Image analysis – Pattern recognition – On-line recognition of handwritten characters
Reexamination Certificate
1995-08-01
2001-03-27
Johns, Andrew W. (Department: 2621)
Image analysis
Pattern recognition
On-line recognition of handwritten characters
Reexamination Certificate
active
06208756
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a hand-written character recognition device for extracting a feature of a hand-written character written on a tablet on the basis of coordinate data of the written character so as to recognize the character, and more particularly to a hand-written character recognition device having means for removing a noise which appears as a sudden variation of coordinate data written on the tablet.
2. Description of the Prior Art
There is known a hand-written character recognition device which is equipped with a character input device such as a tablet (x-y coordinate input unit) having sensors arranged in a matrix form and extracts a character feature on the basis of x-y coordinate data of a character written on the tablet, thereby recognizing the hand-written character.
FIG. 1
is a block diagram showing the basic construction of the hand-written character recognition device. As shown in
FIG. 1
, the hand-written character recognition device includes a tablet
100
, a pre-processing unit
101
, a feature extraction unit
102
, and a character recognition unit
103
. The tablet
100
has an input portion having a sensor system of one of a touch-panel type sensor which is a pressure-sensitive type sensor using a plane resistor, an electrostatic coupling type sensor or a power source induction type sensor, and serves to output x-y coordinate data of a hand-written character. The pre-processing unit successively receives the x-y coordinate data outputted from the tablet
100
at every predetermined time to define x-y coordinate points of the hand-written character. The feature extraction unit
102
extracts a stroke feature of the inputted character using the data of the x-y coordinate points which has been defined in the pre-processing unit
101
. The character recognition unit
103
analyzes the inputted stroke feature obtained by the feature extraction processing in the feature extraction unit
102
so as to recognize the inputted character, and then generates a character code for the inputted character.
In a write operation of a character on the tablet
100
, in accordance with the resolution of the tablet and input unit, a plurality of coordinate points would be detected in x and y directions for one data. Therefore, when a plurality of coordinate points are detected for one data, in the pre-processing unit
101
, a midpoint of these plurality of coordinate points is calculated so as to define an effective x-y coordinate point of the hand-written character used for the subsequent feature extraction.
However, in such a hand-written character recognition device, especially when a character is written through a finger, a plurality of coordinate points are detected in each of x and y directions. In addition, a write speed and a write pressure are not necessarily constant (that is, the write-in operation is not necessarily stably carried out). Therefore, the calculated x-y coordinate points defined in the pre-processing unit includes some x-y coordinate points deviated from the actual locus of the hand-written character (hereinafter referred to as “noise data” or “noise coordinate point”). The frequent occurrence of the noise data causes the feature extraction processing for the input stroke to be more complicated and unreliable.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a hand-written character recognition device in which noise data contained in an x-y coordinate data outputted from a tablet is removed, so that a processing load in a feature extraction processing for an input stroke is reduced and thus a more accurate feature extraction can be performed.
According to one aspect of the present invention, there is provided a hand-written character recognition device including: input unit, having input portion, for successively detecting x-y coordinate points of a hand-written character written on the input portion; vector calculation unit for calculating a vector between the detected x-y coordinate points; angle calculation unit for calculating an angle between the vectors calculated by the vector calculation unit; noise identifying unit for analyzing positional variation of the coordinate points on basis of the calculated vectors and the calculated angles, and identifying coordinate points whose positional variation exceed a predetermined variation range as noise coordinate points; and noise removing unit for removing noise coordinate points from the coordinate points detected by the input unit.
The basic technical idea of this invention is based on such an experimental and empirical rule that there is no rapid or sudden variation in the locus of a hand-written character. On the basis of this basic technical idea, the movement of the x-y coordinate data is checked in time-series in the noise removing processing, and those x-y coordinate data rapidly or suddenly varied are removed as noise data. Namely, when the handwritten character recognizing device identifies a coordinate data as a noise coordinate data or not, the device discriminates whether the coordinate data to be judged is within the predetermined variation range which is determined in accordance with a plurality of coordinate points inputted prior to and subsequent to that coordinate data.
Actually, the vector calculation unit successively calculates, for example, a vector between the detected first and second coordinate points, a vector between the detected second and third coordinate points, a vector between the detected first and third coordinate points on the basis of the x-y coordinate data of a hand-written character which are successively detected by the tablet. The angle calculation unit calculates angles between the calculated vectors. The noise identifying unit analyzes the positional relationship between the first, second, third and fourth coordinate points on the basis of the calculated vectors and angles so as to judge whether the second and third coordinate points between the above four coordinate points are varied over a predetermined range or level. If the variation of these coordinate points is over the predetermined range or level, these coordinate points are removed as noise data.
REFERENCES:
patent: 4365235 (1982-12-01), Greanias
patent: 4608658 (1986-08-01), Ward
patent: 4817034 (1989-03-01), Hardin, Sr. et al.
patent: 5023918 (1991-06-01), Lipscomb
patent: 5038382 (1991-08-01), Lipscomb
Johns Andrew W.
Pioneer Electronic Corporation
Pitney Hardin Kipp & Szuch LLP
LandOfFree
Hand-written character recognition device with noise removal does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Hand-written character recognition device with noise removal, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Hand-written character recognition device with noise removal will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2439744