Ophthalmic Lens Interferential Coatings for NIR Reflection Control
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Solution Overview
Problem
Existing eye tracking devices using deep red and NIR light sources suffer from multiple reflections on ophthalmic lenses, leading to noise for the detector and inaccurate pupil location, with prior art not addressing reflectance at lower incidence angles or directional differences in reflectance on optical surfaces.
Innovation Solution
An optical device with highly efficient antireflective coatings on both the front and rear faces of ophthalmic lenses, reducing reflections in the deep red and NIR range at angles up to 45°, using alternating layers of low and high refractive index materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If deep red and NIR light sources are used for eye tracking, then measurement accuracy and reliability are improved, but multiple reflections on ophthalmic lenses generate noise for the detector
Solution Approach 1:
The patent applies anti-reflective coatings that convert the harmful reflection effect into a beneficial low-reflectance property. The coatings are specifically designed to reduce reflectance in the deep red and NIR wavelength ranges, transforming the problematic reflections into minimal interference, thereby enabling accurate eye tracking measurements without noise contamination.
Solution Approach 2:
The patent changes the optical parameters of the lens surfaces by applying multi-layer anti-reflective coatings with specific refractive indices and thicknesses. These parameter changes optimize the reflectance characteristics across different wavelengths (visible, deep red, and NIR ranges) and angles of incidence, allowing the system to maintain measurement accuracy while minimizing harmful reflections.
2Reliability
If prior art antireflective coatings are used at high incidence angles (35° and 75°), then NIR reflectance is reduced at those specific angles, but performances at lower incidence angles remain unknown and directional differences are not addressed
Solution Approach 1:
The patent designs anti-reflective coatings with multi-functional characteristics that effectively reduce reflectance across a broad range of incidence angles (0° to 45°) and across multiple wavelength ranges (visible, deep red, and NIR). This universal design eliminates the need for angle-specific coatings, providing consistent performance regardless of the light source direction relative to the lens surface.
Solution Approach 2:
The patent optimizes coating parameters including the number of layers, refractive indices, and thicknesses to achieve broad-angle effectiveness. By carefully selecting and adjusting these parameters, the coatings maintain low reflectance across the entire 0°-45° incidence angle range, addressing the directional differences that prior art failed to resolve.
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
Minimizes noise reflections, enabling accurate and reliable eye feature measurements by limiting light interference, enhancing visual comfort and aesthetics.
Implementation Method 1
The mean reflectance of the rear interferential coating is lower than or equal to 2.5% for wavelengths ranging from 700 nm to 2500 nm, at an angle of incidence lower than or equal to 45°
Implementation Method 2
The front interferential coating and the rear interferential coating each comprise at least four layers, each layer having a refractive index either lower than the refractive index of all the adjacent layers, or higher than the refractive index of all the adjacent layers
Data Source
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AI summary
This optical device comprises an ophthalmic lens and a light source emitting in the deep red and near infrared region. The ophthalmic lens has front and rear faces coated with interferential coatings. The mean reflectance of the rear interferential coating is lower than or equal to 2.5% for wavelengths ranging from 700 nm to a predetermined maximum wavelength lower than or equal to 2500 nm, at an angle of incidence lower than or equal to 45°. At an angle of incidence lower than or equal to 45°, for wavelengths ranging from 700 nm to the predetermined maximum wavelength, the mean reflectance of the front interferential coating is either lower than or equal to 2.5% if the source is directed towards the front face of the ophthalmic lens, or higher than or equal to 25% if the source is directed towards the rear face of the ophthalmic lens.