What is the three-dimensional image in the holographic reconstruction optical path diagram?

Virtual image is a virtual image in a certain proportion to the original object, and the image seen is in the direction of the original object.

Holography, 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. In the typical off-axis holographic optical path layout, the beam emitted by the laser is divided into two beams by the beam splitter B, and one beam is directly projected on the holographic negative H (a high-resolution photosensitive material) after being reflected by the mirror M, which is called reference light; Another beam illuminates an object, and the light reflected (or transmitted) by the object is called object light. The interference between the object light and the reference light on the holographic negative constitutes a very complex and fine interference fringe pattern. These interference fringes record the amplitude and phase information of object light and its contrast and position change. Holographic negatives become holograms after conventional development and fixation. The appearance of hologram seems to have nothing to do with the appearance of the original object, but it records all the information of the object light in the form of optical coding.

The application of holographic technology in photography is far superior to ordinary photography. Ordinary photography is based on the principle of lens imaging, which projects a three-dimensional scene onto a flat photosensitive floor to form a light intensity distribution. The recorded photos have no stereoscopic effect, because the images obtained from the photos are the same from all angles. Holography reproduces the object light wave accurately. When we "look" at the light wave of this object, we can observe different sides of the reproduced stereoscopic image from all angles, just like seeing a real object, with depth of field and parallax. If we shoot two Mercedes-Benz cars side by side, then when we change the observation direction, the blocked part of the latter car will be exposed.