Computerized Handwriting Duplication System

The present invention relates to a system for duplicating handwriting, and in particular relates to a programmed, general purpose digital computer for capturing in memory a digitized handwriting sample, such as a signature, and for driving a plotter to replicate that signature.

In today's modern society where there is a wide use of the mail system for sending substantially the same letter to a large number of different addressees, there is a need for replicating an actual signature on each letter in order to enhance the credibility of the letter. On the other hand, it would be nearly impossible for the sender of the letter to sign literally thousands of such letters. For example, heads of large organizations or companies often send letters to each of their employees or members, respectively, and like to have the personal touch of an actual signature. Similarly, members of Congress send out large numbers of letters to their constituents and if they had to sign each letter, they would spend a large part of their time doing nothing but signing the letters. Other uses would be in the advertising field by, for example, charitable organizations soliciting contributions, or companies advertising their products through the mails.

With the modern age of computers and multiple printers, a large number of individually typewritten letters can be mass produced. Such letters would largely loose their effectiveness unless they were "signed" with an authentic signature. In addition, occasionally there is the desire to handwrite a postscript to the letter below the signature. Obviously, the time requirements for such activity could be prohibitive to the sender.

This problem has been solved, to some extent, by prior art machines which are basically analog devices that "trace" a previously written signature. While these analog machines have generally proven to be satisfactory, they do have a number of drawbacks and disadvantages. For example, they tend to be extremely heavy, and thus not readily portable. Secondly, the machine is fairly limited to a simple signature and thus could not be used also to "handwrite" a message in the form of a note or postscript to a typed letter. Furthermore, these machines are fairly singular in their use, thereby requiring a relatively large capital expenditure for a singular use. Other disadvantages include the difficulty in providing, on the one hand, security and, on the other hand, easy accessibility by authorized persons and easy reproduction of any one of a plurality of signatures or handwritten messages.

The present invention provides a method and apparatus for replicating a handwritten word at a determinable location on a piece of paper. Such a word can include a person's signature as well as a handwritten note by that person. The present invention utilizes a computer connected to a means for providing a plurality of coordinate points that together represent the handwritten word. In a preferred embodiment, the computer refines the raw data received from the coordinate producing means and provides the refined data to a plotter which replicates the handwritten word at a predetermined location on a piece of paper. The refined data points are stored in a memory that is accessible by the computer, which in a preferred embodiment is a floppy disc. The computer is a general purpose, programmable computer that is controlled by a computer program according to the present invention.

Thus, the present invention provides a readily transportable computer program and data base that can be utilized on any compatible general purpose, programmable computer. In a specific embodiment of the present invention, the computer program includes a security subroutine which is used to assign a security code to each handwritten word or signature, and which, before it will drive the plotter to replicate the signature requires the correct presentation of that associated security code.

In a preferred embodiment of the invention, the handwritten word is written on a digitizer pad that produces a plurality of raw coordinates which together represent the handwritten word. The computer operating under the computer program refines the raw coordinate data by adjusting certain data points that fall outside a predetermined value so as to smooth a line connecting all the coordinates. The raw coordinate data is also compressed by the computer program by deleting coordinates that are not relevant. The raw data is further refined by translating it from absolute values to relative values. According to the method of the present invention, the coordinates are produced of a plurality of representative points which when connected by a line replicate a handwritten word. The plurality of point coordinates are stored in a memory of a digital computer. The handwritten word is replicated by providing a piece of paper to a plotter which has a writing implement associated therewith, providing the computer with the starting location on the paper of where the word is to be begun, and using the computer to provide the starting location and the plurality of point coordinates to the plotter so as to drive the plotter and the writing implement from the starting location to produce the handwritten word on the paper.

Other features, objects and advantages of the present invention are set forth in or are apparent from the detailed description set forth hereinbelow.

FIG. 1 is a schematic block diagram of an apparatus for duplicating a signature according to the present invention;

FIG. 2 is a top plan view of a digitizer pad depicting the layout of the pad for use with a computer program according to the present invention including the layout of an input keyboard;

FIGS. 3A, 3B and 3C are photoduplications of three signatures, FIG. 3A being a duplication of the actual signature as written by D. L. Hardin, FIG. 3B being a replication of the signature of FIG. 3A by an embodiment of the present invention in which the greatest amount of smoothing was utilized, and Fig. 3C being a replication of the signature of FIG. 3A in which there has been no smoothing; FIG. 3D is an enlarged portion of FIG. 3C; and FIG. 3E is an enlarged portion of FIG. 3D, both used to illustrate the smoothing algorithm utilized by the present invention;

FIG. 4 is a schematic flow chart of the main menu of a computer program according to the present invention;

FIGS. 5, 6 and 7 are a schematic flow chart of the program routine used to replicate a signature;

FIGS. 8, 8A and 8B, collectively, and FIGS. 9 and 10 are schematic flow charts of the signature recording program routine;

FIG. 11 is a schematic flow chart of the program routine for displaying the log of the history of a particular signature file;

FIG. 12 is a schematic flow chart of the program routine that erases a signature file;

With reference now to the figures in which like numerals represent like elements throughout the several views, and in particular with reference to FIG. 1, a computerized hardware duplication system 10 is depicted. System 10 is based on a general, programmable digital microcomputer 12. Microcomputer 12 can be any one of a number of commercially available microcomputers, such as an IBM PC brand computer or a compatible thereto. Microcomputer 12 is bidirectionally, electrically connected to a RAM buffer 14 and a program memory 16 which can be a ROM. Alternatively, program memory 16 can be a floppy disc or hard disc, and then when the program is needed it can be transferred to the directly accessible RAM memory of microcomputer 12. Microcomputer 12 also includes off-line memory such as disc memory 18. Disc memory 18 can be either a hard disc or a floppy disc driven by appropriate mechanical drives.

