Helmet-Mounted Displays: - USAARL - The - U.S. Army

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John C. Mora and M elissa H. Ledford
Figure of Merit (FOM): A metric which quantifies some aspect of image
quality.
Flashblindness: A temporary loss of vision as a result of sudden high level
of luminance, e.g., nuclear explosion.
Forward looking infrared (FLIR): A thermal imaging sensor where
sensor output is based on infrared radiation (usually between 3-5 or 8-12
micron spectral range) generated by the external scene. FLIRs are used for
targeting acquisition and aircraft pilotage on both the AH-64 Apache and
the newly developed RAH-66 Comanche.
Frame rate: The frequency of frames produced per second (expressed in
Hertz (Hz)).
Frangibility: The ability of a subsystem or component to separate from the
major system. Some helmet and display system designs may employ
helmet mounted displays, eye protection devices, etc., which actively or
passively separate from the helmet under crash conditions.
Frankfurt plane: The eye-ear plane in which the human skull is placed in
a position so that the lower margins of the eye socket and the upper margins
of the auditory opening are on the same horizontal plane.
Ghost image: A spurious image produced as a result of an echo or
reflection in the transmission of a image or signal.
Halation: A halo or glow surrounding a bright spot on a fluorescent screen
or a photographic image.
Health hazard assessment (HHA): Assessment of risk to the health and
effectiveness of personnel who test, use, and maintain the system. Hazards
can arise from characteristics of the system itself or from the environment
in which it operates.
Helmet Integrated Display Sight System (HIDSS): A partiallyoverlapped
biocular helmet-mounted display system under development for
the RAH-66 Comanche helicopter consisting of two components: pilot
retained unit (PRU) and an aircraft retained unit (ARU). The PRU is the
basic helmet with visor assembly; the ARU is a front piece consisting of
two image sources and optical relays attached to a mounting bracket.
Human factors engineering assessment (HFEA): Analysis of acceptable
human engineering design criteria, principles and practices.
Hyperstereopsis: A condition of exaggerated depth perception which
occurs as a result of separation of the sensors greater than the eyes of the
user.
Illuminance: A measure of visible energy falling on a surface.