Classifications

• • G—PHYSICS
  • G06—COMPUTING OR CALCULATING; COUNTING
  • G06F—ELECTRIC DIGITAL DATA PROCESSING
  • G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
  • G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
  • G06F3/02—Input arrangements using manually operated switches, e.g. using keyboards or dials
  • G06F3/023—Arrangements for converting discrete items of information into a coded form, e.g. arrangements for interpreting keyboard generated codes as alphanumeric codes, operand codes or instruction codes
  • G06F3/0233—Character input methods
• • G—PHYSICS
  • G06—COMPUTING OR CALCULATING; COUNTING
  • G06F—ELECTRIC DIGITAL DATA PROCESSING
  • G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
  • G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
  • G06F3/02—Input arrangements using manually operated switches, e.g. using keyboards or dials
  • G06F3/023—Arrangements for converting discrete items of information into a coded form, e.g. arrangements for interpreting keyboard generated codes as alphanumeric codes, operand codes or instruction codes
  • G06F3/0233—Character input methods
  • G06F3/0237—Character input methods using prediction or retrieval techniques
• • G—PHYSICS
  • G06—COMPUTING OR CALCULATING; COUNTING
  • G06F—ELECTRIC DIGITAL DATA PROCESSING
  • G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
  • G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
  • G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
  • G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
  • G06F3/0414—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means using force sensing means to determine a position
  • G06F3/04144—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means using force sensing means to determine a position using an array of force sensing means
• • G—PHYSICS
  • G06—COMPUTING OR CALCULATING; COUNTING
  • G06F—ELECTRIC DIGITAL DATA PROCESSING
  • G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
  • G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
  • G06F3/048—Interaction techniques based on graphical user interfaces [GUI]
  • G06F3/0487—Interaction techniques based on graphical user interfaces [GUI] using specific features provided by the input device, e.g. functions controlled by the rotation of a mouse with dual sensing arrangements, or of the nature of the input device, e.g. tap gestures based on pressure sensed by a digitiser
  • G06F3/0488—Interaction techniques based on graphical user interfaces [GUI] using specific features provided by the input device, e.g. functions controlled by the rotation of a mouse with dual sensing arrangements, or of the nature of the input device, e.g. tap gestures based on pressure sensed by a digitiser using a touch-screen or digitiser, e.g. input of commands through traced gestures
  • G06F3/04883—Interaction techniques based on graphical user interfaces [GUI] using specific features provided by the input device, e.g. functions controlled by the rotation of a mouse with dual sensing arrangements, or of the nature of the input device, e.g. tap gestures based on pressure sensed by a digitiser using a touch-screen or digitiser, e.g. input of commands through traced gestures for inputting data by handwriting, e.g. gesture or text
• • G—PHYSICS
  • G06—COMPUTING OR CALCULATING; COUNTING
  • G06F—ELECTRIC DIGITAL DATA PROCESSING
  • G06F2203/00—Indexing scheme relating to G06F3/00 - G06F3/048
  • G06F2203/048—Indexing scheme relating to G06F3/048
  • G06F2203/04808—Several contacts: gestures triggering a specific function, e.g. scrolling, zooming, right-click, when the user establishes several contacts with the surface simultaneously; e.g. using several fingers or a combination of fingers and pen

Definitions

• the present invention is related to providing input to a processor comprising a sensor pad having a surface and a sensor array for sensing pressure at the surface and producing signals corresponding to the pressure at the surface.
• references to the "present invention” or “invention” relate to exemplary embodiments and not necessarily to every embodiment encompassed by the appended claims.
• the present invention is related to providing input to a processor comprising a sensor pad having a surface and a sensor array for sensing pressure at the surface and producing signals corresponding to the pressure at the surface where the sensor array has columns and rows of electrodes that are spaced apart a distance greater than a width of a single electrode that are covered with resistive material which is disposed in the spaces between the electrodes.
• Multi-touch interfaces are gaining increasing interest. Among the recent developments has been Perceptive Pixel's FTIR device, as well as Microsoft's recently introduced Microsoft Surface and Apple's iPhone with multi-touch screen. What these devices lack is very low cost in a compact form factor that could be used with ordinary computing devices such as the desktop PC or laptop.
• the present invention is a multi-touch method and apparatus that may be used instead of a mouse with any of a variety of computing devices. It can also replace a tablet drawing device (such as a Wacom tablet). It is preferably a low cost device that may rival the cost of current mouse devices (e.g. $30 to $50).
• the apparatus consists of a sensor which preferably contains an array or grid of sensors. Preferably this would be made using FSR technology (force sensitive resistance) or other relatively low cost sensing technology.
• An FSR sensor array may cost in the range of $10 per square foot and can readily provide, for example, an array of 32x32 sensing elements.
• Multiplexers and AID converters may be employed to translate multiple touches on the FSR or other sensor array into a stream of position and pressure data.
• a relatively low cost processor may be employed in processing the raw data.
• the entire cost of manufacturing may ultimately be in the range of $20.
• Methods have been developed to translate or map a time-sampled stream of relatively low-resolution position data plus associated pressure data into sub-pixel resolution positional data using information that can be derived from the raw data and the fact that the data being processed represents one or more fingers that are in contact with the apparatus.
• Capacitive Array- Capacitive array sensors [14] have recently become popularized by devices such as the iPhone [I]. These sensors detect changes in capacitance due to the proximity of a conductor such as metal or a part of the human body (body capacitance). However, they are insensitive to dielectric materials.
• Compressible Capacitive Array Another form of capacitive array sensor is the flexible sensor produced by Pressure Profile Systems [10].
• a compressible material is placed between column and row electrodes. As pressure is applied, the material compresses increasing the capacitive coupling of an AC signal between row and column electrodes.
• One drawback of these sensors is that complex and expensive electronics are required to read out pressure from the array because an oscillatory signal must be fed into the column electrode and picked up at the row electrode.
• these sensors can be affected by stray capacitance in the environment.
• IMP ADs these sensors do not have the inherent ability to bilinearly interpolate the forces that are applied. Thus, either an extremely high resolution of electrodes or a thick force-spreading material must be employed to get the kind of positional accuracy that is possible with IMPAD.
• Optical - Another class of approaches for measuring force applied over a surface are the optical approaches as employed by Perceptive Pixel's FTIR display [4] and Microsoft Surface [7].
• FTIR FTIR
• a special material is placed over a rigid transparent surface, hi Microsoft's approach, the material diffuses light (typically IR) traveling through it while in Perceptive Pixel's approach or the material diffuses light traveling in the plane of the transparent surface when pressure is applied. In both approaches, this diffused light is then picked up by a camera located behind the surface.
• these approaches scale very well for large input devices, they are very limited because they require mounting the material on a rigid glass, and require a large volume of space for an unobstructed camera view.
• these approaches are susceptible to stray light and can only be used in controlled environments without sudden lighting changes.
• Resistive Surface sensors are the sensors most traditionally used in POS (Point of Sale) and touch screen devices produced by companies such as EIo Touchsystems. Like IMP AD, these devices have two continuous sheets of FSR material in contact with each other. However, rather than having rows and columns of electrodes, the sheets of FSR material are only connected at the edges. Thus, these sensors can only sense the centroid and total amount of applied pressure and cannot distinguish multiple points of pressure from a single point of pressure.
• Resistive Array - Resistive array sensors are basically an array of FSR cells arranged in a grid pattern. Some examples of these are the array sensors produced by TekScan and the transparent sensors used by the jazzMutant Lemur [S]. Similar to IMPAD, these sensors are read out by a grid of column and row electrodes. However, the sensors employ discrete FSR elements rather than a sheet of continuous FSR material, because they cannot accurately be used to determine the position of pressure applied between adjacent rows or columns. Thus, either an extremely high resolution of electrodes or a thick force-spreading material must be employed to get the kind of positional accuracy that is possible with IMPAD.
• Capacitive devices can't measure force but can measure contact area.
• the present invention pertains to an apparatus for providing input to a processor.
• the apparatus comprises a sensor pad having a surface and a sensor array for sensing pressure at the surface and producing signals corresponding to the pressure at the surface.
• the sensor array having columns and rows of electrodes that are covered with resistive material which fills in the spaces between the electrodes and acts as a linear resistor between the electrodes and measures pressure on the pad surface between the electrodes.
• the apparatus comprises an interface in contact with the sensor pad and in communication with the sensor array which couples to the processor to communicate the signals to the processor.
• the present invention pertains to a method for providing input to a processor.
• the method comprises the steps of sensing pressure with a sensor pad having a surface and a sensor array for sensing the pressure at the surface.
• the present invention pertains to an apparatus for providing input to a processor.
• the apparatus comprises a sensor pad having a surface and a sensor array for sensing pressure at the surface and producing signals corresponding to the pressure at the surface.
• the sensor array has columns and rows of electrodes that are covered with resistive material which is disposed in the spaces between the electrodes.
• the apparatus comprises an interface in contact with the sensor pad and in communication with the sensor array which couples to the processor to communicate the signals to the processor.
• the present invention pertains to a method for providing input to a processor.
• the method comprises the steps of sensing pressure with a sensor pad having a surface and a sensor array for sensing the pressure at the surface.
• the sensor array having columns and rows of electrodes that are covered with resistive material which is disposed in the spaces between the electrodes and measures pressure on the pad surface between the electrodes.
• the present invention pertains to a sensor pad.
• the pad comprises a surface.
• the pad comprises a sensor array for sensing pressure at the surface and producing signals corresponding to the pressure at the surface.
• the sensor array having columns and rows of electrodes that are covered with resistive material which is disposed in the spaces between the electrodes.
• the present invention pertains to an apparatus for providing input to a processor.
• the apparatus comprises a sensor pad having a surface and means for sensing pressure at the surface and producing signals corresponding to the pressure at the surface.
• the sensing means having columns and rows of electrodes that are covered with resistive material which is disposed in the spaces between the electrodes.
• the apparatus comprises an interface in contact with the sensor pad and in communication with the sensor array which couples to the processor to communicate the signals to the processor.
• Figure 1 is an assembly diagram of a sensor pad of the present invention.
• Figure 2 is a diagram regarding use of the sensor pad.
• Figure 3 is a use diagram of the sensor pad.
• Figure 4 is a circuit diagram of the sensor pad.
• Figure 5 is an overhead view of the sensor pad showing all layers.
• Figure 6 is an overhead view of the bottom layer of the sensor said.
• Figure 7 shows the VHB seal layer only of the sensor pad.
• Figure 8 shows the top layer only of the sensor pad.
• Figure 10 is a screen capture of five fingers pressing against the sensor pad simultaneously.
• Figure 11 is a screen capture of five fingers pressing against the sensor pad simultaneously.
• Figure 12 shows a cross-section of the sensor pad.
• Figure 13 shows a linear drop-off in voltage between a source wire and its two neighbors in regard to a force on the sensor pad.
• Figure 14 shows a user pressing his hands down on the IMP AD.
• Figure 15 is an illustration of the IMP AD principle in operation.
• Figure 16a shows a foot on the EVIP AD.
• Figure 16b shows the resulting pressure image displayed on a computer screen.
• Figure 17a shows a heavy block sitting on the IMPAD.
• Figure 17b shows the resulting pressure image of figure 16a.
• Figure 17c shows the pressure image when a user pushes down on the upper left side of the block of figure 17a.
• Figure 18 illustrates the principle of operation of IMPAD.
• Figure 19a shows an array of discrete sensors returns the wrong position for a pen touch.
• Figure 19b shows that IMPAD interpolates the signal between two successive sensors to compute the correct touch position.
• Figure 20 is a schematic of one embodiment of the IMPAD.
• Figure 21 is a schematic of a small format IMPAD.
• Figure 22 is a schematic of a large IMPAD.
• Figure 23 is a plot that shows the output of four different sensors when pressure is applied at the point in between two column and two row electrodes.
• Figure 24a shows pressure on a single point between two adjacent row electrodes and two adjacent column electrodes.
• Figure 24b is a representative circuit diagram regarding figure 24a.
• Figure 25 shows a fairly linear output versus position curve that is obtained as a result of plugging in values for Rf that are significantly higher than Rc, Rr, and Rr'.
• Figure 26 shows much less linear output versus position curve that is obtained as a result of plugging in values for Rf which are similar in magnitude to Rc, Rr and Rr'.
• Figure 27a shows two layers of uncompressed spongy conductive materials.
• Figure 27b shows two layers of compressed spongy material, with increased area of contact between them.
• Figure 28 shows a fibrous and cloth like woven structure embodiment of the sensor pad.
• Figures 29a, 29b and 29c show a representation of the sensor pad with every row/column active, every nth row/column active, and only the first and last row/column active, respectively.
• Figure 30 shows a time varying sequence of operation of the sensor pad organized into 2N time steps.
• Figure 31 shows a representation of the surface being touched at a single point in regard to row and column.
• Figure 32 shows a representation where half of a touch is on the left side of a connector and half of the touch is on the right side of the connector.
• Figure 33 shows a representation of transducting rubber material placed between the two layers 1 and 5 of the electrodes.
• Figure 34 shows strips of FSR material printed over the electrodes.
• Figure 35 shows a representation of the in plane resistance created by layers 2 and 4 can be broken between every other pair of electrodes.
• Figure 36 shows a representation of the sensor pad with drone electrodes.
• Figure 37 shows a transparent mesh embodiment of the present invention.
• Figure 38 shows an NxN sensor with diagonal conducting lines.
• Figure 39 shows the embodiment of figure 38 where only tile is active.
• Figure 40 shows another embodiment of the present invention.
