Diffractive Optical Element for Narrowband AR Angle Reflection
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Solution Overview
Problem
Existing AR systems face challenges in implementing both narrowband response and adjustment of reflection at abnormal angles, which are crucial for efficient virtual-real image fusion, due to the limitations of current optical combiners like semi-reflective semi-transparent mirrors and polarization beam splitters.
Innovation Solution
A diffractive optical element with grating components and optical waveguides that periodically change in a specific dimension, allowing for narrowband response and adjustment of reflection at abnormal angles, enhancing diffraction efficiency and light transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a semi-reflective semi-transparent mirror is used as the optical combiner, then the device structure is simple, but it cannot implement both narrowband response and adjustment on reflection at an abnormal angle
Solution Approach 1:
The patent changes the optical parameters of the combiner by introducing a diffractive optical element with specific grating structures. The grating period, depth, and orientation are optimized to achieve wavelength-selective (narrowband) reflection and abnormal angle reflection adjustment, replacing the broadband, fixed-angle reflection of traditional mirrors
Solution Approach 2:
The patent employs a composite optical system combining a waveguide layer with diffractive grating structures. This composite structure integrates the light-guiding function with the wavelength-selective reflection function, enabling both narrowband response and abnormal angle control in a single component
2Volume of moving object
If a compact AR system is designed, then the volume is reduced, but the transmittance of ambient light and reflectivity of projected light cannot be simultaneously optimized
Solution Approach 1:
The patent utilizes the diffractive grating structure's ability to control light in the angular domain (abnormal angle reflection) and wavelength domain (narrowband response). By operating in these additional optical dimensions rather than relying on simple geometric reflection, the system achieves high optical performance in a compact form factor
Solution Approach 2:
The grating parameters (period, depth, orientation) are specifically optimized to achieve wavelength-selective reflection with high efficiency. This parameter optimization enables the compact combiner to maintain high reflectivity for projected light while preserving high transmittance for ambient light
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 diffractive optical element enables efficient diffraction imaging in a compact volume with high transmittance of ambient light and reflectivity of projected light, facilitating miniaturization and improved user experience in AR and VR devices.
Implementation Method 1
Light in a specific band may be selected based on the diffractive optical element by using the M optical waveguides that periodically change in the second dimension
Implementation Method 2
A grating structure is formed by using the grating components periodically distributed in the first dimension
Implementation Method 3
The N optical waveguides include M optical waveguides that periodically change in a second dimension
Implementation Method 4
A grating structure is formed by using the grating components periodically distributed in the first dimension, so that a function of adjusting reflection at an abnormal angle is implemented
Implementation Method 5
Light in a specific band may be selected based on the diffractive optical element by using the M optical waveguides that periodically change in the second dimension, that is, a narrowband response is implemented
Data Source
AI summary
Example diffractive optical elements and terminal devices are disclosed. One example diffractive optical element includes grating components periodically distributed in a first dimension. The grating component includes N optical waveguides. The N optical waveguides include M optical waveguides that periodically change in a second dimension. At least two of the M optical waveguides that periodically change in the second dimension have different structures. An included angle between the second dimension and the first dimension is greater than 0 degrees and less than 180 degrees. N is an integer greater than 1. M is an integer greater than 1 and not greater than N.