GB2117154A - Hand-written character recognition device - Google Patents

Abstract

Programmable hand-written character recognition device operates in various programmable modes to recognise and operate on character patterns derived from sets of digitised X-Y co-ordinate signals generated through electro-magnetic beat frequency coupling of pen signal generating means with device detecting means via receiving means comprising transverse arrays of microprocessor controlled switchable looped antennae located within a writing board 1. The coupled signals are processed to convert one or more analogue signals to digital form and indicative of the periodic point position and directional movements of a pen 3 upon a writing surface. Developed programs may be stored in bar code form for reloading into the device by use of a light pen, routines being provided for the recognition of standard character patterns as well as individually stylized character patterns in a device learning mode and usable in conjunction with special job functions such as shorthand and book-keeping. <IMAGE>

Description

SPECIFICATION Programmable hand written character recognition device This invention relates to a programmable hand written character recognition device in which the periodic point position and directional movements of a pen upon a writing surface are converted into streams of electronic signals in the form of digitized X-Y co-ordinates, complete sets of which are representative of the characters being written or hand printed by the user'and which the device has been programmed to recognise and operate on.

The device has wide and beneficial application in many areas of commerce and industry, both in the public and private sectors, and particularly in any data processing activity in which the data to be processed is first gathered or taken down in writing and then re-entered or typed into a computer terminal, since the device permits the data to be captured at source without the need for expensive and time consuming duplication through a keyboard. Data thus captured may be transmitted directly to a computer, including remotely located computers which can be accessed via the telephone network, or be stored on magnetic tape, disks floppy or hard, or any other suitable magnetic data storage medium for subsequent transmission to external host computers or other data handling/processing devices. Data may also be stored within buffer memories located within the device.A further advantage of the device is that data may be entered into computer system by persons unskillqd in the use of keyboards.

Hitherto, devices capable of recognising handwriting or handprint have of necessity imposed rather rigid and arbitrary disciplines on the user as to how particular characters are to be formed to ensure successful recognition owing the the wide variation in individual writing styles with which people write the same characters, and because limited memory resources require a standard method of character recognition to be stored in a Read Only Memory. Furthermore, such devices have tended to be limited in their use to that of a data capture terminal which depends on an external host computer for the data processing function.

An object of the present invention is to provide a device that while capable of operating in the above mentioned modes, has the greatly extended capability of being readily programmed by the user to recognise specifically that particular users style of writing or handprint and, further, to act on or carry out data processing routines on that data in a stand alone mode as well as when so required in co-operation with an external host computer. A programmable device of this type has many advantages since it can be personalised to the user thereby greatly reducing and perhaps even eliminating entirely the rigid writing disciplines that would otherwise be imposed by the more generalised recognition routines, and moreover the numerous function or application programs that may be employed make for vastly greater versatility in device operation.For example, a user may load into a Random Access Memory included within the device a routine example of that users writing style, followed by a job function program such as a routine to automatically total and balance ledger accounts as they are posted by the user, thereby preventarithmetic or other posting errors. Examples of other job function programs include routines for wordprocessing and text editing; shorthand notation recognition; telex message preparation; interpretation of the format of pre-printed forms usable with the device; writing computer programs; arithmetic and computational processes as well as internal device control and external device interface and communications controls. Sometimes it is much simpler to collect data by entering a mark such as a tick or a cross in a ballot box in response to a question requiring a "Yes" or "No" answer on a pre-printed form.

This too is an example of a function program which the device may execute as are programs for graph plotting, line drawing and graphics.

Any suitable method or combination of methods of programming the device may be used.

For example, programs may be down loaded from an external host computer or may be loaded from any conventional storage medium such as magnetic tape or disks via cassette players, disk drivers etc. Preferably, however, the combination of programming methods includes means for enabling the user to originate new programs and load them interactively into the device, and means for re-loading stored pre-written programs when other electronic storage devices are not available. The first means is preferably provided by use of the pen which would otherwise be used for entering data. Such programs may then be later dumped to tape or disk or transmitted to external computer devices and so arranged to convert the program into permanent bar code form. This process would also be applied to recognition routines and any other functional routines.The second means is preferably provided by the use of a light pen designed to read bar codes and which is wiped over the printed bar code version of the program. The inital interactive loading of an individuals style of handwriting or handprint is preferably accomplished in response to pre-programmed prompts from the device via a display device thereby enabling the user to enter one or more examples of each alphabetic, numeric or symbolic character for storing in the memory of the device and from which subsequently an electronic representation of that users character set may be copied out as mentioned above to enable the preparation of a permanent and re-usable program in bar code forms. Verification routines are preferably included in such said interactive programming routines to test that the device has correctly recognized individual characters and correctly accepted data entered.Completed programs once converted to bar code form may then be furnished to the user in book form having loose leaf pages.

