U.S. patent application number 13/606261 was filed with the patent office on 2012-12-27 for capacitive sensor and detection method using the same.
This patent application is currently assigned to EGALAX_EMPIA TECHNOLOGY INC.. Invention is credited to CHENG-HAN LEE, CHI-HAO TANG.
Application Number | 20120327026 13/606261 |
Document ID | / |
Family ID | 46454889 |
Filed Date | 2012-12-27 |
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United States Patent
Application |
20120327026 |
Kind Code |
A1 |
LEE; CHENG-HAN ; et
al. |
December 27, 2012 |
CAPACITIVE SENSOR AND DETECTION METHOD USING THE SAME
Abstract
The present invention provides a capacitive sensor and a
detection method using the same. The capacitive sensor of the
present invention includes a plurality of detecting plates arranged
sequentially. Each detecting plate is provided with the same
driving signal. According to the difference between signals of each
detecting plate and another detecting plate, detecting plates
touched or approached by external objects can be identified.
Inventors: |
LEE; CHENG-HAN; (Taipei
City, TW) ; TANG; CHI-HAO; (Taipei City, TW) |
Assignee: |
EGALAX_EMPIA TECHNOLOGY
INC.
Taipei City
TW
|
Family ID: |
46454889 |
Appl. No.: |
13/606261 |
Filed: |
September 7, 2012 |
Current U.S.
Class: |
345/174 |
Current CPC
Class: |
G06F 3/04164 20190501;
G06F 3/04166 20190501; G06F 3/0446 20190501; H03K 17/9622 20130101;
G06F 2203/04106 20130101; G06F 3/047 20130101; G06F 3/041 20130101;
G06F 2203/04112 20130101; H03K 2017/9602 20130101; H03K 17/962
20130101; G06F 2203/04104 20130101; G06F 3/04186 20190501 |
Class at
Publication: |
345/174 |
International
Class: |
G06F 3/044 20060101
G06F003/044 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 7, 2011 |
TW |
100100564 |
Claims
1. A capacitive sensor comprising: a plurality of sequentially
arranged detecting plates; at least one reference plate disposed
between the detecting plates; a memory for storing a lookup table,
wherein the lookup table defines corresponding relationships
between a plurality of signal differences or amounts of change in
signal difference and the detecting plate being touched/approached;
and a controller that simultaneously provides an electrical signal
to each detecting plate, and provides the electrical signal or a DC
potential to the reference plate, so that the signal difference or
the amount of change in signal difference is generated by
subtraction between signals of each detecting plate and another
detecting plate, and determines if at least one detecting plate is
touched or approached by at least one external object by using the
lookup table based on the signal differences.
2. The capacitive sensor of claim 1, wherein the controller
designates one of the detecting plates as a specific detecting
plate, and each signal difference or the amount of change in signal
difference is generated by subtraction between signals from one of
non-specific detecting plates and the specific detecting plate.
3. The capacitive sensor of claim 1, wherein each signal difference
or the amount of change in signal difference is generated by
subtraction between signals from one of the detecting plates and a
preceding detecting plate.
4. A capacitive sensor comprising: a plurality of sequentially
arranged detecting plates; at least one reference plate disposed
between the detecting plates; and a controller that simultaneously
provides an electrical signal to each detecting plate, and provides
the electrical signal or a DC potential to the at least one
reference plate, or simultaneously provides an electrical signal to
each reference plate, so that a signal difference is generated by
subtraction between signals from each of the detecting plate and a
preceding detecting plate, and the signal differences are combined
to form a plurality of continuous signal differences, and each
signal difference of the continuous signal differences is added to
all the preceding or following signal differences to generate a
plurality of continuous recovered signal values, and it is
determined whether at least one detecting plate is touched or
approached by at least one external object based on the continuous
recovered signal values.
5. The capacitive sensor of claim 4, wherein the continuous
recovered signal values further include an additionally added zero
and each of the continuous recovered signal values correspond to
one of the detecting plates, respectively.
6. The capacitive sensor of claim 5, wherein a detecting plate
corresponding to a recovered signal value that exceeds the smallest
value among the continuous recovered signal values by a threshold
is determined to be touched or approached by an external
object.
7. The capacitive sensor of claim 5, wherein the controller further
includes generating an average of the continuous recovered signal
values, wherein a detecting plate corresponding to a recovered
signal value that exceeds the average is determined to be touched
or approached by an external object.
8. The capacitive sensor of claim 4, further comprising a memory
for storing a lookup table, wherein the lookup table defines
corresponding relationships between the continuous recovered signal
values and the detecting plate being touched or approached, and the
controller determines if at least one detecting plate is touched or
approached by at least one external object by using the lookup
table based on the continuous recovered signal values.
9. A capacitive sensor comprising: a plurality of sequentially
arranged detecting plates; at least one reference plate disposed
between the detecting plates; a means for simultaneously providing
an electrical signal to each detecting plate and providing the
electrical signal or a DC potential to the reference plate, or
simultaneously providing an electrical signal to each reference
plate; a means for generating a signal difference by subtraction
between signals from each of the detecting plate and a preceding
detecting plate and combining the signal differences to form a
plurality of continuous signal differences; a means for adding each
signal difference of the continuous signal differences to all the
preceding or following signal differences to generate a plurality
of continuous recovered signal values; and a means for determining
if at least one detecting plate is touched or approached by at
least one external object based on the continuous recovered signal
values.
10. The capacitive sensor of claim 9, wherein the continuous
recovered signal values further include an additionally added zero
and each of the continuous recovered signal values correspond to
one of the detecting plates, respectively.
11. The capacitive sensor of claim 10, wherein a detecting plate
corresponding to a recovered signal value that exceeds the smallest
value among the continuous recovered signal values by a threshold
is determined to be touched or approached by an external
object.
12. The capacitive sensor of claim 10, further comprising a means
for generating an average of the continuous recovered signal
values, wherein a detecting plate corresponding to a recovered
signal value that exceeds the average is determined to be touched
or approached by an external object.
13. The capacitive sensor of claim 9, further comprising a memory
for storing a lookup table, wherein the lookup table defines
corresponding relationships between the continuous recovered signal
values and the detecting plate being touched or approached, and the
controller determines if at least one detecting plate is touched or
approached by at least one external object by using the lookup
table based on the continuous recovered signal values.
