Patent Publication Number: US-8537138-B2

Title: Optical touch apparatus having a light guide with scattering particles

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority benefit of Taiwan application serial no. 98140208, filed on Nov. 25, 2009. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention is related to a touch apparatus, and more particularly, to an optical touch apparatus. 
     2. Description of Related Art 
     With the development of optoelectronic technology, a user&#39;s requirements may no longer be satisfied by using a mouse to control objects in a computer and a screen. Hence, interfaces more user-friendly than the mouse have been gradually developed. In these user-friendly interfaces, the touch method by using fingers is closest to human experiences in the daily life. In particular, it is easier for elders and children to touch an object with fingers than the mouse. This has been partially proved by the adoption of the touch screen in some automatic teller machines. 
     In addition, for a conventional laptop, if no mouse is externally connected, a touch pad and a track point next to the keys are usually used to control the cursor. However, controlling the cursor by the touch pad or the track point next to the keys may not be easier than a mouse for normal users. A touch panel disposed on the monitor is able to solve such problem. Because the control method of the touch panel is an intuitive control method, in which the user directly touches the monitor to control the objects. Therefore, when the touch panel is applied to the laptop, even if the operating conditions make the user inconvenient to externally connect the mouse, the user is capable of agilely operating the laptop by the touch panel. 
     Currently, touch panels are roughly classified into resistive-type, capacitive-type, optical-type, acoustic-wave-type, and electromagnetic-type. Generally, an optical-type touch panel includes a display, a light source, a light guide unit, a detector, and a processor. The light source is disposed next to a display area to generate a beam. The beam passes through the light guide unit and then is detected by the detector. When an object touches the panel, the processor determines a position of a touch point according to a change in light intensity detected by the detectors. In addition, the uniformity of the luminance of the beam passing through the light guide board affects the accuracy in determining the touch point. The more uniform the luminance is, the higher the accuracy is. However, according to prior art, the luminance of the beam passing through the light guide board is non-uniform, so that the accuracy in determining the position of the touch point is also lower. 
     SUMMARY OF THE INVENTION 
     The invention provides an optical touch apparatus having higher accuracy in determining a touch point. 
     Other objects and advantages of the invention may be further comprehended by reading the technical features described in the invention as follows. 
     One embodiment of the invention provides an optical touch apparatus adapted to a display area. The optical touch apparatus includes at least one light source, at least one light guide unit, and at least one optical detector. The light source is disposed next to the display area and capable of providing a beam. The light guide unit is disposed next to the display area and in a transmission path of the beam. The light guide unit includes a light guide body and a scattering structure. The light guide body has a first surface, a second surface opposite to the first surface, at least one light incident surface connecting the first surface and the second surface, a third surface connecting the light incident surface, the first surface, and the second surface, and a fourth surface opposite to the third surface and connecting the light incident surface, the first surface, and the second surface. The beam is capable of entering the light guide body through the light incident surface and is capable of being transmitted from the first surface to a sensing space in front of the display area. The scattering structure is disposed on at least one of the second surface, the third surface, and the fourth surface, so that the beam is scattered to the first surface. The scattering structure has a plurality of scattering patterns separated from each other, and each of the scattering patterns includes a resin composition and a plurality of scattering particles. The scattering particles are dispersed in the resin composition, and a ratio of a weight percentage of the scattering particles to a weight percentage of the resin composition is equal to or greater than 0.1. The optical detector is disposed next to the display area and capable of detect a change in light intensity of the beam in the sensing space. 
