Dual-Frequency Direct Time-of-Flight Depth Mapping
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Solution Overview
Problem
Direct Time-of-Flight (dToF) systems face challenges in achieving high precision and accuracy due to the need for large temporal bins, which reduce system precision and accuracy, and also face memory and computational costs when using global shutters, especially in generating and processing histograms.
Innovation Solution
Implementing a dual-frequency dToF system that uses two different frequencies to provide a longer time interval and higher accuracy, and employing a mosaic of pixels to capture and interpolate depth maps, reducing memory usage by sharing histograms and reducing the number of ToF pulses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If large temporal bins are used in dToF systems, then the measurement range is improved, but the precision and accuracy deteriorate
Solution Approach 1:
The patent divides the measurement process into multiple frequency components. By using dual-frequency modulation, the system segments the time-of-flight measurement into two different periodic measurements, allowing for a longer effective measurement range while maintaining fine temporal resolution through the combination of both frequency measurements.
Solution Approach 2:
The patent changes the modulation frequency parameter to resolve the contradiction. By operating at two different frequencies simultaneously, the system achieves an extended unambiguous range (determined by the lower frequency) while maintaining high precision (determined by the higher frequency), thus resolving the trade-off between range and precision.
2Loss of information
If global shutters are used to capture depth maps, then the completeness of depth information is improved, but the memory and computational costs deteriorate
Solution Approach 1:
The patent extracts only the essential depth information needed at each frequency phase, rather than storing complete histograms for all pixels simultaneously. By processing and storing only the critical phase-dependent depth measurements, the system reduces memory requirements while maintaining the ability to reconstruct complete depth maps.
Solution Approach 2:
The patent performs preliminary depth calculations at intermediate frequency phases, storing only the necessary intermediate results rather than complete raw data. This preliminary processing reduces the memory burden while preserving all information needed for final depth map reconstruction.
3Loss of information
If global shutters are used to capture depth maps, then the completeness of depth information is improved, but the computational costs deteriorate
Solution Approach 1:
The patent segments the depth mapping computation into multiple frequency-specific processing stages. By dividing the computational task across different frequency measurements and processing them separately, the system reduces the complexity of any single computational step while achieving complete depth information through integration of all frequency data.
Solution Approach 2:
The patent performs partial depth calculations at intermediate frequency phases, computing only the portion of depth information necessary at each stage. This partial computation approach reduces overall computational complexity while ensuring complete depth map generation through subsequent integration of all partial results.
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
The dual-frequency approach enhances precision and accuracy while reducing memory and computational costs, allowing for more efficient generation of depth maps with reduced power consumption and increased resolution.
Implementation Method 1
Direct time-of-flight (dToF) technology is based on measuring the time it takes an emitted signal to propagate to an object or target (in an environment) and return back to a sensor
Implementation Method 2
dToF light pulses are emitted at a first temporal pulsing frequency and a second temporal pulsing frequency that is not colinear with the first temporal pulsing frequency
Data Source
AI summary
Time-of-Flight (TOF) light pulses are emitted at a first temporal pulsing frequency and a second temporal pulsing frequency. ToF return signals are detected by a light detector of a ToF sensor and a wrapped histogram may be generated. As part of generating unwrapped histograms, a selected index may be identified to provide a ToF distance from ToF distances of the ToF return signals.