Kaiser Electronics' Advanced Rotorcraft Helmet Display Sighting System is a Biocular Helmet Mounted Display (HMD) for Rotary Wing Aviators. Advanced Rotorcraft HMDs requires low head supported weight, low center of mass offsets, low peripheral obstructions of the visual field, large exit pupils, large eye relief, wide field of view (FOV), high resolution, low luning, sun light readability with high contrast and low prismatic deviations. Compliance with these safety, user acceptance and optical performance requirements is challenging. The optical design presented in this paper provides an excellent balance of these different and conflicting requirements. The Advanced Rotorcraft HMD optical design is a pupil forming off axis catadioptric system that incorporates a transmissive SXGA Active Matrix liquid Crystal Display (AMLCD), an LED array backlight and a diopter adjustment mechanism.

Helmet-Mounted Display Sighting System (HMDSS) for advanced rotorcraft requires an extra high luminance backlight to provide the needed display contrast ratio under high ambient lighting conditions. Light Emitting Diode (LED) is selected as the source of illumination because of its high efficiency, compactness, high reliability, and high luminous intensity. This paper describes typical designs of high efficiency and high luminance LED backlight that meets these requirements. Design issues such as light collection efficiency, spatial and angular uniformity, power consumption, color shift, and other optical performance of the backlight will be addressed. With proper selection of LED and adequate optical design, more than 30,000 fl. using only 1.5 watts electrical power is achieved.

Helmet Mounted Displays (HMDs) typically utilize off axis optical systems that result in distorted images. In order to minimize the weight on the pilot's head, a pixilated display, such as an Active Matrix liquid Crystal Display (AMLCD), is utilized as the imaging source. Pixelated displays based on AMLCDs cannot correct distortions or perform spatial transformations as easily as an analog CRT-based systems using electron beam deflection. An advanced rotorcraft HMDSS is a digital system where correcting the distortion within the digital domain is desired to eliminate the inaccuracies of converting to analog, correcting the distortion and converting back to digital. Other system requirements necessitate that the input video be rescaled to provide the proper image to the optical system in order to have the FLIR imagery overlay the real world as the pilot looks through the canopy. To optimize image resolution with minimum sensor size, the FLIR system scans in column mode. As this is not compatible with conventional AMLCD scanning, the FLIR video data must be converted to a row scan. This function, which normally results in additional frame delay, will also be described, together with methods for reducing the latency. The physical constrains of the helmet and the desire to use identical AMLCD devices meant that the devices are rotated between sides of the helmet. This rotation requires that the video image be scanned horizontally and vertically flipped creating another complexity in the design. Requirements for a helmet mounted image intensified television camera to be displayed as an image by itself or overlaid with symbology provided from external video creates additional complexity for distortion correction within the optical chain and will be discussed in this paper. All of these modes require that the video be manipulated in varying degrees of complexity. The enabling technology described in this paper is a complex integrated circuit that allows the user to program the required functions of rotation, scaling, overlays and distortion with minimum latency achieving an effective solution for an advanced rotorcraft Helmet Mounted Display Sight Subsystem (HMDSS).

Helmet Mounted Displays (HMDs) are used to provide pilots with out-the-window capabilities for engaging tactical threats. The first modern system to be employed was the Apache Integrated Helmet Display Sighting System (IHADSS). Using an optical tracker and multiple sensors, the pilot is able to navigate and engage the enemy with his weapons systems cued by the HMD in day and night conditions. Over the next several years HMDs were tested on tactical jet aircraft. The tactical fighter environment - high G maneuvering and the possibility of ejection - created several problems regarding integration and head-borne weight. However, these problems were soon solved by American, British, Israeli, and Russian companies and are employed or in the process of employment aboard the respective countries' tactical aircraft. It is noteworthy that the current configuration employs both the Heads-Up Display (HUD) as well as the HMD. The new Joint Strike Fighter (JSF), however, will become the first tactical jet to employ only a HMD. HMDs have increasingly become part of the avionics and weapons systems of new aircraft and helicopter platforms. Their use however, is migrating to other military applications. They are currently under evaluation on Combat Vehicle platforms for driving tasks to target acquisition and designation tasks under near-all weather, 24-hour conditions. Their use also has penetrated the individual application such as providing data and situational awareness to the individual soldier; the U.S. Army's Land Warrior Program is an example of this technology being applied. Current HMD systems are CRT-based and have many short-comings, including weight, reliability. The emergence of new microelectronics and solid state image sources - Flat Panel Displays (FPDs) - however, has expanded the application of vision devices across all facets of military applications. Some of the greatest contributions are derived from the following Enabling Technologies, and it is upon those technologies and their applications to HMDs that this paper will address: · Active Matrix Liquid Crystal Displays; improved response times, compensation films · Sub-micron electronics · Backlight Technology to address brightness issues across the spectrum of operations · Distortion Correction to compensate for optical aberrations in near-real time.

