Head- and helmet-mounted displays can benefit greatly from new image generating technologies. This paper describes a liquid crystal digital scanner-based head-mounted display (DS-HMD) that has been developed at Physical Optics Corporation (POC). The HMD consists of low power light emitting diodes (LEDs), a liquid crystal digital scanner, and image projection optics produced by POC's proprietary holography technology. Modulating the individual LEDs while synchronously scanning perpendicularly generates a 2D image. The paper describes design, fabrication, and performance measurements for an actually implemented experimental liquid crystal digital scanner system, and design and fabrication of the holographic components.

While many HMD designs exhibit see-through capability and a relatively narrow field of view (FOV), the HMD design presented int his paper is purposely immersive since it seeks operational roles requiring anthropomorphic telepresence, which seeks to procure its operator the impression of being at a remote location. This technology is applicable in situations where it is deemed too expensive and/or hazardous to send an operator on site. The HMD developed for this purpose exhibits SVGA resolution, and achieves a FOV of approximately 84 degrees through compact 6-element eyepieces. It is color and stereo capable, and the usual degradation in effective resolution due to RGB triads from conventional composite color display devices is circumvented by the use of a sequential color technique, which yields a very acceptable image quality with acceptable pixelation, in spite of the high FOV. Several add-ons to this HMD, greatly enhancing its capabilities, have also been developed and will be described briefly; they include translucentgraphical overlays, an embryo of real-time video CODEC technology that could enable fully digitized visual telepresence at acceptable bandwidths, the associated robotics complementing the HMD and enabling actual telemanipulations, and finally, a time delay (in static environments) and motion compensation algorithm.

Virtual Retinal Display^TM technology is a retinal scanning display (RSD) technology being developed at Microvision, Inc., for a variety of applications including microdisplays. An RSD scans a modulated light beam onto a viewer's retina to produce a perceived image. Red, green and blue light sources, such as lasers, laser diodes or LEDs combine with Microvision's proprietary miniaturized scanner designs to make the RSD very well suited for head-worn and helmet-mounted displays (HMD). This paper compares the features of RSD technology to other display technologies such as the cathode ray tubes or matrix-based displays for HMD and other wearable display applications, and notes important performance advantages due to the number of pixel- generating elements. Also discussed are some fundamental optical limitations for virtual displays used in the HMD applications.

This paper addresses the development of eyewear based displays for portable, personal electronics. The personal electronic system applications include the wearable personal computer, portable digital video disk player, and the cellular telephone. We describe progress on integrated eyewear systems, as well as on clip-on systems that can attach to ordinary eyewear. We conclude with a short description of a system that will include a camera, display, and audio system.

As technology moves toward mobile computing, evaluation of these technologies, such as head-mounted and glasses-mounted displays, and human performance associated with their use in essential to their successful development. This paper presents the results of one such evaluation.

The relatively new notion that visual perception is served by two functionally distinct visual systems, the focal and the ambient, is supported by research evidence accumulated over the past thirty years. The focal system provides detailed information about the world, is controlled by attention and receives input from the fovea. Its performance is highly dependent on image focus and luminance level. The ambient visual system contributes continuously and importantly to spatial orientation, stability of the visual world, and locomotion. It responds to large areas of optical flow int he visual field and therefore most of its input comes from the peripheral retina. Ambient functions are carried out largely without conscious awareness and are relatively impervious to image defocus and luminance level. The evidence for the ambient visual system is reviewed and its functional characteristics are described.

Generic rotorcraft daylight helmet-mounted visually coupled display system requirements are described in this paper, followed by a short history of the Army's AIHS Program, a review of Microvision's technology, and performance test results of the project phase I and preliminary phase II HMD system deliverables.

Stereoscopic presentation is appropriate to helicopter flight guidance, because it allows the use of new 3D flight guidance symbology, which is perceived naturally by the pilot. Stereoscopy acts particularly well with 3D symbology, as it provides a good perception of depth of field. Upon completion of the experimental study, twelve test persons evaluated the support offered for flight guidance. The results will be presented in the paper.

