Table of contents

Novel optical wavelet joint transform correlators (WJTCs) are presented in this paper. Instead of computing the correlation between the target and the reference patterns, these optical WJTCs compute the correlation between the wavelet transform coefficients of the target and reference patterns. It incorporates the efficient feature detection and noise suppression capabilities of wavelet transformation and the inherent high speed and 2-D nature of optics. The feature extraction and target identification operations are performed in a single step. By suitably choosing the wavelet functions and their dilation factors, these wavelet correlators are capable of effectively recognizing targets in me presence of clutter and noise. Since the reference pattern can be updated conveniently, WJTCs are suitable for adaptive programmable operation. In this paper, a family of wavelet functions that can be represented very simply in the frequency domain and thus are suitable for optical implementation are described. The principle and optical architecture of optical WJTC are presented. Preliminary experimental results are provided.

A systematic study by envelope and prism coupler waveguide methods based on 62%+or-0.5%, atomic concentration of Zn in sputtered ZnO films has been made. In this paper, we report the propagation loss and transmission characteristics of ZnO films. The results show that if sputtering pressuring is varied from 0.30-0.31 mTorr, in the sputtering environment of 50% Ar+50% O₂ and the substrate temperature between 300 degrees C to 350 degrees C, thereby increasing the transition energy (LMM) of Zn from 992.4 to 993.6 eV (in the elemental form), the refractive index reduces drastically to 1.75+or-0.05 (in visible and near IR region) and propagation losses are estimated to be 1-4 dB/cm. The best film has a visible transmission of about 85% and is optically clear with a bandgap of 3.3 eV.

In this heterodyne interferometer for measuring small displacements, an electro-optic modulator is used as a frequency shifter. It has some merits, such as, free from the mechanical vibration, simple and compact optical structure, and a general and inexpensive electrical signal processing circuit can be used without decreasing the measuring resolution and easily operated in real time.

A miniaturized low-noise metal-film bolometer detector array capable of recording radiation spanning a wide spectral range is presented. The bolometers consist of structured gold layers coated with a black nickel layer to reduce the reflectivity in the long-wavelength range. Investigation of the device`s photoresponse showed sufficient sensitivity at wavelengths lambda =4 mm to 6 AA. The detector unit meets high-vacuum requirements, is bakeable up to 300 degrees C, can withstand high nuclear radiation doses, is insensitive to thermal and electromagnetic interferences and can be operated in high magnetic fields. The cooling time of the bolometer is determined by its thermal properties, being about 70 ms in air. The device has meanwhile been successfully used in a few fusion plasma experiments.

The measurement of deviation of microscope stage from squareness to the optical axis is an important parameter in optical testing of microscopes. This test ensures that when the deviation is in the permitted limits, the optical axis of the microscope is normal to the stage and hence the movement of the microscope tube is in normal direction to the stage. In the present article a simple method to measure the deviation of the microscope stage from squareness to its optical axis has been described using a parallel plate and autocollimators. Test results on a few microscopes have been presented.

Higher-order descriptions of Gaussian beams for the so-called standard, localized approximation and modified localized approximation cases are provided. One of the applications of this work is the study of interaction between a highly focused Gaussian beam and an infinite cylinder, which will be published elsewhere.