Input is provided to microcomputer 12 through a digitizer pad 20 and stylus or cursor 22. An operating embodiment of the present invention used a commercially available digitizer pad manufactured by the GTCO Corporation of Rockville, Md. The signatures reproduced as FIGS. 3B and 3C were produced by GTCO digitizer pad Model DIGI-PAD 5. This digitizer pad is fully described in the DIGI-PAD User's Manual Serial Number 21A71D4, Revision E dated Feb. 29, 1984.

The DIGI-PAD digitizer pad 20 operates on an electromagnetic principle based upon measuring the time for an electromagnetic signal to travel down an axis. The wave front is generated by a rapidly switched current signal in a matrix of conducting wires embedded in a rigid tablet. The electromagnetic wave is used to produce an absolute coordinate system of information. The DIGI-PAD system also includes a stylus or cursor having an inductance coil which is operable at high signal switching levels. The DIGI-PAD digitizer pad utilizes a complex signal that is induced in the cursor coil by an electromagnetic field created by the sequentially pulsed current applied to consecutive tablet matrix wires. This system provides a means for measuring the cursor position relative to an aribitrary reference point or orgin on the tablet (which for Digi-Pad 5 is located in the lower left hand corner as seen in FIG. 2) as a result of the linear relationship between the distance and time the current signal arrives as sensed by the cursor coil. The electronics provided with the digitizer pad, which is disclosed in greater detail in the aforementioned user's manual, utilizes a precision clock source set to a digital counter at the moment the electromagnetic signal passes the tablet reference point. The count in the clock is frozen when the detection circuitry connected to the cursor coil senses the phase reversal that occurs when the current signal sweeps past. The contents of the counter then contains a number that is precisely related to the cursor position on the cursor pad. The digitizer pad also contains a Cartesian X-Y scanning system to determine the horizontal and vertical positions.

The DIGI-PAD digitizer pad also produces two positive signals that are indicative of the relative location of cursor 22 with respect to the surface of pad 20. The pad produces a "one" together with location information when cursor 22 is in contact with digitizer pad 20 and produces a "zero" together with location information when cursor 22 is located proximate to the surface of digitizer pad, but not in contact therewith. In a preferred embodiment of the present invention, the contact indication is provided by a switch located in cursor 22, which switch is activated by pressing cursor 22 against the surface of digitizer pad 20. A third type of indication is also possible from digitizer pad 20 when cursor 22 is not located proximate to the surface of digitizer pad 20. This indication is simply the transmission of no location information. If microcomputer 12 were receiving information from digitizer pad 20 starting at a timed pulse and no information were received until a known time interval later, then this lack of received information would be indicative of cursor 22 being not proximate to the surface of digitizer pad 20. For the DIGI-PAD 5 digitizer pad, the proximate lock height is one inch. Such a pad has a maximum scan rate of 200 X and Y points per second with a resolution and repeatability of 0.001 inches.

To "write" the signatures in FIGS. 3B and C, the Digi-Pad 5 digitizer pad was configured to provide 200 coordinate pairs of continuous information per second at a Baud rate of 9600 with parity disabled and using an eight bit character in the serial Input/Output RS232 mode. It was also configured to include a pushbutton code with space and carriage return, but no line feed, with a five digit ASCII, high resolution packed binary character of inch data being transmitted.

With reference to FIG. 2, the top surface of digitizer pad 20 is depicted. Digitizer pad 20 is utilized not only for recording a signature or other written note, but also for providing input commands to microcomputer 12. Digitizer pad 20 includes a paper location area 24 outlined by a perimeter border 26. Area 24 in the presently preferred embodiment is 81/2 inches by 11 inches so that a standard sheet of paper can be accurately located. Located inside border 26 is a signature rectangle 28 having a signature line 30, the beginning of which is marked with an "X" 31. By defining the location for placing the signature, a more simplified computer program, described below and disclosed in the microfiche appendix, can be used with digitizer pad 20, to accurately locate the signature when it is being recorded and to cause it to be accurately reproduced at a different, and usually lower, location on paper. This simplification results from the use of a constant offset from "X" 31 to a point that is indicated in area 24 by an operator using cursor 22, as described in greater detail hereinbelow.

Digitizer pad 20 also has a keyboard area 32 which contains three types of indicia: alphabet, numbers, and commands. The alphabet indicia are located in the upper portion of keyboard area 22 and each letter of the alphabet is located in its own square, such as alphabet square 34 for the letter "A". The numbers of keyboard area 32 are located in a midportion thereof with each number being in its own numerical square, such as numerical square 36 for the number "9". Keyboard 32 is also provided with four commands, three of which are located in the lower portion thereof. These are the "yes" command box 38, the "no" command box 40 and the "reset" command box 42. However, for ease of use, a forth command box 44 for the command "enter" is located between alphabet squares 34 and numerical squares 36.

Althought the operation of keyboard area 32 is described in greater detail hereinbelow, for ease of understanding the present invention the use of keyboard area 32 will be described now. As mentioned above, when cursor 22 is placed anywhere within the active area of pad 20 and in proximity to the surface thereof, the coordinates of the location of the tip of cursor 22 is provided by the counter of the electronics of pad 20 when cursor 22 senses the travelling current pulses. Thus, it should be obvious to those skilled in the art that, for example, the letter "A" can be provided to the computer simply by placing cursor 22 over the area defined by "A" and then using software to decode the received position information of cursor 22 with the known position of the "A" square 34.

