Patent Publication Number: US-2013229387-A1

Title: Optical touch device, passive touch control system, and input detection method

Description:
FIELD OF THE INVENTION 
     The present invention is related generally to an optical touch control technology and, more particularly, to an optical touch device and input detection method for a passive touch control system. 
     BACKGROUND OF THE INVENTION 
     Touch devices allow intuitional input operation for users and may further provide more convenient operation in some applications. There have been many touch control systems that were well known in related arts, which include touch screens to receive touch input by some specific pointers. A passive touch control system is advantageous over an active touch system in that it does not require any specific pointers and thus even a human finger can be a pointer for touch input. Well known passive touch screens include resistive type devices and capacitive type devices, both of which nevertheless have some unconquerable problems. Specifically, resistive and capacitive touch screens can only detect physical touches applied thereto, and have low position resolution. In addition, a resistive touch screen uses a flexible film to receive pressing of a stylus for generating deformation to identify a touch point, and thus is less durable and can only work when the force received is large enough. A capacitive touch screen is stronger, but needs to charge and discharge its sensor traces for input detection, and thus it takes higher power consumption and a longer time for input detection. For either a resistive touch screen or a capacitive touch screen, the input detection includes scanning all its sensor traces for completing a frame of raw data and thus requires high-speed scanning and high-speed calculation, and even with a high-speed hardware, the time for obtaining one frame of data is still relatively long, which makes the frame rate hard to be increased and the response to input operation slower. 
     U.S. Pat. No. 6,803,906 uses a projector to project a picture output by a computer onto a touch screen, and four cameras fixed at the four corners of the touch screen to shot on the touch screen with overlapping fields of view. The images acquired by these cameras are then compared with each other by a digital signal processor (DSP) to detect the presence of pointers touching the touch screen. In comparison with resistive and capacitive touch screens, this art improves nothing but the position resolution, yet it requires further higher operational speed and more expensive hardware. 
     Conventional passive touch control systems have one more common defect that all of them can not be directly applied to existing monitors, and touch screens are very expensive. 
     SUMMARY OF THE INVENTION 
     An objective of the present invention is to provide an optical touch device for a passive touch control system. 
     Another objective of the present invention is to provide a simple and low-cost optical touch device. 
     Yet another objective of the present invention is to provide an optical touch device to be position mapping to entire or a part of the picture displayed on a monitor. 
     Still another objective of the present invention is to provide a passive touch control system based on an optical touch device and an input detection method for the passive touch control system. 
     According to the present invention, an optical touch device includes a touch surface having a position mapping relationship with entire or a part of a picture displayed on a monitor, a light source optically coupled to the touch surface to provide light to project to the touch surface, an image sensor unit optically coupled to the touch surface to capture an image by receiving light from the touch surface and generate an input signal carrying the image, a processing unit electrically coupled to the image sensor unit to receive the input signal, identify the image carried by the input signal to detect if any object contacts the touch surface or suspends over the touch surface and a position of each detected object, and generate an absolute position signal according to the detected position to point to a mapped position on the picture, a movement detection module to detect movement of the optical touch device and generate a relative movement signal accordingly, and a transmission interface electrically coupled to the processing unit and the movement detection module to convert the absolute position signal and the relative movement signal into an output signal. 
     According to the present invention, an optical touch device includes a touch surface having a position mapping relationship with entire or a part of a picture displayed on a monitor, a first light source optically coupled to the touch surface to provide first light to project to the touch surface, a second light source optically coupled to an operational plane having the optical touch device thereon to provide second light to project to the operational plane, an image sensor unit optically coupled to the touch surface and the operational plane, respectively, to capture a first image by receiving first reflected light from the touch surface and generate a first input signal carrying the first image, and to capture a second image by receiving second reflected light from the operational plane and generate a second input signal carrying the second image, a processing unit electrically coupled to the image sensor unit to receive the first and second input signals, identify the first image carried by the first input signal to detect if any object contacts the touch surface or suspends over the touch surface and a position of each detected object, generate an absolute position signal according to the detected position to point to a mapped position on the picture, identify the second image carried by the second input signal to detect movement of the optical touch device, and generate a relative movement signal according to the detected movement of the optical touch device, and a transmission interface electrically coupled to the processing unit to convert the absolute position signal and the relative movement signal into an output signal. 
