Patent Publication Number: US-2010117972-A1

Title: Electronic device with infrared touch input function

Description:
RELATED APPLICATIONS  
     This application is related to copending applications entitled, “ELECTRONIC DEVICE WITH INFRARED TOUCH INPUT FUNCTION”, filed ______ (Atty. Docket No. US 23304); “ELECTRONIC DEVICE WITH INFRARED TOUCH INPUT FUNCTION”, filed ______ (Atty. Docket No. US23305); and “ELECTRONIC DEVICE WITH INFRARED TOUCH INPUT FUNCTION”, filed ______ (Atty. Docket No. US24653). 
    
    
     BACKGROUND  
     1. Technical Field 
     The disclosure relates to electronic devices with an input function and, particularly, to an electronic device with infrared touch input function. 
     2. General Background 
     It is well known that an infrared input system comprises a circuit board having a first pair of opposed sides positioned parallel to a first axis and a second pair of opposed sides positioned parallel to a second axis, the second axis being perpendicular to the first axis, each of the second pair of sides connecting the first pair of sides, all four sides defining a generally rectangular touch input area, a linear array of light emitting devices along each side, and a light detection device positioned at each corner of the circuit board; and a controller coupled to the light emitting devices and the light detection devices, wherein the controller sequentially activates each linear array and activates the light detection devices positioned at corners of the circuit board opposed to the activated array of light emitting devices. The system can discern the location of a touch within the information display area by implementing an algorithm on x, y coordinates detected by the detectors, which is complicated and time consuming. 
     Therefore, it is necessary to provide a electronic device with infrared touch input function to implement the functions in a simpler way. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded, schematic view showing an electronic device with an infrared touch input function in accordance with a first exemplary embodiment. 
         FIG. 2  is a schematic diagram showing the electronic device of  FIG. 1 . 
         FIG. 3  is a block diagram showing an internal configuration of the electronic device of  FIG. 1 . 
         FIG. 4  is a flowchart implemented by the electronic device of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1-2 , the electronic device  100  includes an infrared input device  1 , a central processing unit (CPU)  2 , and a display unit  3 . The CPU  2  is electronically connected to the infrared input device  1  and the display unit  3 . The display unit  3  may be a flat panel display disposed sides defining an information display area. 
     The infrared input device  1  may include a circuit board  12  having two pairs of oppositely disposed sides (L 1 , L 2 , L 3 , and L 4 ) defining an open area corresponding in size and shape to the information display area. The circuit board  12  includes at least one light emitting device  10  and a linear array of light detecting devices  11  (Q 1 -Q 8 ). In an exemplary embodiment, the light emitting devices  10  are organic light emitting diodes that emit light in the infrared (IR) range (D 1 ), and the light detecting devices  11  are light phototransistors (Q 1 -Q 8 ). The light detecting devices  11  can be positioned on one side or two adjacent sides of the circuit board  12 . The light emitting device  10  is positioned at one corner of the circuit board  12  and faces the light detecting devices  11 . The light detecting devices  11  are used for detecting infrared light emitted by the light emitting device  10 . For example, in the exemplary embodiment, the light emitting device  10  is positioned at the top right corner of the circuit board  12 . 
     The CPU  2  is configured to control the display unit  3  to display a plurality of menu options corresponding to the light detecting devices  11 . The number of the menu options displayed will be the same as the number of the light detecting devices  11 . As shown in  FIG. 2 , there are  8  menu options A-H respectively corresponding to the light detecting devices Q 1 -Q 8 . When one menu option is touched by a user, an infrared light path between the light emitting device  10  and the corresponding light detecting device  11  is obstructed, as a result, the corresponding light detecting device  11  does not detect the infrared light emitted by the corresponding light emitting device  10 . The CPU  2  is configured to determine the menu option touched by the user when the corresponding light detecting device  11  detects an interruption of the infrared light emitted by the corresponding light emitting device  10  and thereby performs a function corresponding to the menu option. 
       FIG. 3  is a block diagram showing the internal configuration of the electronic device  1 . The infrared input device  1  further includes a micro-controller  13  connected to the CPU  2  and an analog/digital (A/D) converter  14  connected to the micro-controller  13 . The collectors of Q 1 -Q 8  are commonly connected together respectively via resistances R 1 -R 8  to form a node S. The node S is further connected with the A/D converter, and a voltage source Vcc via a resistance R 0 . The emitters of Q 1 -Q 8  are connected to ground. The anode of the light emitting device  10  is further connected to the voltage source Vcc, and the cathode of the light emitting devices  10  is connected to ground. 
     When none of the menu options is being touched, the infrared light paths between the light emitting device  10  and the light detecting devices  11  are unobstructed, and all the light detecting devices  11  detect the infrared light, thereby the node S is grounded via R 1 -R 8 . Voltage across the node S equals Vcc*(R 1 * . . . R 7 *R 8 )/(R 0 *(R 1 + . . . R 7 +R 8 )+R 1 * . . . R 7 *R 8 ). When one menu option is touched, take menu option A for example, the infrared light path between Q 1  and D 1  is obstructed, thereby R 1  is not connected to ground. The voltage across the node S is then equal to Vcc*(R 2 * . . . R 7 *R 8 )/(R 0 *(R 2 + . . . R 7 +R 8 )+R 2 * . . . R 7 *R 8 ). The A/D converter  14  converts the voltage across the node S into digital values and sends the digital values to the micro-processor  13 . R 0 -R 8  may be set to different values to make the digital values different for different conditions of different menu option being touched. The micro-controller  13  is further configured to determine which infrared light path is obstructed according to the digital value. 
       FIG. 4  is a flowchart implemented by the electronic device  100 . 
     In step S 11 , the micro-controller  13  detects whether the digital values are changed. If yes, the procedure goes to step S 12 , if no, the micro-controller  13  continues to detect. In step S 12 , the micro-processor  13  determines the infrared light path being obstructed according to the digital value sent to the CPU  2 . For example, the micro-processor  13  looks up a table that records relationship of the digital values and corresponding infrared light paths, and determines the infrared light path according to the table. In step S 13 , the CPU  2  determines which menu option is touched corresponding to the infrared light path being obstructed, and sends a control signal to the CPU  2 . In step S 14 , the CPU  2  performs functions corresponding to the menu option being touched according to the control signal. 
     In order to avoid misoperation, only when the time of the changed digital values remaining same lasts for a predetermined time, the micro-processor  13  sends the control signal to the CPU  2  to perform the functions corresponding to the menu option. 
     Although the present disclosure has been specifically described on the basis of an exemplary embodiment thereof, the disclosure is not to be construed as being limited thereto. Various changes or modifications may be made to the embodiments without departing from the scope and spirit of the disclosure.