U.S. patent application number 14/224228 was filed with the patent office on 2015-10-01 for electromagnetic sensing touch screen.
This patent application is currently assigned to NETIO TECHNOLOGIES CO., LTD.. The applicant listed for this patent is NETIO TECHNOLOGIES CO., LTD.. Invention is credited to Chun Hsiao Wang.
Application Number | 20150277632 14/224228 |
Document ID | / |
Family ID | 54190319 |
Filed Date | 2015-10-01 |
United States Patent
Application |
20150277632 |
Kind Code |
A1 |
Wang; Chun Hsiao |
October 1, 2015 |
ELECTROMAGNETIC SENSING TOUCH SCREEN
Abstract
The present invention discloses an electromagnetic sensing touch
screen, which includes a display panel, a sensing capacitor matrix,
select units, voltage controlled oscillators (VCOs), digital
potentiometers, EM (electromagnetic) wave receive/detection units,
a standard EM wave transmit unit and a control unit. A single
detection unit consists of a corresponding select unit, VCO,
digital potentiometer and EM wave receive/detection unit. The
control unit drives the standard EM wave transmit unit to transmit
standard EM wave, and further controls the EM wave
receive/detection units to receive sensed capacitance values from
the sensing capacitor matrix in a scanning manner. As a result,
each EM wave receive/detection unit generates a respective
detection signal for determining the location of the finger(s) and
checking how the finger(s) approaches to or actually touches the
sensing capacitor matrix, thereby generating finger location
information and implementing the multipoint touch and display
function.
Inventors: |
Wang; Chun Hsiao; (Taipei
City, TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NETIO TECHNOLOGIES CO., LTD. |
Taipei City |
|
TW |
|
|
Assignee: |
NETIO TECHNOLOGIES CO.,
LTD.
Taipei City
TW
|
Family ID: |
54190319 |
Appl. No.: |
14/224228 |
Filed: |
March 25, 2014 |
Current U.S.
Class: |
345/174 |
Current CPC
Class: |
G06F 3/044 20130101;
G06F 3/046 20130101 |
International
Class: |
G06F 3/046 20060101
G06F003/046; G06F 3/044 20060101 G06F003/044 |
Claims
1. An electromagnetic sensing touch screen for detecting a location
of at least one finger by use of frequency drift for
electromagnetic (EM) wave to implement a multi-touch display
function, comprising a display panel, a sensing capacitor matrix,
select units, voltage controlled oscillators (VCOs), digital
potentiometers, EM (electromagnetic) wave receive/detection units,
a standard EM wave transmit unit and a control unit, wherein the
corresponding select unit, VCO, digital potentiometer and EM wave
receive/detection unit constitutes a single detection unit; wherein
the display panel is connected to an external image input device to
receive image information and display an image; wherein the sensing
capacitor matrix possesses full or part transparency, and is
provided close to the display panel, the sensing capacitor matrix
comprising a plurality of sensing capacitor units, each
corresponding to one specific region of the image displayed by the
display panel, the sensing capacitor unit used to generate a sensed
capacitance value by changing an equivalent capacitance value
according to how the finger approaches; wherein the select unit is
connected to a corresponding one of the sensing capacitor units of
the sensing capacitor matrix, and comprises a plurality of
multiplexers hierarchically arranged for selecting one of the
sensed capacitance values from the sensing capacitor matrix as a
final sensed capacitance value and a resonant capacitance for the
VCO based on a scan select signal generated by the control unit,
and transferring the sensed capacitance value selected; wherein the
VCO receives the final sensed capacitance value and a voltage
control signal generated by the digital potentiometer for
controlling a varactor diode so as to generate a local oscillation
signal with a local oscillation frequency; wherein the EM wave
receive/detection unit uses the local oscillation signal of the VCO
to receive a standard EM wave from the standard EM wave transmit
unit, a detection signal is generated through a detection
operation, and the standard EM wave contains a standard signal;
wherein the control unit is connected to the select units, the
digital potentiometers and the EM wave receive/detection units to
perform a finger detection operation for generating the scan select
signal used to control each select unit to select the final sensed
capacitance value, and the control unit simultaneously receives the
detection signal and performs frequency modulation to generate the
frequency control signal; wherein the digital potentiometer
receives the frequency control signal to perform potential
adjustment so as to generate the voltage control signal such that
the VCO adjusts the local oscillation frequency of the local
oscillation signal according to the voltage control signal; and
wherein the standard EM wave transmit unit is driven by the control
unit to generate and transmit the standard EM wave to the EM wave
receive/detection units.
