently generated by the counter  502  belongs to the selected set of counting numbers, the controller  503  outputs one impulse.  
         [0030]     In step S 3 , the photo sensor unit  504  executes at least one capture operation according to the impulse of the capture signal F 41 . In step S 4 , the light emitting unit  505  executes a light emitting operation according to the impulse of the light emitting signal F 42 . Note that because the light emitting unit  505  operates in coordination with the photo sensor unit  504 , the selected set of counting numbers for the light emitting signal F 42  must comprise all numbers in the selected set of counting numbers for the capture signal F 41 , such that the light emitting unit  505  executes the light emitting operation each time when the photo sensor unit  504  executes the capture operation.  
         [0031]     Next, in the conditional C 1 , the controller  503  detects whether the frequency of the capture signal F 41  is less than a first preset value, 60 Hz. There are two cases here. First, when the optical mouse is in a normal mode, for example being moved, the controller  503  selects all multiples of 2 as the selected set of counting numbers to generate the capture signal F 41 . The counting numbers T generated by the counter  502  are increased from 0 to 3000 by increments of 1 in one second. Thus, the frequency of the capture signal F 41  is 1500 Hz, greater than the first preset value, 60 Hz, so the process ends. It is noted here that in practice the controller  503  uses the same numbers as each selected set of counting numbers to generate the capture signal F 41  and the light emitting signal F 42 . Thus, the capture signal F 41  and the light emitting signal F 42  have the same frequency value. Therefore, the light emitting unit  505  executes the light emitting operation each time the photo sensor unit  504  executes the capture operation.  
         [0032]     Second, when the optical mouse is in a standby mode, for example being left idle for some duration, the two selected sets of counting numbers comprise different numbers. The selected set of counting numbers for the capture signal F 41  is determined so as to decrease the frequency of the capture signal F 41  to be 30 Hz for reducing power consumption. As shown by the upper wave in  FIG. 4 , the counting numbers T corresponding to the capture signal F 41  are t 41  ( 100 ), t 42  ( 120 ), t 43  ( 200 ), and t 44  ( 220 ).  
         [0033]     Because the frequency of the capture signal F 41 ,  30   z , is less than a first preset value, 60 Hz, the conditional C 1  is true, and the process goes to step S 5 . It is noted here that the light emitting unit  505  must operate in coordination with the photo sensor unit  504 , thus the counting numbers T corresponding to the capture signal F 41 , t 41 , t 42 , t 43 , and t 44 , are also used to generate the light emitting signal F 42 . For convenience, those counting numbers t 41 , t 42 , t 43 , and t 44  are referred to as original counting numbers for the light emitting signal F 42  hereinafter.  
         [0034]     In step S 5 , the controller  503  inserts two impulses P 51  and P 52  between two successive impulses P 421  and P 422  of the light emitting signal F 42  as shown in  FIG. 4 . In practice, this is done by evenly or randomly selecting some numbers between two successive original counting numbers as new counting numbers for the light emitting signal F 42 . Thus, the equivalent frequency corresponding to any two successive impulses of an updated light emitting signal F 42  generated by the controller  503  according to updated counting numbers is greater than a second preset value, 60 Hz, which is an acceptable flicker rate.  
         [0035]     In this embodiment as shown in the lower wave in  FIG. 4 , t 51  ( 133 ), t 52  ( 143 ), t 53  ( 166 ), and t 54  ( 176 ) are the new counting numbers selected by the controller  503  corresponding to the two inserted impulses P 51  and P 52 . Thus, the frequency of the updated light emitting signal F 42  generated by the controller  503  according to the updated counting numbers is increased to 90 Hz. Additionally, the equivalent frequency corresponding to any two successive impulses of the updated light emitting signal F 42  is 90 Hz, greater than the second preset value, 60 Hz. The process ends after the step S 5  is executed.  
         [0036]     It is noted here that the photo sensor unit  504  executes the capture operation according to the impulses P 411  and P 412  of the capture signal F 41  as shown by the upper wave in  FIG. 4 . Similarly, the light emitting unit  505  executes the light emitting operation according to the impulses P 421 , P 51 , P 52 , and P 422  of the light emitting signal F 42  as shown in the lower wave in  FIG. 4 . In the upper wave, when the counting number presently generated by the counter  502  is t 41  ( 100 ) or t 43  ( 200 ), the voltage level of the capture signal F 41  switches from LOW to HIGH, and the photo sensor unit  504  executes at least one capture operation. When the counting number presently generated by the counter  502  is t 42  ( 120 ) or t 44  ( 220 ), the voltage level of the capture signal F 41  switches from HIGH to LOW, and the photo sensor unit  504  stops the capture operation. Similarly, in the lower wave, when the counting number presently generated by the counter  502  is t 41  ( 100 ), t 51  ( 133 ), t 53  ( 166 ), or t 43  ( 200 ), the voltage level of the light emitting signal F 42  switches from LOW to HIGH, and the light emitting unit  505  executes at least one light emitting operation. When the counting number presently generated by the counter  502  is t 42  ( 120 ), t 52  ( 143 ), t 54  ( 176 ), or t 44  ( 220 ), the voltage level of the light emitting signal F 42  switches from HIGH to LOW, and the light emitting unit  505  stops the light emitting operation.  
         [0037]     In summary, when the photo sensor unit operates at a low frequency, the frequency of the light emitting unit can be adjusted accordingly to be greater than an acceptable flicker rate, thus avoiding perceptible flickers, reducing power consumption, and prolonging life of the light emitting unit.  
         [0038]     While the invention has been described by way of example and in terms of the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.