     According to the present invention, a passive touch control system includes a monitor, a host electrically coupled to the monitor, and an optical touch device electrically coupled to the host. The host controls the monitor to display a picture, and the optical touch device has a touch surface having a position mapping relationship with entire or a part of the picture. The optical touch device includes a light source optically coupled to the touch surface to provide light to project to the touch surface, an image sensor unit optically coupled to the touch surface to capture an image by receiving light from the touch surface and generate an input signal carrying the image, a processing unit electrically coupled to the image sensor unit to receive the input signal, identify the image carried by the input signal to detect if any object contacts the touch surface or suspends over the touch surface and a position of each detected object, and generate an absolute position signal according to the detected position to point to a mapped position on the picture, a movement detection module to detect movement of the optical touch device for generating a relative movement signal, and a transmission interface electrically coupled to the processing unit, the movement detection module, and the host, to convert the absolute position signal and the relative movement signal into an output signal, and transmit the output signal to the host. The host generates a control signal corresponding to the mapped position according to the output signal. 
     According to the present invention, a passive touch control system includes a monitor, a host electrically coupled to the monitor, and an optical touch device electrically coupled to the host. The host controls the monitor to display a picture, and the optical touch device has a touch surface having a position mapping relationship with entire or a part of the picture. The optical touch device includes a first light source optically coupled to the touch surface to provide first light to project to the touch surface, a second light source optically coupled to an operational plane having the optical touch device thereon to provide second light to project to the operational plane, an image sensor unit optically coupled to the touch surface and the operational plane, respectively, to capture a first image by receiving first reflected light from the touch surface and generate a first input signal carrying the first image, and to capture a second image by receiving second reflected light from the operational plane and generate a second input signal carrying the second image, a processing unit electrically coupled to the image sensor unit to receive the first and second input signals, identify the first image carried by the first input signal to detect if any object contacts the touch surface or suspends over the touch surface and a position of each detected object, generate an absolute position signal according to the detected position to point to a mapped position on the picture, identify the second image carried by the second input signal to detect movement of the optical touch device, and generate a relative movement signal according to the detected movement of the optical touch device, and a transmission interface electrically coupled to the processing unit and the host to convert the absolute position signal and the relative movement signal into an output signal, and transmit the output signal to the host. The host generates a control signal corresponding to the mapped position according to the output signal. 
     According to the present invention, a passive touch control system includes an optical touch device and a monitor, the optical touch device has a touch surface, and an input detection method for the passive touch control system establishes a position mapping relationship between the touch surface and entire or a part of a picture displayed on the monitor, detects movement of the optical touch device to generate a relative movement signal, detects if any object contacts the touch surface or suspends over the touch surface and a position of each detected object, and generates an absolute position signal according to the detected position to point to a mapped position on the picture, and generates a control signal corresponding to the mapped position according to the absolute position signal and the relative movement signal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other objectives, features and advantages of the present invention will become apparent to those skilled in the art upon consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a block diagram of a passive touch control system according to the present invention; 
         FIG. 2A  and  FIG. 2B  illustrate operation of the optical touch device shown in  FIG. 1 ; 
         FIG. 3A  is a simplified diagram showing a mechanical switch below a touch surface; 
         FIG. 3B  is a simplified diagram showing a display unit below a touch surface; 
         FIG. 4  is a hardware arrangement of the optical touch device shown in 
         FIG. 1 ; 
         FIG. 5  is a block diagram of another passive touch control system according to the present invention; 
         FIG. 6  is a hardware arrangement of the optical touch device shown in  FIG. 5 ; and 
