Optical systems with holographic gratings
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Solution Overview
Problem
Existing optical systems in electronic devices, such as virtual and augmented reality headsets, face challenges in achieving desired optical performance while minimizing bulkiness and unsightliness of components.
Innovation Solution
The use of a waveguide system with a surface relief grating structure (SRG) that includes titanium dioxide nanoparticles, modulated in depth and size to enhance optical efficiency, and a blazed grating with encapsulation for efficient image propagation and coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional diffraction gratings are used in optical systems, then spectral separation can be achieved, but the system becomes sensitive to wavelength drift and requires precise alignment
Solution Approach 1:
The grating lobe is segmented into multiple discrete orders (e.g., -1, 0, +1) that are spatially separated. By selecting only the zeroth-order transmitted beam and blocking other orders, the system achieves wavelength-insensitive operation without requiring precise alignment tolerances
Solution Approach 2:
The harmful higher-order diffraction lobes are extracted and removed from the optical path using blocking elements. Only the desired zeroth-order beam is allowed to pass through, eliminating the sensitivity to wavelength drift while maintaining spectral separation functionality
2Measurement precision
If spectral separation is implemented in optical systems, then wavelength discrimination is achieved, but ghost images and reduced signal quality occur due to multiple diffraction orders
Solution Approach 1:
The patent converts the potentially harmful higher-order diffraction lobes into a beneficial selection criterion. By deliberately choosing to transmit only the zeroth-order beam and blocking all other orders, the system transforms the multi-order diffraction problem into a simple spatial filtering solution that eliminates ghost images while maintaining spectral separation
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 SRG structure improves optical efficiency by maximizing light coupling and expansion, ensuring uniform brightness across the field of view, while reducing component bulk and improving aesthetics.
Implementation Method 1
holographic grating having a first surface and a second surface opposite the first surface, each surface including a plurality of discrete diffraction orders
Implementation Method 2
an optical system including a light source, a sample, a detector, a first optical element positioned between the light source and the sample, a second optical element positioned between the sample and the detector
Data Source
Figure 1
Figure 2
Figure 3A~3C
AI summary
An electronic device may have a display system. The display system may include a waveguide, an input coupler, and a surface relief grating (SRG) structure. The SRG structure may be formed from a high-index material that includes titanium dioxide nanoparticles. To increase the refractive index of the high-index material, the ratio of the size of the nanoparticle core to the size of the capping layer may be increased. The high-index material may also include nanoparticles of different sizes to increase the packing density of the nanoparticles. The SRG structure may be depth modulated in a lateral direction to maximize efficiency. The SRG structure may include slanted ridges covered by an encapsulant. The SRG structure may include a blazed grating with ridges that are covered by a coating and encapsulated by an encapsulant.