BAE SYSTEMS are developing a high performance Helmet Mounted Display system for the US Marine corps AH-1Z attack helicopter. This paper presents an overview of the design solution, as well as details of the rational behind the design and some of the lesson learnt. Finally, it gives some indicators as to future growth.

Helmet Mounted Displays (HMD) are now an essential element in fast jet aircraft cockpits and the demanding safety requirements must be maintained. Exposure to high-speed air- blast was a fundamental requirement of a developmental HMD produced by BAE SYSTEMS. Safety criteria based on stability, strength and aerodynamic loads meant that reliance on an empirical development was no longer appropriate. Success was achieved from a combination of experience, analysis, design and testing. Computational Fluid Dynamics modeling combined with validation testing in a wind tunnel provided a vital understanding of the aerodynamic loads developed during the windblast event and significantly reduced developmental risk.

Automatic test and calibration has become a valuable feature in many consumer products--ranging from antilock braking systems to auto-tune TVs. This paper discusses HMDs (Helmet Mounted Displays) and how similar techniques can reduce life cycle costs and increase sustainable performance if they are integrated into a program early enough. Optical ATE (Automatic Test Equipment) is already zeroing distortion in the HMDs and thereby making binocular displays a practical reality. A suitcase sized, field portable optical ATE unit could re-zero these errors in the Ready Room to cancel the effects of aging, minor damage and component replacement. Planning on this would yield large savings through relaxed component specifications and reduced logistic costs. Yet, the sustained performance would far exceed that attained with fixed calibration strategies. Major tactical benefits can come from reducing display errors, particularly in information fusion modules and virtual `beyond visual range' operations. Some versions of the ATE described are in production and examples of high resolution optical test data will be discussed.

Increasing interest in helmet-mounted displays (HMDs) has fueled research in variable transmittance visors (VTVs) because a VTV can reduce glare and increase HMD contrast in bright lighting conditions. The ideal VTV will be an electrically controllable light valve that allows the pilot to adjust visor transmittance (tint) to the level appropriate to the ambient lighting conditions. Liquid- crystal based devices can provide an efficient method for accomplishing this. Because flight helmets utilize polycarbonate visors, VTVs must be implemented on complex curved, plastic substrates. Liquid crystal devices, however, are typically implemented on flat glass substrates. We present a novel system, Variable Attenuation Liquid Crystal Device (VALiD), which can be utilized for this application. VALiD is a dichroic dye and liquid crystal based guest-host system. Our specific configuration allows for a fast system that fails to the clear state. Furthermore, the degree of polarization dependence can be tailored for use in different applications. VALiD has been implemented on thin, flexible, flat plastic substrates. Recently, this has been extended to doubly curved polycarbonate substrates and a prototype has been fabricated. In this paper we present the characteristics of this technology.

This paper examines the light transmission, reflection, and scattering characteristics of military helmet visors used for see-through helmet-mounted displays (HMDs). HMDs used for the within-visual-range counter-air mission normally use the inner surface of the helmet visor to reflect the HMD image to the pilot's eye. This approach is popular because it minimizes any optical structures that interfere with the pilot's vision, while also maximizing see-through to the ambient scene. In most cases, a reflective coating, which increases the cost of the helmet visor significantly, must be applied in the inner surfaces in order to achieve enough contrast between the HMD image and the external light passing through the visor. Recently, with the development of high luminance miniature cathode-ray-tubes, it has been possible to eliminate the reflective coatings on neutral density helmet visors having a see-through range of 13 - 35%. This paper examines the light management properties of both types of visors. The paper stresses measurement techniques that produce repeatable results and what these results might imply about visual performance under operational lighting conditions.

