U.S. patent application number 13/923213 was filed with the patent office on 2014-02-13 for position detecting device and position indicator thereof.
This patent application is currently assigned to WACOM CO., LTD.. The applicant listed for this patent is WACOM CO., LTD.. Invention is credited to Yuji Katsurahira.
Application Number | 20140043301 13/923213 |
Document ID | / |
Family ID | 49036425 |
Filed Date | 2014-02-13 |
United States Patent
Application |
20140043301 |
Kind Code |
A1 |
Katsurahira; Yuji |
February 13, 2014 |
POSITION DETECTING DEVICE AND POSITION INDICATOR THEREOF
Abstract
A position detecting device includes: a position indicator
including a signal generator configured to generate an
alternating-current signal, a plurality of electrodes, a switch
circuit configured to supply the alternating-current signal to
selected one(s) of the electrodes based on a predetermined
electrode-selection pattern, and a pattern information transmitter
configured to transmit pattern information indicating a set
predetermined pattern. A tablet includes electrodes disposed in a
flat surface manner, a signal position detector configured to
obtain a coordinate position of the alternating-current signal
transmitted from said selected one(s) of the electrodes on a tablet
surface based on distribution of a signal level induced in each of
the tablet electrodes by the alternating-current signal, a pattern
information receiver, and a rotation angle calculator configured to
calculate a rotation angle of the position indicator about a
perpendicular direction to the tablet surface based on a plurality
of coordinate positions obtained according to the received pattern
information.
Inventors: |
Katsurahira; Yuji; (Saitama,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
WACOM CO., LTD. |
SAITAMA |
|
JP |
|
|
Assignee: |
WACOM CO., LTD.
SAITAMA
JP
|
Family ID: |
49036425 |
Appl. No.: |
13/923213 |
Filed: |
June 20, 2013 |
Current U.S.
Class: |
345/179 |
Current CPC
Class: |
G06F 3/0441 20190501;
G06F 2203/04104 20130101; G06F 3/03545 20130101; G06F 3/0446
20190501; G06F 3/0442 20190501 |
Class at
Publication: |
345/179 |
International
Class: |
G06F 3/0354 20060101
G06F003/0354 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 8, 2012 |
JP |
2012-176102 |
Claims
1. A position detecting device comprising: a position indicator
configured to transmit an alternating-current signal; and a tablet
capable of being capacitively coupled to the position indicator,
wherein the position detecting device obtains a position indicated
by the position indicator on the tablet by capacitively coupling
the position indicator and the tablet, the position indicator
includes: a signal generator configured to generate an
alternating-current signal, a plurality of electrodes disposed at a
position indicating part of the position indicator, a switch
circuit configured to supply the alternating-current signal to
selected one(s) of the plurality of electrodes based on a
predetermined electrode-selection pattern, and a pattern
information transmitter configured to transmit, to the tablet,
pattern information indicating a set predetermined pattern when the
pattern is switched by the switch circuit, and the tablet includes:
a plurality of tablet electrodes disposed in a flat surface manner,
a signal position detector configured to obtain a coordinate
position of the alternating-current signal transmitted from said
selected one(s) of the electrodes on a tablet surface based on
distribution of a level of a signal induced in each of the tablet
electrodes disposed in the flat surface manner by the
alternating-current signal transmitted from the position indicator,
a pattern information receiver configured to receive the pattern
information transmitted from the position indicator, and a rotation
angle calculator configured to calculate a rotation angle of the
position indicator about a perpendicular direction to the tablet
surface based on a plurality of coordinate positions obtained
according to the received pattern information.
2. The position detecting device according to claim 1, wherein: in
the position indicator, a first electrode and a second electrode
are disposed at the position indicating part as the plurality of
electrodes, the switch circuit alternately selects the first and
second electrodes and supplies the alternating-current signal to
the selected one of the electrodes, and the pattern information
transmitter transmits first pattern information to the tablet when
the first electrode is selected by the switch circuit, and
transmits second pattern information to the tablet when the second
electrode is selected by the switch circuit; and in the tablet, a
first coordinate is obtained by the signal position detector when
the first pattern information is received by the pattern
information receiver, and a second coordinate is obtained by the
signal position detector when the second pattern information is
received by the pattern information receiver, and the rotation
angle of the position indicator about the perpendicular direction
to the tablet surface is calculated based on the first coordinate
and the second coordinate.
3. The position detecting device according to claim 1, wherein: in
the position indicator, a first electrode and a second electrode
are disposed at the position indicating part as the plurality of
electrodes, and the switch circuit always supplies the
alternating-current signal to the first electrode and switches
supply of the alternating-current signal to the second electrode
between an on (supply)- and off (no supply)-state, and the pattern
information transmitter transmits first pattern information to the
tablet when the supply of the alternating-current signal to the
second electrode is set to the on-state by the switch circuit, and
transmits second pattern information to the tablet when the supply
of the alternating-current signal to the second electrode is set to
the off-state by the switch circuit; and in the tablet, a
coordinate corresponding to a midpoint position of the first and
second electrodes of the position indicator is obtained as a first
coordinate by the signal position detector when the first pattern
information is received by the pattern information receiver, and a
coordinate corresponding to a position of the first electrode of
the position indicator is obtained as a second coordinate by the
signal position detector when the second pattern information is
received by the pattern information receiver, and the rotation
angle of the position indicator about the perpendicular direction
to the tablet surface is calculated based on the first coordinate
and the second coordinate.
4. A position detecting device comprising: a position indicator
that transmits an alternating-current signal; and a tablet capable
of being capacitively coupled to the position indicator, wherein
the position detecting device obtains a position indicated by the
position indicator on the tablet by capacitively coupling the
position indicator and the tablet, the position indicator includes:
a signal generator configured to generate an alternating-current
signal, at least three electrodes disposed at a position indicating
part of the position indicator, a switch circuit configured to
supply the alternating-current signal to selected one of the
electrodes based on a predetermined electrode-selection pattern,
and a pattern information transmitter configured to transmit, to
the tablet, pattern information indicating a set predetermined
pattern when the pattern is switched by the switch circuit, and the
tablet includes: a plurality of tablet electrodes disposed in a
flat surface manner, a signal position detector configured to
obtain a coordinate position of the alternating-current signal
transmitted from said selected one of the electrodes on a tablet
surface based on distribution of a level of a signal induced in
each of the tablet electrodes disposed in the flat surface manner
by the alternating-current signal transmitted from the position
indicator, a pattern information receiver configured to receive the
pattern information transmitted from the position indicator, and a
tilt angle calculator configured to calculate a tilt angle of the
position indicator relative to the tablet surface based on at least
three coordinate positions and at least three signal intensities
obtained corresponding to at least three kinds of predetermined
electrode-selection patterns indicated in the pattern information
received by the pattern information receiver.
5. The position detecting device according to claim 4, wherein the
switch circuit of the position indicator sequentially selects one
of the at least three electrodes.
6. A position indicator used for inputting an indicated position on
a tablet based on capacitive coupling with the tablet, the position
indicator comprising: a signal generator configured to generate an
alternating-current signal; a plurality of electrodes that are
disposed at a position indicating part and configured to transmit
the alternating-current signal to the tablet; a switch circuit
configured to supply the alternating-current signal to selected
one(s) of the plurality of electrodes based on a predetermined
electrode-selection pattern; and a pattern information configured
to transmit, to the tablet, pattern information indicating a set
predetermined pattern when the pattern is switched by the switch
circuit.
7. The position indicator according to claim 6, wherein a first
electrode and a second electrode are disposed at the position
indicating part as the plurality of electrodes, the switch circuit
alternately selects the first and second electrodes and supplies
the alternating-current signal to the selected one of the
electrodes, and the pattern information transmitter transmits first
pattern information to the tablet when the first electrode is
selected by the switch circuit, and transmits second pattern
information to the tablet when the second electrode is selected by
the switch circuit.
8. The position indicator according to claim 6, wherein a first
electrode and a second electrode are disposed at the position
indicating part as the plurality of electrodes, the switch circuit
always supplies the alternating-current signal to the first
electrode and switches supply of the alternating-current signal to
the second electrode between an on (supply)- and off (no
supply)-state, and the pattern information transmitter transmits
first pattern information to the tablet when the supply of the
alternating-current signal to the second electrode is set to the
on-state by the switch circuit, and transmits second pattern
information to the tablet when the supply of the
alternating-current signal to the second electrode is set to the
off-state by the switch circuit.
9. A position indicator that has a pen shape and is used for
inputting an indicated position on a tablet based on capacitive
coupling with the tablet, the position indicator comprising: a
plurality of electrodes provided at a position indicating part of
the position indicator, and are arranged on a surface perpendicular
to a pen axis direction.
10. The position indicator according to claim 9, wherein the
position indicating part has a core body capable of axially moving
in response to an axial load and the plurality of electrodes are
formed integrally with the core body.
11. The position indicator according to claim 9, wherein the
position indicating part has a chassis to enclose a core body, and
the plurality of electrodes are provided at a tip part of the
chassis.