     Due to the above, the embodiments of the invention may have at least one of the following advantages. In each of the scattering patterns of the optical touch apparatus according to the embodiments of the invention, the ratio of the weight percentage of the scattering particles to the weight percentage of the resin composition is equal to or greater than 0.1, so that the scattering particles in the scattering patterns are beneficial to adjusting the emitted light shape of the beam passing through the scattering patterns. Hence effects of uniformed emitted luminance of the light guide unit are achieved, thereby enhancing the accuracy in determining the touch point by the optical touch apparatus. 
     Other objectives, features and advantages of the invention will be further understood from the further technological features disclosed by the embodiments of the invention wherein there are shown and described preferred embodiments of this invention, simply by way of illustration of modes best suited to carry out the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
         FIG. 1A  is a structural schematic diagram of an optical touch display apparatus according to an embodiment of the invention. 
         FIG. 1B  is a schematic cross-sectional view of an optical touch apparatus in  FIG. 1A  along line I-I. 
         FIG. 2A  is a three-dimensional view of a light guide unit and a light source in  FIG. 1A . 
         FIG. 2B  is a three-dimensional view of a light guide body and a scattering structure in  FIG. 2A . 
         FIG. 2C  is a schematic cross-sectional view of the light guide unit in  FIG. 2A  along line II-II. 
         FIG. 2D  is a three-dimensional view of the light guide body and scattering structure of the light guide unit in  FIG. 1A . 
         FIG. 3A  is a light intensity distribution diagram of a first surface of the light guide unit detected by an optical detector in  FIG. 1A . 
         FIG. 3B  is a light intensity distribution diagram of the first surface of the light guide unit detected by the optical detector when the scattering structure is formed by a transparent ink layer. 
         FIG. 4A  is a light intensity distribution curve diagram of a light beam passing through the scattering pattern and emitted from a first surface of the light guide body according to an embodiment of the invention, in which there are different ratios of scattering particles to a resin composition. 
         FIG. 4B  is a light intensity distribution curve diagram of the light beam passing through the scattering pattern having scattering particles with different particles sizes and emitted from the first surface of the light guide body according to an embodiment of the invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings which form a part hereof, and in which are shown by way of illustration specific embodiments in which the invention may be practiced. In this regard, directional terminology, such as “top,” “bottom,” “front,” “back,” etc., is used with reference to the orientation of the Figure(s) being described. The components of the invention can be positioned in a number of different orientations. As such, the directional terminology is used for purposes of illustration and is in no way limiting. On the other hand, the drawings are only schematic and the sizes of components may be exaggerated for clarity. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the invention. Also, it is to be understood that the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless limited otherwise, the terms “connected,” “coupled,” and “mounted” and variations thereof herein are used broadly and encompass direct and indirect connections, couplings, and mountings. Similarly, the terms “facing,” “faces” and variations thereof herein are used broadly and encompass direct and indirect facing, and “adjacent to” and variations thereof herein are used broadly and encompass directly and indirectly “adjacent to”. Therefore, the description of “A” component facing “B” component herein may contain the situations that “A” component directly faces “B” component or one or more additional components are between “A” component and “B” component. Also, the description of “A” component “adjacent to” “B” component herein may contain the situations that “A” component is directly “adjacent to” “B” component or one or more additional components are between “A” component and “B” component. Accordingly, the drawings and descriptions will be regarded as illustrative in nature and not as restrictive. 
     Referring to  FIGS. 1A ,  1 B, and  2 A to  2 C, an optical touch display apparatus  40  of an embodiment of the invention includes a display  50  and an optical touch apparatus  100 . According to the embodiment, the display  50  includes a display area  52  and an outer frame  54  surrounding the display area  52 . The optical touch apparatus  100  may be disposed on the outer frame  54  or be integrated as a part of the outer frame  54 . The display  50  is, for example, a liquid crystal display (LCD), a plasma display panel (PDP), an organic light emitting diode (OLED) display, a cathode ray tube (CRT) display, a rear projection display, or another kind of display, while the display area  52  is a surface for displaying frames to a user. According to other embodiments, the display area  52  may also be a display region on a projection screen, meaning that the optical touch apparatus  100  is capable of being used with a projection apparatus and disposed next to the display region on the projection screen. 