Inertial trackers have been successfully applied to a wide range of HMD applications including virtual environment training, VR gaining and even fixed-base vehicle simulation, in which they have gained widespread acceptance due to their superior resolution and low latency. Until now, it has been impossible to use inertial trackers in applications which require tracking motion relative to a moving platform, such as motion-base simulators, virtual environment trainers deployed on board ships, and live vehicular applications including helmet-mounted cueing systems and enhanced vision or situational awareness displays. This paper describes a new technique which makes it possible to use inertial head- tracking systems on-board moving platforms by computing the motion of a `tracking' Inertial Measurement Unit (IMU) mounted on the HMD relative to a `reference' IMU rigidly attached to the moving platform. Detailed kinematic equations are derived, and simulation results are provided for the particular case of an inertial tracker with drift correction by means of ultrasonic ranging sensors, but the conclusions can be applied to hybrid inertial trackers involving optical, magnetic, or RF drift correction as well.

The Panoramic Night Vision Goggle (PNVG) has begun operational test and evaluation with its 100-degree horizontal by 40-degree vertical field of view (FOV) on different aircraft and at different locations. Two configurations of the PNVG are being evaluated. The first configuration design (PNVG I) is very low in profile and fits underneath a visor. PNVG I can be retained by the pilot during ejection. This configuration is interchangeable with a day helmet mounted tracker and display through a standard universal connector. The second configuration (PNVG II) resembles the currently fielded 40-degree circular FOV Aviator Night Vision Imaging Systems (ANVIS) and is designed for non-ejection seat aircraft and ground applications. Pilots completed subjective questionnaires after each flight to compare the capability of the 100-degree horizontal by 40-degree vertical PNVG to the 40-degree circular ANVIS across different operational tasks. This paper discusses current findings and pilot feedback from the flight trials objectives of the next phase of the PNVG program are also discussed.

FLILO is an Enhanced Vision System (EVS); which enhances Situational Awareness for safe low level/night time and moderate weather flight operations (including: take- off/landing, taxiing, approaches, drop zone identification, Short Austere Air Field operations, etc), by providing electronic/real time vision to the pilots. It consists of a series of imaging sensors, an Image Processor and a wide field-of-view (FOV) see-through Helmet Mounted Display (HMD) integrated with a Head Tracker. The current solution for safe night time/low level military flight operations is the use of the Turret-FLIR (Forward-Looking InfraRed). This system requires an additional operator/crew member (navigator) who controls the Turret's movement and relays the information to the pilots. The image is presented on a Head-Down-Display. FLILO presents the information directly to the pilots on an HMD, therefore each pilot has an independent view controlled by their heads position, while utilizing the same sensors that are static and fixed to the aircraft structure. Since there are no moving parts, the system provides high reliability, while remaining more affordable than the Turret-FLIR solution. FLILO does not require a ball-turret, therefore there is no extra drag or range impact on the aircraft's performance. Furthermore, with future use of real-time multi-band/multi-sensor image fusion, FLILO is the right step towards obtaining safe autonomous landing guidance/0-0 flight operations capability.

Recent advances in low-light-level imaging and packaging technology make it possible to integrate high definition, lightweight visible cameras into applications such as helmet imaging systems. Past drawbacks of intensified television including size, weight, limited dynamic range and intensifier halo saturation (blooming) have been overcome with the advent of enabling technologies. These technologies include methods to greatly reduce size and weight, improve the intra-scene dynamic range of the image, intelligently enhance the image through signal processing techniques, and reduce the point source halo in the intensifier itself. This paper provides an overview of the enabling technologies and the benefits to intensified imaging systems they provide. A short video demonstrating the various technologies will be presented. A prototype camera will also be available for viewing.

A Synthesized Night Vision Goggle that will be described int his paper is a new type of night vision goggle with multiple functions. It consists of three parts: main observing system, picture--superimposed system (or Cathode Ray Tube system) and Charge-Coupled Device system.

Application Specific Integrated Lenses (ASILs), based on a unique holographic polymer dispersed liquid crystal material system, which offer high efficiency, fast switching and low power are being developed for display and telecommunication applications. The basic properties and key benefits of ASILs in wearable displays are reviewed.