12. The position indicator according to claim 9, wherein the
position indicating part has a core body and two electrodes are
provided on opposing sides of the core body to oppose each
other.
13. The position indicator according to claim 9, wherein the
position indicating part has a core body and three electrodes are
provided equiangularly around the core body.
14. The position indicator according to claim 9, wherein the
position indicating part is a pen tip part of the position
indicator.
15. The position indicator according to claim 9, further comprising
a switch circuit configured to supply an alternating current signal
to selected one(s) of the plurality of electrodes based on a
predetermined electrode-selection pattern.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application claims priority under 35 U.S.C.
119(a) to Japanese Patent Application No. 2012-176102, filed Aug.
8, 2012, which is incorporated by reference herein.
BACKGROUND
[0002] 1. Technical Field
[0003] The present invention relates to position detecting devices
and position indicators thereof, and particularly to a position
detecting device capable of detecting a tilt of a position
indicator having a pen shape, and/or a rotation angle of the
position indicator about an axis defined by the perpendicular
direction to a tablet surface, and a position indicator
thereof.
[0004] 2. Description of the Related Art
[0005] As this type of device, a position detecting device of the
electromagnetic induction system is disclosed in Patent Document 1
(Japanese Patent Laid-open No. Hei 8-30374). According to an
embodiment example of Patent Document 1, two magnetic cores are
juxtaposed at the tip portion of a position indicator having a pen
shape, and a control coil wound around only one magnetic core and a
transmission coil that is so wound as to bundle two magnetic cores
are provided. Both ends of the control coil are controlled to the
on- or off-state by an electronic switch. Based on this, the
distribution of magnetic flux made by a current flowing in the
transmission coil is controlled to calculate a rotation angle of
the position indicator about the pen axis (aligned with the
perpendicular direction to the tablet surface), which is obtained
as two coordinate positions in the position detecting device
(hereinafter referred to as a "tablet" in this specification).
[0006] In another embodiment example of Patent Document 1, three
magnetic cores are juxtaposed at the tip portion of a position
indicator having a pen shape, and three control coils wound around
the respective magnetic cores and a transmission coil that is so
wound as to bundle three magnetic cores are provided. By
controlling the respective control coils similarly, a tilt of the
position indicator relative to the tablet is calculated.
SUMMARY OF THE INVENTION
[0007] The pen-shaped position indicator of the above-described
Patent Document 1 has a problem that the pen is thick because two
magnetic cores are juxtaposed at the tip part. Attempting to thin
the magnetic cores to solve this problem causes the following
problems.
[0008] As a first problem, the distance between the centers of two
magnetic cores is shortened and thus the distance between two
coordinates detected by the tablet is also shortened. This lowers
the resolution and accuracy in calculation of a rotation angle.
This is attributed also to the switch to control the control coil.
This analog switch is configured by a semiconductor circuit and
therefore it is difficult to sufficiently lower the resistance
value when it is turned on. Accordingly, it is difficult to
sufficiently suppress magnetic flux passing through the magnetic
core surrounded by the control coil. Therefore, two coordinates
detected by the tablet are obtained as values closer to each other
than the actual core positions.
[0009] A second problem in thinning the magnetic cores is that
shock due to, e.g., dropping of the pen breaks the core more
easily. That the use purpose of this kind of device is shifting to
portable tablets in recent years is also one of the reasons why
demands for slimmer pens are increasing.
[0010] Another problem (third problem) of the position detecting
device described in Patent Document 1 is that integration with
(finger) touch detection is difficult. In recent years, multi-touch
input of the electrostatic induction system has come to be widely
used and demands for a tablet device allowing both multi-touch
input (by a finger) and pen input are increasing. However, in
contrast to a tablet of the electrostatic induction system, which
uses a sensor obtained by arranging electrodes along the X
direction and the Y direction, the tablet of the electromagnetic
induction system of Patent Document 1 needs to have a sensor
obtained by arranging loop coils and therefore it is difficult to
provide the tablet sensor as a sensor compatible with both
multi-touch input and pen input.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0011] According to aspects of the invention, all of the
above-described first, second, and third problems are solved.
Specifically, according to a first aspect, a thin position
indicator is provided whose rotation angle and tilt relative to the
tablet surface can be accurately obtained.
[0012] According to a second aspect, a tough (durable) position
indicator is provided that is not easily broken due to shock of,
e.g., being dropped even when it is made to have a thin
profile.
[0013] According to a third aspect, a position detecting device is
provided, in which a sensor part of a touch panel based on the
electrostatic coupling system can be used also as a tablet
part.
[0014] According to an exemplary embodiment, a position detecting
device is provided that uses electrostatic coupling between a
tablet and a position indicator. In the case of using
electromagnetic induction as in the invention described in Patent
Document 1 described above, if the coil of the position indicator
is thinned, not only the accuracy of detection of coordinates and
rotation angle is significantly lowered but also a core material as
the core of the coil is easily broken. The present invention makes
improvements for the position detecting device of the electrostatic
coupling system, in which a coil does not need to be used in the
position indicator, and has the following configuration.
[0015] The position indicator includes a signal generator that
generates an alternating-current signal, a plurality of electrodes
disposed at a position indicating part (e.g., a pen tip part), a
switch circuit that supplies the alternating-current signal to
selected one(s) of the electrodes based on a predetermined
electrode-selection pattern, and a pattern information transmitter
that transmits, to the tablet, pattern information indicating a set
predetermined pattern when the pattern is switched by the switch
circuit.
[0016] The tablet includes a plurality of electrodes disposed in a
flat surface manner and a signal position detector that obtains the
coordinate position of the alternating-current signal transmitted
from said selected one(s) of the electrodes on the tablet surface
based on distribution of the level of a signal induced in each of
the tablet electrodes disposed in the flat surface manner. The
tablet further includes a pattern information receiver that
receives the pattern information transmitted from the position
indicator, and a rotation angle calculator that calculates a
rotation angle of the position indicator about the perpendicular
direction to the tablet surface based on a plurality of coordinate
positions obtained according to the received pattern
information.
[0017] Furthermore, as another mode of the present invention, the
present invention has the following configuration in conjunction
with the above-described configuration.
[0018] In the position indicator, at least three electrodes are
provided at the position indicating part (e.g., the pen tip part)
and at least three kinds of predetermined patterns are provided as
electrode-selection patterns selectable by the switch circuit.
[0019] The tablet includes the plurality of electrodes disposed in
a flat surface manner and the signal position detector that obtains
the coordinate position of the alternating-current signal
transmitted from said selected one(s) of the electrodes on the
tablet surface based on distribution of the level of a signal
induced in each of the plurality of electrodes disposed in the flat
surface manner by the alternating-current signal transmitted from
the position indicator. The tablet further includes the pattern
information receiver that receives the pattern information
transmitted from the position indicator, and a tilt angle
calculator that calculates a tilt angle of the position indicator
relative to the tablet surface based on at least three coordinate
positions and at least three signal intensities obtained according
to the at least three kinds of predetermined patterns indicated by
the pattern information received by the pattern information
receiver.
[0020] According to embodiments of the present invention, the
plural electrodes are provided at the position indicating part
(e.g., pen tip part) of the position indicator and the driven
electrode(s) is switched time-wise serially. This allows for
determining a rotation angle of the position indicator about the
perpendicular direction to the tablet surface as well as a tilt of
the position indicator relative to the tablet surface.
[0021] According to embodiments of the present invention,
electrostatic coupling with the tablet is used. Thus, the position
indicator, whose rotation angle and tilt can be obtained, can be
realized in a thin profile.
[0022] According to embodiments of the present invention, a
magnetic material such as a ferrite core does not need to be used
for the position indicator. Therefore, even when the position
indicator, whose rotation angle and tilt can be obtained, is formed
into a thin shape, the position indicator is not easily broken due
to shock from, e.g., being dropped.
