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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75

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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

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SE

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mA

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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