(rad). A unit of angular measure equal to the
angle subtended at the center of a circle by an arc whose length is equal to
the radius of the circle.
one radian = 57.3 degrees
or 2π radians = 360 degrees
(L). Radiant power per unit area of a radiating
surface per unit solid angle of emission expressed as
W/(cm2.sr); radiometric equivalent of brightness.
Radiant energy (Q). Energy in the form of
electromagnetic waves usually expressed in units of joules. Commonly used to
describe the output of pulsed lasers.
3.1.44 Radiant exposure
(H). The radiant energy per unit area incident
upon a given surface. It is used to express exposure dose to pulsed laser
radiation and is commonly expressed in J/cm2
3.1.45 Radiant flux or
power (Φ). The
time rate of flow of radiant energy given in units of watts. Commonly used to
describe the output power of CW lasers or the average output power of
Radiant intensity (I). Radiant power in a given
direction - radiant flux emitted from the source per unit solid angle
(steradian), in the direction of propagation, usually expressed in
Reflectance or reflectivity (ρ). The ratio of
total reflected radiant flux to total incident radiant flux.
Repetitively pulsed laser. A pulsed laser with
a sequentially reoccurring pulsed output.
Service. The performance of those procedures or
adjustments described in the manufacturer's service instructions which may
affect any aspect of the product's performance for which this MIL-STD has
applicable requirements. It does not include maintenance or
operation as defined in this section. This definition is equivalent to DOD
concepts of maintenance above the organizational level .
3.1.50 Solid angle
(Ω). (The ratio of the area on the surface of a
sphere to the square of the radius of that sphere.
It is expressed in steradians (sr).