     The optical touch apparatus  100  includes at least one light source  110  (four light sources  110   a ,  110   b ,  110   c , and  110   d  are exemplarily shown in  FIG. 1 ), at least one light guide unit  130  (three light guide units  130   a ,  130   b , and  130   c  are exemplarily shown in  FIG. 1 ), and at least one optical detector  120  (two optical detectors  120   a  and  120   b  are exemplarily shown in  FIG. 1 ). The light source  110  is disposed next to the display area  52  and is capable of emitting a beam  112 . The light guide unit  130  is disposed next to the display area  52  and is disposed in the transmission path of the beam  112 . Specifically, the light sources  110   a ,  110   b ,  110   c , and  110   d  respectively emit beams  112   a ,  112   b ,  112   c , and  112   d , the light guide unit  130   a  is disposed in the transmission path of the beam  112   a , the light guide unit  130   b  is disposed in the transmission paths of the beams  112   b  and  112   c , and the light guide unit  130   c  is disposed in the transmission path of the beam  112   d.    
     According to the embodiment, the light source  110  includes an invisible light emitting diode capable of emitting an invisible beam. For example, the light source  110  is an infrared light emitting diode, and each of the beams  112   a ,  112   b ,  112   c , and  112   d  is an infrared beam. 
     The optical detectors  120   a  and  120   b  are disposed next to the display area  52 . Each of the optical detectors  120   a  and  120   b  is, for example, a complementary metal-oxide-semiconductor (CMOS) sensor, a charge coupled device (CCD) sensor, a photomultiplier (PMT), or another type of suitable image sensor. 
     The light guide unit  130  includes a light guide body  131  and a scattering structure  150 . 
     The light guide body  131  has a first surface P 1 , a second surface P 2  opposite to the first surface P 1 , and at least one light incident surface P 0  connecting the first surface P 1  and the second surface P 2 . The beam  112  is capable of entering the light guide body  131  through the light incident surface P 0 , and is capable of being transmitted from the first surface P 1  to a sensing space S (the space surrounded by the broken lines shown in  FIG. 1A  and  FIG. 1B ) in front of the display area  52 . 
     According to the embodiment, the light guide body  131  further includes a third surface P 3  and a fourth surface P 4 . The third surface P 3  is connected to the light incident surface P 0 , the first surface P 1 , and the second surface P 2 . The fourth surface P 4  is opposite to the third surface P 3  and is connected to the light incident surface P 0 , the first surface P 1 , and the second surface P 2 . According to the embodiment, the light guide unit  130  further includes a reflector  133  disposed on at least one of the second surface P 2 , the third surface P 3 , and the fourth surface P 4 . Specifically, the reflector  133  is, for example, a reflecting sheet disposed on the second surface P 2 , the third surface P 3 , and the fourth surface P 4 . 
     According to the embodiment, the scattering structure  150  is, for example but not limited to, a Lambertian scattering structure and disposed on the second surface P 2  of the light guide body  131 . According to other embodiments, the scattering structure  150  may also be disposed on at least one of the second surface P 2 , the third surface P 3 , and the fourth surface P 4  of the light guide body  131 , so that the beam  112  is scattered to the first surface P 1 , and the root mean square value D of the differences between the light intensity of the normalized light intensity distribution curve of the beam  112  emitted from the first surface P 1  at each light emission angle and the light intensity of a Lambertian normalized light intensity distribution curve at the same angle is equal to or less than 0.2. Specifically, the normalized light intensity distribution curve of the light beam  112  emitted from the first surface P 1  may be represented by I(θ), meaning that the light intensity I is a function of the light emission angle θ. The range of the light emission angle θ is from −90 to +90 degrees, wherein the direction corresponding to 0 degree is defined as the light emission direction (i.e. the light emission direction D 1  if the light guide unit  130   b  is used as an example) perpendicular to the first surface P 1 ; the positive direction of the light emission angle θ is the clockwise direction on the figure, and the negative direction of the light emission angle θ is the counter-clockwise direction on the figure. In addition, the Lambertian normalized light intensity distribution curve may be represented by L(θ), wherein L(θ)=cos θ, and the range of 0 is from −90 to +90 degrees. By using the Lambertian scattering structure according to the embodiment, the normalized light intensity distribution of the beam  112  emitted from the first surface P 1  complies with the following equation. 
     Root mean square value of the differences between the light intensity 
     
