The Aviation Combined Arms Tactical Trainer - Aviation (AVCATT-A) reconfigurable manned simulator is the Army's newest helicopter training simulator. AVCATT-A is a dynamic reconfigurable system developed for use for combined arms collective training and mission rehearsal through a suite of networked simulators in a simulated battlefield environment. The main purpose of AVCATT-A is to effectively train aviation aircrews in a collective training environment. The AVCATT-A visual system is required to support realistic collective/combined arms training with the required fidelity to fly nap-of-the-earth (NOE) or conduct multi-ship operations. To meet this high level of expectation requires that the visual system be capable of performing all necessary collective tasks and supporting individual tasks with no negative training transfer or physical impacts on crewmembers. In addition to these stringent training requirements for the visual system, the AVCATT-A simulator must be reconfigurable for five different cockpits and be readily deployable. The solution was found in a combination of state-of-the-art technology where the standard projection dome is replaced by a combination of rear-screen projection displays and a Head-Mounted Display (HMD) which provides all the Out-The-Window (OTW) visual imagery.

Kopin's miniature Active Matrix Liquid Crystal Displays (AMLCD's) are rapidly becoming the display technology of choice in a wide range of military head mounted and sensor viewer applications. These low power, ruggedized displays operate from -37°C to +65°C with excellent imaging characteristics and reliability. Kopin and the US Army Night Vision and Electronic Sensors Directive (NVESD) are co-operatively developing high resolution, full-color displays for day/night operations and image fusion applications. Kopin is leveraging the successful development of its monochrome SXGA (1280 x 1024) AMLCD to develop a color SXGA display and a color SVGA (800 x 600) display. Color technology approaches evaluated for these new products included color filters, frame sequential color, binary optic phase plate spot sequential color, and diffractive optic column sequential color. These approaches all involve frame sequential operation with the exception of color filters. A generic color frame sequential mode was selected for the SXGA display design that will allow operations of all frame-sequentially based approaches. This display facilitates color technology changes and upgrades by replacing the backlight assembly. The color filter approach was selected for the SVGA display. Both color technologies are used for Kopin commercial display products. Performance data and specifications for Kopin's displays will be presented with reference to military (HMD and weapon sight), industrial, and commercial applications. Analytical results and data from color approaches investigated will be presented and compared. Application extensions that utilize the new color technologies developed will be highlighted.

Helmet-mounted displays (HMDs), while not new, are a unique method of providing pilotage and targeting imagery to aviators. Although there are a number of HMDs in various phases of design, the AH-64s Integrated Helmet and Display Sighting System (IHADSS) is currently the Army's only fielded integrated HMD. A number of studies have investigated the visual and perceptual issues associated with the monocular optical design of the IHADSS in combination with the AH-64s forward looking infrared (FLIR) thermal sensor (Pilots Night Vision System - PNVS). While these systems have greatly enhanced the operational effectiveness of the AH-64, they have resulted in reports of physiological complaints, degraded visual cues, and both static and dynamic illusions. This study investigated the possible role the IHADSS HMD and PNVS may have played in AH-64 Apache accidents. A total of 217 AH-64 accidents (FY85-02) were analyzed and assigned causal factors associated with the use of the IHADSS and PNVS. The resulting analysis failed to identify any significant role between these systems and flight-related accidents.

The Integrated Helmet and Display Sighting System (IHADSS), employed in the U.S. Army's AH-64 Apache helicopter, is used to present pilotage and targeting imagery and symbology. Therefore, in addition to the standard comfort and protection requirements of a helmet system, the IHADSS must provide a stable optical alignment. Fielded in the early 1980's, the IHADSS is still the Army's only integrated helmet-mounted display (HMD). In an attempt to perform both the standard protective role of a helmet and to serve as a mounting platform for an optical sight, the IHADSS had to make certain design compromises that have resulted in some user satisfaction issues. A joint survey of U.S. and U.K. AH-64 aviators was conducted to identify and quantify these issues. Survey findings indicated that while a majority of aviators found the quality, comfort and satisfaction of fit to be acceptable, a significant proportion of aviators have encountered problems associated with obtaining proper helmet size, availability of replacement components, and substantial variation in fitting expertise. Results of this survey can assist in ongoing and future HMD helmet system designs.

In order to evaluate near-to-eye virtual displays with optics, Night Vision and Electronic Sensors Directorate designed, developed, and integrated the Near to Eye Display Test Station (NDTS). The system utilizes kinematically interchangeable sensor heads to capitalize on the strengths of each sensor for the applications/measurements for which its best suited. The station allows the user to evaluate a near to eye display at a system level without separation of the eyepiece from the image source (“no disassembly required”). Mechanical, optical, electronics, and software components all needed to be carefully designed and integrated to maintain accuracy and precision above those required for display evaluation. Geometric and luminance internal calibration subsystems have been characterized by the test station with results that can be correlated.