Liquid crystal display (LCD) display backlighting systems are commonly designed for portable devices and observation with the unaided eye. This paper addresses technical issues to providing a low profile, high brightness LCD backlight for a visual system such as a helmet mounted display. A parametric approach is developed and illustrated, but limits consideration to monochromatic light-emitting diode light sources. The analysis is based on first order optical considerations, and considers both spatial and angular uniformity of illumination. The conditions imposed by the application are also considered, that is, an LCD viewed under magnification by the human eye.

There exist many applications in military and commercial fields where rugged, lightweight microdisplays are required for helmet mounted and viewfinder display systems. Such applications typically involve the display of high resolution symbology but increasingly also include the display of full motion video. Examples of these kinds of image sources include thermal imaging and weapon sighting. Active matrix electroluminescent (AMEL) microdisplay technology developed at Planar has uniquely satisfied the demanding environmental and power requirements of military and commercial helmet mounted display and viewfinder systems. Recent advances have extended the use of AMEL microdisplays to applications requiring the display of high grayscale content, while significantly reducing the size, cost, and power of the system electronics required to drive the display. This capability has been enabled through the development of an analog addressing architecture. This paper provides a background of the analog architecture and the advantages gained by using this approach. Specifications and interface requirements are discussed for a monochrome 640 X 512 display developed using this architecture.

A miniature 1280 by 1024 transmissive active matrix liquid crystal display (AMLCD) was developed for the helmet-mounted display in the RAH-66 Comanche helicopter. To meet the stringent environmental and optical performance requirements, improvements were made in the AMLCD's operating temperature range, viewing angle, pixel size, and transmission. These features were combined with technology previously developed to provide uniform gray scale, rapid optical response times, and ultra high-brightness imagery for the combination of high-resolution FLIR imagery and flight symbology viewable in daytime environments.

A wireless handheld computer in a telephone handset form factor is being developed. The Communicator device contains a StrongArm SA-1110 microprocessor, and a high-resolution color microdisplay and a virtual image display system. The current optical system is based on a viewfinder style eyepiece. The system under development will have a flip out mirror, reducing the overall package size. The existing display is an analog 4-input 800 by 600 pixel device. The next generation display is an integrated digital display based on a sampled-ramp architecture. The processor interface uses a shadow frame buffer for efficient graphics memory access.

A combat vehicle visualization system is described that enhances the situation awareness of the vehicle commander. The system consists of a 360 degree(s) panoramic sensor, a gimbaled 8 - 12 micrometers infrared sensor, and a helmet-mounted display with head tracker. The helmet-mounted display can display the fused sensor data to aid the commander in vehicle maneuvering and threat acquisition while buttoned up. It can also display situation awareness information down-loaded from the tactical internet while standing in the hatch. Construction and operation features will be described.

BAE SYSTEMS are developing a high performance Helmet Mounted Display system for the Eurofighter/Typhoon combat aircraft. This paper presents an overview of the design solutions, as well as details of the development program status. Finally, it gives some indicators as to future growth applications.

Aviation simulators can be made low-cost, reconfigurable and transportable by using Head-Mounted Displays as the primary image source. With the growth of these applications, there has been a move towards smaller systems, with shorter and shorter distances between the trainee and the screen used for out-the-window visuals. As this distance gets shorter, the HMD depth of focus, the zone of single vision and the interpupillary distance settings begin to have an impact on the user's viewing comfort. This paper will address some of these issues and make recommendations for implementing HMDs in this new generation of simulators.

This paper presents the results to date of an aggressive program of concept and development to provide an effective and economical mode of training for Unmanned Aerial Vehicle remote pilots. The Virtual Reality Flight Trainer is a full- function simulator that exploits the versatility of the 3D Head-Mounted Display, in conjunction with the pilot's conventional, hand-held, flight control box to provide the essential hands-on experience necessary for the development of the pilot's expertise, previously only achieved at the risk of costly flight hardware.

