RESISTIVE GRID GRAPHIC DATA TABLET

• US 3,668,313 A
• Filed: 04/30/1970
• Issued: 06/06/1972
• Est. Priority Date: 04/30/1970
• Status: Expired due to Term

• Current Assignee: Herbert Dym
• Original Assignee: Herbert Dym
• Inventors: Dym, Herbert
• Primary Examiner(s): Cooper, William C.
• Assistant Examiner(s): Kundert, Thomas L.
• Application Number:
  US05/033,462
• Time in Patent Office: 768 Days
• Field of Search: 178/18,19 340/347 33/1M
• US Class Current: 178/18.05
• CPC Class Codes: G06F 3/044 by capacitive means
• CPC Class Codes: G06F 3/0441 using active external devices, e.g. active pens, for receiving changes in electrical potential transmitted by the digitiser, e.g. tablet driving signals

Abstract

A two-dimensional graphic data entry tablet for transforming a positional information into a digital input to a computer system. The tablet structure consists of two continuous resistance lines superimposed on each other. Each of these lines being in the form of a grid and representing position in one of said two dimensions. A voltage differential is applied to each of the grids in order to create a voltage gradient along the path of the grid wires. An analog positional information is created by sensing grid voltage with a capacitively coupled stylus. By having the stylus viewing area cover a plurality of wires, the sensed potential averages out and represents a position directly related to the center location of the stylus on the faceplate of the tablet. The resistive grid lines provide the dual function of resistive bleeding and presenting a potential gradient to a capacitively coupled stylus.

Claims

1. A system for translating two-dimensional positional information into electrical signals that represent any position on a two-dimensional surface comprising:

a tablet structure having a first and second grid plane each consisting of a plurality of closely spaced resistive lines;

said resistive lines of said first grid plane being arranged so as to lie along a first dimension and said plurality of resistive lines of said second grid plane being arranged to lie along a second dimension;

said resistive Lines in each of said planes being connected at alternate ends so as to form two independent continuous electrical paths each associated with only one of said dimensions;

signal source means for applying a potential differential across said grid planes;

capacitively coupled sensing means having an effective sensing area over a plurality of said closely spaced lines;

so that said resistive lines are in sufficient proximity to each other relative to the effective sensing area of said sensing means so that the electrical field generated by the plurality of resistive lines in each of said planes appears as a continuous potential gradient in a dimension orthogonal to the dimension in which the lines are arranged;

said two-dimensional positional information being created by the placement of said sensing means in close proximity of the face of said tablet, so that upon the application of a potential differential across said grid planes, electrical signals proportional to said two-dimensional positional information is detected by said sensing means.

2. A system as defined in claim 1 wherein said resistive lines are of constant resistivity.

3. A system as defined in claim 2 further comprising:

control means for sequentially applying a potential differential to said first and second grid planes respectively;

4. A system as defined in claim 3 further comprising signal switching means for first applying a potential differential across said grid planes and secondly applying an equal potential across said grid planes.

5. A system as defined in claim 4 wherein said resistive lines in each of said grid planes are arranged parallel to each other.