Optical Expander Device for Wide Color Image Display
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Solution Overview
Problem
Existing optical expander devices for virtual display devices face challenges in displaying wide color images due to leakage of red and blue light at corner points, leading to non-uniform brightness and color distortion, as they fail to confine light by total internal reflection, especially when expanding the angular width of the image.
Innovation Solution
The optical expander device employs a waveguide plate with two different routes for red and blue light, using spectral filters to prevent leakage and ensure total internal reflection, allowing both colors to be confined and combined for uniform image display, with grating periods and orientations optimized for each color to prevent incomplete images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single expander element is used to expand the light beam in both transverse directions, then the device structure is simple, but red or blue light at corner points fails to fulfill total internal reflection, causing color loss
Solution Approach 1:
The single expander element is divided into two separate expander elements (first expander element and second expander element). Each expander element is optimized for specific light propagation directions, enabling red and blue light at corner points to fulfill total internal reflection conditions while maintaining device functionality.
Solution Approach 2:
Different expander elements are designed with different grating periods and orientations tailored to specific light propagation requirements. The first expander element has grating vectors optimized for certain directions, while the second expander element has grating vectors optimized for other directions, ensuring each region of the optical path handles appropriate wavelengths effectively.
2Adaptability or versatility
If the angular width of the virtual image is expanded, then the field of view is increased, but red or blue light leaks at corner points, causing non-uniform brightness and color distortion
Solution Approach 1:
The optical path is segmented into two distinct routes, each handled by dedicated expander elements. This segmentation allows independent optimization of each route for specific wavelength ranges, preventing color leakage and maintaining uniformity even when the angular width is expanded.
Solution Approach 2:
The grating periods and orientations of the expander elements are specifically adjusted to match the expanded angular requirements. By changing these parameters, the device maintains proper total internal reflection conditions across the expanded field of view, preventing color distortion at corner points.
3Manufacturing precision
If the grating period is optimized for one color, then that color is properly confined, but other colors may leak, causing incomplete image display
Solution Approach 1:
The grating structure is segmented into multiple expander elements, each with grating periods optimized for specific color ranges. This allows red light to be properly confined by one expander element while blue light is handled by another, enabling complete multi-color image display without leakage.
Solution Approach 2:
Each expander element is designed with locally optimized grating parameters (period and orientation) suited to the specific wavelength range it handles. This local optimization ensures that each color component is properly confined while maintaining overall system versatility for displaying complete color images.
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 solution ensures uniform brightness and complete color display across the expanded image, preventing leakage and distortion, thereby enhancing the visual quality of wide color images in virtual display devices.
Implementation Method 1
an in-coupling element (DOE1) to form first guided light (B1a) and second guided light (B1b) by diffracting input light (IN1)
Implementation Method 2
a first expander element (DOE2a) to form third guided light (B2a) by diffracting the first guided light (B1a)
Implementation Method 3
a second expander element (DOE2b) to form fourth guided light (B2b) by diffracting the second guided light (B1b)
Implementation Method 4
an out-coupling element (DOE3) to form first output light (OB3a) by diffracting the third guided light (B2a), and to form second output light (OB3b) by diffracting the fourth guided light (B2b)
Implementation Method 5
The in-coupling element (DOE1) has a first grating period (d1a) for forming the first guided light (B1a), and wherein the in-coupling element (DOE1) has a second different grating period (d1b) for forming the second guided light (B1b)
Data Source
AI summary
An optical device (EPE1) comprises a waveguide plate (SUB1) comprising an in-coupling element (DOE1), a first expander element (DOE2a), a second expander element (DOE2b) and an out-coupling element (DOE3), wherein the out-coupling element (DOE3) is arranged to form combined output light (OUT1) by combining the first output light (OB3a) with the second output light (OB3b), wherein the in-coupling element (DOE1) has a first grating period (d1a) for forming the first guided light (B1a), and wherein the in-coupling element (DOE1) has a second different grating period (d1b) for forming the second guided light (B1b), wherein the optical device (EPE1) comprises a first spectral filter region (C2a) to prevent coupling of red light from the in-coupling element (DOE1) to the out-coupling element (DOE3) via the first expander element (DOE2a). The optical device (EPE1) can display a color image with an extended field of view.