Returning to FIG. 1, computerized handwriting duplication system 10 further comprises two output devices, a video monitor 46 and an X-Y plotter 48. Video monitor 46 is a standard, commercially available video monitor together with a video board located in microcomputer 12. In the present embodiment of the invention, video monitor can simply be an alphanumeric monitor and need not be a color or graphics quality monitor.

Plotter 48 is a conventional, commercially available X-Y plotter, such as Model 595 manufactured by Houston Instrument, Inc. of Austin, Tex., and described in their publication entitled "PC Series Digital Plotter Operation Manual" No. MI-1050 (1984). For the purpose of describing the presently preferred embodiment of the present invention, the Houston Instruments plotter will be described. This plotter is a small, rugged plotter designed for use with personal computers, such as the IBM PC computer. The plotter uses the Houston Instrument Digital Microprocessor Plotting Language (DM/PL) for operation with the microcomputer. Such plotter is a tabletop unit with all electronic circuitry provided. The plots can be produced on standard sized paper (81/2 by 11 inches) by moving the plotting paper vertically in and out and moving the drawing pen transversely back and forth to produce the desired plot. The plotter receives its operating instructions from the microcomputer using standard RS-232C signals. The Model 595 plotter also has a provision for using and selecting one of four different pens. This is done by mounting the four pens on a rotatable housing that can be controlled by the host computer. The plotter has a buffer of 256 bites and utilizes 7 data bits with a selectable one parity bit and two stop bits. The model 595 plotter used to replicate signatures in FIGS. 3B and C was configured with a 9600 baud rate for data with no parity and bit number 8 to set to a 1. In performance, it has a maximum speed of 3 inches per second in the axial direction and 4.2 inches per second in the diagonal direction, and has an addressable resolution of 0.001 inches, 0.005 inches, 0.1 mm, or 0.025 mm. The plotter has grit wheels and pinch wheels for grasping the paper while plotting. The grit wheels have small particles on their periphery which make small indentations in the paper, thereby preventing slippage while plotting. The plotter can be manually fed, one sheet at a time, or can be coupled to a paper feeder.

In the embodiment depicted in FIG. 1, plotter 48 is coupled to an automatic paper feeder physically mounted on top of plotter 48 and feeds one sheet of paper at a time. Paper feeder 50 receives software commands from microcomputer 12 and provides status signals back to microcomputer 12. Similarly, plotter 48 receives its programming commands and data commands from microcomputer 12 and returns status commands to microcomputer 12.

With reference now to FIGS. 4 through 12, and also to the appendix, the computer program which operates system 10 will now be described. Initially, it is noted that the computer program is written in Microsoft basic to be run under the MSDOS operating system. With respect to FIG. 4, a main menu selection routine 80 is depicted. When the computer is powered up, an autoexec.bat program (not shown) in the DOS operating system causes computer 12 to load main menu routine 80 into program memory 16. The main program begins in process box 82 where an introductory message is displayed on video monitor 46 (see Appendix, beginning at line 240). The screen of video monitor 46 is then blanked and a message of "Good morning, afternoon or evening", as the case may be, is displayed together with the message "Do you want to use a previously recorded signature?; (yes/no)". The program then proceeds to decision box 100 while the program awaits an answer from the operator.

The operation of the choice selection and entry will now be described. As soon as an entry is made by touching cursor 22 to the appropriate command box 38, 40 or 42 (FIG. 2). The program branches to subroutine 5200 (see program listing) where the keyboard entry is denoted "CHOICE$" and the program calls subroutine at line 12470 of the program listing. This subroutine returns the selected key pad item and first initializes the possible variables. When the digitizer pad 20 is touched, an interrupt is sent to the program and the program branches to a third nested subroutine at program line 12400 (because the GTCO digitizer pad is being used). At this subroutine, the point touched on digitizer pad 20 is called XY$ by the statement:

XY$=input$(13,#1).

The program then converts data to inches with the command:

XD=0.001*VAL(MID$)XY$,2,5)): YD=0.001*VAL(MID$)XY$,8,5)).

The program executes a coordinate transform to convert the absolute value received to the overlay orientation as depicted in FIG. 2. For the present example, this is simply the program line:

X=11-YD: Y=XD.

The point touched on the digitizer pad has now been converted to inches and transformed to the proper X-Y coordinate system. The program checks beginning with program line 12500 whether the point coordinates that have been provided by cursor 22 touching digitizer pad 20 are within the limits of the key pad area. Depending upon which one of a series of IF THEN tests are true, the appropriate subroutine is called. Since presumably a command box has been touched, the program will branch to program line 12710 where the program converts the entered point into a position within the appropriate function area and where entries falling near the boundary lines are eliminated. The program lines for making these calculations are as follows:

YC=Y/1.5-INT(Y/1.5): XC=X=0.5-INT(X=0.5)

IF YC<0.04 or YC>0.96 OR XC<0.05 OR XC>0.95 THEN RETURN FUNC=CINT(X-7)

IF FUNC=1 THEN CHOICE$="YES": GOTO 12810

IF FUNC=2 THEN CHOICE$="NO"; GOTO 12810

IF FUNC=3 THEN CHOICE$="RESET": GOTO 12810

The first two lines check that the point is not within 0.05 inches of the line. The next line rounds the input point to an integer and then substracts 7 from it and the remainder will either be a 1, representing the choice of "yes", a 2 representing the choice of "no" or a 3 representing the choice of "reset". The function has now been selected and it is printed on the screen of monitor 46 and the program responds appropriately.

