Patent Publication Number: US-8976156-B2

Title: Camera module and optical touch screen using the same

Description:
TECHNICAL FIELD 
     The teachings in accordance with the exemplary embodiments of this invention relate generally to a camera module and an optical touch screen using the same. 
     BACKGROUND ART 
     A touch screen or touch panel is a display which can detect the location of touches within the display area, usually performed either with the human hand or a stylus. This allows the display to be used as an input device, removing the keyboard and/or the mouse as the primary input device for interacting with the display&#39;s content. 
     Technically speaking, the commonly used touch screens employ resistive, capacitive, ultrasonic wave, electromagnetic, vector force and optical (Infrared) touch modes. Among these types of touch screens, resistive type is the most common one, which has approximately 60% of market share (the second is capacitive type with around 24% of market share). Each of these types of touch screens has its own features, advantages and disadvantages. 
     Now, these touch screens are briefly explained. 
     The resistive is a common type of touch screen technology. It is a low-cost solution found in many touch screen applications, including hand-held computers, PDA&#39;s, consumer electronics, and point-of-sale-applications. The resistive touch screens are such that a pair of resistive layers facing with each other is provided on a touch screen element. The pressed position is detected by contact between the resistive layers so that one of the resistive layers is formed on a flexible film for deformation during pressing. As mentioned above, the resistive film type is widely used, but disadvantageous due to degraded mechanical and environmental reliability. At the same time, although the resistive touch screen today are widely used on consuming electronic products, it is unable to identify multiple contact points simultaneously on its display area. 
     The ultrasonic wave touch screen first converts an electric signal into an ultrasonic wave through a transducer, and then directly transmits the ultrasonic wave through a surface of the touch panel. When the touch panel is used, the ultrasonic wave may be absorbed by contacting a pointer to cause attenuation, and an accurate position of the contact is obtained through comparison and calculation between attenuation amounts before and after use. The surface acoustic wave touch screen is disadvantageous due to generation of noise and/or susceptibility to noise. 
     The electromagnetic type touch screen is such that, in the field of magnetism, a magnetic field is normally generated by a coil due to electromagnetism and said magnetic field induces a voltage in another coil, also called receiver coil, under the premise that the magnetic field strength changes in the receiver coil. It is clear that a non-moving receiver coil is not capable to measure a non-altering magnetic field since no voltage is induced by said magnetic field. There are already means, which can measure a position and/or orientation of a receiver means in relation to a specific magnetic field generating means. To measure the orientation in a 3-dimensional space normally three orthogonal arranged probes are used to calculate the coordinates. These arrangements are most of the time very bulky, space taking and needs a special stylus. 
     The capacitance type touch screen adopts capacity changes generated from the combination of static electricity between arranged transparent electrodes and a human body, so as to detect coordinates of the contact position through a generated induced current. That is, the capacitance type touch screen includes one substrate having an electrode formed thereon. In the capacitance type touch panel, when, for example, a finger contacts and approaches the touch panel, a variation in capacitance between the electrode and the finger is detected, thereby detecting input coordinates. Since the capacitance type touch panel is a non-contact type, it has high durability, excellent environmental and mechanical reliability due to changeable upper barrier layer unlike the resistive film type touch panel. However, the capacitance type touch panel has disadvantages in that it is difficult to input information with fingers or a pen. 
     The optical type touch screens principally use no films for touch recognition such that transmittance is 100%. Furthermore, no reflexibility, degradation of brightness and blurring of displays are generated from these optical touch screens. Maintenance of transmittance and brightness in displays is an important factor for image clarity, such that an optical type is adequate for implementation of high quality screens. Furthermore, the optical type touch screens utilize the principle of light source reception and blocking, such that no load is applied to a sensor as detection is not performed by physical or electrical contacts, which increases reliability for use in factory monitoring, various automation equipment and ATM&#39;s. The optical type touch screens are advantageously free from such materials as films or ITO (Indium Tin Oxide) protective films to have less susceptibility to scratches or external shocks and a lower error probability including erroneous operation. 
     DISCLOSURE OF INVENTION 
     Technical Problem 
     The present invention is directed to solve an object to enhance a touch sensitivity by preventing light leakage. 