According to the present invention there is provided a programmable hand written character recognition device comprising a special pen having, within one or more appropriate housings, pen signal generating means; a writing board transducer surface having either sharing said housing or having one or more separate housings, pen signal receiving means and pen signal detecting means operable in response to a signal either from or to the pen when said pen is positioned thereon for detecting and indicating the positional co-ordinates of the pen in terms of a digital electronic signal; one or more of said housings containing, in integrated circuit form, data processing means including at least: a microprocessor or microcomputer system of eight, sixteen or thirty-two bit architecture (or larger) interfacing with or controlling, in addition to said pen means and transducer means, sufficient random access read/write memory arranged to store individual hand writing recognition routines and samples of individual writing styles, job function and application programs, manipulative routines, intermediate and final results of character recognition and processed data and operable in conjunction with buffer memory; sufficient read only memory storing a dedicated generalised character recognition routine and or other dedicated control routines; and appropriate input/output ports and port control means capabilities to interface the device with such parallel and serially oriented peripheral devices or external systems as it may be desired to use in connection with the said device, such that detected pen signals are operated on by the relevant recognition and processing routines and the recognised character and data is stored in the said read/write memory or buffer memory from where it may be transmitted to external systems.

The device may process data within its own internal circuitry and communicate the results to external system such as remote computers, display devices or data storage devices.

Alternatively, the device may communicate representations of recognised characters to such external devices and do so interactively with said devices so as to receive data instructions, commands or requests from such devices to which it may respond. Data or representations of data may thus be transmitted to teletypers, line printers, cathode ray visual display units, liquid crystal displays or any other suitable visual display means usuable with said device. Similarly, for initial programming and program loading the device may receive data or representations of data from external devices via bar code readers.

Visual display means are desirable for use with the device in order that the user may verify from observation of the display that character recognition is occurring correctly.

The device may be operable with pre-printed forms, plain paper and paper that is essentially plain other than for feint rulings and line numbered margins and in any of these modes the device may be used as a word processor for preparing texts of letters and reports and any other written records, thereby enabling a user unskilled in the use of typewriter keyboards to compose, edit and prepare in more or less a freehand manner texts and messages which may subsequently be printed out by a typewriter or line printer type device interfaced with said device.

Papers used with the device may be in single sheets or padded into straw board backed sets.

Preferably, means are provided for consistently placing said forms onto the writing surface in a pre-defined registered position recognisable by the device upon the entering of a registration character or mark and held securely in that position to prevent misregistration problems arising. In the case of single sheet forms these may be held agains an "L" shaped head and side stop which may be adjustable for head and side lay and a recognition character or mark entered from which the device may calculate correction factors. Alternatively, a spring loaded clamp may be used in conjunction with the head stop such that forms may be inserted beneath the clamp and held by pressure exerted by the spring.

Registration pins may be used to secure forms that have been suitably pre-punched with register holes. For padded forms, which may also be held securely in position by a spring clamp means of appropriate size, there may be provided a sleeve or elasticated band under which the strawboard backing of the pad may be inserted. As preferred, however, a securing mechanism comprising adjustable jaws are used to hold the head comers of the pad in secure register, and preferably all of said securing means are provided as demountable optical accessories to suit different user preferences. Said means may be attached to the device by insertion into a recessed "T" shaped channel located within the writing board surface and above the writing area, or alternatively may be attached to suitably placing mounting posts.

With form or pad placed in device accepted register, data entries written by the pen may generate a datum having two or more portions, the first of which may represent the location or address of the position on the form at which the data entry is being made, the second of which may represent the character being written at that location and any other portion if so used representing some special feature or token concerning that character such as whether it is upper or lower case, said datum being provided for transmission to external host computer systems or for direct use in internal device data processing.

As has been mentioned the device is operable in two recognition modes: a disciplined mode using a standard generalised character recognition routine permanently stored in ROM; and a flexible mode utilising a user interactive character recognition routine loaded into RAM and which routine may be stored permanently in bar code form. It will be appreciated that the recognition routines or algorithm thus held in these respective memories may be similar, the same and of any well known type: see for example "Pattern Recognition Learning and Thought", by Lenoard Uhr (Prentice Hall). An advantage of the interactive recognition routine is that it also provides a means for developing improvements in character recognition algorithms.

Preferably, character indicating data received by the device from the writing board is processed as a set of time sequential digital co-ordinate position signals which are stored in a group of memory locations or in a memory table. The recognition routine is applied to testing or reading the contents of such memory locations so as to assemble the character and a character so recognised by said routine is stored in a preselected memory location, from where it may be transmitted to any co-operating external host computer system, subsequently verified and returned to the device for display on the display device means or acted upon in similar fashion by the device itself according to its mode of use.

Direct memory accessing techniques are preferably employed in the processing of information stored in the memories provided within the device.

The following description refers in more detail to the above mentioned pen signal generating, receiving and detecting means provided in accordance with the present invention and which enable a coupling between pen and writing board surface to occur in such a manner that the position and movements of the pen relative to the writing board may be converted into digital signals representating X-Y co-ordinates. It is to be understood that while for simplicity of explanation the description refers to signal passing from pen to the writing board, signal passing may just as easily and no less preferably be effected in the opposite direction with minimal modification to circuitry and is therefore an alternative embodiment of the present invention.