Hence, referring again to FIG. 4, if the yes selection is touched by the operator, as shown in decision box 100 the program branches through an off page connector 102 to FIG. 5. If the no selection is touched, the program proceeds to a decision box 200. Finally, if the reset command box 42 is touched, the program branches back to the top of decision box 100.

Assuming that the operator selected the "yes" option to the question of whether a previous signature is to be used, the program branches to the "USE" routine and enters process box 104. In process box 104, the program displays all of the signatures which are presently stored on the floppy disc in the default disc drive of microprocessor 12, indicated as disc memory 18. In decision box 106, the program ascertains from the operator whether the desired signature is on the file. At this point, the operator can select reset, in which case the program branches through off page connector 84 back to the main menu routine 80 of FIG. 4. If the operator positions cursor 22 on NO command box 40, the program branches through off page connector 107 back to FIG. 4 and into decision diamond 200 where the main menu asks whether the operator wishes to record a new signature. Assuming that the operator selects the "YES" command box 38 with cursor 22, the program then enters process box 108 where the program causes the screen of video monitor 46 to display a request for the entry of the identification of the desired signature. The signature file identification is provided by the operator touching the appropriate alphabet square 34 or numerical square 36. On the other hand, the operator can also select reset command box 42 in which case the program immediately branches back to FIG. 4 through off page connector 84, or can select the "NO" command box 40 in which case the program branches back to the top of process box 108. When the operator selects the appropriate alphanumeric square, the program uses a similar locating subroutine as described above with respect to the command boxes 38, 40 and 42.

To summarize, the program first makes an in-bounds check and then uses a similar mathematical algorithm to check for the particular alphanumeric square that has been touched. Once the selection has been decoded, the selection is displayed on video monitor 46. The program waits until another alphanumeric box is selected, thereby repeating the foregoing process, or until the enter command box 44 is selected. Once the enter command box 44 is selected, the program continues to decision box 110 where the program checks whether the requested signature is present. If the requested signature is not present, the program branches to process box 112 where the program causes video monitor 46 to display the message "insert proper disc and touch `yes` when okay", and then branches back to the top of process box 104.

If the signature is present and the operator enters the response "yes" by touching cursor 22 to command box 38, the program will continue to process box 114. In process box 114 the program requests the entry of the security code corresponding to the signature identification. However, the operator can also select the "reset" command box, whereupon the program branches back through off page connector 84 to FIG. 4. As with the selection of the signature identification, the operator, if an error is made, can restart the security code by touching "NO" command box 40. Also as with the entry of the signature identification, the selection of the appropriate alphanumeric square will result in the selection being displayed on video monitor 46. The process will continue until the "enter" command box 44 is touched.

When the enter command box 44 is touched, the program will branch to decision box 116 whereupon the program will check the security code. If the code is incorrect, the program will index a counter so that no more than three tries or guesses at the security code can be attempted. The program does this in decision box 118 and if the number of tries is greater than or equal to three, the program branches back to FIG. 4 through off page connector 84. If the number of tries is less than three, the program branches back to the top of process box 114 where the operator is again asked to enter the security code. Assuming the security code is correct, the program continues to process box 120 where the programs asks the number of signatures which the operator wishes to have written. Again, the operator is given the opportunity to change his or her mind by selecting the "no" command box 40, in which case the program branches back to the top of process box 120. Alternatively, the operator can touch the "reset" command box 42 whereupon the program branches back to FIG. 4 through off page connector 84.

As described above, the program will decode the selected number depending upon which numerical square 36 cursor 22 touches. If the wrong square is touched, (e.g. alphabet square 34) the program indicates an error and again asks for the number of signatures to be written. The selected numbers are displayed on video monitor 46 and the program continues as soon as the "enter" command box 44 is touched. The program then determines in decision box 122 whether one or greater than one signatures have been selected and the program branches respectively through off page connector 124 and 126 to the appropriate routine depicted in FIG. 6 or FIG. 7.

If the operator selects just one signature to be replicated, then the program continues through off page connector 124 to FIG. 6 where the software in process box 128 asks the operator to place the cursor 22 on digitizer pad 20 at the location where the signature is to be replicated. The operator is also given the choice to touch "reset," whereupon the program branches through off page connector 84 to the main menu depicted in FIG. 4. As soon as the operator touches digitizer pad 20 with cursor 22, the program calculates where the signature is to be placed and then enters decision box 130 where a determination is made whether the entire signature will be within the boundary capabilities of plotter 48 (FIG. 1). If the program calculates that the signature will not be within proper bounds, then the program branches to decision box 132 where the operator is asked whether the signature should be used anyways. If the operator touches the "reset" command box 42, the program branches back to the main menu through off page connctor 84. Alternatively, if the operator selects "no" command box 40, then the program branches back to the top of process box 128 where the procedure is repeated. If the program determines in decision box 130 that the signature is within the boundary limits, or if the operator indicates to use the signature anyway, the program proceeds to process box 134 where paper feeder 50 is commanded to feed a sheet of paper to plotter 48. The program then proceeds to decision box 136 where the program determines whether there is a print ready command from the plotter 48. Typically, plotter 48 provides such a command by using a hardwired handshanking signal connected to microcomputer 12 as an input signal.

If the program determines in decision box 136 that plotter 48 is not ready, the program branches to process box 138 where the program runs the "not ready" routine. This routine notifies the operator by displaying a message on video monitor 46 that the plotter is not ready and that the operator should attend to the error condition. The program then branches back to the top of process box 134 where the program waits until it receives an indication that the paper has been properly fed. If the program determines in decision box 136 that plotter 48 is ready, the program proceeds to process box 140 where the program instructs plotter 48 to feed the paper and commence printing the signature at the location indicated by the operator in process box 128. It is noted that the paper which is fed is usually a typed letter that simply needs a signature or handwritten postscript before it can be sent.

