Abstract:
An optically-sensitive touch display includes a processor with n output ports and n input ports. A scanning circuit includes n column wires and n row wires, constituting a matrix including numerous intersection points. Each intersection point contains a light emitter and a light receiver, and in a scanning period, the processor receives a signal as to a change in resistance at a particular intersection, enabling the processor to determine that a touch ahs been applied to a particular intersection point.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The present disclosure relates to touch displays, and particularly to a touch display sensitive to light. 
         [0003]    2. Description of Related Art 
         [0004]    Although conventional touch displays can satisfy basic requirement, a new type of touch display sensitive to light is still needed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    Many aspects of the present disclosure are better understood with reference to the following drawings. The units in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Moreover, in the drawings, like reference numerals designate corresponding portions throughout the several views. 
           [0006]      FIG. 1  is a block diagram of an optical touch display, in accordance with an exemplary embodiment. 
           [0007]      FIG. 2  is a schematic diagram of a scanning circuit of the optical touch display of  FIG. 1 , in accordance with an exemplary embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0008]    Embodiments of the present disclosure will be described, with reference to the accompanying drawings. 
         [0009]    Referring to  FIGS. 1-2 , an embodiment of an optical touch display  100  is illustrated. The display  100  includes a processor  10 , a scanning circuit  20 , a number of light emitters  30 , a number of light receivers  40 , and a control circuit  50 . The processor  10  includes a power port  12  connected to a power source Vcc and a ground port  14 . The processor  10  further includes n output ports K1˜Kn and n input ports M1˜Mn. 
         [0010]    The scanning circuit  20  includes n column wires P1˜Pn and n row wires L1˜Ln, constituting a matrix including intersection points. The n column wires P1˜Pn are respectively connected to the n output ports K1˜Kn in sequence. The n row wires L1˜Ln are respectively connected to the n input ports M1˜Mn in sequence via n voltage comparators. That is, the column wire P1 is connected to the output port K1, the column wire P2 is connected to the output K2, . . . , the column wire Pn is connected to the output port Kn. The row wire L1 is connected to the input port M1 via the voltage comparator  60 , the row wire L2 is connected to the input port M2 via the voltage comparator  60 , . . . , and the row wire Ln is connected to the input port Mn via the voltage comparator  60 . In this embodiment, each voltage comparator  60  includes a first input port (not shown), a second input port (not shown), and an output port (not shown). The input voltage at the first input port is the reference voltage, and the second input port is connected to one row wire. The voltage comparator  60  controls the output port of the voltage comparator  60  to output a digital-high voltage or a digital-low voltage according to a comparison between the reference voltage and the voltage at the second input port. 
         [0011]    In this embodiment, each light emitter  30  is arranged at one intersection point in the matrix, and can emit light in any outward direction. Each light receiver  40  is arranged at one intersection point, with two ends of each light receiver  40  being connected to one column wire and one row wire. When one intersection point is touched, the light from the light emitter  30  at that intersection point is reflected to the light receiver  40  at the same intersection point. In this embodiment, when one light receiver  40  receives light, the resistance of the light receiver  40  changes, thus the voltage at the second input port of each voltage comparator  60  accordingly changes. When the change of the resistance of one light receiver  40  falls within a preset range, the voltage at the output port of the voltage comparator  60  is high. 
         [0012]    In a scanning period, the processor  10  first sets the voltages at all the n output ports K1˜Kn to be low simultaneously, and then sets the voltages at each of the n outputs K1˜Kn to be high in sequence. When the voltage at one output port is high, the processor  10  directs the control circuit  50  to first turn on all the light emitters  30  simultaneously, and then turn off all the light emitters  30  simultaneously. Upon the voltage at one output port being set to be high, when the processor  10  detects that the voltage of one input port is high when the light emitters  30  are on, and the voltage at the one input port is changed from high to low when the light emitters  30  are off, the processor  10  determines that a touch has been applied to the intersection point of the column wire connected to the output port at which voltage is high and the row wire connected to the input port at which voltage changes from high to low. For example, if the intersection point P1L1 formed by the column wire P1 and the row wire L1 is touched by a finger, when the voltage at the output port K1 is high, and the light emitter  30  at the intersection point P1L1 is on, the light from that light emitter  30  is reflected by the finger to the light receiver  40  at the intersection point P1L1. The resistance of that light receiver  40  accordingly changes, and the change falls within the preset range, thus the voltage at the output port of the voltage comparator  60  is set to be high, and the voltage of the input port M1 is accordingly high. When the light emitter  30  at the intersection point P1L1 is off, the light receiver  40  at the intersection point P1L1 cannot receive outside light because the finger is blocking the light, thus the resistance of that light receiver  40  does not change, and the voltage at the output port of the voltage comparator  60  is set to be low, and the voltage at the input port M1 is accordingly changed from high to low. Therefore, the processor  10  determines that the intersection point P1L1 has been touched. The processor  10  can determine touches on all intersection points within one scanning period. 
         [0013]    In this embodiment, all the column wires are equidistant, and all the row wires are equidistant. In this embodiment, the processor  10  constitutes a Descartes coordinate system by regarding the column wire P1 as the y-axis, the row wire Ln as the x-axis, and the intersection point between the column wire P1 and the row wire Ln as the origin. The processor  10  determines the coordinates of any touched intersection point according to the coordinate system, the distance between each two adjacent column wires, and the distance between each two adjacent row wires. In other embodiment, the processor  10  can make determinations based on other coordinate systems. 
         [0014]    Although the present disclosure has been specifically described on the basis of the exemplary embodiment thereof, the disclosure is not to be construed as being limited thereto. Various changes or modifications may be made to the embodiment without departing from the scope and spirit of the disclosure.