2. The electromagnetic sensing touch screen as claimed in claim 1,
wherein the sensing capacitor units are arranged in a matrix having
X columns and Y rows.
3. The electromagnetic sensing touch screen as claimed in claim 1,
wherein the EM wave receive/detection unit comprises an antenna and
a signal detector, the antenna receives the standard EM wave, and
the signal detector detects the detect signal indicating the
intensity of the standard EM wave received.
4. The electromagnetic sensing touch screen as claimed in claim 1,
wherein the control unit is implemented by a MCU
(microcontroller).
5. The electromagnetic sensing touch screen as claimed in claim 1,
wherein the digital potentiometer comprises an electrically
erasable potentiometer (EEPOT).
6. The electromagnetic sensing touch screen as claimed in claim 1,
wherein the finger detection operation of the control unit
comprises an initialization operation and a detection operation,
the initialization operation corrects the touch operation by
compensating the drift caused by the respective units or
environment, and the detection operation detects the location of
the finger to generate finger location information, and transfers
the finger location information to an external processing unit or
device, comprising a USB (Universal Serial Bus) device or
computer.
7. The electromagnetic sensing touch screen as claimed in claim 6,
wherein the initialization operation comprises steps of: checking
whether it is needed to correct after power on, if not, the sensing
capacitor units are corrected, and if yes, performing subsequent
steps; driving the standard EM wave transmit unit to transmit the
standard EM wave when the finger is away from the sensing capacitor
matrix; the control unit transferring the scan select signal to
each of the select units such that the select unit sequentially
receives the sensed capacitance values generated by the sensing
capacitor units, and generates the final sensed capacitance value
for scanning all effective regions of the display panel; the VCO
generating the local oscillation signal based on the final sensed
capacitance value; and the control unit at the same time receiving
the local oscillation signals of all the VCOs and generating the
frequency control signal for compensation, the digital
potentiometer generating the voltage control signal, and the VCO
receiving the voltage control signal to adjust the local
oscillation frequency of the local oscillation signal until the
control unit correctly determines the finger does not approach to
or touch the sensing capacitor unit, and the control unit storing
the frequency control signal as voltage control information such
that the sensing capacitor units are corrected.
8. The electromagnetic sensing touch screen as claimed in claim 6,
wherein the detection operation comprises steps of: sequentially
scanning all the sensing capacitor units to determine whether a
touch action occurs; the control unit directly employing the
voltage control information previously stored to transfer the
frequency control signal to the digital potentiometer for
generating the voltage control signal when the finger approaches to
or touches any one of the sensing capacitor units; the digital
potentiometer receiving the voltage control signal and adjusting
the local oscillation frequency of the local oscillation signal
according to the final sensed capacitance value of the select unit,
and the final sensed capacitance value changes if the finger
approaches to or touches the sensing capacitor unit such that the
local oscillation frequency changes and a frequency drift with
respect to the standard EM wave occurs; the EM wave
receive/detection unit employing the local oscillation signal to
detect the standard EM wave, and generating the detection signal
representing how close the finger approaches to the sensing
capacitor units or the finger touches the sensing capacitor units;
and the control unit determining whether the frequency drift occurs
or the degree of the frequency drift according to the detection
signal such that the location of the corresponding sensing
capacitor unit is taken as the location of the finger if the
intensity of the detection signal is lower than a preset threshold,
the finger location information further transferred, the finger
location information is generated and transferred, returning to the
step of sequentially scanning all the sensing capacitor units to
determine whether the touch action occurs, and repeating the
subsequent steps.
9. The electromagnetic sensing touch screen as claimed in claim 1,
wherein the sensing capacitor unit are substantially sensing
capacitor nodes formed by a plurality of horizontal driving lines
and a plurality of vertical sensing lines, which are interlaced to
each other, and the driving line and the sensing lines interlaced
are not physically in contact, but separated by a distance or by a
high impedance film.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention generally relates to a touch screen,
and more specifically to an electromagnetic sensing touch screen
using the frequency drift of the specific electromagnetic wave to
detect the finger(s) location and implement a function of
multipoint touch and display.
