U.S. patent number RE34,187 [Application Number 07/485,669] was granted by the patent office on 1993-03-02 for coordinates input system.
This patent grant is currently assigned to Wacom Co. Ltd.. Invention is credited to Azuma Murakami, Toshiaki Senda, Tsuguya Yamanami.
United States Patent |
RE34,187 |
Yamanami , et al. |
March 2, 1993 |
Coordinates input system
Abstract
Disclosed is a coordinates input system having a tablet
constituting a coordinates input portion, a position designating
device such as a stylus pen, and a position detection circuit
adapted to drive said tablet and detect a position at which
coordinates are input by said position designating device. The
system comprises: an antenna coil disposed around a coordinates
input range of said tablet; and a tuning circuit disposed in said
position designating device and including a coil and a capacitor,
wherein radio waves are generated by said antenna coil by
application of an AC signal of a predetermined frequency thereto,
and the status of said tuning circuit is discriminated by a signal
of said antenna coil at the time when the transmission of said
radio waves is suspended, thereby detecting the status of said
position designating device. Hence, this coordinates input system
is capable of detecting the status of the position designating
device without connecting the position designating device and other
circuits by means of a cord and without providing the position
designating device with a conventionally employed complicated
signal generating circuit, a battery, and the like.
Inventors: |
Yamanami; Tsuguya (Saitama,
JP), Senda; Toshiaki (Saitama, JP),
Murakami; Azuma (Kanagawa, JP) |
Assignee: |
Wacom Co. Ltd. (Saitama,
JP)
|
Family
ID: |
27323519 |
Appl.
No.: |
07/485,669 |
Filed: |
February 27, 1990 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
76962 |
Jul 23, 1987 |
04786765 |
Nov 22, 1988 |
|
|
Foreign Application Priority Data
|
|
|
|
|
Jul 26, 1986 [JP] |
|
|
61-171684 |
Aug 20, 1986 [JP] |
|
|
61-194492 |
Aug 28, 1986 [JP] |
|
|
61-202483 |
|
Current U.S.
Class: |
178/18.07;
178/19.07; 345/179 |
Current CPC
Class: |
G06F
3/03545 (20130101); G06F 3/046 (20130101) |
Current International
Class: |
G06F
3/033 (20060101); G08C 021/00 () |
Field of
Search: |
;178/18,19 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
47-67704 |
|
Jun 1972 |
|
JP |
|
49-11432 |
|
Jan 1974 |
|
JP |
|
57-116883 |
|
Jan 1979 |
|
JP |
|
56-129871 |
|
Aug 1981 |
|
JP |
|
56-150086 |
|
Oct 1981 |
|
JP |
|
57-57449 |
|
Apr 1982 |
|
JP |
|
58-180303 |
|
Nov 1983 |
|
JP |
|
59-3537 |
|
Jan 1984 |
|
JP |
|
61-8809 |
|
Jan 1986 |
|
JP |
|
Primary Examiner: Schreyer; Stafford D.
Attorney, Agent or Firm: Lowe, Price, LeBlanc &
Becker
Claims
What is claimed is:
1. A coordinates input system having a tablet constituting a
coordinates input portion, a position designating device such as a
stylus pen, and a position detection circuit adapted to drive said
tablet and detect a position at which coordinates are input by said
position designating device, said system comprising:
an antenna coil disposed around a coordinates input range of said
tablet; and
a tuning circuit disposed in said position designating device and
including a coil and a capacitor,
wherein radio waves are generated by said antenna coil by
application of an AC signal of a predetermined frequency thereto,
and the status of said tuning circuit is discriminated by a signal
of said antenna coil at the time when the transmission of said
radio waves is suspended, thereby detecting the status of said
position designating device.
2. A coordinates input system according to claim 1, wherein
switching means for turning ON (or OFF) the connection between said
coil and said capacitor is disposed in said tuning circuit, and
when only a position of coordinates to be input is designated, said
position designating device is used by turning said switching means
ON (or OFF).
3. A coordinates input system according to claim 1, wherein said
tablet is arranged such that a tablet body and said antenna coil
are accommodated in a casing made of a non-metallic material, such
as a synthetic resin.
4. A coordinates input system according to claim 1, further
comprising a magnetism generator for designating a position.
5. A coordinates input system according to claim 1, wherein said
antenna coil is arranged such that a conductive wire provided with
an insulation coating, such as polyvinyl chloride, is disposed
around said coordinates input range of said tablet.
6. A coordinates input system according to claim 1, wherein said
tuning circuit includes a variable capacitor.
7. A coordinates input system having a tablet constituting a
coordinates input portion, a position designating device such as a
stylus pen, and a position detection circuit adapted to drive said
tablet and detect a position at which coordinates are input by said
position designating device, said system comprising:
a plurality of tuning circuits disposed in said position
designating device, each of said plurality of tuning circuits
including a coil and a capacitor to constitute a set and being
adapted to transmit radio waves with mutually equivalent tuning
frequencies and different phases in response to an external
signal;
switching means disposed in said position designating device and
adapted to turn ON and OFF the connection between said coil and
said capacitor of each of said tuning circuits; and
an antenna coil disposed around a coordinates input range of said
tablet;
wherein radio waves are generated by said antenna coil when an AC
signal of a frequency identical with that of said tuning frequency
is intermittently applied to said antenna coil, and the status of
the position and operation of said position designating device is
detected when signals responded to by said tuning circuits during
suspension of transmission of said radio waves are received by said
antenna coil, and
the ON-OFF status of said switching means with respect to said
tuning circuits is discriminated by means of input signals having
mutually different phases with respect to output signals of said
antenna coil.
8. A coordinates input system having a tablet constituting a
coordinates input portion, a position designating device such as a
stylus pen, and a position detection circuit adapted to drive said
tablet and detect a position at which coordinates are input by said
position designating device, said system comprising:
a tuning circuit disposed in said position designating device, said
tuning circuit including a set of a coil, a capacitor, and/or a
resistor and being adapted to generate radio waves with mutually
equivalent tuning frequencies and a change in the phase in response
to an external signal by changing any of the values of said coil,
said capacitor, and/or said resistor in correspondence with the
status of use of said position designating device; and
an antenna coil disposed around a coordinates input range of said
tablet;
wherein radio waves are generated by said antenna coil when an AC
signal of a frequency identical with that of said tuning frequency
is intermittently applied to said antenna coil, and the status of
the position and operation of said position designating device is
detected when signals responded to by said tuning circuit during
suspension of transmission of said radio waves are received by said
antenna coil, and
the status of use of said position designating device is
discriminated by means of input signals having mutually different
phases with respect to output signals of said antenna coil.
.Iadd.
9. An implement for designating one of plural characteristics
thereof and a position thereof to a tablet including means for
signalling indications of the implement characteristic and position
comprising
a cordless housing adapted to be manually held and manually moved
proximate a surface of the tablet, the housing including:
a tuned circuit having no electric power supply connected to it,
the tuned circuit including
reactance means including several reactances comprising an inductor
and a capacitor, and
plural manually activated switches for connecting said several
reactances together in different combinations to provide plural
resonant frequencies for the tuned circuit in response to different
ones of the plural manually activated switches being activated to
signal a selected characteristic;
the housing being constructed so that waves having a magnetic
component can be coupled without wires between a reactance of the
tuned circuit and a structure outside of the housing. .Iaddend.
.Iadd.
10. The implement of claim 9 wherein the variable reactance
includes a variable capacitor. .Iaddend. .Iadd.
11. The implement of claim 9 wherein the switch means is activated
in response to the implement region bearing against the tablet
surface. .Iaddend. .Iadd.12. The implement of claim 9 wherein the
switch means is
manually activated. .Iaddend. .Iadd.13. An implement for signalling
position thereof to position detecting coils for a tablet
associated with a surface with which the implement is adapted to be
moved comprising:
a cordless housing adapted to be manually held and manually moved
relative to the surface, the housing including:
a region adapted to be moved relative to the surface,
a tuned circuit having no electric power supply connected to it,
the tuned circuit including
reactance means comprising an inductor, a capacitor and a variable
reactance having at least several reactance values correlated with
at least several pressure values of a region of the implement being
urged against the surface;
the housing being constructed so that waves having a magnetic
component can be coupled without wires between a reactance of the
tuned circuit and a structure outside of the housing; and
means in proximity to the region for generating and supplying a
magnetic field to the position detecting coils for the implement.
.Iaddend.
.Iadd. . The implement of claim 13 wherein a fixed capacitor is
connected in circuit with said variable reactance. .Iaddend.
.Iadd.15. The implement of claim 13 wherein the field generating
and supplying means comprises a magnet. .Iaddend. .Iadd.16. The
implement of claim 13 wherein
the housing is formed as a writing pen. .Iaddend. .Iadd.17. In
combination,
a tablet including position detecting coils arranged in two
coordinate directions,
a manually held implement having a region adapted to be moved
relative to a surface of the tablet associated with the position
detecting coils, the implement including:
a cordless housing adapted to be manually held and manually moved
relative to the surface, the housing including:
a tuned circuit having no electric power supply connected to it,
the tuned circuit including
an inductor and a capacitor, and
a variable reactance having a reactance value responsive to the
pressure exerted by said region against the surface;
the housing being constructed so that waves having magnetic
components can be coupled without wires between a reactance of the
tuned circuit and a structure outside of the housing,
means in proximity to the region for generating and supplying a
magnetic field to the position detecting coils for the implement;
and
means responsive to the magnetic field coupled between the
implement and the coils for signalling the position of the
implement relative to the two coordinate directions, the signalling
means responding to variations of the variable reactance to
indicate the width of a line as a function of
implement position on the surface. .Iaddend. .Iadd.18. The
combination of claim 17 wherein the housing is formed as a writing
pen. .Iaddend.
