Depth Camera Phase Measurement Multiplexing
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Solution Overview
Problem
Conventional head-mounted displays (HMDs) for virtual or augmented reality systems face inefficiencies in determining depth information due to the use of structured light or time of flight depth cameras, which result in inefficient sensor usage and complex computational requirements to disambiguate optical paths.
Innovation Solution
A depth camera assembly in the HMD emits a series of periodic illumination patterns with phase shifts, allowing each pixel to independently determine depth by relating captured intensities to phase shifts, optimizing sensor usage and simplifying depth calculation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If structured light depth cameras use patterns with different characteristics in different portions, then depth measurement capability is improved, but sensor usage efficiency deteriorates (less than 10% of sensor pixels collect light)
Solution Approach 1:
The illumination source projects sinusoidal fringe patterns that vary periodically in space, creating alternating bright and dark regions. By capturing multiple images with different phase shifts of these periodic patterns, the system enables each sensor pixel to independently determine depth through phase analysis, achieving both accurate depth measurement and efficient sensor utilization.
2Area of stationary object
If time of flight depth cameras illuminate multiple sensor pixels to perform a single depth measurement, then depth coverage is improved, but computational complexity increases for resolving optical paths
Solution Approach 1:
The patent replaces complex computational methods for resolving optical paths with a simpler optical interference approach. By using phase-shifted sinusoidal patterns and analyzing intensity variations at each pixel, the system determines depth through straightforward phase calculation rather than complex computational disambiguation of multiple optical paths.
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 approach enables efficient and accurate depth determination in the HMD's local area, improving the performance and efficiency of depth sensing in virtual or augmented reality systems.
Implementation Method 1
The illumination source is configured to emit a series of periodic illumination patterns (e.g., a sinusoid) into the local area. Each periodic illumination pattern of the series is phase shifted by a different amount.
Implementation Method 2
The imaging device captures frames including the periodic illumination patterns via a sensor including multiple pixels
Implementation Method 3
depth determination using fringe interferometry
Data Source
AI summary
A depth camera assembly (DCA) determines distances between the DCA and objects in a local area within a field of view of the DCA. The DCA projects a series of sinusoidal patterns into the local area DCA and captures images of the sinusoidal patterns via a sensor. Each pixel of the augmented sensor includes a plurality of charge bins, and charge accumulated by a photodiode of a pixel during different time intervals (e.g., times when different sinusoidal patterns are emitted) is stored in a different charge storage bin. Charge may be retrieved from different charge storage bins to determine depth from the DCA.