Patent Publication Number: US-2017371438-A1

Title: Method and system for transcribing marker locations, including erasures

Description:
RELATED APPLICATIONS 
     The present invention claims benefit of priority to U.S. Provisional Patent Application No. 62/095,051 filed 21 Dec. 2014, the contents of which are incorporated herein by reference in each jurisdiction that permits incorporation of material by reference. In other jurisdictions that do not permit incorporation of material by reference, Applicant reserves the right to insert matter into the present specification from any material that is stated herein to be incorporates by reference, without such inserted matter being new matter. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to systems for determining and transcribing digital marker locations using acoustical energy. 
     BACKGROUND 
     Location determining and transcription systems (“location capture systems”) are known for locating and recording marker or electronic pen strokes on an ordinary surface, such as that of an ordinary whiteboard, on paper, on a projection screen, or on a flat-display surface. Luidia, Inc., the assignees of the present invention, has long been making a system called eBeam® that provides for recording strokes made on a surface such as an ordinary whiteboard using ordinary dry-erase markers inside an electronic marker sleeve. Such a marker sleeve converts an ordinary marker to an electronic marker. The marker sleeve and hence the electronic marker includes a transmitter for transmitting acoustic pulses and a transmitter for transmitting electromagnetic pulse signals, e.g., infrared (IR) pulses, and such a device, when used with a capture unit placed adjacent to an area, e.g., a whiteboard, is usable for locating and transcribing locations of the marker. Such an electronic marker is often referred to as a marker herein when the context is clear that such marker includes the transmitting element or elements. The capture unit typically includes two or more acoustic sensors for receiving the transmitted ultrasound and an infrared sensor to detect the IR pulses. The capture unit in some versions may include a processing engine with memory, and in some of these versions, processing and storage may be local. The capture unit includes an interface, e.g., a wireless connection or USB connection, to send information to a remote device. Examples of remote devices include, a so-called ““smart” phone that includes a processor, e.g., a phone operating under the iOS®, ANDROID®, or some other mobile device operating system, a tablet, a computer, personal digital assistant (PDA), a projector that includes a processor and memory, a TV or other flat-screen display device that includes a processor and memory, and so forth. Such a system, in combination with the computer, captures the marker strokes on or for remote device, including the color of the marker and any erasing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a simplified diagram of an example system that is connectable to a host device, and that includes aspects of the present invention. 
         FIG. 2  shows block diagram some elements of the system of  FIG. 1 , including an embodiment of the present invention. 
         FIG. 3  shows a simplified perspective view of the system that includes a marker (including sleeve), a receiver, and some erasure cap elements, including aspects of an embodiment of the present invention. 
         FIG. 4  shows a receiver, a marker sleeve (with marker), and a charging bracket with marker stroke determining capability, into which elements described herein may be included such that the combination operates as an embodiment of the invention. 
         FIG. 5  shows a vertical receiver arrangement with two whiteboards, one on the left and one on the right of the receiver, illustrating a feature of an embodiment of the invention. 
         FIG. 6  shows a perspective view of an example eraser that operates in an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     Overview 
     Described herein is an apparatus for capturing marker stroke locations, including erasures. The marker, e.g., a sleeve of the marker includes a transmitter of acoustic pulses and an erasure cap detector that detects when a removable erasure cap is attached to the marker, in which situation, the marker locations being tracked capture erasures. A receiver includes two or more sensors to sense the acoustic pulses, the receiver operable to determine and track marker locations. When there is no erasure cap attached, the marker locations being tracked capture strokes. Another embodiment is a method of capturing marker stroke locations, including erasures, using marker includes a transmitter of acoustic pulses and an erasure cap detector that detects when a removable erasure cap is attached to the marker. Also described herein is a method of capturing marker stroke locations, including erasures, using the marker that includes a transmitter of acoustic pulses and the erasure cap detector that detects when the removable erasure cap is attached to the marker. 
     Particular embodiments of the invention include an apparatus configured to capture strokes made by a marker, including capturing erasures when a removable erasure cap is attached to the marker. The apparatus includes a receiver configured to be placed on or close to an edge of a surface. The receiver includes at least two acoustic sensors located at pre-defined locations relative to each other and arranged to sense acoustic signals transmitted from the marker when the marker in an active area of the surface adjacent to the locations of the acoustic sensors. In some embodiments, the receiver includes a sensor of electromagnetic energy pulses transmitted from the marker. 
     The marker includes at least one transmitter to transmit acoustic signals detectable by the acoustic sensors. In some embodiments the marker further includes a transmitter that transmits electromagnetic energy, e.g., infrared (IR) pulses. 
