Abstract:
An electronic pen comprises a writing means ( 7 ), a guiding element ( 9 ) for the writing means ( 7 ), a detector ( 15 ) for recording images, and an image processor ( 30 ) for calculating positions of the pen based on said images. The guiding element ( 9 ) and the detector ( 15 ) are arranged in a common mounting part ( 5 ). A mounting part ( 5 ) for an electronic pen is also disclosed. The mounting part ( 5 ) has means ( 11, 16 ) for arranging a guiding element ( 9 ) for a writing means ( 7 ) and a detector ( 15 ) for recording images in predetermined positions. Moreover, a method of making an electronic pen is disclosed. A guiding element ( 9 ) for a writing means ( 7 ) and a two-dimensional detector ( 15 ) are arranged in a common mounting part ( 5 ).

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention concerns an electronic pen comprising a writing means, a guiding element for the writing means, a detector for recording images as well as an image processor for calculating positions of the pen based on said images. The invention also concerns a mounting part for an electronic pen as well as a method of making an electronic pen.  
         BACKGROUND ART  
         [0002]    Pens of the type described by way of introduction are known from e.g. U.S. Pat. No. 5,774,602 which discloses an electronic pen for storing of handwriting. This pen comprises a writing means, a means for recording images of what is being written using the writing means and means for storing and transferring the images.  
           [0003]    U.S. Pat. No. 5,652,412 discloses an electronic pen with a pen point, means for detecting the position of the pen point on a writing base and a storing means for storing information about the position of the pen point.  
           [0004]    WO 00/25293 discloses an electronic pen which has a pen point, a two-dimensional camera for recording images of a surface adjacent to the pen point and circuits for determining the movement of the pen point by analyzing the images.  
           [0005]    Different kinds of sensors can be arranged in the pen for determining its position, for instance acceleration sensors, as disclosed in U.S. Pat. No. 5,434,371 and U.S. Pat. No. 6,130,666, optical sensors, as disclosed, in addition to the above, in U.S. Pat. No. 5,294,792, U.S. Pat. No. 5,852,434 and WO 00/73983, pressure sensors, as disclosed in U.S. Pat. No. 6,104,388, or mechanical sensors, as disclosed in U.S. Pat. No. 5,294,792 and U.S. Pat. No. 6,130,666.  
           [0006]    These prior-art pens suffer from the drawback that they are difficult to manufacture since the location of the components included varies too much between different items of pens. As a result, many pens must be rejected in manufacture with the ensuing increased costs.  
           [0007]    The prior-art pens are besides sensitive to shocks since there is a risk that the components inside the pen are displaced relative to each other if, for instance, the pen is dropped onto the floor.  
           [0008]    In some prior-art electronic pens, the position of the ink cartridge in the pen is controlled, for instance, by means of a threaded metal cone which is screwed to the casing at the front end of the pen, in the same way as in ordinary ball point pens. The camera can in such electronic pens be fixed to the printed circuit board in the pen. Variations in the thread of the metal cone and in the screwing to the casing result in the position of the ink cartridge in the pen varying between different items of pens. The position of the camera on the printed circuit board and the location of the printed circuit board in the pen may also vary, which causes further variations in the important distance between the pen point and the camera. Also with these pens, it will be difficult to achieve the desired accuracy in manufacture.  
         SUMMARY OF THE INVENTION  
         [0009]    The object of the present invention therefore is to provide an electronic pen which is improved in relation to prior art, as well as an improved method of making the same.  
           [0010]    A further object of the invention is to provide a mounting part which is intended for an electronic pen and which allows safer mounting of the interior of the pen than has been possible so far.  
           [0011]    One more object is to provide a mounting part for an electronic pen which is intended to constitute a front portion of the pen.  
           [0012]    According to the invention, these and other objects as will appear from the following description are now achieved by an electronic pen and a mounting part as well as by a method according to the independent claims, preferred embodiments and variants being defined in the dependent claims.  
           [0013]    The inventive electronic pen thus uses a common mounting part for mounting of the guiding element and the detector for recording of images. This results in greater safety as regards the location of the guiding element and the detector in relation to each other. Moreover, increased shock resistance of the pen is achieved owing to a decreased risk of the components in the pen being displaced relative to each other, for instance if the pen is dropped. The relative position of the guiding element and the detector is important for the function of the electronic pen since it determines the possibility of determining the position of the pen with repeatability.  
