Reference beam
Encyclopedia
A reference beam is a laser
beam used to read and write holograms. It is one of two laser beams used to create a hologram. In order to read a hologram out, some aspects of the reference beam (namely its angle of incidence
, beam profile and wavelength
) must be reproduced exactly as when it was used to write the hologram. As a result, usually reference beams are Gaussian beam
s or spherical wave beams (beams that radiate
from a single point) which are fairly easy to reproduce.
The other beam used to write a hologram is the signal beam
or object beam.
Laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...
beam used to read and write holograms. It is one of two laser beams used to create a hologram. In order to read a hologram out, some aspects of the reference beam (namely its angle of incidence
Angle of incidence
Angle of incidence is a measure of deviation of something from "straight on", for example:* in the approach of a ray to a surface, or* the angle at which the wing or horizontal tail of an airplane is installed on the fuselage, measured relative to the axis of the fuselage.-Optics:In geometric...
, beam profile and wavelength
Wavelength
In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...
) must be reproduced exactly as when it was used to write the hologram. As a result, usually reference beams are Gaussian beam
Gaussian beam
In optics, a Gaussian beam is a beam of electromagnetic radiation whose transverse electric field and intensity distributions are well approximated by Gaussian functions. Many lasers emit beams that approximate a Gaussian profile, in which case the laser is said to be operating on the fundamental...
s or spherical wave beams (beams that radiate
Radiate
Radiate is a verb. See radiation.Radiate may also refer to an antic Roman bronze coin....
from a single point) which are fairly easy to reproduce.
The other beam used to write a hologram is the signal beam
Signal beam
A signal beam or object beam is one of at least two laser beams used to write holograms. The signal beam is the beam that carries the information to be stored in the hologram. In the case of a holographic picture, this beam is reflected off the object being recorded, into the media...
or object beam.