Earlier this year Optical Engineering published a paper with twenty-seven coauthors. This notable event stimulated your editor to consider some of the problems and protocol of the listing of coauthors. What follows is a rather unordered set of observations on what I believe to be a very important topic.

Raman spectroscopy is one of the most versatile methods of molecular analysis. The Raman effect consists of the appearance of displaced lines in the spectrum of monochromatic light scattered by substances. The Raman scattered radiation is spectrally shifted by an amount which corresponds to the vibrational or rotational energy for a transition of the molecule in question. The magnitudes of these displacements provide an unambiguous identification ("fingerprint") of the measured species. The amount of light which is scattered at a given wavelength (intensity of the spectral line) is a measure of molecular concentration.

It is the aim of the present work to show some departures from the well-known optical Bloch equations usually obtained when the damping of a two-level system driven by a Glauber coherent mode of the radiation field is treated in the Markovian approximation. In particular, we show that for an arbitrary intensity we have a set of 4 n optical Bloch equations which can be reduced to the usual optical Bloch equations when the population of the mode becomes important. A criterion for the quasi-classical evolution can be deduced. Obviously, in both limits of an arbitrarily weak or strong excitation intensity the Mollow's results are obtained. In addition, we do not need here the introduction of a particular form like the plane wave used by Mollow for the corresponding classical field--as the problem is solved explicitly.

An oceanographic Raman lidar has been shown to be an effective tool for immediate (early) applications in Navy and National Oceanographic and Atmospheric Administration (NOAA) programs. Remote sensing of the depth of the ocean mixed layer will be of significant importance both in acoustic propagation prediction and in long range weather and climate forecasting. The characteristics that are required in a dual polarization Raman lidar for this measurement are discussed. The feasibility of the concept has been tested in field experiments which have measured gradients to an accuracy of 0.5°C. The parameters of an airborne measurement system concept are described.

A brief historical review of Raman scattering as applied to remote sensing in the atmosphere is given. Recent data on relevant cross sections are tabulated. System performance characteristics of some of the more important measurements of the Raman lidar are reviewed and compared with experimental results to date. Comparisons are made with alternative methods of atmospheric probing with particular emphasis on differential absorption lidar (DIAL) system performance. System performance capabilities are reassessed on the basis of the latest available hardware and a near-term outlook is projected.

The pyrochlore structure is an oxygen-deficient derivative structure based upon fluorite in which one-eighth of the oxygen atoms are removed forming an array of ordered vacancies. All of the rare-earth titanates crystallize into the pyrochlore structure with the exception of Nd2Ti2O7. Raman spectra of these materials exhibit extensive line broadening in excess of disorder arising from the crystallinity of the materials as determined by x-ray diffraction. Spectra obtained at liquid nitrogen temperature (128 K) exhibit a marked narrowing of Raman lines and an overall enhancement in intensity. The thermal dependence of the Raman linewidth is attributed to a dynamically disordered dipole caused by titanium ions shifting off of their equipoints. Measurements of dielectric permittivity made down to liquid helium temperature (4.25 K) support this hypothesis.

A Raman polychromator system is described which makes use of a concave grating, two objectives with f-numbers lower than 1, and a multi-channel detector. The system provides a very large optical throughput and should be suitable for analysis of gaseous and liquid samples--especially in cases where the concentration of the compounds investigated is rapidly varying. This is demonstrated by measurements at automobile exhaust gases and by an on-line detection of high-pressure liquid chromatography (HPLC)-fractions.

A Nd/YAG based coherent anti-Stokes Raman spectroscopy (CARS) system has been used in a variety of studies in inorganic chemistry and related fields. The results illustrate the strengths and limitations of CARS. Those described include high temperature vapors in sapphire cells (cesium sulfate and potassium perrhenate), and high temperature melts (potassium sulfate).

Coherent anti-Stokes Raman scattering (CARS) has become a very powerful tool in the measurement of temperature and concentrations in practical combustion environments. The technique is also proving to be useful in the study of other types of reactive media including plasmas, photodissociation studies, and excited-state relaxations. This paper reviews several research areas involving reactive or transient species where the spectral and temporal properties of CARS have been exploited.