     Technical problems to be solved by the present invention are not restricted to the above-mentioned, and any other technical problems not mentioned so far will be clearly appreciated from the following description by skilled in the art. 
     Solution to Problem 
     An object of the invention is to solve at least one or more of the above problems and/or disadvantages in a whole or in part and to provide at least the advantages described hereinafter. In order to achieve at least the above objects, in whole or in part, and in accordance with the purposes of the invention, as embodied and broadly described, and in one general aspect of the present invention, there is provided a camera module, the module characterized by: a holder formed with a stair unit and opening; an infrared light emitting diode mounted at the stair unit for emitting an infrared; and an image sensor detecting the infrared through the opening. 
     Preferably, the stair unit is formed at an upper surface of the holder, and the opening is formed at a bottom surface of the holder. 
     Preferably, the holder is formed at one side with a first groove and is formed at the other side with a second groove, and the opening connects the first groove and the second groove, and the stair unit is formed at one lateral surface. 
     Preferably, the first groove is formed with an object lens, the second groove is formed with an infrared pass filter that passes an infrared of a particular wave band, and a printed circuit board mounted with the image sensor is attached to the holder for blocking the second groove. 
     Preferably, the infrared pass filter is implemented by coating an infrared pass filter material on a glass. 
     In another general aspect of the present invention, there is provided an optical touch screen using a camera module, the screen characterized by: a flat plate display panel; a case mounted and assembled with the flat plate display panel; a bracket assembled on the case; a camera module mounted on the bracket and including a holder formed with a stair unit and an opening, an infrared light emitting diode mounted on the stair unit for emitting an infrared, and an image sensor detecting the infrared through the opening. 
     Preferably, the bracket includes first and second fixtures fixed on the case, and a connection connected to the first and second fixtures, wherein the camera module is mounted to a rear surface of the connection. 
     Preferably, the connector is mounted at a front surface with an infrared pass filter. 
     Preferably, the infrared pass filter includes a first infrared pass filter passing infrared emitted from the infrared light emitting diode, and a second infrared pass filter transmitting the infrared to the opening by passing the infrared detected by the image sensor. 
     Preferably, the connection of the bracket includes first and second passages, the first infrared pass filter is aligned on the first passage, and the second infrared pass filter is aligned on the second passage. 
     Preferably, a light leakage prevention lug is formed at the connection of the bracket between the first and second passages. 
     Preferably, the light leakage prevention lug is accommodated at the stair unit. 
     Preferably, the optical touch screen further includes a case assembled and mounted with the flat plate display panel and the bracket. 
     Preferably, the case takes the shape of a square ring. 
     Preferably, three inner corners of the square ring-shaped case are fixed by brackets on which the camera module is mounted, and one inner corner of the square-ring shaped case is mounted with a dummy bracket on which the camera module is not mounted. 
     Preferably, a retro reflector is mounted on an inner lateral surface of the case among the brackets. 
     ADVANTAGEOUS EFFECTS OF INVENTION 
     The camera module according to the present invention has an advantageous effect in that a stair unit of a holder is mounted with an infrared light emitting diode and an image sensor is so positioned as to allow detecting infrared through an opening of the holder, whereby the infrared emitted from the infrared light emitting diode can be prevented from entering the image sensor to enhance a touch sensitivity. 
     The optical touch screen according to the present invention has an advantageous effect in that an aperture is mounted at a bracket mounted with a camera module to dispense with an additional aperture structure and to reduce a manufacturing cost. 
