Showing papers by "Ruikang K. Wang published in 1995"

Synthetic discriminant function fringe-adjusted joint transform correlator

Abstract: A synthetic discriminant function (SDF) fringe-adjusted joint transform correlator is proposed that is able to provide a high degree of image distortion invariance and classify different objects in the input scene. The SDF reference function, which is displayed alongside the input scene, is a linear combination of the training image set. An iterative algorithm is presented and utilized to obtain the linear combination coefficients from the nonlinear equations of the fringe-adjusted joint transform correlation (JTC) system. When compared with the SDF-based classical JTC and binary JTC, the SDF fringe-adjusted JTC delivers a better capability to give localized equal correlation peak heights for the same class of objects. Furthermore, when the input scene contains the different objects from the different classes of images, the SDF fringe-adjusted JTC is shown to efficiently classify the different target objects and reject the nontarget object in the input scene, whereas the SDF-based classical JTC and binary JTC fail to achieve this.

Multilevel phase- and amplitude-encoded modified-filter synthetic-discriminant-function filters.

Abstract: The performance of the modified-filter synthetic-discriminant-function (MfSDF) filter with multilevel phase and amplitude (MLAP) constraints is investigated with various in-plane rotated images from an in-class Bradley armored personnel carrier vehicle and an out-of-class Abram MI tank; this is of interest because of the commercial availability of liquid-crystal televisions, which are able to encode the gray-level amplitude and/or the discrete multilevel phase information. The evaluation is performed to explain better the image-distortion range that can be covered effectively by MLAP/MfSDF filters. The results show that the MLAP/MfSDF filter offers much-improved correlator system performance with a greater allowable image-distortion range while maintaining 100% discrimination between in-class and out-of-class images; furthermore, it shows an improved ability to accommodate the input image noise when compared with the MfSDF filter with a binary phase-only constraint. Thus the MLAP/MfSDF can be implemented effectively by a hybrid optical/digital correlator system to track a vehicle or a tank dynamically as it moves along a random trajectory across the input field.

Wiener filter: synthetic discriminant function for target identification

Abstract: The Wiener filter, which has been used extensively for image restoration and signal processing, is employed for robust optical pattern recognition and classification. The Wiener filter is formulated to incorporate the in-class image and the out-of-class noise image into a single step filter construction. It is compared with the classical matched filter (CMF) and phase-only filter (POF), demonstrating a superior discrimination capability. The Wiener filter is incorporated into a synthetic discriminant function (SDF); correlation results show that it is tolerant to image distortion. With a 30 degree out-of-plane rotation between training set images, the Wiener filter-SDF achieves a 100% success rate in discriminating one-class of images from another. The CMF-SDF and POF-SDF fail to achieve 100% discrimination even at rotation increments of 15 degrees.

Nd:YAC laser sterilization of escherichia coli and bacillus stearothermophilus

Abstract: Photodynamic Therapy (PDT) means tumor treatment achieved through tumorspecific photosensitizer and photoradiation excitation. The basic concept of photoluminescence was already known at the beginning of this century. However, recent developments in photobiology, endoscopy, laser equipments and medical electronics have resulted in rapid progress. The mechanism of the cytocidal effects of PDT is considered to be as follows: when photosensitizer absorbed by a tumor is exposed to light, it absorbs light energy and enters an unstable excited singlet state. When returning from this unstable excited state to the stable ground state, the energy of the triplet status of photosensitizer is transferred to the oxygen in tissue, the excitation of which produces excited singlet oxygen. Singlet oxygen has toxic effects on tissue, thus making it possible to treat tumors. A derivative of hematoporphyrin was used as a photosensitizer clinically. Recently in Japan, Canada, The Netherlands and USA, Photofrin (Porfimer sodium) is used clinically. Laser equipment included argon dye laser, gold vapor laser and copper dye laser. A recently-developed excimer dye laser has shown better tissue penetration characteristics. Also Nd-YAG OF0 lasers, KTP lasers and diode lasers are under development. PDT is indicated for the curative treatment of early stage cancer lesions and sometimes for the palliative treatment of advanced cancer lesions. In the latter there are possibilities of combination with chemotherapy, radiotherapy and surgery. A total of more than 3,000 tumors have been treated so far in the world. The author describes the present status of photodynamic therapy in the world and especially on the application of this therapy as curative treatment in early stage cancer. The International Photodynamic Association was focused to promote studies in this field. The First Conference was held in Tokyo by Hayata in 1986. The second in London by Carruth in 1988, the third in Buffalo by Dougherty in 1990, the fourth in Milan by Spinelli in 1992 and the fifth was held in Jacksonville, USA by Cortese in 1994. With increasjng govemmental approval as a clinical modality much attention is being paid to PDT and the IPA has been developing accordingly. The next conference will be held in Melbourne, Australia in March 1996. ThL2 1130

R. K. Wang, I. A. Watson, C. R. Chatwin

Abstract: To improve correlation performance, we give further consideration to the filter- encoding constraint applied to the SDF construction. The idea is to synthesize the SDF from the linear combination of a set of training images that are already filter modulated, i.e. preprocessed, so that the constructed SDF is dominated by the higher, not the lower, frequency components of the individual training-set image. The filter-encoding constraint is then applied to the SDF. For convenience this is called the modified fSDF (MfSDF).

Performance of tuneable photo-refractive filters

Abstract: The use of the widely available photorefractive material, Bismuth Silicon Oxide (BSO), as a tunable holographic filter’ is an extremely effective optical technique with which the performance of optical correlators’ can be improved. This approach was physically implemented as part of a matched filter by Young and Chatwin,; it exploits selective erasure of spatial frequencies at the Fourier plane in the photorefractive material BSO. Experimental shows that the tuneable photo-refractive (TPR) filter not only gives sharp correlation peaks and good discrimination ability but is updateable and tuneable in real time via a variable attenuator, see Fig. 1. The spatial frequency weighting of the TPR correlation operation can be tuned by varying the amplitude of the plane wave reference beam U, via the attenuator shown in Fig. 1. The ratio between U, at zero spatial frequency, and U3 is defined as