Dichroic Coatings Reduce Color Cross-Coupling in HMD Waveguides
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Mixed-reality computing devices face challenges in reducing color cross-coupling and forward-projection of holographic image light, leading to sharp edge defects and security concerns, particularly in head-mounted display (HMD) systems where conventional solutions like polarizing filters and bandpass filters increase bulk and weight.
Innovation Solution
The implementation of thin film dichroic coatings as reflectors on waveguide-based optical combiners in HMD devices, which act as narrowband reflectors for RGB colors over the angular range of the field of view, reducing cross-coupling and blocking forward-projected light while allowing real-world light to pass through.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional solutions like polarizing filters and bandpass filters are used to reduce color cross-coupling and block forward-projected light, then color uniformity and light security are improved, but device bulk and weight increase
Solution Approach 1:
The patent applies thin film dichroic coatings directly onto the waveguide surfaces to create wavelength-selective reflectors. These thin film coatings are significantly thinner and lighter than conventional bulk optical filters like polarizing filters or bandpass filters, while achieving the same function of reducing color cross-coupling and blocking forward-projected light. The thin film structure maintains color uniformity without adding substantial weight to the HMD device.
Solution Approach 2:
The patent uses composite material structures by combining dichroic coatings with waveguide substrates. The dichroic coatings consist of multiple thin layers with different refractive indices deposited onto the waveguide, creating a composite structure that provides wavelength-selective reflection. This composite approach achieves superior color uniformity and light security while minimizing weight compared to using separate conventional filter components.
2Reliability
If conventional filters are used to reduce color cross-coupling, then display quality is improved, but device bulk increases
Solution Approach 1:
The patent replaces bulk conventional filters with thin film dichroic coatings that are deposited directly onto the waveguide surfaces. These thin film coatings are extremely thin compared to conventional filters, significantly reducing the overall thickness of the optical combiner assembly while maintaining the same function of reducing color cross-coupling and improving display quality through enhanced color uniformity.
Solution Approach 2:
The patent merges the dichroic coating functionality directly into the waveguide structure by depositing the coatings onto the waveguide surfaces. This integration eliminates the need for separate conventional filter components, reducing device bulk and thickness while maintaining display quality. The coating is applied directly to the waveguide, combining the waveguide and filter functions into a single integrated component.
3Reliability
If dichroic coatings are applied as thin film reflectors, then color uniformity is improved without adding bulk, but manufacturing complexity increases
Solution Approach 1:
The patent replaces mechanical filter assemblies with optical coating processes. Instead of assembling separate conventional filters that require mechanical mounting and alignment, the dichroic coatings are applied directly to the waveguide surfaces using optical deposition techniques. This substitution of mechanical assembly with optical coating processes simplifies manufacturing while achieving superior color uniformity through precise wavelength-selective reflection.
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
This solution improves color uniformity and light security by minimizing sharp edge defects and reducing unwanted light projection, enhancing the overall display quality and user experience without adding bulk to the HMD device.
Implementation Method 1
The dichroic coatings for the reflectors are thin film interference coatings, implemented using alternating layers of materials having different refractive indices, that reflect wavelengths in a predetermined range while transmitting other ranges of wavelengths over a specified angular range.
Implementation Method 2
Reflectors comprising thin film dichroic coatings are located on various components of a waveguide-based optical combiner... The dichroic coatings implement narrowband reflectors for each of one or more colors of an RGB (red, green, blue) color model
Implementation Method 3
alternating layers of materials having different refractive indices, that reflect wavelengths in a predetermined range while transmitting other ranges of wavelengths
Data Source
AI summary
Reflectors comprising thin film dichroic coatings are located on various components of a waveguide-based optical combiner in a see-through display of a head-mounted display (HMD) device to reduce color cross-coupling in holographic images and reflect forward-projected holographic image light back to a user's eye. The dichroic coatings implement narrowband reflectors for each of one or more colors of an RGB (red, green, blue) color model over the angular range associated with the field of view (FOV) of the virtual portion of the see-through display. Utilization of the dichroic coatings can improve virtual display uniformity and lessen sharp edge defects by reducing cross-coupling and may also improve light security by reducing the forward-projected holographic image light that escapes from the HMD device.