• Figure 41 is a diagram showing how drone conductors can be tied to active lines with capacitors to combine resistive and capacitive sensing.
• Figure 42 is a diagram showing how drone electrically inductive loops can be formed using return wires on the back of the sensor.
• Figure 43 shows a layout of vertical electrodes for a circular UnMousePad that is made by distorting a grid.
• Figure 44 shows a layout of horizontal electrodes for a circular
• UnMousePad that is made by distorting a grid.
• Figure 45 shows a layout of vertical electrodes and drone lines for a circular UnMousePad that is made by distorting a grid.
• Figure 46 shows a layout of horizontal electrodes and drone lines for a circular UnMousePad that is made by distorting a grid.
• Figure 47 shows a layout of circular UnMousePad showing both radial and concentric circle electrodes on top and bottom sensor layers.
• Figure 48 shows a layout of circular UnMousePad showing both radial and concentric circle electrodes as well as drone lines on top and bottom sensor layers.
• Figure 49 is an image of a foot sensor grid (without drone electrodes) with column and row electrodes overlaid on top of each other.
• the apparatus 100 comprises a sensor pad 140 having a surface 16 and a sensor array 18 for sensing pressure at the surface 16 and producing signals corresponding to the pressure at the surface 16.
• the sensor array 18 having columns 20 and rows 22 of electrodes 24 that are preferably spaced apart a distance greater than a width of a single electrode 24 that are covered with resistive material which fills in the spaces 26 between the electrodes 24 and acts as a linear resistor between the electrodes 24 and measures pressure on the pad 140 surface 16 between the electrodes 24.
• the apparatus 100 comprises an interface 28 in contact with the sensor pad 140 and in communication with the sensor array 18 which couples to the processor 120 to communicate the signals to the processor 120.
• the pad 140 is portable.
• the interface 28 is preferably configured to couple with a USB cable 30.
• the array detects multiple simultaneous contact points on the surface 16.
• the apparatus 100 preferably includes a display 32 in communication with the processor 120 that displays the signals on the screen.
• the electrodes 24 are spaced at least 1/8 inches apart.
• the resistive material preferably has a conductivity which varies with pressure.
• the sensor pad 140 preferably has a first sensor layer 34 with column 20 electrodes 24, and a second sensor layer 36 with row 22 electrodes 24.
• the pad 140 has a spacer with a gap disposed between the first layer and the second layer.
• the pad 140 preferably senses pressure at the surface 16 by detecting voltages at row 22 and column 20 intersections that are near areas where the first and second layers are touching.
• pressure at all points on the surface 16 is measured by applying a positive voltage on each row 22 one at a time, and then reading out voltage values on each column 20 one at a time.
• the pad 140 can operate like a track pad.
• the pad 140 can operate as a tablet.
• the pad 140 can detect a corresponding shape to the pressure applied to the surface 16.
• the present invention pertains to a method for providing input to a processor 120.
• the method comprises the steps of sensing pressure with a sensor pad 140 having a surface 16 and a sensor array 18 for sensing the pressure at the surface 16.
• the producing step includes the step of measuring each time a scan of the pad 140 occurs by the processor 120, pressure at all points on the surface 16 by applying a positive voltage on each row 22 one at a time, and then reading out voltage values on each column 20 one at a time.
• the present invention pertains to an apparatus 100 for providing input to a processor 120.
• the apparatus 100 comprises a sensor pad 140 having a surface 16 and a sensor array 18 for sensing pressure at the surface 16 and producing signals corresponding to the pressure at the surface 16.
• the sensor array 18 having columns 20 and rows 22 of electrodes 24 that are preferably spaced apart a distance greater than a width of a single electrode 24 that are covered with resistive material which is disposed in the spaces 26 between the electrodes 24.
• the apparatus 100 comprises an interface 28 in contact with the sensor pad 140 and in communication with the sensor array 18 which couples to the processor 120 to communicate the signals to the processor 120.
• the sensor pad 140 measures a proportional location of any touched point upon the surface 16, between two electrode columns 20 that adjoin the touch point and two electrode rows 22 that adjoin the touch point.
• the sensor pad 140 can include at least one drone electrode 38, as shown in figure 36, disposed between at least two electrode rows 22 and two electrode columns 20.
• the sensor pad 140 can include transparent conductors.
• the skin can be transparent.
• the present invention pertains to a method for providing input to a processor 120.
• the method comprises the steps of sensing pressure with a sensor pad 140 having a surface 16 and a sensor array 18 for sensing the pressure at the surface 16.
• the sensor array 18 having columns 20 and rows 22 of electrodes 24 that are preferably spaced apart a distance greater than a width of a single electrode 24 that are covered with resistive material which is disposed in the spaces 26 between the electrodes 24 and measures pressure on the pad 140 surface 16 between the electrodes 24.
• the present invention pertains to a sensor pad 140.
• the pad 140 comprises a surface 16.
• the pad 140 comprises a sensor array 18 for sensing pressure at the surface 16 and producing signals corresponding to the pressure at the surface 16.
• the sensor array 18 having columns 20 and rows 22 of electrodes 24 that are preferably spaced apart a distance greater than a width of a single electrode 24 that are covered with resistive material which is disposed in the spaces 26 between the electrodes 24.
• the present invention pertains to an apparatus 100 for providing input to a processor 120.
• the apparatus 100 comprises a sensor pad 140 having a surface 16 and means for sensing pressure at the surface 16 and producing signals corresponding to the pressure at the surface 16.
• the sensing means having columns 20 and rows 22 of electrodes 24 that are preferably spaced apart a distance greater than a width of a single electrode 24 that are covered with resistive material which is disposed in the spaces 26 between the electrodes 24.
• the apparatus 100 comprises an interface 28 in contact with the sensor pad 140 and in communication with the sensor array 18 which couples to the processor 120 to communicate the signals to the processor 120.
• the sensing means can be the sensor array 18.
• the UnMousePad is a thin, flexible, low cost multi-touch input device.
• An UnMousePad (otherwise called the “pad” or “sensor” herein) was built that is approximately 3.5" x 3.5" in size, approximately 20 thousandths of an inch thick, and has 9 rows and 9 columns.
• the sensor consists of two sides. Each side consists of a series of silver traces printed on a polyester backing and overprinted with FSR (Force Sensing Resistor) ink. The two sides are placed perpendicular to each other creating a sensing matrix. Readout of values is performed by powering on one row 22 electrode 24 at a time to a voltage of +5V while connecting the other row 22 electrodes 24 to ground.
• FSR Forward Sensing Resistor
• the voltage is sampled on each of the columns 20 one column at a time by using the analog pins on a microcontroller, while grounding all of the other column 20 lines.
• the design of the FSR pad naturally creates a voltage gradient on the input side of the sensor between the powered row 22 and the grounded rows 22, and likewise, a gradient in how much current flows to the currently sensed column 20 and the grounded column 20.
• the continuous FSR also acts as the resistor going to ground which creates an output voltage, so that it is not necessary to provide additional resistors to read the output. No other approach exists for doing multi-touch input which does not require any circuitry for reading the pressure from the multi-touch pad besides the printed sensor and a microcontroller.
• the only minor and inexpensive bit of circuitry that is needed is a voltage regulator to power the microcontroller and circuitry to provide USB connectivity.
• the control of sampling, analog to digital conversion, and data processing is performed by the microcontroller which communicates with a computer using a USB cable 30.
• PIC24HJ256GP210 which has 256KB of flash program memory, 16KB of RAM, 32 analog inputs, and 53 digital inputs and costs approx $4.56 in volume.
• a sensor can be made with a resolution of 32x53. With quarter inch spacing between rows 22 and columns 20, this allows construction of a sensor as large as 8"xl3" in area.
• Simultaneous scanning can also be effected as follows: power on multiple columns 20 and multiple rows 22 thereby sampling a larger portion of the sensor simultaneously. This allows multi-scale sampling; starting at a coarser resolution and doing finer grained scanning, if necessary, in areas in which a touch has been detected.
• An un-mousepad can be used to simulate a large multi-touch floor pad. This would allow one to prototype a multi-touch floor pad at one's desk without requiring the floor pad to be physically present.
• An un-mousepad can be used to develop and experiment with multi-touch applications. Because it does not need to replace the user's computer screen, keyboard, or mouse, the un-mousepad can be complimentary to computer systems that computer users already have. Also, because it is not attached to a screen, the un-mousepad can be comfortably placed and used on a desk. In long-term use situations this is much less tiring than requiring the user to hold up an arm to touch a multi-touch sensor installed on a computer screen.
• An un-mousepad can be used as a very expressive musical instrument or animation input device.
• An un-mousepad widget kit/ API An un-mousepad widget kit/ API.
• a software toolkit could be built atop the un-mousepad hardware platform that would allow a software developer to implement a custom interface consisting of touch sensitive widgets. Developers could be provided with pre-made widgets such as a linear slider, a circular slider, a knob, a push-button, a force-sensitive push button, a toggle-button, and an XY input pad.
• An Abstract Programming Interface 28 API handles all of the work of translating the raw data from the sensor into simple floating point outputs/events for each widget that the application could read without the developer being required to know low level details about the operation of the sensor.
• the kit would allow developers to print out the custom user interface 28 overlays from their home printer. If the un-mousepad is 8.5" x 11" in extent, the same size as a standard laser-printer output, then developers do not need to cut the paper overlay, but rather can put the overlay right on the sensor, thereby creating a custom printed controller visualization.
• the API can also make accessible special controls that only respond to a subset of gestures, such as quick taps, or only to fingers and not pens and not palms, or only to palms and not fingers or pens, or only to ball bounces or long term events. Controls can be provided that when calibrated can measure weight or shape. In this way, controllers using the API can be used to create musical instruments, puppeteering interfaces, and interfaces for a wide variety of games and design applications.
• the UnMousePad can be used as a way to virtually draw or write on the screen. The user can even put paper under the pad to get both a hard copy and a virtual copy.
• Another application is in the enhancement of coloring books, or grammar books, where a child can get feedback on their progress as they color in or write on the pages.
• the pads can be designed in such that they can be trimmed down to smaller sizes without damaging the electronics. This feature is useful for making all sorts of custom interfaces of different dimensions, and as a tool for prototyping sensors in industrial products. In small manufacturing runs of products, it may be cheaper to use an off-the-shelf UnMousePad than to design a custom membrane switch or FSR input device.
• small silicone button pads can be layered over the UnMousePad surface 16 that have the tactile feel of a button, and that pops in and out when pressed.
• a thin layer of adhesive can be used to adhere the button in place.
• UnMousePad Flexible displays can be placed over the UnMousePad sensor.
• e-ink is developing a flexible display technology whereby color-changing capsules are sandwiched between two layers of polyester. Because the UnMousePad is made of polyester, one half of it could be printed right on the underside of an e-ink display. As long as the display 32 is flexible enough for force to be sensed through it, and is not damaged by pressure, it can be placed over an UnMousePad sensor. Alternatively, the UnMousePad can be manufactured with transparent inks so that it can be placed over a traditional computer display 32.
• Interface cable (such as a USB cable) to computer.
• Interface cable (such as a USB cable) to computer.
• VHB around edges should go right up to the start of the FSR material, but should not go over the FSR material. All the traces around the edges should be covered with VHB. The traces in the tail region should be left exposed. There should be at least one small air gap in the VHB on the left side of the sensor to keep a vacuum from forming inside the sensor. The traces on the tail should be exposed so that a ZIF or zebra connector can be put on in the future. For testing, the traces can be isolated with a piece of paper. .1 inch spaced connectors will be cramped to the rightmost part of the tail.
• VHB around edges should go right up to the start of the FSR material, but should not go over the FSR material. All the traces around the edges should be covered with VHB.
• the traces in the tail region should be left exposed. There should be at least one small air gap in the VHB on the left side of the sensor to keep a vacuum from forming inside the sensor.
• the traces on the tail should be exposed so that a ZIF or zebra connector can be put on in the future. For testing, the traces can be isolated with a piece of paper. .1 inch spaced connectors will be cramped to the rightmost part of the tail.
• VHB seal layer only. VHB around edges should go right up to the start of the FSR material, but should not go over the FSR material. All the traces around the edges should be covered with VHB. The traces in the tail region should be left exposed. There should be at least one small air gap in the VHB on the left side of the sensor to keep a vacuum from forming inside the sensor. The traces on the tail should be exposed so that a ZIF or zebra connector can be put on in the future. For testing, the traces can be isolated with a piece of paper. .1 inch spaced connectors will be cramped to the rightmost part of the tail.
• VHB around edges should go right up to the start of the FSR material, but should not go over the FSR material. All the traces around the edges should be covered with VHB. The traces in the tail region should be left exposed. There should be at least one small air gap in the VHB on the left side of the sensor to keep a vacuum from forming inside the sensor. The traces on the tail should be exposed so that a ZIF or zebra connector can be put on in the future. For testing, the traces can be isolated with a piece of paper. .1 inch spaced connectors will be cramped to the rightmost part of the tail. [00154] Algorithms for processing input data:
• UnMousePads have been built that are 8.5"xl l" in size and have a resolution of 1/4" with 29 rows and 19 columns.
• OFFSET V ALUE is a small experimentally determined value which eliminates false sensor activations.
• the Pad measures the pressure at all points along its surface 16, interprets that data, and sends the data to a computer over an interface 28 such as USB.
• an interface 28 such as USB.
• the Pad can detect when it is not being touched, when it is being touched with a single finger, a stylus, or any other object, or when it is being touched at multiple points by fingers, styluses or other objects.