Various coupling methods may be used, for example an ultra high frequency sound wave may be directed from the pen toward the writing surface for reception and detection in suitable transducers located within or upon the writing board. Another method that may be used is to detect a heating and cooling effect of switched X-Y co-ordinate elements within the writing board by means of an infra-red detecter within the pen.

The preferred method of coupling employed in accordance with the present invention is based upon the principle that two different electromagnetic frequencies may, like other resonances, be mixed or beaten together as interference in a suitable detector circuit to produce an intermediate frequency or heterodyne such as is customarily used in metal locating apparatus to indicate the presence of metal objects by means of an audible tone, and which signal being an analogue signal similar to a low power radio signal having an alternating magnetic field, may be received through an arrangement of microprocessor controlled anntenae, amplified in said detector or detectors, differenced in a differential amplifier and converted in an analogue to digital converter circuit into a digital co-ordinate signal.

Thus in accordance with this invention there is provided a beat frequency oscillator stage comprising a fixed reference oscillator operable at one end and preferably fairly high frequency; a variable oscillator operable at a second frequency either higher or lower than the first oscillator, and driving a miniaturised centre tapped search coil located with the barrel of the pen; an arrangement of microprocessor/microcomputer controlled multiplexed or scan polled arrays of receiving antennae located within the writing board surface; suitable detector means circuitry which preferably includes peak level detecting means, differencing means, signalling means and converting means such that when the pen is brought into proximity with the writing surface a signal, which may be pulsed or continuous and which is initiated by switching means responsive to pressure contact by the pen point upon the writing material surface, or to a change in the relative resistances between the pen point and the writing material surface, is passed or coupled via one or more members of the receiving means arrayed antennae into said detecting means to produce the heterodyne signal therein representative of the position of the pen thereon in terms of a digital X-Y co-ordinate.

The receiving means antenna arrays may comprise arrays of dipole antenna, with one set being provided for the X co-ordinate direction, and a second array set being provided transverse to the first array set for the Y co-ordinate direction; said arrays being formed by etching the copper surface of printed circuit copper clad boards.As preferred, however, the antennae are, in accordance with the present invention are formed as elongated rectangular loops which may be overlapped by a predetermined scale by means of multi-layer board construction, which boards may be rigid or flexible, and are routed to the detecting means via complimentary metal oxide silicon analogue transmission gates or bilateral switches which are interposed between the ends of the loops and the detecting means, the control inputs of the bilateral switches being polled or multiplexed under program control from the microprocessor/microcomputer. Thus each individual antenna may be scanned in any desired order, sequence, combination or pattern under program control.Normally, however, the antenna will be polled in adjacent pairs of antenna within the same antenna array and alternating between the X-Y co-ordinate arrays by means of additional bilateral switches used to block the sampling of two arrays simultaneously. In this way each receiving antenna in each antennae array is tested separately for the presence of a signal since one array is tested at a time and the pair found to have a signal present are differentiated by the differencing amplifier forming part of the detector means such that the resultant signal may provide, in conjunction with appropriate AND gating, a signal uniquely representing the position of the pen in terms of X-Y co-ordinates defined by the respective antennae and which co-ordinates may be further resolved through converting the associated analogue signal to digital form in the A/D converter.

The detecting means for use with the present invention may be any suitable transistorised radio signal receiving and amplifying circuit or mixer detector circuit such as is commonly employed in metal locators, and is preferably provided in duplicate in order that the signal detected by each detector may be differenced in an operational amplifier operating in differential mode. A peak level detector circuit is preferably included as an aid to range control and may be operable in response to a change in the light intensity of visible signalling means which are preferably also included in the device.

The essential basic features and optical optional features of the invention will now be described in greater detail and with reference to the accompanying drawings where these features are shown in preferred form.

Figure 1 is a schematic perspective view of the device showing pen, writing board with housing and display means according to the present invention; Figure 2 is a perspective view of a separate housing usable with the invention and mountable on the housing of Figure 1; Figure 3 is a block diagram of the main essentials of the device; Figure 4 is a schematic cutaway view of the writing board to illustrate the typical arrangement of antennae receiving means arrays and gating with bilateral analogue switches; Figure 5 8 6 are practical circuit diagrams for pen signal generating means; Figure 7 is a practical circuit diagram for the pen signal detecting means; Figure 8 is a practical circuit for differencing the signal detected by the detecting means; Figure 9 is an alternative embodiment of the means illustrated in Figure 7;; Figure 10 is an exploded schematic view of the pen used in the invention; Figure 11 are flowcharts of various control routines applicable to the invention; In Figure 1 the device is shown as comprising a laminated writing board 1 , a rectangular housing 2 both sharing a common base, and a special pen 3. The pen is lead connected to pen signal generating means contained either within said housing 2 via connection sockets 14 and 15, or alternatively to pen signal generating means located in a separate housing having appropriate power supply and connection sockets. The housing 2 has a bevelled front wall 26 in which is let an elongated window behind which a narrow display means 11 may be positioned.Tubular mounting posts 17, 18, 19 s 20 are provided in the corners of the housing to facilitate the mounting of optional extra housings containing additional device circuitry, memories and or other discrete devices such as cassette recorders, floppy disk drives, video disk drives, modems or any other useful aid useable with the device and thereby permitting future expansion of the device capabilities.

