Local Dimming in Light Field Displays for Sunlight Contrast
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Solution Overview
Problem
Conventional augmented-reality systems face challenges in producing high-contrast virtual content against bright real-world light fields, such as direct sunlight, leading to issues like halo-like and ethereal appearance of AR content and inability to display completely black virtual content due to glare and reflections, which violate regulatory brightness requirements.
Innovation Solution
A system and method incorporating local dimming and compensation in light field displays, utilizing tracking means to determine the relative location of a user's eyes and adjusting the transmittance or reflectance of the real-world and synthetic light fields through active optical devices to enhance contrast and clarity of virtual content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional AR systems optically combine synthetic light field with real-world light field, then virtual content can be displayed without glasses, but the brightness of real-world light field (especially in direct sunlight) prevents high-contrast virtual content from being displayed
Solution Approach 1:
The patent divides the optical combiner into multiple independently controllable segments or regions. Each segment can selectively control the transmittance of real-world light and reflectance of synthetic light based on the user's eye location, enabling local dimming of the real-world light field to improve virtual content contrast while maintaining glasses-free operation.
Solution Approach 2:
The patent implements spatially varying optical properties across the optical combiner by using multiple active optical devices at different locations. Each device adjusts its transmittance and reflectance characteristics locally according to the user's eye position, creating high-contrast regions for virtual content while allowing bright real-world light to pass through in other regions.
2Illumination intensity
If the brightness of real-world light field is increased to match sunlight conditions, then visibility of virtual content improves, but completely black virtual content cannot be displayed and halo-like appearance occurs
Solution Approach 1:
The patent uses tracking means to predict the user's eye location in advance and pre-adjusts the transmittance and reflectance of active optical devices before the user's eye reaches that position. This preliminary adjustment ensures that the real-world light field is dimmed in the correct regions before virtual content needs to be displayed, preventing halo effects and enabling completely black virtual content.
Solution Approach 2:
The patent employs tracking means to continuously monitor the user's eye location and provides feedback to the control system. Based on this feedback, the active optical devices dynamically adjust their transmittance and reflectance in real-time, ensuring optimal contrast for virtual content while preventing unwanted light leakage that causes halo effects.
3Illumination intensity
If active optical devices are used to selectively control transmittance and reflectance based on eye location, then high-contrast virtual content is achieved, but system complexity increases
Solution Approach 1:
The patent uses a limited number of active optical devices positioned at strategic locations to control only the critical regions of the optical combiner where virtual content is displayed. Rather than controlling the entire combiner surface, the system applies partial action to specific zones, reducing the total number of devices needed while still achieving high-contrast virtual content.
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
Enables high-contrast virtual content presentation with improved visibility and realistic depth perception, overcoming brightness challenges and regulatory compliance by selectively dimming or reflecting light fields based on user eye locations, providing a robust and reliable augmented reality experience.
Implementation Method 1
an optical combiner arranged on an optical path of the light field display unit and on an optical path of a real-world light field of a real-world environment... The optical combiner is employed to reflect a first part and a second part of the synthetic light field towards the first eye and the second eye of the at least one user, respectively, whilst optically combining the first part and the second part of the synthetic light field with the real-world light field
Implementation Method 2
at least one active optical device, arranged on the optical path of the real-world light field, employed to selectively control at least one of: (i) transmittance of at least a part of the real-world light field passing through at least a portion of the optical combiner
Implementation Method 3
(ii) reflectance of at least a part of a synthetic light field produced by the light field display unit and reflected from at least a portion of the optical combiner
Data Source
Figure 1~2A
Figure 2B~2C
Figure 3A~3B
AI summary
An optical combiner (108, 402) is employed to reflect a first part and a second part of a synthetic light field (116) towards a first eye (122a, 202a, 316a, 322a, 410a) and a second eye (122b, 202b, 316b, 322b, 410b) of user(s) (124), respectively, whilst optically combining the first part and the second part with a real-world light field (114). Portion(s) (412a, 412b) of the optical combiner from which a part of the synthetic light field is reflecting towards a given eye (410a, 410b) of a given user is determined, based on a relative location of the given eye with respect to the optical combiner. Portion(s) of active optical device(s) (110) that corresponds to the portion(s) of the optical combiner are activated, to decrease transmittance of the real-world light field passing through the portion(s) of the optical combiner towards the given eye, and/or to increase reflectance of the synthetic light field being reflected by the portion(s) of the optical combiner towards the given eye.