Diffractive Light Guide Layout for Higher Pupil Fill in Displays
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Solution Overview
Problem
The existing optical systems in image display devices, such as head-mounted displays, suffer from a decrease in image quality due to a low filling factor of the pupil of image light rays in the field of view region, leading to reduced image quality.
Innovation Solution
An optical system is designed with a light guide that includes an incident region, an auxiliary extension region, and an exit extension region with a diffraction structure. This system divides the image light ray into multiple beams, allowing them to emerge at different angles, thereby improving the filling factor of the pupil in the field of view region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional light guide is used, then the structure is simple, but the filling factor of the pupil of image light rays decreases
Solution Approach 1:
The light guide is divided into three distinct functional regions: an incident region for light entry, an auxiliary extension region for beam expansion in a first direction, and an exit extension region for beam expansion in a second direction perpendicular to the first. This segmentation allows each region to optimize its function, thereby improving the filling factor of the pupil without significantly increasing overall structural complexity
Solution Approach 2:
The patent introduces dimensional expansion by adding the auxiliary extension region that expands the beam in a first direction, and then the exit extension region that expands in a second direction perpendicular to the first. This two-dimensional expansion approach increases the filling factor of the pupil by utilizing multiple spatial dimensions rather than simply enlarging the incident region in a single direction
2Manufacturing precision
If the incident region size is increased, then the filling factor of the pupil improves, but the device size increases
Solution Approach 1:
Instead of enlarging the incident region, the patent segments the light guide into multiple functional regions that collectively achieve the desired pupil filling. The auxiliary extension region and exit extension region work together to expand the beam spatially, improving the filling factor without requiring a larger incident region
Solution Approach 2:
The patent utilizes dimensional expansion by introducing beam expansion in both a first direction (auxiliary extension region) and a second perpendicular direction (exit extension region). This multi-directional expansion achieves improved pupil filling without increasing the incident region size, as the expansion occurs in subsequent regions along the light propagation path
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 optical system enhances the filling factor of the pupil of image light rays in the field of view region, leading to improved image quality and reduced size of the incident region.
Implementation Method 1
an exit extension region formed at the body and including a diffraction structure dividing an image light ray propagating in a first propagation direction intersecting a thickness direction of the body
Data Source
AI summary
The optical system includes a light guide including: an incident region allowing an image light ray to enter a body; and an exit extension region including a diffraction structure dividing an image light ray into image light rays and allowing them to emerge from the body. The exit extension region divides the image light ray into first to third image light rays. The first and third image light rays emerge from the exit extension region at different angles to propagate inside the body. The exit extension region includes an overlap part on which the first image light ray and the third image light ray are incident under a condition where they partially overlap with each other. A difference between optical paths of the first image light ray and the third image light ray incident on the overlap part is longer than a coherence length of the image light ray.