The writing board comprises a multipie layer of printed circuit boards, each insulated from the others as necessary, and sandwiched between a rigid base board (which may itself be a circuit board) and a protective top covering such as melamine (Trade name). The circuit boards are preferably as thin as possible and double sided to ensure a writing board of suitable overall thinness and may consist of thin flexible copper laminated film such as Cuflex (Trade name), said circuit boards being etched to provide the receiving means antennae arrays for X 8 Y co-ordinates together with control signal conductor lines and associated circuitry.

An overlay of thin transparent plastic film 4 may be placed upon the writing board and secured by register pins 6 8 7, such film or preferably sets of film, having pre-designated legends or other token symbols and expressions printed in a visible area thereon, such as margins 9, said legends being useful in programming the device, or being programmably recognisable by the device as data input to the device when said legends are touched by the pen, for example ballot box data entry of a numeric or alphabetic character set, or device controls such as cursor control, tabulation, mode selection and any other controls that it may be desired to program the device to respond to.

To facilitate the positioning and securing of individual sheets of paper as well as padded forms upon the writing board a demountable spring loaded clamp plate 22 is preferably provided as one of several accessories, and is mounted by inserting hinged shaft 23 into securing brackets 10 with tension springs 24 s 25 being located in the "T" shaped recessed channel 5. As shown the clamp plate may have integral register pins on its upper surface for securing pre-punched forms, and may in this mode be optionally attached down either side margins 9 of the board.

The vertical front wall of the housing 2 may be used as a head stop for both single leaf forms and padded forms, side lay and securing of forms preferably being provided for by means of spring loaded jaws 12 8 13 slidable within channel 5 when the respective spring beneath said jaws is compressed by depressing the jaw, or "L" shaped side and head lay 8 movable in the same manner.

Connector socket 16 is provided on the bevelled face 26 of the front wall of housing 2 to enable the connection of a suitable light pen capable of reading bar codes used in program loading.

Additional connector sockets or ports (not shown) are preferably provided on the rear wall of the housing 2 to permit connection of the device to mains power supply, external visual display units 21, host computers, or other devices as well as interconnection with circuitry within additional housing mountable on the housing 2. Arrays of light emitting diodes 28 s 29 may be disposed upon the bevelled face 26 of the housing to provide visual indication of device operational status and fault monitoring.

Figure 2 is a perspective view of an additional separate housing 30 which may contain circuitry associated with the device or provided in order to expand the capabilities of the device and securely mountable on the housing 2 of Fig. 1 by inserting sprung pins 31, 32, 33 s 34 into the corresponding tubular mounting posts 17, 18, 19 s 20 in Fig. 1.As shown the housing of Fig. 2 has a compartment 35 accessed via a hinged transparent door 36 which may be used to contain a small cassette recorder device, miniature floppy disk drive, video disk player for data storage, any of such devices being useful in applications where it is desired to store data temporarily prior to transmitting said data in bulk over the telephone lines to remote computer bases, or where it is an advantage to have immediate access locally to particular types of standard data; for example insurer's premium rates for various classes of insurance risk would be invaluable to an insurance brokers business for quotation purposes.As with any other housing usable in this modular fashion with the device, the housing of Fig. 2 also has tubular mounting posts 38, 39, 40 s 41 to accept the mounting of a further housing, said housings being interchangable for access purposes, and being fitted with appropriate connection sockets.

Figure 3 is a block diagram of the main essentials of the device according to the present invention. Since there are many available proprietory microprocessor/computer devices which are usable within the present invention, and such devices vary considerably from one another, the connections shown in the drawing are not intended to portray practical circuitry. It is believed, however, that the details of this description together with the practical circuit diagrams included in the drawings are sufficient in detail and theory to enable any competent electronics constructor to assemble a full working version of this invention.

The schematic drawing of Figure 4 is a partially exposed view of some of the signal receiving means antennae arrays for X s Y co-ordinates connected to quad analogue bilateral switches, two of which are shown 40 -- 41, and illustrating a practical circuit for implementation in accordance with the present invention on two or more printed circuit boards, the conductive areas of which are suitably insulated from each other as required except where shown connected. The X co-ordinate antennae, X1, X2, X3 s X4, and the Y co-ordinate antennae, Y1, Y2, Y3, EF Y4, are shown as elongated loops transversely positioned either on opposite sides of a common printed circuit board or on one side of a board exclusive to each array.For simplicity of explanation the number of antennae shown exposed in the drawing is confined to four of each co-ordinate: they are shown as being spaced one antenna width apart and only one bilateral switch having the same function as switch 41 is shown. It must therefore be clearly understood that in practice the antennae may, by the use of additional circuit boards, be of any desired number according to the size of board and accuracy desired and be overlapped by a pre-determined scale and still be connected in accordance with the concept described herein to the appropriate number of bilateral switches having the function shown for that of switch 41.

