U.S. patent number 10,795,491 [Application Number 15/612,686] was granted by the patent office on 2020-10-06 for position detecting device that selects electrodes having different intervals therebetween while different signals are detected.
This patent grant is currently assigned to Wacom Co., Ltd.. The grantee listed for this patent is Wacom Co., Ltd.. Invention is credited to Yuji Katsurahira.
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United States Patent |
10,795,491 |
Katsurahira |
October 6, 2020 |
Position detecting device that selects electrodes having different
intervals therebetween while different signals are detected
Abstract
A position detecting device obtains information from a stylus
when the stylus moves at high speed, while removing influences of
noise. The position detecting device includes a differential
amplification circuit that amplifies and outputs a difference in a
signal at a first terminal and a signal at a second terminal, and a
selection circuit that selects at least a first electrode of a
sensor, connects at least the first electrode to the first terminal
of the differential amplification circuit, selects at least a
second electrode of the sensor, and connects at least the second
electrode to the second terminal of the differential amplification
circuit. The selection circuit selects electrodes separated by a
first interval in a period in which a position indicated by the
stylus is detected, and selects electrodes separated by a second
interval that is shorter than the first interval in a period in
which data is detected.
Inventors: |
Katsurahira; Yuji (Saitama,
JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Wacom Co., Ltd. |
Saitama |
N/A |
JP |
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Assignee: |
Wacom Co., Ltd. (Saitama,
JP)
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Family
ID: |
1000005097452 |
Appl.
No.: |
15/612,686 |
Filed: |
June 2, 2017 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20170269776 A1 |
Sep 21, 2017 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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PCT/JP2015/080873 |
Nov 2, 2015 |
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Foreign Application Priority Data
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Jan 6, 2015 [JP] |
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2015-000850 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G06F
3/0383 (20130101); G06F 3/046 (20130101); G06F
3/03545 (20130101); G06F 3/0416 (20130101); G06F
3/044 (20130101); G06F 2203/04105 (20130101); G06F
2203/04106 (20130101) |
Current International
Class: |
G06F
3/045 (20060101); G06F 3/041 (20060101); G06F
3/046 (20060101); G06F 3/0354 (20130101); G06F
3/038 (20130101); G06F 3/044 (20060101) |
Field of
Search: |
;345/174 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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103257740 |
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Aug 2013 |
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CN |
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103324368 |
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Sep 2013 |
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CN |
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63-70326 |
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Mar 1988 |
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JP |
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6-187088 |
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Jul 1994 |
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JP |
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8-179887 |
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Jul 1996 |
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JP |
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2014-63249 |
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Apr 2014 |
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JP |
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Other References
Chinese Office Action, dated Sep. 27, 2019, for Chinese Application
No. 201580063017.4, 24 pages. (with English translation). cited by
applicant.
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Primary Examiner: Blancha; Jonathan M
Attorney, Agent or Firm: Seed IP Law Group LLP
Claims
The invention claimed is:
1. A position detecting device having a transparent sensor that
includes a plurality of electrodes composed of a transparent
electrically-conductive material arranged in each of a first
direction and a second direction intersecting each other and that
is disposed over a display device, the position detecting device
receiving a position detection signal by which a position on the
sensor is detected and a data signal generated according to digital
data from a stylus pen, the data signal being different from the
position detection signal, the position detecting device
comprising: a differential amplification circuit that has a first
terminal and a second terminal and, in operation, amplifies and
outputs a difference between a signal at the first terminal and a
signal at the second terminal; and a selection circuit that, in
operation, selects a first electrode group including at least a
first electrode of the electrodes included in the sensor, connects
the first electrode group to the first terminal, selects a second
electrode group including at least a second electrode of the
electrodes included in the sensor, and connects the second
electrode group to the second terminal; wherein the selection
circuit selects electrodes separated by a first interval or a
second interval based on whether the stylus pen transmits the
position detection signal or the data signal, wherein the selection
circuit, in operation, selects electrodes separated by the first
interval as the first electrode and the second electrode in a first
period of time in which the position on the sensor indicated by the
stylus pen is detected based on the position detection signal
transmitted from the stylus pen, while the stylus pen transmits the
position detection signal during the first period of time, and the
selection circuit, in operation, selects electrodes separated by
the second interval as the first electrode and the second electrode
in a second period of time in which the data signal transmitted
from the stylus pen is detected, while the stylus pen transmits the
data signal during the second period of time, the second interval
being different from the first interval.
2. The position detecting device according to claim 1, wherein the
first electrode or the second electrode selected by the selection
circuit in the second period of time in which the data signal is
detected is an electrode at the position on the sensor indicated by
the stylus pen, detected in the first period of time in which the
position indicated by the stylus pen is detected, or is adjacent to
the position on the sensor indicated by the stylus pen.
3. The position detecting device according to claim 1, wherein, in
the second period of time in which the data signal is detected, the
selection circuit, in operation, selects electrodes or electrode
groups adjacent to each other as the first electrode group or the
second electrode group.
4. The position detecting device according to claim 1, wherein the
electrodes selected by the selection circuit in the second period
of time in which the data signal is detected are the first
electrode group and the second electrode group, and a first one of
the first electrode group and the second electrode group is
composed of a plurality of electrodes adjacent to each other, and a
plurality of electrodes of a second one of the first electrode
group and the second electrode group is composed of electrodes
dispersed on two sides of the electrode group composed of the
plurality of electrodes adjacent to each other.
5. The position detecting device according to claim 1, wherein the
stylus pen is provided with a writing pressure detecting circuit
and the position detecting device receives a writing pressure value
that is detected by the writing pressure detecting circuit and is
transmitted from the stylus pen as the digital data.
6. The position detecting device according claim 1, wherein the
stylus pen is provided with a switch and the position detecting
device receives a state of the switch transmitted from the stylus
pen as the digital data.
7. The position detecting device according to claim 1, wherein the
position detecting device receives identification information of
the stylus pen transmitted from the stylus pen as the digital
data.
8. The position detecting device according to claim 1, wherein the
data signal is transmitted from the stylus pen and is obtained by
amplitude shift keying modulation of an alternating-current signal
according to the digital data.
9. The position detecting device according to claim 1, wherein the
position detecting device receives the position detection signal
and the digital data from the stylus pen based on electric field
coupling between an electrode of the sensor and the stylus pen.
10. The position detecting device according to claim 1, wherein the
second interval between the first electrode and the second
electrode in the second period of time in which the data signal is
detected is variable.
11. The position detecting device according to claim 1, wherein the
electrodes selected by the selection circuit in the second period
of time in which the data signal is detected are the first
electrode group and the second electrode group, and a number of
electrodes forming the first electrode group and the second
electrode group is variable.
12. The method according to claim 1, wherein the data signal is
obtained by amplitude shift keying modulation of an
alternating-current signal according to digital data.
