Holography Glossary

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This is a dictionary of Holographic terms. It has been compiled by the members of the Holography Forum for the last few years. Additions and suggestions are welcome.

Further reference can be found in the Books section.

Things to add...

Wiener prism


Sagittal Plane

Tangental Plane

Kerr Medium

KTP, etc




Flash Lamp



Cr:LiSAlF6 - CrLiSAF

AlGaInP diode

Uranium Nitrate - chemical used in toners and developers.



(plate) holder


settling time

splitter - see beam splitter



table - See optic bench

safe light

(development/chemical) tray




object (when used in terms like 'object beam')



play back


swell/swelling (of emulsion)


first surface mirror

HOE (holographic optical element)

immersion lens

Liquid lens

Nd:YAG laser

DPSS laser

Pulsed laser

Q-Switched laser

CW (continuous wave)

Diode Laser



Phase hologram

reversal bleach

rehaloginating bleach

physical development

Colloidal development


post developing

Blink reflex (also known as aversion response) is the closure of the eyelid or movement of the head to avoid an exposure to a noxious stimulant or bright light.

A carcinogen is an agent potentially capable of causing cancer.

A continuous wave (cw) is the output of a laser which is operated in a continuous rather than pulsed mode.

A controlled area is an area in which the occupancy and activity of those present is subject to control and supervision for the purpose of protection from radiation hazards.

The cornea is the transparent outer coat of the human eye, covering the iris and the crystalline lens. The cornea is the main refracting element of the eye.

Diffuse reflection is the change of the spatial distribution of a beam of radiation when the beam is reflected in many directions by a surface or by a medium.

An embedded laser is enclosed in a laser system and has an assigned class number higher than the inherent capability of the laser system. The laser system's lower classification is appropriate because of the engineering features that limit accessible emission.

An enclosed laser is contained in a protective housing. Opening or removing the protective housing provides additional access to laser radiation above the applicable MPE. (An embedded laser is a type of enclosed laser.)

Erythema is the medical term for redness of the skin due to congestion of the capillaries.

Frequency Doubling is a phase-sensitive process where an input (pump) wave (usually a laser beam) can generate a wave with twice the optical frequency in the medium with a similar direction. source

Hurter-Driffield curve is a graphical curve formed by plotting the film density (log of opacity) versus the log of exposure time. Sometimes goes by other names such as characteristic curves, D–logE curves, and D–logH curves.

Infrared radiation (IR) is electromagnetic radiation with wavelengths that lie within the range 0.7 mm to 1 mm.

Intrabeam viewing is the viewing condition in which the source subtends an angle at the eye which is equal to or less than amin, the limiting angular subtense. In simpler terms, the eye views or is exposed to a laser beam directly. This category includes most collimated beams and so-called point sources.

The iris is the circular pigmented membrane that lies behind the cornea of the human eye. The iris is perforated by the pupil.

A joule (J) is a unit of energy (1 joule = 1 watt per second).

A laser is a device that produces an intense, coherent, directional beam of light by stimulating electronic or molecular transitions to lower energy levels. Laser is an acronym for light amplification by stimulated emission of radiation.

A macula is the small, uniquely pigmented and specialized area of the retina.

Maximum permissible exposure (MPE) is the level of laser radiation to which a person may be exposed without hazardous effect on or adverse biological changes in the eye or skin.

The ocular fundus is the back of the eye. The ocular fundus may be seen through the pupil by use of an ophthalmoscope.

Optical density (Dl) is the logarithm to the base ten of the reciprocal of the transmittance: OD = log10(Ei/Et), where OD = optical density, Ei = incident beam irradiance (W/cm2) worst case exposure, and Et = transmitted beam irradiance (MPE limit in W/cm2).

Power is the rate at which energy is emitted, transferred, or received.

Protective housing is an enclosure that surrounds a laser or laser system, preventing access to laser radiation above the applicable MPE level.

Pulse duration is the duration of a laser pulse, usually measured as the time interval between the half-power points on the leading and trailing edges of the pulse.

A pulsed laser is a laser that delivers its energy in the form of a single pulse or train of pulses.

A Q-switch is a device that produces very short (~10–250 ns), intense laser pulses by enhancing the storage and dumping of electronic energy in and out of the lasing medium.

A Q-switched laser is a laser that emits short (~10–250 ns), high-power pulses by means of a Q-switch.

Radiance is radiant flux or power output per unit solid angle per unit area.

Reflection is the deviation of radiation following incidence on a surface.

The retina is the sensory membrane that receives the incident image formed by the cornea and lens of the human eye. The retina lines the inside of the eye.

Second-Harmonic Generation - See frequency doubling.

A spectator is an individual who wishes to observe or watch a laser or laser system in operation and who may lack the appropriate laser safety training.

Specular reflection is a mirrorlike reflection.

Ultraviolet radiation (UV) is electromagnetic radiation with wavelengths smaller than those of visible radiation.

A viewing portal is an opening in an experimental system, allowing the user to observe the experimental chamber. All viewing portals and display screens included as an integral part of a laser system must incorporate a suitable means to maintain the laser radiation at the viewing position at or below the applicable MPE (eye safe) for all conditions of operation and maintenance. It is essential that the material used for viewing portals and display screens not support combustion or release toxic vapors following exposure to laser radiation.

Visible radiation (light) is electromagnetic radiation that can be detected by the human eye. This term is commonly used to describe wavelengths which lie in the range 0.4 to 0.7 mm.

A watt (W) is the unit of power or radiant flux (1 watt = 1 joule per second).

A wavelength is the distance between two successive points on a periodic wave which have the same phase.