Patent Document

TECHNICAL FIELD 
     This invention relates generally to a combined piezo sensor and actuator for use with display devices. 
     BACKGROUND 
     A touchscreen is a monitor, typically based either on Liquid Crystal Display (LCD) or Cathode Ray Tube (CRT) technology, that accepts direct screen input. The ability to accept screen input is facilitated by an external device, such as a light pen, or an internal device, such as a touch overlay and controller, that relays the X,Y coordinates of a screen interaction to a computer controlling the screen display. 
     Resistive LCD touch screen monitors and displays rely on a touch overlay, composed of a flexible top layer and a rigid bottom layer separated by insulating dots, attached to a touchscreen controller. Typically, the inside surface of each of the two layers is coated with a transparent metal oxide coating (ITO) that facilitates a gradient across each layer when voltage is applied. Pressing the flexible top sheet creates electrical contact between the resistive layers, producing a switch closing in the circuit. Control electronics coupled to the overlay alternate voltage between the layers and pass the resulting X and Y touch coordinates to the touchscreen controller. The touchscreen controller data is then passed on to the computer operating system for processing. 
     Resistive touchscreen technology possesses many advantages over other alternative touchscreen technologies, such as acoustic wave, capacitive, Near Field imaging, and infrared. Being highly durable, resistive touchscreens are less susceptible to contaminants that can adversely affect acoustic wave touchscreens. In addition, resistive touchscreens are less sensitive to the effects of scratches that can render resistive touchscreens inoperative. For industrial applications, resistive touchscreens are more cost effective than Near Field imaging touchscreens. 
     It is becoming increasingly common for portable electronic devices to make use of touch screen technology when providing a display. In such instances, a user typically presses upon the display, such as with a finger or other implement, to input data or make a selection from amongst data displayed on the touch screen. Resistive touch screen technology is often used to determine finger position on the screen. Capacitive finger position technology is increasingly utilized but requires careful calibration to distinguish between a “finger on the display” condition and a “click” event. In either case, active tactility is required for a proper user experience. By “active tactility”, it is meant that the display provides tactile feedback to a user to transmit information related to the input or selection of data. Absent such a tactile response, it can be difficult for a user to ascertain if an intended input or selection was registered by the device. 
     Traditional methods for providing tactile feedback include the physical construction of entry keys to provide a “click” upon successful engagement as well as piezo-electric elements to provide a return force or vibration in the event that a key is successfully pressed. When combined, it is common for the touch screen displays and tactile feedback elements to form separate, if complimentary, systems. 
     The requirements of implementing a touch screen display and a separate active tactile feedback in mobile electronic devices are often too demanding when employing traditional solutions. For example, the presence of a tactile feedback layer can add excessive size to a small display. One other drawback associated with traditional touch screens is the degradation of the visual output from the display due to the addition of resistive layers forming the touch sensor. 
     There therefore exists a need for a system providing both touch screen input ability and tactile feedback that is compact and which is compatible with the display devices of mobile platforms. 
     SUMMARY OF THE PREFERRED EMBODIMENTS 
     In accordance with an exemplary embodiment of the invention a device includes a piezo actuator comprising a piezo-electric material, and at least one piezo sensor formed of the piezo-electric material and electrically isolated from the piezo actuator, wherein the piezo actuator and the piezo sensor comprise a generally rectangular expanse. 
     In accordance with another exemplary embodiment of the invention a mobile device includes a sensor/actuator device having a first and second side including a piezo actuator formed of a piezo-electric material, and at least one piezo sensor formed of the piezo-electric material and electrically isolated from the piezo actuator, a display having a first and second side the first side of the display located in opposition to the first side of the sensor/actuator device, and a processor coupled to the piezo actuator and the at least one piezo sensor, wherein each of the sensor/actuator device and the display form a generally rectangular expanse. 
     In accordance with another exemplary embodiment of the invention a method includes providing a sensor/actuator device having a first and second side including a piezo actuator formed of a piezo-electric material, and at least one piezo sensor formed of the piezo-electric material and electrically isolated from the piezo actuator, providing a display having a first and second side the first side of the display located in opposition to the first side of the sensor/actuator device, wherein each of the sensor/actuator device and the display form a generally rectangular expanse, detecting an activation of the at least one piezo sensor in response to a force applied to the display, and operating the piezo actuator to provide tactile feedback in response to the activation of the piezo sensor. 