[0003] 2. the Prior Arts
[0004] Modern computers use graphic user interface as human to
machine interaction, mouse, keyboard and touch screen are commonly
used as input device. The touch screen can be constructed in many
ways, and some typical examples of common technologies to build
touch sensors are shown below:
[0005] 1. Resistive type touch sensor
[0006] 2. Surface capacitance
[0007] 3. SAW
[0008] 4. IR
[0009] 5. Projected capacitance
[0010] Different sensing method can provide different application
problems in final application environment, for example the
Projected capacitance touch sensor will be affected by radio
frequencies emissions that nearby the harmonic of PCT touch sensor
scanning frequency, the touch controller may report false
information cause by the radiate radio noise.
[0011] It is therefore new technique developed to overcome false
operation caused by radiate radio emissions nearby scanning
harmonics, an electromagnetic sensing touch screen can overcome the
RS problems by receiving beacon RF signals that fingers touch can
affect such receiving and can be detected by controller that no
ambient radiate can interference this new method.
[0012] Therefore, it is greatly needed for an electromagnetic
sensing touch screen to implement wirelessly selecting and
controlling the smart television by use of a wireless touch screen
device provided with wireless control and touch screen functions,
which is further enhanced by a smart set-top box and a wireless
router, thereby solving the above problems in the prior arts.
SUMMARY OF THE INVENTION
[0013] The primary object of the present invention is to provide an
electromagnetic sensing touch screen for implement a function of
multipoint touch and display by use of the frequency drift of the
specific electromagnetic wave due to the capacitance change to
detect the finger(s) location. Specifically, the electromagnetic
sensing touch screen comprises a display panel, a sensing capacitor
matrix, select units, voltage controlled oscillators (VCOs),
digital potentiometers, EM (electromagnetic) wave receive/detection
units, a standard EM wave transmit unit and a control unit. A
corresponding select unit, VCO, digital potentiometer and EM wave
receive/detection unit forms a detection unit. The display panel is
connected to an external image input device for receiving image
information and display the corresponding image.
[0014] More specifically, the sensing capacitor matrix is provided
close to the display panel and comprises sensing capacitor units,
each corresponding to a specific region of the image displayed by
the display panel. The sensing capacitor matrix may change the
effective capacitance based on how close the finger(s) is, and thus
the resonant frequency drift is generated.
[0015] Each detection unit is connected to the corresponding
sensing capacitor unit.
[0016] Each select unit comprises a plurality of multiplexers for
receiving the sensed capacitance values from the sensing capacitor
matrix. One of the sensed capacitance values is selected as the
resonant capacitor for the VCO used as a resonant circuit according
to the scan select signal. In case of no touch, the VCO controlled
by the control unit can employ a correction procedure to maintain
the capacitance differences among the sensing capacitor matrix such
that the sensed capacitance values from the sensing capacitor
matrix can be correctly received and taken as the standard signal
upon being touched.
[0017] In addition, the VCO receives the final sensed capacitance
value and the voltage control signal from the corresponding digital
potentiometer for controlling the varactor diode, and generates the
local oscillation signal with the local oscillation frequency. The
EM wave receive/detection unit uses the local oscillation signal to
receive the local standard EM wave, and thus generates the
detection signal. The control unit is connected to the EM wave
receive/detection unit to receive the detection signal, performs
the recognition process for received frequency intensity, and
generates the frequency control signal and the scan select signal.
The digital potentiometer receives the frequency control signal to
perform the digital-to-analog conversion (DAC), and the voltage
control signal is generated. Therefore, when the finger(s)
approaches and the effective capacitance value changes, the
frequency drift is caused due to the change of capacitance such
that the VCO frequency drifts and the intensity of the local
standard EM wave received also changes.
[0018] The local standard EM wave transmit unit is driven by the
control unit to generate the standard EM wave containing the
standard signal with the preset standard frequency, which is
transmitted to each EM wave receive/detection unit.