The ability to model the CARS (coherent anti-Stokes Raman spectroscopy) spectra of combustion molecules is an important part of the process of extracting diagnostic information from CARS signals; measurements of temperature or species concentration usually require that the experimental signatures be analyzed with the aid of computer-synthesized spectra. This dependence on theoretical models arises from spectral interference effects unique to CARS; because it is a nonlinear optical process whose signal strength depends on the squared modulus of the third-order electric susceptibility, the spectral shape is affected by interferences between neighboring Raman transitions and between the resonant and nonresonant contributions to the susceptibility. This paper will review the status of modeling the spectra of molecules important in combustion, such as N2, H2O, and CO2. It will be shown that accurate modeling generally requires highly precise knowledge of line positions and reasonable estimates of Raman linewidths, and the sources of these data will be discussed. In many practical applications, pressures well above atmo-spheric are encountered, and the phenomenon of collisional narrowing can become important. This effect, which has its origins in rotationally inelastic energy transfer between adjacent J-states, gives rise to a pronounced narrowing of signatures with increasing pressure. The status of modeling this effect in N2, H2O, and CO2 will be described, and it will be seen that good agreement with experiment can be achieved using either the Gordon rotational diffusion model or phenomenological models for inelastic energy transfer rates.

This paper describes a method of hybrid processing of data and its applications in various spheres. The principle is to use an optical Fourier transform device coupled to a minicomputer via a mechanically driven diaphragmed monodiode scanning system. The principles and technologies are discussed.

An infrared staring mode imaging sensor was designed to operate with the NASA Infrared Telescope Facility (IRTF) at Mauna Kea, Hawaii. The sensor has a 0.5 arc sec spatial resolution over a 10 arc sec field and is matched to the f/35 focal ratio of the telescope. The focal plane device is a back-side illuminated Schottky infrared charge-coupled device (IRCCD) mosaic with a photoresponse from 1 to 5upm. Astronomical observations are reported at 2.2 um where the IRCCD quantum efficiency is substantially greater than values normally reported for the 3.4 to 4.2 um thermal imaging band.

Optical rangefinders, lidars, and laser tracking systems offer new options for a variety of applications. When a laser system operates in a tracking regime, it must continuously estimate target angle coordinates. This purpose may be achieved by means of a quadrant detector (QD) incorporated in the optical receiver. In this paper, performance of the QD-based laser tracker is evaluated theoretically. Angle measurement span, angle estimation bias, and angle estimation variance are analyzed with the emphasis on the quantitative evaluation of the estimation bias and variance. It is shown that the estimation error contains both systematic error (signal-independent bias) and signal-dependent bias. The systematic error is caused by the signal processing circuitry of the receiver; this error is rather large (up to 1 1.5% of the measurement span), but may be easily cancelled by means of a permanent look-up correction table stored in a ROM (read-only memory). Signal-dependent bias cannot be cancelled with the same technique since it depends on the a priori unknown signal intensity. Fortunately, signal-dependent bias decreases when the SNR (signal-to-noise ratio) increases, at a rate proportional to s/SNR; however, it increases rapidly when the light spot approaches the end of the measurement span. Estimation variance is also evaluated. It is found to decrease when the SNR increases, at a rate roughly proportional to SNR. Estimation variance remains approximately constant as the light spot moves over the measurement span. Thus, the main consequence of the deviation of the light spot from the QD center is the increase of the estimation bias, rather than a change of the estimation variance.

This paper describes the results of recent research undertaken to examine the feasibility of employing laser interferometry to precisely measure absolute distance over extended ranges. Data are presented that show a resolution of 0.03 um (rms) for measurements over distances up to 10 meters. The technology developed for achieving these results is based on two-color, synthetic Michelson interferometry employing a new CO2 laser source. Indeed, the new laser is the key element in this process: it was specifically designed to sequentially switch between four sets of stable R- and P-line pairs and thereby provide a basis for forming simultaneous equations which were employed to greatly reduce the half-wavelength ambiguity typical of single wavelength interferometers. Potential applications to future optical telescopes--particularly the large, multipanel telescopes under consideration for 10-15 years hence--their initial alignment and control, are suggested.

An automated method for making microfiche from roll microfilm is described. The system, called a composing reducing camera (CRC), accepts unperforated 35 mm negative microfilm. A servo-controlled film transport introduces the film, one frame at a time, into a filming gate. An integrating sphere, for uniform illumination, and a xenon flashlamp "freeze" the frame for high resolution imaging. Introduction of a mirror into the optical system permits any frame to be displayed on a television monitor. Provided with a keyboard, an operator may, with the aid of a photocomposer, automatically title the micro-fiche. A complete fiche may be recorded at filming rates up to 8 frames per second in any desired microfiche format.