Different aircraft in different services and countries have their own set of symbology they want displayed on their HMD. Even as flight symbolgy is standardized, there will still be some differences for types of aircraft, different weapons, different sensors, and different countries. As an HMD supplier, we want to provide a system that can be used across all these applications with no changes in the system, including no changes in the software. This HMD system must also provide the flexibility to accommodate new symbology as it is developed over the years, again, with no change in the HMD software. VSI has developed their HMD software to accommodate F-15, F- 16, F-18, and F-22 symbology sets for the Joint Helmet Mounted Cueing System. It also has the flexibility to accommodate the aircraft types and services of the Joint Strike Fighter: Conventional Takeoff and Landing variant for the USAF, Carrier-based Variant for the USN, and the Short Takeoff and Vertical Landing variant for the USMC and U.K. Royal Navy and Air Force. The key to this flexibility is the interface definition. The interface parameters are established at power-on with the download of an interface definition data set. This data set is used to interpret symbology commands from the aircraft OFP during operation and provide graphic commands to the HMD software. This presentation will define the graphics commands, provide an example of how the interface definition data set is defined, and then show how symbology commands produce a display.

This paper describes the design and evaluation of a new flight reference symbology intended for fixed-wing aircraft helmet-mounted display (HMD) use. The symbology is designed to provide continuous ownship status information (airspeed, altitude, heading, and attitude) regardless of pilot line of sight or head movements during tactical engagements. Most existing symbol sets distributed attitude, airspeed, altitude, and heading information across the HMD field of view (FOV). Some symbologies provide the information in close proximity to an attitude reference but the digital information is presented to the outside of the attitude reference. Distributing flight information across the display FOV poses potential usability disadvantages. First, clutter and occlusion problems are spread across the FOV. Second, information that is spread apart may require more scan area to be sampled in order for the observer to retrieve the desired information. Scanning more area may take more time. Third, information cannot be easily moved within the display FOV without creating consistency and interpretation problems. A new symbology was designed to address these problems: The Non Distributed Flight Reference (NDFR) includes a unique feature to allow directional awareness and spatial orientation to be maintained at extremely high angles of climb and dive. Also, because the symbology forms a composite `information stamp', it has potential application for head-up display and head-down display media. A `first look' evaluation of the NDFR concept is discussed.

A chroma-keying technique for the insertion of real objects into a synthetic environment is being evaluated for incorporation into various United States Marine Corps ground combat training and simulation applications. The technique enables the insertion of real objects within the visual frame of a Head-Mounted Display. It allows individuals and actual equipment, such as maps, weapons, and other items, to be effectively inserted into the visual display of a simulated environment.

This paper discusses theoretical issues that are relevant to Helmet-Mounted Display (HMD) attitude direction indicator (ADI) design. An ADI shows the relationship between the aircraft wings and the horizon and pilots use it to determine aircraft attitude (pitch and roll). The ADI is used for maintaining an aircraft attitude, capturing a precise attitude and recovering from an unusual attitude. An attitude indicator is an essential instrument because it provides pilots with orientation information that they do not normally have in instrument flight conditions. Recent work suggests that humans orient themselves within a fixed world-reference frame. We will discuss the relationship between the reference frames used by the human orientation system, the reference frames implemented in existing ADIs, and the reference frames available in a helmet-mounted display. A head tracked HMD system allows a system designer to implement symbology in many reference frames including the head, aircraft, and world reference frames. Traditional head down attitude symbology may not be appropriate for HMD use, and it may conflict with the reference frame used by human orientation systems. Based on the author's review of ADIs and frames of reference, research topics are discussed that examine the role of HMD ADI symbology.

