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.


Abbreviated IR.  The region of the electromagnetic spectrum between the long-wavelength extreme of the visible spectrum (~700nm) and the shortest microwaves (~1mm).

[box]Note: the International Commission on Illumination (CIE) recommended the following division:
IR-A: 700nm – 1400nm
IR-B: 1400nm – 3000nm
IR-C: 3000nm – 1mm[/box]

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. The ionization process creates a population inversion for lasing to occur. A research laser useful for some industrial applications.