CA1080325A - Automatic coordinate determining device - Google Patents
Automatic coordinate determining deviceInfo
- Publication number
- CA1080325A CA1080325A CA253,195A CA253195A CA1080325A CA 1080325 A CA1080325 A CA 1080325A CA 253195 A CA253195 A CA 253195A CA 1080325 A CA1080325 A CA 1080325A
- Authority
- CA
- Canada
- Prior art keywords
- signal
- conductive lines
- maximum
- signals
- scanning
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 239000000523 sample Substances 0.000 claims abstract description 44
- 230000001939 inductive effect Effects 0.000 claims abstract description 25
- 238000004804 winding Methods 0.000 claims description 26
- 238000001514 detection method Methods 0.000 claims description 24
- 230000003534 oscillatory effect Effects 0.000 claims description 20
- 230000015654 memory Effects 0.000 claims description 14
- 230000004044 response Effects 0.000 claims description 10
- 238000001914 filtration Methods 0.000 abstract 1
- 238000010586 diagram Methods 0.000 description 14
- 239000000543 intermediate Substances 0.000 description 5
- 241001422033 Thestylus Species 0.000 description 4
- 230000005284 excitation Effects 0.000 description 4
- 238000000034 method Methods 0.000 description 4
- 230000005674 electromagnetic induction Effects 0.000 description 3
- 230000001965 increasing effect Effects 0.000 description 3
- 238000010276 construction Methods 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 230000004907 flux Effects 0.000 description 2
- 230000006870 function Effects 0.000 description 2
- 230000000149 penetrating effect Effects 0.000 description 2
- 230000002441 reversible effect Effects 0.000 description 2
- 101150087426 Gnal gene Proteins 0.000 description 1
- 101100256746 Mus musculus Setdb1 gene Proteins 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- 239000011810 insulating material Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000010363 phase shift Effects 0.000 description 1
- 230000003252 repetitive effect Effects 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 230000001360 synchronised effect Effects 0.000 description 1
Classifications
-
- G—PHYSICS
- G08—SIGNALLING
- G08C—TRANSMISSION SYSTEMS FOR MEASURED VALUES, CONTROL OR SIMILAR SIGNALS
- G08C21/00—Systems for transmitting the position of an object with respect to a predetermined reference system, e.g. tele-autographic system
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
- G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
- G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
- G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
- G06F3/046—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means by electromagnetic means
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
- G01B7/004—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring coordinates of points
Landscapes
- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- General Physics & Mathematics (AREA)
- General Engineering & Computer Science (AREA)
- Theoretical Computer Science (AREA)
- Electromagnetism (AREA)
- Human Computer Interaction (AREA)
- Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)
- Radar Systems Or Details Thereof (AREA)
- Length Measuring Devices With Unspecified Measuring Means (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
An electrical device for determining the position coordinates of patterns such as graphs and characters which are plotted on a drawing. The device includes a tablet on which a plurality of conductive lines are formed parallel to each other, and a probe consisting of circular coils which are in mutual inductive relation with the conductive lines.
The device determines the coordinate of the probe on the tablet, by selecting and filtering the mixed signal which is produced when scanning signals to the conductive lines combine with induced signals between the probe and the conductive lines.
A wireless probe may be used and a plurality of probes can be used on one tablet.
An electrical device for determining the position coordinates of patterns such as graphs and characters which are plotted on a drawing. The device includes a tablet on which a plurality of conductive lines are formed parallel to each other, and a probe consisting of circular coils which are in mutual inductive relation with the conductive lines.
The device determines the coordinate of the probe on the tablet, by selecting and filtering the mixed signal which is produced when scanning signals to the conductive lines combine with induced signals between the probe and the conductive lines.
A wireless probe may be used and a plurality of probes can be used on one tablet.
Description
1~8~)3Z5 ~:
The present in~ention relates~ to a device for determining positlon coordlnates on a flat surface.
Known devices for determining the coordinates of a point are constructed with a tablet and a stylus pen and the like. One group of such devices includes a tablet which has a plurality of conductive lines located at equal intervals, and a stylus with electromagnetic induction windings to which signals are applied, the conducti~e line ad~acent the stylus pen picks up the signal induced from the stylus pen, whereby the coordinates of the locatlon of the stylus may be determined.
Another type of device iB based on the principle of electromagnetic induction. The position coordlnate is determined by comparing the phase difference of an induced signal on a loop-shaped sensing Iine on the tablet with phase of a slgnal applied to the excitation coil o~ a cursor, whether it is placed within or outside of the line.
In the electromagnetic induction type devices, the circuit for detecting posltion coordlnate~ can be made comparatlvely slmple, because the interval between scanning lines is equal to the resolution ; of the position coordinate. But on the other hand, the devices are sensitive to external noise because these devices use a high impedance sensor.
Another disadvantage of these devices i8 that the scanning circuit is complicated by the large number of lines involved in a large tablet having high resolution. Further, manufacturing technique limits the interval between line8 by which a high resolution can be established.
Devices which determine the coordlnate by continuously detecting the phase di~ference between an excitation signal and an inducéd 9ignal, also have the disadvantage that the absolute coordinate po~ltion csn not be obtalned on the tablet. Because the~e values are determined in such a way as repetitive 180 phase shift. Once the cursor ;
- 1- ~ , 108~ZS
is moved away from the tablet, the established coordinate system is lost.
This can be avoided if the position coordinate is manually stored when the cursor is removed, or when the sensing lines for detecting the absolute coordinate position are newly installed. Such operations require rather difficult procedures or the tablet is made complicated in structure.
In these existing coordinate determining devices, the signal of the sensor and the applied signal should be synchronized.
Also it is required that a cable be connected from the signal processor to the stylus pen or cursor.
In accordance with the invention an automatic coordinate determining device comprises a coordinate tablet having a plurality of parallel conductive lines thereon. A scanning circuit generates scanning signals in response to counting signals, each of tbe output terminals of the scanning circuit being connected to one of the con-ductlve lines for applying the scanning signals successively. A probe for pointing a coordinate positlon has inductive windings and ls used on the coordinate tablet, the windings belng inductively coupled with the conductive lines. An oscillatory signal generator generates signals which are applied to one of the windings or conducti~e lines in mutual inductive relation, or inducing an oscillatory signal in the other. A maximum-signal detecting device detects the maxlmum signal ln the induced signal train which is successively induced in the other of those ln the mutual inductive relatlon according to the scanning on the conductive lines. The maximum-signal detecting device detects the maximum signal in a manner in which at least two success1ve signals respectively induced in two ad~acent conductive lines are compared and the forward signal greater than or equal to the latter is regarded as the maximum signal and is used to generate a detection signal in response to the maximum-signal detection, the detection signal being .~ . : .
_ 2 -., :
1084~325 fed to a gate for passing the counting slgnal corresponding to the maximum - induced signal.
Figure 1 is a schematic perspective view showing a tablet and probe of this invention, Figure 2 is a schematic plan view showing the formation of one set conductive lines, the pitch interval between lines, and the probe, Figures 3a, 3b, and 3c are graphical representations show-~ ing the waveform of the scanning signal produced on the conductive line as shown in Tigure 2 and the lnduced signal which superposes on the scanning signal, Tigure 4 is a graph showing the relationship of the position of the excitation coil placed on the conducti~e lines and the induced voltage developed in the conductive lines, Figure 5 is a graph showing induced wave form in the conductive lines in detail, Figure 6 is a block diagram showing the circuit ~n a probe of thls invention, Figure 7 is a block diagram showing clrcuits in a probe of another embodiment according to this invention, Figure 8 is a schematic diagram showing the automatic ; coordinate determinlng device of the invention, Figure 9 is a graphlcal representation of wave forms of different portions of the circuit sXown in Tigure 8, Figure 10 is a block diagram showing the maximum signal detecting circuit ln Tigure 8, Tigure 11 is a block diagram showing the A,G,C in Figure 8, Tigure 12 is a graphical representation of output of the dividing circuit in ~igure 8, - .
' : .
` J~080325 Fi~u~e 13 ~s ~ g~aph showin~ a co~rection cur~e availed ln the nonvolatile ~emory circult in ~igure 8, Figure 14 ls a block diagram showing another automatlc coordinate determining devlce according to the inventlon, Pigure 15 is a block diagram showing further an automatic coordinate determining device of this invention, and ls on the same sheet as Figure 5.
Flgure 16 is a block diagram showing another embodlment of the invention, Figure 17 is a schematic plan vlew showing a tablet according to the embodiment in Figure 16, and Figure 18 is a block diagram showing another embodiment according to this invention.
Figure 1 is an exploded perspective of a tablet according to this invention. In Figure 1, numerals 1 and 2 represent 1at plates made of insulating material which are installed closely contacted to each other to form ~ulti-layer structure. The flat plates 1 and 2 are provided with a plurality of conductive lines Xl, X2,...,Xn and Yl, Y2,... ,Ym each of which i8 respectively ~ormed in a U~shaped having a pair of parallel lines. The U-shaped conductive lines Xl, X2,...,Xn are spaced parallel to each other and with little gaps g between ad~acent lines as shown in Figure 2, or without any gap. This layout provides efective inductive coupling together with superior sensitivity and accuracy and eliminating portions of the tablet where coordinate determination is not po~sible. The U-shaped conductive lines Y~
~Y2,...Ym on plate 2 have same layout and are arranged perpendicular to the conductive lines Xl, X2,...Xn on plate 1.
