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Optical Engineering

Multiple-target recognition using the discrete rotational Fourier transform
Author(s): Neng-Chung Hu; Kuo-Kan Yu; Hong-I Chang
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Paper Abstract

Much research has been devoted to locating multiple targets on the condition that there is only one pattern in the reference image and more than one such pattern in the input image. We, however, propose a new correlator to locate and display multiple different targets when both the reference and the input images contain many different patterns. This correlator is based on the two-dimensional (2-D) discrete rotational Fourier transform (DRFT), which extends the one-dimensional (1-D) DRFT. Since the DRFT domain of an image contains information both in the spatial domain and in the frequency domain of the image, we use this property to locate and display the matched targets. The DRFT-based correlator first obtains x?[u1,u2]H*?[u1,u2],where x?[u1,u2] and x?[u1,u2] are the DRFTs of the input image and the reference image, respectively; then the inverse discrete Fourier transform (IDFT) of x?[u1,u2]H*?[u1,u2], yields many cone-shaped correlation peaks. A correlation peak stands for a matched pattern between the input image and the reference image. To display the shape of the matched pattern, x?[u1,u2] is shifted according to the position of the correlation peak yielding x?[u1,u2]. Finally, |x?[u1,u2]H*?[u1,u2]| displays the shape of the matched pattern. Like the conventional correlator, the DRFT-based correlator can recognize only the translated versions of the patterns in reference image. The purpose of this approach is to recognize multiple different targets simultaneously. The properties of the proposed 2-D DRFT are also presented.

Paper Details

Date Published: 1 August 2001
PDF: 12 pages
Opt. Eng. 40(8) doi: 10.1117/1.1386371
Published in: Optical Engineering Volume 40, Issue 8
Show Author Affiliations
Neng-Chung Hu, National Taiwan Institute of Technology (Taiwan)
Kuo-Kan Yu, National Taiwan Institute of Technology (Taiwan)
Hong-I Chang, National Taiwan Univ. of Science and Tech. (Taiwan)

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