           [0014]    According to an embodiment of the invention, the mounting part is arranged in a forward portion of the pen and forms part of a front portion of the pen. This means that the mounting part can also be used to seal the forward portion of the pen to protect equipment inside the pen.  
           [0015]    The guiding element for the writing means is in one embodiment formed as a portion of the mounting part. As a result, safe guiding can be effected in a manner that is efficient in terms of production.  
           [0016]    Preferably the guiding element has a through hole which is designed to give the writing means a tight fit. This causes good guiding of the writing means.  
           [0017]    In an additional embodiment, the pen further comprises a light source which is arranged in the mounting part and which gives improved detection of the position of the pen. The mounting in the common mounting part results in great accuracy in the positioning.  
           [0018]    The light source is conveniently a light-emitting diode which is a simple and inexpensive illumination alternative.  
           [0019]    In one embodiment, the detector is a solid-state image sensor.  
           [0020]    The detector is preferably connected to a printed circuit board in the pen by means of a flexible electric coupling. This gives a safe electric contact that allows variations as regards the positioning of the printed circuit board in relation to the detector.  
           [0021]    In one more embodiment, the pen also comprises a sensor which is adapted to sense whether the writing means is pressed against a base and which is arranged in the mounting part. The sensor enables activation of the detector in the pen when the writing means is pressed against a base. The positioning in the mounting part allows easy mounting with great accuracy.  
           [0022]    Preferably the sensor is a pressure sensor. Such sensors are available on the market as standard components with small dimensions.  
           [0023]    An insert adapted to hold a portion of a writing means can further be arranged in a movable and form-fit manner in the mounting part and arranged to be contacted with the sensor as the writing means is being pressed against a base.  
           [0024]    The mounting part of the pen is preferably made of plastic, which is an inexpensive and easily formable material.  
           [0025]    In the inventive pen, the mounting part advantageously is made of injection-molded thermoplastic, which results in a rational manufacturing process.  
           [0026]    The mounting part according to the invention has means for arranging a guiding element for a writing means and a detector for recording images in predetermined positions. Such a mounting part gives great accuracy in the mounting of the guiding element and the detector.  
           [0027]    Preferably, the mounting part has means for arranging a light source. In this manner, a light source for improving the detection can be mounted in a safe way.  
           [0028]    Furthermore the mounting part can have means for arranging a sensor intended to sense whether the writing means is pressed against a base. This results in rational mounting of a sensor which can be used for activation of components in the pen.  
           [0029]    In one embodiment, the mounting part is arranged to be mounted in a forward portion of the pen to constitute part of a front portion of the pen. This means that the components which are arranged in the mounting part can easily be mounted in the forward portion of the pen while at the same time the components in the interior of the pen are protected against damage from the outside.  
           [0030]    The mounting part is preferably made of plastic, which is an inexpensive and formable material.  
           [0031]    Preferably, the mounting part consists of injection-molded thermoplastic and can thus be made in a cost-effective manner.  
           [0032]    The inventive method of making an electronic pen comprises the step of arranging a guiding element for a writing means and a two-dimensional detector in a common mounting part, thereby achieving great accuracy in manufacture.  
           [0033]    According to a preferred variant of the method according to the invention, the guiding element is formed as a portion of the mounting part. This is a rational way of forming the guiding element since it minimizes the number of components included.  
           [0034]    In a variant, a light source is arranged in the mounting part. In this way, a light source for improved detection can be mounted in an efficient way.  
           [0035]    According to a preferred variant of the method according to the invention, the mounting part is arranged in a forward portion of the pen, which allows the arranged components to be safely mounted in the forward portion of the pen. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0036]    The invention will now be described in more detail by way of an embodiment and with reference to the accompanying drawings, in which  
         [0037]    [0037]FIG. 1 is a side view of an electronic pen according to the invention,  
         [0038]    [0038]FIG. 2 is a perspective view of a mounting part according to the invention with components arranged therein,  
         [0039]    [0039]FIG. 3 is a sectional view of the mounting part and some of the components arranged therein,  
         [0040]    [0040]FIG. 4 is a sectional view and illustrates a portion of the mounting part according to an embodiment of the invention, and  
         [0041]    [0041]FIG. 5 is a perspective view and shows in detail a mounting part according to the invention. 