One end of each of the conductlve lines is respectively connected to the outpot terminal of scanning circuits, such as ring-counters, 3 and 4, the other end of each lines is connected to a rectifler , ~ - 4 -" 1080325 Dl, D2~...Dn~m respectively. These recti~iexs have a co~on output llne 1 which ls connected to a power source through register R and to a maximum-signal detecting device M.
The conductive lines Yl, Y2,...Y may be installed on the opposite surface of tablet 1 to the conductive line surface of Xl~ X2,...Xn.
Numeral 5 designates a probe for indicating a coordinate position, which generates alternating magnetic field. The probe 5 is provided with excitation windings 5a having concentric circular and alternative current signal generator 6.
Figure 2 shows schematically the probe 5 located wlth respect to the conductive lines Xl, X2,...Xn. As shown in Figure 2, the conducti~e lines Xl, X2,...Xn are spaced with a pitch r. Pitch r is set to the basic length, i.e. 2n inch or mm (n = 0, 1, 2,...). Each of the conductive lines is connected with a ring counter 3 at one end and the other end is connected to the rectifiers Dl,...Dn. The winding 5a on the probe 5 which is excited by alternating current from the signal generator 6 preferably has an inner diameter larger than 2r.
The gaps g between a pair of parallel lines, a line to ring counter 3 and the line to maximum signal detecting device M of the next U-shaped line, i8 made small, preferably to zero, for eliminating dead areas on the tablet.
Figure 3a shows a time-~oltage chart of the output wave-_~ form applied to the conductive lines from the ring counter 3. The ring counter 3 applies one rectangular wave signal after another to the lines ' Xl~ X2,.. Xn. , . ~ . ' .
When the scanning signal Sl is applied to conductive line Xl, the signal Sl passes through the rectifier Dl to the common output line. On the output line when the signals Sl, S2,...Sn are gi~en to the conductive lines Xl, X2,... Xn respectively, the signal has a random .
~ _ 5 _ : . --: , - : : , . .
.
stepped waVe~orm to the tlme pass~ge as shown in Figure 3b, because of deviations of the forward drop voltage at the rectifiers.
When an alternating current signal is applled ~o the winding 5a, the electromagnetlc induction occurs and consequently an induced voltage is developed in the conductive lines on the tablets 1 and 2.
The maximum magnitude of the induced voltage is obtained at the lines nearest to windings 5a; some lower voltages are also induced in ad~acent lines. But the induced voltages do not appear at the output line unless the scanning signal is applied, since the magni-tude of the induced voltage is very low in comparison with the forward voltage drop (approx. 0.6V - 0.7V) of the rectifiers Dl, D2,...Dn.
The rectifiers are uni-directional. So, when the scanning signal, for example Sl, S2,...Sn as shown in Figure 3a are applied, the scanning current never flows into other scanning lines because the cathode terminals of the rectifiers operate for reverse condition.
The scanning signal is a positive going waveform in Flgure 3a. However, a negative going waveform msy also be u6ed, ln which case, the anode terminal of the rectifiers are commonly connected, and the reverse voltage is fed to the output line. Thus as before, the lnduced voltage does not appear at the output line unless a scanning signal is applied. That is, the signals which can appear at the output line are restricted to the scanning signal and the induced signals carried on the scanning signal.
Therefore, when the probe 5 is placed on an arbitrary position of the tablets (i.e. near conductive line Xl), the induced voltages, in which maximum magnitude is obtained on the conductive line Xl and appear at the output line superposed to the scanning signal, as ~h~wh ln ~igure 3c.
Figure 4 shows the relationshlp between the location of probe 5 in relation to the conductive lines and magnitude of the induced -. - . -108(~325 voltages at the conductive llne~, in Which curves Vl, V2 and ~3 respec-tively represent the lnduced voltages in conductive lines ~ , X2 and X3.
When probe 5 is located at point P, ~c~ ~a and Vb respectively represent the induced voltages in lines Xl, X2 and X3 Probe 5 being located at the center Pl, P2 or P3 of U-shaped line Xl, X2 or X3, magnitude maximum of voltage is induced in line Xl, X2 or X3.
Generally, induced voltage has the maximum magnitude when probe 5 is just at the center of the U-shaped line and gradually decreases in proportion to the deviation of the probe to either side.
The voltage again rises a little, as i8 shown in Pigure 5, after further deviation of the p~obe, making symmetric minor peaks on either side of the maximum peak. A trough between the maximum and a minor peak appears when the probe 5 i8 located at a position where inner flux of windings 5a penetrating through the U-shaped area of the conductive line is equal to outer flux penetrating through the U-shaped area of the same line. This position of the probe is where the center of the winding 5a is approximately half the dlstance of the winding inner diameter from the center of the U-shape. Therefore, if the winding diameter is made 8reater than twice the conductive line pltch r, the induced voltage curve from the center of the U-shaped conductive line to the next U-shaped conductive line continuously decreases. This selection of the windlng lnner diameter with reference to the conductive line pitch is valuable for determining of accurate intermediate coordinate positions, as will be described later.
~igure 6 is a block diagram showing the construction of the probe 5 connected to a signal generator 6. A multi-dividing circuit -7 receives a signal of high frequency from the signal generator 6 and , divides it into several kinds of lower-frequency signals fO fl,... and fk, which are fed to a switching circuit 8 to be selected for exclting windings 5a. Numeral 9 designates a hybrid circuit for combining a .' :
~ ~ - 7 - ~
plurality of fre~uency signals ~ed ~o~ the switching circuit 8, ~or winding 5a. These plural signals which are applied to winding 5a induce signals of their corresponding fre~uencies in the conductive lines for determining the coordlnates o~ the probe and further for other command functions, such as point reading or time-mode reading.
When two or more probes are desired on a wide tablet for simultaneous use by diferent operators, a combination of a signal generator 6, a divider 7, a switching circuit 8 and a plurality of windings 5a, Sb,... and 5k, as shown in Figure 7 is preferred.
Figure 8 is a block diagram of a position coordinate detecting apparatus according to this invention.
In Figure 8, maximum signal detecting device ~ receives the induced signals, as shown at a in Figure 9, from output line o tablets 1 and 2. Device M includes a band-pass filter 10 to pass the signal of frequency fO shown at b in Figure 5, an automatic gain controller 11 to control the level of the signal fed from band-pass filter 10, a rectiier 12 to rectify the signal b in ~igure 9 into the full-wave slgnal e in the,same Pigure, and a low-pa,ss filter 13 to smooth the full-wave signal as h in ~igure 9. In the curve of h in Figure 9, Va d`esignates the maximum signal, Vb the second and Vc the thlrd respectively induced in ad~ac`ent conductive lines and successively transferred in the maximum detecting device M.
The maximum detecting device M further includes an analog to digital converter 14 to convert the smoothed analogue signal into digital signal, and a maximum detecting circuit 15 to compare the succe~sive digital signals from the A-D conVerter 14.
The detail of maximum detecting circuit 15 will now be described hereinater reerring to Figure 10, in which numerals 16 to 18 designate a shift-register to receive the digital signals from A-D
conVerter, numerals 19 and 20 are comparing circuits, comparing circuit 19 . , :
' ' ' ' " ~
- - 8 - ~
. .
.
~8~325 compa~ing the output o~ reglster 16 with that of register 17 and comparing clrcuit 20 comparing the output o~ reglster 16 with that of register 18.
Numeral 21 designates a selecting circuit to select a signal between the output of register 16 and that of register 18 with the control signal from comparing circuit 20.
A signal traln such as h shown in Figure 9 is received by register 16. Register 16 contains the most recent signal, register 17 the next most recent signal, and registér 18 the next most recent signal. When the maximum signal Va reaches register 17, the second largest signal Vb is in register 16 and the signal Vc is in register 18.
At this time, register 17 has a larger signal than that stored in register 16, while, before this step register 17 had a smaller signal.
Accordingly, comparator 19 detects this change and generates a detection signal Mx. Comparator 20 generates a control signal for selecting clrcult 21 to select the output of register 18 with a minus signal when the signal at register 18 is larger than that at register 16, whlle otherwise selecting circuit 21 selects the output of register 16 with a plus ~ignal.
~umeral 22 designates a divlding circuit to make the 20 - second ~rge signal selected by selecting circuit 21 divide the maxi~um ~ignal from register 17. Dividing circuit 22 receives both the outputs of comparing circuit 20 and selecting circuit 21 using the detection signal Mx as a cue signal.
As a result of this dividing operation of dividing circuit 22, spurious signals, such as a deviation of the induced voltage in conductive line~, which is caused by uneveness of the media placed on the tablet, the variation of the impedances of conductive lines, the deviation of alternative magnetic field, and the variation of thickness of the tablet, are all eliminated. Conductive lines in a small area suffer these deviations approximately in the same extent.
, :,.:, :
.. _ g _ .
: : :
- - .. . . .