The development of data generating sensors and computers in a modern fixed wing aircraft is not met by an increase in sensorial performance by the operator to assimilate this data. No new sensor has been developed nor has any drastic increase in data perception been implemented in the human operator since the first manned flight by the Wright brothers. Consequently we have to refine the media and the way in which we present data to the pilot. This document describes a platform for test and evaluation of head mounted technology and some new technologies that can be used for decreasing the pilot's workload. Furthermore, the document describes initial tests done on image quality and design of reflective coatings on visors.

Common techniques of lens design lead to image quality assessment in the plane of the miniature display of a head-mounted display (HMD) instead of image quality in visual space as expected from a usability point of view. In this paper, we present an analysis of HMD performance in visual space including MTF, accommodation, astigmatism, and transverse color smear.

An alternative method for measuring the contrast transfer function (CTF) of a pixilated display is proposed that reduces the amount of time required to perform a high sample rate-small aperture luminance scan as outlined in the Video Electronics Standards Association (VESA) standard for measuring the contrast of an n X n grille. The alternative method proposed by the Night Vision Electronic Sensors Directorate (NVESD) Displays group utilizes round sampling apertures and large step sizes to achieve comparable results to the VESA standard method. Theoretical predictions and experimental measurements demonstrated the equivalency between the proposed large aperture method and the VESA standard method with less than 8% maximum variation and an average of 2.4% variation between the two methods over two different input contrasts and 4 different grille frequencies. Experimental results also show a reduction in time to perform the profile scan by as much as 15:1 for the NVESD proposed test method over the VESA standard method.

With ever-increasing applications for Helmet Mounted Displays (HMD) and current high-volume production rates, the development of automated measurement equipment and techniques for characterization and testing displays becomes paramount to delivering a consistent and quality product. This paper examines the requirements that drive the need for automated HMD testing and the interrelationships that exist between the design of the prime hardware and its test equipment. Topics presented include the following: Design of an automated optical measurement bench that maximizes the use of COTS hardware and software and is readily adaptable to different HMD designs. Specialized tooling requirements. Methods of achieving HMD alignment to the optical Line of Sight (LOS). Development of reusable test software components. Algorithms for predicting the location of images in the HMD reference frame, including coordinate transformations and search algorithms. Issues concerning characterization of image sources and optical components are presented utilizing case studies. Actual production throughput data is compared with data from more traditional test methods to emphasize the advantages of this approach. Finally, actual results of achievable accuracy using the automated optical measurement bench are presented.

The Night Vision & Electronics Sensors Directorate and Kaiser Electronics have continued to further develop the driver's Head-Tracked Vision System (HTVS) which directs dual waveband sensors in a more natural head-slewed imaging mode. The HTVS consists of a Long-Wave Infrared (LWIR) sensor, an image-intensified sensor, a high-speed gimbal, a head-mounted display, and a head-tracker. The first prototype systems have been delivered and have undergone preliminary field trials to characterize the operational benefits of a head-tracked sensor system for tactical military ground applications. This investigation will address the advancements of the HTVS Head-Mounted Display (HMD) and head-tracker, and will discuss the advantages of additive image fusion and feature-level image fusion of the LWIR and image-intensified sensors over single-sensor performance.