         FIG. 7  is a flowchart of an input detection method for a passive touch control system according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  is a system block diagram of a first embodiment according to the present invention, in which a passive touch control system includes a monitor  30 , a host  28  electrically coupled to the monitor  30 , and an optical touch device  10  electrically coupled to the host  28 . The optical touch device  10  includes a touch surface  18  for touch input, a light source  14  optically coupled to the touch surface  18  to provide light to project to the touch surface  18 , and an image sensor unit  20  optically coupled to the touch surface  18  to capture images by receiving light from the touch surface  18  and generate an input signal Si to carry the images for a processing unit  22  to recognize. If there are fingers or other objects contacting the touch surface  18  or suspending over the touch surface  18 , the touch points of the fingers or objects will reflect light to the image sensor unit  20 , so that light spots will appear in the images captured by the image sensor unit  20 . The processing unit  22  then can identify the image carried by the input signal Si to detect if any finger or object contacts the touch surface  18  or suspends over the touch surface  18  by identifying the light spots in the image, and if any finger or object is detected, the processing unit  22  further detects the position of each detected finger or object, and generate an absolute position signal Sp according to the detected positions. The host  28  controls the monitor  30  to display a picture  12 , and the touch surface  18  has a position mapping relationship with entire or a part of the picture  12 . Therefore, the position information contained in the absolute position signal Sp, which indicates the positions of the detected fingers or objects on the touch surface  18 , will point to the mapped positions on the picture  12  due to the position mapping relationship between the touch surface  18  and the picture  12 . As a result, touch operation on the touch surface  18  can be regarded as touch operation on the monitor  30 . The optical touch device  10  further includes a movement detection module  24  to detect movement of the optical touch device  10  and generate a relative movement signal Sm accordingly, and a transmission interface  26  electrically coupled to the processing unit  22 , the movement detection module  24 , and the host  28 , to receive the absolute position signal Sp and the relative movement signal Sm, convert the absolute position signal Sp and the relative movement signal Sm into an output signal So under some communication protocol, and transmit the output signal So to the host  28 . 
     For the hardware implementation, the light source  14  may be an optical device providing visible or invisible light, such as a light emitting diode (LED), the touch surface  18  may be provided by a glass or plastic plate transparent to the light provided by the light source  14 , and the image sensor unit  20  includes an optical sensor, such as a CMOS image sensor (CIS) and a charge coupled device (CCD), to convert the received light into electronic signals, and may further include a lens or a pinhole for imaging on the optical sensor. Preferably, the image sensor unit  20  operates with one or more frame rates to generate images in a unit of frame, and thus the input signal Si will contain image contents in a manner of frame by frame in a time sequence. The movement detection module  24  includes a device capable of movement detection, such as a rolling-ball mechanism, an optical detector, a motion sensor, and a gyroscope. 
     Since the touch surface  18  has a position mapping relationship with entire or a part of the picture  12  displayed on the monitor  30 , operation on the touch surface  18  is equivalent to operation on the picture  12 . The position mapping relationship may be automatically established when the host  28  starts up or when the optical touch device  10  is plugged to the host  28 , or may be established by a user in an application program. In an embodiment, referring to  FIG. 2A , the optical touch device  10  is a handheld device. When a finger  32  contacts the touch surface  18  at a point TP 1  or suspending over it, the absolute position signal Sp 1  generated by the optical touch device  10  will inform the host  28  of a mapped position PL 1  on the picture  12  displayed on the monitor  30 , so the host  28  can display a cursor  34  at the position PL 1 , just like the operation of using a mouse or other pointer. Further, if there is an icon  36  at the position PL 1 , the host  28  may be able to open a document linked to the icon  36  or execute an application program linked to the icon  36 , just like the operation of using a mouse or other pointer to click on the icon  36 . On the other hand, the relative movement signal Sm as a result of that the movement detection module  24  detects movement of the optical touch device  10  will direct the host  28  to operate according to the movement of the optical touch device  10 . For example, as shown in  FIG. 2A , the cursor  34  will be moved to another position PL 2 . Alternatively, the host  28  may perform relevant operation in an application program according to the relative movement signal Sm, for example, moving a picture or an object displayed on the monitor  30 , changing page or minimizing a window displayed on the monitor  30 , depending on the application program running on the host  28 . 
