See-Through Display Optics With Reflective Light Guidance
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Solution Overview
Problem
Existing display devices face issues with high wavelength dependency of diffraction efficiency, requiring bright light sources, large size, and limited wide-angle viewing due to positional changes between the image emission unit and the observer's pupil, and restricted aperture diaphragm diameter.
Innovation Solution
A display device with a plate-shaped transparent member and a light reflecting portion that includes a first and second surface for light reflection, where the light reflecting segments are arranged with varying sizes and pitches to accommodate positional changes and provide a wide angle of view, using a configuration that ensures light is directed to the pupil while another part is absorbed or redirected externally.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a reflective volume hologram diffraction grating is used to guide display image light, then the display device can present visual information, but the high wavelength dependency of diffraction efficiency requires a bright light source, making the device large
Solution Approach 1:
The patent changes the optical mechanism from diffraction-based (wavelength-dependent) to reflection-based (wavelength-independent). By using a mirror or reflective surface instead of a volume hologram diffraction grating, the system eliminates wavelength dependency and achieves efficient light guidance without requiring high-power light sources, thereby reducing device size while maintaining image brightness
Solution Approach 2:
The patent extracts and removes the light source from the head-mounted display device entirely, relying instead on ambient light reflected by the liquid crystal display and subsequent optical elements. This extraction eliminates the need for power-consuming, space-occupying light sources while still achieving sufficient image brightness through environmental light utilization
2Adaptability or versatility
If the width of the reflecting portion is made smaller than the pupil diameter to avoid blocking the field of view, then the real world view is preserved, but a sufficient wide angle of view cannot be obtained
Solution Approach 1:
The patent transitions from a two-dimensional reflecting surface to a three-dimensional curved reflective surface (such as a concave mirror). This dimensional change allows the reflecting portion to maintain a small footprint in the plane perpendicular to the optical axis (avoiding field of view blockage) while providing a large effective reflecting area through the curvature, thereby achieving both a wide angle of view and unobstructed real-world viewing
3Reliability
If the positional relationship among image emission unit, reflecting portion, and eyeball is kept constant, then the display image can be observed, but the display image light becomes invisible when the positional relationship changes during wearing
Solution Approach 1:
The patent employs a curved reflective surface (such as a concave mirror) that dynamically adapts to different pupil positions. The curvature of the reflective surface ensures that reflected light rays converge appropriately regardless of lateral pupil displacement, maintaining reliable image observation while accommodating positional changes that occur during normal wearing without requiring active adjustment mechanisms
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 results in a compact, lightweight display device that maintains a wide angle of view and accommodates positional changes, ensuring bright and uniform image observation without obstructing the external view.
Implementation Method 1
a second surface that faces the first surface and totally reflects the light incident from the light incident surface
Implementation Method 2
the light reflecting portion is provided inside the transparent member corresponding to the first portion of the first surface of the transparent member or in the first portion of the first surface of the transparent member
Data Source
AI summary
Provided is a display device that includes an image display device, a transparent member, and a light reflecting portion. The transparent member includes a first surface facing an observer, a light incident surface, and a second surface that totally reflects light incident from the light incident surface. The first surface includes a first portion and a second portion. A part of light emitted from the image display device is incident from the light incident surface, totally reflected by the second surface, reflected by the light reflecting portion, emitted from the first portion, and reaches a pupil of the observer, and another part of the light emitted from the image display device is incident from the light incident surface, collides with the second portion and does not reach the pupil of the observer.