The measurement of the temperature of objects by remote means is important in science, industry, and other areas. A technique often employed is ratio radiometry, in which the temperature of the object is related to the ratio of the radiometric signals derived from each of two measurement spectral bands. A lingering question as to whether this technique is valid for determining temperature is answered. Although the technique is generally valid, certain spectral-band pairs can produce ambiguous results, namely, the same ratio can be obtained by looking at two objects, each at a particular, yet different temperature. Ambiguities occur only for spectral-band arrangements in which one spectral band is completely contained within the other. Examples are presented to illustrate this finding.
The impact of tilt bias errors in multiple wavefront interferometry is assessed in terms of its effect on the ability to determine piston phase differences between wavefronts from such interferometry. The error in such piston phase determination due to tilt bias has been found to be substantial. On the other hand, several techniques have been found to be viable in which both tilt and piston phase errors may be determined simultaneously from such interferometry with proper algorithms.
Dammann gratings are binary phase gratings that are used to produce a one- or two-dimensional array of equal-intensity light spots. Recently, Dammann gratings have become of interest for their ability to provide the optical power supply to an array of optical logic devices from a single laser source. We present here a feasibility study of Dammann gratings, in which we consider several parameters that are important for the computation and fabrication of the gratings. As a result of this investigation we conclude that Dammann gratings are useful for array sizes up to about 40 x 40 spots. Above that size, problems with the computation of the gratings and with the resolution become dominant.
The design of an all-optical exclusive-OR gate and a set-reset flip-flop is described, and the operation characteristics of both circuits using nonlinear ZnSe interference filters is reported. While both functions could be demonstrated, long-term stability in excess of 30 s was not obtained for the flip-flop operation.
Guided-wave optical interconnections for interchip data transmis-sions and clock distributions are demonstrated. The optical interconnection circuit consists of a silica-based guided-wave circuit, laser diodes, and photodiodes. The interconnection topology adopts the star coupler network used in local area networks as a model. The laser diodes and photodiodes are assembled with the guided-wave circuit by the hybrid integration technique. Preliminary experiments on a four-chip interconnection circuit yield a 340 Mbps data rate and a 250 MHz clock frequency.
The maximum detection range for an infrared system depends on the signal-to-noise ratio of the target. Calculation of the signal from an intrinsic infrared detector with a flat spectral quantum efficiency such as indium antimonide or mercury cadmium telluride is straightforward, and simplifications yielding closed-form solutions can be obtained. Schottky barrier diodes have a complex spectral quantum efficiency function because of the nature of hot carrier photoemission, leading to a complex function for both the signal and noise components. This paper derives a detection range equation for Schottky barrier staring sensor systems using this spectral relationship as well as other parameters unique to these diodes.
A new technique is presented for automatically determining whole-field interference fringe orders. The modulated fringe pattern is collected and processed with an image processing system. The mechanics information included in the fringe pattern is obtained by a demodulating calculation. Special software is designed for photoelastic, holographic, moire, and speckle fringe patterns. The procedure is demonstrated, and some main subroutines are described in detail. The technique is applied to different examples with satisfactory results.
Measured values of critical optical processor performance parameters such as crosstalk and dynamic range generally fall short of the values predicted on the basis of first order design, ray tracing, and diffraction calculations. Normally, the procedure used to design an optical system such as a coherent optical processor does not take into account optical scatter, reflections, and incoherent light in the source. Stray light factors are of critical importance in those systems designed for spectrum analysis or correlation in which the light is collected on a closely spaced array of pixels. If the (bidirectional) transmission distribution function (BTDF) of optical elements were known very near specular (0.01° to 0.001°) and a suitable means of calculating its effect were available, stray light performance could be included in the design procedure. Instruments are now available that can measure the BTDF near the required angles, and an optical design code is also available that can make use of BTDF data. BTDF data for samples of acousto-optic material have been measured close to 0.001°, and the possibility of smaller angles is discussed. The new analysis code has been used to model several simple configurations found in acousto-optic processors. The results are compared with normal calculations (CODE V) and with some measured performance data.
To suppress the change in polarization of the transmitted He-Ne or CO2 laser beam through a system consisting of four spherical mirrors, a system of four separate transparent thin films is designed. Each mirror is initially coated opaquely with silver, and the transparent film for preserving the polarization state is on top of the silver substrate. The thin film designs for the system are obtained using a computer optimization process, and their stability for random thickness errors and for the change in the angle of incidence are checked. The final design obtained for a He-Ne laser beam uses TiO2 film and that for a CO2 laser beam uses PbTe film.
Described here are the optical and image processing aspects of a computer vision system for automated precision measurement of manufactured objects. A multi-magnification, multi-path telecentric imaging system with multiple illumination sources provides broad utility. A general method of deriving digital filters for image analysis is presented.
We reached this modification through a useful discussion with Jacob Politch of the Technion-Israel Institute of Technology. In working out the above result, we referred to A Short Table of Integrals, 4th edition, by B. 0. Peirce, revised by R. M. Foster (Ginn & Co., Boston, 1956).
For several months I have known that I would eventually write this editorial-I just didn't know when. Now the time has arrived. Martha Stockton died at 3 o'clock this after-noon, November 16, 1989, after a lengthy bout with cancer. On behalf of the officers, governors, members, and staff of the Society, I wish to express our heartfelt sympathy to her husband Chuck, her daughter Sara, and the rest of her family and friends. This editorial is dedicated to her memory.
This volume is a revised edition of the 1982 edition of Introduction to Nonlinear Laser Spectroscopy by Marc Levenson. Most of the material in the book is similar to that of the first edition. Fot this reason I will not present a detailed review of the book. It has not changed enough in scope or content to warrant that.