     The receiver is arranged to determine and store locations and time information of the marker in the active area that includes a whiteboard surface, the active area adjacent to the acoustic sensors. The receiver further includes an interface to couple the receiver with a host device, the host device including a host processor and a memory. The receiver is operative, when coupled to the host device, to send determined locations and time information to the host device. 
     When the marker, e.g., a sleeve around the marker has a removable erasure cap thereon, the receiver alone, or in combination with the host device, is operative to accept an indication that the erasure cap is on the marker sleeve. The indication may be as a result of indication made by a user, or may be automatic by automatically detecting presence of the cap in the marker. Responsive to receiving the indication that the erasure cap in on the marker, e.g., on the sleeve, the marker-and-erasure-cap combination causes erasure of previously made strokes (annotations) erasure of previously made strokes at the determined locations of the marker-and-erasure-cap combination on the white board, e.g., those on the same “page.” 
     In some embodiments, the receiver alone, or in combination with the host device, is operative to accept or determine a plurality of indicators of page-flip, and to combine the plurality of indicators to automatically determine a page flip event. A page flip event may include complete erasure of the whiteboard. 
     In a first set of apparatus embodiments, the receiver is physically contained in a housing that includes two ultrasound sensors, sensing circuits therefor, an infrared detector, and in some embodiments, an accelerometer. In some apparatus embodiments, the receiver comprises a processing engine that includes a processor and a software memory, e.g., firmware memory, wherein the software or firmware in the memory includes instructions that when executed cause the determining and the storing of the locations and time information, the sending of the determined locations and time information to a host device with which the receiver is in communication. 
     Particular embodiments of the invention include a method of operating an apparatus that captures marker strokes, the method comprising:
         receiving acoustic signals in at least two acoustic sensors housed in a receiver housing that is placed on or close to an edge of a surface, the sensors located at pre-defined locations relative to each other to sense acoustic signals transmitted from a marker e.g., a marker in a marker sleeve in an active area that comprises the surface adjacent and that is adjacent to the acoustic sensors, and in some versions, an additional sensor that is operative to detect electromagnetic signals, e.g., IR signals transmitted by the marker, the acoustic signals being transmitted from the marker by an acoustic transmitter included in the marker, and the electromagnetic signals being transmitted being transmitted by a transmitter of electromagnetic signals in the apparatus, e.g. in the marker; and   receiving signals from the marker indicative of whether or not an erasure cap is on the marker;   determining locations of the marker in the active area on the surface adjacent to the acoustic sensors and determining time information for the determined locations;   storing the determined locations and time information;   responsive to an indication that the erasure cap is present, sending the determined coordinates and timing information as erasure information of past events to a host device; and, in some versions,   accepting or determining a plurality of indicators of page-flip.       

     Particular embodiments include a non-transitory machine-readable medium coded with instructions, that when executed by a processing system, carry out any one of the above summarized methods. 
     Particular embodiments may provide all, some, or none of these aspects, features, or advantages. Particular embodiments may provide one or more other aspects, features, or advantages, one or more of which may be readily apparent to a person skilled in the art from the figures, descriptions, and claims herein. 
     System Comprising a Marker (with Sleeve) and a Receiver 
     Described herein is a receiver that includes electronics for determining and capturing the locations of an electronic marker or pointer, to provide for a user the ability to create, save, store and retrieve hand written notes on both paper and digital media. 
       FIG. 1  shows a simplified diagram of an example system  100  that may be coupled to a host device  150 —in this drawing, a smart phone  150 , and that includes aspects of the present invention. The system  100  is for sketching or writing on a surface  105  which is assumed to be a whiteboard on which one can write with an electronic marker, or some surface on which one can electronically write with an electronic marker. 
       FIG. 2  shows a more detailed block diagram of the system shown on  FIG. 1 . The system  100  includes a receiver (receiver module  111 ) that is located at the periphery of the surface  105 , e.g., on the edge of the surface. The receiver includes at least two acoustic sensors, e.g., ultrasound sensors with a known spatial relationship between each other.  FIG. 1  shows a receiver  111  with two ultrasound sensors  113 , 115 , and one infrared sensor  117 . There is a known spatial relationship between the ultrasound sensors  113 , 115 . Note that alternatively, a side edge may be selected, and the receiver placed so that the two ultrasound sensors are collinear on a vertical line. The receiver forms an active area  107  on a substantially planar surface adjacent to the location of the acoustic sensors. Active area  107  in one embodiment includes the surface  105 . In one version, the system is calibrated or recalibrated such that the active area  107  is larger than the writing surface, e.g., as shown larger in three of the four edges of the surface  105 . The system includes a processing engine  131  coupled to the sensors  113 , 115 , 117  of the receiver  111 . The processing engine  131  is operative to determine the position of a marker and sleeve combination, hereinafter simply referred to as a marker  103  in the active area  107 , in particular of a tip area  127  of the marker from which ultrasound pulse are emitted (and in some versions, reflected off the page) towards the receiver  111  when the marker is on the page. 
