Work is currently underway to develop visual systems for warriors that provide different images to each eye (both in terms of resolution and visual field size), relying on binocular summation in the brain of the wearer to fuse the images into a common percept. The effect on the user employing such displays is not currently a part of the equipment development process. Literature involving similar visual conditions (either naturally occurring or through medical intervention) suggest that there are significant unresolved issues that must be investigated to determine if such displays may potentially negatively impact the visual perception of the wearer. This paper presents a summary of some of the related analogous conditions and identifies key issues that should be researched in parallel with the hardware.

When wearing a monocular head-mounted display (HMD), one eye views the HMD symbology while both eyes view an out-the-window scene. This may create interocular differences in image characteristics that could disrupt binocular vision by provoking visual suppression, thus reducing visibility of the background scene, monocular symbology, or both. However, binocular fusion of the background scene may mitigate against the occurrence of visual suppression, a hypothesis that was investigated in the present study. Observers simultaneously viewed a static background scene and HMD symbology while performing a target recognition task under several viewing conditions. In a simulated HMD condition observers binocularly viewed a background scene with monocular symbology superimposed. In another condition, viewing was dichoptic (i.e. completely different images were presented to the left and right eyes). Additionally, one control condition was implemented for comparison. The results indicate that for continuously presented targets binocular rivalry did not have significant effects on target visibility. However, for briefly presented targets, binocular rivalry was shown to increase thresholds for target recognition time in HMD and dichoptic viewing conditions relative to the control. Impairment was less in the HMD condition. Thus, binocular fusion of a background scene can partially mitigate against the occurrence of visual suppression. However, some suppression still exists which occurs between monocular pathways. Implications for the integration of monocular HMDs into Air Force training environments will be discussed.

This paper discusses the depth acuity research conducted in support of the development of a Modular Multi-Spectral Stereoscopic (M²S²) night vision goggle (NVG), a customizable goggle that lets the user select one of five goggle configurations: monocular thermal, monocular image intensifier (I²), binocular I², binocular thermal, and binocular dual-waveband (thermal imagery to one eye and I² imagery to the other eye). The motives for the development of this type of customizable goggle were (1) the need for an NVG that allows the simultaneous use of two wavebands, (2) the need for an alternative sensor fusion method to avoid the potential image degradation that may accompany digitally fused images, (3) a requirement to provide the observer with stereoscopic, dual spectrum views of a scene, and (4) the need to handle individual user preferences for sensor types and ocular configurations employed in various military operations. Among the increases in functionality that the user will have with this system is the ability to convert from a binocular I² device (needed for detailed terrain analysis during off-road mobility) to a monocular thermal device (for increased situational awareness in the unaided eye during nights with full moon illumination). Results of the present research revealed potential depth acuity advantages that may apply to off-road terrain hazard detection for the binocular thermal configuration. The results also indicated that additional studies are needed to address ways to minimize binocular incompatibility for the dual waveband configuration.

Background: Since helmet mounted displays (HMDs) are slaved to a pilot's head, head motion is important for the design of HMDs and their symbology. This is particularly true since the lateral tilt of a pilot's head changes when the pilot shifts his/her gaze from the horizon visible outside the cockpit to the instruments inside the cockpit. This change in head tilt, which may contribute to episodes of spatial disorientation and possibly dangerous control input reversal errors, is commonly attributed to a neuro-muscular reflex driven by the apparent tilt of the visible horizon, the so-called optokinetic cervical reflex (OKCR). The present paper: (1) describes head motion in the frequency domain, and (2) elaborates a biomechanical explanation for the observed head tilt that is simpler than the neurological OKCR model. Methods: Fourier spectral decompositions were calculated from archived head pitch, tilt, and azimuth data recorded at 10 Hz from four pilots as they executed a slalom maneuver in an AH Mk 7 Linx helicopter. Pilots A through D performed the slalom 11, 12, 8, and 11 times, respectively, for a total of 42 flights. Results: The Fourier decomposition showed that the typical azimuth spectrum differs from that of pitch, and tilt. Discussion: These results provide: (1) spectral descriptions of head azimuth, pitch, and tilt to aid the design of HMD systems, and (2) further support for the biomechanical model of head tilt.