[0023] According to embodiments of the present invention, a
coordinate position is obtained by electrostatic coupling with the
tablet. Therefore, the tablet sensor can be used commonly as the
sensor for a touch panel of the electrostatic system, while at the
same time achieving a position indicator whose rotation angle and
tilt can be obtained.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0024] FIG. 1 is a structural diagram of a position indicating part
in a position indicator of a first embodiment example of the
present invention;
[0025] FIG. 2 is a sectional view of a core in the position
indicator of the first embodiment example of the present
invention;
[0026] FIG. 3 is a circuit configuration diagram of the position
indicator of the first embodiment example of the present
invention;
[0027] FIG. 4 is a diagram for explaining the operation of the
position indicator of the first embodiment example of the present
invention;
[0028] FIG. 5 is a configuration diagram of a tablet;
[0029] FIG. 6 is a diagram for explaining X-axis whole surface scan
operation in the tablet;
[0030] FIG. 7 is a diagram for explaining transition operation to
partial scan in the tablet;
[0031] FIGS. 8A-8B are diagrams that together constitute a single
diagram of FIG. 8 for explaining partial scan operation in the
tablet of the first embodiment example of the present
invention;
[0032] FIG. 9 is a diagram for explaining the principle of rotation
angle measurement;
[0033] FIG. 10 is a structural diagram of a position indicating
part in a position indicator of a second embodiment example of the
present invention;
[0034] FIG. 11 is a diagram showing the arrangement of electrodes
in the position indicator of the second embodiment example of the
present invention;
[0035] FIG. 12 is a circuit configuration diagram of the position
indicator of the second embodiment example of the present
invention;
[0036] FIG. 13 is a diagram for explaining the operation of the
position indicator of the second embodiment example of the present
invention;
[0037] FIGS. 14A-14B are diagrams that together constitute a single
diagram of FIG. 14 for explaining partial scan operation in a
tablet of the second embodiment example of the present
invention;
[0038] FIG. 15 is a structural diagram of a position indicating
part in a position indicator of a third embodiment example of the
present invention;
[0039] FIG. 16 is a diagram showing the arrangement of electrodes
in the position indicator of the third embodiment example of the
present invention;
[0040] FIG. 17 is a circuit configuration diagram of the position
indicator of the third embodiment example of the present
invention;
[0041] FIG. 18 is a diagram for explaining the operation of the
position indicator of the third embodiment example of the present
invention;
[0042] FIGS. 19A-19B are diagrams that together constitute a single
diagram of FIG. 19 for explaining partial scan operation in a
tablet of the third embodiment example of the present
invention;
[0043] FIG. 20 is a diagram for explaining the principle of
measurement of a tilt of the position indicator of the third
embodiment example of the present invention; and
[0044] FIG. 21 is a diagram for explaining examples of other shapes
of the tip part of the position indicator.
DETAILED DESCRIPTION
[0045] Three embodiment examples will be specifically described
below as position detecting devices and position indicators thereof
according to embodiments of this invention with reference to the
drawings.
First Embodiment Example
[0046] FIG. 1 is a diagram showing the structure of a position
indicating part in a position indicator of a first embodiment
example according to the present invention. In FIG. 1, numeral 11
denotes a core that transmits pressure applied to the pen tip and
it is molded by an insulating material such as plastic. Numeral 12
denotes a variable-capacitance capacitor whose capacitance changes
depending on the writing pressure applied via the core 11 and,
e.g., such as the one disclosed in Japanese Patent Laid-open No.
Hei 4-96212 (Patent Document 2). The variable-capacitance capacitor
12 has a coupling part to the core 11 as disclosed in the
above-described Patent Document 2 and this coupling part is so
configured as to slightly move together with the core 11 depending
on the writing pressure applied to the core 11.
[0047] Numerals 13 and 14 denote electrodes and they are buried in
the core 11. FIG. 2 is a sectional view when the core 11, in which
the electrodes 13 and 14 are buried, is cut. Numeral 15 denotes a
printed board. A terminal of the variable-capacitance capacitor 12
and the electrodes 13 and 14 are connected to the printed board 15
and circuit components to be described later are mounted on the
printed board 15. In the following description, the electrode 13
will be referred to as the L electrode and the electrode 14 will be
referred to as the R electrode.
[0048] FIG. 3 is a circuit configuration diagram of the position
indicator of the first embodiment example according to the present
invention. In FIG. 3, the same component as that in FIG. 1 is shown
by the same numeral. That is, numeral 12 denotes the
variable-capacitance capacitor and numerals 13 and 14 denote the L
electrode and the R electrode, respectively. Transistors TR1 to TR3
configure an oscillation circuit that oscillates with a resonant
frequency depending on a coil L1 and capacitors C1 and C2. A coil
L2 is coupled to the coil L1 and boosts an AC voltage generated in
the coil L1 to supply a signal of a high voltage to the L electrode
13 and the R electrode 14. Numeral 16 denotes an analog switch for
supplying a signal (d) generated in the coil L2 to only either one
of the L electrode 13 and the R electrode 14.
[0049] Numeral 17 denotes a microprocessor that operates based on a
predetermined program and numeral 18 denotes a battery. An output
signal (b) from a terminal P1 of the microprocessor 17 controls the
above-described oscillation circuit to the on- or off-state via a
transistor TR4. An output signal (a) from a terminal P2 is supplied
to the analog switch 16. In the present embodiment example, the L
electrode 13 is selected when the output signal (a) from the
terminal P2 is at the low level and the R electrode 14 is selected
when it is at the high level.
[0050] As described later, the microprocessor 17 sets a terminal P3
to the high level output state or the input state based on the
predetermined program to thereby charge/discharge the
variable-capacitance capacitor 12 and obtain the value of the
writing pressure applied to the core 11.
[0051] Numeral 19 denotes a DC/DC converter that boosts the voltage
of the battery 18 to generate a power source of a high voltage VP.
The voltage VP is used as a power source to make the analog switch
16 operate and needs to be a voltage with amplitude higher than
that of the signal d generated in the coil L2. A capacitor C3 is to
add an offset voltage so that the signal (d) generated in the coil
L2 may swing in the range of zero to VP.
[0052] FIG. 4 is a diagram showing the operation of the position
indicator of the first embodiment example configured in this manner
and shows how the signals a, b, c, and d in FIG. 3 change. The
microprocessor 17 carries out control to keep the terminal P1
(signal b) at the high level for a certain period with the terminal
P2 (signal a) set to the low level. Thereby, the signal (d) is
radiated from the L electrode 13 for the certain period
continuously (continuous transmission period: L, in FIG. 4). In
this continuous transmission period, the microprocessor 17 controls
the terminal P3 to obtain the writing pressure applied to the
variable-capacitance capacitor 12. Specifically, the microprocessor
17 sets the terminal P3 to the high level output state to charge
the variable-capacitance capacitor 12.
[0053] Next, the terminal P3 is switched to the input state. At
this time, the charge accumulated in the variable-capacitance
capacitor 12 is discharged by a resistor connected in parallel to
it. Thus, the voltage (c) of the variable-capacitance capacitor 12
gradually decreases. A time Tp from the switch of the terminal P3
to the input state until the voltage c is dropped to a threshold is
obtained. This time Tp is equivalent to the writing pressure to be
obtained and the writing pressure is obtained as a 10-bit value in
the present embodiment example.
[0054] Upon ending this continuous transmission period (L), the
microprocessor 17 controls the terminal P1 to the high or low level
with a predetermined cycle (Td) to thereby perform amplitude-shift
keying (ASK) modulation. At this time, the terminal P1 is
invariably set to the high level as the first round of the control
(start signal: L, in FIG. 4). This is to allow the tablet side to
accurately determine the subsequent data transmission timing.
[0055] In the period of Td following this start signal (L), the
terminal P1 is set to the low level in this operation (sign: L, in
FIG. 4). This is for distinction from the case in which the
terminal P2 (signal a) is set to the high level as described
later.
[0056] Subsequently to the sign (L), the 10-bit writing pressure
data obtained by the above-described operation is sequentially
transmitted. Specifically, the terminal P1 is controlled to the low
level when the transmission data is 0 and the terminal P1 is
controlled to the high level when the transmission data is 1
(writing pressure data transmission period: L, in FIG. 4). FIG. 4
shows the case in which the writing pressure to be transmitted is
"0101110101."
[0057] Upon ending the transmission of the 10-bit writing pressure
data, the microprocessor 17 sets the terminal P2 (signal a) to the
high level to switch the analog switch 16 to the R side. This
provides the state in which a signal is transmitted from the R
electrode 14. Also at this time, the terminals P1 and P3 are
controlled exactly as with the above-described case of transmission
by the L electrode to sequentially execute processing of continuous
transmission (R), start signal (R), sign (R), and writing pressure
data transmission (R). At the time of the sign (R), the terminal P1
is set to the high level.
[0058] In the position indicator of the present embodiment example,
transmission is performed with alternate switching between a first
pattern in which only the L electrode is selected and a second
pattern in which only the R electrode is selected. Furthermore, the
"sign" information following the start signal is set to "0" when
the selection is made in the first pattern and the "sign"
information following the start signal is set to "1" when the
selection is made in the second pattern. Such operation is to
identify, on the tablet side, whether the immediately previous
continuous transmission is from the L electrode or from the R
electrode, and is one of features of the present invention.
[0059] FIG. 5 shows a configuration diagram of the tablet in the
present embodiment example. The present embodiment example shows,
as the tablet, a configuration that obtains indicated position and
rotation angle of a position indicator 20 configured as described
above and is capable also of detecting a touch position by a finger
fg.
[0060] In FIG. 5, numeral 20 denotes the position indicator shown
in FIGS. 1 to 3 and the frequency of a signal transmitted from the
position indicator 20 is defined as f1. Numeral 21 denotes a tablet
sensor whose base material is transparent glass. An X electrode
group arranged in the X direction is provided on the front surface
of the tablet sensor 21 and a Y electrode group arranged in the Y
direction is provided on the back surface. These X electrode group
and Y electrode group are formed as transparent electrodes by
indium tin oxide (ITO). The tablet sensor 21 is disposed on a
display device (not shown) and an input can be made directly to its
display place by the position indicator 20, the finger fg of the
user, etc.
