Abstract:
The invention relates to on-line handwriting recognition. At least one auxiliary line is displayed on a touch sensitive panel. Each of the auxiliary lines constitutes a portion of more than one character of a character set. A character of the character set is drawn on the touch sensitive panel by completing one of the at least one auxiliary line into the character. The drawn character is recognized on the basis of said completion. The invention allows handwriting recognition that is significantly more reliable and easier to use than prior art techniques.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to handwriting recognition. In particular, the invention relates to on-line handwriting recognition in a novel and improved way. 
     2. Description of the Related Art 
     The term “handwriting recognition” refers to a feature of a computer device or corresponding to receive intelligible written input. Handwriting recognition is often classified in two categories: off-line handwriting recognition and on-line handwriting recognition. 
     In off-line handwriting recognition, an image of written text is sensed e.g. from a piece of paper typically by means of optical scanning. Characters included in the written text are then recognized from the scanned image typically by means of suitable software. 
     In on-line handwriting, recognition text is written on e.g. a touch sensitive screen surface with e.g. a pen or a stylus, and the movements of the pen or stylus are sensed on-line. Characters drawn with the pen or stylus are interpreted or recognized by a software application. The touch sensitive screen may e.g. be integrated with an output display, or it may e.g. be adjacent to the output display. On-line handwriting recognition has proven particularly popular in various handheld devices, such as personal digital assistants (PDA), tablet personal computers (tablet PC), and lately also mobile telephones. The term “tablet PC” refers to a type of notebook computer that is equipped with a digitizer tablet and a stylus, and allows a user to handwrite text with the stylus. 
     Prior art on-line handwriting recognition techniques can be broadly categorized into three groups. The first group consists of techniques in which a user writes text more or less as usual, and a software application tries to learn the writing patterns of the user. An example of this technique is the handwriting recognition used by a personal digital assistant known as Apple Newton™. 
     The second group consists of techniques in which a set of pen strokes is predefined for each character. To draw a character, the user does not write as usual. Rather, the user must draw the predefined pen strokes. Examples of this technique include a recognition system known as Graffiti® and used earlier in personal digital assistants by Palm, and a recognition system known as JOT® by Communication Intelligence Corporation which is also used in various personal digital assistants including these days those by Palm. This second group of on-line handwriting recognition techniques is sometimes called character based handwriting recognition. 
     The third group consists of techniques in which a recognition system maintains a database of possible, typically thousands, shapes for each character. The system does not attempt to learn the writing patterns of the user, nor is the user required to draw predefined pen strokes. Rather, the user draws a character as he normally would, and the system searches the database for the closest match. An example of this technique is the handwriting recognition used in Microsoft Windows XP® operating system for tablet PCs. 
     However, all these prior art techniques have their problems. The first group of techniques requires the system to learn the writing patterns of the user. In practice this has proven extremely difficult and the existing applications tend to be unreliable. The second group of techniques requires the user to draw predefined patterns. Therefore the user is required to memorize these predefined patterns in order to be able write. The third group of techniques requires the system to maintain an extensive database, which is particularly problematic for compact handheld devices, which simply may not have enough resources for database maintenance and searches. Furthermore, the prior art techniques typically require the user to draw blindly. That is, the user cannot see the character as it is being drawn, even though some applications may provide a baseline or underline upon which to draw the actual character. Furthermore, the prior art techniques are particularly disadvantageous in situations where the user is being shaken or is otherwise moving. Such situations include for example a user riding a bus and trying to write on his personal digital assistant. Trying to draw predefined patterns blindly in such a situation is extremely difficult. 
     Therefore, the object of the present invention is to alleviate the problems described above and to introduce a solution that allows handwriting recognition that is both more reliable and easier to use than before. 
     SUMMARY OF THE INVENTION 
     A first aspect of the present invention is an on-line handwriting recognition method in which at least one auxiliary line is displayed on a touch sensitive panel. Each of the at least one auxiliary line constitutes a portion of more than one character of a character set. A character of the character set is drawn on the touch sensitive panel by completing one of the at least one auxiliary line into the character. The drawn character is recognized on the basis of the completion. 
     A second aspect of the present invention is a device for on-line handwriting recognition. The device comprises a touch sensitive panel for displaying at least one auxiliary line, each of the at least one auxiliary line constituting a portion of more than one character of a character set. The device further comprises a handwriting recognizer for recognizing a character of said character set drawn on said touch sensitive panel by completing one of said at least one auxiliary line into said character. 