The increased usage of visionic devices necessitates the development of a unified approach to testing and evaluation of such devices. A NATO working group was established to achieve this goal. This paper describes a taxonomy to classify a given visionic device (based on optical design and display type) and to recommend specific test parameters that should be measured to ensure planned operational performance is delivered in the final product.

Helmet-mounted displays (HMDs) are being increasingly used by the military outside of the traditional cockpit environment. In these applications, attention, functional field of view (FOV), and mental workload are important human factors issues. While some research has begun to address these issues, not many have considered how alternative placements of the monocular eyepieces in the visual field effects performance. We investigated task performance using a monocular HMD that was adjustable so that it could be placed within or outside of the FOV of the user. There were three parts to the experiment. In the first part, observers performed a visual search task to serve as a baseline measure of performance. In the second part observers wore the HMD in one of two positions and again performed the search task. Finally in the third part, observers completed the search task while performing a reaction time task that was displayed on the HMD (again placed in the two positions). Results of task performance are discussed in terms of the functional FOV, attentional demands on the user, and differences between tasks to be performed on an HMD. Recommendations are given for design, use, and future research on HMDs.

This is the last in a series of studies designed to establish objective tools that can evaluate vision and cognitive visual performance with head-/helmet-mounted displays (HMDs) in a static environment. These tools will be applied to ongoing studies in an interactive, animated environment that will compare visual performance of biocular and monocular HMDs and evaluate image misalignment tolerance standards during long-term wear (4-6 hours) and during vibration. In this study, saccadic velocity significantly decreased following image misalignment, but not following a corresponding control period without misalignment, showing the measurement to be sensitive to image misalignment in a full-overlap biocular display. Pupil constriction latency significantly increased for both the experimental and control conditions, indicating that, although sensitive to using the optical device, this measurement was not specifically sensitive to a divergent horizontal misalignment of 3.1 milliradians (mrad). These results add saccadic velocity to the tools that we have already established. We also evaluated the visual performance of presbyopic subjects using a full-overlap display and found decreased performance with and without image misalignment. This has implications for helmet-mounted display use by older pilots that certainly warrants further investigation. In previous studies^{6, 7} individuals with accommodative and vergence problems showed reduced performance when there was a small divergent horizontal image misalignment in a partial-overlap biocular display.

The U.S. Army, under the auspices of the Air Warrior Product Office, is developing a modular helmet-mounted display (HMD) for four aircraft series within its helicopter fleet. A design consideration is mounting the HMDs to the HGU- 56P Aviator's Night Vision Imaging System (ANVIS) mount. This particular mount is being considered, presumably due to its inherent cost savings, as the mount is already part of the helmet. Mounting the HMD in this position may have consequences for the daylight performance of these HMDs, as well as increasing the forward weight of the HMD. The latter would have consequences for helmet weight and center-of-mass biodynamic issues. Calculations were made of the increased luminance needed as a consequence of mounting the HMD in front of an HGU-56P tinted visor as opposed to mounting it behind the visor. By mounting in front of the helmet's visor, the HMD's light output will be filtered as light coming from the outside world. Special consideration then would have to be given to the HMD's light source selection process, as not to select a source that would differentially reduce luminance by a mounted visor (e.g., laser protection visors) compared to the ambient light in the aviator's field-of-view.

The objective of this paper is to present the details surrounding the experimental design and flight test program used to evaluate the performance of an Optical Head Tracker (OHT) under dynamic flight and intense solar conditions. This program was a collaborative effort led by the Air Force Research Laboratory (AFRL) in close concert with NASA-Glenn Research Center (NGRC) based in Cleveland Ohio and contractors supporting the laboratory. The thrust of this paper will focus on the experimental design necessary to effectively evaluate the OHT performance, as well as safety of flight considerations necessary to satisfy both AFRL and NASA strict safety requirements. Discussions will include airborne platform selection, modification, and operations necessary to achieve maximum solar exposure on the OHT while ensuring a representative environment was presented to the OHT during the experiment.

