TRANSPARENT SWITCHBOARD

• US 3,758,718 A
• Filed: 02/15/1972
• Issued: 09/11/1973
• Est. Priority Date: 02/15/1972
• Status: Expired due to Term

• Current Assignee: Hans P. Rasmussen
• Original Assignee: Hans P. Rasmussen
• Inventors: Rasmussen, Hans P.
• Primary Examiner(s): Claffy, Kathleen H.
• Assistant Examiner(s): Richardson, Kenneth
• Application Number:
  US05/226,476
• Time in Patent Office: 574 Days
• Field of Search: 178/18,19,20 317/149 340/365,336
• US Class Current: 178/18.01
• CPC Class Codes: G06F 3/041 Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
• CPC Class Codes: G06F 3/045 using resistive elements, e.g. a single continuous surface or two parallel surfaces put in contact

Abstract

A tin oxide coating is formed on a plate of glass and the coating is then etched away from the glass in thin lines to form separate electrical conductors which extend to one end of the plate and connect to either a vertical (column) or horizontal (row) position sensing SCR circuit. A thin transparent insulating coating is formed over the oxide layer except at selected touch points which are positioned in a matrix pattern of vertical columns and horizontal rows. Touching one of these points with a finger bridges the thin line between adjacent conductors to activate trigger circuits in the particular row and column sensing circuits associated with the point touched. The row and column sensing circuits are similar and are powered with a low frequency, AC voltage source. The source for the row circuits is 180* out of phase with the source for the column circuits so that one circuit acts as ground for the other during half of the supply voltage cycle. The signals from the sensing circuits are input to a logic circuit which determines the presence of a '"'"''"'"''"'"''"'"'valid'"'"''"'"''"'"''"'"' touch (indicated by outputs of predetermined duration from only a single column circuit and a single row circuit), stores a binary matrix number associated with the touched point, signals a computer of the presence of a stored number and prevents storage of a new number before receiving an enable signal from the compter.

Claims

1. A system for determining the location in a given surface of a point receiving a predetermined stimulus comprising:

a plurality of spaced points having defined X and Y coordinates in a given surface along mutually perpendicular X and Y axes;

at least two transparent, electrically conductive means extending to the area of each of said points;

X coordinate sensing means connected to one of said two conductive means from each of said points for identifying the X coordinate of a point receiving a predetermined stimulus;

Y coordinate sensing means connected to the other of said two conductive means from each of said points for identifying the Y coordinate of a point receiving a predetermined stimulus;

a carrier plate of transparent, electrically non-conductive material supporting said transparent electrically conduCtive means;

said two transparent electrically conductive means extending to the area of each of said points being formed of non-touching electrically conductive coatings which are electrically separated from each other; and

a coating of transparent, electrically non-conductive material disposed over said conductive coatings except in the area of said points whereby only said points are susceptible to a predetermined stimulus.

2. A system as defined in claim 1 wherein:

a. said spaced points are distributed on said surface in a matrix pattern and are aligned in a plurality of rows and columns extending parallel to the X-axis and the Y-axis, respectively;

b. said matrix pattern and transparent conductive means are distributed over a surface area having defined boundaries with the area included within said boundaries being substantially transparent;

c. said transparent conductive means extend from the area of said points to a remote area beyond said boundaries;

d. all points in a given column have the same X-coordinate and are connected by said transparent electrically conductive means to an X-coordinate sensing means for that column which identifies the X-coordinate for all points in the column; and

e. all points in a given row have the same Y-coordinate and are connected by said transparent electrically conductive means to a Y-coordinate sensing means for that row which identifies the Y-coordinate for all points in the row.

3. A system as defined in claim 2 wherein said coating electrically conductive transparent material includes stannous oxide.

4. A system as defined in claim 2 wherein said two transparent, electrically conductive means extending to the area of each of said points are close enough to each other at each of said points to be simultaneously touched by a human finger applied to one of said points for providing said predetermined stimulus.

5. A system as defined in claim 4 wherein each of said X and said Y-coordinate sensing means include an alternating current, relatively low frequency power supply selectively connected by operation of an electrical switch to an output circuit with said electrical switch being operated by the presence or absence of said stimulus at the point or points with which it is connected by said electrically conductive means.

6. A system as defined in claim 5 wherein:

a. applying a predetermined stimulus to a point electrically connects said two transparent electrically conductive means extending to the area of the point to electrically connect said X and Y-coordinate sensing means to each other; and

b. the power supply of said X-coordinate sensing means is 180* out of phase with the power supply of said Y-coordinate sensing means, whereby one of said sensing means provides a ground for the other during one-half of each power cycle.

7. A system as defined in claim 6 wherein said X and Y-coordinate sensing means include SCR circuits having their gates connected to the stimulus applied to said points to control conduction in said output circuits.

8. A system as defined in claim 4 further including processing means connected with said X and Y-coordinate sensing means for detecting the occurrence of a single stimulus applied to only one of said points.

9. A system as defined in claim 6 further including processing means connected with said X and Y-coordinate sensing means for detecting the occurrence of a single stimulus applied to only one of said points.

10. A system as defined in claim 9 wherein said processing means further includes means for determining the presence of a touch having a predetermined time duration, storing identification information associated with the particular point touched, signaling associated equipment of the presence of stored information and preventing signaling of the presence of new information until said associated equipment provides a predetermined enabling signal.

11. A system for determining the location in a given surface of a point receiving a predetermined stimulus comprising:

a plurality of spaced points having defined X and Y coordinates in a given surface along mutually perpendicular X and Y axes;

at least two transparent, electrically conductive means extending to the area of each of said points;

X coordinate sensing means connected to one of said two conductive means from each of said points for identifying the X coordinate of a point receiving a predetermined stimulus; and

Y coordinate sensing means connected to the other of said two conductive means from each of said points for identifying the Y coordinate of a point receiving a predetermined stimulus, said X and Y coordinate sensing means including an alternating current, relatively low frequency power supply selectively connected by operation of an electrical switch to an output circuit with said electrical switch being operated by the presence or absence of said stimulus at the point or points with which it is connected by said electrically conductive means.

12. A system as defined in claim 11 wherein:

a. applying a predetermined stimulus to a point electrically connects said two transparent electrically conductive means extending to the area of the point to electrically connect said X and Y-coordinate sensing means to each other; and

b. the power supply of said X-coordinate sensing means is 180* out of phase with the power supply of said Y-coordinate sensing means, whereby one of said sensing means provides a ground for the other during one-half of each power cycle.

13. A system as defined in claim 12 wherein said X and Y-coordinate sensing means include SCR circuits having their gates connected to the stimulus applied to said points to control conduction in said output circuits.