Patent Publication Number: US-10775934-B2

Title: Optical touch apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This non-provisional application claims priority under 35 U.S.C. § 119(a) to Patent Application No. 201810112652.2 filed in China, P.R.C. on Feb. 5, 2018, the entire contents of which are hereby incorporated by reference. 
     BACKGROUND 
     Technical Field 
     The instant disclosure relates to a touch apparatus, and in particular, to an optical touch apparatus. 
     Related Art 
     A current conventional projection-type optical touch apparatus mainly consists of a light source, a video camera, and a processor. The light source can project a light beam onto a screen, and an area of the screen that is irradiated becomes an operation area. When an object is in the operation area, the object blocks a part of the light beam that is irradiated by the light source onto the screen to form an object shadow corresponding to the object on the screen, the video camera is used to capture the object, the object shadow, and an image of the operation area, and the processor reads an image of a contact point formed when the object contacts the object shadow, to analyze position information of the contact point in the image by using an image analysis technique. 
     Another conventional projection-type touch apparatus has an outer frame defining a detection area, the outer frame has a plurality of light emitting elements disposed on sidewalls thereof, a light homogenizing layer that is used to homogenize a light source generated by the light emitting elements, and a video camera disposed at a corner thereof and used to shoot the detection area, and the camera is electrically connected to a control apparatus for analyzing image positioning. When a user clicks and touches to enter the detection area, the light source is also blocked at a touch position, and at the same time, the video camera transmits a picture shot in the detection area to the control apparatus to perform image positioning and analyzing, to determine the touch position. 
     The two conventional projection-type touch apparatuses both use a light blocking manner to determine a touch position, and therefore, are easily influenced by other surrounding light beams, causing a problem of misjudgment. Furthermore, the conventional projection-type touch apparatuses also need to project a light source onto a flat surface, to avoid non-uniform light reflection and not to influence determining accuracy. 
     SUMMARY 
     In view of this, an embodiment provides an optical touch apparatus, including a light source unit, an optical signal processing unit, and a position computation unit. The light source unit emits light beams and generates three reference light spots at different positions. The optical signal processing unit is configured to receive three pieces of reflected light information reflected and propagated by the three reference light spots and analyze the three pieces of reflected light information to correspondingly generate three pieces of optical analysis information, each of the three pieces of optical analysis information includes a piece of vibration wave information and a piece of vibration time point information, the piece of vibration wave information includes a touch vibration wave, and the piece of vibration time point information refers to time points at which the touch vibration wave is propagated to reach each of the reference light spots. The position computation unit is electrically connected to the optical signal processing unit and configured to: receive each of the pieces of optical analysis information, obtain a piece of light spot position information of each of the reference light spots and a piece of vibration wave velocity information, the vibration wave velocity information referring to a propagation velocity of the touch vibration wave, and further compute a piece of touch position information according to each of the pieces of light spot position information, each of the pieces of vibration time point information, and the piece of vibration wave velocity information, the touch position information referring to a relative epicenter position that generates the touch vibration wave. 
     As above, the optical touch apparatus in this embodiment of the instant disclosure generates the three reference light spots through the light source unit. When a touch behavior occurs, the optical signal processing unit analyzes the reflected light information reflected and propagated by the three reference light spots, to obtain the time points at which the touch vibration wave generated by the touch is propagated to reach each of the reference light spots, and computes a touch position according to each time point, a wave velocity of the touch vibration wave, and the positions of the three reference light spots. Therefore, this embodiment of the instant disclosure can enhance determining accuracy of a position without being influenced by other surrounding light beams, and furthermore, is not limited to being used on a flat touch surface, thereby greatly enhancing practicability. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of touching of an embodiment of the optical touch apparatus according to the instant disclosure; 
         FIG. 2  is a block diagram of hardware of an embodiment of the optical touch apparatus according to the instant disclosure; 
         FIG. 3  is a schematic diagram of propagation of a touch vibration wave of an embodiment of the optical touch apparatus according to the instant disclosure; 