The Dynamic Tracker Test Apparatus (DTTA) was designed by the Helmet Mounted Sensory Technology (HMST) laboratory to accurately measure azimuth rotation in both static and dynamic conditions. The DTTA was characterized for static position data at various increments through a 360° sweep and for speeds up to 1000°/sec or 17.45 rad/sec. This paper describes the design, construction, capabilities, limitations, characterization and performance of the DTTA.

A critical need exists for a fast, cost-effective, six-degrees-of-freedom (6DOF) tracker that is immune to cockpit and helmet scatterers of magnetic/electrical field energy, vehicle vibration, and harsh lighting conditions. Magnetic and inertial tracking technologies each have limitations that make them undesirable as next generation solutions. Optical tracking technologies, while having occlusion problems, are increasingly seen as the more attractive next generation solution. The optical tracker, developed at Ascension to meet these needs, measures the angle of incidence of point radiating emitters mounted on the helmet. The sensors measure angle of incidence in one dimension and two or three sensors are required to be mounted on the cockpit instrument panel to achieve determination of both position and orientation of a helmet. The sensor uses a transmissivity mask, which is located a known distance above a linear detector array surface. The mask consists of three transmissivity frequencies varying in one dimension. Each point radiating emitter illuminates the mask to cast an image onto the array. The array image is read at a high update rate and a remote processor identifies image phases to determine the image shift along the detector array axis. The three frequencies, being sufficiently separate in frequency to determine a coarse absolute image shift, as well as medium and fine image shifts, are used to determine a high-resolution absolute image shift. The image shift of each sensor is used to compute the plane angle of incidence of each emitter. The minimal system configuration includes two sensors and four emitters or three sensors and three emitters. More sensors and emitters may be used to increase tracker motion box. Flight tests were conducted in August and September of 2005. The phasorBIRD prototype was flown in a test aircraft to evaluate the effect of direct sunlight and vibration on accuracy and noise.

Evaluating a system in flight poses challenges that are not found in a laboratory type environment. This paper discusses some of the issues in conducting an in-flight test to evaluate tracker accuracy, such as head movement, synchronization of time, changing coordinate systems and interpolating data. The paper's technical approach outlines one possible solution to deal with in-flight challenges.

While anecdotal reports suggest that Night Vision Goggles influence spatial navigation and wayfinding (Braithwaite, Douglass, Durnford, and Lucas, 1998), few studies have systematically characterized the nature of these effects. To address this issue, the current study examined the impact of NVGs on navigation and wayfinding performance. One group of participants were required to navigate a walking maze and retrieve target objects while wearing NVGs (experimental condition), while a second control group navigated the maze without NVGs. We measured several performance metrics of navigation and wayfinding. Our results show that navigation and wayfinding with NVGs (experimental group) appeared to be harder, with longer navigation durations and more navigational errors compared to not using NVGs (control group). However, a significant decrease in navigation duration over the course of the wayfinding trials occurred earlier with NVGs, in addition to significant decreases in navigational steps compared to the control group. These results support the notion that NVGs directly affect spatial navigation and wayfinding performance. These degradations in performance should be considered in operational planning and NVG training programs. Further research is necessary to expand our understanding of the impact of NVGs on spatial cognition.

The introduction of Night Vision Goggles (NVGs) into the cockpits of aircraft configured with head-up displays (HUDs) and colored cockpit instruments necessitated the addition of special NVG objective lens filters to ensure NVG/cockpit compatibility. Three classifications have been developed: Class A, B and C, all minus blue filters, but with different transmissivity characteristics customized to make NVGs compatible with particular cockpit configurations. Class C filters, designed for aircraft equipped with holographic HUDs, are constructed of applied reflective coatings with a built-in spectral notch for transmitting the correct light wavelength to make the projected HUD symbology readable. New absorptive glass technology was integrated into the design of an RG-665 minus-blue filter identical to a class B filter but with a physical pinhole and varying glass material thickness to fine tune the filter for optimal transmissivity for NVG/HUD compatibility. A study was conducted to examine the impact these two unique classifications of filters have on visual performance using simulated compatible cockpit lighting in a controlled laboratory. Results indicate the Class C filters significantly outperformed the RG-665 filters with the windscreen condition installed. A discussion of the properties of each type of filter and its effect on NVG visual performance are discussed in this paper.

