Abstract:
A rangefinder, for locating an object moving parallel to a planar surface, is rigidly attached to a carrier that is pivotably movable between an obverse position and a reverse position relative to a planar surface. Preferably, an orienting mechanism is provided for determining which position, obverse or reverse, the carrier and rangefinder are in. Preferably, a pivot, for pivoting the carrier and the rangefinder between the two positions, is rigidly attached either to the plane surface or to an attachment mechanism for reversibly attaching the carrier to the planar surface.

Description:
FIELD AND BACKGROUND OF THE INVENTION 
     The present invention relates to a rangefinder, e.g. for an electronic pen, and, more particularly, to a rangefinder and recorder, e.g. for an electronic pen, that records the user&#39;s handwriting continuously as the user moves from one page to the next. 
       FIG. 1  is a combined plan view and schematic block diagram of a combined rangefinder and recorder  10  for an electronic pen. On a lateral surface  14  of a housing  12  of rangefinder  10  are two spaced-apart ultrasound receivers  16  and an infrared receiver  18  that are operationally connected to rangefinding circuitry  20 . Ultrasound receivers  16 , infrared receiver  18  and rangefinding circuitry  20  operate in a manner that is taught e.g. in U.S. Pat. No. 6,151,014 to track the movement of an electronic pen (not shown) in the plane of  FIG. 1 . The pen periodically emits simultaneous omnidirectional infrared and ultrasound pulses. The infrared pulses are received by infrared receiver  18 . The ultrasound pulses are received by ultrasound receivers  16 . The time delays between the receptions of the individual infrared pulses and the associated individual ultrasound pulses, and the mutual time delays between the receptions of the individual ultrasound pulses at the two ultrasound receivers  16 , are measured by rangefinding circuitry  20  and are used by rangefinding circuitry  20  to locate the pen relative to rangefinder  10  by triangulation. These measurements of the instantaneous location of the pen are sent by rangefinding circuitry  20  to recording/playback circuitry  22  that records the measurements in a flash memory  24  as a record of the handwriting of the user of the pen. Subsequent to the recording, the user may download the record of his/her handwriting from memory  24  via recording/playback circuitry  22  and a USB port  26 . Power for circuitry  20  and  22  and for flash memory  24  is provided by a battery  28 . 
     U.S. Pat. No. 6,151,014 is incorporated by reference for all purposes as if fully set forth herein. 
     In the system composed of rangefinder  10  and the electronic pen, the infrared pulses provide timing signals for timing the arrivals of the ultrasound pulses. In an alternate embodiment (not shown) the electronic pen is connected to rangefinder  10  by a waveguide such as a fiber optic cable and the infrared pulses are transmitted by the pen to the rangefinder via the waveguide. The waveguide is optically coupled to infrared receiver  18  and to the infrared transmitter of the pen. In yet another embodiment (also not shown), the electronic pen emits pulses of electrical voltage as timing pulses. The pulses of electrical voltage are conveyed to rangefinder  10  via flexible electrical conductors; and, instead of infrared receiver  18 , rangefinder  10  is equipped with a detector of such pulses. 
     Rangefinder  10  may be secured e.g. by a clip to a pad of paper to allow the user to record his/her handwriting on the pad. One capability that is lacking in rangefinder  10  is the ability to automatically mark transitions from one sheet of paper to another. Such a capability, as well as others, is provided by the present invention. 
     SUMMARY OF THE INVENTION 
     According to the present invention there is provided a device including: (a) a rangefinder for locating an object moving parallel to a planar surface; and (b) a carrier, to which the rangefinder is rigidly attached, that is pivotably movable between an obverse position relative to the planar surface and a reverse position relative to the planar surface. 
     “Locating” an object means determining the position of the object relative to the rangefinder. Typically, the rangefinder locates the object by triangulation. 
     Preferably, the rangefinder is a passive rangefinder. A “passive” range finder is a rangefinder that does not transmit energy towards the object in order to locate the object. Typically, a “passive” rangefinder locates the object based on signals received from the object. 