     The camera module and the optical touch screen using the same according to the present invention has an advantageous effect in that a light leakage prevention lug is formed at a connection of a bracket, and the camera module and the bracket are so coupled as to accommodate the light leakage prevention lug at a stair unit mounted with an infrared light emitting diode, whereby infrared emitted from the infrared light emitting diode can be prevented from entering an image sensor. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The teachings of the present invention can be readily understood by considering the following detailed description in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a conceptual cross-sectional view illustrating an optical touch screen according to the present invention; 
         FIG. 2  is a conceptual view illustrating a method for detecting a coordinate of a particular area touched on an optical touch screen according to the present invention; 
         FIGS. 3   a  and  3   b  are schematic conceptual views illustrating a linear sensor of an optical touch screen according to the present invention; 
         FIG. 4  is a schematic perspective view illustrating a state in which an optical touch screen is fastened according to the present invention; 
         FIG. 5  is a schematic plan illustrating a case of an optical touch screen according to the present invention; 
         FIGS. 6   a  through  6   d  are schematic plans illustrating a method of assembling an optical touch screen according to the present invention; 
         FIG. 7  is a schematic cross-sectional view illustrating a camera module according to the present invention; 
         FIG. 8  is a schematic cross-sectional view illustrating a camera module according to an exemplary embodiment of the present invention; 
         FIG. 9  is schematic perspective view illustrating a bracket according to the present invention; 
         FIG. 10  is a schematic plan illustrating a connection of a bracket according to the present invention; 
         FIG. 11  is a partially-cut schematic perspective view illustrating a state in which an infrared pass filter is mounted at a bracket according to the present invention; and 
         FIG. 12  is a schematic cross-sectional view illustrating a connected relationship between a camera module and a bracket according to the present invention. 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     The following description is not intended to limit the invention to the form disclosed herein. Consequently, variations and modifications commensurate with the following teachings, and skill and knowledge of the relevant art are within the scope of the present invention. The embodiments described herein are further intended to explain modes known of practicing the invention and to enable others skilled in the art to utilize the invention in such, or other embodiments and with various modifications required by the particular application(s) or use(s) of the present invention. 
     The disclosed embodiments and advantages thereof are best understood by referring to  FIGS. 1-12  of the drawings, like numerals being used for like and corresponding parts of the various drawings. Other features and advantages of the disclosed embodiments will be or will become apparent to one of ordinary skill in the art upon examination of the following figures and detailed description. It is intended that all such additional features and advantages be included within the scope of the disclosed embodiments, and protected by the accompanying drawings. Further, the illustrated figures are only exemplary and not intended to assert or imply any limitation with regard to the environment, architecture, or process in which different embodiments may be implemented. Accordingly, the described aspect is intended to embrace all such alterations, modifications, and variations that fall within the scope and novel idea of the present invention. 
     It will be understood that the terms “comprises” and/or “comprising,” or “includes” and/or “including” when used in this specification, specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof. That is, the terms “including”, “includes”, “having”, “has”, “with”, or variants thereof are used in the detailed description and/or the claims to denote non-exhaustive inclusion in a manner similar to the term “comprising”. 
     Furthermore, “exemplary” is merely meant to mean an example, rather than the best. It is also to be appreciated that features, layers and/or elements depicted herein are illustrated with particular dimensions and/or orientations relative to one another for purposes of simplicity and ease of understanding, and that the actual dimensions and/or orientations may differ substantially from that illustrated. That is, in the drawings, the size and relative sizes of layers, regions and/or other elements may be exaggerated or reduced for clarity. Like numbers refer to like elements throughout and explanations that duplicate one another will be omitted. Now, the present invention will be described in detail with reference to the accompanying drawings. 
       FIG. 1  is a conceptual cross-sectional view illustrating an optical touch screen according to the present invention. 
     An optical touch screen according to the present invention includes a camera module ( 160 ) and a retro reflector ( 170 ), all of which are mounted to a front surface of a flat plate display panel ( 200 ). The camera module ( 160 ) may include an infrared light emitting diode ( 100 ) emitting infrared light, an IR (Infrared) pass filter ( 130 ) that passes only the infrared reflected from the retro reflector ( 170 ), and a linear sensor ( 150 ) detecting an area touched by the incident infrared that has passed the IR pass filter ( 130 ). 
     At this time, the optical touch screen may further include an object lens ( 140 ) collecting the infrared that has passed the IR pass filter ( 130 ). Alternatively, the optical touch screen may be so configured as to allow the light emitted from the infrared light emitting diode ( 100 ) to be emitted through a lens ( 110 ). 
     Furthermore, the retro reflector ( 170 ) reflects the infrared emitted from the infrared light emitting diode ( 100 ), where an incident angle and reflection angle of the infrared are same. Therefore, the infrared light emitting diode ( 100 ) of the camera module ( 160 ) emits an infrared, where the emitted infrared advances along the flat plate display panel ( 200 ) to be reflected from the retro reflector ( 170 ) and incident on the IR pass filter ( 130 ) of the camera module ( 160 ). 
