The subject of this editorial is figures-not the kinds of figures seen on the beach or those displayed in the columns of a ledger. The figures of concern here are those included with manuscripts submitted to Optical Engineering. You might ask, "Why an editorial on figures?" I'll tell you why-because we have been receiving too many crummy ones! I don't wish to exaggerate the severity of the problem, but approximately 11 out of every 10 illustrations submitted are bad. I don't understand the reasons for this, particularly when the journal to which they are being submitted is one involving optics, but it is true.* I just can't figure it out.

Laser Beam Scanning: Opto-mechanical devices, systems, and data Storage Optics-Reviewed by Bruce M. Radl; Integrated Optoelectronics-Reviewed by J.P. Donnelly; Planar Circuits for Microwaves and Lightwaves-Reviewed by Arthur A. Oliner;

In August 1985, forty-eight international papers on x-ray multilayered optics were presented at the SPIE annual symposium in San Diego. The number of presentations given in the three-day conference entitled Applications of Thin-Film Multilayered Structures to Figured X-Ray Optics (SPIE Proceedings Volume 563) reflects the current high level of activity and interest in this field, which continues to rise.

Soon after the discovery of x rays and their property of constructive interference scattering (diffraction) by solids resulting from the ordered array of atoms forming the solids, it was proposed that man-made (synthetic) layered structures might extend the range of utility of this phenomenon into spectral domains not accessible using naturally occurring crystalline materials. The synthesis of such layered materials has been of research interest since the 1920s, and in the past decade processes for the formation of multilayer structures of sufficient quality for x-ray optic applications have been developed. In this paper a brief review of the history of this work is given. The development of effective synthesis processes is then considered and current approaches summarized. The current status of the field of multilayer x-ray optics is then discussed, with emphasis on figured structures. Current limitations and the potential for both technological and scientific advances are then considered.

A computer-controlled electron-beam evaporation system is described that allows fully automated production of soft x-ray reflection coatings with laterally graded d-spacings. Thickness control is done by a combination of measurement of the evaporation rate with a quadrupole mass spectrometer and measurement of the soft x-ray reflection coefficient on a reference substrate during deposition. Graded thickness is obtained by computer-controlled movement of shutters. A result is given for automatic deposition of a multilayer coating. The first results for deposition of a multilayer soft x-ray coating with linearly varying d-spacing are presented.

The isoangle and isobragg are new concepts used in mapping loci of incident and reflected rays associated with a dispersive reflector. An isoangle is a line joining the points of incidence at which the angle of incidence of rays from a point source is the same. An isobragg is the line joining the points of intersection at any surface by rays of the same wavelength that have been reflected according to Bragg's law. Their patterns provide an understanding of why and where we use dispersive multilayered optics in x-ray monochromators and spectrometers with Rowland circle geometry. They have led to the design of an x-ray focusing ring for electron spectroscopy for chemical analysis (ESCA) instrumentation and the possibility of a design for a scanning x-ray microscope.

F. Abeles developed an exact 2 X 2 matrix method for computing reflectance and transmittance of flat stratified structures of arbitrary complex refractive index profile. By distorting the coordinate system for his method from rectangular to confocal ellipsoids of revolution, the same method can be applied to focusing systems. The well-known 1:1 toroidal focusing geometry, corresponding to unit magnification, occurs at the equators of the ellipsoids. Near the equator, if the Bragg angle is not too small, and also close to the axis of foci, curved layers of uniform thickness are often close enough to the ideal profile for satisfactory spatial and spectral resolution. In very thick multilayers with small absorption, uniform layer thickness in the toroidal geometry results in some dispersion with interference fringes on one side of the maximum. Away from the equator or axis, and particularly at low Bragg angles, profiling or gradation of thickness may be necessary for satisfactory resolution. Examples of computations with Abeles's method are shown.

A procedure is described for a detailed characterization of multilayer analyzers that can be effectively applied to their design, optimization, and application for absolute x-ray spectrometry in the 100 to 10,000 eV photon energy region. An accurate analytical model has been developed that is based upon a simple modification of the dynamical Darwin-Prins theory to extend its application to finite multilayer systems and to the low energy x-ray region. Its equivalence to the optical E&M solution of the Fresnel equations at each interface is demonstrated by detailed comparisons for the reflectivity of a multilayer throughout the angular range of incidence of 0° to 90°. A special spectrograph and an experimental method are described for the measurement of the absolute reflectivity characteristics of the multilayer. The experimental measurements at three photon energies in the 100 to 2000 eV region are fit by the analytical modified Darwin-Prins equation (MDP) for 1(0), generating a detailed characterization of two state-of-the-art multilayers: sputtered tungsten-carbon with 2d 70 A and a molecular lead stearate with 2d 100 A. The fitting parameters that are determined by this procedure are applied to help establish the structural characteristics of these multilayers.

Microcleavage transmission electron microscopy (MTEM) has been applied to the study of many properties of multilayered samples. We illustrate the unique capabilities of this technique for obtaining a detailed structural picture of the multilayer in order to study long-range perpendicular thickness drifts, lateral variations, roughness, substrate quality, adherence, thermal stability, composition, and crystallinity.

The influence of thickness errors and boundary imperfections on the performance of a multilayer x-ray mirror is discussed, and it is shown that both can be obtained separately from a measured reflectivity curve at a short x-ray wavelength. Multilayers have greatly reduced scattering compared to single films, and for this reason rough boundaries and gradual transition layers between the film materials give practically identical performance. A simple Debye-Waller factor is not sufficient to describe the performance of a multi-layer with many layers at short wavelengths.

