Optical Device Dual Light Guide Diffraction Angle Brightness Uniformity
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Solution Overview
Problem
Wearable image display apparatuses with diffractive optical devices face issues of brightness unevenness due to decreased diffraction efficiency at larger diffraction angles, especially when expanding the view angle, leading to suboptimal image light distribution.
Innovation Solution
The optical device comprises a first and second light guide body with diffraction elements, where the second light guide body has a diffraction element that diffracts light at a smaller angle than the first, and the grating period of the second diffraction element is greater, allowing for improved diffraction efficiency across a wider view angle range by adjusting the intensity of image light based on incident angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the incident angle range is expanded to widen the view angle, then the view angle is improved, but the diffraction efficiency decreases at one end side where the diffraction angle is large, resulting in brightness unevenness
Solution Approach 1:
The patent divides the single light guide body into two separate light guide bodies (first and second), each handling different angular ranges. The first light guide body processes light with smaller incident angles, while the second light guide body processes light with larger incident angles, thereby segmenting the angular processing to maintain diffraction efficiency across the entire view angle range.
Solution Approach 2:
The patent applies different diffraction element characteristics to different regions of the optical system. The first incidence-side diffraction element and the second incidence-side diffraction element have different grating periods, creating local quality differences that optimize diffraction efficiency for specific angular ranges. This allows each region to be optimized for its specific function.
2Device complexity
If a single light guide body with a diffractive optical device is used, then the device complexity is low, but the diffraction efficiency decreases at large diffraction angles, resulting in brightness unevenness
Solution Approach 1:
The optical system is segmented into two parallel light guide bodies, each with its own diffractive optical elements. This segmentation allows the system to handle different angular ranges separately, maintaining high diffraction efficiency across the entire view angle while distributing the functional load across multiple components.
Solution Approach 2:
The patent combines two light guide bodies with different diffraction characteristics into a single optical system. The first and second light guide bodies are positioned to receive and process light simultaneously, merging their functions to achieve uniform brightness across the entire view angle range while maintaining relatively simple individual component structures.
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
This configuration minimizes brightness unevenness across a wide view angle by enhancing diffraction efficiency in areas where it decreases and maintaining high efficiency in areas where it naturally occurs, resulting in a more uniform virtual image.
Implementation Method 1
a first light guide body (11) including a first light-incident portion (22) provided with a first incidence-side diffraction element (22a), and a second light guide body (12) including a second light-incident portion (32) provided with a second incidence-side diffraction element (32a), wherein the second light guide body (12), when light is caused to enter the first light-incident portion (22), is disposed at a position at which a part of the light passing through the first light guide body (11) enters the second light-incident portion (32)
Data Source
AI summary
An optical device of the present disclosure includes a first light guide body including a first light-incident portion provided with a first incidence-side diffraction element, and a second light guide body including a second light-incident portion provided with a second incidence-side diffraction element, wherein the second light guide body, when light is caused to enter the first light-incident portion, is disposed at a position at which a part of the light passing through the first light guide body enters the second light-incident portion, and the second incidence-side diffraction element is an element that diffracts light of monochromatic color at a smaller angle than the first incidence-side diffraction element does, when the light of monochromatic color is caused to enter at a same angle.