.
De~ining the dev~ation pa~ameter in a small area as ~ , the following equations are represented;
V~ =~ Vs~.,,,,,,.,.--(1) ~ , in equation (1), Vs; theoretical lnduced voltage, V~ ; actual induced voltage.
~ccordingly, in the case of Va and ~b in Figure 9;
Va = c~ Vsa...... .... .(2) Vb C~ VSb---~ -(3) In equations (2) and (3), V8a and V b; theoretical induced voltages of ~`
the maximum signal and the second large signal.
The output of dividing circuit 22 ls, therefore;
VR = Va = c~Vsa = Vsa .................. (4) ~b c~ Vsb Vsb There is no influence of ~ in the output ~R. The output VR is used for determining the intermediate coordinate between a pair of ad~oining çonductive lines, as will be descrlbed later.
Figure 11 is a block diagram showing automatic gain controller 11 in detail, in which numeral 23 designates an amplifier the gain of which i6 controlled by the maxi~um signal from register 17 through a register 24, a digital to analog converter 25 and a differential amplifier 26. Register 24 receives the maximum signal at a cue signal of the detection signal M from comparing circuit 19 and stores it.
By the output of differential amplifier 26, the gain of amplifier 23 is controlled so that the deviation of induced voltages is suppressed. ~ ;
As clarified in the above~description, the induced voltages show unidirectional increasing or decreasing characteristics which gives the maximum magnitude in the nearest conductive line to the winding 5a of probe 5. Accordingly, the divided voltages VR in the equation (4) ~ -represent a curve shown in Figure 12 including "11' as the minimum.
Now referring to Figure 12, the voltage ~R has a non-linear relationship to distance ~(, which means that the distance or :: :
: , , , .. ,-. .. .
1~8~33~S
coordinate between a palr of conductiye lines can not i~mediately be given from the divided voltage ~R
~ or getting the distance, outputs from dividlng circuit 22 shown in Figure 8 are given to a non-volatile memory circuit 27 such as Read Only Memory. Memory circult 27 stores data to indicate a curve shown in Figure 13 corresponding to Flgure 12.
That is, the outputs of di~idlng circuit 22 are converted into true coordinates through memory clrcuit 27 which stores the data to compensate for nonlinearlity along the curve in Figure 13. Actually, when, for example, one tenth of the pitch r of the conducting lines should be determined, distance "a" is divided into six areas as shown in Figure 13, both side areas being one-half of other areas. Memory circuit 27 stores "5" in memories corresponding to addresses of VO to Vl, "4" in memories corresponding to addres6es of V1 to V2,.... ~ "O" in memories corresponding addresses of V5 to V6 so that coordinate number ln 1l length unit is obtained according to the probe position. If far finer division of distance "a" is required, it is preferable for saving memories to provide memorie~ the number of which is e~ual to that of the dlvlslon and to only apply some middle blts of the divlded signal VR to the address of the memory, cutting off lower bits which have no effect on determinlng coordlnate and hlgher blts which represent zeros.
The number of the lower bits to be cut off increases according as the slgnal VR reaches to 1.
Numeral 51 (Figure 8) designates a clock-pulse generator ; to generate clock pulses which are fed to a counter 52. The counting number of said counter 52 is fed to the scanning circuits 3 and 4. ~i The scannlng clrcuit 3 for X-axis decodes the counting numbers into scannlng 6lgnals which are applied to the conductive lines Xl, X2,...Xn successively, and the scanning clrcuit 4 for Y-axis decodes the counting number6 lnto scanning signal6 which are applied to the conductive lines `"~
,- 11 ~
'~
.- . : . . ~ .
1~80325 Yl, Y2,...Y suçcesslvely after the X~axis scanning. After the last scanning signal has been applied to conductive line Xn or Y , counter 52 is reset and again starts to count the clock pulses. Numeral 53 designates a signal detector to alternately detect n or m sending a changing signal with the detection to the clock terminal of a flip-flop 54. An output terminal Q of the flip-flop 54 is connected to scanning ci~cuit 4 and the other output terminal Q is connected to scanning circuit 3, so that the scanning circuits 3 and 4 are alternately enabled to operate as described above.
The counting number of said counter 52 represents a conductive line coordinate in X or Y axis, and it is applied for determining length-unit coordinate, which will be described later.
But the conducti~e lines have respectively positional errors in a strict sense, and it is required to correct these errors for accurate coordinate determination. Therefore, converting means 55 and 56, such as read-only memories, are provided to receive the counting number of said counter 52 for converting it into a corrected conductive line signal. Said converting means 55 and 56 are alternately operated for X- or Y-axis under the control of the outputs Q and Q of said flip-flop 5~. Numeral 57 designates a latch register connected between counter 52 and the palr of converting means 55 and 56 to pass the counting number under the detection signal M of said maximum detecting circuit 15.
Conductive lines of at least one spaced on both the sides of the tablet are not suitable for determining coordinate because of the distortion of inductive effect. Therefore, a signal selector 61 to invalidate the signals corresponding to both-side conductive lines is inserted before said latch register, the end signals to be invalidated being alternately selected according to the outputs Q and Q of flip-flop 54.
The output of said converting means 55 or 56, i.e. the con~
verted length-unlt coordinate signal, and the output of said non~volatile .
~ 080325 .. ' memory or another converting means 27, i.e. the true intermediate co-ordinate signal are ~ed into an operation circuit 58, in which these ~ -signals are added or subtracted in response to the plus or minus signal generated by said maximum detecting circult 15.
The output of said operation circuit 58 is fed to registers 59 and 60, which are alternately enabled to receive the output of opera-tion circuit 58 under the control of the outputs e and ~ of said flip-flop 54.
Thus, the coardinates of the probe 5 are obtained, the X-coordinate from register 59 and the Y-coordinate from register 60.
Signals fl, f2, ...and fk ~Figure 7) are also induced in the conductive lines when wlndings 5a are excited by the corresponding frequency signals of probe 5. These signals are respectively dis-criminated through further band-pass fllters, one of which is shown in Figure 8 with numeral 62. Band-pass filter 62 blocks induced signal f ~or making a point-reading signal. A mono-multi-vibrator 63 receiyes induced signal fl through a level discriminator 64 such as a Schmidt trigger circuit to e:liminate low level noises, and the output of mono-multl-vibrator 63 is used as the point-reading signal with which one point coordinate of probe 5 as it is located is ~ed to exterlor devices !~''" '' ~' such as a computer or to a display panel. Signal f2, f3, ....or fk may be used to instruct the computer or display panel. Further, these signals may be used for simultaneously determining other probe co-ordinates uslng a plurality of probes as shown in Figure 7 and further separate maximum signal detectors. This combination of multi-frequency inducing and a plura~ity of band-pass filters is useful for providing a coordinate determining device with wireless probes.
It is to be noted that, in the above-described embodiment, rectifiers D on conductive l~nes may be replaced with switching elements, in which case the scanning signals successively turn on-and-off the , .
' switching elements fo~ allowing induced signals to be transmitted to the maximum signal detecting device.
It is further to be noted that, with the above replace-ment, a conversion of the mutual inductive relation of the windings and the conductive lines may be achieved, in which the conductive lines on the tablet successively receive exciting signals from the alternating current signal generator and induced signals induced in the windlngs of the probe are fed to the maxlmum signal detecting device.
Further, if so accurate determining of the coordinate is I0 not necessary or very flat media is used, the dividing circuit 22 may be omitted, the maximum signal being directly converted into true co-ordinate signal. This embodiment is shown in Figure 14, in which the same reference numerals are used as in ~igure 8. In Figure 14, the output of an operation circuit 65 which includes maximum signal detecting circuit 15 and nonvolatile memory clrcuit 27 to convert the maximum signal from =aximum signal detecting circuit 15 into the true inter-mediate coordinate, is fed to operatlon circuit 58. Numeral 66 designstes a command generator as described above, which receives various signals respectively generated by induced signal6 f1, f2, ...and fk through band-pass filters 62, 62',.;.62k, level discriminators 64, 64', ...64k, and moDo-multivibrators 63, 63',....63k, and generates, in response to the induced signals, command signals to a register 67.
Register 67 receives the coordinate value in register 59 and sends it to the exterior device such as a computer in response to the commands.
In Figure 15, a curve generator 68 is connected between recti1er 12 and analog to digital converter 14, for converting induced signals into true intermediate coordinates in analogue. Numeral 69 designates a shift register which operates similar to shift registors 16 to 18 in Figure 10, and numeral 70 designates a comparator including C Ow~ q 1 cor~or~t1ng circuits to act as same as those 19 and 20 in Figure 10.
-I .
~ 14 -' .
~n the aboye automatic coo~dln~te dete~:minlng device by the scanning method, a repeated scanning interval is increased when an area of tablet is increased, and conse~uently sampling frequencies at any point is decreased. But the drawback can be completely solved by the embodiment shown in Figure 16. In this embodiment, a limited number of scanning lines near the probe 5 are scanned and further the scanning range is ~aried following to the removal of the probe 5.
. Figure 16 shows a detailed circult diagram for the counter 52 shown in Figure 8. On the diagram, circuits 15 and 52 are respectively corresponding to the maximum magnitude detecting clrcuit 15 and the counter 52 shown in Figure 8.