The quad bilateral switches 40 8 41 each have four input terminals (Pins 1, 4, 8 eft 1 1), four output terminals (Pins 2, 3, 9 8 10), and a control signal terminal for each switch (Pins 5, 6, 12 Er 13), the last mentioned being connected to ground via limiting resistors 42 to 49 respectively. Each output terminal of switch 41 is (the converse also being possible) connected to one side of one X Co-ordinate antenna and one side of one corresponding Y co-ordinate antenna. Thus in the drawing X1 is connected to output terminal one (Pin 2), X2 is connected to output terminal 2 (pin 3), X3 is connected to output terminal 3 (Pin 9) and X4 is connected to output terminal four (Pin 10).The equivalent connection for the respective Y co-ordinate antenna is not visible in the drawing but is to be understood as being completed by conductor lines, on a separate circuit board, passing immediately beneath the corresponding X co-ordinate antenna and turning through 90 degrees to pass under the appropriate Y antenna for connection as indicated. Thus Y1 is connected to output terminal one, Y2 to output terminal two, Y3 to output terminal three and Y4 to output terminal four of quad bilateral switch 41.

The four input terminals (Pins 1, 4, 8 & 1) are common connected to the negative rail 46 of the detector circuits of Fig. 7.

The second side of each alternately paired antenna loop is connected to either capacitor 47 or 48 in Fig. 7 via quad bilateral switch 40 which is interposed between the antennae arrays and the detector circuits. Thus X1 s X3 may be connected to capacitor 47 (Fig. 7) via input/output terminals pins 8 Er 9 and X2 s X4 connected to capacitor 48 (Fig. 7) via input/output terminal pins 10 811 respectively.

Similarly, Y1 s Y3 are connected to capacitor 47 (Fig. 7) via input/output terminal pins 3 s 4 and Y2 Er Y4 are connected to capacitor 48 (Fig. 7) via input/output terminal pins 1 s 2 respectively of bilateral switch 40.

The control input signal terminals (Pins 13, 5, 6 s 12) of bilateral switches 40 Er 41 are connected from the underside of the circuit board to address lines 49 which are normally multiplexed or scanned in pairs and in such sequences under programmed control of the microprocessor/computer that, in respect of switch 41, a pair of adjacent X co-ordinate antenna and a pair of adjacent Y co-ordinate antenna are enabled simultaneously by each signal cycle to pass to quad switch 40 any received pen signal and, in respect of switches 40, each signal cycle alternately enables either the X pair or the Y pair of switches so that the pen signal may be transmitted to the detector circuits for detection and subsequent differentiation in terms of either an X or Y co-ordinate signal.

Referring now to Figures 5 Er 6 which form the pen signal generating means of the device, the practical circuit of Fig. 5 is the reference oscillator stage which may be used either at a preset frequency or with trimming control; the circuit of Fig. 6 is the variable oscillator stage for driving the miniaturised search coil within the pen.

The resistor 75 (Fig. 5) provides base current for transistor 70 and capacitor 72 provides feedback from the oscillatory circuit to the base of the transistor in the correct phase to maintain oscillation. The inductance 68 is an intermediate frequency transformer, the frequency of which is set by capacitor 71 connected across the primary winding 76, the internal capacitor 69, and variable capacitor 74. The secondary winding 77 of the inductor enables the oscillator to be coupled to the heterodyne producing circuits of Fig. 7 or alternatively Fig. 9 in an isolated way so that frequency changes in one oscillator will not pull the frequency of the other.

The variable oscillator stage of Fig. 6 is similar to the reference oscillator. The search coil (not shown) is connected at points 87, 86, and 88 which are the collector, centre tapping and base of transistor 78 connections respectively. The component, coil winding and tapping values are so chosen to give suitable feedback to maintain oscillation at a frequency that avoids causing unnecessary interference.

The dual detector and heterodyne stage shown in Figure 7 is connected at point 46 on the negative rail to the input terminals of the bilateral switch 41 (Fig. 4) and by connection to capacitors 47 Er 48 from the leads designated "Y" and "X" from bilateral quad switch 40 in Fig. 4. The transistors 50 Er 51 in one half of the circuit and 52 8 53 in the other half serve as amplifiers of the beat frequency signal detected in these stages. The connection points at 66 and 67 are shown unconnected and are provided to permit connection of either a small loudspeaker or suitable inductance across the points for the circuit to function.Light emitting diodes 64 Er 65 respectively protected by limiting resistors 640 and 641 provides both a visual indication of the signal appearing across points 66 Er 67 as well as a means for peak level monitoring when coupled into an opto-electronic light level detecting circuit employing Schmitt triggers. The circuits are completed by capacitors 58, 59, 60 Er 61 and resistors 54, 55, 56, 57, 62, and 63.

