On August 20, 2021, HZGL Optical Technology Co., Ltd. released China's first holographic resin optical waveguide, marking another solid step towards lightweight AR glasses.
HZGL is an enterprise dedicated to creating consumer-level AR Internet portals. Its founding team comes from Zhejiang University, Cornell University, and the University of Delaware. At present, the R&D team includes a group of top scholars and experts from the post-80s and post-90s in related fields at home and abroad.
HZGL has established the world's leading multi-functional micro-nano processing center and diffractive waveguide technology center, mastering the full chain technology of holographic bulk optical waveguides, including all aspects of design, manufacturing, and materials, and has more than 170 Chinese and international patents. It has recently focused on overcoming the key technology and mass production links of holographic resin optical waveguides, taking the lead in achieving technological breakthroughs and becoming the second company in the global market that can produce optical waveguide products of this material.
Holographic resin optical waveguide
Compared with the other two common optical solutions in AR glasses-free-form surface and prism solutions, optical waveguides have the advantages of thinness and high penetration of external light. They are considered to be consumer-grade AR glasses that focus on wearing experience and appearance design. The optical solution that will be chosen in the future.
According to the coupling structure of light entering and exiting the optical waveguide, the optical waveguide can be generally divided into geometric optical waveguide and diffractive optical waveguide. The latter can be further subdivided into surface relief grating waveguide (SRG Waveguide) and holographic volume grating waveguide (VHG) according to manufacturing technology. Waveguide). Geometric optical waveguide (or array optical waveguide) and surface relief grating waveguide technology are relatively mature, but the design barriers, process difficulty and manufacturing cost are relatively high. Among the AR glasses currently on the market, Microsoft’s HoloLens 2, Magic Leap One, and AR under Vuzix Glasses, etc., all use surface relief grating waveguides.
Compared with the surface relief grating waveguide, the holographic volume grating waveguide directly interferes in the micron-level photopolymer film through the dual-beam laser holographic exposure to form a nano-level grating structure, so it is more efficient in terms of process and more costly than other optical waveguide technologies. It also has obvious advantages, but the technology maturity is not as good as geometric optical waveguides and surface relief grating waveguides. Companies such as Akonia, Sony, Digilens, and China's HZGL that Apple acquired are all committed to the development and mass production of holographic volume grating waveguides.
The lightweight holographic resin optical waveguide released by HZGL this time is a resin-based holographic optical waveguide independently developed by HZGL. The light transmittance exceeds 90% and the field of view reaches 25°. Not only is the cost much lower than that of the glass substrate. The waveguide also overcomes the additional weight and volume of the glass optical waveguide because it is fragile and the additional protective lens must be added. It is capable of lighter and thinner AR glasses design, and is widely used in high-speed moving scenes including outdoor, sports, military, etc. Various use environments, very cost-effective. The holographic resin optical waveguide currently supports monochrome display, and the color version of the holographic resin optical waveguide has entered the testing phase and is expected to be released next year.
The breakthrough road from technology to mass production
Holographic bulk optical waveguides have extremely high requirements for material stability and quality, and require a highly parallel and almost perfect waveguide surface. The optical principle of the optical waveguide determines that the light enters the optical waveguide to experience many times of total internal reflection. Any flaw on the surface of the waveguide may have an exponential effect on the image quality. Therefore, compared to the relatively mature processing technology of the glass substrate , The resin-based optical waveguide has always been a jewel that is difficult to pick on the technological peak.
Because of this, the design of a mature and mass-produced holographic resin optical waveguide not only requires companies to solve material research and development, grating design algorithm development, and optical simulation software development, but also requires companies to be able to understand the mass production process and yield of holographic materials. The problem is adequately controlled. Take optical software as an example. The mainstream optical software on the market, such as Code V, Zemax, etc., can simulate geometric optics well, but it cannot simulate holographic bulk optical waveguides effectively. R&D companies need to write the corresponding optics by themselves. The tracking program completely simulates the characteristics of the waveguide.
HZGL focused on conquering holographic materials that can achieve wide-wavelength and large-angle grating diffraction, and realized the preparation of holographic materials with uniform thickness and stable performance, ensuring the basis for mass production of holographic resin optical waveguides; at the same time, customized development based on its successfully developed holographic materials The corresponding wide-wavelength, large-angle holographic diffraction grating design algorithm and optical simulation software have been developed, and the holographic film automatic production equipment has been independently developed to realize the automatic production of diffraction gratings and ensure the output and yield of products.
At present, the annual output of holographic resin optical waveguides can reach more than 100,000 pieces, and the yield rate is as high as 95%, which can fully meet the mass production needs of itself and other AR glasses research and development companies.
Low-cost optical waveguide, paving the way for AR consumer market popularization
Compared with the upsurge of all-in-one VR in the consumer market, there are still many obstacles to overcome in the popularization of AR glasses in the consumer market.
The first is the cost issue. The price of AR glasses is often thousands or even tens of thousands of yuan, which is enough to discourage non-fever users, but the price of VR all-in-ones has dropped to around 2,000 yuan, which is more acceptable Much higher
The second is the content ecology. At present, AR glasses have not established a complete content ecology for the consumer market. Compared with VR platforms, different games and film and television content have emerged. At present, the AR content that consumers can experience is still very few;
Finally, the product design. Consumers have higher expectations for the appearance design of AR glasses. The existing AR glasses on the market are still relatively bulky and do not conform to consumers' perception of the term "glasses".
Light Engine and optical devices are one of the core technologies of AR glasses, and they also account for a large part of the cost of AR glasses. The emergence of optical waveguides such as holographic resin optical waveguides that can reduce the cost of AR glasses and improve the bulky experience of AR glasses has undoubtedly promoted the continuous progress of AR glasses and narrowed the distance between AR glasses and consumers. However, the performance of such a new product still needs to be tested by the market.
HZGL`s series of AR glasses independently designed and produced in the past have been used in warehousing, logistics, military and police security, industrial production and other application scenarios. With the launch of holographic resin optical waveguide products, the company will also update its product line simultaneously and launch new models in September. The new AR glasses of the holographic resin optical waveguide, by then, everyone will be able to truly experience the brand new experience brought by the holographic resin optical waveguide.