De-aliasing Indirect Time-of-Flight Depth Measurements
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Solution Overview
Problem
Indirect Time-of-Flight (iToF) depth cameras face limitations due to multicycle aliasing, which affects their ability to accurately determine depth measurements, as objects at specific distances can produce the same phase difference, leading to inaccurate distance calculations.
Innovation Solution
The system compares iToF-based depth information with image-based depth information to identify inconsistencies, using image-based data to adjust iToF depth measurements by adding or subtracting integer numbers of half wavelengths, thereby correcting for errors caused by multicycle aliasing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If iToF phase-difference measurements are used to determine depth, then measurement speed is improved, but measurement precision deteriorates due to multicycle aliasing
Solution Approach 1:
The patent combines iToF phase-difference measurements with alternative depth measurement methods (such as structured light or stereo vision) to resolve multicycle aliasing. By merging multiple measurement approaches, the system maintains the speed advantage of iToF while correcting its precision limitations through cross-validation with other depth estimation techniques.
Solution Approach 2:
The patent introduces an intermediary processing step that uses the phase-difference measurement results as initial estimates, then refines these estimates by comparing them with depth information from other sources. This intermediary refinement process corrects multicycle aliasing errors while preserving the rapid initial measurement capability.
2Adaptability or versatility
If the measurement range is increased beyond half wavelength, then adaptability is improved, but measurement precision deteriorates due to inability to distinguish between multiple depths
Solution Approach 1:
The patent employs multiple periodic measurements at different frequencies or phases. By performing repeated measurements with varying parameters and analyzing the patterns across multiple cycles, the system can distinguish between true depth variations and multicycle aliasing artifacts, thereby maintaining precision across extended measurement ranges.
Solution Approach 2:
The patent adds another dimension to the measurement process by incorporating temporal or frequency variations. Instead of relying solely on single-phase measurements, the system uses measurements taken at multiple time points or frequencies, creating an additional dimension of data that enables disambiguation of depths beyond the half-wavelength limit.
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 enhances the accuracy of depth maps by combining the absolute distance measurements of iToF with the relative depth information from images, providing a more robust and coherent depth representation than either method alone.
Implementation Method 1
An indirect Time-of-Flight (iToF) depth camera may measure a phase difference between an emitted light pulse and the light pulse as received by the iToF depth camera after the light pulse has been reflected by an object in the environment. The iToF depth camera may relate the phase difference to a time-of-flight of the light pulse between emission and reception, based on the speed of light and the frequency of the light pulse.
Implementation Method 2
IToF phase-difference measurements may be cyclic. For example, phase measurements may repeat every integer number of half wavelengths of the light pulse that an object is from an iToF depth camera.
Data Source
AI summary
Systems and techniques are described herein for determining depth information. For instance, a method for determining depth information is provided. The method may include transmitting electromagnetic (EM) radiation toward a plurality of points in an environment; comparing a phase of the transmitted EM radiation with a phase of received EM radiation to determine a respective time-of-flight estimate of the EM radiation between transmission and reception for each point of the plurality of points in the environment; determining first depth information based on the respective time-of-flight estimates determined for each point of the plurality of points in the environment; obtaining second depth information based on an image of the environment; comparing the first depth information with the second depth information to determine an inconsistency between the first depth information and the second depth information; and adjusting a depth of the first depth information based on the inconsistency.