• the user would start by plugging it into a USB port on a computer (assuming we're using a USB interface). The computer would then give power to the Pad, which will cause the Pad to initialize. After the initialization, the computer will detect the Pad, initialize the driver for it (or ask the user to install a driver if it is not already available) and begin reading input data from it.
• the user will begin using the Pad. Whether the user uses a single finger, multiple fingers, a stylus, or any other objects to press on the Pad, the same exact operation will happen, so for purposes of simplicity, we will assume the user is using a single finger.
• the Pad begins scanning the surface 16 of the Pad to detect any pressure that is exerted. Each time it performs a scan, it will measure the pressures at all points on the surface 16. It performs the scanning by applying a positive voltage on each row 22 one at a time, and then reading out the voltage values on each column 20 one at a time.
• the Pad driver or the firmware on the device will emulate a mouse in a similar way as a track-pad on many laptops; thus, in this scenario, the Pad will be able to operate like a regular track-pad.
• the emulation can work in the following way: the position of the mouse will come from the force weighted average position of all the pressure applied on the pad. However, the user may rest their palm on the pad.
• the driver/firmware should have an algorithm to detect palms (as large areas of pressure) and exclude them.
• Clicks can be detected when there is a light tap on the surface 16 (or a quick increase in pressure), right clicks can be detected as a tap by two fingers, and scrolling can be represented by dragging two fingers together, hi this mode, the Pad may also interpret more complex gestures such as using two fingers to scale and rotate, and send scale/rotate signals to applications that support scale and rotate commands.
• the user will be using the Pad as a tablet.
• the software will look for a small point of pressure and feed the position and pressure of that point to the computer while exclude all larger points of pressure (effectively filtering out fingers and palms).
• Mouse down events can be sent when the pressure exceeds a small threshold and mouse up when pressure is released.
• the Pad will be being used as a "raw" multi-touch input device along with application software that understands "raw” multi-touch input.
• the Pad will find all contiguous points of contact on its surface 16 and send a bundle of data to the application for each full scan which will carry a few pieces of information for each point of contact. This information will include the center point of the contact, the total force, and the shape of the contact which will be represented by an ellipse (with the ellipse's width, height and orientation angle being sent over).
• the application will be charged with interpreting the data it receives and doing with it what it wants.
• an application which simulates a touch pond will simply set off a wave any time it detects contact at any point on the pad in the corresponding location in the simulation.
• the Pad will send the raw values that it reads as it is scanning to the computer in the form of a 2D grayscale image where the brightness of each pixel corresponds to the pressure exerted at the matching row 22/column 20 intersection.
• the application will have to do all the processing and interpreting of the data that it receives.
• This mode may be helpful for applications where users are trying to detect the shape or pressure of objects other than fingers, and get an "image" of the pressure applied. For instance, this mode may be useful by scientists or students who want to record the pressure patterns of a tire rolling over the sensor, the weight distribution of an athlete as he steps on a sensor, or the shape of a soccer ball during impact when it bounces on a sensor.
• the user might need software that has been written to support that type of interaction. For instance, a finger painting program that allows children to paint with multiple fingers will have to be able to interpret the multi-touch data from the sensor in order to operate properly. Otherwise, if it can only interpret the mouse input data, it will only allow painting with a single finger. Switching between the four different usage scenarios can happen via a hardware switch on the device or via a control in some configuration software for the device. An API can be provided which will allow the software that is using the device to request what kind of input data it requires. This will free the user from having to manually select the operating mode for the device. Finally, the device can provide several forms of input data simultaneously, allowing applications to select the preferred form of input data that they want.
• those sensors can be made with a very large number of columns 20 and rows 22 to get a good positional resolution, but this makes the electronics for reading the columns 20 and rows 22 very slow and expensive.
• Another way that those sensors can compensate is by putting a soft rubbery pad over the sensor. However, this increases the thickness of the sensor and makes it impossible to write on it with a stylus.
• One of the major improvement of the present invention compared to the prior art is that thin column 20 and row 22 electrodes 24 are used that are spaced appreciably far apart, and are covered with a flood coat of FSR or resistive material which fills in the space between the columns 20 and rows 22. Because the material acts as a linear resistor between the columns 20 and rows 22, the position of a stylus or of a finger that falls in between two columns 20 or two rows 22 can be accurately measured without having an unnecessarily high number of columns 20 and rows 22 and without having to put a rubber pad over the sensor. [00209] In an 8.5" x 11" sensor, there are only have 30 columns and 40 rows which are spaced 1 A" apart. Despite the small number of columns 20 and rows 22, the position of a finger or of a stylus can still be accurately measured, and have it move smoothly over the screen as a user smoothly moves their finger over the sensor.
• Another advantage of the present invention is that it is not necessarily being made to be a multi-touch device that goes over a screen.
• the pad can just as easily be used on a table while looking at a screen which displays the user input.
• a tap can also be used to indicate a click, or a double tap to indicate a double click.
• the stylus can be made to start drawing when a certain level of pressure is reached. The level of pressure can also be applied to vary the thickness of strokes.
• the operating system will then update the position of the cursor and appearance of the cursor on the screen.
• the appearance may change with varying levels of pressure as described above.
• the user would then use this feedback to move their stylus to the point where they want to start drawing.
• the operating system may also send "cursor hover" messages along with cursor position and force to various applications that the cursor is moving over so that the applications can have an idea of where the cursor is.
• the application can use this information to, for example, highlight buttons or hyperlinks when the user moves the cursor over them.
• the application can display the shape of the paint brush in the place where the cursor point is so that the user will have an idea of where they will raw if they push down on the stylus.
• the hardware/driver will register this extra pressure and determine that extra pressure was added to cursor point 0 and notify the operating system. At some point, the hardware/driver will decide that the pressure is high enough to be counted as a "cursor down" event.
• the operating system and/or driver software can have a dialog that allows the user to adjust the threshold pressure at which they want to trigger a "cursor down” event in the same way that users now can adjust mouse sensitivity in the control panels of operating system. When the hardware/driver detects a "cursor down", it will notify the operating system with the pressure and position of the cursor down event.
• the operating system will then give the user some feedback that they've generated a "cursor down” using an audible click and/or a visual change in the appearance of the cursor.
• the operating system will also notify the application that a cursor has touched down at a specific point, sending both the "cursor down" coordinate, the unique ID for the cursor and the current pressure.
• the hardware/driver will notify the operating system of changes in position and pressure by sending "cursor moved" notifications to the operating system using the unique ID to refer to the stylus point and sending down new position and force values.
• the operating system will then send these notifications to the application in which the user is drawing.
• the operating system will also continue to draw the "cursor point" on the screen.
• the application will begin to fill in pixels with black color in the areas where the user has drawn a line and to store an internal representation of where the user has drawn (this may vary with the implementation of the application).
• the user When the user is done drawing the L, he will release pressure from the stylus.
• a "cursor up” event will be generated by the hardware/driver for unique ID 0 and sent to the operating system along with the position and force of the event.
• the operating system will then give the user notification that they have triggered a "cursor up” event. It can do this by playing an audible un-click sound and/or via a visual change to the appearance of the cursor.
• the operating system will then send the "cursor up” event and all the associated information to the application.
• the application will then stop the drawing of the line on screen.
• the hardware/driver will then go back to the state of notifying the operating system of the movements of cursor ID 0 so that it can update its cursor on the screen.
• the operating system will then go back to the state of sending "cursor hover” messages to the applications that the cursor moves over.
• the stylus is lifted, the hardware/driver will detect the stylus being lifted and notify the operating system that they cursor with Unique ID 0 has been lifted along with the position and last recorded force. The operating system will then cease to draw the cursor on the screen.
• the hardware/driver will send the exact same information. However, for each additional finger that makes contact besides the first finger, the new fingers will receive different unique IDs that will distinguish messages sent for the additional fingers versus the messages sent for the first finger. Whenever a finger is released, its unique ID will be returned to a common pool so that it will be possible to reuse it in the future for later finger- touches. [00219] As for how multiple finger tips are interpreted for detecting various gestures, and for what the applications do with the input for multiple fingers, that is mostly up to the operating system and the given application.
• Both the electrodes 24 and the flood coat are made via a screen printing process, the process of which is well known.
• the screens are produced with a photographic process, the process of which is well known.
• the inks are printed in a printing press, as is well known, and then the sensors are put into an oven to dry the inks.
• the electrodes 24 are made of a silver ink which is highly conductive.
• Silver is also preferable because it doesn't corrode.
• the FSR coat is printed with a screen pattern which has a large square opening at the center.
• FSR inks can also have different additives added in to adjust their resistivity and response to pressure. For instance, a carbon ink can be added in to make the FSR ink more resistive. See also WO/2006/138618, incorporated by reference herein.
• FSR force sensitive resistor
• FSR ink is an ink that is resistive and rubbery and has a rough upper surface 16. When it is pressed against a conductive surface 16, it begins to conduct, but the roughness creates air gaps between itself and the surface 16. As more pressure is applied, it conforms to the shape of the surface 16, increasing the surface 16 area that is in contact and conducts more, hi fact, the conductivity has an approximately linear relationship with respect to pressure. The resistivity is 1 /conductivity, so the resistivity actually varies proportionally to the inverse of the pressure. [00225] The following is how signals from the sensor are processed:
• Another improvement on this scheme is to decrease by a larger amount than the amount by which the calibrated value is increased. By doing this, the calibration routine will "prefer” to return to a smaller value. This is useful in the case when a user might tap the sensor repeatedly. During the times that the finger is down, the calibrated value will increase a tiny amount, but when they lift the finger up, the value will quickly return to the correct calibration value.
• the calibration value is simply subtracted from each pressure value obtained in the 2D array from step 2. This is now used as the new array of pressure values, since there is no concern about the steady-state pressures.
• pressures in the array are looked at, and if any of the pressures is larger than a small constant threshold.
• the threshold should be an experimentally determined pressure which is greater than 0 but smaller than the pressure a person applies when lightly touching something. Anywhere where we see a pressure that is greater than the threshold pressure we deem a contact point.
• contact points receive unique IDs such that when a finger/stylus moves, they retain the same unique IDs. This can be done by remembering all of the information about connected segments from the previous frame of data. Then, after we've calculated the positions, forces, and ovals that describe all of the connected segments found in the current frame, we try to match them up with segments from the previous frame. We do this by finding the segment in the previous frame that is closest to the given segment in the current frame. Next, we look at the distance between the two, calculate the speed which the finger/stylus would have had to be going to travel that distance in one frame and decide if that can possibly be the same finger/stylus. Next, we compare their pressures, sizes and oval shapes.
• Filtering on the data may be desired. For instance, it might be desired to filter out palms since we don't want people to accidentally click on things with their palms. This can be done with heuristics such as ignoring a contact point that has a very large surface 16 area, but a low pressure given the surface 16 area.
• Another filtering technique is to try to match palms with fingers. It is known that a palm will usually be found below a finger, so if a large contact point is found below a small contact point, it can be assumed this is a palm.
• this filtering step can be performed in a driver or in the operating system, and it is advantageous to do this in the driver/OS for the same reason as it is advantageous to do the tracking in the driver/OS.
• the same technology described above for a pad can be used for a footpad, simply scaled up to a larger size.
• the foot pad is the identical technology to the hand pad, other than being scaled up to a larger size.
• the number and arrangement of sensing elements and the grid wiring pattern and the electronics and the application software are all the same.
• the size ratio between the hand pad and foot pad happens to be on the order of the difference between a human finger length and a corresponding human foot length, which is about a factor of twelve. But in fact the scaling can be any factor.
• the present invention pertains to a novel sensor modality that enables an inexpensive multi-touch, pressure acquisition device (IMPAD), or pad, as referred to here.
• IMPAD technology can detect multiple points of pressure with continuous bilinear interpolation, permitting both high-frame-rate and high quality imaging of spatially variant pressure upon a surface 16.
• IMPAD sensors are inherently unobtrusive, inexpensive, and very durable, they have many potential uses. They can be placed on massive objects such as the hull of a ship to continuously track water pressure, or along the load bearing structures of buildings in fault zones to track the results of seismic activity. IMP AD sensors can be placed inside the soles of shoes with a resolution fine enough to detect the subtlest of movement to study stance and posture.
• IMPAD has a very wide range of potential applications in many sectors of society, primarily because it enables multi-touch pressure imaging at a low cost in a wide variety of form factors. Applications for which this technology will have a direct and potentially transformative impact include floor mats and entry sensors, bio pressure sensors, musical instruments, baby monitoring, drafting tables, reconfigurable control panels, writing pads, grocery and warehouse shelves, hospital beds, construction materials, wheelchairs and other assistive devices, sports equipment, sports clothing, portable electronic devices and tire pressure sensing.
• IMPAD Inexpensive Multi-Touch Pressure Acquisition Device
• An IMPAD sensor consists of five layers: the first and fifth (outer) layers consist of parallel wires. The direction of the parallel wires on layer 1 is substantially orthogonal to the direction of the parallel wires on layer 5.
• the second and fourth layers consist of electrically conductive material possessing substantial electrical resistance.
• the third (middle) layer consists of a force sensitive resistive (FSR) material — a material whose electrical resistance decreases when compressed by an outside force.
• FSR force sensitive resistive
• This middle layer can be any material whose resistance changes in response to pressure. It is even possible to use a material whose resistance increases as pressure is applied.
• FSR ink As for materials where resistance decreases with pressure, there is FSR ink, FTR (force transducting rubber), and anti-static foam (which conducts more as it is compressed).
