Virtual Image Optical Unit With Stray Light Suppression Filter
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Solution Overview
Problem
Existing virtual image display devices suffer from significant light leakage outside the emission pupil, leading to visibility of the image from the outside, particularly when diffraction gratings are used.
Innovation Solution
Incorporation of a stray light suppression filter on the external side of the second diffraction element to limit the passage of diffracted light, combined with a light-guiding member and diffraction elements to control the direction of image light propagation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a diffraction grating is used as the diffraction element, then the image light can be effectively diffracted toward the emission pupil, but a significant proportion of the image light leaks to the outside
Solution Approach 1:
A stray light suppression filter is introduced as an intermediary component between the second diffraction element and the external environment. This filter selectively blocks diffracted light from escaping while allowing the desired image light to pass through, thereby resolving the contradiction between effective diffraction and light leakage prevention
Solution Approach 2:
The harmful diffracted light is extracted and separated from the main optical path by using the stray light suppression filter. The filter identifies and removes only the unwanted diffracted components while preserving the useful image light, thus solving the light leakage problem without compromising diffraction efficiency
2Ease of operation
If the second diffraction element is provided on the light emission side to form the emission pupil, then the image light can be directed to the observer, but light leaks to the outside enabling the image to be viewed from the outside
Solution Approach 1:
The stray light suppression filter converts the harmful effect of light leakage into a beneficial selective filtering function. By positioning the filter to block only the unwanted diffracted light angles while permitting the desired image light to pass, it transforms the leakage problem into an enhanced image extraction solution with improved privacy
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
Prevents image light from being observed as eye glow or by others, enhancing privacy and reducing external light leakage.
Implementation Method 1
a light-guiding member including a first total reflection surface and a second total reflection surface
Implementation Method 2
a first diffraction element being provided on a light incidence side in association with the light-guiding member
Implementation Method 3
a second diffraction element being provided on a light emission side in association with the light-guiding member
Implementation Method 4
a stray light suppression filter being provided on an external side of an image extraction part provided with the second diffraction element and being configured to limit passage of diffracted light from the second diffraction element
Data Source
AI summary
A virtual image display device includes a display panel being a display element configured to emit image light, a light-guiding member including a first total reflection surface and a second total reflection surface, a first diffraction element being provided on a light incidence side in association with the light-guiding member, a second diffraction element being provided on a light emission side in association with the light-guiding member, and a stray light suppression filter being provided on an external side of an image extraction part provided with the second diffraction element and being configured to limit passage of diffracted light from the second diffraction element.