IMAGE The optical reproduction of an object, produced by a lens or mirror.
A typical positive lens converges rays to form a "real" image which can be photographed.
A negative lens spreads rays to form a "virtual" image which can't be projected.
INCIDENT LIGHT A ray of light that falls on the surface of a lens or any other
object. The "angle of incidence" is the angle made by the ray with a perpendicular
to the surface.
INFRARED RADIATION (IR) Invisible Electromagnetic radiation with wavelengths
which lie within the range of 0.70 to 1000 m. These wavelengths are often broken
up into regions: IR-A (0.7-1.4 m), IR-B (1.4-3.0 m) and IR-C (3.0-1000 m).
INTEGRATED RADIANCE Product of the exposure duration times the radiance. Also
known as pulsed radiance.
INTENSITY The magnitude of radiant energy.
INTRABEAM VIEWING The viewing condition whereby the eye is exposed to all or
part of a direct laser beam or a specular reflection.
ION LASER A type of laser employing a very high discharge current, passing
down a small bore to ionize a noble gas such as argon or krypton.
IONIZING RADIATION Radiation commonly associated with X-Ray or other high energy
electro-magnetic radiation which will cause DNA damage with no direct, immediate
thermal effect. Contrasts with non-ionizing radiation of lasers.
IRRADIANCE (E) Radiant flux (radiant power) per unit area incident upon a given
surface. Units: Watts per square centimeter. (Sometimes referred to as power density,
although not exactly correct).
IRRADIATION Exposure to radiant energy, such as heat, X-rays, or light.