In Figure 16, counter 52 renews sequentially scanning address signals on clock signals from a clock generator 71. Now placing the probe on the desired position on the tablets, signals are induced ::
on the conductive lines, and the maximum detection signal M ls generated x in the maximum magnitude detecting cireuit 15. At the time, the scanning address signal is stored in a register 72 with trigger of the detection signal Mx.
The circuit 73 is a subtracter consisting of Exclusive-OR gate and Full Adder to subtract a value from a setting circuit i4 for designated values from a content of register 72. The subtracted value i~ transfered through a gate 75 to counter 52 to be stored. ::
Maximum-signal detecting circuit 15 gives the detection signal Mx to register 72 to move the content of the register 72 to sub-tractor 73, and further to a controlling circuit 77. Numeral 78 designatés a gate which receives clock signals from clock generator 71 and passes them, on receipt of a control signal from controlling circuit 77, to an M-notation counter 79. A carry signa1 is generated from M-notation counter 79 and this carry signal is fed to controlling circuit .. ~
.
77 and to an OR-gate 80 the circuit of which is fed to J-terminal of 108~)3Z5 counter 52. A ~eset s~gnal o~ a ~ nal ~o~ counte~ 52 is also to be generated in controlling ci~cuit 77.
Controlling circuit 77 operates as follows, if a detection signal M is generated in maximum signal detectlng circult 15 in one scan of the conductive lines, controlllng circuit 77 sendsout an opening signal to gate 78 and further a 3-signal to counter 52 through OR-gate 80 after a desired time delay, so that the output of subtractor 73 is moved to counter 52, whereby presetting the counter 52. The output of subtractor 73 has a value of i-i because, at the time of the detection ~ignal Mx generation, the content i (corresponding to the maximum signal) of register, which is equal to that of counter 52, is moved to subtractor 73 and is sub~racted by the preset value ~ in setting circuit 74. If i is smaller than ;, a carry signal is generated from subtractor 73 so - that gate 75 prohibits the output of subtractor 73 from passing, setting preset value oP counter 52 to zero.
Accordingly, the scanning starts at conductive line Xi ;
immediately after the detection signal Mx generation.
During M pulse counting~ if a detection signal Mx is fed to controlling circuit 77 and to register 72, a J-signal is again applied to counter 52, presetting counter 52 to a subtracted value generated at ~ubtractor 73 in the same manner as described above, and a new scanning begin~ from there. Otherwise, after M pulse counting, i.e. M line scanning, M-notation counter 79 sends out a carry signal to controlling circuit 77 and counter 52. Accordingly, counter 52 is preset to a new subtracted value smaller than the last value of counter 52, and a new scanning begins fro~ there.
If probe 5 is spaced apart from the tablet or at a position on an earlier conductive llne than the initial scanning area, the scanning area reaches at the end line. In this case, neither detection signal Mx nor carry signal of M-notation counter 79 is applied to controlling circuit 77 in longer time than an M-clock passage, and, as a result, . , .
:
controlling cl~cuit 77 sends out a reset slgnal to c~untex 52, whereby a scanning begins from conductive line Xl.
Reerring now to ~igure 17, which is a plan view showing the tablet, on whlch the probe 1s located at XA at first, a scanning operation of aforementioned method wlll be described in particular.
Setting number in setting circuit 74 is four, M of M-notation counter 79 being eight. Counter 52 starts at first to count from one, scanning signal from X1. At line X6 which is the nearest to the probe, i.e.
when the content of counter 52 is six, a detection signal Mx is detected and subtracted number from subtractor 73 becomes "6 - 4 = 2". Accor-dingly, counter 52 is preset to two and the next scanning begins from line X2.
If the probe moves rom XA to XB, the next detection signal Mx is detected when the content of counter 52 is eight, and accordingly, the subtracted number becomes "8 - 4 - 4" and counter 52 is preset to four, the scanning area being shifted as shown in Figure 3.
For both X and Y axes partial scanning, a modi~ication as shown Figure 18 i~ available.
In Figure 18, the samé reference numerals as those in 20 Figure 16 are used for designation with or without suffix X or Y.
Q and Q are respectively connected to those of 1ip-flop 54 in Figure 8.
Numerals 81x, 81y, 82x and 82y designate gates to be opened by signal Q or Q. Numerals 83x and 83y designate gates to be opened by signal from OR-gate 80y or 80x. Other construction and function are similar to those in Figure 16.
With this circuit in ~igure 18, an X-axis partial scanning and a Y-axis partial scanning are alternatively performed.
,'~ ' ' ' .
.
.. .
The present in~ention relates~ to a device for determining positlon coordlnates on a flat surface.
Known devices for determining the coordinates of a point are constructed with a tablet and a stylus pen and the like. One group of such devices includes a tablet which has a plurality of conductive lines located at equal intervals, and a stylus with electromagnetic induction windings to which signals are applied, the conducti~e line ad~acent the stylus pen picks up the signal induced from the stylus pen, whereby the coordinates of the locatlon of the stylus may be determined.
Another type of device iB based on the principle of electromagnetic induction. The position coordlnate is determined by comparing the phase difference of an induced signal on a loop-shaped sensing Iine on the tablet with phase of a slgnal applied to the excitation coil o~ a cursor, whether it is placed within or outside of the line.
In the electromagnetic induction type devices, the circuit for detecting posltion coordlnate~ can be made comparatlvely slmple, because the interval between scanning lines is equal to the resolution ; of the position coordinate. But on the other hand, the devices are sensitive to external noise because these devices use a high impedance sensor.
Another disadvantage of these devices i8 that the scanning circuit is complicated by the large number of lines involved in a large tablet having high resolution. Further, manufacturing technique limits the interval between line8 by which a high resolution can be established.
Devices which determine the coordlnate by continuously detecting the phase di~ference between an excitation signal and an inducéd 9ignal, also have the disadvantage that the absolute coordinate po~ltion csn not be obtalned on the tablet. Because the~e values are determined in such a way as repetitive 180 phase shift. Once the cursor ;
- 1- ~ , 108~ZS
is moved away from the tablet, the established coordinate system is lost.
This can be avoided if the position coordinate is manually stored when the cursor is removed, or when the sensing lines for detecting the absolute coordinate position are newly installed. Such operations require rather difficult procedures or the tablet is made complicated in structure.
In these existing coordinate determining devices, the signal of the sensor and the applied signal should be synchronized.
Also it is required that a cable be connected from the signal processor to the stylus pen or cursor.
In accordance with the invention an automatic coordinate determining device comprises a coordinate tablet having a plurality of parallel conductive lines thereon. A scanning circuit generates scanning signals in response to counting signals, each of tbe output terminals of the scanning circuit being connected to one of the con-ductlve lines for applying the scanning signals successively. A probe for pointing a coordinate positlon has inductive windings and ls used on the coordinate tablet, the windings belng inductively coupled with the conductive lines. An oscillatory signal generator generates signals which are applied to one of the windings or conducti~e lines in mutual inductive relation, or inducing an oscillatory signal in the other. A maximum-signal detecting device detects the maxlmum signal ln the induced signal train which is successively induced in the other of those ln the mutual inductive relatlon according to the scanning on the conductive lines. The maximum-signal detecting device detects the maximum signal in a manner in which at least two success1ve signals respectively induced in two ad~acent conductive lines are compared and the forward signal greater than or equal to the latter is regarded as the maximum signal and is used to generate a detection signal in response to the maximum-signal detection, the detection signal being .~ . : .
_ 2 -., :
1084~325 fed to a gate for passing the counting slgnal corresponding to the maximum - induced signal.
Figure 1 is a schematic perspective view showing a tablet and probe of this invention, Figure 2 is a schematic plan view showing the formation of one set conductive lines, the pitch interval between lines, and the probe, Figures 3a, 3b, and 3c are graphical representations show-~ ing the waveform of the scanning signal produced on the conductive line as shown in Tigure 2 and the lnduced signal which superposes on the scanning signal, Tigure 4 is a graph showing the relationship of the position of the excitation coil placed on the conducti~e lines and the induced voltage developed in the conductive lines, Figure 5 is a graph showing induced wave form in the conductive lines in detail, Figure 6 is a block diagram showing the circuit ~n a probe of thls invention, Figure 7 is a block diagram showing clrcuits in a probe of another embodiment according to this invention, Figure 8 is a schematic diagram showing the automatic ; coordinate determinlng device of the invention, Figure 9 is a graphlcal representation of wave forms of different portions of the circuit sXown in Tigure 8, Figure 10 is a block diagram showing the maximum signal detecting circuit ln Tigure 8, Tigure 11 is a block diagram showing the A,G,C in Figure 8, Tigure 12 is a graphical representation of output of the dividing circuit in ~igure 8, - .
' : .
` J~080325 Fi~u~e 13 ~s ~ g~aph showin~ a co~rection cur~e availed ln the nonvolatile ~emory circult in ~igure 8, Figure 14 ls a block diagram showing another automatlc coordinate determining devlce according to the inventlon, Pigure 15 is a block diagram showing further an automatic coordinate determining device of this invention, and ls on the same sheet as Figure 5.
