Capacitive two dimensional sensor

• US 20020152048A1
• Filed: 04/17/2001
• Published: 10/17/2002
• Est. Priority Date: 04/17/2001
• Status: Active Grant

• Current Assignee: Sentronics Corporation
• Original Assignee: Sentronics Corporation
• Inventors: Hayes, Robert S.
• Granted Patent: US 6,525,547 B2
• Time in Patent Office: Days
• US Class Current: 702/127
• CPC Class Codes: G01D 5/2405 by varying dielectric
• CPC Class Codes: G06V 40/1306 non-optical, e.g. ultrasonic or capacitive sensing

Abstract

A two dimensional array of electrodes for sensing the presence or absence of the ridges in a fingerprint through capacitive measurements. Exciting signals are supplied from outside the array which allows the array to be fabricated from metal and insulator layers on non-semiconductor substrates such as glass or plastic using normal deposition and patterning techniques. A top protective layer consisting of hard, rigid material may be provided. The required electronic circuits are preferably located around the periphery of the array.

Claims

1. An array for sensing surface modulations in a two dimensional plane, said array comprising:

a first protective insulation layer; and

at least one or more conductive layer patterned into a two-dimensional array of pixels positioned below said protective layer, each said pixel containing a drive electrode and a pickup electrode with a gap therebetween.

2. The device of claim 1 wherein said drive electrodes are connected in substantially parallel rows or columns terminating at the periphery of said array.

3. The device of claim 2 wherein each of said pickup electrodes are connected in substantially parallel rows or columns but different from the connection of said drive electrodes and terminating at the periphery of said array.

4. The device of claim 3 wherein a shield conductive layer is interposed between said conductive layers.

5. The device of claim 1 wherein said drive electrodes are connected at the edge of said array to a drive signal consisting of a voltage supplied from a low impedance source and said drive signal is of a time varying nature.

6. The device of claim 5 wherein one line of said drive electrodes is driven at any given time and the other inactive drive electrodes are connected to ground.

7. The device of claim 6 wherein external pickup electronics with low input impedance and sensitive to either charge or current are connected to the ends of said signal pickup lines.

8. The device of claim 7 where the signals from said pickup electronic circuits are combined by multiplexing to form a lesser number of signal channels.

9. The device of claim 1, wherein additional electrodes are added to the periphery of said array, said additional electrodes being driven with a different voltage from the rest of said pixels such that the effects of parasitic capacitance in said sensor structure are substantially canceled.

10. An array for sensing material presence in a two dimensional plane, said array comprising:

a first protective insulation layer; and

at least one or more conductive layer patterned into a two-dimensional array of pixels positioned below said protective layer, each said pixel containing a drive electrode and a pickup electrode with a gap therebetween.

11. The array of claim 10 wherein said material is moisture.

12. The array of claim 10 wherein said material is chemicals.