Lensless joint transform optical correlator for precision indust

Details Lensless joint transform optical correlator for precision indust Lensless joint transform optical correlator for precision indust

1997-08-28

1999-07-06

Spyrou, Cassandra

Optical: systems and elements

Diffraction

Using fourier transform spatial filtering

359565, 356354, 250550, 382278, G02B 2746

Patent

active

059204303

ABSTRACT:
A lensless joint transform correlator optically determines the relative position of two pinholes placed in parallel arms of a Mach-Zehnder interferometer. The Fraunhaufer diffraction patterns combine to form a joint power spectrum signal in the joint transform plane. Because of the interference of the two pinhole signals, an encoded lens comprising a Fresnel zone is formed in the joint Fraunhaufer diffraction pattern which is illuminated with a plane wave, and the output signal is taken in the focal plane of the Fresnel zone and magnifies the input pinhole displacement by a factor of ten, enhancing its use in precision positioning servo systems for mask alignment.

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