Light Guide Device for Virtual Image Display
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing light guide devices for head-mounted displays suffer from color unevenness due to wavelength selectivity of diffraction gratings, leading to inconsistent color representation across the screen.
Innovation Solution
A light guide device design that combines a non-diffraction optical element for horizontal directions and a diffraction optical element for vertical directions, using hologram elements to form virtual images, which reduces color unevenness and allows for a thinner, more compact design while maintaining high brightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If diffraction gratings are used for virtual image formation in all directions, then the light guide device can be made thinner, but color unevenness and wavelength selectivity occur leading to inconsistent color representation
Solution Approach 1:
The light guide device is divided into two functional sections: a first light guide member that forms virtual images without diffraction for horizontal directions, and a second light guide member that uses diffraction optical elements for vertical directions. This segmentation allows each section to specialize in one function, preventing the color unevenness that would result from using diffraction gratings in all directions while still achieving thinness through the diffraction-based second member.
Solution Approach 2:
Different optical mechanisms are applied to different spatial directions: non-diffraction optical systems are used for horizontal virtual image formation where color uniformity is critical, while diffraction optical elements are used for vertical pupil enlargement where wavelength selectivity has less impact on perceived color uniformity. This local differentiation of optical quality resolves the contradiction between thinness and color uniformity.
2Reliability
If diffraction optical elements are used for pupil enlargement, then the pupil size can be reliably enlarged, but streaky unevenness may occur in the image quality
Solution Approach 1:
The device segments the optical functions: the first light guide member handles virtual image formation without diffraction to avoid streaky unevenness, while the second light guide member with diffraction optical elements handles pupil enlargement. By separating these functions into different members, the patent achieves reliable pupil enlargement while preventing image quality degradation.
3Manufacturing precision
If non-diffraction optical systems are used for virtual image formation, then color uniformity is maintained, but the pupil size enlargement becomes more difficult
Solution Approach 1:
The patent divides the optical system into two members with complementary functions. The first member provides color-uniform virtual image formation through non-diffraction optics, while the second member adds pupil enlargement capability through diffraction optical elements. This segmentation allows each component to optimize for its specific function while working together to achieve both color uniformity and pupil enlargement.
Solution Approach 2:
The patent combines two different optical approaches (non-diffraction and diffraction) in a single integrated light guide device. The first and second light guide members are optically coupled to merge their functions, achieving both color uniformity from the non-diffraction section and pupil enlargement from the diffraction section simultaneously.
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 solution effectively reduces color unevenness and enhances brightness by using non-diffraction for horizontal directions and diffraction for vertical directions, avoiding streaky issues and enabling a thinner design.
Implementation Method 1
a pupil size is enlarged by a diffraction optical element with respect to second directions crossing the first directions along the predetermined surface
Implementation Method 2
an optical system that geometrically and optically forms a virtual image may be used
Implementation Method 3
an optical system that geometrically and optically enlarges the pupil size may be used
Data Source
AI summary
A light guide device may be incorporated into a virtual image display apparatus, and functionally includes a light-incident part for entrance of picture lights, a light guide part that guides the picture lights via the light-incident part, and a light-exiting part that outputs the picture lights from the light guide part to a position of an eye. In the light guide device, light guide that enables non-diffraction virtual image formation is performed with respect to lateral first directions and a pupil size is enlarged by first and second diffraction optical elements with respect to longitudinal second directions.