Light Guide With Segmented Reflecting Surfaces For Uniform Virtual Image Display

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Solution Overview

Problem

Existing virtual image display devices face challenges in achieving high light use efficiency and reducing variations in light intensity, leading to discomfort for users.

Innovation Solution

The proposed light guide configuration includes multiple reflecting surfaces, specifically a first and second reflecting surface, which separate the light flux into multiple light fluxes, allowing for efficient propagation and exit from the optical exit, thereby enhancing light use efficiency and reducing light intensity variations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If multiple partial reflection layers are used to separate light flux into multiple angles of view, then the angle of view is widened, but the light intensity variations increase and light use efficiency decreases

Engineering Contradiction:

Improveangle of viewVSAvoidlight intensity variations

Core Design Contradiction:

Adaptability or versatilityVSIllumination intensity

Solution Approach 1:

The light guide is divided into two separate light guide portions: a first light guide portion that receives light from the image display and a second light guide portion that delivers light to the user's eye. This segmentation allows independent optimization of each portion, reducing light intensity variations while maintaining wide angle of view through multiple partial reflection layers.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The first light guide portion acts as an intermediary between the image display and the second light guide portion. It performs the light separation function through multiple partial reflection layers, while the second light guide portion serves as a mediator to uniformly deliver the separated light fluxes to the user's eye, thereby reducing light intensity variations.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If multiple partial reflection layers are used to separate light flux, then the angle of view is widened, but the light use efficiency decreases

Engineering Contradiction:

Improveangle of viewVSAvoidlight use efficiency

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

Dividing the light guide into two portions allows the first portion to focus on efficient light separation with multiple partial reflection layers for wide angle of view, while the second portion optimizes for light transmission efficiency to the user's eye, thereby reducing overall light energy loss.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention changes the structural parameter of the light guide by introducing a two-portion configuration, which alters the light propagation path and reduces the number of reflection interfaces that cause light energy loss, thereby improving light use efficiency while maintaining wide angle of view.

Inventive Principle:

Principle #35Parameter changes

3Loss of energy

If multiple reflecting surfaces are used to separate light flux, then the device complexity increases, but light use efficiency and uniformity are improved

Engineering Contradiction:

Improvelight use efficiencyVSAvoiddevice complexity

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The invention merges the light separation function and light guidance function into a unified two-portion light guide structure. The multiple reflecting surfaces are integrated within the first light guide portion, while the second light guide portion handles light transmission, thereby achieving improved light use efficiency without proportionally increasing device complexity.

Inventive Principle:

Principle #5Merging (Combining)

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 achieves a higher light use efficiency and reduces variations in light intensity, providing a more comfortable and clear virtual image display experience for users.

Implementation Method 1

multiple partial reflection layers, each to separate image light entered through the optical entrance, into reflected light and transmitted light

Methodology Applied

Scientific EffectPartial reflection: Reflection

Implementation Method 2

guides the light through the light guide, emitting the guided light containing image information toward an observer

Methodology Applied

Scientific EffectTotal internal reflection: Total Internal Reflection

Data Source

PatentUS12332449B2Light guide, optical unit, virtual image display device, and head-mounted display

Publication Date: 2025.06.17 RICOH CO LTD

AI summary

A light guide includes: a first light guide portion including: an optical entrance; and multiple reflecting surfaces including at least one first reflecting surface and at least one second reflecting surface, the multiple reflecting surfaces configured to separate a light flux entered through the optical entrance, into multiple light fluxes; and a second light guide portion including an optical exit. The second light guide portion is configured to cause the multiple light fluxes to propagate therethrough and exit from the optical exit. A part of the light flux strikes and reflects off the at least one first reflecting surface to propagate into the second light guide portion. Another part of the light flux strikes and reflects off the at least one second reflecting surface without striking the at least first reflecting surface, to propagate into the second light guide portion.