• the mechanism of operation is as follows (figure 12): One of the wires along layer 1 is sourced to a positive voltage, while all other wires in layer 1 are set to ground. Positive charge flows across the surface 16 from the source wire to its two neighboring wires, via the resistive material in layer 2, creating a linear drop off in voltage between the source wire and its two neighbors (figure 13). [00254] Every two clock cycles, the positive voltage is shifted to the next wire over. If there are N wires across layer 1, the pattern repeats every 2N clock cycles. Meanwhile, at every even clock cycle all over the even numbered wires in layer 5 are metered to output while all of the odd-numbered wires layer 5 are connected to ground. At every odd clock cycle the even-numbered wires are set to ground while the odd-numbered wires are metered to output.
• wires can be scanned serially one by one by powering the desired electrode 24 on layer 1 and reading a voltage from the desired electrode 24 on layer 5 while all other electrodes 24 on layers 1 and 5 are grounded. This generally limits the scanning rate, but may be sufficient for some applications such as those where simpler electronics are used which can only read a single voltage at a time.
• a point touch will produce a non-zero output voltage at each of four clock cycles during the 2N steps of the repeating pattern. These four voltages can be used together to determine not only the magnitude of the pressure at that point, but also the relative location of the point within the square that is bounded by the four nearest wires — two on layer 1 and two on layer 5.
• the above is an idealized description to illustrate the principles.
• the IMPAD mechanism can be implemented in many different ways.
• the wire layers 1 and 5 can be embedded within the resistive layers 2 and 4.
• layers 2 and 4 can themselves be FSR material, with layer 3 implemented as an air gap.
• IMPAD can be implemented as a woven material, in which the wires of layers 1 and 5 form the warp and weft of the cloth, respectively, and each wire is coated with a thin layer of resistive material — external pressure causes greater contact area between these interwoven coated wires.
• the resistive material that comprises layers 2 and 4 do not need to be spread out over the entire surface 16. They can each, for example, run along one edge of the surface 16, or in thin strips along the surface 16, in a direction perpendicular to the direction of the corresponding conductors.
• one or more resistive strips constituting layer 2 can each run perpendicular to the conductors of layer 1
• one or more resistive strips constituting layer 4 can each run perpendicular to the conductors of layer 5.
• IMPAD devices have been built using existing techniques for the manufacture of FSR sensors.
• An implementation of IMP AD consists of two paper-thin 8.5" x 11 " sheets of PET plastic attached together at the edges.
• On the inner side of each sheet is a circuit pattern consisting of parallel electrodes 24 spaced at 1/4" intervals.
• a connector area is provided on one side for attaching electronics, which interface 28 to a computer.
• the electrodes 24 on both sides are over-printed with a solid layer of FSR (Force Sensitive Resistor) ink.
• FSR Force Sensitive Resistor
• the IMP ADs that have been manufactured use an FSR ink, which is semi-conductive and rough at a microscopic scale, so as it compresses, the conductivity between the top and the bottom layers increase in a fashion that is approximately linear with the force applied.
• the FSR ink also allows current to flow along the surface 16 of each sheet between adjacent electrodes 24. This flow allows the IMPAD to simultaneously sense the position and pressure of points that are anywhere between two electrodes 24, making it possible to detect and continuously track all pressure points, even ones smaller than the 1/4" spacing between electrodes 24.
• Figure 14 This image shows a user pressing his hand down on the
• the attached computer displays a contour-line representation of the space- variant pressure exerted on the IMPAD.
• the output lines of the sensor are connected to a circuit board which consists of some shift registers and a micro-controller which acquires readings and relays them to a computer.
• the micro-controller uses the shift registers to power one column 20 electrode 24 at a time, then reads analog voltage values from each even row 22, followed by each odd row 22. It then switches to the next column 20 and repeats for the remaining columns 20.
• the micro-controller converts those analog voltage values to a digital value with an onboard ATD converter. Finally, the micro-controller sends the complete frame of data to the computer.
• Some IMPADs currently capture pressure images at about 50 cycles per second on a grid of 29x39 electrodes 24, and can go up to a frame rate of 500 cycles per second.
• Figure 15 An illustration of the IMPAD principle in operation.
• the darker line represents a powered row 22 electrode 24 on the top layer.
• the lighter lines represent bottom layer column 20 electrodes 24 that are being read by the microprocessor. All other electrodes 24 are grounded.
• the indentation visualizes the effect of exerting a force, which increases contact area between torn and bottom layers.
• Figures 16a and 16b Figure 16a shows a foot pressing down on our
• Figure 16b shows the resulting pressure image displayed on a computer screen.
• Figures 17a- 17c Figure 17a shows a heavy block sitting on the IMPAD.
• Figure 17b shows the resulting pressure image.
• Figure 17c shows the pressure image when a user pushes down on the upper left side of the block.
• EVIPAD behaves more like human skin which intrinsically has a fine resolution for purposes of detecting the location of a single touch and a coarse resolution for purposes of distinguishing 2 adjacent touches. This distinction permits a very inexpensive implementation of BvIPAD devices, both in terms of spacing of sensors, and in terms of the expense and complexity of logic circuitry required.
• Figure 18 Top-discrete sensor's sensitivity with respect to position.
• FIG. 18 illustrates the principle of operation of IMPAD. Note that even a very small change in position can be accurately tracked. Two adjacent touches can be reliably distinguished as distinct if they are spaced apart by twice the distance that separates adjacent wires in the surface 16 - the Nyquist frequency of the device.
• Figure 19a An array of discrete sensors returns the wrong position for a pen touch.
• Figure 19b IMPAD interpolates the signal between two successive sensors to compute the correct touch position.
• IMPAD can use a linear combination of values measured at adjoining sensors to reconstruct pressure signatures from the band limited detected signal with more fidelity (figure 19a) than is possible through the use of an array of independent discrete detectors.
• a point touch will cause a non-zero value at two adjoining sensor elements (figure 19b). If these two successive sensor locations are denoted as a and b, and their respective returned values as p and q, then the correct position of pen contact can be reconstructed as (ap + bq) / (p + q).
• IMP AD Another advantage of IMP AD is that the resistive layers between the column 20 and row 22 electrodes 24 allow a tradeoff between the spatial resolution of a scan and increased read-out speed or reduced power consumption. This is done simply by disconnecting sets of column 20 or row 22 electrodes 24 from both power and ground as if they didn't exist (the disconnection can be done using any electronic logic that can has a high-impedance mode). For instance, if every other column 20 and row 22 electrode 24 is disconnected, the spacial resolution goes down by two, but the scan rate goes up by a factor of four.
• the senor acts as a single bilinear cell which can only measure the centroid and sum of pressure exerted over the entire sensor surface 16. Although this may seems useless, it can allow for the scanning of the sensor at many thousands of frames per second in order to detect very short lived impacts. This permits a "sleep mode", whereby battery powered devices that need to conserve power can idle without drawing significant power as they wait for a touch event to wake them up. Finally, it is possible to adaptively scan the sensor with finer detail only in areas where contact is made or where fine detail is required. This allows for the best of both worlds - providing high resolutions in areas where there is contact, while providing high speed and low power usage over areas with no contact.
• Figure 20 This is the schematic of the first IMPAD sensor. It has a 7.5" x
• Figure 21 This is the schematic of the small format sensor. It has a 42mm x 54mm sensing area with 10 column and 8 row electrodes 24. The spacing between electrodes 24 is 6mm. Because of the small form factor, many of these can be printed at a time, which allows one to experiment with the placement of drone conductor wires and different inks much more rapidly than could be done with the larger form factor sensors.
• Figure 22 This is a schematic of our large sensor. This sensor has a 12" x
• IMPAD devices can also be made in such a way that they can be tiled together to form larger IMPAD surfaces, without any seam between adjacent tiles.
• the M+N control wires are run behind the device (so that there is no visible border around the actively sensing area of the IMPAD), and connect those wires to a small dedicated microcontroller, which is also placed behind the device.
• This microcontroller operates as in all other implementations of IMPAD, as described elsewhere in this document, with the addition of two steps:
• the sensed data is optionally compressed by retaining only non-zero values.
• the compression of the MxN pressure values for each scan is effected as follows: Each contiguous run of n non-zero values within the MxN array of data is collected into a data record. A header is prepended to this data record that indicates two values: (a) the starting index within the MxN length array of this contiguous run of non-zero data values and (b) the number of contiguous non-zero values in the record.
• Each tile sends its data, using a standard network protocol such as UDP, to a computer, which converts each tile's id into a corresponding row 22 and column 20 offset, thereby assembling a high resolution image of pressures sensed from the entire collection of tiles. This high resolution image of pressure is thereby made available for use by any software application.
• a standard network protocol such as UDP
• Inks were also printed with different resistances. It was found that inks with lower resistances tended to output a wider range of output voltages which would saturate the A2D converters on the microcontrollers. Also, when force was applied, it was found that the current flowing between adjacent column 20 electrodes 24 which were being powering would become very high (> 40 niA), which is undesirable for battery powered devices and could potentially damage the electronics.
• Figure 23 The above plot shows the output of four different sensors when pressure is applied at the point in between two column 20 and two row 22 electrodes 24.
• a x 2 is from a sensor printed with two layers of less resistive ink A.
• a x 4 is printed with four layers of ink A.
• B x 2 is from a sensor printed with two layers of more resistive ink B (which has a resistance of 400KOhms per Square).
• B x 4 is printed with four layers of ink.
• Figure 24 The above plot shows the output of four different sensors when pressure is applied at the point where a column 20 and a row 22 electrode 24 overlap.
• the inks are the same as described on the plot above.
• the output from the sensors with two layers of ink A saturating at a very low force.
• the sensors with four layers of ink have more linear output than the sensors with two layers of ink.
• this response is stronger and the curve is less linear than the one above. Improving the consistency of output across the surface 16 of the sensor is one of the goals of our research.
• Vout is the output voltage measured at the active row 22 electrode
• Vsource is the voltage applied to the active column 20 electrode
• Rc is the resistance from a point on the upper FSR surface 16 to a column 20 electrode
• Rr is the resistance from a point on the lower FSR surface 16 to a row 22 electrode
• Rc' is the resistance between two adjacent column 20 electrodes
• Rr' is the resistance between two adjacent row 22 electrodes
• Rf is how the resistance vertically between the two FSR layers varies inversely with respect to the force F.
• Rc is modeled as a potentiometer whose position is controlled by the x position of a touch and affects how much resistance there is to Vsource (x*Rc) and to ground (l-x)*Rc.
• Rr is modeled as a potentiometer whose position is controlled by y with the upper portion going to Vout having a resistance of (y*Rr) and the lower portion going to ground with a resistance of (l-y)*Rr.
• Rc' doesn't affect anything.
• One of the benefits of this formula is that it suggests ways to improve the linearity of the sensor. It was noticed that all of the non-linearity of the sensor was coming from the first four terms in the denominator. The effect of these terms can be reduced by making Rc, Rr and Rr' smaller with respect to Rf. Our first attempt at doing this is to make Rc and Rr smaller by printing drone wires in between column 20 and row 22 electrodes 24 to reduce the resistance along the FSR surface between a pressure point and nearby electrodes 24. These wires are not connected to any circuitry. Their sole purpose is to reduce the resistance from a pressure point to nearby electrodes 24, thereby improving linearity. It is also possible to improve linearity by printing layers of different ink one on top of the other. For instance, printing an ink with very low resistance first followed by a higher resistive FSR ink over the electrodes 24 can lower Ra while keeping Rf high.
• Figure 25 This is a fairly linear output versus position curve that is obtained as a result of plugging in values for Rf that are significantly higher than Rc, Rr, and Rr'.
• Figure 26 This is a much less linear output versus position curve that is obtained as a result of plugging in values for Rf which are similar in magnitude to Rc, Rr, and Rr'. This matches the non-linearity observed in the earliest sensors produced.
• the first IMP AD made use of an off-the-shelf analog to digital converter board which cost over a thousand dollars, was very difficult to wire up to the sensor, and took up a lot of room. Since then, the electronics have been refined and used for scanning the sensors. For instance, it has been found that microcontrollers produced by Microchip that have as many as 32 analog input pins and many digital I/O pins. The advantage of these microcontrollers is that each pin can alternately be set to power an electrode 24, ground it or can be set into a high impedance state. Furthermore, the microcontrollers can scan the sensor at much higher rates than the analog to digital converter boards. On our 29x39 sensor, we have achieved scan rates of 500 frames per second, and it is believed that rates of 2000 frames per second and above are possible.
• the very small form factor devices such as an 8x10 resolution sensor, use a widely available chicken microcontroller board to read the sensor.
• the power dissipated through any given electrode 24 is orders of magnitude lower than the amount that could damage the electronics.
• the gate resistance of the driving electronics was enough to keep the average power dissipation down to a safe level as long as the sensor kept scanning through rows 22 and columns 20 at 50fps.
• the sensor could be flooded with water, pierced or cut, and the electronics would continue operating without any damage.
• the first advantage is that when a voltage reading is taken from an electrode 24 on layer 5, current doesn't have to flow out through that electrode 24 and through a sense resistor or current sensing circuit as in other devices (such as the one made by Tekscan). That is because layer 4 essentially acts as a sense resistor. As a result, the electrode 24 on layer 5 from which voltage is measured carries no current in the steady state, only acting to transfer the same voltage it has to the analog to digital converter, and thus, because current through the electrode 24 is nearly 0, there is almost no voltage drop along that electrode 24.
• the sensor has been used as a way for a person to move their hand over a pressure imaging surface 16 to emulate various types of physical three-dimensional controllers.
