What is the principle of holographic image?

Holography (called holography in Taiwan Province Province) is a photographic technique that records all the information (amplitude and phase) in the reflected (or transmitted) light waves of the photographed object. Holography not only records the intensity (amplitude) of the reflected light wave of the photographed object, but also records the phase of the reflected light wave. If the hologram is irradiated with a special laser, a stereoscopic image can be seen. Holography uses lasers instead of ordinary cameras. The laser beam is divided into two parts by the beam splitter, one of which shines on the photographed scene, which is called the object beam; The other beam of light directly shines on the photosensitive film, that is, the holographic dry plate, which is called reference light. When the light beam is reflected by the object, the reflected light beam also shines on the film, and the film forming process of holography is completed. Holograms are very different from ordinary photos. With the naked eye, there are only some messy stripes on the hologram.

But if you use a laser beam to illuminate the photo, a realistic three-dimensional scene will appear in front of you. Even more amazing, you can see different sides of the original from different angles. Besides, it doesn't matter if you accidentally break the hologram. Pick up a small piece of debris at random and observe it in the same way. The original object can still be displayed completely. The principle of holography is to record the information of objects by using the interference principle of light and the interference of two beams of light.

Ordinary photos are sensitive according to the brightness of light reflected from the scene, and can only record the amplitude information of light. The shot scene is a plane image, which has no stereoscopic sense of reality. Only when the phase information of light can also be recorded and re-presented, photos can give people a three-dimensional sense of distance and depth.

Laser holography does not need the lens used by ordinary cameras, as long as the laser is divided into two beams, one of which illuminates the object and reflects it into object waves; A beam of reference light is aimed at the negative. Because the object wave reflected by the scene has different optical paths and different phases, the result of interference with reference light is that all information is recorded on the negative at the same time.

The holographic negative is covered with interference patterns. Only by illuminating the holographic negative with the same reference light as when recording can the original object wave be reproduced. Moreover, in our eyes, this three-dimensional reproduction phenomenon can not be distinguished from the real thing at all.