13. A method of operating a position detecting device having a
transparent sensor that includes a plurality of electrodes composed
of a transparent electrically-conductive material arranged in each
of a first direction and a second direction intersecting each other
and that is disposed over a display device, the method comprising:
detecting, during a first period of time, a position detection
signal transmitted by a stylus pen; detecting, during a second
period of time, a data signal transmitted by the stylus pen, the
data signal being different from the position detection signal, and
the second period of time being different from the first period of
time; selecting electrodes separated by a first interval or a
second interval based on whether the stylus pen transmits the
position detection signal or the data signal; wherein, during the
first period of time, a first electrode group including at least a
first electrode of the electrodes included in the sensor is
selected by the selecting, while the stylus pen transmits the
position detection signal during the first period of time;
connecting, during the first period of time, the first electrode
group to a first terminal; wherein, during the first period of
time, a second electrode group including at least a second
electrode of the electrodes included in the sensor is selected by
the selecting, while the stylus pen transmits the position
detection signal during the first period of time; connecting,
during the first period of time, the second electrode group to a
second terminal; amplifying and outputting, during the first period
of time, a difference between a signal at the first terminal and a
signal at the second terminal; detecting a position on the sensor
indicated by the stylus pen based on the amplifying and outputting,
during the first period of time, of the difference between the
signal at the first terminal the signal at the second terminal
during the first period of time; wherein, during the second period
of time, a third electrode group including at least a third
electrode of the electrodes included in the sensor is selected by
the selecting, while the stylus pen transmits the data signal
during the second period of time; connecting, during the second
period of time, the third electrode group to the first terminal;
wherein, during the second period of time, a fourth electrode group
including at least a fourth electrode of the electrodes included in
the sensor is selected by the selecting, while the stylus pen
transmits the data signal during the second period of time, wherein
an interval between the third electrode and the fourth electrode is
different from an interval between the first electrode and the
second electrode; connecting, during the second period of time, the
fourth electrode group to the second terminal; amplifying and
outputting, during the second period of time, the difference
between the signal at the first terminal and the signal at the
second terminal; and detecting data transmitted by the stylus pen
based on the amplifying and outputting, during the second period of
time, of the difference between the signal at the first terminal
the signal at the second terminal.
14. The method according to claim 13, wherein the third electrode
or the fourth electrode is an electrode at the position on the
sensor indicated by the stylus pen, or is adjacent to the position
on the sensor indicated by the stylus pen.
15. The method according to claim 13, wherein the third electrode
group or the fourth electrode group includes a plurality of
adjacent electrodes.
16. The method according to claim 13, wherein a first one of the
third electrode group and the forth electrode group includes a
plurality of adjacent electrodes, and a plurality of electrodes of
a second one of the third electrode group and the fourth electrode
group is composed of electrodes dispersed on two sides of the
electrode group that includes the plurality of adjacent
electrodes.
17. The method according to claim 13, further comprising: receiving
the position detection signal transmitted by the stylus pen based
on electric field coupling between an electrode of the sensor and
the stylus pen.
18. The method according to claim 13, further comprising: receiving
the data signal transmitted by the stylus pen based on electric
field coupling between an electrode of the sensor and the stylus
pen.
19. The method according to claim 13, further comprising: varying
the interval between the third electrode and the fourth electrode
group.
20. The method according to claim 13, further comprising: varying a
number of electrodes forming the third electrode group and the
fourth electrode group.
Description
BACKGROUND
Technical Field
This disclosure relates to a position detecting device including a
transparent sensor that is disposed over a front surface of a
display device and that can be operated by both of a finger and a
pen-type position indicator (hereinafter, a pen-type position
indicator will be referred to as stylus pen).
Description of Related Art
In recent years, there has been a configuration that allows input
by a stylus pen in order to easily carry out handwriting character
input and drawing of pictures, illustrations, and so forth
regarding input of a computer. As a pen input technique for this
purpose, a method disclosed in Patent Document 1 (Japanese Patent
Laid-open No. 1988-70326) has been widely used.
According to the method of the above-described Patent Document 1, a
position indicator that is a stylus pen is provided with a resonant
circuit and an indicated position is detected by electromagnetic
induction with a sensor of a tablet as a position detecting device.
In this system, transmission and reception of signals are carried
out by resonance operation between coils (sensor coils=loop coils)
on the sensor side of the position detecting device and the
resonant circuit that is incorporated in the stylus pen and that is
composed of a coil and a capacitor.
In the position detecting device, a sensor coil near the position
of the stylus pen is selected and a signal is transmitted from the
sensor coil. The stylus pen receives it by the coil of the resonant
circuit and returns a signal toward the sensor coil. Plural kinds
of information are included in the returned signal in some cases.
As the information from the stylus pen, there are signals for
position detection, writing pressure information, and so forth. In
the position detecting device, even when the stylus pen is moving,
with following thereof, a signal is transmitted from the sensor
coil near the stylus pen and an exchange of information is carried
out with the position indicator.
In recent years, tablet-type information terminals equipped with a
touch panel have come to be frequently used. In a tablet disclosed
in the above-described Patent Document 1, a sensor that forms the
tablet needs to be provided on the back surface of a display
device. This is because a certain level of current needs to be made
to flow in loop coils provided as sensor coils and therefore it is
impossible to make the sensor transparent.
For this reason, a sensor of a capacitive system obtained by making
a sensor transparent by using transparent electrodes of indium tin
oxide (ITO) or the like has become the mainstream in recent years.
However, this transparent sensor has problems. One of the problems
is a problem that, because the sensor is disposed over a display
screen of a display device in an overlapping manner, the sensor
receives the influence of noise emitted by the display device, e.g.
a liquid crystal or the like, and it becomes difficult to correctly
obtain the coordinate position. Furthermore, the electrodes
composed of ITO have a high resistance value relative to a
conductor based on a conventional copper line. Therefore, it is
difficult to carry out signal transmission and reception in which a
signal is transmitted from the sensor of the tablet and the signal
is received by a stylus pen to be returned to the sensor.
As one of a stylus pen of the capacitive system and a position
detecting device to solve this problem, there is a system in which
the stylus pen has a power supply and a signal is unilaterally sent
out from the stylus pen side to the sensor side of the position
detecting device. Position detecting devices having this system
have been increasing (refer to Patent Document 2 (Japanese Patent
Laid-open No. 2014-63249)).
PRIOR ART DOCUMENTS
Patent Documents
Patent Document 1: Japanese Patent Laid-open No. 1988-70326
Patent Document 2: Japanese Patent Laid-open No. 2014-63249
BRIEF SUMMARY
Technical Problems
The sensor of the position detecting device described in the
above-described Patent Document 2 is a sensor in which plural
transparent electrodes are disposed in each of directions
orthogonal to each other. When the position of a finger as an
indicating body is detected by the position detecting device of
this Patent Document 2, a signal is made to sequentially flow to
the plural electrodes disposed in one direction of the orthogonal
directions and change in the signal is detected by the plural
electrodes disposed in the other direction. Furthermore, when
detecting a position indicated by the stylus pen, the position
detecting device of Patent Document 2 carries out the detection
while sequentially switching the plural electrodes of one and the
other directions.
The stylus pen used in this Patent Document 2 is characterized by
including a power supply and unilaterally transmitting a signal to
the sensor side. Furthermore, in the position detecting device, a
received signal from the stylus pen received by the transparent
electrodes of the sensor is amplified by using a differential
amplification circuit and thereby exogenous noise included in the
received signal is cancelled out. In this case, in the signal
transmitted from the stylus pen, information such as a signal for
position detection for detection of a position indicated by the
stylus pen and information on the value of the writing pressure
applied to the pen tip of the stylus pen is included. The stylus
pen transmits the information on the writing pressure value and so
forth to the sensor as amplitude shift keying (ASK)-modulated data
(attendant information).
Furthermore, the detection of the position indicated by the stylus
pen in the position detecting device is carried out by scanning all
electrodes on the sensor regarding the signal for position
detection from the stylus pen and based on signal distribution
acquired in the scanning. In this position detection, after all
electrodes on the sensor are scanned (global scan) to narrow down
the indicated position of the stylus pen to some extent, processing
of deciding a more detailed position is executed (partial
scan).
Furthermore, in the position detecting device, as for the attendant
information such as the information on the writing pressure value,
a signal is received by the electrode nearest to the indicated
position of the stylus pen identified by the signal for position
detection and thereby the attendant information is obtained.
