Abstract:
A highly sensitive movable touchpad is disclosed in the present invention. It is used for laptop computers and has a slidable template for users to move so that a cursor can be controlled by the touchpad. A resistive or capacitive detecting surface can be applied for detecting users&#39; click, double click, drag, or scroll motion on any point of the surface. Additionally, there is an optical displacement sensor provided under the slidable template for detecting surface information on the back surface of the slidable template. A sequence of images of surface movement are processed by an image processing unit. Then, relative movement information is calculated and sent to an operating system in the computer. The operating system controls the cursor with the relative movement information. The present invention uses edge detectors for dynamically controlling the cursor and calibrating location of the cursor so that positioning of the touchpad is synchronous with the cursor.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a movable touchpad. More specially, the present invention relates to a movable touchpad for a laptop computer. 
     BACKGROUND OF THE INVENTION 
     For convenience of portability, a laptop computer usually has a touchpad near a keyboard to replace a mouse as an input device. Users are not limited to the environment where they use the laptop computer and free from inconvenience that the mouse has to be carried all the way. However, touchpads have defects such as low sensitivity and easy affection by environment. Most users would like to use a mouse rather than a touchpad. 
     A touchpad generally comprises two portions: a touch detecting unit and a touch control unit. The touch detecting unit is used for detecting and receiving touch control location data from users. Then, the touch control location data is sent to the touch control unit. By the touch control unit, the location data is converted into a coordinate. The coordinate is sent to an operating system (OS) of a computer to control location of a cursor. A common touchpad utilizes resistance, capacitance, infrared ray, or surface acoustic wave. 
     However, characteristics of the touchpad are easily influenced by change of the atmospheric pressure to affect operation sensitivity. For example, when the atmospheric pressure becomes lower, human body will lower its internal pressure to adapt to the change of the atmospheric pressure. It causes change of conductivity in the human body. When a capacitive touchpad is used, due to reduction of coupled capacitance formed between the human body and the touchpad, sensitivity of the touchpad decreases accordingly. Hence, users need to exert larger force. On the other hand, when the atmospheric pressure becomes higher, users merely need to exert smaller force. 
     As to a resistive touchpad, the principle thereof is pressure detection on the surface of the touchpad. After voltage transformation, the touch location can be calculated. When the atmospheric pressure becomes lower, users need to exert larger force. When the atmospheric pressure becomes higher, users merely need to exert smaller force. 
     Therefore, under different atmospheric pressures, operating sensitivity of the touchpad will be affected. It is inconvenient for users to change their habit and force in using the touchpad. 
     Touchpads have lower sensitivity in moving. When the sensitivity is increased, precise positioning can not be achieved. Sensitivity and positioning precision will be affected by user contact area. Additionally, when a current touchpad is used to move the cursor, fingers are needed to draw back and forth on the touchpad to move the cursor. When the cursor needs to be moved a longer distance, it is inconvenient for the fingers to draw back and forth many times. 
     Since traditional touchpads are easily influenced by the change of the environmental atmospheric pressure or sweats from the fingers to affect operation sensitivity and positioning precision, it is necessary to provide a touch control device having sensitivity irrespective of change of the environmental atmospheric pressure. Meanwhile, it can provide better control over sensitivity so that a laptop computer can control the cursor with high sensitivity without the aid of a mouse. 
     Therefore, in order to solve problems mentioned above, US Patent Publication No. 2008/0068332 provides a new touchpad device to control the cursor on the screen. Please refer to  FIG. 1 . The invention uses a light source to scan a moving template and reflected light beams from the moving template to calculate movement and location of the cursor corresponding to displacement of the moving template. In addition, there is an automatic homing device for fixing the moving template in a certain point so that the template can be further used to control the cursor. However, the automatic homing device in this invention doesn&#39;t conform to usual practice. There is no detailed study on relation between cursor displacement speed and edge contacting time of the touchpad. It causes new problems and becomes more inconvenient. 
