Civilian use of night vision goggles

Civil aviation operators have expressed an increased interest in conducting night operations with night vision imaging systems. The development of special operational concepts, hardware requirements, training requirements, and regulatory change and oversight is necessary to control for the known performance constraints associated with these devices. In 2001, the Aerospace Medical Association initiated an internal request to review the human factors issues concerning the use of night vision goggles (NVGs) in civilian flight operations. This paper provides some basic information on night vision imaging systems to highlight the Association's position for supporting the appropriate use of NVGs in civilian aviation while concurrently expressing the need for a judicious and studied approach to their deployment.     

Orotrachial intubation in darkness using night vision goggles.

OBJECTIVE: Securing the airway of a wounded soldier while operating in a light-restricted combat environment may be required of forward-deployed military medical personnel. The best method of obtaining such an airway has not been addressed. In this pilot study, the objective was to examine the use of endotracheal intubation using an infrared filtered laryngoscope and night vision goggles. METHODS: The investigators performed endotracheal intubation, using an infrared filter light source laryngoscope, on patients undergoing elective surgical procedures. All intubations took place in a completely darkened operating room. RESULTS: Twenty-one patients (91.3%) were intubated successfully as defined in the study. No adverse outcomes or complications occurred. CONCLUSIONS: This study demonstrates that endotracheal intubation can be performed using a laryngoscope with an infrared filter and night vision goggles with a high success rate in a select population in a darkened environment.     

Mild hypoxia and visual performance with night vision goggles

Military night vision goggles (NVGs) are image intensifiers normally used when the human operator's visual capabilities are unimpaired by oxygen deprivation. However, mountain search team members and aviators sometimes operate with NVG augmentation at altitudes where hypoxic visual decrement is documented. The objective of this research was to investigate the effects of mild hypoxia on monocular visual performance with NVGs. It was found that mild oxygen deprivation significantly affects unaided square-wave grating visual acuity but does not significantly affect NVG-augmented performance. Large differences between visual sensitivities at different spatial frequencies were not differentially affected by mild hypoxia. Supplemental oxygen did significantly improve naked-eye but not NVG-augmented night resolution acuity up to a simulated altitude of 13,000 ft (3,962 m) above sea level (ASL).     

Head and eye movements in visual search using night vision goggles

BACKGROUND: Night-vision goggles (NVGs) provide only a restricted field of view and have other characteristics that may affect the head and eye movements used in visual search. METHODS: We measured head scan patterns, the magnitude and duration of gaze saccades, and fixation duration as subjects searched computer generated imagery either with or without NVGs. Subjects searched for either a large (6 degrees) target on a low-detail background (high conspicuity condition) or a small (2 degrees) target on a high-detail background (low conspicuity condition). RESULTS: All subjects displayed head-scan patterns that were qualitatively similar to those reported in the literature. Although both head-scan speed and amplitude were higher for the NVG condition as compared with the no-NVG condition, the difference was not statistically significant. Head-scan speed did vary significantly with target conspicuity, however. Gaze saccade amplitude varied with target conspicuity but only when NVGs were used. Fixation duration did not vary with either NVG use or target conspicuity. A two-parameter (exponent and scaling parameter) power function was fitted to the amplitude-duration data. The power-function exponents varied from about 0.30 to 0.44, but there was a concommitant variation in the scaling parameter, and the result was no significant difference in the form of the power functions fitted to the data. CONCLUSIONS: NVG use did not significantly affect any of the individual head or eye movement variables involved in searching the computer-generated imagery studied here. However, the decrease in gaze-saccade amplitude with increased target conspicuity when NVGs were used is evidence of the sensitivity of the head and eye movement measurement techniques used here, and suggests that all available measures of response efficiency be considered when evaluating NVGs using complex stimuli.     

