Abstract:
An optical touch sensor is disclosed which comprises a light emitting die placed at a first edge bordering an object surface, a light detecting die placed at a second edge bordering the object surface across from the first edge, a first reflective surface directing light emitted from the light emitting die toward the light detecting die, and a second reflective surface directing light emitted from the light emitting die onto the light detecting die, wherein a light beam traveling from the first reflective surface to the second reflective surface is above and substantially parallel to the object surface.

Description:
BACKGROUND 
       [0001]    The present invention relates generally to touch sensor, and, more particularly, to an optical touch sensor for computer input devices. 
         [0002]    A popular way to position a cursor on a computer display is to use a mouse, which functions by detecting two dimensional motions relative to its supporting surface. Physically, a mouse comprises an object held under one of a user&#39;s hands, with one or more buttons. Clicking or hovering (stopping movement while the cursor is within the bounds of an area) can select files, programs or actions from a list of names, or (in graphical interfaces) through small images called “icons” and other elements. For example, a text file might be represented by a picture of a paper notebook, and clicking while the cursor hovers over this icon might cause a text editing program to open the file in a window. 
         [0003]    A conventional keyboard can detect a pressing of any key thereof, but cannot detect mere touches on the keys. Here, the “touch” refers to a surface of the keyboard being contacted by an object regardless if the key is pressed or not. If the conventional keyboard is a tactile one, the key pressing results from the key being depressed. If the conventional keyboard is a surface one, such as Touch Cover for Microsoft Surface, the key pressing results from a force being applied on the key. As long as the key remains depressed in tactile keyboard or forced upon in surface keyboard, the key is pressed. 
         [0004]    There are significant interests in incorporating mouse functions into a keyboard. One way to do it is to provide a touch tensor to a keyboard to form a combo device that detects touches on a surface of the keyboard, and switching operations of the combo device between a cursor mode and a keyboard mode as programmed. Conventionally the touch sensor employs arrays of light-emitting diodes (LED) to scan the surface of the keyboard with infrared (IR) light. When the scanning light is blocked, a surface touching object is then detected at the blocking location. However, touch sensors employing conventionally packaged LEDs are quite bulky and less accurate. 
         [0005]    As such, what is desired is a touch sensor that can accurately detect touch location and are less protrusive. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0006]      FIG. 1  is a perspective view of a laptop computer with a keyboard. 
           [0007]      FIG. 2  illustrates an infrared-light touch sensing system positioned to detect touch on the keyboard surface. 
           [0008]      FIG. 3  illustrates a LED-based touch coordinate detection system. 
           [0009]      FIG. 4  illustrates an array of LEDs packaged in the same substrate according to an embodiment of the present invention. 
           [0010]      FIG. 5  is a cross-sectional view of a LED package according to an embodiment of present invention. 
           [0011]      FIG. 6  is a cross-sectional view of a keyboard with touch sensing using the LED package of the present invention. 
       
    
    
