Browse Prior Art Database

Coherent Complex Spatial Filter

IP.com Disclosure Number: IPCOM000073366D
Original Publication Date: 1970-Dec-01
Included in the Prior Art Database: 2005-Feb-22
Document File: 2 page(s) / 26K

Publishing Venue

IBM

Related People

Hirsch, PM: AUTHOR [+3]

Abstract

In many applications, particularly in matched filtering, it is desirable to have a filter with a complex function rather than merely a real function. With the well-known basic kinoform technique, the filter which is provided is limited to real functions. A complex filter, including both positive and negative operators, can be provided by first plotting phase phi(x,y) modulo 2n pi (for some integer n) on a photographic film. The film is then Photoreduced, if necessary, and then etched or bleached to produce a relief pattern. Next, an amplitude plot A(x,y) is produced on the same film so that upon illumination of the pattern both phase phi(x,y) and amplitude A(x,y) are produced.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 84% of the total text.

Page 1 of 2

Coherent Complex Spatial Filter

In many applications, particularly in matched filtering, it is desirable to have a filter with a complex function rather than merely a real function. With the well- known basic kinoform technique, the filter which is provided is limited to real functions. A complex filter, including both positive and negative operators, can be provided by first plotting phase phi(x,y) modulo 2n pi (for some integer n) on a photographic film. The film is then Photoreduced, if necessary, and then etched or bleached to produce a relief pattern. Next, an amplitude plot A(x,y) is produced on the same film so that upon illumination of the pattern both phase phi(x,y) and amplitude A(x,y) are produced.

In order to accomplish the present process, a reversible film such as the minicard film manufactured by the Eastman Kodak Company is utilized. This film has the characteristic that the development or etching of the film can be reversed such that another exposure can be made on the film which then can again be bleached or etched. To accomplish this, the film is exposed first to the phase plot, developed, but not fixed, then etched using edge-bleach bath such as Kodak EB-3. It is then washed and dried and finally reexposed to the amplitude plot. The film is then processed to produce a normal black and white image.

Shown is a practical optical system for utilizing the complex filter. A laser provides monochromatic coherent illumination which is imaged by lenses...