[0019] Therefore, the present invention can perform the finger
detection process to correctly detect the location of the
finger(s), and further determine how close the finger(s) approaches
to the sensed capacitor matrix or whether the finger(s) touches the
sensed capacitor matrix. The finger detection process preferably
comprises the initialization operation and the detection
operation.
[0020] Specifically, the control unit first performs the
initialization operation. When the finger(s) is away from the
sensed capacitor matrix, the local oscillation signal frequency of
the VCO does not drift, and the standard EM wave transmitted by the
standard EM wave transmit unit can be received and the received
standard EM wave has the maximum intensity. Meanwhile, the control
unit manipulates the select units to sequentially receive all the
sensed capacitance values from the sensing capacitor matrix and
thus generate the final sensed capacitance signal. Each time, the
final sensed capacitance signal is used to generate the VCO
frequency and receive the local standard EM wave, and particularly
the intensity of the local standard EM wave reversely represents
how the finger(s) approaches to the sensing capacitor matrix. When
all the effective touch regions of the display panel are scanned,
the VCO may each time generate the local oscillation signal based
on the final sensed capacitance signal. Also, the capacitance value
of each sensing capacitor unit possibly varies due to the process
drift such that the local oscillation signals generated by the
different VCOs may have the problem of the resonant frequency drift
if not touched. The present invention can perform the correction
procedure to drive the controller to employ the control information
so that the local oscillation signal is adjusted and the detection
signal generated by the EM wave receive/detection unit for
detecting the standard EM wave is the maximum. At the same time,
the control unit sequentially receives all the local oscillation
signals of the VCOs to generate the voltage control information for
compensation, and the VCO frequency is maintained to the maximum
allowable to be received. Further, the voltage control signal is
generated by the digital potentiometer, and received by the VCO to
continuously adjust the local oscillation frequency of the local
oscillation signal until the control unit correctly assures that
the finger(s) does not approach to or touch the sensing capacitor
units. Then, the control unit stores the voltage control
information and the initialization operation is thus completed.
[0021] In other words, the initialization operation is primarily
intended to correct the whole touch process of the electromagnetic
sensing touch screen according to the present invention so as to
improve the stability and preciseness of the touch function.
[0022] As for the detection operation, the finger(s) may approach
to or touch the sensing capacitor units, the control unit can
directly employ the voltage control information previously stored
to transfer to the VCOs through the digital potentiometers such
that each VCO changes the corresponding local oscillation frequency
based on the finger location, causing the detection signal of the
corresponding EM wave receive/detection unit to change. At this
time, the control unit may generate the corresponding finger
detection information by detecting the detection signal for
presenting the finger location, whether the finger(s) approaches to
or touches the sensed capacitor units.
[0023] Therefore, when the finger(s) is far away, the detection
signal of the EM wave receive/detection unit has the maximum
intensity, and as the finger(s) approaches, the intensity of the
detection signal decreases. It is possible to confirm that the
finger(s) approaches to or touches the sensed capacitor units by
checking if the intensity of the detection signal decreases to a
predetermine threshold, thereby implementing the correct finger
detection operation for the multipoint touch and display
function.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] The present invention can be understood in more detail by
reading the subsequent detailed description in conjunction with the
examples and references made to the accompanying drawings,
wherein:
[0025] FIG. 1 is a view showing the electromagnetic sensing touch
screen according to one of the embodiment of the present
invention;
[0026] FIG. 2 is a view showing one illustrative circuit for the
electromagnetic sensing touch screen according to the present
invention;
[0027] FIG. 3 is a view showing one illustrative circuit for the EM
wave receive/detection unit of the electromagnetic sensing touch
screen according to the present invention;
[0028] FIG. 4 is a view showing one illustrative circuit for the
standard EM wave transmit unit of the electromagnetic sensing touch
screen according to the present invention; and
[0029] FIG. 5 is a flowchart showing the finger detection process
employed in the electromagnetic sensing touch screen according to
the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0030] The present invention may be embodied in various forms and
the details of the preferred embodiments of the present invention
will be described in the subsequent content with reference to the
accompanying drawings. The drawings (not to scale) show and depict
only the preferred embodiments of the invention and shall not be
considered as limitations to the scope of the present invention.
Modifications of the shape of the present invention shall too be
considered to be within the spirit of the present invention.