The effect of night vision devices and degraded visual imagery on self-attitude perception is unknown. Thirteen Army aviators with normal vision flew five flights under various visual conditions in a modified AH-1 (Cobra) helicopter. Subjects estimated their altitude or flew to specified altitudes while flying a series of maneuvers. The results showed that subjects were better at detecting and controlling changes in altitude than they were at flying to or naming a specific altitude. In cruise flight and descent, the subjects tended to fly above the desired altitude, an error in the safe direction. While hovering, the direction of error was less predictable. In the low-level cruise flight scenario tested in this study, altitude perception was affected more by changes in image resolution than by changes in FOV or ocularity.

A helmet-mounted display (HMD) with a partial binocular overlap field-of-view (FOV) is slated for use with the Army's new RAH-66 Comanche helicopter in order to increase the available size of the FOV. The current investigation examined how FOV configurations affect visual performance in a target acquisition task under demanding viewing conditions. Performance was measured by response time and error rate in the full overlap FOV, the convergent partial overlap FOV, and the divergent partial overlap FOV. Fifteen aviators were required to visually scan for and identify the position of a visually degraded random target from a three by three array of similar distractors in a randomly cluttered FOV as quickly as possible while minimizing errors. The results found a tradeoff in enlarging the FOV by the partial overlap method. Performance was best in the full overlap FOV, where response times were fastest, and worst in the divergent partial overlap FOV, where response times were slowest. The performance decrements for partial overlap were confirmed by the accuracy data, where the partial overlap configurations with the slower response times also had a higher number of misses and a lower percentage of first scores (no-miss target acquisitions). These three performance decrements are most pronounced for lateral targets in the monocular regions of the partial overlap FOVs.

Night vision goggles (NVGs) allow pilots to see and navigate under minimal levels of illumination. While NVGs allow the user to see more than they typically could under these levels of illumination, the visual information provided by NVGs has a limited field-of-view. The size of the field-of- view can diminish the pilot's spatial orientation ability in the night flying environment. We examined pilot performance in low level helicopter flight while the pilots were using NVGs with 40 degree(s), and 52 degree(s) fields-of-view. The pilots flew a standardized ADS-33D hover maneuver in a Bell 206 helicopter equipped with an accurate position measurement system. The tests were conducted in simulated night conditions and both subjective and objective measures of task performance were obtained. Pilot Cooper-Harper ratings increased from Level 1 baseline ratings to Level 2 ratings when the NVGs were used, indicating worse performance when using the NVGs. Small rating differences were noticed between the 52 degree(s) and 40 degree(s) field-of-view conditions. Similar trends were noticed in the objective data of altitude, and lateral and longitudinal station keeping errors.

Eyetracking is typically not available in head-mounted displays, and eye motions are thus simply ignored when 2D virtual images are displayed, giving rise to rendered depth errors in generating stereoscopic image pairs in head- mounted displays. We present an investigation and quantification of rendered depth errors linked to natural eye movements in binocular head-mounted displays, or Albertian errors, for three possible eyepoint locations: the center of the entrance pupil, the nodal point, and the center of rotation. Theoretical computations based on the intersection of chief rays concluded that, while the center of rotation yields minimal depth errors if no eyetracking is used, rendered angular errors may in some cases be significant (i.e. up to six degrees). Based on the analysis presented in this paper, we suggest that the center of entrance pupil be chosen for far field applications. The center of rotation of the eye should be chosen for near field applications under the assumption that they emphasize position accuracy versus angular accuracy. Preventing or minimizing rendered depth errors may be required for some high accuracy tasks related, for example, to medical or military visualization.

In this paper a new data processing and calibration method for an eye-tracking device is described. The eye-tracking device is created both by the technology of head mounted display and remote type set-up. The computer analysis of various types; is suggested to obtain the characteristics of image type eye-tracking device. We use fuzzy analysis method to distinguish the position of the pupil and calculate the coordinates of them. With one video CCD camera and frame grabber analyzing a series of images of human pupil during gazing the screen, an auto-calibration algorithm is used to obtain the direction of eye gaze in real time. The computers will provide the functions according to the location where the eye gaze at exceeding 0.5 second. The availability of multipurpose measurement of this eye-tracking system with very simple equipment will be reconfirmed for the advanced research.