A touch-screen display which is able to prevent a displacement of a display position and a touch position. The touch-screen display includes a pointing pen for pointing to a position on the touch panel, and which may represent a position of an operator's eye. Moreover, the touch-screen display includes a correction unit for correcting the pointing position pointed to by the pointing pen. Therefore, the displacement of display position and a touch position caused by an angle of an operator's line of sight can be compensated for.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a touch-screen display, which may be set on a 
personal computer, a mobile computer, etc., as a displaying and pointing 
device, and particularly, this invention relates to a touch-screen display 
with a function of eliminating an input error caused by a difference 
between a displayed point and a touched point by an angle of a line of 
sight. 
2. Discussion of the Background 
Touch-screen displays have been set on a personal computer, a mobile 
computer, etc. as a displaying and pointing device. These touch-screen 
displays have a display apparatus and an invisible touch panel, and the 
invisible touch panel is set over the display apparatus. In these 
touch-screen displays, some icons, characters, etc., are displayed on the 
display apparatus. An operator touches the icons, characters, etc., 
displayed on the display apparatus, and a touch point is detected and 
thereby the operator's input is detected. In addition, characters can be 
input by a handwriting input using an input pen. 
FIGS. 8a and 8b show a section view of a touch-screen display. A touch 
panel 3 is set over a display panel 2, for example a LCD (a liquid crystal 
display). Because the touch panel 3 is invisible, an operator sees icons, 
characters, etc., displayed on the display panel 2. In this touch-screen 
display, when a point just above an icon displayed on the display panel 2 
is touched, this icon is selected. 
As shown in FIGS. 8a and 8b, a gap G exists between the display panel 2 and 
the touch panel 3. FIG. 8a shows a case that an operator sees the display 
panel 2 from just above an icon "A" displayed on the display panel 2. In 
this case, the icon "A", a point B on the touch panel above the icon "A" 
and the operator's eyes are all in a line. Therefore, when the operator 
selects the icon "A", the point B is touched and the icon "A" is selected. 
On the other hand, FIG. 8b shows a case that an operator sees the display 
panel 2 from a point not above the icon "A" displayed on the display panel 
2. In this case, the icon "A", point B and the operator's eyes are not all 
in a line, and instead the icon "A", point B' and the operator's eyes are 
all in a line. However, the point B' is not located just above the icon 
"A". Therefore, when the operator selects the icon "A", the point B' is 
touched, and as a result the icon "A" may not be selected. In addition, in 
a case of a handwriting input, wrong information may be input. 
Japanese Patent Laid-Open No. 5-224816 shows a touch-screen display for 
preventing the problem just described. This touch-screen display has a 
two-layer touch panel. In this touch-screen display, first, in operator 
touches the first layer touch panel. A touching point is displayed and 
thereby the operator can evaluate a difference between a displayed point 
and a touched point resulting from any deviation in an angle of a line of 
sight. Next, the operator touches the second layer touch panel for an 
input. 
The above-mentioned touch-screen display in Japanese Patent Laid-Open No. 
5-224816 has some problems. First, the operator has to operate knowing a 
difference between a displayed point and a touched point resulting from 
any deviation in an angle of a line of sight at each input, and therefore 
an operation is complicated. Second, when an operator touches the first 
layer touch panel knowing a difference between a displayed point and a 
touched point resulting from any deviation in an angle of a line of sight, 
by a strong touching by the operator, the second layer touch panel may be 
inadvertently touched too, and a wrong information may be thereby input. 
Third, the two-layer touch panel may is expensive. 
Japanese Patent Laid-Open No. 7-210317 also shows a touch-screen display, 
and in this touch-screen display, a touch panel automatically moves 
according to an angle of tilting of a display panel. Moreover, Japanese 
Patent Laid-Open No. 7-141109 shows a touch-screen display which has a 
light-producing device on a handset of a phone and more than one 
photoreceptor around a display panel. The photoreceptors receive light 
from the light-producing device on a handset and a position of the handset 
is detected, and a position of displaying and the touch panel is 
corrected. 
The above-mentioned touch-screen display in Japanese Patent Laid-Open No. 
7-210317 is complicated because this touch-screen display has to move the 
touch panel. Further, the touch-screen display in Japanese Patent 
Laid-Open No. 7-141109 requires a specialized handset. 
SUMMARY OF THE INVENTION 
Accordingly, an object of the present invention is to provide a novel 
touch-screen display which obviates the above-mention problems. 