       
         
           
             D 
             = 
             
               
                 
                   
                     ∑ 
                     
                       
                         ( 
                         
                           
                             I 
                             ⁡ 
                             
                               ( 
                               θ 
                               ) 
                             
                           
                           - 
                           
                             L 
                             ⁡ 
                             
                               ( 
                               θ 
                               ) 
                             
                           
                         
                         ) 
                       
                       2 
                     
                   
                   N 
                 
               
               ≤ 
               0.2 
             
           
         
       
     
     In other words, the light intensity distribution of the beam  112  emitted from the first surface P 1  is similar to the Lambertian distribution, so that there is uniform luminance on the first surface P 1 . According to the embodiment, the above root mean square value D is, for example, 0.063106. However, according to other embodiments, the above root mean square value may be 0.075269, 0.121543, or another value equal to or smaller than 0.2. 
     According to the embodiment, the light guide units  130   a  and  130   b  are respectively disposed at two adjacent sides of the display area  52 , the light guide units  130   b  and  130   c  are respectively disposed at two adjacent sides of the display area  52 , and the light guide units  130   a  and  130   c  are respectively disposed at two opposite sides of the display area  52 . The first surface P 1  of the light guide unit  130  may face the sensing space S. The first surface P 1  of the light guide unit  130   a  and the first surface P 1  of the light guide unit  130   b  are in the detection range of the optical detector  120   b , and the first surface P 1  of the light guide unit  130   b  and the first surface P 1  of the light guide unit  130   c  are in the detection range of the optical detector  120   a . The optical detector  120  is used to detect the change in the light intensity of the beam  112  in the sensing space S. According to the embodiment, the optical touch apparatus  100  further includes a processing unit  140  electrically connected to the optical detector  120  (i.e. electrically connected to the optical detectors  120   a  and  120   b ). The processing unit  140  determines the position of the touch object relative to the display area  52  according to the change in light intensity when a touch object  60  enters the sensing space S. 
     Specially, when the touch object  60  approaches or touches the display area  52 , the touch object  60  blocks the beam  112  emitted from the first surface P 1  of each light guide unit  130   a ,  130   b , and  130   c  and entering the optical detectors  120   a  and  120   b , so that dark spots on the images are sensed by the optical detectors  120   a  and  120   b . By analyzing the positions of the dark spots, the processing unit  140  is able to calculating the position of the touch object  60  relative to the display area  52 , thereby achieving a touch effect. The touch object  60  is, for example, the finger of the user, a tip of a stylus, or another suitable object. In addition, the processing unit  140  is, for example, a digital signal processor (DSP) or other kind of suitable processing circuit. The processing unit  140  may be electrically connected to a processor of an operating platform, such as a computer, cell phone, personal digital assistant (PDA), digital camera, or to processors of other kind of electronic device, and the processor of the operating platform is capable of converting a signal of the position of the touch object  60  relative to the display area  52  into various kinds of control functions. According to other embodiments, the position of the touch object  60  relative to the display area  52  may be calculated by the processor of the operating platform instead of by the processing unit  140 . 
     According to the embodiment, the scattering structure  150  includes a plurality of scattering patterns  152  which are separated from each other. The scattering patterns  152  are capable of making the beam  112  emitted from the first surface P 1  have a light intensity distribution similar to the Lambertian intensity distribution. The scattering patterns  152  are arranged in a direction substantially perpendicular to the light incident surface P 0  (the normal direction of the surface). In addition, according to the embodiment, the number density of the scattering patterns  152  at a region close to the light source  110  is less than the number density of the scattering patterns  152  at a region away from the light source  110 . For example, the number density of the scattering patterns  152  increases along the direction away from the light source  110 . Moreover, the light guide unit  130   b  has two light incident surfaces P 0  opposite to each other, and the two light incident surfaces P 0  are the light incident surfaces  132   b  and  134   b . The light sources  110   b  and  110   c  are respectively disposed next to the two light incident surfaces  132   b  and  134   b  opposite to each other, and the number density of the scattering patterns  152  at a region close to one of the light incident surfaces  132   b  and  134   b  is less than the number density of the scattering patterns  152  at a region in the middle between the light incident surfaces  132   b  and  134   b . For example, the number density of the scattering patterns  152  increases from two ends of the light guide unit  130   b  towards the middle. 