     More preferably, the rangefinder includes a timing signal receiver (for example an infrared receiver or a detector of electrical voltage pulses) and two ultrasound receivers. Most preferably, the rangefinder includes circuitry for tracking an object, such as an electronic pen, that includes a timing signal transmitter and an ultrasound transmitter by locating the object based on timing signals received by the timing signal receiver from the timing signal transmitter and on ultrasound pulses received by the ultrasound receivers from the ultrasound transmitter. The timing signal receiver may receive the timing signals via free space or via a hardwired channel from the object. A “hardwired channel” is a (typically flexible) connector that connects the object to the rangefinder and that supports propagation of the timing signals. A typical example of such a hardwired channel is a fiber optic cable that supports the propagation of infrared timing signals. Another typical example of such a hardwired channel is a pair of flexible electrical conductors that support the propagation of electrical voltage timing signals. 
     Preferably, the device also includes an orienting mechanism for determining whether the rangefinder and the carrier are in the obverse position or in the reverse position. Most preferably, the device also comprises a pivot for pivoting the carrier and the rangefinder between the obverse position and the reverse position, and the orienting mechanism includes a mechanical switch that is operationally coupled to the pivot. Alternatively or additionally, the rangefinder has an obverse side and a reverse side, and the orienting mechanism includes one or more transmitters, an obverse receiver in the obverse side of the rangefinder, and a reverse receiver in the reverse side of the rangefinder. Alternatively or additionally, the orienting mechanism includes one or more proximity detectors for detecting proximity to a marker in the plane surface. In one embodiment, the proximity detector is a magnetometer, such as a Hall effect sensor, and the markers are asymmetrically placed permanent magnets. In another embodiment, the proximity detector is a metal detector, and the markers are asymmetrically placed pieces of metal. 
     Preferably, the device also includes the planar surface and a pivot. The pivot, that is rigidly attached to the planar surface, is for pivoting the carrier and the rangefinder between the obverse position and the reverse position. Most preferably, when the rangefinder is in either the obverse position or the reverse position, with a workpiece on the planar surface that has a distal surface that is substantially parallel to the planar surface and that has a workpiece thickness equal to at most a maximum thickness intervening between the rangefinder and the planar surface, the pivot allows the rangefinder to lie substantially flat on the distal surface. 
     Alternatively, the device also includes an attachment mechanism for reversibly attaching the carrier to the planar surface, and a pivot. The pivot, that is rigidly attached to the attachment mechanism, is for pivoting the carrier and the rangefinder between the obverse position and the reverse position while the carrier is attached to the planar surface. Most preferably, while the carrier is attached to the planar surface, when the rangefinder is in either the obverse position or the reverse position, with a workpiece on the planar surface that has a distal surface that is substantially parallel to the planar surface and that has a workpiece thickness equal to at most a maximum thickness intervening between the rangefinder and the planar surface, the pivot allows the rangefinder to lie substantially flat on the distal surface. 
     Preferably, the rangefinder includes an indicator light that is visible both when the rangefinder is in the obverse position and when the rangefinder is in the reverse position. More preferably, the rangefinder has an obverse side and a reverse side, and the indicator light includes a light source and a light propagation mechanism for directing light from the light source to emerge from both the obverse side of the rangefinder and the reverse side of the rangefinder. Most preferably, the light propagation mechanism includes a waveguide. 
     Preferably, the device also includes a folder that in turn includes a cover board and a base board. The cover board and the base board are reversibly movable, relative to each other, between an open configuration and a closed configuration. In the open configuration, a surface of the cover board and a surface of the base board define the planar surface that the object moves parallel to. In the closed configuration, the surface of the cover board faces the surface of the base board. 
     Most preferably, the device also includes an orienting mechanism for determining whether the folder is in the open configuration or in the closed configuration. When the folder is in the open configuration, the orienting mechanism also determines whether the rangefinder and the carrier are in the obverse position or in the reverse position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various embodiments are herein described, by way of example only, with reference to the accompanying drawings, wherein: 
         FIG. 1  is a combined plan view and schematic block diagram of a prior art combined rangefinder and recorder for an electronic pen; 
         FIG. 2  is a plan view of a folder having attached thereto a combined rangefinder and recorder for an electronic pen; 
         FIGS. 3A and 4A  are perspective views of two embodiments of the pivot of  FIG. 2 ; 
         FIGS. 3B and 4B  are partial side views of folders with the pivots of  FIGS. 3A and 4A ; 
         FIG. 5A  is a partial plan view of an alternate embodiment of the folder of  FIG. 2 ; 
         FIG. 5B  is a partial side view of the folder of  FIG. 5B ; 
         FIG. 6  illustrates mechanisms for sensing whether the rangefinder of  FIG. 2  is in the obverse position or in the reverse position; 
         FIG. 7  shows an indicator light of the rangefinder of  FIG. 2 ; 
         FIG. 8  shows a rangefinder and recorder, for an electronic pen, attached to a clip. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The principles and operation of a rangefinder according to the present invention may be better understood with reference to the drawings and the accompanying description. 