[0061] Numeral 22 denotes an X selection circuit that selects one
electrode from the X electrode group and numeral 23 denotes a Y
selection circuit that selects one electrode from the Y electrode
group. The present embodiment example will be explained based on
the assumption that the number of X electrodes is 40 (X1 to X40)
and the number of Y electrodes is 30 (Y1 to Y30).
[0062] Numeral 24 denotes an oscillator for supplying a drive
signal to the Y electrodes when the present embodiment example is
operated for touch detection and the oscillation frequency is
defined as f2. Numeral 25 denotes a switch circuit that switches
the connection target of the Y electrode selected by the Y
selection circuit 23 to the oscillator 24 or the side of an
amplification circuit to be described later. Numeral 26 denotes a
control circuit to control the respective parts in the tablet of
the present embodiment example. Specifically, when this device is
operated for touch detection, a control signal e from the control
circuit 26 to the switch circuit 25 is set to the high level "1" to
select the side of the oscillator 24. When this device detects the
position indicator 20, the control signal e is set to the low level
"0" to select the amplification circuit side.
[0063] Numeral 27 denotes a switch circuit. It selects the X
electrode selected by the X selection circuit 22 or selects the Y
electrode selected by the Y selection circuit 23 via the switch
circuit 25 to connect it to an amplification circuit 28.
Specifically, when this device is operated for touch detection, a
control signal f from the control circuit 26 to the switch circuit
27 is set to the low level "0" to select the side of the X
selection circuit 22. When this device is operated to detect the
position indicator 20 and the X-axis coordinate of the position
indicator 20 is to be obtained, the control signal f is set to the
low level "0" to select the side of the X selection circuit 22.
When this device is operated to detect the position indicator 20
and the Y-axis coordinate of the position indicator 20 is to be
obtained, the control signal f is set to the high level "1" to
select the side of the Y selection circuit 23.
[0064] In FIG. 5, numeral 28 denotes the amplification circuit and
numeral 29 denotes a gain control circuit. The output of the
amplification circuit 28 is connected to the gain control circuit
29 and is so set as to become an output signal at a proper level by
a control signal g from the control circuit 26.
[0065] Numeral 30 denotes a band-pass filter circuit having a
predetermined band width centered at the frequency f1 or the
frequency f2. This center frequency is switched by a control signal
h from the control circuit 26. The frequency is switched to f1 when
this device carries out operation of detecting the position
indicator 20, and is switched to f2 when touch detection operation
is carried out.
[0066] In FIG. 5, numeral 31 denotes a detection circuit and
numeral 32 denotes an analog/digital (AD) converter. Numeral 33
denotes a microprocessor. An output signal of the band-pass filter
circuit 30 is detected by the detection circuit 31 and is converted
to a digital value by the AD conversion circuit 32 based on a
control signal j from the control circuit 26. This digital data k
is read and processed by the microprocessor 33.
[0067] The control circuit 26 supplies a control signal m and a
control signal n to the X selection circuit 22 and the Y selection
circuit 23, respectively, to select one electrode from each of the
X electrode group and the Y electrode group.
[0068] The microprocessor 33 includes ROM and RAM inside and
operates by a program stored in the ROM. The microprocessor 33
outputs a control signal p to control the control circuit 26 so
that the control circuit 26 may output the control signals e to j,
m, and n at predetermined timing.
[0069] Operation when the tablet of the present embodiment example
configured in this manner performs touch detection will be briefly
described. As described above, in the touch detection, the switch
circuit 25 is connected to the side of the oscillation circuit 24
to supply the drive signal to the Y electrode selected by the Y
selection circuit 23. Furthermore, the X electrode selected by the
X selection circuit 22 is connected to the amplification circuit 28
via the switch circuit 27 and the signal level from the
amplification circuit 28 is converted to a digital value by the AD
conversion circuit 32 via the gain control circuit 29, the
band-pass filter circuit 30, and the detection circuit 31.
[0070] At this time, if a finger is made to touch the intersection
of the respective electrodes selected by the X selection circuit 22
and the Y selection circuit 23, the detected signal level is lower
than the level when a finger is absent. Therefore, if the signal
level when a finger is absent is obtained in advance for all
intersections of the X electrodes and the Y electrodes, the touch
position can be obtained from the position at which the signal
level is lowered.
[0071] Operation when the tablet of the present embodiment example
detects indicated position and rotation angle of the position
indicator 20 will be described below. The microprocessor 33 outputs
the control signal p to the control circuit 26 so that the control
signal e may be set to the low level "0" to select the
amplification circuit side in the switch circuit 25 and the control
signal f may be set to the low level "0" to select the X electrode
side in the switch circuit 27. In this state, only the X electrode
selected by the X selection circuit 22 is connected to the
amplification circuit 28 and the Y electrode is connected to
neither the amplification circuit 28 nor the oscillation circuit
24.
[0072] FIG. 6 shows X-axis whole surface scan operation for
obtaining the rough X-direction position of the position indicator
20 on the tablet sensor 21. The microprocessor 33 makes the control
circuit 26 output the control signal m that causes the X selection
circuit 22 to select the electrode X1, and reads the signal level
(k) at this time. The microprocessor 33 reads the signal level (k)
while making the control circuit 26 sequentially switch the
electrode selected by the X selection circuit 22 to the electrodes
X2, X3, X4 . . . .
[0073] At this time, if the detected signal level does not reach a
predetermined value with all electrodes X1 to X40, the
microprocessor 33 determines that the position indicator 20 is not
present on the tablet sensor 21 and repeats the operation of FIG.
6. If a signal at a level equal to or higher than the predetermined
value is detected from any of the electrodes X1 to X40, the
microprocessor 33 stores the number of the X electrode from which
the highest signal level is detected (in FIG. 6, X11).
[0074] Upon getting to know that the position indicator 20 is
present near the electrode X11, the microprocessor 33 carries out
transition operation to partial scan. FIG. 7 is a diagram for
explaining the transition operation to the partial scan in the
tablet. This transition operation to the partial scan is operation
for the microprocessor 33 to synchronize the timing with the
operation of the position indicator 20 by detecting the start time
of the continuous transmission period of the position indicator 20
when the position indicator 20 repeats operation like that shown in
FIG. 4, and to obtain the rough position about the Y-axis.
[0075] In FIG. 7, the microprocessor 33 controls the control
circuit 26 so that the X selection circuit 22 may select the
electrode X11 obtained in the above-described X-axis whole surface
scan operation. At this time, a signal corresponding to the signal
transmitted from the position indicator 20 is induced in the
electrode X11 and a voltage corresponding to its signal level is
generated in the detection circuit 31. The microprocessor 33 makes
the AD conversion circuit 32 operate with a constant cycle to read
the signal level (k). This cycle of the operation of the AD
conversion circuit 32 is set to a time sufficiently shorter than
the cycle of transmission by the position indicator 20 in the
writing pressure data transmission period.
[0076] When the signal level output by the AD conversion circuit 32
is equal to or higher than a predetermined value for a certain time
(Ts) continuously, the microprocessor 33 determines that the
continuous transmission period of the position indicator 20 has
been started and transitions to Y-axis whole surface scan operation
(FIG. 7). This time Ts is set to a time sufficiently longer than
the cycle of transmission by the position indicator 20 in the
writing pressure data transmission period.
[0077] The microprocessor 33 controls the control circuit 26 so
that the control signal f may be set to the high level "1" to
select the Y electrode side in the switch circuit 27. Furthermore,
the Y selection circuit 23 sequentially selects the electrodes from
Y1 to Y30 and the AD conversion circuit 32 is operated to read the
signal level (k). At this time, the microprocessor 33 stores the
electrode from which the highest signal level is detected. The
explanation of the present embodiment example will be made based on
the assumption that the highest signal level is detected from the
electrode Y20.
[0078] After the Y selection circuit 23 selects the last electrode
Y30 and detection of the signal level is ended, the microprocessor
33 carries out operation for waiting for the end of the continuous
transmission period of the position indicator 20. The
microprocessor 33 controls the control circuit 26 so that the
control signal f may be set to the low level "0" to select the X
electrode side in the switch circuit 27. Furthermore, the
microprocessor 33 carries out control to make the X selection
circuit 22 select the electrode X11. At this time, a signal at a
level equal to or higher than the above-described predetermined
value is detected if transmission from the position indicator 20
still continues. The time at which the received signal level comes
short of the predetermined value is the end time of the continuous
transmission from the position indicator 20. Subsequently, the
position indicator 20 enters the writing pressure data transmission
period. However, the detailed position of the position indicator 20
has not yet been obtained at this timing. Thus, the microprocessor
33 does not read writing pressure data and transitions to partial
scan operation shown in FIGS. 8A-8B.