     One version of the receiver  111  includes a rechargeable battery  145  and a mechanism for connecting to a charger. Referring momentarily to  FIG. 4 , a charging station  140  is provided that includes a receptacle  141  into which the receiver  111  may be inserted, and when so inserted, has its battery  145  charged (and also into which the marker  103  may be inserted for storage and for charging of the marker&#39;s battery). 
     In one embodiment of the marker  103 , the tip in area  127  is a marking tip of the marker in the sleeve. This embodiment includes a sleeve body, the marker tip  127 , and a transmitter of ultrasound pulses  123  in the sleeve body close to the tip  127  arranged to transmit ultrasound pulses detectable by the receiver  111  when the marker is in the active area  107  and pressed into the whiteboard surface  105 . In one version, the marker, by way of being inside a marker sleeve, includes electronics to drive the ultrasound transmitter  123  to transmit a set of ultrasonic pulses detectable by the ultrasound sensors  113 ,  115  when the tip  127  is pressed against the whiteboard surface  105 , using, for example, a switch in the marker sleeve, called a pen down switch. The marker  103  shown in  FIG. 1  also includes an infrared (IR) transmitter  125  driven by the electronics module  121  and that transmits IR pulses detectable by the IR sensor  117  of the receiver  111  when the tip  127  is pressed against the whiteboard surface  105 . The IR pulses are synchronized with the ultrasound pulses. 
     One embodiment of the marker sleeve  103  further includes one or more buttons each having a switch. When a button is depressed and the marker sleeve is in the active state, so that when pressed in the active area, the transmitters  123 , 125  transmit energy in a particular form related to which button was depressed. In some embodiments of the invention, the function of the buttons may be programmed, e.g., to be the left or right buttons of a mouse device. Thus, an aspect of some embodiments is that a button of the marker sleeve can provide various optional functions, in the same manner as the different buttons of a mouse or other marker, e.g., for a computer. 
     In some embodiments, the marker  103 , e.g., its sleeve also includes a rechargeable battery  147 . In this description, each of the marker  103  and receiver  111  has a receiver battery  145  and marker battery  147 , respectively. The charging station  140  (also shown in  FIG. 4 ) is included for charging the batteries. The charging station  140  includes a receptacle  143  designed to hold the marker  103  and recharge the battery  147 , and the receiver charger receptacle  141  designed to receive the receiver  111  and charge its battery  145 . The couplings between the marker sleeve and its receptacle and between the receiver and receiver charger receptacle  141  are via respective sets of contacts on the respective receptacles in station  140 . Alternative embodiments use contactless coupling, e.g., inductive coupling. 
     The signal transmitted by the transmitters  123 , 125  of the marker sleeve  103  may be modulated or digitally coded using the electronics module  121  to identify a particular marker function, e.g., that the marker represents a marking device of one color or another, or that the marker represents an eraser, or whether the marker represents a marking device drawing a thin line or a thick line, or whether the button(s), in the marker are functionally the same as the left or right buttons of a mouse, and so forth. One version of the marker sleeve includes a pressure detector, so that the more pressure is applied to the marker tip when the marker is in the sleeve, the thicker the strokes determined and recorded by the receiver  111 . 
     The Erasure Cap 
     Referring still to  FIG. 1 , one embodiment of the system includes an erasure cap  151  that includes an eraser tip  155  that can erase dry marker marks, and that has a pre-determined width. The erasure cap  151  allows for making small corrections to the digitized content from the whiteboard. Since the digital signal is tracked as a single point on the surface, the point can be represented as an area having a physical size, e.g., an area such as a circular area having a diameter. In one embodiment the size, e.g., diameter is pre-defined. In one embodiment, the size, e.g., diameter is settable. In one embodiment, the size, e.g., diameter is 30 mm. Those in the art would understand that the 30 mm is approximate, e.g., between 27 and 33 mm. This is an optimal size for erasing letters between other letters when writing normally on the whiteboard. Of course alternate embodiments might have a different size, and another alternative may have several erasure caps similar to cap  151 , but of different sizes. 