     Referring again to the drawings,  FIG. 2  is a plan view of an open folder  100  having a cover board  102  and a base board  104  hinged to a spine  106 . On the surface  110  of base board  104  is a stack  112  of writing paper. On the surface  108  of cover board  102  is a stack  114  of writing paper. Surfaces  108  and  110 , in combination with the surface  116  of spine  106 , define a joint planar surface of folder  100  when folder  100  is opened as shown. Rigidly attached to spine  106  is a pivot  118 . A bar  120  is attached to pivot  118  in a manner that renders bar  120  pivotably attached to spine  106  via pivot  118 . A combined rangefinder and recorder  122  of the present invention is rigidly attached to bar  120 . Bar  120  and rangefinder  122  are drawn with solid lines to the right of spine  106  to show rangefinder  122  in an obverse position for recording a user&#39;s handwriting as the user writes on stack  112 , and with dashed lines to the left of spine  106  to show rangefinder  122  in a reverse position for recording a user&#39;s handwriting as the user writes on stack  114 . 
     Pivot  118  allows a user to pivot rangefinder  122  between the obverse position on stack  112  and the reverse position on stack  114 . When rangefinder  122  is in the obverse position, an obverse side  124  of rangefinder  122  faces down to stack  112  and so is invisible, and a reverse side  126  of rangefinder  122  faces up and so is visible. When rangefinder  122  is in the reverse position, reverse side  126  of rangefinder  122  faces down to stack  114  and so is invisible, and obverse side  124  of rangefinder  122  faces up and so is visible. 
     Rangefinder  122  inherits from rangefinder  10  ultrasound receivers  16 , infrared receiver  18  and the associated internal components of rangefinder  10 , except that the recording and playback circuitry of rangefinder  122  is enhanced to support the functionality of rangefinder  122  that is described below. (How to modify recording and playback circuitry  22  to support the enhanced functionality of rangefinder  122  relative to rangefinder  10  will be clear to those skilled in the art and need not be described explicitly.) For example, rangefinder  122  includes an obverse infrared transceiver (transmitter+receiver)  128  in obverse side  124  and a reverse infrared transceiver (transmitter+receiver)  130  in reverse side  126 . Rangefinder  122  also includes several indicator lights  132  for indicating to the user the state of rangefinder  122 . For example, one of indicator lights  132  can be unlit when rangefinder  122  is powered down, green when rangefinder  122  is powered up, and red when the battery of rangefinder  122  is low in power. 
     Transceivers  128  and  130  are operationally connected to the recording and playback circuitry of rangefinder  122 . Each transceiver  128  and  130  periodically emits an infrared pulse and waits a suitably short amount of time to detect a corresponding infrared reflection. When rangefinder  122  is in the obverse position, transceiver  128  detects reflections from stack  112  and transceiver  130  does not detect reflections. When rangefinder  122  is in the reverse position, transceiver  130  detects reflections from stack  114  and transceiver  128  does not detect reflections. While rangefinder  122  is being pivoted from the obverse position to the reverse position or from the reverse position to the obverse position, neither transceiver  128  detects reflections. 
