U.S. patent number 10,768,748 [Application Number 16/234,268] was granted by the patent office on 2020-09-08 for position indicator, position detecting device, position detecting circuit, and position detecting method.
This patent grant is currently assigned to Wacom Co., Ltd.. The grantee listed for this patent is Wacom Co., Ltd.. Invention is credited to Hideyuki Hara.
United States Patent |
10,768,748 |
Hara |
September 8, 2020 |
Position indicator, position detecting device, position detecting
circuit, and position detecting method
Abstract
A position indicator includes a housing and circuitry. The
circuitry transmits a plurality of signal blocks successively to a
position detecting device. Each of the signal blocks includes a
position detection signal, a first modulated signal acquired by
modulating one part of a plurality of divided parts of position
indicator identification information, and a second modulated signal
acquired by modulating current position indicator status
information acquired successively from a signal supplied to a
control terminal or from a voltage state of the control terminal.
The position indicator transmits the plurality of divided parts of
position indicator identification information by transmitting the
plurality of signal blocks.
Inventors: |
Hara; Hideyuki (Tokyo,
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: |
1000005042671 |
Appl.
No.: |
16/234,268 |
Filed: |
December 27, 2018 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20190129572 A1 |
May 2, 2019 |
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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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15209547 |
Jul 13, 2016 |
10209829 |
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PCT/JP2014/051296 |
Jan 22, 2014 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G06F
3/0418 (20130101); G06F 3/03545 (20130101); G06F
3/0416 (20130101); G06F 3/044 (20130101); G06F
3/046 (20130101) |
Current International
Class: |
G06F
3/044 (20060101); G06F 3/046 (20060101); G06F
3/041 (20060101); G06F 3/0354 (20130101) |
Field of
Search: |
;345/170-178 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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101714037 |
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May 2010 |
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CN |
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103401663 |
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Nov 2013 |
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CN |
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8-221180 |
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Aug 1996 |
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JP |
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8-234902 |
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Sep 1996 |
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JP |
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2007-257359 |
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Oct 2007 |
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JP |
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2011-086253 |
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Apr 2011 |
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JP |
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297109 |
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Feb 1997 |
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TW |
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451155 |
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Aug 2001 |
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TW |
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Other References
International Search Report, dated Mar. 25, 2014, for International
Application No. PCT/JP2014/051296, 1 page. cited by applicant .
Chinese Office Action, dated Feb. 19, 2020, for Chinese Application
No. 201480073758.6, 16 pages. cited by applicant.
|
Primary Examiner: Davis; Tony O
Attorney, Agent or Firm: Seed IP Law Group LLP
Claims
The invention claimed is:
1. A signal processing method, comprising: receiving, at a position
detecting device, first information and second information
different from the first information transmitted from a position
indicator, wherein the first information is represented in a
digital signal of a first defined number of bits and is divided
into a plurality of information parts respectively represented in
digital signals of a second defined number of bits smaller than the
first defined number of bits, and wherein each of the information
parts is received with the second information, storing one of the
information parts, which is received, in a memory, performing a
comparison between said one of the information parts stored in the
memory and another one of the information parts, and processing the
second information based on a result of said comparison.
2. The signal processing method according to claim 1, wherein the
first information is information unique to the position
indicator.
3. The signal processing method according to claim 2, wherein the
information unique to the position indicator is at least one of ID
information that identifies the position indicator, user ID
information assigned to the position indicator, and manufacturer
information of the position indicator.
4. The signal processing method according to claim 1, wherein the
second information is pressure information detected by the position
indicator.
5. The signal processing method according to claim 4, wherein the
pressure information is pen tip pressure information of the
position indicator.
6. The signal processing method according to claim 4, wherein the
pressure information is side pressure information of the position
indicator.
7. The signal processing method according to claim 1, comprising:
outputting the second information according to the result of said
comparison.
8. The signal processing method according to claim 1, comprising:
combining the received plurality of information parts of the first
information to obtain the first information.
9. The signal processing method according to claim 8, comprising:
when detecting an error in the received plurality of information
parts, re-receiving the plurality of information parts
retransmitted from the position indicator and combining the
re-received plurality of information parts to obtain the first
information.
10. The signal processing method according to claim 9, comprising:
detecting an error in the received plurality of information parts
based on an error-detecting code assigned to the information
parts.
11. The signal processing method according to claim 9, comprising:
when detecting an error in the received plurality of information
parts, re-receiving the plurality of information parts
retransmitted from the position indicator and combining the
re-received plurality of information parts to obtain the first
information.
12. The signal processing method according to claim 1, comprising:
performing said comparison in response to receiving said another
one of the information parts.
13. The signal processing method according to claim 1, comprising:
storing the second information in the memory.
14. A signal processing method, comprising: receiving, at a
position detecting device, first information and second information
different from the first information transmitted from a position
indicator, wherein the first information is represented in a
digital signal of a first defined number of bits and is divided
into a plurality of information parts respectively represented in
digital signals of a second defined number of bits smaller than the
first defined number of bits, and wherein each of the information
parts is received with the second information in a signal block,
storing one of the information parts, which is received, in a
memory, performing a comparison between said one of the information
parts stored in the memory and another one of the information
parts, and processing the second information based on a result of
said comparison.
15. The signal processing method according to claim 14, comprising:
receiving a plurality of signal blocks respectively including the
plurality of information parts of the first information and the
second information, and combining the received plurality of
information parts of the first information to obtain the first
information.
16. The signal processing method according to claim 15, comprising:
when detecting an error in the received plurality of signal blocks
based on an error-detecting code assigned to the signal blocks,
re-receiving the plurality of signal blocks retransmitted from the
position indicator and combining the re-received plurality of
information parts to obtain the first information.
17. A signal processing method, comprising: receiving, at a
position detecting device, first information transmitted from a
position indicator, wherein the first information is represented in
a digital signal of a first defined number of bits and is divided
into a plurality of information parts respectively represented in
digital signals of a second defined number of bits smaller than the
first defined number of bits, storing the received plurality of
information parts in a memory, and combining the received plurality
of information parts to obtain the first information.
18. The signal processing method according to claim 17, wherein the
first information is information unique to the position
indicator.
19. The signal processing method according to claim 18, wherein the
information unique to the position indicator is at least one of ID
information that identifies the position indicator, user ID
information assigned to the position indicator, and manufacturer
information of the position indicator.
20. The signal processing method according to claim 17, comprising:
detecting an error in the received plurality of information parts
based on an error-detecting code assigned to the information parts.
Description
BACKGROUND
Technical Field
The present disclosure relates to a position indicator, and more
particularly to a position indicator that transmits large-size
information to a position detecting device. The present disclosure
also relates to a position detecting device configured to detect
the position of such a position indicator, a position detecting
circuit for use by the position detecting device, and a position
detecting method for detecting the position of such a position
indicator.
Description of the Related Art
There exist touch-sensitive input systems configured to include a
position detecting device that is a plate-like input unit, and a
position indicator such as an electronic pen or a cursor. On some
position detecting devices, a simple rod or a human fingertip may
be used as the position indicator. Such input systems are usually
called tablets or digitizers. They are utilized extensively for
inputting texts and illustrations to computers such as personal
computers and tablet terminals.
The position detecting device has a plurality of linear conductors
(e.g., loop coils) arranged in a matrix pattern. The position
detecting device is configured to detect the position of the
position indicator on the basis of voltages or their variations
generated by the linear conductors being approached by the position
indicator.