With power applied to the circuit of Fig. 7 but with no control signal applied to any of the bilateral switches 40 8 41 in Fig. 4 the light emitting diodes 64 ear 65 will be brightly illuminated. Immediately a control signal is applied to any of the bilateral switches the light emitting diodes wnl be substantially dimmed. If, however, at that moment a pen signal is received by any of the receiving means antennae it will pass through the pairs of switches that have been switched on by the control signal and cause the light emitting diodes to re-illuminate with an intensity that appears to be related to the proximity of the pen to the receiving means array and at the beat frequency produced by the oscillators.The signal is then preferably tapped by respective connections (not shown) either at points 66 Er 67 or from the light emitting diodes to pass to the differencing circuit shown in Figure 8.

The circuit of Fig. 9 is an alternative mixer type circuit that may be used in conjunction with the circuits of Fig. 7 for heterodyne production, the tapping point between diodes 106 Ear 107 being connected to capacitor 79 in Fig. 6 while connection points 109 Er 110 are connected to the secondary coil of inductor 68 in Fig. 5 at points1128113.

Referring to Figure 8, the operational amplifier 89 is used in differential mode with gain to test the respective signals level received from each of the detector circuits at its input terminals via capacitors 97 Er 98; resistors 92 8 93 with resistors 91 Er 94, forming potential dividers to give the necessary gain. The signals are preferably rectified either before being input to the operational amplifier in which case the capacitor 97 Er 98 may be dispensed with, or following differentiation. The signal may also optionally be integrated to provide an average signal -level.

Since the operational amplifier is preferably operated with a split power supply, resistors 103 8 105 with capacitors 101 enable a split power supply to be provided to the amplifier using a single power source. An offset null connection is provided by means of variable resistor 90 and capacitors 95 ear 96 decouple the negative and positive supply rails. A buffer driving stage comprising PNP transistor 100 with resistor 99 enable the differentiated signal to be visually indicated by light emitting diode 105 protected by limiting resistor 104, and which signal is preferably gated in suitable logic circuitry and digitised in the analogue to digital converter stage. It will be appreciated that the analogue signal being processed in this way has a minima and maxima voltage level which, when rectified before or after the differentiation process, provides a direct current signal proportional to the amplitude of the original analogue signal, and in conjunction with associated peak level and preferably sample and hold means and suitable calibration programmed into the microprocessor, or included in the device circuitry, the linearity of such signal is resolvable in the analogue to digital converter such that a range of co-ordinates are indicated in relation to each antenna thus effectively deviding the board into as many unique X-Y co-ordinates with relatively few antennae as the circuitry will allow.

The alternate stream of digitised X Er Y coordinates samples produced whenever the pen is in contact with the writing material surface are then processed, via buffering, by the microprocessor/microcomputer and stored in sequential memory locations in the read/write memory such that, according to whether or not the device has been pre-programmed user interactively, said memory thus contains either a first representation, or, a first and a second representation in co-ordinate form of the character entered, together with the co-ordinate indication at which that character was written on the writing document.The character recognition routine stored either in the read only memory or in a reserved portion of the read/write memory is then applied to the character assembled in the random access memory to effect a match in accordance with comparison parameter sets and attribution selection features defined by the recognition algorithm and the character so matched to its label is, according to the mode of operation selected for the device, transferred to an output buffer for sampling by the input/output interface for interpretation, processing and display handling by the external host computer or is similarly processed by the data processing circuitry internally of the device.In the event of a mismatch to the first parameter set the routine continues to apply successive parameter sets and attribution selection features to the character search until all parameter sets have been used, when, if still no match has been effected, an error condition is displayed and the user is afforded a fresh opportunity to re-enter the character, such entry being possible either by writing the character again or by making a ballot box type entry from a film legend of the character.

Referring to Figure 10, the pen shown disassembled, may be specially fabricated or may be a common ball point pen suitably modified to fulfill the functions described for the device, and is preferably constructed of a plastics material. In the drawing the pen is shown as comprising a two part pen barrel having a nose cone 120 and barrel stem 122 for containing an ink reservoir inserted in sub-assembly 140. The cone has external screw thread 121 for mating with internal screw thread 123 of the barrel stem. Leads ends 130 from signal generating circuits of Figs. 5 Er 6 and pressure switching means are offered through aperture 133 into chamber 1 32 within barrel 122 for connection externally of the chamber to the miniaturised search coil 126 wound on hollow coil former 125.In order to facilitate easy insertion and removal of ball point refills within cavity 1 31 of former 125 without damaging the wire connections to the coil, lead connections are made via printed circuit tracks 129 formed on a spine of Cuflex or similar flexible film 127 and fastened with adhesive to former 1 31 and tubular connector 128. Once connected the assembly is inserted into chamber 132, surplus lead being withdrawn through aperture 133, and is permanently bonded with adhesive to the chamber wall, the depth of insertion being controlled by the narrowing of the chamber end.

Conductive tracks are also provided on spine 127 to facilitate electrical connection with the metal casing and or point of the ink reservoir which is inserted through the coil former and seated against a membrane wall 135 positioned across tube 128 which it divides into two compartments.

