Abstract:
A cursor control method for an electronic device. The electronic device comprises a detecting window and a cursor shown on a monitor. An object is disposed on the detecting window. A laser diode with a laser cavity is provided to generate a plurality of laser beams with different polarization in a plurality of continuous time periods. A first and a second laser beams are guided to the detecting window, to impinge on the object along first and second incident axes, which reflects the first and second laser beams causing them to re-enter the laser cavity. A converting unit converts the electric variation of laser cavity caused by a self-mixing effect and Doppler periods into first and second electric signals to determine the displacement of the cursor.

Description:
BACKGROUND  
       [0001]     The invention relates to an optical pointing sensor, and in particular to an optical pointing sensor employing a self-mixing effect and time division multiplexing.  
         [0002]     A conventional mouse emits beams via a light emitter. The beams are reflected by an object and received by an optical receiver. Relative displacement between the optical mouse and the object, which is used to control the positioning of a cursor on a monitor, is obtained by analysis of the reflected beam signal, as disclosed in U.S. Pat. No. 6,246,482, U.S. Pat. No. 6,330,057, U.S. Pat. No. 6,424,407 and U.S. Pat. No. 6,452,683.  
         [0003]     Additionally, European Patent No. EP-A0 942 285 discloses a modified optical input device comprising an optical detecting module, which is typically disposed in an optical mouse, disposed in an arbitrary electronic device, such as a keyboard, a laptop or a personal digital assistant. A transparent window is disposed on a housing of the electronic device. When a finger moves on the transparent window, the relative displacement between the finger and the transparent window is available via optical detecting of a conventional optical mouse to control the cursor or other pointing devices.  
         [0004]     Because the conventional optical detecting module requires a light emitter and a light receiver and the positions thereof must be predetermined, the optical detecting module occupies considerable space and may be not be applicable in compact electronic devices.  
         [0005]     An embodiment of cursor control method of the invention, for an electronic device comprising a detecting window on which an object is disposed and a cursor shown on a monitor, comprises the following steps:  
         [0006]     A laser diode with a laser cavity, which generates a plurality of laser beams with different polarization in a plurality of continuous time periods, is provided.  
         [0007]     A first laser beam is guided to the detecting window and impinges on the object along a first incident axis, which reflects the first beam causing it to re-enter the laser cavity.  
         [0008]     Electric variation in the laser cavity in a plurality of first time periods is measured to generate a plurality of first electric signals.  
         [0009]     A second laser beam is guided to the detecting window and impinges on the object along a second incident axis, which reflects the second beam causing it to re-enter the laser cavity.  
         [0010]     Electric variation in the laser cavity in a plurality of second time periods is measured to generate a plurality of second electric signals.  
         [0011]     Displacements of the object in the first and second incident axes respectively are obtained from the first and second electric signals.  
         [0012]     The displacement component in a first measuring axis and a second measuring axis are calculated from the displacements in the first and second incident axes to determine displacement of the cursor.  
         [0013]     The cursor control method further comprises the following step:  
         [0014]     The displacement component in a third measuring axis is calculated from the predetermined angle and the first and second incident axes, wherein the first measuring axis, the second measuring axis and the third measuring axis are orthogonal. When the displacement component of the object in the third measuring axis exists, the displacement component of the object defines a select signal.  
         [0015]     The cursor control method further comprises the following step:  
         [0016]     A third laser beam is guided to the detecting window. When the third laser beam is reflected into the laser cavity, the displacement components in the first and second measuring axes define a scroll signal.  
         [0017]     The angle between the first and second incident axes is between 75° and 150°. The first incident axis has a predetermined angle between 0° and 45° with respect to the detecting window, and the second incident axis has a predetermined angle between 0° and 45° with respect to the detecting window.  
         [0018]     An embodiment of an electronic device of the invention comprises a main body having a monitor displaying a cursor, and an optical pointing sensor with a detecting window bearing an object. The optical pointing sensor comprises a laser diode, a second optical path, a detecting unit, a converting unit and an operation unit. The laser diode having a laser cavity generates a plurality of laser beams of different polarization in a plurality of continuous time periods. The first optical path guides a first laser beam to the detecting window to impinge on the object along a first incident axis, which reflects the first beam causing it to re-enter the laser cavity. The second optical path guides a second laser beam to the detecting window, to impinge on the object along a second incident axis, which reflects the second beam to re-enter the laser cavity. The detecting unit measures the electric variation of the laser cavity in a plurality of first and second time periods and generates a plurality of first and second electric signals, wherein the electric variation is caused by the Doppler effect of the first and second laser beam. The converting unit obtains displacements of the object in the first and second incident axes respectively from the first and second electric signals. The operation unit calculates the displacement component in a first measuring axis and a second measuring axis from the displacements in the first and second incident axes.  