New advancements in charged-coupled device (CCD) technology allow for further investigation into the spatial nature of night vision goggle (NVG) noise distributions. This is significant because it is common practice in new NVG technology to combine image intensifiers with CCDs for night vision imaging. In this study, images of NVG noise are recorded by a CCD camera while varying input radiance and using multiple goggle types. Noise distributions characterized using histograms of these images are analyzed and fitted with curves. Using the changes in the distribution and relating distribution changes (coefficient changes) to input radiance and goggle performance provides a very accurate noise characterization. This study finds that a Weibull distribution seems more appropriate than a Poisson distribution, producing higher correlation coefficient fits. In addition, the paper suggests possible ways the noise models developed here can impact advancements in NVG image enhancement using this new technology.

Several studies and many anecdotal reports indicate that aircrew members focus night vision goggle (NVG) eyepiece lenses to more negative powers than would be expected based on refractive error, presumably due to instrument myopia, "dark focus" myopia, and other factors. Excessive negative power stimulates accommodation, introducing risks from discomfort, fatigue, and blurred vision. Aircrew members are trained to employ specific adjustment techniques to minimize "over-minusing" of eyepiece lens powers, but those techniques are prone to error. The currently fielded AN/AVS-9 NVG (F4949) has a focus range of (+2.0) to (-6.0) diopters, and meets the needs of most aircrew. However, the new AN/AVS-10 NVG panoramic night vision goggle (PNVG) has a fixed focus of (-1.0) diopters due to engineering design constraints. Accessory snap-on lenses are available, but data are needed to optimize the distribution of lens powers to be acquired and maintained. This study involved the characterization of vision (visual acuity, perceived quality, and comfort) as a function of: 1) eyepiece focus setting using trial lenses; 2) F4949 eyepiece focus adjustments using a point source vs. a Hoffman 20/20 box; and 3) PNVG eyepiece lens selections using a lens bar vs. snap-on lens selections. Eight subjects with normal (20/20 corrected) vision ranging in age from 23 years to 49 participated in this study. The experiments were conducted in the Aerospace Vision Experimental Laboratory and the Dynamic Vision Assessment Facility at Wright Patterson AFB, Ohio using F4949 and PNVG devices with a custom-designed NVG-compatible computer-based visual acuity acquisition system.

A compact, binocular see-through, monocular display HMD has recently been manufactured by Rockwell Collins. This HMD allows for the projection of symbology on one eye using a unique see-through display while leaving the user's unaided eye completely unobscured. The HMD uses a prismatic element to project the symbology near infinity. An aspheric corrector is used in conjunction with the prismatic element to enable the user to experience binocular vision as well as symbology overlay. Distortion, resolution, dipvergence/convergence, contrast, and luminance are discussed.

An important capability has been developed for the AH-64 that provides increased mission effectiveness and improved flight safety. First introduced for the Integrated Helmet and Display Sighting Subsystem (IHADSS) on the Agusta A-129, the Symbology Display Unit (SDU) provides IHADSS symbology to the aviator through the Aviator's Night Vision Imaging System (ANVIS) (Night Vision Goggles). Specifically designed for compatibility with the AH-64 and the Legacy IHADSS display and head tracking system, the SDU provides seamless integration of this critical capability into the cockpit. The SDU has been adapted to the IHADSS on the AH-64 and is currently in early fielding within both the US and UK fleets. Although the use of ANVIS on the AH-64 is not a new concept, the ability to display IHADSS symbology integrated with the head tracker is. With the display of IHADSS symbology within the ANVIS field of view, additional capabilities and benefits are realized, including sighting and weapons control, mission performance during poor FLIR conditions, increased target recognition, and improved safety realized by the availability of heads-up pilotage information.