.Iadd. . The combination of claim 17 wherein the variable reactance
has at least several values correlated with at least several of
said exerted pressures, the signalling means responding to the at
least several values of the reactance to indicate which of the at
least several pressures is
being exerted. .Iaddend. .Iadd.20. In combination,
a tablet including position detecting coils arranged in two
coordinate directions, a markable surface superposed with said
tablet in said two coordinate directions,
a manually held implement for changing markings on the display
surface including
an inductor and a capacitor, and
a switch activated while a region of the implement is proximate the
surface for connecting the capacitor and inductor in circuit with
each other so that the tuned circuit has a predetermined resonant
frequency;
the housing being constructed so that waves having a magnetic
component can be coupled without wires between a reactance of the
tuned circuit and a structure outside of the housing,
means in proximity to the region for generating and supplying a
magnetic field to the position detecting coils for the implement,
the position detecting coils being in proximity to and associated
with the display, and
means responsive to the magnetic field coupled between the
implement and the coils while the switch is activated for
signalling the position of the
implement relative to the two coordinate directions. .Iaddend.
.Iadd.21. The combination of claim 20 wherein the tuned circuit
includes a variable reactance having a reactance value responsive
to the pressure exerted by said region against the surface, wherein
the signalling means responds to variations of the variable
reactance to indicate the pressure of the implement on the surface
as a function of implement position on the
surface. .Iaddend. .Iadd.22. The combination of claim 21 wherein
the variable reactance has at least several values responsive to at
least several pressures exerted by said region against the surface.
.Iaddend.
.Iadd.23. The combination of claim 20 wherein the housing is formed
as a writing pen. .Iaddend. .Iadd.24. The combination of claim 20
wherein said implement has different characteristics associated
with it, said housing further including:
(a) a plurality of said tuned circuits, each of said tuned circuits
having reactances with different values, and
(b) switch means for selectively connecting the reactances of the
different plural tuned circuits in circuit with each other as a
function of the
selected characteristic of the implement. .Iaddend. .Iadd.25. The
combination of claim 20 wherein the switch is activated in response
to the region being urged against the surface. .Iaddend. .Iadd.26.
A method of identifying which one of plural characteristics is
possessed by an object in proximity to a coil and determining the
location of the object, each of the characteristics being
associated with different valued reactances of a tuned circuit on
the object so that different tuned circuits are associated with
different characteristics, the different valued reactances causing
the tuned circuit to couple waves including a magnetic component
and having different angular modulations with the coil, the method
comprising the steps of supplying the coil with AC energy including
a predetermined frequency, coupling the energy from the coil to the
tuned circuit on the object, the tuned circuit on the object
interacting with the energy coupled with it as a function of the
value of the reactances of the tuned circuit so that there is a
different angular modulation of the waves coupled between the coil
and the tuned circuit as a function of the characteristics
associated with the different tuned circuits and the predetermined
frequency, detecting the angular modulation of the waves coupled
between the coil and the tuned circuit to identify the
characteristic of the object, and detecting the position of the
object by coupling energy between the object and a region including
the coil, said region including a two dimensional array of
detectors that interact with
the coupled energy. .Iaddend. .Iadd.27. The method of claim 26
wherein the energy at the predetermined frequency is coupled from
the coil to the tuned circuit on the object during a first interval
and the wave having angular modulation is coupled from the tuned
circuit on the object to the coil during a second interval while
the energy at the predetermined frequency is not coupled to the
coil. .Iaddend. .Iadd.28. The method of claim 27 wherein the
angular modulation is phase modulation and the detecting step
includes detecting the phase of the phase modulation of the
electric wave coupled to the coil during the second interval.
.Iaddend.
.Iadd.29. A method of identifying a characteristic of an implement
from one of plural different characteristics, the implement
including: (a) means for modifying markings on a display surface
while a region of the implement is proximate the display surface
and (b) a tuned circuit with components selectively connected to
each other to have a predetermined resonant frequency while the
region of the implement is proximate the surface, the identified
characteristic being associated with a tuned circuit having one of
plural reactance combinations, each of said plural different
characteristics being associated with one of said plural reactance
combinations,
the method comprising
modifying the markings on the display surface by moving the region
proximate the display surface while the reactances are connected to
each other in one of said reactance combinations to provide a tuned
circuit having the resonant frequency,
determining which one of the reactance combinations the tuned
circuit has by coupling a wave having a magnetic component at the
resonant frequency between a coil and the tuned circuit, the tuned
circuit interacting with the wave coupled with it as a function of
the value of the reactances of the tuned circuit so that there is
different angular modulation of the wave coupled between the coil
and the tuned circuit is a function of the characteristics
associated with the different tuned circuits and the predetermined
frequency, and
detecting the angular modulation of the waves coupled between the
coil and the tuned circuit to identify the characteristic of the
implement being
moved proximate the display surface. .Iaddend. .Iadd.30. The method
of claim 29 wherein the wave is coupled from a source of the
frequency to the tuned circuit. .Iaddend. .Iadd.31. The method of
claim 30 wherein the wave is coupled from the source to the tuned
circuit during a first interval and the angle modulated wave is
coupled from the tuned circuit to a detector for the predetermined
frequency during a second interval. .Iaddend. .Iadd.32. The method
of claim 31 further including the step of detecting the position of
the object by coupling energy between the object and a region
including the surface, said region including a two dimensional
array of detectors that interact with the coupled energy.
.Iaddend. .Iadd.33. The method of claim 29 further including the
step of detecting the position of the object by coupling energy
between the object and a region including the surface, said region
including a two dimensional array of detectors that interact with
the coupled energy.
.Iaddend. .Iadd.34. In combination, a coil, an object having one of
plural different predetermined characteristics, the object being
adapted to be selectively in proximity to the coil, the object
including a tuned circuit having a predetermined resonant
frequency, different one of said characteristics being associated
with different combinations of reactances of the tuned circuit,
means for supplying AC energy at the resonant frequency to the
coil, the tuned circuit on the object in proximity to the coil
interacting with a wave including a magnetic component resulting
from the energy coupled to the coil as a function of the value of
the reactances of the tuned circuit so that there is different
angular modulation of the waves coupled between the coil and the
turned circuit as a function of the characteristics associated with
the different tuned circuits and the predetermined frequency, means
for detecting the angular modulation of the waves coupled between
the coil and the tuned circuit to identify the characteristic of
the object, and means for detecting the position of the identified
object, said position detecting means coupling energy between the
object and a region including the coil, said region including a
two-dimensional array of detectors for interacting with the
coupled energy. .Iaddend. .Iadd.35. The combination of claim 34
wherein the modulation is detected by supplying the coil during a
first interval with the AC energy at the predetermined frequency,
the means for detecting being activated to be responsive to energy
coupled back to the coil from the tuned circuit during a second
interval while the coil is not supplied with the AC energy at the
one predetermined frequency. .Iaddend.
.Iadd. The combination of claim 34 wherein the object is in the
form
of a pen. .Iaddend. .Iadd.37. The combination of claim 34 wherein
said object further includes:
(a) a plurality of said tuned circuits, each of said tuned circuits
having reactances with different values, and
(b) switch means for selectively connecting the reactances of the
different plural tuned circuits in circuit with each other as a
function of a selected characteristic of the object. .Iaddend.
.Iadd.38. The combination of claim 34 further including a surface
in proximity to the coil, the object including
a cordless housing adapted to be manually held and manually moved
relative to the tablet, the housing including:
means positioned in a region thereof adapted to be moved proximate
the tablet,
the tuned circuit having no electric power supply connected to it,
the tuned circuit including
an inductor and a capacitor, and
a switch activated in response to the region being proximate the
tablet for connecting the capacitor and inductor in circuit with
each other so that the tuned circuit has a predetermined resonant
frequency;
the housing being constructed so that waves having magnetic
components can be coupled without wires between a reactance of the
tuned circuit and a
structure outside of the housing. .Iaddend. .Iadd.39. The
combination of claim 38 wherein the switch is activated in response
to the region being urged against the surface. .Iaddend. .Iadd.40.
Apparatus for determining which one of plural different
characteristics is possessed by an object in a region and the
position of the object, different ones of said characteristics
being associated with different tuned circuit combinations of
reactances, each of said tuned circuit combinations having a
different resonant frequency, comprising a coil in the region,
means for supplying AC energy at the resonant frequency to the
coil, the tuned circuit on said object in proximity to the coil
interacting with an electric wave resulting from the energy coupled
to the coil as a function of the value of the reactances of the
tuned circuit so that there is a different angular modulation of
the waves coupled between the coil and the tuned circuit as a
function of the characteristics associated with the different tuned
circuits and the frequency of the supplied AC energy, means for
detecting the angular modulation of the wave coupled between the
coil and the tuned circuit to identify the characteristic of the
object, and means for detecting the position of the identified
object, said position detecting means coupling energy between the
object and a region including the coil, said region including a
two-dimensional array of detectors for
interacting with the coupled energy. .Iaddend. .Iadd.41. The
apparatus of claim 40 wherein the modulation is detected by
supplying the coil during a first interval with the AC energy at
the predetermined frequency, the means for detecting being
activated to be responsive to energy coupled back to the coil from
the tuned circuit during a second interval while the coil is not
supplied with the AC energy at the one predetermined frequency.