     Initially, there is writing paper in stack  112  and stack  114  is absent. Rangefinder  122  is in the obverse position. The user writes on the top sheet of stack  112  with an electronic pen. The recording and playback circuitry of rangefinder  122  receives an indication from transceiver  128  that transceiver  128  is detecting reflections and an indication from transceiver  130  that transceiver  130  is not detecting reflections. These indications tell the recording and playback circuitry of rangefinder  122  that rangefinder  122  is in the obverse position. Rangefinder  122  tracks the location of the electronic pen in the manner of rangefinder  10  and records the motion of the electronic pen as a record of the handwriting of the user on the obverse side of the top sheet. When the user finishes writing on the obverse side of the top sheet of stack  112 , the user pivots bar  120  and rangefinder  122  to a position in which bar  120  is perpendicular to surfaces  108 ,  110  and  116 . Both transceivers  128  and  130  send indications to the recording and playback circuitry of rangefinder  122  that transceivers  128  and  130  are not detecting reflections. These indications tell the recording and playback circuitry of rangefinder  122  that rangefinder  122  is transiting from the obverse position to the reverse position. Consequently, the recording and playback circuitry of rangefinder  122  records an obverse-to-reverse page break. The user turns the sheet over and places the sheet on surface  108 , thereby initiating stack  114 . The user completes the pivoting of rangefinder  122  to the reverse position. When rangefinder  122  reaches stack  114 , the recording and playback circuitry of rangefinder  122  receives an indication from transceiver  128  that transceiver  128  is not detecting reflections and an indication from transceiver  130  that transceiver  130  is detecting reflections. These indications tell the recording and playback circuitry of rangefinder  122  that rangefinder  122  is in the reverse position. Rangefinder  122  resumes tracking the location of the electronic pen in the manner of rangefinder  10  and records the motion of the electronic pen as a record of the handwriting of the user on the reverse side of the top sheet. When the user finishes writing on the reverse side of the former top sheet of stack  112 , the user pivots bar  120  and rangefinder  122  back to the position in which bar  120  is perpendicular to surfaces  108 ,  110  and  116 . Both transceivers  128  and  130  send indications to the recording and playback circuitry of rangefinder  122  that transceivers  128  and  130  are not detecting reflections. These indications tell the recording and playback circuitry of rangefinder  122  that rangefinder  122  is transiting from the reverse position to the obverse position. Consequently, the recording and playback circuitry of rangefinder  122  records a reverse-to-obverse page break. The user returns range finder  122  to the obverse position, on the second sheet of stack  112 , and continues writing on the obverse side of the second sheet of stack  112 , while rangefinder  122  resumes tracking the electronic pen and recording the user&#39;s handwriting. Use of folder  100  continues in this manner, with rangefinder  122  recording the user&#39;s handwriting on the obverse and reverse sides of the sheets of paper while inserting directional (obverse-to-reverse or reverse-to-obverse) page breaks as needed, until the user finishes writing. 
     When the user finishes writing, the user closes folder  100  so that surface  108  and stack  114  face surface  110  and stack  112 . The recording and playback circuitry of rangefinder  122  receives indications from both transceivers  128  and  130  that both transceivers  128  and  130  are receiving reflections. Consequently, recording and playback circuitry powers down rangefinder  122  into sleep mode to conserve battery power. When the user again opens folder  100 , the recording and playback circuitry of rangefinder  122  receives indications from one or both of transceivers  128  and  130  that the transceiver is not receiving reflections, and consequently powers up rangefinder  122 . 
     Pivot  118  is structured so that rangefinder  122  lies flat on stack  112  when rangefinder  122  is in the obverse position and so that rangefinder  122  lies flat on stack  114  when rangefinder  122  is in the reverse position, as long as stack  112  or  114  is not too thick.  FIG. 3A  shows, in perspective view, one embodiment of pivot  118 , a pivot  118 A, that is so structured. Pivot  118 A includes an arch  140  through which runs a pin  142  that is rigidly connected by two connecting rods  144  to bar  120 .  FIG. 3B  is a partial side view of a folder  100  whose pivot  118  is such a pivot  118 A, showing that rangefinder  122  lies flat on stack  112  when the thickness t of stack  112  is less than or approximately equal to a height h that is equal to the interior height of arch  140  minus the thickness of pin  142 .  FIG. 4A  shows, in perspective view, another such embodiment  118 B of pivot  118 . Pivot  118 B is a mechanical linkage between spine  106  and bar  120  that includes an upright  150 , an arm  152  and two revolute joints  154  and  156 .  FIG. 4B  is a partial side view of a folder  100  whose pivot  118  is such a pivot  118 B, showing that rangefinder  122  lies flat on stack  112  when the thickness t of stack  112  is less than or approximately equal to a height h′ that is the distance from surface  116  of spine  106  to bar  120  when arm  154  is perpendicular to spine  106  (as shown in phantom). 