Various specific schemes for position detection include the
capacitance system and the electromagnetic induction system. The
capacitance system involves using capacitance generated between the
position indicator and linear conductors. The capacitance system
may be further classified into the self-capacitance system that
detects the change in voltage on each linear conductor, and the
mutual capacitance system that detects the change in potential
difference between the linear conductors intersecting with each
other. The self-capacitance system may be still further classified
into a system in which the position detecting device impresses a
voltage to the linear conductors, and another system in which the
position indicator transmits a signal to the linear conductors
causing them to generate voltages. The former system may be
employed where the position indicator cannot transit a signal as
when the fingertip is used as the position indicator. The latter
system may be utilized where the position indicator can transmit a
signal. Meanwhile, the electromagnetic induction system is a system
in which the position detecting device uses the linear conductors
as a transmission antenna to transmit electromagnetic waves to the
position indicator which in turn transmits a signal for detection
by the position detecting device using the linear conductors as a
receiving antenna. With the electromagnetic induction system, the
transmission and the reception are performed on a time-sharing
basis.
The detection of the position by the position detecting device is
explained below using an example of the self-capacitance system in
which the position indicator transmits a signal. With this system,
the position detecting device detects the position while the
position indicator keeps transmitting a determined continuous
signal. During the transmission of the continuous signal by the
position indicator, the linear conductors individually generate
higher voltages the shorter their distance to the position
indicator. The position detecting device individually scans a
plurality of linear conductors for levels (voltages) to detect the
linear conductor bearing the highest voltage among the conductors
arranged in the X direction and the linear conductor carrying the
highest voltage among the conductors arranged in the Y direction
perpendicular to the X direction. The voltages of the two detected
linear conductors and the voltages of nearby linear conductors are
substituted in a determined mathematical formula, and the result
calculated by the formula is acquired as the position of the
position indicator. This calculating method allows the position of
the position indicator to be detected with a resolution finer than
the pitch at which the linear conductors are arranged.
Meanwhile, some of the position indicators capable of transmitting
signals are configured to transmit not only the above-mentioned
continuous signal but also various items of information. Specific
examples of the information to be transmitted include writing
pressure information, on-off information (side switch information)
about switches typically provided on the side surface or the like
of the position indicator, and an identifier (ID) unique to each
position indicator. Patent Document 1 discloses a typical position
detector that transmits such items of information to a position
detecting device.
The transmitting of the diverse items of information from the
position indicator and the transmitting of the continuous signal
therefrom are performed on a time-sharing basis. An example
disclosed in Patent Document 1 is cited here to give a specific
description of the two kinds of transmitting on a time-sharing
basis. The position indicator first transmits the continuous
signal. During the continuous signal transmission, the position
detecting device detects the position of the position indicator.
Within a determined time of the completion of the continuous signal
transmission, the position detecting device transmits a determined
control signal (command) to the position indicator. Upon receipt of
the control signal, the position indicator transmits information
corresponding to the content of the control signal to the position
detecting device. Although not described in Patent Document 1,
there are cases where the position indicator transmits various
items of information regardless of the control signal from the
position detecting device.
PRIOR ART DOCUMENT
Patent Document
Patent Document 1: Japanese Patent Laid-open No. 2011-086253
BRIEF SUMMARY
Technical Problem
In recent years, the size of the information (bit count)
transmitted from the position indicator to the position detecting
device has increased considerably. For example, the ID unique to
each position indicator includes such diverse items of information
as the individual number, owner identification code, device type,
and manufacturer number of the position indicator. The information,
if it includes check bits, can amount to not less than 60 bits.
As described above, the transmitting of diverse items of
information from the position indicator and the transmitting of the
above-mentioned continuous signal for position detection are
performed on a time-sharing basis. It follows that with a growing
size of the transmitted information entailing a longer transmission
time, the number of times the continuous signal is sent per unit
time decreases. This means that there is a trade-off relation
between the sampling rate of the position information and the
amount of the information transmitted. An excessively large size of
the transmission information may make it impossible for the
operation of position detection to follow the rapid movement of the
position indicator. For this reason, the existing input systems can
transmit only up to a certain size of information from the position
indicator to the position detecting device.
An embodiment facilitates a position indicator transmitting
large-size information to a position detecting device without
reducing the sampling rate of position information.
Technical Solution
According to an embodiment, there is provided a position indicator
that transmits to a position detecting device a plurality of signal
blocks successively, each of the signal blocks including a
continuous signal for position detection and a first modulated
signal acquired by modulating one of a plurality of divided
information parts constituting first information. The position
indicator transmits the entire first information by transmitting
the plurality of signal blocks.
According to an embodiment, there is provided a position detecting
device that receives from a position indicator a plurality of
signal blocks successively, each of the signal blocks including a
continuous signal for position detection and a first modulated
signal acquired by modulating one of a plurality of divided
information parts constituting first information. The position
detecting device detects position information indicating the
position of the position indicator from each of the signal blocks
on the basis of the continuous signal, and acquires the first
information on the basis of the first modulated signal included in
each of the plurality of signal blocks.
According to an embodiment, there is provided a position detecting
circuit connected to receiving circuitry. The position detecting
circuit receives a plurality of signal blocks successively from a
position indicator via the receiving circuitry, each of the signal
blocks including a continuous signal for position detection and a
first modulated signal acquired by modulating one of a plurality of
divided information parts constituting first information. The
position detecting circuit detects position information indicating
the position of the position indicator from each of the signal
blocks on the basis of the continuous signal, and acquires the
first information on the basis of the first modulated signal
included in each of the plurality of signal blocks.
According to an embodiment, there is provided a position detecting
method including: a transmitting step of transmitting a plurality
of signal blocks successively from a position indicator to a
position detecting circuit, each of the signal blocks including a
continuous signal for position detection and a first modulated
signal acquired by modulating one of a plurality of divided
information parts constituting first information; and a receiving
step of receiving the plurality of signal blocks successively to
detect position information indicating the position of the position
indicator from each of the signal blocks on the basis of the
continuous signal, while acquiring the first information on the
basis of the first modulated signal included in each of the
plurality of signal blocks.
Advantageous Effect
In an embodiment, the first information is divided into a plurality
of signal blocks each including a continuous signal for position
detection, before the signal blocks are transmitted. This
facilitates the position indicator transmitting large-size
information to the position detecting device without reducing the
sampling rate of the position information.
In an embodiment, a position indicator comprises a housing; and
circuitry, which, in operation, transmits a plurality of signal
blocks successively to a position detecting device, each of the
signal blocks including: a position detection signal; a first
modulated signal acquired by modulating one part of a plurality of
divided parts of position indicator identification information; and
a second modulated signal acquired by modulating current position
indicator status information acquired successively from a signal
supplied to a control terminal or from a voltage state of the
control terminal, wherein the position indicator transmits the
plurality of divided parts of position indicator identification
information by transmitting the plurality of signal blocks. In an
embodiment, the first modulated signal includes information
indicative of a position of the one of the plurality of divided
parts in the position indicator identification information. In an
embodiment, the first modulated signal includes an error-detecting
code to detect an error in the one of the plurality of divided
parts of the position indicator identification information. In an
embodiment, each bit of the first and second modulated signals is
transmitted in a clock cycle during which a signal level of the bit
is at a first level for at least a portion of the clock cycle; and
a signal level of the position detection signal remains at a second
level different from the first level over a time period longer than
the clock cycle. In an embodiment, a number of the plurality of
divided parts of position indicator identification information is
three. In an embodiment, the position indicator status information
includes writing pressure information indicating a pressure sensed
by the position indicator, and at least one of: side switch
information indicating an on-off state of a switch provided on the
position indicator; charging request information indicating whether
the position indicator needs to be charged; tilt information
indicating a tilt angle of the position indicator relative to the
position detecting device; and rotation information acquired by a
rotation sensor incorporated in the position indicator. In an
embodiment, the position indicator comprises: a core body, which,
in operation, contacts the position detecting device, wherein the
writing pressure information is information acquired by detecting
pressure applied to the core body while the position detection
signal is in an active state.
