Holography

Holography records light’s amplitude and phase as an interference pattern, then reconstructs the wavefront by diffraction. The resulting image can show depth and change with viewing angle.

Interference: The superposition of waves that produces reinforcement or cancellation according to their relative phase. A reference wave and reflected light form the fringes that encode a hologram.
Electromagnetic wave: A coupled oscillation of electric and magnetic fields that propagates through space and carries energy. Visible light is the wave whose amplitude and phase holography records.
Dennis Gabor: A Hungarian-British physicist who developed holography and received the 1971 Nobel Prize in Physics. Gabor proposed and demonstrated the original wavefront-reconstruction method in 1948.
Holographic interferometry: An optical measurement technique that compares holographic wavefronts to reveal tiny changes in an object’s shape or position. Interference between reconstructed states makes minute deformation visible.
Photography: The creation of images by recording light from a scene on a photosensitive or electronic medium. Ordinary photography records intensity, while holography preserves phase information indirectly.
Diffraction: The bending and spreading of waves as they pass edges or apertures or encounter structured materials. Illumination diffracts from recorded fringes to reconstruct the object wavefront.
Optical phase: The position within a cycle of an optical wave, measured relative to a reference. Holography captures phase indirectly through its effect on interference.
History of holography: The development of holographic theory, recording methods, and applications from Gabor’s proposal onward. The field’s progress depended on lasers and later advances in recording materials.
Digital holography: Holography in which a digital sensor records an interference pattern and computation reconstructs the wavefront. It replaces photographic recording and enables numerical refocusing and measurement.
Stereoscopy: A method of producing perceived depth by presenting different images to the two eyes. Stereoscopy supplies binocular depth cues; holography reconstructs a view-dependent light field.

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