     At this time, the IR pass filter ( 130 ) passes only the infrared that has been reflected from the retro reflector ( 170 ), and the infrared that has passed the IR pass filter ( 130 ) is incident on the linear sensor ( 150 ). In a case a particular area of the flat plate display panel ( 200 ) is touched by a finger of a hand ( 250 ) while a user views an image displayed on the flat plate display panel ( 200 ), the infrared is blocked from the touched area to form a black spot on the linear sensor ( 150 ), whereby a coordinate of the touched particular area can be detected. 
     Furthermore, the flat plate display panel ( 200 ) is situated under an area between the infrared light emitting diode ( 100 ) and the retro reflector ( 170 ), and in a case a user touches a particular area of an image displayed on the flat plate display panel, a driving signal is generated that corresponds to a coordinate detected by the linear sensor ( 150 ), whereby various functions including screen change, sound adjustment, screen movement, screen enlargement and screen reduction can be performed. At this time, the flat plate display panel may be one of an LCD (Liquid Crystal Display), an FED (Field Emission Display), a PDP (Plasma Display Panel), an EL (Electroluminescence), an OLED (Organic Light Emitting Diode), and an electronic paper display panel. 
       FIG. 2  is a conceptual view illustrating a method for detecting a coordinate of a particular area touched on an optical touch screen according to the present invention, and  FIGS. 3   a  and  3   b  are schematic conceptual views illustrating a linear sensor of an optical touch screen according to the present invention. 
     The camera module of the optical touch screen may be installed at two or three corner areas of the flat plate display panel ( 200 ). For example, as illustrated in  FIG. 2 , in a case first and second camera modules ( 161   a ,  161   b ) are mounted on two corner areas ( 211 ,  212 ) of the flat plate display panel ( 200 ), and a predetermined area ( 250 ) of the flat plate display panel ( 200 ) is touched, the touched predetermined area ( 250 ) is blocked of infrared, and each linear sensor of the first and second camera module ( 161   a ,  161   b ) is formed with a black spot. Therefore, the linear sensor can detect a coordinate of the touched particular area using a position of the black spot. 
     Each of the linear sensors ( 150   a ,  150   b ) of the first and second camera module ( 161   a,    161   b ) is mounted with 1st to nth sensing pixel ( 151 ,  152 ,  153 ,  154 ,  155 ) as illustrated in  FIGS. 3   a  and  3   b . At this time, in a case the particular predetermined area of the flat plate display panel ( 200 ) is touched, one of the 1st to nth sensing pixel ( 151 ,  152 ,  153 ,  154 ,  155 ) is formed with the black spot. Furthermore, because each of the linear sensors ( 150   a ,  150   b ) of the first and second camera module ( 161   a ,  161   b ) is installed at a different position from that of the touched area, there is a high probability that the sensing pixel of the linear sensor ( 150   a ) of the first camera module ( 161   a ) is differently positioned from the linear sensor ( 150   b ) of the second camera module ( 161   b ). 
     For example, as depicted in  FIG. 3   a , a black spot ( 251 ) is formed at the second sensing pixel ( 152 ) on the linear sensor ( 150   a ) of the first camera module ( 161   a ), and as illustrated in  FIG. 3   b , a black spot ( 251 ) is formed at the fourth sensing pixel ( 154 ) on the linear sensor ( 150   b ) of the second camera module ( 161   b ). 
     Meanwhile, as shown in  FIG. 2 , if a crosswise direction of the flat plate display panel ( 200 ) is defined as x axis, and a lengthwise direction of the flat plate display panel ( 200 ) is defined as y axis, a coordinate of the touched area ( 250 ) can be extracted, if a connection line (S 1 ) from the touched area ( 250 ) to the linear sensor ( 150   a ) of the first camera module ( 161   a ), a first angle (θ 1 ) formed by a crosswise direction of the flat plate display panel ( 200 ), a connection line (S 2 ) from the touched area ( 250 ) to the linear sensor ( 150   b ) of the second camera module ( 161   b ), a second angle (θ 2 ) formed by a crosswise direction of the flat plate display panel ( 200 ) and a crosswise length of the flat plate display panel ( 200 ) are known. 