         [0019]     The operation unit calculates the displacement component in a third measuring axis from the predetermined angle and the first and second incident axes. The first measuring axis, the second measuring axis and the third measuring axis are orthogonal. When the displacement component of the object in the third measuring axis exists, the displacement component of the object defines a select signal.  
         [0020]     A first optical guider and a first polariscope having first polarization on the first optical guider are disposed in the first optical path. A second optical guider and a second polariscope having second polarization on the second optical guider are disposed on the second optical path.  
         [0021]     The optical detecting device further comprises a third optical path on which a third optical guider and a polariscope having a third polarization on the third optical guider are disposed to guide a third laser beam to the detecting window and re-enter the laser cavity. When the third laser beam is reflected into the laser cavity, the displacement components in the first and second measuring axes define a scroll signal.  
         [0022]     The first, second and third optical guiders are optical fibers.  
         [0023]     The optical detecting sensor further comprises an optical coupling unit disposed between the laser diode, the first, second and third optical paths to couple the first, second and third laser beams into the first, second and third optical paths and guide the first, second and third laser beams re-entering the laser cavity.  
         [0024]     The first incident axis intersects the second incident axis at a measuring point. The angle between the first and second incident axes is between 75° and 150°. The first incident axis has a predetermined angle between 0° and 45° with respect to the detecting window, and the second incident axis has a predetermined angle between 0° and 45° with respect to the detecting window. In addition, the first incident axis and the second axis cannot intersect.  
         [0025]     The detecting unit can be a voltage sensor or current sensor for measuring electric variation in the laser cavity and outputting a corresponding signal. The operation unit and the control unit can be integrated into a micro-controller. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0026]     The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:.  
         [0027]      FIG. 1A  is a side view of an optical pointing sensor of the invention;  
         [0028]      FIG. 1B  is a top view of  FIG. 1A ;  
         [0029]      FIG. 1C  is a schematic view depicting focusing of the first laser beam and the second laser beam at different points;  
         [0030]      FIG. 2  is an operation sequence diagram of the optical pointing sensor of the invention;  
         [0031]      FIG. 3A  is a schematic view of the optical pointing sensor in the first time period;  
         [0032]      FIG. 3B  is a schematic view of the optical pointing sensor in the second time period;  
         [0033]      FIG. 4  depicts the measuring circuit of the optical pointing sensor of the invention;  
         [0034]      FIG. 5  depicts an electronic device with the optical pointing sensor of the invention;  
         [0035]      FIGS. 6A-6D  depict various embodiments of the optical pointing sensor of the invention;  
         [0036]      FIG. 7  depicts another embodiment of the electronic device of the invention. 
     
    
     DETAILED DESCRIPTION  
       [0037]     Referring to  FIGS. 1A and 1B , an optical pointing sensor  100  is used to detect displacement components in measuring axes of an object, such as a finger, on a detecting window. The optical pointing sensor  100  comprises a first optical path  21 , a second optical path  22 , and a laser diode  20  on a substrate  2 , a detecting unit  30 , a converting unit  40  and an operation unit  50 .  
         [0038]     The laser diode  20 , as disclosed in U.S. Pat. No. 5,465,263, can change the characteristics of a laser cavity  28  via external voltage or digital control to generate laser beams with different polarization. Thus the optical pointing sensor  100  controls the laser diode  20  via a simple circuit to generate laser beams with different polarization in a plurality of time periods, which serves as a detecting light source.  
         [0039]     The optical pointing sensor  100  comprises a first optical path  21  and a second optical path  22 . The front of the first optical path  21  is adjacent to the front of the second optical path  22 , and both fronts are aligned with the laser diode  20  to couple the laser beam from the laser diode  20  and guide the laser beam to the detecting window  4  and the object. The first optical path  21  comprises a first light guider  211  and a first polariscope  212  disposed at the front of the first light guider  211 . The second optical path  22  comprises a second light guider  221  and a second polariscope  222  disposed at the front of the second light guider  221 . Only a first laser beam P 1  with first polarization is allowed to pass through the first optical path  21 , and only a second laser beam P 2  with second polarization is allowed to pass through the second optical path  22 . The first and second light guider  221  and  222  are optical fibers. As the first and second optical paths  21  and  22  extend to the bottom of the detecting window  4  respectively, the first laser beam P 1  passes through the first optical path  21  along a first incident axis a 1  to the object, and the second laser beam P 2  passes through the second optical path  22  along a second incident axis a 2  to the object.  