To achieve the objects, the present invention provides a novel touch-screen 
display which has a display panel and a touch panel which is layered on 
the display panel, and further having a pointing pen for pointing to a 
position on the touch panel and inputting a position of an operator's eye, 
a detecting unit for detecting a position of the pointing pen as a 
position of the operator's eye, a correction value decision unit for 
deciding a correction value according to the position of the pointing pen 
detected by the detecting unit, and a correcting unit for correcting a 
pointing position pointed by the pointing pen according to the correction 
value decided by the correction value decision unit. In this way, the 
present invention achieves an operation to provide a novel touchscreen 
display which is able to prevent a displacement between a display position 
and a touch position.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to the drawings, wherein like reference numerals designate 
identical or corresponding parts throughout the several views, FIG. 1 is a 
diagram of a touch-screen display 1 of the present invention and a 
pointing pen 5 for inputting a position. In FIG. 1, a touch-screen display 
1 includes a display panel 2 and an invisible touch panel 3. The 
touch-screen display 1 has a rectangular display window 10a of a casing 10 
and an operator can see the display panel 2 through the display window 
10a. The display panel 2 may be a LCD (liquid crystal display). 
The touch panel 3 is layered on the display panel 2 and is held by the 
casing 10. Four photoreceptors 4a, 4b, 4c and 4d are set on the casing 10. 
The photoreceptors 4a, 4b, 4c and 4d each may include a photodiode. 
The pointing pen 5 includes a pen tip 5a, and the pen tip 5a can contact 
the touch panel 3 for an operator to input a position. The pointing pen 5 
includes a light-producing device 6 on a pen head 5b and a communicating 
button 7 on a pen grip 5c. The light-producing device 6 may be an infrared 
light-emitting diode. 
FIG. 2 is a block diagram of the touch-screen display 1 of the present 
invention. In FIG. 2, the touch-screen display 1 includes a control unit 8 
which controls all of the units of the touch-screen display 1, a display 
control unit 9 which controls the display panel 2 according to commands 
from the control unit 8, and a touch panel control unit 10 which 
calculates coordinate data of a touching position on the touch panel 3 
according to information from the touch panel 3 and sends the coordinate 
data to the control unit 8. When the display panel 2 is used as a monitor 
of a personal computer, the control unit 8 can be shared with a control 
unit of the personal computer. 
The control unit 8 includes a CPU, ROM and RAM (not shown) in which are 
stored programs, and the control unit 8 includes a correction value 
decision circuit 82, a position correcting circuit 83 and a view point 
detecting circuit 81. The view point detecting circuit 81 in the control 
unit 8 calculates a position of the light-producing device 6 as an 
operator's view point according to a time difference of receiving a light 
from the light-producing device 6 by the photoreceptors 4a, 4b, 4c and 4d. 
The correction value decision circuit 82 decides a correction value 
according to the position of the light-producing device 6 which is 
calculated by the view point detecting circuit 81, and the position 
correcting circuit 83 corrects an input position according to the 
correction value output from the correction value decision circuit 82. 
FIG. 3 is a flowchart of a process of the touch-screen display 1 of the 
present invention. When an operator uses this touch-screen display 1, 
first, a decision of a correction value is executed. At step S1, an 
operator places the pointing pen 5 in front of the operator's eye. FIG. 4 
shows as an example a situation in which an operator places the pointing 
pen 5 in front of the operator's eye. At step S2, the operator pushes the 
communicating button 7 of the pointing pen 5. According to pushing the 
communicating button 7 by the operator, a process of a decision of a 
correction value starts, see step S3. 
In the process of a decision of a correction value, photoreceptors 4a, 4b, 
4c and 4d receive a light from the light-producing device 6 on the 
pointing pen 5 and a correction value is decided according to time 
differences of receiving the light by the photoreceptors 4a, 4b, 4c and 
4d. A time difference in receiving the light about an X-axis direction Tx 
and a time difference of receiving the light about a Y-axis direction Ty 
are expressed by the following expression, in which K1 is a receiving time 
of light at the photoreceptor 4a, K2 is a receiving time of light at the 
photoreceptor 4b, K3 is a receiving time of light at the photoreceptor 4c 
and K4 is a receiving time of light at the photoreceptor 4d: 
Tx=K1-K3, 
Ty=K2-K4. 
FIG. 5 is a diagram of a circuit for performing the time difference 
decision. The circuit for performing the time difference decision is a 
part of the view point detecting circuit 81. The circuit for performing 
the time difference decision includes a time-delay circuit 11a which 
delays an output signal from the photoreceptor 4a by a time T1, a 
time-delay circuit 11c which delays an output signal from the 
photoreceptor 4c by a time T1, a time-delay circuit 11b which delays an 
output signal from the photoreceptor 4b by a time T2 and a time-delay 
circuit 11d which delays an output signal from the photoreceptor 4d by a 
time T2. Moreover, the circuit for performing the time difference decision 
includes D-type flip-flop circuits (hereinafter expressed F/F) 12a, 12b, 
12c and 12d. 