.Iaddend. .Iadd.42. Apparatus for determining the position of and
which one of plural characteristics is included in an implement
positioned proximate a detecting surface, the implement including a
tuned circuit having a predetermined resonant frequency identifying
the characteristic, different tuned circuits with different
combinations of reactances being associated with the different
characteristics, comprising
a tablet in the region for coupling energy to the implement,
a coil associated with the tablet for supplying AC energy at the
resonant frequency to the tuned circuit, the tuned circuit on the
implement causing angle modulation of the current flowing in the
coil, the angle modulation being different for different ones of
said tuned circuits to provide an identification of the different
characteristics, and
means for sensing the angle modulation of the current flowing in
the coil and responding to the sensed angle modulation for
indicating the identified characteristic associated with the tuned
circuit and responsive to energy coupled between the tablet and the
implement for indicating the position of the implement on the
tablet. .Iaddend. .Iadd.43. The apparatus of claim 42 wherein the
angle modulation is detected by supplying the coil during a first
interval with the AC energy at the predetermined frequency, the
means for sensing being activated to be responsive to energy
coupled back to the coil from the tuned circuit during a second
interval while the coil is not supplied with the AC energy at the
predetermined frequency. .Iaddend. .Iadd.44. In combination, a
position sensing tablet, a coil associated with the tablet, an
implement having one of plural characteristics adapted to be
selectively placed proximate the tablet, the tablet and the
implement having structures for coupling energy between them, the
implement including a tuned circuit having a predetermined resonant
frequency, different tuned circuits with different combinations of
reactances associated with the different characteristics, means for
supplying AC energy at the predetermined resonant frequency to the
tuned circuit, the tuned circuit on the implement causing angle
modulation of the current flowing in the coil, the angle modulation
being different for different ones of said tuned circuits to
provide an identification of the different characteristics, and
means for sensing the angle modulation of the current flowing in
the coil and responding to the sensed angle modulation for
indicating the identified characteristic associated with the tuned
circuit and responsive to energy coupled between the tablet and the
implement for indicating the position of the implement on the
tablet. .Iaddend. .Iadd.45. The combination of claim 44 wherein the
change is detected by supplying the coil during a first interval
with the AC energy at the predetermined frequency, the means for
sensing being activated to be responsive to energy coupled back to
the coil from the tuned circuit during a second interval while the
coil is not supplied with the AC energy at the one
predetermined frequency. .Iaddend. .Iadd.46. A method of
determining the position of an implement on a tablet, the implement
including a tuned circuit with a predetermined resonant frequency
and a variable reactance connected in circuit with the tuned
circuit, the variable reactance having at least several values that
change as a function of at least several pressures exerted by the
implement on a surface proximate the tablet, the tablet including a
coil, comprising the steps of:
exciting the coil with AC energy having approximately the same
frequency as the resonant frequency, the tuned circuit interacting
with the AC energy to change the AC current flowing in the coil as
a function of the at least several exerted pressures, detecting the
position of the implement on the tablet in response to an energy
field coupled between the tablet and the implement, and responding
to the AC current flowing in the coil and the detected implement
position to indicate the value of the at least several exerted
pressures at the detected implement positions on the surface.
.Iaddend. .Iadd.47. The method of claim 46 wherein the exerted
pressure is indicated by detecting angle modulation imposed on the
current flowing in the coil in response to the interaction between
the AC energy and the tuned circuit. .Iaddend. .Iadd.48. The method
of claim 46 wherein the exerted pressure is indicated by detecting
phase modulation imposed on the current flowing in the coil in
response to the interaction between the AC energy and the tuned
circuit. .Iaddend. .Iadd.49. The method of claim 46 wherein the
coil is excited during a first interval with the AC energy at the
predetermined frequency, and the indication is derived by
responding to energy coupled back to the coil from the tuned
circuit during a second interval while the coil is not excited by
the AC energy at the
predetermined frequency. .Iaddend. .Iadd.50. Apparatus for
signalling the width of a trace resulting from an implement being
moved relative to and against a surface, the implement including a
region adapted to be moved across and against the surface and a
tuned circuit having a resonant frequency, the circuit including a
variable reactance controlled in response to the width of a trace
produced in response to the pressure of the region on the surface,
the apparatus including a coil in proximity to the surface, means
for energizing the coil with an AC wave having substantially the
same frequency as the resonant frequency, the tuned circuit
interacting with the AC wave to angle modulate the AC wave as a
function of the width of the trace, and means for detecting the
angle modulation of the angle modulated AC wave to indicate trace
width.
.Iaddend. .Iadd.51. The apparatus of claim 50 wherein the means for
indicating exerted pressure includes means for detecting angle
modulation imposed on the current flowing in the coil in response
to the interaction between the AC energy and the tuned circuit.
.Iaddend. .Iadd.52. The apparatus of claim 50 wherein the means for
indicating exerted pressure includes means for detecting phase
modulation imposed on the current flowing in the coil in response
to the interaction between the AC energy
and the tuned circuit. .Iaddend. .Iadd.53. The apparatus of claim
50 wherein the angle modulation is detected with a detector
responsive to the angle modulation of angle modulated current
flowing in the coil in response to the interaction between the AC
wave and the tuned circuit. .Iaddend. .Iadd.54. The apparatus of
claim 53 wherein the coil is energized with the resonant frequency
during a first interval and the detector is responsive to the angle
modulated current during a second interval while the coil is not
energized with the resonant frequency.
.Iaddend. .Iadd.55. The implement of claim 50 wherein the reactance
is responsive to the pressure exerted by the region on the surface
so that the modulation is a function of the pressure exerted by the
region against the surface. .Iaddend. .Iadd.56. The apparatus of
claim 50 wherein the variable reactance has at least several values
corresponding to at least several trace widths so that the angle
modulation has at least several values, the means for detecting
indicating the value of the at least
several angle modulated values. .Iaddend. .Iadd.57. A method of
signalling the width of a trace resulting from an implement being
moved relative to and against a surface, the implement including a
region adapted to be moved across and against the surface and a
tuned circuit having a resonant frequency, the circuit including a
variable reactance controlled in response to the width of a trace
produced by the region on the surface, comprising energizing a coil
in proximity to the surface with an AC wave having substantially
the same frequency as the resonant frequency, the tuned circuit
interacting with the AC wave to angle modulate the AC wave as a
function of the width of the trace resulting from the region being
pressed on the surface, and detecting the angle modulation of the
angle modulated AC wave to indicate trace width.
.Iaddend. .Iadd.58. The method of claim 57 wherein the angle
modulation is detected by detecting the angle modulated current
flowing in the coil in response to the interaction between the AC
wave and the tuned circuit. .Iaddend. .Iadd.59. The method of claim
58 wherein the coil is energized with the resonant frequency during
a first interval and the angle modulation of the angle modulated
current is detected during a second interval while the coil is not
energized with the resonant
frequency..Iaddend. .Iadd.60. The method of claim 57 wherein the
reactance is responsive to the pressure exerted by the region on
the surface so that the modulation is a function of the pressure
exerted by the region against the surface. .Iaddend. .Iadd.61. In
combination,
an implement including a region adapted to be moved across a
surface and a tuned circuit having a resonant frequency, the
circuit including a variable reactance controlled in response to
the width of a trace resulting from the region being on the
surface,
apparatus for signalling the width of the trace resulting from the
implement being on the surface, the apparatus including:
a coil in proximity to the surface,
means for energizing the coil with an AC wave having substantially
the same frequency as the resonant frequency, the tuned circuit
interacting with the AC wave to angle modulate the AC wave as a
function of the width of the trace produced by the region on the
surface, and
means for detecting the angle modulation of the angle modulated AC
wave to
indicate line width. .Iaddend. .Iadd.62. The combination of claim
61 wherein the angle modulation is detected with a detector
responsive to the angle modulation of angle modulated current
flowing in the coil in response to the interaction between the AC
wave and the tuned circuit. .Iaddend. .Iadd.63. The combination of
claim 62 wherein the coil is energized with the resonant frequency
during a first interval and the detector is responsive to the angle
modulated current during a second interval while the coil is not
energized with the resonant frequency.
.Iaddend. .Iadd.64. The combination of claim 61 further including
means for indicating the position of the implement and the
accompanying detected pressure on the surface. .Iaddend. .Iadd.65.
The implement of claim 61 wherein the reactance is responsive to
the pressure exerted by the region on the surface so that the
modulation is a function of the pressure
exerted by the region against the surface. .Iaddend. .Iadd.66. In
combination, a coil, an object having one of plural different
predetermined characteristics, the object being adapted to be
selectively in proximity to the coil, the object including a tuned
circuit having a predetermined resonant frequency, different ones
of said characteristics being associated with different
combinations of reactances of the tuned circuit, means for
supplying AC energy at the resonant frequency to the coil, the
tuned circuit on the object in proximity to the coil interacting
with a wave including a magnetic component resulting from the
energy coupled to the coil as a function of the value of the
reactances of the tuned circuit so that there is different angular
modulation of the waves coupled between the coil and the tuned
circuit as a function of the characteristics associated with the
different tuned circuits and the predetermined frequency, and means
for detecting the angular modulation of the waves coupled between
the coil and the tuned circuit to identify the characteristic of
the object, the object further including means for generating and
supplying a field including a magnetic component to a tablet
including two-coordinate position detecting coils for the object,
the position detecting coils responding to the field to signal the
object
position. .Iaddend. .Iadd.67. In combination, a coil, an object in
the form of a pen having one of plural different predetermined
characteristics, the object being adapted to be selectively in
proximity to the coil, the object including a tuned circuit having
a predetermined resonant frequency, different ones of said
characteristics being associated with different combinations of
reactances of the tuned circuit, means for supplying AC energy at
the resonant frequency to the coil, the tuned circuit on the object
in proximity to the coil interacting with a wave including a
magnetic component resulting from the energy coupled to the coil as
a function of the value of the reactances of the tuned circuit so
that there is different angular modulation of the waves coupled
between the coil and the tuned circuit as a function of the
characteristics associated with the different tuned circuits and
the predetermined frequency, and means for detecting the angular
modulation of the waves coupled between the coil and the tuned
circuit to identify the characteristic of the object. .Iaddend.
.Iadd.68. In combination, a position detecting tablet including a
coil, an object having one of plural different predetermined
characteristics, the object being adapted to be selectively in
proximity to the coil, the object including a tuned circuit having
a predetermined resonant frequency, different ones of said
characteristics being associated with different combinations of
reactances of the tuned circuit, means for supplying AC energy at
the resonant frequency to the coil, the tuned circuit on the object
in proximity to the coil interacting with a wave including a
magnetic component resulting from the energy coupled to the coil as
a function of the value of the reactances of the tuned circuit so
that there is different angular modulation of the waves coupled
between the coil and the tuned circuit as a function of the
characteristics associated with the different tuned circuits and
the predetermined frequency, and means for detecting the angular
modulation of the waves coupled between the coil and the tuned
circuit to identify the characteristic of the object,
the object including
a cordless housing adapted to be manually held and manually moved
relative to the tablet, the housing including:
means positioned in a region thereof adapted to be moved proximate
the tablet,
the tuned circuit having no electric power supply connected to it,
the tuned circuit including
an inductor and a capacitor, and
a switch activated in response to the region being proximate the
tablet for connecting the capacitor and inductor in circuit with
each other so that the tuned circuit has a predetermined resonant
frequency;
the housing being constructed so that waves having magnetic
components can be coupled without wires between a reactance of the
tuned circuit and a structure outside of the housing. .Iaddend.