     In one embodiment, the erasure cap  151  is designed to form an airtight seal when on the marker  103  to prevent the marker tip from drying out. One embodiment of the marker  103  comprises an erasure cap detector  129 , located for example in the sleeve of the marker, and operative to detect when the erasure cap is on the marker covering the tip. One embodiment of erasure cap  151  includes indicators detectable by the erasure cap detector  129 . In one versions, the indicators comprise one or more magnets  153  to generate a magnetic field that can be sensed by the erasure cap detector  129 , and the erasure cap detector  129  comprises one or more proximity sensors  128 , which in one embodiment, includes one or more Hall-effect sensors and an electronic circuit coupled thereto to detect when the one or more magnets are in close proximity. Such combination of Hall-effect sensors and electronics are commonly available. When the erasure cap  151  is placed on the front of the marker, the one or more Hall-effect sensors are activated by the magnetic field and indicate the electronic circuit to switch to from marking mode to erasing mode. 
     The erasure cap  151  is mechanically arranged to push the marker inside against the pen down switch as if the user were drawing on the whiteboard. When the erasure cap  151  is in place, the marker transmits a signal to the sensor that is different than that of a marking stroke, and the signal is interpreted in the client software as an eraser stroke. 
     Additionally, the marker  103  is programmed to cause the system not to make unwanted eraser marks on the board as the user places the cap on the marker. The marker  103  includes a memory that indicates the mode when the marker last transmitted, e.g., that it is currently in marking mode wherein the marker made a stroke without the erasure cap  151  on. When the erasure cap  151  is applied, the magnet is sensed by the erasure cap detector, and the mode is switched to erase mode, so that the data pulse that is normally emitted when the cap is applied is now muted. When the erasure cap  151  is next used on the board surface, it works normally (unmuted) to transmit the erasure cap  151  signal to the sensor. 
     While one embodiment uses a magnet and switch combination, there are several alternative methods of signalling that the erasure cap  151  is on. Three examples of such alternatives include:
         a light sensor on the sleeve body that detects the presence of the cap when it covers the light sensor in a different way compared to the normal cap;   an IR sensor on the marker sleeve body that detects the IR signal via a light path from the IR transmitter to the IR sensor. The light path is broken by an arm on the erasure cap  151 ; and   a simple sprint loaded pin switch in the sleeve body positioned so that the switch is depressed when the erasure cap  151  is placed on the marker.       

       FIG. 3  shows a simplified perspective view of the system that includes the receiver  111 , the maker  103  comprising a sleeve with a marker tip therein, the erasure cap  151 , and four rings  303 ,  305 ,  307 , and  309 , each to indicate a different color. In one embodiment, the sleeve body  103  can accommodate any one of several different rings to indicate the color of the marker covered by the sleeve. Each ring is encoded, e.g., by a one or more metal jumpers on a corresponding plurality of pins. In rings  303 ,  305 , and  307  (the ring  309  is on the marker&#39;s sleeve body), there are four possible jumper locations, and in each, a different set of three is present. Four possible jumper positions on the ring allow for up to 16 different types of markers, e.g., different colors, different widths, and so forth. The invention is not limited to any number of jumper positions. In general, N pins would allow for 2 N  different marker types. Alternate methods of indicating color or other marker characteristics also are possible within the scope of the invention. 
     According to another embodiment of the invention, one of the codes is used for a ring that is the side mount for an erasure cap  151 , such that when the erasure cap  151  is mounted rather than, or in addition to one of the alternate rings, the electronics in the marker, e.g., the marker sleeve recognizes that an erasure cap  151  is mounted, and so sends out a code with the IR transmission that is recognized as indicative of a n erase. 
     Yet another alternate embodiment allows for erasers of different size and/or different shape. In such an embodiment, there are a plurality of alternate erasure caps with using different types of elements or methods of indicating, e.g., a plurality of switches and grooves, or a plurality of arms able to cover one or more holes on the marker sleeve body for one or more light sensors, the number of light sensors not necessarily the same as the number of covering arms. 
       FIG. 6  shows a larger perspective view of an erasure cap  151  than shown in  FIGS. 1 and 3 , according to an embodiment of the invention. 
     One version of the marker sleeve  103  has a low power state that draws a relatively small, e.g., minute amount of power, as is common ins so-called “sleep-mode”. Invoking any of the buttons moves the state to an active state and further provides an indication of which button was invoked. 
     When operational, the location determining system  100  is able to determine the position of the marker sleeve  103  in the active area  107 , and thus capture the marker strokes written on the surface  105 . 