     The host  28  may work with the object detection and movement detection functions of the optical touch device  10  to generate control signals. In an embodiment, the host  28  does not execute the control operation corresponding to the absolute position signal Sp until it learns from the relative movement signal Sm that the optical touch device  10  has its movement having been zero or lower than a preset value over a period of time, to prevent operation conflict. Also, according to user&#39;s setting, the absolute position signal Sp and the relative movement signal Sm may be combined to generate a specific control signal. For example, when a finger  32  is placed at a position on the touch surface  18  that is mapping to the position of a speaker icon  36  on the monitor  30 , and the optical touch device  10  is moved vertically, a control signal for adjusting the volume will be generated. 
     In another embodiment, referring to.  FIG. 2B , when a finger  32  on or over the touch surface  18  slides from a position TP 1  to another position TP 2 , the host  28  can detect this slide of the finger  32  from the continuous variation of the absolute position signal Sp, and then move a cursor  34  on the monitor  30  from a position PL 1  to another position PL 2 . 
     From the embodiments illustrated by  FIG. 2A  and  FIG. 2B , it is shown that even if the monitor  30  is not a touch screen, the control function realized by the optical touch device  10  can allow users to perform intuitional and quick input operation. 
     In an embodiment, for realizing click operation, referring to  FIG. 1  and  FIG. 2A , the light source  14  may operate in a weak light mode or an intensive light mode. In the intensive light mode, when a finger  32  suspends over the touch surface  18 , although the finger  32  is not physically contacting the touch surface  18 , the light reflected by the finger  32  is still intensive enough to image the finger  32  onto the image sensor unit  20 , so the image sensor unit  20  can capture the image of the finger  32 , and further detect the position of the finger  32 . In the weak light mode, the image sensor unit  20  can capture the image of a finger  32  only when the finger  32  contacts the touch surface  18 . The optical touch device  10  switches the light source  14  between the two modes, for detecting the suspension position of a finger  32  to generate the absolute position signal Sp, and further generating a click signal when the finger  32  contacts the touch surface  18 . 
     In an embodiment, as shown in  FIG. 3A , the optical touch device  10  further includes a mechanical switch  38  below or beside the touch surface  18 , so that when the touch surface  18  is pressed by a finger  32 , not only the optical touch device  10  will detect the position of the finger  32  and generate an absolute position signal Sp accordingly, but also the switch  38  will be pressed to trigger a button signal as a click signal, like the operation of clicking a button of a mouse for selection operation. 
     In an embodiment, as shown in  FIG. 3B , the optical touch device  10  further includes a display unit  40  overlapped with the touch surface  18  thereon, for displaying a corresponding picture to the picture  12  displayed on the monitor  30 . As shown in  FIG. 2A  and  FIG. 2B , the corresponding picture shown on the touch surface  18  allows users to intuitionally operate the optical touch device  10  by referring thereto. 
       FIG. 4  is a hardware arrangement of the optical touch device  10  shown in  FIG. 1 , in which the movement detection module  24  is mounted at the bottom of a housing  100  such that when the housing  100  is placed on an operational plane  42 , the movement detection module  24  is close to the operational plane  42 , and similarly to a typical optical mouse, the movement detection module  24  includes a light source  44  to provide light to project to the operational plane  42  through a lens and then reflected by the operational plane  42  to impart on an image sensor  46  through another lens, the image sensor  46  keeps its image capturing, and a processing unit (not shown in the figure) generates a movement signal Sm according to the varying images. In this embodiment, the touch surface  18  is on the upper surface of a light guide plate  50  mounted at the top of the housing  100 , and the light source  14  is fixed to a lateral of the light guide plate  50  and provides light of a specific wavelength, for example infrared ray, to project to the light guide plate  50 , and the provided light penetrating into the light guide plate  50  propagates within the light guide plate  50  by internal total reflection and has a portion scattered by the light guide plate  50  to penetrate through the touch surface  18  outward. If a finger  32  contacts the touch surface  18  or suspends over the touch surface  18 , the finger  32  will establish a reflective surface at the touch point to reflect light back into the housing  100  and thus imparting on the image sensor unit  20 . In an embodiment, the light guide plate  50  only allows invisible light, such as infrared ray, to pass therethrough, thereby preventing interference caused by ambient visible light. 
