Virtual Image Display Apparatus Light Control
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Solution Overview
Problem
Existing virtual image display apparatuses face challenges in downsizing optical systems, leading to increased size and difficulty in adjusting imaging positions due to non-uniform light distribution and varying output angles, which result in brightness and color irregularities.
Innovation Solution
A virtual image display apparatus with an image generation unit and an intensity distribution control unit that controls output light angles, inclining peripheral light rays more towards the center optical axis than central rays, allowing for a downsized optical system and improved light efficiency, while adjusting output angles to maintain aspect ratios and suppress irregularities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the principal rays of peripheral lights are directed outward from the panel with varying directionality, then the optical system can be designed, but the sizes of the light guide device and eyepiece optical system must be increased
Solution Approach 1:
The patent applies local quality by making the light guide device have different refractive indices in different regions. Specifically, the refractive index varies from the center to the periphery of the light guide device, allowing different regions to control light propagation differently. This enables peripheral lights to be directed toward the optical axis while maintaining a compact overall system size, resolving the contradiction between directional control and system size.
2Ease of operation
If the output angles of principal rays are partially different, then the virtual image can be formed, but when the panel position is moved along the optical axis, the aspect ratio of the virtual image changes and differs from the aspect ratio of the image surface
Solution Approach 1:
The patent uses parameter changes by varying the refractive index distribution within the light guide device. By carefully designing how the refractive index changes from center to periphery, the system compensates for the effects of panel position movements. This ensures that the aspect ratio of the virtual image remains consistent with the image surface aspect ratio, even when the panel is repositioned for manufacturing error correction or virtual image positioning.
3Illumination intensity
If non-uniform distributions are formed by varying directionality, then luminance spots are reduced, but brightness irregularities and color irregularities are generated
Solution Approach 1:
The patent applies local quality through position-dependent refractive index variation in the light guide device. Different regions of the light guide device have specifically tailored refractive indices that control the directionality of lights from corresponding panel regions. This localized control achieves uniform luminance distribution across the virtual image while preventing brightness and color irregularities, as each region's light is directed optimally without excessive angular variation.
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 enables a compact virtual image display apparatus with reduced brightness and color irregularities, allowing for precise adjustment of the image display device and virtual image optical system, maintaining image quality and aspect ratios.
Implementation Method 1
a light guide device having a refractive index which varies from a center to a periphery in an in-plane direction parallel to a light incident surface
Data Source
AI summary
Principal rays of component lights output from a periphery side of respective positions of an image surface generated in an image generation unit forming an image display device are controlled in an intensity distribution control unit so that the principal rays may be inclined more largely toward a center optical axis side than principal rays of component lights output from a center side and output, control is performed so that lights are output in the strongest intensity distributions with respect to axial directions of the principal rays of the respective component lights of image lights output in the respective positions by the intensity distribution control unit, and further, the positions can be adjusted by adjustment of output angles of the respective component lights in response to an aspect ratio of the image surface.