Depth Camera Assembly Using Fringe Interferometry for HMDs
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Solution Overview
Problem
Conventional head-mounted displays (HMDs) for virtual and augmented reality systems face inefficiencies in depth measurement due to structured light and time of flight depth cameras, which result in inefficient light usage and computational complexity in disambiguating optical paths.
Innovation Solution
A depth camera assembly in the HMD that uses a series of periodic illumination patterns with phase shifts, where each pixel independently determines depth based on captured intensities, and optical filters to capture intensity information from different wavelengths, optimizing pixel usage and reducing computational complexity.
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 achieved, but sensor pixel utilization efficiency deteriorates (less than 10% of sensor pixels collect light)
Solution Approach 1:
The patent applies periodic action by projecting sinusoidal illumination patterns at multiple phase shifts (0, 90, 180, 270 degrees) across the entire sensor array. This periodic modulation allows every pixel to capture varying intensity values that encode depth information, achieving full sensor utilization while maintaining depth measurement capability through phase-based detection.
2Measurement precision
If time of flight depth cameras use multiple sensor pixels to measure depth independently, then depth measurement capability is improved, but computational complexity increases due to optical path disambiguation requirements
Solution Approach 1:
The patent replaces complex computational optical path disambiguation with a simplified optical interference measurement system. By using a displaced illumination source to create spatially varying phase shifts and employing sinusoidal patterns with known phase relationships, the system directly encodes depth information in intensity measurements, eliminating the need for computationally intensive optical path resolution algorithms.
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 enables more efficient depth measurement by optimizing pixel usage and simplifying computational processes, improving the accuracy and efficiency of depth determination in virtual and augmented reality systems.
Implementation Method 1
Depth camera assembly using fringe interferometry via multiple wavelengths
Implementation Method 2
The sensor includes a set of optical filters positioned to form multiple regions of adjacent pixels. Different optical filters are configured to pass different wavelengths of light
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 each having different wavelengths into the local area DCA and captures images of the sinusoidal patterns via a sensor. Optical filters configured to pass different wavelengths of light are positioned within the sensor to form regions including adjacent pixels. Hence, pixels in a region capture light having a wavelength passed by an optical filter corresponding to the region. If the DCA projects sinusoidal patterns having different wavelengths at different times, the sensor is gated with an illumination source so regions of the sensor capturing light having a specific wavelength capture light while the illumination source emits the specific wavelength and not while the illumination source emits other wavelengths.