The purpose of using the differential amplification circuit in the
position detecting device described in Patent Document 2 is to
cancel noise that gets mixed in the signal received from the stylus
pen. In the position detecting device described in Patent Document
2, the sensor electrode connected to the positive terminal of the
differential amplification circuit and the sensor electrode
connected to the negative terminal in the partial scan at the time
of position detection processing based on the signal for position
detection are each one electrode and are separated by a
predetermined distance. The reason why the electrodes separated by
the predetermined distance are selected is as follows.
Specifically, the intensity of the signal is important in the case
of detecting the signal for position detection. However, if the
electrodes connected to the positive terminal and negative terminal
of the differential amplification circuit are adjacent, the signal
for position detection from the stylus pen is similarly received in
the adjacent electrodes and the signal for position detection that
should be detected originally is cancelled out by differential
amplification, so that the signal intensity thereof becomes
low.
However, meanwhile, the effect of noise reduction by differential
amplification is lowered when the distance between the electrodes
connected to the positive terminal and negative terminal of the
differential amplification circuit is set longer, so that the
position detection processing receives the influence of noise.
At the time of reception of a signal for data detection in this
position detecting device, the electrodes connected to the positive
terminal and negative terminal of the differential amplification
circuit are each fixed as one electrode of the sensor nearest to
the indicated position by the stylus pen, detected in the partial
scan of the position detection processing based on the signal for
position detection.
In the partial scan at the time of position detection, the
above-described electrodes separated by the predetermined distance
are connected to the positive terminal and negative terminal of the
differential amplification circuit and the indicated position by
the stylus pen is detected. Thus, what is detected as the sensor
electrode nearest to the indicated position by the stylus pen is a
respective one of these electrodes separated by the predetermined
distance. For this reason, at the time of reception of the signal
for data detection in the position detecting device, the electrodes
connected to the positive terminal and negative terminal of the
differential amplification circuit are electrodes separated by the
predetermined distance as in the position detection. Therefore, in
the case of Patent Document 2, the signal including the attendant
information to be detected is greatly affected by noise in the
position detecting device.
Moreover, in recent years, the cases in which attendant information
such as identification information (identification (ID)) of a
stylus pen is also transmitted to the sensor side besides
information on the writing pressure value have been increasing.
Furthermore, the data size gradually becomes larger also in the
identification information and the cases in which the attendant
information is sent over a long time after transmission of the
signal for position detection have been increasing. Specifically,
there arise the need to set data of the writing pressure value to
e.g. 12 bits due to increase in the level of detail of the writing
pressure data although conventionally the data of the writing
pressure value is approximately 8 bits, and to transmit
identification information of approximately 30 bits specific to a
stylus pen.
The attendant information transmitted from the stylus pen as the
signal for data detection in an attendant information transmission
period is received from one electrode connected to one of the
positive terminal and negative terminal of the differential
amplification circuit. However, there is also the case in which the
stylus pen gets far away from the above-described one receiving
electrode before the attendant information transmitted from the
stylus pen can be completely received, such as the case in which
the stylus pen is moved on the sensor at high speed by the user. In
such a case, in the position detecting device, there is a
possibility that it becomes impossible to correctly receive the
attendant information from the stylus pen and the correctness of
the writing pressure data is lost or identification information is
incorrectly detected.
In view of the above problems, this disclosure intends to provide a
position detecting device configured to be capable of correctly
obtaining attendant information from a stylus pen stably even when
the stylus pen moves at high speed while removing the influence of
noise.
Technical Solution
In order to solve the above-described problems, this disclosure
provides a position detecting device having a transparent sensor
that includes a plurality of electrodes composed of a transparent
electrically-conductive material arranged in each of a first
direction and a second direction intersecting each other and that
is disposed over a display device, the position detecting device
receiving a position detection signal by which a position on the
sensor is detected and a data signal generated according to digital
data from a stylus pen, the position detecting device including: a
differential amplification circuit that has a first terminal and a
second terminal and, in operation, amplifies and outputs a
difference between a signal at the positive terminal and a signal
at the negative terminal; and a selection circuit that, in
operation, selects a first electrode group including at least a
first electrode of the electrodes included in the sensor, connects
the first electrode group to the first terminal, selects a second
electrode group including at least a second electrode of the
electrodes included in the sensor, and connects the second
electrode group to the second terminal; wherein the selection
circuit, in operation, selects electrodes separated by a first
interval as the first electrode and the second electrode in a
period in which the position on the sensor indicated by the stylus
pen is detected based on the position detection signal, and the
selection circuit, in operation, selects electrodes separated by a
second interval as the first electrode and the second electrode in
a period in which the data signal is detected, wherein the second
interval is shorter than the first interval.
According to the position detecting device in accordance with this
disclosure with the above-described configuration, in the
differential amplification circuit, in the period in which the data
signal is detected, an interval between an electrode connected to
the first terminal and an electrode connected to the second
terminal is set to a shorter interval than an interval between the
electrodes in the period in which the indicated position by the
stylus pen is detected. Therefore, the noise reduction effect due
to the differential amplification becomes larger and it becomes
possible to more correctly detect attendant information from the
data signal.
Furthermore, according to the position detecting device in
accordance with this disclosure, the first electrode group composed
of plural electrodes in which the first electrode is included and
the second electrode group composed of plural electrodes in which
the second electrode is included are connected to the first
terminal and second terminal of the differential amplification
circuit. Thus, it is possible to acquire the data signal from these
plural electrodes even when the stylus pen moves at high speed.
Therefore, it becomes possible to completely acquire the attendant
information. Accordingly, the attendant information can be
correctly obtained stably even when the stylus pen moves at high
speed.
Furthermore, this disclosure is preferable if the following
configuration is employed. Specifically, in the period in which the
data signal is detected, the selection circuit selects electrodes
or electrode groups adjacent to each other as the first electrode
group and the second electrode group. Moreover, one of the first
electrode group and the second electrode group is composed of
plural electrodes adjacent to each other and plural electrodes of
the other of the first electrode group and the second electrode
group are composed of electrodes dispersed on both sides of the
electrode group composed of the plural electrodes adjacent to each
other.
In this case, in reception of data such as writing pressure data
from the stylus pen, a predetermined number of successive
electrodes centered at the indicated position of the stylus pen are
selected and connected to the positive terminal (or negative
terminal) of the differential amplification circuit. Furthermore,
in such a manner as to be dispersed on two sides of the selected
electrodes, the same number of electrodes are selected and
connected to the negative terminal (or positive terminal). Due to
this, even when the stylus pen moves at high speed, the indicated
position of the pen does not get out of the area selected and
connected to the above-described positive terminal (or negative
terminal) and the data such as the writing pressure data can be
surely received. Thus, a discontinuity of a line does not occur
even when rapid writing or drawing is carried out, and input with
favorable operability can be made.
Furthermore, because the same number of electrodes are selected and
connected to the negative terminal (or positive terminal) in such a
manner as to be dispersed on two sides of the area of the electrode
group selected as the positive terminal (or negative terminal),
noise can be surely cancelled even when plural electrodes are
selected and connected to each of the positive terminal and
negative terminal of the differential amplification circuit, and
the position detecting device stably operates.
Advantageous Effect
According to this disclosure, it is possible to provide a position
detecting device configured to be capable of correctly obtaining
attendant information from a stylus pen stably even when the stylus
pen moves at high speed while removing the influence of noise.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagram showing a configuration of a transparent sensor
of a position detecting device according to one or more embodiments
of this disclosure.
FIG. 2 is a sectional view of the transparent sensor of the example
of FIG. 1.
FIG. 3 is a configuration diagram of a position detecting device
according to one or more embodiments of this disclosure.