Including night vision capabilities in Helmet Mounted Displays has been a serious challenge for many years. The use of "see through" head mounted image intensifiers systems is particularly challenging as it introduces some peculiar visual characteristics usually referred as "hyperstereopsis". Flight testing of such systems has started in the early nineties, both in US and Europe. While the trials conducted in US yielded quite controversial results, convergent positive ones were obtained from European testing, mainly in UK, Germany and France. Subsequently, work on integrating optically coupled I² tubes on HMD was discontinued in the US, while European manufacturers developed such HMDs for various rotary wings platforms like the TIGER. Coping with hyperstereopsis raises physiological and cognitive human factors issues. Starting in the sixties, effects of increased interocular separation and adaptation to such unusual vision conditions has been quite extensively studied by a number of authors as Wallach, Schor, Judge and Miles, Fisher and Ciuffreda. A synthetic review of literature on this subject will be presented. According to users' reports, three successive phases will be described for habituation to such devices: initial exposure, building compensation phase and behavioral adjustments phase. An habituation model will be suggested to account for HMSD users' reports and literature data bearing on hyperstereopsis, cue weighting for depth perception, adaptation and learning processes, task cognitive control. Finally, some preliminary results on hyperstereopsis spatial and temporal adaptation coming from the survey of training of TIGER pilots, currently conducted at the French-German Army Aviation Training Center, will be unveiled.

The Advanced Helmet Mounted Display (AHMD), augmented reality visual system first presented at last year's Cockpit and Future Displays for Defense and Security conference, has now been evaluated in a number of military simulator applications and by L-3 Link Simulation and Training. This paper presents the preliminary results of these evaluations and describes current and future simulator and training applications for HMD technology. The AHMD blends computer-generated data (symbology, synthetic imagery, enhanced imagery) with the actual and simulated visible environment. The AHMD is designed specifically for highly mobile deployable, minimum resource demanding reconfigurable virtual training systems to satisfy the military's in-theater warrior readiness objective. A description of the innovative AHMD system and future enhancements will be discussed.

We present the design and early evaluation results of the world's highest pixel pitch full-color 800x3x600- pixel, active matrix organic light emitting diode (AMOLED) color microdisplay for consumer and environmentally demanding applications. The design premises were aimed at improving small area uniformity as well as reducing the pixel size while expanding the functionality found in existing eMagin Corporations' microdisplay products without incurring any power consumption degradation when compared to existing OLED microdisplays produced by eMagin. The initial results of the first silicon prototype presented here demonstrate compliance with all major objectives as well as the validation of a new adaptive gamma correction technique that can operate automatically over temperature.

We report progress in developing high-contrast, wide symmetrical viewing angle multi-domain vertical alignment (MVA) AMLCD's with a full color SXGA resolution (1280x1024x3 dots). These MVA displays are fabricated with a smooth surface and without either protrusions or an ITO slit-pattern geometry. Intrinsic fringe fields in each pixel control the LC alignment and formation of domains. We have achieved contrast ratios greater than 1000, and symmetrical viewing angles greater than 120 degrees. A 3840x1024 dot array was developed with integrated color pixel filters to create a 1280x1024 color pixel array. The pixel design, display driver operation, and color mosaic were optimized for MVA operation. Pixel shapes were developed to control domain formation and to maximize light transmission using 3-D modeling and test displays. New LC materials were investigated to increase transmission and to minimize voltage drive requirements. Improvements have been made in this MVA liquid crystal display to bring the fabrication process closer to manufacturing. Key results include striation-free displays with spun-on polyimide alignment layers, elimination of boundary stick via pixel design, overall viewing angle improvement with an MVA-matched wide viewing polarizer, and transmission improvements with high delta n LC, cell gap, driving mode, LED and BEF backlight combination. Performance data and specifications for Kopin's color filter MVA and TN displays will be presented with reference to military, industrial, and commercial applications.