The need for the helmet-mounted display (HMD) to present flight, navigation, and weapon information in the pilot's line-of-sight has continued to rise as helicopter missions increase in complexity. To obtain spatial correlation of the direction of the head line-of-sight and pilotage imagery generated from helicopter-mounted sensors, it is necessary to slave the sensors to the head motion. To accomplish this task, a head-tracking system (HTS) must be incorporated into the HMD. There are a variety of techniques that could be applied for locating the position and attitude of a helmet-mounted display. Regardless of the technology, an HTS must provide defined measurements of accuracy. System parameters include motion box size, angular range, pointing angle accuracy, pointing angle resolution, update rate, and slew rate. This paper focuses on a hybrid tracker implementation in which a combination of optical and inertial tracking using strap-down gyros is preferred. Specifically, this tracker implementation is being examined for the high-accuracy attack rotorcraft market which requires a high degree of accuracy. The performance and resultant cost of the tracker components are determined by the specific needs of the intended application. The paper will also indicate how the various requirements drive the cost, configuration, and performance of the resultant hybrid head-tracker.

In spite of an immense increase in interest in helmet-mounted displays (HMDs) over the pass 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 that will be useful in filling this void. Various analysis techniques have been applied to investigate characteristics of elevation 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.

When a Helmet-Mounted Display (HMD) system is used in an aircraft cockpit, the usual intent is to overlay symbols or images in the display on their real-world object counterparts. The HMD system determines a pointing angle (in aircraft coordinates) to the real-world object. This pointing angle is sent to the Mission Computer (MC) for use by other aircraft systems and is used by the HMD to position symbology in the HMD image. The accuracy of the HMD is defined as the error of the pointing angle sent to the MC versus the real-world angle to the object. This error is usually given in terms of milli-radians (mrad). Note that having the symbol in the HMD image overlay the corresponding object in the real world does not necessarily ensure an accurate pointing angle. One example of HMD use is to position an aiming cross in the display over an aircraft in the sky. The pointing angle to that aircraft is sent via the MC to another sensor (radar, missile, targeting pod) which then locks onto that aircraft or object. The accuracy requirement is to get the other sensor pointed at an angle to detect the same aircraft. There are aircraft integration issues to ensure target acquisition, but these will not be covered in this paper. One component of the HMD system is a tracker system, and the tracker system's accuracy is often looked at as the HMD accuracy. However, the accuracy of the tracker system is only one piece of the total HMD system accuracy, and as trackers get better, they may not even be the largest error component. This paper identifies the various error components of the HMD system installed in the aircraft cockpit and discusses the techniques used for minimizing errors and improving accuracy.

Optical design is one of the major limiting factors for making any sensor and display feasible in a head-mounted application. This is especially the case for multispectral (dual-color) sensing systems because they may employ two sensors instead of one. Various approaches can be made to incorporate a multispectral imaging system in a head mounted application. One of these is to use an entrance aperture that is common to two separate sensors. This type of design is attractive in that it provides co-aligned sensors in a relatively compact package. However, multispectral, head-mounted optics pose unique challenges that must be overcome by both the designer and fabricator of such a system. This paper will examine these challenges and pose conceivable optical solutions.

Distortion is an issue that arises when designing Army Helicopter sensor packages. F-Theta versus F-Tan-Theta distortion is consistently one of the most important and least understood facets of the system. This is especially important when dealing with multiple sensors that have to use the same display. Arriving at the optimized optical solution can be a very involved and difficult design process. This paper explains what the problems are, the possible solutions, and the results of the design choices made along the way. It will elaborate on how each design choice affects image resolution, field of view (FOV), sensor fusion, and the apparent motion artifacts that are caused by mismatched distortions. The goal is to develop a better understanding of the problem, which will enable us to design the best possible optical system for the helicopter pilot.

Visors are an important component in modern helmet-mounted displays (HMDs). In addition to their more conventional use as eye protection, they can be used as the final element in the optical system that relays visual information to the observer. To enhance their usefulness as the final optical element (as a beam splitter or image combiner), visors are sometimes coated to increase their reflectivity and improve the efficiency of the optics. However, pilots often object to the addition of reflective patches, indicating, among other reasons, that they decrease observed target contrast and, therefore, decrease target detection range. This paper will examine the impact of the additional reflective coating on visual performance through a helmet-mounted display visor. It will propose design parameters based on the spectral nature of the coating that might make it more useful to both the HMD designer and to the HMD wearer. Finally, this paper will examine visual phenomena that may affect visual performance through a coated visor.

