See-through Display Light Trap Stray Light Management

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Solution Overview

Problem

Head-mounted displays (HMDs) with see-through capabilities suffer from stray light issues, which reduce image sharpness and contrast by scattering light within the optics, causing black areas to appear gray and affecting the augmented reality view.

Innovation Solution

The implementation of an upper optical module with a DLP display and a light trap system that directs 'on' and 'off' pixel light differently, using polarized light and TIR wedges to manage stray light, ensuring that 'off' pixel light is absorbed rather than reflected, thereby maintaining image clarity and contrast.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If see-through optics are used in HMDs, then the user can view the environment, but stray light scatters within the optics reducing image sharpness and contrast

Engineering Contradiction:

Improvesee-through capabilityVSAvoidimage sharpness and contrast

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent extracts and removes stray light from the optical path by introducing light traps at specific locations within the optics. These light traps capture and absorb scattered light before it can reach the user's eye, thereby eliminating the harmful stray light while preserving the see-through capability and improving image sharpness and contrast.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent converts the harmful effect of stray light into a beneficial outcome by using the scattered light itself to illuminate the light traps. The stray light that would normally degrade image quality is instead captured and absorbed by strategically placed light traps, transforming it from a harmful factor into a mechanism that enhances image sharpness and contrast by preventing further scattering.

Inventive Principle:

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

2Measurement precision

If stray light is reduced to improve contrast, then black areas become darker, but the see-through view quality deteriorates

Engineering Contradiction:

ImprovecontrastVSAvoidsee-through view brightness

Core Design Contradiction:

Measurement precisionVSIllumination intensity

Solution Approach 1:

The patent applies local quality by placing light traps at specific locations where stray light concentrates, rather than uniformly reducing light throughout the entire optical path. This localized approach allows contrast to be improved in specific areas where stray light degrades image quality, while preserving overall illumination intensity and see-through view brightness in other areas.

Inventive Principle:

Principle #3Local quality

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 solution enhances the contrast and sharpness of images displayed in HMDs, providing deeper blacks and reducing stray light, thereby improving the see-through view by ensuring that only intended light reaches the user's eye.

Implementation Method 1

using polarized light and TIR wedges to manage stray light

Methodology Applied

Scientific EffectTotal internal reflection: Total Internal Reflection

Implementation Method 2

using polarized light and TIR wedges to manage stray light

Methodology Applied

Scientific EffectPolarization: Polarisation

Data Source

PatentUS9529195B2See-through computer display systems

Publication Date: 2016.12.27 OSTERHOUT GROUP INC

AI summary

Aspects of the present invention relate to providing see-through computer display optics.