Diffractive Optical Grating for Narrowband AR Reflection Control
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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, particularly in compact and lightweight designs.
Innovation Solution
A diffractive optical element with grating components and optical waveguides that periodically change in specific dimensions, allowing for narrowband response and adjustment of reflection at abnormal angles, enhancing diffraction efficiency and light transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a semi-reflective semi-transparent mirror is used as the optical combiner, then the structure is simple and easy to manufacture, but it cannot achieve both narrowband response and adjustment on reflection at abnormal angle, resulting in low transmittance of ambient light and low reflectivity of projected light in compact volume
Solution Approach 1:
The patent applies parameter changes by modifying the optical path difference and phase difference parameters of the interferometric structure. By adjusting the thickness of the transparent plate and the angle of incidence, the system achieves both narrowband spectral response and controllable reflection at abnormal angles, resolving the contradiction between manufacturing simplicity and functional versatility
Solution Approach 2:
The patent employs a composite structure combining a transparent plate with interferometric elements that have specific refractive index properties. This composite design enables simultaneous achievement of narrowband response through interference effects and adjustable reflection characteristics, while maintaining a relatively simple manufacturing process
2Adaptability or versatility
If a polarization beam splitter is used as the optical combiner, then reflection at abnormal angle can be adjusted, but it cannot achieve narrowband response, resulting in low transmittance of ambient light in compact volume
Solution Approach 1:
The patent utilizes parameter changes by controlling the optical path difference and phase difference in the interferometric structure. By adjusting the thickness of the transparent plate and the angle of incidence, the system achieves both narrowband spectral response and controllable reflection at abnormal angles, resolving the contradiction between manufacturing simplicity and functional versatility
3Volume of moving object
If a waveguide lens is used as the optical combiner, then compact volume can be achieved, but it cannot implement both narrowband response and adjustment on reflection at abnormal angle, resulting in low transmittance of ambient light and low reflectivity of projected light
Solution Approach 1:
The patent applies parameter changes by modifying the optical path difference and phase difference parameters of the interferometric structure. By adjusting the thickness of the transparent plate and the angle of incidence, the system achieves both narrowband spectral response and controllable reflection at abnormal angles, resolving the contradiction between manufacturing simplicity and functional versatility
Solution Approach 2:
The patent introduces an additional dimensional parameter by using a transparent plate with specific thickness to create optical path difference. This dimensional approach enables the system to achieve narrowband response and reflection adjustment capabilities while maintaining a compact overall structure, effectively resolving the volume versus functionality contradiction
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
Enables efficient diffraction imaging in a compact volume with high transmittance of ambient light and reflectivity of projected light, suitable for AR and VR devices.
Implementation Method 1
Light in a specific band may be selected by the M optical waveguides that periodically change in the second dimension
Implementation Method 2
CN 105 899 983 A, discloses guided mode resonance devices and their application in optical sensors, optical filters and security devices
Implementation Method 3
The optical combiner needs to transmit actual ambient light, and also needs to reflect projected light of the projection system to human eyes
Implementation Method 4
The optical combiner is a core optical component for virtual-real image fusion, and is also one of key optical components that determine user experience of the AR system
Data Source
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AI summary
A diffractive optical element and a terminal device are disclosed. The diffractive optical element is applicable to an AR device and a head-up display HUD device in the augmented reality AR field; a VR device in the virtual reality VR field; or a filter, an optical splitter, and a spectrum detection device. The 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. Light in a specific band at a specific angle can be selected by using the M optical waveguides that periodically change in the second dimension, to implement both a narrowband response and adjustment on reflection at an abnormal angle.