Helmet mounted displays (HMDs) provide essential pilotage and fire control imagery information for pilots. To maintain system integrity and readiness, there is a need to develop an image quality-testing tool for HMDs. There is currently no such tool. A framework for development of an image quality tester for the Integrated Helmet and Display Sighting System (IHADSS) used in the U.S. Army's AH-64 was proposed in Hsieh et al. This paper presents the prototype development, summarizes the bench test findings using three IHADSS helmet display units (HDUs), and concludes with recommendations for future directions. The prototype consists of hardware (two cameras, sensors, image capture/data acquisition cards, battery pack, HDU holder, moveable rack and handle, and computer) and software algorithms for image capture and analysis. Two cameras with different apertures were mounted in parallel on a rack facing the HDU holder. A handle was designed to allow users to position the HDU in front of the two cameras. The HMD test pattern was then captured. Sensors are used to detect the position of the holder and whether the HDU was angled correctly in relation to the camera. Two sets of unified algorithms were designed to detect features presented by the two cameras. These features include focus, orientation, displacement, field-of-view, and number of gray-shades. Images of test pattern were captured and analyzed, and used to develop a specification for each inspection feature. Experiments were conducted to verify the robustness of the algorithms. A worst-case scenario for factors such as clock-wise and counterclockwise tilt, degree of focus, magnitude of brightness and contrast, and shifted images were set up and evaluated. Bench testing of three field-quality HDUs indicate that the image analysis algorithms are robust and able to detect the desired image features. Suggested future work includes development of a learning algorithm to automatically develop or revise feature specifications as the number of inspection samples increases.

The U.S Army Night Vision and Electronic Sensors Directorate (NVESD) evaluated a wide field of view HMD technology demonstrator developed by Kaiser Electronics. Primary performance and design characteristics addressed are total field of view, system contrast transfer function, eye box parameters, binocular alignment/stability, residual distortion and head borne mass. The HMD technology demonstrator was designed and built within one year between 1999 to 2000 and was developed to prove novel design and fabrication concepts in the visor, relay optics, optical interfaces, and optical platform structure. The HMD technology demonstrator system is based on a modified HGU-55 helmet and utilizes a bifurcated visor design resulting in a total head borne weight of 4.11 lbs (including MBU-20P Oxygen mask). The system provides a maximum binocular field of view of 52.7° X 29.6°and binocular overlap of 29.5° with an on-axis limiting resolution of 0.76 cy/mr. The uncompensated binocular misalignment was less than 0.29 mr RMS horizontal and 0.24 mr RMS vertical. Other useful system characteristics include right/left independently adjustable IPD mechanisms and a visor/display retraction and removal mechanism operable with a single gloved hand.

Non-contact optical distance measurement using intensity modulated light is exploited to realize a helmet tracking system that tracks the motion of a helmet with six degrees of freedom (6-DOF), i.e., x, y, z, roll, pitch, yaw. A discussion of system robustness of an all-optical helmet tracking system will be given. This will include the tracker's transmitter redundancy, algorithm control, and immunity to effects, that plague existing tracker systems, such as magnetic fields and metallic objects. The tracker can be implemented in any type of fixed-wing, rotary-wing aircraft or ground vehicle of any type and shape. Applications for the new tracker technology include, but are not limited to, manufacturing robotics, telesurgery, motion capture, helmet and body tracking. This talk will include a description of the system architecture, hardware and software. Data will be shown with a discussion of system errors.

A helmet tracker is a critical element in the path that delivers targeting and other sensor data to the user of a helmet-mounted display (HMD) in a military aircraft. The original purpose of an HMD was to serve as a helmet-mounted sight and provide a means to fully utilize the capabilities of off-boresight munitions. Recently, the role of the HMD has evolved from being strictly a targeting tool to providing detailed flight path and situation awareness information. These changes, however, have placed even greater value on the visual information that is transferred through the helmet tracker to the HMD. Specifically, the timeliness and accuracy of the information, which is of critical importance when the HMD is used as a targeting aid, is of even greater importance when the HMD is used to display flight reference information. This is especially relevant since it has been proposed to build new military aircraft without a physical head-up display (HUD) and display HUD information virtually with an HMD. In this paper, we review the current state of helmet tracker technology with respect to use in military aviation. We also identify the parameters of helmet trackers that offer the greatest risk when using an HMD to provide information beyond targeting data to the user. Finally, we discuss the human factors limitations of helmet tracker systems for delivering both targeting and flight reference information to a military pilot.