[0031] Please refer to FIG. 1 illustrating the electromagnetic
sensing touch screen according to one of the embodiment of the
present invention. As shown in FIG. 1, the electromagnetic sensing
touch screen according to the present invention generally comprises
a display panel 10, a sensing capacitor matrix 20, a plurality of
select units 30, a plurality of voltage controlled oscillators
(VCOs) 40, a plurality of digital potentiometers (EEPOT) 50, a
plurality of EM (electromagnetic) wave receive/detection units
(RXV) 60, a standard EM wave transmit unit (STX) 70 and a control
unit 80. In particular, the select units 30, the VCOs 40, the
digital potentiometers 50, the EM wave receive/detection units 60,
the standard EM wave transmit unit 70 and the control unit 80
constitute a touch panel. Additionally, the corresponding select
unit 30, VCO 40, digital potentiometer 50 and EM wave
receive/detection unit 60 constitutes a single detection unit UA.
Thus, the electromagnetic sensing touch screen of the present
invention substantially comprises a plurality of detection units
UA. Specifically, the present invention employs the EM wave
frequency drift to detect the location of the finger(s) and
generate the finger location information, thereby implementing the
multipoint touch and display function.
[0032] The display panel 10 is preferably an electronic device with
the function of display, like LCD panel, connected to the image
input device, like the display card or the graphics chip for the
computer, used to receive the image information and display the
corresponding image.
[0033] Specifically, the sensing capacitor matrix 20 is fully or
partly transparent, and provided close to the display panel 10. The
sensing capacitor matrix 20 generally comprises a plurality of
sensing capacitor units 21, arranged in X columns and Y rows of a
matrix. Each sensing capacitor unit 21 corresponds to one specific
region of the image displayed by the display panel 10. The sensing
capacitor units 21 are substantially sensing capacitor nodes formed
by a plurality of horizontal driving lines (not shown) and a
plurality of vertical sensing lines (not shown), which are
interlaced to each other. The driving line and the sensing lines
interlaced are not physically in contact, but separated by a
distance or by a high impedance film. The sensing capacitor matrix
20 may change the effective capacitance value based on how close
the finger(s) FG approaches, thereby generating the sensed
capacitance value CV.
[0034] The select unit 30 of each detection unit UA is connected to
one corresponding sensing capacitor unit 21 of the sensing
capacitor matrix 20, and preferably comprises a plurality of
multiplexers (not shown), like 4:1 multiplexers or 8:1
multiplexers, which are hierarchically arranged for receiving all
the sensed capacitance values CV from the sensing capacitor matrix
20, selecting one sensed capacitance value CV as the final sensed
capacitance value FC according to the scan select signal SS, and
then outputting the final sensed capacitance value FC.
[0035] The VCO 40 receives the final sensed capacitance value FC
and the voltage control signal VS from the digital potentiometer
50, and generates the local oscillation signal LC corresponding to
the local oscillation frequency. That is, the local oscillation
frequency is adjusted according to the final sensed capacitance
value FC and the voltage control signal VS. Therefore, if the
voltage control signal VS does not change, the local oscillation
frequency will change as the final sensed capacitance value FC
changes such that the local oscillation frequency may change due to
the finger(s) FG approaching to or touching the sensing capacitor
matrix 20.
[0036] The EM wave receive/detection unit 60 receives the local
oscillation signal for receiving the standard EM wave RFS
containing the standard signal with the preset frequency from the
standard EM wave transmit unit 70, and generates the detection
signal DS after the detection process, wherein the standard EM wave
RFS has a preset standard frequency. It is preferred that the EM
wave receive/detection unit 60 is implemented by a circuit that
comprises an antenna (not shown) for receiving the standard EM wave
RFS, and a signal detector (not shown) for detecting the detection
signal DS, which represents the intensity of the received signal.
In the practical operation, the closer the local oscillation
frequency of the local oscillation signal gets to the
super-heterodyne standard frequency of the standard EM wave RFS,
the larger the detection signal DS, and this indicates that the
finger(s) gets away from the sensing capacitor matrix 20.
Alternatively, as the frequency drift between the local oscillation
frequency and the standard frequency becomes larger, that is, the
finger(s) gets closer to the sensing capacitor matrix 20, the touch
function is activated if the detection signal DS reaches the preset
threshold.