         [0040]     The laser diode  20  serves as a light receiver. Part of the laser beams reflected or scattered by the object pass through the first optical path  21  or the second optical path  22  and re-enter the laser cavity  28  of the laser diode  20  causing a self-mixing effect in the laser cavity  28  resulting in electric variation in the laser cavity  28 . Reference to the self-mixing-effect can be found in following documents, “Small laser Doppler velocimeter based on the self-mixing effect in a diode laser”, Applied Optics, Vol. 27, No. 2, Jan. 15, 1988, Pages 379-385 and “Laser Doppler velocimeter based on the self-mixing effect in a fiber-coupled semiconductor laser”, Applied Optics, Vol. 31, No. 8, Jun. 20, 1992, Pages 3401-3408.  
         [0041]     Referring to the cited documents, when the object moves with respect to the laser diode  20 , the frequency of the reflected laser beam changes due to the Doppler Effect. The laser diode  20  generates a variation Δg due to the self-mixing effect. The variation Δg has the following correlation:  
         Δ   ⁢           ⁢   g     =       -     K   L       ·     (         4   ⁢     π   ·   v   ·   f   ·   t       c     +       4   ⁢     π   ·     L   0     ·   t       c       )           
 
 wherein K is a coupling constant of the laser cavity  28  and the reflected laser beam, v is the speed of the object with respect to the laser diode  20 , f is a primary frequency, t is the time period and c is the light velocity. 
 
         [0042]     The variation Δg can be measured via the detecting unit  30 , which generates an electric signal. The Doppler Effect modulates the frequency of the electric signal. The electric signal is digitized by the converting unit  40  and calculated by the operation unit  50  to obtain the displacement of the object in the first incident axis al and the second incident axis a 2  to acquire the displacement components in the first measuring axis x, the second measuring axis y and the third measuring axis z.  
         [0043]     In  FIGS. 1A and 1B , the first incident axis al and the second incident axis a 2  intersects at a measuring point O. The first incident axis a 1  and the second incident axis a 2  have a predetermined angle α which is from 0° to 75°. The angle β between the first and second incident axes a 1  and a 2  is from 75° to 150°. The displacement in the first incident axis a 1  and the second incident axis a 2  can be obtained by the geometric relationship between the first incident axis a 1 , the second incident axis a 2  and the detecting window  4 . The displacement includes distance, velocity and direction. The displacement component in the first measuring axis x and the second measuring axis y can be calculated via the geometric relationship between the first incident axis a 1 , the second incident axis a 2  and the detecting window  4 . Additionally, in  FIG. 1C , it is possible that the first laser beam P 1  and the laser beam P 2  are focused at a point near the measuring point O rather than the measuring point O.  
         [0044]     Although the optical pointing sensor  100  has only two incident axes, the operation unit  50  is capable of determining the displacement component in the z axis via angle α and β. When the displacement has a component in the z axis, the displacement defines a select signal, whereby the optical pointing sensor  100  is able to detect the x-y displacement component and the selecting operation. The detecting window can be a virtual surface or a physical surface, such as a surface comprised of transparent material (glass or plastic).  
         [0045]     Referring to  FIGS. 2 and 3 A, a first time period t 1  can be divided into three sub-time periods, tp 1 , ts 1  and td 1 . In period tp 1 , the laser diode  20  provides the first laser beam P 1  passing through the first optical path  21  along the first incident axis to the object, and the reflected laser beam passing through the first optical path  21  re-enters the laser cavity  28 . In period ts 1 , the laser diode  20  creates a variation due to self-mixing effect. In period td 1 , the detecting unit  30 , converting unit  40  and the operation unit  50  acquire the displacement in the first incident axis a 1 . In  FIGS. 2 and 3 B, the first time t 2  can be divided into three sub time periods, tp 2 , td 2  and td 2 . In period tp 2 , the laser diode  20  provides the second laser beam P 1  passing through the second optical path  22  along the second incident axis to the object, and the reflected laser beam passing through the second optical path  22  re-enters the laser cavity  28 . In period ts 1 , the laser diode  20  creates a variation due to self-mixing effect. In period td 1 , the detecting unit  30 , converting unit  40  and the operation unit  50  acquire the displacement in the second incident axis a 2 . The displacement components in the first measuring axis x, the second measuring axis y and the third measuring axis z is available via the operation unit  50 .  
         [0046]      FIG. 4  depicts a measuring circuit of the optical pointing sensor. The laser diode  20  is serially connected to a voltage source  31  and a resistance  32  to serve as a voltage divider. In this embodiment, the detecting unit  30  is a voltage sensor serially connected to a capacitor  33  to shield high frequency noise. When the laser diode  20  generates a variation Δg, the detecting unit  30  detects a voltage variation which is converted into a digital signal comprising distance, velocity and direction via the converting unit  40 . The operation unit  50  calculates the digital signal to obtain the displacement component in the measuring axes. The detecting unit  30  can be a current sensor, and the detecting method is well known.  