In an embodiment, a position detecting device comprises: a sensor;
and signal processing circuitry coupled to the sensor, wherein the
signal processing circuitry, in operation, receives from a position
indicator a plurality of signal blocks successively, each of the
signal blocks including: a position detection signal; a first
modulated signal acquired by modulating one part of a plurality of
divided parts of position indicator identification information; and
a second modulated signal acquired by modulating current position
indicator status information acquired successively; and detects
position information indicating the position of the position
indicator from each of the signal blocks based on the position
detection signal, acquires the current position indicator status
information based on the second modulated signal, and acquires the
one part of the position indicator identification information based
on the first modulated signal. In an embodiment, the signal
processing circuitry, in operation, acquires the plurality of
divided parts of the position indicator identification information
by receiving the plurality of signal blocks. In an embodiment, when
the signal processing circuitry detects an error in acquisition of
position indicator identification information, the signal
processing circuitry continues to detect position information
indicating the position of the position indicator based on the
position detection signal and to acquire current position indicator
status information based on the second modulated signal. In an
embodiment, the first modulated signal includes information
indicative of a position of the one of the plurality of divided
parts in the position indicator identification information; and the
signal processing circuitry, in operation, acquires the position
indicator identification information by combining the respective
parts included in each of the plurality of signal blocks based on
the information indicative of the position of the respective parts
included in each of the plurality of signal blocks. In an
embodiment, the first modulated signal includes an error-detecting
code to detect an error in the one part of the plurality of divided
parts of the position indicator identification information; and for
each of the signal blocks, the signal processing circuitry, in
operation, determines whether the part of the position indicator
identification information included in the first modulated signal
associated with the signal block is accurate based on the
error-detecting code included in the first modulated signal. In an
embodiment, the signal processing circuitry, from a time when the
plurality of signal blocks start being received until reception
thereof is completed, retains a plurality of pieces of the position
information acquired from the position detection signal included in
each of the plurality of signal blocks, and a plurality of pieces
of the current position indicator status information acquired from
the second modulated signal included in each of the plurality of
signal blocks. In an embodiment, when the signal processing
circuitry successfully acquires the position indicator
identification information from the plurality of signal blocks, the
signal processing circuitry associates the retained pieces of the
position information and the retained pieces of the current
position indicator status information with the acquired position
indicator identification information. In an embodiment, the signal
processing circuitry, in operation, is coupled to a processor; and
while the position indicator identification information is being
acquired, the signal processing circuitry outputs to the processor
each of the retained pieces of the position information and each of
the retained pieces of the current position indicator status
information. In an embodiment, the signal processing circuitry, in
operation, is coupled to a processor; and the signal processing
circuitry, in operation, associates the retained pieces of the
position information and the retained pieces of the current
position indicator status information with the acquired position
indicator identification information before outputting the
associated information to the processor.
In an embodiment, a system, comprises: receiving circuitry, which,
in operation, receives a plurality of signal blocks successively
from a position indicator, each of the signal blocks including: a
position detection signal; a first modulated signal acquired by
modulating one part of a plurality of divided parts of position
indicator identification information; and a second modulated signal
acquired by modulating current position indicator status
information acquired; and position detecting circuitry, coupled to
the receiving circuitry, wherein the position detecting circuitry
detects position information indicating the position of the
position indicator from each of the signal blocks based on the
position detection signal, acquires the current position indicator
status information based on the second modulated signal, and
acquires the one part of the plurality of divided parts of the
position indicator identification information based on the first
modulated signal included in each of the plurality of signal
blocks. In an embodiment, the first modulated signal includes
information indicative of a position of the one of the plurality of
divided parts in the position indicator identification information;
and the position detecting circuitry, in operation, acquires the
position indicator identification information by combining the
respective parts included in each of the plurality of signal blocks
based on the information indicative of the position of the
respective part included in each of the plurality of signal blocks.
In an embodiment, the first modulated signal includes an
error-detecting code to detect an error in the one part of the
plurality of divided parts of the position indicator identification
information; and for each of the signal blocks, the position
detecting circuitry, in operation, determines whether the part of
the position indicator identification information included in the
first modulated signal associated with the signal block is accurate
based on the error-detecting code included in the first modulated
signal. In an embodiment, from a time when the plurality of signal
blocks start being received until reception thereof is completed,
the position detecting circuitry, in operation, stores a plurality
of pieces of the position information acquired from the position
detection signal included in each of the plurality of signal blocks
and a plurality of pieces of the current position indicator status
information acquired from the second modulated signal included in
each of the plurality of signal blocks in a storage circuit. In an
embodiment, when the position detecting circuitry successfully
acquires the position indicator identification information from the
plurality of signal blocks, the position detecting circuitry
associates the stored pieces of the position information in the
storage circuit and the stored pieces of the current position
indicator status information in the storage circuit with the
acquired position indicator identification information. In an
embodiment, the system comprises: a processor coupled to the
position detecting circuitry, wherein the position detecting
circuitry associates the stored pieces of the position information
in the storage circuit and the stored pieces of the current
position indicator status information in the storage circuit with
the acquired position indicator identification information before
outputting the associated information to the processor.
In an embodiment, a method comprises: transmitting a plurality of
signal blocks successively from a position indicator to a position
detecting circuit, each of the plurality of signal blocks
including: a position detection signal for position detection; a
first modulated signal acquired by modulating one part of a
plurality of divided parts of position indicator identification
information; and a second modulated signal acquired by modulating
current position indicator status information acquired successively
from a signal supplied to a control terminal or from a voltage
state of the control terminal; receiving the plurality of signal
blocks successively; detecting position information indicating the
position of the position indicator from each of the received signal
blocks based on the position detection signal; acquiring the
current position indicator status information based on the second
modulated signal from each of the signal blocks; and acquiring the
plurality of divided parts of the position indicator identification
information based on the first modulated signal included in each of
the plurality of signal blocks.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
FIG. 1 is a block diagram illustrating a system configuration of a
touch-sensitive input system 1 and functional blocks of a tablet 10
attached to the input system 1 of an embodiment.
FIG. 2A is a circuit diagram illustrating examples of an internal
circuit of an electronic pen 20 indicated in FIG. 1 and FIG. 2B is
a schematic block diagram illustrating functional blocks of a
controller 40 indicated in FIG. 2A.
FIG. 3A is a timing chart illustrating various examples of signals
related to the electronic pen 20 indicated in FIG. 2A and FIG. 3B
is a timing chart illustrating various signals related to the
tablet 10 indicated in FIG. 1.
FIG. 4A is a schematic view illustrating an example structure of a
unique ID stored in a unique ID storage section 40a indicated in
FIG. 2B and FIG. 4B is a schematic view illustrating an example
structure of a transmission information block TIB generated by an
oscillation control section 40c indicated in FIG. 2B.
FIG. 5 is a schematic view illustrating the sequence in which a
plurality of transmission information blocks TIB generated by the
oscillation control section 40c indicated in FIG. 2B are
transmitted in an embodiment.
FIGS. 6A and 6B are explanatory views of example processing
performed by the tablet 10 indicated in FIG. 1.
FIG. 7 is a circuit diagram illustrating an internal circuit of a
variation of the electronic pen 20 according to an embodiment.
DETAILED DESCRIPTION
Embodiments are described below in detail with reference to the
accompanying drawings.