Flgure 16 is a block diagram showing another embodlment of the invention, Figure 17 is a schematic plan vlew showing a tablet according to the embodiment in Figure 16, and Figure 18 is a block diagram showing another embodiment according to this invention.
Figure 1 is an exploded perspective of a tablet according to this invention. In Figure 1, numerals 1 and 2 represent 1at plates made of insulating material which are installed closely contacted to each other to form ~ulti-layer structure. The flat plates 1 and 2 are provided with a plurality of conductive lines Xl, X2,...,Xn and Yl, Y2,... ,Ym each of which i8 respectively ~ormed in a U~shaped having a pair of parallel lines. The U-shaped conductive lines Xl, X2,...,Xn are spaced parallel to each other and with little gaps g between ad~acent lines as shown in Figure 2, or without any gap. This layout provides efective inductive coupling together with superior sensitivity and accuracy and eliminating portions of the tablet where coordinate determination is not po~sible. The U-shaped conductive lines Y~
~Y2,...Ym on plate 2 have same layout and are arranged perpendicular to the conductive lines Xl, X2,...Xn on plate 1.
One end of each of the conductlve lines is respectively connected to the outpot terminal of scanning circuits, such as ring-counters, 3 and 4, the other end of each lines is connected to a rectifler , ~ - 4 -" 1080325 Dl, D2~...Dn~m respectively. These recti~iexs have a co~on output llne 1 which ls connected to a power source through register R and to a maximum-signal detecting device M.
The conductive lines Yl, Y2,...Y may be installed on the opposite surface of tablet 1 to the conductive line surface of Xl~ X2,...Xn.
Numeral 5 designates a probe for indicating a coordinate position, which generates alternating magnetic field. The probe 5 is provided with excitation windings 5a having concentric circular and alternative current signal generator 6.
Figure 2 shows schematically the probe 5 located wlth respect to the conductive lines Xl, X2,...Xn. As shown in Figure 2, the conducti~e lines Xl, X2,...Xn are spaced with a pitch r. Pitch r is set to the basic length, i.e. 2n inch or mm (n = 0, 1, 2,...). Each of the conductive lines is connected with a ring counter 3 at one end and the other end is connected to the rectifiers Dl,...Dn. The winding 5a on the probe 5 which is excited by alternating current from the signal generator 6 preferably has an inner diameter larger than 2r.
The gaps g between a pair of parallel lines, a line to ring counter 3 and the line to maximum signal detecting device M of the next U-shaped line, i8 made small, preferably to zero, for eliminating dead areas on the tablet.
Figure 3a shows a time-~oltage chart of the output wave-_~ form applied to the conductive lines from the ring counter 3. The ring counter 3 applies one rectangular wave signal after another to the lines ' Xl~ X2,.. Xn. , . ~ . ' .
When the scanning signal Sl is applied to conductive line Xl, the signal Sl passes through the rectifier Dl to the common output line. On the output line when the signals Sl, S2,...Sn are gi~en to the conductive lines Xl, X2,... Xn respectively, the signal has a random .
~ _ 5 _ : . --: , - : : , . .
.
stepped waVe~orm to the tlme pass~ge as shown in Figure 3b, because of deviations of the forward drop voltage at the rectifiers.
When an alternating current signal is applled ~o the winding 5a, the electromagnetlc induction occurs and consequently an induced voltage is developed in the conductive lines on the tablets 1 and 2.
The maximum magnitude of the induced voltage is obtained at the lines nearest to windings 5a; some lower voltages are also induced in ad~acent lines. But the induced voltages do not appear at the output line unless the scanning signal is applied, since the magni-tude of the induced voltage is very low in comparison with the forward voltage drop (approx. 0.6V - 0.7V) of the rectifiers Dl, D2,...Dn.
The rectifiers are uni-directional. So, when the scanning signal, for example Sl, S2,...Sn as shown in Figure 3a are applied, the scanning current never flows into other scanning lines because the cathode terminals of the rectifiers operate for reverse condition.
The scanning signal is a positive going waveform in Flgure 3a. However, a negative going waveform msy also be u6ed, ln which case, the anode terminal of the rectifiers are commonly connected, and the reverse voltage is fed to the output line. Thus as before, the lnduced voltage does not appear at the output line unless a scanning signal is applied. That is, the signals which can appear at the output line are restricted to the scanning signal and the induced signals carried on the scanning signal.
Therefore, when the probe 5 is placed on an arbitrary position of the tablets (i.e. near conductive line Xl), the induced voltages, in which maximum magnitude is obtained on the conductive line Xl and appear at the output line superposed to the scanning signal, as ~h~wh ln ~igure 3c.
Figure 4 shows the relationshlp between the location of probe 5 in relation to the conductive lines and magnitude of the induced -. - . -108(~325 voltages at the conductive llne~, in Which curves Vl, V2 and ~3 respec-tively represent the lnduced voltages in conductive lines ~ , X2 and X3.
When probe 5 is located at point P, ~c~ ~a and Vb respectively represent the induced voltages in lines Xl, X2 and X3 Probe 5 being located at the center Pl, P2 or P3 of U-shaped line Xl, X2 or X3, magnitude maximum of voltage is induced in line Xl, X2 or X3.
Generally, induced voltage has the maximum magnitude when probe 5 is just at the center of the U-shaped line and gradually decreases in proportion to the deviation of the probe to either side.
The voltage again rises a little, as i8 shown in Pigure 5, after further deviation of the p~obe, making symmetric minor peaks on either side of the maximum peak. A trough between the maximum and a minor peak appears when the probe 5 i8 located at a position where inner flux of windings 5a penetrating through the U-shaped area of the conductive line is equal to outer flux penetrating through the U-shaped area of the same line. This position of the probe is where the center of the winding 5a is approximately half the dlstance of the winding inner diameter from the center of the U-shape. Therefore, if the winding diameter is made 8reater than twice the conductive line pltch r, the induced voltage curve from the center of the U-shaped conductive line to the next U-shaped conductive line continuously decreases. This selection of the windlng lnner diameter with reference to the conductive line pitch is valuable for determining of accurate intermediate coordinate positions, as will be described later.
~igure 6 is a block diagram showing the construction of the probe 5 connected to a signal generator 6. A multi-dividing circuit -7 receives a signal of high frequency from the signal generator 6 and , divides it into several kinds of lower-frequency signals fO fl,... and fk, which are fed to a switching circuit 8 to be selected for exclting windings 5a. Numeral 9 designates a hybrid circuit for combining a .' :
~ ~ - 7 - ~
plurality of fre~uency signals ~ed ~o~ the switching circuit 8, ~or winding 5a. These plural signals which are applied to winding 5a induce signals of their corresponding fre~uencies in the conductive lines for determining the coordlnates o~ the probe and further for other command functions, such as point reading or time-mode reading.
When two or more probes are desired on a wide tablet for simultaneous use by diferent operators, a combination of a signal generator 6, a divider 7, a switching circuit 8 and a plurality of windings 5a, Sb,... and 5k, as shown in Figure 7 is preferred.
Figure 8 is a block diagram of a position coordinate detecting apparatus according to this invention.
In Figure 8, maximum signal detecting device ~ receives the induced signals, as shown at a in Figure 9, from output line o tablets 1 and 2. Device M includes a band-pass filter 10 to pass the signal of frequency fO shown at b in Figure 5, an automatic gain controller 11 to control the level of the signal fed from band-pass filter 10, a rectiier 12 to rectify the signal b in ~igure 9 into the full-wave slgnal e in the,same Pigure, and a low-pa,ss filter 13 to smooth the full-wave signal as h in ~igure 9. In the curve of h in Figure 9, Va d`esignates the maximum signal, Vb the second and Vc the thlrd respectively induced in ad~ac`ent conductive lines and successively transferred in the maximum detecting device M.
The maximum detecting device M further includes an analog to digital converter 14 to convert the smoothed analogue signal into digital signal, and a maximum detecting circuit 15 to compare the succe~sive digital signals from the A-D conVerter 14.
The detail of maximum detecting circuit 15 will now be described hereinater reerring to Figure 10, in which numerals 16 to 18 designate a shift-register to receive the digital signals from A-D
conVerter, numerals 19 and 20 are comparing circuits, comparing circuit 19 . , :
' ' ' ' " ~
- - 8 - ~
. .
.
~8~325 compa~ing the output o~ reglster 16 with that of register 17 and comparing clrcuit 20 comparing the output o~ reglster 16 with that of register 18.
Numeral 21 designates a selecting circuit to select a signal between the output of register 16 and that of register 18 with the control signal from comparing circuit 20.
A signal traln such as h shown in Figure 9 is received by register 16. Register 16 contains the most recent signal, register 17 the next most recent signal, and registér 18 the next most recent signal. When the maximum signal Va reaches register 17, the second largest signal Vb is in register 16 and the signal Vc is in register 18.
At this time, register 17 has a larger signal than that stored in register 16, while, before this step register 17 had a smaller signal.
