DISCRIMINATION-SENSITIVE ROTATION-INVARIANT JOINT-TRANSFORM CORRELATOR USING GRADIENT PREPROCESSING AND CIRCULAR HARMONIC COMPONENTS

The advantage of discrimination sensitivity of a preprocessed binarize d joint-transform correlator (PBJTC) has been combined with the rotati onal tolerance of circular harmonic component (CHC) analysis to realiz e a JTC which gives a discrimination-sensitive, rotation-invariant pat tern recognition system. Both computer simulation and experimental res ults are provided. The use of gradient preprocessing and adaptive bina rization helps in suppressing the sidelobes otherwise associated with a conventional CHC-based JTC. The simulation study shows that such a c omposite JTC gives a sharp correlation peak for the rotated target and discriminates nontarget, producing a very low crosscorrelation peak t hat stays below the detection threshold. Although it involves two addi tional improvisation steps (gradient preprocessing and computation of the CHCs), they can be performed prior to the correlation operation, a nd the simple binarization process can be realized faster optically al ong with a dedicated digital comparator. (C) 1998 Society of Photo-Opt ical Instrumentation Engineers. [S0091-3286(98)01301-4].