14. A capacitive sensor comprising: a plurality of sequentially
arranged detecting plates; and a controller that simultaneously
provides an electrical signal to each detecting plate, so that a
signal difference is generated by subtraction between signals from
each of the detecting plate and a preceding detecting plate, and
the signal differences are combined to form a plurality of
continuous signal differences, and each signal difference of the
continuous signal differences is added to all the preceding or
following signal differences to generate a plurality of continuous
recovered signal values, and it is determined whether at least one
detecting plate is touched or approached by at least one external
object based on the continuous recovered signal values.
15. The capacitive sensor of claim 14, wherein the continuous
recovered signal values further include an additionally added zero
and each of the continuous recovered signal values correspond to
one of the detecting plates, respectively.
16. The capacitive sensor of claim 15, wherein a detecting plate
corresponding to a recovered signal value that exceeds the smallest
value among the continuous recovered signal values by a threshold
is determined to be touched or approached by an external
object.
17. The capacitive sensor of claim 15, wherein the controller
further includes generating an average of the continuous recovered
signal values, wherein a detecting plate corresponding to a
recovered signal value that exceeds the average is determined to be
touched or approached by an external object.
18. The capacitive sensor of claim 14, further comprising a memory
for storing a lookup table, wherein the lookup table defines
corresponding relationships between the continuous recovered signal
values and the detecting plate being touched or approached, and the
controller determines if at least one detecting plate is touched or
approached by at least one external object by using the lookup
table based on the continuous recovered signal values.
19. A capacitive sensor comprising: a plurality of sequentially
arranged detecting plates; at least one reference plate disposed
between the detecting plates; a means for simultaneously providing
an electrical signal to each detecting plate and providing the
electrical signal or a DC potential to the reference plate, or
simultaneously providing an electrical signal to each reference
plate; a means for generating a signal difference by subtraction
between signals from each of the detecting plate and a preceding
detecting plate and combining the signal differences to form a
plurality of continuous signal differences; a means for adding each
signal difference of the continuous signal differences to all the
preceding or following signal differences to generate a plurality
of continuous recovered signal values; and a means for determining
if at least one detecting plate is touched or approached by at
least one external object based on the continuous recovered signal
values.
20. The capacitive sensor of claim 19, wherein the continuous
recovered signal values further include an additionally added zero
and each of the continuous recovered signal values correspond to
one of the detecting plates, respectively.
21. The capacitive sensor of claim 20, wherein a detecting plate
corresponding to a recovered signal value that exceeds the smallest
value among the continuous recovered signal values by a threshold
is determined to be touched or approached by an external
object.
22. The capacitive sensor of claim 20, further comprising a means
for generating an average of the continuous recovered signal
values, wherein a detecting plate corresponding to a recovered
signal value that exceeds the average is determined to be touched
or approached by an external object.
23. The capacitive sensor of claim 19, further comprising a memory
for storing a lookup table, wherein the lookup table defines
corresponding relationships between the continuous recovered signal
values and the detecting plate being touched or approached, and the
controller determines if at least one detecting plate is touched or
approached by at least one external object by using the lookup
table based on the continuous recovered signal values.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. application Ser.
No. 13/344,745, filed on Jan. 6, 2012, which are herein
incorporated by reference for all intents and purposes. This
application claims the benefit of Taiwan Application Serial No.
100100564 filed on Jan. 7, 2011.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a capacitive sensor and a
detection method using the same, more particularly, to a capacitive
sensor capable of detecting multiple touches simultaneously and a
detection method using the same.
[0004] 2. Description of the Prior Art
[0005] In portable electronic devices, many physical human-machine
interfaces are required for allowing users to input data or
command. One of the most commonly used interfaces is mechanical
keypads, but they are prone to damage due to over usage, especially
those most frequently used keypads. Moreover, keypads may be
accidentally pressed when portable electronic devices are stowed
away, resulting in elastic fatigue or poor contact of the
keypads.
[0006] On smart phones or tablet PCs, capacitive sensors are often
used as the keypads. Compared to physical keypads, the capacitive
sensors do not have the problem of being damage due to over usage.
However, since monitors usually emit a lot of noise, and the noise
continuously fluctuates, the capacitive sensors may make
misjudgments due to these noise interferences.
[0007] From the above it is clear that prior art still has
shortcomings. In order to solve these problems, efforts have long
been made in vain, while ordinary products and methods offering no
appropriate structures and methods. Thus, there is a need in the
industry for a novel technique that solves these problems.
SUMMARY OF THE INVENTION
[0008] The present invention provides a capacitive sensor and a
detection method using the same. The capacitive sensor of the
present invention includes a plurality of detecting plates arranged
sequentially. Each detecting plate is provided with the same
driving signal. According to the difference between signals of each
detecting plate and another detecting plate, detecting plates
touched or approached by external objects can be identified. The
present invention is capable of detecting one detecting plate or
simultaneously a plurality of detecting plates being touched or
approached.
[0009] The capacitive sensor of the present invention can be
covered with an insulating protective layer. Detection is allowed
without physical contact, thus avoiding the problem of elastic
fatigue or poor contact encountered by the mechanical keypads after
long use. Moreover, the capacitive sensor of the present invention
performs detection by comparing the signal differences between the
detecting plates, so it has a better noise resistance and is
suitable to be installed in front of a display. In addition, it is
capable of simultaneously detecting multiple touches.
[0010] An objective of the present invention is to overcome the
shortcomings of the prior art by providing a novel capacitive
sensor and a detection method, in which a signal of one reference
plate is compared with a signal of each detecting plate, or signals
between the detecting plates are compared to determine if a
detecting plate is touched or approached by an external object.
This is very practical.
[0011] The objective of the present invention can be accomplished
by the following technical scheme. A capacitive sensor proposed by
the present invention may include: a plurality of sequentially
arranged detecting plates; at least one reference plate disposed
between the detecting plates; a memory for storing a lookup table,
wherein the lookup table defines corresponding relationships
between a plurality of signal differences or amounts of change in
signal difference and the detecting plate being touched/approached;
and a controller that simultaneously provides an electrical signal
to each detecting plate, and provides the electrical signal or a DC
potential to the reference plate, so that the signal difference or
the amount of change in signal difference is generated by
subtraction between signals of each detecting plate and another
detecting plate, and determines if at least one detecting plate is
touched or approached by at least one external object by using the
lookup table based on the signal differences.
