APPENDIX G. GLOSSARY-continued

TB 430133

Intrabeam

Viewing a laser source from within the beam. The beam may be direct or

specularly reflected.

Iris

A colored membrane separating the cornea and lens of the eye, responsible

for controlling the incoming light by contraction and dilation of the papillary

opening.

Irradiance

The power per unit area on a given surface, in units of

Wattspersquarecentimeter (W/cm2).

Isotropic

A spherically uniform distribution of electromagnetic energy in space. Also, a

uniform response pattern for a detection system, usually an array of three

orthogonal antennas.

Joule (J)

A unit of energy (1 Wattsecond).

Joule/cm2

A unit of radiant exposure used in measuring the amount of energy per unit

area of absorbing surface, or per unit area of a laser beam.

Laser

Acronym for "Light Amplification by the Stimulated Emission of Radiation." A

source of intense, coherent and directional optical radiation. It is composed

of an active lasing medium, an energy source, a resonant optical cavity, and

an output coupler.

Lens (of the eye)

Structure of the eye that serves to focus light on the retina.

Low frequency; the band of frequencies between approximately 30 and 300

kHz.

Micrometer (m)

A measure of length equal to 106 meter.

Microwave (uW)

Electromagnetic frequencies between 300 MHz and 300 GHz.

Monopole Antenna

A vertical linear antenna electrically fed at its base.

A measure of length equal to 109 meter.

Nanometer (nm)

Optical Density (OD)

A logarithmic expression for the attenuation provided by an optical

attenuating medium, such as an eye protection filter.

Overexposure

Exposure above the applicable exposure limit for a time period equal to or

exceeding the appropriate averaging time.

Partial Body (PB) Exposure

Refers to a nonuniform RF field exposure over the body. The limits for PB

exposure do not apply for direct exposure of the eyes or testes.

Permissible Exposure Limit

The safety standard for RF radiation. The PEL is dependent on the

(PEL)

frequency of operation and the exposure time.

Phased Array Antenna

An antenna composed of two or more active elements where the radiation

pattern of the beam is enhanced in one or more directions (see also Antenna

Array).

Power

The time rate at which energy is transmitted or used by a system; also, the

rate at which work is done. The unit is the Watt.

Power Density Level (PDL)

The intensity of radiofrequency radiation expressed in units of milliwatt per

square centimeter (mW/cm2) or power per unit area.

Pulse Duration

Duration of a pulse; the time interval between the halfpeakpower points on

the leading and trailing edges of the pulse.

Pulsed Laser

A laser that delivers its energy in short pulses, as distinct from a continuous

wave (CW) laser which is on continuously.

RADAR

Acronym for RAdio Detection And Ranging. A system that transmits a

pulsemodulated signal toward some target and evaluates the return

(reflected) signal to determine some characteristic of that target such as

speed and/or distance.

Radiant Energy

Energy in the form of electromagnetic waves usually expressed in units of

joules. Commonly used to describe the output of pulsed lasers.

G-2