This PDF file contains the editorial “Editorial: Let's Keep Discussion of the Hubble at Cryogenic Temperatures” for OE Vol. 29 Issue 08

This PDF file contains the editorial “Book Rvw: Computer Vision for Electronics Manufacturing," edited by Martin D. Levine for OE Vol. 29 Issue 08

This PDF file contains the editorial “Book Rvw: Fiber Optics Handbook: For Engineers and Scientists," edited by Frederick C. Allard for OE Vol. 29 Issue 08

A picture is as good as a thousand words. No wonder the success of many of our engineering endeavors is determined in terms of a displayed end product. Interestingly, however, display devices serve both as input and output to information processing systems. Finally, our eyes have to make sense ofthe displayed information.

A technique has been developed and demonstrated to present full color stereoscopic imagery using standard projection display systems. This polarized color multiplexing technique (patent application filed) does not require additional image sources beyond those contained within the original 2-D display system. A full-resolution image is delivered to each eye, without increasing the video bandwidth of the original display. The approach separates the primary image colors between right eye and left eye views and uses polarization to alternate the colors every frame, thus generating a full color 3-D image on the projection screen. Any stereopair video source can be used, such as dual cameras, dual VCRs, or computer generated imagery. Either commercially available or custom threechannel projection systems (CRT, light valve, or laser) can be transformed into a stereoscopic display for group viewing.

An integrated taut shadow mask color CRT in sizes 5 x 5 and 6 x 6 inches has been developed for heads down displays in jet fighter and helicopter applications. Completely viewable in a full sunlight ambient environment, these CRTs can display high resolution maps and tactical information while withstanding the rugged vibration environment of a military aircraft.

A new 50° x 60° field of view helmet-mounted display (HMD) with a tilted catadioptric combiner has been designed, fabricated, and tested. The tilted cat display concept allows a wide-FOV display to be designed that has a 3:1 display brightness improvement over the conventional folded catadioptric approach, provides a similar improvement in combiner seethrough transmissions, and requires only a small tilt on the optically powered combiner that minimizes the complexity of the optics. Large-FOV HMDs with see-through capability require tilted, optically powered surfaces with complex optical systems for the display projection and relay. The optical performance of a tilted, optically powered element becomes more asymmetric as the tilt increases, and to maintain a resultant wellresolved symmetric display image, additional nonsymmetric, tilted, decentered lens elements are required. The tilted cat combiner permits a practical display optical system to be defined for a 60° FOV. The highresolution performance levels of the smaller FOV displays were obtained, with the resolution limited only by the CRT's resolution. A summary of the design considerations, development process, and demonstrated performance data for the 60° tilted cat HMD are presented.

The fiber optic helmet-mounted display (FOHMD), developed by CAE Electronics Ltd. for the U.S. Air Force Human Resources Laboratory, requires large-format coherent fiber optic cables to support the demanding full color, high-resolution display requirements plus provide flexibility, durability, and light weight and be up to 2.1 m in length. Currently, FOHMD cables are linear arrays of multifibers separated by inactive material spacers to achieve a lightweight cable with a large cross section. This multifiber approach, with 5 ?m diameter individual fibers, delivers high performance by using chromatic multiplexing to improve resolution and wash out the inactive spacer structure. Reduced fiber breakage and improved fiber alignment have also significantly increased the optical performance of the system. To achieve still higher image quality, a technically more difficult process is also being explored. Several small experimental cables have been assembled using leachable, fused multifibers arrayed in a hexagonal pattern. Improved cable drawing technology will allow for precise assembly of hexagonal components into a full format bundle. This new fiber optic cable technology has the potential of providing image transmission capability equal to 10 million pixels. When coupled with chromatic enhancement, the FOHMD optics will deliver a resolution equal to 1 .5 arcmin per pixel over a large field of view.

Night imaging systems based on image intensification (12) tubes are a major factor in the night operation capability of military aircraft. A major problem associated with the use of these systems is the detrimental effect on performance caused by internal cockpit lighting. Instrument lamps, caution lamps, utility lights, and other light sources inside the cockpit activate the automatic gain control circuits of the intensification tubes, thereby reducing their sensitivity to external natural and artificial illumination. In 1986, a tn-service specification, MIL-L-85762, "Lighting, aircraft, interior, night vision imaging system compatible," was adopted to resolve the cockpit lighting problems. MIL-L-85762 defines the measurement instrumentation and techniques required to certify lighting components as "Night Vision Imaging System (NVIS) compatible." Ongoing efforts related to MIL-L-85762 include characterization of lighting incompatibilities in current U.S. Army aircraft, implementation of programs to modify the lighting in incompatible cockpits, and certification of proposed lighting components for future aircraft systems.

