Liquid crystal modulated optical amplifier for night vision imaging

People with degenerative retinal diseases such as retinitis pigmentosa, may have adequate day vision but suffer from poor night vision. We have tested newly developed night vision goggles (NVG) to help these patients overcome their night blindness, thereby promoting more opportunities for normal activities at night or in the dark. A total of 42 subjects with night blindness due to retinitis pigmentosa, choroideremia, cone rod dystrophy, or Bardet Biedl syndrome were recruited and clinically examined (visual acuity, visual field, and contrast sensitivity). Using an experienced mobility trainer, we tested binocular NVG on the subjects in two locations: a dark room and a 1 to 2 h outside course at night that provided different levels of difficulties (i.e., obstacles, brightness, and contrast). The assessment of which patients benefited from the NVG was predominantly based on the subjective evaluation of the mobility trainer, followed by their graded responses on two questionnaires. Based on the evaluation of the mobility trainer, 23 (61%) of the 42 subjects experienced improved mobility and orientation with the NVG outdoors, and 19 (39%) subjects did not. The ophthalmic data demonstrated that a visual acuity better than 20/100 and a visual field > 5 degrees (Goldmann perimetry III4) is necessary to benefit from NVG usage. In addition, subjective responses on increased mobility and independence were positively correlated with successful NVG testing. Night vision goggles have the ability to improve poor night vision in subjects with visual acuity > 20/100 and a visual field > or = 5 degrees (Goldmann: III4). In so doing, NVG can help overcome the obstacles experienced by many people suffering from night blindness. NVG, therefore, have the potential to greatly improve quality of life.

Objectives: The night vision goggles (NVGs) used for aviation can overcome the limitations of the human eye to see in the dark and augment the night vision well enough to enable safe flying and mission accomplishment. The technology, however, has some limitations that need to be defined so that safe flying envelopes can clearly be understood and operational possibilities can be optimally explored within that envelope. Further, the luminance level of NVG displays which operates in twilight to low photopic range affects dark adaptation of the eye post-de-goggling of NVG. Hence, the assessment of visual adaptation time through Gen-2++ NVG under different illumination conditions using contrast sensitivity (CS) and visual acuity (VA) as parameters was the desired objective of the study. Material and Methods: In a prospective repetitive measure design, a total of 64 volunteered participants were examined for their visual adaptation time through Gen 2++ NVG post-de-goggling using Pelli-Robson CS chart and United States Air Force (USAF) 1951 tribar chart in the NVG Lab at two different locations. The visual adaptation time was measured under three different illuminations: Full moon (FM), half moon (HF), and quarter moon (QM). Furthermore, log CS values and VA of participants were measured under three ambient moonlight conditions with unaided eyes and using NVG. Results: The average recovery time post-de-goggling of NVG for CS (i.e., CS value before wearing NVG) was 1 min 34 s for FM, 2 min 50 s for HF, and 4 min 01 s for QM conditions. The average recovery time for VA (i.e., VA value before wearing NVG) was 1 min 29 s for FM, 3 min 01 s for HF, and 5 min 32 s for QM conditions. The results of this study brought out that visual adaptation time post-de-goggling of Gen 2++ NVG increased significantly for both CS and VA with decreasing ambient moonlight illumination ( P < 0.001). This study also brought out that the logarithm of the minimum angle of resolution value of CS and VA under three ambient light illuminations decreased significantly with a decrease in illumination both during unaided eye and NVG usage. Post hoc analysis revealed that there was a significant difference in visual adaptation time in both CS and VA between all three ambient light conditions ( P < 0.001). Conclusion: This study has estimated the time for dark adaptation required after de-goggling NVG use in different ambient moonlight levels for Gen 2++ NVG using CS and VA charts. The values based on CS can be considered in terms of time required for the detection of objects while that of VA can be attributed to the time for recognition of the object. The visual adaptation time post-de-goggling of NVG is very crucial and critical during approach, landing, and taxiing on the runway under dim light conditions for the accomplishment of mission safety. However, keeping in view the dynamic changes in night sky illuminations during flying operations, the findings of the study need to be validated in operational conditions.