A touch-sensitive input system 1 of an embodiment is configured to
include a tablet 10 (position detecting device) having a plurality
of electrodes (linear conductors) 11X and 11Y arranged in a matrix
pattern, an electronic pen 20 (position indicator) designed to
transmit a signal, and a computer 30 (processor) coupled to the
tablet 10, as illustrated in FIG. 1.
The input system 1 is of the self-capacitance type. The tablet 10
is configured to detect the position of the electronic pen 20 on
the basis of voltages generated by the electrodes 11X and 11Y
receiving the signal transmitted from the electronic pen 20. In the
ensuing paragraphs, the structure of the tablet 10 and that of the
electronic pen 20 will be described first, followed by a
description of the electronic pen 20 in operation and a description
of the tablet 10 in operation, in that order.
As illustrated in FIG. 1, the tablet 10 is configured to include a
tablet sensor 11, a selection circuit 12, an amplifier circuit 13,
a band-pass filter 14, a detector circuit 15, a sample hold circuit
16, an analog-to-digital converter circuit 17, and a microprocessor
18 (position detecting circuit). Of these components, the tablet
sensor 11, selection circuit 12, amplifier circuit 13, band-pass
filter 14, detector circuit 15, sample hold circuit 16, and
analog-to-digital converter circuit 17 function as the receiving
circuitry for receiving signals from the electronic pen 20.
The tablet sensor 11 is configured to have a transparent glass
substrate, not illustrated. The plurality of electrodes 11X extend
in the X direction over the substrate surface (the face close to
the electronic pen 20) and are arranged an equal distance apart
from each other in the Y direction perpendicular to the X
direction. The plurality of electrodes 11Y extend in the Y
direction over the back side of the substrate (the face away from
the electronic pen 20) and are arranged an equal distance apart
from each other in the X direction. The electrodes 11X and 11Y are
transparent conductors. The electrodes may be formed of indium tin
oxide (ITO), for example. In an embodiment, as many as 30
electrodes 11X and 40 electrodes 11Y may be provided.
The tablet sensor 11 is disposed on a display device, not
illustrated. Since the tablet sensor 11 is formed of the
above-mentioned transparent members, an image displayed on the
display device is transmitted through the tablet sensor 11 and is
visible by the user of the input system 1. In this manner, the
input system 1 allows the user to experience writing with the
electronic pen 20 on the image displayed on the display device.
From an opposite point of view, it is because the tablet sensor 11
is disposed on the display device that the tablet sensor 11 is
formed of the transparent members. An embodiment may also be
applied to tablets that have no display area. In this case, the
tablet sensor 11 need not be formed of transparent members. That
means the tablet sensor 11 may comprise, for example, copper wires
instead of ITO.
The selection circuit 12 selects one of the electrodes 11X and 11Y
and couples the selected electrode to the amplifier circuit 13. The
amplifier circuit 13 is supplied with the voltage of the electrode
selected by the selection circuit 12. As will be explained later in
more detail, the electronic pen 20 is configured to
amplitude-modulate a sine wave signal of a determined frequency
using the transmission information. On each of the electrodes 11X
and 11Y develops a voltage signal reflecting the amplitude of the
sine wave signal thus transmitted.
The amplifier circuit 13 amplifies the voltage signal supplied from
the selection circuit 12 and outputs an amplified voltage signal to
the band-pass filter 14. The band-pass filter 14 extracts only the
component of the above-mentioned determined frequency from the
voltage signal output from the amplifier circuit 13, and outputs
the extracted component to the detector circuit 15. The detector
circuit 15 generates an envelope signal S1 by envelope-detecting
the voltage signal output from the band-pass filter 14, and outputs
the generated envelope signal S1 to the sample hold circuit 16. The
sample hold circuit 16 performs the sample and the hold operations
a determined time apart on the envelope signal S1 output from the
detector circuit 15. The analog-to-digital converter circuit 17
generates a digital signal S2 by subjecting to analog-to-digital
conversion the signal being held by the sample hold circuit 16, and
outputs the generated digital signal S2 to the microprocessor
18.
The electronic pen 20 transmits signals through binary amplitude
shift keying (ASK), as will be described later. The
analog-to-digital converter circuit 17 assumes that the input
signal was modulated through multi-value ASK when converting the
input signal to the digital signal S2. This process is intended to
let the microprocessor 18 acquire an approximate value of the
voltage represented by the voltage signal output from the selector
circuit 12.
The microprocessor 18 is a processor that incorporates a storage
device 19 and operates on programs held in the storage device 19.
The storage device 19 includes a read only memory (ROM) and a
random access memory (RAM), for example. The operations performed
by the microprocessor 18 include controlling the selector circuit
12, sample hold circuit 16, and analog-to-digital converter circuit
17; and causing the storage device 19 temporarily to store the
information represented by the digital signal S2 supplied from the
analog-to-digital converter circuit 17 before outputting the
information to the computer 30 at a suitable timing.
As illustrated in FIG. 2A, the electronic pen 20 is configured to
have a controller 40, a voltage converter circuit 41, a diode 42,
capacitors 43 to 46, a resistive element 47, switches 48 and 49, a
vibrator or oscillator 50, a conductor core 51 (core body), a tip
conductor 52, and a charging terminal 53.
The controller 40 is a processor that includes a ROM and a RAM. The
controller 40 is configured to operate in synchronism with a clock
signal generated by the vibrator 50 and in conformity with the
description of programs stored in the ROM. The cycle of the clock
signal is 60 microseconds for example. In addition to the terminals
connected to the vibrator 50, the controller 40 has a power supply
terminal Vcc, a ground terminal GND, and control terminals P1 to
P6.
The power supply terminal Vcc is connected with the capacitor 43
via the voltage converter circuit 41. The capacitor 43 is an
electric double layer capacitor that serves as the power source of
the electronic pen 20. The capacitor 43 is configured to have its
anode connected to the input terminal of the voltage converter
circuit 41, with the cathode of the capacitor 43 being grounded.
The voltage converter circuit 41 is a direct current-to-direct
current (DCDC) converter acting to convert the voltage across the
capacitor 43 to a rated voltage of the controller 40.
Although this embodiment uses an electric double layer capacitor as
the power source, this is not limitative. Alternatively, other
power configurations may be employed, such as a primary battery
such as a lithium battery or a dry cell, or a secondary battery
such as a nickel-hydrogen storage cell may be used as the power
source.
The anode of the capacitor 43 is also connected to the charging
terminal 53 via the diode 42. The charging terminal 53 is made up
of two terminals: a positive terminal and a negative terminal. The
anode of the capacitor 43 is connected with the positive terminal
of the charging terminal 53. The negative terminal is grounded
inside the electronic pen 20. The charging terminal 53 is a
terminal to which an external power supply unit is connected. When
the external power supply unit is connected to the charging
terminal 53, the capacitor 43 is charged. In an embodiment, a
dedicated battery charger (not illustrated) of the electronic pen
20 is used as the external power supply unit.
The capacitor 44 is connected interposingly between the power
supply terminal Vcc and the ground terminal GND. The capacitor 44
is provided to stabilize the power supply voltage fed from the
voltage converter circuit 41 to the controller 40. In an
embodiment, the capacitor 44 is an aluminum electrolytic capacitor
of from tens to hundreds of .mu.F, for example.
The voltage converter circuit 41 is configured to perform either
step-down operation or step-up operation in accordance with the
voltage across the capacitor 43. That is, the maximum voltage
across the capacitor 43 is designed to exceed the rated voltage of
the controller 40. It follows that while the capacitor 43 is being
fully charged, the voltage across the capacitor 43 exceeds the
rated voltage of the controller 40. In this case, the voltage
converter circuit 41 performs step-down operation to bring the
voltage supplied to the power supply terminal Vcc down to the rated
voltage of the controller 40. On the other hand, if the capacitor
43 is insufficiently charged, the voltage across the capacitor 43
may fall below the rated voltage of the controller 40. In this
case, the voltage converter circuit 41 performs step-up operation
to bring the voltage supplied to the power supply terminal Vcc up
to the rated voltage of the controller 40.
