Joewono Widjaja

Use of wavelet analysis for improving autofocusing capability

Abstract A novel method for improving autofocusing capability by using wavelet-based correlation is proposed. Experimental results show that the proposed wavelet-based analysis could detect slightly out-of-focus images. Therefore, it could improve autofocusing capability.

Detection performance of wavelet-based joint transform correlation.

The detection performance of a wavelet-based joint transform correlator (JTC) is studied by use of two types of images with different spatial-frequency contents and contrast. The simulation results show that, in comparison with an amplitude-modulated JTC, the performance for intraclass pattern recognition can be optimized by using a single wavelet filter.

Real-time joint transform correlator using compressed reference images

A real-time implementation of a joint transform correlator by using JPEG-compressed reference images is proposed in order to solve storage problems and improve the time response of automatic target recognition systems. The correlation performance is studied quantitatively by using two types of images with different spatial-frequency contents. The simulation results show that in comparison with the compressed high-spatial-frequency images, the joint transform correlator using the compressed low-spatial-frequency reference image offers better recognition performance in that it is robust to noise and contrast difference for a wide range of compression levels.

Direct analysis of in-line particle holograms by using wavelet transform and envelope reconstruction method

Summary We propose a new digital method for sizing particles and tracking their positions from an in-line hologram by using a combination of a wavelet transform and a reconstruction of the envelope functions. In the proposed method, the hologram is recorded by a charge-coupled device (CCD) sensor. The wavelet transform of digitized holograms gives information about the position of particles, while the reconstruction of envelope functions provides the size of particles. Preliminary theoretical and experimental verifications are presented. The system limitation of the method is discussed.

Optical wavelet-matched filtering by four-wave mixing in photorefractive media

Abstract A novel real-time optical processor is proposed for implementing wavelet-matched filtering that uses four-wave mixing in photorefractive media. An edge enhancement property of the wavelet transform and an improved pattern recognition capability of the proposed method are demonstrated experimentally. The results verify the usefulness of the proposed method compared to the conventional matched filtering by four-wave mixing.

Experimental verifications of a joint transform correlator using compressed reference images

Single-target and multiple-target detections by using a joint transform correlator (JTC) with compressed reference images are experimentally verified. Two high-contrast images with different spatial-frequency content are used as test scenes. Although an effect of the additive noise on detection performance of the proposed correlator is more severe than that of the compression, the experimental results confirm the feasibility of implementing the JTC with compressed reference images.

ANFIS-based fingerprint-matching algorithm

A new method for fingerprint identification is proposed, using an ANFIS-based matching algorithm, which is suitable for large-scale identification systems. In this algorithm, the Gabor transform is used to extract features of fingerprints, while ANFIS is trained to identify the resultant Gabor features. Experimental verifications show that this proposed matching algorithm has high accuracy.

Real-time generation of the Wigner distribution function by means of a single acousto-optic modulator

Abstract A new real-time optical processor is proposed for generating the Wigner distribution function of time signals. The optical system in the processor is simple since it only employs a single acousto-optic modulator. Verification of the present method is accomplished by means of an integrated detection system consisting of a scanning mirror, a photomultiplier, and an interface circuit. Experimental results are presented for cosine and chirp signals, and show a good agreement with the theory.

Wavelet filter for improving detection performance of compression-based joint transform correlator

A new method for improving fingerprint detections by a compression-based joint transform correlator (JTC) via wavelet filter is proposed. The simulation results show that the proposed method has advantages over the conventional compression-based JTC in that detection performance can be maximized to be higher than a classical JTC by using a smaller file size for the compressed-reference images.

Wavelet transform-based autofocus camera systems

A new autofocusing mechanism based on wavelet transform is proposed. Our proposed method takes advantage of the fact that an autocorrelation of a wavelet-transformed signal gives a sharper correlation peak than a conventional autocorrelation does.