• a pressure imaging surface 16 to emulate various types of physical three-dimensional controllers.
• the first device consists of a controller with an embedded trackball, hi this case XY movement of the controller results in XY movement of the object, rocking back and forth of the controller results in movement of the object along the Z. axis, and rotations of the embedded trackball with the fingers results in XYZ rotation of the object.
• IMPAD IMPAD
• the initial implementation of IMPAD had an effective dynamic range of one part in 50. This dynamic range is sufficient for many multi-touch-based user interface 28 applications, but not for all uses. Below the smallest measurable level there is noise, which might be due to any of a variety of sources, including cross talk between the conductors on the surface 16, imperfections in manufacture, and stray induced signals in the control circuitry.
• Dynamic range can be increased in a way that is analogous to high dynamic range optical imaging. In this approach, the pressure image measurement is time multiplexed, hi successive time slices, the sensitivity of the logic circuitry is varied. When the circuit is set for high sensitivity, the device is sensitive to very fine touches, saturating to the maximum of its attainable range at a relatively low pressure.
• the device When the circuit is set to low sensitivity, the device is less sensitive, but is able to detect higher pressures before becoming saturated. To achieve this, we vary the resistance of the read out circuit over time, driving the circuit with varying voltages and varying the sensitivity of the analog to digital converter.
• the interpolating nature of EVIP AD can also be used to increase scan speed by scanning with high resolution only in the areas where contact is made. This is done using a coarse-to-fine approach which first scans the sensor with low resolution and determines which areas to re-scan with higher resolution. This can be combined with high dynamic range sensing in such a way the sensor can adjust on the fly to the pressure levels that it senses in the lower resolution scans to improve the accuracy of the high resolution scans. This has the potential to reduce the number of measurements needed to get a high quality scan of the device leading to reductions in price, increases in scan speed and quality, and allows reductions in power consumption of IMPAD.
• Opaque IMPAD devices can be used below.
• Flexible displays such as
• Plastic Logic's flexible display which uses elnk technology or the OLED displays being developed by companies like Samsung.
• EVIP AD technology For such implementations two distinct components are used: transparent versions of the FSR material itself, and transparent conductors. Traditionally, transparent conductors have been printed with Indium Tin Oxide (ITO) which is toxic and has a very high resistance. However, recently, transparent conductors using carbon nano-tubes have become available.
• ITO Indium Tin Oxide
• a wide variety of materials can be used as the force sensitive resistive element.
• the basic mechanism which can be found at either the microscopic or macroscopic scale some conductive material within a spongy or compressible substrate of insulating material. Increased pressure applied to the mixture results in an increase in the average area of contact between adjoining conductive elements (figure 27), thereby reducing the resistance between the materials at that point.
• Examples of force sensitive resistive materials include FSR inks, antistatic foams, and force transducting rubbers.
• Antistatic foams generally consist of a polymer substrate, such as nylon, coated with a thin layer of a conductor such as copper. Electricity flows between the copper clad fibers, thereby allowing static charge to even out across the fibers. Because they are squishy and may take time to recover their original shape after being squeezed, the output from such foams might be less accurate and repeatable than from FSR inks. However, they can be used in situations where a soft, stretchable sensor is needed. For example, such sensors can be used in hospital beds or wheelchairs to prevent patients from developing bedsores, and in cribs to monitor the breathing of infants.
• Force transducing rubbers are typically made of rubber or silicone that is infused with small sized particles of carbon which conduct more electricity as they are squeezed closer together.
• the use of these rubbers may allow for the construction of sensors that don't require an air gap and may perform better in harsh environments and in situations where stretching forces may be applied to the sensor.
• solid materials such as concrete can be infused with conductive particles that change their conductivity when very large forces are applied.
• sensors can be incorporated into building materials in order to pre-emptively detect the failure of bridges, buildings, roofs and walls, or to detect damage after it occurs.
• More exotic materials that can be used to sense force such as carbon nano-tubes.
• materials with anisotropic conductive properties can be created, thereby improving characteristics of the sensors such as the linearity of interpolation.
• Conductive or ferromagnetic fluids or gels can also be used as the FSR medium, allowing the sensing of pressure distributions of fluids or magnetic fields.
• Positional smoothness For any single touch, the extent to which the sensed position of that touch varies smoothly as the position of the touch is varied, rather than jumping discontinuously from one quantized value to another;
• Multitouch discrimination Given two touches, how close to each other they can be placed and yet still be distinguished as two distinct touches.
• Sensor arrays 18 which are built from discrete sensors necessarily have similar values for positional accuracy and multitouch discrimination, and also have poor position smoothness for touches that have a small diameter compared with the extent of the spacing between sensors.
• IMP AD allows positional accuracy and multitouch discrimination to be decoupled, so that very fine positional accuracy can be combined with very coarse multitouch discrimination. Also, IMP AD has very good positional smoothness even for touches that have very small diameter. [00326] This is true because, as was shown above in figure 28, each of the widely spaced sensor lines of IMPAD is able to measure the distance of any touch between two sensor lines, even if the touch does not actually make contact with either of the two sensor lines. Not only can a touch that lies completely between two adjoining sensor lines be detected, but in fact the proportional distance of that touch between the two adjoining sensor lines can be accurately computed, using the proportionality formula (ap + bq) / (p + q) that was previously described above. Therefore, even though multitouch discrimination is relatively coarse - due to the relatively wide spacing of adjoining sensor lines -positional accuracy and positional smoothness can nonetheless both be very high.
• An IMPAD connecting wire does not need to be active. This can be done by the electronics by setting the pin on the microcontroller or shift register connected to the wire into a high impedance state (which electrically disconnects the wire from the rest of the electronics). In this state, the wire acts in effect as if it were a drone conductor. If only every Nth connector line along its row 22 and column 20 connector lines, respectively, is actively used (where N is an integer greater than one), then if we keep the scan rate the same, the total power usage decreases by a factor of N A 2, or the power usage can be kept the same while the scan rate is increased by a factor of N ⁇ 2, in either case, the resolution of multitouch discrimination decreases by a factor of N.
• IMPAD can be placed into an IDLE mode by scanning only every Nth connector line, hi this mode it can very rapidly detect the presence of a touch upon its surface 16. Once such a touch is detected, IMPAD can be switched to a higher resolution active mode, in which it scans every connector line rather than every Nth connector line, hi the limit, one can deactivate every wire except for the first and last column 20 and row 22, essentially turning the entire sensor into a single bilinear sensor. [00329] It is also possible to use a coarse resolution mode in which only every Nth connecting wire is actively switched in order to sense a low resolution image over the surface 16 (figure 29).
• IMPAD can be switched to a higher resolution mode only for those rows 22 and columns 20 that encompass any detected touch.
• This strategy confers the advantage that the IMP AD can operate with a lower power requirement, and higher speed without sacrificing multitouch resolution since the higher power required for switching every row 22 and column 20 connector line need only be employed for those rows 22 and columns 20 where a touch has been detected.
• One surface 16 can be referred to arbitrarily as the "top surface”, and the other surface as the "bottom surface”. This is an arbitrary designation, for clarity of exposition, since the entire device can be flipped over, thereby switching the top and bottom surfaces, without any effect on the operation of the device.
• the connectors on the top surface are organized into rows 1 through N of parallel electrically conducting control lines, each of which is connected to the logic circuitry of the device.
• the connectors on the bottom surface are organized into columns 1 through M of electrically conducting control lines, each of which is connected to the logic circuitry of the device.
• successive control lines can be separated by zero or more parallel passive electrically conductive lines. All adjoining parallel electrically conductive lines in the device are connected to each other by an electrical resistive element.
• One method for scanning an IMPAD device is through a simple MxN scan: Each of the N input rows is set to positive voltage in turn, with the other N- 1 input rows all set to ground. Meanwhile, the voltage at each of the M output columns 20 is read out in turn, while the other M-I output columns 20 are all set to ground. The time to perform such a scan is MxN clock-cycles. Our lowest resolution implementations of IMPAD employ this MxN method.
• An MxN scan has the advantage of simplicity, but as N and M become large, scanning time becomes larger than is desirable for performance at interactive rates. For example, if the clock-cycle time is one microsecond, then a 300x300 scan will take 0.09 seconds, which is three times greater than the 30 millisecond time of a video screen refresh, and is therefore too long for acceptable interactive performance as a computer/human interface 28. For this reason, the current invention also implements another scanning method which is considerably faster, requiring only 2N time steps.
• the 2N time step method is able to scan the entire device in only 600 clock-cycles, which results in a scan time of 0.0006 seconds - far faster than is needed for real-time performance.
• achieving this maximum rate requires employing multiple analog to digital converters, which adds expense to the device.
• a 0.0006 second scan is not generally required, and therefore fewer analog to digital converters can be employed, while still maintaining a scan rate of several hundred scans per second, which is comfortably greater than is required for real time performance.
• the electrical signals to the top surface remain the same as in time-step 2j. Meanwhile, all of the control lines on the bottom surface in odd numbered columns (1, 3, 5, ...) are metered, and all of the even numbered columns (0, 2, 4, ...) are set to ground. The measured output voltage at each of these odd lines is converted into a digital signal, and these digital signals are sent to a computer.
• the total scanning cycle therefore consists of 2N steps, where for each step M/2 output signals are sent to the computer.
• A is the voltage measured at time-step 2j at row i
• B is the voltage measured at time-step 2j+l at row i+1
• C is the voltage measured at time-step 2j+2 at row i
• D is the voltage measured at time-step 2j+3 at row i+1.
• the sensitivity at (i+lj) will be u*(l-v)
• the sensitivity at (i,j+l) will be (l-u)*v
• the sensitivity at (i+l,j+l) will be u*v.
• Using the present invention it is possible to determine how small a touch is in extent by observing the time- varying signal returned by that touch as it moves over the IMPAD surface. This is useful in distinguishing, for example, the touch of a human finger (large) from the touch of blunt eraser (somewhat small) from the touch of a sharp pen tip (extremely small).
• a touch having very small extent crosses a column 20 control line i
• the measured voltage at columns i-1 and i+1 will drop to essentially zero.
• the measured voltage at rows j-1 and j+1 will drop to essentially zero.
• a material which conducts more as it compresses such as a Force Transducting Rubber material can be placed between the two layers 1 and 5 of electrodes 24 (figure 33). Drone wires can be used in such a configuration to improve linearity of the sensor.
• Drone electrodes 24 are ones that are placed between the column 20 and row 22 electrodes 24 but are not directly connected to electronics (figure 36). It has been found that placing drone electrodes 24 between the other electrodes 24 greatly improves the linearity of the device (which affects its ability to accurately measure the position of a contact point between two electrode wires), and also the sensitivity of the device across the surface 16 (so pressure applied at the intersection of two electrodes 24 creates the same level of activation as pressure applied at in the middle between four electrodes 24). We found that in general, as the number of drone electrodes 24 is increased, accuracy improves, but only up to the point where electrical noise and irregularities due to sensor manufacture take over. Drone electrodes 24 are described in more technical detail in earlier sections.
• drone electrodes 24 essentially create a resistive surface 16 which conducts really well in one direction and poorly in another.
• There may be other technologies that can be used to create such a surface 16 such as depositing a layer of carbon nano-tubes on the surface 16 that are all aligned in the same direction.
• Electrodes 24 can be skipped and left disconnected. These skipped electrodes 24 in effect become drone conductors, contributing to the accuracy of the device even though they are not electrically hooked up or do not contribute in some way other than being physically present as opposed to the other electrodes 24, such as the row 22 and column 20 electrodes 24 which are hooked up and contribute to the sensing by doing more than simply being physically present.
• the drone electrodes 24 in one view can be considered not active, while electrodes 24 that are not drone electrodes 24 are active electrodes 24.
• IMPAD is a revolutionary technology because it significantly reduces the cost and complexity of pressure imaging devices and because its construction may allow it to be incorporated into places where other approaches would fail. Thus, it enables many applications that would have previously been too expensive or impractical to realize.
• IMPAD may enable:
• IMPAD is a very general enabling technology, which can be incorporating into diverse applications, including writing implements, surgical implements, grip handles for operating machinery, as inserts into shoes or other clothing, inside of components of engines and other machinery, and molded into chairs and automobile seats in order to measure posture.
• IMPAD as an inexpensive backing layer for writing pads allows writers to use their own pen and any paper they wish. Stroke information is gathered by IMPAD, which tracks the time-varying total pressure and centroid position of the impression that the pen makes through the intervening layers of paper of the pad. This information can be either stored for later retrieval or interactively sent to a computer for immediate use.
• Inexpensive floor coverings of arbitrary size can deliver high quality real-time pressure images of feet or shoes. Each time the pressure image of a foot step is detected, that information can be combined with a data record indicating the current time. This time-stamped footstep can then be relayed to a networked digital computer, which stores this information. By accessing the stored foot/time information, it is possible to count the rate at which people travel through a particular location.
• IMP AD may also be used in security applications to detect traffic in restricted areas. It may be used to track people as they walk through an area by the pressure profile of their shoe and other stride characteristics. It can also be used to track wheeled devices such as shopping carts, fork-lifts or robots. This can, for instance, be used to recreate the path that particular people take through a store, to detect suspicious activity in an airport, or to detect a person who has collapsed in a hospital.
• An IMPAD device can be incorporated into the manufacture of the outer surfaces of a moving vehicle. Because the material of the IMPAD device consists only of layers of paint and thin conductive material, the entire IMPAD device can be incorporated below the outer layer of paint on a vehicle body or wing surface, without compromising either structural integrity or weatherproofing.