The voltage converter circuit 41 is also connected to the control
terminals P1 and P2 of the controller 40. When the controller 40
supplies a determined control signal to the voltage converter
circuit 41 via the control terminal P1, the voltage converter
circuit 41 detects the voltage across the capacitor 43 and outputs
to the control terminal P2 a signal representing the detected
voltage value. The controller 40 is configured, given the signal
thus supplied, to determine whether or not the capacitor 43 needs
to be charged.
The input system 1 has the function of notifying the user of an
insufficiently charged state of the capacitor 43. What follows is a
more specific explanation of this function. The controller 40 is
configured to transmit to the tablet 10 a signal representing the
result of the determination of whether or not the capacitor 43
needs to be charged (a specific method of transmitting the signal
will be discussed later). The computer 30 receives the signal via
the tablet 10. If the signal indicates the need to charge the
capacitor 43, an indication to that effect is displayed typically
on a display device, not illustrated. The indication allows the
user to know the need for charging the electronic pen 20. Given the
indication, the user places the electronic pen 20 on the
above-mentioned battery charger to start charging the capacitor
43.
The control terminal P3 is grounded via the capacitor 45 and the
resistive element 47. The capacitor 45 is a variable capacitance
capacitor coupled to the conductor core 51, and is configured to
vary in capacitance depending on the pressing force (writing
pressure) in effect when the electronic pen 20 is pressed against
the tablet 10. The controller 40 is configured to acquire the
writing pressure from the capacitance of the capacitor 45, as will
be discussed later in more detail.
The method of detecting the pressing force (writing pressure) is
not limited to the use of a variable capacitance capacitor as
described above. The electronic pen 20 may be configured to detect
the pressing force (writing pressure) using other methods. For
example, an alternative method may involve detecting the pressing
force in terms of changes in inductance of plurality of ferrite
cores being moved. Another method may involve using semiconductor
devices, namely micro electro mechanical systems (MEMS) to detect
the pressing force. Still another method may involve optically
detecting the pressing force.
The control terminals P4 and P5 are grounded via the switches 48
and 49, respectively. The switches 48 and 49 are disposed on the
surface of the electronic pen 20 (side switches) and are operable
by the user. The controller 40 has the function of determining the
on-off states of the switches 48 and 49 from the voltage states of
the control terminals P4 and P5. Although this embodiment has two
switches 48 and 49, there may be provided no switch, one switch, or
three or more switches instead.
The control terminal P6 is coupled to the conductor core 51 via the
capacitor 46. The conductor core 51 is structured to protrude from
the tip conductor 52 at the tip of the housing of the electronic
pen 20. The tip conductor 52 is grounded.
The electronic pen 20 has the function of transmitting an
amplitude-modulated sine wave signal of a determined frequency, as
mentioned above. This sine wave signal is generated by the
controller 40. The controller 40 is configured to output the sine
wave signal from the control terminal P6. The sine wave signal thus
output is fed to the conductor core 51 via the capacitor 46. Note
that the capacitor 46 is provided to remove the direct-current bias
component from the sine wave signal. The sine wave signal reaching
the conductor core 51 is output as electromagnetic waves and
received by the electrodes 11X and 11Y of the tablet 10 as
discussed above.
The structure of examples of the tablet 10 and that of the
electronic pen 20 were explained above. What follows is an
explanation of example content of the information sent from the
electronic pen 20 to the tablet 10, followed by an explanation of
an example transmission operation performed by the electronic pen
20.
As illustrated in FIG. 2B, the controller 40 of the electronic pen
20 is functionally configured to have a unique ID storage section
or circuitry 40a, an information acquisition section or circuitry
40b, an oscillation control section or circuitry 40c, and an
oscillator 40d.
The unique ID storage section 40a stores a unique ID given
beforehand to the electronic pen 20. The unique ID is information
unique to this electronic pen 20 and is different from the ID
assigned to any other electronic pen 20. For example, the unique ID
is structured to include or indicate the individual number of the
electronic pen 20, the owner identification code (e.g., user ID
assigned to the electronic pen owner) of the electronic pen 20, and
the type and the manufacturer number of the electronic pen 20. The
unique ID may be 51 bits in size, for example.
The information acquisition section 40b is configured to acquire
the unique ID from the unique ID storage section 40a and to also
acquire other diverse information from the signals supplied to the
above-mentioned control terminals P2 to P5 or from their voltage
states. What follows is an explanation of various examples of items
of information that may be acquired by the information acquisition
section 40b through the control terminals.
The control terminal P2 is supplied with the signal representing
the voltage across the capacitor 43 as described above. On the
basis of this signal, the information acquisition section 40b
determines whether or not the capacitor 43 needs to be charged, and
generates charging request information indicating the result of the
determination. The charging request information is, for example,
one-bit information that is 1 when charging is needed and 0 when
charging is not needed.
The information acquisition section 40b is also configured to
acquire writing pressure information representing the
above-mentioned writing pressure from the voltage state of the
control terminal P3. FIG. 3A illustrates example changes in the
voltage state of the control terminal P3 in effect when the writing
pressure information is acquired. As illustrated in the figure, the
writing pressure information is acquired while a continuous signal
CS for position detection is being sent.
More specifically, the information acquisition section 40b
references the potential on the control terminal P3 as the power
supply potential over a determined time period after the electronic
pen 20 has started to transmit the continuous signal CS. The power
supply potential is 1.5 V, for example. This operation is intended
to detect the writing pressure in effect at that point in time.
That is, the operation causes the capacitor 45 to accumulate the
charges of which the amount varies depending on the capacitance of
the capacitor 45 in effect at the time. Since the capacitance of
the capacitor 45 varies with the writing pressure as described
above, the amount of the charges accumulated in the capacitor 45
reflects the writing pressure.
The information acquisition section 40b then places the control
terminal P3 in the high-impedance state. This causes the capacitor
45 to discharge the accumulated charges through the resistive
element 47. The information acquisition section 40b measures an
elapsed time Tp from the time the capacitor 45 starts being
discharged until the potential of the control terminal P3 reaches
0.75 V, half the power supply potential of 1.5 V. The larger the
capacitance of the capacitor 45, the longer the elapsed time Tp
thus measured. The information acquisition section 40b can thus
acquire the writing pressure information from the measured elapsed
time Tp. The writing pressure information acquired in this manner
is 10 to 12 bits in size.
The information acquisition section 40b further generates side
switch information representing the on-off states of the switches
48 and 49 from the voltage states of the control terminals P4 and
P5. Since this embodiment has two switches, the side switch
information is 2 bits in size.
The information acquisition section 40b supplies the oscillation
control section 40c with the diverse information thus acquired
(e.g., unique ID, charging request information, writing pressure
information, and side switch information). The information
acquisition section 40b may also acquire information other than the
information described above and feed such information to the
oscillation control section 40c. The other information may include
tilt information representing the tilt angle of the electronic pen
20 relative to the tablet 10, fingerprint information acquired by a
fingerprint sensor incorporated in the electronic pen 20, grip
strength information acquired by a pressure sensor incorporated in
the electronic pen 20, rotation information acquired by a rotation
sensor incorporated in the electronic pen 20, and power supply
state information indicative of the charged state of the power
source, for example.