FIG. 4 is a diagram showing an internal structure example of a
stylus pen used in a position detecting device according to one or
more embodiments of this disclosure.
FIG. 5 is a diagram showing a circuit example of the stylus pen of
the example of FIG. 4.
FIG. 6 is a signal waveform diagram in the circuit example of the
stylus pen in FIG. 5.
FIG. 7 is a diagram showing an X-axis whole-surface scan operation
in a position detecting device according to one or more embodiments
of this disclosure.
FIG. 8 is a diagram showing a transition operation to a partial
scan in a position detecting device according to one or more
embodiments of this disclosure.
FIG. 9 is a diagram showing a partial scan operation in a position
detecting device according to one or more embodiments of this
disclosure.
FIG. 10 is a diagram for explaining an existing example of a
selection method of electrodes in detection processing of attendant
information in a position detecting device.
FIG. 11 is a diagram for explaining an example of a selection
method of electrodes in detection processing of attendant
information in a position detecting device according to one or more
embodiments of this disclosure.
FIG. 12 is a diagram for explaining an example of a selection
method of electrodes in detection processing of attendant
information in a position detecting device according to one or more
embodiments of this disclosure.
FIG. 13 is a diagram for explaining an example of a selection
method of electrodes in detection processing of attendant
information in a position detecting device according to one or more
embodiments of this disclosure.
FIG. 14 is a diagram showing a partial scan operation in a position
detecting device according to one or more embodiments of this
disclosure.
FIG. 15 is a diagram for explaining an example of a selection
method of electrodes in detection processing of attendant
information in a position detecting device according to one or more
embodiments of this disclosure.
FIG. 16 is a diagram showing a partial scan operation in a position
detecting device according to one or more embodiments of this
disclosure.
MODES FOR CARRYING OUT THE DISCLOSURE
FIG. 1 is a diagram showing a configuration of a transparent sensor
combined with a display unit integrally in a position detecting
device according to one or more embodiments of this disclosure. In
FIG. 1, numeral 11 denotes a liquid crystal display (LCD) panel and
numeral 12 denotes a transparent sensor having electrodes formed by
indium tin oxide (ITO). Numeral 12a denotes ITO glass obtained by
arranging plural X-electrodes 12d formed of lines of the ITO
electrodes in the X-direction, of the X-direction and the
Y-direction orthogonal to each other. Numeral 12b denotes ITO glass
obtained by arranging plural Y-electrodes 12e formed of lines of
the ITO electrodes in the Y-direction. Numeral 12c denotes a
transparent insulating sheet having a uniform thickness and is
formed of a polyethylene terephthalate (PET) film, for example.
The transparent sensor 12 is made by bonding the ITO glass 12a and
the ITO glass 12b in such a manner that the respective ITO surfaces
are made to face each other and the transparent insulating sheet
12c is interposed therebetween. The transparent sensor 12 is
disposed to overlap with the LCD panel 11 in such a manner that the
position detection area just overlaps with the display area of the
LCD panel 11. The X-electrodes 12d on the ITO glass 12a and the
Y-electrodes 12e on the ITO glass 12b are connected to a printed
circuit board, not shown in the diagram, via a flexible board, not
shown in the diagram, by an anisotropic conductive film (ACF)
connection.
FIG. 2 is a sectional view obtained by cutting the transparent
sensor 12 over the Y-electrode 12e. In this embodiment, the side of
the ITO glass 12a is the operation surface side and the exposed
surface to the external in this ITO glass 12a serves as a touch
surface 12f.
FIG. 3 is a configuration diagram of a position detecting device
according to one or more embodiments of this disclosure. In FIG. 3,
numeral 12 denotes the transparent sensor. Numeral 13 denotes an
X-electrode selection circuit that is connected to the X-electrodes
12d of the transparent sensor 12 and selects two pairs of
electrodes from the X-electrodes 12d for connection to a positive
terminal and a negative terminal of a differential amplification
circuit 17, respectively. Numeral 14 denotes a Y-electrode
selection circuit that is connected to the Y-electrodes 12e of the
transparent sensor 12 and selects two pairs of electrodes from the
Y-electrodes 12e for connection to the positive terminal and a
negative terminal of the differential amplification circuit 17,
respectively. In the present embodiment example, a description will
be made based on the assumption that the number of X-electrodes 12d
is 40 (X1 to X40) and the number of Y-electrodes 12e is 30 (Y1 to
Y30).
In FIG. 3, the X-electrode selection circuit 13 and the Y-electrode
selection circuit 14 are so shown as to select one electrode among
the plural X-electrodes 12d and the plural Y-electrodes 12e of the
transparent sensor 12 for connection to each of the positive
terminal and the negative terminal of the differential
amplification circuit 17. However, these X-electrode selection
circuit 13 and Y-electrode selection circuit 14 are configured to
be capable of simultaneously selecting plural electrodes among the
plural X-electrodes 12d and the plural Y-electrodes 12e of the
transparent sensor 12 for connection to each of the positive
terminal and the negative terminal of the differential
amplification circuit 17.
Numeral 15 denotes a stylus pen 15, and a signal of a constant
frequency is supplied between an electrode at the tip part and a
peripheral electrode surrounding it.
Numeral 16 denotes a switching circuit, and it selects one or more
electrodes selected by the X-electrode selection circuit 13 or one
or more of the electrodes selected by the Y-electrode selection
circuit 14 and connects the selected electrodes to the differential
amplification circuit 17. Specifically, when the X-axis coordinate
of the position indicated by the stylus pen 15 is obtained, a
control signal a from a control circuit 18 is set to a low level
"0" to select one or more electrodes selected by the X-electrode
selection circuit 13. Furthermore, when the Y-axis coordinate of
the position indicated by the stylus pen 15 is obtained, the
control signal a is set to a high level "1" to select one or more
electrodes selected by the Y-electrode selection circuit 14. In
this case, one or more electrodes selected by the X-electrode
selection circuit 13 for connection to the positive terminal of the
differential amplification circuit 17 or one or more electrodes
selected by the Y-electrode selection circuit 14 for connection to
the positive terminal of the differential amplification circuit 17
is connected to a non-inverting input terminal (positive terminal)
of the differential amplification circuit 17 and one or more
electrodes selected by the X-electrode selection circuit 13 for
connection to the negative terminal of the differential
amplification circuit 17 or one or more electrodes selected by the
Y-electrode selection circuit 14 for connection to the negative
terminal of the differential amplification circuit 17 is connected
to an inverting input terminal (negative terminal) of the
differential amplification circuit 17.
Numeral 19 denotes a band-pass filter circuit having a
predetermined bandwidth centered at the frequency of the signal
output by the stylus pen 15, and an output signal j from the
differential amplification circuit 17 is supplied thereto through a
switch 20. The switch 20 is controlled to the on-state or off-state
by a control signal b from the control circuit 18. Specifically,
when the control signal b is at the high level "1," the switch 20
is set to an on-state and the output signal j from the differential
amplification circuit 17 is supplied to the band-pass filter
circuit 19. When the control signal b is at the low level "0," the
switch 20 is set to an off-state and the output signal j from the
differential amplification circuit 17 is not supplied to the
band-pass filter circuit 19.
An output signal k of the band-pass filter circuit 19 is subjected
to detection by a detection circuit 21 and is converted to a
digital value by an analog-to-digital conversion circuit
(hereinafter, abbreviated as the AD conversion circuit) 22 based on
a control signal c from the control circuit 18. Digital data d from
this AD conversion circuit 22 is read and processed by a
microprocessor (MCU) 23. Here, a period during which the switch 20
is in the on-state is a reception period in which sampling is
carried out by the AD conversion circuit 22 and a signal is
converted to a digital signal. A period during which the switch 20
is in the off-state is a reception-stopped period in which sampling
is not carried out by the AD conversion circuit 22. The reception
period and the reception-stopped period alternate based on the
on-state and off-state of the switch 20.