       FIG. 2  shows a more detailed, but still simplified block diagram of the system  100  that includes an embodiment of the invention. System  100  includes the marker sleeve  103 , the receiver  111  and the host device  150 . The system  100  includes an embodiment of the invention and further includes a communication link between the receiver  111  and the host device  150 . The ultrasound sensors  113 , 115  and IR sensor  145  are coupled to a processing engine  131  that includes a processor  203  that in one embodiment is a DSP device, although in alternative devices, this could be a field programmable gate array or a custom integrated circuit. The processor  203  includes or is coupled to a memory  205  for software, e.g., firmware, coupled to processing elements of the processor  203 , e.g., via a bus subsystem. Note that while the various processing elements, e.g., multiply-add units, general purpose logic units, and so forth, are shown as a single processor  203  in  FIG. 2 , those in the art will understand that this does not imply that there is only a single processing element in processing engine  131 . 
     The receiver  111  includes one or more input/output (I/O) interfaces, e.g., one or more of a USB interface, a Bluetooth wireless interface, and a Wi-Fi wireless interface. Other I/O interfaces of course may be included in different embodiments. The I/O interface(s) are shown as a single block  213  in  FIG. 2 . 
     In one embodiment, aspects of the present invention include methods that are implemented by sets of instructions in the memory  205 , e.g., firmware instructions. Furthermore, while embodiments of the invention use a DSP device, it would be clear to those in the art that any processor with sufficient processing power, e.g., a microprocessor or microcontroller, may be substituted for the DSP device, or alternately, that one or more programmable logic devices, or even hardwired logic may be used, e.g., as an application specific integrated circuits (ASIC) or custom chip. 
     When an IR signal is detected via the IR sensor  117 , a switch connects the output of the ultrasound sensors  113 , 115  such that by the time the ultrasound signals arrive from the marker sleeve  103 , the received ultrasound pulses are input via respective serial ports to the processing engine  131 . 
     A timing generator  215  sends time information to the engine  131 . The received ultrasonic pulses together with time information and any information on the state of any buttons on the marker sleeve  103  are sent to the processing engine  131  to determine the times of arrival of the ultrasound pulses relative to the times of arrival of the IR signal. The relative times of arrival together with information on the state of any buttons on the marker sleeve  103  are further processed by processing engine  131 . 
     The firmware memory  205  coupled to the processor  203 , which, if a DSP device, may include built-in DSP firmware memory (as all or part of firmware memory  105 ), and more memory, e.g., additional static RAM, such RAM being all or part of a memory  211 . 
     In one embodiment the firmware memory stores instructions  206  that when carried out by processor  203  to determine the locations of the marker sleeve  103 , timing information, and one or more other indications, including any new page indications or indicators. The pulses transmitted by the IR transmitter in the marker sleeve  103  are assumed to travel much faster than the ultrasound pulses, e.g., “instantaneously.” The IR pulses received by the IR receiver  117  and the ultrasound pulses received by the ultrasound sensors  113 , 115  are recorded in the location determining system  111 . In one embodiment, the operation of the location determining of receiver  111  includes determining the times of arrival of the pulses. The location determining system  111  calculates positions of the marker&#39;s tip based on the arrival times at the two ultrasonic detector positions. The time reference is generated by the IR sensor. In one embodiment, the calculations rely on accurate recording of waveforms of the received pulses. 
     The locations, timing information, and other indicators in one embodiment are stored as  251  in the memory  211 . One version of the receiver and marker sleeve combination is usable stand-alone without being connected to the host device  150 . The receiver and marker sleeve combination is also usable while connected to a host device  150 , in which case the locations (as coordinates), timing information, and indicators are transmitted to the host device  150  in real time. 
     In the stand-alone use case, at some stage, communication is established with the host device  150 , and the locations (as coordinates), timing information, and indicators  251  from memory are transmitted to the host device  150 . 
     The host device  150  is also shown in  FIG. 1  and in more detail, in  FIG. 2 , and includes standard components such as a processor  221 , memory  223 , a USB interface  227 , a display  225 , one or more wireless interfaces  231 , a touch screen  233 , a (virtual or physical) keyboard, a battery, and so forth. Aspects of the present invention are implemented, in one embodiment, as instructions  229  in the host device  150 , shown in  FIG. 2  as in memory  223 . The memory  223  also includes such instructions for such functionality as character recognition, etc., and of course, the usual functions of the device  150 , e.g., as a phone etc. 
     The receiver  111  also includes a new page button  119  to provide the user with the ability to indicate when the whiteboard surface  105  will represent a new page. 
     In one embodiment, the receiver sends the host device location information in the form of A, B un-normalized coordinates, and signals about the type of marker, e.g., color, line thickness, and so forth. Calibration may be carried out using the marker and receiver. 