The oscillation control section 40c is a circuit that controls the
oscillator 40d in operation to output to the oscillator 40d a
signal modulated through binary ASK. The oscillator 40d is
configured to generate a sine wave signal of a determined frequency
and to output the generated sine wave signal to the control
terminal P6. The output of the signal from the oscillator 40d is
turned on or off under control of the oscillation control section
40c on the basis of the diverse information supplied from the
information acquisition section 40b, for example. As a result of
this, the signal output from the control terminal P6 is modulated
through binary ASK, as illustrated in FIG. 3A. The oscillator 40d
of this embodiment is configured to operate in synchronism with the
clock signal generated by the vibrator 50. Alternatively, the
oscillator 40d may be configured to oscillate at another frequency
without synchronizing with the clock signal. In such a case, the
oscillator 40d may be disposed outside the controller 40 in a
position connected to the control terminal P6.
Although this embodiment utilizes binary ASK, other modulation
methods may obviously be used instead. For example, another type of
amplitude modulation such as multi-value ASK, frequency shift
keying, phase shift keying, or quadrature amplitude modulation may
be adopted alternatively.
Described below in detail with reference to FIGS. 3A, 4A, 4B and 5
is an example transmission operation performed by the electronic
pen 20 using the oscillation control section 40c and the oscillator
40d.
The oscillation control section 40c and the oscillator 40d are
configured to transmit signals successively in units of a signal
block. FIG. 3A illustrates an example of the signal block. In the
example of FIG. 3A, one signal block is assigned a time period of 5
milliseconds. The first-half time period of 2.2 milliseconds is
assigned to transmitting the continuous signal CS for position
detection. The above-described diverse information is transmitted
by use of the second-half time period of 2.8 milliseconds.
In the example of FIG. 3A, the position information is detected
every 5 milliseconds by the tablet 10. If position information
detection is performed at a frequency in this range, the phenomenon
of the computer 30 being unable to give display fast enough to keep
up with the rapid movement of the electronic pen 20 does not
usually happen.
On the other hand, in the example of FIG. 3A, it is impossible to
transmit an entire unique ID in a single signal block. That is, the
oscillation control section 40c of this embodiment is configured to
operate at a single rate regarding the clock signal (one cycle
Td=60 microseconds) generated by the vibrator 50 illustrated in
FIG. 2A, as well as to perform modulation through binary ASK as
discussed above. Thus the amount of information that can be
transmitted in 2.8 milliseconds is merely up to 46 bits
(2.8/0.06.apprxeq.46.7). Considering the time required to transmit
a start signal SS, to be described later, the amount of the
information that can be actually sent drops further to
approximately 43 bits. It follows that if the unique ID is 51-bit
information as mentioned above, the entire unique ID cannot be sent
in a single signal block.
The second-half portion of the signal block is explained more
specifically below. As illustrated in FIG. 3A, the second half of
the signal block includes a start signal SS and a transmission
information block TIB. The start signal SS is a known signal
notifying the tablet 10 that the transmission of the continuous
signal CS is completed. The start signal SS signal is transmitted
following the continuous signal CS. The transmission information
block TIB is structured with a signal modulated on the basis of the
diverse information acquired by the information acquisition section
40b.
Here, the oscillation control section 40c provides on-off control
of the output of the oscillator 40d based on the transmission
information in synchronism with the rising edges of the clock
signal generated by the vibrator 50 illustrated in FIG. 2A, and
turns off the output of the oscillator 40d in synchronism with the
falling edges of the clock signal. This fixes to 0 the amplitude of
the transmitted signal in the second half of one clock cycle. As a
result, the signal involving the transmission information block TIB
is an intermittent signal that always includes a low level (first
level) period at intervals of one clock cycle as illustrated in
FIG. 3B. This structure is adopted so that the continuous signal CS
for position detection (a signal that remains at the high level
(second level) over a period longer than one clock cycle) and the
transmission information block TIB will be clearly distinguished
from each other.
The internal structure of the transmission information block TIB is
explained below in more detail. The program that regulates the
operation of the oscillation control section 40c categorizes
beforehand each of the various items of information acquired by the
information acquisition block 40b into one of two types: the type
of information that can be transmitted in one transmission
information block TIB, and the type of information that cannot be
transmitted in one transmission information block TIB. The former
type of information will be referred to as the second information
and the latter type of information as the first information
hereunder. With this embodiment, the unique ID is categorized as
the first information, and other items of information (charging
request information, writing pressure information, and side switch
information) are categorized as the second information. Of the
other items of information mentioned above, e.g., tilt information,
fingerprint information, grip strength information, and rotation
information, the fingerprint information and the grip strength
information may be categorized as the first information because of
their relatively large sizes, and the rotation information may be
categorized as the second information because of its relatively
small size. The tilt information may be categorized as the first
information if its size is large and as the second information if
its size is small.
The oscillation control section 40c has the function of dividing
the first information into a plurality of information parts. FIG.
4A illustrates an example of the unique ID as the first
information. In this example, the oscillation control section 40c
divides the unique ID, which is made up of bits D0 to Dx having
x+1-bit information, into as many as n ID blocks (information
parts) each having m bits. At the time of dividing, the oscillation
control section 40c provides each information part with a division
number (division information) indicating the position of that
information part inside the first information. In the example of
FIG. 4A, the oscillation control section 40c provides the ID blocks
with block numbers A, B, . . . , n-1, n serving as the division
numbers. Where the unique ID is 51 bits in size, the number n may
be "3" (the unique ID is divided into three parts each 17 bits
long). The block numbers A, B, . . . , n-1, n are a-bit information
each.
The oscillation control section 40c also has the function of
generating an error-detecting code for the receiving side to detect
an error. ID block check bits, b bits, illustrated in FIG. 4B
constitute a typical error-detecting code. In an embodiment, the
error-detecting code is a parity code or a cyclic code, for
example.
The oscillation control section 40c generates the above-mentioned
information part and error-detecting code every time a signal block
is transmitted, in ascending order of the corresponding division
numbers. Based on the generated information and on the latest
second information, the oscillation control section 40c generates a
transmission information block TIB to be included in each signal
block. FIG. 4B illustrates an example of a transmission information
block TIB thus generated.
The above-described points are reiterated below using the examples
of FIGS. 4A and 4B. The oscillation control section 40c generates
each ID block and the corresponding ID block check bits in the
order of block numbers A, B, . . . , n-1, n. Every time an ID block
is generated, the oscillation control section 40c generates a
y+1-bit transmission information block TIB made up of bits P0 to Py
together with the second information of c bits that includes the
acquired information, the latest writing pressure information, the
latest side switch information, and the latest charging request
information.
FIG. 5 illustrates typical n transmission information blocks TIB
generated successively as a result of the above-described process.
Each of these n transmission information blocks TIB is associated
with one of the division numbers (block numbers A, B, . . . , n-1,
n). The transmission information blocks TIB are generated in the
order of the division numbers. After completing the generation of
the transmission information blocks TIB associated with all
division numbers, the oscillation control section 40c returns to
the smallest division number and repeats the same block generating
process.
At the time of signal transmission, the oscillation control section
40c turns on the output of the oscillator 40d for a determined time
period to transmit the continuous signal CS for position detection,
as illustrated in FIG. 3A. The oscillation control section 40c then
provides on-off control of the output of the oscillator 40d to
transmit the start signal SS. Thereafter, the oscillation control
section 40c provides on-off control of the output of the oscillator
40d on the basis of generated transmission information blocks
TIB.
The signal blocks thus transmitted each constitute a signal made up
of the continuous signal CS, start signal SS, and transmission
information block TIB, as illustrated in FIG. 3A. The transmission
information block TIB comprises a second modulated signal obtained
by modulating the second information and by a first modulated
signal acquired by modulating one of a plurality of divided
information parts making up the first information, as illustrated
in FIG. 4B.
