Browse Prior Art Database

Device for Making High Resolution Interdigital Transducers

IP.com Disclosure Number: IPCOM000074555D
Original Publication Date: 1971-May-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 4 page(s) / 73K

Publishing Venue

IBM

Related People

Lean, EG: AUTHOR [+4]

Abstract

This is an interferometric device for fabricating large-area, high-resolution interdigital transducers of either uniform or continuously variable spacing.

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Device for Making High Resolution Interdigital Transducers

This is an interferometric device for fabricating large-area, high-resolution interdigital transducers of either uniform or continuously variable spacing.

Referring to Fig. A, there is shown a system for fabricating a high-resolution interdigital transducer. A single-mode laser beam 10 is split into two equal parts by beam splitter 12. Each portion of the split beam then passes through a focusing lens 14 and then through a cylindrical lens 16. The two sets of lenses 16 may or may not have the same optical parameters. Each cylindrical lens 16 produces a cylindrical wavefront at the plane of the photoresist 18 with radii of curvature rl and r2, which are determined by the lens parameters and their relative positions. The two cylindrical wavefronts impinge upon the recording photoresist plane at a mutual angle alpha.

The following proof demonstrates that the two beams produce sinusoidal intensity fringes whose spatial frequency varies linearly along the x-axis or whose spatial phase varies quadratically with x. These properties are required for a chirped, time compression type transducer. Furthermore, it should be apparent that the ordinary transducer, with constant finger spacing, is that the ordinary transducer, with constant finger spacing, is just a special case of the more general relationship established in the following proof.

From the essential system geometry shown in Fig. A, we note that

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(Image Omitted)

It is evident that apart from Phi, the argument of the cosine function is exactly of the form of a linearly chirped signal.

The extraneous phase term phi contains higher order terms (aberrations) which for proper choice of parameters a, b(1) and b(2) could be made negligible, or the cylindrical lenses could be so designed (parabolic surfaces) that these terms disappear. Simil...