     In an embodiment of the invention, the device further comprises a drawing instrument for drawing a character of said character set on said touch sensitive panel by completing one of said one or more auxiliary lines into said character. 
     A third aspect of the present invention is a device for on-line handwriting recognition. The device comprises a touch sensitive input/output means for displaying at least one auxiliary line, each of the at least one auxiliary line constituting a portion of more than one character of a character set. The device further comprises a handwriting recognition means for recognizing a character of said character set drawn on said touch sensitive input/output means by completing one of said at least one auxiliary line into said character. 
     In an embodiment of the invention, the device further comprises a drawing means for drawing a character of said character set on said touch sensitive input/output means by completing one of said at least one auxiliary line into said character. 
     A fourth aspect of the present invention is a computer program embodied on a computer readable medium for on-line handwriting recognition. The computer program controls a data-processing device to perform the step of recognizing a character of a character set drawn on a touch sensitive panel, the character having been drawn by completing one of at least one auxiliary line into the character, the at least one auxiliary line being displayed on the touch sensitive panel and each of the at least one auxiliary line constituting a portion of more than one character of the character set, and the recognizing being performed on the basis of the completion. 
     In an embodiment of the invention, the at least one displayed auxiliary line includes at least one of a first auxiliary line essentially in the form of a vertical line, a second auxiliary line essentially in the form of letter “C” and a third auxiliary line essentially in the form of “           ”. The vertical line may be e.g. perpendicular, or it may be leaning e.g. slightly forwards, i.e. essentially in the form of a slash character “/”.
     The invention allows handwriting recognition that is both more reliable and easier to use than before. The user is not required to draw blindly, nor is the user required to memorize any predefined patterns. Rather, the user simply completes a pre-displayed auxiliary line into the intended character. Thus, handwriting recognition in accordance with the principles of the present invention is significantly easier to use than prior art handwriting recognition techniques. Furthermore, no system, device, or software application is required to learn the writing patterns of the user. Thus, handwriting recognition in accordance with the principles of the present invention is significantly more reliable than prior art handwriting recognition techniques. 
     The reliability of the handwriting recognition in accordance with the principles of the present invention is further enhanced by the fact that the user typically only draws little parts of a character in order to complete the character thus minimizing the probability of mistakes and non-intelligibly drawn patterns. The reliability of the handwriting recognition in accordance with the principles of the present invention is still further enhanced by the fact that the starting point of the completion typically limits the possibilities of which character the user intends to draw thus facilitating correct recognition. For example, if the user starts to draw a horizontal line extending from the base of an auxiliary vertical line to the right, the software application is able to immediately deduce that the user intends draw either letter E, L or Z. Due to the enhanced reliability of the handwriting recognition, the invention is particularly suitable for use in situations in which the user and/or the device which the user is writing on is vibrating or trembling for some reason and thus the user is not able to write as clearly as normally. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and constitute a part of this specification, illustrate embodiments of the invention and together with the description help to explain the principles of the invention. In the drawings: 
         FIG. 1  is a flow diagram illustrating a method according to an embodiment of the present invention, 
         FIG. 2  illustrates three exemplary auxiliary lines according to an embodiment of the present invention, 
         FIG. 3  is a block diagram illustrating a device according to an embodiment of the present invention, 
         FIG. 4   a  illustrates completion of various characters based on an auxiliary line essentially in the form of a vertical line according to an embodiment of the present invention, 
         FIG. 4   b  illustrates completion of various characters based on an auxiliary line essentially in the form of letter “C” according to an embodiment of the present invention, and 
         FIG. 4   c  illustrates completion of numerals based on auxiliary lines according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made in detail to the embodiments of the invention, examples of which are illustrated in the accompanying drawings. 
       FIG. 1  illustrates an exemplary embodiment of the method of the present invention relating to on-line handwriting recognition. At step  101  at least one auxiliary line is displayed on a touch sensitive panel. Each of the at least one auxiliary line constitutes a portion of more than one character of a character set. That is, each auxiliary line has been pre-selected so that the auxiliary line is a part of at least two characters. The more characters of the character set a single auxiliary line is a part of, the more characters can be drawn by completing the auxiliary line. 
     A character of the character set is drawn on the touch sensitive panel by completing one of the at least one auxiliary line into the intended character, step  102 . In other words, only the missing parts of the intended character are drawn by the user around the auxiliary line. The drawn character is then, at step  103 , recognized on the basis of the completion. That is, the drawn character is recognized on the basis of the parts the user drew. 