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 describes the research and experimental flight testactivities conducted by the Italian Air Force Official Test Centre (RSV) in collaboration with Alenia S.p.A. and Cranfiled University, in order to confer the Night Vision Imaging Systems (NVIS) capability to the Italian TORNADO IDS (Interdiction and Strike) and ECR (Electronic Combat and Reconnaissance) aircraft. The activities included various Design, Development, Test and Evaluation (DDT&E) activities, including Night Vision Goggles (NVG) integration, cockpit instruments and external lighting modifications, as well as various ground test sessions and a total of eighteen flight test sorties. RSV and Litton Precision Products were responsible of coordinating and conducting the installation activities of the internal and external lights. Particularly, an iterative process was established, allowing an in-site rapid correction of the major deficiencies encountered during the ground and flight test sessions. Both single-ship (day/night) and formation (night) flights were performed, shared between the Test Crews involved in the activities, allowing for a redundant examination of the various test items by all participants. An innovative test matrix was developed and implemented by RSV for assessing the operational suitability and effectiveness of the various modifications implemented. Also important was definition of test criteria for Pilot and Weapon Systems Officer (WSO) workload assessment during the accomplishment of various operational tasks during NVG missions. Furthermore, the specific technical and operational elements required for evaluating the modified helmets were identified, allowing an exhaustive comparative evaluation of the two proposed solutions (i.e., HGU-55P and HGU-55G modified helmets). The results of the activities were very satisfactory. The initial compatibility problems encountered were progressively mitigated by incorporating modifications both in the front and rear cockpits at the various stages of the test campaign. This process allowed a considerable enhancement of the TORNADO NVIS configuration, giving a good medium-high level NVG operational capability to the aircraft. Further developments also include the internal/external lighting for the Italian TORNADO “Mid Life Update” (MLU) and other programs, such as the AM-X aircraft internal/external lights modification/testing and the activities addressing low-altitude NVG operations with fast jets (e.g., TORNADO, AMX, MB-339CD), a major issue being the safe ejection of aircrew with NVG and NVG modified helmets. Two options have been identified for solving this problem: namely the modification of the current Gentex HGU-55 helmets and the design of a new helmet incorporating a reliable NVG connection/disconnection device (i.e., a mechanical system fully integrated in the helmet frame), with embedded automatic disconnection capability in case of ejection. Other relevant issues to be accounted for in these new developments are the helmet dimensions and weight, the NVG usable FOV as a function of eye-relief distance, and helmet centre of gravity (moment arms) with and without NVG (impact on aircrew fatigue during training and real operational missions).

This paper describes the research and experimental flight test activities conducted by the Italian Air Force Official Test Centre (RSV), in collaboration with Alenia Aermacchi and Cranfield University, in order to confer night vision imaging systems (NVIS) capability to the Italian TORNADO Interdiction and Strike and Electronic Combat and Reconnaissance aircraft. The activities included design, development, test, and evaluation activities, including night vision goggle (NVG) integration, cockpit instruments, and external lighting modifications, as well as various ground test sessions and a total of 18 flight test sorties. RSV and Litton Precision Products were responsible for coordinating and conducting the installation of the internal and external lights. Particularly, an iterative process was established allowing in-site rapid correction of the major deficiencies encountered during the ground and flight test sessions. Both single-ship (day/night) and formation (night) flights were performed, with testing activities shared among the test crews involved, allowing for a redundant examination of the various test items by all participants. An innovative test matrix was developed and implemented by RSV for assessing the operational suitability and effectiveness of the various modifications implemented. Also important was the definition of test criteria for Pilot and Weapon Systems Officer workload assessment during the accomplishment of various operational tasks during NVG missions. Furthermore, the specific technical and operational elements required for evaluating the modified helmets were identified, allowing an exhaustive comparative evaluation of the two proposed solutions (i.e., HGU-55P and HGU-55G modified helmets). The initial compatibility problems encountered were progressively mitigated by incorporating modifications in both front and rear cockpits at various stages of the test campaign. This process allowed considerable enhancement of the TORNADO NVIS configuration, giving good medium- to high-level NVG operational capability to the aircraft. Further developments also include the internal/external lighting for the Italian TORNADO “Mid-Life Update” and other programs such as AMX aircraft internal/external light modification/testing and the activities addressing low-altitude NVG operations with fast jets (e.g., TORNADO, AMX, MB-339CD), with a major issue being the safe ejection of aircrew with NVG and NVG modified helmets. Two options have been identified for solving this problem, namely, the modification of the current Gentex HGU-55 helmets and the design of a new helmet incorporating a reliable NVG connection/disconnection device (i.e., a mechanical system fully integrated in the helmet frame) with embedded automatic disconnection capability in case of ejection. Other relevant issues to be accounted for in these new developments are the helmet dimensions and weight, the NVG usable field of view as a function of eye-relief distance, and the helmet's center of gravity (moment arms) with and without NVG (effect on aircrew fatigue during training and real operational missions).

