Hologram
Definition
A 3D image recorded and reconstructed with laser light — capturing not just brightness but the full wavefront.
Technical definition
An interference pattern recorded between a reference beam and light scattered from an object. Illuminating the developed pattern with the reference beam diffracts light to reconstruct the original wavefront, producing a true three-dimensional image with parallax.
Example
Security holograms on credit cards: tilt the card and the image shifts with real parallax — impossible to photocopy because a photo cannot capture the wavefront.
Common confusion
Most ‘holograms’ in sci-fi (projected floating images) are not holograms at all — they are Pepper's ghost illusions or volumetric displays. True holography requires recording interference with coherent light.