Capacitive two dimensional sensor

• US 6,525,547 B2
• Filed: 04/17/2001
• Issued: 02/25/2003
• Est. Priority Date: 04/17/2001
• Status: Expired due to Fees

• Current Assignee: Sentronics Corporation
• Original Assignee: Sentronics Corporation
• Inventors: Hayes, Robert S.
• Primary Examiner(s): Oda, Christine
• Assistant Examiner(s): KERVEROS, JAMES C
• Application Number:
  US09/837,828
• Publication Number:
  US 20020152048A1
• Time in Patent Office: 679 Days
• Field of Search: 324/662, 324/671, 324/678, 324/690, 382/124, 382/127
• US Class Current: 324/662
• 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 electrods 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 of one or two dimensional patterns of pixels for sensing surface modulations of an external impinging body, said array comprising a first conductive layer and first and second insulation layers, said first conductive layer being patterned into an array of pixels, each of said pixels containing a drive electrode and a pickup electrode with a gap therebetween and a second patterned conductive layer, said array not including an integrated circuit.

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 1 further including a third conductive layer interposed as a shield layer between said first and second conductive layers, said shield layer preventing cross talk due to electric fields between first and second 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 of one or two dimensional pattern of pixels for sensing the presence of an external material, said array comprising first and second conductive layers and first and second insulation layers, said first conductive layer being patterned into an array of pixels, each said pixel containing a drive electrode and a pickup electrode with a gap therebetween, said first insulation layer being positioned over said pixel array and said second insulation layer being interposed between said first and second conductive layers and a second patterned conductive layer, said array not including an integrated circuit.

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

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