     Furthermore, the first angle (θ 1 ) and the second angle (θ 2 ) are changed according to the position of the touched area ( 250 ), and in response thereto, the 1st to the nth sensing pixel ( 151 ,  152 ,  153 ,  154 ,  155 ) of the linear sensors ( 150   a ,  150   b ) are subdivided. That is, each of the 1st to the nth sensing pixel ( 151 ,  152 ,  153 ,  154 ,  155 ) of the linear sensors ( 150   a ,  150   b ) corresponds to the first angle (θ 1 ) and the second angle (θ 2 ). 
     Therefore, in a case a black spot is formed on one of the sensing pixel of the 1st to the nth sensing pixel ( 151 ,  152 ,  153 ,  154 ,  155 ) of the linear sensors ( 150   a ,  150   b ) on the first and second camera modules ( 161   a ,  161   b ), the first angle (θ 1 ) and the second angle (θ 2 ) can be known, whereby a coordinate (x, y) of the touched area ( 250 ) can be extracted. 
     Furthermore, the optical touch screen may include a coordinate extraction calculator capable of extracting real time a coordinate (x, y) of the touched area ( 250 ) touched by the aforementioned method or other methods, in a case a predetermined area ( 250 ) of the flat plate display panel ( 200 ) is touched. 
       FIG. 4  is a schematic perspective view illustrating a state in which an optical touch screen is fastened according to the present invention, and  FIG. 5  is a schematic plan illustrating a case of an optical touch screen according to the present invention. 
     The optical touch screen according to the present invention may include a case ( 300 ) on which the flat plate display panel ( 200 ) is mounted, where the case ( 300 ) may be called a case top. The case ( 300 ) takes the shape of a square ring, and as shown in  FIG. 5 , an inner lateral surface of the square ring is mounted with the retro reflector ( 170 ), and two or three corner areas of the square ring is mounted and assembled with camera modules ( 161   a ,  161   b ,  161   c ). 
     At this time, the camera modules ( 161   a ,  161   b ,  161   c ) are mounted on brackets ( 271 ,  272 ,  273 ), and each of the brackets ( 271 ,  272 ,  273 ) is mounted at three square ring corners. Furthermore, a balance one square ring corner is mounted with a dummy bracket ( 280 ) that is not mounted with a camera module. That is, the optical touch screen includes the flat plate display panel ( 200 ), the square ring-shaped case ( 300 ) on which the flat plate display panel ( 200 ) is assembled and attached, the brackets assembled on corners of the case ( 300 ), and the camera modules ( 161   a ,  161   b ,  161   c ). At least one of the brackets is a bracket that is not mounted with the camera modules ( 161   a ,  161   b ,  161   c ). An inner lateral surface of the case ( 300 ) in the brackets is mounted with the retro reflector ( 170 ). The retro reflector ( 170 ) is also mounted on the dummy bracket ( 280 ). 
       FIGS. 6   a  through  6   d  are schematic plans illustrating a method of assembling an optical touch screen according to the present invention. 
     The method of assembling an optical touch screen according to the present invention is to first prepare the square ring shaped case ( 300 ), as illustrated in  FIG. 6   a.    
     Next, the brackets ( 271 ,  272 ,  273 ) mounted at three square ring corners of the square ring shaped case ( 300 ) are fixed, and the dummy bracket ( 280 ) that is not mounted with the camera modules ( 161   a ,  161   b ,  161   c ) is fixed at one inner lateral corner of the square ring shaped case ( 300 ) ( FIG. 6   b ). 
     In the brackets ( 271 ,  272 ,  273 ) mounted with the camera modules ( 161   a ,  161   b,    161   c ), infrared is emitted from the camera modules ( 161   a ,  161   b ,  161   c ) and the brackets ( 271 ,  272 ,  273 ) are formed with openings (not shown) through which the infrared can be incident reflected from the retro reflector ( 170 ). The dummy bracket ( 280 ) is not formed with an opening which is not needed. 
     Successively, an inner lateral surface of the case in the brackets ( 271 ,  272 ,  273 ,  280 ) is mounted with a frame ( 171 ) for fixing the retro reflector ( 170 ) ( FIG. 6   c ). Referring to  FIG. 6   c , the brackets ( 271 ,  272 ,  273 ,  280 ) means the brackets ( 271 ,  272 ,  273 ) that are mounted with camera modules ( 161   a ,  161   b ,  161   c ) and the dummy bracket ( 280 ) that is not mounted with camera module. 