The wide field of view night vision goggles (WNVG) are the next generation of night vision goggles (NVGs). They have a significantly increased horizontal field of view and a weight similar to the current AN/AVS-9, which only has a 40 degree circular field-of-view (FOV). Due to complicated optics and weight issues, the WNVG will have a fixed-focus eyepiece; this is different from the AN/AVS-9 (Figure 1), which has a continuously adjustable +2.0 to -6.0 diopter (D) range for each eyepiece. Site visits were made to several Special Operations Squadrons to survey aircrew members about the WNVG with a fixed-focus eyepiece and optional clip-on lenses. This paper addresses aircrew acceptance of the use of snap-on/helper lenses in place of continuously adjustable eyepieces.

The concept of head-mounted projective display (HMPD) has been recently proposed as an alternative to conventional eyepiece-type head-mounted displays (HMDs). An HMPD consists of a pair of miniature projection lenses and flat panel displays mounted on the head and retro-reflective sheeting material placed strategically in the environment. Recent efforts have been made to demonstrate the feasibility of the imaging concept and prototypes have been built. Our research indicates that the quality and properties of the retro-reflective material play critical roles in the overall imaging quality of HMPDs. The retro-reflective sheeting material is commonly used in traffic control and photonic lighting systems, rather than optimized for imaging purpose as in the HMPDs. The size and shape of the microstructures cause artifacts on images. In this paper, we will mainly focus on the evaluation of the various existing retro-reflective materials, and the examination of the impact of the material characteristics on imaging properties. The basic structures of the existing materials are briefly reviewed, the characteristic parameters used to quantify the material properties are defined, and a few samples are evaluated. The characteristics of interest include: the size and shape of the microstructure, the distribution pattern and density of the microstructure, retro-reflectivity, the profile of the reflected light, diffraction artifacts and ghost imaging. Finally, a comprehensive analysis are presented to examine how the material characteristics play their roles in an imaging system, such as the HMPD, and predict the imaging artifacts caused by these characteristics.

The paper will outline Retinal Scanning Display (RSD) technology fundamentals and detail some of the potential advantages this technology offers to military HMD applications. We will also present current performance level achieved and the roadmap ahead.

This paper outlines the design trade-offs and measured results of scanner architectures for use in high resolution Retinal Scanning Displays: Mechanical resonant for horizontal scanning, and MEMS-based pinch correction and vertical linear scanners. Analysis steps and techniques used to model and minimize dynamic deformations are covered. This paper also discusses two types of scanners and associated mirror flatness issues. Dynamic flatness modeling and performance results are presented, followed by thermally induced deformations and possible athermalize solutions for MEMS-type scanning mirrors. Theory, FEA dynamic and thermal analysis, experimental results, and methods to reduce mirror deformation are discussed.

A general overview of high resolution Retinal Scanning Display system and the requirements for driving electronics are presented. Intra-beam pixel positioning mechanisms that provide integral adjustment capability are detailed. Horizontal raster correction is achieved with high accuracy direct digital synthesis.

The numerical aperture of the light emanating from display pixels in a given display system determines 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. Accounting for positional freedom of the eye and relative display placement defines the required expansion of the limited input NA for producing the desired exit pupil size for the display system. Although there are many approaches to performing this task of NA conversion, or exit pupil expansion, many of them exhibit wavelength dependencies, causing the envelope of the intensity profile in the exit pupil plane to be non- overlapping or inconsistent versus pixel location, resulting in uniformity or color variations and often efficiency loss. This paper will look at a microlens array approach to exit pupil expansion for color display systems that will be shown as wavelength independent in terms of diffraction envelope.

This paper will start with a brief discussion of the high-resolution retinal scanning display (RSD) system architecture. The remainder of the paper will concentrate on the design and implementation of a miniaturized light modulation system used within a multi-beam RSD. Significant size and weight reduction, and good modularity are obtained using a custom designed, multi-channel AOM having the outgoing diffracted beam in-line with the incoming beam. Optical and mechanical design considerations of the acousto-optic based modulator and of the color combining module will be covered.

