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Pattern Recognition by Surface Acoustic Waves

IP.com Disclosure Number: IPCOM000074486D
Original Publication Date: 1971-May-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Barrakette, ES: AUTHOR [+2]

Abstract

An optical-electrical converter useful for pattern recognition uses surface acoustic waves. A piezoelectric substrate 1 has a plurality of tapped delay lines 2 located on its top surface. These delay lines are coated with a thin layer of photoconductive film, such as CdS, ZnO, and CaAs. Each delay line has an input transducer 3 located adjacent to it. Electrical square-wave pulse trains 4 are applied to each transducer 3 in order to produce surface acoustic waves which travel below delay lines 2. The acoustic waves are electrically tapped as they propagate along the delay lines and produce trains of electrical output signals corresponding to square-wave pulses 4.

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Pattern Recognition by Surface Acoustic Waves

An optical-electrical converter useful for pattern recognition uses surface acoustic waves. A piezoelectric substrate 1 has a plurality of tapped delay lines 2 located on its top surface. These delay lines are coated with a thin layer of photoconductive film, such as CdS, ZnO, and CaAs. Each delay line has an input transducer 3 located adjacent to it. Electrical square-wave pulse trains 4 are applied to each transducer 3 in order to produce surface acoustic waves which travel below delay lines 2. The acoustic waves are electrically tapped as they propagate along the delay lines and produce trains of electrical output signals corresponding to square-wave pulses 4.

An optical imaging system (not shown) projects optical images of various characters, such as A, onto substrate 1. The electrical output from the delay lines is shorted at locations on which the optical image is incident, due to the photoconductive coating. Therefore, the train of output electrical pulses corresponding to input square-wave pulses 4 is interrupted at those locations where the light image strikes substrate 1. Consequently, electrical outputs E0, E1, and E2 are representative of the input optical image.

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