The x-ray diffracting properties of several types of layered synthetic microstructures (LSMs) and their use in the measurement of elements traditionally covered by the acid phthalate and Langmuir-Blodgett diffracting structures have been extended in this application to cover oxygen, nitrogen, carbon, and boron. A major problem in working in the longer wavelength region is that large incremental differences in wavelength per atomic number step make it difficult to obtain well-balanced combinations of wavelength range and angular dispersion with the limited set of "natural" diffracting structures (crystals) available. In contrast, it is possible to produce LSM structures with more desirable diffraction and dispersion properties over most of the long wavelength characteristic x-ray emission region. By developing structures that suppress higher order spectra and by clever selection of substrate composition, we have been able to extend both performance and range of application beyond initial expectations. This paper describes some of the work that has been done to provide such optimization and then discusses results obtained in the application of these diffracting structures for spectrochemical analysis.

Layered synthetic microstructure (LSM) x-ray optics may be used to couple a conventional glancing incidence x-ray mirror to a high sensitivity x-ray detector. The LSM mirror is a thin-film multilayer optic that effectively reflects only narrow spectral slices of the incident radiation by Bragg diffraction. By the use of figured LSM optics, it is possible to magnify the x-ray image produced by the primary mirrors so as to maintain their high inherent spatial resolution when used with currently available solid-state detectors. The results of theoretical design and analysis studies of several Spectral Slicing X-Ray Telescope (SSXRT) systems utilizing LSM mirrors figured as hyperboloids, spheres, ellip-soids, and constant optical path aspheric elements are presented. The rms spot size and point response function calculations are given for telescopes in which the LSM optics are designed to yield magnifications of 2 X, 6 X, and 8 X. The results of tilt and decentration studies are discussed. It has been demonstrated that the off-axis optical performance of the SSXRT is superior to that produced by the conventional glancing incidence primary mirror alone. The Stanford/Marshall Space Flight Center Rocket X-Ray Telescope, which will utilize normal incidence LSM optics to couple a Wolter-Schwarzschild primary mirror to high resolution detectors for solar x-ray/EUV studies, is briefly discussed.

A review of adaptive image transform coding techniques is given. Adaptive techniques are superior to nonadaptive procedures; however, their implementation requires a significant degree of added complexity. A major aspect of adaptive transform coding is the understanding and utilization of the local statistical structure of the image. Rate adaptive communication and buffer feedback are also important aspects of adaptive coding procedures. The discussion emphasizes the image quality aspect of the coding process.

A low loss, wideband, compact, polarization-preserving fiber-optic directional coupler (PPFDC) has been developed for use in future coherent optical fiber transmission systems or gyroscopes. The PPFDC is made of two 200-pm-diameter sapphire ball lenses, a 3dB beam splitter, and four conical alumina-ceramic ferrules with flat reference planes to preserve polarization at the connection of the fibers. Built-in thermal stress change in the fiber is minimized because the fiber is polished only for the short length within the straight ferrule. The optical and mechanical axes are tilted, so cross-talk light from the fiber endfaces or lens surfaces is avoided. The optical directivity of the PPFDC is more than 50 dB, and return loss is more than 40 dB in the 1.3 kim wavelength region. The excess loss is less than 1 dB in the 1.2 to 1.4 Am wavelength range. The extinction ratio is more than 25 dB. The length of the coupling region of the PPFDC is about 1 mm including the two ball lenses and beam splitter. Spectral linewidths of a fiber-interfaced distributed-feedback (DFB) laser diode are measured by a delayed self-homodyne detection scheme, using the PPFDC. Experimental results of a novel polarization-preserving fiber-optic gyroscope using a phase-modulating PPFDC showed reasonable sensitivity and stability. These experimental results verified the above-mentioned characteristics of the PPFDC.

Instrumentation for studying the propagation of near-millimeter waves has been designed and is currently being implemented at a 1 mile long test site in Sandusky, Ohio. An optically pumped near-millimeter (NMM) wave laser, used as a source of radiation for frequencies near 300 GHz, is located at one end of this site. The laser beam spot size arriving at the other end of the propagation path is controlled by a two-lens optical system placed at the laser's output. The receiver system consists of a parabolic reflector, a focal plane scanning system, and a fast-response liquid-helium-cooled InSb detector, all of which is controlled by a 68000-based microcomputer. Measurement of the characteristics of the received beam is based upon a quasi-optical method. The temperature/humidity atmospheric structure parameters and hydrometeor characteristics along the path are obtained simultaneously with the propagation measurements. These two measurements are then correlated to provide a meteorologically well-verified propagation model for near-millimeter wavelengths.

This paper addresses the problem of estimating the profile, or silhouette, of a ship target from a sequence of forward-looking infrared (FLIR) imagery obtained at video rates. We are specifically interested in the performance of multiframe processing techniques compared with single-frame methods. Our approach to multiframe signal processing combines spatial and temporal processing in two stages: first, a target profile is extracted from each image frame by a segmentation algorithm; second, the resulting sequence of profiles is temporally filtered in order to increase the signal-to-noise ratio. Long sequences of FLIR imagery tend to exhibit several characteristic forms of non-Gaussian noise (random speckle, occlusions, and flaring) caused by various atmospheric and background phenomena, as well as instrument noise. Simple temporal averaging is inadequate in this environment. In this paper we develop a combination of spatial and temporal processing algorithms that may be used to overcome the signal-to-noise ratio problems associated with these noise effects. A recursive temporal median filter in conjunction with a simple spatial segmentation algorithm is proposed for this purpose. Experimental results based on a database of FLIR ship imagery are presented in support of the spatiotemporal processor. Although the approach is developed for ship targets, we feel it could be adapted for a broader class of FLIR applications.