The program proceeds from process box 140 into a timing loop 142 whereupon if no interruption is indicated the program branches back to the top of process box 128 through on page connector 144. On the other hand, while the signature is being printed, video monitor 46 displays a message instructing the operator that the process can be halted by touching "reset" command box 42. Should the operator thus respond, the program is interrupted and proceeds to process box 146 where the program halts and displays a message to the operator on video monitor 46 to indicate by touching "reset" command box 44 if the operation is to be terminated or the "yes" command box 38 if the single signature mode is to be rerun. If the operator touches the "yes" command box 38, the program branches through on page connector 144 back to process box 128. On the other hand, if the operator touches "reset" command box 42, the program branches to decision box 148 where the operator is asked whether the same signature is to be reused. If the operator touches "reset" command box 42, the program branches through off page connector 84 back to the main menu routine of FIG. 4. On the other hand, if the operator touches the yes command box 38, then the program branches back through off page connector 150 to the use routine depicted in FIG. 5 at the top of process box 120, where the operator is again asked to enter the number of signatures to be written.

If in decision box 122, FIG. 5, the program determines that the operator has requested more than one signature, then the program branches through off page connector 126 to FIG. 7. The program proceeds through the same initial steps beginning with process box 128 and continuing through process box 140 as described above with respect to FIG. 6 for a single signature replication. However, from process box 140, as shown in FIG. 7, the program proceeds to decision box 152 where the computer keeps track of the number of signatures that have been printed. If the number of signatures which has been completed is not equal to the number indicated by the operator in decision box 122, FIG. 5, the program branches back to the top of process box 134. As the program controls plotter 48 to write the signatures on a plurality of sheets, the operator is kept apprised of the progress by the message "Printing #.sub.-- of .sub.-- ; touch reset to terminal" being displayed on video monitor 46. Thus, the program indicates not only the number of pages to be printed, but also the current page which is being printed. As in the subroutine for the single signature replication, the operator can terminate the job at any time simply by touching reset command box 42 with cursor 22. The program poles digitizer pad 20 upon completion of each signed sheet. If it detects that the reset command box has been touched, the program branches to decision box 154 where the following message is indicated:

job temrinated at number .sub.-- of .sub.--

touch yes to resume current signature

touch reset to start another job.

Thus, if the operator touches yes command box 38, the program branches back to the top of process box 134. If either the no or reset command boxes 40 or 42 are touched, the program branches to decision box 156 where the program asks the operator to indicate whether the current signature should be reused or whether another job is to be started. If the operator touches reset command box 42, the program branches through off page connector 84 back to the main menu in FIG. 4. On the other hand, if the operator indicates that the current signature is to be reused, the program branches back through off page connector 150 to the top of process box 120 in FIG. 5.

Returning again to FIG. 4, as mentioned above, the program asks the operator in decision box 200 whether a new signature is to be recorded. If that is the case, a program branches through off page connector 202 to FIG. 8 where the program enters the signature recording routine, and in particular a capture subroutine 204, which is depicted in FIG. 8A.

Subroutine 204 begins in process box 206 where the program first initializes digitizer pad 20, sets up ram buffer 14, and prepares the system to commence accepting a large number of data points at the rate of 200 points per second. Then, the program gives the operator a start tone and begins to receive data. As mentioned above, the computer will receive data from the digitizer from the commencement of the start tone. If cursor 22 is not located proximate to the surface of digitizer pad 20 (about an inch above the top thereof), then no data will be sent to the computer and effectively only zeros will be stored. When cursor 22 is located proximate to digitizer pad 20, but is not pressing on the pad, digitizer pad 20 will give a "pen down" signal. When cursor 22 is pressing down on digitizer pad 20, a switch is thrown therein and a "pen down" signal is produced by digitizer pad 20. Thus, from process box 206 the program proceeds to a decision box 208 where the program awaits the receipt of a "pen up" or a "pen down" signal. If neither signals are present, the program will branch to process box 210 and will load a zero in buffer 14. After a time delay (of about 0.005 second), the program branches back to the top of decision box 208. As soon as digitizer pad 20 indicates that cursor 22 is proximate thereto, the program determines in decision box 208 whether a "pen up" or a "pen down" signal has been received. If a "pen up" signal has been received, the program in process box 212 prefaces the X-Y coordinate received from digitizer pad 20 with a zero, then in process box 214 stores the number in buffer memory 14. The program then proceeds to decision box 216 where the program again determines whether cursor 22 is not proximate to digitizer pad 20. As long as cursor 22 is proximate to but not touching digitizer pad 20, the program continues to loop to the top of decision box 208. When the program receives a "pen down" signal, it branches to a process box 216 where it prefaces the X-Y coordinate received from digitizer pad 20 with a "1". The program then proceeds as described above by storing the received number in buffer memory 14, and determining whether cursor 22 is not proximate to digitizer pad 20 in decision box 216.

Thus, it can be seen that in the process of a person signing his or her signature, initially a number of zeros will preceed the raw data received from digitizer pad 20. Then, a number of coordinates preceeded by a "0" will be stored, and finally, a number of coordinates preceeded by a "1" will be stored. As the signature is being written, the pen may be lifted from the surface of digitizer pad 20, such as to begin a new word or to dot an "i." At that time, cursor 22 still remains proximate to digitizer pad 20, but the pen down signal is no longer received. Therefore, the digitizer pad still produces an X-Y coordinate, but the program through decision box 208 in process box 212 will preceed the coordinates with a "0." As soon as cursor 22 is again placed into contact with digitizer pad 20, the pen down signal will be received and the coordinates will be preceded by a "1." When the signer is done with the signature or other handwritten message, cursor 22 is lifted away from being proximate to digitizer pad 20 and the program determines in decision box 216 that the cursor is no longer proximate to the surface of digitizer pad 20. At this point, the program returns through terminal 217 to the record routine depicted in FIG. 8.

