Optical Waveguide Reflection Grating Coupling Efficiency
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Solution Overview
Problem
Optical waveguide devices face challenges in coupling efficiency due to the large coupling-in region size and thin lens thickness, leading to lower brightness and uniformity in dense field of view applications.
Innovation Solution
The optical waveguide device incorporates a waveguide substrate with a coupling-in grating, a coupling-out grating, and a reflection grating. The reflection grating utilizes the zero-order diffraction light to improve coupling-in efficiency and enhance the brightness and uniformity of the dense field of view.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the coupling-in region size is increased to adapt to the aperture of the light-emitting device, then the light-emitting device can be properly coupled into the waveguide, but the lens thickness must be reduced to maintain lightness and thinness, causing the +1 order diffraction light to hit the coupling-in grating and substrate multiple times, reducing coupling efficiency
Solution Approach 1:
The patent converts the harmful multiple reflections of +1 order diffraction light into a beneficial effect by introducing a reflecting region with a reflection grating. This reflection grating redirects the +1 order light that would otherwise be lost back into the waveguide, transforming the harmful multiple reflections into useful light propagation paths that improve overall coupling efficiency.
Solution Approach 2:
The patent introduces a reflecting region as an intermediary element between the coupling-in grating and the substrate. This reflecting region acts as a mediator to redirect light paths, preventing direct harmful reflections while enabling controlled light redirection through the reflection grating, thus improving coupling efficiency without changing the coupling-in region size.
2Length of moving object
If the lens thickness is reduced to meet lightness and thinness requirements, then the device becomes lighter and thinner, but the +1 order diffraction light hits the coupling-in grating and substrate multiple times, resulting in lower coupling efficiency in dense field of view
Solution Approach 1:
The patent converts the harmful multiple reflections caused by thin lens into a beneficial effect. The reflecting region with reflection grating captures the +1 order light that would otherwise be lost due to multiple reflections and redirects it back into the waveguide, transforming the harmful reflection pattern into useful light propagation that improves coupling efficiency in dense field of view.
Solution Approach 2:
The patent addresses the thin lens problem by adding a new dimensional element - the reflecting region on the substrate side. This creates a new optical path dimension that compensates for the reduced lens thickness, enabling light control through reflection rather than solely through refraction in the thick lens.
3Device complexity
If the zero-order diffraction light is allowed to propagate away from the coupling-out grating, then the coupling-in process is simplified, but a lot of energy is wasted and the dense field of view darkens
Solution Approach 1:
The patent merges the functions of the coupling-in process and zero-order light management by integrating the reflecting region into the existing waveguide structure. The reflection grating in the reflecting region works together with the coupling-in grating to redirect zero-order light back into the waveguide, combining light coupling and light redirection functions into a unified system that improves energy utilization without significantly increasing complexity.
Solution Approach 2:
The reflecting region serves multiple functions: it reflects +1 order diffraction light back into the waveguide, redirects zero-order diffraction light away from the coupling-out grating back into the waveguide, and maintains the overall waveguide structure. This multi-functional element improves energy utilization across different light orders without requiring separate systems for each function.
4Adaptability or versatility
If the coupling-in region size is increased, then the light-emitting device aperture is accommodated, but the uniformity of the dense field of view deteriorates due to multiple reflections and energy waste
Solution Approach 1:
The patent converts the harmful multiple reflections that cause non-uniformity in the dense field of view into a beneficial effect. By introducing the reflecting region with reflection grating, the previously harmful reflections are redirected into controlled paths that contribute to uniform light distribution, improving both aperture accommodation and field of view uniformity simultaneously.
Solution Approach 2:
The patent applies local quality improvement by introducing the reflecting region specifically in areas where multiple reflections occur. The reflection grating is positioned to address local reflection problems in the coupling-in region, creating localized light redirection that improves overall uniformity without requiring global changes to the entire waveguide structure.
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 proposed solution increases the coupling-out brightness and improves the uniformity of the dense field of view by effectively utilizing the energy of the zero-order diffraction light with the reflection grating.
Implementation Method 1
a coupling-in grating disposed in the coupling-in region of the first surface of the waveguide substrate and configured to receive input light within a predetermined field of view, diffract at least a portion of the input light to form positive first-order diffraction light and zero-order diffraction light
Implementation Method 2
couple the light into the waveguide substrate, such that the light can propagate within the waveguide substrate through total reflection
Implementation Method 3
a reflection grating disposed in the reflection region of the second surface and configured such that a portion of the zero-order diffraction light forms positive first-order reflection light through diffraction
Implementation Method 4
a coupling-out grating disposed in the coupling-out region of the waveguide substrate and configured to couple at least a portion of the light propagating into the coupling-out grating out of the waveguide substrate through diffraction
Data Source
AI summary
An optical waveguide device and a display device are provided. The optical waveguide device includes a waveguide substrate having a coupling-out region and first and second surfaces with coupling-in and reflection regions, a coupling-in grating disposed in the coupling-in region to diffract input light to form positive first-order and zero-order diffraction light, a coupling-out grating disposed and a reflection grating disposed in the reflection region such that portion of the zero-order diffraction light forms positive first-order reflection light through diffraction. A light spot of the zero-order diffraction light first projected onto the second surface has a first profile at least partially located in the reflection region. A projection of the reflection region on the first surface partially overlaps with the coupling-in region, and a ratio of area of an overlapping portion to that of the coupling-in region is less than or equal to 40%.