Lidar Phase Ambiguity Resolution via Periodic Wave Comparison
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Solution Overview
Problem
Current 3D camera systems using Time-of-Flight (TOF) methods face limitations in accurately measuring distances beyond one period of a laser pulse due to phase ambiguity, requiring high temporal resolution counters for precise distance calculation.
Innovation Solution
A lidar device that emits and receives laser pulses, generating and comparing periodic waves to calculate distance based on phase differences, with a counter to count periods and resolve phase ambiguity, allowing for accurate distance measurement beyond one laser pulse period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a Time-of-Flight method is used to measure distance, then distance measurement capability is achieved, but phase ambiguity occurs when measuring distances beyond one laser pulse period
Solution Approach 1:
The patent uses periodic waves with different frequencies to modulate the laser pulse emission and reception timing. By generating first and second periodic waves with different frequencies and comparing their phases, the system can determine the number of complete periods elapsed during the laser pulse flight time, thereby resolving phase ambiguity and enabling accurate distance measurement beyond one period.
Solution Approach 2:
The patent changes the frequency parameter of the periodic waves used for phase comparison. By using periodic waves with different frequencies (first frequency for emission timing, second frequency for reception timing), the system can calculate the number of periods and resolve phase ambiguity, transforming the measurement capability from limited to one period to extended beyond one period.
2Measurement precision
If high temporal resolution counters are used to resolve phase ambiguity, then distance measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The patent replaces the need for high temporal resolution counters with a phase comparison method using periodic waves. Instead of directly counting time intervals with high-precision counters, the system uses frequency comparison of periodic waves generated at emission and reception moments, substituting a complex timing measurement system with a simpler phase detection approach.
3Device complexity
If phase comparison is performed without counting periods, then device complexity is reduced, but distance measurement accuracy deteriorates due to phase ambiguity
Solution Approach 1:
The patent introduces periodic waves as an intermediary mechanism between the laser pulse timing and the phase comparison process. By generating periodic waves synchronized with pulse emission and reception, and comparing their phases, the system obtains information about the number of periods elapsed without requiring direct high-precision time counting, thus maintaining accuracy while reducing complexity.
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
Enables precise distance calculation without the need for high temporal resolution counters, effectively overcoming phase ambiguity and improving distance measurement accuracy for both short-range and long-range applications.
Implementation Method 1
the algorithm of the 3D camera generally utilizes a Time-of-Flight (TOF) method
Implementation Method 2
The light receiver may include an avalanche photo diode (APD) or a single photon avalanche diode (SPAD)
Data Source
AI summary
A lidar device includes a light source configured to emit a laser pulse to an object, a light receiver configured to receive the laser pulse reflected by the object, a first periodic wave generator configured to generate a first periodic wave when the light source emits the laser pulse and generate a second periodic wave when the light source receives the laser pulse, and a first comparator configured to compare a phase of the first periodic wave and a phase of the second periodic wave to each other. The lidar device calculates a distance between the lidar device and the object based on a phase difference determined by the first comparator.