     SUMMARY OF THE INVENTION 
     In order to solve the problems and inconvenience in the prior art mentioned above, the present invention provides a movable touchpad for a computer. It has a slidable template for users to touch and move. It can also provide users with feeling of movement to control location of the cursor of the computer. There is a resistive or capacitive surface above the slidable template for providing users with click, double click or drag function on any location of the surface. Additionally, an optical detecting device is provided below the slidable template for detecting displacement optical speckle images of the back surface of the slidable template. The optical speckle images are continuously processed by an image processor. Relative displacement data are calculated and sent to the operating system of the computer for the operating system to control location of the cursor. Furthermore, the present invention also uses a edge detecting device. The edge detecting device not only provides a dynamic control over the cursor, but also calibrates the location of the cursor to synchronize the movement of the slidable template and the corresponding movement of the cursor. 
     By replacing a conventional capacitive or resistive touchpad with a slidable template to control movement of a cursor, it can avoid adverse influence on moving the touchpad caused by change of atmospheric pressure. Besides, an optical mechanism using invariant optical speckle imaging device and method with a slidable template has higher sensitivity and linearity. Thus, it doesn&#39;t need to move fingers back and forth frequently on the touchpad for achieving a long movement of a cursor. It can reduce fatigue of fingers. Accordingly, prevention of wrist injury caused by long time use of a mouse and finger injury caused by long time use of a traditional touchpad can be achieved by the present invention. Furthermore, a slidable template can provide users with good feeling like using a mouse. 
     In accordance with an aspect of the present invention, a highly sensitive movable touchpad for a digital apparatus having a cursor, includes: a slidable template having a front surface exposed and a back surface with a specific texture; a limiting member, for limiting the slidable template within a moving range and providing the slidable template with a low friction, surrounding the slidable template and exposing central portion of the front surface of the slidable template; an optical displacement detecting device, located below the slidable template, for detecting movement of the slidable template, including: a light source, for emitting light beams to illuminate the back surface of the slidable template; an image sensor for receiving speckle images formed by light beams scattered by the back surface; and an image processor for obtaining relative location, moving direction and speed of the slidable template by comparison of the speckle images; and a control unit for controlling corresponding movement of the cursor of the digital apparatus according to the relative location, moving direction and speed obtained from the image processor. 
     Preferably, the limiting member has an opening around central portion of the back surface of the slidable template for exposing the back surface to be illuminated by the light beams from the light source. 
     Preferably, the optical displacement detecting device further includes a lens for converting the light beams emitted from the light source into parallel light beams to illuminate the back surface of the slidable template. 
     Preferably, the optical displacement detecting device further includes an imaging module for receiving the scattered light beams and generating diffractive light beams. 
     Preferably, the imaging module includes an imaging lens and an aperture. 
     Preferably, the movable touchpad further includes a capacitive touch switch located on the slidable template for providing the slidable template with touch functions. 
     Preferably, the touch functions include single click, double click, drag and scroll. 
     Preferably, the movable touchpad further includes a resistive touch switch located on the slidable template for providing the slidable template with touch functions. 
     Preferably, the touch functions include single click, double click, drag and scroll. 
     Preferably, the front and back surfaces of the slidable template are form of an identical material. 
     Preferably, the front and back surfaces of the slidable template are form of different rigid materials. 
     Preferably, the slidable template is made of aluminum. 
     Preferably, the front and back surfaces of the slidable template have different surface characteristics. 
     Preferably, the surface characteristics include roughness and texture. 
     Preferably, the movable touchpad further includes a edge detecting device, provided at four sides of the limiting member, for detecting whether the slidable template reaches limit of the moving range. 
     Preferably, the edge detecting device includes a miniaturized touch switch, sensor or button switch. 
     Preferably, the edge detecting device provides a edge contact signal to the image processor for synchronizing the movement of the slidable template and the corresponding movement of the cursor. 
     Preferably, the edge contact signal is a digital pulse. 
     Preferably, the light source is a light emitting diode (LED) or laser diode (LD). 
     Preferably, the image processor is a central processing unit (CPU), field programmable gate array (FPGA), digital signal processor (DSP) or application-specific integrated circuit (ASIC). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a prior art of a touch control device. 
         FIG. 2  illustrates a touchpad of the present invention. 
         FIG. 3  illustrates a first embodiment of the present invention. 
         FIG. 4  illustrates a second embodiment of the present invention. 
         FIG. 5  illustrates another touchpad of the present invention. 
         FIG. 6  illustrates a third embodiment of the present invention. 
         FIG. 7  shows a relationship between cursor movement speed and contact time of the touchpad and the edge in the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The goal of the present invention is to provide a highly sensitive movable touchpad. It can provide control over cursor with good sensitivity and touch control functions. The movable touchpad can be applied to laptop computers. It can also be applied to joysticks, remote controls and any interfaces using a cursor for browsing. 
