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BACKGROUND OF THE INVENTION
The present invention relates to coordinate reading devices which utilize
magnetostrictive material as vibration transmission media.
Graphical data devices requiring position location are commonly employed in
computer data input devices to constitute desired work force saving
systems. In such devices, coordinate reading devices utilizing
magnetostrictive vibration wave delay in magnetostrictive material, (such
as shown in U.S. Pat. Nos. 3,846,580 and 3,904,821), are used widely
because such devices are simple to construct and easy to operate.
Thus, a general explanation of a known such coordinate reading system is
described below referring to FIG. 1.
The device shown in FIG. 1 consists of a tablet 1, a detector 2 having a
pick-up coil and an input/output control 3 which is connected with the
tablet 1 and the detector. The control 3 may be connected to an outside
device 4 which may be any work force saving system.
To read the coordinates of a desired graphical pattern, (e.g. a circuit
network, an electrocardiograph, an X-ray photograph or map), a pen or
cursor type detector 2 traces the graphical pattern placed on the tablet
1. The tracing of the pattern forms analog data which is detected as X and
Y axis deflections from a zero point, and the deflections are transformed
into digital quantities of the input/output control 3 as X and Y
coordinate data which is applied to a computer or printer.
As described, the device performs coordinate analysis in a one dimensional
plane or in a two dimensional plane which measures X and Y axis deviation,
utilizing a magnetostrictive vibration wave delay which is transmitted in
a magnetostrictive material. In a two dimensional plane, tablet 1 has two
magnetostrictive vibration transmission paths Lx and Ly which are vibrated
by excitation coils Wx and Wy respectively to transmit X and Y axis
vibration waves.
To form such magnetostriction vibration transmission paths Lx and Ly,
rolled thin sheet or electroplated film separated from a base plate of
electrostrictive material is cut into rectangles of the desired area.
Exciting coils Wx and Wy are arranged at two edges of the rectangle
respectively. In this case, no visible lines Lx and Ly are present.
Another method utilizes two such sheets, one for each of the X and Y axes,
and forms many slits through the sheets by a photoetching process, to
obtain substantial magnetostrictive vibration transmission lines Lx and Ly
on each sheet. The sheets are layed together with an insulation sheet
therebetween so that the slits are orthogonal to each other and the edges
of the sheets are secured by a suitable adhesive material. The desired
exciting coils Wx and Wy for the X and Y axis are applied to the sheets
respectively. Some other tablets have rolled thin ribbon-shaped sheets, or
rolled alloy wires.
In the above mentioned tablet 1, an exciting pulse current is applied to
each exciting coil Wx and Wy to vibrate the magnetostrictive material
sheet, to produce an excitation magnetic field which excites the sheet to
produce a magnetostrictive vibration which is transmitted in the
transmission path Lx and Ly to the other ends thereof. A detector 2
approaches a point P to be measured. Magnetic flux changes produced by the
electrostrictive vibration which is propagated to the point P induce a
voltage in the detector coil. Since the propagation delay time of the
vibration wave corresponds to distance along the coordinate axis, the time
difference between the detected time at point P and pulse current
application time to the excitation coil is measured by counting clock
pulses which can be used as coordinate values along an X or Y axis. The
delay time is alternately read along X and Y axis. Any desired clock pulse
generation and counting system may be used.
FIG. 2 shows the two dimensional tablet 1 as an actual device. Essential
parts of the table 1, i.e., the above-mentioned vibration transmission
media consisting of a magnetostrictive material must be magnetized to a
suitable magnetic potential before reading operation. The magnetizing must
be repeated with a predetermined period in relation to the frequency of
the reading operation and time delay. Conventionally, a bar magnet 5 moves
slowly from one corner diagonally as shown by arrow 6.
