3D Lens Back Reflectance Reduction via Absorbing Thin Films
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Solution Overview
Problem
Current 3D color separation glasses with optical interference filters suffer from significant back reflectance, causing visual distractions due to ambient light reflections, especially in high-intensity projection systems like 6P cinema, where increased light sources exacerbate the issue of unwanted reflections of the viewer's face and environment.
Innovation Solution
A 3D lens with reduced back reflectance is designed by incorporating a stack of non-absorbing thin film layers with one or more absorbing thin film layers, optimizing the thickness and positioning of these layers to achieve substantial transmittance for desired wavelength bands while minimizing back reflectance, thereby reducing visual distractions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If optical interference filters with non-absorbing thin film layers are used to maximize transmittance in passbands, then the transmittance of desired wavelength bands is improved, but back reflectance of ambient light increases causing visual distraction
Solution Approach 1:
The patent changes the optical parameters of the thin film layers by introducing absorbing materials with specific extinction coefficients and refractive indices. The absorbing layers are positioned at specific thicknesses within the multilayer stack to modify the reflectance and transmittance characteristics, thereby reducing back reflectance while maintaining acceptable transmittance in passbands.
Solution Approach 2:
The patent employs composite thin film structures combining both absorbing and non-absorbing materials in a multilayer stack. This composite approach allows the system to simultaneously achieve wavelength-selective filtering through interference effects while using the absorbing layers to reduce unwanted back reflectance of ambient light.
2Object-generated harmful factors
If absorbing thin film layers are incorporated to reduce back reflectance, then visual distraction from ambient light reflections is reduced, but transmittance of desired wavelength bands decreases
Solution Approach 1:
The patent applies local quality by positioning absorbing layers at specific locations within the multilayer thin film stack, rather than uniformly distributing absorption throughout. The absorbing layers are placed at strategic positions where they can most effectively reduce back reflectance while minimizing their impact on passband transmittance, exploiting the local optical field distribution.
Solution Approach 2:
The patent carefully controls the parameters of the absorbing layers, including their thickness, extinction coefficient, and refractive index, to optimize the trade-off between reducing back reflectance and maintaining passband transmittance. By adjusting these parameters, the design achieves acceptable levels of both performance metrics.
3Illumination intensity
If high-intensity projection systems like 6P cinema are used to improve image brightness, then the brightness of displayed images is improved, but back reflectance and visual distraction are exacerbated
Solution Approach 1:
The patent applies preliminary anti-action by incorporating absorbing layers into the optical filter stack before the high-intensity projection system is used. This pre-configured absorption capability is designed to counteract the increased back reflectance that will occur when high-intensity light sources are employed, thereby mitigating visual distraction even in bright viewing conditions.
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 solution significantly reduces visual distractions by lowering the relative change in transmittance to luminance back reflectance ratio to less than 0.5, maintaining high transmittance for desired images while substantially blocking unwanted images, even in high-intensity projection environments.
Implementation Method 1
optical interference filters are usually employed to achieve the colour separation by having substantial transmitting and reflecting bands
Implementation Method 2
incorporating one or more substantially absorbing thin film layers
Implementation Method 3
The undesired bands of light are blocked primarily by reflectance
Implementation Method 4
The thin film materials are arranged with adjacent layers have alternating high and low refractive indices
Data Source
AI summary
An optical interference coating with reduced back reflectance for 3D glasses based on colour separation has a substantial transmittance at one or more passbands over the visible spectral range in order to view the desired left (right) eye image and a substantial reflectance and absorption at one or more different blocking bands over the visible spectral range in order to block the undesired right (left) eye image while simultaneously reducing the back reflectance of visible light towards the viewer's eye. The thicknesses and materials are chosen such that the left eye reduced back reflectance 3D coated lens transmits the desired left eye image and blocks the right eye image while the right eye reduced back reflectance 3D coated lens transmits the desired right eye image and blocks the left eye image so that a 3D image can be viewed whilst substantially reducing distracting back reflections from the coated lenses.