The membrane may incorporate a strain gauge connected to the conductive tracking to provide the pressure contact switching action required to energise the coil. Alternatively the switching action may be operable by arranging for the external switching circuitry to respond to a change in the conductivity or resistance of the pen point when applied to the writing surface, such as may be detected by a field effect transistor switch.

The connection pads of copper tracks 129 are in practice confined within portion 136 of tube 128, lead ends being confined on the other side of the membrane 135 within portion 137 of the tube. The nose cone may then be screwed into position so that the pen point protrudes from the front opening of the pen barrel.

From the foregoing it will be recognised that the device described may be programmed to carry out a virtually unlimited repertoire of main control and sub-routine controls as well as user job functions, its virtuosity being limited only by the size of memory and the power of the microcomputer/processor included within the device and which may be added to by the addition of additional circuit housings. A few of the many possible program routines are shown by way of example in Figure 1 1-13,which deal with the interactive programming and a program loading of the device using pen and bar code reader pen (Fig. 1 3), the assembly of characters in coordinate form (Fig. 2) and character recognition by ROM or RAM in Fig. 11.

Thus has been described a highly versatile character recognition device having a novel approach to programming for pattern and character recognition and which may be used independently of or in conjunction with host computers for the processing of hand written data.

Claims (Filed on 15th March 1983) 1. A programmable hand written character recognition device in which the periodic point position and directional movements of a writing instrument upon a writing surface are converted into streams of electronic signals in the form of digitized X-Y co-ordinates, complete sets of which are representative of the characters being written or hand printed by the user and which the device can be programmed to recognise and operate on.

2. A device as in claim 1, and comprising a special pen having, within one or more appropriate housings, pen signal generating

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (16)

**WARNING** start of CLMS field may overlap end of DESC **. unique X-Y co-ordinates with relatively few antennae as the circuitry will allow. The alternate stream of digitised X Er Y coordinates samples produced whenever the pen is in contact with the writing material surface are then processed, via buffering, by the microprocessor/microcomputer and stored in sequential memory locations in the read/write memory such that, according to whether or not the device has been pre-programmed user interactively, said memory thus contains either a first representation, or, a first and a second representation in co-ordinate form of the character entered, together with the co-ordinate indication at which that character was written on the writing document.The character recognition routine stored either in the read only memory or in a reserved portion of the read/write memory is then applied to the character assembled in the random access memory to effect a match in accordance with comparison parameter sets and attribution selection features defined by the recognition algorithm and the character so matched to its label is, according to the mode of operation selected for the device, transferred to an output buffer for sampling by the input/output interface for interpretation, processing and display handling by the external host computer or is similarly processed by the data processing circuitry internally of the device.In the event of a mismatch to the first parameter set the routine continues to apply successive parameter sets and attribution selection features to the character search until all parameter sets have been used, when, if still no match has been effected, an error condition is displayed and the user is afforded a fresh opportunity to re-enter the character, such entry being possible either by writing the character again or by making a ballot box type entry from a film legend of the character. Referring to Figure 10, the pen shown disassembled, may be specially fabricated or may be a common ball point pen suitably modified to fulfill the functions described for the device, and is preferably constructed of a plastics material. In the drawing the pen is shown as comprising a two part pen barrel having a nose cone 120 and barrel stem 122 for containing an ink reservoir inserted in sub-assembly 140. The cone has external screw thread 121 for mating with internal screw thread 123 of the barrel stem. Leads ends 130 from signal generating circuits of Figs. 5 Er 6 and pressure switching means are offered through aperture 133 into chamber 1 32 within barrel 122 for connection externally of the chamber to the miniaturised search coil 126 wound on hollow coil former 125.In order to facilitate easy insertion and removal of ball point refills within cavity 1 31 of former 125 without damaging the wire connections to the coil, lead connections are made via printed circuit tracks 129 formed on a spine of Cuflex or similar flexible film 127 and fastened with adhesive to former 1 31 and tubular connector 128. Once connected the assembly is inserted into chamber 132, surplus lead being withdrawn through aperture 133, and is permanently bonded with adhesive to the chamber wall, the depth of insertion being controlled by the narrowing of the chamber end. Conductive tracks are also provided on spine 127 to facilitate electrical connection with the metal casing and or point of the ink reservoir which is inserted through the coil former and seated against a membrane wall 135 positioned across tube 128 which it divides into two compartments. The membrane may incorporate a strain gauge connected to the conductive tracking to provide the pressure contact switching action required to energise the coil. Alternatively the switching action may be operable by arranging for the external switching circuitry to respond to a change in the conductivity or resistance of the pen point when applied to the writing surface, such as may be detected by a field effect transistor switch. The connection pads of copper tracks 129 are in practice confined within portion 136 of tube 128, lead ends being confined on the other side of the membrane 135 within portion 137 of the tube. The nose cone may then be screwed into position so that the pen point protrudes from the front opening of the pen barrel. From the foregoing it will be recognised that the device described may be programmed to carry out a virtually unlimited repertoire of main control and sub-routine controls as well as user job functions, its virtuosity being limited only by the size of memory and the power of the microcomputer/processor included within the device and which may be added to by the addition of additional circuit housings. A few of the many possible program routines are shown by way of example in Figure 1 1-13,which deal with the interactive programming and a program loading of the device using pen and bar code reader pen (Fig. 1 3), the assembly of characters in coordinate form (Fig. 2) and character recognition by ROM or RAM in Fig. 11. Thus has been described a highly versatile character recognition device having a novel approach to programming for pattern and character recognition and which may be used independently of or in conjunction with host computers for the processing of hand written data. Claims (Filed on 15th March 1983)

1. A programmable hand written character recognition device in which the periodic point position and directional movements of a writing instrument upon a writing surface are converted into streams of electronic signals in the form of digitized X-Y co-ordinates, complete sets of which are representative of the characters being written or hand printed by the user and which the device can be programmed to recognise and operate on.