.Iadd.69. In combination, a coil, an object having one of plural
different predetermined characteristics, the object being adapted
to be selectively in proximity to the coil, the object including a
tuned circuit having a predetermined resonant frequency, different
ones of said characteristics being associated with different
combinations of reactances of the tuned circuit, means for
supplying AC energy at the resonant frequency to the coil, the
tuned circuit on the object in proximity to the coil interacting
with a wave including a magnetic component resulting from the
energy coupled to the coil as a function of the value of the
reactances of the tuned circuit so that there is different angular
modulation of the waves coupled between the coil and the tuned
circuit as a function of the characteristics associated with the
different tuned circuits and the predetermined frequency, and means
for detecting the angular modulation of the waves coupled between
the coil and the tuned circuit to identify the characteristic of
the object, the object further including means for generating and
supplying a field including a magnetic component to a tablet
including two-coordinate position detecting coils for the object,
the position detecting coils responding to the field to signal the
object position. .Iaddend. .Iadd.70. A manually held implement
adapted to be urged against a surface comprising:
a cordless housing shaped as a writing pen adapted to be manually
held and manually moved on the surface, the housing including:
a region adapted to be moved across the surface,
a tuned circuit having no electric power supply connected to it,
the tuned circuit including
a variable pressure responsive reactance coupled to the region so
that the width of a trace resulting from the region being on the
surface is determined by the value of the variable reactance, the
housing being constructed so that waves having a magnetic component
are coupled without wires between a reactance of the tuned circuit
and a structure outside of the housing. .Iaddend. .Iadd.71. A
signalling method comprising moving a region of an implement
including a tuned circuit having a resonant frequency against a
surface, varying the value of a reactance of the tuned circuit in
response to the pressure exerted by the region on the surface as
the implement is being moved relative to the surface, energizing a
coil in proximity to the surface with an AC wave having
substantially the same frequency as the resonant frequency, the
tuned circuit interacting with the AC wave to angle modulate the AC
wave as a function of the pressure exerted by the region on the
surface, and detecting the angle modulation of the angle modulated
AC wave to indicate the exerted pressure. .Iaddend. .Iadd.72. The
method of claim 71 wherein the detected exerted pressure is
commensurate with the width of a trace resulting from the region
being pressed against the surface. .Iaddend. .Iadd.73. The method
of claim 72 further including detecting the position of the region
on the surface accompanying the detected trace width. .Iaddend.
.Iadd.74. The method of claim 71 further including detecting the
position of the region on the
surface accompanying the detected exerted pressure. .Iaddend.
.Iadd.75. A method of detecting the status of an implement in a
coordinate input device comprising:
emitting a wave having a magnetic component from an emitting means
of a position detecting tablet,
responding to the emitted wave to excite a tuned circuit in a
position designating implement, the tuned circuit when excited
emitting a wave having a frequency determined by the resonant
frequency of the tuned circuit,
receiving a wave having a magnetic component in a wave receiving
means of said tablet, and
deriving an indication of the status of said position designating
implement in response to the received wave being the wave emitted
by the tuned circuit, said waves emitted from and received by the
tablet being emitted
and received in the same loop coil. .Iaddend. .Iadd.76. The method
of claim 75 wherein said waves emitted from and received by the
tablet are
alternately emitted and received. .Iaddend. .Iadd.77. A method of
detecting a pen-down status of a stylus in a coordinate input
device comprising:
emitting a wave having a magnetic component from an emitting means
of a position detecting table,
responding to the emitted wave to excite a tuned circuit in a
position designating implement, the tuned circuit when excited
emitting a wave having a frequency determined by the resonant
frequency of the tuned circuit,
receiving a wave having a magnetic component in a wave receiving
means of said tablet, and
deriving an indication that the stylus is in a pen-down status in
response to the received wave being the wave emitted by the tuned
circuit, said waves emitted from and received by the tablet being
emitted and received
in the same loop coil. .Iaddend. .Iadd.78. The method of claim 77
wherein said waves emitted from and received by the tablet are
alternately emitted and received. .Iaddend. .Iadd.79. A method of
determining which of plural switches is being operated in a
position designating implement of a coordinate input device, each
of the switches being associated with a different resonant
frequency of a tuned circuit means, comprising:
emitting a wave having a magnetic component from an emitting means
of a position detecting tablet,
responding to the emitted wave to excite the tuned circuit means as
a function of which of the switches is operated by handling, the
resonant circuit when excited emitting a wave having a frequency
determined by the activated switch,
receiving the wave emitted by the tuned circuit means in a wave
receiving means of said tablet, and
detecting which resonant circuit emits the wave received by said
wave receiving means to determined which switch is being operated.
.Iaddend. .Iadd.80. The method of claim 79 wherein said waves
emitted from and received by the tablet are emitted and received in
the same loop coil.
.Iaddend. .Iadd.81. The method of claim 80 wherein said waves
emitted from and received by the tablet are alternately emitted and
received. .Iaddend. .Iadd.82. The method of claim 79 wherein said
waves emitted from and received by the tablet are alternately
emitted and received. .Iaddend.
.Iadd.83. An implement having different characteristics associated
therewith for designating one of the characteristics and a position
to be detected by a tablet including means for signalling
indications of the implement characteristic and position
comprising
a cordless housing adapted to be manually held and manually moved
proximate a surface of the tablet, the housing including:
a plurality of tuned circuits having no electric power supply
connected to them, the plurality of tuned circuits including
an inductive and a capacitive reactance, each of said tuned
circuits having reactances with different values,
a switch adapted to be activated while a region of the implement
moves proximate the surface for connecting the capacitor and
inductor in circuit with each other so that the tuned circuit has a
predetermined resonant frequency, and
switch means for selectively connecting the reactances of the
different plural tuned circuits in circuit with each other as a
function of the selected characteristic of the implement;
the housing being constructed so that waves having a magnetic
component can be coupled without wires between a reactance of the
tuned circuit and structure outside of the housing. .Iaddend.
.Iadd.84. An implement having different characteristics associated
therewith for signalling one of the characteristics and position
thereof to position detecting coils for a tablet associated with a
surface with which the implement is adapted to be moved
comprising:
a cordless housing adapted to be manually held and manually moved
relative to the surface, the housing including:
a region adapted to be moved relative to the surface,
a plurality of tuned circuits having no electric power supply
connected to them, the plurality of tuned circuits including
an inductive and capacitive reactance, each of said tuned circuits
having a reactance with a different value,
a switch adapted to be activated while a region of the implement
moves proximate the surface for connecting the capacitor and
inductor in circuit with each other so that the tuned circuit has a
predetermined resonant frequency, switch means for selectively
connecting the reactances of the different plural tuned circuits in
circuit with each other as a function of the selected
characteristic of the implement:
the housing being constructed so that waves having a magnetic
component can be coupled without wires between a reactance of the
tuned circuit and a structure outside of the housing, and
means in proximity to the region for generating and supplying a
magnetic field to the position detecting coils for the implement.
.Iaddend.
.Iadd. . In combination,
a tablet including position detecting coils arranged in two
coordinate directions,
a manually held implement having different characteristics
associated with it and a region adapted to be moved relative to a
surface of the tablet associated with the position detecting coils,
the implement including:
a cordless housing adapted to be manually held and manually moved
relative to the surface, the housing including:
a plurality of tuned circuits having no electric power supply
connected to them, the tuned circuits including
an inductive and capacitive reactance,
each of said tuned circuits having reactances with different
values, and
switch means for selectively connecting the reactances of the
different plural tuned circuits in circuit with each other to
provide different resonant frequencies of the tuned circuits as a
function of the selected characteristic of the implement;
the housing being constructed so that waves having magnetic
components can be coupled without wires between a reactance of the
tuned circuit and a structure outside of the housing;
means in proximity to the region for generating and supplying a
magnetic field to the position detecting coils for the implement;
and
means responsive to the magnetic field coupled between the
implement and the coils for signalling the characteristic of the
implement and the position of the implement relative to the two
coordinate directions.
.Iaddend. .Iadd.86. A method of detecting the status of an
implement in a coordinate input device comprising:
emitting a wave having a magnetic component from an emitting means
of a position detecting tablet,
responding to the emitted wave to excite a tuned circuit in a
position designating implement, the tuned circuit when excited
emitting a wave having a frequency determined by the resonant
frequency of the tuned circuit,
receiving a wave having a magnetic component in a wave receiving
means of said tablet, and
deriving an indication of the status of said position designating
implement in response to the received wave being the wave emitted
by the tuned circuit, said waves emitted from said received by the
tablet being
alternately emitted and received. .Iaddend. .Iadd.87. A method of
detecting a pen-down status of a stylus in a coordinate input
device comprising:
emitting a wave having a magnetic component from an emitting means
of a position detecting tablet,
responding to the emitted wave to excite a tuned circuit in a
position designating implement, the tuned circuit when excited
emitting a wave having a frequency determined by the resonant
frequency of the tuned circuit,
receiving a wave having a magnetic component in a wave receiving
means of said tablet, and
deriving an indication that the stylus is in a pen-down status in
response to the received wave being the wave emitted by the tuned
circuit, said waves emitted from and received by the tablet being
alternately emitted and received. .Iaddend. .Iadd.88. A
characteristic and position designating implement in a coordinate
input device, comprising:
a housing shaped to be manually held,
plural tuned circuits each having a different predetermined
resonant frequency associated with a different characteristic of
the implement and a separate switch, said circuits being carried by
said housing, said tuned circuits being excited by a wave including
a magnetic component as emitted from a tablet and coupling a wave
including a magnetic component to said tablet. .Iaddend. .Iadd.89.