[0012] The objective of the present invention can be further
accomplished by the following technical scheme. A capacitive sensor
of proposed by the present invention may include: a plurality of
sequentially arranged detecting plates; at least one reference
plate disposed between the detecting plates; and a controller that
simultaneously provides an electrical signal to each detecting
plate, and provides the electrical signal or a DC potential to the
at least one reference plate, or simultaneously provides an
electrical signal to each reference plate, so that a signal
difference is generated by subtraction between signals from each of
the detecting plate and a preceding detecting plate, and the signal
differences are combined to form a plurality of continuous signal
differences, and each signal difference of the continuous signal
differences is added to all the preceding or following signal
differences to generate a plurality of continuous recovered signal
values, and it is determined whether at least one detecting plate
is touched or approached by at least one external object based on
the continuous recovered signal values.
[0013] The objective of the present invention can be further
accomplished by the following technical scheme. A capacitive sensor
of proposed by the present invention may include: a plurality of
sequentially arranged detecting plates; and a controller that
simultaneously provides an electrical signal to each detecting
plate, so that a signal difference is generated by subtraction
between signals from each of the detecting plate and a preceding
detecting plate, and the signal differences are combined to form a
plurality of continuous signal differences, and each signal
difference of the continuous signal differences is added to all the
preceding or following signal differences to generate a plurality
of continuous recovered signal values, and it is determined whether
at least one detecting plate is touched or approached by at least
one external object based on the continuous recovered signal
values.
[0014] Compared with the prior art, the present invention has
advantages and beneficial effects. By using the above technical
schemes, the capacitive sensor of the present invention and the
detection method using the same have at least the following
advantages and beneficial effects: [0015] 1. Capable of detecting
one or simultaneously a plurality of external object touch(es) or
approach(es). [0016] 2. Capable of detecting one or simultaneously
a plurality of changes in the status of signal(s). [0017] 3. High
noise resistance. It can be disposed in front to a display that
emits noise of different levels.
[0018] The above description is only an outline of the technical
schemes of the present invention. Preferred embodiments of the
present invention are provided below in conjunction with the
attached drawings to enable one with ordinary skill in the art to
better understand said and other objectives, features and
advantages of the present invention and to make the present
invention accordingly.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] The present invention can be more fully understood by
reading the following detailed description of the preferred
embodiments, with reference made to the accompanying drawings,
wherein:
[0020] FIGS. 1 to 4 are schematic diagrams illustrating a
capacitive sensor in accordance with a first embodiment of the
present invention;
[0021] FIG. 5 is a schematic diagram illustrating a detection
method of a capacitive sensor in accordance with a second
embodiment of the present invention;
[0022] FIG. 6 is a flowchart illustrating a detection method of a
capacitive sensor that uses signal differences in accordance with a
third embodiment of the present invention;
[0023] FIG. 7 is a schematic diagram illustrating a capacitive
sensor in accordance with a fourth embodiment of the present
invention;
[0024] FIG. 8 is a schematic diagram illustrating a capacitive
sensor in accordance with a fifth embodiment of the present
invention;
[0025] FIG. 9 is a schematic diagram illustrating a capacitive
sensor in accordance with a sixth embodiment of the present
invention; and
[0026] FIG. 10 is a flowchart illustrating a detection method of a
capacitive sensor in accordance with a ninth embodiment of the
present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0027] Some embodiments of the present invention are described in
details below. However, in addition to the descriptions given
below, the present invention can be applicable to other
embodiments, and the scope of the present invention is not limited
by such, rather by the scope of the claims. Moreover, for better
understanding and clarity of the description, some components in
the drawings may not necessary be drawn to scale, in which some may
be exaggerated relative to others, and irrelevant parts are
omitted.
[0028] According to a first embodiment of the present invention, a
capacitive sensor is provided, which may include one first
conductive line, at least a second conductive line, at least a
reference plate, at least a detecting plate, a controller and a
shielding line. The at least one detecting plate defines (or
segments) at least a space, and all reference plates are
electrically coupled to the first conductive line. In addition,
each detecting plate is electrically coupled to a second conductive
line. Moreover, the controller provides electrical signals to the
first conductive line and every second conductive lines, and the
difference between signals of each second conductive line and the
first conductive line is used for determining whether each detector
is approached or touched by an external object.
[0029] As shown in FIG. 1, a capacitive sensor 1 includes a first
conductive line 13, at least a second conductive line 14, at least
a detector 10 and a controller 16, wherein each detector 10
includes a detecting plate 11 and a reference plate 12. The
reference plate 12 is in an inverted U shape which defines a space.
The detecting plate 11 is within this space, and electrically
coupled to a second conductive line 14. Although there are three
detectors 10 shown in FIG. 1, one with ordinary skill in the art
can appreciate that the number of detectors is not limited to
three.
[0030] In an example of the present invention, a capacitive sensor
includes at least a detector. Each detector includes a detecting
plate and at least one reference plate. The at least one reference
plate defines a space, in which the detecting plate resides.
[0031] As shown in FIG. 2, a capacitive sensor 2 includes a first
conductive line 13, at least a second conductive line 14, at least
a detector 20 and a controller 16, wherein each detector 20
includes a detecting plate 21 and two reference plates 22. The two
reference plates 22 and the first conductive line 13 together
define a space. The detecting plate 21 resides within this space,
and electrically coupled to a second conductive line 14. The space
can be regarded as defined by the two reference plates 22 and the
first conductive line 13. Although there are three detectors 20
shown in FIG. 2, one with ordinary skill in the art can appreciate
that the number of detectors 20 is not limited to three.
[0032] In another example of the present invention, the capacitive
sensor includes multiple spaces defined by at least one reference
plate, and all reference plates are electrically coupled to a first
conductive line. Each detecting plate is in a space and
electrically coupled to a respective second conductive line. For
example, adjacent detecting plates are separated by one or more
reference plates.
[0033] As shown in FIG. 3, a capacitive sensor 3 includes four
spaces defined by one reference plate 32 or four reference plates
32 (e.g. one integral reference plate or four individual reference
plates connected together). Each space is provided with a detecting
plate 31.
[0034] Alternatively, as shown in FIG. 3, a capacitive sensor 4
includes multiple spaces defined by one reference plate 42 or
multiple reference plates 42 (e.g. one integral reference plate or
multiple individual reference plates connected together). Each
space is provided with a detecting plate 41.
[0035] In addition, in FIGS. 1 to 4, a shielding line 15 generally
surrounds the first conductive line 13, the at least one second
conductive line 14, the at least one reference plate (12, 22, 32,
42) and the at least one detecting plate (11, 21, 31, 41), and is
electrically coupled to the controller 16. In an example of the
present invention, the first conductive line 13 and the all the
second conductive lines 14 are arranged in parallel to the
controller 16. The shielding line 15 can be composed of one or more
lines, arranged at either side of the first conductive line 13 and
all of the second conductive lines 14. In another example of the
present invention, there are two shielding lines 15 arranged in
parallel at either side of the first conductive line 13 and all of
the second conductive lines 14.