     The present invention is illustrated in detailed by three embodiments. 
     First Embodiment 
     As shown in  FIG. 2  and  FIG. 3 , a movable touchpad comprises a slidable template  202  and a housing  204 . The slidable template  202  is provided in the housing  204 . The housing  204  has an upper opening on the top surface and a lower opening on the bottom surface. The upper opening is for fingers to touch. The slidable template  202  is movable and exposed externally via the upper opening of the housing  204  for users to use fingers to control movement. Please refer to  FIG. 2 .  FIG. 2  shows a longitudinal sectional view of the housing  204  and slidable template  202  (with central portion of the housing  204  omitted for easy understanding) in the upper portion of the figure and a top view thereof in the lower portion of the figure. The housing  204  has a space for accommodating the slidable template  202 . A main function of the housing  204  is to provide the slidable template  202  with a low sliding friction and limit moving range of the slidable template  202 . The moving range has the same aspect ratio as that of the screen. Hence, when the slidable template  202  moves in the limited moving range, the cursor can be moved to any point of the screen. 
     As shown in  FIG. 3 , an optical displacement detecting device  206  is installed below the slidable template  202  for detecting displacement of the slidable template  202 . At the lower opening of the housing  204 , a light source  2061  (LED or LD) of the optical displacement detecting device  206  can be used to illuminate the back surface of the slidable template  202 . 
     The front surface of the slidable template  202  is formed with a material which provides users&#39; fingers with comfortable touching feeling. The back surface of the slidable template  202  is advantageous to the optical displacement detecting device  206  for detecting displacement. For example, for a LED light source, the back surface is rough so as to be convenient for displacement calculation. However, for a laser light source, the back surface is well scattering so as to catch good contrast optical speckle images for calculating optical speckles displacement. Therefore, the slidable template  202  can be made of a single rigid material (for example, aluminum), composed rigid materials (front and back surfaces of the slidable template  202  having different materials), or any two materials having different surface characteristics (such as roughness and texture) in the front and back surfaces of the slidable template  202 , to satisfy the requirements that the front surface needs good feeling and the back surface needs to perform optical displacement detection. 
     Another function of the slidable template  202  is to prevent light beams from the light source  2061  from hurting human eyes. 
     In addition to the light source  2061 , the optical displacement detecting device  206  comprises a lens  2062 , an imaging lens  2063 , an aperture  2064 , an image sensor  2065  and an image processor  2066 . The imaging lens  2063 , aperture  2064  and image sensor  2065  form an optical detecting mechanism. The lens  2062  converts light beams from the light source  2061  into parallel light beams and send the parallel light beams to the back surface of the slidable template  202 , and scattered light beams are generated. The imaging module composed of the imaging lens  2063  and aperture  2064  is used to receive scattered light beams and generate several diffractive light beams. After the light beams emitted from the light source  2061  are illuminated to the back surface of the slidable template  202  via the lens  2062 , the imaging lens  2063  and aperture  2064  will form shadows and optical speckles of the back surface of the slidable template  202  onto the image sensor  2065  for converting the received optical speckles into imaging signals. Later, the imaging signals representing continuous movement of the optical speckles are sent to the image processor  2066  to obtain a displacement signal of the slidable template  202 . The displacement signal is sent to a driver of a computer  208  for providing location control to the cursor. The image processor  2066  is in charge of imaging processing and displacement calculation. It generates location data with respect to the slidable template  202  according to the received optical speckles. Relative location, moving direction and speed of the slidable template  202  can be obtained according to the location data. The image processor  2066  is a central processing unit (CPU), field programmable gate array (FPGA), digital signal processor (DSP) or application-specific integrated circuit (ASIC). 
     Second Embodiment 
     As shown in  FIG. 4 , most elements and their functions of the present embodiment are the same as those in  FIG. 3 . A movable touchpad of the second embodiment has a slidable template  302 , a housing  304 , and an optical displacement detecting device  306  (including a light source  3061 , a lens  3062 , an imaging lens  3063 , an aperture  3064 , an image sensor  3065  and an image processor  3066 ). Members having like functions will be identified by like reference numerals and overlapping descriptions will be omitted. In this embodiment, the slidable template  302  is a combination of different rigid materials. The back surface of the slidable template  302  is used as an optical blocker and a detected surface for the optical displacement detecting device  306 . 