As described above, every time a transmission information block TIB
is generated, the oscillation control section 40c generates a
signal block. On the basis of the signal blocks thus generated, the
oscillation control section 40c provides on-off control of the
output of the oscillator 40d. As a result of this process, the
entire first information is eventually transmitted. The
transmission operation performed by the electronic pen 20 takes
place as described above.
Described below in detail with reference to FIGS. 1, 3B and 6 is a
series of example operations performed by the tablet 10 ranging
from detection of the electronic pen 20 to receipt of the
information sent from the electronic pen 20.
At a stage where the electronic pen 20 has yet to be detected, the
microprocessor 18 of the tablet 10 repeats the operation of
detecting a rise in the voltage of each of the electrodes 11X.
Specifically, the microprocessor 18 monitors the digital signal S2
output from the analog-to-digital converter circuit 17 while
causing the selection circuit 12 to select all electrodes 11X one
by one. When detecting a voltage rise on one electrode 11X as a
result of this operation, the microprocessor 18 proceeds to measure
the voltage of each of the electrodes 11Y. Specifically, the
microprocessor 18 monitors the digital signal S2 while causing the
selection circuit 12 to select all electrodes 11Y one by one. When
detecting a voltage rise on one electrode 11Y, the microprocessor
18 determines that the electronic pen 20 is approaching the point
of intersection between that electrode 11Y and the electrode 11X on
which the voltage rise was detected. If voltage rises are detected
on a plurality of electrodes 11X or on a plurality of electrodes
11Y, the electronic pen 20 may be determined to be approaching one
of the electrodes that bears the highest voltage.
In the example of FIG. 3B, the electrodes 11X are structured to
include electrodes 11X9 to 11X13 arranged in the Y direction, and
the electrodes 11Y are structured to include electrodes 11Y18 to
11Y22 arranged in the X direction. It is also illustrated that the
electrode 11X on which the voltage rise was detected in the above
process is the electrode 11X11, and that the electrode 11Y on which
the voltage rise was detected is the electrode 11Y20. In the course
of the ensuing description, the example in FIG. 3B will be referred
to.
When it is determined that the electronic pen 20 is approaching the
point of intersection between the electrode 11X11 and the electrode
11Y20, the microprocessor 18 causes the selection circuit 12 to
select the electrode 11X11. In this state, the microprocessor 18,
while monitoring the digital signal S2, waits for reception of the
continuous signal CS supposed to be sent from the electronic pen
20.
When the electronic pen 20 starts transmitting the continuous
signal CS, the voltage of the envelope signal S1 rises, as
illustrated in FIG. 3B. As a result, the voltage value represented
by the digital signal S2 also rises. Upon detecting this voltage
rise, the microprocessor 18 determines whether or not that state
continues for a determined time Ts. The determined time Ts is set
to be longer than one cycle Td of the above-mentioned clock signal
so that the signal of the transmission information block TIB will
not be mistaken for the continuous signal CS.
If it is determined that the voltage rise has continued for the
determined time Ts, the microprocessor 18 causes the selection
circuit 12 to select the electrode 11X11 and a plurality of
electrodes 11X nearby (five electrodes 11X9 to 11X13 in the example
of FIG. 3B) one by one. From the digital signal S2, the
microprocessor 18 acquires the voltage level of each of the
selected electrodes. Of a plurality of voltage levels obtained as a
result of such measurement, the highest voltage level is stored
into the storage device 19 as a peak voltage VPX. The voltage
levels of two adjacent electrodes 11X on both sides of the
electrode 11X on which the peak voltage VPX was observed are stored
into the storage device 19 as voltages VAX and VBX.
The microprocessor 18 then causes the selection circuit 12 to
select the electrode 11Y20 and a plurality of electrodes 11Y nearby
(five electrodes 11Y18 to Y22 in the example of FIG. 3B one by one.
From the digital signal S2, the microprocessor 18 measures the
voltage level of each of the selected electrodes. Of a plurality of
voltage levels obtained as a result of such measurement, the
highest voltage level is stored into the storage device 19 as a
peak voltage VPY. The voltage levels of two adjacent electrodes 11Y
on both sides of the electrode 11Y on which the peak voltage VPY
was observed are stored into the storage device 19 as voltages VAY
and VBY.
The microprocessor 18 is configured to perform the above-described
voltage measuring operation for the duration of the continuous
signal CS (e.g., the above-mentioned time period of 2.2
milliseconds). This is intended to suitably receive the start
signal SS and the transmission information block TIB following the
continuous signal CS. From an opposite point of view, the duration
of the continuous signal CS for 2.2 milliseconds may be determined
as a necessary and sufficient time period in which the
microprocessor 18 completes the above-described voltage measuring
operation.
The microprocessor 18 calculates the position information on the
electronic pen 20 on the basis of the voltages stored into the
storage device 19 as described above. For example, the voltages may
be substituted into following mathematical expressions (1) and (2)
to obtain coordinates (X, Y) as the position information on the
electronic pen 20. In these expressions, P.sub.X stands for the X
coordinate of the electrode 11X on which the peak voltage VPX was
detected, P.sub.Y for the Y coordinate of the electrode 11Y on
which the peak voltage VPY was detected, D.sub.X for the pitch at
which the electrodes 11X are arranged, and D.sub.Y for the pitch at
which the electrodes 11Y are arranged.
.times. ##EQU00001##
The microprocessor 18 then waits for reception of the start signal
SS by monitoring the digital signal S2, while causing the selection
circuit 12 to keep selecting the electrode 11X on which the peak
voltage VPX was detected. When detecting the receipt of the start
signal SS, the microprocessor 18 starts receiving the transmission
information block TIB upon elapse of a determined time Tw from the
time t1 at which the start signal SS was received. The transmission
information block TIB is received as a sine wave signal modulated
using binary ASK as described above. The sine wave signal is
converted to the digital S2 typically by the analog-to-digital
converter circuit 17 before being supplied to the microprocessor
18.
Described below in detail with reference to FIG. 6 is an example of
the operation of the microprocessor 18 in connection with the
process of receiving the transmission information block TIB.
Every time the continuous signal CS for position detection is
received, the microprocessor 18 acquires the position information
on the electronic pen 20 as described above, and stores the
acquired position information into the storage device 19. Also,
every time the transmission information block TIB including the
second information and an information part of the first information
is received, the microprocessor 18 acquires the second information
and the information part from the block TIB and stores them into
the storage device 19.
FIG. 6A schematically illustrates the items of information thus
acquired. As illustrated in this figure, the tablet 10 receives a
plurality of signal blocks in the order of the above-mentioned
division numbers. It should be noted that the signal blocks may or
may not be received in ascending order of the division numbers
starting from the smallest division number. In the example of FIG.
6A, a block number B is received first, followed by block numbers
C, . . . , n-1, n, A, B, C, . . . , in that order.
The microprocessor 18 continuously acquires the information parts
from each of the successively received signal blocks. Upon
completion of the acquisition of all information parts constituting
the first information, the microprocessor 18 combines the acquired
information parts based on the division numbers to obtain the first
information.
Some information parts acquired by the microprocessor 18 may
contain a bit error that occurred during the transmission. Every
time an information part is acquired, the microprocessor 18
determines whether or not that information part is accurate (e.g.,
whether or not it includes any bit error) using the error-detecting
code included in the same transmission information block TIB as the
information part. If it is determined that the information part is
not accurate, the microprocessor 18 does not use that information
part for combination with the other information parts and defers
executing the combining process until the signal block of the same
division number is again received, while causing the storage device
19 to hold the second information and the position information. In
this manner, the microprocessor 18 can acquire the first
information free of error. FIG. 6A illustrates an example in which
an error is detected in an ID block (illustrated crossed out)
included in the signal block associated with the division number C
received second. In this case, the microprocessor 18 waits for the
signal block associated with the division number C to be again
received, before combining the received information parts to
acquire the first information.