An example of such raw data is depicted in appendix 1. This data represents the signature written in FIG. 3a.

When the program returns to the record routine in Fig. 8, it enters a decision box 218 to determine whether the recording is complete. When the recording is complete, the program branches to decision box 220 where the program determines whether to accept the data or not. Basically, the program simply checks all of the data received to make sure that it is in the correct format. The expected format is blocks of 12 digits where the first digit of the block is a zero or one, the next five digits are the absolute position in ten thousandths of an inch in the X direction, then a space, then five digits to indicate in tens of thousandths of an inch the absolute position in the Y direction. If the data is unacceptable, the program provides that message on video monitor 46 that the operator should either touch reset command box 42 or the no command box 40 depending upon whether the operator desires to return to the main menu depicted in FIG. 4 or whether the operator wishes to try again and record another signature. If the data was received in the correct format and is acceptable to the program, the program proceeds to subroutine box 222 where the program processes the data and tests the data further. The refine subroutine is depicted in greater detail in FIG. 8b. First, the subroutine proceeds to process box 224 where the program compacts the data by deleting all coordinates that have a leading zero. Then the subroutine calls a nested subroutine in subroutine box 226 for smoothing the compacted data. The smoothing subroutine is described in greater detail hereinbelow with respect to FIG. 3. Smoothing subroutine 226 also changes the data from absolute to relative and further inserts the computer commands necessary to operate plotter 48. From subroutine box 226, the program stores the refined data to disc in storage box 228. An example of refined data obtained from the raw data listed in appendix 1 is shown in appendix 2, and is explained in greater detail hereinbelow. From storage box 228, the program proceeds to terminal 230 where the program returns to the main subroutine depicted in FIG. 8 and enters decision box 232.

The program in decision box 232 asks the operator whether the signature should be accepted or not. If the operator touches the yes command box 38, the program proceeds to decision box 234 where the program asks the operator whether the operator desires a sample plot or not. If the data is not acceptable, the program branches to decision box 236 where the program asks the operator whether the signature is to be redone. If the operator indicates yes, then the program branches back to the top of subroutine box 204. If the operator touches no or reset command boxes 40 or 42, the program branches back through off page connector 84 to the main menu routine of FIG. 4. If when the program is in decision box 234, the operator indicates that no sample plot is desired, the program also branches back to the main menu routine of FIG. 4 through off page connector 84.

If the operator responds that a sample plot is desired, the program then proceeds through a series of steps similar to steps in process boxes 134 through 140 of FIG. 6. Therefore, from decision box 234, the program proceeds to process box 238 where the paper is prefed from paper feeder 50 to plotter 48 (FIG. 1), the program waits in decision box 240 until the paper is ready, and then in process box 242 the program commands plotter 48 to feed and print the paper. From process box 242 the program proceeds to a decision box 244 where the operator is asked whether the sample signature is to be saved or not. The operator has three choices. If the operator touches reset command box 42, the program returns to the main menu routine of FIG. 4 through offpage connector 84. If the operator touches the yes command box 38, the program branches through off page connector 246 to a continuation of the recording routine depicted in FIG. 9. If the operator touches the no command box 40, the program branches through off page connector 248 to a reprocess subroutine depicted in FIG. 10.

Continuing the recording routine in FIG. 9, the program enters input box 250 where the operator is asked to supply the identification for the desired signature. The operator can supply a signature identification of either letters or numbers by touching the appropriate alphanumeric squares 34 or 36 on digitizer pad 20. These letters and numbers are decoded as described hereinabove. Alternatively, the operator can touch reset command box 42 if a particular signature identification is not wanted and the program branches back to the top of input box 250. As the operator selects each letter or number, it is displayed on video monitor 46. When the operator is satisfied with the signature identification, the operator touches the enter command box 42 and the program proceeds to decision box 252. In decision box 252, the program determines whether the identification has been previously used. If the identification has been previously used, the program branches to process box 254 where the message "Identification already used" is printed on video monitor 46. From process box 254, the program branches back to the top of input box 250. If the identification has not been previously used, then the program proceeds to input box 256 where the operator is asked to supply a security code. As with the signature identification, the operator can touch the no or reset command boxes 40 or 42 to reject a selected entry and the program will return to the top of input box 256. When the operator is satisfied with the selected security code, the enter command box 44 is touched and the program proceeds to decision box 458 where the program verifies whether the selected security code is proper or not by checking to see if it contains only acceptable values and is of the correct length, and by asking the operator to enter the security code and then comparing this later entered code with the first selected code. If the code is not proper, the operator is asked whether to abort or to reenter the signature identification and security code. If the operator responds by touching the no command box 40, the program branches back to the beginning of input box 250. If the reset command box 42 is touched, the program branches back to the main menu routine through off page connector 84. If the operator verifies the code and reenters the same code as previously selected, the program proceeds to process box 260 where the signature identification and security code are stored on disc memory 18 (FIG. 1). After saving the signature identification and code, the program proceeds back to the main menu routine through off page connector 84.

