Human Factors in the Design of Tactical Display Systems for the Individual Soldier (1995)

Head/Helmet-Mounted Display

• Always available

• Does not have to be held in the hand or manipulated

• Can easily be aligned on target or terrain feature

• Wide field of view

• Can be used to guide movement

• Added information improves situation awareness of medium to long-range environment

• Added weight on head

• Off center CG

• More complex and fragile than hand-held display

• Precision/alignment requirements more severe

• Wide field of view results in inadequate resolution

• Display information content may overload or distract user, reducing situation awareness

Monocular Helmet-Mounted Display

• Minimum weight

• Simplest HMD; less alignment required

• Eye with no display remains dark adapted

• Eye with no display continues to sample real world

• Severe visual rivalry problems, such as target suppression (involuntary) and “cognitive switching”

• CG is off sideways as well as forward

• Smallest FOV; least information capability; more and larger head movements required

• No depth information

• Difficulty to navigate on uneven terrain

Biocular Helmet-Mounted Display

• Wider FOV, more information, easier to navigate

• No interocular rivalry

• Less complex to adjust than binocular

• Heavier than monocular

• Poor resolution

• Incorrect depth information

• Isolates user from environment

Binocular Helmet-Mounted Display

• Can provide stereo viewing

• Better depth information for mobility

• Better target recognition

• Heaviest optics

• Alignment and adjustments more complex and critical

Helmet-Mounted Display with See–Through (Transparent Optics)

• Display content can be integrated with the real world scene

• Referenced navigational and targeting data can provide “where to look” guidance

• User retains visual contact with the real world

• Display collimation interferes with eye's accommodative response to the real world

• Display luminance interferes with eye's luminance adaptation to the real world

• Display content may obscure objects in the real world (clutter)

• Unstable registration of display image on the real world may induce disorientation

• Effects of weight and CG of a selected set of Helmet-Mounted Display optics configurations upon mobility, agility, fatigue

• Effects of improved helmet liners on display stability and comfort

• Tradeoff analysis of adjustable vs preset or automatic controls in electronics, optics

• Field–of–View, resolution, contrast requirements for object detection and recognition, mobility

• Effects of display information on local situation awareness

• Effects of binocular rivalry on object detection and recognition, mobility, fatigue, disorientation

• Optimum information content for a small display

• Effects of anomalous stereo, parallax information on object detection and recognition, motion judgment, mobility

• Effects of larger FOV on optimizing information context

• Effects of stereo vision on object detection and recognition, mobility

• Assessment of precision and registration requirements

• Determination of how display characteristics may interfere with perception of the real world (i.e., collimation, luminance, display content)

• Analysis of display context and positioning to enhance perception of the real world through the display

• Assess registration requirements

Helmet-Mounted Display without See–Through (World Occluded)

• Less complex (lighter) optics

• Minor misregistration with real world less noticeable

• User is isolated from real world

• Major misregistration with real world is less detectable and can result in serious positioning errors

• Significant re–adaptation time to real world when display is removed

Helmet-Mounted Display with Integrated Symbology and Sensor Image

• Much more information can be coded symbolically

• Critical features (eg. targets, navigation way points, supply drops) can be localized and enhanced

• Remote sensor and intelligence information can be integrated

• Users must be trained to use symbology

• Luminance, depth, and apparent size of symbology must be integrated with the sensor image and world

• A tendency to load the user with more information than needed avoided

• Unstable symbology can induce motion illusions, disorientation, loss of balance

Helmet-Mounted Display with Remote Sensor Image (e.g, Offset Sensor, Laser Sight on Weapon)

• Information not locally available may be integrated

• Weapons may be aimed without exposure

• Movement with sensors not collocated with the eye can induce motion and position illusions resulting in errors, disorientation, motion sickness

• Differences in scale, optical axis, resolution of multiple sources can induce error and confusion

Hand-Held Display (See Through as Telescope or Binoculars)

• No added weight on head

• Quick to align; user controls registration

• Can be stored when not needed

• Better mobility for running, taking cover

• Must be unstowed to use

• Fatiguing to use for sustained periods

• Cabling could become unwieldy

Hand-Held Display (no See Through)

• Light and simple

• Can allocate higher resolution for maps, schematics

• Very limited functionality

• Must be stowed, hooked into gear, computer

Displays with Nonvisual Wavelength Sensor Images

• Users can see at night and in poor visibility weather conditions

• Nonvisual image characteristics (e.g., thermal signature) can add information for object I.D.