     Referring back to  FIG. 1 , in an embodiment, the optical touch device  10  further includes a light control unit  16  electrically coupled to the light source  14  to control the light source  14 . For example, the light control unit  16  may turn off the light source  14  when the host  28  is shutdown or standby. Alternatively, the light control unit  16  may maintain the light source  26  at a small mute current when the host  28  is standby, or may only turn on the light source  14  when the image sensor unit  20  is going to capture images. Additionally, the light control unit  16  may be electrically coupled to the processing unit  22 , receive a control signal Sc from the processing unit  22 , and control the light source  14  according to the control signal Sc. For example, the processing unit  22  may identify the brightness of one or more images carried by the input signal Si to determine the control signal Sc for the light control unit  16  to adjust the light intensity provided, to optimize the clarity of the images captured by the image sensor unit  20 . Preferably, the light source  14  is blinking fast during image capturing, so that the image sensor unit  20  will capture images while the light source  14  emits light and does not emit light, respectively, and then the processing unit  22  uses the difference between the images captured while the light source  14  is on and off for image processing and identification to suppress the interference caused by the ambient light. Since the image taken by the image sensor unit  20  when the light source  14  is off is the background value caused by the ambient light, the interference caused by the ambient light can be eliminated or reduced by removing this background value before image identification. In other embodiments, it may switch the light projecting to the touch surface  18  by other means, for example using a shutter, such that the image sensor unit  20  can capture images when the light is on and off, respectively. 
       FIG. 5  is a system block diagram of a second embodiment according to the present invention, in which an optical touch device  48  uses some common components to carry out object detection and movement detection. In this embodiment, a touch surface  18 , a light source  14 , a light control unit  16 , an image sensor unit  54 , a processing unit  56 , and a transmission interface  26  are configured and operate as the embodiment shown in  FIG. 1  to detect object on the touch surface  18  to generate an absolute position signal Sp, and a light source  44 , a light control unit  52 , the image sensor unit  54 , and the processing unit  56  replace the movement detection module  24  shown in  FIG. 1  to detect movement of the optical touch device  48  to generate a relative movement signal Sm. Since the optical touch device  48  uses a single image sensor unit  54  and a single processing unit  56  to accomplish the object detection and the movement detection, the costs can be reduced. As shown in  FIG. 6 , in a hardware implementation of the optical touch device  48 , the optical components are properly arranged, including lens and reflector to establish the optical paths, such that the light reflected from the touch surface  18  and the light reflected from the operational plane  42  both incident upon the image sensor unit  42 . Referring to  FIG. 5  and  FIG. 6 , the processing unit  56  provides control signals Sc 1  and Sc 2  for the light control units  16  and  52  to control the light sources  14  and  44 , respectively, for example, turning on and off the light sources  14  and  44  or adjusting light intensity of the light sources  14  and  44 . Preferably, the light source  14  and  44  are controlled to provide light alternately in a time sequence, such that when the light source  14  emits light, the image sensor unit  54  captures images by receiving light from the touch surface  18  for generating an input signal Si 1 , and when the light source  44  emits light, the image sensor unit  54  captures images by receiving light from the operational plane  42  for generating an input signal Si 2 . The processing unit  56  processes the input signals Si 1  and Si 2  separately, thereby generating an absolute position signal Sp and a relative movement signal Sm, respectively, for the transmission interface  26  to convert into an output signal So for a host  28 . In different embodiments, the processing unit  56  may generate a control signal according to the absolute position signal Sp and the relative movement signal Sm for the transmission interface  26 . Preferably, the image sensor unit  54  operates with one or more frame rates to generate images in a unit of frame, so that the input signals Si 1  and Si 2  contain frames of image contents in a manner of frame by frame in a time sequence, respectively. The processing unit  56  compares the image contents of two or more successive frames in the input signal Si 2  to identify variation of the images captured from the operational plane  42  for detecting movement of the optical touch device  48 . Preferably, the processing unit  56  may identify brightness of one or more images detected from the input signals Si 1  and Si 2  to adjust light intensity of the light sources  14  and  44  for optimizing the clarity of the captured images, respectively. 