A collaborative occupational health study has been undertaken by Headquarters Director Army Aviation, Middle Wallop, UK, and the U.S. Army Aeromedical Research Laboratory, Fort Rucker, Alabama, to determine if the use of the monocular helmet-mounted display in the Apache AH Mk 1 attack helicopter has any long-term (10-year) effect on visual performance. This paper describes the protocol, methodology, development and initial execution phase of this study. The test methodology consists primarily of a battery of vision tests selected to capture changes in visual performance (with an emphasis on binocular visual functions) of Apache aviators over their flight career. It is anticipated that the number of Apache aviators will level out to approximately 70 by the end of the first three years of the study. Non-Apache aviators will serve as a control group.

To meet the goal of 24-hour, all-weather operation, U.S. Army aviation uses a number of imaging sensor systems on its aircraft. Imagery provided by these systems is presented on helmet-mounted displays (HMDs). Fielded systems include the Integrated Helmet Display Sighting System (IHADSS) used on the AH-64 Apache. Proposed future HMD systems such as the Helmet Integrated Display Sighting System (HIDSS) and the Microvision, Inc., Aircrew Integrated Helmet System (AIHS) scanning laser system are possible choices for the Army's RAH-66 Comanche helicopter. Ever present in current and future HMD systems is the incompatibility problem between the design-limited physical eye relief of the HMD and the need to provide for the integration of laser and nuclear, biological and chemical (NBC) protection, as well as the need to address the changing optical and vision requirements of the aging aviator. This paper defines the compatibility issue, reviews past efforts to solve this problem (e.g., contact lenses, NBC masks, optical inserts, etc.), and identifies emerging techniques (e.g., refractive surgery, adaptive optics, etc.) that require investigation.

Combat developers and aviation program managers require knowledge of helmet-mounted display (HMD) performance under operational conditions in order to determine HMD luminance and contrast requirements. In order to ease this problem, we developed a computer model that predicts available gray-shades based on hardware, ambient light condition, and HMD properties. Included in the model are windscreens, visors, laser protection devices, and properties of developed and fielded HMDs. A graphical user interface and user variables specification allow the developer/manager to model HMDs in specific aircraft. Included with the model is a color model that predicts see-through color imagery. The model produces a visualization of see-through imagery superimposed with HMD symbology based upon model predictions. This allows the user to view simulated imagery as though he were wearing the HMD.

A web-based study was conducted to determine the continuing presence and frequency of visual complaints reported by pilots using the monocular Integrated Helmet and Display Sighting System (IHADSS) helmet-mounted display (HMD) of the AH-64 Apache helicopter. A total of 216 pilots responded to the survey, which addressed areas of visual symptoms experienced during and/or after flight, helmet fit, and acoustics. Ninety-two percent of the pilots responding to the survey reported at least one visual symptom. The most frequently reported symptom for both during and after flight was visual discomfort. One out of four respondents reported having some difficulty in purposefully alternating between visual inputs to the two eyes. Approximately two-thirds of the pilots responding expressed reasonable satisfaction with their current helmet fit.

Head-up displays (HUDs) or helmet-mounted displays (HMDs) that provide pilots with world-referenced symbology or imagery require critical alignment and minimal time delays. In this paper, some aspects of system accuracy and latency will be discussed in the context of the Enhanced and Synthetic Vision System (ESVS), which is displayed on an HMD. In a joint program, the Canadian Department of National Defence (DND), CAE Inc., CMC Electronics, and the Flight Research Laboratory of the National Research Council of Canada integrated and flight-tested an enhanced and synthetic vision system. The goal of the program was to examine the potential of the ESVS concept for search and rescue operations. Despite obvious misalignments between the enhanced and synthetic images, the current system demonstrated the potential of ESVS systems with most of the test pilots able to navigate at low altitude in low visibility in an area without prepared navigation aids. The flight tests highlighted the system potential- the synthetic imagery provided continuous virtual VFR conditions, while the enhanced sensor generally provided more accurate spatial data and obstacle avoidance information. The ESVS program finished with the first helicopter flight test of both enhanced and synthetic visual displays presented on an HMD. While this milestone was successfully achieved, there is clearly a need for improved technology and further research to implement safe and effective ESVS systems. The system alignment was found to be a complex and perplexing issue. It was not possible to align the system within the precise tolerances generally accepted for HUD-equipped aircraft and, in fact, errors that were an order of magnitude greater than the recommendations were common. Errors built up in such a way that the system developers needed to develop an interim alignment solution and pilots were forced to deal with relatively large angular offsets. This was less than optimal, but proved to be sufficient for the tasks in the trials. However, it is clear that a rigorous alignment procedure is required to satisfy the strict requirements of an all-weather system that would support aggressive maneuvering and navigation in unknown terrain.