The control circuit 18 supplies a control signal e to the
X-electrode selection circuit 13 and thereby the X-electrode
selection circuit 13 selects two pairs of X-electrodes for
connection to the positive terminal and the negative terminal of
the differential amplification circuit 17, respectively.
Furthermore, the control circuit 18 supplies a control signal f to
the Y-electrode selection circuit 14 and thereby the Y-electrode
selection circuit 14 selects two pairs of Y-electrodes for
connection to the positive terminal and the negative terminal of
the differential amplification circuit 17, respectively.
The microprocessor 23 internally includes a read only memory (ROM)
and a random access memory (RAM) and operates by a program stored
in the ROM.
The microprocessor 23 outputs a control signal g based on the
program stored in the ROM to control the control circuit 18 so that
the control circuit 18 may output the control signals a to f at
predetermined timings. The control circuit 18 generates the control
signals a to f to carry out signal reception and AD conversion in
synchronization with a horizontal synchronizing pulse h.
[Configuration Example of Stylus Pen 15]
FIG. 4 shows an internal structure example of the stylus pen 15
used in the present embodiment. In FIG. 4, a core 30 is provided at
the tip part and an electrode 31 is buried inside the core 30. At
the periphery of the core 30 excluding the tip part, a shield
electrode 32 is provided to surround the core 30. The shield
electrode 32 is connected to a part at which the potential is most
stable (GND; ground electrode) in the circuit. This shield
electrode 32 has an effect of preventing a detected coordinate
value from deviating even when the stylus pen 15 is put with a tilt
on the transparent sensor 12.
Numeral 33 denotes a variable-capacitance capacitor that is
physically coupled to the core 30 and whose capacitance changes
depending on the writing pressure applied through the core 30.
Numeral 34 denotes a printed circuit board and numeral 35 denotes a
battery. An oscillation circuit that oscillates at a constant
frequency is provided on the printed circuit board 34 and the
oscillation output thereof is supplied to the electrode 31. The
writing pressure applied to the variable-capacitance capacitor 33
is turned to a binary code by an operation to be described later to
control the oscillation circuit and thereby an ASK-modulated signal
is output. An ASK modulation circuit for this purpose is also
provided on the printed board 34.
FIG. 5 shows one example of the circuit of the stylus pen 15. In
FIG. 5, the same component as FIG. 4 is represented by the same
symbol. Numeral 31 denotes the electrode provided at the tip part
of the stylus pen 15. Numeral 35 denotes the battery and numeral 33
denotes the variable-capacitance capacitor whose capacitance
changes depending on the writing pressure. In FIG. 5, a coil L1, a
capacitor C1, and a capacitor C2 form part of the oscillation
circuit and the oscillation output thereof is induced to a coil L2
coupled to the coil L1 and is supplied to the electrode 31.
In FIG. 5, numeral 36 denotes a central processing unit (CPU), and
it operates in accordance with a predetermined program. A control
signal p from an output terminal P1 of the CPU 36 is connected to
the above-described oscillation circuit and controls the
oscillation to an activated state or a stopped state. The
oscillation circuit stops the oscillation when the control signal p
is at the low level "0," and carries out the oscillation when the
control signal p is at the high level "1." The variable-capacitance
capacitor 33 is connected in parallel to a resistor and is
connected to a terminal P2 of the CPU 36. The operation of the
stylus pen 15 will be described in such a manner that the signal of
this terminal P2 is defined as q and the signal supplied to the
electrode 31 is defined as r.
FIG. 6 shows the respective waveforms of the signals p, q, and r in
FIG. 5. The CPU 36 keeps output of the high level "1" as the signal
p for a certain period to continue the operation of the oscillation
circuit. In this period, coordinate detection operation to be
described later is carried out on the position detecting device
side. Furthermore, the CPU 36 detects the writing pressure applied
to the variable-capacitance capacitor 33 in the continuous
transmission period during which this signal p is at the high level
"1." To carry out this writing pressure detection, the CPU 36 sets
the terminal P2 to the output of the high level "1" after starting
the above-described continuous transmission. This causes the signal
q to become the high level "1" and the variable-capacitance
capacitor 33 is charged by the voltage of the battery 35.
Upon the completion of this charge, the CPU 36 sets the terminal P2
to the input setting, i.e. a high-impedance setting. The charge
accumulated in the variable-capacitance capacitor 33 is thereby
discharged by the resistor connected in parallel to the
variable-capacitance capacitor 33 and therefore the voltage of the
signal q, i.e. the terminal P2, gradually decreases. When the
voltage of the terminal P2 becomes a predetermined threshold
voltage or lower in the CPU 36, the internal logic becomes the low
level. The CPU 36 measures, as Tp (see FIG. 6), the time from the
switching of the terminal P2 to the input setting to the reaching
of the voltage of the terminal P2 to the above-described threshold
or lower. This time Tp changes depending on the capacitance of the
variable-capacitance capacitor 33, i.e. the magnitude of the
writing pressure. Therefore, the CPU 36 obtains the time Tp
measured in the range from zero to the maximum of the writing
pressure as a 10-bit digital value.
After the end of the above-described continuous transmission
period, a little later the CPU 36 carries out ASK modulation by
controlling the terminal P1 according to this 10-bit writing
pressure data. Specifically, the CPU 36 sets the terminal P1 to the
low level when the data is "0" and sets it to the high level when
the data is "1." In FIG. 6, a start signal as the first data is
sent out as "1" invariably. The purpose of this is to enable the
microprocessor 23 to correctly predict the timing of subsequent
data. In FIG. 6, a time Td is the cycle at which one-bit data is
sent out.
Next, a description will be made about how the position detecting
device of the present embodiment configured in this manner detects
the coordinate position and writing pressure data of the stylus pen
15.
[Example of Detection Processing of Indicated Position by Stylus
Pen 15]
FIG. 7 shows an X-axis whole-surface scan operation. Specifically,
FIG. 7 shows the X-axis whole-surface scan operation in which the
X-electrode selection circuit 13 sequentially selects all
X-electrodes and receives a signal and thereby an approximate
position at which the stylus pen 15 is put is obtained. First, the
microprocessor 23 outputs the control signal g to the control
circuit 18 to carry out control to cause the switching circuit 16
to select the X-side and to select the X-electrode X1 for
connection to the positive terminal side of the differential
amplification circuit 17 and select, in this example, the
X-electrode X6 located across four electrodes from the X-electrode
on the positive terminal side for connection to the negative
terminal of the differential amplification circuit 17.
Next, the microprocessor 23 carries out control to increment each
of the numbers of the electrodes selected by the X-electrode
selection circuit 13 and select the X-electrode X2 and the
X-electrode X7 for connection to the positive terminal and the
negative terminal of the differential amplification circuit 17,
respectively. In this state, the signal level is obtained similarly
to the above description. At this time, signal reception and AD
conversion are carried out in synchronization with the horizontal
synchronizing pulse h.
Similarly, the microprocessor 23 obtains the signal level while
sequentially incrementing the numbers of the X-electrodes selected
by the X-electrode selection circuit 13 and carries out this
operation until the selection for connection to the positive
terminal of the differential amplification circuit 17 becomes the
X-electrode X35 and the selection for connection to the negative
terminal of the differential amplification circuit 17 becomes the
X-electrode X40.
If the value of the AD conversion output d does not reach a certain
level in the above-described all cases at this time, the
microprocessor 23 determines that the stylus pen 15 does not exist
on the transparent sensor 12, and repeats the above-described
X-axis whole-surface scan operation.