Aviation helmets have always served as an interface between technology and flyers. The functional evolution of helmets continued with the advent of radio when helmets were modified to accept communication components and later, oxygen masks. As development matured, interest in safety increased as evident in more robust designs. Designing helmets became a balance between adding new capabilities and reducing the helmet's weight. As the research community better defined acceptable limits of weight-tolerances with tools such as the “Knox Box” criteria, system developers added and subtracted technologies while remaining within these limits. With most helmet-mounted technologies being independent of each other, the level of precision in mounting these technologies was not as significant a concern as it is today. The attachment of new components was acceptable as long as the components served their purpose. However this independent concept has become obsolete with the dawn of modern helmet mounted displays. These complex systems are interrelated and demand precision in their attachment to the helmet. The helmets' role now extends beyond serving as a means to mount the technologies to the head, but is now instrumental in critical visual alignment of complex night vision and missile cueing technologies. These new technologies demand a level of helmet fit and component alignment previously not seen in past helmet designs. This paper presents some of the design, integration and logistical issues gleaned during the development of the Joint Helmet Mounted Cueing System (JHMCS) to include the application of head-track technologies in forensic investigations.

Pilot cueing is a valuable use of Head Mounted Displays (HMDs) as it greatly helps the user to visually locate electronically identified targets. It is well known that a target which is hard to spot in the sky can be easily tracked and studied after it has been visually located. Transients, including sun glint, can reveal much about distant targets as they are visually studied. This is implicit in the "Visual Rules of Engagement". The term "Virtual Beyond Visual Range" has been coined to reflect the fact that optimized HMD cueing can extend visual identification to ranges previously covered only by radar data. The visual acquisition range can drop by a factor of three, however, when HMD image correlation errors expand the uncertainty zone a pilot must visually search. We have demonstrated that system errors, tolerable for off axis missile targeting, can produce this large drop in operational effectiveness. Studies using the Spectron SE1430 HMD analysis system have shown that errors of this magnitude can develop in current HMD models, and that these errors were neither identified by "ready room" tests nor were they correctable in the cockpit. The focus of this study was to develop affordable techniques to quantify the relationship of combat effectiveness to HMD defects for this and other advanced operating modes. When combined with field monitoring of HMD degradation, this makes economic optimization of the HMD supply/maintenance model possible while fulfilling operational mission requirements.

Night Vision Goggles allow the user to see in extremely low illumination levels but the visual information provided by Night Vision Goggles has a limited field-of-view that diminishes handling-qualities in the night flying environment. Panoramic Night Vision Goggles were designed to correct this problem by providing a 100° horizontal field-of-view which is larger than currently used Night Vision Goggles. However, in the first generation Panoramic Night Vision Goggle, the improved field of view came at the cost of diminished resolution, contrast and central overlap area when compared to conventional Night Vision Goggles. This paper describes an evaluation that was conducted in the variable stability NRC Bell-205 helicopter to examine the influence on system handling qualities of the Panoramic Night Vision Goggles and a 46° field-of-view UK Night Vision Goggle. Five pilots flew the ADS-33D hover, sidestep and pirouette manoeuvres in simulated night conditions with the UK Night Vision Goggle and the Panoramic Night Vision Goggle. Both subjective and objective measures of task performance were obtained. Handling-qualities ratings showed the pirouette was performed better with the Panoramic Night Vision Goggles. This was the only manoeuvre where there was a clear-cut handling qualities improvement when using the Panoramic Night Vision Goggles. Other manoeuvres such as the sidestep and hover did not show definitive handling qualities rating differences between the two Night Vision Goggle types. The flight test results were interpreted in terms of the design trade-offs of the two night vision systems, with regard to the different acuity, binocular overlaps and fields-of-view.

This paper presents results obtained during a flight evaluation of Night Vision Devices (NVDs) equipped with a symbology injection capability. The NVDs used represented both conventional and wide (Panoramic) Field of View Night Vision Goggle (PNVG) systems. The evaluation was conducted at the National Research Council of Canada Bell 205 Flying Simulator under the auspices of the Technical Co-operation Programme. 6 Pilots from 4 nations participated in the trial and some 36 hours of flight data and pilot performance were recorded. The metrics used to evaluate Pilot performance included conventional Visual Cue Ratings, estimates of workload, and objective measures obtained through advanced data-analysis techniques. The trial used both conventional ADS-33D manoeuvres and a novel 'Racetrack’ course. The paper concludes that although PNVG compare favourably with NVGs the clarity of image currently available in standard NVGs surpasses that of the PNVG and negates some of the advantages gained by the wider Field of View. The manoeuvres favoured by the NVG include those where a high degree of foveal attention demanding processing is being performed, for example navigation tasks. The manoeuvres favoured by the PNVG include those where a more automatic peripheral processing is being performed, for example in reducing drift in the hover.

