TOF Ranging System with Dual-Frequency Amplitude Modulation
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Solution Overview
Problem
Time-of-flight (TOF) ranging systems face ambiguity in distance measurement due to the periodicity of phase shift, where multiple distances result in the same phase shift, limiting the maximum range and accuracy.
Innovation Solution
The system employs dual-frequency amplitude modulation with a rational ratio between the sampling signals, allowing for disambiguation of distances by integrating the modulated signal over specific phases and using two superimposed amplitude modulations to calculate phase differences, thereby resolving the ambiguity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the light intensity modulation frequency is lowered to increase ambiguity distance, then the maximum range is improved, but the accuracy of distance measurements deteriorates
Solution Approach 1:
The patent divides the single frequency measurement into multiple frequency measurements. By using multiple modulation frequencies (e.g., f1, f2, f3), the system segments the distance measurement problem into several phase shift measurements at different frequencies, each providing information about different distance ranges, thereby resolving the contradiction between range and accuracy
Solution Approach 2:
The patent adds the frequency dimension to the measurement process. Instead of using a single frequency, the system measures phase shifts at multiple frequencies, effectively moving from a one-dimensional measurement (single frequency) to a multi-dimensional measurement (multiple frequencies), which allows disambiguation of distances beyond the single-frequency ambiguity limit
2Measurement precision
If multiple different distances yield the same phase shift, then the periodicity of phase shift is exploited for measurement, but the distance ambiguity increases
Solution Approach 1:
The system uses feedback from multiple frequency measurements to resolve ambiguity. By comparing phase shift measurements at different frequencies, the system can determine which distance is correct, as each frequency provides complementary information that feedback into the overall distance calculation
Solution Approach 2:
The patent combines measurements from multiple frequencies to create a composite distance measurement. Just as composite materials combine different materials to achieve superior properties, this system combines multiple phase shift measurements at different frequencies to achieve unambiguous distance measurement that overcomes the limitations of any single frequency
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 unambiguous distance measurement beyond the traditional ambiguity distance, improving the accuracy and range of TOF systems by disambiguating phase shifts and enhancing measurement precision.
Implementation Method 1
Time-of-flight (TOF) ranging systems face ambiguity in distance measurement due to the periodicity of phase shift
Implementation Method 2
The system employs dual-frequency amplitude modulation with a rational ratio between the sampling signals, allowing for disambiguation of distances by integrating the modulated signal over specific phases
Data Source
AI summary
An embodiment includes a method, comprising: receiving a modulated signal having modulation; generating a first signal in response to the modulation and a first sampling signal; generating a second signal in response to the modulation and a second sampling signal; and generating a distance in response to the first signal and the second signal. A ratio of a frequency of the first sampling signal to a frequency of the second sampling signal is a rational number.