         FIG. 4  is a block diagram of hardware of another embodiment of the optical touch apparatus according to the instant disclosure; 
         FIG. 5  is a schematic diagram of irradiation of an embodiment of the optical touch apparatus according to the instant disclosure; 
         FIG. 6  is a schematic diagram of irradiation of another embodiment of the optical touch apparatus according to the instant disclosure; and 
         FIG. 7  is a schematic diagram of propagation of a touch vibration wave of another embodiment of the optical touch apparatus according to the instant disclosure. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a schematic diagram of touching of an embodiment of the optical touch apparatus according to the instant disclosure, and  FIG. 2  is a block diagram of hardware of an embodiment of the optical touch apparatus according to the instant disclosure. As shown in  FIG. 1  and  FIG. 2 , in this embodiment, the optical touch apparatus  1  includes a light source unit  10 , an optical signal processing unit  20 , and a position computation unit  30 . 
     In an embodiment, the light source unit  10  may be specifically a projection light source (for example, a laser unit, an infrared unit, or an ultraviolet unit), to emit a light beam to irradiate an object. For example, as shown in  FIG. 1 , the light source unit  10  may be a laser unit that emits a laser beam. In this embodiment, the light source unit  10  emits three laser beams L 1 , L 2 , and L 3  to correspondingly irradiate an operation area A (for example, a desktop, a wall, a ground, or a screen) with a reflecting function and generate three reference light spots M 1 , M 2 , and M 3  at different positions in the operation area A. In the embodiment in  FIG. 1 , the three reference light spots M 1 , M 2 , and M 3  are respectively located at three corners of the operation area A, but embodiments are not limited thereto. The three reference light spots M 1 , M 2 , and M 3  may be respectively located at any other positions in the operation area A. A user may perform a touch input in the operation area A. 
     In an embodiment, the optical signal processing unit  20  may be specifically a micro-processor, a micro-controller, a field programmable gate array, or a logic circuit. As shown in  FIG. 1  and  FIG. 2 , in this embodiment, the optical signal processing unit  20  and the light source unit  10  are located at a same side of the operation area A, to receive three pieces R 1 , R 2 , and R 3  of reflected light information respectively reflected and propagated by the three reference light spots M 1 , M 2 , and M 3 . As shown in  FIG. 1 , in an embodiment, the optical signal processing unit  20  may include a light-sensitive element  21 , and for example, the light-sensitive element  21  may be a charge-coupled device (CCD), a complementary metal-oxide semiconductor (CMOS), a CMOS active pixel sensor, a photodiode, or a photoresistor, to receive the three pieces R 1 , R 2 , and R 3  of reflected light information through the light-sensitive element  21 . 
     Furthermore, as shown in  FIG. 1  and  FIG. 2 , the optical signal processing unit  20  may analyze the three pieces R 1 , R 2 , and R 3  of reflected light information to correspondingly generate three pieces D 1 , D 2 , and D 3  of optical analysis information. Each of the three pieces D 1 , D 2 , and D 3  of optical analysis information includes a piece of vibration wave information and a piece of vibration time point information, the vibration wave information includes a touch vibration wave W, and the piece of vibration time point information is time points at which the touch vibration wave W is propagated to reach each of the reference light spots M 1 , M 2 , and M 3 . 
     Specifically, as shown in  FIG. 1  and  FIG. 3 , when the user performs a touch input in the operation area A, a touched position in the operation area A generates a piece of vibration wave information. For example, in the embodiment in  FIG. 1 , the user contacts a position in the operation area A by a finger to form a touch point A 1 , the touch point A 1  that is touched generates vibration wave information containing the touch vibration wave W. In specific, the touch vibration wave W is a vibration wave generated when an object is touched, and the touch vibration wave W is gradually diffused in all directions. When it is assumed that the surface of the operation area A is a uniform flat surface, the touch vibration wave W is uniformly diffused and propagated in all directions by using the touch point A 1  as a center. Therefore, as shown in  FIG. 3 , the touch vibration wave W is propagated toward each of the reference light spots M 1 , M 2 , and M 3 . When the touch vibration wave W is respectively propagated to reach each of the reference light spots M 1 , M 2 , and M 3 , the vibration wave information is transmitted to the optical signal processing unit  20  along with the pieces R 1 , R 2 , and R 3  of reflected light information reflected and propagated by each of the reference light spots M 1 , M 2 , and M 3 , and the optical signal processing unit  20  may respectively analyze each of the pieces R 1 , R 2 , and R 3  of reflected light information carrying the vibration wave information and take the touch vibration wave W in the vibration wave information and the time points at which the touch vibration wave W is respectively propagated to reach each of the reference light spots M 1 , M 2 , and M 3 . 