Integrated Panoramic Night Vision Goggles (IPNVGs) are the prototype night vision goggles (NVGs) and may be the next generation of NVGs. The AN/AVS-9 (F-4949) NVGs, worn by Air Force aircrews, have continuously adjustable eyepieces (from +2.0 diopters (D) to -6.0 D). Unlike the F-4949s, IPNVGs have a fixed-focus eyepiece at -1.0 D. However, previous research has shown that some operators are very insistent that their visual acuity is impaired if they do not have eyepiece settings on the order -2.0 D or more, where they are currently setting their NVGs. The proposed solution is to provide “snap-on” lenses to the IPNVGs in order to obtain a selection of settings. The purpose of this study is to determine if NVGs with this discrete number (two) of “snap-on” lenses are acceptable or if additional lenses are required.

Pilots, developers, and other users of night-vision goggles (NVGs) have pointed out that different NVG image intensifier tubes have different subjective noise characteristics. Currently, no good model of the visual impact of NVG noise exists. Because it is very difficult to objectively measure the noise of a NVG, a method for assessing noise subjectively using simple psychophysical procedures was developed. This paper discusses the use of a computer program to generate noise images similar to what an observer sees through an NVG, based on filtered white noise. The images generated were based on 1/f (where f is frequency) filtered white noise with several adjustable parameters. Adjusting each of these parameters varied different characteristics of the noise. This paper discusses a study where observers compared the computer-generated noise images to true NVG noise and were asked to determine which computer-generated image was the best representation of the true noise. This method was repeated with different types of NVGs and at different luminance levels to study what NVG parameters cause variations in NVG noise.

Visual performance through night-vision devices (NVDs) is a function of many parameters such as target contrast, objective and eyepiece lens focus, signal/noise of the image intensifier tube, quality of the image intensifier, night-vision goggle (NVG) gain, and NVG output luminance to the eye. The NVG output luminance depends on the NVG sensitive radiance emitted (or reflected) from the visual acuity target (usually a vision testing chart). The primary topic of this paper is the standardization (or lack thereof) of the radiance levels used for NVG visual acuity testing. The visual acuity chart light level might be determined in either photometric (luminance) units or radiometric (radiance) units. The light levels are often described as “starlight,” “quarter moon,” or “optimum” light levels and may not actually provide any quantitative photometric or radiometric information. While these terms may be useful to pilots and the users of night-vision devices, they are inadequate for accurate visual performance testing. This is because there is no widely accepted agreement in the night vision community as to the radiance or luminance level of the target that corresponds to the various named light levels. This paper examines the range of values for “starlight,” “quarter moon,” and “optimum” light commonly used by the night vision community and referenced in the literature. The impact on performance testing of variations in target luminance/radiance levels is also examined. Arguments for standardizing on NVG-weighted radiometric units for testing night-vision devices instead of photometric units are presented. In addition, the differences between theoretical weighted radiance and actual weighted radiance are also discussed.

A brief study has been conducted to investigate several visual anomalies reported by test pilots using a Display Night Vision Goggle (DNVG) that superimposed symbols onto the intensified image seen by the right eye. A survey of relevant research suggests that one oddity, an apparent focus mis-match between the scene image and the injected symbols, is an irremovable facet of the perception of bright, contrasting, overlaid symbols. A second oddity, an uncomfortable and distracting blurring of the under-stimulated left eye during periods of flight in cloud, was eventually experienced by several people in a laboratory simulation, the effect being more noticeable if the under-stimulated eye was the dominant eye. A subsequent apparent enlargement of the HUD symbols and a post-flight focussing delay by the left eye seemed to be after-effects of whatever caused the ocular discomfort. As about 30% of the population are left eye dominant, the disturbing discomfort and aftermath could affect this proportion of pilots using a right-eye DNVG. Although further work is needed to understand the phenomena, it would be wise to warn aircrew and enable the symbol injection unit to be fitted to either channel of the DNVG.