2. A device as in claim 1, and comprising a special pen having, within one or more appropriate housings, pen signal generating

means; a writing board transducer surface having, either sharing or having one or more separate housings, pen signal receiving means and pen signal detecting means operable in response to a signal from the pen when said pen is positioned thereon for detecting and indicating the positional co-ordinates of the pen in terms of a digital electronic signal; one or more of said housings containing, in integrated circuit form, data processing means including at least: a microprocessor or microcomputer system of eight, sixteen or thirty-two bit architecture interfacing with or controlling, in addition to said pen means and transducer means, sufficient random access read/write memory arranged to store individual hand writing recognition routines and samples of individual writing styles; job function and application programs, manipulative routines, intermediate and final results of character recognition and processed data and operable with buffer memory; sufficient read only memory storing a dedicated generalised character recognition routine and or other dedicated device control routines; and appropriate input/output ports and port control means capabilities to interface the device with such paraliel and serially oriented peripheral devices or external systems as it may be desired to use in connection with the said device, such that detected pen signals are operated on by the relevant recognition and processing routines and the recognised character and data is stored in the said read/write memory or buffer memory from where it may be transmitted to external systems.

3. A device as in Claims 1 and 2 wherein said pen signal generating means provides electromagnetic coupling with pen signal receiving means of said writing transducer surface of one or more analogue electrical signals the characteristics of which signals is differentially sampled measured and resolved in terms of amplitude, phase or frequency and converted to digital form to provide the positional X-Y coordinates usable in character recognition.

4. A device as in claim 3 in which coupling between pen signal generating and receiving means and detecting means is achievable by mixing two different electro-magnetic frequencies together in a suitable detector circuit to produce an intermediate frequency in said circuit.

5. A device as in claim 3 and 4 wherein said pen signal generating means includes a beat frequency oscillator stage having a fixed reference oscillator operable at one fairly high frequency, that is to say of the order of kilohertz rather than hertz, and a variable oscillator stage operable at a higher or lower frequency to said first oscillator and energising a miniature search coil mounted within the barrel of the special pen such that signal coupling may be effected with the pen at some distance above the writing board.

6. A device as in claims 2, 3 and 4 in which the pen signal receiving means comprises a dual arrangement of microprocessor controlled switchable arrays of elongated rectangular looped antennae, one co-ordinate array being transverse to the other co-ordinate array, and located beneath or within the writing board surface by means of etched conductive tracks etched on one or more copper clad circuit boards.

7. A device as in claim 6 wherein the signals received in said antennae are routed to said detecting means via CMOS analogue transmission gates or bilateral switches, said switches being switchable under microprocessor control in any desired order, sequence or combination to permit sampling, measurement and conversion of detected signals to digital form.

8. A device as in claim 7 wherein signal detecting means includes a duality of said detecting means which may incorporate a peak level sensing means and provides amplification, mixing and differencing of detecting signals.

9. A device as in claims 1,2 and 3 programmable for various modes of operation including a generalised character recognition mode, an individualistic or stylized character recognition learning mode, and specialized job function executing mode for operating on particular data.

10. A device as claim 9 wherein stylized character samples for recognition by the device in learning mode are loaded interactively by use of the special pen in response to pre-programmed prompts including an agreed protocol for dealing with ambiguities, subjected to verification routines and the character patterns thus learned are stored in random access read/write memory.

11. A device as in claim 10 in which interactively learned and developed recognition programs may be output via device port means and copied onto external storage means including conversion of such data to optical bar code form.

12. A device as in claims 9 and 11 in which developed programs for character recognition and job function routines stored externally of the device in bar code form may be reloaded into the device by means of a light pen responsive to such code.

13. A device as in claim 2 wherein said pen includes a contact pressure on/off switch responsive to strain or resistive changes and activating suitable logic gating to indicate when the pen is in contact with the writing surface.

14. A device as in claim 1 and 2 and including demountable register pips or clamp mechanism accessories for holding writing sheets and padded forms in secure consistent pre-defined registered position on the writing board surface, and for securing film overlays bearing programmable legends.

1 5. a device as in claim 2 wherein the modular housings are interconnectable by means of sprung mounting posts to permit expansion of the capabilities.

16. A programmable hand written character recognition device programmable and operable in a variety of ways and substantially as herein described with reference to the accompanying drawings.