[0037] The control unit 80 can be implemented by a microcontroller
(MCU), connected to all the select units 30, the digital
potentiometers 50 and the EM wave receive/detection units 60 for
generating the scan select signal SS used to control each select
unit 30 to select the final sensed capacitance value FC and at the
same time receive the detection signal DS so as to perform the
frequency modulation and generate the frequency control signal CS,
which is further received by the digital potentiometer 50.
[0038] The digital potentiometer 50 is preferably implemented by
the electrically erasable potentiometer (EEPOT) available in the
present market, such as X9313 provided by Xicor Inc. or MX5128 chip
provided by MAXIM Integrated Products, Inc., which performs the
potential adjustment based on the frequency control signal CS so as
to generate the voltage control signal VS. The VCO 40 may adjust
the local oscillation frequency of the local oscillation signal LC
according to the voltage control signal VS.
[0039] The standard EM wave transmit unit 70 is driven by the
control unit 80 to generate the standard EM wave RFS, which is
further transmitted to the EM wave receive/detection unit 60 of
each detection unit UA.
[0040] To further explain the practical operations and the aspects
of the present invention in detail, please refer to FIG. 2 showing
one illustrative circuit for the electromagnetic sensing touch
screen according to the present invention. However, it should be
noted that the circuit disclosed in FIG. 2 is only an illustrative
example, and not intended to limit the scope of the present
invention. In other words, those electronic devices with the
equivalent functions mentioned above are all included in the
present invention. For example, the fact that the final sensed
capacitance value FC will eventually change is employed by the
illustrative circuit to cause the local oscillation frequency to
accordingly change, or alternatively, the final sensed capacitance
value FC is connected to the resonant tank circuit and used to
cause the receive frequency of the receiver to drift such that the
intensity of the standard received signal changes due to the
frequency drift of the receiver.
[0041] More specifically, one of the primary aspects of the present
invention is that the wireless manner using the radio receiver and
transmitter is employed to determine whether the received signal
changes, and thus, all the designs using the resonant tank circuit
and the phenomenon of the resonant frequency drift should be
included in the scope of the present invention, regardless of the
types of transmitter or receiver provided.
[0042] In the circuit shown in FIG. 2, four detection units UA are
included, and the sensing capacitor matrix 20 comprises 32.times.4
sensing capacitor units 21, which are divided into four groups,
each group comprising 32 sensing capacitor units 21. Therefore, the
finger location with respect to 32 regions of the display panel 10
can be detected. Also, each select unit 30 may comprise four 8:1
multiplexers and one 4:1 multiplexer so as to sequentially select
the final sensed capacitance value FC from the 32 sensed
capacitance values CV generated by the 32 sensing capacitor units
21 according to the scan select signal SS.
[0043] The control unit 80 may also employ the 4:1 multiplexer and
the pre-scaler (or the frequency divider) to sequentially select
the local oscillation signal LC generated by the VCO 40 of the 4
detection units UA based on the select signal. In particular, the
select signal of the control unit 80 should fit the scan select
signal SS for correcting and confirming the oscillation frequency
of each VCO 40.
[0044] Moreover, the control unit 80 is further connected to the
external processing unit or device, like USB (Universal Serial Bus)
device or computer, so as to take the sensing capacitor unit 21
according to the scan select signal SS as the finger location
information indicating the finger location when the finger(s)
approaches to or touches the sensing capacitor matrix 20, and
transfer the finger location information. At the same time, the
processing unit or device performs the corresponding preset
electrical operation, such as executing the preset operation for
the icon with respect to the finger location, including
transferring the files or the messages, opening the files,
performing the execution files, super linking to specific website,
or activate specific device like web camera or network phone.