Accordingly, comparator 19 detects this change and generates a detection signal Mx. Comparator 20 generates a control signal for selecting clrcult 21 to select the output of register 18 with a minus signal when the signal at register 18 is larger than that at register 16, whlle otherwise selecting circuit 21 selects the output of register 16 with a plus ~ignal.
~umeral 22 designates a divlding circuit to make the 20 - second ~rge signal selected by selecting circuit 21 divide the maxi~um ~ignal from register 17. Dividing circuit 22 receives both the outputs of comparing circuit 20 and selecting circuit 21 using the detection signal Mx as a cue signal.
As a result of this dividing operation of dividing circuit 22, spurious signals, such as a deviation of the induced voltage in conductive line~, which is caused by uneveness of the media placed on the tablet, the variation of the impedances of conductive lines, the deviation of alternative magnetic field, and the variation of thickness of the tablet, are all eliminated. Conductive lines in a small area suffer these deviations approximately in the same extent.
, :,.:, :
.. _ g _ .
: : :
- - .. . . .
.
De~ining the dev~ation pa~ameter in a small area as ~ , the following equations are represented;
V~ =~ Vs~.,,,,,,.,.--(1) ~ , in equation (1), Vs; theoretical lnduced voltage, V~ ; actual induced voltage.
~ccordingly, in the case of Va and ~b in Figure 9;
Va = c~ Vsa...... .... .(2) Vb C~ VSb---~ -(3) In equations (2) and (3), V8a and V b; theoretical induced voltages of ~`
the maximum signal and the second large signal.
The output of dividing circuit 22 ls, therefore;
VR = Va = c~Vsa = Vsa .................. (4) ~b c~ Vsb Vsb There is no influence of ~ in the output ~R. The output VR is used for determining the intermediate coordinate between a pair of ad~oining çonductive lines, as will be descrlbed later.
Figure 11 is a block diagram showing automatic gain controller 11 in detail, in which numeral 23 designates an amplifier the gain of which i6 controlled by the maxi~um signal from register 17 through a register 24, a digital to analog converter 25 and a differential amplifier 26. Register 24 receives the maximum signal at a cue signal of the detection signal M from comparing circuit 19 and stores it.
By the output of differential amplifier 26, the gain of amplifier 23 is controlled so that the deviation of induced voltages is suppressed. ~ ;
As clarified in the above~description, the induced voltages show unidirectional increasing or decreasing characteristics which gives the maximum magnitude in the nearest conductive line to the winding 5a of probe 5. Accordingly, the divided voltages VR in the equation (4) ~ -represent a curve shown in Figure 12 including "11' as the minimum.
Now referring to Figure 12, the voltage ~R has a non-linear relationship to distance ~(, which means that the distance or :: :
: , , , .. ,-. .. .
1~8~33~S
coordinate between a palr of conductiye lines can not i~mediately be given from the divided voltage ~R
~ or getting the distance, outputs from dividlng circuit 22 shown in Figure 8 are given to a non-volatile memory circuit 27 such as Read Only Memory. Memory circult 27 stores data to indicate a curve shown in Figure 13 corresponding to Flgure 12.
That is, the outputs of di~idlng circuit 22 are converted into true coordinates through memory clrcuit 27 which stores the data to compensate for nonlinearlity along the curve in Figure 13. Actually, when, for example, one tenth of the pitch r of the conducting lines should be determined, distance "a" is divided into six areas as shown in Figure 13, both side areas being one-half of other areas. Memory circuit 27 stores "5" in memories corresponding to addresses of VO to Vl, "4" in memories corresponding to addres6es of V1 to V2,.... ~ "O" in memories corresponding addresses of V5 to V6 so that coordinate number ln 1l length unit is obtained according to the probe position. If far finer division of distance "a" is required, it is preferable for saving memories to provide memorie~ the number of which is e~ual to that of the dlvlslon and to only apply some middle blts of the divlded signal VR to the address of the memory, cutting off lower bits which have no effect on determinlng coordlnate and hlgher blts which represent zeros.
The number of the lower bits to be cut off increases according as the slgnal VR reaches to 1.
Numeral 51 (Figure 8) designates a clock-pulse generator ; to generate clock pulses which are fed to a counter 52. The counting number of said counter 52 is fed to the scanning circuits 3 and 4. ~i The scannlng clrcuit 3 for X-axis decodes the counting numbers into scannlng 6lgnals which are applied to the conductive lines Xl, X2,...Xn successively, and the scanning clrcuit 4 for Y-axis decodes the counting number6 lnto scanning signal6 which are applied to the conductive lines `"~
,- 11 ~
'~
.- . : . . ~ .
1~80325 Yl, Y2,...Y suçcesslvely after the X~axis scanning. After the last scanning signal has been applied to conductive line Xn or Y , counter 52 is reset and again starts to count the clock pulses. Numeral 53 designates a signal detector to alternately detect n or m sending a changing signal with the detection to the clock terminal of a flip-flop 54. An output terminal Q of the flip-flop 54 is connected to scanning ci~cuit 4 and the other output terminal Q is connected to scanning circuit 3, so that the scanning circuits 3 and 4 are alternately enabled to operate as described above.
The counting number of said counter 52 represents a conductive line coordinate in X or Y axis, and it is applied for determining length-unit coordinate, which will be described later.
But the conducti~e lines have respectively positional errors in a strict sense, and it is required to correct these errors for accurate coordinate determination. Therefore, converting means 55 and 56, such as read-only memories, are provided to receive the counting number of said counter 52 for converting it into a corrected conductive line signal. Said converting means 55 and 56 are alternately operated for X- or Y-axis under the control of the outputs Q and Q of said flip-flop 5~. Numeral 57 designates a latch register connected between counter 52 and the palr of converting means 55 and 56 to pass the counting number under the detection signal M of said maximum detecting circuit 15.
Conductive lines of at least one spaced on both the sides of the tablet are not suitable for determining coordinate because of the distortion of inductive effect. Therefore, a signal selector 61 to invalidate the signals corresponding to both-side conductive lines is inserted before said latch register, the end signals to be invalidated being alternately selected according to the outputs Q and Q of flip-flop 54.
The output of said converting means 55 or 56, i.e. the con~
verted length-unlt coordinate signal, and the output of said non~volatile .
~ 080325 .. ' memory or another converting means 27, i.e. the true intermediate co-ordinate signal are ~ed into an operation circuit 58, in which these ~ -signals are added or subtracted in response to the plus or minus signal generated by said maximum detecting circult 15.
The output of said operation circuit 58 is fed to registers 59 and 60, which are alternately enabled to receive the output of opera-tion circuit 58 under the control of the outputs e and ~ of said flip-flop 54.
Thus, the coardinates of the probe 5 are obtained, the X-coordinate from register 59 and the Y-coordinate from register 60.
Signals fl, f2, ...and fk ~Figure 7) are also induced in the conductive lines when wlndings 5a are excited by the corresponding frequency signals of probe 5. These signals are respectively dis-criminated through further band-pass fllters, one of which is shown in Figure 8 with numeral 62. Band-pass filter 62 blocks induced signal f ~or making a point-reading signal. A mono-multi-vibrator 63 receiyes induced signal fl through a level discriminator 64 such as a Schmidt trigger circuit to e:liminate low level noises, and the output of mono-multl-vibrator 63 is used as the point-reading signal with which one point coordinate of probe 5 as it is located is ~ed to exterlor devices !~''" '' ~' such as a computer or to a display panel. Signal f2, f3, ....or fk may be used to instruct the computer or display panel. Further, these signals may be used for simultaneously determining other probe co-ordinates uslng a plurality of probes as shown in Figure 7 and further separate maximum signal detectors. This combination of multi-frequency inducing and a plura~ity of band-pass filters is useful for providing a coordinate determining device with wireless probes.
It is to be noted that, in the above-described embodiment, rectifiers D on conductive l~nes may be replaced with switching elements, in which case the scanning signals successively turn on-and-off the , .
' switching elements fo~ allowing induced signals to be transmitted to the maximum signal detecting device.
It is further to be noted that, with the above replace-ment, a conversion of the mutual inductive relation of the windings and the conductive lines may be achieved, in which the conductive lines on the tablet successively receive exciting signals from the alternating current signal generator and induced signals induced in the windlngs of the probe are fed to the maxlmum signal detecting device.
Further, if so accurate determining of the coordinate is I0 not necessary or very flat media is used, the dividing circuit 22 may be omitted, the maximum signal being directly converted into true co-ordinate signal. This embodiment is shown in Figure 14, in which the same reference numerals are used as in ~igure 8. In Figure 14, the output of an operation circuit 65 which includes maximum signal detecting circuit 15 and nonvolatile memory clrcuit 27 to convert the maximum signal from =aximum signal detecting circuit 15 into the true inter-mediate coordinate, is fed to operatlon circuit 58. Numeral 66 designstes a command generator as described above, which receives various signals respectively generated by induced signal6 f1, f2, ...and fk through band-pass filters 62, 62',.;.62k, level discriminators 64, 64', ...64k, and moDo-multivibrators 63, 63',....63k, and generates, in response to the induced signals, command signals to a register 67.
Register 67 receives the coordinate value in register 59 and sends it to the exterior device such as a computer in response to the commands.