The magnetizing operation is performed before a series of reading. However,
as the magnetizing function should be applied to the vibration
transmission media in the tablet 1 uniformly and in a predetermined
accurate direction, much skill is necessary to move the bar magnet so as
to prevent the disturbing of an accurate coordinate reading operation. The
moving speed of the bar magnet 5 also affects the reading accuracy of the
tablet 1. Further, the distance from the surface of the bar magnet 5 to
the tablet 1 also affects the reading accuracy. The difficult magnetizing
operation must be repeated frequently whenever the exciting condition of
the vibration transmission media is damped. As shown in FIG. 2, the
effective reading area 11 is arranged within an outside casing 12 of the
tablet 1.
When a magnetic disturbance is applied to the magnetostrictive material in
the tablet 1, e.g., a disturbance caused by placing a magnet 7 on the
tablet 1, the magnetizing effect of the tablet 1 is disturbed greatly, and
the reading accuracy and reading function are also disturbed. Thus, after
the magnet 7 is removed, the above-mentioned bar magnet magnetizing must
be applied. Magnetic disturbance sources such as the magnet 7 are commonly
present in stationery and business instruments so that care must be paid
to prevent such a magnet from being placed near the tablet 1. When an
operator does not know or notice that such a magnetic disturbance has been
applied to the tablet 1, the coordinate readings which result are
completely unreliable.
SUMMARY OF THE INVENTION
A primary object of the invention is to provide a coordinate reading device
which eliminates the manual magnetizing operation.
To attain the above-mentioned object, a coordinate reading device including
magnetostrictive vibration transmission media of magnetostrictive material
to attain coordinate readings along at least one dimension includes,
according to the present invention, at least one fixed magnetizing coil
mounted adjacent at least one side surface of said vibration transmission
media to regularly magnetize the entire effective coordinate reading
region of the media in a substantially uniform fashion, and at least one
magnetizing current supply means to apply a magnetizing current to said
fixed magnetizing coil.
Thus, the magnetizing operation is easy and uniform, and by magnetizing
just before reading, disturbance effects are completely eliminated.
A further object of the present invention is to provide a coordinate
reading device which regulates the magnetic spin distribution of
magnetostrictive material which forms the vibration transmission media, to
eliminate reading errors between first and second readings after a unit
effective excitation which is applied just after magnetizing.
To attain the object, a coordinate reading device including
magnetostrictive vibration transmission media of magnetostrictive material
to attain coordinate readings along at least one direction includes,
according to a feature of the present invention, a preparatory exciting
system to apply at least one pre-excitation signal to the exciting coil of
said vibration transmission media before said coil receives its unit
effective excitation.
Thus, magnetic spin distribution in the magnetostrictive material is
regulated, i.e., the directional property of the magnetization vector is
adjusted to the magnetostrictive vibration before an actual reading, so
that the reading error is greatly mitigated and reading accuracy is
improved.
The other objects and advantages of the present invention will become
apparent from the following detailed description of preferred embodiments
with the accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is an illustration to explain the general operation of a known
coordinate reading device;
FIG. 2 is an illustration of a conventional magnetizing device;
FIG. 3 is a diagrammatic view of a one dimension coordinate reading device
according to the present invention;
FIG. 4 is a diagrammatic view of a two dimension coordinate reading device;
FIG. 5 shows another embodiment of a two dimension coordinate reading
device;
FIG. 6 is a circuit diagram of a preparatory exciting system, according to
the present invention;
FIG. 7 is a pulse timing chart of a preparatory exciting and automatic
magnetizing shown in FIG. 6;
FIGS. 8(A) and (B) are timing charts between magnetizing current and
exciting output;
FIGS. 9(A) and (B) show other embodiment of magnetizing coils shown in
FIGS. 3-5; and
FIGS. 10(A)-(C) show other embodiments of the magnetizing coils shown in
FIGS. 9(A) and (B).
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
FIGS. 3-5 show the diagrammatic construction of coordinate reading devices
according to the present invention. FIG. 3 shows a one-dimension reading
device and FIGS. 4 and 5 show two embodiments of a two dimension reading
device. As shown in FIGS. 3-5, fixed magnetizing coils 20, 20x, 20y and
20' are wound about tablet 1, according to the present invention. The
magnetizing coils 20, 20x, 20y and 20' are wound about a vibration
transmission media 1 formed by a desired magnetostrictive material to
accurately magnetize the effective reading region 11 shown in FIG. 3 and
regions 11x and 11y shown in FIG. 4 of the vibration transmission media 1.