[0036] In an example of the present invention, the first conductive
line 13 and at least one second conductive line 14 are connected to
the controller 16 in parallel. For example, portions of the first
conductive line 13 and at least one second conductive line 14 are
arranged in parallel on a flat printed circuit board or a soft
cable. In addition, the shielding line 15 (one or two lines) is/are
arranged at either side of the first conductive line 13 and at
least one second conductive line 14. In an example of the present
invention, the shielding line 15, the first conductive line 13 and
at least one second conductive line 14 are provided with the same
electrical signal simultaneously. As such, when there is no
external object, both sides of each conductive line of the first
conductive line 13 and the at least one second conductive line 14
have symmetric electric field. Thus, when there is no external
object, there are symmetric electric fields at both sides of the
portions of the first conductive line 13 and the at least one
second conductive line 14 that are connected to the controller 16
in parallel. In another example of the present invention, the
shielding line 15 can also be provided with a DC potential, e.g.
grounded. In yet another example of the present invention, the
shielding line 15 can be provided with the same electrical signal
as the first conductive line 13.
[0037] One with ordinary skill in the art can appreciate that the
shapes of the detecting plates of the present invention are not
limited to square, rectangle, fan, triangle, circle, ellipse,
polygon, or other geometric shapes.
[0038] In an example of the present invention, the electrical
signal provided to the first conductive line and the second
conductive line can be a pulse width modulated (PWM) signal or
other types of AC signals, such as a sine wave; the present
invention is not limited as such. The electrical signal can be
continuously provided. In an example of the present invention, the
electrical signal can be continuously provided at intermittent
intervals. In an example of the present invention, the electrical
signal can be continuously provided continually.
[0039] In addition, the controller can detect capacitive coupling
of the conductors of the first and second conductive lines through
an integrator to determine the magnitude of the signals or the
magnitude of the changes in the signals. One with ordinary skill in
the art can appreciate that the signal difference can also be
generated by other elements such as a subtractor, and regardless of
whether it is in analog or digital form; the present invention is
not limited as such.
[0040] Although in the above descriptions, the first conductive
line is electrically coupled to the reference plates, the present
invention is not limited to the first conductive line being
electrically coupled to the reference plates, it can be
electrically coupled to one of the above multiple detecting plates.
In other words, the reference plates can be provided with the
abovementioned electrical signal by other circuits, and the first
conductive line and each of the second conductive lines are
electrically coupled to one of the multiple detecting plates,
respectively.
[0041] FIG. 5 is a detection method of a capacitive sensor
according to a second embodiment of the present invention. First,
in step 510, a first conductive line 13 and a plurality of second
conductive lines 14 are provided. Then, in step 520, an electrical
signal is continuously provided to the first conductive line 13 and
each of the second conductive lines 14. In addition, in step 530,
each time the electrical signal is provided, based on a signal
difference between each second conductive line 14 and the first
conductive line 13, the signal of each second conductive line 14 is
identified as belonging to a first type or a second type.
[0042] In an example of the present invention, steps 520 and 530
can be carried out by the above controller 16. The first conductive
line 13 and each second conductive line 14 provided in step 510 are
electrically coupled to at least one conductor, respectively. The
total dimension of the at least one conductor electrically coupled
with the first conductive line 13 substantially equals to the total
dimension of the at least one conductor electrically coupled with
each second conductive line 14. For example, in FIGS. 1 to 4, the
first conductive line 13 is electrically coupled to multiple
reference plates 12, 22, 32 and 42, and each second conductive line
14 is electrically coupled to one detecting plate 11, 21, 31 and
41. One with ordinary skill in the art can appreciate that the
detecting plate 11 can be composed of multiple sub-detecting
plates, and each second conductive line 14 may be electrically
coupled to the multiple sub-detecting plates. In an example of the
present invention, the at least one conductor electrically coupled
with the first conductive line 13 defines a plurality of spaces,
and the at least one conductor electrically coupled with each
second conductive line 14 resides in one of these spaces.
[0043] Since the total dimension of the at least one conductor
electrically coupled with the first conductive line 13
substantially equals to the total dimension of the at least one
conductor electrically coupled with each second conductive line 14,
when there is no external object touching or approaching any of the
conductors, the signals of the first conductive line 13 and each
second conductive line 14 will be substantially equal to each
other. In an example of the present invention, an insulating layer
can be overlaid above all of the conductors. The insulating layer
can be transparent or opaque, such as a transparent glass or film.
When there is an external object approaching or touching the
capacitive sensor, it may be approaching or touching the insulating
layer.
[0044] The external object can be physically or virtually grounded,
and can, for example, be a body part (e.g. a finger) of a human
standing on the ground. When the external object touches or
approaches a conductor, the amount of change in the conductor's
signal varies with the distance and area approached by the external
object. Thus, when an external object simultaneously approaches or
touches a detecting plate and a portion of a reference plate, the
area of the detecting plate approached or touched by the external
object will be relatively larger than the area of the reference
plate approached or touched by the external object. In other words,
the amount of change in signal of the second conductive line 14
electrically coupled to the detecting plate approached or touched
by the external object will be greater than the amount of change in
signal of the first conductive line 13 (electrically coupled to all
reference plates). On the contrary, the amount of change in signal
of the second conductive line 14 not electrically coupled to the
detecting plate approached or touched by the external object will
be less than the amount of change in signal of the first conductive
line 13. Therefore, according to the signal of the second
conductive line 14 electrically coupled to the detecting plate
approached or touched by the external object and the signal of the
first conductive line 13, a detecting plate can be determined as
being approached or touched by an external object (e.g. one of the
first and second types) or not approached or touched by any
external object (e.g. the other of the first and second types).
[0045] For example, the touch or approach of the external object
will cause the signal to be reduced. Thus, the difference between
the signals of each second conductive line 14 and the first
conductive line 13 can be used to determine whether the detecting
plate to which each second conductive line 14 electrically coupled
is being approached or touched. For example, if the difference
between signals is greater or less than a threshold, then it
indicates the approach or touch of an external object.