Seventeen subjects searched for, and then monitored, 3, 6, or 9 stationary targets in order to detect and shoot 3 threats. The targets were located in an area 1200 left and right and 900 upward, from straight ahead. They were viewed on a helmet-mounted display (HMD) by making appropriate head movements. The HMD had five different sizes of field-ofview (FOV), ranging in width from 200 to 1200. Subjects hit fewer threats and were threatened for longer durations with small FOVs than with large FOVs. The decrement in performance was dependent on the number of targets. Optimum performance with 3, 6, and 9 targets required FOVs of 200, greater than 200, and greater than 600, respectively. Subjects moved their head less, but faster, with large FOVs than with small FOVs. Also, there was an apparent inverse relation between head velocity while performing the task and error at replacing the targets afterward. It was interpreted that head velocity was mediated by the certainty with which subjects remembered target locations. It appeared that performance at the task was limited by how well subjects integrated information about target locations and not by how fast or how much they could move their heads.

The concepts of dynamic modulation transfer function (DMTF) and degree of degradation (DD) are used for analyzing gray level image display of a phosphor based display system. Real-time restoration of the motion-degraded display images may be accomplished using one or more inverse filters whose characteristics depend on the magnitude and direction of the motion. Both DMTF and DD characteristics are used in the restoration of motion-degraded images.

A miniature display device, recently available commercially, is aimed at providing a portable, inexpensive means of visual information communication. The display is head mounted in front of one eye with the other eye's view of the environment unobstructed. Various visual phenomena are associated with this design. The consequences of these phenomena for visual safety, comfort, and efficiency of the user were evaluated: (1) The monocular, partially occluded mode ofoperation interrupts binocular vision. Presenting disparate images to each eye results in binocular rivalry. Most observers can use the display comfortably in this rivalrous mode. In many cases, it is easier to use the display in a peripheral position, slightly above or below the line of sight, thus permitting normal binocular vision of the environment. (2) As a head-mounted device, the displayed image is perceived to move during head movements due to the response of the vestibulo-ocular reflex. These movements affect the visibility of small letters during active head rotations and sharp accelerations. Adaptation is likely to reduce this perceived image motion. No evidence for postural instability or motion sickness was noted as a result of these conflicts between visual and vestibular inputs. (3) Small displacements of the image are noted even without head motion, resulting from eye movements and the virtual lack of display persistence. These movements are noticed spontaneously by few observers and are unlikely to interfere with the display use in most tasks.

The modulation transfer function (MTF) and contrast transfer function (CTF) are considered for discrete systems. The MTF and CTF are derived for the charge-coupled device (CCD). The analysis presented considers the full effects of sampling on device response. Experimental tests of the CTF for a line-array CCD are presented. The MTF and CTF are shown to be multivalued functions for discrete systems.

A generalized minimum resolvable temperature difference (MRTD) formulation is identified for the characterization of infrared detection systems. The generalized MRTD equation can be adapted to suit the needs of any IR system to be tested. As an illustration, the MRTD of a staring lR detection system is derived from the generalized MRTD formulation.

Accurate experimental characterization of the imaging properties of scanned time-delay-and-integrate (TDI) charge-coupled imagers (CCIs) requires careful consideration ofthe electro-mechanical and electro optical control of the associated scanned imaging hardware configuration. We describe an electro-optical imaging hardware system that is designed to provide precise electronic control of the scanned image motion and image capture processes when using a TDI CCI. This, along with the ability to vary important optical parameters, allows parametric characterization of TDI CCI imaging capabilities within the context of the system (optics plus scanned TDI CCI) modulation transfer function. Several examples of multi-frequency bar pattern images, recorded with the electro-optical scanned imaging system using a TDI CCI, are provided to qualitatively illustrate the important experimental details and parametrics.

The present paper outlines the requirements for the performance of x-ray mirrors at the European Synchrotron Radiation Facility (ESRF), to be built in Grenoble, France. It is shown that present-day surface preparation techniques are about adequate to achieve conservation of the source emittance, although some improvements are needed in special cases. It is much harder to conserve brilliance, where thermal deformation is the major obstacle. Here substantial research and development efforts are absolutely indispensable. Two possible ways are indicated to solve the heat problem: cryogenic cooling of silicon-based mirrors and adaptive optical systems. In the first case thermal deformations are drastically reduced, and in the second they can be compensated by mechanical forces. Our results are based on theoretical considerations of scattering by nonideal surfaces and on a thermomechanical analysis, which are also given. For layered synthetic microstructures the technological problems appear to be still more difficult. Because the critical photon energy of the ESRF 6 GeV storage ring and of most of its insertion devices is between 10 and 20 keV or even higher, the discussion is limited to hard x-ray optics.

Grazing incidence x-ray optics for x-ray astronomical applications are used outside the earth's atmosphere. These devices require a large collection aperture and the imaging of an x-ray source that is essentially placed at infinity. The ideal testing system for these optical elements has to approximate that encountered under working conditions; however, the testing of these optical elements is notoriously difficult with conventional x-ray generators. Synchrotron radiation (SR) sources are sufficiently brilliant to produce a nearly perfect parallel beam over a large area while still retaining a flux considerably higher than that available from conventional x-ray generators. A facility designed for the testing of x-ray optics, particularly in connection with x-ray telescopes, is described. It is proposed that this facility will be accommodated at the Synchrotron Radiation Source at the Daresbury Laboratory in the United Kingdom.

