Browse Prior Art Database

Acoustical Touch Panel

IP.com Disclosure Number: IPCOM000089846D
Original Publication Date: 1977-Dec-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Fajans, J: AUTHOR

Abstract

This device consists of a thin, bendable transparent panel spaced slightly above a second piece of transparent material. The top panel is sufficiently flexible that the pressure of the user's finger results in a small contact area between the plates, producing a local acoustical coupling. Acoustical plane wave impulses are generated at fixed times in orthogonal directions by two long piezoelectric crystals mounted on adjacent sides of the lower plate. Two piezoelectric crystals, mounted similarly on the upper plate, are used as acoustical detectors.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 91% of the total text.

Page 1 of 1

Acoustical Touch Panel

This device consists of a thin, bendable transparent panel spaced slightly above a second piece of transparent material. The top panel is sufficiently flexible that the pressure of the user's finger results in a small contact area between the plates, producing a local acoustical coupling. Acoustical plane wave impulses are generated at fixed times in orthogonal directions by two long piezoelectric crystals mounted on adjacent sides of the lower plate. Two piezoelectric crystals, mounted similarly on the upper plate, are used as acoustical detectors.

The local acoustical coupling results in a spherical wave originating from the point of contact in the upper plate when an impulse is present in the lower plate. The coordinate in the direction perpendicular to the plane wave will be related to the time between the impulse generation in the lower plate and its detection in the upper plate, specifically: u = (T-T(o))upsilon/2. where u is the coordinate perpendicular to the plane wave, T(o) is the time of impulse generation, T is the detection time, and upsilon is the velocity of acoustical waves in the material.

An alternate method would place both the detector and the generator in the upper panel (in effect using the piezoelectric crystals to perform both tasks) and relying on the reflected wave generated at the point of contact.

The acoustical touch panel offers the possibility of an inexpensive touch panel, as there are no mechanically complex...