Production of high performance optical spatial filters

Details Production of high performance optical spatial filters Production of high performance optical spatial filters

1982-12-27

1985-05-14

Arnold, Bruce Y.

350 369, G03H 116, G02B 522

Patent

active

045168334

ABSTRACT:
High performance optical spatial filters are produced photographically with an apparatus that directs a coherent beam of light through or off a subject and into a lens. The lens focuses the diffracted and/or reflected light to define a Fourier transform of the subject information. A filter is produced by exposing a photographic plate at the Fourier transform plane, processing the plate, and repositioning it. A hologram is recorded through the processed plate with the apparatus, which directs a reference beam to a holographic recording plane. A second photographic plate is placed at the transform plane and exposed with light directed through the hologram from a direction conjugate to the reference beam. The second plate is then processed. Successive generations of filters may also be produced. A method of using the filters for isolating nonperiodic defects in IC photomasks and wafers is also disclosed.

REFERENCES:
patent: 3614232 (1971-10-01), Mathisen
patent: 3630596 (1971-12-01), Watkins
patent: 3658420 (1972-04-01), Axelrod
patent: 3738752 (1973-06-01), Heinz et al.
patent: 3790280 (1974-02-01), Heinz et al.
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patent: 4000949 (1977-01-01), Watkins
Hauke F. E. et al., "Light Range Extending Method", IBM Tech. Disclosure Bulletin, vol. 14, No. 11, Apr. 1972, pp. 3391-3392.
Dammann H., et al., "Removal of Nonperiodic Structures from a Periodic Image by Means of Spatial Filtering", Optics Communications, vol. 3, No. 4, pp. 251-253.
"Filtering of Defects in Integrated Circuits with Orientation Independent", 10 Applied Optics, 2097, (Sep., 1971) Will and Pennington.

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