Upon completion of the acquisition of the first information, the
microprocessor 18 associates a plurality of pieces of position
information and a plurality of pieces of second information held so
far in the storage device 19 with the acquired first information.
As needed, the microprocessor 18 associates each of the pieces of
position information and each of the pieces of second information
with the acquired first information before outputting them to the
computer 30. This enables the microprocessor 18 and the computer 30
to process both the position information and the second information
received up to the completion of the acquisition of the first
information as the information associated with the first
information.
Under the above scheme, the computer 30 cannot acquire the position
information and the second information until the tablet 10
completes the acquisition of the first information. This can cause
the user to experience delays in the processing of the computer 30,
such as delayed display of the locus of the electronic pen 20. To
bypass this phenomenon, the tablet 10 may output at least some
information parts to the computer 30 without waiting for completion
of the acquisition of the first information.
As a specific example, the microprocessor 18 may have a function of
storing one or more first information parts acquired in the past.
Until acquisition of the entire first information is completed,
every time a new signal block is received, the microprocessor 18
may estimate the currently received first information part on the
basis of the division numbers and ID blocks included in the signal
blocks received so far and the first information stored in the
past. Even before acquisition of the first information as a whole
is completed, the microprocessor 18 may associate the successively
received position information and second information with the
estimated first information and output the combined information
successively to the computer 30.
For example, it may happen that the electronic pen 20 enters a
detectable area of the tablet sensor 11 but immediately leaves it
so that acquisition of the first information is incomplete. In that
case, the example function above enables the computer 30 to process
the position information, writing pressure information, and other
information by use of the estimated first information. This makes
it possible to display the locus of the electronic pen 20 even if
the first information (unique ID) cannot be recognized due to
excessively rapid "in-and-out movements" of the electronic pen
20.
As a more specific example, suppose that, of the transmission
information blocks TIB illustrated in FIG. 6A, only two
transmission information blocks TIB associated with the division
numbers A and B are acquired as a result of rapid "in-and-out
movements" of the electronic pen 20. In this case, if the
microprocessor 18 has acquired and stored the associated first
information in the past, the microprocessor 18 may compare the ID
blocks included in the two transmission information blocks TIB with
the stored first information (unique ID). This allows the
microprocessor 18 to estimate the entire first information
including the ID blocks associated with the division numbers C to
n. That in turn enables the computer 30 to process the position
information, writing pressure information, and other information
acquired from the two transmission information blocks TIB as the
information on the electronic pen 20 having the estimated first
information.
As described above, the input system 1 of this embodiment divides
the first information, which is too large to be transmitted in one
transmission information block TIB, into a plurality of signal
blocks each including the continuous signal CS for position
detection before transmitting the signal blocks. This makes it
possible for the electronic pen 20 to transmit large-size
information to the tablet 10 without reducing the sampling rate of
the position information.
Because the division number is assigned to each signal block, the
tablet 10 can correctly restore the first information on the basis
of the division numbers. Since the error-detecting code is attached
to each signal block, it is also possible to prevent the
restoration of the first information based on an erroneous
information part.
The tablet 10 retains in the storage device 19 the received second
information as well as the position information obtained before
acquisition of the first information is completed. It follows that
upon completion of the acquisition of the first information, the
tablet 10 can make effective use of such retained information as
the information associated with the first information.
Although example embodiments have been described above, this is not
limitative. It is evident that embodiments can be implemented in
diverse forms within the scope and spirit thereof.
For example, although the input system 1 explained in conjunction
with the above embodiments is configured to perform position
detection and communication by use of a self-capacitance type
touch-sensitive panel, embodiments can also be adapted
advantageously to other types of systems. For example, embodiments
may be adapted to a mutual capacitance type touch panel or to an
input system that performs position detection and communication
using the electromagnetic induction scheme.
FIG. 7 illustrates a structure of an electronic pen 20a for use
with an input system that performs position detection and
communication using the electromagnetic induction scheme. As
illustrated in the figure, the electronic pen 20a is configured to
have a controller 60, a power supply circuit 61, and a resonant
circuit 62. The resonant circuit 62 is made up of a coil 63, a
capacitor 64, and a variable capacitance capacitor 65. The
capacitor 64 and the variable capacitance capacitor 65 are
connected in parallel to the coil 63. A capacitor 66 is further
connected to the resonant circuit 62 via a switch 67.
The resonant circuit 62 is configured to resonate with
electromagnetic waves of a determined frequency transmitted from a
position detecting device (tablet). The controller 60 is configured
to transmit a signal using induced power generated by resonance.
That signal may be structured in the same manner as the signal
blocks used by the above-described embodiment. Thus the input
system that performs position detection and communication using the
electromagnetic induction scheme may, as with the input system 1 of
the above-described embodiment, transmit large-size information
from the position indicator to the position detecting device
without reducing the sampling rate of the position information.
Although it was explained that the above embodiment transmits both
the first and the second information in each signal block, it is
not mandatory to transmit the second information. Embodiments may
thus be adapted advantageously to electronic pens that do not
transmit the second information.
It was also explained in conjunction with the above embodiment that
the transmission information blocks TIB are sent as an intermittent
signal including, at intervals of a determined time period
(specifically one clock cycle), a time period during which each
transmission information block TIB is at the low level and that the
continuous signal CS remains at the high level over a period longer
than the determined time period. Alternatively, the transmission
information blocks TIB may be sent as an intermittent signal
including a time period during which each transmission information
block TIB is at the high level, with the continuous signal CS
remaining at the low level over a time period longer than the
determined time period.
It was further explained in conjunction with the above embodiment
that as illustrated in FIG. 3A, the entire continuous signal CS for
use in detecting the position of the position indicator is
transmitted in one pass. Alternatively, the continuous signal CS
may be transmitted in a plurality of divided parts.
DESCRIPTION OF REFERENCE SYMBOLS
1 Input system 10 Tablet 11 Tablet sensor 11X, 11Y Electrode 12
Selection circuit 13 Amplifier circuit 14 Band-pass filter 15
Detector circuit 16 Sample hold circuit 17 Analog-to-digital
converter circuit 18 Microprocessor 19 Storage device 20 Electronic
pen 30 Computer 40 Controller 40a Unique ID storage section 40b
Information acquisition section 40c Oscillation control section 40d
Oscillator 41 Voltage converter circuit 42 Diode 43 to 46, 64 to 66
Capacitor 47 Resistive element 48, 49, 67 Switch 50 Vibrator 51
Conductor core 52 Tip conductor 53 Charging terminal 60 Controller
61 Power supply circuit 62 Resonant circuit 63 Coil CS Continuous
signal P1 to P6 Control terminal S1 Envelope signal S2 Digital
signal TIB Transmission information block SS Start signal
The various embodiments described above can be combined to provide
further embodiments. All of the U.S. patents, U.S. patent
application publications, U.S. patent applications, foreign
patents, foreign patent applications and non-patent publications
referred to in this specification and/or listed in the Application
Data Sheet are incorporated herein by reference, in their entirety.
Aspects of the embodiments can be modified, if necessary to employ
concepts of the various patents, applications and publications to
provide yet further embodiments.
These and other changes can be made to the embodiments in light of
the above-detailed description. In general, in the following
claims, the terms used should not be construed to limit the claims
to the specific embodiments disclosed in the specification and the
claims, but should be construed to include all possible embodiments
along with the full scope of equivalents to which such claims are
entitled. Accordingly, the claims are not limited by the
disclosure.
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