Tablet for use in a coordinate digitizer

• US 3,974,332 A
• Filed: 03/10/1975
• Issued: 08/10/1976
• Est. Priority Date: 12/03/1974
• Status: Expired due to Term

• Current Assignee: Pentel Kabushiki Kaisha
• Original Assignee: Pentel Kabushiki Kaisha
• Inventors: Tagata, Genichi, Abe, Kiyomi, Shishido, Yoshio, Sugino, Tadaaki, Yamashiro, Yoshiharu
• Primary Examiner(s): Robinson, Thomas A.
• Application Number:
  US05/556,980
• Time in Patent Office: 519 Days
• Field of Search: 178/18, 178/19, 178/20, 340/365 C, 340/173 CA, 340/146.3 SY, 340/146.3 MA, 235/61.11 H, 179/90 K, 200/46, 346/139 C
• US Class Current: 178/18.08
• CPC Class Codes: G06F 2203/04107 Shielding in digitiser, i.e. guard or shielding arrangements, mostly for capacitive touchscreens, e.g. driven shields, driven grounds
• CPC Class Codes: G06F 3/0445 using two or more layers of sensing electrodes, e.g. using two layers of electrodes separated by a dielectric layer
• 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: H03K 17/98 having a plurality of control members, e.g. keyboard

Abstract

A capacitively coupled tablet for use with an electrically conductive pen comprises segments each including at least one lattice point of a matrix which comprises groups of spaced conductors which are disposed along coordinate axes. The segments are mutually electrically isolated by an electrically conductive shield layer having apertures which correspond to the surface area of the respective segments, and are marked with corresponding characters to serve as keys. An electrically insulating layer is disposed between the shield layer and the groups of conductors, and a similar surface layer is disposed on the shield layer.

Claims

1. In a coordinate digitizer tablet of the type including a matrix of conductors comprised of a first group of spaced conductors disposed to define a first coordinate axis, and a second group of spaced conductors disposed to define a second coordinate axis, said first group and said second group of conductors being superposed and mutually oriented so that the conductors comprising said two groups cross to define lattice points of said matrix at the cross-over points of the respective conductors defining said matrix;

and means mutually electrically insulating said conductors;

said conductors sequentially receiving in operation electrical pulses which are sensed by capacitive coupling with the matrix to indicate the position on said matrix with respect to the coordinate axes to which the capacitive coupling is made;

the improvement which comprises;

an electrically conductive shield layer disposed overlying said matrix and defining an electrical shield, said shield having means defining therethrough apertures positioned to expose said lattice points and dimensioned to define unshielded segments of said matrix for capacitive coupling therewith and to substantially prevent capacitive coupling with other portions of said matrix thereby to substantially prevent sensing of electrical signals applied to the respective electrical conductors defining other lattice points of said matrix;

means electrically insulating said shield from said matrix; and

a surface insulative layer disposed on a major surface of said shield opposite said matrix.

2. A tablet according to claim 1 in which each of the unshielded segments contains a single lattice point.

3. A tablet according to claim 1 in which each of the unshielded segments contains a plurality of lattice points, and wherein the conductors of a respective group extending through a single unshielded segment are connected in common.

4. A tablet according to claim 1 in which the surface layer includes outwardly extending portions on the surface thereof which physically divide the unshielded segments.