Wide Field-of-View Virtual Image Projector Using Input Wedge

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Solution Overview

Problem

Conventional virtual image projectors for eyeglasses have a limited field-of-view, causing the projected images to appear too far away and restricting the wearer's ability to see both virtual and external objects effectively.

Innovation Solution

A wide field-of-view virtual image projector is implemented using a spatial light modulator that injects light rays into an input wedge, which increases the fan-out angle and diffracts light to generate a virtual image with enhanced horizontal and vertical fields-of-view, achieved by combining a spatial light modulator with an input wedge and diffraction gratings.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If a small virtual image projector is placed on eyeglasses, then the device size is reduced and can be worn on eyeglasses, but the field-of-view becomes limited and the virtual image appears too far away

Engineering Contradiction:

Improveprojector sizeVSAvoidfield-of-view

Core Design Contradiction:

Volume of moving objectVSAdaptability or versatility

Solution Approach 1:

The optical system is segmented into distinct functional components: a spatial light modulator for image generation, an input wedge for beam expansion, and an output light guide for diffraction. This segmentation allows each component to be optimized independently, enabling a compact overall size while achieving a wide field-of-view through the coordinated function of each segment.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The input wedge expands the light beam in the angular dimension, transforming a narrow input beam into a wider fan-out angle output beam. This dimensional transformation in the angular space allows the compact projector to achieve a wide field-of-view without increasing its physical footprint.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Adaptability or versatility

If the fan-out angle is increased to widen the field-of-view, then the virtual image appears closer and more immersive, but the optical system becomes more complex

Engineering Contradiction:

Improvefield-of-viewVSAvoidoptical system complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The input wedge serves as an intermediary optical element between the spatial light modulator and the output light guide. It mediates the transformation from a narrow beam to a wide fan-out angle beam, enabling the wide field-of-view function while maintaining a relatively simple and compact overall optical system structure.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The input wedge changes the angular parameter of the light beam, transforming it from a narrow angle to a wide fan-out angle. This parameter change enables the wide field-of-view without requiring complex optical arrangements, as the wedge geometry inherently provides the angular expansion.

Inventive Principle:

Principle #35Parameter changes

3Adaptability or versatility

If diffraction gratings are used to increase horizontal field-of-view, then the virtual image width is expanded, but the manufacturing precision requirements increase

Engineering Contradiction:

Improvehorizontal field-of-viewVSAvoiddiffraction grating precision

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The diffraction function is segmented and integrated into the output light guide rather than being a separate component. This integration reduces the number of precision-matched interfaces and simplifies manufacturing, as the diffraction grating is formed as part of the light guide structure rather than being a separate precision component that requires precise alignment.

Inventive Principle:

Principle #1Segmentation

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 allows for a wider and more immersive virtual image projection, enabling the wearer to see virtual images closer to the eye while maintaining visibility of external objects, with improved vertical and horizontal fields-of-view, making the technology suitable for head-mounted displays like eyeglasses.

Implementation Method 1

The spatial light modulator is controlled to inject light rays into the input wedge effective to diffract the light rays out of the output light guide to generate a virtual image

Methodology Applied

Scientific EffectDiffraction: Diffraction

Implementation Method 2

The input wedge acts to output the light rays with an increased fan-out angle into an output light guide positioned proximate the input wedge

Methodology Applied

Scientific EffectRefraction: Refraction

Data Source

PatentUS8988474B2Wide field-of-view virtual image projector

Publication Date: 2015.03.24 MICROSOFT TECHNOLOGY LICENSING LLC

AI summary

This document describes techniques and apparatuses for implementing a wide field-of-view virtual image projector. A wide field-of-view virtual image projector may include a spatial light modulator configured to inject light rays into an input wedge. The input wedge acts to output the light rays with an increased fan-out angle into an output light guide positioned proximate the input wedge. The spatial light modulator is controlled to inject light rays into the input wedge effective to diffract the light rays out of the output light guide to generate a virtual image.