Electrostatic capacitance detecting device

• US 6,448,790 B1
• Filed: 10/25/2000
• Issued: 09/10/2002
• Est. Priority Date: 10/26/1999
• Status: Expired due to Fees

• Current Assignee: Citizen Holdings Co., Ltd. (Citizen Electronics Company Limited)
• Original Assignee: Citizen Watch Co Limited (Citizen Electronics Company Limited)
• Inventors: Imai, Toshio
• Primary Examiner(s): Oda, Christine K.
• Application Number:
  US09/695,426
• Time in Patent Office: 685 Days
• Field of Search: 324/661, 324/662, 324/663, 324/671, 324/686, 324/519, 361/283.1, 382/124, 382/115
• US Class Current: 324/661
• CPC Class Codes: G06V 40/1306 non-optical, e.g. ultrasonic or capacitive sensing

Abstract

Bias charge is injected from a bias power supply line 3 into a detecting electrode 11 constituting an electrostatic capacitance element between an object to be detected to accumulate charge in accordance with its electrostatic capacitance, and when the charge is distributed between the electrostatic capacitance element and a capacitance element 12 which has been reset to a reset potential, a holding voltage of the capacitance element 12 changes in accordance with the amount of charges accumulated in the detecting electrode 11, and thus a signal is outputted regarding the change in holding voltage as an amount of change in gate potential of a source follower amplifier element 13, thereby detecting the capacitance of the electrostatic capacitance element between the object to be detected and the detecting electrode 11.

Claims

1. An electrostatic capacitance detecting device, comprising:

a detecting electrode constituting an electrostatic capacitance by being brought into contact with or put close to an object to be detected through a protection film;

a bias switch element for injecting bias charges into said detecting electrode;

a charge transfer switch element for transferring signal charges accumulated in said detecting electrode in response to a timing signal for signal detection;

a capacitance element for converting the signal charges transferred thereto via said charge transfer switch element into a voltage signal;

a source follower amplifier element, for receiving and amplifying a holding voltage of said capacitance element;

a readout selection switch element provided on a source side of said source follower amplifier element; and

a reset switch element for providing said capacitance element with a reset potential, wherein said detecting electrode, said bias switch element, said charge transfer switch element, said capacitance element, said source follower amplifier element, said readout selection switch element, and said reset switch element are provided on a semiconductor substrate.

2. An electrostatic capacitance detecting device according to claim 1, wherein each of said bias switch element, said charge transfer switch element, said reset switch element, said source follower amplifier element, and said readout selection switch element is a MOS transistor.

3. An electrostatic capacitance detecting device, comprising:

a detecting area constituted by arranging two-dimensionally a plurality of detecting cells each including a detecting electrode constituting an electrostatic capacitance by being brought into contact with or put close to an object to be detected through a protection film, a bias switch element for injecting bias charges into said detecting electrode, a charge transfer switch element for transferring signal charges accumulated in said detecting electrode in response to a timing signal for signal detection, a capacitance element for converting the signal charges transferred thereto via said charge transfer switch element into a voltage signal, a source follower amplifier element for receiving and amplifying a holding voltage of said capacitance element, a readout selection switch element provided on a source side of said source follower amplifier element, and a reset switch element for providing said capacitance element with a reset potential;

readout row selection means for selecting a readout row in said detecting area; and

readout column selection element for selecting a readout column in said detecting area, wherein said detecting area, said readout row selection means, and said readout column selection element are provided on a semiconductor substrate.

4. An electrostatic capacitance detecting device according to claim 3,

wherein said readout row selection means is a first shift register for controlling said readout selection switch element of said each detecting cell for each readout row, and

wherein said readout column selection element is composed of vertical signal lines for sending-out output signals from said readout selection switch elements of said detecting cells together for each readout column, a single detection signal output line, column selection switch elements provided between said vertical signal lines and said single detection signal output line respectively, and a second shift register for controlling said column selection switch elements.

5. An electrostatic capacitance detecting device according to claim 3, wherein each of said bias switch element, said charge transfer switch element, said reset switch element, said source follower amplifier element, and said readout selection switch element constituting said each detecting cell is a MOS transistor.

6. An electrostatic capacitance detecting device according to claim 4, wherein each of said bias switch element, said charge transfer switch element, said reset switch element, said source follower amplifier element, and said readout selection switch element constituting said each detecting cell, and said column selection switch element in said readout column selection means is a MOS transistor.

7. An electrostatic capacitance detecting device, comprising:

a detecting electrode constituting an electrostatic capacitance element by being brought into contact with or put close to an object to be detected through a protection film;

a bias switch element for injecting bias charges into said detecting electrode;

a charge transfer switch element for transferring signal charges accumulated in said detecting electrode in response to a timing signal for signal detection;

a capacitance element for converting the signal charges transferred thereto via said charge transfer switch element into a voltage signal;

a source follower amplifier element for receiving and amplifying a holding voltage of said capacitance element; and

a readout selection switch element provided on a source side of said source follower amplifier element, wherein said detecting electrode, said bias switch element, said charge transfer switch element, said capacitance element, said source follower amplifier element, and said readout selection switch element are provided on a semiconductor substrate.

