Birefringent Depth Sensing for Low-Power XR Headsets
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Solution Overview
Problem
Existing depth sensing technologies in extended reality (XR) headsets face high power consumption, limited frame rate, and safety concerns related to laser emissions, while event cameras have lower resolution and update frequency, limiting their effectiveness in complex scenes.
Innovation Solution
An apparatus and method combining iToF and event cameras by using a scanning light source, birefringent layer, and imaging sensor to split light into O-ray and E-ray images, allowing for high-resolution depth mapping with low power consumption and real-time processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If indirect Time-of-Flight (iToF) cameras are used for depth sensing, then depth information can be captured in real-time, but power consumption increases significantly
Solution Approach 1:
The patent combines iToF technology with event camera technology into a hybrid system. The iToF component provides real-time depth capture capability while the event camera component provides low-power operation. By merging these two technologies, the system achieves real-time depth sensing with reduced overall power consumption compared to using iToF alone.
Solution Approach 2:
The system uses periodic scanning of laser lines through the scene, where the scanning light source sequentially illuminates different regions. This periodic action allows the system to capture depth information over time with lower instantaneous power requirements compared to continuous illumination, while still maintaining real-time depth map generation.
2Productivity
If indirect Time-of-Flight (iToF) cameras are used for depth sensing, then depth information can be captured, but frame rate capability is limited
Solution Approach 1:
The system performs preliminary depth measurements using the iToF component during the scanning process. By pre-capturing depth information along the scanned lines and using event camera data to fill in between-scans, the system builds up a complete depth map more rapidly, effectively increasing the frame rate capability.
Solution Approach 2:
The hybrid system maintains continuous depth sensing operation where the iToF component continuously measures depth along scanned lines and the event camera continuously monitors changes. This continuous operation from both components ensures high frame rate capability and responsiveness to dynamic scenes.
3Measurement precision
If scanning light source is used to illuminate environment, then depth information can be obtained, but eye exposure to laser emissions becomes a safety concern
Solution Approach 1:
The system uses partial illumination by scanning thin laser lines through the scene rather than illuminating the entire field of view continuously. This partial action approach obtains sufficient depth information along the scanned paths while significantly reducing the total laser energy exposure to eyes compared to full-field continuous illumination.
Solution Approach 2:
The scanning light source rapidly moves through the scene, skipping across different regions in quick succession. This rushing through approach minimizes the dwell time of laser exposure at any single location, reducing cumulative eye exposure while still capturing complete depth information through the sequential scanning process.
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
Achieves high-resolution depth maps with increased frame rates, low power consumption, and enhanced safety, suitable for dynamic XR environments.
Implementation Method 1
a birefringent layer adapted to receive and split reflected scan pattern from the environment into an ordinary ray (O-ray) image and an extraordinary ray (E-ray) image
Data Source
AI summary
Disclosed is an apparatus and a method for depth sensing that includes a scanning light source configured to sequentially illuminate an environment utilizing a scan pattern. The apparatus also includes a birefringent layer adapted to receive and split reflected scan pattern from the environment into an ordinary ray (O-ray) image and an extraordinary ray (E-ray) image. The apparatus further includes an imaging sensor positioned along an optical path of the birefringent layer to capture the O-ray image and the E-ray image as transmitted therefrom. The apparatus further includes a processor configured to compute differences between positions of the O-ray image and the E-ray image and derive a depth map of the environment based on the computed differences.