Key Takeaways
- Augmented Reality (AR) glasses use waveguide technology to project virtual pictures onto the real world, providing immersive experiences in healthcare, manufacturing, and defense.
- Achieving high-quality AR displays depends on waveguide designs that balance transparency with a wide field of view.
- Geometric and diffracted waveguides each have distinct advantages in terms of form factor and image quality.
- Waveguide displays are a viable AR option for integrating virtual content with real-world visibility due to their optimized light control through total internal reflection (TIR).
Introduction to AR Glasses
Augmented reality (AR) glasses are advanced gadgets that use waveguide technology to seamlessly merge real-world views with computer-generated information like images, audio, and films.
These virtual images are superimposed onto the real world, giving consumers a richer and more realistic experience.
AR technology has found uses in a variety of industries, including defense, industrial manufacturing, healthcare, entertainment, and education, dramatically improving how people engage with digital information in real-time across a wide range of professional and personal settings.
AR optics use waveguide designs to project display content directly into the user's line of sight, allowing them to see the real environment while interacting with virtual material.
AR optics' main components are the AR display, the eye, and an optical lens. Unlike virtual reality (VR), which sets a display screen directly in front of the user's eyes, AR glasses position the display near the temple or forehead to avoid interfering with real-world imaging.
To provide a high-quality visual experience, the lens amplifies the image, modifies the optical path, and sends it off-axis to the human eye while maximizing the field of view (FOV). In addition, the lens must remain transparent to ensure a clear view of the real world.
Types of AR Glasses
Different optical methods have been explored in the development of AR glasses. Prisms, free-form surfaces, Birdbath optics, and optical waveguides are today's four most common optical systems.
- Prisms: This approach combines semi-transparent and semi-reflective prisms to project images to the eye, providing a hybrid experience of real and virtual content. However, prism-based optics have a limited field of vision, limiting their application scenarios.
- Optical Waveguides: Optical waveguides are a promising AR technology that uses total internal reflection (TIR) to transfer light through a glass substrate and straight to the human eye.
- Free-Form Surface: This approach uses reflecting surfaces to project graphics. Birdbath is a variation that employs a polarizing beam splitter to reflect light from a free-form surface into the user's eye. Despite being lightweight and cost-effective, it has a lower transmittance due to many reflections and transmissions, reducing image brightness.
Total Internal Reflection and Optical Waveguides
Optical waveguides are narrow and highly transparent, perfect for consumer AR applications. These waveguides use a polished glass substrate to couple and retain light by total internal reflection.
The waveguide transmits images off-axis by reflecting them numerous times within the glass before directing them to the human eye. Its transparency also allows real-world signals to reach the user's sight, flawlessly blending virtual and real visuals.
Total internal reflection effect. Image Credit: Avantier Inc.
Total Internal Reflection (TIR)
TIR is a commonly observed optical phenomenon. When light travels from a medium of higher density to one of lower density and the angle of incidence surpasses a specific critical angle, it is completely reflected within the medium.
TIR has a variety of applications, including optical fibers, light rods, and prisms, which use this phenomenon to control light routes.
Different types of light guides. Image Credit: Avantier Inc.
Types of Optical Waveguides in AR Glasses
The AR glasses optical waveguide system consists of a display and an optical lens that uses TIR principles to transport light. Light is directed into and out of the lens at certain angles, which is essential for achieving efficient TIR. There are two major types of optical waveguides:
- Geometric Optical Waveguide: Mirrors act as a geometric optical waveguide, reflecting light into the lens. A semi-reflective mirror generates the optical signal while maintaining real-world light transmission. Although this configuration reduces light loss and improves imaging, it necessitates sophisticated coating and adhesion techniques.
- Diffracted Optical Waveguide: This technique uses a grating structure to input and output light. Gratings direct light efficiently by altering structural parameters such as period and depth. There are two major types of diffracted optical waveguides:
- Volume Holographic Waveguide: The Volume Holographic Waveguide uses laser interference to induce periodic refractive index changes, resulting in great diffraction efficiency and outstanding image quality. However, the fabrication process is more difficult.
- Surface Relief Waveguide: A low-cost, low-quality imaging system with etched or embossed periodic gratings on a glass surface.
Although these varied waveguide types have a range of advantages and disadvantages, they continue to drive innovation in consumer AR and display technology.
Geometric optical waveguide. Image Credit: Avantier Inc.
Diffracted optical waveguide. Image Credit: Avantier Inc.
In conclusion, integrating advanced optical technology into augmented reality glasses marks a substantial advancement in how we engage with digital content. AR glasses could transform technology across sectors and improve everyday lives by seamlessly combining the virtual and real worlds.
As this technology evolves, advancements in optical waveguides and other optical technologies will be essential in improving the performance and usefulness of AR systems.
The future of augmented reality seems promising, with new advances that will transform our knowledge of information interaction and redefine the limits of human experience.
This information has been sourced, reviewed, and adapted from materials provided by Avantier Inc.
For more information on this source, please visit Avantier Inc.