A manually held implement adapted to be urged against a surface
comprising:
a cordless housing adapted to be manually held and manually moved
on the surface, the housing including:
a region adapted to be moved across the surface,
a tuned circuit having no electric power supply connected to it,
the tuned circuit including
a variable reactance coupled to the region so that at least several
pressures produced by the region on the surface control the at
least several values of the variable reactance, the housing being
constructed so that waves having a magnetic component can be
coupled without wires between a reactance of the tuned circuit and
a structure outside of the housing. .Iaddend. .Iadd.90. A method of
signalling the width of a trace resulting from an implement being
moved relative to and against a surface, the implement including a
region adapted to be moved across and against the surface and a
tuned circuit having a resonant frequency, the circuit including a
variable reactance having at least several values controlled in
response to at least several pressures produced by the region on
the surface, comprising energizing a coil in proximity to the
surface with an AC wave having substantially the same frequency as
the resonant frequency, the tuned circuit interacting with the AC
wave to angle modulate the AC wave as a function of the at least
several pressures produced by the region on the surface, and
detecting the angle modulation of the angle modulated AC wave to
indicate which of the at least several pressures is being exerted
on the surface and the trace width. .Iaddend. .Iadd.91. In
combination,
an implement including a region adapted to be moved across a
surface and a tuned circuit having a resonant frequency, the
circuit including a variable reactance having at least several
values controlled in response to at least several pressures
produced by the region on the surface,
apparatus for signalling the at least several pressures produced by
the implement on the surface, the apparatus including:
a coil in proximity to the surface,
means for energizing the coil with an AC wave having substantially
the same frequency as the resonant frequency, the tuned circuit
interacting with the AC wave to angle modulate the AC wave to at
least several values as a function of the at least several
pressures produced by the region on the surface, and
means for detecting the value of the at least several values of the
angle modulation of the angle modulated AC wave to indicate which
of the at least several pressures is being exerted on the surface.
.Iaddend. .Iadd.92. A position designating implement in a
coordinate input device, comprising:
a housing,
a tuned circuit carried by the housing, the circuit having a
resonant frequency varied in response to handling, said tuned
circuit being excited by a wave having a magnetic component as
emitted from a tablet to couple a wave having a magnetic component
to said tablet, the resonant frequency being varied to at least
several values by at least several pressures of a structure in the
housing on the tablet surface. .Iaddend.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a coordinate input system and,
more particularly, to a coordinate input system which is capable of
detecting the status of a position designating device which has
designated only the position of coordinates to be input as well as
the status of various types of operation designated by the
same.
2. Statement of the Related Art
Hitherto, a system has been known for detecting the status
(hereafter referred to as the "pen-down status") of a position
designating device which has designated only the position of
coordinates to be input on a tablet. This system is arranged such
that a switching means is provided in the position designating
device and is turned ON (or OFF) only in the pen-down status, and
timing signals based on the ON (or OFF) status of the switching
means are transmitted to a position detecting circuit via a cord or
by the use of ultrasonic waves or infrared ways.
However with a system of the type in which timing signals are
transmitted from the position designating device via a cord, there
has been a drawback in that the cord causes a hindrance to he
operating efficiency of the position designating device. In
addition, with a system of the type in which timing signals are
transmitted by the use of ultrasonic waves or infrared rays, a
transmitter, a signal generating circuit, a battery, and the like
must be provided in the position designating device per se. Hence,
there has been a drawback in that the arrangement of the position
designating device becomes complicated and large in size and
weight, thereby aggravating the operating efficiency of the
position designating device.
SUMMARY OF THE INVENTION
Accordingly, a primary object of the present invention is to
provide a coordinate input system which is capable of detecting the
status of a position designating device without deteriorating the
operating efficiency of the position designating device.
To this end, according to the present invention, there is provided
a coordinates input system having a tablet constituting a
coordinates input portion, a position designating device such as a
stylus pen, and a position detection circuit adapted to drive the
tablet and detect a position at which coordinates are input by the
position designating device, the system comprising: an antenna coil
disposed around a coordinates input range of the tablet; and a
tuning circuit disposed in the position designating device and
including a coil and a capacitor, wherein radio waves are generated
by the antenna coil by application of an AC signal of a
predetermined frequency thereto, and the status of the tuning
circuit is discriminated by a signal of the antenna coil at the
time when the transmission of the radio waves is suspended, thereby
detecting the status of the position designating device.
According to this aspect of the invention, the tuning circuit which
has received radio waves from the antenna coil resonates or does
not resonate with a substantially identical frequency or an
identical or different phase in correspondence with its status,
reflects or does not reflect radio waves whose frequency is
substantially identical and whose phase is identical or different.
From the fact that signals are ore are not generated by the antenna
coil which has suspended the transmission of radio waves on the
basis of the reflected radio waves, the status of the tuning
circuit can be discriminated and the status of the position
designating device can be detected. Accordingly, no cord is
required for connecting the position designating device and other
circuits, and it suffices only to provide the position designating
device with a tuning circuit, including a coil and a capacitor.
Therefore, a conventionally employed complicated signal generating
circuit, a battery and the like become unnecessary, so that it is
possible to provide a position designating device which excels in
operating efficiency, and its status can be detected
accurately.
A second object of the present invention is to provide a coordinate
input system which is capable of detecting the positional status of
a position designating device as well as the status of various
types of operation designated by the same.
To this end, according to another aspect of the present invention,
there is provided a coordinates input system having a tablet
constituting a coordinates input portion, a position designating
device such as a stylus pen, and a position detection circuit
adapted to drive the tablet and detect a position at which
coordinates are input by the position designating device, the
system comprising; a plurality of tuning circuits disposed in the
position designating device, each of the plurality of tuning
circuits including a coil and a capacitor to constitute a set and
being adapted to transmit radio waves with mutually equivalent
tuning frequencies and different phases in response to an external
signal; switching means disposed in the position designating device
and adapted to turn ON and OFF the connection between the coil and
the capacitor of each of the tuning circuits; and an antenna coil
disposed around a coordinates input range of the tablet; wherein
radio waves are generated by the antenna coil when an AC signal of
a frequency identical with that of the tuning frequency is
intermittently applied t the antenna coil, the status of the
position and operation of the position designating device is
detected when signals responded to by the tuning circuits during
suspension of transmission of the radio waves are received by the
antenna coil, and the ON-OFF status of the switching means with
respect to the tuning circuits is discriminated by means of input
signals having mutually different phases with respect to output
signals of the antenna coil.
According to this aspect of the invention, when the switches of the
tuning circuits are ON, the tuning circuits resspectively transmit
signals with peculiar phase differences with respect to signal
transmitted by the antenna coil, and the antenna coil receives the
same. The positional and operational status of the position
designating device can be detected by reception of the signals.
Discrimination can be made as to which of the switches of the
position designating devices has been turned ON by input signals
having mutually different phases. Accordingly, no cord is required
for connecting the position designating device and other circuits,
and it suffices only to provide the position designating device
with a plurality of tuning circuits each including a coil and a
capacitor. Therefore, a conventionally employed complicated signal
generating circuit, a battery and the like become unnecessary, and
the operational status of the plurality of switches provided in the
position designating device can be discriminated without using a
cord, thereby permitting color designation and erasure designation
for the input pen by means of the switches. Thus, it is possible to
provide a position designating device which excels in operating
efficiency.
A third object of the present invention is to provide a coordinate
input system which is capable of detecting the positional status of
a position designating device, the status of its use, and the like
without causing any hindrance to the operating efficiency
thereof.
To this end, according to still another aspect of the present
invention, there is provided a coordinates input system having a
tablet constituting a coordinates input portion, a position
designating device such as a stylus pen, and a position detection
circuit adapted to drive the tablet and detect a position at which
coordinates are input by the position designating device, the
system comprising: a tuning circuit disposed in the position
designating device, the tuning circuit including a set of a coil, a
capacitor, and/or a resistor and being adapted to generate radio
waves with mutually equivalent tuning frequencies and a change in
the phase in response to an external signal by changing any of the
values of the coil, the capacitor, and/or the resistor in
correspondence with the status of use of the position designating
device; and an antenna coil disposed around a coordinates input
range of the tablet; wherein radio waves are generated by the
antenna coil when an AC signal of a frequency identical with that
of the tuning frequency is intermittently applied to the antenna
coil, the status of the position and operation of the position
designating device is detected when signals responded to by the
tuning circuit during suspension of transmission of the radio waves
are received by the antenna coil, and the status of use of the
position designating device is discriminated by means of the input
signals having mutually different phases with respect to output
signals of the antenna coil.
According to this aspect of the invention, any of the values of the
coil, the capacitor, and the resistor of the tuning circuit changes
in accordance with the status of use of the position designating
device, which in turn causes the phase of the tuning circuit to
undergo change with respect to an input signal of the antenna coil,
and the tuning circuit thereby responds to the same and transmits a
signal. The antenna coil receives that signal. The positional and
operational status of the position designating device can be
detected by reception of the signal. The status of use of the
position designating device can be discriminated in accordance with
a change in the phase of the input signal. Accordingly, no cord is
required for connecting the position designating device and other
circuits, and it suffices only to provide the position designating
device with a tuning circuit, including a coil and a capacitor.
Therefore, a conventionally employed complicated signal generating
circuit, a battery and the like become unnecessary. In addition,
signals corresponding to the status of use of the position
designating device can be received without using a cord, and the
operational status of the switch provided in the position
designating device can be discriminated without using a cord.
Hence, it becomes possible to designate, for instance, the size of
a line drawn in correspondence with a pressing force of an input
pen. Thus, it is possible to provide a position designating device
which excels in operating efficiency.
The above and other objects, features, and advantages of the
present invention will become apparent from the following detailed
description of the invention when read in conjunction with the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view illustrating an outline of a first
embodiment of the present invention;
FIG. 2 is a cross-sectional view of an input pen;
FIG. 3 is a block diagram of a timing control circuit;
.[.FIG. 4 is a diagram illustrating waveforms of various sections
shown in FIG. 3;.].
.Iadd.FIGS. 4A-4G are respectively exemplary of waveforms at points
(A)-(G), FIG. 3; .Iaddend.
FIG. 5 is a perspective view of a position designating device
illustrating a second embodiment;
FIG. 6 is a cross-sectional view of the input pen;
FIG. 7 is a block diagram of the timing control circuit in a case
where two switches are provided;
.[.FIG. 8 is a diagram illustrating waveforms of various sections
shown in FIG. 7;.].
.Iadd.FIGS. 8A-8Gb are respectively waveforms at points (A)-(Gb),
FIG. 7; .Iaddend.
.[.FIG. 9 is a diagram illustrating the operation of a phase
detector shown in FIG. 7;.].
.Iadd.FIGS. 9A, 9B, 9C and 9D are waveforms indicating the
operation of a phase detector in FIG. 7 in response to waves
applied thereto differing in phase by 0.degree., 90.degree.,
180.degree. and 270.degree., respectively; .Iaddend.