[0045] One illustrative circuit of the EM wave receive/detection
unit 60 is shown in FIG. 3. Similar to the circuit of the
traditional radio receiver, the EM wave receive/detection unit 60
generally comprises an antenna ATT, a radio frequency amplifier
RFAMP, a mixer MXR, a filter FTR, a intermediate frequency
amplifier IFAMP, a demodulator DEM and an audio amplifier ADAMP,
which are connected in series. Specifically, the radio frequency
amplifier RFAMP, the mixer MXR, the filter FTR, the intermediate
amplifier IFAMP, the demodulator DEM and the audio amplifier ADAMP
constitutes the above signal detector. In the actual operation, the
antenna ATT receives the standard EM wave RFS, the mixer MXR
receives the local oscillation signal LC, and the filter FTR, the
intermediate amplifier IFAMP, the demodulator DEM and the audio
amplifier ADAMP perform the predetermined processes, respectively,
so as to generate the detection signal DS. It should be noted that
the EM wave receive/detection unit 60 is not limited by the circuit
shown in FIG. 3, but all the equivalent circuits for the EM wave
receive/detection unit 60 are included in the scope of the present
invention.
[0046] Since the standard EM wave RFS and the EM wave
receive/detection unit 60 are not allowed to be interfered by the
external signals, and the detection function should not be
affected, it is preferred that the circuit of the EM wave
receive/detection unit 60 and the circuit of the antenna ATT and
the standard EM wave RFS can be directly connected together through
the electrical coupling device. Besides, the grounded shield mask
is added to prevent interference due to the external signals.
[0047] The electromagnetic sensing touch screen according to the
present invention may also employ other receive means like direct
detection, regeneration or super regeneration receiver, and further
utilize the phenomenon of the resonant frequency drift resulted
from the change of the capacitance value to detect the touch
action.
[0048] Further refer to FIG. 4 showing one illustrative circuit for
the standard EM wave transmit unit 70 of the electromagnetic
sensing touch screen according to the present invention. As shown
in FIG. 4, the standard EM wave transmit unit 70 comprises two
transistors Q1 and Q2, two capacitors C1 and C2, two inductors L1
and L2, one antenna E1, two resistors R1 and R2, and one oscillator
Y1. The control unit 80 is connected to the resistor R2 for control
the transistor Q1 to turn on or turn off so as to control the
transmission of the standard EM wave RFS. It should be noted that
the circuit shown in FIG. 4 is only illustrative, and thus, other
elements or devices with the equivalent wireless transmission
function can be applied to the standard EM wave transmit unit
70.
[0049] Therefore, the overall function provided by the
electromagnetic sensing touch screen of the present invention
substantially generally includes using the control unit 80 to
perform the finger detection for correctly detecting the location
of the finger(s) FG in the sensing capacitor matrix 20, and
determining how close the finger(s) FG approaches to the sensing
capacitor matrix 20 or whether the finger(s) FG touches the sensing
capacitor matrix 20. More specifically, as shown in FIG. 5, the
finger detection comprises the initialization operation S1 and the
detection operation S2.
[0050] Specifically, the control unit 80 first performs the
initialization operation S1, comprising the steps S5, S10, S20,
S30, S40 and S45. Firstly, in the step S5, it is checked that the
correction process is needed for the sensing capacitor units after
power on. If the correction process is not needed, the step S45 is
directly performed by straightly using the original correction data
to correct the sensing capacitor units. If the correction process
is needed, the step S10 is performed.
[0051] In the step S10, the standard EM wave transmit unit 70 is
driven to transmit the standard EM wave RFS when the finger(s) FG
is far away from the sensing capacitor matrix 20.
[0052] Next, the step S20 is performed by using the control unit 80
to transfer the scan select signal SS to control each select unit
30 such that the select unit 30 sequentially receives they sensed
capacitance values CV generated by the sensing capacitor units 21,
and thus generates the final sensed capacitance value FC for
controlling the frequency of the local oscillation signal LC.
Whether the standard EM wave RFS is received is used to scan all
the effective regions of the display panel 10.
[0053] In the step 30, the VCO 40 generates the local oscillation
signal LC based on the final sensed capacitance value FC. Since
there exists some difference among the capacitances of the sensing
capacitor units 21 due to the process drift, the local oscillation
signals LC generated by different VCOs 40 also have the problem of
frequency drift. As a result, the detection signal DS generated by
the EM wave receive/detection units 60 according to the local
oscillation signals LC will vary.