Microvision's Spectrum^TM SD2500 is a candidate technology for the Modular Integrated Helmet Display System (MIHDS)program. This HMD design is intended to provide a full-color, see-through, daylight and night-readable, moderate-resolution (800X600 pixels) display. The employed technology is that of scanning lasers. This paper presents the testing results for the latest version of this prototype system.

We report design and test of a high brightness laboratory-breadboard LED/LCOS HMD system employing a 0.78-inchdiagonal 1280× 768 ferroelectric liquid-crystal-on-silicon microdisplay and a red-green-blue LED. With an 8× viewing optic giving a 35°-diagonal field of view, the system yielded brightnesses greater 40,000 cd/m² (12,000 fL) in colorsequential mode and greater than 100,000 cd/m² (30,000 fL) in monochrome mode, at LED power consumptions of 1.1 W and 3.3 W, respectively. The illumination optics employed a rectangular light pipe and tailored diffuser to efficiently fill the microdisplay panel aperture and exit pupil. The high efficiency of such image generators facilitates display readability in see-through HMDs operating in high-ambient-light environments, as well as enabling ultra-low power HMDs (less than 100 mW total) for dismounted users of battery-powered systems.

Daylight readability of hand-held displays has been an ongoing issue for both commercial and military applications. In an effort to reduce the effects of ambient light on the readability of military displays, the Naval Research Laboratory (NRL) began investigating and developing advanced hand-held displays. Analysis and research of display technologies with consideration for vulnerability to environmental conditions resulted in the complete design and fabrication of the hand-held Immersive Input Display Device (I2D2) monocular. The I2D2 combines an Organic Light Emitting Diode (OLED) SVGA+ micro-display developed by eMagin Corporation with an optics configuration inside a cylindrical housing. A rubber pressure-eyecup allows view ability only when the eyecup is depressed, eliminating light from both entering and leaving the device. This feature allows the I2D2 to be used during the day, while not allowing ambient light to affect the readability. It simultaneously controls light leakage, effectively eliminating the illumination, and thus preserving the tactical position, of the user in the dark. This paper will examine the characteristics and introduce the design of the I2D2.

An immersive viewing engine providing basic telepresence functionality for a variety of application types is presented. Augmented reality, teleoperation and virtual reality applications all benefit from the use of head mounted display devices that present imagery appropriate to the user's head orientation at full frame rates. Our primary application is the viewing of remote environments, as with a camera equipped teleoperated vehicle. The conventional approach where imagery from a narrow field camera onboard the vehicle is presented to the user on a small rectangular screen is contrasted with an immersive viewing system where a cylindrical or spherical format image is received from a panoramic camera on the vehicle, resampled in response to sensed user head orientation and presented via wide field eyewear display, approaching 180 degrees of horizontal field. Of primary interest is the user's enhanced ability to perceive and understand image content, even when image resolution parameters are poor, due to the innate visual integration and 3-D model generation capabilities of the human visual system. A mathematical model for tracking user head position and resampling the panoramic image to attain distortion free viewing of the region appropriate to the user's current head pose is presented and consideration is given to providing the user with stereo viewing generated from depth map information derived using stereo from motion algorithms.

The use of Helmet-Mounted Display/Tracker (HMD/Ts) is becoming widespread for air-to-air, within visual range target acquisition for a tactical fighter pilot. HMD/Ts provide the aircrew with a significant amount of information on the helmet, which reduces the burden of the aircrew from having to continually look down in the cockpit to receive information. HMD/Ts allow the aircrew to receive flight and targeting information regardless of line-of-sight, which should increase the aircrew's situation awareness and mission effectiveness. Current technology requires that a pilot wearing a Helmet Mounted Display/Tracker be connected to the aircraft with a cable. The design of this cable is complex, costly, and its use can decrease system reliability. Most of the problems associated with the use of cable can be alleviated by using wireless transmission for all signals. This will significantly reduce or eliminate the requirements of the interconnect cable/connector reducing system complexity, and cost, and enhancing system safety. A number of wireless communication technologies have been discussed in this paper and the rationale for selecting one particular technology for this application has been shown. The problems with this implementation and the direction of the future effort are outlined.