• Sensors have resolution, contrast, color limitations whose effects on viewing must be trained

• Added weight, complexity

• User becomes dependent on systems that can fail

• Nonvisual characteristic (e.g., thermal signature) can be misleading, and interpretation must be trained.

• Effects of display on local situation awareness

• Effects of misregistration on mobility

• Adaptation effects

• Value added, optimum location, interference effect of each symbolically coded datum must be assessed in isolation, and in conjunction with other display content

• Effects of misadjusted symbology luminance, depth, location in perception of the real world

• Optimization of information content for specific tasks

• Training requirements

• Effects of unstable symbology on orientation, mobility

• Assess requirements for integrating scale, resolution, optical axis of multiple images

• Assess disorientation effects of remote sensor display

• Assess ergonomic requirements for storage, deployment, cabling

• Conduct performance tradeoff analysis versus same display content on an HMD

• Assess ergonomic requirements

• Evaluate functionality for maps, schematics, computer I/O

• Assess available resolution and contrast in relation to specific task requirements

• Evaluate enhanced information and mis–information potential of non–visual object recognition characteristics

• Assess training requirements

Displays with Synthetic (Computer-Generated) Images from Map or Intelligence Data

• Creative designers can provide the user with significantly improved information on own position, local environment (what is around the corner, where are the mines)

• Creative designers can bury the user in useless information

• Display resolution limits the amount of useful information that can be presented

• Computer processing limitations (power-heat, weight) limit the sophistication to reduce/integrate useful information

Auditory Displays

• Light weight

• Always available

• Does not interfere with vision or visual processing

• Can be very time efficient

• Does not hinder movement or manipulation of tools

• Can isolate the user from the local environment if head phones are used

• Added weight and complexity

• Less suitable for complex information

• Can interfere with processing of local auditory information and distract user

• Severely affected by high local noise levels (i.e. loss or misinterpretation of message)

Tone Displays

• Good for warning, cues

• Meaning of signals must be trained

• Limited set of tones can be recognized

• Low information content

Speech

• Complex information can be sent

• Meaning is intrinsic

• Message content is flexible

• Can be time intensive

• Vulnerable to masking, loss of data

• Can distract user from an ongoing task

Controls (Local Display and Computer Equipment)

• Allows user to select functions, modulate display, and system parameters

• Added weight

• Added complexity

• Added training

• Can distract user from correct task priority (e.g., attempts to communicate rather than fire)

Manual Controls (Buttons, Switches)

• Familiar to users

• Simple to operate

• Can be made very rugged (e.g., membrane, capacitance switches)

• Limited functionality can result in proliferation of controls to serve required needs (e.g., buttons on helicopter controls)

Conventional Computer Keyboard

• Very flexible

• Standardized I/O

• Very complex

• Fragile

• Redundant functionality

• Heavy and bulky

Programmable or Menu-Driven Control

• Flexible

• Compact

• Can be made rugged

• Can have high functionality with limited keyset

• Efficient design of functions and control structure is difficult

• Users must be well trained in operation

• Value added, optimum geometric design and location and interference effects of each information datum must be assessed in isolation and as integrated with other information on the display, in the context of specific task requirements

• Assess training requirements

• Assess effects on local situation awareness of headphones, bone conduction speakers

• Assess effect of environmental noise upon message reception

• Define optimum content and format of messages in the context of specific task requirements

• Assuming a limited set of tones may be used, define task specific uses of warnings and cues and assess performance

• Assess training requirements

• Evaluate effects of incoming messages as distractors

• Evaluate effect upon local situation awareness

• Assess tendency to “tune out” messages (dependent upon perceived appropriateness and usefulness of messages)

• Assess number of functions which require user control in the context of specific task requirements

• Define and test minimum control sets

• Assess need for full complexity

• Assess ergonomics requirement

• Define and test optimum control sets in the context of specific task requirements

• Assess training requirements

• Assess ergonomic considerations

• Determine feedback requirements

Speech Control

• Frees hands for other tasks

• Natural communication

• Suitable for discrete commands

• Poor for analog control

• Current technology is error prone

• Vulnerable to environmental noise

• May require user to speak at inappropriate times

• Define appropriate functions in terms of discrete versus analog control functions and test performance

• Assess effect of environmental noise