[0079] FIGS. 8A-8B are diagrams that together constitute a single
diagram of FIG. 8 for explaining the partial scan operation in the
tablet of the present embodiment example. When the signal level
output by the AD conversion circuit 32 is equal to or higher than
the predetermined value for the certain time (Ts) continuously
while the electrode X11 is selected, the microprocessor 33
determines that the continuous transmission period of the position
indicator 20 has been started and transitions to coordinate
detection operation (step 1 in FIG. 8A). This time Ts is the same
as that explained with FIG. 7 and is set to a time sufficiently
longer than the cycle of transmission by the position indicator 20
in the writing pressure data transmission period.
[0080] In order to obtain the X coordinate of the signal from the
position indicator 20, the microprocessor 33 makes the X selection
circuit 22 sequentially select five electrodes centered at X11 (X9
to X13) with the control signal f kept at the low level "0," and
makes the AD conversion circuit 32 operate to read the signal level
(step 1). At this time, the number of the electrode from which the
highest signal level is detected (X11, in this example) and this
signal level (Vpx0) are stored. In addition, the levels detected
with both electrodes adjacent to this electrode are stored as Vax0
and Vbx0 (step 1).
[0081] Next, in order to obtain the Y coordinate of the signal from
the position indicator 20, the microprocessor 33 sets the control
signal f to the high level "1." Furthermore, the microprocessor 33
makes the Y selection circuit 23 sequentially select five
electrodes centered at Y20 (Y18 to Y22) and reads the signal level
(step 1). At this time, the number of the electrode from which the
highest signal level is detected (Y20, in this example) and this
signal level (Vpy0) are stored. In addition, the levels detected
with both electrodes adjacent to this electrode are stored as Vay0
and Vby0 (step 1). The obtained signal levels Vpx0, Vax0, Vbx0,
Vpy0, Vay0, and Vby0 are used for calculation of coordinate values
by a calculation equation to be described later.
[0082] Next, the microprocessor 33 carries out operation for
waiting for the end of the continuous transmission period of the
position indicator 20. The microprocessor 33 sets the control
signal f to the low level "0" and carries out control to make the X
selection circuit 22 select the electrode X11, from which the peak
level is detected in the above-described coordinate detection
operation. At this time, the time at which the received signal
level comes short of the predetermined value is the end time of the
continuous transmission from the position indicator 20 (step
1).
[0083] Upon detecting the end of the continuous transmission from
the position indicator 20, the microprocessor 33 enters operation
of detecting the timing of the start signal transmitted prior to
writing pressure data (step 2). The microprocessor 33 carries out
control to repeatedly activate the AD conversion circuit 32 with
the electrode X11 selected, and stores the time at which the signal
level becomes equal to or higher than the above-described
predetermined value as t1. The microprocessor 33 starts operation
of data reception from the position indicator 20 from the time
after waiting for a certain time Tw from the time t1 (step 2). This
time Tw is set to the time from the end of transmission of the
start signal from the position indicator 20 to the timing at which
the signal level received by the tablet becomes almost zero, and
this time is obtained in advance.
[0084] The microprocessor 33 activates a timer (not shown)
simultaneously with the timing at which the above-described waiting
time reaches Tw. This timer repeatedly counts values from zero to
the value corresponding with the above-described time Td (cycle of
data transmission from the position indicator 20) (step 2). In the
operation period of one cycle of the timer, the microprocessor 33
repeatedly activates the AD conversion circuit 32 and reads the
signal level. If the signal level during this period never reaches
the above-described predetermined value, the microprocessor 33
determines that transmission from the position indicator 20 is not
made and stores the data of this round as "0." If a signal level
equal to or higher than the predetermined value is detected in this
period, the microprocessor 33 determines that transmission from the
position indicator 20 is made and stores the data of this round as
"1" (step 2).
[0085] The above-described timer count is performed eleven times
and 11-bit data is stored. In this data, the data of the first
round is equivalent to the "sign" shown in FIG. 4. Because this
sign is 0 in step 2 in FIG. 8A, it turns out that the coordinates
calculated from the signal levels Vpx0, Vax0, Vbx0, Vpy0, Vay0, and
Vby0 obtained in step 1 are the coordinate position corresponding
to the L electrode of the position indicator 20. The remaining
10-bit data represents the writing pressure value measured in the
position indicator 20 in the period of step 1.
[0086] Although the electrode from which the maximum level is
detected (X11) is selected from the X-axis electrodes and data is
received in step 2, this step may be carried out by selecting the
electrode from which the maximum level is detected (Y20) from the
Y-axis electrodes.
[0087] Upon ending the reception of the 11-bit data in step 2, the
microprocessor 33 transitions to operation of detecting the start
of the continuous transmission period of the position indicator 20.
The microprocessor 33 repeatedly detects the signal level received
with the electrode X11 selected. When this reception level is equal
to or higher than the predetermined value for the certain time (Ts)
continuously, the microprocessor 33 determines that the continuous
transmission period of the position indicator 20 has been started
and transitions to coordinate detection operation (step 3 in FIG.
8B).
[0088] In order to obtain the X coordinate of the signal from the
position indicator 20, the microprocessor 33 makes the X selection
circuit 22 sequentially select five electrodes centered at X11 (X9
to X13) with the control signal f kept at the low level "0," and
makes the AD conversion circuit 32 operate to read the signal level
(step 3). At this time, the number of the electrode from which the
highest signal level is detected (X11, in this example) and this
signal level (Vpx1) are stored. In addition, the levels detected
with both electrodes adjacent to this electrode are stored as Vax1
and Vbx1 (step 3).
[0089] Next, in order to obtain the Y coordinate of the signal from
the position indicator 20, the microprocessor 33 sets the control
signal f to the high level "1." Furthermore, the microprocessor 33
makes the Y selection circuit 23 sequentially select five
electrodes centered at Y20 (Y18 to Y22) and reads the signal level
(step 3). At this time, the number of the electrode from which the
highest signal level is detected (Y20, in this example) and this
signal level (Vpy1) are stored. In addition, the levels detected
with both electrodes adjacent to this electrode are stored as Vay1
and Vby1 (step 3). The obtained signal levels Vpx1, Vax1, Vbx1,
Vpy1, Vay1, and Vby1 are used for calculation of coordinate values
by a calculation equation to be described later.
[0090] Next, the microprocessor 33 carries out operation for
waiting for the end of the continuous transmission period of the
position indicator 20. The microprocessor 33 sets the control
signal f to the low level "0" and carries out control to make the X
selection circuit 22 select the electrode X11, from which the peak
level is detected in the above-described coordinate detection
operation. At this time, the time at which the received signal
level comes short of the predetermined value is the end time of the
continuous transmission from the position indicator 20 (step
3).
[0091] Upon detecting the end of the continuous transmission from
the position indicator 20, the microprocessor 33 enters operation
of detecting the timing of the start signal transmitted prior to
writing pressure data (step 4). The microprocessor 33 carries out
control to repeatedly activate the AD conversion circuit 32 with
the electrode X11 selected, and stores the time at which the signal
level becomes equal to or higher than the above-described
predetermined value as t2. The microprocessor 33 starts operation
of data reception from the position indicator 20 from the time
after waiting for the certain time Tw from the time t2 (step 4).
This Tw is set to the same time as that in step 2.
[0092] The microprocessor 33 activates the timer simultaneously
with the timing at which the above-described waiting time reaches
Tw and receives 11-bit data from the position indicator 20 exactly
as with the above-described step 2 (step 4). The data of the first
round is equivalent to the "sign" shown in FIG. 4. Because this
sign is 1 in step 4 in FIG. 8B, it turns out that the coordinates
calculated from the signal levels Vpx1, Vax1, Vbx1, Vpy1, Vay1, and
Vby1 obtained in step 3 are the coordinate position corresponding
to the R electrode of the position indicator 20. The remaining
10-bit data represents the writing pressure value measured in the
position indicator 20 in the period of step 3. In this manner,
identification as to which electrode of the position indicator 20
the transmission is made from is allowed by the specific data value
from the position indicator 20. This is one of features of the
present invention.
[0093] Although the electrode from which the maximum level is
detected (X11) is selected from the X-axis electrodes and data is
received also in step 4, this step may be carried out by selecting
the electrode from which the maximum level is detected (Y20) from
the Y-axis electrodes.
[0094] In the present embodiment example, the transmission from the
position indicator 20 by the L electrode and the transmission by
the R electrode are alternately repeated. Therefore, by repeatedly
carrying out step 1 to step 4 in FIG. 8B as the operation of the
tablet side, the coordinates, rotation angle, and writing pressure
of the position indicator 20 can be continuously obtained.
[0095] The method for obtaining the coordinate position and
rotation angle of the position indicator 20 from the reception
levels obtained in the above-described step 1 and step 3 will be
described below.
[0096] Coordinate values (X0, Y0) by the L electrode of the
position indicator 20 are calculated from the reception levels
Vpx0, Vax0, Vbx0, Vpy0, Vay0, and Vby0 obtained in step 1 by the
following equation (1) and equation (2), respectively.
X 0 = P x 0 + Dx 2 .times. V bx 0 - V ax 0 2 .times. V px 0 - V ax
0 - V bx 0 ( 1 ) ##EQU00001##
[0097] In this equation, Px0 is the coordinate position of the
electrode from which the maximum level is detected regarding the X
axis (X11, in this example) and Dx is the arrangement pitch between
the X-axis electrodes.