       FIG. 5A  is a partial plan view, and  FIG. 5B  is a partial side view, of an alternate embodiment of folder  100 . In this alternate embodiment, bar  120 , instead of being rigidly attached to rangefinder  122 , is pivotably attached to a lateral surface of rangefinder  122  by a revolute joint  121 . Instead of being pivotably attached to a pivot on surface  116  of spine  106 , the other end of bar  120  is pivotably attached to a lateral surface of spine  106  by a revolute joint  119 . 
       FIG. 3B  also shows a first alternative mechanism, instead of transceivers  128  and  130 , for sensing whether rangefinder  122  is in the obverse position or the reverse position. One end of a cable  146  is secured to the side of arch  140  that faces cover board  102 . The other end of cable  146  is secured to a spring-loaded switch  148  on the distal side of rangefinder  122 . When rangefinder  122  is in the obverse position, as shown in  FIG. 3B , cable  146  pulls switch  148  to a position that indicates to the recording and playback circuitry of rangefinder  122  that rangefinder  122  is in the obverse position. When rangefinder  122  is in the reverse position, cable  146  relaxes and the spring in switch  148  pulls switch  148  to a position that indicates to the recording and playback circuitry of rangefinder  122  that rangefinder  122  is in the reverse position. Cable  146  and switch  148  are shown outside bar  120  and rangefinder  122  only for illustrational clarity. In practice, cable  146  is threaded through bar  120  and rangefinder  122 , and switch  148  is inside rangefinder  122 . 
     Second and third alternative mechanisms, instead of transceivers  128  and  130 , for sensing whether rangefinder  122  is in the obverse position or the reverse position, are illustrated in  FIG. 6 . Two markers  134  are disposed asymmetrically towards the top of folder  100 , one marker  134  in cover board  102  and the other marker  134  in base board  104 . Rangefinder  122  includes a sensor that is sensitive to the proximity of the material of which markers  134  is composed. In the second alternative mechanism, markers  134  are permanent magnets and the sensor is a magnetometer such as a Hall effect sensor. In the third alternative mechanism, markers  134  are metallic and the sensor is a metal detector. 
       FIG. 7  shows an indicator light  132 . Indicator light  132  is a parallelipipedal slab  160  of a transparent material with a relatively high index of refraction for visible light. A green light emitting diode (LED)  162  and a red LED  164  are optically coupled to slab  160  at its interior edge  168 . The housing of rangefinder  122  is slotted at its distal end to accommodate indicator lights  132  with their distal edges  170  flush with the distal side of rangefinder  122 , with their obverse edges  172  flush with obverse side  124  of rangefinder  122 , and with their reverse edges  174  flush with reverse side  126  of rangefinder  122 . Indicator lights  132  are separated within rangefinder  122  by air gaps, so that slabs  160  act as waveguides; most of the light injected into slabs  160  at edges  168  by LEDs  162  and  164  is reflected internally in slabs  160  and emerges at edges  170 ,  172  and  174 . Therefore, a user can see light emerging from indicator lights  132  whether rangefinder  122  is in its obverse position or rangefinder  122  is in its reverse position. 
       FIG. 8  shows, in schematic perspective view, an alternative embodiment  200  that combines pivot  118 , bar  120  and rangefinder  122  with a clip  202  made of a resiliently elastic material. Clip  202  includes two jaws  204  and  206  biased together by a spring  208 . In embodiment  200 , pivot  118  is rigidly attached to upper jaw  204 , just as pivot  118  is rigidly attached to spine  106  in the embodiment of  FIG. 2 . Note that in both  FIG. 2  and  FIG. 8 , pivot  118  is represented schematically, and could be configured mechanically as pivot  118 A of  FIGS. 3A and 3B , or as pivot  118 B of  FIGS. 4A and 4B , or in any other suitable manner. Embodiment  200  is intended for use with folders that include just cover board  102 , base board  104  and spine  106 . Clip  202  is used to clip embodiment  200  reversibly to spine  106  of one of these folders. While embodiment  200  is clipped to the folder, rangefinder  122  is pivotable between an obverse position and a reverse position relative to the folder and is used just as in the single-folder embodiment of  FIG. 2 . Embodiment  200  may be transferred by the user from one folder to another. 
     While the invention has been described with respect to a limited number of embodiments, it will be appreciated that many variations, modifications and other applications of the invention may be made. Therefore, the claimed invention as recited in the claims that follow is not limited to the embodiments described herein.