       FIGS. 2 and 4   a - 4   c  further illustrate the use auxiliary lines and how to complete them into characters according to an exemplary embodiment of the present invention.  FIG. 2  discloses a first auxiliary line  201 , which is essentially in the form of a vertical line, a second auxiliary line  202  essentially in the form of letter “C” and a third auxiliary line  203  essentially in the form of “           ”. As can be seen, in the exemplary embodiment of  FIGS. 2 and 4   a - 4   b , the vertical auxiliary line  201  is leaning slightly forwards, i.e. it is essentially in the form of a slash character. However, the vertical auxiliary line may as well be e.g. perpendicular.
       FIG. 4   a  illustrates how to complete the vertical auxiliary line  201  of  FIG. 2  into various upper case letter characters. The dash line represents the pre-displayed vertical auxiliary line  201  of  FIG. 2 , and the solid lines represent the various parts of the various characters the user needs to draw. Correspondingly,  FIG. 4   b  illustrates how to complete the second auxiliary line  202  of  FIG. 2  into various upper case letter characters. The dash line represents the pre-displayed second auxiliary line  202  of  FIG. 2 , and the solid lines represent the various parts of the various characters the user needs to draw. As can be seen from  FIGS. 4   a - 4   b , utilizing just the two exemplary auxiliary lines of  FIG. 2 , most upper case western letter characters can easily be drawn. For example, letter “I” can be drawn by adding a dot on top of the pre-displayed vertical auxiliary line  201  of  FIG. 2 . Letter “L” can be drawn by adding a short horizontal line to the right of the base of the pre-displayed vertical auxiliary line  201  of  FIG. 2 . Letter “O” can be drawn by closing the gap of the pre-displayed second line  202  of  FIG. 2 . 
       FIG. 4   c  illustrates how to complete numerals by using the aforementioned auxiliary lines. It should be noted that  FIG. 4   c  illustrates only one embodiment how to use the auxiliary lines. 
       FIG. 3  illustrates an exemplary embodiment of the device of the present invention relating to on-line handwriting recognition. The device  300  comprises a touch sensitive panel  301  for displaying two auxiliary lines  311  and  312 , each of which constitutes a portion of more than one character of a character set. The device  300  further comprises a drawing instrument  320  for drawing a character of the character set on the touch sensitive panel by completing one of the two auxiliary lines into the intended character. In another embodiment of the invention, characters may be drawn using e.g. a finger, and therefore, the drawing instrument  320  may not be needed. The device  300  further comprises a handwriting recognizer  340  for recognizing the drawn character on the basis of the completion. 
     In the exemplary embodiment of  FIG. 3 , the device  300  is a handheld device, such as a personal digital assistant or a mobile telephone. In the exemplary embodiment of  FIG. 3 , the touch sensitive panel  301  is a display screen at the bottom of which the three auxiliary lines  311 ,  312  and  313  are located. However, the touch sensitive panel may as well be an element separate from a display, as is known to those skilled in the art. The auxiliary lines  311 ,  312  and  313  may be fixed, e.g. painted on the display screen  301 , or they may be drawn on the display screen  301  by the device  300  in the same manner as everything else presented on the display. In the exemplary embodiment of  FIG. 3 , the drawing instrument  320  is a pen or a stylus with which the user may write on the touch sensitive display screen  301 . In the exemplary embodiment of  FIG. 3 , the handwriting recognizer  340  is implemented as a software application. However, the handwriting recognizer  340  may as well be implemented in hardware, or as a combination of hardware and software. 
     When writing text, the user simply completes one of the auxiliary lines  311 ,  312  or  313  into the intended characters one character at a time. For example, if writing the word “NOKIA”, the user first completes auxiliary line  311  into letter “N” in the manner illustrated in  FIG. 4   a . Then, the user completes auxiliary line  312  into letter “O” in the manner illustrated in  FIG. 4   b . Then, the user completes auxiliary line  311  into letter “K” in the manner illustrated in  FIG. 4   a . Then, the user completes auxiliary line  311  into letter “I” in the manner illustrated in  FIG. 4   a . Finally, the user completes auxiliary line  311  into letter “A” in the manner illustrated in  FIG. 4   a.    
     It is obvious to a person skilled in the art that with the advancement of technology, the basic idea of the invention may be implemented in various ways. The invention and its embodiments are thus not limited to the examples described above, instead they may vary within the scope of the claims.