The concept of “metaverse” has made VR/AR devices rise again, including AR glasses, VR headsets and other new products have been released one after another, which shows us the popularity of the VR/AR industry. Whether it is a VR device or an AR device, sensor devices play a crucial role in the realization of functions, such as wearing detection, eye tracking, gesture recognition, screen management, etc. AR glasses also need to display the light source of the optical machine and display management. Sensors that help the display module achieve a natural fusion of display tone and light changes in the physical environment, enhancing the integrated experience of virtual and real environments.
So, to what stage has the current AR glasses optical technology progressed, and what latest solutions have been given by ams and Osram, the global leader in optical solutions, to meet market demands?
Multiple AR glasses display technologies coexist
In terms of optical solutions, ams Osram has built a leading portfolio of optical solutions, with different solutions for industrial/enterprise users as well as ordinary consumers. Sun Wenxuan, system solution engineering manager of ams Osram, said that ordinary consumers’ requirements for glasses are “comfort is king”, while industrial/enterprise users generally require “function priority” for AR glasses.
From a technical point of view, VR is to solve real-time processing during transmission and interaction, as well as 3D vertigo, while AR is to solve problems in the optical part. Therefore, when developing new products, manufacturers will focus on challenging different technical bottlenecks. At present, the display technology of AR glasses includes three parts, one is passive micro-display technology, the other is active micro-display technology, and the third is scanning display technology.
Different display technologies have different advantages and disadvantages. Sun Wenxuan mentioned that the technical solution of DLP/LCOS plus LED is very mature and has the advantages of high brightness and high color gamut. The disadvantage is that the volume will be relatively large and there will be relatively limited. Light etendue. If it is the solution of DLP/LCOS plus laser, in addition to the advantages similar to LED, its volume is smaller than the optomechanical of LED, but the display will be a bit larger than that of Micro LED and LBS technology. Due to some interference effects caused by chromaticity, it is difficult to improve the image quality. Because the Micro OLED in active display technology is not suitable for the display scene of environmental fusion, the brightness is far from enough in sunlight.
With the development of technology, some manufacturers have used Micro LED technology on AR glasses since last year, but it is still in the initial stage of development. Sun Wenxuan pointed out that the biggest technical difficulty is that the integration of RGB is very difficult. The difficulty of scanning display technology is that the system is relatively complex. Judging from the current situation, there is no one-size-fits-all solution, and manufacturers need to achieve trade-offs between application requirements and technical challenges.
New LED “MOSAIC” solution, smaller size, higher eye-catching brightness
In order to meet the market demand, ams Osram proposed two optical solutions for AR glasses, one is to provide LED light source in the LED micro-projection solution of DLP/LCOS, and the other is to provide RGB laser in LBS scanning display technology.
For LED micro-display systems, ams Osram provides different solutions such as dual-channel dichroic mirrors and light guide solutions. In order to reduce the size of the optomechanical machine and increase the light energy of LEDs, ams Osram has developed a new LED technology. The chips are arranged in a field shape, and there are RGGB four-chip version and RRGGBB six-chip version.
According to Sun Wenxuan, the improvement of the new LED is reflected in two aspects. One is that the color uniformity of the LEDs arranged in the field will be greatly improved compared to the LEDs arranged in a line. The second is that the distance between the chip surface and the package surface is further reduced. The original 0.44mm is reduced to 0.15mm, which allows the optical components to be closer to the chip, making it easier to collect light and more uniform in color.
It has become an inevitable trend for the micro-display screen of AR glasses to develop towards higher performance such as high brightness, low latency, and low power consumption. Generally speaking, AR glasses need to reach 800nit-1000nit under strong light. In the specific application, ams Osram has researched on the LED of the RGGB four-chip version and concluded that: taking 1W LED electric power as an example, it can output a luminous flux of 50lm. After passing through the front-end optical system, it can maintain about The luminous flux of 5 to 10lm, and then matched with different optical waveguide types, can finally achieve an eye-catching brightness ranging from 350nits to 6500nits.
AR glasses are becoming lighter
As can be seen from the new products released in the past two years, AR glasses are all showing a trend of lightweight design, which also brings challenges to AR glasses display technology. Generally speaking, the acceptable optomechanical volume for industrial/enterprise users is around 10-3cc, while the optomechanical volume required by consumers is close to about 1cc. A study by ams and Osram found that the optomechanical volume that can be achieved by the traditional LED+LCOS/DLP solution is about 5 to 10cc, and the optomechanical volume of the MOSAIC LED+DLP/LCOS solution is about 3-5cc.
In order to further reduce the size of the optomechanical, ams Osram has launched the RGB three-in-one laser module Vegalas™, which is expected to reduce the size of the optomechanical to less than 1cc. So, how much eye-catching brightness can the RGB laser module display solution achieve, how much power is consumed, and how to match the corresponding optical power of each chip? If the target of 1500nits eye-catching brightness is set, it is estimated that the total optical power of this solution is about 78mW, and then based on the current efficiency that each chip can achieve, it requires about 0.8W of electrical power input. It is understood that the program has entered the design verification stage.
Based on the latest display solutions from ams and Osram, AR glasses are trending towards smaller and thinner. After the price of AR glasses drops and the consumer market gradually opens up, a better AR experience will be just around the corner.