In Figure 15, a curve generator 68 is connected between recti1er 12 and analog to digital converter 14, for converting induced signals into true intermediate coordinates in analogue. Numeral 69 designates a shift register which operates similar to shift registors 16 to 18 in Figure 10, and numeral 70 designates a comparator including C Ow~ q 1 cor~or~t1ng circuits to act as same as those 19 and 20 in Figure 10.
-I .
~ 14 -' .
~n the aboye automatic coo~dln~te dete~:minlng device by the scanning method, a repeated scanning interval is increased when an area of tablet is increased, and conse~uently sampling frequencies at any point is decreased. But the drawback can be completely solved by the embodiment shown in Figure 16. In this embodiment, a limited number of scanning lines near the probe 5 are scanned and further the scanning range is ~aried following to the removal of the probe 5.
. Figure 16 shows a detailed circult diagram for the counter 52 shown in Figure 8. On the diagram, circuits 15 and 52 are respectively corresponding to the maximum magnitude detecting clrcuit 15 and the counter 52 shown in Figure 8.
In Figure 16, counter 52 renews sequentially scanning address signals on clock signals from a clock generator 71. Now placing the probe on the desired position on the tablets, signals are induced ::
on the conductive lines, and the maximum detection signal M ls generated x in the maximum magnitude detecting cireuit 15. At the time, the scanning address signal is stored in a register 72 with trigger of the detection signal Mx.
The circuit 73 is a subtracter consisting of Exclusive-OR gate and Full Adder to subtract a value from a setting circuit i4 for designated values from a content of register 72. The subtracted value i~ transfered through a gate 75 to counter 52 to be stored. ::
Maximum-signal detecting circuit 15 gives the detection signal Mx to register 72 to move the content of the register 72 to sub-tractor 73, and further to a controlling circuit 77. Numeral 78 designatés a gate which receives clock signals from clock generator 71 and passes them, on receipt of a control signal from controlling circuit 77, to an M-notation counter 79. A carry signa1 is generated from M-notation counter 79 and this carry signal is fed to controlling circuit .. ~
.
77 and to an OR-gate 80 the circuit of which is fed to J-terminal of 108~)3Z5 counter 52. A ~eset s~gnal o~ a ~ nal ~o~ counte~ 52 is also to be generated in controlling ci~cuit 77.
Controlling circuit 77 operates as follows, if a detection signal M is generated in maximum signal detectlng circult 15 in one scan of the conductive lines, controlllng circuit 77 sendsout an opening signal to gate 78 and further a 3-signal to counter 52 through OR-gate 80 after a desired time delay, so that the output of subtractor 73 is moved to counter 52, whereby presetting the counter 52. The output of subtractor 73 has a value of i-i because, at the time of the detection ~ignal Mx generation, the content i (corresponding to the maximum signal) of register, which is equal to that of counter 52, is moved to subtractor 73 and is sub~racted by the preset value ~ in setting circuit 74. If i is smaller than ;, a carry signal is generated from subtractor 73 so - that gate 75 prohibits the output of subtractor 73 from passing, setting preset value oP counter 52 to zero.
Accordingly, the scanning starts at conductive line Xi ;
immediately after the detection signal Mx generation.
During M pulse counting~ if a detection signal Mx is fed to controlling circuit 77 and to register 72, a J-signal is again applied to counter 52, presetting counter 52 to a subtracted value generated at ~ubtractor 73 in the same manner as described above, and a new scanning begin~ from there. Otherwise, after M pulse counting, i.e. M line scanning, M-notation counter 79 sends out a carry signal to controlling circuit 77 and counter 52. Accordingly, counter 52 is preset to a new subtracted value smaller than the last value of counter 52, and a new scanning begins fro~ there.
If probe 5 is spaced apart from the tablet or at a position on an earlier conductive llne than the initial scanning area, the scanning area reaches at the end line. In this case, neither detection signal Mx nor carry signal of M-notation counter 79 is applied to controlling circuit 77 in longer time than an M-clock passage, and, as a result, . , .
:
controlling cl~cuit 77 sends out a reset slgnal to c~untex 52, whereby a scanning begins from conductive line Xl.
Reerring now to ~igure 17, which is a plan view showing the tablet, on whlch the probe 1s located at XA at first, a scanning operation of aforementioned method wlll be described in particular.
Setting number in setting circuit 74 is four, M of M-notation counter 79 being eight. Counter 52 starts at first to count from one, scanning signal from X1. At line X6 which is the nearest to the probe, i.e.
when the content of counter 52 is six, a detection signal Mx is detected and subtracted number from subtractor 73 becomes "6 - 4 = 2". Accor-dingly, counter 52 is preset to two and the next scanning begins from line X2.
If the probe moves rom XA to XB, the next detection signal Mx is detected when the content of counter 52 is eight, and accordingly, the subtracted number becomes "8 - 4 - 4" and counter 52 is preset to four, the scanning area being shifted as shown in Figure 3.
For both X and Y axes partial scanning, a modi~ication as shown Figure 18 i~ available.
In Figure 18, the samé reference numerals as those in 20 Figure 16 are used for designation with or without suffix X or Y.
Q and Q are respectively connected to those of 1ip-flop 54 in Figure 8.
Numerals 81x, 81y, 82x and 82y designate gates to be opened by signal Q or Q. Numerals 83x and 83y designate gates to be opened by signal from OR-gate 80y or 80x. Other construction and function are similar to those in Figure 16.
With this circuit in ~igure 18, an X-axis partial scanning and a Y-axis partial scanning are alternatively performed.
,'~ ' ' ' .
.
.. .
Claims (20)
1. An automatic coordinate determining device comprising a coordinate tablet having a plurality of parallel conductive lines thereon, a scanning circuit generating scanning signals in response to counting signals, each of the output terminals of said scanning circuit being connected to one of said conductive lines for applying the scanning signals successively, a probe for pointing a coordinate position having inductive windings and spaced on said coordinate tablet for making mutual inductive relation with said conductive lines, an oscillatory signal generator to generate a signal which is applied to one of said inductive windings or said conductive lines, for inducing an oscillatory signal in the other, and a maximum-signal detecting device (M) to detect the maximum signal in the induced signal train which is successively induced in the other of those in the mutual inductive relation according to the scanning of the conductive lines, said maximum-signal detecting device detecting the maximum signal in a manner in which at least two successive signals respectively induced in two adjacent conductive lines are compared and the former signal greater than or equal to the latter is regarded as the maximum signal and to generate a detection signal in response to the maximum-signal detection, said detection signal being fed to a gate for passing the counting signal corresponding to the maximum induced signal.
2. An automatic coordinate determining device as claimed in Claim 1, wherein the oscillatory signal from said oscillatory signal generator is applied to the inductive windings of said probe, for inducing signal in said conductive lines, and said conductive lines have a common output line (1) to the maximum-signal detecting device.
3. An automatic coordinate determining device as claimed in Claim 1, wherein said maximum-signal detecting device compares the latter signal with the signal before the former signal, generating a minus signal when the latter is smaller and otherwise a plus signal, and which further comprises a converting means to convert said maximum induced signal into the corresponding true intermediate positional value, and an operation means to add or subtract the intermediate positional value to or from the counting signal from said gate, the addition or the subtraction being selected by the plus or minus signal of said maximum-signal detecting device.
4. An automatic coordinate determining device as claimed in Claim 1, wherein said maximum-signal detecting device compares the latter signal with the signal before the former signal, detecting the second largest signal from these two signals and generating a minus signal when the latter is smaller and otherwise a plus signal, and which further comprises a dividing circuit to get the ratio of the maximum-signal to the second large signal, a converting means to convert said ratio into the corresponding true intermediate positional value, and an operation means to add or subtract the intermediate positional value to or from the counting signal from said gate, the addition or the sub-traction being selected by the plus or minus signal of said maximum-signal detecting device.
5. An automatic coordinate determining device as claimed in Claim 4, wherein said converting means includes a non-volatile memory which stores true values corresponding to intermediate positions between a pair of adjacent conductive lines and which receives said ratio from said maximum-signal detecting device as an address signal for selecting the corresponding true intermediate positional value among the stored values.
6. An automatic coordinate determining device as claimed in Claim 1, wherein said maximum-signal detecting device compares the latter signal with the signal before the former signal, detecting the second largest signal from these two signals and generating a plus signal when the latter is smaller and otherwise a minus signal, and which further comprises a dividing circuit to get the ratio of the maximum signal to the second largest signal, a first converting means to convert said ratio into the corresponding true intermediate positional value, a second converting means to convert said counting signal into the corresponding corrected coordinate signal, and an operation means to add or subtract the intermediate positional value to or from the corrected coordinate signal from said second converting means, the addition or the subtraction being selected by the plus or minus signal of said maximum-signal detecting device.
7. An automatic coordinate determining device as claimed in Claim 2, wherein the output terminals of said scanning circuit are respectively connected direct to said conductive lines, successively giving carrier signals on the conductive lines, and a plurality of rectifying means having a proper threshold voltage, each of which is connected with one of said conductive lines, and further which comprises a filter connected to said rectifying means for selectively passing the induced signals therethrough to said maximum-signal detecting device.