Alternatively, the signal difference at the time when there is no
external object can be used as the reference. For example, the
signal difference detected in an initial period is used as the
signal difference when there is no external object approaching or
touching the capacitive sensor, and is compared with the signal
difference detected at subsequent multiple continuous detecting
periods. When the difference between the signal differences of the
initial period and the detecting period is greater or less than a
threshold, then it indicates the approach or touch of an external
object. In an example of the present invention, when the difference
between signals exceeds a preset range or when the difference
between the signal differences of the initial period and the
detecting period exceeds a preset range, then it indicates the
approach or touch of an external object; else, it indicates no
external object. The preset range can be less or greater than a
threshold.
[0046] In an example of the present invention, the sign (i.e.
positive or negative) of the difference between signals or the
difference between the signal differences of the initial and the
detecting periods can be used for determining whether it belongs to
the first type or the second type. For example, when the difference
between the signal of the first conductive line 13 and a second
conductive line 14 is a positive value, then this second conductive
line 14 belongs to one of the first and second types, whereas when
the difference between the signal of the first conductive line 13
and a second conductive line 14 is a negative value, then this
second conductive line 14 belongs to the other of the first and
second types.
[0047] Therefore, when some of the detecting plates are approached
or touched while some are not, a conductive plate electrically
coupled to at least one second conductive line 14 will be
identified as belonging to the first type, while another conductive
plate electrically coupled to at least one second conductive line
14 will be identified as belonging to the second type, wherein a
conductor electrically coupled to the first conductive line 13 is
touched or approached by the external object.
[0048] By comparing the signals of each second conductive line 14
with the first conductive line 13 in the capacitive sensor of the
present invention, one or more detecting plates touched or
approached by external object(s) can be determined. The comparison
of signals of the two can be made by using a comparator, or the
comparison of the difference between the signal differences of the
two can be made by a differential amplifier. Furthermore, the
signals of the two can be converted into a digital difference
before comparing, or the signals of the two can be converted into
digital values before comparing. The present invention includes but
is not limited to these comparison methods, and one with ordinary
skill in the art can recognize that there are other ways of
comparing signals, which will not be further described herein.
[0049] The capacitive sensor of the present invention can be used
in keypad application, as shown in FIGS. 1 and 2. For example, each
detecting plate can correspond to an independent keypad. The
capacitive sensor of the present invention can simultaneously
detect the pressing of multiple keypads. Keypads can also be
designed as arrow keys, such as that shown in FIG. 3, wherein there
are four arrow keys, namely, up, right, down and left arrow keys.
One with ordinary skill in the art can appreciate arrow keys in
other directions, such as eight-directional arrow keys, or
multi-directional arrow keys, such as that shown in FIG. 4, which
forms a ring-shaped multi-directional arrow keys used in
applications such as a jog dial.
[0050] In an example of the present invention, there can be a
compound-type capacitive sensing device, for example, with multiple
sets of capacitive sensors. Each capacitive sensor includes the
abovementioned first conductive line, the at least one second
conductive line, the at least one reference plate, the at least one
detecting plate, the controller and the shielding line. The at
least one detecting plate defines (or segments) at least one space,
and all of the reference plates are electrically coupled to the
first conductive line. Moreover, each detecting plate is
electrically coupled to a second conductive line. In addition, the
controller provides an electrical signal to the first conductive
line and each of the second conductive line. According to the
signal difference between each of the second conductive line and
the first conductive line, it can be determined whether each
detector is approached or touched by an external object. As such,
all of the detecting plates form a detecting plate matrix.
[0051] These capacitive sensors can have their own independent
first conductive line 13 and second conductive lines 14, and are
directly connected to the controller 16 or jointly connected to the
conductive line of the controller 16 and controlled by a switching
circuit, wherein at any one time, the first conductive line 13 and
the second conductive lines 14 of only one capacitive sensor are
electrically coupled to the controller 16.
[0052] FIG. 6 is a detection method for a capacitive sensor using
signal differences according to a third embodiment of the present
invention. First, in step 610, a reference value and multiple
detection values are provided continuously in multiple periods, and
in step 620, one of these periods is regarded as an initial period,
while other periods are regarded as detection periods. For example,
the first period is regarded as the initial period, or any one
period can be regarded as the initial period. Steps 610 and 620 can
be repeated.
[0053] Next, in step 630, in the initial period, the difference
between each detection value and the reference value is recorded as
an initial difference for each detection value. In each detection
periods, the difference between each detection value and the
reference value is recorded as a detection difference for each
detection value. Moreover, in step 650, in each detection period,
each detection value for which the detection difference is greater
or less than the initial difference by a threshold is identified as
one of a first type and a second type, whereas each detection value
for which the detection difference is not greater or not less than
the initial difference by a threshold is identified as the other of
the first type and the second type. Steps 630, 640 and 650 can be
performed iteratively along with steps 610 and 620. In addition,
steps 610 to 650 can be carried out by the above controller 16.
[0054] The aforementioned method can be applied to a capacitive
sensor that performs detection using signal difference. The
capacitive sensor may include: a first conductive line; at least
one second conductive line; at least one reference plate defining
at least one space, wherein all reference plates are electrically
coupled to the first conductive line; at least one detecting plate,
each resides in one of the at least one space and is electrically
coupled to one of the at least one second conductive line; and a
controller. It performs at least the following operations of:
continuously providing an electrically signal to the first
conductive line and each second conductive line in multiple periods
to obtain a reference value and multiple detection values;
regarding one of these periods as an initial period, and the other
periods as detection periods; in the initial period, recording the
difference between each detection value and the reference value as
an initial difference for each detection value; in each detection
periods, recording the difference between each detection value and
the reference value as a detection difference for each detection
value; and in each detection period, identifying each detection
value for which the detection difference is greater or less than
the initial difference by a threshold as one of a first type and a
second type, and identifying each detection value for which the
detection difference is not greater or not less than the initial
difference by a threshold as the other of the first type and the
second type.
[0055] In an example of the present invention, the reference value
is generated based on the signal of at least one reference plate.
The at least one reference plate defines a plurality of spaces.
Each detection value is generated based on the signal of one of a
plurality of detecting plates, each detecting plates resides in one
of these spaces.
[0056] In another example of the present invention, if each
detection value identified as the first type has a detection
difference greater than the initial difference, then each detection
value identified as the second type has a detection difference less
than the initial difference. On the contrary, if each detection
value identified as the first type has a detection difference less
than the initial difference, then each detection value identified
as the second type has a detection difference greater than the
initial difference. For example, in some detection periods, the
reference value and the at least one detection value are changed,
both changed to larger values or a smaller values, wherein the
amount of change in the at least one detection value is
significantly larger than that in the reference value, resulting in
the detection difference for the at least one detection value to
become larger or smaller. On the contrary, the detection
differences for other detection values will have the opposite
changes.
