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  Handwriting recognition systemUSPTO Application #: 20060088215Title: Handwriting recognition system Abstract: In order to improve the accuracy of recognition of hand-written input using a stylus, output signals from a plurality of accelerometers representing x and y axis acceleration and deceleration are sampled at a predetermined rate and passed through a digital bandpass filter to remove high frequency components and dc components arising from gravity. X and y vectors derived from the original x and y input signals are passed to a classifier using a hidden Markov model. Bandpass filtering improves the robustness of the interpretation of the vectors against stored templates which may be templates of individual characterisations or of whole words. (end of abstract) Agent: Nixon & Vanderhye, PC - Arlington, VA, US Inventor: Benjamin P. Milner USPTO Applicaton #: 20060088215 - Class: 382187000 (USPTO) Related Patent Categories: Image Analysis, Pattern Recognition, On-line Recognition Of Handwritten Characters The Patent Description & Claims data below is from USPTO Patent Application 20060088215. Brief Patent Description - Full Patent Description - Patent Application Claims
RELATED APPLICATION [0001] This is a division of our copending commonly assigned application Ser. No. 09/914,262 filed Aug. 24, 2001 which was, in turn, a 35 U.S.C. .sctn.371 US national phase of PCT/GB00/01052 filed Mar. 21, 2000 and claiming priority from European application 99302270.6 filed Mar. 24, 1999. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to a handwriting recognition system and more particularly to a hardware and an algorithm for implementing such a system. [0004] 2. Related Art [0005] In PCT application number GB98/0316 (Publication No. WO99/22338) there is disclosed a portable computer in the form of a pen-type casing. Incorporated within the casing is at least one accelerometer which is used to detect movement of the pen with respect to its environment. By using the instrument for handwriting it is possible to effect data entry or transmission of signals reflecting movement, the user using either a pen tip mounted switch or a finger operated switch to indicate that movement is effecting a written input. [0006] There are many other pen-type input devices on the market in addition to stylus scroll pallets typically used in so-called palm top computers where handwriting recognition has been used. Such devices often require very precise movement which may not reflect natural handwriting movements for the user. One of the problems which makes characteristic handwriting recognition difficult is that while the underlying movement made by an individual to represent a particular letter may be consistent an element reflecting user movements due to stress and other factors will be present. BRIEF SUMMARY OF THE INVENTION [0007] According to an exemplary embodiment the present invention there is provided a handwriting recognition system comprising means responsive to input analogue signals representative of movement of a handheld writing device, sampling means to provide signals representative of the acceleration of the writing device in at least x axis and y axis channels at a predetermined capture sampling rate, and filtering means to remove dc level components and to provide smoothing of the output whereby signals representative of movement of the pen over a period are supplied to a classifier for comparison with a template representative of characters formed. [0008] The classifier may use hidden Markov modelling (HMM) techniques using a large number of states to determine the character defined by movement. The system may include an input indicative of a user's intention that the movement is representative of character writing. [0009] According to a feature of the present there is provided a method of analysing signals from a moving handheld device, the method comprising sampling signals at a predetermined rate, passing signals through a bandpass filter to remove dc level and excess acceleration components, sampling the filtered output to provide a series of vectors representing the position of the handheld device at periodic intervals and using a classifier to compare the sample sets with predetermined templates to determine the character for output. BRIEF DESCRIPTION OF THE DRAWINGS [0010] A handwriting recognition system in according with the invention will now be described by way of example only with reference to the accompanying drawing of which: [0011] FIG. 1 is a block schematic diagram of the system; [0012] FIG. 2 shows relative positioning of the x and y axis of the handwriting device of FIG. 1; [0013] FIG. 3 is a schematic diagram of the handheld writing device of FIG. 1 in a particular position; [0014] FIG. 4 shows relative input and output vector streams from the system of FIG. 1; and [0015] FIGS. 5 to 9 show comparative templates for a number of different letters. DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS [0016] Referring first to FIG. 1, an input device 1 such as a stylus produces x and y vector streams 2 and 3 which are fed into a sampling unit 4. The outputs x and y are generally from accelerometers or other position sensing devices within the stylus 1. Also feeding the sampling unit 4 is an output 5 from a switch indicated here as being in the nib section of the stylus 1 such that contact between the switch 6 and a surface is indicative of the stylus being used in a writing mode. It will be appreciated that the nib switch 6 when incorporated in a non-surface contacting stylus, such as that disclosed in the previously referred PCT application, may be replaced by a user operable switch. [0017] The output of the sampling unit 4, which samples the incoming streams at 60 Hz for example, is passed to a bandpass filter arrangement 7 and thence to a down sampling unit 8 which produces digitised vectors x and y over a period of time. The x and y vectors are passed to a classifier 9, which uses a hidden Markov model to carry out a comparison between the vectors and templates representing written characters. The classifier 9 may be arranged to output to a visual display 10. [0018] More specifically, the stylus 1 for example comprises a simple plastic casing containing the electronics for transferring information to a PC. Two accelerometers mounted in the stylus, for example, are used to produced the x and y outputs. The nib switch is a simple on/off switch connected to determine when pressure is being applied to the pen nib and can therefore detect when a pen for stylus 1 is writing. [0019] Turning briefly to FIG. 2, the two accelerometers mounted in the top of the pen measure acceleration across their plane such that effectively they measure acceleration along the x axis 11 and the y axis 12 of the writing surface 14. The acceleration measured by the sensors is made up of two components, acceleration due to gravity and the acceleration as a result of stylus movement. It will be appreciated that the acceleration due to gravity is always present, such that when the pen is exactly horizontal both sensors would measure acceleration of 1 g. As the angle of the pen to the horizontal changes (as shown for example in FIG. 3), the accelerometers are subject to Sin .theta..times.1 g where .theta. is the inclination angle of the stylus 1. Continue reading... Full patent description for Handwriting recognition system Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Handwriting recognition system patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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