Northrop Grumman Electro-Optical Systems (NGEOS) has concentrated in recent years on the development of advanced night vision goggle (NVG) systems. These NVGs developments concentrate on past operational deficiencies such as high light/bright source conditions during military operations in urban terrain (MOUT), poor individual movement technique (IMT) infantry operations, and obscured battlefield and reduced weather conditions. The first area of NVG advancement involves direct image intensifier (I²) replacement involving automatic gated power supply technology for wide dynamic NVG operation and advanced Generation III halo free I² technology for reduction of NVG image halo and “blooming” artifacts. The second significant development area is NVG individual movement technique (IMT) deficiencies such as reduced field of view, reduced depth perception, center of gravity problems, and limited operation flexibility. These issues of NVG IMT have resulted in the development of an IMT enhanced night vision goggle for the U.S. Army's enhanced night vision goggle (ENVG). Finally, Northrop Grumman EOS is developing a NVG with the capability of producing optimized real-time image fusion from an image intensified sensor and uncooled long wavelength infrared (LWIR) sensor. This new technology allows for optimum imaging in battlefield obscured and laser polluted environment. These image fusion NVG development efforts have concentrated on both optical overlay image fusion and digital image fusion. This paper will compare and contrast these two types of image fusion technologies.

The United States' armed forces continue to be presented with increased challenges in adverse operational environments with increasing risk and complexity - especially at night. To ensure continued operational success and battlefield superiority during darkness, our armed forces must be equipped with night vision (NV) systems providing increased situational awareness. Doing so will significantly enhance threat detection and engagement, as well as survivability, thus ensuring greater mission success. Northrop Grumman Electro-Optical Systems (EOS) continues to develop its Wide Field of View (WFOV) image intensification (I²) night vision system for ground forces. This system will provide a significant increase in visual coverage enabling US forces to continue "to own the night". Until now, NV systems have typically been limited to a 40-degree field of view (FOV), vertically and horizontally. This limited FOV reduces off-axis detection, restricts an individual soldier's recognition and engagement capabilities and hinders added peripheral vision. To counter this operational deficiency, EOS proposes the Wide Field of View (WFOV) night vision binocular. The WFOV system will have a 70-degree horizontal FOV, with a 55-degree vertical FOV. The increased FOV will result in increased situational awareness of soldiers' surrounding environment (including terrain, hazards, threat, etc) during normal night operations. It will also allow for rapid and safer movement, especially in MOUT operations. Additionally, the increased visual coverage of large areas will enable soldiers to detect and engage targets faster and with greater reliability. The WFOV binocular will significantly enhance survivability, threat detection and engagement, and hence, greater mission success rate.

Generation III image intensifiers, employing gallium arsenide (GaAs)photocathodes, enable high speed gating into sub-nanosecond range. By utilizing high speed gating techniques, a number of important applications are realized in military rugged ground and aviation applications. Recent advancements toward size, weight, and power reduction of gated I²-based systems have have expanded the scope of applicability of these gating techniques into the battery-powered portable platforms. We present a survey of applications that are expanding from military to commercial applications as high speed gated power supply advancements are realized in the industry.

In July 2002, the US Army Robotics Study Team tested man-portable robots and controllers in combat for the first time. These robots quickly explored caves, bunkers, and other objectives in Afghanistan via remote control while the soldiers remained in secure positions. These systems, developed in less than a month, are still in use a year later. The M7 systems are based on equipment first prototyped for the Land Warrior program and clearly demonstrate that helmet-mounted display technology has reached a deployable state of the art for the infantry soldier. Further work on human factors and ergonomics are the new focus of development for this type of equipment.

The Canadian Soldier Information Requirements Technology Demonstration (SIREQ TD) soldier modernization research and development program has conducted experiments to help determine the types and amount of information needed to support wayfinding across a range of terrain environments, the most effective display modality for providing the information (visual, auditory or tactile) that will minimize conflict with other infantry tasks, and to optimize interface design. In this study, seven different visual helmet-mounted display (HMD) designs were developed based on soldier feedback from previous studies. The displays and an in-service compass condition were contrasted to investigate how the visual HMD interfaces influenced navigation performance. Displays varied with respect to their information content, frame of reference, point of view, and display features. Twelve male infantry soldiers used all eight experimental conditions to locate bearings to waypoints. From a constant location, participants were required to face waypoints presented at offset bearings of 25, 65, and 120 degrees. Performance measures included time to identify waypoints, accuracy, and head misdirection errors. Subjective measures of performance included ratings of ease of use, acceptance for land navigation, and mental demand. Comments were collected to identify likes, dislikes and possible improvements required for HMDs. Results underlined the potential performance enhancement of GPS-based navigation with HMDs, the requirement for explicit directional information, the desirability of both analog and digital information, the performance benefits of an egocentric frame of reference, the merit of a forward field of view, and the desirability of a guide to help landmark. Implications for the information requirements and human factors design of HMDs for land-based navigational tasks are discussed.

