Computer graphics processing and selective visual display system – Display peripheral interface input device – Touch panel
Reexamination Certificate
2001-04-26
2004-07-13
Saras, Steven (Department: 2675)
Computer graphics processing and selective visual display system
Display peripheral interface input device
Touch panel
C345S173000, C345S175000
Reexamination Certificate
active
06762753
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a touch panel device for detecting the touch of a finger or an object, and more specifically relates to a touch panel device using IDTs for detecting such a touch by detecting a cutoff of a surface acoustic wave.
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 an object. 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.
Examples of known touch panel devices for detecting the position touched by a finger or an object are classified into: {circle around (1)} a resistance film type; {circle around (2)} an electrostatic capacity type; {circle around (3)} an electromagnetic induction type; and {circle around (4)} an ultrasonic wave type. Although both {circle around (1)} and {circle around (2)} are of types using a light lucent conductive film of, for example, ITO (Indium Tin Oxide), the light lucent conductive film is not perfectly transparent, and therefore these types have a problem in the aspect of brightness because about 20% of the quantity of light is lost when light from a liquid crystal display surface passes through a touch panel unit. Besides, in the case where a touch panel device of such a type is employed in a reflective type liquid crystal display device, since light passes through the touch panel unit twice, the brightness problem is enhanced. On the other hand, type {circle around (3)} has a difficulty in reducing the size and also has a problem that a special input pen is required.
In contrast, type {circle around (4)} detects a position touched by a finger or an object by propagating a surface acoustic wave (hereinafter also referred to as the “SAW”) along a glass plate serving as a non-piezoelectric substrate, for example, and detecting attenuation of the surface acoustic wave caused by the touch of the finger or object on the glass plate (Japanese Patent Application Laid-Open No. 55-153041/1980, etc.). This ultrasonic wave type achieves an excellent transparency and requires no special input pen.
However, in conventional touch panel devices of the ultrasonic wave type, since transducers for generating surface acoustic waves and detecting the same are constructed by ceramic transducers, this type of touch panel devices have problems, such as difficulty in reducing the thickness and size, higher costs of the parts and difficult mounting, in comparison with the touch panel devices of other types. Moreover, it is necessary to provide a reflector along the edge of the glass plate, resulting in high costs on the whole.
Therefore, there has been proposed a type in which an IDT (Inter Digital Transducer: comb-like electrode) capable of being formed collectively using a photolithography technique is used as a transducer (Japanese Patent Applications Laid-Open Nos. 6-43995/1994, 6-75688/1994, 6-75689/1994, 6-149459/1994, 11-21925/1999, etc.). This type allows mass production, thereby achieving a reduction in the costs.
In this touch panel device, a plurality of excitation elements, each composed of an input IDT and a piezoelectric thin film, are provided on one end of the glass plate, and a plurality of receiving elements, each composed of an output IDT and a piezoelectric thin film similarly, are provided on the other end of the glass plate at positions opposite to the excitation elements. Electric signals are inputted to the respective excitation elements to excite the surface acoustic waves and propagate the surface acoustic waves along the glass plate, and the propagated surface acoustic waves are received by the receiving elements. Then, if a finger or an object touches the propagation path of the surface acoustic wave along the glass plate, the surface acoustic wave is attenuated. It is therefore possible to detect whether touching is made and the touched position by detecting whether there is attenuation in the level of the receiving signals of the receiving elements.
FIG. 1
is an illustration showing the structure of such a conventional touch panel device using IDTs. In
FIG. 1
, numeral
1
is a glass plate, and a plurality of input IDTs
2
for exciting a surface acoustic wave are arranged into a line on one end of each of the X-direction and Y-direction of the glass plate
1
so that the input IDTs
2
correspond to a plurality of tracks, respectively. Moreover, a plurality of output IDTs
3
for receiving the surface acoustic wave are arranged stepwise on the other end of each of the X-direction and Y-direction of the glass plate
1
so that the output IDTs
3
face the input IDTs
2
. With such a positional arrangement, the distance between the input IDT
2
and output IDT
3
is varied according to each track so as to vary the receiving timing in the respective output IDTs
3
, so that a track on which the receiving signal is attenuated can be identified accurately.
In the touch panel device having such a structure, the output IDTs
3
need to be arranged stepwise so as to vary the time from the excitation of the surface acoustic wave to the reception thereof in each track, and therefore problems arise that, a region for providing the input IDTs
2
and output IDTs
3
(hereinafter referred to as the “frame region”) is wide and a region where the touched position is detectable (hereinafter referred to as the “detection region”) is relatively narrow as shown in FIG.
1
. Such problems become severer as the number of tracks is increased, and thus this positional arrangement is not practicable. Hence, there is a demand for the development of a touch panel device which is capable of identifying the respective tracks by a technique different from a technique based on the difference in the propagation time, and capable of arranging not only the input IDTs
2
but also the output IDTs
3
into a line.
BRIEF SUMMARY OF THE INVENTION
It is an object of the present invention to provide a touch panel device capable of arranging both of the input IDTs and output IDTs respectively into a line, narrowing a frame region and widening a detection region.
Another object of the present invention is to provide a touch panel device capable of always accurately detecting a touched position without being affected by a change in a temperature environment.
A touch panel device according to the first aspect is a touch panel device comprising a plurality of input IDTs for exciting surface acoustic waves and a plurality of output IDTs for receiving the surface acoustic waves, correspondingly to a plurality of tracks of a non-piezoelectric substrate, for propagating surface acoustic waves along the non-piezoelectric substrate between the input IDTs and the output IDTs and detecting a position of an object touching the non-piezoelectric substrate based on results of receiving the surface acoustic waves by the output IDTs, wherein each of the plurality of input IDTs has a wideband electrode structure, each of the plurality of output IDTs has a matched filter structure for obtaining an output signal upon receipt of a specific signal sequence, and the specific signal sequence is varied according to each of the plurality of tracks.
In the touch panel device of the first aspect, each input IDT has a wideband electrode structure, and each output IDT has a matched filter structure for obtaining an output upon receipt of a specific signal sequence, so that each output IDT outputs an output signal only when it receives a specific signal sequence set for itself but outputs no output signal upon receipt of other signal sequences. Moreover, since the specific signal sequence is varied according to each of a plurality of tracks, the output
Nakazawa Fumihiko
Sano Satoshi
Satoh Yoshio
Alphonse Fritz
Fujitsu Limited
Saras Steven
Westerman Hattori Daniels & Adrian LLP
LandOfFree
Touch panel device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Touch panel device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Touch panel device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3251789