The terminals of the magnetizing coils are connected to a magnetizing
current source 30 to effect a substantially uniform regular magnetization.
Vibration exciting coils Wx and Wy which are provided to produce x and y
axis magnetostrictive vibration waves are also shown.
Input/output control 3A includes the magnetizing current source 30, a
preparatory exciting system 60 and a coordinate transducer system 50. In
addition, stylus 2 shown in FIG. 1 and not shown in FIGS. 3-5 is also
connected with the control 3A. The coordinate transducer system 50
corresponds to a conventional count circuit section of known tablet
controllers and includes clock pulse circuits, amplifiers, signal
amplifier circuits, various logic circuits, gate circuits, delay circuits
reset pulse generating circuits, counters and digital indication and
output circuits. The preparatory exciting system 60, according to the
present invention includes a plurality of delay circuits, logic circuits
and a true exciting section, and will be explained in detail afterwards
referring to FIGS. 6 and 7.
In the two dimension tablet shown in FIG. 4, the fixed magnetizing coils
20x and 20y may be energized simultaneously before reading, or may be
energized separately in a suitable period corresponding to the reading
conditions. The tablet shown in FIG. 5 includes the magnetizing coil 20'
which is inclined at angles .theta.x and .theta.y to the direction of
magnetostrictive vibration waves Xw and Yw which are produced by the
magnetostrictive vibration exciting coils Wx and Wy respectively. The
angles .theta.x and .theta.y may be equal to each other or may be equal to
the angle of diagonal line of effective reading region which may be
generally square.
The magnetizing current source 30 applies the desired magnetizing current
corresponding to the characteristics of the tablet 1. The current source
30 may include a magnetizing current pulse producing circuit which
produces regular magnetizing current pulses, and timing control circuit
which initiates the magnetizing current pulse at suitable timing
intervals. Alternately, the current source 30 may include a D.C.
magnetizing current producing circuit which produces a D.C. magnetizing
current and the above mentioned timing circuit.
FIGS. 6 and 7 respectively show a circuit diagram of the two dimension
reading device shown in FIGS. 4 and 5 and timing chart of the circuit.
The circuit shown in FIG. 6 includes a stylus switch SW1 which is included
in the pen or cursor type detector 2 shown in FIG. 1. The detected signal
from the stylus or detector 2 is supplied to the input/output control 3A
of the coordinate reading device through a suitable signal processing
circuit, e.g.--the conventional chatter prevention circuit 100, shown in
FIG. 6. In such a circuit 100, resistor 106 is connected to a DC supply
voltage Vs. The voltage at the input to NAND gate 102 is equal to the
voltage Vs until the switch SW1 is closed. When switch SW1 is closed, the
voltage output of gate 102 becomes a logic "1". However, due to switch
bounce or chatter, the voltage at the input to gate 102 does not merely
change from Vs to zero volts but instead may traverse the range of
voltages a number of times. Capacitors 101 and 103 serve to snub the
shorter voltage transients caused by the switch bounce but cannot
eliminate them entirely. Therefore, NAND gates 104 and 105, formed into a
flip-flop are added to reduce the effects of the switch bounce transients.
Such a circuit 100 is conventional and widely used in the industry. The
input/output control 3A includes the magnetizing current source 30, the
coordinate transducer system 50 and the preparatory exciting system 60 as
shown in FIGS. 3-5.
The preparatory exciting system 60 includes a plurality of delay circuits
D.sub.1 -D.sub.4, a logic circuit and a main exciting system 40. Each of
the delay circuits D.sub.1 -D.sub.4 comprise dual one-shot multivibrator
delay circuits and may be constructed from commercially available dual
one-shot integrated circuit chips. As shown in the timing circuit of FIG.