     In accordance with another exemplary embodiment of the invention a program of machine-readable instructions, tangibly embodied on an information bearing medium and executable by a digital processor, performs actions directed toward interacting with a sensor/actuator device, the actions comprising receiving an input signal indicative of a pressure applied to at least one piezo sensor formed of a piezo-electric material, the at least one piezo sensor being electrically isolated from a coplanar piezo actuator formed of the piezo-electric material, processing the input signal to determine an activation of the at least one piezo sensor, and operating the piezo actuator in response to the activation of the at least one piezo sensor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other aspects of these teachings are made more evident in the following Detailed Description, when read in conjunction with the attached Drawing Figures, wherein: 
         FIG. 1   a . is a top view of an exemplary embodiment of a sensor/actuator device of the invention. 
         FIG. 1   b . is a side view of an exemplary embodiment of a sensor/actuator device of the invention and a display device. 
         FIG. 2 . is a diagram of an exemplary embodiment of the circuit connections for configuring a sensor/actuator of the invention. 
         FIG. 3 . is a diagram of an exemplary embodiment of a mobile device for practicing the invention. 
     
    
    
     DETAILED DESCRIPTION 
     In an exemplary embodiment of the present invention, there is provided a combined piezo sensor and piezo actuator device. The piezo sensors utilize a piezo element to generate an electrical signal in response to physical pressure, such as the force exerted by a user&#39;s finger, so as to detect user input. The piezo actuator utilizes a similar piezo element to provide tactile feedback, such as vibration, to a user of the device. Preferably, both the piezo sensors and the piezo actuator are fabricated from a single piezo-electric element so as to be both coplanar and electronically isolated from one another. The difference in operation between the piezo sensors and the piezo actuator is achieved through a coupling of the piezo sensors and the piezo actuator to a voltage source and a differential voltage measurement device respectively as described more fully below. 
     With reference to  FIGS. 1   a - 1   b , there is illustrated an exemplary embodiment of a sensor/actuator device  15  according to the invention. The sensor/actuator device  15  may form, but is not limited to, a display device, touch pads, and keypads.  FIG. 1   a  is a top view of the sensor/actuator device  15 . Sensor/actuator device  15  is formed of a piezo actuator  13  about which is disposed at least one piezo sensor  11 . As the sensor/actuator device  15  will be situated below a display device, such display devices being typically of a generally rectangular construction, the sensor/actuator device  15  is likewise preferred to be of a generally rectangular shape. 
     The sensor/actuator device  15  is preferably formed of a single piece of piezo-electric material forming a single piezo element  23 . Preferred piezo-electric materials include, but are not limited to, serial and parallel bimorph piezo-electric materials. To form the piezo-electric material, piezoceramics can be deposited onto a metal sheet functioning as a middle electrode of the bimorph structure using a sintering process. During production, a masking operation can be performed to isolate the piezo sensors  11  from the piezo actuator  13 . The mask can be a mechanical frame covering the areas to be isolated during a sintering process. This isolation results in piezo sensors  11  which are electrically isolated from the piezo actuator  13  while remaining structurally coupled via a ground electrode  19 ′. Such an isolation can be achieved through a physical isolation in the form of a gap  21  formed between each of the piezo sensors  11  and the piezo actuator  13 . In addition, post fabrication, but before poling the piezo-electric material, an electrical insulator can be deposited into the gaps  21  to maintain the electrical isolation of the piezo sensors  11  from the piezo actuator  13 . In addition, isolated areas can be produced by depositing a dielectric material over the areas. The dielectric material survives the sintering process. In another exemplary embodiment, the piezo sensors  11  and piezo actuator  13  can be isolated from each other through a process of etching or otherwise mechanically removing the piezo material between them. Typically, after performing the poling, procedures requiring high temperatures or mechanical stresses are to be avoided as they can degrade the piezoelectricity of the element. 
     As illustrated, there are four piezo sensors  11  fabricated into the sensor/actuator device  15 . These piezo sensors  11  are generally rectangular in shape and are located about a periphery of, or proximate, the piezo actuator  13 . Specifically, the piezo sensors  11  are located in the corners of the generally rectangular sensor/actuator device  15 . The piezo actuator  13  extends in continuous fashion between the piezo sensors  11  covering the remainder of the generally rectangular expanse of sensor/actuator device  15 . The invention, however, is not so limited. Rather the invention is drawn to broadly encompass any number of piezo sensors  11  electrically isolated from a piezo actuator  13  and structurally coupled via a ground electrode  19 ′ whereby the piezo sensors  11  and the piezo actuator  13  reside in the same general plane. For example, a single piezo sensor  11  can be entirely surrounded by the piezo actuator  13  and separated by a gap. 