FIG. 10 is a block diagram of the timing control circuit in a case
where four switches are provided;
.[.FIG. 11 is a waveform-diagram illustrating the operation of the
phase detector shown in FIG. 10;.].
.Iadd.FIGS. 11A, 11B, 11C and 11D are waveforms indicating the
operation of phase detectors in FIG. 10, in response to waves
applied thereto differing in phase by 0.degree., 90.degree.,
180.degree. and 270.degree., respectively; .Iaddend.
FIG. 12 is a cross-sectional view of the input pen illustrating a
third embodiment of the present invention;
FIG. 13 is a block diagram of a timing control circuit thereof;
.[.FIG. 14 is a diagram illustrating waveforms of various sections
shown in FIG. 13;.].
.Iadd.FIGS. 14A-14F are exemplary waveforms at points (A)-(F), FIG.
13; .Iaddend.
.[.FIGS. 15 and 16 are waveform diagrams illustrating the operation
of phase detectors shown in FIG. 13; and.].
.Iadd.FIGS. 15A, 15B, 15C and 15D are waveforms indicating the
operation of a phase detector in FIG. 13, in response to waves
applied thereto differing in phase by 0.degree., 90.degree.,
180.degree. and 270.degree., respectively;
FIGS. 16A, 16B, 16C and 16D are waveforms indicating the operation
of another phase detector in FIG. 13, in response to waves applied
thereto and to a phase shifter differing in phase by 0.degree.,
90.degree., 180.degree. and 270.degree., respectively; and
.Iaddend.
FIG. 17 is a diagram illustrating relationships between a pressing
force of a core member and the size of a line.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 illustrates a first embodiment of the present invention. In
the drawings, reference numeral 1 denotes a tablet; 2, a position
designating device (hereafter referred to as the "input pen"); 3, a
position detection circuit and 4, a timing control circuit.
The tablet 1 is arranged such that a tablet body 12 and an antenna
coil 13 are accommodated in a casing 11 which is made of a
non-metallic material such as a synthetic resin. The tablet body 12
is connected to the position detection circuit 3, while the antenna
coil 13 is connected to the timing control circuit 4.
The tablet body 12 is driven by the position detection circuit 3
and constitutes a detection section for detecting a position
designated by the input pen 2. The tablet body 12 is disposed
substantially in the center of the casing 11. Incidentally, a frame
14 drawn on an upper panel 11a of the casing indicates a range of
the input of coordinates thereof.
As for the tablet body 12 and the position detection circuit 3, it
is possible to use, for instance, those described in Japanese
patent Application No. 32244/1984 "Position Detection Device" (see
Japanese Patent Laid-Open No. 176133/1985) and Japanese Patent
Application No. 238532/1983 "Coordinate Position Detection Device"
(see Japanese Patent Laid-Open No. 129616/1985), both filed by the
present applicant. The former device is arranged such that a
multiplicity of magnetostrictive transmitting media are disposed
parallel with the surface of the tablet body 12 such that some of
the magnetostrictive transmitting media are disposed at right
angles with others, and magnetostrictive vibrations are imparted
periodically from one end to the other. When the input pen 2
approaches the same, the magnetostrictive vibration at that
location is enhanced by means of a bar magnet provided thereto. By
making use of this phenomenon, the position detection circuit 3
detects X-Y coordinates thereof through the time duration of
propagation to that location. One the other hand, the latter device
is arranged such that magnetostrictive media, some of which are
disposed at right angles with others, are excited by an AC current,
and inducted voltages thereof are fetched by detection coils, X-Y
coordinates are detected by making use of the phenomenon in which,
when a similar input pen approaches the same, the permeability of
the magnetostrictive media changes locally with a resultant change
in induced voltages.
The antenna coil 13 is arranged such that a conductive wire
provided with an insulation coating such as polyvinyl chloride is
disposed around the periphery of the coordinates inputting range of
the tablet body 12, i.e., in the casing of this embodiment, on the
rear surface of the upper panel 11a of the casing 11 around the
frame 14. Incidentally, although the conductive wire is given one
turn in the illustrated example, a plurality of turns may be
provided, as required.
The input pen 2 incorporates a tuning circuit 22 which includes a
magnetism generator for designating a position, e.g., a bar magnet
21, a coil, and a capacitor.
FIG. 2 illustrates a detailed structure of the input pen 2 which is
arranged as follows: A core member 24, such as a ball-point pen,
the bar magnet 21 having a through-hole capable of slidably
accommodating the core member 24, a coil spring 25, and a tuning
circuit 22 constituted by a switch 221, a coil 222 with a core, a
capacitor 223, and a variable capacitor 224 are incorporated, in
that order starting from a tip of the input pen 2, as an integral
combination inside a pen shaft 23 which is constituted by a
non-magnetic material, such as a synthetic resin, or, for instance,
aluminum. A cap 26 is installed at a rear end thereof.
The switch 221 is arranged such that, when the core member 24 is
pressed into the inside of the pen shaft 23 by, for instance,
pressing a tip thereof against the surface of the tablet, the
switch 221 is turned ON by being pressed from a rear end thereof
via the coil spring 25. In addition, as is also shown in FIG. 3,
the capacitor 223 and the variable capacitor 224 are connected to
each other in parallel. One end of the coil 222 is connected to
ends of the capacitor 223 and the variable capacitor 224 via the
switch 221, while the other end of the coil 222 is connected to the
other ends thereof, thereby constituting a known parallel resonance
circuit.
It should be noted that values of the coil 222, the capacitor 223,
and the variable capacitor 224 are selected in such a manner as to
resonate (to be tuned) with the frequency of radio waves
transmitted from the antenna coil 13.
FIG. 3 shows a detailed arrangement of the timing control circuit
4. In the drawing, reference numeral 401 denotes an oscillator;
402, a frequency demultiplication counter; 403, 404 denote NAND
gates; 405 denotes a transmission terminal; 406, a reception
terminal; 407, 408, denote reception changeover switches; 409, 410,
411, amplifiers; 412 denotes a filter; 413, a phase detector; 414,
a low-pass filter; 415, a comparator; and 416, an output
terminal.
FIG. 4 is a waveform diagram of signals in each section shown in
FIG. 3. Hereafter, a detailed description will be made of
operation.
A clock pulse of, say 910 kHz generated by the oscillator 401 is
divided into 1/2 and 1/32 by the frequency demultiplication counter
402. A pulse signal A of 455 kHz obtained by dividing the frequency
into 1/2 is input to one input terminal of the NAND gate 403, while
a pulse signal of 28.44 kHz obtained by dividing the frequency into
1/32 is input to the other input terminal. Its output is further
sent to the NAND gate 404, and becomes a signal B in which a 455
kHz pulse signal is sent or is not sent for each 28.44 kHz, as
shown in FIG. 4.
The signal B is sent to the antenna coil 13 via the transmission
terminal 405 and is transmitted as radio waves. At that juncture,
if the switch 221 is ON in the tuning circuit 22 of the input pen
2, the tuning circuit 22 resonates with radio waves that are
transmitted. Since the tuning circuit 22 continues to resonate
while being attenuated while the transmission on the transmission
side is stopped, the tuning circuit 22 generates a signal C as
shown in FIG. 4, and the signal C is transmitted as radio waves by
the coil 222 and is received by the antenna coil 13.
Since the reception changeover switches 407, 408 have already been
changed over by the aforementioned 28.44 kHz pulse signal, the
reception changeover switches 407, 408 receive signals from the
reception terminal 406 only during the period when transmission is
suspended. The input signal becomes a signal D as shown in FIG. 4
if the switch 221 of the tuning circuit 22 is ON, while the input
signal becomes a signal D' if it is OFF. The input signal D is
amplified into a signal D by the amplifiers 409, 410, a component
of noise is eliminated through a mechanical filter 412 having a
resonance frequency of 455 kH, and the signal is then is
transmitted to the phase detector 413 via the amplifier 411.
The 455 kHz pulse signal A has already been input to the phase
detector 413. At this juncture, if the phase of the input signal E
coincides with the phase of the pulse signal A, a signal F, in
which a lower half of the signal E is inverted, as shown in FIG. 4,
is output.
The signal F is converted into a flat signal by means of a low-pass
filter 414 having a sufficiently low cut-off frequency, and is
input to one input terminal of the comparator 415. A predetermined
threshold voltage VT has been input to the other input terminal of
the comparator 415, the output of the low-pass filter 414 is
compared with the threshold voltage VT, and a high (H) level signal
G is output to the output terminal 416.
Incidentally, in the case of the signal D', the signal level is
"0", including those of both signals E and F, and the level of the
signal G becomes low (L).
If the signal G is transmitted to the position detection circuit 3
on the basis of a definition that when the signal G is at high
level, the status is that of pen down, and that when it is at low
level, the status is not that of pen down, the input of a position
can be effected simply by pressing the tip of the input pen 2
against the tablet at a position where coordinates are to be input,
by operating the input pen 2 on the tablet 1.
Incidentally, although, in the foregoing embodiment, a changeover
is effected by the turning ON and OFF of the switch in the tuning
circuit 22 to determine whether or not it is a pen-down status, it
is possible to provide an alternative arrangement in which the
capacity of the capacitor in the tuning circuit is varied on the
basis of the operation of the input pen 2, and the phase of the
reflected signal is changed to alter the waveform of the signal F,
thereby making it possible to vary an output level of the low-pass
filter. Thus, the switch per se is not essential.
FIG. 5 shows a second embodiment of the present invention. In the
drawing, reference numeral 1 denotes the tablet; 2, the position
designating device (hereafter referred to as the "input pen"); and
3, the timing control circuit. The details of these components are
the same as those of the above-described first embodiment except
for the portions that are described below.
The input pen 2 incorporates the magnetism generator for
designating a position, such as the bar magnet 21, and two sets of
tuning circuits 22a, 22b, each set including the coil and the
capacitor.