7, the output b of one half of delay circuit D.sub.1 is a pulse of
predetermined pulse-width whose leading edge occurs immediately after the
leading edge of pulse a present at the output of gate 105, the generation
of pulse b triggered by the leading edge of pulse a. The second half of
circuit D.sub.1 is triggered by the falling edge of pulse b to produce a
pulse c of predetermined width. The leading edge of pulse b triggers
circuit D.sub.3 to generate pulse h having a narrow pulse-width with
respect to pulses a-c. The trailing edge of pulse c triggers one-half of
circuit D.sub.2 to generate pulse d of a predetermined pulse-width.
The second half of circuit D.sub.2 is triggered by the trailing edge of
pulse d to generate pulse e of a predetermined pulse-width. Pulses c and e
are combined in OR gate 106 to trigger the two halves of circuit D.sub.4.
One-half of circuit D.sub.4 triggered by the leading edges of the pulse
output of gate 108 generating pulse f while the second half of circuit
D.sub.4 is triggered by the trailing edges of the pulse output of gate 108
generating pulses g. The circuit shown in FIG. 6 is constituted from
digital integrated circuit networks, however, desired discrete circuit
elements may be used.
As shown in FIG. 6, the delay circuit D.sub.3 controls the magnetizing
timing to form an automatic magnetizing circuit. Thus, the magnetizing
current source 30 is triggered by pulse signal h which is produced when
the switch Sw1 is turned on.
The delay circuits D.sub.1 and D.sub.2 product suitably delayed preparatory
exciting control pulses b, c, d, and e, which trigger circuit D.sub.3,
whose output pulses thereof are applied to the main exciting system 40 as
pre-excitation trigger pulses f and g, so that the main exciting system 40
is excited once or twice as the switch SW1 is closed but before the actual
reading is started.
The main exciting system 40 supplies the desired exciting current to the X
and Y exciting coils which are associated with the magnetostrictive
vibration transmission media as shown in FIG. 1, and the output thereof
are the exciting pulse currents X.sub.E and Y.sub.E as shown in FIG. 6.
Thus, the preparatory exciting system 60 according to the present invention
initiates the main exciting system 40 by pulse signals f and g to generate
pulse currents to regulate the magnetic vector distribution of the
vibration transmission media, before the exciting outputs X.sub.E and
Y.sub.E from the main exciting system 40 are supplied for use as the unit
effective exciting outputs during the coordinate reading operation. The
actual circuitry used in the magnetizing current source 30 and the main
exciting system 40 has not been illustrated in the drawings or discussed
in detail herewith since such circuitry is conventional and known to those
of skill in the art.
Preferably, at least one preparatory excitation current pulse is applied to
the X-axis component before main excitation and at least one preparatory
excitation current pulse is applied to the Y-axis component. However, the
X and Y-axis components may be generated sequentially, or both components
may be generated simultaneously. Further, the preparatory excitation
current pulses may be applied intermittently, in place of being applied
every energization of the switch SW1.
The timing of the preparatory excitation is arranged such that, after the
magnetostrictive vibration in the vibration transmission media produced by
the preparatory excitation is sufficiently attenuated, the main excitation
is applied.
The control pulses b and c may be combined into a single pulse. A circuit
to produce such a combined control pulse is well known in the art
(e.g.--an OR gate).
The coordinate transducer system 50 produces desired coordinate analysis
output from the excitation transmission delay in the magnetostriction
vibration transmission media caused by the excitation of the main
excitation system 40 and based on the detected signal from the stylus; the
output of system 50 generated by processing the signals in the
above-mentioned circuit.
FIGS. 8(A) and (B) show relative timing charts between magnetizing function
by the magnetizing current source 30 and the reading operation. In the
FIGS. 8(A) and 8(B), T.sub.E is the magnetizing period, Tx is the reading
period of the coordinate value along the X-axis, and Ty is the reading
period of the coordinate value along the Y-axis.
In FIG. 8(A), 30P(31P) is a trigger pulse of the magnetizing current pulse
which is controlled by magnetizing output pulse of magnetizing current
pulse production circuit 32 outputted to the fixed magnetizing coils 20x
and 20y and is applied by the timing control circuit 31 such as shown in
FIG. 4.