[0057] One with ordinary skill in the art can appreciate that the
reference value and each detection value are not necessarily
substantially equal to each other at the initial period, i.e. they
can be substantially equal to each other or not. Similarly, one
with ordinary skill in the art can appreciate that the dimensions
of the conductors electrically coupled to the first conductive line
and each second conductive line can be substantially equal to each
other or not; the present invention includes but is not limited to
the dimensions of the conductors electrically coupled to the first
conductive line and each second conductive line being the same.
[0058] In addition, the above first and second types may represent
two states with one indicates status change, while the other
indicates no status change. For example, the first type may
indicate that the conductor is touched or approached by an external
object or a signal changed as a result of this, whereas the second
type may indicate that the conductor is not touched or approached
by an external object or a signal is not changed. Moreover, it can
be applied to switches, for example, when the reference value
exceeds a threshold, and the amount of change in at least one
detection value is significantly larger than that in the reference
value, the detection difference for a detection value not changed
will be greater than a threshold, which can be used for detecting
the detection value not changed, and as one of on and off states,
while the other detection values are used as the other one of on
and off states.
[0059] Referring to FIG. 7, a capacitive sensor 7 provided
according to a fourth embodiment of the present invention is shown.
The capacitive sensor 7 includes multiple reference plates 72 and
multiple detecting plates 71. In addition, the present embodiment
further includes a touch sensor 17 adjacent to the capacitive
sensor 7. Although five detectors 70 are illustratively shown as an
example, one with ordinary skill in the art can appreciate that the
number of detectors includes but is not limited to five. When an
external object approaches or touches the touch sensor 17, the
touch sensor 17 can provide sensing information of the location of
the external object for interpreting into the location of the
external object. For example, the sensing information can be
received by the controller 16 for determining the location of the
external object. One with ordinary skill in the art can appreciate
that the touch sensor 17 can be capacitive, resistive,
surface-acoustic-wave type, infrared, optical and the like, wherein
the detection method for the corresponding sensing information is
prior art, and thus will not be further explained.
[0060] In an example of the present invention, the area of one side
of detecting plates 71 facing the touch sensor 17 is smaller than
that of the other side, wherein the area of the side facing the
touch sensor 17 and the area of the other side can be areas among a
range with the same width between the two sides. For example, the
detecting plates 71 can be triangular, wherein one angle points
towards the touch sensor 17 as shown in FIG. 7. Alternatively, for
example, the side facing the touch sensor 17 can be of an arc
shape, such as a semi-circle or a semi-ellipse.
[0061] The area of the side of the detecting plates 71 facing the
touch sensor 17 depends on the distance between the detecting
plates 71 and the touch sensor 17.
[0062] For example, when an external object simultaneously
approaches or touches the touch sensor 17 and a detecting plate 71
as shown by a touch range 77 in FIG. 7, the area of the detecting
plate 71 touched or approached by the external object is very
small, such that the above difference between signals or the
difference between the signal differences in the initial period and
the detection period may not exceed the preset range, and no valid
touch is determined. On the contrary, when an external object
approaches or touches mostly a detecting plate 71 as shown by a
touch range 78 in FIG. 7, the above difference between signals or
the difference between the signal differences in the initial period
and the detection period is then enough to exceed the preset range.
As such, problems associated with accidental touching when the
capacitive sensor 7 and the touch sensor 17 are in close proximity
to each other can be lessened.
[0063] In the above descriptions, the phrase "the dimensions of two
substantially equal to each other" means that the dimensions of
these two are the same or substantially the same, for example, the
difference between the two is within 10%, e.g. one is greater than
the other by 10%. The total dimension of at least one conductor
electrically coupled with the first conductive line 13 being
substantially equal to the total dimension of at least one
conductor electrically coupled with each second conductive line 14
means that difference between the total dimension of at least one
conductor electrically coupled with the first conductive line 13
and the total dimension of at least one conductor electrically
coupled with each second conductive line 14 is within 10%.
[0064] In the above descriptions, self-capacitive detection is
employed, wherein the difference between signals of the first
conductive line and the second conductive line provided with the
electrical signal is used for the determination of an external
object. In a capacitive sensor provided according to the present
invention, the difference between signals of the detecting plates
is used for the determination.
[0065] Referring to FIG. 8, a capacitive sensor 8 proposed
according to a fifth embodiment of the present invention is shown.
A first conductive line 13 is electrically coupled to one detecting
plate 21, and reference plates 22 are provided with an electrical
signal by a third conductive line 18. In addition, referring to
FIGS. 5 and 6 and their associated descriptions for the
determination based on the difference between signals of the first
conductive line 13 and the second conductive line 14 provided with
the electrical signal, and this will not be described again.
[0066] The present embodiment can also be applied to FIGS. 1, 2, 3,
4 and 7, except that the first conductive line is no longer used
for comparing signal difference with the second conductive lines,
but simply used for providing the electrical signal. The comparison
of signal difference is performed between each detecting plate and
another detecting plate, that is, between each second conductive
line and another second conductive line. In an example of the
present invention, the determination is based on the difference
between signals of each second conductive line and a referenced
second conductive line, as shown in FIG. 8. For example, the first
one or the last one of the second conductive lines is used as the
referenced second conductive line for generating a signal
difference with every other second conductive line to determine
whether the detecting plate electrically coupled with the every
other second conductive line is touched or approached by an
external object. Assuming that the interference of the noise coming
from a display on each detecting plate substantially equal to each
other, generating signal difference from a pair of signals can
effectively suppress the noise from the display.
[0067] Assuming there are detecting plates a, b and c, and signal
differences Sa-b and Sa-c are generated based on the above, which
detecting plate(s) is being touched or approached by external
object(s) can be determined according to the following table.
TABLE-US-00001 TABLE 1 Detecting plate(s) being touched Sa-b Sa-c
none or (a, b and c) 0 0 a - - b + 0 c 0 + a & b 0 - a & c
- 0 b & c + +
[0068] "+", "-" and "0" shown in Table 1 indicates that the signal
difference is a positive value, a negative value and null,
respectively. In actual practice, signals of the detecting plates
will vary due to the influence of the environment, so there may be
error. In view of this, "+", "-" and "0" can be regarded as
positive values that are greater than a null range, negative values
that are less than the null range, and values that fall within the
null range. Alternatively, "+", "-" and "0" can be regarded as
positive values that are greater than a positive threshold value,
negative values that are less than a negative threshold value, and
values that fall within a null range. The example in Table 1 is
shown having a lookup table with three detecting plates, but one
with ordinary skill in the art can appreciate that lookup tables
with four, five or more.
