The storage capacity of a matched filter array can be increased by superposing a number of target diffraction patterns at each individual location in the corresponding multiple holographic lens array during matched filter fabrication. All required target orientations and scale size views can be accommodated in this manner. The Fourier transform properties of coherently added target diffraction patterns are described in this paper. The composite input image for coherent addition of Fourier patterns consists of rotated and translated target views. The Fourier transform of the composite input is derived, and several properties are described. When the target array has radial symmetry, matched filter optimization can be easily carried out.
Binary phase-only filters (BPOFs) are a viable candidate for the replacement of matched filters in real-time image processing and pattern recognition applications. The original BPOFs were binarized versions of the real or imaginary parts of the Fourier transform. Recently, a filter has been proposed that is the binarized Hartley transform. In this paper, the noise performance of the binarized Hartley phase-only filter is analyzed and compared with other BPOFs as well as with the phase-only and matched filters. It is well known that the matched filter optimizes the signal-to-noise ratio. Further, it can be shown that the matched filter phase is the optimum phase-only filter. A bound on the BPOF signal-to-noise ratio relative to that of the phase-only filter is derived. Finally, the analysis is applied to the generalized form of the binarized Hartley transform.
A catadioptric Cassegrain optical system is described that permits simultaneous operation as an infrared (IR) imager and a millimeter wave (MMW) radar through a common aperture. Separation of IR and MMW focal points is achieved by use of suitable dichroic coatings and substrate materials. We have evaluated our design by building a prototype and measuring its performance in the laboratory, with particular attention given to isolating the degradation suffered by each mode due to the presence of the other. We present our test results and conclude from an analysis of the data that although our design is feasible, improvements are needed both in the design of the secondary element and in the technology for conductive dichroic coatings.
The system design of an automated meridian scanning photometer developed for the Canadian Auroral Network is described. The instrument operates unattended year round in an arctic environment. The instrument has considerable on-board processing capability for data analysis, communication functions, and fail-safe operation.
A deterministic approach is used to derive the total number of platforms, sensor elevation field of view, and sensor/space-object maximum range requirements for the preliminary design of space-based surveillance systems in polar orbits that provide continuous multiple global or polar cap above-the-horizon (ATH) viewing. These requirements are determined as a function of surveillance platform altitude, the minimum and maximum space object altitudes of interest, and the multiplicity of continuous global or polar cap ATH coverage desired. Example trade-offs are given for platform altitudes between 500 and 2500 km.
This paper presents some preliminary success in the computerizing of data reduction in shearography. Computerization is made possible by the introduction of a fringe carrier technique that removes the ambiguities in fringe interpretation. The technique is based on superposing a set of carrier fringes upon the deformation fringes. The resulting fringe pattern has monotonically increasing fringe orders, thereby allowing the fringe orders to be determined in a straightforward manner and without ambiguity. It is shown that the data deduction process can be computerized. The deformed carrier fringe pattern is digitized, and the displacement derivatives are then automatically deduced by means of digital image processing.
A high speed programmable fiber optic binary data generator is presented. Data generation is accomplished by time-multiplexing the outputs of a number of laser diodes. Programmability is achieved by individual control of each laser diode. A 500 Mbit/s RZ prototype that uses 32 laser diodes is presented along with experimental results of a 3.85 Gbit/s RZ four-channel system.
A novel noncontact, nondestructive method for measuring the active layer thickness of InP/InGaAsP double heterostructure laser materials has been developed. This method is principally based on the evaluation of the net absorption through the active layer by measuring the transmission light power. It is proposed that troublesome effects such as reflection, scattering, and unnecessary absorption through the other layers can be canceled out by using a pair of light sources with wavelengths slightly longer and shorter than the peak wavelength in photoluminescence. A prototype system including a personal computer and an auto-moving X-Y stage can evaluate the distribution of the active layer thickness over the entire wafer with an accuracy of better than 10 nm.
A new recording technique for Hopfield-type dynamic auto-associative memories is proposed. The new technique is based on the finite and exponentially convergent algorithm of Ho and Kashyap for the solution of a system of linear inequalities. Associative neural memories recorded with the proposed algorithm are shown to be superior to those recorded with the Hopfield outer-product and Kohonen generalized-inverse techniques. The new recording algorithm is characterized by high capacity, high convergence rates to stored memories and low convergence rates to false and oscillatory states. The issue of stable false and oscillatory states is raised, and it is shown that such states appear to have a direct Boolean logic relationship with the stored memories.
The technique of phase measuring by spatially modulated carrier fringes is applied to analyzing holographic and shearographic fringes. The algorithm employed is a simplified version of the Fourier transform method and does not require any special device such as the frequency modulator used in time domain phase detection techniques. Analyzed phase data are numerically differentiated to calculate full-field distributions of flexural curvature and twist, which correspond to flexural strains.
The optical replication process and its advantages and disadvantages are reviewed. Substrate dimensional stability under normal exposure to thermal and dynamic stresses is identified as an important issue in the design and stability of replicas and the selection of materials for their fabrication. An analysis is presented to help in the selection of materials that are of particular interest in the construction of surfaces with low dynamic deflection. Typical manifestations of loss of dimensional stability for some of these materials are described. Data are presented for materials and methods of processing that were found to be particularly successful in overcoming problems of dimensional stability.
The fabrication and assembly of a compact rotational shearing interferometer with variable shear and phase compensation is described. The interferometer has been used for seeing measurements and interferometric imaging in optical astronomy.
The traditional optical test for an off-axis segment of a parabolic mirror utilizes an autocollimation flat and requires considerable test-bay space. We describe several other test configurations that will minimize space requirements. One method involves a null corrector, and three others require no auxiliary test optics. Combinations of the methods described will be useful in providing full independent evaluation of the figure of the segment under test.
Direct phase matching measurements are a powerful way to characterize the frequency conversion properties of small (submillimeter) crystals of new nonlinear materials. These measurements represent a level of characterization lying between powder tests and detailed refractive index and d coefficient determinations. Since crystals as small as 100um can be studied, a decision to pursue the development of a material can be made at an early stage of crystal growth. Representative data on some new harmonic generators are presented to illustrate various features of the technique.
The special issues of Optical Engineering for 1989 will again cover a variety of important and timely topics in optics, as can be seen from the editorial schedule that appears on this page. In the first special issue of 1989, which will address polarization considerations in optical systems, will be the February issue, and Russell Chipman will serve as a guest editor. Then in March, Sing Lee and Ravi Athale will serve as co-guest editors for a special issue on optical computing.
It is unusual to find a book devoted strictly to electrical engineering reviewed in this column. However, pulsed power technology plays an important part in the design of many laser systems, and the system engineer should be aware of the prroblems and difficulties involved. Such a series as Advances in Pulsed Power Technology should be useful to many professionals in the optical field.