     The processing system of location capture system  111  further accepts input indicative of the erasure cap being present on the sleeve. One embodiment also includes detection of coding of colors. In one embodiment, the information sent to the host device is in the form of A,B un-normalized coordinates, and signals about the type of marker, e.g., color, whether eraser or marker, and so forth. In one embodiment, the system is pre-calibrated to cover an area larger than typical whiteboards. In another, a selector determines one of a set of standard sizes and whether the board is in landscape or in portrait orientation. The of A,B un-normalized coordinates are automatically normalized to x,w coordinates in the active area  107 . 
     Calibration may be separately carried out, for example, in the host device to convert the un-normalized A,B coordinates to x,y coordinates in the active area, e.g. to strokes in the active area. 
     Timing information also is determined. In addition, events such as those that signal marker up and marker down are sent, and erasure cap on. Such events are provided in as (marker-up,timestamp) where the marker-up is the marker-up event and the timestamp is an indication of the time that the event occurred. A,B coordinates are provided in the form of ((A,B), markertype, any error), where the markertype indicates the color, whether an eraser, width, etc. Furthermore, an eraser is regarded as a special erasing marker that erases an area around its coordinate, such that erasure regions also are transmitted. Also events such as one or more buttons on the sleeve being pressed are sent. Thus, the host device, after calibration, accepts a marker down event and a marker up event with a stream of coordinates in between that represents a contiguous line. 
     In some versions, the system  100  uses a firmware program  206  installed in the receiver  111  to determine and to store the marker strokes that the device captures and to implement the actions of the programmable buttons. 
       FIG. 4  shows a receiver, a marker sleeve, and a charging bracket with marker-stroke determining capability, into which elements described herein may be included such that the combination operates as an embodiment of the invention. 
     Accelerometer 
     The receiver may include one or more physical sensors that provide indications of a page flip. The sensors are used to detect relative motion between the receiver  111  and the surface  105 , or motion in the combination of the receiver  111  and the surface  105 . 
     Some embodiments include an accelerometer  231 , or other similar sensor of change of motion. Accelerometers are inexpensive and reliable, because of their use in laptops to detect the laptop being dropped (to part a hard disk therein), and more so because of their use in smart phone and tablet devices, of which more than a billion have been made. 
     The receiver  111  in one embodiment is configured, via firmware, to monitor the accelerometer  231  output. If the accelerometer output was nearly still for some amount of time, and has high acceleration (above a threshold that depends on the particular accelerometer), there is high likelihood that the user has picked up the receiver  111  in order to move it. In one improved, estimation is made to ascertain whether or not the receiver  111  the angle of the receiver relative to horizontal or vertical positioning. 
     Dual-Side Capture 
     One aspect of the inventive receiver, in the case of horizontal receiver placement, can detect ultrasound from an active region above the receiver and also can detect ultrasonic pulses from a second active region below the receiver. This arrangement allows a single receiver to detect a larger area. 
       FIG. 5  shows a vertical receiver arrangement with two whiteboards, one on the left and one on the right of the receiver. The receiver has one pair of acoustic sensors, e.g., microphones (or MEMS receivers) and two of IR receivers. A circuit measures the IR intensity of each IR receiver and reports to the processor which side the signal is coming from. This is tracked and notes are recorded into two separate pages in the user software. The user may jump back and forth from the left side to the right side, randomly drawing notes on both sides, using one pen at a time. 
     This allows the user to record notes on an effective area of 16 feet in width and 5 feet in height. 
     Auto Calibration 
     In one embodiment, the smart marker system does not require the user to perform a calibration process. This improves usability, allowing the user to focus on the content they are creating with very little start up time. 
     The receiver contains an accelerometer which measures the angle of the receiver when it is placed on the whiteboard surface. Using this angle measurement combined with the IR sensor circuit to know where the signal is coming from, a virtual rectangle is projected on the board surface which defines the virtual boundary of the capture area. The receiver will emit an audible and visual alert if the user attempts to write outside of this virtual boundary. 
     With auto calibration, the content created will always be level (as it was drawn) and right-side up. 
     Recording to Memory 
     One aspect of a marker system embodiment is recording flexibility by using internal memory in the receiver. Even when the user is has not connected the sensor to a computing device such as a smartphone or laptop PC, everything they writes/draws on the board is stored in memory and can be imported later to their device. 
