-Instrument Introduction

Holography can achieve high-density storage, encryption, and three-dimensional display of objects. Holography is different from conventional photography in that it records not the planar image of a three-dimensional object on a film, but the light field itself. Conventional photography only records changes in the surface light intensity of the object being photographed, that is, only the amplitude of the light is recorded, while holographic photography records all information of the light wave, including the phase of the light wave in addition to the amplitude. All information of the three-dimensional object's light wave field is stored in a recording medium.

Holography involves two processes: recording and reproducing. After being split, a coherent beam of light forms two beams of light. One beam of light illuminates the object to be recorded, and the light waves scattered from the object are called object light; The other beam of light directly illuminates the holographic dry plate at a certain angle to the object light, which is called the reference light. The coherent superposition of object light and reference light produces fine interference fringes similar to gratings, which are recorded on a dry plate to form a holographic film, known as holographic recording. After illuminating the hologram with the original reference light, the diffracted light waves reproduce the wavefront of the object light at the time of recording, thus reproducing the same three-dimensional image as the original object.