Moreover, in FIG. 7, the case in which the stylus pen 15 is put
near the X-electrode X11 of the transparent sensor 12 is shown. In
this case, as shown in FIG. 7, the signal levels of the AD
conversion output d have a peak value when the X-electrode X11 is
selected for connection to either the positive terminal or the
negative terminal of the differential amplification circuit 17 by
the X-electrode selection circuit 13. The approximate position of
the stylus pen 15 can be obtained from the distribution of the
signal levels when the selection of the X-electrode is updated in
this manner. When it turns out that the stylus pen 15 is put near
the X-electrode X11 from the signal level distribution of FIG. 7,
subsequently transition operation to partial scan is carried
out.
In the X-axis whole-surface scan operation shown in FIG. 7, the
interval corresponding to four electrodes is set between the
electrode selected by the X-electrode selection circuit 13 for
connection to the positive terminal of the differential
amplification circuit 17, and the electrode selected by the
X-electrode selection circuit 13 for connection to the negative
terminal of the differential amplification circuit 17. However, the
number of electrodes may be set to a number other than four.
FIG. 8 shows the transition operation to partial scan. The timing
when the stylus pen 15 enters the continuous transmission period in
FIG. 6 is detected. In addition, the Y-direction approximate
position of the stylus pen 15 in the transparent sensor 12 is
obtained. Also at this time, that signal reception and AD
conversion are carried out in synchronization with the horizontal
synchronizing pulse h is the same as the above description.
First, the microprocessor 23 outputs the control signal g to the
control circuit 18 to carry out control to cause the switching
circuit 16 to select the X-side and to cause the X-electrode
selection circuit 13 to select the X-electrode X11 and the
X-electrode X16 for connection to the positive terminal and the
negative terminal of the differential amplification circuit 17,
respectively. When the stylus pen 15 enters the continuous
transmission period shown in FIG. 6 at this time, the signal level
output from the AD conversion circuit 22 repeatedly becomes a
predetermined value or higher. When the signal level is detected
beyond the predetermined value repeatedly for a predetermined time
Ts (see FIG. 8) or longer, the microprocessor 23 determines that
the stylus pen 15 has entered the continuous transmission period,
and makes transition to Y-axis whole-surface scan operation. This
predetermined time Ts is set to a time sufficiently longer than the
cycle Td of transmission by the stylus pen 15 in the data
transmission period.
In order to carry out a Y-axis whole-surface scan operation, the
microprocessor 23 outputs the control signal g to the control
circuit 18 to cause the switching circuit 16 to select the Y-side
and to cause the Y-electrode selection circuit 14 to select the
Y-electrode Y1 and the Y-electrode Y6 for connection to the
positive terminal and the negative terminal of the differential
amplification circuit 17, respectively. Subsequently, the
microprocessor 23 obtains the signal level while incrementing the
numbers of the electrodes selected by the Y-electrode selection
circuit 14 one by one similarly to the X-axis whole-surface scan,
and carries out this operation until the positive terminal is
connected to the Y-electrode Y25 and the negative terminal is
connected to the Y-electrode Y30. Also at this time, similarly to
the X-axis whole-surface scan, a signal distribution is obtained in
which the signal level of the AD conversion output d has a peak
value when the electrode near the stylus pen 15 is selected for
connection to either the positive terminal or the negative terminal
of the differential amplification circuit 17. In the present
embodiment, the following description will be made based on the
assumption that the stylus pen 15 is put near the Y-electrode
Y20.
By the operation of FIG. 7 and FIG. 8 described above, it turns out
that the stylus pen 15 is put near the intersection of the
X-electrode X11 and the Y-electrode Y20. Subsequently, the
microprocessor 23 makes a transition to a partial scan operation in
which five X-electrodes centered at the X-electrode X11 and five
Y-electrodes centered at the Y-electrode Y20 are sequentially
selected and the signal level is obtained.
FIG. 9 is a diagram showing the partial scan operation. When the
signal level output from the AD conversion circuit 22 is equal to
or higher than a predetermined value for the predetermined time Ts
continuously in the state in which the X-electrode selection
circuit 13 selects the X-electrode X11 and the X-electrode X16 for
connection to the positive terminal and the negative terminal of
the differential amplification circuit 17, the microprocessor 23
determines that the period of continuous transmission from the
stylus pen 15 has been started, and makes a transition to the
coordinate detection operation (step 1 in FIG. 9). This time Ts is
similar to that described in FIG. 8 and is set to a time
sufficiently longer than the cycle Td of the digital signal
transmitted by the stylus pen 15 in the data transmission
period.
In order to obtain the X-coordinate of the stylus pen 15, in the
state in which the switching circuit 16 selects the X-side, the
microprocessor 23 causes the X-electrode selection circuit 13 to
sequentially select five X-electrodes centered at the X-electrode
X11 (X9 to X13) for connection to the positive terminal of the
differential amplification circuit 17 and reads the signal level
(step 1). At this time, the X-electrodes X14 to X18 are selected by
the X-electrode selection circuit 13 as X-electrodes for connection
to the negative terminal of the differential amplification circuit
17, which are sufficiently separated from the X-electrodes selected
by the X-electrode selection circuit 13 for connection to the
positive terminal of the differential amplification circuit 17.
In the present embodiment, four times of detection are carried out
regarding the same electrodes and the average level thereof is
stored as the received-signal level.
In FIG. 9, the number of the X-electrode selected for connection to
the positive terminal of the differential amplification circuit 17
when the highest signal level is detected (here, X11) and the
signal level VPX thereof are stored. Furthermore, the levels
detected with both adjacent X-electrodes thereof are stored as VAX
and VBX (step 1).
Next, in order to obtain the Y-coordinate of the stylus pen 15,
with the switching circuit 16 caused to select the Y-side, the
microprocessor 23 causes the Y-electrode selection circuit 14 to
sequentially select five Y-electrodes centered at the Y-electrode
Y20 (Y18 to Y22) for connection to the positive terminal of the
differential amplification circuit 17 and reads the signal level
(step 1). At this time, the Y-electrode selection circuit 14
selects the Y-electrodes Y23 to Y27 as Y-electrodes for connection
to the negative terminal of the differential amplification circuit
17, which are sufficiently separated from the Y-electrodes selected
by the Y-electrode selection circuit 14 for connection the positive
terminal of the differential amplification circuit 17. Also at this
time, signal reception and AD conversion are carried out in
synchronization with the horizontal synchronizing pulse h. In
addition, four times of detection are carried out regarding the
same electrodes and the average level thereof is stored as the
received-signal level.
Furthermore, the number of the Y-electrode selected for connection
to the positive terminal of the differential amplification circuit
17 when the highest signal level is detected (here, Y20) and the
signal level VPY thereof are stored. Furthermore, the levels
detected with both adjacent electrodes thereof are stored as VAY
and VBY (step 1).
The signal levels VPX, VAX, VBX, VPY, VAY, and VBY obtained here
are used for calculation of coordinate values based on calculation
expressions to be described later.
Subsequently, the microprocessor 23 carries out an operation for
waiting for the end of the period of continuous transmission from
the stylus pen 15. The microprocessor 23 carries out control to
cause the switching circuit 16 to select the X-side. In addition,
the microprocessor 23 carries out control to cause the X-electrode
selection circuit 13 to select the X-electrode X11, with which the
peak is detected in the above-described coordinate detection
operation, for connection to the positive terminal of the of the
differential amplification circuit 17 and to select the X-electrode
X16 for connection to the negative terminal of the differential
amplification circuit 17. The clock time when the level of the
signal received in this state becomes lower than the predetermined
value is the end clock time of the period of continuous
transmission from the stylus pen 15 (step 1).