     The front surface of the slidable template  302  is provided with a capacitive or resistive touch switch  3022 . When an object, such as a finger, touches the touch switch  3022 , a touch detection signal will be sent to the image processor  3066  of the optical displacement detecting device  306 . In addition to image processing and displacement calculation, the image processor  3066  performs detection of touch detection signal and determination of the kind of cursor functions, such as single click, double click, drag or scroll. Then, the image processor  3066  sends the detected displacement signal as mentioned in the first embodiment and touch detection signal to a driver of a computer  308  to provide cursor location control and cursor functions. 
     Third Embodiment 
     A slidable template is equally partitioned into several regions which are mapped correspondingly to various portions of the screen. Users control displacement and direction of movement of the slidable template to map the movement of the slidable template to the movement of the cursor on the screen. Since the slidable template is confined in a limited moving range, in order to have a better dynamic control for the cursor, such as gaming control, a edge detecting device is incorporated. 
     The edge detecting device can be a miniaturized touch switch, sensor, button switch or I/O contacts. It provides a edge contact signal which can be a digital pulse. The edge detecting device detects contact time of the slidable template and the edge detecting device. 
     Please refer to  FIG. 5  and  FIG. 6 . A left edge detecting device  4052 , a right edge detecting device  4054 , a top edge detecting device  4056  and a bottom edge detecting device  4058  are installed at the left, right, top and bottom sides (seen from the top view) inside a housing  404 . The edge detecting devices are to detect whether a slidable template  402  contacts edges of the moving range or not. When the slidable template  402  contacts the edges, an image processor  4066  of an optical displacement detecting device  406  will receive a edge contact signal. The optical displacement detecting device  406  includes a light source  4061 , a lens  4062 , an imaging lens  4063 , an aperture  4064 , the image sensor  4065  and the image processor  4066 . Members having like functions are identified by like reference numerals and overlapping descriptions will be omitted. The edge contact signal is a digital pulse. The slidable template  402  holds stationary after it contacts the edge detecting device. While the slidable template  402  is stationary, the image processor  4066  will keep receiving the digital pulses to determine stationary status and contact time of the slidable template  402 . Now, in order to ensure that the cursor moves in synchronization with the slidable template  402  to the edge of the screen, the image processor  4066  reports an predicted moving speed of the cursor to a computer  408  to cause the cursor to contact the edge of the screen while the slidable template  402  is stationary. 
     As shown in  FIG. 7 , the abscissa represents contact time (t) of the slidable template  402  and the edge and the ordinate represents movement speed (v) of the cursor. Time t is set to zero while the slidable template  402  first contacts the edge detecting device. Segment (a) represents a situation where 0≦t≦T 1  and the computer  408  controls the cursor to move to the edge at a constant speed V. Segment (b) represents a situation where T 1 ≦t≦T 2  and moving speed of the cursor will increase linearly. It can also increase exponentially as Segment (c). When t≧T 2 , the speed drops to zero as Segment (d). Before the cursor arrives at the screen edge, location of the cursor is calculated by the image processor  4066  and the image processor  4066  sends out predicted displacement data. After the cursor arrives at the screen edge, the speed drops to zero and the cursor stops moving. Values of time T 1 , time T 2 , speed V, slope of Segment (b) and curvature of the Segment (c) can be set by a configuration program of the computer  408 , and sent to the image processor  4066 . 
     Furthermore, users can also decide to adopt Segment (a), (b) or (c). For example, when T 1 =0 and T 2 ≠0, Segment (a) is not applicable, and only Segment (b) or (c) is workable. When T 1 ≠0 and T 1 =T 2 , only Segment (a) is workable. When T 1 =T 2 =0, the cursor arrives at the screen edge if the slidable template contacts the edge, and no movement of the cursor can be seen. 
     The edge detecting devices can provide not only dynamic control over the cursor, but also adjustment for the location of the cursor to synchronize movement of the slidable template with that of the cursor on the screen. 
     The present invention is not limited to the embodiments above. For example, the moveable touchpad of the second embodiment can be integrated with that of the third embodiment. 
     While the invention has been described in terms of what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention needs not be limited to the disclosed embodiments. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims, which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.