     In addition, the light guide body  131  of the light guide unit  130   a  (referring to  FIG. 2D ) has one light incident surface P 0 , and the light incident surface P 0  is a light incident surface  132   a . The number density of the scattering patterns  152  increases from the end close the light incident surface  132   a  to the end away from the light incident surface  132   a . The light guide unit  130   c  and the scattering patterns  152  on the light guide unit  130   c  are similar to the light guide unit  130   a  and the scattering patterns  152  on the light guide unit  130   a , while the positions of the first surface P 1  and the second surface P 2  of the light guide unit  130   c  are opposite from the positions of the first surface P 1  and the second surface P 2  of the light guide unit  130   a.    
     Since the optical touch apparatus  100  according to the embodiment adopts the Lambertian scattering structure (which is the scattering structure  150 ), the light intensity distribution of the beam  112  emitted from the first surface P 1  is similar to the Lambertian distribution, and uniform luminance is on the first surface P 1 . Therefore, when the touch object  60  does not enter the sensing space S, the optical detector  120  may detect uniform luminance at each sensing angle. Hence, when the touch object  60  enters the sensing space S, the processing unit  140  is capable of accurately calculating the position of the touch object  60  relative to the display area  52  by analyzing data of the light intensity distribution transmitted from the optical detector  120 , so that the problem of misjudgment of the position of the touch object  60  caused by non-uniform luminance on the first surface P 1  is improved. 
     According to the embodiment, each of the scattering patterns  152  includes a resin composition  154  and a plurality of scattering particles  156 . The resin composition  154  is, for example, a transparent ink layer but not limited to it. The resin composition  154  is disposed on the second surface P 2 . According to other embodiments, the resin composition  154  may also be disposed on at least one of the second surface P 2 , the third surface P 3 , and the fourth surface P 4 . The scattering particles  156  are dispersed in the resin composition  154 . Through cooperation of the resin composition  154  and the scattering particles  156 , the Lambertian scattering structure is formed. In the embodiments of the invention, the Lambertian scattering structure is not limited to being formed by the resin composition and the scattering particles. According to other embodiments, the Lambertian scattering structure may also be any structure capable of making the beam  112  emitted from the first surface P 1  have a light intensity distribution similar to the Lambertian intensity distribution. 
     Referring to both  FIGS. 3A and 3B , from left to right, the angular range of detection by the optical detector  120   a  is from the light incident surface  132   b  of the light guide unit  130   b  to the light incident surface  134   b  of the light guide unit  130   b . Referring to  FIG. 3B , when the scattering structure is formed by the transparent ink layer and does not contains any scattering particles, the light emission angle θ of the beam  112  emitted from the first surface P 1  and by the light source  110   b  deviates towards the positive direction, and the light emission angle θ of the beam  112  emitted from the first surface P 1  by the light source  110   c  deviates towards the negative direction. Hence, the beam  112  emitted by the light source  110   c  directly irradiates the optical detector  120   a  and causes a stronger light intensity, and the beam emitted by the light source  110   b  deviates from the optical detector  120   a  and causes a weaker light intensity. Hence, the light intensity distribution in  FIG. 3B  is non-uniform and is higher at the right side of  FIG. 3B , thereby easily causing misjudgment of a position of a touch point. Referring to  FIG. 3A , since the optical touch apparatus  100  according to the embodiment adopts the transparent ink layer with the scattering particles  156 , the light intensity distribution of the beam  112  emitted from the first surface P 1  of the light guide unit  130   b  is similar to the Lambertian intensity distribution. Hence, the optical detector  120   a  is capable of detecting the uniform light intensity distribution as shown in  FIG. 3A , thereby effectively lowering the misjudgment rate of the position of the touch point by the optical touch apparatus  100  and the optical touch display apparatus  40  according to the embodiment. In other words, the accuracy in determining the position of the touch point by the optical touch apparatus  100  and the optical touch display apparatus  40  is enhanced. 
     In order to make clear the characteristics of the invention, the following illustrates the scattering structure  150  in detail. The scattering structure  150  has the plurality of scattering patterns  152  separated from each other, and the scattering patterns  152  are disposed on at least one of the second surface P 2 , the third surface P 3 , and the fourth surface P 4  opposite to the light emitting surface in the light guide body  131 . In particular, a designer may adjust the composition ratio of the resin composition  154  to the plurality of scattering particles  156  in the scattering patterns  152  to adjust the emitted light shape of the beam  112 , so that the beam  112  achieves a uniform effect. In application, by adjusting a suitable ratio of the resin composition  154  to the plurality of scattering particles  156  in the scattering patterns  152 , the normalized light intensity distribution curve of the beam  112  achieves an effect similar to an effect of the Lambertian normalized light intensity distribution curve. 