Next, a method for obtaining the coordinate position of the stylus
pen 15 from the reception levels obtained in the above-described
step 1 will be described.
From the reception levels VPX, VAX, VBX, VPY, VAY, and VBY obtained
in step 1, the coordinate values (X, Y) of the stylus pen 15 are
each calculated by the following expressions.
X=Px+(Dx/2).times.((VBX-VAX)/(2.times.VPX-VAX-VBX)) (Expression
1)
Px is the coordinate position of the X-electrode with which the
maximum level is detected in the X-axis (here, X11), and Dx is the
arrangement pitch between the X-electrodes.
Y=Py+(Dy/2).times.((VBY-VAY)/(2.times.VPY-VAY-VBY)) (Expression
2)
Py is the coordinate position of the Y-electrode with which the
maximum level is detected in the Y-axis (here, Y20), and Dy is the
arrangement pitch between the Y-electrodes.
The above-described calculation expressions, (Expression 1) and
(Expression 2), are one example and are not necessarily the optimum
method. The optimum calculation method changes also depending on
the width and pitch of the X-electrodes and the Y-electrodes and
the electrode shape of the stylus pen 15.
In the above-described embodiment, in the detection processing of
the position indicated by the stylus pen 15 in step 1, the
electrodes selected by the X-electrode selection circuit 13 and the
Y-electrode selection circuit 14 for connection to the positive
terminal of the differential amplification circuit 17 are near the
stylus pen 15. However, the electrodes selected by the X-electrode
selection circuit 13 and the Y-electrode selection circuit 14 for
connection to negative terminal of the differential amplification
circuit 17 may near the stylus pen 15. Furthermore, the electrodes
selected by the X-electrode selection circuit 13 and the
Y-electrode selection circuit 14 for connection to the positive
terminal and the negative terminal of the differential
amplification circuit 17 have four electrodes therebetween.
However, the electrodes selected by the X-electrode selection
circuit 13 and the Y-electrode selection circuit 14 for connection
to the positive terminal and the negative terminal of the
differential amplification circuit 17 may have another number of
electrodes therebetween. It is preferable that the two electrodes
selected by the X-electrode selection circuit 13 and the
Y-electrode selection circuit 14 for connection to the positive
terminal and negative terminal of the differential amplification
circuit 17 be located across such a number of electrodes as to
provide an interval somewhat wider than the radiation region of an
electric field radiated from the electrode 31 of the stylus pen
15.
In the above-described embodiment, coordinate detection on the
X-axis side and coordinate detection on the Y-axis side regarding
the position indicated by the stylus pen 15 are carried out with
switching by the switching circuit 16. However, the differential
amplification circuit, the AD conversion circuit, and so forth may
be provided on the X-axis side and the Y-axis side separately and
reception processing may be simultaneously executed.
In the above-described embodiment, one electrode is selected by
each of the X-electrode selection circuit 13 and the Y-electrode
selection circuit 14 for connection to the positive terminal and
negative terminal of the differential amplification circuit 17,
respectively. However, the same number of plural electrodes may be
simultaneously selected.
In the present embodiment, the signal level is obtained four times
regarding the same electrodes in the partial scan to obtain the
X-coordinate and Y-coordinate of the position indicated by the
stylus pen 15. However, the signal level may be obtained one time
regarding the same electrodes or another number of times may be
employed.
[Example of Detection Processing of Attendant Information from
Stylus Pen 15]
Next, an example of detection processing of writing pressure data
as an example of attendant information transmitted from the stylus
pen 15 will be described. In the position detecting device of this
embodiment, detection of attendant information is carried out based
on a signal from the stylus pen 15 received by an electrode or an
electrode group fixedly selected by either the X-electrode
selection circuit 13 or the Y-electrode selection circuit 14. The
fixedly-selected electrode or electrode group is selected in such a
manner that the X-electrode or Y-electrode detected in the vicinity
of the indicated position of the stylus pen 15 by position
detection processing (X-axis whole-surface scan or Y-axis
whole-surface scan) is included in either the positive terminal or
negative terminal of the differential amplification circuit 17. In
the following description, explanation will be made as the case in
which detection of attendant information is carried out based on a
signal from the X-electrode or X-electrode group selected by the
X-electrode selection circuit 13.
When detecting the end of the period of continuous transmission
from the stylus pen 15, the microprocessor 23 starts an operation
of detecting the timing of the start signal shown in FIG. 6,
transmitted prior to writing pressure data (step 2).
At this time, as shown in FIG. 9, the clock time when the signal
level has become equal to or higher than the above-described
predetermined value is stored as t1. The microprocessor 23 starts
an operation of receiving data from the stylus pen 15 from the
clock time after waiting for a certain time Tw from the clock time
t1 (step 2). This time Tw is defined as the time until the level of
the received signal almost disappears after the end of transmission
of the start signal from the stylus pen 15, and is set to a time
obtained in advance.
The microprocessor 23 activates a timer, not shown in the diagram,
simultaneously with the reaching of the above-described waiting
time to the time Tw. This timer repeatedly counts the time from
zero to the value corresponding with the above-described time Td
(cycle of data transmission from the stylus pen 15) (step 2). In
the operation period of one cycle of the timer, the microprocessor
23 repeatedly carries out signal reception and AD conversion and
reads the signal level. If the signal level during this period
never reaches the above-described predetermined value, the
microprocessor 23 determines that transmission from the stylus pen
15 is absent, and stores the data of this round as "0." If a signal
level equal to or higher than the predetermined value is detected
in the period, the microprocessor 23 determines that transmission
from the stylus pen 15 is present, and stores the data of this
round as "1" (step 2).
The above-described count of the timer is made ten times and 10-bit
data is stored. This 10-bit data corresponds to the 10-bit writing
pressure data shown in FIG. 7. In FIG. 9, the case in which the
writing pressure data is "0101110101" is shown.
Upon the end of reception of the 10-bit writing pressure data in
step 2, transition is made to the operation of detecting the start
of the period of continuous transmission from the stylus pen 15
(step 1) and the microprocessor 23 repeatedly carries out the
operation of FIG. 9.
<Selection of Electrodes in Detection Processing of Attendant
Information>
Conventionally, in detection of attendant information, two
electrodes separated by the same interval as the electrodes
selected to be connected to the positive terminal and the negative
terminal in the period to detect the position of the stylus pen 15
are selected. However, one of the electrodes is the electrode
detected as the vicinity of the indicated position of the stylus
pen 15 by position detection processing.
FIG. 10 is a diagram for explaining the selection state in the
X-electrode selection circuit 13 at the time of this existing
detection processing of attendant information. As described above,
in this embodiment, the electrode near the position indicated by
the stylus pen 15 is the X-electrode X11. Thus, the positive
terminal of the differential amplification circuit 17 is connected
to this X-electrode X11 and the X-electrode X16 located across four
electrodes from the X-electrode X11 is connected to the negative
terminal of the differential amplification circuit 17.
Thus, the interval between the electrode connected to the positive
terminal and the electrode connected to the negative terminal is
large and the detection processing becomes more susceptible to
noise in the selection method of electrodes in the example of FIG.
10. Therefore, in this embodiment, at the time of detection
processing of attendant information, the selection of the
electrodes connected to the positive terminal and the negative
terminal of the differential amplification circuit 17 by the
X-electrode selection circuit 13 (same applies also to the case of
the Y-electrode selection circuit 14) is changed from the selection
at the time of detection of the indicated position of the stylus
pen 15, and a shorter interval than the interval between the
electrodes connected to the positive terminal and the negative
terminal at the time of detection of the indicated position of the
stylus pen 15 is employed.