     In the embodiment in  FIG. 1  and  FIG. 3 , since distances between each of the reference light spots M 1 , M 2 , and M 3  and the touch point A 1  are different, the time points at which the touch vibration wave W is respectively propagated to reach each of the reference light spots M 1 , M 2 , and M 3  are also different. As shown in  FIG. 3 , in this embodiment, since, compared with the reference light spot M 2 , the reference light spot M 1  is far away from the touch point A 1 , a time point at which the touch vibration wave W is propagated to reach the reference light spot M 1  is later than a time point at which the touch vibration wave is propagated to reach the reference light spot M 2 . 
     The optical signal processing unit  20  may learn that the pieces R 1 , R 2 , and R 3  of reflected light information carry the vibration wave information in the following manner, to obtain the vibration wave information contained in each pieces D 1 , D 2 , and D 3  of optical analysis information. For example, in an embodiment, the touch vibration wave W is in a frequency domain that is different from a frequency domain of laser beams L 1 , L 2 , and L 3 . For example, the laser beams L 1 , L 2 , and L 3  emitted by the light source unit  10  are at a high frequency (for example, from 3 MHz to 300 MHz), the frequency domain of the touch vibration wave W may be a low frequency domain (for example, below 3 KHz). However, the foregoing frequency values are only examples, but embodiments are not limited thereto, and the low frequency may range from 3 KHz to 30 KHz, 300 Hz to 3 KHz, or 30 Hz to 300 Hz. The optical signal processing unit  20  may recognize the pieces R 1 , R 2 , and R 3  of reflected light information carrying the touch vibration wave W according to a difference between a frequency domain of the touch vibration wave W and a frequency domain of the laser beams L 1 , L 2 , and L 3 . The frequency domain of the touch vibration wave W and the frequency domain of the laser beams L 1 , L 2 , and L 3  are only examples. Actually, the touch vibration wave W and the laser beams L 1 , L 2 , and L 3  can be recognized provided that they belong to different frequency domains. For example, the frequency domain of the touch vibration wave W may be a low frequency (LF), a very low frequency (VLF), an ultra low frequency (ULF), or a super low frequency (SLF), and the frequency domain of the projection light L 1  may be a medium frequency (MF), a high frequency (HF), a very high frequency (VHF), an ultra high frequency (UHF), or a super high frequency (SHF), but embodiments are not limited thereto. 
     In another embodiment, the light source unit  10  may also be an optical modulation unit that modulates the emitted laser beams L 1 , L 2 , and L 3  to be modulation light beams (modulation lighting). For example, the laser beams L 1 , L 2 , and L 3  may be high-frequency signal light beams between 3 MHz and 300 MHz, the pieces R 1 , R 2 , and R 3  of reflected light information reflected and propagated by each of the reference light spots M 1 , M 2 , and M 3  are correspondingly modulated reflected light information (carrying the vibration wave information), and the optical signal processing unit  20  may demodulate the pieces of modulated reflected light information according to a Fourier transformation, to generate the pieces D 1 , D 2 , and D 3  of optical analysis information. Furthermore, since the laser beams L 1 , L 2 , and L 3  and the pieces R 1 , R 2 , and R 3  of reflected light information are modulation signal light beams, they may be prevented from being interfered with other surrounding light beams having other frequency signals, so that the optical signal processing unit  20  can analyze and generate the pieces D 1 , D 2 , and D 3  of optical analysis information more accurately and rapidly. 
     Alternatively, in an embodiment, the optical signal processing unit  20  may also obtain a piece of laser spot information according to each of the pieces R 1 , R 2 , and R 3  of reflected light information and correspondingly obtain the vibration wave information in each of the pieces D 1 , D 2 , and D 3  of optical analysis information through analyzing the laser spot information. For example, the optical signal processing unit  20  may be a laser analyzer to analyze each piece of laser spot information, to obtain a period, a wavelength, an amplitude, a frequency, a phase, or a combination thereof of a laser spot generated correspondingly when the laser beams L 1 , L 2 , and L 3  irradiate the operation area A. The optical signal processing unit  20  may recognize the pieces R 1 , R 2 , and R 3  of reflected light information carrying the touch vibration wave W according to a difference between the touch vibration wave W and the period, wavelength, amplitude, frequency, phase, or a combination thereof of the laser spot. 
