[Original] volumetric 3-dimensions display (3D display technology)

I recently studied the three-dimensional display technology (which is a broad extension of optical communication technology, I personally think) and found that this field is really "charming". I will share it with you in the close-up ;)

Currently, the three-dimensional display technology can be divided into glasglasses-based stereoscopic, autostereoscopic displays, and hologram) and Three-dimensional Display (volumetric 3-D display.

The first two types of technologies are familiar to everyone. They all adopt the parallax method to give people the feeling of 3D display: the left and right eyes show slightly different images, respectively, to deceive the brain and make the observer feel 3D. Because the 3D scene constructed by artificially making the parallax is not natural, it increases the mental workload of the observer, so it may be a headache for a long time. Holographic technology uses not digital means, but Optical Interference and diffraction. Generally, it can only generate static 3D optical scenarios and has requirements on the observation angle, it is not suitable for human-computer interaction applications.

Body 3D display is different from the first three. It is a 3D technology that truly achieves dynamic effects. It allows you to see 3d pivoting images in sci-fi movies that are generally "floating" in the air. Currently, the 3D display technology can be divided into two types: swept-volume display and solid-volume display. Among them, the former masterpiece is felix3d and perspecta, while the latter masterpiece is called depthcube.

Felix3d has a very intuitive structure framework. It is a spiral-based rotation structure, as shown in. A motor drives a high-speed rotation of a spiral surface, then, the R/G/B laser will gather a bunch of chromium light into the spiral surface through the optical positioning system to generate a color highlight. When the rotation speed is fast enough, the spiral surface looks transparent, and the highlight is like floating in the air, becoming a pixel (space pixel, voxel ), multiple such voxel forms a straight line and a decent object until it forms a 3D object. The process is intuitive, isn't it?

Perspecta may be the most remarkable achievement in the 3D display field of the scanning body. It adopts a cylindrical axis rotation and spatial projection structure, as shown in, unlike felix3d, its rotating structure is simpler. It is an upright projection screen driven by a motor, which rotates at a frequency of up to 730 rpm and is made of thin translucent plastic. When a 3D object needs to be displayed, perspecta will first generate 198 profiles of the object through software (rotate along the Z axis, the average rotation of 2 ° not to capture a vertical profile perpendicular to the X-Y plane), the resolution of each section is 798x798 pixels, the average projection screen per rotation of 2 ° less, perspecta uses another profile to be projected on the screen. When the screen is rotated at high speed and multiple sections are rotated at high speed, we will find that, A natural 3D object that can be fully observed appears!

From the above, we can see that the projection Frame Rate of perspecta has reached 198 × 730/60 = FPS. This speed is enough to spoof our eyes and generate real 3D scenes using the temporary effect of vision; because each frame requires 798x798 pixels, the amount of data required per second is as high as 2409x798 ^ 2x3) /1024 ^ 3 = 4.286 GB! Given the limited excitation time of a common laser, felix3d cannot provide such a high bandwidth and frame rate. A 3D image in Felix can only reach 10 thousand pixels at most, perspecta can display nearly 1 billion individual pixels. To achieve such high display accuracy, perspecta adopts the digital light processing technology. The core of perspecta is three DLP optical Chips Based on Micro-electromechanical systems (MEMS, each chip is equipped with a high-speed light-emitting array consisting of more than one million digital micro-mirror devices, the three DLP chips are responsible for the R/G/B three-color images respectively and are synthesized into an image, which is reflected by the fixed Optical System in the base and the optical relay lens that rotates synchronously with the motor, it is finally projected onto the screen. It is worth mentioning that perspectaOn PCPlug-and-play, which is compatible with 3DS MAX and OpenGL.

Although the almost perfect 3D display capability and simple structure greatly reduce the manufacturing cost of perspecta and become the most likely physical display device to enter the electronic consumption market, like all other scanning body display technologies, it has a fatal weakness-"brightness" and "rotation ". The displayed structure of omnidirectional open projection has a low lumen value, which is vulnerable to background light. High-speed rotation requires a high degree of stability for the placement platform, the desktop cannot be shaken at will. Otherwise, the pixel may be blurred or even unable to be imaged at all. Therefore, it cannot be used in hosts, aircraft and their maritime vessels. To solve this problem, smart people have proposed solid state display technology.

Early solid state display technology, such as solidfelix, mainly used a wholeCubeAs a display medium, the crystal is doped with rare earth elements. When two coherent infrared lasers intersect at a spatial point in the crystal, they will trigger the light, this system is still in the lab stage. The depthcube system represents the highest achievement of the current solid state display technology. It adopts a very special method: stacked LCD screen to achieve three-dimensional display, its shape is like a TV set in 1980s. Its structure is shown in. The display medium of depthcube is made up of 20 LCD screens. The resolution of each screen is 1024 × 748, the interval between the screen and the screen is about 5mm; the LCD pixels of these special screen have special electronic control optical properties. When the screen is powered on, the liquid crystal of this pixel will become parallel to the beam propagation mode like the Louver leaves, so that the beam that shines on this point transparently passes through, and when the voltage to it is 0, this liquid crystal pixel will become opaque, so as to diffuse reflection on the beam, forming a voxel that exists in the LCD stack. At any time, 19 LCD screens are transparent, with only one screen being opaque and white diffuse reflection; depthcube will quickly switch between the 20 screens to display the 3D object section and generate the longitudinal depth. It also uses a kind of 3D depth anti-aliasing) display technology to expand the depth of the 20 screens, so that 1024x748x20 physical body space resolution to achieve up to 1024x748x608 X Display resolution; like perspecta, depthcube also uses DLP imaging technology. Because depthcube has a single viewing angle and is mainly on the front of the display, it does not need frame rates as high as perspecta, it only needs to display 1200 sections per second to produce enough body display effect.

The last thing to say is that all body display technologies can only generate a translucent 3D perspective, rather than an opaque 3D object. This is because a ray of light cannot block the propagation of another ray of light, therefore, there is no need to use a complex hidden mechanism in 2D 3D display technology to perform additional Z-depth processing on 3D images. In addition, at present, the State Key Laboratory of optical instruments of Zhejiang University is actively conducting research on the body display technology in China, and has made gratifying progress.

I have read everything aboveOfDo you, like me, have confidence that we will be able to see sci-fi movies in the near future in a comprehensive 3D Human-Computer Interaction experience?

References:
1. actuality Corp.-http://www.actuality-systems.com
2. Felix 3D display-http://www.felix3d.com
3. genex technologies-http://www.genextech.com
4. lightspace technologies-http://lightspacetech.com
5. holoverse-http://www.holoverse.com
6. helical Display System-http://www.laserfx.com/Backstage.LaserFX.com/Archives/Archives8.html
Deep-http://www.spectrum.ieee.org/apr05/1104
8. Lin yuanfang and others, a three-dimensional display system based on a rotating two-dimensional light-emitting diode array
9. Lin yuanfang, et al., pixel Attribute Analysis of a three-dimensional display system based on a two-dimensional rotating screen, Journal of photon
10. Lin yuanfang, et al., used a rotating luminous screen to reproduce the principle and Deviation Analysis of three-dimensional images, and photoengineering

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