Y 0 = P y 0 + y 2 .times. V by 0 - V ay 0 2 .times. V py 0 - V ay 0
- V by 0 ( 2 ) ##EQU00002##
[0098] In this equation, Py0 is the coordinate position of the
electrode from which the maximum level is detected regarding the Y
axis (Y20, in this example) and Dy is the arrangement pitch between
the Y-axis electrodes.
[0099] Similarly, coordinate values (X1, Y1) by the R electrode of
the position indicator 20 are calculated from the reception levels
Vpx1, Vax1, Vbx1, Vpy1, Vay1, and Vby1 obtained in step 3 by the
following equation (3) and equation (4), respectively.
X 1 = P x 1 + Dx 2 .times. V bx 1 - V ax 1 2 .times. V px 1 - V ax
1 - V bx 1 ( 3 ) ##EQU00003##
[0100] In this equation, Px1 is the coordinate position of the
electrode from which the maximum level is detected regarding the X
axis (X11, in this example) and Dx is the arrangement pitch between
the X-axis electrodes.
Y 1 = Py 1 + Dy 2 .times. V by 1 - V ay 1 2 .times. V py 1 - V ay 1
- V by 1 ( 4 ) ##EQU00004##
[0101] In this equation, Py1 is the coordinate position of the
electrode from which the maximum level is detected regarding the Y
axis (Y20, in this example) and Dy is the arrangement pitch between
the Y-axis electrodes.
[0102] FIG. 9 is a principle diagram for calculating a rotation
angle 8 of the position indicator 20 about the axis defined as the
perpendicular direction to the tablet surface, based on two pairs
of coordinate values (X0, Y0) and (X1, Y1). In this diagram, the
orientation of the R electrode corresponding to the coordinate
values (X1, Y1) is defined by employing the positive direction of
the Y axis as the basis (.theta.=0) and defining the range of
.theta. as -180.degree.<.theta..ltoreq.+180.degree.. In this
case, the rotation angle .theta. of the position indicator 20 is
calculated from X0, Y0, X1, and Y1 as shown by the following
equations (5) to (9).
[0103] When Y1>Y0
.theta. = tan - 1 ( X 1 - X 0 Y 1 - Y 0 ) ( 5 ) ##EQU00005##
[0104] When Y1=Y0 and X1>X0
.theta.=90.degree. (6)
[0105] When Y1=Y0 and X1<X0
.theta.=-90.degree. (7)
[0106] When Y1<Y0 and X1.gtoreq.X0
.theta. = 180 .degree. + tan - 1 ( X 1 - X 0 Y 1 - Y 0 ) ( 8 )
##EQU00006##
[0107] When Y1<Y0 and X1<X0
.theta. = - 180 .degree. + tan - 1 ( X 1 - X 0 Y 1 - Y 0 ) ( 9 )
##EQU00007##
[0108] In the present embodiment example, the Y-axis positive
direction is defined as the basis of the rotation angle and the
orientation of the R electrode (relative to the basis) is obtained
as an angle. However, the X axis may be defined as the basis and
the orientation of the L electrode may be obtained.
[0109] In the present embodiment example, the same information
(writing pressure) is sent both in data transmission by the L
electrode and in data transmission by the R electrode of the
position indicator 20. However, another kind of information may be
sent in one of them or only sign information may be sent as one of
the data to shorten the time. Furthermore, only one of the L
electrode and the R electrode may be used for data transmission and
the tablet may determine the electrode, with which the immediately
previous continuous transmission is performed, based on whether
data transmission from the position indicator 20 has been made.
Moreover, the frequency of transmission may be changed between
transmission from the L electrode and transmission from the R
electrode to differentiate them or the length of the continuous
transmission may be changed for differentiation.
[0110] In the present embodiment example, the electrodes of the
position indicator 20 are exposed to the tip part of the core 11.
However, they may be covered by the material of the core 11, such
as plastic.
Second Embodiment Example
[0111] FIG. 10 is a diagram showing the structure of a position
indicating part in a position indicator of a second embodiment
example according to the present invention. In FIG. 10, the same
part as that in FIG. 1 is given the same reference numeral. That
is, numeral 12 denotes a variable-capacitance capacitor whose
capacitance changes depending on the writing pressure and numeral
15 denotes a printed board. A core 35 is coupled to the
variable-capacitance capacitor 12 and the writing pressure applied
to the tip of the core 35 is detected. Numeral 36 denotes a chassis
and a hole through which the core 35 passes is made at its tip
part.
[0112] Two electrodes 37 and 38 are provided at the tip part of the
chassis 36 and FIG. 11 is a diagram showing the arrangement
thereof. The following description will be so made that the
electrodes 37 and 38 are called the L electrode and the R
electrode, respectively.
[0113] FIG. 12 is a circuit configuration diagram of the position
indicator of the second embodiment example according to the present
invention. In FIG. 12, the same part as that in FIG. 3 or FIG. 10
is given the same reference numeral. That is, numeral 12 denotes
the variable-capacitance capacitor. Numerals 37 and 38 denote the L
electrode and the R electrode, respectively. Numerals 17, 18, and
19 denote a microprocessor, a battery, and a DC/DC converter,
respectively.
[0114] The difference between the configuration of the position
indicator of the second embodiment example shown in FIG. 12 and the
configuration of the position indicator 20 of the first embodiment
example shown in FIG. 3 is as follows. In the first embodiment
example, one of two electrodes is connected to the coil L2 with
alternate switching. In contrast, in the present embodiment
example, the electrode 37 (L electrode) is always connected to the
coil L2 and an analog switch 39 is provided between the electrode
38 (R electrode) and the coil L2 and is controlled to the on- or
off-state.
[0115] Specifically, when the terminal P2 (signal a) of the
microprocessor 17 is set to the high level, the analog switch 39
becomes the on-state and thus the signal (d) generated in the coil
L2 is applied to both the L electrode and the R electrode. When the
terminal P2 (signal a) of the microprocessor 17 is set to the low
level, the analog switch 39 becomes the off-state and thus the
signal (d) generated in the coil L2 is applied to only the L
electrode.
[0116] The voltage VP obtained by the DC/DC converter 19 is used as
a power supply to operate the analog switch 39 similarly to the
first embodiment example.
[0117] FIG. 13 is a diagram showing the operation of the position
indicator of the second embodiment example and shows how the
signals a, b, c, and d in FIG. 12 change. The microprocessor 17
carries out control to keep the terminal P1 (signal b) at the high
level for a certain period with the terminal P2 (signal a) set to
the high level. Thereby, the signal (d) is radiated from the L
electrode and the R electrode for the certain period continuously
(continuous transmission period: L+R, in FIG. 13). In this
continuous transmission period, the microprocessor 17 obtains the
writing pressure applied to the variable-capacitance capacitor 12
similarly to the first embodiment example.
[0118] Upon ending this continuous transmission period, the
microprocessor 17 performs ASK modulation by controlling the
terminal P1 with the cycle Td exactly as with the first embodiment
example. A sign (L+R) following the start signal at this time is
set to "0" indicating that the immediately previous continuous
transmission is made by two electrodes. Subsequently to this sign
transmission, 10-bit writing pressure data obtained in the
above-described continuous transmission period is transmitted
similarly to the first embodiment example.
[0119] Upon ending the transmission of the writing pressure data,
the microprocessor 17 sets the terminal P2 (signal a) to the low
level to turn off the analog switch 39. This provides the state in
which a signal is transmitted from only the L electrode 37. Also at
this time, the terminal P1 is similarly controlled to perform
continuous transmission (L) and writing pressure detection is
performed.
[0120] Upon ending this continuous transmission period, the
microprocessor 17 sets the terminal P2 (signal a) to the high level
so that the subsequent data transmission may be made by two
electrodes. The purpose thereof is to allow the tablet to surely
detect data of the writing pressure and so forth by transmitting
the data by two electrodes. The microprocessor 17 performs ASK
modulation by controlling the terminal P1 with the cycle Td
similarly to the above description. A sign (L) following the start
signal at this time is set to "1" indicating that the immediately
previous continuous transmission is made by only the L electrode.
Subsequently to this sign transmission, 10-bit writing pressure
data obtained in the above-described continuous transmission period
is sequentially transmitted.
[0121] In the position indicator of the present embodiment example,
transmission is performed with alternate switching between a first
pattern in which both the L electrode and the R electrode are
selected and a second pattern in which only the L electrode is
selected. Furthermore, the "sign" information following the start
signal is set to "0" when the selection is made in the first
pattern and the "sign" information following the start signal is
set to "1" when the selection is made in the second pattern. Such
operation is to identify, on the tablet side, whether the
immediately previous continuous transmission is from two electrodes
or from only the L electrode, and is one of features of the present
invention.
[0122] Also in the present embodiment example, the tablet having
the same configuration as that of the first embodiment example
(FIG. 5) is used. Operation of detecting indicated position and
rotation angle when the position indicator of the present
embodiment example is placed on the tablet of FIG. 5 will be
described below.