       [0012]    The drawings accompanying and forming part of this specification are included to depict certain aspects of the invention. A clearer conception of the invention, and of the components and operation of systems provided with the invention, will become more readily apparent by referring to the exemplary, and therefore non-limiting, embodiments illustrated in the drawings, wherein like reference numbers (if they occur in more than one view) designate the same elements. The invention may be better understood by reference to one or more of these drawings in combination with the description presented herein. 
       DESCRIPTION 
       [0013]    The present invention relates to an optical touch sensor designed, particularly, for keyboard-and-mouse combo devices to provide cursor input for computers. A preferred embodiment of the present invention will be described hereinafter with reference to the attached drawings. 
         [0014]      FIG. 1  is a perspective view of a laptop computer  100  with a conventional keyboard  105  for entering text, etc. The laptop computer  100  has a base unit  102  containing the keyboard  105 , and a display panel  115  which is hinged to the base unit  102  by hinges  118 . A skilled computer user can generally type on the keyboard  105  with both hands  123  and  124 . An optical touch sensor can detects whether or not the surface of the keyboard  105  is touched without interfering with regular keyboard operations. 
         [0015]      FIG. 2  illustrates an infrared-light touch sensing system positioned to detect touches on the surface of the keyboard  105 . The infrared-light touch sensing system includes an infrared light emitter  202  and an infrared light receiver  208 . The infrared light travels across the surface of the keyboard  105 . A finger  124  or any other object touching the surface of the keyboard  105  blocks the infrared light from being received by the infrared light receiver  208 . As a result, the touch can be detected. 
         [0016]    Referring back to  FIG. 1 , the infrared light emitter  202  can be positioned along one edge of the keyboard  105  and the infrared light receiver  208  can be positioned along the opposite edge of the keyboard  105 . In order to obtain coordinates of a touch, two sets of the infrared light touch sensors will be needed with one set positioned on the horizontal edges and the other on the vertical edges. 
         [0017]      FIG. 3  illustrates a LED-based touch coordinate detection system which comprises a pair of horizontally placed LED arrays  312  and  315  and a pair of vertically placed LED arrays  322  and  325 . The LED arrays  312  and  322  controllably emit light, and the LED arrays  315  and  325  correspondingly detects light. If light is blocked at certain detecting LEDs, then coordinates of the blocking object can be extracted from the corresponding LED locations. Pitches P1 and P2 between two adjacent LEDs determine accuracy of the LED touch coordinate detection system, i.e., the smaller the pitches P1 and P2, the more accurate the touch coordinate detection system is. 
         [0018]    Conventionally LED dies are individually packaged and then mounted into an array as shown in  FIG. 3 . Even though individual LED die size can be very small, individually packaged LED is large due to the packaging material. Reduction of the pitches P1 and P2 using conventionally packaged LEDs is limited. 
         [0019]      FIG. 4  illustrates an array of LED dies  410 [0:n] packaged in the same substrate  402  according to an embodiment of the present invention, where n is an integer. Each die  410 [ i ] has an anode  415 [ i ] on the top and a cathode on the bottom (not shown), where i is an integer between 0 and n. Wire bonding may be used to connect each anode  415  to an external lead (not shown). In order to separate leads more widely, leads of adjacent LED dies  410 [0] and  410 [1] may be placed on opposite sides of the substrate  402 . For instance, if the lead for anode  415 [0] is placed on the upper side of the substrate  402 , the lead for anode  415 [1] is placed on the lower side of the substrate  402  as shown in  FIG. 4 . The cathodes of all the LED dies  410 [0:n] can be commonly connected to a single external lead (not shown). Because the LED dies  410 [0:n] are bare dies, pitch between juxtaposing units is mostly limited by the size of the LED dies  410 [0:n] themselves. Therefore, a LED array formed in this way can have very fine pitches. 
         [0020]      FIG. 5  is a cross-sectional view of a LED package  500  according to an embodiment of present invention. The LED package  500  comprises a LED die  410  horizontally mounted on the surface of a substrate  402 , leads  512  and  515 , and a plastic shell  502 . The lead  512  is connected to a cathode of the LED die  410  at the bottom thereof. The lead  515  is wire bonded an anode of the LED die  410  on the top thereof. The plastic shell  502  is made of a material transparent to infrared, and has a slanted flat surface  505  on the top which is coated with a reflective material for reflecting light emitted from the LED die  410 . As shown in  FIG. 5 , the LED die  410  emits light  530  upwardly and, the slanted flat surface  505  redirects the light  532  to a horizontal direction. In embodiments, the slanted flat surface  505  is angled at 45 degrees to the horizontal surface, so that majority of the reflected light  530  travel in parallel to the horizontal surface. In embodiments, an entire length of a LED array is covered by one piece of the plastic shell  502  which is molded into a desired shape. 
         [0021]    Although  FIG. 5  shows a light emitting LED package  500 , a skilled artisan would recognize that a light detecting LED package can have the same structure as that of the light emitting LED package  500 . In some applications, light emitting LED and light detecting LED can be interchangeably used. 
         [0022]      FIG. 6  is a cross-sectional view of a keyboard with touch sensing using the LED package  500  shown in  FIG. 5 . A light emitting LED package  500 [0] is mounted on a printed circuit board  602  with a top portion protruding through an opening  623  on a keyboard enclosure  620 . A light detecting LED package  500 [1] is mounted on another printed circuit board  604  with a top portion protruding through an opening  625  on the other side of the keyboard enclosure  620 . Light beam  630  traveling from the LED package  500 [0] to the LED package  500 [1] is slightly above and substantially parallel to a surface of the keyboard  620 . 
         [0023]    Referring again to  FIG. 6 , in order to protect the reflective surface of the LED package  500 , an added member  642 [0] is attached to a top part of the LED package  500 [0], and an added member  642 [1] is attached to a top part of the LED package  500 [1]. The added members  642  and  644  also ornament the protruding LED packages  500 [0:1]. In embodiments, the added members  642 [0:1] are molded plastic covering only the slanted reflective surface of the LED packages  500 [0:1], respectively, and are conveniently made symmetrical. In other embodiments, the added member  642  is made of a dark material, when being attached to the slanted surface of the LED package  500 , the slanted surface becomes reflective. 
         [0024]    While this disclosure has been particularly shown and described with references to exemplary embodiments thereof, it shall be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit of the claimed embodiments.