[0069] In addition to determining directly from the signal
difference, the amount of change in the signal difference may also
be used for determination. For example, each signal difference
under no presence of an external object is used as the baseline for
comparison in each of the subsequent detections so as to determine
the amount of change of each signal difference. Thus, Sa-b and Sa-c
in the previous example can be replaced by the amount of change in
signal differences .DELTA.Sa-b and .DELTA.Sa-c.
[0070] The above signal difference can be the signal difference
between each detecting plate with one specific detecting plate, or
between each detecting plate and a preceding detecting plate, or
between each detecting plate and a following detecting plate.
[0071] When there are N detecting plates, there are N-1 signal
differences between detecting plates and the preceding (or
following) detecting plates. Thus, the amount of change in signal
difference is N-1 continuous amounts of change in signal
difference. In the following descriptions, the amount of change in
signal difference is used for illustration, but signal difference
instead of the amount of change in signal difference is also
applicable.
[0072] The above continuous amounts of change in signal difference
can be used to recover the amounts of change in signals of the
detecting plates. For example, each amount of change in signal
difference is added to (or subtracted from) the sum of all
preceding (or following) amounts of change in signal differences to
generate a plurality of continuous amounts of change in signal. For
example, there are N-1 amounts of change in signal difference, so
each amount of change in signal difference is added to the sum of
all preceding amounts of change in signal differences to generate
N-1 amounts of change in signal. Since there is no amount of change
in signal difference preceding the first amount of change in signal
difference, so it is assumed that the amount of change in signal
preceding the first amount of change in signal is null, which is
regarded as the 0.sup.th amount of change in signal. As such, N
amounts of change in signal can be generated corresponding to the
above N detecting plates.
[0073] The first to the N-1.sup.th amounts of change in signal
correspond to the amount of change of the amount of change of the
0.sup.th signal. Assuming that the above N detecting plates are the
0.sup.th, 1.sup.st . . . N-1.sup.th detecting plates, they
correspond to the 0.sup.th, 1.sup.st, . . . N-1.sup.th amount of
change in signal, respectively, and the 0.sup.th amount of change
in signal is null.
[0074] Assuming a small range around zero as the center is the null
range, any amount of change in signal that falls within this null
range is regarded as within the error range of null. When no
external object is touching or approaching the 0.sup.th detecting
plate, other amount of change in signal corresponding to no
touch/approach will fall within the null range, while the amount of
change in signal corresponding to a touch/approach will be a
positive or negative value outside the null range. In order to
facilitate the following descriptions, in this example, the amount
of change in signal corresponding to a touch/approach is a positive
value. On the contrary, when an external object is touching or
approaching the 0.sup.th detecting plate, the amount of change in
signal corresponding to a touch/approach will fall within or close
to the null range, while the amount of change in signal
corresponding to no touch/approach will be a negative value.
[0075] Assuming there are detecting plates a, b and c, the signal
differences generated as mentioned before are .DELTA.Sa-b and
.DELTA.Sb-c can be used for determining which detecting plate(s) is
touched/approached by an external object.
[0076] Obviously, the amount of change in signal representing a
touch/approach will be greater than the smallest amount of change
in signal and greater than a threshold. In an example of the
present invention, the controller determines that a detecting plate
is approached by an external object based on comparison of the
amount of change in signal with a threshold greater than the
smallest amount of change in signal. For example, if detecting
plates b and c are touched/approached by external object(s), then
the amounts of change in signal difference .DELTA.Sa-b and
.DELTA.Sb-c will be "+" and "0", respectively, and the amounts of
change in signal .DELTA.Sa, .DELTA.Sb and .DELTA.Sc recovered from
the amounts of change in signal difference .DELTA.Sa-b and
.DELTA.Sb-c are "0", "+" and "+", respectively, thereby determining
detecting plates b and c are touched/approached by external
object(s).
[0077] In another example of the present invention, a detecting
plate is determined to be approached by an external object if the
amount of change in signal is greater than the smallest amount of
change in signal by a threshold. Alternatively, when the amount of
change in at least one signal is less than a negative threshold, a
detecting plate is determined to be approached by an external
object if the amount of change in signal is greater than this
negative threshold. Alternatively, a detecting plate is determined
to be approached by an external object if the amount of change in
signal is greater than a positive threshold. For example, if
detecting plates a and b are touched/approached by external
object(s), then the amounts of change in signal difference
.DELTA.Sa-b and .DELTA.Sb-c will be "0" and "-", respectively, and
the amounts of change in signal .DELTA.Sa, .DELTA.Sb and .DELTA.Sc
recovered from the amounts of change in signal difference
.DELTA.Sa-b and .DELTA.Sb-c are "0", "0" and "-", respectively.
Since the smallest one of the three is "-", and assuming that "0"
is greater than "-" by a threshold, then it can be determined that
detecting plates a and b are touched/approached by external
object(s) by "0" as the amounts of change in signal .DELTA.Sa and
.DELTA.Sb.
[0078] In still another example of the present invention, an
average of all signals is used as the determination basis. The
controller determines a detecting plate is approached by an
external object if the amount of change in signal is greater than
the determination basis or greater than the determination basis by
a threshold. In other words, an amount of change in signal greater
than a positive (or negative) threshold indicates a detecting plate
is touched or approached by an external object. Accordingly, one
can determine a detecting plate is touched or approached by an
external object regardless of whether the smallest amount of change
in signal is "0" or "-".
[0079] Referring to FIG. 9, a capacitive sensor 9 proposed by a
sixth embodiment of the present invention is shown. The reference
plates are provided with the electrical signal by the third
conductive line 18, and each detecting plate 21 is electrically
coupled to a fourth conductive line 19. The fourth conductive lines
19 coupled to the detecting plates 21 are arranged sequentially in
the order of the detecting plates 21. The signal difference between
each fourth conductive line 19 and an adjacent fourth conductive
line 19 is used for determination, for example, the signal
difference between each fourth conductive line 19 and an
immediately preceding fourth conductive line 19 is used for
determination, or the signal difference between each fourth
conductive line 19 and an immediately following fourth conductive
line 19 is used for determination. In other words, FIG. 9 employs
mutual capacitive coupling to generate signals on the fourth
conductive lines 19.