[0054] Then in the step S40, the local oscillation signals LC of
all VCOs 40 are sequentially received by the control unit 80,
preferably through the 4:1 multiplexer and/or the pre-scaler and/or
the frequency divider so as to calculate the frequency without
compensation by a lookup table and generate the frequency control
signal CS for compensation. The voltage control signal VS is
subsequently generated by the digital potentiometer 50 and received
by the VCO 40, thereby adjusting the local oscillation frequency of
the local oscillation signal LC for compensating the difference due
to the different locations of the sensing capacitor units provided
in the sensing capacitor matrix 20 in case of no capacitor being
touched. As a result, a closed loop for self-control is formed such
that the local oscillation frequency after compensation fits
desired value for receiving the standard EM wave. The above
correction process continues until all the control units 80
generate the local oscillation frequency after compensation for
correctly receiving the standard EM wave when the finger(s) FG does
not approach to or touch the sensing capacitor units 21. At this
time, the control unit 80 stores the frequency control signal CS as
the voltage control information. Finally, the step S45 is performed
to finish the correction process for the sensing capacitor units
21. The initialization operation S1 is thus completed.
[0055] In short, the initialization operation S1 is primarily
intended to correct the touch operation of the whole
electromagnetic sensing touch screen for compensating the drift
caused by the respective units or the environment, thereby
improving the stability and preciseness of the touch function.
[0056] As for the detection operation S2, the steps SSA, S50, S60,
S70 and S80 are included. Firstly, in the step SSA, all the sensing
capacitor units are sequentially scanned. It is primarily intended
to determine if the touch action happens. Next, in the step S50,
when the finger(s) FG approaches to or touches any one of the
sensing capacitor units 21, the control unit 80 directly uses the
voltage control information stored to transfer the frequency
control signal CS to the digital potentiometer 50 generating the
voltage control signal VS. Subsequently, the step S60 is performed
by driving the VCO 40 to receive the voltage control signal VS and
adjust the local oscillation frequency of the local oscillation
signal LC according to the final sensed capacitance value FC of the
select unit 21. If the finger(s) FG approaches to or touches any
one of the sensing capacitor units 21, the local oscillation signal
LC changes, and accordingly, the local oscillation frequency
changes. As a result, the frequency drift with respect to the
standard EM wave RFS occurs.
[0057] In the step S70, the EM wave receive/detection units 60
employs the local oscillation signal LC to detect the standard EM
wave RFS, and generates the detection signal DS indicating how
close the finger(s) FG approaches to or touches the sensing
capacitor units 21. The step S80 is then performed by using the
control unit 80 to determine whether the frequency drift happens or
the degree of the frequency drift based on the detection signal DS.
If the intensity of the detection signal DS is lower than the
preset threshold, the location of the corresponding sensing
capacitor unit 21 is taken as the location of the finger(s) FG, and
the finger location information further transferred. Finally, back
to the step S5A, in which all the sensing capacitor units are
sequentially scanned, the subsequent steps are repeated.
[0058] From the above description, one of the aspects of the
present invention is to employ the electromagnetic wireless
transmission for the EM wave to implement the touch function for
the touch screen. In other words, the standard EM wave transmit
unit transmits the standard EM wave, and the EM wave
receive/detection unit receives and detects the standard EM wave so
as to generate the detection signal by use of the local oscillation
signal. Since the finger(s) affects the capacitance value of the
sensing capacitor unit in the sensing capacitor matrix, the local
oscillation frequency of the local oscillation signal drifts. The
variation of the intensity of the detection signal is used to
determine whether the frequency drift between the local oscillation
signal and the standard EM wave occurs, thereby simultaneously
detecting the location of at least one finger approaching to or
touching any sensing capacitor unit. As a result, the finger
location information is generated.
[0059] Therefore, as for the whole function, the present invention
employs the scan select signal to perform the scan/detection
operation for all the sensing capacitor units of the sensing
capacitor matrix in each scanning cycle. At the same time, the
location of at least one finger approaching to or touching any
sensing capacitor unit is detected, thereby implementing the
multi-touch display function for correctly detecting the gestures
of the fingers such as pressing, sliding, dragging, expanding,
kneading or rotating.
[0060] Although the present invention has been described with
reference to the preferred embodiments, it will be understood that
the invention is not limited to the details described thereof.
Various substitutions and modifications have been suggested in the
foregoing description, and others will occur to those of ordinary
skill in the art. Therefore, all such substitutions and
modifications are intended to be embraced within the scope of the
invention as defined in the appended claims.
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