Light Guide Plate Intermediate Diffraction Grating Brightness
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Solution Overview
Problem
Light guide plates with corrugated type diffraction gratings suffer from uneven brightness, particularly at pixel positions in the corners of the image, due to the spreading of light beams, leading to reduced visualized brightness and visibility issues in augmented reality image display devices.
Innovation Solution
Incorporating an intermediate diffraction grating between the incident and exit diffraction gratings, with a periodic linear corrugated pattern, to shift and reflect light beams, ensuring they align with the exit circle and improve brightness by adjusting the angle and pitch of the intermediate grating to correct position gaps and enhance diffraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple light guide plates are stacked to achieve wide viewing angle, then viewing angle is improved, but device complexity and weight increase
Solution Approach 1:
The patent segments the diffraction grating structure into multiple functional zones: incident diffraction grating, intermediate diffraction grating, and exit diffraction grating. Each zone performs a specific function in controlling light propagation, replacing the need for multiple stacked light guide plates while achieving similar optical effects.
Solution Approach 2:
The patent introduces an intermediate diffraction grating positioned between the incident and exit gratings, adding a dimensional element to the light control path. This intermediate structure enables precise control of light beams in the thickness direction of the light guide plate, achieving wide viewing angle without stacking multiple plates.
2Adaptability or versatility
If corrugated type diffraction grating is used, then wide viewing angle is achieved, but uneven brightness occurs particularly at corner regions
Solution Approach 1:
The intermediate diffraction grating acts as a mediator between the incident and exit diffraction gratings. It controls and redirects light beams that would otherwise spread unevenly, ensuring uniform brightness distribution across the exit surface including corner regions while maintaining the wide viewing angle capability.
Solution Approach 2:
The patent applies different diffraction grating structures at different locations: the incident diffraction grating at the input side, the exit diffraction grating at the output side, and the intermediate diffraction grating positioned specifically to control light paths to corner regions. Each location has optimized grating characteristics to address local brightness requirements.
3Quantity of substance
If light beams are replicated and spread spatially, then image information is distributed across multiple beams, but brightness at corner pixel positions decreases
Solution Approach 1:
The intermediate diffraction grating provides feedback control for light beam distribution. By analyzing the propagation paths of replicated beams, the intermediate grating redirects beams toward corner regions that would otherwise receive insufficient light, balancing the brightness distribution across all pixel positions.
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 configuration improves the brightness and uniformity of the image perceived by the user, reducing uneven brightness and enhancing visibility across the entire image display area, including corner regions.
Implementation Method 1
an incident diffraction grating which diffracts incident imaging light
Implementation Method 2
the wavenumber vector of the light is further converted to a wavenumber vector K1 that allows for total reflection of the light internally in the light guide plate
Implementation Method 3
an intermediate diffraction grating existing in optical paths from the incident diffraction grating to the exit diffraction grating
Implementation Method 4
the intermediate diffraction grating has a first region on one side of the imaginary line and a second region on another side of the imaginary line and reflects at least a subset of the imaging light at least once in each of the first region and the second region
Implementation Method 5
an exit diffraction grating through which the imaging light goes out
Implementation Method 6
a wavenumber vector K of light emitted from the projector becomes K0 when the light is refracted upon entering the light guide plate according to Snell's law
Data Source
AI summary
To improve brightness of an image to be perceived by a user and enhance visibility there is provided a light guide plate including an incident diffraction grating which diffracts incident imaging light, an exit diffraction grating through which the imaging light goes out, and an intermediate diffraction grating existing in optical paths from the incident diffraction grating to the exit diffraction grating. In this light guide plate, a periodic linear corrugated pattern is formed as the incident diffraction grating, and when an imaginary line is established that passes through an incident point of imaging light onto the incident diffraction grating and is parallel with a periodic direction of the corrugated pattern, the intermediate diffraction grating has a first region on one side of the imaginary line and a second region on another side of the imaginary line.