Improving Night Vision Goggle Performance with Human Systems Integration of material, perceptual,
cognitive and training factors
AsMA Annual Meeting, 16 May 2013
Colonel (ret) Steven C. Hadley, MDColonel (ret) Steven C. Hadley, MDUSA & USAF Pilot-Physician, CFS (ret)USA & USAF Pilot-Physician, CFS (ret)Aerospace Ophthalmologist ,USAFSAMAerospace Ophthalmologist ,USAFSAM
Associate Professor Uniformed Services University Med SchoolAssociate Professor Uniformed Services University Med School
Presentation Overview
I have no financial disclosures reference this lecture
I have no medication recommendations or off-label use of medications
All data from open public source: unclassified
Personally funded & Non-retribution:
My personal views and does not represent USAFSAM, 711 HPW, AFRL, USAF, USSOCOM or DoD official policy
Background
Terminology
Night Vision Devices (NVDs) Night Vision Goggles (NVGs)
Forward Looking Infrared (FLIR)
Low Light Television (LLTV)
Terminology
Night Vision Devices (NVDs) Night Vision Goggles (NVGs)
Forward Looking Infrared (FLIR)
Low Light Television (LLTV)
ANVIS-9 (AN/AVS-9) F4949
Image Intensifier I2
Image Intensification
NVGs & Radiation of the Night Sky
Gen II & Gen III NVGs
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175
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125
100
75
50
25
0300 350 400 450 500 550 600 650 700 750 800 850 900 950
GENERATION II GENERATION III (ground use)
PH
OT
OC
AT
HO
DE
RE
SP
ON
SE
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mA
/W)
WAVELENGTH (nm)
GENERATION III (aviation)
Current NVG Systems
PNVG
PVS 14
PVS 7 PVS 15
AN/AVS-9 (F4949)
LONGWAVE IR (FLIR) IMAGES
Transmittance of Electromagnetic Energy
FLIR Improves Visibility in Fog
Visible 768x494 FLIR 320x240
Photos courtesy of Goodrich
Human Systems Integration and Night Vision Goggles
“We must quit manning the equipment and start equipping the man.”**
**General Max Thurman, USA
Generation III+ NVG• increased spectral sensitivity of the device (relative
responsiveness to light levels)
• improved ability of the device to provide more details and contrasts from the environment in very low light levels ion barrier to protect the photocathode and an increased number of tubules in the microchannel plate
• contains gallium arsenide photocathodes and improved phosphors resulting in increased acuity and contrast sensitivity, especially in low illumination
• third generation provides a greater eye relief, the distance from the eye to the NVG eyepiece (Hatley 2001)
Helmet mount• Goal: Mounting NVGs on helmets in an efficient,
effective, secure, and comfortable manner• “Coupling” the NVGs with any head movement
keeps the image displayed constantly to the user’s eyes
• improves situation awareness (SA) and performance (Newman, 2002)
• a forward shift in the center of gravity of the head induce an additional physical force to support the weight of the NVGs
• increased helmet mass to 3.0-3.6 kg
Helmet mount• Risks with increased weight
• neck muscle strain • fatigue and• increased risk of severe neck injury as a result of
inertia moment in a crash. (U.S. Navy: Shender 2009; the Royal Australian Air Force: Oppermann, 2008; and the Canadian Armed Forces Adam, 2004)
Helmet mount• Frontal position as the cause of neck strain rather than
added weight (JHMCS) (Sovelius, 2008) (Lecompte, 2008)
• Corrected with counter weight (CW) decreased dorsal neck muscles strain (Thuresson et al., 2005); (McEntire, 2000); Zhao, 2009)
• Less metabolic and hemodynamic stress (Harrison et al. 2007)
• Ejection seats: battery pack/CW cannot be rear mount • Physical therapy and neck strengthening exercises
reduced neck stain complaints 70% (SOMA 2007)
Focus and fit of the NVGs-TRAINING
• NVGs requires two preparatory tasks:• NVG goggle alignment
• Vertical adjustment• Tilt alignment• Eye relief• Binocular interpupilary distance adjustment
• Focusing of both the objective and the eyepiece lenses. (Antonio, Joralmon, Fiedler, and Berkley 1994)
• Hoffman Focusing Box
OpticalOptical
AxisAxis
VisualVisual
AxisAxis
Fore and AftFore and Aft
Right IPDRight IPD
AdjustmentAdjustment
Tilt AdjustmentTilt Adjustment
Diopter Focus Diopter Focus
RingRing
Left IPDLeft IPD
AdjustmentAdjustment
ObjectiveObjective
Focus RingFocus Ring
Binocular Assembly
Night Vision GoggleAdjustment Training Effectiveness
Focus and fit of the NVGs-TRAINING
• NVGs training consistently indicated as a critical gap
• Many mishaps due to lack of adequate, frequent or recurrent NVG training (Biberman 1992; Manton 2000, Johnson 2004)
• Training is required for perceptual and cognitive skills • detecting and determining type of terrain, • different lighting; different albedos, • judging distance and closure rates, detecting and
estimating the distance to obstacles etc.