Three variations of the non-distributed flight reference (NDFR) off-boresight helmet-mounted display (HMD) symbology were evaluated along with the Mil-Std-1787C HUD symbology and an off-boresight HMD symbology called the Visually Coupled Acquisition and Targeting System (VCATS), for interpretation of ownship status information. Using twenty predetermined flight path segments lasting 3 to 5 seconds each, the NDFR, NDFR plus climb-dive angle reference, mini-arc NDFR, Standard HUD, and VCATS symbologies were compared for recall of ownship status information. Twelve military or civilian rated pilots participated. Pilots viewed all five symbology formats with ownship status information recalled at the end of each flight path. Pilots provided feedback of ownship status using a free recall methodology. Mil-Std-1787C HUD served as the baseline measure of comparison with the primary comparison of interest being the off-boresight HMD symbology formats. The study's aim was to evaluate the baseline NDFR format along with alternate symbology designs to arrive at an HMD symbology for off-boresight applications that is highly usable in terms of awareness of aircraft state and orientation. The results of the study showed that, although no single NDFR format proved best for all information categories, taken as a group, the NDFR symbology proved to be the preferred symbology format for the information categories investigated. The NDFR format equaled recall performance for Standard HUD and outperformed or equaled the VCATS off-boresight symbology. Further evaluation of the NDFR concept is planned using pilot-in-the-loop HMD simulations evaluating modifications to the NDFR for trend information and attitude determination and investigating display compatibility with the virtual HUD concept.

The Air Force Research Laboratory (AFRL) has been working to optimize helmet-mounted display (HMD) symbology for off-boresight use. One candidate symbology is called the non-distributed flight reference (NDFR). NDFR symbology allows ownship status information to be directly referenced from the HMD regardless of pilot line of sight. The symbology is designed to aid pilot maintenance of aircraft state awareness during the performance of off-boresight tasks such as air-to-ground and air-to-air target acquisition. Previous HMD symbology research has shown that pilots spend longer periods of time off-boresight when using an HMD and therefore less time referencing primary displays in the aircraft cockpit. NDFR may provide needed information for the pilot to safely spend longer periods of search time off-boresight. Recently, NDFR was flight tested by the USAF Test Pilot School at Edwards AFB, CA, aboard the VISTA F-16 (Variable Stability In-flight Simulator Test Aircraft) during operationally representative air-to-air and air-to-ground tasks, as well as unusual attitude recoveries. The Mil-Std-1787B head-up display (HUD) symbology and another off-boresight HMD symbology called the Visually Coupled Acquisition and Targeting System (VCATS) were evaluated as comparison symbol sets. The results of the flight test indicate a clear performance advantage afforded by the use of off-boresight symbology compared to HUD use alone. There was a significant increase in the amount of time pilots looked off-boresight with both the NDFR and VCATS symbologies. With the NDFR, this increase was achieved without an associated primary task performance tradeoff. This was true for both air-to-ground and air-to-air tasks.