     Through a combination of hardware and software, many usability problems are solved by this. For example, in the case a smart-phone is used with an application program (an app) for capture, if the user decided to navigate away from the app while using the whiteboard, the strokes will instead be recorded to memory and merged back to the app when the connection is restored. Without this memory and memory management function, the content would be lost. In one embodiment, a user may record up to 10,000 average density pages of notes. 
     New Page Button 
     The receiver  111 , and/or in some embodiments, the transmitting marker sleeve  103  contains the new-page button. Pressing it once, momentarily, at any point in time creates a new page in memory, and the previous page is saved. The new page is blank, allowing you to erase what is on the board. 
     In one version, the same button changes to a duplicate page button when pressed and held for 2 seconds. The duplicate page feature functions like a snapshot. It makes a copy of whatever you see on the board. This has use advantages over new-page depending on the usage scenario. It can work much like a “Build”” in presentation software, such as “Microsoft PowerPoint”®, or allows you to easily make variations of a drawing—maintaining aspects of the drawing that are left on the board from page to page. 
     Charging/Working Cradle 
     Referring to  FIG. 4 , in one embodiment, the charging station  140  serves multiple purposes. 
     Charging station  140  functions as the primary charger for the sensor and marker sleeve. It is powered by a USB cable that requires 5 v at 500 mah or higher. The sensor and pen can be fully charged in 3 hours. 
     Charging station  140  functions as the carry case for the sensor and sleeve. 
     Charging station  140  also functions as an on-board charging holder. This allows the user to place the charger on the board surface and continue to use the sensor for an unlimited amount of time. 
     Charging station  140  also provides a convenient place to store the marker pen when you are done writing. If the user would like to take the sensor and receiver on a business trip, they simply grab them and go. The components remain charged and ready until you choose to use them in a portable way. 
     While the description above is for a device/system that includes an interactive marker-stroke capture system that uses active marker (with its sleeve), the inventive method and system can easily be applied to interactive marker capture systems as well as interactive tablets with styluses, touch based tablets and other non-keyboard character based methods of input. Additional data such as voice recording can be captured and synchronized to the marker data stream. 
     One embodiment includes handwriting recognition. There are many methods of recognizing handwriting known in the art, and such details are left out in the interest of brevity. 
     General 
     Unless specifically stated otherwise, as apparent from the following discussions, it is appreciated that throughout the specification discussions utilizing terms such as “processing,” “computing,” “calculating,” “determining” or the like, refer to the action and/or processes of a host device or computing system, or similar electronic computing device, that manipulate and/or transform data represented as physical, such as electronic, quantities into other data similarly represented as physical quantities. 
     In a similar manner, the term “processor” may refer to any device or portion of a device that processes electronic data, e.g., from registers and/or memory to transform that electronic data into other electronic data that, e.g., may be stored in registers and/or memory. 
     The methodologies described herein are, in one embodiment, performable by one or more processors that accept machine-readable instructions, e.g., as firmware or as software, that when executed by one or more of the processors carry out at least one of the methods described herein. In such embodiments, any processor capable of executing a set of instructions (sequential or otherwise) that specify actions to be taken may be included. Thus, one example is a programmable DSP device. Another is the CPU of a microprocessor or other computer-device, or the processing “core” part of a larger ASIC. A processing system may include a memory subsystem including main RAM and/or a static RAM, and/or ROM. A bus subsystem may be included for communicating between the components. The processing system further may be a distributed processing system with processors coupled wirelessly or otherwise, e.g., by a network. If the processing system requires a display, such a display may be included. The processing system in some configurations may include a sound input device, a sound output device, and a network interface device. The memory subsystem thus includes a machine-readable non-transitory medium that is coded with, i.e., has stored therein a set of instructions to cause performing, when executed by one or more processors, one of more of the methods described herein. Note that when the method includes several elements, e.g., several steps, no ordering of such elements is implied, unless specifically stated. The instructions may reside in the hard disk, or may also reside, completely or at least partially, within the RAM and/or other elements within the processor during execution thereof by the system. Thus, the memory and the processor also constitute the non-transitory machine-readable medium with the instructions. 
     Furthermore, a non-transitory machine-readable medium may form a software product. For example, it may be that the instructions to carry out some of the methods, and thus form all or some elements of the inventive system or apparatus, may be stored as firmware. A software product may be available that contains the firmware, and that may be used to “flash” the firmware. 
     Note that while some diagram(s) only show(s) a single processor and a single memory that stores the machine-readable instructions, those in the art will understand that many of the components described above are included, but not explicitly shown or described in order not to obscure the inventive aspect. For example, while only a single machine is illustrated, the term “machine” shall also be taken to include any collection of machines that individually or jointly execute a set (or multiple sets) of instructions to perform any one or more of the methodologies discussed herein. 
