Water Repellent Layer for Head-Mounted Display Waterproofing

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Solution Overview

Problem

Existing head-mounted image display apparatuses face challenges in maintaining waterproof properties, leading to potential fluid infiltration due to gaps between the light-guiding member and the casing, which can cause image deviation and reliability issues, especially in environments where rainwater or moisture is present.

Innovation Solution

A display device with a water repellent layer positioned between the optical member and the frame member's inner surface, preventing fluid infiltration by converting capillary gaps into droplets that are too large to pass through the gaps, thus enhancing waterproofing and maintaining optical member precision during assembly.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a waterproof member such as a packing is disposed between each surface of the light-guiding member and an external case forming the casing and is pressed, then waterproofing is improved, but the light-guiding member is moved from a position to which the image light can reliably be guided

Engineering Contradiction:

ImprovewaterproofingVSAvoidpositioning precision of light-guiding member

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

A support member is introduced as an intermediary component between the light-guiding member and the external case. The support member holds the light-guiding member at a predetermined position and supports its weight, preventing direct contact and pressure from the waterproof member. This allows the waterproof member to press against the support member rather than the light-guiding member, maintaining both waterproofing and positioning precision.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Manufacturing precision

If the waterproof member is not installed in the circumference of the light-guiding member, then positioning precision is maintained, but a fluid may be infiltrated into a frame member from a portion between the light-guiding member and the casing

Engineering Contradiction:

Improvepositioning precision of light-guiding memberVSAvoidfluid infiltration

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The support member serves as a mediator that enables the waterproof member to be installed around the light-guiding member without directly contacting it. The waterproof member is disposed between the support member and the external case, creating a sealed path that prevents fluid infiltration while the support member continues to hold the light-guiding member at its precise position.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The sealing function is segmented from the positioning function. The support member handles positioning while the waterproof member handles sealing, allowing both functions to be optimized independently without interfering with each other.

Inventive Principle:

Principle #1Segmentation

3Manufacturing precision

If the waterproof member is installed in a portion that does not contribute to reflection of the light-guiding member, then positioning is maintained, but a slight gap occurs between one surface of the light-guiding member and the external case due to tolerance and heat of material, and thus a fluid such as water infiltrates into the casing via the gap due to capillarity

Engineering Contradiction:

Improvepositioning of light-guiding memberVSAvoidfluid infiltration via capillarity

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The support member acts as an intermediary structure that provides a surface for the waterproof member to contact. The waterproof member is disposed between the support member and the external case, sealing the gap caused by thermal expansion and manufacturing tolerances. This prevents capillary infiltration while maintaining the light-guiding member's position and optical reflection surfaces.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 water repellent layer effectively suppresses fluid infiltration into the frame member, ensuring the optical member's accurate positioning and maintaining image reliability, even in wet environments, by converting capillary gaps into droplets that cannot enter the frame member, thereby improving the waterproof properties of the display device.

Implementation Method 1

a fluid such as water infiltrates into the casing via the gap due to capillarity

Methodology Applied

Scientific EffectCapillary action: Capillary Action

Implementation Method 2

the fluid infiltrating into the gap due to capillarity becomes a droplet due to the water repellent effect of the water repellent layer

Methodology Applied

Scientific EffectWater repellent effect: Hydrophobe

Data Source

PatentUS10345581B2Display device and head mounted image display apparatus

Publication Date: 2019.07.09 SEIKO EPSON CORP

AI summary

A display device includes: an optical member that guides incident image light; a frame member that includes an opening in which a part of the optical member is inserted and holds the optical member; and a water repellent layer that is located between the optical member and an inner surface of the opening.