Understand the principle of holographic projection of Hatsune Miku Los Angeles concert, is it projected directly on holographic projection film by air or projector?

Orthographic holographic display, also known as virtual imaging technology, is a technology that records and reproduces the real three-dimensional image of an object by using the principles of interference and diffraction.

Shooting principle

The first step is to record the light wave information of the object by using the interference principle, which is the shooting process: the object.

Holographic projection shooting process

The object forms a diffuser beam under laser irradiation; The other part of the laser beam, as a reference beam, hits the holographic negative and interferes with the object light beam, converting the phase and amplitude of each point on the object light wave into spatially varying intensity, thus recording all the information of the object light wave by using the contrast and interval between interference fringes. Negative recording interference fringes become holograms, or holograms, after being developed and fixed.

The second step is to reproduce the light wave information of the object by using the diffraction principle, which is the imaging process: the hologram is like a complex grating. Under the irradiation of coherent laser, the diffracted light waves of linearly recorded sinusoidal holograms can generally give two images, namely the original image (also called the initial image) and the yoke image. The reproduced image has strong stereoscopic effect and real visual effect. Every part of the hologram records the light information of every point on the object, so in principle, every part of the hologram can reproduce the whole image of the original object. Through multiple exposures, multiple different images can be recorded on the same negative, and they can be displayed separately without interference.

Before 3D projection, the object should be photographed at 120. Readers who have seen 3D movies should know that if they take off 3D glasses, the picture will appear ghostly and blurred. This is because there is not one picture on the screen, but the superposition effect of two pictures from different angles.

In order to simulate the "binocular effect", we must take one to the left and one to the right. When shooting, there are actually two 3D cameras working at the same time, one of which is biased to the left of the actor to record the left image; One is to tilt to the actor's right, record the image on the right, and then process the two images with a computer, which becomes the source of the 3D movie.

Visual principle

Note: This is the visual principle in 3D imaging. Slightly different from this, holographic projection actually presents a 3D image.

Everyone has two eyes, and the angle of view of each eye is about 80 degrees, but the angle of view of the two eyes together is only 120 degrees, which means that the 40-degree angle of view is coincident, so what we see with our left and right eyes is actually different. For example, if you close your left eye and look at it with your right eye, or vice versa, you can test the effect, and the objects received by your left and right eyes can be forwarded to your brain to judge the distance of the objects and form a stereoscopic impression. Simulating this process forms 3D stereo technology.

After the shooting, in the projection room, the 3D film source is placed on the screen at a certain angle, and the audience needs to wear 3D glasses to watch. Looking closely at 3D glasses, we will find that there are dense pinstripes on the left and right lenses in different directions. The left lens grating and the right lens grating form an angle of 90 degrees with each other. It is these stripes that we can see a wonderful three-dimensional picture.

After photography is completed, the image is decomposed according to binocular effect, so that the left eye can only see the left picture and the right eye can only see the right picture. Only in this way can the brain judge the distance and produce a three-dimensional sense. When projecting, the left-leaning picture and the right-leaning picture use different projection light. Although the color pictures are the same, the vibration direction of the projected light is different. The vibration directions of left-leaning pictures and right-leaning pictures are perpendicular to each other. Because the polarizer can only transmit the light whose vibration direction is parallel to the grating, the images seen by both eyes are respectively formed by the light transmitted through polarized glasses.

In this way, the overlapping pictures are decomposed, and the left eye only sees the left picture, and the right eye only sees the right picture. Because of the binocular effect, we have a sense of distance and three-dimensional sense.