8. An electrostatic capacitance detecting device according to claim 7,

wherein each of said bias switch element, said charge transfer switch element, said source follower amplifier element, and said readout selection switch element is a MOS transistor.

9. An electrostatic capacitance detecting device, comprising:

a detecting area constituted by arranging two-dimensionally a plurality of detecting cells each including a detecting electrode constituting an electrostatic capacitance element by being brought into contact with or put close to an object to be detected through a protection film, a bias switch element for injecting bias charges into said detecting electrode, a charge transfer switch element for transferring signal charges accumulated in said detecting electrode in response to a timing signal for signal detection, a capacitance element for converting the signal charges transferred thereto via said charge transfer switch element into a voltage signal, a source follower amplifier element for receiving and amplifying a holding voltage of said capacitance element, and

a readout selection switch element provided on a source side of said source follower amplifier element;

readout row selection means for selecting a readout row in said detecting area; and

readout column selection means for selecting readout column in said detecting area, wherein said detecting area, said readout row selection means, and said readout column selection means are provided on a semiconductor substrate.

10. An electrostatic capacitance detecting device according to claim 9,

wherein said readout row selection means is a first shift register for controlling said readout selection switch element of said each detecting cell for each readout row, and

wherein said readout column selection means is composed of vertical signal lines for sending-out output signals from said readout selection switch elements of said detecting cells together for each readout column, a single detection signal output line, column selection switch elements provided between said vertical signal lines and said single detection signal output line respectively, and a second shift register for controlling said column selection switch elements.

11. An electrostatic capacitance detecting device according to claim 9, wherein each of said bias switch element, said charge transfer switch element, said source follower amplifier element, and said readout selection switch element constituting said each detecting cell is a MOS transistor.

12. An electrostatic capacitance detecting device according to claim 10, wherein each of said bias switch element, said charge transfer switch element, said source follower amplifier element, and said readout selection switch element constituting said each detecting cell, and said column selection switch element in said readout column selection element is a MOS transistor.

13. An electrostatic capacitance detecting device, comprising:

a detecting electrode constituting an electrostatic capacitance element by being brought into contact with or put close to an object to be detected through a protection film;

a charge transfer switch element for transferring signal charges accumulated in said detecting electrode in response to a timing signal for signal detection;

a capacitance element for converting the signal charges transferred thereto via said charge transfer switch element into a voltage signal;

a source follower amplifier element for receiving and amplifying a holding voltage of said capacitance element;

a readout selection switch element provided on a source side of said source follower amplifier element; and

a reset switch element for providing said capacitance element with a reset potential, wherein said detecting electrode, said transfer switch element, said capacitance element, said source follower amplifier element said readout selection switch element, and said reset switch element are provided on a semiconductor substrate.

14. An electrostatic capacitance detecting device according to claim 13, wherein each of said charge transfer switch element, said reset switch element, said source follower amplifier element, and said readout selection switch element is a MOS transistor.

15. An electrostatic capacitance detecting device, comprising:

a detecting area constituted by arranging two-dimensionally a plurality of detecting cells each including a detecting electrode constituting an electrostatic capacitance element by being brought into contact with or put close to an object to be detected through a protection film, a charge transfer switch element for transferring signal charges accumulated in said detecting electrode in response to a timing signal for signal detection, a capacitance element for converting the signal charges transferred thereto via said charge transfer switch element into a voltage signal, a source follower amplifier element for receiving and amplifying a holding voltage of said capacitance element, a readout selection switch element provided on a source side of said source follower amplifier element, and a reset switch element for providing said capacitance element with a reset potential;

readout row selection means for selecting a readout row in said detecting area; and

readout column selection means for selecting a readout column in said detecting area, wherein said detecting area, said readout row selection means, and said readout column selection means are provided on a semiconductor substrate.

16. An electrostatic capacitance detecting device according to claim 15,

wherein said readout row selection means is a first shift register for controlling said readout selection switch element of said each detecting cell for each readout row, and

wherein said readout column selection means is composed of vertical signal lines for sending-out output signals from said readout selection switch elements of said detecting cells together for each readout column, a single detection signal output line, column selection switch elements provided between said vertical signal lines and said single detection signal output line respectively, and a second shift register for controlling said column selection switch elements.

17. An electrostatic capacitance detecting device according to claim 15, wherein each of said charge transfer switch element, said reset switch element, said source follower amplifier element, and said readout selection switch element constituting said each detecting cell in is a MOS transistor.

18. An electrostatic capacitance detecting device according to claim 16, wherein each of said charge transfer switch element, said reset switch element, said source follower amplifier element, and said readout selection switch element constituting said each detecting cell, and said column selection switch elements in said readout column selection means are transistors.