This paper covers the various techniques that are currently being used and developed to fabricate grazing incidence x-ray optics for the energy range from about 0.2 to 20 keV. Techniques covered will include diamond turning, thin foils, epoxy/carbon-fiber replication, electroforming replication, and float glass/Kirkpatrick-Baez techniques.

Grazing incidencesystems, such as extreme ultraviolet and x-ray telescopes, produce images that differ qualitatively from those of conventional normal incidence systems. Among the more well known effects are increased scatter due to the short radiation wavelengths, and pronounced pupil diffraction patterns due to the high obscuration ratios. However, a much less well known effect is the rapidly increasing intensity very near the center of the image. Within a substantial part of the image core, the intensity can be shown to increase inversely with the image radius ("1/r" behavior). This behavior applies to both pupil diffraction and scatter effects. One ofthe important implications is that the full-width-half-maximum (FWHM) for the image is inherently and misleadingly small and is thus not a suitable image descriptor for grazing incidence systems. In this paper, we first review the well-known scatter and diffraction effects. We then give some intuitive explanations for the less well known "1/r" behavior of the intensity, derive the mathematics to define the effect quantitatively, and give some examples.

Measurements in our laboratory have recently shown that the pulse quantum yield (counts/photon) of Csl x-ray photocathodes, measured near grazing incidence, depends on the linear polarization state of the incident beam. These results have implications both for the fundamental understanding ofthe x-ray photoeffect and, since Csl is well known as a cathode material of high (unpolarized) quantum efficiency in the 0.1 to 1.0 keV band, for the development of high-throughput astronomical x-ray polarimetry. This paper, concentrating on the latter topic, describes the practical accommodation of a photoemission polarimeter at (or near) the focus of a satellite x-ray telescope. Problems of device format, instrumental polarization, and data compression are discussed with reference to the Composite X-ray Polarimeter recently proposed for the European Space Agency High Throughput Spectroscopy mission (XMM). Examples of the sensitivity of this instrument are given. In the second part of the paper, some recent laboratory measurements are presented. These concern the variation in the number of x-ray photoelectrons with the polarimetric azimuth of a Csl cathode.

The reflectivity of grazing incidence W/C multilayer mirrors can be optimized by progressively refining structural features through sputter deposition parameter optimization. In addition to the configuration of system geometry, the deposition rate, substrate temperature, and working gas pressure significantly affect the multilayer structure morphology. Of these parameters, working gas pressure has an overwhelming effect. The energy and distribution of sputtered adatoms, directly influenced by the sputtering gas pressure, affects the reactivity at and the reconstruction of vapor deposited surfaces. The interface abruptness is therefore affected by working gas pressure. The reduction in interfacial atomic intermixing (hence roughness) generally follows with decreased working gas pressure. Correspondingly, the improved reflective efficiency becomes more noticeable as measured from short through long x-ray wavelengths. Structural and reflectivity improvements in the W/C multilayer mirror system, characterized qualitatively using cross-section electron microscopy and quantitatively using x-ray diffraction, will be correlated to an optimization of the sputter deposition parameter—working gas pressure.

We examine the effect of using rotations for generation of the left- and right-eye perspective views of a stereoscopic image. We show that this approach to stereoscopic display of perspective views results in vertical parallax between the left- and right-eye views and we present an analytic expression that characterizes this parallax in terms of the center of rotation, the location of the image plane, and the angle of rotation. We also derive an analytic expression that shows that the rotation of the perspective views results in a semicylindrical stereo window with center at approximately (0, 0, R/2) and radius R/2, where R is the distance from the center of rotation to the center of projection. When this semicylindrical window is mapped to a flat display surface, relative depth relationships can be distorted.

The visual contrast sensitivity function (CSF) has found increasing use in image compression as new algorithms optimize the display- observer interface in order to reduce the bit rate and increase the perceived image quality. In most compression algorithms, increasing the quantization intervals reduces the bit rate at the expense of introducing more quantization error. The CSF can be used to distribute this error as a function of spatial frequency such that it is undetectable by the human observer. Thus, instead of being mathematically lossless, the compression algorithm can be designed to be visually lossless, with the advantage of a significantly reduced bit rate. However, the CSF is strongly affected by image noise, changing in both shape and peak sensitivity. This work describes a model of the CSF that includes these changes as a function of image noise level by using the concepts of internal visual noise. The model is tested in the context of image compression with an observer study.

Low-conductivity, laser-irradiated thin films such as the chalcogenides employed for optical data storage can display manifestations of significant through-thickness thermal gradients. A combined Laplacetra nsform, Fou rier-i nteg ral method was used to derive the tern peratu re distributions in such films, and the results were used to examine the effects of some marking parameters on through-thickness thermal gradients. The results were in good qualitative agreement with experimental observations.