What does holography mean? Introduction to holography.

1. Holography is a photographic method that can record and reproduce three-dimensional (stereoscopic) images of objects without lenses. It is a technology that can record the amplitude and phase information of light wave front from objects and reproduce this light wave when necessary.

2. 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. In order to record the amplitude and phase information of light waves at the same time, the phase difference between two light waves can be determined by using the optical path difference of object light and reference light with the help of a coherent reference light. Therefore, with the help of reference light, the amplitude and phase information of light waves from objects can be recorded.