     As shown in  FIG. 1  to  FIG. 3 , the position computation unit  30  may be specifically a micro-processor, a micro-controller, a field programmable gate array, or a logic circuit. The position computation unit  30  is eclectically connected to the optical signal processing unit  20  to receive the pieces D 1 , D 2 , and D 3  of optical analysis information analyzed by the optical signal processing unit  20 . The position computation unit  30  further obtains light spot position information (X 1 , Y 1 ), (X 2 , Y 2 ), and (X 3 , Y 3 ) of each of the reference light spots M 1 , M 2 , and M 3  and vibration wave velocity information V, and the vibration wave velocity information V refers to a propagation velocity of the touch vibration wave W. For example, as shown in  FIG. 3 , when a position in the operation area A is touched, the touch vibration wave W is generated and is propagated in all directions by using the operation area A as a medium, the vibration wave velocity information V is a wave velocity (for example, five meters per second, ten meters per second, or fifteen meters per second) of propagation of the touch vibration wave W and may be different according to a material of the operation area A (for example, a desktop, a wall, a ground, or a screen). In some embodiments, the vibration wave velocity information V may be built in the position computation unit  30  or input into the position computation unit  30  from the outside (as shown in  FIG. 2 ), but embodiments are not limited thereto. 
     In some embodiments, the position computation unit  30  may obtain light spot position information (X 1 , Y 1 ), (X 2 , Y 2 ), and (X 3 , Y 3 ) of each of the reference light spots M 1 , M 2 , and M 3  in the following manner. As shown in  FIG. 1  to  FIG. 3 , the optical signal processing unit  20  may analyze the three pieces R 1 , R 2 , and R 3  of reflected light information respectively reflected and propagated by the three reference light spots M 1 , M 2 , and M 3 , and then learns the positions of the three reference light spots M 1 , M 2 , and M 3  to obtain the light spot position information (X 1 , Y 1 ), (X 2 , Y 2 ), and (X 3 , Y 3 ) and transmit the light spot position information (X 1 , Y 1 ), (X 2 , Y 2 ), and (X 3 , Y 3 ) to the position computation unit  30 , so that the position computation unit  30  may obtain the light spot position information (X 1 , Y 1 ), (X 2 , Y 2 ), and (X 3 , Y 3 ) of the three reference light spots M 1 , M 2 , and M 3 . 
     Alternatively, as shown in  FIG. 4 , in another embodiment, the position computation unit  30  may be electrically connected to the light source unit  10 , and the light spot position information (X 1 , Y 1 ), (X 2 , Y 2 ), and (X 3 , Y 3 ) obtained by the position computation unit  30  are transmitted by the light source unit  10 . Specifically, a position of the operation area A onto which a light beam is irradiated may be determined by the light source unit  10  by default. For example, in an embodiment in  FIG. 1 , directions and angles of the three laser beams L 1 , L 2 , and L 3  emitted by the light source unit  10  may be determined in advance, so that the three laser beams L 1 , L 2 , and L 3  are correspondingly irradiated onto the predetermined positions in the operation area A to form the three reference light spots M 1 , M 2 , and M 3 . Therefore, the light source unit  10  may obtain light spot position information (X 1 , Y 1 ), (X 2 , Y 2 ), and (X 3 , Y 3 ) of the three reference light spots M 1 , M 2 , and M 3  in advance and transmit the light spot position information (X 1 , Y 1 ), (X 2 , Y 2 ), and (X 3 , Y 3 ) to the position computation unit  30 . 
     Furthermore, as shown in  FIG. 1  to  FIG. 3 , the position computation unit  30  may compute touch position information (X c , Y c ) according to the light spot position information (X 1 , Y 1 ), (X 2 , Y 2 ), and (X 3 , Y 3 ), and information of vibration time points at which the touch vibration wave W is respectively propagated to reach each of the reference light spots M 1 , M 2 , and M 3 , and vibration wave velocity information V. As shown in  FIG. 3 , the touch position information (X c , Y c ) refers to a relative epicenter position (that is, the position of the touch point A 1 ) generating the touch vibration wave W. A computation manner of the touch position information (X c , Y c ) is described as follows with reference to the drawings. 
     As shown in  FIG. 1  to  FIG. 3 , according to the description in the foregoing embodiment, the position computation unit  30  may respectively obtain the light spot position information (X 1 , Y 1 ), (X 2 , Y 2 ), and (X 3 , Y 3 ) of the three reference light spots M 1 , M 2 , and M 3  and the vibration wave velocity information V of the touch vibration wave W, and when the touch behavior occurs (for example, the user contacts a position in the operation area A by a finger to form the touch point A 1 ), the optical signal processing unit  20  may analyze the three pieces R 1 , R 2 , and R 3  of reflected light information respectively reflected and propagated by the three reference light spots M 1 , M 2 , and M 3  to obtain the time points at which the touch vibration wave W is propagated to reach each of the reference light spots M 1 , M 2 , and M 3 . For example, the time point at which the touch vibration wave W is propagated to reach the reference light spot M 1  is T 1 , the time point at which the touch vibration wave W is propagated to reach the reference light spot M 2  is T 2 , and the time point at which the touch vibration wave W is propagated to reach the reference light spot M 3  is T 3 . Accordingly, it is assumed that a touch time point of the touch point A 1  is T c , and it is known that the distances between the touch point A 1  (X c , Y c ) and the position information (X 1 , Y 1 ), (X 2 , Y 2 ), and (X 3 , Y 3 ) of the three light spots, and the vibration wave velocity information V have the following relationships in the three equations.
 