8. An automatic coordinate determining device as claimed in Claim 1, wherein said output terminals of the scanning circuit are respectively connected to controlling terminals of switching elements, each of which is provided on one of said conductive lines for selectively passing the oscillatory signal induced in the conductive lines by said inductive windings or directly generated by said oscillatory signal generator.
9. An automatic coordinate determining device as claimed in Claim 4, wherein each of said conductive lines having a U-shaped portion.
10. An automatic coordinate determining device as claimed in Claim 9, wherein the U-shaped portions of the conductive lines have equal distance between the parallel lines thereof and are placed parallel and with little gap or without gap.
11. An automatic coordinate determining device as claimed in Claim 4, wherein said conductive lines are spaced in equal distances and the scanning address signals for at least one conductive line at both sides of the tablet prohibit said operation means to operate.
12. An automatic coordinate determining device comprising a coordinate tablet having a plurality of parallel conductive lines thereon, a scanning circuit generating scanning signals in response to scanning address signals, each of the output terminals of said scanning circuit being engaged to one of said conductive lines for applying the scanning signals successively, a probe for pointing a coordinate position having inductive windings ant spaced on said coordinate tablet in mutual inductive relation with said conductive lines, an oscillatory signal generator to generate an oscillatory signal which is applied to one of those in the mutual inductive relation, said inductive windings or said conductive lines, for inducing an oscillatory signal in the other, a maximum-signal detecting device to detect the maximum-signal in the induced signal train which is successively induced in the other of those in the mutual inductive relation according to the scanning of the conductive lines, said maximum-signal detecting device detecting the maximum-signal in a manner in which at least two successive signals respectively induced in two adjacent conductive lines are compared and the former signal greater than or equal to the latter is regarded as the maximum signal and to generate a detection signal in response to the maximum-signal detection, said detection signal being fed to a gate for passing the scanning address signal corresponding to the maximum induced signal through, a starting address determining means to determine the next starting address of said scanning address signals according to the address corresponding to the detected maximum signal, and a scanning number limiting means to set the number of said scanning address signals from a starting address.
13. An automatic coordinate determining devices as claimed in Claim 12, wherein said maximum-signal detecting device includes a band-pass filter to discriminate the signals induced in said conductive lines, a rectifying means to convert each of the successive induced signals passed through said band-pass filter into a direct current signal, and an analog to digital convertor to convert the direct current signals into digital signals which are compared for detecting the maximum signal.
14. An automatic coordinate determining device as claimed in Claim 13, further comprising one or more auxiliary oscillatory signal generating means to generate second or higher oscillatory signals which selectively alternate or combine with said oscillatory signal of the oscillatory signal generator to be applied to said inductive windings, the frequency of said second or higher oscillatory signals being different from that of said oscillatory signal, and auxiliary band-pass filters, the number of which being equal to that of said auxiliary oscillatory signal generators, to respectively discriminate the oscillatory signals of the corresponding auxiliary oscillatory signal generators.
15. An automatic coordinate determining device as claimed in Claim 14, wherein the outputs of said auxiliary band-pass filters are fed to command devices to generate command signals such as coordinate point-reading or time-mode reading.
16. An automatic coordinate determining device as claimed in Claim 4, wherein said maximum-signal detecting device has an auto-matic gain controlling circuit to control the induced signals in response to the maximum signal value so as to gain a constant maximum signal value.
17. An automatic coordinate determining device as claimed in Claim 2, wherein said coordinate tablet is provided with a second set of parallel conductive lines (y) spaced thereon perpendicular to the first set of said parallel conductive lines, the conductive lines of said second set also having said common output line (?), and further which comprises a second scanning circuit generating scanning signals for said second set of conductive lines, the two scanning circuits receiving scanning address signals alternately, and a coordinate convert-ing means to discriminate the scanning signals for said second set of conductive lines from those for the first set of conductive lines and to convert the scanning signals into the corresponding coordinate signals.
18. An automatic coordinate determining device as claimed in Claim 4, wherein said coordinate tablet is provided with a second set of parallel conductive lines spaced thereon perpendicular to the first set of said parallel conductive lines, and further which comprises a second scanning circuit generating scanning signals for said second set of conductive lines, the two scanning circuits receiving scanning address signals alternately, and a coordinate converting means to discriminate the scanning signals for said second set of conductive lines from those for the first set of conductive lines and to convert the scanning signals into the corresponding coordinate signals.
19. An automatic coordinate determining device as claimed in Claim 4, said conductive lines are located with an equal pitch of an times (n : an integral number or zero) of the basic length unit apart from adjoining conductive lines.
20. An automatic coordinate determining device as claimed in Claim 10, wherein said conductive lines hare an equal pitch and said inductive windings have a diameter larger than or equal to two times of said pitch.
Applications Claiming Priority (5)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP50062191A JPS51138124A (en) | 1975-05-23 | 1975-05-23 | Automatic coordinate reader |
| JP50064470A JPS5927949B2 (en) | 1975-05-28 | 1975-05-28 | Automatic coordinate reading device |
| JP50138002A JPS599951B2 (en) | 1975-11-17 | 1975-11-17 | Jidouza Hiyouyomi Torisouchinosou Sahoushiki |
| JP50138905A JPS5263026A (en) | 1975-11-19 | 1975-11-19 | Coordinates reader |
| JP1359476A JPS5296825A (en) | 1976-02-10 | 1976-02-10 | Coordinates readout unit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1080325A true CA1080325A (en) | 1980-06-24 |
Family
ID=27519523
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA253,195A Expired CA1080325A (en) | 1975-05-23 | 1976-05-25 | Automatic coordinate determining device |
Country Status (10)
| Country | Link |
|---|---|
| CA (1) | CA1080325A (en) |
| CH (1) | CH595613A5 (en) |
| DE (1) | DE2622941C2 (en) |
| FR (1) | FR2312012A1 (en) |
| GB (1) | GB1525649A (en) |
| HK (1) | HK49282A (en) |
| IT (1) | IT1061979B (en) |
| NL (1) | NL185427C (en) |
| NO (1) | NO149446C (en) |
| SE (1) | SE420655B (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5983238A (en) * | 1982-11-04 | 1984-05-14 | Sony Corp | Position detector |
| GB2140562B (en) * | 1983-04-22 | 1986-10-08 | Robert John Collins | Current-ratio digitisers |
| DE3325811A1 (en) * | 1983-07-18 | 1985-01-31 | Aschauer Georg | Device for detecting hand-written symbols for further processing in EDP systems/data acquisition device |
| JPH0654460B2 (en) * | 1986-07-12 | 1994-07-20 | アルプス電気株式会社 | Coordinate detection method |
| HUT49003A (en) * | 1988-01-22 | 1989-07-28 | Tamas Ban | Method and device for determining position of points characterized by planar coordinates |
| US7868874B2 (en) | 2005-11-15 | 2011-01-11 | Synaptics Incorporated | Methods and systems for detecting a position-based attribute of an object using digital codes |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3461454A (en) * | 1968-06-06 | 1969-08-12 | Ibm | Position identifying device |
| US3648277A (en) * | 1970-07-21 | 1972-03-07 | Science Accessories Corp | Magnetic graphical data device |
| GB1340522A (en) * | 1971-01-14 | 1973-12-12 | Quest Automation | Apparatus for converting graphical information into co-ordinate data |
| US3873770A (en) * | 1974-03-21 | 1975-03-25 | Bendix Corp | Digital position measurement system with stylus tilt error compensation |
-
1976
- 1976-05-21 GB GB21182/76A patent/GB1525649A/en not_active Expired
- 1976-05-21 DE DE2622941A patent/DE2622941C2/en not_active Expired
- 1976-05-21 IT IT49614/76A patent/IT1061979B/en active
- 1976-05-21 SE SE7605788A patent/SE420655B/en not_active IP Right Cessation
- 1976-05-21 FR FR7615404A patent/FR2312012A1/en active Granted
- 1976-05-21 NL NLAANVRAGE7605478,A patent/NL185427C/en not_active IP Right Cessation
- 1976-05-21 NO NO761742A patent/NO149446C/en unknown
- 1976-05-24 CH CH653476A patent/CH595613A5/xx not_active IP Right Cessation
- 1976-05-25 CA CA253,195A patent/CA1080325A/en not_active Expired
-
1982
- 1982-11-25 HK HK492/82A patent/HK49282A/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| SE7605788L (en) | 1976-11-24 |
| CH595613A5 (en) | 1978-02-15 |
| NL7605478A (en) | 1976-11-25 |
| FR2312012B1 (en) | 1982-04-09 |
| NO761742L (en) | 1976-11-24 |
| FR2312012A1 (en) | 1976-12-17 |
| IT1061979B (en) | 1983-04-30 |
| SE420655B (en) | 1981-10-19 |
| GB1525649A (en) | 1978-09-20 |
| NL185427C (en) | 1990-04-02 |
| NL185427B (en) | 1989-11-01 |
| HK49282A (en) | 1982-12-03 |
| DE2622941C2 (en) | 1986-01-30 |
| NO149446B (en) | 1984-01-09 |
| NO149446C (en) | 1984-04-25 |
| DE2622941A1 (en) | 1976-12-09 |
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