     In the optical touch devices  10  and  48 , the touch surface  18  is on a stiff plate such as a glass or plastic plate, so is highly durable. The positions of the objects on the touch surface  18  are acquired through optical sensing and thus, not only the images can be obtained instantly, but also the position resolution depends on the resolution of the image sensor unit  20  or  54 , which is much higher than the existing resistive and capacitive touch devices. Moreover, the light sources  14  and  44  may be realized by LEDs that consume less power. 
       FIG. 7  is a flowchart of an input detection method for a passive touch control system in an embodiment according to the present invention, in which step  58  performs movement detection by an optical touch device, such as illustrated by the above embodiments, to detect movement of the optical touch device, if the optical touch device moves, a corresponding relative movement signal will be generated and contain its moving direction and displacement, step  60  performs object detection by the optical touch device to detect if any object contacts or suspends over a touch surface, such as illustrated by the above embodiments, and if any object is detected, the position of each detected object will be further detected and a corresponding absolute position signal will be generated. Then, in step  62 , a host compares the detection result of the previous steps  58  and  60  to preset conditions to determine if any preset condition is matched. If it is, step  64  is performed for generation of a control signal according to the absolute position signal and/or the relative movement signal; otherwise, the process returns to step  58 . In an embodiment, if step  62  confirms that the displacement of the optical touch device detected by step  58  is smaller than a preset value, the displacement will be ignored and the process returns to step  58 . In another embodiment, if step  62  confirms that the displacement of the optical touch device detected by step  58  is greater than a preset value, and that the position of the object detected by step  60  is substantially the same as that of the previous detection, step  64  will generate a control signal for moving a cursor. In yet another embodiment, if step  62  confirms that the displacement of the optical touch device detected by step  58  is smaller than a preset value, and that the position of the object detected by step  60  has no object in the previous detection and is mapping to a position on the mapped picture where an icon or a link exists, step  64  will generate a control signal for clicking on the icon or the link. In still another embodiment, if step  62  confirms that the displacement of the optical touch device detected by step  58  is greater than a present value, and that the position of the object detected by step  60  is substantially the same as that of the previous detection and is mapping to a position on the mapped picture where an icon exists, step  64  will generate a control signal for dragging the icon. In a further embodiment, if step  62  confirms that the displacement of the optical touch device detected by step  58  is greater than a present value, and that the position of the object detected by step  60  is substantially the same as that of the previous detection and is mapping to a position on the mapped picture where words exist, step  64  will generate a control signal for selecting the words. By generating control signals as these examples, the method not only provides control functions as a mouse, but also realizes all possible operation traditionally performed on a touch screen. 
     The above embodiments also demonstrate that the present invention uses an optical touch device to establish a passive touch control system and thus is suitable to all types of monitors, without need of either expensive touch screens or high-speed calculation, but merely requiring a computer or a device having a processor as a host. Thus, the present invention can be readily applied to an existing system without using expensive or additional hardware. In comparison with touch screens, an optical touch device according to the present invention is simpler and less cost, and is more durable than resistive and capacitive touch screens, while providing high position resolution. 
     While the present invention has been described in conjunction with preferred embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and scope thereof as set forth in the appended claims.