• the resulting time-varying pressure upon the outer surface can be monitored to detect changes in pressure that can be used to make decisions to improve steering or other control. For example, if data from the IMP AD device is used to detect that the air flow over the upper surface of an airplane wing is transitioning from laminar flow to turbulent flow - which indicates the imminent onset of a stall condition - then the angle of attack of that wing can be immediately decreased under control of computer software, without the need for human intervention, or the risk of human error.
• the pressure sensitive IMPAD layer allows a vehicle's onboard computer to detect contact and damage. Interpolating nature of the IMP AD sensor allows even coarse resolution sensors to pinpoint the location of any damage, thereby enabling quick repair.
• Continual monitoring of pressure patterns of an automobile tire against the road avoids dangerous tire blowout conditions, and allows the on-board computer on an automobile to alert the driver to the need to change or check tires.
• the more accurate time- varying information about the pressure of each tire against the road can also be used by electronic suspensions to adjust themselves to provide better traction or mileage.
• the IMPAD sensor can also instantaneously detect tears or punctures in the tire. Because the IMPAD technology is very thin and therefore does not appreciably change the physical profile of a surface 16, the IMPAD mechanism can be incorporated directly and unobtrusively as part of the manufacture of the tire, just inside the tread.
• Many interactive multimedia applications can benefit from a pressure-sensitive multi-touch input device, including digital painting, animation and shape modeling, the design of animated characters, 3D sculpting of virtual parts in Computer Aided Design applications, and rapid creation of artistic assets for computer games and film production.
• the same IMPAD device can independently detect both small pen touches and hand gestures - and can distinguish between the former and the latter because the pressure signal from a pen touch influences only a single square upon the IMPAD surface bounded by two adjoining rows 22 of conductor lines and two adjoining columns 20 of conductor lines, whereas the pressure from a finger or palm straddles many rows 22 and columns 20.
• a single IMPAD device can be used to by a human operator wielding a pen or stylus in one hand to use painting or sculpting software, while gesturing with the other hand to holonomically translate, rotate and scale a virtual workspace, such as a virtual painting canvas which is implemented in software or a virtual 3D object that is being sculpted, which is implemented in software.
• an artist can adjust the height features of a virtual terrain, implemented in software, to be used in a computer game or computer animated film, by simultaneously applying different amounts of pressure with the different parts (fingers and palms) of one or both hands, or by running a tool with a complex pressure signature, such as a paint brush, over the IMPAD surface.
• multiple parts of an animated figure can be simultaneously moved in different amounts and in different directions, by using different fingers of one or both hands, each finger being used to move the apparent position of one part or joint of an animated figure that consists of many connected parts or joints.
• the IMPAD can simultaneously and accurately detect pressure changes of many touches over its surface 16, it enables a form of text entry that is potentially faster than the standard QWERTY or Dvorak methods of touch typing.
• the typist can merely place all ten fingers in fixed locations, and indicate a "key press” simply by flexing a finger without physically moving it. This flexion is detected by the computer as a momentary increase in pressure at the location of that finger on the surface 16. Because there is no requirement that the finger physically move, such a gesture is significantly faster than is the action of moving a finger to a key over a keyboard to the location of a key and then striking that key.
• the typist can hit a special NEXT_KEY one or more times, which indicates that successive matching words further down in the word list be used rather than the most frequently used matching word.
• Variants of this family of techniques can also be implemented, in which more characters are associated with each finger. This frees up particular fingers to be mapped to punctuation, numerical digits and so forth. Also, by depressing multiple fingers simultaneously, the typist can indicate various shift states, such as a shift to a capital letters character set, a numeric character set, or a punctuation character set. Additional information can also be obtained by analyzing the pressure exerted by the palms of the user. For instance applying pressure to one or the other palm can be used to switch to a capital letter or a numeric character set. Also, applying pressure to the left, right, top or bottom sides of the palm can be used to switch into different states or activate various shortcut commands. For instance tilting the palm to the right may activate a pen mode where a pen is being tracked. Placing the palm flat on the table can be used as a gesture to disable or enable the multi-touch device.
• IMPAD sensors can be incorporated into both the seat and the back of a wheelchair, and connected to an onboard computer, which can be made small and portable, in order to measure time- varying pressure of various parts of the user's body against the chair surface.
• an onboard computer which can be made small and portable, in order to measure time- varying pressure of various parts of the user's body against the chair surface.
• a health-care worker can be alerted, or else the patient, if mobile enough to respond by shifting his/her body position, can be alerted, or else a motorized device can be activated within the chair that causes the patient's body to shift sufficiently so as to remove the danger.
• IMPAD sensors can be incorporated into the mattress of a hospital bed, and connected to an onboard computer, in order to measure time-varying pressure of various parts of the user's body against the bed surface.
• a substantial period of time e.g.: an hour or more
• a health-care worker can be alerted, or else the patient, if mobile enough to respond by shifting his/her body position, can be alerted, or else a motorized device can be activated within the bed that causes the patient's body to shift sufficiently so as to remove the danger.
• an IMPAD sensing surface can be embedded into the mattress of a baby's crib.
• the IMPAD is connected to a computer.
• Information from IMPAD to this computer is analyzed to determine whether the movement and breathing pattern of the infant is normal or abnormal. If an abnormal pattern is detected, the computer can immediately send a signal to alert a parent, guardian or health care worker.
• IMPAD be used to create inexpensive computer-interfaces for existing musical instruments, but it can also be used to rapidly build entirely new types of musical instrument.
• IMPAD is capable of measuring extremely rapid changes in pressure to any part of its surface 16, it can be used to measure the velocity at which a hammer ceases touching the IMPAD surface, in response to a keypress by the player, as well as the time and velocity at which the hammer regains contact with the IMPAD surface, in response to a keylift by the player. This information is sufficient to completely capture all of the subtleties of the player's performance, at a far lower cost than can be achieved using existing methods for digital capture of a piano performance.
• an IMPAD surface can be built into the top surface of the neck of a guitar, hi such an instrument, when interfaced to a computer, there is no need for strings.
• the player can move his/her fingers about the fret board to play the instrument. Even the smallest movement of the player's fingers suffices to create a musical effect, such as pitch vibrato (small rapid changes in pitch that the player effects by wiggling a finger in the longitudinal direction of the fret board) or volume vibrato (small rapid changes in volume that the player effects by wiggling a finger so as to rapidly vary the pressure exerted by the finger against the fret board).
• IMPAD surfaces can also be built into electronic drums allowing for the detection of the strength at which the drum is hit by multiple drum-sticks.
• the position at which the drum-sticks strike can be used to modulate the sound in a way similar to the way a real-drum's sound changes form a higher pitched sharper sound when the side is struck to a deeper, richer sound when the center is struck.
• Any load-bearing structure such as a building or bridge, can fail when it is overstressed, and such failure can lead to both loss of lives and enormous expense.
• An inexpensive way to warn of such impending failure, before it reaches the critical stage, is to embed EVIPAD devices into support structures. Because IMPAD has low power requirements and is inexpensive and because even a coarse resolution IMPAD device can measure the exact center of a stress point, EVIPAD can be incorporated effectively for this purpose in situations for which previous technologies would be either inadequate or too expensive or both:
• the embedded IMPAD device can be connected to a small, inexpensive and low-power microprocessor, which is also embedded into the structural member.
• the microprocessor which periodically polls the EVIPAD, detects an pressure pattern over the EVIPAD surface which deviates from the expected pressure pattern, it can send an alarm to a computer, using some transmission method such as a signal across a wired or wireless network or a signal on a particular radio frequency, thereby identifying the at-risk structural member.
• This technique can be used for buildings, bridges, boat/submarine hulls, wind turbines, ship sails and any other structures for which it might be desired.
• IMPAD provides an inexpensive way to enable true pressure sensitive multi-touch over the entire front or rear or side surfaces, or all surfaces, of a portable electronic information device.
• IMPAD When used on the front surface, IMPAD is manufactured so as to be transparent, by using clear Force Sensitive Resistive materials and transparent conductors, as described elsewhere in this document.
• the use of IMPAD to send user information to the computer processor 120 within such a device enables much more subtle and expressive gestures by the user, and therefore a much richer gesture vocabulary for user interaction, than can be achieved through interfaces that do not provide spatially variant pressure information to the computer.
• a gesture consisting of a stroke across the surface followed by a press (i.e.: momentary increase in finger pressure against the surface) can be distinguished from a simple stroke gesture.
• the ability to recognize and therefore respond to gestures that include variations in pressure distinguishes IMP AD base interfaces from interfaces based on input methods such as capacitive sensing, which do not have the ability to measure variations in pressure.
• IMPAD can be incorporated into the handle of any instrument that is held in the human hand, such as a scalpel, hammer, tennis racket, golf club, and the space and time varying pressure of the user's grip can be sent to a small onboard microprocessor within the tool for analysis or for storage pending later analysis. If a tool is potentially dangerous, such as a power saw or electric drill, IMPAD can be used to rapidly sense and respond to any abnormality in the grip, which indicates that the tool is about to slip from the user's hand, and the power to the tool can be rapidly shut off in response.
• a tool is potentially dangerous, such as a power saw or electric drill
• the information from the IMPAD device within the grip can be processed by a computer, and this processed information can be used to give suggestions to the user about how to improve aspects of their grip to as to improve performance.
• IMP AD device Other objects or equipment related to user performance can also be covered with an IMP AD device, so as to monitor how they interact with other objects.
• balls and floors and walls of sports facilities can provide feedback to assist both scoring and performance evaluation, hi the case of a ball with an IMP AD device either on or just below its outer surface, a microprocessor is placed inside the ball, and the information gathered from the IMPAD device by this microprocessor can either be immediately transmitted wirelessly to a computer, or else stored in the microprocessor's onboard memory for later retrieval, depending upon the needs of the application.
• an IMP AD device By incorporating IMP AD into clothing (an IMP AD device can be formed in a cloth-like structure as described elsewhere in this document), and sending the information thus gathered to a small microprocessor which is worn on the body, pressure and flexing of the body during athletic performance can be monitored, to assist both in evaluative feedback and in avoidance of overexertion or unhealthy posture or other practice.
• An IMPAD surface placed in any part of a shoe or other footwear not just underneath the foot, but also, for example, the toe, the heel and the sides of the foot, comprehensive information about the forces acting upon any or all parts of the foot can be gathered.
• IMPAD devices can also be incorporated into inexpensive and lightweight gloves, and this information sent to a computer that is worn on the body.
• This computer can either immediately process this information, store it for later retrieval, or transmit it to a remote computer, so that all touch and grip information can be continually monitored.
• One application of monitoring of limb movement, of forces upon the foot, and of hand/finger grip information is in performance capture, which can be used for animation and puppetry control, for manipulation and navigation within virtual reality environments, for the control of robotic devices, and for therapeutic and other physiological monitoring.
• IMPAD could also be incorporated into sporting equipment such as bats, golf-clubs and tennis racquets to give players instant feedback about their strokes. It can also be detected into surfaces of playing fields to detect the impact of balls.
• One application area for IMPAD is for use in lining surfaces that adjoining gaseous or liquid volumes that have spatially varying pressure, such as lining the inside of water pipes with IMP AD based materials in order to monitor the flow and pressure buildup.
• EVIPAD layers can be incorporated into the outer hulls of ships or submarines and the wings and fuselages of airplanes.
• Porous constructions of the IMP AD that allow fluids to flow through them can sense flows through valves and tubes and thereby detect impurities or objects in those flows.
• Woven structures enable high material strength and flexibility and stretching capability.
• IMP AD is formed into woven structures by coating of thin wires with force sensitive resistive sheaths. These coated wires are woven into a warp and weft structure. Passive wires between the actively controlled wires along each of the two axes increase the bilinearity of the response, as with other implementations of IMPAD (figure 18).
• the following further describes and adds to the above.
• a transparent mesh embodiment of IFSR can be implemented as follows.
• pitch of the lines can be made to match the pixel pitch of a digital display device, such as an LCD display that contains a TFT electronic grid, hi such devices, the TFT grid itself is not transparent. If the pitch of the pattern of parallel conducting lines matches the pixel pitch of the display, then when the final IFSR sensor device is laid atop the digital display the sensor will align with one of the two dimensions of the display's TFT grid. The overlaid conducting lines will thereby obstruct only the already opaque TFT grid, and therefore the presence of the sensor over the display surface will not appreciably diminish either the brightness or the clarity of the display device.
• the FSR material can be placed by an ink-jet process, or by an etching process, or by any other known method for laying patterned ink upon a surface.
• the single unit thus formed becomes one side of a two-sided IFSR sensor (5).
• This "mesh embodiment" of an IFSR sensor allows rays of light to pass, unimpeded, through the clear portions of the grid pattern, hi particular, the grid pattern does not impede the viewing of a digital display upon which the sensor has been placed, assuming that the pitch of the sensor's grid pattern matches the pitch of the pixels of the digital display, and that the TFT array between the pixels of the digital display are aligned with the printed grid pattern of the sensor.
• the senor behaves the same as any other embodiment of an IFSR sensor. It possesses the same area-interpolating force-imaging capability, the same external wiring and electronics, and the same scanning algorithm for read-out of time-varying force images.
• the resulting sensor has different length conductive lines, due to the different added lengths of the return wires, which results in differences in electrical resistance between different conductive lines. This property can make it more difficult to accurately determine the pressure at all parts of the sensor.
• conductive lines are run diagonally across the sensor surface, at a 45 degree angle from the orientation of the sensor borders. Conductive lines along one surface are run from the bottom right to the top left, whereas conductive lines along the other surface are run from the bottom left to the top right.