     In detail, each of the scattering patterns  152  includes the resin composition  154  and the plurality of scattering particles  156 , and the scattering particles  156  are dispersed in the resin composition  154 . The contents of the scattering particles  156  and the resin composition  154  in the scattering patterns are calculated as weight percentages. In other words, when the ratio of the weight percentage of the scattering particles  156  in the scattering patterns  152  to the weight percentage of the resin composition  154  in the scattering patterns  152  is equal to or greater than 0.1, the scattering patterns  152  may be sufficiently used to adjust the light shape of the beam  112 . As shown in  FIGS. 3A and 3B  described above, the beam  112  emitted from the light guide body  131  are more uniform when the content of the scattering particles  156  in the scattering patterns  152  comply with the above relationship, so that the optical detector  120  effectively detects whether there is a change in light intensity caused by touching in the sensing space S, thereby preventing misjudgment of touching. 
     In addition, according to the embodiment, since the content of the scattering particles  156  in the scattering patterns  152  is less than the content of the resin composition  154  in the scattering patterns  152 , such as the ratio of the scattering particles  156  to the resin composition  154  being 0.1, in each of the scattering patterns  152  as shown in  FIGS. 2B to 2D , the resin composition  154  may be viewed as a continuous phase, the scattering particles  156  may be viewed as a dispersed phase dispersed in the continuous phase, and the scattering particles  156  are, for example, embedded in the resin composition  154 . 
     In practice application, by adjusting the scattering particles  156  and the composition ratio of the plurality of scattering particles  156  in the scattering pattern  152 , the light shape of the beam  112  passing through the scattering patterns  152  are more suitable for product requirements. For example, in one kind of application, if the light shape of beam emitted from the light guide body  131  is to comply with the Lambertian light shape, the ratio of the scattering particles  156  to the resin composition  154  may be appropriately increased. Specifically, the ratio of the scattering particles  156  to the resin composition  154  is preferably smaller than or equal to 1.5. The contents of the scattering particles  156  and the resin composition  154  are calculated in weight percentages. Moreover, from a view of light usage efficiency, when the contents of the scattering particles  156  and the resin composition  154  in the scattering patterns  152  are calculated in weight percentages, the ratio of the scattering particles  156  to the resin composition  154  is preferably greater than or equal to 0.5 and smaller than or equal to 1.5. 
     In other words, when the content of the scattering particles  156  in the scattering patterns  152  is greater than the content of the resin composition  154  in the scattering patterns  152 , such as the ratio of the scattering particles  156  to the resin composition  154  is 1.5, and the scattering particles may protrude from the surface of the resin composition, so that the surface of the resin composition is slightly uneven and formed as a tiny concave/convex structure surface. The invention, however, does not limit the manner in which the scattering particles are dispersed in the resin composition. 
     Referring to  FIG. 4A , the light shapes of the beam  112  are shown under the conditions that the ratio of the scattering particles  156  to the resin composition  154  is 0.1, 1, and 1.5. As shown in  FIG. 4A , when the ratio of the scattering particles  156  and the resin composition  154  changes, the light intensity distribution curve diagram of the beam  112  changes accordingly. In detail, when the weight percentage of the scattering particles  156  in the scattering patterns  152  to the weight percentage of the resin composition  154  in the scattering patterns  152  is equal to or greater than 0.1, the light shape of the emitted beam  112  is substantially changed. Moreover, as shown in  FIG. 4A , when the ratio of the weight percentage of the scattering particles  156  in the scattering patterns  152  to the weight percentage of the resin composition  154  in the scattering patterns  152  is 1 or 1.5, the light shape of the beam  112  passing through the scattering patterns  152  is similar to the shape of Lambertian light. 
     It should be noted that, the ratio of the scattering particles  156  to the resin composition  154  in the scattering patterns  152  is not specifically limited; as long as the scattering particles  156  added into the resin composition  154  are sufficient, effects of adjusting the emitted light shape of the beam  112  are achieved. In other words, the scattering patterns  152  are capable of substantially adjusting the emitted beam  112  to have a predetermined light shape when the ratio of the weight percentage of the scattering particles  156  in the scattering patterns  152  to the weight percentage of the resin composition  154  in the scattering patterns  152  is equal to or greater than 0.1. For example, as shown in  FIG. 4A , in an application wherein the predetermined light shape is the Lambetian light shape, the ratio of the scattering particles  156  to the resin composition  154  in the scattering patterns may be adjusted to substantially 1 or 1.5, so that the emitted beam  112  is adjusted to have the predetermined Lambertian light form. Hence, in the invention, the ratio of the scattering particles  156  to the resin composition  154  in the scattering patterns  152  is not limited to a specific value, but is suitably adjusted according to predetermined requirements on the light shape of the emitted beam. 