FIG. 6 shows a detailed structure of the input pen 2 which is
arranged as follows: The core member 24, such as a ball-point pen,
the bar magnet 21 having a through-hole capable of slidably
accommodating the core member 24, the coil spring 25, and two sets
of tuning circuits 22a, 22b, constituted by switches 221a, 221b,
the coil 222 with an iron core, two capacitors 223a, 223b, and two
variable capacitors 224a, 224b for fine adjustment, as shown in
FIG. 7, are incorporated, in that order starting from a tip of the
input pen 2, as an integral combination inside the pen shaft 23
which is constituted by a non-magnetic material, such as a
synthetic resin. The cap 26 is installed at a rear end thereof.
The switch 221a is arranged such that, when the core member 24 is
pressed into the inside of the pen shaft 23 by, for instance,
pressing a tip thereof against the surface of the tablet, the
switch 221 is turned ON by being pressed from a rear end thereof
via the coil spring 25. The switch 221b sends a signal to a
separate host computer (not shown) each time the switch 211b is
turned ON by a pressing operation when the switch 221a is ON, and
is adapted to designate, for instance the changeover of color or
coloring of a certain portion in correspondence with the number of
ON operations thereof. In addition, as is also shown in FIG. 7, the
capacitor 223a and the variable capacitor 224a are connected to
each other in parallel. One end of the coil 222 is connected to
ends thereof via the switch 221a, while the other end of the coil
222 is connected to the other ends thereof, thereby constituting
one parallel resonance circuit 22a. The capacitor 223b, the
variable capacitor 224b, the coil 222, and the switch 221b are
similarly connected to each other. In this case, the arrangement is
such that when both switches 221a, 221b are turned ON, the other
parallel resonance circuit 22b is formed.
It should be noted that the resonance circuits 22a, 22b are set in
such a manner that the resonance circuit 22a has the same phase as
that of radio waves transmitted from the antenna coil 13 and
resonates (is tuned) with the frequency thereof, while the
resonance circuit 22b resonates with a phase difference of
180.degree. therebetween. Since the resonance circuits 22a, 22b are
set as described above, selectivity Q=R/(.omega..sub.0 L) (where
.omega..sub.0 is an angular velocity of resonance; R is a value of
resistance; and L is an inductance) changes, so that a phase shift
occurs. At the same time, although a resonance frequency also
changes, resonance is made possible.
FIG. 7 shows a detailed arrangement of the timing control circuit
4. In the drawing, reference numeral 401 denotes the oscillator
(OSC); 402, the frequency demultiplication counter; 403, 404 denote
NAND gates; 405 denotes the transmission terminal; 406, the
reception terminal; 404, 408, denote reception changeover switches;
409, 410, 411, amplifiers; 412 denotes the filter; 413, the phase
detector (PSD); 414, the low-pass filter (LPF); 415a, 415b denote
comparitors; and 416a, 416b, output terminals.
FIG. 8 is a waveform diagram of signals of various sections shown
in FIG. 7, Hereafter, a detailed description will be made of
operation.
A clock pulse of, say 910 kHz generated by the oscillator 401 is
divided into 1/2 and 1/32 by the frequency demultiplication counter
402. The pulse signal A of 455 kHz obtained by dividing the
frequency into 1/2 is input to one input terminal of the NAND gate
403, while a pulse signal of 28.44 kHz (with a pulse width of 17.6
.mu.s) obtained by dividing the frequency into 1/32 is input to the
other input terminal. Its output is further sent to the NAND gate
404, and becomes the signal B in which a 455 kHz pulse signal is
sent or is not sent for each 17.6 .mu.s, as shown in FIG. 8.
The signal B is sent to the antenna coil 13 via the transmission
terminal 405 and is transmitted as radio waves. At that juncture,
for example, if the switch 221a is ON in the tuning circuit 22a of
the input pen 2, the tuning circuit 22a resonates with the
transmitted radio waves. Since the tuning circuit 22a continues to
resonant while being attenuated while the transmission on the
transmission side is stopped, the tuning circuit 22a generates the
signal C as shown in FIG. 8, and the signal C is transmitted as
radio waves by the coil 222 and is received by the antenna coil
13.
The reception changeover switches 407, 408, which have been changed
over for each 17.6 .mu.s by the aforementioned 28.44 kHz pulse
signal, receive signals from the reception terminal 406 only during
the period of suspension of transmission. The input signal becomes
the signal D as shown in FIG. 8 if the switch 221a of the tuning
circuit 22a is ON, while the input signal becomes the signal D' if
it is OFF. The input signal D is amplified int the signal D by the
amplifiers 409, 410, a component of noise is eliminated through the
mechanical filter 412 having a resonance frequency of 455 kHz, and
the signal is then is transmitted to the phase detector 413 via the
amplifier 411. Incidentally, the amplifier 410 has an automatic
level control function to set the signal E to a fixed
amplitude.
The 455 kHz pulse signal A has already been input to the phase
detector 413. At this juncture, since the phase of the input signal
E is made to coincide with the phase of the pulse signal A, the
signal F, in which a lower half of the signal E is inverted, as
shown in FIG. 8, is output.
The signal F is converted into a flat signal by means of the
low-pass filter 414 having a sufficiently low cut-off frequency,
and is input to input terminals of the the comparators 415a, 415b.
A predetermined threshold voltage+VT has been input to the other
input terminals of the comparator 415a, the output of the low-pass
filter 414 is compared with the threshold voltage +VT, and the high
(H) level signal Ga is output to the output terminal 416a.
Incidentally, in the case of the signal D', the signal level is
"0", including those of both signals E and F, and the level (not
shown) of the signal Ga becomes low (L).
If the signal Ga is transmitted to the position detection circuit 3
on the basis of a definition that when the signal Ga is at high
level, the status is that of pen down, and that when it is at low
level, the status is not that of pen down, the input of a position
can be effected simply by pressing the tip of the input pen 2
against the tablet at a position where coordinates are to be input,
by operating the input pen 2 on the tablet 1.
In giving a description of a case where the switch 221b is
operated, description will be made of the operating waveform of the
phase detector 413 including a case where the above-described
switch 221a alone is operated.
If it is assumed that a signal obtained by the frequency
demultiplication by 1/2 of the frequency demultiplication counter
402 is e.sub.R as the input of the phase detector 413, and,
referring to FIG. 9(A), since this is a square wave having an
amplitude of 1, if an angular velocity thereof is assumed to be
.omega..sub.R, we have from the Fourier expansion the following
formula:
Furthermore, if it is assumed that a signal from the amplifier 411
is e.sub.i, and that this signal is constituted by a synchronous
component e.sub.S determined by a maximum value E.sub.S and an
angular velocity .omega..sub.S as well as a nonsynchronous
component e.sub.N which is noise and determined by a maximum value
E.sub.N and an angular velocity .omega..sub.N, since the angular
velocity .omega..sub.S =.omega..sub.R, we have
At tis juncture, if the switch 221a alone is ON, the phase of the
signal e.sub.R and that of e.sub.S are identical, and if an output
of the phase detector 413 is assumed to be e.sub.0, we have
##EQU1## Here, since a DC component is included only in the first
term sin.sup.2 .omega..sub.R t, and the remainder is an AC
component, if we focus our attention only on the DC component as
the output of the low-pass filter 414 to which the output of the
phase detection is imparted, and if that output is assumed to be
e.sub.0, from sin.sup.2 .omega..sub.R t=(1/2){1-cos 2107 .sub.R t},
we have
Formula (4) shows a mean value of the signal e.sub.0 in FIG.
9(A).
Next, when the switches 221a, 221b are turned ON, if it is assumed
that a phase difference between the signal e.sub.R and the signal
e.sub.S is .phi., then .phi.=180.degree., and if the first term of
Formula (3) is assumed to be e'.sub.0, we have
Since the second term is an AC component, the DC output e.sub.0
becomes as follows:
Since .phi.=180.degree., we have
Formula (6) shows a mean value of the signal e.sub.0 in FIG. 9 (C),
the signal e.sub.0 is input to the comparators 415a, 415b. The
comparator 415b compares the signal with a predetermined threshold
voltage-VT, and a signal Gb of low (L) level is output to the
output terminal 416b.
It should be noted that when the switch 221b is OFF, the signal
e.sub.0 is constantly greater than the threshold voltage-VT, and
its output signal Gb is constantly set to high (H) level (not
shown).
FIG. 10 illustrates an input pen which is used in place of the
input pen 2 shown in FIG. 6, and is provided with four sets of
tuning circuits RE.sub.1 -RE.sub.4 and four switches SW.sub.1
-SW.sub.4 for selectively turning them ON by an operation. In this
input pen, a shifter (SHIFT) 417 for advancing by 90.degree. the
signal e.sub.R, which is obtained by dividing the frequency by 1/2
by the frequency demultiplication counter 402, is added to the
arrangement shown in FIG. 7. Furthermore, also added to the same
are a phase detector 413' for receiving signals from the shifter
417 and those from the amplifier 411 as well as a low-pass filter
414' for fetching a DC component from its output, so as to fetch
operation signals for the switches SW.sub.1 to SW.sub.4 from four
comparators 415a-415d.
Incidentally, the above-described tuning circuits RE.sub.1
-RE.sub.4 are made to cope with, for instance, designation of
various colors, the aforementioned coloring designation, and
erasure designation by making the portion of the cap 26 of the
input pen 2 a rotary type.
Description will be given hereafter of the operation of the circuit
shown in FIG. 11, centering on portions that differ from those of
FIG. 7.
Referring again to FIG. 9, the signals e.sub.S obtained by the
tuning circuits RE.sub.1 -RE.sub.4 respectively have phase
differences of 0.degree., 90.degree., 180.degree., and 270.degree.
with respect to the to the signal e.sub.0, as shown in (A), (B),
(C), and (D). With respect to the phase differences of 90.degree.
and 270.degree., for instance, e.sub.0 equals zero if is assumed
that .phi.=90.degree. and .phi.=270.degree. in Formula (6).
Accordingly, in order to detect the signal e.sub.0 when
.phi.=90.degree. and .phi.=270.degree., the signal e.sub.R is
advanced 90.degree., as shown in FIG. 11. Consequently, cos .phi.
is replaced by sin .phi., and the output of the low-pass filter
414' in this case becomes the mean average e.sub.0 =(2/.pi.)E.sub.S
of the signal e.sub.0 of FIG. 11 (B) when .phi.=90.degree.. When
.phi.=270.degree. , said output becomes the mean value e.sub.0
=-(2/.pi.)E.sub.S of the signal shown in FIG. 11(D). Similarly,
output signals Gc, Gd are obtained by the comparators 415c,
415d.