( T   1   −T   c )× V =√{square root over (( X   1   −X   c ) 2 +( Y   1   −Y   c ) 2 )}
 
( T   2   −T   c )× V =√{square root over (( X   2   −X   c ) 2 +( Y   2   −Y   c ) 2 )}
 
( T   3   −T   c )× V =√{square root over (( X   3   −X   c ) 2 +( Y   3   −Y   c ) 2 )}
 
     (X 1 , Y 1 ), (X 2 , Y 2 ), and (X 3 , Y 3 ) and V are all known numbers and T 1 , T 2 , and T 3  are known time points. Therefore, solutions of the three unknown numbers T c , X c , and Y c  can be obtained according to the foregoing three simultaneous equations, so as to obtain the touch point A 1  (X c , Y c ) through computation. For example, in an embodiment, if assuming that T c  is a certain time point, approximate solutions of X c  and Y c  may be obtained by using an iterative operation according to the method of least square, so as to obtain the touch point A 1  (X c , Y c ). 
     The following describes an example of a computation method in which the three simultaneous equations use the method of least square. It is assumed that the touch time point of the touch point A 1  is T c  and the time for propagating the touch vibration wave W is t i (X, Y), and it can be known through theoretical computation that, the measured time for an i th  reference light spot M 1 , M 2 , and M 3  should be π i =t i (X, Y)+T c , where 
     
       
         
           
             
               
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     The theoretical computation and the actual measurement have a following error value res i :
 
res i   =T   i −π i   c   i   −t   i ( x,y )  (1)
 
     c i  is an actually measured transmission time for respectively propagating the touch vibration wave W to the reference light spots M 1 , M 2 , and M 3 , and according to the computation manner of the method of least square, X=x+dx, Y=y+dy, c=t+dt are substituted into the foregoing formula (1), then the formula (1) is rewritten as a Taylor expansion to be arranged as the following formula: 
     
       
         
           
             
               
                 
                   
                     
                       
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     The foregoing formula (2) is treated by using the method of least square, making: 
     
       
         
           
             
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     To minimize the error value, 
     
       
         
           
             
               
                 
                   
                     
                       
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     The foregoing formula (3) is substituted into f(x,y) to obtain three equation sets which are rewritten as a matrix form: 
     
       
         
           
             
               
                 
                   
                     
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                                 ∑ 
                                 
                                   i 
                                   = 
                                   1 
                                 
                                 3 
                               
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               
                                 b 
                                 i 
                               
                             
                           
                           
                             3 
                           
                         
                       
                       ] 
                     
                     ⁡ 
                     
                       [ 
                       
                         
                           
                             dx 
                           
                         
                         
                           
                             dy 
                           
                         
                         
                           
                             dt 
                           
                         
                       
                       ] 
                     
