Virtual Image Display Apparatus with Optical-Directivity Changing Section
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Solution Overview
Problem
Existing virtual image display apparatuses suffer from luminance spots and inefficient use of illumination light due to uneven light distribution and tilt angles, particularly at the edges of the display area, where the tilt of illumination light increases, leading to reduced luminance and wasted light.
Innovation Solution
A virtual image display apparatus incorporating an optical-directivity changing section that adjusts the directivity of image light by bending it at different angles depending on the position, using elements like prism arrays, Fresnel lenses, or micro lens arrays, to match the angle characteristics of light beam capturing, ensuring uniform luminance across the display area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the display element emits light beams at large tilt angles to cover the viewing area, then the angle of view is improved, but luminance becomes uneven and luminance spots occur
Solution Approach 1:
The patent applies local quality by varying the tilt angle of illumination light according to the position on the display element. The illuminating device is designed to emit light at different tilt angles for different regions (center vs. edges) of the display element, matching the angle characteristics of light beam capturing at each position. This resolves the contradiction by allowing large tilt angles at edges for wide viewing while maintaining appropriate tilt angles at center for high luminance.
2Illumination intensity
If the illumination light is emitted with small tilt angle from the display element, then luminance is high at the center, but illumination light is not effectively utilized at upper and lower ends
Solution Approach 1:
The patent implements local quality by making the tilt angle of illumination light position-dependent. At the center region of the display element, the illumination light is emitted with small tilt angles to maintain high luminance. At the upper and lower end regions, the illumination light is emitted with progressively larger tilt angles to ensure effective light utilization and prevent energy loss. This resolves the contradiction between center luminance and overall illumination efficiency.
3Adaptability or versatility
If the tilt of illumination light increases at lateral positions, then the angle coverage is improved, but luminance falls and belt-like luminance spots occur
Solution Approach 1:
The patent applies local quality by adjusting the tilt angle of illumination light according to lateral positions on the display element. At lateral positions where larger tilt angles are needed for angle coverage, the illuminating device is designed to emit light with appropriate tilt angles that match the light beam capturing characteristics at those positions. This prevents luminance fall and belt-like luminance spots while maintaining wide lateral angle coverage.
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 suppresses luminance spots and improves the efficiency of illumination light use by aligning the image light directivity with the angle characteristics of light beam capturing, maintaining high luminance and reducing light wastage across the entire display area.
Implementation Method 1
an optical-directivity changing section (38) that changes the directivity of image light GL emitted from the image display device (11) and forms a non-uniform distribution
Implementation Method 2
a light guide section that guides the image light captured from the light incident section using total reflection on first and second reflection surfaces extending while being opposed to each other
Data Source
AI summary
An advantage of some aspects of the invention is to provide a virtual image display apparatus in which occurrence of luminance spots is suppressed to improve efficiency of use of illumination light. In the virtual image display apparatus of the invention, an optical-directivity changing section forms a non-uniform distribution concerning the directivity of image lights GL emitted from an image display device. Therefore, even when an angle of a light beam emitted from the image display device and effectively captured into the eye EY of an observer is substantially different depending on a position of the image display device, it is possible to form the image lights GL having directivity corresponding to such an angle characteristic of light beam capturing. It is possible to suppress occurrence of luminance spots to improve efficiency of use of illumination light.