Optical Element with Half Mirror Layer for Stray Light Control
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Solution Overview
Problem
Head-mounted displays face challenges in maintaining a small size and preventing contrast ratio deterioration due to stray light, which is exacerbated by the use of layered optical elements that spread image light but increase device size and cost.
Innovation Solution
An electro-optical device featuring a light source with various angle components and a first optical element composed of light guiding materials bonded via a half mirror layer, where the angles and refractive index are optimized to minimize stray light generation without the need for additional light shielding, allowing for a compact and cost-effective design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If a layered body including long plane-parallel plate, half mirror, and total reflection mirror is employed to spread image light, then the image light can be spread to be larger than the diameter of the eyes, but the emitted beam is discharged in many directions requiring additional light shielding countermeasures which increases device size and cost
Solution Approach 1:
The optical element is divided into multiple light guiding materials (first, second, and third light guiding materials) with different refractive indices, each segment controlling specific light paths and angles to achieve precise light distribution without requiring additional shielding components
Solution Approach 2:
The patent utilizes different refractive indices (n1, n2, n3) for the light guiding materials to control light propagation angles and paths, enabling precise control over light distribution patterns and eliminating the need for additional light shielding countermeasures
2Object-affected harmful factors
If additional light shielding countermeasures are installed to prevent stray light, then contrast ratio can be improved, but device size increases and cost increases
Solution Approach 1:
The optical element itself generates the light distribution pattern through its internal structure of light guiding materials with different refractive indices, eliminating the need for external light shielding components. The multi-material structure inherently controls stray light through its designed optical paths
3Ease of operation
If light is incident at 45 degrees in the technology of JP-A-7-325267, then light can be guided, but stray light is generated similarly to the layered body case
Solution Approach 1:
The patent employs multiple refractive indices (n1, n2, n3) for the light guiding materials to precisely control light propagation angles, allowing light guidance without generating stray light. The specific refractive index combinations enable controlled refraction that prevents unwanted light dispersion
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 stray light generation, maintains a high contrast ratio, and enables a compact device configuration by ensuring that incident and emitted light have consistent angles, reducing image distortion and the necessity for additional light shielding.
Implementation Method 1
a first part of the light is a light incident from the incident surface, is guided thereto, reflected by the second surface, and is incident on the emitting surface
Implementation Method 2
The first optical element includes a plurality of light guiding materials, the plurality of light guiding materials are bonded to each other via a half mirror layer
Implementation Method 3
with a refractive index of the plurality of light guiding materials
Data Source
AI summary
An electro-optical device includes: a light source which generates a light beams having various angle components; and a first optical element includes a plurality of light guiding materials are bonded to each other via a half mirror layer.The first optical element includes a first surface and a second surface, an incident surface is formed so as to intersect the first surface at a first angle, an emitting surface is formed so as to intersect the first surface at a second angle.A first part of the light is a light reflected by the second surface, and is incident on the emitting surface. The first optical element is formed so that the first part of the light is reflected by the emitting surface, with angles of the first angle and the second angle, and with a refractive index of the plurality of light guiding materials.