Computer modeling of airbag-induced ocular injury in pilots wearing night vision goggles

BACKGROUND: Airbags have saved lives in automobile crashes for many years and are now planned for use in helicopters. The purpose of this study was to investigate the potential for ocular injuries to helicopter pilots wearing night vision goggles when the airbag is deployed. METHODS: A nonlinear finite element model of the human eye was created. Ocular structures such as the fatty tissue, extraocular muscles, and bony orbit were included. The model was imported into Madymo (Mathematical Dynamical Models) and used to determine the worst-case position of a helicopter pilot wearing night vision goggles. This was evaluated as the greatest Von Mises stress in the eye when the airbag was deployed. RESULTS: The worst-case position was achieved by minimizing the distance between the eyes and goggles, having the occupant look directly into the airbag, and making initial contact with the airbag halfway through its full deployment. Simulations with the goggles both remaining fastened to and breaking away from the aviator helmet were performed. Finally, placing a protective lens in front of the eyes was found to reduce the stress to the eye but increase the force experienced by the surrounding orbital bones. CONCLUSION: The finite element model of the eye proved effective for evaluating the experimental parameters.     

Helicopter cockpit seat side and trapezius muscle metabolism with night vision goggles

INTRODUCTION: Documented neck strain among military helicopter aircrew is becoming more frequent and many militaries use helicopters that provide pilots with the option of sitting in the left or right cockpit seat during missions. PURPOSE: The purpose of this study was to use near infrared spectroscopy (NIRS) to investigate the physiological changes in trapezius muscle oxygenation and blood volume during night vision goggle (NVG) flights as a function of left and right cockpit seating. METHODS: There were 25 pilots who were monitored during NVG flight simulator missions (97.7 +/- 16.1 min). Bilateral NIRS probes attached to the trapezius muscles at C7 level recorded total oxygenation index (TOI, %), total hemoglobin (tHb), oxyhemoglobin (Hbo2), and deoxyhemo-globin (HHb). RESULTS: No significant differences existed between variables for pilots seated in the right cockpit seat as compared with the pilots seated in the left cockpit seat in either trapezius muscle (pTOI = 0.72; ptHb = 0.72; pHbo2 = 0.57; pHHb = 0.21). CONCLUSION: Alternating cockpit seats on successive missions is not a means to decrease metabolic stress for helicopter pilots using NVG. This suggests that cockpit layout and location of essential instruments with respect to the horizontal and the increased head supported mass of the NVG may be important factors influencing metabolic stress of the trapezius muscle.     

航空夜视镜人机工效学问题研究进展

目的 概述航空夜视镜的工效学问题及国内外所采取的技术策略,为国内航空夜视镜的研制提供工效学设计的理论参考.资料来源与选择 国内外相关的研究论文和研究报告、学术专著和因特网资料.资料引用 国内外发表的研究论文和研究报告16篇,论著1部,因特网资料2篇.资料综合 概述驾驶舱照明与夜视镜兼容、夜视镜再调焦与内外舱交替观察、图像亮度增益、夜视场和使用夜视镜飞行员的生命保障问题及其相关的技术策略.结论 有必要进一步进行工效学研究,解决好国产航空夜视镜使用中可能产生的工效学问题和生命保障问题.     

Effect of night vision goggles on performance of advanced life support skills by emergency personnel

Night vision goggles (NVGs) are used by military personnel operating in low-light environments. It is not known whether NVGs can be used by medical personnel to provide emergency care under such conditions. This was a randomized controlled study to determine the effect of NVGs on the performance of intravenous line insertion (IVI) and endotracheal intubation (El) on training manikins. Emergency physicians and paramedics were randomized to perform EI and IVI in ambient light or in total darkness using NVGs. Each skill was repeated three times, and averages were determined. The average times for EI in ambient light and with NVGs were 48.4 and 188.2 seconds, respectively (SE of 13.4 seconds for both; p < 0.0001). The average times for IVI in ambient light and with NVGs were 34.7 and 73.7 seconds, respectively (SE of 4.1 seconds for both; p < 0.0001). Emergency personnel were able to successfully perform these skills using NVGs, but their times were significantly longer than in ambient light.     

Use of night vision goggles and low-level light source in obtaining intravenous access in tactical conditions of darkness.

OBJECTIVE: The tactical environment of the nighttime battlefield precludes the use of white light to perform medical procedures. This study sought differences between two alternatives to white light used to facilitate intravenous access. A comparison was made between night vision goggles (NVG) and a low level light source (Fingerlite). METHODS: Fifty-eight volunteers were paired. Each member of the pair attempted intravenous access on his or her partner in darkness using both techniques. One attempt per method was allowed. Success was confirmed by the free flow of blood from the catheter. RESULTS: Of the 58 attempts using NVG, 32 were successful and 26 failed. In the Fingerlite group, there were 46 successful attempts and 12 failures. These differences reached statistical significance (p < 0.02). CONCLUSION: This study suggests that in conditions requiring darkness, a Fingerlite offers a clinical advantage over NVG in obtaining intravenous access.     

