WIMI’s Dr. Guo Songrui: The development and application prospect of holographic technology: light field collection

October 14 21:27 2020

Beijing, China – “Holography” comes from the Latin vocabulary, and its meaning is: all, compound. According to the current common knowledge in mainstream technology filed, holography specifically refers to “holographic technology”, which is a technology for reproducing diffracted light emitted by objects. The holographic technology uses the principle of interference to record the light wave messages of the object, and uses the principle of diffraction to reproduce the light wave messages of the object, helping users to store all the light information of the object. Thus, the observer can observe the different positions of the object in all directions, and the stored light information records all the light distribution in the three-dimensional space. Therefore, holographic technology is also a kind of optical storage and reproduction technology.

The earliest holographic technology was discovered by Denise Gabor (1900-1979), a Hungarian physicist, who won the Nobel Prize in Physics in 1971. However, this technology was first used in electron microscopes to record and display electronic holograms. The earliest use in the field of optics was after the invention of laser technology in 1960.

The holographic recording is different from ordinary photography. An ordinary camera only records the intensity of the object’s light field. The hologram records the intensity of the reference light and the object light after interference. When it needs to be reproduced, it is only necessary to use the reference light to show the amplitude of the object light that fully characterizes the object information.

The hologram production process uses a laser. The laser beam is strictly split 1:1 by a beam splitter. One beam of light shines on the surface of the object to be photographed, and the other beam directly shines on the photosensitive film (holographic dry plate). Moreover, this light is also called the reference beam. When the object beam is reflected by the object, its reflected beam is also irradiated on the film, completing the hologram shooting process.

There are several major characteristics of holograms: 1. Omni-directional information recording. The holographic picture records the omnidirectional and comprehensive illumination information of the object, so that the object can be observed from different angles during observation. 2. Learning the whole picture from the parts. When part of the holographic picture is damaged, the whole picture of the object can still be seen from the remaining part. 3. The amount of stored information is huge, and multiple holographic photos can be recorded hierarchically on the holographic film. Moreover, they will not interfere with each other when displaying the picture.

Based on the characteristics of holograms mentioned above, the application prospects of holograms are quite broad, but it is not an easy task to collect light fields to form a hologram in the early stage of technological development. Early technical methods were either expensive, such as using the aforementioned laser to irradiate objects, or using camera arrays; or collecting information was limited and inefficient, for example, the light field acquisition systems based on a fixed turntable. After 2000, with the development of digital camera shooting technology and light field shooting technology gradually attracted the attention of researchers, the light field collection technology of the single camera came into being. Until now, the light field collection technology has truly reached the civilian level.

The common light field shooting techniques are divided into two categories: integral imaging and aperture coding imaging:

Among them, integral imaging is achieved by adding a microlens array or a micromirror array in front of the sensor to realize the collection of images of the light field viewpoints in different directions. There are more well-known integral imaging devices, including the lens array lens launched by Adobe, the Pelican lens array camera on the mobile phone, the Lytro light field camera, the R series light field camera of Raytrix, and so on.

The shooting based on the compressed light field is to add an optical mask between the camera lens and the sensor to achieve compression encoding of the light entering the camera aperture. The more well-known equipment is the prototype of the light field camera developed by Babacan et al. They proposed to use the method of encoding mask and programmed aperture to capture light field viewpoints in different directions, which can obtain light field with high spatial resolution.

Among them, the microlens array has the advantages of low cost and small size, but its disadvantage is that the image resolution loss is serious. The coding imaging technology has the advantages of small size, no loss of resolution, but its advantages are low signal-to-noise ratio and low light field quality.

From the perspective of the development of light field cameras, encoding-based light field acquisition equipment breaks the mutual restriction between angular resolution and viewpoint image resolution. The redundant information in the light field can be removed through machine learning, and the light field can be restored from a small amount of information. In the future 4K era, the advantage of not losing resolution will be the focus of this technology.

In the near future, when light field acquisition equipment develops to a sufficiently high resolution, as well as has fast enough acquisition speed, and cheap, the light field data, as a kind of rich media data, is stored in a large amount of non-overlapping data that can be passed through a single point. The complete picture of data information will become a new data treasure house for data scientists to research and mine. In particular, unexpected achievements may be obtained in many fields, such as holographic recognition, holographic payment, holographic authentication, and so on.

Guo Songrui:

Doctor of Computer Science and Technology Engineering from Hunan University, studied mixed reality and augmented reality technology at the State Key Laboratory of Scientific Computing of the Chinese Academy of Sciences, and participated in the research and development of multiple key projects.

About WIMI Hologram Cloud Inc.

WiMi Hologram Cloud, Inc. (NASDAQ: WIMI), whose commercial operations began in 2015, operates an integrated holographic AR application platform in China and has built a comprehensive and diversified holographic AR content library among all holographic AR solution providers in China. Its extensive p