Holographic Display Absorption Layer for Ghosting Reduction

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Solution Overview

Problem

The existing eyeglass-type display devices using retinal projection methods suffer from a narrow Eyebox and viewing angle, leading to image overlap due to multiple light rays reflecting from different directions, causing ghosting effects.

Innovation Solution

A display device with a transparent plate, a transmission hologram, a reflection hologram, and an absorption layer, where the absorption layer is formed by combining an absorption member and a transparent member to absorb part of the reproduction light not reflected on the reflection hologram's surface, preventing image overlap by controlling the direction of light rays entering the user's eye.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a reflection hologram is used to reflect light duplicated by a transmission hologram to be focused on the Eyebox, then the viewing angle is enlarged, but multiple light rays from different reflections enter the eye from different directions causing image overlap and ghosting

Engineering Contradiction:

Improveviewing angleVSAvoidimage clarity

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The harmful reflected light rays that cause ghosting are extracted and removed from the optical path by the absorption layer, which selectively absorbs these specific light rays while allowing the useful image-forming light to pass through to the user's eye

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The absorption layer converts the harmful effect of multiple reflected light rays causing ghosting into a beneficial outcome by selectively absorbing these stray light rays, thereby improving image clarity and eliminating the ghosting effect while preserving the enlarged viewing angle

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Reliability

If the absorption layer is made entirely of absorption member to block reflected light, then ghosting is prevented, but the user's field of view is restricted

Engineering Contradiction:

Improveimage clarityVSAvoidfield of view

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The absorption layer is designed with local quality by combining absorption members and transparent members in a specific pattern, where absorption members are positioned to selectively block harmful reflected light rays while transparent members are positioned to allow useful light and external view to pass through, thereby maintaining both image clarity and field of view

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The absorption layer is constructed as a composite structure combining absorption members and transparent members, where the absorption members have high light absorption properties to block reflected light, while the transparent members have high light transmission properties to maintain the user's field of view and allow external light to pass through

Inventive Principle:

Principle #40Composite materials

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 prevents image overlap and secures a wider field of view by absorbing part of the reproduction light, ensuring that images are not viewed from different directions, thus eliminating ghosting effects and maintaining a clear external view.

Implementation Method 1

a transmission hologram provided between the one principal surface of the transparent plate and the image light emission unit, and configured to duplicate the image light emitted from the image light emission unit to transmit the image light as reproduction light

Methodology Applied

Scientific EffectDiffraction: Diffraction

Implementation Method 2

a reflection hologram provided such that one principal surface faces the other principal surface of the transparent plate, and configured to reflect, on the one principal surface, the reproduction light transmitted by the transmission hologram and passing through the transparent plate toward the eye of the user

Methodology Applied

Scientific EffectReflection: Reflection

Implementation Method 3

an absorption layer provided on the other principal surface side of the reflection hologram, the absorption layer being formed by combining an absorption member configured to absorb a part of the reproduction light reflected on the one principal surface of the reflection hologram

Methodology Applied

Scientific EffectAbsorption (EM radiation): Absorption (EM radiation)

Data Source

PatentUS20240377641A1Display device

Publication Date: 2024.11.14 NTT DOCOMO INC

AI summary

A display device includes a transparent plate, an image light emission unit configured to emit image light toward one principal surface of the transparent plate, a transmission hologram configured to duplicate the image light emitted from the image light emission unit to transmit the image light as reproduction light, a reflection hologram provided on the other principal surface side of the transparent plate, and configured to reflect, on the one principal surface, the reproduction light transmitted by the transmission hologram and passing through the transparent plate toward an eye of the user, and an absorption layer provided on the other principal surface side of the reflection hologram, the absorption layer being formed by combining an absorption member configured to absorb a part of the reproduction light not reflected on the one principal surface of the reflection hologram and a transparent member.