Two frames of reference (exocentric and egocentric) and two points of view (first-person and second-person) were contrasted in two experiments to measure their effect on wayfinding performance. Twelve male infantry soldiers used three helmet-mounted display designs (second-person exocentric, second-person egocentric, first-person egocentric) to locate bearings to waypoints. From a constant location, participants were required to face waypoints presented at offset bearings of 25°, 65° and 125°. The egocentric display supported faster performance times than the exocentric display, significantly faster at the largest offset. Faster times were attributed to fewer head misdirection errors and better display compatibility with expectations of spatial orientation. The second-person display supported significantly faster performance times than the first-person display at all offset levels. However, the time differences were not attributed to accuracy or head misdirection errors. Other display features, such as amount of information or field of view may have contributed to the differences. There were no qualitative differences between displays for ease of use, acceptance for land navigation, or mental demand. Implications for the design of helmet-mounted displays for land-based navigational tasks are discussed.

Defects of painted surfaces have proven to be visually disturbing even when their depth is only a few microns. Most inspection approaches neither enable a reliable classification of small defects nor provide a suitable human-machine interface to identify areas to be refinished. Consequently, in most cases the inspection still takes place manually and visually - an unsatisfactory compromise that lacks both objectivity and reproducibility. Our approach combines the reliability of automated methods with the acceptance and flexibility of human-based techniques. The measurement principle is based on deflectometry, and features a significantly higher sensitivity than triangulation methods. The developed system consists of a light source based on a digital micromirror device (DMD), a screen where defined patterns are projected on, as well as a mobile inspection device equipped with a head-mounted display (HMD) and a video camera. During operation, the camera captures images of different patterns reflected in the surface. By combining several images using one of the two techniques described to enhance surface defects, the resulting feature image is displayed in the HMD. This procedure takes place in real time and is repeated continuously. The system performance is demonstrated with the visual inspection of car doors. Promising results show that our prototype allows a reliable yet cost-efficient inspection of painted surfaces matching the needs of automotive industry.

Telepresent walking creates the sensation of walking through a target environment, which is not directly accessible to a human, e.g. because it is remote, hazardous, or of inappropriate scale. A mobile teleoperator replicates user motion and collects visual and auditory information from the target environment, which is then sent and displayed to the user. While walking freely about the user environment, the user perceives the target environment with the sensors of the teleoperator and feels as if walking through the target environment. Without additional processing of the user's motion data, the size of the target environment to be explored is limited to the size of the user environment. Motion compression extends telepresent walking to arbitrarily large target environments without making use of scaling or walking-in-place metaphors. Both travel distances and turning angles are mapped with ratio 1:1.

Conventional head-mounted displays (HMDs) consisting of a pair of miniature projection lenses, beam splitters, and miniature displays mounted on the helmet, as well as phase conjugate material placed strategically in the environment have been redesigned to integrate the phase-conjugate material into a complete see-through embodiment. Some initial efforts of demonstrating the concept was followed by an investigation of the diffraction effects versus image degradation caused by integrating the phase-conjugate material internally in the HMD. The key contribution of this paper lies in the conception, and assessment of a novel see-through HMD. Finally, the diffraction efficiency of the phase-conjugate material is evaluated, and the overall performance of the optics is assessed in both object space for the optical designer and visual space for possible users for this technology.

Biocular helmet-mounted display (HMD) design flexibility and cost are directly related to image misalignment tolerance standards. Currently recommended tolerance levels are based on highly variable data from a number of studies. This paper presents progress of an ongoing study to evaluate optometric measures sensitive to misalignment in partial-overlap biocular optical systems like that proposed for the Comanche RAH-66 helicopter helmet integrated display sighting system (HIDSS). Horizontal divergent and relative vertical misalignments (offsets) of see-through biocular symbology viewed against a simulated daytime background were chosen for this study. Misalignments within and just beyond current tolerance recommendations were evaluated using pre, pre and post, and during measures of visual performance. Data were obtained from seven experimental and four control subjects. The diplopia responses from experimental and control subjects were essentially the same. However, accommodative facility showed a rate decrement following exposure to both types of misalignment. Horizontal heterophorias showed definite post-misalignment increases. Subject responses to questionnaires universally indicated increased adaptation to (ease with) visual tasks over the testing period.