The timing control circuit 31 also controls the excitation timing of the
excitation coils Wx and Wy of the tablet 1. In this case, to the fixed
magnetizing coils 20x and 20y, a magnetizing current pulse initiated by
the trigger pulse 31P from the timing control circuit may be applied
separately, such that the coil 20x is energized just before the X-axis
coordinate reading period Tx and the coil 20y is energized just before the
Y-axis coordinate reading period Ty.
FIG. 8(B) is a timing chart showing that a DC magnetizing current 30P
(32P') is applied to the fixed magnetizing coil 20' shown in FIG. 5. Tx
and Ty are reading periods of the X- and Y-axis coordinate values. Tp is
the trigger timing of the excitation coils Wx and Wy. In this case, the
timing control circuit 31' may initiate the DC magnetizing current
production circuit 32' to apply a magnetizing current to the coil 20'
during a series of coordinate reading operations such as that shown in
FIG. 8(B) or only before the reading operation such as that shown in FIG.
8(A).
The control system based on various timing charts may be selected
corresponding to a reading process either of a one-shot mode or a
continuous mode, and the selected timing is programmed to attain desired
operability of the device corresponding to its operational conditions.
Other embodiments of fixed magnetizing coils, according to the present
invention are shown in FIGS. 9 and 10. The magnetizing coils shown in
FIGS. 9 and 10 are not wound about the vibration transmission media 1, and
are placed on one or both surfaces of the media 1.
As shown in FIG. 9(A), a fixed magnetizing coil 20A is placed on both
surfaces of the tablet 1. The magnetizing coils 20A for the X- and Y-axis
may be placed on one surface of the tablet 1. Inclined magnetizing coil
20A' corresponding to the wound coil 20' shown in FIG. 5 is placed on one
surface of the two dimension tablet 1 as shown in FIG. 9(B). The shapes of
the magnetizing coils 20A and 20A' are arranged so as to magnetize the
effective reading region of the vibration transmission media 1, to obtain
a substantially uniform and regular magnetized condition.
Various shapes of the magnetizing coils are shown in FIGS. 10(A), (B) and
(C). A loop shaped coil 20B, a coil 20C having non-uniform spacing, and a
wave form coil 20D are shown respectively. These coils may be wound about
the tablet 1, or may be placed on one or both sides of the tablet 1.
In the inclined magnetizing coils 20' and 20A' shown in FIGS. 5 and 9(B),
angles .theta.x and .theta.y (shown only in FIG. 5) between the conductor
of the magnetizing coil 20' or 20A' and X- and Y-axis direction vibration
wave lines Xw and Yw which are transmitted in the tablet 1 can be arranged
at any desired angle.
It will be appreciated that the coordinate reading device according to the
invention comprises a fixed magnetizing coil means and a magnetizing
current source which supplies magnetizing current to the coil means. Thus,
the difficult and time consuming magnetizing operation is greatly
simplified and magnetizing is easily and automatically performed. As
explained the magnetizing operation may be performed just before reading,
so that the device can recover from any magnetic disturbance which might
be applied to the device. Also, as the magnetizing operation is uniform,
reading accuracy is stabilized and improved.
Further, by combining the magnetization control system with the preparatory
exciting system 60, according to another feature of the present invention,
the coordinate reading process has stability and improved accuracy, and
completely compensates for magnetic disturbances.
The preparatory exciting system 60 is initiated by stylus or reading
operation pen, i.e., the detector 2 shown in FIG. 1, in the circuit shown
in FIG. 6. The preparatory exciting system may be operated with any
suitable control pulse generator.
As described in detail, the coordinate reading device having preparatory
exciting system 60 completely compensates for any magnetic disturbance
effect to the tablet 1 and also regulates the magnetic vector distribution
in the magnetostrictive vibration transmission media, so that the measured
coordinate analysis value has a high accuracy and high reliability.
Further, the preparatory exciting system 60 includes an automatic
magnetizing circuit which has the delay circuit D.sub.3 arranged so that,
as shown in FIG. 8, the magnetizing operation can be performed
automatically and at most preferable timing.
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