Focus and fit of the NVGs-TRAINING
• The results of numerous studies demonstrated that perceptual and cognitive skills can be enhanced through thorough initial, and frequent recurrent training, resulting in greater task performance and better spatial orientation (Ruffner 1998;2004 Reising 1995; Niall 1999)
• Use of a Virtual Terrain Board (USAF-VTB 3.1,
Night Readiness) has been proven to more efficiently train aircrew with greater task performance
Headaches and other risks• Headaches were frontal and between the temples after
NVG missions (Manton 2000)
• Headache was the most commonly reported symptom in a 10-year study of night vision devices (Rash 2009)
• Usually last less than 1 hr. • Often linked to the duration of using NVGs• Headaches were associated with reports of visual
difficulties• Usually reported by new or non current aircrew• Properly trained aircrew in adjustment of NVG
decreased headaches by 90% (Joralmon 2009)
Headaches and other risks
Long-term impacts of NVG use •14% of the high NVG hr users indicated concern about the long-term effects of NVG on eyesight (Manton 2000)
•In a 10-year occupational health study of NVG users • No evidence prolonged use of the helmet-mounted
night vision device produced any meaningful changes in visual performance between the two eyes.
• No indication that long term use resulted in negative physiological effects, especially related to vision devices (Rash 2004; 2009)
NVG mishaps
• Two thirds of the accidents were related to vision disruptions, distortions, and disorientations attributable to NVGs (Renshaw (2007)
• The most common reported incident NVGs low illumination conditions was midair near-collisions caused by perceptual errors of estimation (e.g., problems with estimating closure rates) and judging distances and clearances from other aircraft/obstacles (distances from NVG user, not linear distance)
• Earlier studies reported that pilots tended to overestimate or underestimated distances to objects viewed through NVGs (Brickner, 1987; DeLucia 1995; Hadani, 1991; Reising 1995)
• Specific training strategy in distance closure rates, judging distances and clearances decreased errors to zero (Niall 1999)
Stereopsis and depth perception
• NVG users focus the goggles to infinity• One does not have much stereopsis in such conditions
even in unaided daylight vision, especially with 40° FOV
• In contrast, studies showed that depth acuity was better when the targets were viewed binocularly than when viewed with monocular or binocular NVGs
• Across all conditions, participants performed much faster and performed fewer errors with binocular goggles
• Monovision (Dominant eye focused distance; non dominant
eye near) consistently performed worse (Merritt 2006)
Hyperstereopsis
• Occurs when the tubes are not positioned directly in front of eyes
• Increased interocular separation, objects appear closer than they actually are (Newman 2009)
• Adaptation to hyperstereopsis was found to be possible after 5 to 30 hours of training (Newman 2009; Priot 2006)
• Hyperstereopsis greatly increases stereopsis and depth perception abilities
• Consider one trained crew in formation or pilot in AC trained in hyperstereopsis for specific missions
• KC-46
Cognitive PerformanceSpatial orientation and disorientation.
• NVGs’ narrower-than-normal circular 40° FOV • Users constantly scan the peripheral scene to
build and maintain an accurate visual picture• Maintains SA but may also result in physical
and mental fatigue as well as spatial disorientation
• One third of helicopter accidents involving spatial disorientation were associated with the restricted NVG FOV (Alvarez 1997; Johnson, 2004; Negrette, 1998)
Cognitive PerformanceSpatial orientation and disorientation.
• Errors made by aircrew flying NVGs related them to cognitive aspects and loss of SA with restricted FOV• Loss of accurate perception
• lack of motion parallax cues • comprehension (e.g., incomplete mental model
attributable to spatial disorientation)• projection (e.g., misdiagnosis of impending spatial
disorientation)• Fixed-wing, helo pilots and ground forces using
PNVGs vs. NVGs had better performance in threat detection, sorting and targeting, offensive maneuvering and survivor ID (Geiselman 1999, SOMA 2007; 2009)
PANORAMIC NVG100 DEGREE FIELD OF VIEW
NVGs civilian applications
• Emergency medical service • Pipeline, power line, fence and walled surveillance
area • General civil aviation• News teams • Maritime search-and-rescue operations • Law enforcement (police, border control, SWAT
teams • Performance of medical operations in low-light
conditions • Enhanced mobility in the dark by people who suffer
from night blindness
NVG human performance based almost solely on military experience
• Military pilots are select group with known cognitive, mental, visual acuity (e.g., Salazar et al., 2003)
• Assumptions held for military aircrews may not be relevant to civilian users of NVGs
• Important to consider military aviation missions are totally different from civilian NVG applications (Hawley 1991)
• Training• Aircraft NVG compatibility• Flight environment NVG compatibility
• Consequently, caution must be exercised when considering the practical implications and their potential generalizability to nonmilitary domains and applications
NVDs: NVG vs. FLIRNVG - reflected light & near IR
Image reflective contrast Require some illumination Penetrate moisture effectively Attenuated by smoke, haze & dust
FLIR - emitted heat (mid & far IR) Images thermal contrast Totally independent of light Penetrates smoke and haze Attenuated by moisture (humidity)
NVGs & FLIR are complimentary sensors
Multispectral Night Vision Devices
NVG NVG + Thermal
Questions?
Solar / LunarSolar / Lunar
Forward Looking Infrared (FLIR)
• Thermal Imaging
• Technology based on fact that all objects warmer than absolute zero emit (radiate) heat
• Can discriminate between objects with a temperature difference of less than 1 degree
• Or objects of the same temperature - if they emit heat at different rates