     Thus, one embodiment of each of the methods described herein is in the form of a non-transitory machine-readable medium coded with, i.e., having stored therein a set of instructions for execution on one or more processors, e.g., one or more processors that are part of the receiver forming a marker stroke capture system. 
     Note that, as is understood in the art, a machine with application-specific firmware for carrying out one or more aspects of the invention becomes a special purpose machine that is modified by the firmware to carry out one or more aspects of the invention. This is different than a general purpose processing system using software, as the machine is especially configured to carry out the one or more aspects. Furthermore, as would be known to one skilled in the art, if the number the units to be produced justifies the cost, any set of instructions in combination with elements such as the processor may be readily converted into a special purpose ASIC or custom integrated circuit. Methodologies and software have existed for years that accept the set of instructions and particulars of, for example, the processing engine  131 , and automatically or mostly automatically great a design of special-purpose hardware, e.g., generate instructions to modify a gate array or similar programmable logic, or that generate an integrated circuit to carry out the functionality previously carried out by the set of instructions. Thus, as will be appreciated by those skilled in the art, embodiments of the present invention may be embodied as a method, an apparatus such as a special purpose apparatus, an apparatus such as a data DSP device plus firmware, or a non-transitory machine-readable medium. The machine-readable carrier medium carries host device readable code including a set of instructions that when executed on one or more processors cause the processor or processors to implement a method. Accordingly, aspects of the present invention may take the form of a method, an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form a computer program product on a non-transitory machine-readable storage medium encoded with machine-executable instructions. 
     Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to one of ordinary skill in the art from this disclosure, in one or more embodiments. 
     Similarly it should be appreciated that in the above description of example embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the Detailed Description are hereby expressly incorporated into this Detailed Description, with each claim standing on its own as a separate embodiment of this invention. 
     Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination. 
     Furthermore, some of the embodiments are described herein as a method or combination of elements of a method that can be implemented by a processor of a host device system or by other means of carrying out the function. Thus, a processor with the necessary instructions for carrying out such a method or element of a method forms a means for carrying out the method or element of a method. Furthermore, an element described herein of an apparatus embodiment is an example of a means for carrying out the function performed by the element for the purpose of carrying out the invention. 
     In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the invention may be practiced without these specific details. In other instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description. 
     As used herein, unless otherwise specified the use of the ordinal adjectives “first”, “second”, “third”, etc., to describe a common object, merely indicate that different instances of like objects are being referred to, and are not intended to imply that the objects so described must be in a given sequence, either temporally, spatially, in ranking, or in any other manner. 
     Any discussion of prior art in this specification should in no way be considered an admission that such prior art is widely known, is publicly known, or forms part of the general knowledge in the field. 
     In the claims below and the description herein, any one of the terms comprising, comprised of or which comprises is term that means including at least the elements/features that follow, but not excluding others. Thus, the term comprising, when used in the claims, should not be interpreted as being limitative to the means or elements or steps listed thereafter. For example, the scope of the expression a device comprising A and B should not be limited to devices consisting only of elements A and B. Any one of the terms including or which includes or that includes as used herein also means including at least the elements/features that follow the term, but not excluding others. Thus, including is synonymous with and means comprising. 
     Similarly, it is to be noticed that the term coupled, when used in the claims, should not be interpreted as being limitative to direct connections only. The terms “coupled” and “connected,” along with their derivatives, may be used. It should be understood that these terms are not intended as synonyms for each other. Thus, the scope of the expression a device A coupled to a device B should not be limited to devices or systems wherein an output of device A is directly connected to an input of device B. It means that there exists a path between an output of A and an input of B which may be a path including other devices or means. “Coupled” may mean that two or more elements are either in direct physical or electrical contact, or that two or more elements are not in direct contact with each other but yet still co-operate or interact with each other. 
     Thus, while there has been described what are believed to be the preferred embodiments of the invention, those skilled in the art will recognize that other and further modifications may be made thereto without departing from the spirit of the invention, and it is intended to claim all such changes and modifications as fall within the scope of the invention. For example, any formulas given above are merely representative of procedures that may be used. Functionality may be added or deleted from the block diagrams and operations may be interchanged among functional blocks. Steps may be added or deleted to methods described within the scope of the present invention. 
     Note that the claims attached to this description form part of the description, so are incorporated by reference into the description, each claim forming a different set of one or more embodiments. Therefore, in those jurisdiction that do not permit incorporation of material by reference, a copy of each of the claims may be pasted into the specification at some later date as a description of a set of embodiments, and does not form new matter.