Curved Diffractive Waveguide Gratings for Bright, Uniform Displays
Solution Overview
Problem
Existing diffractive optical waveguides face challenges in achieving high brightness and uniformity due to difficulties in designing cross-sectional shapes that improve light energy distribution and processing accuracy, leading to non-uniform light output.
Innovation Solution
The use of a diffractive optical waveguide with a cross-section of optical unit structures featuring smooth, curved contours allows for high-precision conformity and mass production, enabling better control over coupling-out efficiency and uniformity through curve equation design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional cross-sectional shapes (circular, rectangular, or rhombic) are used for optical unit structures, then the structure is easy to manufacture, but a bright line appears in the middle of the image and light energy distribution becomes non-uniform
Solution Approach 1:
The patent applies curvature by using a Gaussian bell curve function to define the cross-sectional shape of optical unit structures. This curved contour design replaces conventional straight-edged shapes and enables continuous variation of the diffusion coefficient across the structure, thereby achieving uniform light energy distribution and eliminating the bright line defect in the displayed image.
2Illumination intensity
If different cross-sectional shapes are proposed to improve brightness and uniformity, then light distribution may be improved, but processing accuracy deteriorates and the processed shape deviates from the designed shape
Solution Approach 1:
The patent employs a photoresist layer as a disposable sacrificial material during the manufacturing process. This photoresist is patterned to define the curved cross-sectional shapes of optical unit structures, then removed after transferring the pattern to the waveguide substrate. This approach enables precise curved shape formation through standard photolithography without requiring complex processing steps, thereby maintaining both shape conformity and manufacturing simplicity.
3Use of energy by moving object
If cross-sectional shapes are optimized for light distribution, then coupling-out efficiency may improve, but the complexity of designing and processing these shapes increases
Solution Approach 1:
The patent utilizes parameter changes by varying the diffusion coefficient continuously across the cross-section of optical unit structures according to a Gaussian bell curve distribution. This parameter variation is achieved through controlled modification of the photoresist layer thickness or refractive index during photolithography, allowing precise control of light diffusion without adding structural complexity. The approach enables high coupling-out efficiency while maintaining compatibility with standard manufacturing processes.
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 approach results in high brightness and uniformity in the display device, suppressing middle bright lines and enhancing light distribution across the field of view.
Implementation Method 1
Diffraction-based display technology has developed rapidly in recent years... the diffractive optical waveguide is provided with a coupling-in grating and a coupling-out grating on the waveguide substrate; the coupling-in grating couples incident light carrying image information into the waveguide substrate; the coupling-out grating propagates and expands the light carrying image information
Data Source
Figure 1~2
Figure 3A(a)~4
Figure 5A(a)~6(b)
AI summary
A diffractive optical waveguide is disclosed, in which a grating structure comprises a plurality of optical unit structures arranged in an array, a cross-section of an optical unit structure has a shape with two small ends and a large middle part, length L and maximum width W of the cross-section satisfy 0.2L≤W≤0.8L, and contour curves each are formed between an upper vertex and a left vertex, the upper vertex and a right vertex, a lower vertex and the left vertex, and the lower vertex and the right vertex, respectively. A display device comprising the same and a design and formation method for the same are also disclosed. The cross-section of the optical unit structure has a curved contour, with edges which are smooth and have very good processability. Also, the cross-section with curve contour of the optical unit structure has a very high degree of design freedom.