Computer graphics processing and selective visual display system – Display peripheral interface input device – Touch panel
Reexamination Certificate
2001-08-03
2004-11-09
Hjerpe, Richard (Department: 2674)
Computer graphics processing and selective visual display system
Display peripheral interface input device
Touch panel
C178S018020, C178S018050
Reexamination Certificate
active
06816153
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a touch-panel device for detecting a touched position of a finger of an operator, conductive pen or the like to a surface of a touch-panel which has an arrangement that a conductive membrane is provided on a surface of a substrate. More particularly, the present invention relates to a touch-panel device which is used for a tablet for selecting and for touching by a user for responding questions, or which is used for selecting information item (menu) by a user which is displayed on a surface of a display {CRT(Cathode Ray Tube), liquid crystal panel or the like } connected to a computer information processing system, especially.
RELATED ART
Such touch-panel device is proposed in Patent Application Publication No. Shou 56-500230 gazette entitled “Touch-panel system and method”, Japanese Patent Laid-Open Publication No. Shou 63-108423 gazette entitled “Finger touching type coordinates outputting apparatus”, Japanese Patent Publication No. hei 6-12508 gazette entitled “contact type position detection apparatus” and the like.
FIG. 11
is a schematic diagram useful in understanding touching position detection principal of those devices.
To both ends of a conductive membrane
1
on a touch-panel, one end of current measurement resistors
2
,
3
are connected, respectively. The other end of the current measurement resistors
2
,
3
have a common connection point. The common connection point is connected to an AC power source
4
one end of which is connected to the ground. The conductive membrane
1
is touched at its arbitrary point using a finger, or an impedance Z such as a conductive pen or the like one side of which is connected to the ground.
Under this condition, it is supposed that the resistance value of the conductive membrane
1
between one end and the finger is R
L
, that the resistance value of the conductive membrane
1
between the other end and the finger is R
H
, and that the entire resistance of the conductive membrane
1
is R
0
. Further, the resistance of the current measurement resistors
2
,
3
are determined to be the resistance value R
K
, and the voltages of the both ends of the current measurement resistors
2
,
3
are determined to be V
1
and V
2
, respectively.
When such assumptions are made, the following equation is satisfied.
R
L
R
0
=
R
K
(
V
2
-
V
1
)
R
0
(
V
1
+
V
2
)
+
V
2
V
1
+
V
2
(
I
)
From this equation (1), a touching point of a finger can be detected based only upon the measurement values of voltages V
1
and V
2
.
Japanese Patent Publication No. Hei 6-12508 entitled “Contact type position detection apparatus” discloses an arrangement that electrodes are provided at outer peripheral sections of the conductive membrane of position detection region, the electrodes having smaller resistance value with respect to the conductive membrane.
The “Touch-panel system and method” and the “Finger touching type coordinates output apparatus” have following disadvantages.
a. In the equation (1), the resistance value of the resistance of the conductive membrane should be substituted. But, when a constant value is input, detection accuracy is lowered depending upon the change following passage in time of the conductive membrane and the installment environment of the conductive membrane. Further, when the resistance value is measured at every position detection and when the resistance value is substituted, measurement circuitry becomes complicated and expensive. Furthermore, changing in resistance value of the conductive membranes is great therefore yield of mass produced conductive membranes is lowered. As a result, a touch-panel is increased in cost.
b. Electrodes made of low resistance conductive material have resistance value which are provided outer peripheral section of the conductive membrane. Therefore, the value which is R
L
/R
0
at both ends in X-axis or Y-axis becomes 0 or 1 at corner sections and becomes a value different from 0 or 1 at sections which are not the corner sections, as is illustrated in FIG.
9
. As a result, detection accuracy is greatly lowered when the equation (1) is employed.
The “Contact type position detection apparatus” has following disadvantage.
Improvement in values for sections apart from both edges in X-axis or Y-axis is insufficient, the values being different from 0 or 1, as is illustrated in FIG. X
2
.
The present invention was made in view of the above problems.
It is an object of the present invention to offer a touch-panel device which has high position detection accuracy, and which can be manufactured with a low cost.
It is another object of the present invention to offer a touch-panel device which has high position detection accuracy, and which has short operating and processing time, and which can be manufactured with a low cost.
SUMMARY OF THE INVENTION
A touch-panel device of claim
1
according to the present invention is a touch-panel device which comprises a touch-panel including a substrate and a conductive membrane provided on the substrate, an AC current generation section for supplying AC currents to the conductive membrane through a first point and a second point which are at outer peripheral sections of the conductive membrane, and current measurement sections for measuring a first current supplied through the first point and a second current supplied through the second point, and wherein a touched position is calculated based upon the measured first current and the measured second current, and
The touch-panel device is characterized in that the device comprises an impedance which is connected by interposing a switch between one end of the AC current generation section and a connection point of the first point and one end of the current measurement section, at least, and wherein
A touch position on the touch-panel is calculated based upon a current measurement value measured by the current measurement means when the switch is turned ON and another current measurement value measured by the current measurement means when the switch is turned OFF.
When this touch-panel device is employed, a touch position on the touch-panel is calculated based upon a current measurement value measured by the current measurement means when the switch is turned ON and another current measurement value measured by the current measurement means when the switch is turned OFF. Therefore, variation in resistance value of the conductive membrane or changing in resistance value of the conductive membrane following passage of time are not needed to be taken into consideration which is described later, so that touch-position detection with high accuracy is realized.
A touch-panel device of claim
2
according to the present invention is characterized in that the switch is turned ON and turned OFF at every constant interval, a current measurement value measured by the current measurement means when the switch is turned ON is memorized, and a touch position on the touch-panel is calculated based upon the memorized current measurement value and a current measurement value measured by the current measurement means when the switch is turned OFF.
When this touch-panel device is employed, changing in resistance of the conductive membrane following passage of time is applied correction calculation and is renewed and memorized at every constant interval, therefore touch-position detection with high accuracy is realized. Further, it is not necessary that the switch is turned ON and turned OFF and self-correction calculation is applied at every touch position detection, therefore a measurement time is shortened.
A touch-panel device of claim
3
according to the present invention is a touch-panel device which comprises a touch-panel including a substrate and a conductive membrane provided on the substrate, an AC current generation section for supplying AC currents to the conductive membrane through a first point and a second point which are at outer peripheral sections of the conductive membrane, and current measurement sections for measuring a first current supplied t
Kobayashi Toshiyuki
Yamada Tsutomu
Fatahi-yar M.
Gunze Limited
Hjerpe Richard
Smith , Gambrell & Russell, LLP
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