This paper summarizes advancements in ruggedization and miniaturization of high performance Retinal Scanning Display (RSD) Systems. This paper focuses initially on the photonics subsystem, which has been reduced to less than 4% the size of earlier versions. The paper then presents successful results of environmental testing on critical components of the photonics subsystem to demonstrate the system enhancements in optical modulation, fiber coupling and color combining. This paper also reports success in environmental testing of the color combing modules, which proves the viability of this critical component and sets the stage for future environmental qualification of the RSD systems in military and other environmentally stringent applications.

The numerical aperture of the light emanating from display pixels in a given display system determines the exit pupil size. In retinal scanning displays, the exit pupil is defined by the scanner optics, creating a rastered, projected image at an intermediate plane, typically resulting in an exit pupil approximately the size of an eye's pupil. Positional freedom of the eye and relative display placement define the required expansion of the limited input NA for producing the desired exit pupil size for the display system. Currently Microvision utilizes an optical element comprised of two Microlens Arrays (MLAs) in tandem to expand the NA. The dual-MLA system has demonstrated exit pupil size that is independent of color; and uniformity of the beamlet structure is quite Top-Hat like. To further improve the perceived image quality, Microvision has now refined the optical system to minimize interference effects in the Exit Pupil plane that were caused by the coherent nature of the light source. We describe here a single refractive double-sided aspheric element that diminishes this interference effect by converting an input Gaussian beam profile to a Top-Hat profile. We also discuss the theory behind the use of a Gaussian-to-Top-Hat Converter, the tradeoffs associated with its use, as well as experimental results showing the uniformity improvements when using a Top-Hat converter element in conjunction with the MLA-based Exit Pupil Expander. In addition, we report the progress of environmental testing of the Exit Pupil Expander (EPE).

A series of studies was conducted to improve the Army aviator's ability to perform night missions by developing innovative symbols that capitalize on the advantages of new wide field-of-view (WFOV) helmet-mounted displays (HMDs). The most important outcomes of the research were two new symbol types called the Cylinder and the Flight Path Predictor. The Cylinder provides a large symbolic representation of real-world orientation that enables pilots to maintain the world frame of reference even if the visibility of the world is lost due to dust, smoke, snow, or inadvertent instrument meteorological conditions (IMC). Furthermore, the Cylinder is peripherally presented, supporting the “ambient” visual mode so that it does not require the conscious attention of the viewer. The Flight Path Predictor was developed to show the predicted flight path of a maneuvering aircraft using earth-referenced HMD symbology. The experimental evidence and the pilot interview results show that the new HMD symbology sets are capable of preventing spatial disorientation, improving flight safety, enhancing flight maneuver precision, and reducing workload so that the pilot can more effectively perform the critical mission tasks.

The helmet-mounted display (HMD) will be used as the sole means of displaying head-up information to the pilot in future U.S. Air Force (USAF) fixed-wing tactical aircraft. For current fighter aircraft that employ the use of a stand-alone head-up display (HUD), the HMD will be integrated to provide the off-boresight symbology component of the head-up presentation. The symbology for on- and off-boresight use has to be designed to insure the effective interaction between display formats for conveyance of information to the pilot when transitioning between on- and off-boresight viewing angles. This is true for legacy aircraft where the symbology is presented in part by the HUD for on-boresight use with the HMD utilized for the off-boresight application and also for HUD-less aircraft, such as the Joint Strike Fighter, where symbology will be presented solely on the HMD. The Air Force Research Laboratory has been developing HMD symbology to meet the requirements to certify the HMD as a primary flight reference (PFR) for USAF fixed-wing tactical aircraft. This symbology has been designed to maximize the transference of attitude awareness to the pilot when switching between on- and off-boresight attitude references to help insure the pilot achieves correct awareness of spatial orientation. This paper describes the previous research that examined the ASAR for HUD applications, the design of the AFRL ASAR HUD symbology to replace the climb-dive ladder, and the planned flight test evaluation of the ASAR HUD for endorsement as a PFR.

Ownship status helmet-mounted display (HMD) symbology for off-boresight use in fixed-wing tactical aircraft serves to convey aircraft state information (e.g., airspeed, heading, altitude, and attitude) to the pilot for increased situation awareness and maintenance of spatial orientation. A recent flight test evaluation of HMD symbology conducted by the Air Force Research Laboratory (AFRL) and the Edwards AFB Test Pilot School (TPS) indicated a clear performance advantage afforded by the use of off-boresight symbology compared to HUD use alone. The results indicated that the Non-Distributed Flight Reference (NDFR) was the best format of the HMD symbol sets evaluated and served as a good information/orientation aid off-boresight but needs further development to realize its tactical benefit. Specifically, the TPS recommendations pointed to a need for an improved rate-of-change (i.e., trend) indicator for airspeed and altitude, as well as an improvement to the off-boresight attitude reference concerning attitude precision (i.e., climb-dive), particularly near straight and level flight. Based on these recommendations, AFRL modified the original design of the NDFR symbology to satisfy the deficiencies noted by the Edwards AFB TPS. Two variants of the NDFR format with modifications for conveying trend information for airspeed and altitude as well as precision of aircraft attitude were evaluated along with the Mil-Std-1787D HUD symbology and baseline NDFR format. The study examined the four symbol sets during two simulated operationally representative air-to-air intercept tasks that employed the use of an HMD for the off-boresight visual acquisition of a target aircraft. Overall, the NDFR/Odometer symbology allowed a significantly higher amount of off-boresight viewing time while equaling the HUD and other off-boresight symbol sets for primary task performance and proved to be the preferred format for trend mechanization based on pilot comments.

