Holography

Abstract

Looking at holographic images is exciting! Some appear to float in space; some appear in full color; some change color as you move your head; some even show subjects that move.

Glossary of Terms

amplitude hologram

A hologram that modulates the reference beam through absorption.

bleaching

Dissolving silver particles to make the emulsion more transparent and the reconstructed image brighter. Bleaching changes an amplitude hologram into a phase hologram.

Bragg reflection

Strong reflection at certain angles by diffraction of light from planes of recorded fringes. Bragg’s law shows how the angle depends upon the spacing of the planes and the wavelength of the light.

coherent light

Light having a fixed relationship between the phase of light waves of a single wavelength.

Denisyuk hologram

A reflection hologram in which a single beam serves as both reference beam and object beam by passing through the emulsion twice.

hologram

A recording of interference fringes from which a three-dimensional image can be reconstructed.

holographic interferogram

A holographic recording using two or more images to show motion or some other time-dependent phenomenon.

Lippmann photography

A technique for making color photographs that makes use of Bragg reflection .

object beam

Portion of the laser beam that illuminates the object.

orthoscopic image

A holographic image that has normal front to back perspective.

phase hologram

A transparent hologram in which the fringes modulate the phase of the reference beam during image reconstruction.

pseudocolor hologram

A hologram in which the emulsion thickness is varied to produce colors different from the light used to record it.

pseudoscopic image

An image that is reversed front to back.

rainbow hologram

A hologram whose image changes color as the viewpoint is moved up and down.

real image

An image that can be projected on a screen.

real-time holographic interferometry

Creating an interference pattern between an object and its hologram in order to see how much the object has moved or changed.

reference beam

Portion of the laser beam that goes directly to the film or camera.

reflection hologram

A hologram that can be viewed from the front as if it were a painting.

time-average interferogram

Combining many holograms in the same image; in the case of a vibrating object, the nodes appear as bright lines and fringes of equal amplitude occur in the antinodal regions.

transfer hologram

Hologram that uses the real image from another hologram as its object.

transmission hologram

A hologram that is viewed by illuminating it from behind with monochromatic light.

TV hologram

A hologram that is created by electronically comparing the reference beam and the object beam .

virtual image

An image that cannot be projected on a screen.