On-axis HMD Optical Configuration with Achromatic Doublet Lenses

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Solution Overview

Problem

See-through head-mounted displays (HMDs) face challenges due to off-axis optical configurations that introduce significant optical aberrations, require low error tolerances for alignment, and include apertures that cause diffractions and weight issues, leading to reduced image quality and comfort.

Innovation Solution

An on-axis optical configuration with achromatic doublet lenses and a slim, removable beam splitter, allowing greater misalignment tolerance and eliminating apertures for improved image quality and comfort.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If off-axis optical configuration is used, then see-through capability is achieved, but optical aberrations increase and alignment tolerance decreases

Engineering Contradiction:

Improvesee-through capabilityVSAvoidalignment tolerance

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The patent inverts the conventional off-axis optical configuration to an on-axis configuration. By placing the beam splitter and retro-reflector screen in line with the optical path rather than at an angle, the system achieves see-through capability while dramatically improving alignment tolerance and reducing optical aberrations.

Inventive Principle:

Principle #13The other way round (Inversion)

2Manufacturing precision

If additional optical elements are added to correct aberrations, then image quality improves, but device weight and complexity increase

Engineering Contradiction:

Improveimage qualityVSAvoiddevice weight

Core Design Contradiction:

Manufacturing precisionVSWeight of moving object

Solution Approach 1:

The patent converts the harmful effect of the on-axis configuration (which naturally reduces aberrations) into a beneficial feature by eliminating the need for additional correction elements. The simple on-axis geometry inherently provides better optical performance without requiring extra lenses or complex correction mechanisms.

Inventive Principle:

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

3Ease of operation

If apertures are included in the optical configuration, then optical path is defined, but diffractions and interferences increase

Engineering Contradiction:

Improveoptical path definitionVSAvoidimage quality

Core Design Contradiction:

Ease of operationVSManufacturing precision

Solution Approach 1:

The patent extracts and eliminates apertures from the optical configuration. By using the natural boundaries of the housing and optical elements themselves to define the optical path, the system avoids introducing diffractions and interferences that would degrade image quality.

Inventive Principle:

Principle #2Taking out (Extraction)

4Manufacturing precision

If complex supporting housing structures are used, then alignment precision improves, but manufacturing cost increases

Engineering Contradiction:

Improvealignment precisionVSAvoidmanufacturing cost

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The patent changes the critical parameter from alignment precision (which would require complex structures) to inherent tolerance robustness. By designing an on-axis configuration that is naturally more tolerant of misalignments, the system achieves good alignment performance with simpler, less expensive housing structures.

Inventive Principle:

Principle #35Parameter changes

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 on-axis configuration maintains image resolution, reduces manufacturing costs, and enhances user comfort by minimizing weight and optical aberrations, while the adjustable design ensures proper alignment and image focus.

Implementation Method 1

achromatic doublet lenses and a slim, removable beam splitter, allowing greater misalignment tolerance and eliminating apertures for improved image quality and comfort

Methodology Applied

Scientific EffectAchromatic lens refraction: Refraction

Implementation Method 2

a slim, discrete, removable, and adjustable COTS (commercial off-the-shelf) optical element positioned in front of the user's eyes

Methodology Applied

Scientific EffectLight reflection and transmission: Reflection

Data Source

PatentUS8159751B2Apparatus for head mounted image display

Publication Date: 2012.04.17 MIGUEL MARQUES MARTINS

AI summary

Image display device having an image source generating an image, a beam splitter positioned at forty five degrees to the main optical path, to project and focus the image generated by the image source into the entrance pupil of the human eye, two achromatic standard doublet lenses positioned perpendicularly to the main optical path and placed between the image source and the beam splitter, and configured to amplify, collimate, and correct optical aberrations of said image, wherein the image source, beam splitter and the doublet lenses are in an on-axis configuration and the image display device comprises two mounting brackets parallel to the main optical axis, each having an extremity part holding an edge of the beam splitter and the other extremity pivotally attached to a housing, allowing the brackets and beam splitter to rotate in an axis perpendicular to the main optical path.