[0123] Also in the present embodiment example, operation for
obtaining the rough position of the position indicator is carried
out as shown in FIGS. 6 and 7 similarly to the first embodiment
example. In FIG. 7, the Y-axis whole surface scan operation after
detection of continuous transmission from the position indicator
may be carried out in the continuous transmission period in which
transmission from the position indicator is made by two electrodes
or may be carried out in the continuous transmission period in
which transmission is made by only the L electrode. The explanation
of the present embodiment example will also be made based on the
assumption that the signal of the maximum level is detected from
the electrode X11 in the X-axis whole surface scan operation in
FIG. 6 and the signal of the maximum level is detected from the
electrode Y20 in the Y-axis whole surface scan operation in FIG.
7.
[0124] FIGS. 14A-14B are diagrams that together constitute a single
diagram of FIG. 14, which shows partial scan operation of the
second embodiment example. The difference of the partial scan
operation according to the present embodiment example from the
partial scan operation of the first embodiment example (FIGS.
8A-8B) is as follows. In the present embodiment example, the
coordinates obtained by coordinate detection operation (step 1 in
FIG. 14A) immediately before the "sign" data from the position
indicator is transmitted as "0" indicate the midpoint position
between the L electrode and the R electrode (i.e., the position of
the core 35). Furthermore, the coordinates obtained by coordinate
detection operation (step 3 in FIG. 14B) immediately before the
"sign" data from the position indicator is transmitted as "1"
indicate the position corresponding to the L electrode. The other
operation is the same as that in the first embodiment example.
[0125] Also in the present embodiment example, coordinate values
indicating the midpoint position between the L electrode and the R
electrode of the position indicator are calculated as (X0, Y0) from
the reception levels Vpx0, Vax0, Vbx0, Vpy0, Vay0, and Vby0
obtained in step 1 by using the above-described equation (1) and
equation (2).
[0126] Furthermore, coordinate values corresponding to the position
of the L electrode of the position indicator are calculated as (X1,
Y1) from the reception levels Vpx1, Vax1, Vbx1, Vpy1, Vay1, and
Vby1 obtained in step 3 by using the above-described equation (3)
and equation (4).
[0127] The principle diagram of FIG. 9 is applied also to the
present embodiment example, so that the orientation of the L
electrode corresponding to the coordinate values (X1, Y1) is
defined by employing the positive direction of the Y axis as the
basis (.theta.=0) and defining the range of .theta. as
-180.degree.<.theta..ltoreq.+180.degree.. In this case, the
rotation angle .theta. of the position indicator is calculated by
the above-described equations (5) to (9) with use of X0, Y0, X1,
and Y1 in exactly the same way.
[0128] In the present embodiment example, the same information
(writing pressure) is sent both in data transmission by two
electrodes of the position indicator and in data transmission by
only the L electrode. However, another kind of information may be
sent in one of them or only sign information may be sent as one of
the data to shorten the time. Furthermore, data transmission may be
performed only at the time of the transmission by two electrodes
and the tablet may make the determination depending on whether data
transmission from the position indicator has been made.
Alternatively, the length of the continuous transmission may be
changed to differentiate the transmission.
[0129] Although the electrodes of the position indicator are
provided at the tip part of the chassis 36 in the present
embodiment example, they may be provided on the core 35 similarly
to the first embodiment example.
Third Embodiment Example
[0130] FIG. 15 is a diagram showing the structure of a position
indicating part in a position indicator of a third embodiment
example according to the present invention. In the present
embodiment example, an example is shown in which three electrodes
are disposed in the position indicator and a tilt of the position
indicator relative to the tablet is obtained in addition to a
rotation angle thereof.
[0131] In FIG. 15, the same part as that in FIG. 10 is given the
same reference numeral. That is, numeral 12 denotes a
variable-capacitance capacitor whose capacitance changes depending
on the writing pressure. Numerals 15, 35, and 36 denote a printed
board, a core, and a chassis, respectively.
[0132] Three electrodes 40, 41, and 42 are provided at the tip part
of the chassis 36 and FIG. 16 is a diagram showing the arrangement
thereof. These three electrodes are connected to the printed board
15 by a connection line (not shown).
[0133] FIG. 17 is a circuit configuration diagram of the position
indicator of the third embodiment example according to the present
invention. In FIG. 17, the same part as that in FIG. 15 or FIG. 3
is given the same reference numeral. That is, numeral 12 denotes
the variable-capacitance capacitor. Numerals 40 to 42 denote the
electrodes. Numerals 17, 18, and 19 denote a microprocessor, a
battery, and a DC/DC converter, respectively.
[0134] The difference of the configuration shown in FIG. 17 from
the first embodiment example (FIG. 3) is as follows. In the first
embodiment example, one of two electrodes is connected to the coil
L2 with alternate switching. In contrast, in the present embodiment
example, one of three electrodes 40 to 42 is connected to the coil
L2 with sequential switching. An analog multiplexer 43 is provided
between the electrodes 40 to 42 and the coil L2 and one is selected
among the electrode 40, the electrode 41, and the electrode 42 by
setting of two terminals of the microprocessor 17 (P2 and P4).
Signals from two terminals of the microprocessor 17 (P2 and P4) are
referred to collectively as the "signal a" here.
[0135] The voltage VP obtained by the DC/DC converter 19 is used as
a power supply to operate the analog multiplexer 43 similarly to
the first embodiment example.
[0136] FIG. 18 is a diagram showing the operation of the position
indicator of the third embodiment example and shows how the signals
a, b, c, and d in FIG. 17 change. The microprocessor 17 carries out
control to keep the terminal P1 (signal b) at the high level for a
certain period with the electrode 40 selected by the setting by the
signal a. Thereby, the signal (d) is radiated from the electrode 40
for the certain period continuously (continuous transmission period
1, in FIG. 18). In this continuous transmission period, the
microprocessor 17 obtains the writing pressure applied to the
variable-capacitance capacitor 12 similarly to the first embodiment
example.
[0137] Upon ending this continuous transmission period, the
microprocessor 17 performs ASK modulation by controlling the
terminal P1 with the cycle Td exactly as with the first embodiment
example. The "sign" following the "start signal" at this time is
set to "0" indicating that the immediately previous continuous
transmission is made by the electrode 40. Subsequently to this sign
transmission, 10-bit writing pressure data obtained in the
above-described continuous transmission period 1 is transmitted
similarly to the first embodiment example.
[0138] Upon ending the transmission of the writing pressure data,
the microprocessor 17 switches the setting by the signal a to
select the electrode 41, and similarly controls the terminal P1 to
perform continuous transmission (continuous transmission period 2,
in FIG. 18). At this time, writing pressure detection like that
performed in continuous transmission period 1 is not performed in
the present embodiment example.
[0139] Upon the end of this continuous transmission period 2, the
microprocessor 17 performs ASK modulation by controlling the
terminal P1 with the cycle Td while keeping of the selection of the
electrode 41 by the setting by the signal a. The "sign" following
the start signal at this time is transmitted as "1."
[0140] Upon ending this sign transmission, the microprocessor 17
switches the setting by the signal a to select the electrode 42,
and similarly controls the terminal P1 to perform continuous
transmission (continuous transmission period 3, in FIG. 18). Also
at this time, writing pressure detection like that performed in
continuous transmission period 1 is not performed.
[0141] Upon the end of this continuous transmission period, the
microprocessor 17 performs ASK modulation by controlling the
terminal P1 with the cycle Td while keeping of the selection of the
electrode 42 by the setting by the signal a. Also at this time, the
"sign" following the start signal is transmitted as "1."
[0142] In the position indicator of the present embodiment example,
the following patterns are set: a first pattern in which only the
electrode 40 is selected, a second pattern in which only the
electrode 41 is selected, and a third pattern in which only the
electrode 42 is selected. Transmission is performed with sequential
repetition of the patterns, i.e., like in the second pattern
subsequently to the first pattern, in the third pattern
subsequently to the second pattern, and in the first pattern
subsequently to the third pattern. Furthermore, the "sign"
information following the start signal is set to "0" when the
selection is made in the first pattern and the "sign" information
following the start signal is set to "1" when the selection is made
in the second pattern and the third pattern. Therefore, the tablet
side can identify which electrode of the position indicator a
signal is transmitted from by considering the above-described
transmission order. These operations are one of features of the
present invention.
[0143] Also in the present embodiment example, the tablet having
the same configuration as that of the first embodiment example
(FIG. 5) is used. Operation of detecting indicated position,
rotation angle, and tilt relative to the tablet surface when the
position indicator of the present embodiment example is placed on
the tablet of FIG. 5 will be described below.
[0144] Also in the present embodiment example, operation for
obtaining the rough position of the position indicator is carried
out as shown in FIGS. 6 and 7 similarly to the first embodiment
example. In FIG. 7, any electrode may be used for transmission from
the position indicator in the continuous transmission period in
which the Y-axis whole surface scan operation after detection of
continuous transmission from the position indicator is carried out.
