What is the principle of holography using light?

Holography is based on the interference principle of light, so the light source must have good coherence. The appearance of laser provides an ideal light source for holography. This is because laser has good spatial and temporal coherence. In the experiment, a good hologram can be obtained by shooting small diffuse objects with He-Ne laser.

Light wave is an electromagnetic wave, which carries amplitude and phase information in its propagation. Ordinary photography uses photosensitive materials (such as photographic negatives) as recording media, and uses lens imaging system (such as camera) to image objects on the photosensitive materials. It only records the intensity distribution image of light waves from objects, that is, amplitude information, but does not include phase information. So ordinary photography can only take two-dimensional (plane) images.