For example, as shown in FIG. 11, although that the X-electrode X11
near the indicated position of the stylus pen 15 is employed as the
X-electrode connected to the positive terminal is the same, the
microprocessor 23 controls the X-electrode selection circuit 13 so
that the X-electrode X14 located across two electrodes from the
X-electrode connected to the positive terminal may be employed as
the electrode connected to the negative terminal.
According to this example of FIG. 11, two electrodes whose interval
is shorter than in the position detection processing are selected
to be connected to the positive terminal and negative terminal of
the differential amplification circuit 17. Thus, noise of these two
electrodes is approximate and the effect of noise reduction becomes
larger, which makes it possible to detect the attendant information
more correctly.
However, along with an increase in the number of bits of the
attendant information due to addition of identification information
and so forth besides the writing pressure data as the attendant
information transmitted from the stylus pen 15, the transmission
time of the attendant information from the stylus pen 15 becomes
longer. This makes it difficult to acquire the attendant
information when the stylus pen 15 moves at high speed. Therefore,
in this embodiment, as described below, as each of the electrodes
connected to the positive terminal and negative terminal of the
differential amplification circuit 17, not one electrode but an
electrode group composed of plural electrodes is employed. This
allows solving of the problem of the above-described noise and the
problem of the difficulty in acquisition of attendant information
when the stylus pen 15 moves at high speed. In this case, the
number of electrodes forming a first electrode group and the number
of electrodes forming a second electrode group are set to the same
number.
<First Example of Electrode Selection>
FIG. 12 shows a first example of electrode selection at the time of
detection processing of attendant information. In this example of
FIG. 12, the X-electrode selection circuit 13 is controlled by the
microprocessor 23 to connect, as the first electrode group, three
electrodes of the X-electrode X11 near the indicated position of
the stylus pen 15 detected by position detection processing and the
X-electrode X10 and the X-electrode X12 on both adjacent sides of
the X-electrode X11 to the positive terminal of the differential
amplification circuit 17 and connect, as the second electrode
group, three electrodes of the X-electrode X14 located across two
electrodes from the X-electrode X11 and the X-electrode X13 and the
X-electrode X15 on both adjacent sides of the X-electrode X14 to
the negative terminal of the differential amplification circuit 17.
In step 2 of FIG. 9, the selected electrodes in the case of this
example are shown.
If the electrodes are selected in this manner, the X-electrode X11
is near the indicated position of the detected stylus pen 15 and,
even when the stylus pen 15 moves from the X-electrode X11 by
moving at high speed, the signal from the stylus pen 15 can be
received by the X-electrode X10 or the X-electrode X12 on both
sides of the X-electrode X11. Therefore, the position detecting
device can acquire all of the attendant information from the stylus
pen 15.
Furthermore, in the case of this example of FIG. 12, the first
electrode group composed of the X-electrodes X10, X11, and X12
connected to the positive terminal of the differential
amplification circuit 17 and the second electrode group composed of
the X-electrodes X13, X14, and X15 connected to the negative
terminal are adjacent. Therefore, noise included in both electrode
groups is approximately the same and it becomes possible to
effectively cancel the noise.
<Second Example of Electrode Selection>
FIG. 13 shows a second example of electrode selection at the time
of detection processing of attendant information. This example of
FIG. 13 is the same as the first example in that the X-electrode
selection circuit 13 is controlled by the microprocessor 23 to
connect, as the first electrode group, three electrodes of the
X-electrode X11 near the indicated position of the stylus pen 15
and the X-electrode X10 and the X-electrode X12 on both adjacent
sides of the X-electrode X11 to the positive terminal of the
differential amplification circuit 17.
In this second example, plural electrodes forming the second
electrode group connected to the negative terminal of the
differential amplification circuit 17 are set on both sides of the
first electrode group. Specifically, in the example of FIG. 13, the
X-electrode selection circuit 13 electrically connects the
X-electrodes X8, X9, and X13 located on both sides of the first
electrode group to form the second electrode group, and connects
the second electrode group to the negative terminal of the
differential amplification circuit 17. In FIG. 14, a timing chart
at the time of partial scan operation in the case of this second
example is shown.
In this second example, the position of the detected stylus pen 15
is at substantially the center of the plural electrodes composed of
the first electrode group and the second electrode group, and it
becomes possible to acquire the attendant information more surely
even when the stylus pen 15 moves at higher speed. Furthermore,
according to this second example, the electrodes connected to the
positive terminal of the differential amplification circuit 17 and
the electrodes connected to the negative terminal are closer than
in the case of the first example. Thus, the noise reduction effect
due to the differential amplification becomes larger than in the
first example and the detection processing becomes robuster against
noise.
<Third Example of Electrode Selection>
FIG. 15 shows a third example of electrode selection at the time of
detection processing of attendant information and is a modification
example of the second example. This third example is an example of
the case of enabling reception of attendant information whichever
side the stylus pen 15 moves toward at high speed when the position
of the stylus pen 15 exists at an intermediate position between the
X-electrode X11 and the X-electrode X12.
Specifically, in this third example, the X-electrode selection
circuit 13 is controlled by the microprocessor 23 to connect
electrodes as follows. Specifically, the position of the stylus pen
15 detected by position detection processing is deemed as the
center and the X-electrodes X10, X11, X12, and X13 as two
electrodes on each of both sides of the position are connected to
the positive terminal of the differential amplification circuit 17
as the first electrode group. In addition, the X-electrodes X8, X9,
X14, and X15 as two electrodes on each of both sides of the first
electrode group are connected to the negative terminal of the
differential amplification circuit 17. In FIG. 16, a timing chart
at the time of partial scan operation in the case of this third
example is shown.
In this embodiment, as shown in FIG. 9, FIG. 14, and FIG. 16, at
the time of detection processing of attendant information, the
first electrode group and the second electrode group that are each
composed of plural X-electrodes are connected to the positive
terminal and negative terminal of the differential amplification
circuit 17. Thus, also whether the stylus pen 15 has entered the
continuous transmission period is detected in the predetermined
time Ts, the detection is carried out based on the difference
between the first electrode group and the second electrode group,
which are composed of plural X-electrodes. Therefore, it becomes
possible to detect whether the stylus pen 15 has entered the
continuous transmission period more easily than in the case of
using the difference between electrodes as each one electrode as in
the existing configuration.
Furthermore, according to the above-described first example to
third example, in the detection processing of attendant
information, the first electrode group and the second electrode
group that are each composed of plural X-electrodes are connected
to the positive terminal and negative terminal of the differential
amplification circuit 17. Thus, there is also an effect that
detection of the attendant information also becomes easier than in
the case of using the difference between electrodes as each one
electrode as in the existing configuration.
In the above-described explanation, the X-electrode X11, with which
the maximum level has been detected, is selected from the
X-electrodes and data is received in step 2, in which detection of
attendant information is carried out. However, this may be carried
out by selecting the Y-electrode Y20, with which the maximum level
has been detected among the Y-electrodes.
Moreover, in the above-described embodiment, the positive terminal
side is caused to include the electrode near the stylus pen 15 as
the electrode selected by the X-electrode selection circuit 13 and
the Y-electrode selection circuit 14. However, the electrodes may
be so selected that the negative terminal side includes the
electrode near the stylus pen 15.
DESCRIPTION OF REFERENCE SYMBOLS
11 . . . LCD panel, 12 . . . Transparent sensor, 13 . . .
X-electrode selection circuit, 14 . . . Y-electrode selection
circuit, 15 . . . Stylus pen, 16 . . . Switching circuit, 17 . . .
Differential amplification circuit, 23 . . . Microprocessor
* * * * *