• This arrangement forms a set of diamond shaped tiles, thereby maintaining the property that conductive lines and the top and bottom surfaces, respectively, cross at a right angle.
• all electrical connections to the controlling electronic circuitry can be made along the bottom edge.
• Each conductive line along the left edge of the first surface is shorted to the correspondingly positioned conductive line along the left edge of the second surface, hi addition, each conductive line along the right edge of the first surface is shorted to the corresponding conductive line along the right edge of the second surface.
• all conducting lines of the sensor are of the same length (thereby guaranteeing equal electrical resistance for all conducting lines), and there is no need for the addition of return lines.
• Figure 38 shows an NxN sensor with diagonal conducting lines.
• (1) represents one of the conducting lines of the first surface (in gray).
• (2) represents one of the conducting lines of the second surface (in black).
• (3) represents a shorting of a conducting lines of the first surface with the conducting line of the second surface that is coincident with it where both conducting lines cross the left edge of the sensor.
• (4) highlights the bottom edge of the sensor, where the ends of all 2N conducting lines are available for connection with the controlling electronic circuitry.
• (5) represents an edge view of the bottom edge of the sensor. In the lower half in this view are the N ends of conducting lines that lie along the first surface where they terminate at the bottom edge of the sensor (shown in gray). In the upper half in this view are the N ends of conducting lines that lie along the second surface where they terminate at the bottom edge of the sensor (shown in black).
• tile In figure 39 only tile is active, and this tile has been marked with a large black dot.
• two successive conducting lines are activated by the controlling electronic circuit to create an electrical potential difference across the marked tile along the first surface, along one of the tile's two diagonal dimensions.
• One of these conducting lines i contains the source voltage and the other i+1 is connected to ground.
• each of 2N 2 unique diamond shaped tiles of the sensor are individually measured in sequence, by successively setting possible ordered pairs of such conducting wires to different values of (i,,i+l) and (j j+1), where i +1 ⁇ j.
• the entire sensor can be stretched along one dimension, so that each of the diamond shaped tiles are elongated in one dimension.
• this diagonal arrangement for conducting wires is particularly suitable for woven cloth embodiments, using the under/over structure of woven conductors coated with FSR material as previously described, because all of the electrical connections to the controlling electronic circuitry can be localized along one edge of the cloth, which can function as a seam of the cloth fabric. This arrangement of conductors is shown in figure 40.
• FSR can be placed on just one side of the sensor.
• the other side can be covered with a resistive material that is not an FSR.
• the combination of the two materials pressing together will act as an FSR.
• the other side can have exposed wires and/or drones with a resistive strip running along one edge to provide for the interpolative quality on the other side.
• the UnMousePad... where the FSR does not form a continuous surface, having breaks in it.
• the FSR on one side can be replaced with resistive material. All of the embodiments can be mixed and matched, so that one embodiment is on the top surface and another embodiment is on the bottom surface.
• One or both sides of a sensor can be printed on a rigid material (for example PCB).
• a rigid material can act as a base for the sensor. If a rigid material is thin enough, or flexible enough, it can also be possible to sense force through it.
• Really large UnMousePad surfaces (for applications such as ballrooms or dance floors) can be created by placing strips of material together on the top side and placing perpendicular strips of material on the other side together. The strips of material would have electrodes running along it covered with FSR.
• Really long UnMousePad surfaces for covering hallways or walls
• the second side would need to have return wires running along it which can be printed on the opposite side of the material and connected with vias, or can be printed on the same side and separated with a layer of dielectric (this same principle can also be used on smaller/shorter sensors).
• grids of electrodes are sometimes used in capacitive devices such as the Apple iPhone, and are also used in magnetic devices such as Wacom's tablets. Because our sensors use low frequency analog voltages, it is possible to simultaneously use the grid of electrodes for magnetic or capacitive sensing. This could either be done simultaneously or in separate time-slices from the force sensing.
• capacitive sensor electronics would simply need to be electrically connected to the electrodes and/or drone lines of the UnMousePad sensor. If multiple electrodes or drones need to be tied together in order to reduce the resolution of the capacitive sensing (thereby reducing cost), they can be tied together using small capacity capacitors between each other to avoid disrupting resistive force sensing. This is because the low frequency analog signals used for force sensing will not go through the capacitors, while the high frequency signals used for capacitive sensing will just go through the capacitors as if they did't there. [00459] To make a magnetic sensor, electrically inductive loops need to be created on the sensor surface.
• the return wires can form loops with the electrodes, drone lines, or both.
• small capacity capacitors can be placed to in the path of the current on these loops on each return wire. As with capacitive sensing, the capacitors will interrupt the flow of low frequency analog signals, allowing for force sensing, while allowing high frequency signals used for magnetic sensing to pass through.
• the UnMousePad principle can apply to sensing of other natural phenomena besides force.
• they may be used to measure light waves, sound waves, or any other electromagnetic wave.
• a material such as that used in Hamamatsu sensors, which change their resistance in response to incoming light, can be disposed between the two layers of a transparent or partially transparent UnMousePad.
• a material which generates voltage such as a piezo-electric transducer
• FSR electrical resistance
• a material which changes its electrical resistance in response to stimulation by electromagnetic waves, including electromagnetic waves that are outside of the visible spectrum, such as microwaves or infrared light.
• Figure 41 is a diagram showing how drone conductors can be tied to active lines with capacitors to combine resistive and capacitive sensing. Note that a similar pattern of conductive lines, rotated by 90 degrees is used on the second layer of the sensor in accordance with standard UnMousePad technology.
• Figure 42 is a diagram showing how drone electrically inductive loops can be formed using return wires on the back of the sensor. Capacitors are put into the path of the current flowing on return lines to preserve resistive sensing ability. Note that a similar pattern of conductive lines, rotated by 90 degrees is used on the second layer of the sensor in accordance with standard UnMousePad technology.
• Non conducting liquids such as mineral oil can be placed between the two layers of FSR material.
• this reduces optical scattering from the surface of the transparent ink.
• this prevents other liquids such as water from entering the sensor, while also making the sensor react less to quickly applied forces, which is desirable when using the sensor to measure slowly varying forces.
• This also makes the sensor filter out forces due to bending and forces due to atmospheric pressure, or pressure of a fluid that presses on the outside of the sensor.
• One possible application of such a sensor is for coat the hulls of ships or submarines to detect collisions or potentially dangerous situations.
• the liquid within the sensor keeps the two sides of the sensor from touching despite pressure that is applied to it from the outside; the liquid also prevents the pickup of quickly changing variations in pressure such as those caused by waves.
• any forceful or long-lasting non-uniform pressure applied to the sensor such as the pressure due to collision with sand, a rock, a dock or another vessel would be detected, and could be used to alert the captain or crew of a potentially dangerous situation.
• a force sensitive rubber such as the one made by peratech
• similar flexible material which has a conductivity which increases with applied pressure for example, rubber, gel or silicone rubber impregnated with conductive particles
• FSR resistor
• the sensor will have proper conducting/interpolating properties along the surface of the two sides as well as proper force sensing properties in the direction perpendicular to the sensor surface.
• the electrodes on the top and bottom layer of the sensor can be first coated with a resistive material. Then, the force sensitive rubbery material can be disposed in between the two layers.
• Force sensitive rubbery material can be molded into various shapes and can be made into sheets that could go between electrodes of an upper and lower layer. It can have varying thicknesses in various parts, which is useful in embodiments such as shoe insoles that sense pressure.
• the material can also be injected between two sensor layers in a liquid form and allowed to solidify, therefore eliminating any air gap between the layers.
• the solidifying can be performed by mixing a hardener into the material in liquid form, injecting it, and allowing the hardener to chemically react and solidify.
• a material can be chosen that is solid at room temperature, but liquid at a higher temperature. The material can be heated to where it becomes a liquid, injected between the two layers, and allowed to harden.
• Electrodes Another way to form electrodes, besides screen printing silver conductor, is by depositing a thin film of metal such as nickel or other conducting material (using sputtering) and then etching it with a mask and acid, laser etching, or mechanical etching (scratching away material) to form the desired electrode pattern.
• the electrodes can be then be made thicker using electro-plating.
• a voltage needs to be applied to the electrodes to be electroplated. This can be done efficiently by having a wire that connects all the electrodes together on one end, near the area where electronics are normally connected, and runs to an area where a connection can be made to a circuit used for electroplating.
• Electrodes which are metal have the advantage of lower electrical resistance, and thus more accurate sensing. They can also be made thinner than printed silver electrodes, while still maintaining good electrical conductivity and resiliency. Thinner electrodes further improve the accuracy of sensing.
• Another way to form electrodes is to etch grooves into glass, plastic or other substrate.
• the etching can be affected by chemical etching with a mask, with lasers, or via mechanical means such as scratching away material.
• a material with grooves can be created by molding, where the mold is machined in such a way as to create sheets of material with grooves.
• the substrate with grooves on it can be coated with a layer of conducting material such as a thin coat of copper or other metal.
• the top layer can be removed, leaving only the material in the grooves.
• the advantage of this approach is that the upper surface will be smooth, with conductors that actually have some thickness to them, reducing their resistance.
• Another way to form electrodes is to sandwich alternate thin layers of conductive and nonconductive materials, thereby forming a block of material consisting of a "zebra" pattern. After the material is fully cured into a solid, it can be sliced into thin layers in a direction at a non-zero angle to the orientation of the original planar layers. This process results in thin solid sheets that contain alternating stripes of conducting and non-conducting material.
• Another way to form electrodes is to laminate thin conductors, for example, made of strips of thin copper foil onto a substrate such as plastic.
• This is a technique that is used in industry to create some varieties flat flex cables (FFC).
• FFC flat flex cables
• This technique has the advantage of not creating any waste material, thus it can be less expensive than methods requiring etching.
• It is also a very good technique for creating large scale sensors such as those used to cover floors and walls, because high precision alignment of electrodes is not as important.
• Connection can be made to sensors manufactured in this way using zero insertion force (ZIF) sockets, with crimp-on connectors, zebra connectors or other z-axis conductors pushed up. against a circuit board, or by printing a wiring pattern in a subsequent printing step to connect the electrodes to external electronics.
• ZIF zero insertion force
• Ink-jet printing has the advantage of being able to form very fine patterns in any desired configuration. It can also form a very smooth layer of FSR ink.
• a further advantage of ink-jet printing is that there is no waste material, thus it can be less expensive than methods requiring etching, there is also virtually no added production cost incurred from modifying sensor patterns or designs.
• Another way to form a very smooth layer of FSR ink is to vibrate the substrate at a high frequency in random directions after applying FSR ink via a method such as ink-jet printing or screen printing, but before the ink is dried.
• the vibration acts to evenly distribute the FSR ink, forming a smooth upper surface, which in turn improves the accuracy of sensing in the final product.
• the UnMousePad can be tested electrically by connecting wires to each side of each electrode and measuring resistance between electrodes as well as conductivity of electrodes.
• the pressure sensitivity of the UnMousePad can be tested by fully assembling a sensor, and then either applying known pressures at known points (and measuring for the correct output from the electronics), or by applying an even pressure over the entire sensor and checking for a signal that is the same over the whole sensor.
• a rubber gasket can be provided on the edges to prevent leakage of gas.
• the UnMousePad can be scanned with an optical scanner, such as the scanners commonly used for scanning sheets of paper and photographic slides.
• an optical scanner such as the scanners commonly used for scanning sheets of paper and photographic slides.
• paper-scanning mode the scanner will see all the details of the sensor surface, but will not see where there are holes.
• slide-scanning mode we shine light through the sensor while it is being scanned. All holes thereby show up as bright spots. Both of these scan modes can be combined and performed simultaneously if different colors of light are used for scanning the surface and for scanning for holes.
• a large high resolution image of the sensor can be obtained.
• This image can be analyzed by known software means to look for defects.
• the image can also be stored in an archive in order to track the effect of defects over time, and to be able to see whether a sensor had originally contained manufacturing damage, should the sensor fail at some point during its operational lifetime.
• UnMousePad sensor In many situations it may be desirable to mount the UnMousePad sensor so that one side is attached to a rigid surface. This protects the sensor from being creased.
• the second advantage is that if the sensor is placed on an uneven surface, then the sensor can incorrectly register bumps on the surface as touches. Placing the sensor on top of a rigid surface avoids this.
• the enclosure of the UnMousePad can be made to cover the edges.
• the enclosure can physically hold the top and bottom of the UnMousePad together without requiring double sided adhesive such as VHB, thereby reducing assembly costs.
• the traces of the UnMousePad running to the electronics on the top and bottom layer need to be insulated from each other.
• the top and bottom surface of the UnMousePad need to be kept in alignment with respect to each other by some mechanical means, such as pins or screws that go through registration holes that are cut into both layers.
• the UnMousePad can be covered with a soft material such as a rubber or silicone.
• the material can be optionally covered with a smooth, thin coat of a material such as synthetic cloth or Teflon to provide a smooth upper surface for easy gliding of fingers.
• the sensor can also be covered with a rougher surface such as paper, or a plastic with paper texture for more comfortable writing.
• the UnMousePad can be placed on top of a rubbery surface. If the sensor is thin enough, the surface below the UnMousePad will cushion the user's fingers as they strike the UnMousePad. In this configuration, the surface can also be coated with a smooth surface, or by a surface with paper texture.
• Two textures can be provided by coating the outsides of the two sides of the UnMousePad with different materials.