                   
                   = 
                   
                     [ 
                     
                       
                         
                           
                             
                               ∑ 
                               
                                 i 
                                 = 
                                 1 
                               
                               3 
                             
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             
                               
                                 res 
                                 i 
                               
                               ⁢ 
                               
                                 a 
                                 i 
                               
                             
                           
                         
                       
                       
                         
                           
                             
                               ∑ 
                               
                                 i 
                                 = 
                                 1 
                               
                               3 
                             
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             
                               
                                 res 
                                 i 
                               
                               ⁢ 
                               
                                 b 
                                 i 
                               
                             
                           
                         
                       
                       
                         
                           
                             
                               ∑ 
                               
                                 i 
                                 = 
                                 1 
                               
                               3 
                             
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             
                               res 
                               i 
                             
                           
                         
                       
                     
                     ] 
                   
                 
               
               
                 
                   ( 
                   4 
                   ) 
                 
               
             
           
         
       
     
     Suitable numbers x=x 0 , y=y 0 , and t=t 0  are selected to substitute into the foregoing formula (4), res i  is substituted into the value of the foregoing formula (1), and the values of dx, dy, and dt can be computed, then, x=x 1 =x 0 +dx, y=y 1 =y 0 +dy, t=t 1 =t 0 +dt are substituted into the formula (4) to compute new values of dx, dy, and dt, iteration is repeated till √{square root over (dx 2 +dy 2 )}&lt;m, in which m is an order of magnitude of the error after the computation formula is converged, and an approximate value of a coordinate of the touch point A 1  (X c , Y c ) is finally obtained. 
     In an actual example, as shown in  FIG. 3 , it is assumed that a coordinate of an unknown touch point A 1  (X c , Y c ) is (2, 7), the known light spot position information (X 1 , Y 1 ), (X 2 , Y 2 ), and (X 3 , Y 3 ) of the three reference light spots M 1 , M 2 , and M 3  is respectively (0, 8), (10, 8), and (10, 0), the time points T 1 , T 2 , and T 3  at which the touch vibration wave W is propagated to reach each of the reference light spots M 1 , M 2 , and M 3  are respectively 3 hours, 5 minutes, and 10.063 seconds, 3 hours, 5 minutes, and 9.224 seconds, and 3 hours, 5 minutes, and 9.806 seconds, and the vibration wave velocity information V is 10 mm/s. Firstly, the coordinate of the touch point A 1  (X c , Y c ) may be guessed to be (5, 4), for example, the guessed coordinate may be a coordinate that maintains a same distance from (X 1 , Y 1 ), (X 2 , Y 2 ), and (X 3 , Y 3 ) respectively, and it is assumed that the touch time point T c  is 3 hours, 5 minutes, and 8 seconds. Therefore, the propagation time for propagating the touch vibration wave W to the reference light spot M 1  is 1.224 seconds, the propagation time for propagating the touch vibration wave W to the reference light spot M 2  is 1.806 seconds, and the propagation time for propagating the touch vibration wave W to the reference light spot M 3  is 2.063 seconds, the guessed value is substituted into the foregoing formulas (1) to (3), and the following parameters are calculated: 
     
       
         
           
             { 
             
               
                 
                   
                     
                       
                         res 
                         1 
                       
                       = 
                       0.6297 
                     
                   
                 
                 
                   
                     
                       
                         res 
                         2 
                       
                       = 
                       
                         - 
                         0.2093 
                       
                     
                   
                 
                 
                   
                     
                       
                         res 
                         3 
                       
                       = 
                       0.3727 
                     
                   
                 
               
               , 
               
                 { 
                 
                   
                     
                       
                         
                           
                             a 
                             1 
                           
                           = 
                           
                             - 
                             0.0781 
                           
                         
                       
                     
                     
                       
                         
                           
                             a 
                             2 
                           
                           = 
                           0.0781 
                         
                       
                     
                     
                       
                         
                           
                             a 
                             3 
                           
                           = 
                           
                             - 
                             0.0781 
                           
                         
                       
                     
                   
                   , 
                   
                     { 
                     
                       
                         
                           
                             
                               b 
                               1 
                             
                             = 
                             0.0625 
                           
                         
                       
                       
                         
                           
                             
