Computer graphics processing and selective visual display system – Display peripheral interface input device – Touch panel
Reexamination Certificate
1998-08-07
2001-05-29
Shalwala, Bipin (Department: 2673)
Computer graphics processing and selective visual display system
Display peripheral interface input device
Touch panel
C178S018030
Reexamination Certificate
active
06239788
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a coordinate input device and display-integrated type coordinate input device for use in computers, word processors, for example.
2. Related Art
As an input device for effecting an input into a computer, a word processor or the like, there is a well known tablet capable of inputting figures and letters, giving instructions for command execution and effecting other functions under instructions from a pen, a finger or the like. As an input device developed from the above tablet, a display-integrated type tablet device that commonly uses the electrodes and drive circuits of an LCD (Liquid Crystal Display) panel for the achievement of an inexpensive structure is disclosed in the prior art reference of Japanese Patent Laid-Open Publication No. HEI 5-53726.
This display-integrated type tablet device has a construction as shown in
FIG. 35
, where a switchover circuit
2
selects a detection control circuit
3
in a coordinate detection period under the control of a control circuit
1
. Then, on the basis of signals from the detection control circuit
3
, a segment electrode drive circuit
4
generates a segment electrode scanning signal to sequentially scan the segment electrodes X of an LCD panel
5
. Subsequently, a common electrode drive circuit
6
generates a common electrode scanning signal to sequentially scan the common electrodes Y. An x-coordinate detection circuit
7
and a y-coordinate detection circuit
8
detect the coordinates of the tip of an electronic pen
9
on the basis of an induction voltage induced at the tip electrode of the electronic pen
9
. On the other hand, the switchover circuit
2
selects a display control circuit
10
during a display period and controls the segment electrode drive circuit
4
and the common electrode drive circuit
6
, thereby displaying an image on the LCD panel
5
.
There is further disclosed a transparent digitizer that is concurrently used as a touch panel for detecting the position of an operator's finger or a codeless pen in the prior art reference of Japanese Patent Laid-Open Publication No. HEI 8-179871. This touch panel and transparent digitizer has a construction as shown in FIG.
36
. When it operates as a digitizer, an AC signal oscillated from an oscillation pen
11
is received as a voltage of the electrode X of a first tablet
12
and a voltage of the electrode Y of a second tablet
13
, the voltages being induced by electrostatic capacitive coupling. Then, a signal level obtained every adjacent electrodes X
n
and X
n+1
or adjacent electrodes y
m
and Y
m+1
is subjected to a balance processing in a balance input circuit
14
, and only necessary frequency signal is taken out through a band-pass filter
15
. A control circuit
16
detects the position of the oscillation pen
11
based on the above signal.
When operating as a touch panel, the control circuit
16
controls analog switches
17
and
18
to sequentially apply a signal from a signal oscillator
19
to the electrodes X and the electrodes Y. Then, by detecting a change in electrostatic capacitance of the electrodes that are facing each other, the position that the finger touches is detected.
A touch panel for detecting the position of the operator's finger is disclosed in the prior art reference of Japanese Patent Laid-Open Publication No. SHO 60-123927. In this touch panel, one electrode that is sequentially selected out of a plurality of electrodes arranged parallel to one another is connected to a signal detection circuit, while the other electrodes are connected to a signal source for generating an AC signal. Then, a signal induced at the electrode by the electrostatic capacitance between the operator's finger and the electrode is detected by the above signal detection circuit, and the position that the finger touches is detected based on this detection signal. In this case, if the width of the electrode located on the upper side is wide in detecting the signal induced at the electrode positioned on the lower side, the upper electrode disadvantageously functions as an electrostatic shield, so that sufficient signal detection cannot be performed. Therefore, the width of the electrode located on the upper side is narrower than the width of the electrode located on the lower side.
However, the aforementioned prior art display-integrated type tablet device, touch panel and transparent digitizer and touch panel have.
In the above display-integrated type tablet device, an infinitesimal induction voltage induced at the tip electrode of the electronic pen
9
is amplified and transmitted to the x-coordinate detection circuit
7
and the y-coordinate detection circuit
8
, and both the detection circuits
7
and
8
detect the x-coordinate value and the y-coordinate value. Therefore, a cable arranged between the electronic pen
9
and both the detection circuits
7
and
8
is required. The cable causes a sense of incongruity in the operator, and its pull force significantly reduces the operability of the electronic pen
9
. Furthermore, when the above cable is located in a position on the LCD panel
5
at which the operator is about to look, the screen is not easy to view, resulting in a bad operability. Furthermore, due to the above construction, pointing cannot be executed by finger touch.
In contrast to the above, the touch panel and transparent digitizer requires no cable between the oscillation pen
11
and the control circuit
16
, achieving a codeless pen. However, the oscillation pen
11
must be mounted with an oscillation circuit and a battery for driving this oscillation circuit, which increase the weight and significantly reduce the operability. Additionally, the above battery must be periodically replaced, which is troublesome.
Furthermore, when mounting this touch panel and transparent digitizer on the display device for the provision of a display-integrated type tablet, there is an increase in number of components for the reason that the control circuit of the digitizer and the control circuit of the display device are independent of each other. Moreover, an adjusting process is necessary for the coincidence of a detection point with a display point in an assembling process, as a consequence of which the number of processes increases to cause a cost increase. Additionally, the touch panel and transparent digitizer is provided with the electrodes X and Y formed of an ITO (Indium Tin Oxide) film for example, part of light from the above display device is reflected and absorbed by the electrodes X and Y, causing a deterioration in visibility. Furthermore, for the mounting of the touch panel and transparent digitizer on the display device, the thickness of the device increases to significantly hinder the achievement of a thin lightweight structure.
The common use of the electrodes X and Y of the above touch panel and transparent digitizer as the electrodes of the display device for the formation of a display-integrated type tablet is very difficult for the following reasons.
That is, generally in a display device employing a liquid crystal display, an EL (electroluminescence) display, a plasma display or the like, electrodes that are perpendicular to each other are arranged on two substrates separated at a specified interval. As an example, a cross-section of a duty ratio type LCD device of STN (Super Twisted Nematic) type or the like is shown in FIG.
37
.
Although schematically shown in
FIG. 37
, practically an upper glass substrate
21
and a lower glass substrate
22
have a thickness of about 0.7 mm, and an upper polarizing plate
23
and a lower polarizing plate
24
have a thickness of about 0.1 mm. In contrast to this, a liquid crystal spacer
25
has a thickness of 7 &mgr;m, so that a distance from the electrodes
26
and
27
to a finger
28
is about 100 times a distance from a segment electrode
26
to a common electrode
27
.
Furthermore, a transparent protection panel for protecting an LCD device is sometimes mounted on thi
Iwahashi Hiroyuki
Katagiri Masayuki
Nohno Hitoshi
Nozaki Kiyohiro
Takahama Kengo
Piziali Jeff
Shalwala Bipin
Sharp Kabushiki Kaisha
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