Light Guide Member External Light Noise Reduction
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Solution Overview
Problem
Head-mounted display apparatuses suffer from external light noise interference, where unnecessary external light is diffracted towards the observer, overlapping with the image and degrading the viewing experience.
Innovation Solution
Incorporating a polarizing member or a multilayer film mirror at the external light incidence portion of the light guide member, which blocks or transmits light based on polarization characteristics or incident angles, to prevent external light from reaching the observer's eyes, while allowing image light to be diffracted and viewed effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a diffractive optical element is used to direct image light toward the observer's eyes, then the image visibility is improved, but external light noise is also diffracted toward the eyes, degrading the image quality
Solution Approach 1:
The patent applies local quality by making the light guide member have different optical properties at different locations. The first region (where image light enters) has optical properties that guide image light effectively, while the second region (where external light enters) has different optical properties that prevent external light from reaching the observer's eyes. This spatial differentiation of optical properties allows the system to simultaneously achieve good image visibility and external light rejection.
Solution Approach 2:
The patent changes optical parameters of the light guide member across different regions. Specifically, the refractive index, absorption coefficient, or scattering properties are varied between the first region and the second region. This parameter variation enables the light guide member to selectively guide image light while blocking external light, resolving the contradiction between image visibility and external light noise.
2Illumination intensity
If the light guide member is made translucent to allow external light to pass through for see-through functionality, then the external field visibility is improved, but external light noise interferes with the image
Solution Approach 1:
The light guide member is designed with spatially varying optical properties: the first region maintains translucency for external field visibility, while the second region has modified optical properties (such as different refractive index or absorption characteristics) that block external light noise. This local differentiation allows simultaneous achievement of external field visibility and noise rejection.
Solution Approach 2:
The light guide member acts as an intermediary element that selectively transmits or blocks different light paths. By positioning the second region to intercept external light before it reaches the observer's eyes, the system mediates between the need for external field visibility and the need to eliminate external light noise interference.
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
Effectively inhibits external light noise from overlapping with the image, enhancing the clarity and visibility of both the image and the external field in a see-through state by selectively blocking or transmitting light based on polarization efficiency and incident angles.
Implementation Method 1
a first diffractive optical element provided in the light emission portion... The image light emitted from the image light emission portion is diffracted by the first diffractive optical element and reaches the eyes of an observer
Implementation Method 2
a polarizing member provided in the external light incidence portion... since the polarizing member is provided in the external light incidence portion of the light guide member, even when unnecessary external light is forced to be incident on the light guide member, it is possible to inhibit the unnecessary external light from reaching the eyes of the observer
Data Source
AI summary
A display apparatus includes an image forming device, first and second light guide members that respectively have first and second light incidence portions and first and second light emission portions, a first diffractive optical element provided in the first light emission portion, a second diffractive optical element provided in the second light emission portion, and a first external light noise reduction element provided over the second light guide member. The first external light noise reduction element overlaps the first and second light emission portions. The first light incidence portion overlaps the second light incidence portion. Image light from the image forming device is incident on the first light incidence portion. A part of the image light is guided in the first light guide member. Another part of the image light is incident on the second light incidence portion and is guided in the second light guide member.