Computer graphics processing and selective visual display system – Display peripheral interface input device – Touch panel
Reexamination Certificate
2001-09-25
2004-06-15
Liang, Regina (Department: 2675)
Computer graphics processing and selective visual display system
Display peripheral interface input device
Touch panel
C178S018040
Reexamination Certificate
active
06750853
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a touch panel device for detecting the touch of an object, such as a finger and a pen, on the touch panel device, and more particularly relates to a touch panel device using IDTs (Inter Digital Transducers), for detecting the touched position by detecting attenuation and cutoff of surface acoustic wave (SAW).
With the spread of computer systems, mainly personal computers, there has been used a device for inputting new information or giving various instructions to a computer system by pointing at a position on a display screen of a display device on which information is displayed by the computer system, with a finger or a pen. In order to perform an input operation with respect to the information displayed on the display screen of the display device of a personal computer or the like by a touching method, it is necessary to detect a touched position (indicated position) on the display screen with high accuracy.
Well known examples of touch panel device for detecting a position touched by an object such as a finger and a pen are a device using a resistance film, and a device using ultrasonic waves. In the former device using a resistance film, a change in the resistance of the resistance film caused by the touch of the object on the resistance film is detected. This device has the advantage of low consumption of power, but has the problems in the aspects of the response time, detection performance and durability.
By contrast, in the device using ultrasonic waves, a position touched by the object is detected by propagating surface acoustic waves along a non-piezoelectric substrate, for example, and detecting attenuation of the surface acoustic waves caused by the touch of the object such as a finger and a pen on the non-piezoelectric substrate.
FIG. 1
is an illustration showing the structure of such a conventional touch panel device using surface acoustic waves (the first conventional example). A first surface acoustic wave oscillator
52
a
and a second surface acoustic wave oscillator
52
b
are provided at the upper left corner of a rectangular panel
51
, a first surface acoustic wave receiver
53
a
is disposed at the lower left corner thereof, and a second surface acoustic wave receiver
53
b
is positioned at the upper right corner thereof. Moreover, reflectors
54
a
,
54
b
,
54
c
and
54
d
whose reflection surfaces are formed at an equal pitch are disposed at the four sides of the panel
51
, that is, the upper side, lower side, left side and right side, respectively.
Here, a surface acoustic wave excited by the first surface acoustic wave oscillator
52
a
is reflected by the reflection surfaces of the reflector
54
a
, scanned and propagated on the panel
51
in a vertical direction (Y-axis direction), further reflected by the reflection surfaces of the reflector
54
b
, and then received by the first surface acoustic wave receiver
53
a
. Meanwhile, a surface acoustic wave excited by the second surface acoustic wave oscillator
52
b
is reflected by the reflection surfaces of the reflector
54
c
, scanned and propagated on the panel
51
in a lateral direction (X-axis direction), further reflected by the reflection surfaces of the reflector
54
d
, and then received by the second surface acoustic wave receiver
53
b
.
FIG. 2
illustrates how such a surface acoustic wave is propagated.
In this example, since the surface acoustic waves enter each receiver after being reflected twice, they reach each receiver at intervals of t
i
=2D/V
s
(D: the reflection surfaces formation pitch, V
s
: the propagation speed of the surface acoustic waves).
FIG. 3
shows a time-series reception signal obtained by each receiver at this time. When an object is touching the panel
51
, since the level of the reception signal corresponding to that position is attenuated, it is possible to detect whether the panel
51
is touched by the object and the touched position by analyzing such a reception signal.
In order to increase the time resolution, i.e., in order to enable detection in a short time, a technique of shortening t
R
of
FIG. 3
by increasing the propagation speed of the surface acoustic waves may be used; and in order to increase the spatial resolution, a technique of reducing the reflection surfaces formation pitch D may be employed. In order to detect the touched position with high precision, it is necessary to totally improve both of the time resolution and spatial resolution.
FIG. 4
shows a structural example of the first and second surface acoustic wave oscillators
52
a
and
52
b
. The surface acoustic wave is excited by applying a voltage through an electrode
56
to a wedge-shaped piezoelectric body
55
fabricated on the panel
51
. Since the speed of this surface acoustic wave depends on the piezoelectric body
55
, it is impossible to increase the speed. Moreover, in general, since the reflectors
54
a
,
54
b
,
54
c
and
54
d
are fabricated by cutting work, it is not easy to form the reflection surfaces at a very small pitch. It is thus difficult to improve the time resolution and spatial resolution and detect the touched position with high precision.
In contrast to such a touch panel device, the present inventors are carrying out research and development of a touch panel device that requires no reflector and uses IDTs, capable of being formed collectively using a photolithography technique, as transducers. In this touch panel device, elements, each composed of an IDT and a piezoelectric thin film, are used as an excitation element for exciting a surface acoustic wave and a receiving element for receiving a propagated surface acoustic wave.
FIG. 5
is an illustration showing the structure of such a conventional touch panel device using the IDTs (the second conventional example). In
FIG. 5
, numeral
61
represents a rectangular non-piezoelectric substrate, and a plurality of excitation elements
62
, each composed of an input IDT and a piezoelectric thin film, for exciting surface acoustic waves are arranged into a line on one end of each of the X-direction and Y-direction of the non-piezoelectric substrate
61
so that the excitation elements
62
correspond to a plurality of tracks, respectively. Moreover, a plurality of receiving elements
63
, each composed of an output IDT and a piezoelectric thin film, for receiving the surface acoustic waves are arranged into a line on the other end of each of the X-direction and Y-direction of the non-piezoelectric substrate
61
so that the receiving elements
63
face the excitation elements
62
.
In the touch panel device shown in
FIG. 5
(hereinafter referred to as the “discrete-IDT type touch panel device”), a burst wave is applied to each excitation element
62
to excite the surface acoustic wave and propagate it along the non-piezoelectric substrate
61
, and the propagated surface acoustic wave is received by each receiving element
63
. Moreover, when an object touches the propagation path of the surface acoustic wave on the non-piezoelectric substrate
61
, the surface acoustic wave is attenuated. Accordingly, it is possible to detect the presence or absence of the touch of the object and the touched position by detecting whether the reception signal level of the receiving elements
63
is attenuated or not.
In addition, the present inventors proposed a touch panel device (third conventional example) in which the excitation elements and the receiving elements are arranged so as to propagate surface acoustic waves in an oblique direction (diagonal direction) of the substrate.
FIG. 6
is an illustration showing the structure of the IDTs of such a touch panel device (hereinafter referred to as the “inclined continuous-IDT type touch panel device”). An excitation element
72
is disposed at one peripheral portion of a rectangular substrate
71
. This excitation element
72
has an IDT
76
comprising facing electrode bases
74
and a plurality of comb-like electrode fingers
75
extended from the electrode bases
74
alternately. Besides,
Katsuki Takashi
Nakazawa Fumihiko
Sano Satoshi
Takahashi Yuji
Liang Regina
Westerman Hattori Daniels & Adrian LLP
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