With reference now to FIG. 10, the program proceeds through offpage connector 248 from FIG. 8 if the operator indicates that the signature is not to be saved. The program enters decision box 260 and asks the operator whether to reprocess the signature. It is noted, as described hereinbelow, that the operator can select the reprocessing level. This can be done at this time and is described in greater detail hereinbelow.

If the operator indicates to reprocess the signature, then the program proceeds to process box 262 where the operator is requested to select the smoothing level desired. This procedure is also described hereinbelow. As soon as the operator selects the smoothing level by touching the appropriate numerical square 36, and then touches the enter command box 44, the program branches back to the recording routine of FIG. 8 through offpage connector 264 and the data is reprocessed in subroutine box 222 and the subsequent steps repeated.

If the operator selects not to reprocess the data, the program branches to decision box 266 where the operator is asked whether another signature is to be recorded. If the operator touches the yes command box 38, then the program branches back to the top of the recording routine (beginning in FIG. 8) through offpage connector 202. On the other hand, if the operator touches the reset command box 42 when asked by the program when in decision box 260 or 266, then the program branches back to the main menu routine depicted in FIG. 4 through offpage connector 84.

Returning once again to the main menu routine in FIG. 4, if the operator when asked whether to record a new signature in decision box 200 touches the no command box 40, the program proceeds to decision box 300. In decision box 300, the program asks the operator whether a review of the signature log is desired. The program keeps track of all uses of a particular signature file, the particular user and the date and time of use to provide desirable accounting information to the operator. The purpose of the log routine 300 is to provide the information that has been kept to the operator. As with decision boxes 100 and 200, the operator can select "reset", "yes", or "no". If the operator selects "yes", the program branches through offpage connector 302 to decision box 304 (FIG. 11).

In decision box 304, the program instructs the operator to supply the identification of the signature file that is desired. As with other selection procedures, decision box 304 requires the operator to supply the name of the signature identification by touching the appropriate one or ones of the alphanumeric square 34 and 36. The selected square is displayed on video monitor 46 (FIG. 1). If the operator makes a mistake or desires a different identification number, he or she touches the no command box 40, and the program branches back to the top of decision box 304. The operator also has the option of returning to the main menu routine depicted in FIG. 4 by touching reset command box 42, whereupon the program branches through off page connector 84 back to the top of decision box 100 in FIG. 4.

As soon as the operator has selected the identification of the signature file and has touched the enter command box 44, the program branches to decision box 304. In decision box 304, the system checks to see that the signature is on file. If the signature is not on file, the operator is prompted by a message displayed on video monitor 46 to install a new diskette. If the signature identification identifies a signature that is on file, the system proceeds to process box 308 where the log information is caused to be displayed on video monitor 46. When the operator is finished with the display, he or she can touch yes, no, or reset command boxes 38, 40 or 42 to return the system back to the main menu routine depicted in FIG. 4 through offpage connector 84.

Returning to FIG. 4, if the operator touches the no command box 40 when the program box is in decision box 300, the program branches to decision box 400. In decision box 400, the program prompts the operator by displaying a message on video monitor 46 asking if the operator desires to erase a signature. If the operator touches yes command box 38, the program branches through offpage connector 402 to decision box 404 in FIG. 12. Alternatively, the operator can touch reset command box or no command box 42 or 40, whereupon the system returns back to the beginning of decision box 100.

In decision box 404 of the erase routine, the program displays the signatures on the diskette and asks the operator by printing a message on video monitor 46 whether the signature sought to be erased is on file. If the operator touches no or reset command boxes 40 or 42, the system branches back through offpage connector 84 to the main menu routine in FIG. 4. If the operator touches the yes command box 38, the system branches to process box 406 where the operator is instructed to enter the identification code of the signature on file. As the operator selects the appropriate alphanumeric squares 34 and 36, the selected choice is displayed on video monitor 46. If the operator makes an error, the operator can touch the no command box 40 and the program will return to the top of process box 406. When the operator touches the enter command box 44, the program branches to decision box 408. In decision box 408, the program ascertains whether the file for the requested signature identification code is present on the installed diskette. If the file is not present, the program branches to process box 410 whereupon the message "Signature not present" is printed on video monitor 46, and the program branches to the top of decision box 404. If the requested signature file is present, the program proceeds to process box 412. In process box 412, the program requests the operator to verify that the selected signature file is in fact to be erased by displaying an appropriate message on video monitor 46. If the operator touches the no or reset command boxes 40 or 42, the program branches back to the main menu routine through offpage connector 84. If the operator touches the yes command box 38, the program proceeds to process box 414. In process box 414, the program erases the identified signature file and then returns to the main menu routine through offpage connector 84.

As mentioned above with respect to nested refine subroutine 222 (FIG. 8B) of the recording routine, the present invention also involves refining the received signature. The refined subroutine 22 involves not only compacting data but also smoothing the signature in accordance with a preselected, variable amount of smoothing. The algorithm for performing the smoothing function will now be described with reference being had to FIGS. 3A through 3E and Appendices 1 and 2.

As mentioned above, digitizer pad 20 sends 200 points per second to microcomputer 12. After the program has disregarded all points generated when cursor 22 was not touching the top of digitizer pad 20 and "compacting" the remaining points, the program performs a smoothing function on the remaining points Basically, the computer compares all the remaining points in sets of three, beginning with the first point generated, and then proceeding in the direction of the drawn line. FIG. 3A shows a signature of D.L. Hardin as actually written on digitizer pad 20 while the recording routine was being run. The point coordinates which form the signature data as actually received by microcomputer 12 and stored in ram buffer 14 are depicted in Appendix 1, attached hereto. The data as produced does not have carriage returns or spaces between the X and Y coordinates. However, for the purposes of display, a basic program was written to print the data in the format as it appears in Appendix 1. There are six data points listed in each row in pairs of two. Thus, columns A and B represent, respectively, the X and Y coordinates of a single point and columns C and D represent the X and Y coordinates of the next point adjacent to the point appearing in columns A and B.