     
    
     DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0042]    The electronic pen  1  in FIG. 1 has a body  2  with a forward portion  2   a  and a cap  3  with a clip  4 . In the forward portion  2   a  of the pen  1 , a mounting part  5  is arranged partly inside a casing  6 , as illustrated in FIGS. 2 and 3. The mounting part  5  constitutes part of the interior of the pen  1  and has an inner end  12  facing inwards in the casing  6  and an outer end  13  facing out of the casing  6 , as shown in FIG. 2. An ink cartridge  7  with a pen point  8  is inserted into a tubular mounting aid  32  and, in the portion adjacent to the pen point  8 , inserted into a guiding element in the form of a pen point guide means  9  with a through hole  31 , which in a portion adjacent to the outer end  13  of the mounting part  5  is cylindrical and in a portion adjacent to the inner end  12  of the mounting part  5  is conical with the widest opening at the inner end  12 . Between the ink cartridge  7  and the inside of the mounting aid  32  there is a certain play  10 . A play (not shown) can correspondingly be found between the ink cartridge  7  and the inside of the pen point guide means  9 . The mounting aid  32  is inserted and fixed in a first mounting hole  11  in the mounting part  5 . The first mounting hole  11  has adjacent to the inner end  12  of the mounting part  5  a first recess  14 . A camera  15  is inserted and fixed in a second mounting hole  16  which adjacent to the inner end  12  of the mounting part  5  has a second recess  17  and adjacent to the outer end  13  of the mounting part  5  a third recess  18 . The camera  15  is connected by means of a flexible electric coupling  19  to a printed circuit board  28 . The camera  15  consists of imaging optical components and a solid-state image sensor, such as a CCD or a CMOS sensor. A light-emitting diode  20  is inserted and fixed in a third mounting hole  21 , which has three walls  21   a ,  21   b ,  21   c  inclined relative to each other. In the second mounting hole  16  there is also optics  33  for angling the optical axis C of the camera  15 . Optics (not shown) for guiding and/or forming a light cone emitted by the light-emitting diode can correspondingly be arranged in the third mounting hole  21 . The interior of the pen also contains other electronic components, such as a processor  30  (schematically illustrated).  
         [0043]    When the electronic pen  1  is not used, the cap  3  is normally arranged on the forward portion  2   a  of the pen  1  and then protects the pen point  8  and other components in the forward portion  2   a  of the pen  1 . The clip  4  can then be used to fix the pen  1 , for instance, in a shirt pocket. When the pen  1  is to be used, the cap  3  is removed and the pen  1  is set in a standby position, which may cause an image processor in the form of a processor  30  to be activated. When the pen point  8  of the pen  1  is pressed against a base  29 , the ink cartridge  7  is allowed to move somewhat in its longitudinal direction owing to the play  10  between the ink cartridge  7  and the inside of the pen point guide means  9  and the mounting aid  32  respectively. The ink cartridge  7  exerts a pressure upon a pressure sensor  24  in the pen  1 . Signals from the pressure sensor  24  are used to fully activate equipment, such as the camera  15  and the light-emitting diode  20 , in the electronic pen  1 .  
         [0044]    In an embodiment as illustrated in FIG. 4, a rear end portion  22  of the ink cartridge  7  is inserted into an insert  23 , which is movably arranged in a space  25  formed in the mounting part  5 . The pressure sensor  24  is attached to a wall in the space  25 . The space  25  is designed so that the insert  23  can move towards and away from the pressure sensor  24  but simultaneously so that the insert  23  cannot move out of the space  25 . The insert  23  is designed in such manner that it can hold various makes of similar ink cartridges, which makes it possible to use exchangeable ink cartridges for ordinary ball point pens. The insert  23  ensures good contact with the pressure sensor  24  when the pen point  8  of the ink cartridge  7  is pressed against the base  29  and at the same time prevents inconvenience such as ink leaking out and damaging the pressure sensor  24 . The design of the space  25  causes the insert  23  to stay in the right place when an ink cartridge  7  is removed from the pen  1  to be exchanged. The play  10  between the ink cartridge  7  and the inside of the mounting aid  32  ensures that the ink cartridge  7  can be removed from the pen  1  with minor resistance only. When mounting a new ink cartridge  7 , the mounting aid  32  ensures that the ink cartridge  7  is correctly positioned in the interior of the pen.  
         [0045]    Other types of sensors can also be used to activate the pen  1  when the pen point  8  is pressed against a base  29 . For instance, part of an open electric circuit can be arranged (not shown) in the position of the pressure sensor  24 . In this case, the insert  23  is provided with two metal pins or sheets which, as the pen point  8  is being pressed against a base  29 , come into contact with and close the electric circuit in the space  25 .  