[0080] Accordingly, in an example of the present invention, the
capacitive sensor includes a plurality of sequentially arranged
detecting plates, at least one reference plate and a controller.
The at least one reference plate is disposed between the detecting
plates in a manner such as those shown in FIGS. 1, 2, 3, 4, 7, 8
and 9. In addition, the controller simultaneously provides an
electrical signal to the at least one reference plate and each
detecting plate, and determines if at least one detecting plate is
touched or approached by at least one external object based on the
signal difference between each detecting plate and another
detecting plate. Moreover, the controller determines if at least
one detecting plate is touched or approached by at least one
external object based on the amount of change in signal difference
before and after the touch/approach by the at least one external
object.
[0081] Accordingly, a seventh embodiment of the present invention
is a capacitive sensor, which includes a plurality of sequentially
arranged detecting plates; at least one reference plate disposed
between the detecting plates; a memory for storing a lookup table
that defines corresponding relationships between a plurality of
signal differences or amounts of change in signal difference and
the detecting plate(s) being touched/approached; and a controller.
The controller simultaneously provides an electrical signal to each
detecting plate, and provides the electrical signal or a DC
potential to the at least one reference plate, or the controller
simultaneously provides an electrical signal to each reference
plate so that the signal difference or the amount of change in
signal difference is generated by subtraction between signals of
each detecting plate and another detecting plate. Furthermore, the
controller determines if at least one detecting plate is touched or
approached by at least one external object by using the lookup
table based on the signal differences.
[0082] In an example of the present invention, the controller
designates one of the detecting plates as the specific detecting
plate, and each signal difference or the amount of change in signal
difference is generated by subtraction between signals from one of
non-specific detecting plates and the specific detecting plate. In
another example of the present invention, each signal difference or
the amount of change in signal difference is generated by
subtraction between signals from one of the detecting plates and a
preceding detecting plate.
[0083] A eighth embodiment of the present invention is a capacitive
sensor, which includes a plurality of sequentially arranged
detecting plates; at least one reference plate disposed between the
detecting plates to separate each detecting plate; and a
controller. The controller simultaneously provides an electrical
signal to each detecting plate, and provides the electrical signal
or a DC potential to the at least one reference plate, so that a
signal difference is generated by subtraction between signals from
each of the detecting plate and a preceding detecting plate, and
the signal differences are combined to form a plurality of
continuous signal differences. Moreover, the controller adds each
signal difference of the continuous signal differences to all the
preceding or following signal differences to generate a plurality
of continuous recovered signal values, and determines if at least
one detecting plate is touched or approached by at least one
external object based on the continuous recovered signal
values.
[0084] The continuous recovered signal values further include an
additionally added zero. Each of the continuous recovered signal
values correspond to one of the detecting plates, respectively. The
recovered signal values can be the above recovered signals or the
recovered amount of change in signal. In an example of the present
invention, a detecting plate corresponding to a recovered signal
value that exceeds the smallest among the continuous recovered
signal values by a threshold is determined to be touched or
approached by an external object. In another example of the present
invention, the controller further includes generating an average of
the continuous recovered signal values, wherein a detecting plate
corresponding to a recovered signal value that exceeds the average
is determined to be touched or approached by an external object. In
still another example of the present invention, a memory for
storing a lookup table is further included, wherein the lookup
table defines the corresponding relationships between the
continuous recovered signal values and detecting plate(s) being
touched or approached, and the controller determines if at least
one detecting plate is touched or approached by at least one
external object by using the lookup table based on the continuous
recovered signal values.
[0085] Some operations of the controller mentioned before can be
achieved by a processor in cooperation with software. Thus, in an
example of the present invention, a capacitive sensor includes: a
plurality of sequentially arranged detecting plates; at least one
reference plate disposed between the detecting plates to separate
each detecting plate; a means for simultaneously providing an
electrical signal to each detecting plate and providing the
electrical signal or a DC potential to the reference plate; a means
for generating a signal difference by subtraction between signals
from each of the detecting plate and a preceding detecting plate
and combining the signal differences to form a plurality of
continuous signal differences; a means for adding each signal
difference of the continuous signal differences to all the
preceding or following signal differences to generate a plurality
of continuous recovered signal values; and a means for determining
if at least one detecting plate is touched or approached by at
least one external object based on the continuous recovered signal
values.
[0086] Referring to FIG. 10, a detection method of a capacitive
sensor proposed by a ninth embodiment of the present invention is
shown. First, in step 1010, a plurality of sequentially arranged
detecting plates and at least one reference plate are provided, the
at least one reference plate is disposed between the detecting
plates to separate each detecting plate. Next, in step 1020, an
electrical signal is simultaneously provided to each detecting
plate and the electrical signal or a DC potential is provided to
the reference plate, or an electrical signal is simultaneously
provided to each reference plate. Then, in step 1030, a signal
difference is generated by subtraction between signals from each of
the detecting plate and a preceding detecting plate, and the signal
differences are then combined to form a plurality of continuous
signal differences. Next, in step 1040, each signal difference of
the continuous signal differences is added to all the preceding or
following signal differences to generate a plurality of continuous
recovered signal values. Then, in step 1050, it is determined
whether at least one detecting plate is touched or approached by at
least one external object based on the continuous recovered signal
values. Other details of this embodiment are already disclosed in
previous descriptions, and will not be described further.
[0087] In the above descriptions, there are two kinds of
detections, namely self capacitive detection and mutual capacitive
detection. In self capacitive detection, an electrical signal is
simultaneously provided to each detecting plate and the electrical
signal or a DC potential is provided to the reference plates. In
mutual capacitive detection, an electrical signal is simultaneously
provided to each reference plate. The reference plate is disposed
between the detecting plates for separating them. For example,
there might be other circuits underneath the capacitive sensor, if
there is no reference plate, then capacitive coupling between some
of the detecting plates and the circuits underneath may cause
signal changes, such that the signal differences are not null even
when there is no presence of any external object. On the contrary,
if one can ensure that said problem will not happen, then the
reference plate is not necessarily needed.
[0088] In other words, in the case of no reference plate, self
capacitive detection is employed, wherein an electrical signal is
simultaneously provided to each detecting plate.
[0089] The above embodiments are only used to illustrate the
principles of the present invention, and they should not be
construed as to limit the present invention in any way. The above
embodiments can be modified by those with ordinary skill in the art
without departing from the scope of the present invention as
defined in the following appended claims.
* * * * *