• one side can be coated with a rubbery material which is coated with a smooth cloth suitable for touch interaction, while the other side can be coated with a more rigid material that has a paper texture suitable for writing.
• Another example is a material which is rubbery on one side for use as a drum instrument, and smooth on the other for use as a guitar-like instrument that allows the player to easily slide fingers between notes.
• materials which can be removed and replaced on the surface of the UnMousePad can be provided. These surfaces can be tacky, magnetic, or have other mounting means so that they do not slide laterally across the surface of the UnMousePad in an undesirable way.
• ALTERNATE READOUT ELECTRONICS To sense light touches, it is desirable to be able to detect very low voltage on the sensor outputs. Furthermore, for more accurate tracking and sensing, it is desirable to detect small variations in voltage. This can be achieved with several approaches which can be used one at a time or in combination. One approach is to use an A2D converter with more output bits. More bits generally imply that smaller variations in voltages can be measured. A second approach is to lower the analog voltage reference of the A2D converter. This lowers the upper limit of the range of the voltages that are read (such that voltages above a analog voltage reference cannot be read at all). However, at the same time, this also allows for more precise reading of voltages below the analog voltage reference value.
• Another way of improving the sensor's sensitivity is to use a voltage gain amplifier that can amplify small voltages before those voltages have been sent to the A2D converter.
• the sensitivity can be varied in real-time to allow for high-dynamic-range scanning.
• the number of bits scanned can be varied, with approach 2, the analog voltage reference can be switched dynamically, and with approach 3, the amount of gain can be varied during scans as required.
• a bank of sense resistors can be connected to each of the output lines of the sensor on one side, and to ground on the other side. This arrangement allows the sensing of all outputs simultaneously or of several outputs at a time, without requiring the use of digital electronics to ground the pins.
• the sense resistors need to have a very small resistance, and the outputs generally need to be amplified with an analog gain amplifier.
• the use of low resistance in the sense resistors avoids blurring of the force image.
• the configuration thus described has the advantage of improving the linearity of position readout of the sensor device.
• each of the outputs of the sensor can be connected to a current-to- voltage amplifier.
• the current-to-voltage amplifiers force all the outputs of the sensor to ground, while simultaneously allowing voltages to be read out that correspond to the amount of current flowing through each sensor output pin that is requires to force the pin voltage to ground.
• the configuration thus described has the advantage of improving the linearity of position readout of the device.
• the current-to-voltage amplifier can serve the purpose of amplifying the signal, which can improve sensing of small forces and small variations in forces applied to the sensor.
• Shift registers can be used to drive the pins of the sensor inputs to a small positive voltage, such as +5 V or +3.3 V, or to ground. Any number of shift registers can be chained together to expand the size of the sensed surface. By shifting several bits into a shift register that have several 1 values in a row, either followed or preceded, or both, by 0 values, we can power multiple inputs simultaneously. The configuration thus described effectively scans the sensor at a lower resolution, but with a faster scan rate.
• analog multiplexors to select channels for A2D conversion can be used in combination with logic that can drive the lines either to ground, or into a high impedance state.
• Logic that enables this ability includes: shift registers which have an output enable input (which can force all outputs of the shift register into a high-impedance state), port expanders that can switch between output or input states, shift registers that have open-drain or open-collector outputs, general purpose microcontroller I/O pins, some types of programmable logic arrays (PLAs), or shift registers used in combination with inverting/non-inverting buffers that contain open-drain or open-collector outputs.
• PDAs programmable logic arrays
• pin 1 of mux 1 can connect to pin 1 of the sensor
• pin 1 of mux 2 can connect to pin 2 of the sensors
• pin 2 of mux 1 can connect to pin 3 of the sensor
• pin 2 of mux 2 can connect to pin 4 of the sensor, and so on.
• the common outputs of the multiplexers can be connected together electrically and then go to whatever A2D converter is used. With this configuration, we can simultaneously read out from any 2 adjacent pins of the sensor by connecting both to the A2D converter input simultaneously.
• One skilled in the art can see that by chaining more multiplexers in this way, an arbitrarily large number of adjacent pins can be simultaneously connected to a single input of an A2D converter.
• a shift-register or multiple shift-registers, can be used to shift in the modes for the pins, and then to latch the result onto the output, all in one step.
• an I2C bus or a serial UART bus can be used to communicate with the chip.
• programmable logic such as an FPGA, PLA, CPLD or
• SPLD coupled with one or more A2D converters in place of a microcontroller to read out values from the sensors. It is also possible to use such programmable logic in combination with a microcontroller to read out values from the sensors.
• programmable logic in combination with a microcontroller to read out values from the sensors.
• the use of a microcontroller in previous examples is illustrative, and ones skilled in the art will appreciate that other types of logic such as the programmable logic mentioned in this paragraph may take the place of a microcontroller to perform readout and processing of forces from our sensors.
• column and row electrode connections to electronics are made in generally the same area of the sensor, with wires from the row electrodes running around the sensor to wind up in the same area as the wires from the column electrodes.
• This configuration is just one possible configuration for these connecting wires.
• One alternate configuration is to run wires from column electrodes vertically to a circuit board that is either above or below the senor, while running wires from row electrodes horizontally to a separate circuit board that is either to the left or to the right of the sensor. This configuration shortens the paths along which the wires connecting to electronics must run, and reduces the amount of border area needed for the wires. It also separates the electronics used for driving the columns from the electronics used for reading the rows into two circuit boards.
• the circuit boards may be connected to each other electrically with a separate electrical connection, consisting of one or more wires, to allow them to talk to each other.
• the combination of the pressure images recorded from the two scans may be combined by averaging or other means to produce a more accurate final pressure image. All that is necessary to create such circuitry is to connect both row and column electrodes to circuitry that can individually power them, ground them, put them into a high impedance mode, or read their voltage with an analog-to-digital converter.
• the upscaled image resulting from #1 can be smoothed by convolving the upscaled image with a Gaussian or other blur kernel.
• This blurring operation improves the detection of peaks in the peak detection stage, which allows for more reliable detection of fingers that are near to each other.
• This blurring operation also reduces the probability of detecting multiple peaks when there should really be just one peak.
• This misreading can happen as a result of upscaling of a pressure image that contains a saddle-point.
• the blur kernel is made to have a radius similar to the radius of a typical human finger, in order to optimize for finger detection.
• the blurred pressure image should only be used for detection of peaks and those areas that surround them. This blurred pressure image should not be used for calculation of forces and positions, because the blurring can introduce errors into such calculations.
• This expected location can be estimated by linearly extrapolating the motion of the touch, for example, by assuming that the touch will continue to move at the same velocity with which it has moved over the last two frames or data, or by assuming that it will move along the same curve along which it has moved during the last three frames of data with corresponding velocity and acceleration. Because the added biasing image has one half the strength of the detection threshold, for the touch to be forgotten the force exerted by the touch would need to drop to half the detection threshold. This algorithm removes the problem that was earlier described of unwanted momentary transitions between the 0 and 1 states. The image which has the biasing images added in should be used only for peak detection of touches, and for finding touch areas.
• touch merge and touch split events are useful in downstream software which uses these events.
• the detection of these events can be performed in the following way: We can detect touch merges when a touch that is nearby another touch disappears, and the resulting touch, detected in the next frame, has a force that is approximately equal the sum of the forces of the two touches from the previous frame.
• an event should be sent to the downstream software indicating that a touch with ID A, and a touch with ID B have merged into a touch with a new ID C (where A, B, and C are different unique identifiers).
• a pen can be detected because the movement of the pen across successive drone wires causes small fluctuations in amplitude, thereby creating a corresponding oscillation in measured force as the pen moves over the sensor surface. This is due to the fact that there is slightly more conductivity at those locations where the pen tip is nearest to the intersection between two conductors than when the pen tip is furthest away from such intersections. This phenomenon does not occur in response to a finger touch because a finger has a contact area that is very large compared with the spacing between drone wires. The touch of a finger effectively creates an area integral that causes any potential fluctuation to be cancelled out by the contributions from different locations within the area of the finger touch.
• UnMousePad sensor The principle of the UnMousePad sensor is applicable to applications in which the rows and columns to not run in straight lines, are not strictly parallel and/or do not cross each other at a 90 degree angle.
• an UnMousePad sensor grid can be continually distorted so that it fills a circle (see figures 43-49).
• a circular sensor can be created by providing one side of the sensors with wires that go out from the center to the outside in a radial fashion, while the other side of the sensor is provided with lines that form concentric rings (see figure 43).
• An UnMousePad sensor can also be a distorted grid.
• Drone conductors can be disposed between electrodes in just the same way as with an UnMousePad sensor that has a regular grid. [00504] Connections to the sensor can be made in such a way that parts can be trimmed without damaging the sensor.
• Figure 43 shows a layout of vertical electrodes for a circular UnMousePad that is made by distorting a grid. Wires run around the periphery to connect the electrodes to a bus (visible on the lower right), where an electrical connection to circuitry can be made.
• Figure 44 shows a layout of horizontal electrodes for a circular
• UnMousePad that is made by distorting a grid. Wires run around the periphery to connect the electrodes to a bus (visible on the lower right), where an electrical connection to circuitry can be made.
• Figure 45 shows a layout of vertical electrodes and drone lines for a circular UnMousePad that is made by distorting a grid. Wires run around the periphery to connect the electrodes to a bus (visible on the lower right), where an electrical connection to circuitry can be made.
• Figure 46 shows a layout of horizontal electrodes and drone lines for a circular UnMousePad that is made by distorting a grid. Wires run around the periphery to connect the electrodes to a bus (visible on the lower right), where an electrical connection to circuitry can be made.
• Figure 47 shows a layout of circular UnMousePad showing both radial and concentric circle electrodes on top and bottom sensor layers.
• Figure 48 shows a layout of circular UnMousePad showing both radial and concentric circle electrodes as well as drone lines on top and bottom sensor layers.
• Figure 49 is an image of a foot sensor grid (without drone electrodes) with column and row electrodes overlaid on top of each other. The column electrodes are drawn with solid lines, and the row electrodes are drawn with dotted lines. The grid has an 8 x 10 resolution. It is distorted in such a way as to match the natural shape of a foot, so that it can be used as an insole. Wires connecting to electronics are not shown. In a physical embodiment, the wires from the rows and columns could run to the area under the arch, where a microcontroller could be embedded.
• the UnMousePad can be placed onto skateboards or in balance boards in order to detect the position and balance of a person. These devices can be used for stationary purposes such as for athletic training or to provide input for video games. These devices can also be used for moving powered vehicles, which would, under computer control, move in response to subtle changes in pressure by the user's feet, and could also actively help to balance the user like a segway.
• UnMousePad can be used as part of the inside lining of a robotic suit
• the suit (such as the suit in IronMan). This will allow the suit to sense forces applied to it by the wearer of the suit, thereby causing actuators/servos in the suit to move so as to match the desired position of the wearer, with the velocity and force desired by the wearer.
• the UnMousePad can be used to create robot skin.
• the robot can be coated with UnMousePads of varying resolutions in varying places. For instance, fingertips can be coated with very high resolution UnMousePads, while arms can be coated with lower resolution UnMousePads, thereby mimicking the variable resolution characteristics of human skin at different parts of the human body.
• UnMousePads of varying resolutions in varying places. For instance, fingertips can be coated with very high resolution UnMousePads, while arms can be coated with lower resolution UnMousePads, thereby mimicking the variable resolution characteristics of human skin at different parts of the human body.
• an UnMousePad can be used over golf clubs and tennis racquets. More generally, it may be placed over the surfaces of sporting equipment where players, balls, or other objects make contact with the sporting equipment. For instance, UnMousePad sensors may be placed on the face of a golf club and around the handle. Sensors in this configuration can then be used to improve the player's performance by giving them feedback. This feedback may include such information as which part of the club face is striking the ball, with what velocity the club face is striking the ball, whether the player is slicing the ball and the direction and amount of the slice.
• the sensors around the club handle can tell the player where and how well they are holding the club, whether the club is sliding or loosening during any part of the stroke, and the amount of force that is transmitted to the player's hands during impact. Similar information can be recorded for other sporting equipment coated with UnMousePad sensors. This information, besides just being used for improving the athlete's performance, can also be used to record and to broadcast statistics and interesting information to viewers of a sporting event, or fans of a particular athlete.
• UnMousePad can act as a regular QWERTY or
• the home-row position of a software keyboard can be indicated to computer software based on the position of the user's palm (assuming that the user is resting their palm on the sensor).
• a virtual keyboard can be made to move together with the location of the user's hand, thereby allowing the user to assume a comfortable typing position whereby the hands are placed a comfortable distance apart.
• the keyboard can also be split into two halves that each can individually be positioned with respect to the two hands.
• the virtual keyboard's two halves can be displayed on-screen or directly onto the surface of the UnMousePad, in the case where there is a display device incorporated into the UnMousePad.
• the user can be given visual feedback on where the user is typing by displaying the location of the user's palms and the position of finger touches on a display screen that shows an image of the two virtual keyboard halves. Because the keyboard is virtual, its layout can be modified to suit individual user preferences/needs.
• a user can initiate typing mode by a gesture, such as placing palms and fingertips down on the UnMousePad with a drumming motion (letting each fingertip fall on the UnMousePad in succession).
• Keyboard typing mode can be deactivated with another gesture, such as a flicking gesture of the entire left or right hand, to indicate that the user wants to flick the keyboard away.
• a tactile overlay made of silicone rubber, etched glass, molded plastic, or some other shaped material, can be placed over the UnMousePad to provide a physical keyboard layout.

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• 2009
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