Position indicator, variable capacitor, position input device and computer system
A position indicator ( 100 ) has a variable capacitor 200 , a resonant circuit ( 36 ) configured with a position indicating coil ( 13 ) and a resonant capacitor ( 15 a ), and a rod ( 11 ). The variable capacitor ( 200 ) has a flat disc-shaped dielectric ( 1 ) having two mutually opposite surfaces ( 1 a, 1 b ), an electrode ( 2 ) provided on one surface ( 1 a ) of the dielectric ( 1 ), a hole ( 1 c ) extending between the two mutually opposite surfaces of the dielectric, a conductive portion electrically connecting both ends of the hole, and a conductive elastic member ( 3 ) provided near the other surface ( 1 b ) of the dielectric ( 1 ). The conductive elastic member ( 3 ) is arranged on one end of the rod ( 11 ). When a pen pressure in the direction of arrow “a” is applied to the other end of the rod ( 11 ), the conductive elastic member ( 3 ) is pressed against the dielectric ( 1 ) so as to be flattened, and the capacitance of the variable capacitor ( 200 ) changes in response to the change in the contact area between the conductive elastic member ( 3 ) and the dielectric ( 1 ).
1. A position indicator comprising:
a variable capacitor;
a resonant circuit configured with a position detecting coil and a capacitor connected with the variable capacitor; and
a rod passing through the position detecting coil,
wherein the variable capacitor includes a dielectric having two mutually opposite surfaces, an electrode arranged on one surface of the dielectric and having a predetermined area, a hole penetrating through the dielectric between the two mutually opposite surfaces of the dielectric, a conductive portion electrically connecting both ends of the hole to one another, and a conductive elastic member arranged near the other surface of the dielectric, and
wherein one end of the rod is connected to the conductive elastic member, and the other end of the rod serves as a position-indicating point.
2. The position indicator according to claim 1 , wherein the conductive portion is formed by inserting a conductive pin into the hole.
3. The position indicator according to claim 2 , wherein one end portion of the conductive pin in a longitudinal direction is provided with a flat pin head portion, and the other surface of the dielectric is provided with a stepped portion recessed around the hole, the depth of the stepped portion being equal to or slightly greater than the thickness of the pin head portion.
4. The position indicator according to claim 1 , wherein the conductive portion is formed by forming a conductive layer on an inner wall of the hole.
5. The position indicator according to claim 1 , wherein a contact area of the conductive elastic member and the dielectric changes in response to a pen pressure applied to the rod.
6. A variable capacitor comprising:
a dielectric having two mutually opposite surfaces;
an electrode arranged on one surface of the dielectric and having a predetermined area;
a hole penetrating through the dielectric between the two mutually opposite surfaces of the dielectric;
a conductive portion electrically connecting both ends of the hole to one another; and
a conductive elastic member arranged near the other surface of the dielectric.
7. The variable capacitor according to claim 6 , wherein the conductive portion is formed by inserting a conductive pin into the hole.
8. The variable capacitor according to claim 7 , wherein one end portion of the conductive pin in a longitudinal direction is provided with a flat pin head portion, and the other surface of the dielectric is provided with a stepped portion recessed around the hole, the depth of the stepped portion being equal to or slightly greater than the thickness of the pin head portion.
9. The variable capacitor according to claim 6 , wherein the conductive portion is formed by forming a conductive layer on an inner wall of the hole.
10. The variable capacitor according to claim 6 , wherein the conductive elastic member has a predetermined hardness so as to deform and change a contact area with the dielectric in response to a pressure applied to the conductive elastic member.
11. The variable capacitor according to claim 6 , wherein the dielectric has a flat shape.
12. A position input device comprising:
a position indicator; and
a position detector,
wherein the position indicator includes: a variable capacitor; a resonant circuit configured with a position detecting coil and a capacitor connected with the variable capacitor; and a rod passing through the position detecting coil, where the variable capacitor has a dielectric having two mutually opposite surfaces, an electrode arranged on one surface of the dielectric and having a predetermined area, a hole penetrating through the dielectric between the two mutually opposite surfaces of the dielectric, a conductive portion electrically connecting both ends of the hole to one another, and a conductive elastic member arranged near the other surface of the dielectric, and where one end of the rod is connected to the conductive elastic member, and the other end of the rod serves as a position-indicating point, and
wherein the position detector detects, near the position-indicating point, a signal transmitted from the position detecting coil.
13. The position input device of claim 12 , which is further configured to detect a pen pressure applied to the rod.
14. The position input device of claim 13 , wherein a pen pressure is reflected in a phase difference between a signal transmitted from the position detector and a signal received by the position detector from the resonant circuit.
15. The position input device of claim 13 , wherein the variable capacitor is formed as part of a time-constant circuit, and a pen pressure is reflected in a number of waves generated by the resonant circuit during a time period corresponding to a time constant of the time-constant circuit.
16. A computer system including a central processing unit, the system comprising:
a position indicator; and
a position detector,
wherein the position indicator includes: a variable capacitor; a resonant circuit configured with a position detecting coil and a capacitor connected with the variable capacitor; and a rod passing through the position detecting coil, where the variable capacitor has a dielectric having two mutually opposite surfaces, an electrode arranged on one surface of the dielectric and having a predetermined area, a hole penetrating through the dielectric between the two mutually opposite surfaces of the dielectric, a conductive portion electrically connecting both ends of the hole to one another, and a conductive elastic member arranged near the other surface of the dielectric, and where one end of the rod is connected to the conductive elastic member, and the other end of the rod serves as a position-indicating point,
wherein the position detector detects, near the position-indicating point, a signal transmitted from the position detecting coil, and
wherein the computer system converts a pen pressure detected by the variable capacitor into a data signal, using the central processing unit.
17. The computer system of claim 16 , wherein a pen pressure is reflected in a phase difference between a signal transmitted from the position detector and a signal received by the position detector from the resonant circuit.
18. The computer system of claim 16 , wherein the variable capacitor is formed as part of a time-constant circuit, and a pen pressure is reflected in a number of waves generated by the resonant circuit during a time period corresponding to a time constant of the time-constant circuit.