Optical Technology and AR Eyewear
AR smart glasses, a relatively new form of wearable tech, overlay computer-generated information onto a user’s surroundings. These glasses typically connect to smartphones via Bluetooth or WiFi.
Israel-based Lumus has introduced Z-Lens 2D waveguide technology, which makes it easier to produce smaller and lighter AR eyeglasses. It also allows for seamless prescription eye integration.
Optical technology
Optical technology is a branch of physics that deals with the behavior and properties of light. This includes the ways we can manipulate it, as well as how it interacts with other electromagnetic waves such as radio and microwaves. This can be done by using a variety of devices, including mirrors and lenses.
In everyday life, you probably use optics a lot. Whether it’s your alarm clock, TV remote control or credit card, the technology behind each one is optical. It is the same technology that made our supermarket barcode scanner, CD player and smartphone holograms possible.
Bulk optics manufacturers have spent centuries designing lenses and mirrors to deliver real-world images to the eye. But today, optics must compete with electronics in digital domains where light can transmit and process information much faster than electricity.
As such, the industry has grown to include a wide range of companies that make and sell optical devices for a variety of applications. These include astronomy, microscopy, photography and visual correction as well as information-processing applications that complement or compete with electronics such as imaging and projection, data storage, communications, industrial robotics, precision measurement and machining.
Optics are also essential to the transportation of digital data over fiber optics. These fibers, which are hair-thin threads of glass, allow a beam of light to carry information similar to the way that electricity can ar eyewear be carried in metal wires. The ability to transport high-bandwidth signals over fiber has revolutionized telecommunications, and is currently the most common means of transferring data across the internet.
A key element of this technology is micro-optics, which can be used in various components such as optical isolators, circulators, GFFs, WDM couplers, switches and variable optical attenuators. These devices can be inserted into the free space region of the micro-optic fiber collimator assemblies to provide in-line functionality without the need for additional modules, as shown in Fig. 7.3.
Unlike traditional AR glasses, which rely on planar waveguides to project 3D augmentation or overlay content, CREAL’s light-field optical engine recreates light the way it happens in the real world. It also offers multiple perspectives of a single digital scene and sends 6000 images per second to each eye, ensuring a seamless, immersive experience.
Optical design
Optical design plays an important role in AR eyewear. This includes creating optical systems for head-mounted displays (HMDs), analyzing stray light, designing diffractive optical elements and controlling aberrations.
AR glasses use several different types of lens technologies. The most common are birdbath and geometric waveguide. These are patterned with transflective mirrors and prisms that bounce light from the display before it enters the wearer’s eyes.
These optical systems have some advantages over traditional lens designs, such as mechanical tolerance and ease of form-factor design. However, they come with a few disadvantages. One of the most significant is that birdbath lenses lose most of the light bounced from the display to the wearer’s eyes. This can result in darkening the real world and distracting the wearer from augmented reality.
Another important advantage of waveguides is that they are scalable and can be manufactured in large volumes. This is a big deal for AR, since it can bring on a surge of thin and lightweight AR smart glasses to the market.
In order to develop an AR HMD, optical engineers need a suite of software tools. These include software to trace rays through the system and optimize them, analyze stray light in the system, design diffractive optical elements and control aberrations.
Similarly, the mechanical engineer needs a CAD package to create the system layout and perform thermal and structural analysis. An electrical engineer may also be required to track the user’s eye motion and send a signal to the optical system.
This can be done with freeform optical design software that provides robust virtual prototyping for a wide range of applications. It can help reduce design iterations and repeated prototypes, cutting development costs.
It can also help with target distances and clipping planes. Achieving a realistic rendering of an AR experience requires a clear view of a target, and this can be difficult in a HMD with a fixed camera position.
Metasurfaces can overcome this problem by enabling the refractive surface to bend rays, thus increasing the angle of reflection and increasing the resolution. They can also increase the viewing distance by adjusting the diffraction pattern.
Optical materials
Optical materials are an important component in AR eyewear. They can enhance visual performance, increase field of view, provide wearable comfort and offer design features. In addition, they can be manufactured with mass production-compatible materials to enable affordability.
Currently, most augmented reality (AR) head-mounted display eyeglasses use gratings to reflect contextual information from a miniprojector to the viewer’s eyes. However, gratings scatter and disperse the real-world light that passes through the glass. The distortions become worse when multiple sets of gratings are used to handle different colors from the miniprojector.
A new metasurface that can gather the light rays entering an AR/VR eyepiece from all directions and direct them directly into the human eye is a promising solution. Designed to defy conventional laws of reflection, the metasurface is made of nanophotonic silver nanostructures imprinted on a thin metallic film that conforms to a freeform optic.
By writing the metasurfaces onto the freeform optic, scientists at the University of Michigan created a new optical component called a ar eyewear metaform that can gather and redirect light rays entering an AR/VR eyeset from all directions. The metaform can be fabricated with electron beam lithography, a new technique that cuts away sections of the thin-film metasurface where the silver nanostructures need to be deposited.
The metaforms can be written on any mirror or lens and used in sensors and mobile cameras. This makes them a versatile component that can be integrated into AR eyewear and other applications where high transparency is required.
Another potential solution is to combine a see-through metalens with an imaging lens to create an optical see-through lens that can selectively act as a transmission-type eyepiece for virtual imaging and as transparent glass through which to view a real-world scene when the device is located in front of the user’s eyes. The combination can reduce the volume of the device, which can improve wearability, and a holographic method can reconstruct a virtual image with different focal lengths when the devices are in front of the user’s eyes.
Various types of transparent materials are available for making dielectric coatings, polarizers and other optical components. They can be deposited in different deposition processes, but they require good thickness uniformity and high optical homogeneity, as well as low scattering losses. They also need to be robust and not be sensitive to temperature changes.
Optical processing
Optical processing is a set of techniques that use light to manipulate and modify images. It includes linear (correlation and convolution) and nonlinear (logarithm transformation, thresholding, analog-to-digital conversion) operations.
During image processing, information in an object is analyzed and synthesized by a camera, hologram or other optical device. The analyzed image is then transferred to a computer for further analysis or modification. In this way, the manipulated images are transformed to another type of image and can be presented in a format suitable for displaying or printing.
For instance, a pair of AR glasses can display real-time navigation directions to someone driving a car or show information about drones to the pilot flying them. They could also provide remote experts with live documentation about a specific situation, as well as help large enterprises improve efficiency and quality control.
Most of these glasses include a combination of microdisplays and lenses that combine light from the micro displays with light from the real world, then project augmented information on the real scene to the human eye. For example, an AR headset consists of a beam-shaping lens, in-coupling prism and prescription lens that work together to image the real scene and augmented information in the eye.
However, even the most sophisticated augmented reality technologies cannot deliver a perfect blend of contextual information and the external environment. For this reason, a lot of effort is being put into developing seamless scalable prescriptions for these devices.
One possible solution to this problem is wavelength-selective metasurface lenses, which can reflect or scatter the light from a miniprojector that is placed in front of an AR headset or eyeglasses to provide context-specific information to a user’s eyes. The metasurfaces are thinner than a hair and can be incorporated into AR goggles that look and feel like regular glasses.
Besides delivering real-time contextual information, these optical processors can also be used to accelerate many of the most demanding AI applications that require a lot of computation power, while using far less energy than a silicon processor. For instance, they can execute optical correlation and convolution operations via APIs or Tensorflow interface to unlock new levels of AI and pattern recognition potential in a wide range of image-processing applications.