                               b 
                               2 
                             
                             = 
                             
                               - 
                               0.0625 
                             
                           
                         
                       
                       
                         
                           
                             
                               b 
                               3 
                             
                             = 
                             
                               - 
                               0.0625 
                             
                           
                         
                       
                     
                   
                 
               
             
           
         
       
     
     The foregoing parameters are substituted into the formula (4) to obtain: 
     
       
         
           
             
               
                 [ 
                 
                   
                     
                       0.0183 
                     
                     
                       
                         - 
                         0.0049 
                       
                     
                     
                       
                         - 
                         0.0781 
                       
                     
                   
                   
                     
                       
                         - 
                         0.0049 
                       
                     
                     
                       0.0117 
                     
                     
                       
                         - 
                         0.0625 
                       
                     
                   
                   
                     
                       
                         - 
                         0.0781 
                       
                     
                     
                       
                         - 
                         0.0625 
                       
                     
                     
                       3 
                     
                   
                 
                 ] 
               
               ⁡ 
               
                 [ 
                 
                   
                     
                       dx 
                     
                   
                   
                     
                       dy 
                     
                   
                   
                     
                       dt 
                     
                   
                 
                 ] 
               
             
             = 
             
               [ 
               
                 
                   
                     
                       - 
                       0.0946 
                     
                   
                 
                 
                   
                     0.0291 
                   
                 
                 
                   
                     0.7931 
                   
                 
               
               ] 
             
           
         
       
     