The ray optic evaluation method of gradient-index (GRIN) rod lenses is described. The feature of this method is to utilize the fact that the ray path in an inhomogeneous refractive index medium is determined uniquely by the initial condition given externally. Some numerical examples of the ray tracing on one-quarter pitch and one-half pitch GRIN lenses and simple expressions corresponding to the refractive index profile are shown.

A dimensional analysis of laser surface alloying (LSA) using measurable experimental variables and known thermophysical properties has been carried out to identify useful dimensionless parameters influencing LSA. Measured solute contents from a two-level factorial experiment alloying nickel into AISI 1020 steel substrates are plotted against these parameters and found to vary hyperbolically. Similar trends are shown to be contained in published data alloying chromium into 1020 steel. The two parameters make good physical sense, point to mechanisms in LSA, and may be used for process control. One parameter is the laser surface alloying parameter (LASAP), where LASAP = P/pud2, and P is incident laser power (W), p is surface gas pressure (N/m2), u is traverse speed (m/s), and d is beam diameter (m). The other is the laser processing parameter (LAPP), where LAPP = Pd/(pau2d2) and p, d, u are as above, whilep is the substrate density (kg/m3) and a is the substrate thermal diffusivity (m /s).

The results of the evaluation of a breadboard, edge-actuated, modal, deformable mirror are given. The mirror was designed to correct for focus and two axes of astigmatism in the Zernike formulation using three actuators. The dynamic response of the mirror, with single mode input, is down 3 dB at 150 Hz with a phase shift of 75°. For single mode input, the surface deformation with static input is linear to at least ±0.1 10.6 (±1.1 um) with cross coupling to the other modes less than 10%. Calibration curves derived from the single mode input data are included. With multimode static inputs, the surface deformation deviation from the calibration curves is generally less than 0.02 10.6.

An improved method has been devised to measure the apex angle of a 60° prism based upon the knowledge of refractive indices and by measuring the angle of minimum deviation at different wavelengths. It is found that the error in measurement of the apex angle is less than 3% and that this method could supplement the other techniques used in an optical laboratory.

In this paper, we describe the basic principle and aberration properties of both single-element and two-element catadioptric magnifiers which have been designed and fabricated. These magnifiers are capable of producing visual magnification of 15 to 20 times with large eye-relief, and they are useful for reading microfiche having frame sizes of 16 mmX12 mm and 12 mmX9 mm. It has been found that by changing the shape of the single-element catadioptric magnifier, field curvature and distortion can be improved by considerable amounts. A much better improvement has, however, been obtained with the two-element system.

Numerous adaptive contrast enhancement techniques have been developed to improve the visual utility of imagery. Most of these techniques involve the use of neighborhood operators, and some require manual input of scene-dependent functions to operate properly on different images. The local range modification (LRM) technique described in this paper does not involve neighborhood operators in the conventional sense of the word nor does it require design of scene-dependent functions, yet it yields results comparable to more computation-intensive techniques. In this paper, a unified description of the spatial filter-based adaptive contrast enhancement algorithms is presented. LRM is then described and qualitatively compared with the other algorithms in terms of efficiency, effectiveness, and artifact generation.

Simultaneous two-way communications through a single fiber with solid-state lasers as source are described. A system was designed to use the same optical subsystem for transmitting as for receiving at each of the two communicating stations. A multilayer, single-mode, elliptical fiber capable of preserving the two orthogonally polarized modes of propagation was used as the transmission medium. The multilayer configuration was constructed to confine most of the energy in the fiber core to minimize losses to absorption in the claddings. Separation of the beams was made by a duplexer capable of distinguishing the difference in polarity of the two beams.

Images of Saturn received from Pioneer 11 suffer from geometrical distortions due to the curvilinear scan lines and the unequal sampling intervals in orthogonal directions, which are inherent in spin-scan imaging. In this paper we discuss geometrical image rectification by polynomial transformation based on control points. Factors that affect the accuracy of reconstruction are shown to include the spatial distribution and spatial density of control points and the order of the polynomial distortion model. A computer implementation of the technique is described.