Previously, we presented an experiment in which we defined minimum, but not sufficient, luminance contrast ratios for color recognition and legibility for helmet-mounted display (HMD) use. In that experiment, observers made a subjective judgement of their ability to recognize a color by stopping the incremental increase in contrast ratio of a static display. For some target color/background combinations, there were extremely high error rates and in these cases sufficient contrast ratios were not achieved. In the present experiment, we randomly presented one of three target colors on one of five backgrounds. The contrast ratio of the target on the background ranged from 1.025:1 up to 1.3:1 in steps of 0.025. As before, we found that observers could accurately identify the target colors at very low contrast ratios. In addition, we defined the range in which color recognition and legibility became sufficient (>= 95% correct). In a second experiment we investigated how ell observers did when more than one color appeared in the symbology at one time. This allowed observers to compare target colors against each other on the five backgrounds. We discuss our results in terms of luminance contrast ratio requirements for both color recognition as well as legibility in HMDs.

Recent technological advances allow symbology to be displayed on the pilot's visor. A major benefit of this is that the pilot will be able to take this information with them when they look off-boresight. However, when looking off-boresight the question arises as to what is the best orientation, or frame of reference, for attitude symbology against the horizon (i.e., forward or line-of-sight) in order to maximize interpretation and performance. This study tested five different symbologies (standard HUD, visually coupled acquisition and targeting symbology, arc segmented attitude reference, theta ball, and non-distributed flight reference) of which three have both forward and line-of-sight orientations. The experiment consisted of two different tasks, with the pilots performing either facing the monitor or rotated 90 degree(s) and looking over their shoulder (off-boresight). In the first task, pilots maintained straight and level flight with simulated turbulence. The second task had pilots interpret a static representation of their attitude and respond via a key press, and then the display went live and they had to fly to a new commanded attitude. This second task was similar to a recovery from unusual attitude methodology, except the end state was never straight and level. Instead, a second unknown end state attitude was commanded by the experiment. Results indicate that performance is better when the symbology is forward as opposed to line-of-sight referenced. Further, performance was best in both tasks for the non-distributed flight reference. We discuss these results in terms of implications for helmet-mounted display symbology design.

Helicopter flight using night-vision devices (NVDs) is difficult to perform, as evidenced by the high accident rate associated with NVD flight compared to day operation. The approach proposed in this paper is to augment the NVD image with synthetic cueing, whereby the cues would emulate position and motion and appear to be actually occurring in physical space on which they are overlaid. Synthetic cues allow for selective enhancement of perceptual state gains to match the task requirements. A hover cue set was developed based on an analogue of a physical target used in a flight handling qualities tracking task, a perceptual task analysis for hover, and fundamentals of human spatial perception. The display was implemented on a simulation environment, constructed using a virtual reality device, an ultrasound head-tracker, and a fixed-base helicopter simulator. Seven highly trained helicopter pilots were used as experimental subjects and tasked to maintain hover in the presence of aircraft positional disturbances while viewing a synthesized NVD environment and the experimental hover cues. Significant performance improvements were observed when using synthetic cue augmentation. This paper demonstrates that artificial magnification of perceptual states through synthetic cueing can be an effective method of improving night-vision helicopter hover operations.

As a cockpit display medium, HMDs have unique characteristics that must be considered when integrating these systems into aircraft. Two primary advantages of HMDs are that they display information directly in the pilot’s line of sight and they allow for off-boresight cueing and targeting of weapon systems. It is important to note that these two advantages of HMDs can also be viewed as two disadvantages. Because HMD symbology is displayed in the pilot’s line of sight, the display can obscure the out-the-window scene. There is also anecdotal evidence that offboresight targeting information presented in a HMD may cause pilot fixation, leading to reduced situational awareness. HMDs offer capabilities never before available in any type of cockpit display device - specifically, the ability to present an egocentric, augmented reality display presentation throughout the full field of regard of the pilot’s natural vision. Capitalizing on the unique capabilities of helmet mounted displays will provide increased spatial and situational awareness throughout all regimes of flight, especially in low visibility or high workload conditions. During this effort, Navy and Boeing team members developed several operational helmet-mounted display (HMD) symbology formats that fulfilled the primary flight reference (PFR) requirements. Team members down-selected a set of concepts for evaluation in a flight simulator. These concepts were integrated and evaluated using pilot-in-theloop simulations in the Crewstation Technology Laboratory (CTL) at the Naval Air Warfare Center Aircraft Division in Patuxent River, MD. This paper details the first series of evaluations on these formats. Additional evaluations will be performed on the second iteration of the formats during in the summer of 2002.

