Reduced noise touch screen apparatus and method

• US 20030058226A1
• Filed: 10/24/2002
• Published: 03/27/2003
• Est. Priority Date: 08/22/1994
• Status: Active Grant

• Current Assignee: Logan L. Pease, William Bertram
• Original Assignee: Logan L. Pease, William Bertram
• Inventors: Pease, Logan L., Bertram, William K.
• Granted Patent: US 6,734,843 B2
• Time in Patent Office: Days
• US Class Current: 345/173
• CPC Class Codes: G06F 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment
• CPC Class Codes: G06F 3/044 by capacitive means

Abstract

A touch screen having a high or fine resolution at relatively low cost is provided. In one embodiment, electrodes are placed directly on the surface of a CRT screen without the need for an electrode positioned on the rear surface. The touch screen may include a conductive coating and a protective coating which are preferably provided in a single vacuum chamber step. A high gain system including a high-frequency sampling bandpass filter provide discrimination of the desired signal over noise. A screen calibration technique is used to achieve linearization in order to convert the electric signals obtained from the screen into data indicative of the position of a touch on the screen.

Claims

1. A touch screen for determination of a touch position with a resolution of less then one inch, comprising:

a cathode ray tube (CRT) having a display region with an exterior and an interior surface;

a transparent conductive coating placed directly on said exterior surface of said CRT; and

a plurality of electrodes placed directly on said exterior surface of said CRT, in the absence of electrodes placed on said interior surface.

2. A touch screen, as claimed in claim 1, wherein said plurality of electrodes are formed from materials selected from the group consisting of silver epoxies and a mixture of silver and low-temperature-melting glass.

3. A touch screen, as claimed in claim 1, wherein said touch screen is provided by a process that includes only a single vacuum step.

4. A method of making a touch screen apparatus for detecting touch at a preselected location on a touch screen surface with a resolution of less than one inch, comprising:

providing a CRT, having a front surface;

applying a plurality of bar electrodes directly to the front surface;

depositing a transparent conductive coating to the front surface to provide an electrical path between the bar electrodes; and

applying a transparent protective coating over the conductive coating.

5. The method of claim 4 wherein the plurality of bar electrodes are made of a glass and silver compound.

6. The method of claim 4, wherein the conductive coating is made of silver epoxy.

7. The method of claim 4, wherein the protective coating is made of indium.

8. A method, as claimed in claim 4, wherein said steps of depositing a transparent conductive coating and said step of applying a transparent protective coating are conducted in a vacuum chamber.

9. A method, as claimed in claim 4, wherein only a single vacuum process is needed to perform the method of making a touch screen apparatus.

10. A method, as claimed in claim 4, wherein said method of making a touch screen apparatus is performed in the absence of substantially modifying the size or shape of said bar electrodes after said step of applying a plurality of bar electrodes.