As soon as the signer position cursor 22 proximate to the top of digitizer pad 20, digitizer pad 20 commenced sending points to microcomputer 12 at the rate of two hundred points per second. Because cursor 22 was not in contact with digitizer pad 20, the first group of points in the uppermost box of Appendix 1 have the X coordinate (i.e. the value in columns A, C, E, G, I and K) preceded by a "0". Thus, digitizer pad 20 sent thirty-eight points to microcomputer 12 from the time cursor 22 was proximate to digitizer pad 20 until the "pen down" signal was sent. The first point in which the "pen down" signal was sent has the coordinates listed in columns E and F in row 7. Thus, the absolute position from the origin of digitizer pad 20, which is in the lower left hand corner thereof, is X=2.976 inches, Y=9.37 inches. This point was generated at location 502 in the signature of FIG. 3A. It can also be seen that the X coordinate in column E is preceded by the number "1" indicating that the "pen down" signal has been received by microcomputer 12. Every five thousandths of a second, digitizer pad 20 sent the coordinates of a point. As can be seen from FIG. 3A, the signers pen moved downwardly toward the bottom left hand corner of digitizer pad 20. Thus it can be expected that both the X and the Y coordinates should decrease. This can be seen in the next coordinate point listed in columns G and H of row 7 whereby the absolute value of the X position changed by two thousandths of an inch toward the left hand side, but the Y position did not change at all. Since each point is sent every five thousandths of a second, the space between points will simply be a function of the time it takes the signer to move the pen over digitizer pad 20. In row 46,. columns G and H, it can be seen that for one hundredths of a second the computer received a pen up signal because the X coordinate is preceded by a "0". Based on a review of the signature, it can be seen that the signers pen did not leave the paper except to place a dot above the i, the dot being denoted by numeral 504. It is believed that the pen up signal received in row 46, as well as the pen up signals received in rows 48 and 49 are probably the result of the signers simply not bearing down on the pen. In any case, they are aberations in the overall signature. It can be noticed that there is a distance between the absolute positions of the point coordinates located before and after the groups of "pen up" coordinates. This is one reason why the signatures should be smoothed with a smoothing program. A further observation is that dot 504 in FIG. 3A can be seen in the raw data in Appendix A in the entire row 56. This means that it took six data points or three hundredths of a second for the signer to dot the "i" of the signature. It should also be observed that the coordinates of the dot are substantially the same, thereby confirming that these data points do indeed designate dot 504.

The operation of the smoothing algorithm will be briefly explained with reference to FIGS. 3D and 3E. Basically, the computer compares all of the points in sets of three, beginning with the first point generated and then proceeding in the direction of the drawn line. After performing the smoothing function on the first three points, the remote end point is dropped and a new set of three points is considered by adding the next point along the line. Thus, as shown in FIG. 3E, the first set of three points are 506, 508, and 510, and the second set of three points are 508, 510 and 512.

For each three point set, the computer calculates the equation for a straight line using the two end points. Next, the computer calculates the perpendicular distance, delta d, that the midpoint is off the calculated line. As shown in Fig. 3E, delta d is the distance between point 510 and dashed line 512 in a direction that is perpendicular to line 512 as indicated by dash line 514. The perpendicular distance, delta d, is then compared with a predesignated tolerance value, and if that tolerance value is exceeded, then the coordinates of the midpoint, 0.510 in FIG. 3E, are changed to bring the perpendicular distance, delta d, to within the selected tolerance value. In the present embodiment of the present invention, the selected tolerance values are from a maximum smoothing of 0.001 inches to 0.005 inches, in steps of 0.001 inches, for the least amount of smoothing.

FIG. 3B represents the result of the program applying the maximum amount of smoothing to the signature written and appearing in FIG. 3A. On the other hand, FIG. 3C is the plotted signature corresponding to that plotted in FIG. 3B, but without any smoothing whatsoever.

As mentioned above, after the smoothing algorithm has been performed on all of the received raw data, the program calculates the relative distance between points. This is done because plotter 48 operates faster using relative points than using absolute points, although the latter could also be used. In addition, it is noted that the smoothing algorithm is performed on the absolute data (see program line 15080 in the microfiche) because it is simplest. However, the program could also smooth after the relative values are calculated. The part of the program that calculates the relative values begins at line 15280 of the program. In addition, as can be seen from Appendix 2, the smoothing subroutine also supplies printer commands. The program first applies the command "A" to indicate that the following two data points are absolute values. The program supplies the absolute value for the first set of coordinates received after a pen down signal has been received. Following the absolute value, the program supplies the commands "R" and "D" to instruct plotter 48 that the subsequent points are relative movement positions from the preceding point and to place the plotter pen into contact with the paper, respectively. When a pen up signal is received after a pen down signal, the program supplies the commands "U" and "A" after the relative data point to instruct the plotter to raise the plotter pen from the paper and to move to the absolute position given by the next coordinate. All of the plotter commands in Appendix 2 are circled. It is noted that the set of points for the signature having the identification of "DLH100" and the identification "DLH5" represent the actual coordinates which were used to plot signatures in FIGS. 3C (where there was no smoothing) and FIG. 3B (where there was maximum smoothing). Appendix 3 contains a computer program listing.

The present invention has now been described with respect to a presently preferred embodiment thereof. Obviously, other features and modifications of the present invention would be apparent to those skilled in the art. ##SPC1##