With the introduction of the night-vision goggle (NVG) into vehicle cockpits, the transfer of visual information to the observer became more complex. The problem emanated from the image intensifier tube photocathode spectral response. NVGs were capable of sensing and amplifying visible cockpit light, making observation of the scene outside of the cockpit, the primary use for NVGs, difficult. Over the years, several documents were published outlining night vision imaging system (NVIS) compatible lighting performance. These documents limited the permissible amount of light visible to image intensifier tubes that cockpit displays could emit, enhancing pilot visual performance. Recent advances in short wave infrared (SWIR) sensor technology make it a possible alternative to image intensifiers for night imaging application. However, while popular SWIR cameras are not particularly sensitive to visible light, they may be sensitive to other display emissions not attenuated by state-of-the-art NVIS filters. This paper examines the possibility of expanding the traditional treatment of vehicle cockpit compatibility to include new, novel vision enhancement devices yet to be designed and vehicle cockpit geometry.

General liquid crystal (LC) materials have considerably large birefringence in wide frequency regions in the electromagnetic wave spectra, extending to the THz, millimeter wave (MMW), and microwave. LC materials can potentially be applied to some excellent control devices in novel frequency regions as display devices in optics regions. However, the birefringence of LC materials synthesized for display applications generally decreases by approximately half in the MMW region. Furthermore, the small remaining absorption loss in the MMW region must lead to a fatal device loss, as the LC layer becomes extremely large in the application field. New LC materials beyond the display application have been desired in novel LC application fields. In this work, a new class of LC materials consisting of hydrogen bonding is evaluated in the MMW region for the first time. Some optical properties different from those of conventional LC materials are discovered. The most distinct property is that the birefringence of the hydrogen-bonded LC materials in the MMW region becomes considerably larger than that in visible rays, which is totally inversion in relation with conventional LC materials. The absorption coefficients are as small as those of the best LC materials developed for microwave applications. Although some disadvantages are associated with the application of actual devices in this stage, the distinct dispersion properties make a breakthrough imminent in this application fields.

Rotary wing aircraft are being tactically flown closer and closer to the ground in an effort to take maximum advantage of concealment and protection afforded by trees, man-made structures and terrain features. In recent years, night vision goggles have been used to aid the pilot in his/her flight duties. It has been noted, however, that visual transition from the outside environment into the cockpit (and vice versa) requires manual refocusing of the goggles. This requires the pilot to remove his hand from one or the other of the controls, thus compromising safe flight. In this study, eight U.S. Army aviators hovered an instrumented Army JUH-1H helicopter ten feet above the ground at night under four visual conditions using the unaided eye (normal night vision) and three configurations of the AN/PVS-5 night vision goggles (NVG). The NVG configurations included: (1) 40° field-of-view piano tubes focused at infinity; (2) a bifocal arrangement in which the bottom 14% of the field was focused at approximately 22 inches; and (3) a bifocal arrangement with the bottom 24% focused at 22 inches. Aircraft status and control position monitors were scanned at a rate of 20 times per second and recorded on a seven-track magnetic tape via the helicopter in-flight monitoring system (HIMS). Subsequent review and analysis of these data indicate no significant difference between configurations in terms of control movements. In terms of aircraft status variables, radio measured altitude indicated a large variability under the 40° piano NVG. However, hover behavior stabilized significantly in the bifocal condition. Subjective pilot responses supported these observations.

Night vision goggles (NVGs) are becoming an increasingly important tool in military aviation. They provide superior visual capability over unaided night vision, but any reduction in goggle performance can have a serious effect on flight safety and operational effectiveness. This study shows that the use of the ANV 20/20 focusing aid provides an effective method for aircrew to obtain a better visual capability than is currently obtained by focusing on distant features of the landscape or distant lights. Visual acuities using the current and proposed focusing methods were compared in 50 aircrew. The visual acuity showed an average improvement of 18% with the proposed method compared with the current method. This was found to be statistically significant (p < 0.01). Using the current method of focusing there was a significant (p < 0.01) difference in the visual acuity achieved between the right and left tubes/eyes. Using the ANV 20/20 there was no difference between tubes/eyes. ANV 20/20 was found to improve visual acuity when using NVG as well as enabling the user to achieve equal visual acuities with both eyes.