     Thereafter, the retro reflector ( 170 ) is fixed at the frame ( 171 ) and the dummy bracket ( 280 ) ( FIG. 6   d ), where the retro reflector ( 170 ) can be fixed without blocking each opening of the brackets ( 271 ,  272 ,  273 ) mounted with camera modules ( 161   a,    161   b ,  161   c ). Following the assembly process of  FIG. 6   d , the flat plate display panel ( 200 ) is mounted on the case ( 300 ). 
       FIG. 7  is a schematic cross-sectional view illustrating a camera module according to the present invention. 
     The camera module according to the present invention includes a holder ( 380 ) formed with a stair unit ( 381 ) and an opening ( 383 ), an infrared light emitting diode ( 100 ) mounted at the stair unit ( 381 ) for emitting an infrared (G 1 ), and an image sensor ( 150 ) detecting the infrared (G 2 ) through the opening ( 383 ). 
     The stair unit ( 381 ) may be formed at an upper surface of the holder ( 380 ), and the opening ( 383 ) is formed at a bottom surface of the holder ( 380 ). Therefore, the stair unit ( 381 ) and the opening ( 383 ) are formed at an area different from that of the holder ( 380 ) to prevent the infrared (G 1 ) emitted by the stair unit ( 381 ) and the infrared (G 2 ) incident through the opening ( 383 ) from being intervened therebetween, whereby the infrared incident on the image sensor ( 150 ) is free from infrared (G 1 ) component emitted from the infrared light emitting diode ( 100 ). 
     Therefore, the camera module according to the present invention is advantageous in that the image sensor ( 150 ) is so positioned as to detect the infrared (G 2 ) through the opening ( 383 ) at the holder ( 380 ) by mounting the infrared light emitting diode ( 100 ) at the stair unit ( 381 ) at the holder ( 380 ), whereby the infrared emitted from the infrared light emitting diode ( 100 ) is prevented from entering the image sensor ( 150 ). 
     That is, the camera module according to the present invention is assembled in a two-tier structure where a light emitting unit and a light receiving unit are separated from each other, as shown in  FIG. 7 . 
       FIG. 8  is a schematic cross-sectional view illustrating a camera module according to an exemplary embodiment of the present invention. 
     Referring to  FIG. 8 , the camera module according to an exemplary embodiment of the present invention includes a holder ( 380 ) formed at one side with a first groove ( 382 ) and formed at the other side with a second groove ( 384 ) and an opening ( 383 ) that connects the first groove ( 382 ) and the second groove ( 384 ) and with a stair unit ( 381 ) formed at one lateral surface, where the first groove ( 382 ) is formed with an object lens ( 140 ), the second groove ( 384 ) is formed with an infrared pass filter ( 131 ) that passes an infrared of a particular wave band, a printed circuit board ( 151 ) mounted with the image sensor ( 150 ) is attached to the holder ( 380 ) for blocking the second groove ( 384 ), and the stair unit ( 381 ) is mounted with an infrared light emitting diode ( 100 ). 
     At this time, the infrared pass filter ( 131 ) may be implemented by coating an infrared pass filter material on a glass that passes infrared of a particular wavelength band. The glass functions as a cover plate for protecting the image sensor. The stair unit ( 381 ) is mounted with the infrared light emitting diode ( 100 ). 
     Therefore, the infrared emitted from the infrared light emitting diode ( 100 ) advances to an upper surface of the flat plate display panel to be reflected by the retro reflector, where the reflected infrared passes the object lens ( 140 ) and the infrared pass filter ( 131 ) that passes infrared of a particular wavelength band to be incident on the image sensor ( 150 ) and to detect the touch. 
       FIG. 9  is schematic perspective view illustrating a bracket according to the present invention, and  FIG. 10  is a schematic plan illustrating a connection of a bracket according to the present invention. 
     As noted above, the camera module is mounted at the bracket ( 271 ), and the bracket ( 271 ) is mounted at the case. 