     As noted above, it is preferred that the combination of the piezo actuator  13  and the piezo sensors  11  combine to form a generally rectangular shape as the sensor/actuator device  15  is intended to correspond to the general size and shape of a display. In addition, as will be made clear below, the electrical connections required to operate the sensor/actuator device  15  are most efficiently realized when the piezo sensors  11  are located about the periphery of the sensor/actuator device  15 . 
     With reference to  FIG. 1   b , there is illustrated a side view of an exemplary embodiment of the sensor/actuator device  15  of the invention. As is evident, both the piezo actuator  13  and piezo sensors  11  are formed of a single piezo element  23 . In the present example, the piezo element  23  is a parallel bimorph piezo element  23  formed with three electrodes  19 . Electrodes  19 ,  19 ″ are coupled to opposing outer surfaces of the piezo element  23 , while electrode  19 ′ extends through and divides the piezo element  23  into two pieces and is coupled to ground. There is further illustrated display  17 . Display  17  may be any display device capable of presenting visual information in the form of an image upon display  17  and flexible enough to allow a pressure applied to an outer surface of the display  17  to generate an electrical output from the piezo sensors  11  as described more fully below. Typical displays  17  include, but are not limited to, liquid crystal displays (LCDs). 
     As discussed above, the sensor/actuator device  15  is preferably approximately the same size and shape as the display under which it rests. Display  17  is therefore illustrated as extending across an expanse, in two dimensions exclusive of a thickness, approximately equal to the expanse over which the sensor/actuator device  15  extends. Typical dimensions of thickness for the sensor/actuator device  15  range from approximately 0.3 to 0.7 mm. A side of display  17  is separated from a side of the sensor/actuator device  15  by a distance d. In operation, and as depicted, the distance d is of a value sufficiently small so as to allow a force F applied to an outer surface of the display  17  to be transmitted to a piezo sensor  11  to an extent great enough to be sensed as described below. Conversely, the display  17  provides sufficient flexibility to allow vibrations generated by the piezo actuator  13  to pass through the display  17  to be sensed by a user. Display  17  can also reside such that a side of display  17  rests in contact with a side of the sensor/actuator device  15 . In such an instance, the distance d is approximately equal to zero. 
     With reference to  FIG. 2 , there is illustrated a wiring diagram of an exemplary embodiment by which the sensor/actuator device  15  of the invention can be operated. It is a property of piezo-electric materials that physical deformation, as occurs when pressure is applied, gives rise to an electrical current. Conversely, when an electrical charge is applied to a piezo-electric material, a physical deformation of the piezo-electric material can be induced. 
     As illustrated, the piezo actuator  13  is coupled to a voltage pump  35  for providing a voltage to the piezo actuator  13 . Specifically, voltage pump  35  provides a voltage to the external electrodes  19 ,  19 ″ of the piezo actuator  13 . When a voltage is applied by the voltage pump  35  to the piezo actuator  13 , the piezo actuator  13  bends in response. Repeated stressing of the piezo actuator  13  via the application of a plurality of applications of voltage to the piezo actuator  13  will result in a vibration of the piezo actuator  13 . Similarly, a single application and cessation of applied voltage to the piezo actuator  13  can approximate the tactile sensation of a “click”. In a preferred embodiment, the piezo actuator  13  operates in a 31-mode. A 31-mode actuator  13  produces displacement perpendicular to an electric field applied parallel to the piezo element  23 . Typical voltages for application to the piezo actuator  13  operating in a portable electronic device range from approximately 25 volts to approximately 185 volts. 
     Similarly, as illustrated, each piezo sensor  11  is coupled to a differential potential measurement device  31  for measuring a differential electrical potential formed across the piezo sensor  11  when physically deformed. When a pressure, such as that resulting from a force F, is applied to a piezo sensor  11 , a sensor signal is generated. In the exemplary embodiment illustrated, this sensor signal is measured by the differential potential measurement device  31  as the difference between the negative signal (with respect to ground) from a front surface of the piezo sensor  11  (the side closest to display  17 ) and a positive signal from an opposing rear surface of the piezo sensor  11 . Preferably, each piezo sensor  11  is operated in a 33-mode. A 33-mode sensor produces a voltage differential across opposing surfaces when deformed in a direction parallel to the direction of the polarization of the piezo element  23 . 
     There is further illustrated a control device, processor  33 , for controlling the operation of the voltage pump  35  and for receiving an output signal from the differential potential measurement device  31  indicative of the activation of a piezo sensor  11 . In the embodiment shown, an A/D converter is coupled to both the differential potential measurement device  31  and the processor  33  for converting the analog signal of the differential potential measurement device  31 , indicative of the force applied to a piezo sensor  11 , to a digital output signal capable of reception by the processor  33 . 
