Technologies for All Photochromic Lenses in AR Glasses

This article mainly provides technical knowledge and summarizes the technologies of all photochromic lenses in AR glasses.

Photochromic Working Principle

Photochromic lenses are based on the photochemical reactions of inorganic compounds or organic molecules. These materials undergo reversible structural changes when exposed to UV light, which leads to increased absorption of visible light and causes the lenses to darken. When the UV light source is removed, the molecular structure reverts, and the lenses gradually return to a transparent state.

Materials

Typical materials include inorganic compounds such as AgCl and AgBr, as well as organic compounds like indoline oxides or spirochromes. Under UV irradiation, Ag+ ions are reduced to metallic silver particles, forming centers for color change.

Disadvantages

There is a need to balance the color-changing speed, color uniformity, durability, and light transmittance of the materials. Additionally, ensuring the stability of lens performance under varying temperature conditions is a significant challenge.

Principle of Electrochromism

Electrochromic technology relies on reversible redox reactions, adjusting the transfer of ions or charges within the lens by applying an external voltage. This process alters the optical properties of the lens materials (such as tungsten oxide and nickel oxide), changing the light transmission or color of the lenses. Electrochromic lenses typically consist of a multilayer structure, including a transparent conductive electrode, an active coloring layer, an ion-conducting layer, and a counter electrode layer.

Materials and Structure

Typical electrochromic materials include tungsten oxide, vanadium oxide, and nickel oxide. These materials change their light absorption characteristics through oxidation or reduction reactions when a voltage is applied. The structure of electrochromic lenses is generally a multilayer composite, with a typical stack structure of transparent conductive oxide/electrochromic layer/electrolyte layer/counter electrode layer. This design allows the lenses to effectively adjust light in various environments.

Advantages and Disadvantages

The main advantage of electrochromic lenses is their ability to provide precise control over brightness and color, making them suitable for a variety of environments and applications. However, key issues that need further research and improvement include the response time, durability (for instance, the electrochromic function of my AR glasses suddenly failed), and performance consistency at different temperatures.

Thermochromic Technology

Working Principle

Thermochromic technology utilizes the sensitivity of materials to temperature changes, adjusting optical properties through temperature-induced chemical or physical changes. Typical thermochromic materials undergo phase transitions at specific temperatures, resulting in significant changes in their optical transmittance or reflectance.

Materials

Main materials include liquid crystal polymers and vanadium dioxide (VO2). VO2 undergoes a transition from a semiconductor to a metal at a critical temperature (approximately 68°C), significantly altering its reflectance of infrared light. Although thermochromic materials are suitable for automatic adjustments within specific temperature ranges, their application in AR glasses is relatively limited due to the slow and difficult-to-control nature of temperature changes.

Liquid Crystal Technology

Working Principle

Liquid crystal technology is based on the ability of liquid crystal materials to modulate light under the influence of an electric field. By controlling the voltage applied to the liquid crystal molecules, the alignment of these molecules can be altered, thus regulating the light intensity passing through the lens. This technology is similar to the working principle of liquid crystal displays (LCD), but focuses more on dimming and color-changing applications.

Structure

Liquid crystal lenses typically consist of two transparent electrode layers with liquid crystal material filled in between. When the voltage changes, the arrangement of the liquid crystal molecules alters, affecting the polarization state of the light and consequently changing the lens's transmittance.

Advantages and Disadvantages

Liquid crystal lenses offer advantages such as fast response times, wide dimming ranges, and low energy consumption. However, they also face challenges, requiring precise control of the orientation and uniformity of the liquid crystal molecules, as well as ensuring stability in both low and high-temperature environments.

The following technologies are cutting-edge

Full Spectrum Smart Glass

Technology Integration

Full spectrum smart glass technology combines electrochromic, photochromic, and liquid crystal technologies to enable precise adjustments across the visible and infrared spectrum. This technology is typically achieved through multilayer composite materials and nanoscale film structures, enhancing optical performance and adaptability.

Nanotechnology

The use of nanoparticles or nanomaterials can significantly improve the optical performance of the lenses, ensuring quick response times and efficient color changes while effectively reducing energy consumption. This feature allows full spectrum smart glass to excel in various environments.

Future Applications

Full spectrum smart glass is particularly suitable for high-end AR glasses that require dynamic adjustments. For instance, in brightly lit outdoor environments, this smart glass can provide the best visual experience while ensuring that displayed content remains clear and visible, offering broad prospects for future AR applications.

Electrochromic Liquid Crystal Technology Principle

Adjustment Functionality

Electrochromic liquid crystal lenses can adjust not only light transmission but also the focal length of the lenses. By applying different voltages, the refractive index of the liquid crystal material changes, allowing for dynamic focusing and adjustments for near and far vision. This functionality is especially important for various AR applications.

Materials and Design

Using high birefringence liquid crystal materials combined with complex electrode designs allows for focal adjustments ranging from micrometers to millimeters. This precise adjustment capability is crucial for applications that need to accommodate both close reading and long-distance viewing.

Future Outlook

Future electrochromic liquid crystal lenses will incorporate light-sensitive components and processing chips to achieve automated vision adjustments and personalized optimization. This advancement will greatly enhance user experience, making AR glasses more intelligent and practical.