Dismiss
InnovationQ will be updated on Sunday, Oct. 22, from 10am ET - noon. You may experience brief service interruptions during that time.
Browse Prior Art Database

Image Classification by Symmetry Measurements

IP.com Disclosure Number: IPCOM000092584D
Original Publication Date: 1966-Dec-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 22K

Publishing Venue

IBM

Related People

Leybourne, JJ: AUTHOR

Abstract

Two-dimensional image 30 can be characterized, according to its symmetry, by making measurements on the Fraunhoffer diffraction pattern of the image.

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 100% of the total text.

Page 1 of 2

Image Classification by Symmetry Measurements

Two-dimensional image 30 can be characterized, according to its symmetry, by making measurements on the Fraunhoffer diffraction pattern of the image.

Coherent light source 20 impinges on image 30 and a Fraunhoffer diffraction pattern of image 30 is produced by transform lens 40. The Fraunhoffer diffraction pattern impinges on mask 50 which is a photographic negative of the diffraction pattern of image 30. Either image 30 or mask is rotated. The coincident light passing through mask 50 is collected by lens 60 for detection by photodetector
70. The output of photodetector 70, as a function of the angular position of the Fraunhoffer diffraction pattern of image 30, is the rotational autocorrelation function of the Fraunhoffer diffraction pattern of two-dimensional image 30.

An alternative to rotating image 30 is the use of a rotating prism between image 30 and transform lens 40 to rotate the diffraction pattern. A dove prism, a penchan prism, or other image rotating can be used. A photochromic material can be used to automatically produce mask 50, avoiding the need for developing a photographic negative. This is achieved by using a pulsed laser to make the mask and a continuous source of coherent light 20 to make the measurements. A limited number of photochromic masks are sufficient as each can be reused after returning to its ambient state.

1

Page 2 of 2

2

[This page contains 1 picture or other non-text object]