SENSING DEVICE HAVING CAPACITIVE FORCE SENSOR WITH SATURATED OUTPUT AT MINIMUM CAPACITANCE

• US 20080252615A1
• Filed: 04/10/2008
• Published: 10/16/2008
• Est. Priority Date: 04/11/2007
• Status: Abandoned Application

• Current Assignee: Silverbrook Research Pty Limited
• Original Assignee: Silverbrook Research Pty Limited
• Inventors: Shipton, Gary
• Application Number:
  US12/100,408
• Publication Number:
  US 20080252615A1
• Time in Patent Office: Days
• US Class Current: 345/174
• CPC Class Codes: G01D 2205/90 Two-dimensional encoders, i.e. having one or two codes extending in two directions
• CPC Class Codes: G01D 5/3473 Circular or rotary encoders
• CPC Class Codes: G01D 5/34746 Linear encoders
• CPC Class Codes: G01L 1/144 with associated circuitry G01L1/146 and G01L1/148 take precedence
• CPC Class Codes: G01L 1/146 for measuring force distributions, e.g. using force arrays G01L1/148 takes precedence
• CPC Class Codes: G06F 3/03545 Pens or stylus
• CPC Class Codes: G06F 3/0383 Signal control means within the pointing device

Abstract

A sensing device is provided for interacting with a substrate. The sensing device has a force sensor for detecting whether the sensing device is interacting with the substrate and an image sensor for sensing coded data disposed on the substrate. The force sensor has a capacitive sensor circuit incorporating a sensor capacitor having a variable capacitance C_sen and a reference capacitor relatively arranged so that the capacitive sensor circuit is near saturation when C_sen is at a minimum expected value.

Claims

1. A sensing device for interacting with a substrate, said sensing device comprising:

a force sensor for detecting whether the sensing device is interacting with the substrate; and

an image sensor for sensing coded data disposed on the substrate, said force sensor comprising a capacitive sensor circuit incorporating a sensor capacitor having a variable capacitance C_sen and a reference capacitor relatively arranged so that the capacitive sensor circuit is near saturation when C_sen is at a minimum expected value.

2. A sensing device as claimed in claim 1 comprising a processor configured for generating interaction data using the sensed coded data.

3. A sensing device as claimed in claim 1 configured such that the image sensor senses the coded data only when the force sensor detects that the sensing device is interacting with the substrate.

4. A sensing device as claimed in claim 1 selected from the group comprising:

a clicker lacking a nib or stylus, a pointer having a non-marking stylus; and

a pen having a marking nib.

5. A sensing device as claimed in claim 1, wherein the sensor capacitor is a parallel plate capacitor having one fixed plate and one movable plate.

6. A sensing device as claimed in claim 5, wherein the movable plate is configured to move relative to the fixed plate due to a pressure force exerted on the movable plate thereby altering separation of the plates and said capacitance C_sen.

7. A sensing device as claimed in claim 5, wherein a compression spring is connected to the movable plate.

8. A sensing device as claimed in claim 1, wherein the capacitive sensor circuit is a sigma-delta convertor circuit.

9. A sensing device as claimed in claim 8, wherein correlated double sampling is applied to an integrator of the sigma-delta convertor circuit.