In a case of Tx&gt;T1, in other word, when the photoreceptor 4a does not 
receive a light from the light-producing device 6 until a time T1 after 
the photoreceptor 4c receives a light from the light producing device 6, 
an output Q of the F/F 12a is at a low level. And in a case of Tx&lt;-T1, in 
other words, when the photoreceptor 4c does not receive a light from the 
light-producing device 6 until a time T1 after the photoreceptor 4a 
receives a light from the light-producing device 6, an output Q of the F/F 
12c is at a low level. 
In the example of positioning of the operator's eye as shown in FIG. 4, the 
distance between the photoreceptor 4a and the light-producing device 6 is 
longer than the distance between the photoreceptor 4c and the 
light-producing device 6. When a difference of the distances is larger 
than some predetermined value, the photoreceptor 4a does not receive a 
light from the light-producing device 6 until a time T1 after the 
photoreceptor 4c receives a light from the light-producing device 6, and 
thus Tx&gt;T1 holds. Therefore, when Tx&gt;T1 holds, the view point detecting 
circuit 81 detects that the position of the operator's eye, in other words 
an angle of a line of sight, is as shown in FIG. 4. 
By these processes, the angle of a line of sight is detected according to 
the outputs from the F/Fs 12a, 12b, 12c and 12d (see step S4 and step S5 
in FIG. 3). After these detecting steps, at step S6, the correction value 
decision circuit 82 in the control unit 8 decides the position of the 
operator's eye according to some condition, for example a table of FIG. 6. 
In FIG. 6, characters of the "position of operator's eye", for example 
"H.sub.1 V.sub.3 ", may express nine areas such as shown in FIG. 7. The 
position of the operator's eye is decided according to the detected time 
differences in the X-direction and Y-direction. 
The displacement of a display position and a touch position is small in the 
center of the touch-screen display 1. When a position of an operator's eye 
is H.sub.1 V.sub.3, in other words lower left, the touch position deviates 
in a direction of lower left. In this case, a correction value of the 
X-axis is "+.alpha.", a correction value of the Y-axis is "+.beta.". The 
correction value of the X-axis "+.alpha." corrects the touch position of 
the X-axis in an upper direction and the correction value of the Y-axis 
"+.beta." corrects the touch position of the Y-axis to the right. 
Therefore, the displacement between a display position and a touch 
position is reduced. 
The correction value is stored, for example in a RAM in the control unit 8, 
and the process for performing the decision of the correction value is 
then finished. In the embodiment shown, a position of an operator's eye 
falls within nine areas, however, more than nine areas can be adopted by 
increasing the delay circuits 11 and a number of F/Fs 12. 
At step S8 in FIG. 3, after a decision of a correction value, an inputting 
position by the pointing pen 5 is started. In this inputting, a corrected 
coordinate value is generated by adding the correction value to the value 
from the touch panel control unit 10 in FIG. 2. 
In this embodiment, the pointing pen 5 includes the light-producing device 
6 and photoreceptors 4a, 4b, 4c, 4d placed around the touch panel 2. 
However, another system can be used. For example, the pointing pen 5 may 
have a sound source as a substitute for the light-producing device 6, and 
microphones can then be placed around the touch panel 2. In this system, 
when an operator pushes the communicating button 7, the sound source, for 
example a buzzer, outputs sound and more than one microphone receives the 
sound and detects a position of the operator,'s eye. Moreover, another 
flat display can be used as a substitute for the LCD panel, for example, a 
plasma display and FED. 
This invention may be conveniently implemented using a conventional general 
purpose digital computer or microprocessor programmed according to the 
teachings of the present specification, as will be apparent to those 
skilled in the computer art. Appropriate software coding can readily be 
prepared by skilled programmers based on the teachings of the present 
disclosure, as will be apparent to those skilled in the software art. The 
invention may also be implemented by the preparation of application 
specific integrated circuits or by interconnecting an, appropriate network 
of conventional components, as will be readily apparent to those skilled 
in the art. 
Obviously, numerous additional modifications and variations of the present 
invention are possible in light of the above teachings. It is therefore to 
be understood that within the scope of the appended claims, the present 
invention may be practiced otherwise than as specifically described 
herein. 
This application is based on Japanese patent application 8-260231 filed in 
the Japanese Patent Office on Sep. 9, 1996, the entire contents of which 
are hereby incorporated by reference.