Sensor with pressure-induced varied capacitance

• US 20090115735A1
• Filed: 11/06/2007
• Published: 05/07/2009
• Est. Priority Date: 11/06/2007
• Status: Abandoned Application

• Current Assignee: Himax Technologies Ltd. (Himax Technologies Incorporated)
• Original Assignee: Himax Technologies Ltd. (Himax Technologies Incorporated)
• Inventors: Chuang, Kai-Lan
• Application Number:
  US11/983,060
• Publication Number:
  US 20090115735A1
• Time in Patent Office: Days
• US Class Current: 345/173
• CPC Class Codes: G02F 1/13338 Input devices, e.g. touch panels
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• CPC Class Codes: G06F 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes
• CPC Class Codes: G06F 3/0447 Position sensing using the local deformation of sensor cells

Abstract

A sensor with pressure-induced varied capacitance is disclosed. Each sensor pixel circuit of the sensor includes a touch capacitor, a charge TFT for storing charge at the touch capacitor according to a previous scan line, and a readout TFT for reading out voltage across the touch capacitor according to a present scan line.

Claims

1. A sensor, comprising:

an active matrix area having a plurality of sensor pixel circuits arranged in matrix form; and

a plurality of scan lines and readout lines arranged in the active matrix area such that the scan lines and the readout lines respectively cross each other at one of the sensor pixel circuits,

wherein each of the sensor pixel circuits includes a touch capacitor, a charge TFT for storing charge at the touch capacitor according to a previous scan line, and a readout TFT for reading out voltage across the touch capacitor according to a present scan line.

2. The sensor according to claim 1, further comprising a scan driver for sequentially asserting the scan lines.

3. The sensor according to claim 1, further comprising a readout circuit for analyzing analog signals outputted from the active matrix area, and then converting the analog signals into digital signals.

4. The sensor according to claim 1, further comprising an image processing circuit for determining location and image of the object or objects.

5. The sensor according to claim 3, wherein the readout circuit comprises:

a plurality of integrating circuits connected to receive output of the active matrix area, wherein the integrating circuits respectively connect to the readout lines.

6. The sensor according to claim 5, wherein each of the integrating circuits comprises:

an integrator operational amplifier;

a feedback capacitor connected between output and inverting input of the integrator operational amplifier;

a predetermined reset voltage connected to non-inverting input of the integrator operational amplifier; and

a reset transistor having source and drain connected across ends of the feedback capacitor, and a gate connected to a reset signal.

7. The sensor according to claim 6, wherein the readout circuit further comprises:

a multiplexer for inputting the outputs of the integrator operational amplifiers, among which one of the outputs is selected according to readout line selecting signals; and

a comparator for comparing the analog signal of the selected readout line with a predetermined reference voltage.

8. The sensor according to claim 1, wherein:

the readout TFT having one of source/drain being electrically connected to associated readout line, gate being electrically connected to the associated scan line of present row, and other one of the source/drain being electrically connected to the charge TFT and the touch capacitor at a node;

the charge TFT having one of source/drain being electrically connected to the readout TFT at the node, gate being electrically connected to the associated scan line of previous row, and the other one of the source/drain being electrically connected to the associated scan line of the present row; and

the touch capacitor having one plate being electrically connected to the node and other plate being electrically connected to a common voltage.

9. A sensing method, comprising:

asserting a scan line of previous row;

reaching a low voltage at a node of present row;

asserting a scan line of present row;

reading out voltage at the node of the present row; and

integrating the readout voltage, thereby absence or presence of an object is distinguishable according to different integrated readout voltage due to different touch capacitance at the node.

10. The sensing method according to claim 9, further comprising:

converting analog signals of the integrated readout voltages into digital signals.

11. The sensing method according to claim 10, further comprising:

processing the digital signals to determine location and image of the object or objects.