FIGS. 12 to 17 show a third embodiment of the present invention.
The tablet 1, the position designating device 2, the position
detection circuit 3, and the timing control circuit 4 are the same
as those of the first embodiment except for the portions which will
be described below.
The input pen 2 incorporates the tuning circuit 22 which includes
the magnetism generator for designating a position, e.g., the bar
magnet 21, the coil, the capacitor, and a resistor.
FIG. 12 illustrates a detailed structure of the input pen 2 which
is arranged as follow: The core member 24, such as a ball-point
pen, the bar magnet 21 having a through-hole capable of slidably
accommodating the core member 24, the coil spring 25, and the
tuning circuit 22 constituted by the switch 221, the coil 222 with
a core, the capacitor 223, and the variable capacitor 224 for fine
adjustment, and a pressure variable capacitor 225 are incorporated,
in that order starting from the tip of the input pen 2, as an
integral combination inside the pen shaft 23 constituted by a
non-magnetic material, such as a synthetic resin. The cap 26 is
installed at a rear end thereof.
The switch 221 is arranged such that, when the core member 24 is
pressed into the inside of the pen shaft 23 by, for instance,
pressing a tip thereof against the surface of the tablet, the
switch 221 is turned ON by being pressed from a rear end thereof
via the coil spring 25. In addition, the capacity of the pressure
capacitor is adapted to change by a pressing force of the core
member 24, and is adapted to designate the size of a line to be
drawn on the basis of a change in the capacity corresponding to the
pressing force. In addition, as is also shown in FIG. 13, the
capacitor 223, the variable capacitor 224, and the pressure
variable capacitor 225 are connected to each other in parallel. One
end of the coil 222 is connected to ends thereof via the switch
221, while the other end of the coil 222 is connected to the other
ends thereof, thereby constituting the parallel resonance circuit
22.
It should be noted that the resonance circuit 22 is set by being
adjusted by the variable capacitor 224 so as to resonate (to be
tuned) with the frequency of radio waves transmitted from the
antenna coil 13. Since the capacity of the pressure variable
capacitor 225 changes, selectively Q=R/(.omega..sub.0 L) (where
.omega..sub.0 is an angular velocity of resonance; R is a value of
resistance; and L is an inductance) changes, so that a phase shift
occurs in the resonance circuit 22. At the same time, although a
resonance frequency also changes, resonance is made possible.
FIG. 13 shows a detailed arrangement of the timing control circuit
4. In the drawing, reference numeral 401 denotes the oscillator
(OSC); 402, the frequency demultiplication counter; 403, 404 denote
NAND gates; 405 denotes the transmission terminal; 406, the
reception terminal; 404, 408 denote reception changeover switches;
409, 410, 41, amplifiers; 412 denotes the filter; 413, 413' denote
phase detectors (PSD); 414 denotes the phase shifter (SHIFT); 415,
415' denote the low-pass filters (LPF); 416 denotes a phase angle
computing device (PHASE); and 417 an output terminal.
FIG. 14 is a waveform diagram of signals in each section shown in
FIG. 13. Hereafter, a detailed description will be made of
operation.
A clock pulse of, say, 910 kHz generated by the oscillator 401 is
divided into 1/2 and 1/32 by the frequency demultiplication counter
402. The pulse signal A of 455 kHz obtained by dividing the
frequency into 1/2 is input to one input terminal of the NAND gate
403, while a pulse signal of 28.44 kHz (with a pulse width of 17.6
.mu.s) obtained by dividing the frequency into 1/32 is input to the
other input terminal. Its output is further sent to the NAND gate
404, and becomes the signal B in which a 455 kHz pulse signal is
sent or is not sent for each 17.6 .mu.s, as shown in FIG. 8.
The signal B is sent to the antenna coil 13 via the transmission
terminal 405 and is transmitted as radio waves. At that juncture,
for example, if the switch 221a is ON in the tuning circuit 22a of
the input pen 2, the tuning circuit 22a resonates with the
transmitted radio waves. Since the tuning circuit 22a continues to
resonate while being attenuated while the transmission on the
transmission side is stopped, the tuning circuit 22a generates the
signal C as shown in FIG. 8, and the signal C is transmitted as
radio waves by the coil 222 and is received by the antenna coil
13.
The reception changeover switches 407, 408, which have been changed
over for each 17.6 .mu.s by the aforementioned 28.44 kHz pulse
signal, receive signals from the reception terminal 406 only during
the period of suspension of transmission. The input signal becomes
the signal D as shown in FIG. 8 if the switch 221a of the tuning
circuit 22a is ON, while the input signal becomes the signal D' if
it is OFF. The input signal D is amplified into the signal D by the
amplifiers 408, 410, a component of noise is eliminated through the
mechanical filter 412 having a resonance frequency of 455 kHz, and
the signal is then is transmitted to the phase detector 413 via the
amplifier 411. Incidentally, the amplifier 410 has an automatic
level control function to set the signal E to a fixed
amplitude.
The 455 kHz pulse signal A has already been input to the phase
detector 413. At this juncture, since the phase of the input signal
E is made to coincide with the phase of the pulse signal A, the
signal F, in which a lower half of the signal E is inverted, as
shown in FIG. 14, is output.
The shifter 414 has already advanced the pulse signal A by
90.degree. and has imparted that signal to the phase detector 413.
After receiving the signal E and the signal in which the signal A
is advanced 90.degree., the phase detector 413 delivers an output
to a signal F' which will be described below.
The signals F, F' are converted into flat signals by means of the
filters 415, 415' having sufficiently low cut-off frequencies, and
are input to the phase angle computing device 416.
Now, if it is assumed that a signal obtained by the frequency
demultiplication by 1/2 of the frequency demultiplication counter
402 is e.sub.R as the input of the phase detector 413, and,
referring to FIG. 15(A), since this is a square wave having an
amplitude of 1, if an angular velocity thereof is assumed t be
.omega..sub.R, we have from the Fourier expansion the following
formula:
Furthermore, if it is assumed that a signal from the amplifier 411
is e.sub.i, and that this signal is constituted by a synchronous
component e.sub.S determined by a maximum value E.sub.S and an
angular velocity .omega..sub.S as well as a nonsynchronous
component e.sub.N which is noise and determined constituted by a
maximum value E.sub.N and an angular velocity .omega..sub.N, since
the angular velocity .omega..sub.S =.omega..sub.R, we have
When the signals e.sub.R and e.sub.S are of the same phase, if it
is assumed that the output of the phase detector is e.sub.0 (the
signal F in FIGS. 13 and 14), we have ##EQU2## Here, since a DC
component is included only in the first term sin.sup.2
.omega..sub.R t, and the remainder is an AC component, if we focus
our attention only on the DC component as the output of the
low-pass filter 414 to which the output of the phase detection is
imparted and if that output is assumed to be e.sub.0, from
sin.sup.2 .omega..sub.R t=(1/2){1-cos 2.omega..sub.R t}, we
have
Formula (10) shows a mean value of the signal e.sub.0 in FIG.
15(A).
Next, when the capacity of the pressure variable capacitor 225
changes, and when the phase difference .phi. occurs between the
signals e.sub.R and e.sub.S, and if the first term of Formula (9)
is assumed to be e'.sub.0, we have
Since the second term is an AC component, the DC output e.sub.0
becomes as follows:
If it is assumed that .phi.=180.degree., we have
Formula (12) shows a mean value of the signal e.sub.0 in FIG.
15(C), and the signal e.sub.0 is input to the phase angle computing
device 416.
Considered next are cases where the phase differences of the signal
e.sub.S with respect to the signal e.sub.R have become 0.degree.,
90.degree., 180.degree., and 270.degree., respectively, as shown in
FIG. 15(A), (B), (C), and (D). For instance, with respect to the
phase differences of 90.degree. and 270.degree., E.sub.0 equals
zero if it is assumed that .phi. in Formula (12) equals 90.degree.
or 270.degree.. Accordingly, in order to detect the signal e.sub.0
including the region of these phase differences, the signal e.sub.R
is advanced 90.degree. by the shifter 414, as shown in FIG. 16.
Consequently, cos .phi. in Formula (12) is replaced by sin .phi.,
and if the mean value of a signal e.sub.90 (the signal F' in FIG.
13) shown in FIG. 16 is this case is assumed to be e.sub.90, the
following formula is derived
and the signal e.sub.90 is input to the phase angle computing
device 417. The phase angle computing device 416 computes the phase
angle from Formulae (12) and (13). Since e.sub.90 /e.sub.0 =sin
.phi./cos .phi., we have
thus a signal with a phase angle .phi. of Formula (14) is output
from the output terminal 417 to a microcomputer (not shown)
accommodated in the tablet 1.
It should be noted that although, in this embodiment, the
responding phase of the tuning circuit 22 is altered by the
pressure variable capacitor 225, an alternative arrangement may be
provided such that variable resistor by the use of pressure
sensitive rubber or the like may be employed, or the inductance of
the coil 222 may be made variable.
FIG. 17 is a diagram illustrating the relationships between a
pressing force (g) of the core member 24 and codes for designating
the size of a line to be drawn. A signal representing a phase angle
.phi. and output from the output terminal 417 in correspondence
with an analog-like pressing force is converted by the
microcomputer into a digital code which designates the size of a
line, and the size is thus designated. Incidentally, when the
pressing force is zero, both signals e.sub.0, e.sub.90 in Formula
(14) become zero, so that the phase angle .phi. becomes inconstant.
The phase angle computing device 416 detects that inconstancy, and
discrimination is made that the switch 221 is OFF. In carrying out
this discrimination, thresholds which slightly exceed zero may be
provided for the signals e.sub.0, e.sub.90, and a logical sum of
the result of comparison with the thresholds may be monitored. If a
definition is given that when the phase angle .phi. is thus
detected, it is a pen-down state, and that when it is inconstant,
it is not a pen-down state, and if the discriminated signal is sent
to the phase detection circuit 3, it is possible to input a
position by operating the input pen 2 on the tablet 1 and simply by
pressing the tip of the input pen 2 against the tablet at a
position where coordinates are to be input.
* * * * *