Method of multivariant intraclass pattern recognition

• US 4,487,476 A
• Filed: 04/28/1981
• Issued: 12/11/1984
• Est. Priority Date: 04/28/1981
• Status: Expired due to Fees

• Current Assignee: The United States of America As Represented By The Secretary of Agriculture
• Original Assignee: United States Of America As Represented By The Secretary Of The Air Force
• Inventors: Hester, Charles F., Casasent, David P.
• Primary Examiner(s): ARNOLD, BRUCE
• Application Number:
  US06/258,500
• Time in Patent Office: 1,323 Days
• Field of Search: 350/162.13, 364/822, 356/71
• US Class Current: 382/211
• CPC Class Codes: G06V 10/92 using spatial domain filters, e.g. joint transform correlators
• CPC Class Codes: Y10S 359/90 Methods

Abstract

A method of recognizing different perspective views or images (i.e., multivariant views) of the same object (i.e., intraclass patterns). Each intraclass pattern, or different representation of the same object, is described as an orthonormal basis function expansion, and a single averaged matched spatial filter is produced from a weighted linear combination of these functions. The method eliminates the multiple matched spatial filters, and the extensive postprocessing of the matrix output from a multichannel correlator, which are used in the prior art.

Claims

1. A method of pattern recognition comprising the steps of:

inputting a transform F of an input object f into a correlator;

inputting said transform F into a matched spatial filter having a transmittance proportional to H* wherein said H* is a conjugate transform of a multiclass reference function defined by h, said matched filter outputting a transform FH*, and

forming a transform correlation product f * h of FH*.

2. A method of constructing a single matched spatial filter (MSF) having thereon a transformer of a multiclass reference function h, said method comprising the steps of:

calculating an average filter equation of said multiclass reference function h;

constructing an average filter h given said average filter equation;

placing said average filter h at a first position in a plane correlator;

forming a transform H of said multiclass reference function h by a lens in said plane correlator,

placing a recording medium in a second position at a focus of said lens, and

recording on said medium said transform H coherently interferring with a plane wave reference beam incident at a selected angle, said recording medium thereafter being a MSF H* having a transmittance that is proportional to said transform H*.

3. A method of constructing a single MSF as defined in claim 2 wherein said constructing of an average filter uses the Vander Lugt method.