         [0046]    When a user writes with the activated pen  1 , in the same way as with an ordinary pen, the area adjacent to the pen point  8  is illuminated by the light-emitting diode  20 . The camera  15  records images of the writing base  29  and a processor  30  calculates based on these images the position of the pen  1 . Here, preferably a specific pattern (not shown) in the writing base  29  is used, for instance of the type as described in PCT Publications WO 00/73983 and WO 01/26033. The camera  15  records images of areas adjacent to the pen point  8  of the pen  1 . With the aid of the pattern in the writing base  29 , the position of the pen  1  can at any moment be determined thereby, and in this way, that written by the user can be recorded. The camera  15  is preferably a solid-state image sensor, but also other types of two-dimensional detectors can be used, for instance those which can read chemical, acoustic, electromagnetic, capacitive or inductive marks.  
         [0047]    In order to determine the position of the pen  1 , the distance between the pen point  8  and the camera  15  is crucial. The necessary depth of field of the camera  15  is proportional to the distance in the plane of the base  29  between the pen point  8  and the optical axis C of the camera  15 . For the design of the camera  15  it is therefore important that this distance be well defined. Therefore it is important for the location of the camera in relation to the pen point guide means  9  of the ink cartridge  7  not to vary to any considerable extent between different items of pens. The mounting part  5  enables mounting of the ink cartridge  7  and the camera  15  with great accuracy.  
         [0048]    In contrast to prior-art pens, where the pen point guide means and the camera have been attached in different parts of the interior of the pen, the guiding element or the pen point guide means  9  and the camera  15  are according to the present invention arranged in a common mounting part  5 . This results in considerably improved accuracy in the manufacture of the pen  1  since several sources of variations are eliminated. The mounting part is formed with three mounting holes  11 ,  16 ,  21  for mounting of the mounting aid  32 , the camera  15  and the light-emitting diode  20 , respectively. The first mounting hole  11  simultaneously constitutes the pen point guide means  9 .  
         [0049]    In previous electronic pens, the light-emitting diode is mounted on the printed circuit board, with the ensuing variations in the position of the light-emitting diode in relation to the pen point guide means and the camera. According to the invention, the light-emitting diode  20  is advantageously mounted in the common mounting part  5 . This ensures that the area scanned by the camera  15  is given good illumination, which improves the possibilities of determining with great accuracy the position of the pen  1 .  
         [0050]    The mounting part  5  is injection-molded of a thermoplastic consisting of polycarbonate and ABS plastic. Also other materials, such as thermosetting plastics or metals, can be used in the mounting part  5 . The forming can also be effected by, for instance, casting or milling.  
         [0051]    In the manufacture of an electronic pen according to the invention, the pen point guide means  9  is designed as part of the first mounting hole  11  in the mounting part  5 . The pen point guide means  9  can also be formed as a separate part which is inserted into the first mounting hole  11 . The mounting aid is inserted into the first recess  14  of the mounting hole  11 . Optics  33  for angling the optical axis C of the camera  15  is arranged in the second mounting hole  16 . The camera  15  is inserted into the second recess  17  in the second mounting hole  16 .  
         [0052]    The light-emitting diode  20  is inserted into the third mounting hole  21 . The positioning is controlled by means of line contact between the light-emitting diode  20  and the two outer angled walls  21   a ,  21   c . As a result, the light-emitting diode is safely mounted and cannot be angled from its correct position in the third mounting hole  21 . The third mounting hole  21  has three inclined walls  21   a ,  21   b ,  21   c , and the safe positioning is achieved by means of line contact with at least, and preferably, two of these. The light-emitting diode is fixed by means of glue, for instance hot melt adhesive.  
         [0053]    A protective sheet of glass  26  can be mounted over the outer end  13  of the mounting part  5  on the one hand to provide an even surface and, on the other hand, to protect the components arranged in the mounting part  5 .  
         [0054]    The mounting part  5  and the mounted components  9 ,  15 ,  20  are fixed in the forward portion  2   a  of the pen  1 . Owing to this location, the mounting part constitutes a holder for the pen point guide means  9 , the camera  15  and the light-emitting diode  20  and at the same time part of a front portion  27  for sealing the forward portion  2   a  of the pen  1 . Otherwise the location of the mounting part  5  can be selected anywhere at any desired point in the pen  1 . A printed circuit board  28  is attached inside the casing  6  of the pen  1  and the camera  15  is connected to the printed circuit board  28  by means of a flexible electric coupling  19 . Additional components, such as the processor  30 , are mounted in the interior of the pen  1  before the casing  6  is sealed.