     In addition, for the same light guide body  131 , the invention does not limit that the composition ratio of the scattering particles  156  to the resin composition  154  in the scattering patterns  152  of the same light guide body  131  is the same. In detail, for the same light guide body  131 , in the scattering patterns  152  located at different positions, the ratio of the scattering particles  156  to the resin composition  154  in the scattering patterns  152  may be adjusted according to the positions of the scattering patterns  152  relative to the optical detectors  120 , the number of the optical detectors  120 , and the number of the light guide bodies  131  in the light guide unit  130 . In other words, each ratio of the scattering particles  156  to the resin composition  154  in the plurality of scattering patterns  152  on the same light guide body  131  may be substantially different from each other. Alternatively, considering the obtainment of raw materials, mass productivity, and the cost of manufacturing, slight variation between each ratio of the scattering particles  156  to the resin composition  154  in the scattering patterns  152  is allowable for the scattering patterns  152  on the same light guide body, so that each ratio of the scattering particles  156  to the resin composition  154  in the scattering patterns  152  may be substantially different from each other. 
     Based on the above concept, a designer may adjust the compositions of the scattering patterns  152  on different positions of each of the light guide bodies  131  according to the size of the optical touch apparatus, the characteristics (such as the refractive index) of the light guide unit  130 , and the relative positions of the light guide unit  130  and the optical detector  120 , so that the beam  112  emitted from the light guide body may have uniform effects. Hence, the detection sensitivity and the accuracy in determining the touch point by the optical detector  120  are enhanced, thereby preventing the optical touch apparatus from performing unwanted functions. 
     The designer may further fine tune the directivity of the beam  112  in an auxiliary manner by adjusting the particle size of the scattering particles when the ratio of the scattering particles  156  to the resin composition  154  in the scattering patterns  152  is equal to or greater than 0.1. Details are described below with reference to  FIG. 4B . The particle size of the scattering particles  156  is not specifically limited. In detail, according to the embodiment, the particle size of the scattering particles  156  is substantially in the range from 1 μm to 30 μm. 
     Referring to  FIG. 4B , the light shapes of the emitted beam are shown when the particle size of the scattering particles is 1 μm, 15 μm, and 30 μm. As shown in  FIG. 4B , when the particle size of the scattering particles is 1 μm, the light intensity is stronger when the light emission angle is 0 degree. In other words, the emitted beam has higher optical directivity. On the other hand, when the particle size of the scattering particles is 15 μm, compared with the light intensity distribution when the particle size is 1 μm, the light intensity distribution is more uniform when the particle size is 15 μm. Still referring to  FIG. 4B , when the particles size of the scattering particles is 30 μm, the light intensity distribution of the beam passing through the scattering patterns is further uniformed. 
     In other words, when the particle size of the scattering particles  156  is smaller, the optical directivity of the beam  112  passing through the scattering pattern  152  is enhanced; when the size of the scattering particles  156  is close to the wavelengths of visible light, there tends to be slight loss in optical energy, and the light usage efficiency is lowered. On the other hand, when the particles size of the scattering particles  156  is larger, the light usage efficiency of the beam  112  passing through the scattering patterns  152  is enhanced. According to the embodiment, the particles size of the scattering particles  156  is substantially equal to 2 μm, so that the optical directivity and light usage efficiency of the beam  112  passing through the scattering patterns  152  are enhanced. 
     On the basis of adjusting the emitted light shape of the beam  112  by the scattering patterns  152 , by considering other design requirements, the refractive index of the scattering patterns  152  may be further adjusted according to the ratio of the scattering particles  156  to the resin composition  154 , the refractive index of the scattering particles  156 , and the refractive index of the resin composition  154 , so that the light usage efficiency of the beam is further enhanced when the emitted light shape is changed. According to the embodiment, the refractive index of the light guide body  131  is, for example, 1.49. In order to enhance the light usage efficiency, in the scattering patterns  152  arranged on the second surface P 2 , the refractive index of the resin composition  154  is in the range from 1.4 to 1.55, and the refractive index of the scattering particles  156  is in the range from 1.4 to 1.7. 