Digital Night Vision sensor technology has the potential to provide significant new night vision capabilities for military aviators. Before new capabilities can fielded, however, the combined sensor-processor-display chain must achieve a level of night vision performance on-par with current-generation photo-multiplier tube (PMT) - based night vision goggles across the entire range of lighting conditions. This paper provides an overview of Rockwell Collins’s design of an ISIE-11 based Digital Night Vision Goggle (DNVG) intended to eventually replace traditional PMT goggles in a variety of military aviation and infantry applications. It also reports on an initial series of evaluations performed by Boeing aircrew in laboratory and flight environments. Laboratory lighting levels ranged from "overcast starlight" to "full moon", and airborne evaluations in a light aircraft were conducted under "starlight" and "half-moon" conditions at a realistic tactical altitude. Each evaluation provided a direct comparison between a modern PMT NVG and the DNVG prototype. Inputs from the flight evaluation were subsequently implemented in DNVG image processing software.

IntroductionThe use of night vision goggles (NVGs) by medical staff operating in active combat areas may present a tactical advantage in maintaining unit concealment. This study seeks to assess the...

Night vision goggles are becoming an increasingly important tool in military aviation. They provide superior visual capability over unaided night vision, but any reduction in goggle performance can have a serious effect on flight safety and operational effectiveness. This study shows that the use of a standard adjustment procedure in a night vision goggle (NVG) test lane, with a resolution chart, provides an effective method for aircrew to obtain better visual capability than is currently obtained by focusing on distant features of the landscape. Visual acuity (VA) was measured for 20 aircrew representing all crew positions, after using both the current adjustment method and the proposed method for adjusting ANVIS NVGs. The average visual acuity showed an improvement from 6/19 (s.d. = 3.9) with the current method to 6/13 (s.d. = 2.8) with the proposed method. However, NVG test lanes cannot be used with goggles which have fixed infinity objective lenses eg Nite.

: The requirements to assess the compatibility of aircraft cockpit lighting with night vision goggles (NVGs) are defined in MIL-L-85762A, Lighting, Aircraft, Interior, Night Vision Imaging System (NVIS) Compatible. However, the procedures specified to evaluate cockpit lighting are primarily specific to the laboratory environment, with only a few assessments specific to the field environment. This report describes the procedures used by Armstrong Laboratory's Aircrew Training Research Division (AL/HRA) to conduct a field evaluation of aircraft cockpit lighting. The evaluation procedures are divided into Planning, Evaluation Preparation, Assessment Procedures, and Results. This report can also be used as a guideline for other organizations that need to conduct NVG-compatible cockpit lighting evaluations.

: The characterization of the lighting conditions during field testing on night vision intensifier systems requires more information than can be obtained by a photometer. The Follow-on-Evaluation (FOE) testing of AN/PVS-7 Night Vision Goggles at Fort Benning, GA (Oct 86-Dec 86) required a radiometric characterization of the nighttime spectral content in the region encompassing that of the generation two and generation three image intensifier photocathodes (400 to 920nm) used in the goggles. A night sky radiometer (NSR) measuring system was designed and fabricated by the Center for Night Vision and Electro- Optics for the purpose of characterizing the night sky spectral content during the FOE test. This report discusses the design features of the NSR, its measuring techniques, and the results of the night sky conditions during the FOE test at Fort Benning.

Night vision goggles (NVG's) are being used increasingly in military and civilian environments. Despite the use of these devices, relatively few tests exist to assess visual performance through NVG's. Hyperacuity tasks may provide a sensitive index of performance through night vision devices. In this study, grating vernier acuity was measured through NVG's. As reported previously, a power law relation was observed between vernier acuity and stimulus contrast. Comparison of vernier acuity with and without NVG's indicated that performance is limited by the contrast transfer of the device. Vernier acuity measurements can be used to assess the quality of vision and quantity of contrast transferred through night vision devices.