     Referring to  FIG. 9 , the bracket ( 271 ) includes first and second fixtures ( 271   a ,  271   c ) fixed at the case, and a connection ( 271   b ) connected to the first and second fixtures ( 271   a ,  271   c ). 
     The connection ( 271   b ) of the bracket ( 271 ) is formed with a first passage ( 273   a ) through which infrared emitted from the camera module passes, and a second passage ( 273   b ) through which infrared incident on the camera module passes. At this time, as shown in  FIG. 10 , the second passage ( 273   b ) may take the shape of an aperture that adjusts an amount of infrared incident on the camera module. Each of the first and second passages ( 273   a ,  273   b ) may be mounted with first and second infrared pass filters. 
     Furthermore, as shown in  FIG. 10 , the second passage ( 273   b ) may be formed with a groove ( 273   c ) mounted with the second infrared pass filter, and the first passage ( 273   a ) may be directly formed with the first infrared pass filter. 
     Therefore, the infrared emitted from the camera module is emitted from the first passage ( 273   a ) of the bracket ( 271 ), reflected from the retro reflector mounted at the case and incident on the camera module through the second passage ( 273   b ) that takes the shape of an aperture at the bracket ( 271 ), thereby detecting the touch. 
     At this time, the size of the aperture-shaped second passage ( 273   b ) can adjust the amount of incident infrared. For example, a large size of second passage ( 273   b ) can receive a larger amount of infrared than a small size of second passage ( 273   a ). 
     As a result, the optical touch screen according to the present invention is advantageous in that an aperture is formed at a bracket mounted with the camera module to dispense with an additional aperture structure and to therefore reduce the manufacturing cost. 
     MODE FOR THE INVENTION 
       FIG. 11  is a partially-cut schematic perspective view illustrating a state in which an infrared pass filter is mounted at a bracket according to the present invention, and  FIG. 12  is a schematic cross-sectional view illustrating a connected relationship between a camera module and a bracket according to the present invention. 
     The camera module is mounted at a rear surface of the connection ( 271   b ) of the bracket ( 271 ), and first and second infrared pass filters ( 410 ,  420 ) are mounted at a front surface of the connection ( 271   b ) of the bracket ( 271 ). At this time, the first infrared pass filter ( 410 ) is aligned on the first passage ( 273   a ) of the connection ( 271   b ) at the bracket ( 271 ), and the second infrared pass filter ( 420 ) is aligned on the second passage ( 273   b ), as illustrated in  FIG. 12 . 
     Furthermore, a light leakage prevention lug ( 273   d ) may be formed between the first and second passages ( 273   a ,  273   b ) of the connection ( 271   b ) at the bracket ( 271 ) 
     At this time, in a case the camera module is mounted at the connection ( 271   b ) of the bracket ( 271 ), the light leakage prevention lug ( 273   d ) is accommodated at the stair unit ( 381 ) mounted with the infrared light emitting diode ( 100 ), such that the infrared emitted from the infrared light emitting diode ( 100 ) advances only to the first passage ( 273   a ), instead of entering the image sensor ( 150 ). 
     Therefore, the present invention is such that the camera module can be optically aligned by a simple assembly process of mounting the first and second infrared pass filters ( 410 ,  420 ) with the connection ( 271   b ) of the bracket ( 271 ) to advantageously simplify the processes. 
     Furthermore, the connection ( 271   b ) of the bracket ( 271 ) is formed with the light leakage prevention lug ( 273   d ), and the camera module and the bracket are so coupled as to allow the stair unit ( 381 ) mounted with the infrared light emitting diode ( 100 ) to be accommodated with the light leakage prevention lug ( 273   d ), whereby the infrared emitted from the infrared light emitting diode ( 100 ) is advantageously prevented from entering the image sensor. 
     The previous description of the present invention is provided to enable any person skilled in the art to make or use the invention. Various modifications to the invention will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other variations without departing from the spirit or scope of the invention. Thus, the invention is not intended to limit the examples described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein. 
     Industrial Applicability 
     The present invention has an industrial applicability in that the camera module is so configured as to prevent interference between infrared emitted from an infrared light emitting diode and infrared incident on an image sensor, and the camera module is mounted with an optical touch screen to thereby enhance a touch sensitivity of the optical touch screen.