     While only one differential potential measurement device  31  is illustrated, a separate differential potential measurement device  31  is preferably coupled to each individual piezo sensor  11 , with the output of each differential potential measurement device  31  coupled to one or more A/D converters similarly coupled to the processor  33 . In an exemplary embodiment, each piezo sensor  11  corresponds to an image or to part of an image displayed upon display  17  and intended to be selected. As a result, applying a force to a portion of the display  17  corresponding to a portion of the displayed image to be selected, under which rests a piezo sensor  11 , results in a signal being sent to the processor  33  indicative of an activation of the associated piezo sensor  11 . In the instance that the processor  33  has access to the image data displayed upon display  17 , such as through access to a memory in which the image is stored, the processor  33  can correlate the individual piezo sensor  11  activated to an intended logical selection of an image element, such as a button, by a user. 
     The processor  33  is any device or element capable of receiving an input, performing actions upon the input, and issuing an output in response thereto. In the exemplary embodiment illustrated, the processor  33  receives an input indicative of the activation of a piezo sensor  11  and issues an output to the voltage pump  35  in response thereto. More specifically, the processor  33  receives a digital input signal from A/D converter  35  when a force F is applied to a piezo sensor  11 . The processor  33  can compare the received input signal to a threshold value, either stored internally or in external memory coupled to the processor  33 , for determining if the force F applied to the piezo sensor  11  is of sufficient magnitude to indicate an activation of the piezo sensor  11 . 
     If the input signal is deemed to be of sufficient magnitude (greater than or equal to the threshold value), the processor proceeds to instruct the piezo actuator  13  to provide tactile feedback indicative of the activation of a piezo sensor  11 . As described above, the voltage pump  35  may be instructed by the processor  33  to provide an output voltage to the piezo actuator  13  of sufficient form and magnitude to produce a single “click” or a vibration of the piezo actuator  13 . In this manner, the processor  33  functions to detect the activation of individual piezo sensors  11  in response to the application of pressure upon one or more piezo sensors  11  and to provide tactile feedback thereto. 
     With reference to  FIG. 3 , there is illustrated a diagram of an exemplary embodiment of an implementation of the invention in a mobile device or station  300 . In a preferred embodiment, mobile device  300  is a mobile telephone. Mobile device  300  is formed of a processor  33 . Processor  33  is coupled to the display  17 , the piezo sensors  11 , the piezo actuator  13 , and a memory  39  upon which is stored data required by the processor  33 , such as a threshold value. 
     In general, the various embodiments of the mobile device  300  can include, but are not limited to, cellular telephones, portable electronic devices, personal digital assistants (PDAs) having wireless communication capabilities, portable computers having wireless communication capabilities, image capture devices such as digital cameras having wireless communication capabilities, gaming devices having wireless communication capabilities, music storage and playback appliances having wireless communication capabilities, Internet appliances permitting wireless Internet access and browsing, as well as portable units or terminals that incorporate combinations of such functions. 
     The embodiments of this invention involving the determination of an activation of a piezo sensor  11  and the subsequent provision of a tactile response via operation of the piezo actuator  13  may be implemented by computer software executable by a data processor of the mobile device  300 , such as the processor  33 , or by hardware, or by a combination of software and hardware. 
     The memory  39  may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The data processor  33  may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on a multi-core processor architecture, as non-limiting examples. 
     In general, the various embodiments such as controlling the display  17 , the piezo sensors  11 , and the piezo actuator  13 , may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. For example, some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device, although the invention is not limited thereto. While various aspects of the invention may be illustrated and described as block diagrams, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof. 
     Certain embodiments of the inventions may be practiced in various components such as integrated circuit modules. The design of integrated circuits is by and large a highly automated process. Complex and powerful software tools are available for converting a logic level design into a semiconductor circuit design ready to be etched and formed on a semiconductor substrate. 
     Programs, such as those provided by Synopsys, Inc. of Mountain View, Calif. and Cadence Design, of San Jose, Calif. automatically route conductors and locate components on a semiconductor chip using well established rules of design as well as libraries of pre-stored design modules. Once the design for a semiconductor circuit has been completed, the resultant design, in a standardized electronic format (e.g., Opus, GDSII, or the like) may be transmitted to a semiconductor fabrication facility or “fab” for fabrication. 
     Although described in the context of particular embodiments, it will be apparent to those skilled in the art that a number of modifications and various changes to these teachings may occur. Thus, while the invention has been particularly shown and described with respect to one or more exemplary embodiments thereof, it will be understood by those skilled in the art that certain modifications or changes may be made therein without departing from the scope and spirit of the invention as set forth above, or from the scope of the ensuing claims.

Technology Category: 3