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In many sci-fi scenes, we often see people using cool stereoscopic display

In recent days, an article in Nature magazine introduced a device called MATD

Three-dimensional display on “Super Marines” (Source: Movie “Super Marines”)

First, “sound” helps to make science fiction a reality

People’s imaginary holographic projection is capable of directly projecting images in the air, but the current general holographic projection technique is performed on a medium that reflects this information by using the three-dimensional optical information of the already acquired object. show. The simplest holographic projection uses the Pepper’s illusion principle—using translucent semi-reflective glass to make a three-dimensional image reflected on the glass in the eye, while the real background can also pass through the glass, producing an image that exists in the real world. The illusion of.

On the visual level, the media used in this device is different from other holographic projections. Through the “sounding” to control a lightweight common plastic – “expanded polystyrene” particles suspended in the air. The particle is an excellent reflective material that can achieve the same brightness anyway at an observer’s angle. Through the top RGB illumination system, a three-dimensional pattern of color that can be viewed from various angles is produced, and in the future, a truly immersive “3D somatosensory movie” can be produced.

Schematic diagram of the working principle [Source: Reference 1]

Second, what is the “sound”? How do you manipulate these particles?

First we must know that the essence of sound is a pressure wave. In life, the movement of the strings, loud singing, etc. are transmitted to the ear by pressure waves, causing the tympanic membrane to vibrate, so that we can hear pleasant or melodious sounds.

The sonar is a sophisticated computational simulation of the sound waves produced by multiple sound sources, so that sound waves can create a “trap”-like mechanism somewhere in space. The particles are in the most stable state in the “trap”. Once they deviate from the original position, they will have a resilience opposite to the direction of motion to return to their original position. By moving the “trap” position, it is possible to control the corresponding movement of the particles, thereby causing the picture in the stereoscopic display to change. The fastest speed of the particles in the device is about 3 m/s, which can produce various complicated stereoscopic image effects.

Sound Map [Source: Reference 2]

The sonar controls the earth in the rotation of particles [Source: Reference 1]

Three, one “镊” three, not only visible but also audible

The device uses a more subtle approach to the touch level. We all know that sound is transmitted in the form of waves, and sound waves that can be generated by periodically repeating vibrations. For the duty cycle in which pressure is generated in one cycle of the sound wave generated by “sounding”, 75% of the portion is used for controlling the position and motion of the particles, and the remaining 25% is used for the formation of the sense. The frequency of the sound wave is chosen to be 250Hz, avoiding the sensitive range of human hearing

Tactile test [Source: Reference 1]

On the audible level, the frequency of the “sound” itself is beyond the scope of the human ear, so there is no need to worry about noise when using it. The device encodes most of our auditory frequency range so that the “sound” itself produces a sound that the human ear can hear. Which includes the sound generated by the capture particles in all directions.And the sound that is transmitted to the user because of the user’s touch. Perhaps we can use this principle to create a “display” that blind people can also operate through different sounds.

Fourth, technology development, let humans step into the “science fiction world”

This is the working principle of a “trinity” stereoscopic display device that can be seen, touched and audible based on “sounding” technology. Now “sounding” technology also has great application potential. Similar to the “Light” of the 2018 Nobel Prize in Physics, it also controls particles through the lowest energy “trap.” At the same time as the scorpion is accurate, the device uses a lower “sound” energy, has less impact on cells, and can control the contact of cells in a set manner, so it has great application prospects in the field of cell information transmission. .

Sound Control Particle Motion [Source: Reference 4]

The device in the paper is out of the shackles of traditional displays that require a display screen. Using only one working principle gives people three sensory experiences, making people feel that the world in science fiction movies is close at hand. ,exciting.

Maybe in the future where this three-in-one stereoscopic display technology is mature, distant relatives can see and touch each other, students can observe and manipulate the combination of molecules in person, and blind people can also make artistic creations as they wish. With the constant efforts of scientists, the illusions of the past are gradually becoming a reality.

References

[1] Hirayama R, Plasencia D.M., Masuda N, et al. A volumetric display for viSual, tactile and audio presentation using acoustic trapping.

[2]https://www.interaliamag.org/emerging-ideas/asier-marzo/attachment/acoustic-tweezers/

[3] Shi J, Ahmed D, Mao X, et al. Acoustic tweezers: patterning cells and microparticles using standing surface acoustic waves (SSAW)[J]. Lab on a Chip, 2009, 9(20): 2890-2895.

[4] Courtney CRP, Demore CEM, Wu H, et al. Independent trapping and manipulation of microparticles using dexterous acoustic tweezers [J]. Applied Physics Letters, 2014, 104( 15): 154103.

[5] Yang Yiqian. Perceptual Threshold of Whole Body Vibration in Human Body[J]. Civil Engineering and Environmental Engineering, 2012 (S2): 54-60.