In this paper, we shall present an overview of research in augmented reality technology and applications conducted in collaboration with the 3DVIS Lab and the MIND Lab. We present research in the technology of head-mounted projective displays and tracking probes. We then review mathematical methods developed for augmented reality. Finally we discuss applications in medical augmented reality and point to current developments in distributed 3d collaborative environments.

Visualizing information in three dimensions provides an increased understanding of the data presented. Furthermore, the ability to manipulate or interact with data visualized in three dimensions is superior. Within the medical community, augmented reality is being used for interactive, three-dimensional (3D) visualization. This type of visualization, which enhances the real world with computer generated information, requires a display device, a computer to generate the 3D data, and a system to track the user. In addition to these requirements, however, the hardware must be properly integrated to insure correct visualization. To this end, we present components of an integrated augmented reality system consisting of a novel head-mounted projective display, a Linux-based PC, and a commercially available optical tracking system. We demonstrate the system with the visualization of anatomical airways superimposed on a human patient simulator.

Achieving large-scale production of helmet mounted systems in airborne platforms challenges the resources of both customers and developers. Commonality of technology and subsystems, and between different HMD products for multiple platforms, reduces development costs and improves lifecycle costs, making HMD systems affordable. Achieving such commonality, under the constraints of varying operational needs and diverse operating environments, is a multidisciplinary challenge. Elbit Systems Ltd., Helmet Mounted System Division, has fielded in the last two decades thousands of HMD systems for both fighters and helicopters. Commonality has always played a key role in the development of new HMD systems. This paper shares experience and discusses approaches of implementing commonality into HMD system design.

Along with the rapid development of wearable computer and multi-medium technology, many units need to be mounted on the helmet such as micro display, camera, voice input and output components, even some devices for safety and security purpose. If these units and components are controlled by the wearable computer directly, it would make the interface between helmet and wearable computer complicated. The better way is to add a controller to the helmet, then the wearable computer only need to interface with the controller. The helmet controller controls all of the functional components of helmet. Of cause, it should be noticed that the dimensions of the components must be small since the volume of helmet for the controller is very limited. The core of the helmet controller we designed is composed of a digital signal processor (DSP) and field programmable logical array (FPGA). The DSP carries out the function of encoding, decoding, compression, encryption, synthesis, and filtering of image and voice signals. FPGA drives and controls a micro display, controls the functional components, as well. All of these reduced the amount of elements, enlarged the integration level, which realized the helmet controller microminiaturization.

The Crew Systems Group at QinetiQ Farnborough, formerly part of the Defence Evaluation and Research Agency (DERA), have recently conducted development and flight evaluations of two monocular display systems that provided dynamic symbology for the pilot. The systems were the Pilkington Optronics (now Thales) Guardian monocular Helmet Mounted Display (HMD) used for daytime operations and the QinetiQ Display Night Vision Goggles (DNVGs) used at night. Test flights of the two systems were performed in a modified Jaguar T2B combat aircraft, that was based at the QinetiQ Boscombe Down research facility. Good performance was obtained from each system with both producing clear, legible symbology. During day and night Air to Ground (A-G) sorties both the Guardian and the DNVGs were used for simulated attacks and reconnaissance tasks on a variety of operationally realistic targets. In addition the Guardian HMD was used with an ASRAAM in the day Air to Air (A-A) environment to provide high off-boresight capability. The results from the test program have validated a range of significant capability enhancements offered by either a HMD or a DNVG, and have provided a significant increase in the technical and operational understanding of fast-jet helmet display systems.

The Helmet Mounted Display has been in development for over 25 years and with few exceptions those systems in service have incorporated a miniature Cathode Ray Tube as the display source. The exceptions have been the use of Light Emitting Diodes in Helmet Sighting displays. The argument for Flat Panel Displays has been well rehearsed and this paper provides a summary of the available technologies but with a rationale for a decision to use Reflective Liquid Crystal devices. The Paper then describes sources of illumination and derives the luminance required from that source.