Night vision goggles, human factors aspects--a questionnaire survey of helicopter aircrew

Night vision goggles have become an essential component of military aviation. They provide superior visual capability over unaided night vision, but there are several inherent limitations associated with human factors and systems limitations. This study used a questionnaire survey of Army helicopter aircrew to investigate the incidence of human factors problems which continued after NVG use, with particular reference to visual problems and neck discomfort. It also looked at hardware interaction problems, such as cockpit lighting, and other aspects of NVG use, such as training and aircrew concerns. The issues are described and analysed, and areas of concern, which may have bearings on operational effectiveness and/or safety, have been highlighted.     

Effects of extended hypoxia on night vision

The effects of 16 d of sustained hypoxia (4300-m equivalent) on the dark adaptation threshold function were studied in 12 male subjects measured periodically (days 2,4,6,9,11,13,16 of exposure) over a 20-min test period for both red and green stimuli using a new computerized dark adaptometer. Comparison with sea level performance showed negligible elevations of thresholds for red response, but highly significant impairment of green response (p less than 0.00001) over almost the entire dark adaptation function. These losses peaked between the sixth and ninth day followed by little recovery, except at the eleventh day when the subjects descended briefly to 3200 m elevation. Impairments developed rapidly again upon return to the original higher altitude. The results differ from previous findings after shorter exposure periods, which showed only slight impairments of the early segment of dark adaptation. Implications of the results are discussed.     

一种微光夜视成像系统设计

目的 设计一种微光夜视成像系统,用于飞行人员夜间视觉体验训练.方法 采用LED光源调光技术、视频信号处理技术、DLP投影显示技术及光学系统设计技术,设计了一种由7个子系统组成的微光夜视成像系统,采用ZEMAX光学设计软件对成像质量进行了仿真分析.结果 DMD处光源辐射照明的均匀性为86.6％,投射主镜光学系统场曲<0....     

An automated portable night vision testing system

This report describes a new testing system designed to assess night vision parameters of the military population in the field, and to quantify the effects of various environmental stress factors, such as extended exposure to high altitude, on the dark adaptation process. The instrument is based on an established procedure for dark adaptation measurement in which the subject continuously adjusts the threshold luminance of a recurrently flashing stimulus. The device described here represents a modernized version of the original technique, which features an automated testing procedure and provides for computerized data translation of the dark adaptation function. It also offers the advantages of rugged construction and field portability not available in clinical style instruments.     

The effects of acceleration forces on night vision

The effects of Gy and Gz acceleration forces on cone-type mesopic vision threshold values are examined. An experiment has been conducted on the Dynamic Environment Simulator, a three-axis human centrifuge, to reproduce an acceleration environment in a simulated night-flight combat situation. Acceleration environments studied were levels of +1 Gz, + 1Gy, +1.4 Gz, +2 Gz, +3 Gz, and +2 Gy in combination with +1 Gz. A visual task was performed which determined 20/50 visual acuity illumination threshold values. Physiological parameters recorded were arterial oxygen saturation (SaO2) by ear oximetry, heart rate, and visual acuity threshold values. There were 10 male subjects, all members of the United States Air Force. Their ages ranged from 25-39 years (mean +/- S.D., 29.1 +/- 4.3). Results were zero means obtained by self-pairing with +1 Gz controls. Analysis was done by self-pairing, two-tailed t test. Results showed no significant shift in luminance threshold values at +1 Gy or +1.4 Gz, and significant increases in luminance thresholds at the 0.01 level for +2 Gz, +3 Gz, and +2 Gy in combination with +1 Gz.     

Visual efficiency of pilot using of the night vision glasses

Questionnaires filled out by 24 helicopter pilots using the night vision glasses (NVG) showed that minimization of the risk of visual discomfort was, first of all achieved through proper adjustment of image brightness and setting NVG time limits. The experiments enabled determination of the most favorable range of brightness (0.67-1.79 cd/m2) and rationalization of the necessity of individual adjustment depending on the light conditions and flight objectives, and NVG usage regulations to preclude visual fatigue.