     The simultaneous equations are solved to obtain dx=3.7266, dy=2.0570, and dt=0.2102, thereby obtaining a coordinate point that is (x+dx, y+dy)=(5−3.7266, 4+2.0570)=(1.2734, 6.0570). After (1.2734, 6.0570) is substituted into the formula to perform an iterative operation, a new coordinate point (2.1818, 7.0058) is obtained again, and the coordinate point (2.1818, 7.0058) is slightly different from the coordinate (2, 7) of the touch point A 1  (X c , Y c ), a coordinate point (2.0036, 7.0016) is obtained after performing the iterative operation for many times, and when a change of the coordinate point is less than 0.0001 if the iterative operation is continued to be performed, a final coordinate point (2.0036, 7.0016) that is different from the coordinate (2, 7) of the touch point A 1  (X c , Y c ) by being less than 1% is obtained. 
     In view of the above, the optical touch apparatus  1  in this embodiment of the instant disclosure generates the three reference light spots M 1 , M 2 , and M 3  through the light source unit  10 . When a touch behavior occurs, the optical signal processing unit  20  analyzes the reflected light information R 1 , R 2 , and R 3  reflected and propagated by the three reference light spots M 1 , M 2 , and M 3 , to obtain the time points at which the touch vibration wave W generated by the touch is propagated to reach each of the reference light spots M 1 , M 2 , and M 3 , and computes a touch position (X c , Y c ) according to each time point, a wave velocity of the touch vibration wave W, and the positions (X 1 , Y 1 ), (X 2 , Y 2 ), and (X 3 , Y 3 ) of the three reference light spots M 1 , M 2 , and M 3 . Therefore, compared with a conventional method of determining a touch point by using a light blocking manner, this embodiment of the instant disclosure can enhance determining accuracy of a touch position without being influenced by other surrounding light beams, and furthermore, is not limited to being used on a flat touch surface, thereby greatly enhancing practicability. 
       FIG. 5  is a schematic diagram of irradiation of another embodiment of the optical touch apparatus according to the instant disclosure. This embodiment is different from the embodiment in  FIG. 1  in that, a light source unit  10 ′ is a projection light source, for example, a light-emitting diode (LED) or another light source (for example, a halogen lamp or an infrared lamp), or the light source unit  10 ′ may also be a projector (for example, an LED pico projector or a laser pico projector) to emit a projection light beam to correspondingly project the whole operation area A and generate a plurality of light spots in the operation area A, and the optical signal processing unit  20  may selectively receive the three pieces R 1 , R 2 , and R 3  of reflected light information reflected and propagated by at least three light spots (herein are reference light spots M 1 , M 2 , and M 3 ), so as to perform analysis. 
       FIG. 6  and  FIG. 7  are a schematic diagram of irradiation and a schematic diagram of propagation of a touch vibration wave of another embodiment of the optical touch apparatus according to the instant disclosure. This embodiment is different from the embodiment in  FIG. 1  in that, the light source unit  10  may also emit more than three laser beams to generate more light spots. For example, in this embodiment, the light source unit  10  emits four laser beams L 1 , L 2 , L 3 , and L 4  to correspondingly irradiate four corners of the operation area A and generate three reference light spots M 1 , M 2 , and M 3  and an auxiliary light spot M 4  at different positions (herein are four corners) in the operation area A. The optical signal processing unit  20  further receives a piece R 4  of auxiliary reflected light information reflected and propagated by the auxiliary light spot M 4 , analyzes the piece R 4  of auxiliary reflected light information to correspondingly generate a piece D 4  of auxiliary optical analysis information, and transmits the piece D 4  of auxiliary optical analysis information to the position computation unit  30  (as shown in  FIG. 4 ). The piece D 4  of auxiliary optical analysis information includes vibration wave information and time point information, and the time point information refers to a time point at which the touch vibration wave W is propagated to reach the auxiliary light spot M 4 . That is, the optical signal processing unit  20  not only analyzes the pieces R 1 , R 2 , and R 3  of reflected light information to obtain time points at which the touch vibration wave W is respectively propagated to reach each of the reference light spots M 1 , M 2 , and M 3 , but also analyzes the piece R 4  of auxiliary reflected light information to obtain a time point at which the touch vibration wave W is propagated to reach the auxiliary light spot M 4 . 
     Furthermore, the position computation unit  30  may obtain position information (X 4 , Y 4 ) of the auxiliary light spot M 4  synchronously and computes touch position information (X c , Y c ) according to the auxiliary optical analysis information and the position information (X 4 , Y 4 ). That is, the position computation unit  30  may obtain information of four light spots (three reference light spots M 1 , M 2 , and M 3  and an auxiliary light spot M 4 ) (including position information, time points at which the touch vibration wave W is propagated to each of the light spots, and a wave velocity of the touch vibration wave W). 
     In an embodiment, the position computation unit  30  computes first touch position information (X c , Y c ) according to the light spot position information (X 1 , Y 1 ), (X 2 , Y 2 ), and (X 3 , Y 3 ) of the foregoing three reference light spots M 1 , M 2 , and M 3 , the information of the vibration time points at which the touch vibration wave W is respectively propagated to reach each of the reference light spots M 1 , M 2 , and M 3 , and the vibration wave velocity information V, and further performs a verification action through the information of the auxiliary light spot M 4 . For example, the position computation unit  30  may further compute second touch position information (X c , Y c ) based on the information of the reference light spots M 1  and M 2  and the auxiliary light spot M 4 , so as to perform comparison and verification with the first touch position information (X c , Y c ), thereby further enhancing the computation accuracy of the touch position. 
     In another embodiment, the position computation unit  30  may also take information of three different light spots to compute the touch position information (X c , Y c ) for many times, for example, the position computation unit  30  may compute the first touch position information (X c , Y c ) based on the information of the three reference light spots M 1 , M 2 , and M 3 , the second touch position information (X c , Y c ) based on the information of the reference light spots M 1  and M 2  and the auxiliary light spot M 4 , and the third touch position information (X c , Y c ) based on the information of the reference light spots M 2  and M 3  and the auxiliary light spot M 4 . Furthermore, the position computation unit  30  performs interactive comparison and determining on the foregoing multiple pieces of computed touch position information (X c , Y c ) to output the final touch position information (X c , Y c ), to further enhance computation accuracy of the touch position. For example, it is assumed that the multiple pieces of touch position information (X c , Y c ) computed by the position computation unit  30  are the same, and the position computation unit  30  may select one piece as final touch position information (X c , Y c ). It is assumed that the multiple pieces of touch position information (X c , Y c ) computed by the position computation unit  30  have small differences, and the position computation unit  30  can take a relative center point of the multiple pieces of touch position information (X c , Y c ) as final touch position information (X c , Y c ). 
     Although the instant disclosure has been described in considerable detail with reference to certain preferred embodiments thereof, the disclosure is not for limiting the scope of the invention. Persons having ordinary skill in the art may make various modifications and changes without departing from the scope and spirit of the invention. Therefore, the scope of the appended claims should not be limited to the description of the preferred embodiments described above.