     In terms of manufacturing, the above scattering structure  150  may be manufactured by print fabrication. In further detail, the resin composition  154 , the scattering particles  156 , and a solvent may be pre-mixed to form a scattering material. Next, the scattering material is, for example, sprayed on the light guide body  131  by a printing process. In addition, a curing process is used for removing the solvent to cure the scattering material sprayed on the light guide body  131 , and the scattering structure  150  is formed by the plurality of scattering patterns  152  separated from each other. The curing process is, for example, an ultraviolet light curing process or a baking process. Hence, according to the actual printing process, a solvent with a suitable material and viscosity may be selected. For example, according to the embodiment, the solvent is a composition including 90% 3,5,5-trimethyl-2-cyclohexene-1-one and 10% 4-methyl-3-penten-2-one. 
     The following further describes the resin composition  154  and the scattering particles  156  in the scattering patterns  152 . 
     The resin composition: in terms of light usage efficiency, according to an embodiment, a material having high optical transmittance in the visible light range may be selected as the resin composition. For example, the optical transmittance of the resin composition in the visible light range is equal to or greater than 90%, and the resin composition in the scattering patterns is, for example, the transparent ink layer. Specifically, the resin composition is formed by a composition including poly methylmethacrylate resin. According to the embodiment, the constituents for forming the resin composition further include an aromatic hydrocarbon compound, a dibasic ester, cyclohexanone, and silicon dioxide. 
     In terms of the fact that the resin composition has superb optical transmittance and better light usage efficiency, the contents of each compound in the constituents of the resin composition comply with the following relationships: the content of the poly methylmethacrylate resin is, for example, 20-30 wt %, the content of the aromatic hydrocarbon compound is 20-30 wt %, the content of the dibasic ester is 20-30 wt %, the content of the cyclohexanone is 10-20 wt %, and the content of the silicon dioxide in the resin composition is equal to or less than 10 wt %. 
     The so called scattering particles are particles capable of making incident light beams have different emission directions. The particle size of the scattering particles is, for example, 1 μm to 30 μm, and the selection of the particle size and considerations for the refractive index are illustrated above and hence not repeated described. Specifically, the scattering particles may include, but are limited to, one of titanium dioxide, silicon dioxide, and poly methylmethacrylate resin, or any combination thereof. According to other embodiments, other scattering particles may be selected. 
     It should be noted that the scattering patterns  152  formed by mixing the resin composition and the scattering particles  156  complying with the above relationships have effects of sufficiently changing the emitted light shape and have superb light usage efficiency, so that the light guide unit  130  utilizing the scattering patterns  152  has effects of the uniform light intensity distribution. Therefore, compared with a conventional optical touch apparatus, the optical touch apparatus of the invention utilizes the scattering patterns  152  having the resin composition  154  and the scattering particles  156 , and the resin composition  154  and the scattering particles  156  comply with specific relationships, so that light uniformity of the beam passing through the light guide unit  130  and been emitted into the sensing space is enhanced, thereby enhancing the accuracy in determining the touch point by the optical touch apparatus. 
     In summary, the embodiments of the invention have at least one of the following advantages. By adjusting the ratio of the scattering particles to the resin composition in the scattering patterns, the light shape of the beam passing through the light guide body is sufficiently adjusted, so that the overall emitted light intensity (luminance) of the light guide body is uniform, thereby enhancing the accuracy in determining the touch point by the optical touch apparatus. 
     The foregoing description of the preferred embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form or to exemplary embodiments disclosed. Accordingly, the foregoing description should be regarded as illustrative rather than restrictive. Obviously, many modifications and variations will be apparent to practitioners skilled in this art. The embodiments are chosen and described in order to best explain the principles of the invention and its best mode practical application, thereby to enable persons skilled in the art to understand the invention for various embodiments and with various modifications as are suited to the particular use or implementation contemplated. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents in which all terms are meant in their broadest reasonable sense unless otherwise indicated. Therefore, the term “the invention”, “the present invention” or the like does not necessarily limit the claim scope to a specific embodiment, and the reference to particularly preferred exemplary embodiments of the invention does not imply a limitation on the invention, and no such limitation is to be inferred. The invention is limited only by the spirit and scope of the appended claims. The abstract of the disclosure is provided to comply with the rules requiring an abstract, which will allow a searcher to quickly ascertain the subject matter of the technical disclosure of any patent issued from this disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Any advantages and benefits described may not apply to all embodiments of the invention. It should be appreciated that variations may be made in the embodiments described by persons skilled in the art without departing from the scope of the invention as defined by the following claims. Moreover, no element and component in the present disclosure is intended to be dedicated to the public regardless of whether the element or component is explicitly recited in the following claims.