Recent advances in display technology have made it possible to superimpose color-coded symbology on the images produced by night vision goggles (NVGs). The resulting color mixture shifts the symbology's hue and saturation, which can impede recognition of the color code. We are developing luminance-contrast specifications for color-coded NVG symbology to ensure accurate color recognition.

Rotorcraft autorotation is a particularly challenging and hazardous maneuver. Reasons for this include: 1) Highly coupled aircraft dynamics, 2) Highly non-linear aircraft dynamics, 3) Critical aircraft states must be extracted from various sources that are not co-located, making pilot synthesis difficult, 4) Instrument scales and depiction methods make integration of state information difficult, 5) Pilot unfamiliarity with entry conditions/terminal constraints, and 6) A pilot's scanning strategy must usually undergo rapid and unnatural transitions during the maneuver. This paper puts forward a novel training display and methodology that takes advantage of automation's potential as a high-speed decision aid and the strengths of human pattern recognition and conditioning. The methodology applies optimal control theory to solve for a helicopter's trajectory and the required control inputs. A preview of the commanded input suite is displayed to the pilot, which will dynamically update as the vehicle state changes in time. Using this the pilot should be able to execute numerous autorotation maneuvers previously considered outside the operational envelope, in addition to performing 'standard' autorotations with a high degree of control consistency and accuracy. The preview display's function can also be extended to serve as an on-board pilot cueing aid. An autorotation cue set developed from functional requirements is presented, along with results of a preliminary experiment incorporating the display.

In spite of an immense increase in interest in helmet-mounted displays (HMDs) over the past two decades, there have been few studies on head motion while using HMDs in operational flight. Rotary-wing flights conducted using a number of HMD configurations have resulted in a head position database what will be useful in filling this void. Various analysis techniques have been applied to investigate characteristics of roll (tilt) head position distributions for a slalom flight maneuver for four visual environments: good visual environment (daytime, unaided), night vision goggles, HMD with thermal imagery, and HMD with thermal imagery and symbology

One issue of head mounted display design relates to the tradeoff between field of view (FOV) and resolution, which can lead to reduced visual acuity (VA). Essentially, an increase in FOV causes a decrease in visual acuity, for a given LCD display that has a fixed number of pixels. The effects of enhanced brightness on VA using two different types of retro-reflective material (cubed or beaded) were tested using a 52 deg. FOV projective helmet mounted display with VGA resolution. Three lighting conditions were also tested. Based on the display size, resolution, and FOV, we estimated a maximum visual acuity of 4.1 minutes of arc. In a counter-balanced between measures design, subjects' psychometric acuity functions were determined using a computer-generated 4AFC Landolt C test presented stereoscopically and probit analysis. The results confirmed that the maximum visual acuity possible within the setup was 4.1 arc minutes, the limit imposed by the microdisplay, and not the retroreflective material.

The Modular Integrated Display and Sight Helmet (MiDASH) is designed to meet utility, reconnaissance, and attack helicopter mission requirements. It provides twenty-four hours day and night head out flight, Nap-Of-The-Earth (NOE) capability. The system includes observation system and weapons system cueing in an integrated comfortable helmet. The MiDASH offers wide field of view (WFOV), see-through, binocular night imagery, flight information and LOS (Line Of Sight) cueing for day and night operations. The system provides aircraft flight data as well as warning & threats information, allowing the pilot to fly head out during the entire mission, day and night. This relieves the pilot from the need to switch between outside and cockpit scan. The system thus decreases pilot workload while enhancing mission effectiveness, situational awareness, and safety of flight. The MiDASH test and evaluation program included lab tests, human factors tests and flight tests. The paper presents the MiDASH system and discusses the flight test and evaluation program. It details the goals, success criteria, and methods. The paper also addresses flight training, and details the main findings and observations.