The explanation of the present embodiment example will also be made
based on the assumption that the signal of the maximum level is
detected from the electrode X11 in the X-axis whole surface scan
operation in FIG. 6 and the signal of the maximum level is detected
from the electrode Y20 in the Y-axis whole surface scan operation
in FIG. 7.
[0145] FIGS. 19A-19B together constitute a single diagram of FIG.
19, which shows partial scan operation of the third embodiment
example. Also in the present embodiment example, after a signal
continuing for the certain time (Ts) or longer from the position
indicator is detected, coordinate detection operation of the X axis
and the Y axis is carried out. Then, data sent subsequently to
continuous transmission from the position indicator is received.
This data is transmitted subsequently to the "start signal" also as
shown in FIG. 18. In the present embodiment example, if "0" is
received as the "sign" following immediately after the "start
signal," the data reception operation is continuously carried out
to receive 10-bit writing pressure data. If "1" is received as the
"sign," the data reception operation is ended and transition to
operation for detecting continuous transmission from the position
indicator is made.
[0146] In FIG. 19A, "0" is received as the sign in step 2. Thus, in
the immediately previous coordinate detection operation (step 1),
the level and coordinate position based on a signal transmitted
from the electrode 40 of the position indicator are obtained. In
the subsequent coordinate detection operation (step 3), the level
and coordinate position based on a signal transmitted from the
electrode 41 of the position indicator are obtained. In the further
subsequent coordinate detection operation (step 5), the level and
coordinate position based on a signal transmitted from the
electrode 42 of the position indicator are obtained.
[0147] In the present embodiment example, in order to obtain the
tilt of the position indicator by using the reception levels
obtained in the respective coordinate detection operations of step
1, step 3, and step 5, the gain value set in the gain control
circuit 29 of the tablet circuit (FIG. 5) is set identical in these
respective coordinate detection operations.
[0148] Coordinate values (X1, Y1) by the electrode 40 of the
position indicator are calculated from the reception levels Vpx1,
Vax1, Vbx1, Vpy1, Vay1, and Vby1 obtained in step 1 by the
above-described equation (3) and equation (4).
[0149] Furthermore, coordinate values (X2, Y2) by the electrode 41
of the position indicator are obtained from reception levels Vpx2,
Vax2, Vbx2, Vpy2, Vay2, and Vby2 obtained in step 3 by the
following equation (10) and equation (11).
X 2 = Px 2 + D x 2 .times. V bx 2 - V ax 2 2 .times. V px 2 - V ax
2 - V bx 2 ( 10 ) ##EQU00008##
[0150] In this equation, Px2 is the coordinate position of the
electrode from which the maximum level is detected regarding the X
axis (X11, in this example) and Dx is the arrangement pitch between
the X-axis electrodes.
Y 2 = Py 2 + Dy 2 .times. V by 2 - V ay 2 2 .times. V py 2 - V ay 2
- V by 2 ( 11 ) ##EQU00009##
[0151] In this equation, Py2 is the coordinate position of the
electrode from which the maximum level is detected regarding the Y
axis (Y20, in this example) and Dy is the arrangement pitch between
the Y-axis electrodes.
[0152] Coordinate values (X3, Y3) by the electrode 42 of the
position indicator are obtained from reception levels Vpx3, Vax3,
Vbx3, Vpy3, Vay3, and Vby3 obtained in step 5 by the following
equation (12) and equation (13).
X 3 = Px 3 + Dx 2 .times. V bx 3 - V ax 3 2 .times. V px 3 - V ax 3
- V bx 3 ( 12 ) ##EQU00010##
[0153] In this equation, Px3 is the coordinate position of the
electrode from which the maximum level is detected regarding the X
axis (X11, in this example) and Dx is the arrangement pitch between
the X-axis electrodes.
Y 3 = Py 3 + Dy 2 .times. V by 3 - V ay 3 2 .times. V py 3 - V ay 3
- V by 3 ( 13 ) ##EQU00011##
[0154] In this equation, Py3 is the coordinate position of the
electrode from which the maximum level is detected regarding the Y
axis (Y20, in this example) and Dy is the arrangement pitch between
the Y-axis electrodes.
[0155] Coordinate values (X0, Y0) corresponding to the core 35 of
the position indicator can be obtained as the center point of three
obtained coordinate values (X1, Y1), (X2, Y2), and (X3, Y3) by the
following equation (14) and equation (15).
X 0 = X 1 + X 2 + X 3 3 ( 14 ) Y 0 = Y 1 + Y 2 + Y 3 3 ( 15 )
##EQU00012##
[0156] The principle diagram of FIG. 9 is applied also to the
present embodiment example, so that the orientation of the
electrode 40 corresponding to the coordinate values (X1, Y1) is
defined by employing the positive direction of the Y axis as the
basis (.theta.=0) and defining the range of .theta. as
-180.degree.<.theta..ltoreq.+180.degree.. In this case, the
rotation angle .theta. of the position indicator is calculated by
the above-described equations (5) to (9) with use of X0, Y0, X1,
and Y1 in exactly the same way.
[0157] In the present embodiment example, a tilt of the position
indicator can be obtained from the respective received signal
intensities from three electrodes of the position indicator. As the
received signal intensity, the level at the time of the X-axis
coordinate detection may be used or the level at the time of the
Y-axis coordinate detection may be used. Here, the level at the
time of the X-axis coordinate detection is used.
[0158] Received signal intensity (V1) by the electrode 40 is
obtained by correction calculation by the following equation (16)
based on the X electrode positions of the tablet.
V 1 = V px 1 + ( V ax 1 - V bx 1 ) 2 8 .times. ( 2 V px 1 - V ax 1
- V bx 1 ) ( 16 ) ##EQU00013##
[0159] Received signal intensity (V2) by the electrode 41 is
obtained by the following equation (17).
V 2 = V px 2 + ( V ax 2 - V bx 2 ) 2 8 .times. ( 2 V px 2 - V ax 2
- V bx 2 ) ( 17 ) ##EQU00014##
[0160] Received signal intensity (V3) by the electrode 42 is
obtained by the following equation (18).
V 3 = V px 3 + ( V ax 3 - V bx 3 ) 2 8 .times. ( 2 V px 3 - V ax 3
- V bx 3 ) ( 18 ) ##EQU00015##
[0161] FIG. 20 is a principle diagram for obtaining the tilt of the
position indicator by using the received signal intensities V1, V2,
and V3 from three electrodes. In FIG. 20, the height direction from
the sensor surface (21 in FIG. 5) of the tablet is employed as the
z axis and the coordinate axes are so set that the center G of an
equilateral triangle configured by A, B, and C corresponding to the
tips of the electrodes 40, 41, and 42, respectively, of the
position indicator exists on the yz plane and point A corresponding
to the tip of the electrode 40 exists on the z axis. When the
coordinates of the respective points at this time are represented
as point A (0, 0, z1), point B (x2, y2, z2), point C (x3, y3, z3),
and point G (0, yg, zg), the tilt (.theta.x, .theta.y) of the
position indicator is obtained as shown by the following equation
(19) and equation (20).
sin .theta. x = z 2 - z 3 r ( 19 ) ##EQU00016##
(r: the length of one side of the equilateral triangle)
sin .theta. y = 2 z 1 - z 2 - z 3 r 3 ( 20 ) ##EQU00017##
(slope of the segment coupling point A and the midpoint between B
and C)
[0162] The distances (z1, z2, z3) of point A, point B, and point C,
which are the tip positions of three electrodes of the position
indicator, from the tablet sensor surface are almost inversely
proportional to the received signal intensities V1, V2, and V3.
Therefore, the relationships are represented as the following
equation (21) and equation (22) with use of .alpha. as a
proportionality coefficient.
[0163] z1=.alpha./V1, z2=.alpha./V2, z3=.alpha./V3 therefore,
.theta.x and .theta.y are represented as follows
.theta. x = sin - 1 .alpha. ( V 3 - V 2 ) r V 2 V 3 ( 21 ) .theta.
y = sin - 1 .alpha. ( 2 V 2 V 3 - V 1 V 3 - V 1 V 2 ) r V 1 V 2 V 3
3 ( 22 ) ##EQU00018##
[0164] Because .alpha./r is a constant, obtaining this value in
advance can obtain .theta.x and .theta.y from the above
relationship equations.
[0165] Although three electrodes of the position indicator are
provided at the tip part of the chassis 36 in the present
embodiment example, they may be provided on the core like in the
first embodiment example.
[0166] In the present embodiment example, rotation angle and tilt
of the position indicator can be detected. Therefore, it is
possible to shape the tip part in an asymmetric (non-symmetric)
shape like those shown in FIG. 21 for example; then, software may
be used to generate (detect user input of) drawings according to
the obtained rotation angle and tilt.
[0167] It should be understood by those skilled in the art that
various modifications, combinations, sub-combinations and
alterations may occur depending on design requirements and other
factors insofar as they are within the scope of the appended claims
or the equivalents thereof.
* * * * *