         [0047]      FIG. 5  depicts an electronic device with the optical pointing sensor of the invention. As the optical pointing sensor is so compact, it is applicable to handheld devices, such as laptops, cell phones, personal digital assistants and a remote control unit for controlling a cursor. For the sake of simplicity, only a personal digital assistant is cited in  FIG. 5 .  
         [0048]     In  FIG. 5 , a personal digital assistant (PDA)  200  has a screen  250  displaying a cursor  255 . The optical pointing sensor  100  is disposed under the screen  250  and connected to a control unit  260  of the PDA  200 . When a finger moves on the optical pointing sensor  100 , control unit  260  moves the cursor  255  according to the x and y displacement measured by the optical pointing sensor  100  and determines the select signal according to z displacement.  
         [0049]      FIGS. 6A  to  6 D depict various other embodiments of the optical pointing sensor comprising optical coupling units coupling laser beams with different polarizations into different optical paths. Referring to  FIG. 6A , the optical pointing sensor has a first polariscope  25   a  and a second polariscope  25   b . The first polariscope  25   a  allows only allows passage of the first laser beam P 1  with the first polarization therethrough and reflects other laser beams with other polarization. The second polariscope  25   b  only allows passage of the third laser beam P 3  with third polarization therethrough and reflects other laser beams with other polarization. The first, second and third laser beam sP 1 ˜P 3  are coupled into the first, second and third optical paths  21 ,  22  and  23  to measure displacement of an object in three incident axes for cursor control.  
         [0050]     The embodiment of the optical coupling unit of  FIG. 6B , similar to that of  FIG. 6A , comprises two polariscopes  25   a  and  25   b  and a reflective mirror  26  which improves the design of the optical path and functions to split the laser beams.  
         [0051]      FIG. 6C  depicts an optical coupling unit comprising two polariscopes  25   a  and  25   b  and a lens  27  configured in a triangle. The laser diode  20  is disposed in the middle of the triangle. The incident direction of each laser beam has a 60° angle with respect to each lens, whereby the first, second and third laser beams P 1 ˜P 3  can be coupled into the first, second and third optical paths  21 ,  22  and  23 .  
         [0052]      FIG. 6D  depicts an optical coupling unit comprising three polariscopes  25   a ,  25   b  and  25   c  and a lens  27  configured in a square. The laser diode  20  is disposed in the middle of the square. The incident direction of each laser beam has a 45° angle with respect to each lens, whereby the first, second, third and fourth laser beams P 1 ˜P 4  can be coupled into the first, second, third and fourth optical paths  21 ,  22 ,  23  and  24 .  
         [0053]      FIG. 7  depicts another embodiment of the electronic device of the invention. In this embodiment, a cell phone is cited. For the sake of simplicity, depiction of the screen and keypad thereof are omitted.  
         [0054]     In  FIG. 7 , a mobile phone  300  comprises an optical pointing sensor  100 , a control unit  360  and three detecting windows  4   a ,  4   b  and  4   c . The first detecting window  4   a  is disposed on the right side of the cell phone  300 . The second and third detecting windows  4   b  and  4   c  are disposed on the left side of the cell phone  300 . When the cell phone  300  is held by a right hand, the thumb corresponds to the first detecting window  4   a , the first finger corresponds to the second detecting window  4   b  and the second finger corresponds to the third detecting window  4   c.    
         [0055]     The optical pointing sensor  100  has four optical paths  21 ˜ 24 . The first optical path  21  and the second optical path  22  are used to measure the thumb displacement in x, y and z axes on the first detecting window  4   a . The third optical path  23  detects the first finger displacement in the z axis on the second detecting window  4   b . The fourth optical path  24  detects the second finger displacement in the z axis on the second detecting window  4   c . When the thumb moves with respect to the first detecting window  4   a , control unit  360  controls the cursor on the screen to move or perform a select operation. When the first finger touches the second detecting window  4   b  or moves with respect to the z axis of the second detecting window  4   b , the reflected laser beam of a third laser beam enters the laser cavity of the laser diode. The movement of the thumb on the first detecting window  4   a  can be defined as a scroll signal used to scroll the screen. When a second finger touches the third detecting window  4   c  or moves with respect to the z axis of the third detecting window  4   c , the reflected laser beam of a fourth laser beam enters the laser cavity of the laser diode to perform a particular hot key operation or other function via control unit  360  or a software application program.  
         [0056]     While the invention has been described by way of example and in terms of preferred embodiment, it is to be understood that the invention is not limited thereto. 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.