Interference Coating for Eye-Tracking Lenses With NIR Filtering
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Solution Overview
Problem
Existing optical articles in augmented and virtual reality devices suffer from ghost images and reflections that degrade image quality and limit eye tracking performance, while conventional solutions to reduce infrared light exposure can compromise the effectiveness of eye tracking systems or lead to eye discomfort.
Innovation Solution
A multilayered interferential coating with specific refractive index layers and an absorbing dye is applied to optical articles, providing low reflection in the visible range, low reflection in the near-infrared range used by eye trackers, and high reflection in the near-infrared range from the environment, enhancing transparency and reducing harmful infrared exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a conventional antireflective coating is applied to reduce visible reflection, then visibility and cosmetic appearance are improved, but reflection in the near-infrared region increases causing ghost images and reducing eye tracking performance
Solution Approach 1:
The patent divides the spectrum into different segments and applies different optical properties to each segment. The multilayered coating structure segments the wavelength ranges, with specific layer combinations designed to transmit visible light while reflecting near-infrared wavelengths, thereby resolving the contradiction between visible light transmission and near-infrared reflection control
Solution Approach 2:
The patent uses composite multilayered structures combining materials with different refractive indices (such as TiO2, SiO2, Ta2O5, Nb2O5) to create interference effects that selectively transmit visible light and reflect near-infrared light. This composite approach allows simultaneous optimization of visible transmission and near-infrared reflection properties
2Reliability
If the optical article is made highly transparent to near-infrared wavelengths for eye tracking compatibility, then eye tracking performance is improved, but harmful near-infrared light from the environment reaches the eyes increasing power consumption and potential damage
Solution Approach 1:
The patent applies local quality by creating spatially varying optical properties across different wavelength ranges. The multilayered coating provides high transmission in the 800-900 nm eye tracking range while providing high reflection in the 900-2000 nm harmful range, allowing the same optical article to simultaneously satisfy eye tracking requirements and environmental protection needs
Solution Approach 2:
The patent changes the optical parameters (refractive index, layer thickness) of the coating layers to achieve wavelength-selective transmission and reflection. By precisely controlling layer thicknesses and refractive indices, the coating transitions from uniform transmission to selective transmission, enabling differentiation between eye tracking wavelengths and harmful environmental wavelengths
3Object-generated harmful factors
If multiple reflections are reduced in the visible region, then ghost images are minimized and visual comfort is improved, but the same approach increases power consumption by allowing more near-infrared light to reach the eye
Solution Approach 1:
The patent introduces dynamic wavelength selectivity into the optical coating system. The multilayered structure dynamically responds to different wavelengths by providing reflection for visible and harmful near-infrared wavelengths while transmitting eye tracking wavelengths, thereby reducing ghost images without increasing power consumption
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The coating maintains high transparency and reduces ghost images, supports effective eye tracking, and protects the eyes from excessive infrared light, while ensuring industrial feasibility and wearer comfort.
Implementation Method 1
The coating comprises a stack of at least one high refractive index layer (HI) and at least one low refractive index layer (LI), wherein said multilayered interferential coating has or imparts to the optical article: a mean reflection factor in the near infrared (NIR) region ranging from 900 nm to 2000 nm, noted RmNIR, that is higher than or equal to 12%
Implementation Method 2
The transparent substrate comprises at least one absorbing dye which absorbs in the near infrared region at a wavelength ranging from 900 to 2000 nm
Implementation Method 3
said multilayered interferential coating has or imparts to the optical article: a mean light reflection factor in the visible region, noted Rv, that is lower than or equal to 2.5%
Data Source
AI summary
The invention relates to an optical article comprising a transparent substrate with a front main face and with a rear main face, at least one of the main faces being coated with a multilayered interferential coating comprising a stack of at least one high refractive index layer (HI) having a refractive index higher than or equal to 1.55 and at least one low refractive index layer (LI) having a refractive index layer lower than 1.55, wherein said multilayered interferential coating has: ▪ mean light reflection factor in the visible region, noted R v, that is lower than or equal to 2.5% for at least an angle of incidence lower than or equal to 35°; ▪ a mean reflection factor for wavelengths ranging from 800 nm to 900 nm, noted R mET (800-900), that is lower than or equal to 1.5% at an angle of incidence lower than or equal to 20°, characterized in that: ⋅▪ said multilayered interferential coating has a mean reflection in the near infrared (NIR) region ranging from 900 nm to 2000 nm, noted RmNIR, that is higher than or equal to 11.5% at an angle of incidence lower than or equal to 20° and/or said transparent substrate comprises at least one absorbing dye which absorbs in the near infrared region at a wavelength ranging from 900 to 2000 nm.