3D Time-of-Flight Phase Decoding for Long-Range Sensing
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Solution Overview
Problem
Conventional indirect time-of-flight (iToF) sensing systems suffer from flare effects and reduced accuracy due to ambiguity in phase shift determination beyond the period of emitted signals.
Innovation Solution
A time-of-flight (ToF) 3D sensing system that generates emitted and received signals with specific phase shifts in basis and supplemental periods, using a flag signal to define supplemental periods, allowing accurate distance determination without flare effects, even beyond the maximum resolvable distance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional iToF sensing systems adopt two or more modulated light signals with different frequencies to achieve de-aliasing, then the measurement precision is improved, but the device complexity increases and flare effect occurs with reduced accuracy
Solution Approach 1:
The measurement period is segmented into a basis period and multiple supplemental periods. The basis period uses the original emitted signal frequency for normal phase measurement, while supplemental periods use a doubled frequency for unambiguous phase determination beyond the maximum resolvable distance. This segmentation resolves the contradiction by providing different measurement strategies for different distance ranges, achieving high precision without requiring complex multi-frequency signal processing throughout the entire measurement cycle.
Solution Approach 2:
The system preliminarily determines whether the object distance exceeds the maximum resolvable distance before performing phase measurement. Based on this preliminary assessment, it selectively activates either the basis period measurement or supplemental period measurement with doubled frequency. This preliminary action avoids the need for continuous complex multi-frequency processing, reducing device complexity while maintaining measurement precision.
2Adaptability or versatility
If the basis period alone is used for distance measurement, then the device complexity is reduced, but the working range is limited to the maximum resolvable distance
Solution Approach 1:
The system dynamically adjusts the signal frequency based on the measured distance. During the basis period, it uses the original emitted signal frequency for normal operation. When the object distance exceeds the maximum resolvable distance, it automatically switches to supplemental periods with doubled frequency. This dynamic adaptation extends the working range without requiring permanently complex signal generation circuitry, as the system only activates the extended frequency capability when needed.
Solution Approach 2:
The measurement process is organized into periodic basis periods and supplemental periods. The basis period operates at the original frequency for routine measurements within the maximum resolvable distance. When distance exceeds this limit, supplemental periods with doubled frequency are periodically activated to provide unambiguous phase determination. This periodic structure extends working range while keeping the average system complexity low, as the complex doubled-frequency operation occurs only periodically when needed.
3Adaptability or versatility
If multiple frequencies are used for de-aliasing, then the working range is extended, but flare effect occurs reducing measurement accuracy
Solution Approach 1:
The system applies different measurement qualities to different distance ranges. For objects within the maximum resolvable distance, it uses the simple basis period measurement at original frequency, avoiding flare effects. For objects beyond this distance, it locally applies the supplemental period measurement with doubled frequency to achieve unambiguous phase determination. This local quality differentiation extends working range while maintaining high measurement accuracy by avoiding flare effects in the primary measurement range.
Solution Approach 2:
The invention extracts the phase measurement function into separate basis period and supplemental period operations. The basis period handles normal-range measurements without flare effects, while the supplemental period with doubled frequency is extracted and activated only when distance exceeds the maximum resolvable distance. This extraction allows the system to extend working range through selective use of doubled frequency, while maintaining measurement accuracy by keeping the flare-free basis period measurement as the primary operation.
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 system achieves high accuracy and large working range by determining phase shifts accurately, mitigating flare effects and multipath interference, enabling precise distance measurement.
Implementation Method 1
measuring a distance between the sensor (e.g., camera) and the object to be determined based on time-of-flight technique by measuring the round trip time of an artificial light signal
Data Source
AI summary
A time-of-flight (ToF) three-dimensional (3D) sensing system includes a projector that generates an emitted light corresponding to an emitted signal; a sensor that generates a received signal according to a reflected light; and a decoder that determines a distance between the sensor and the object according to the received signal. The emitted signal associated with the emitted light is generated in a basis period, and the received signal associated with the reflected light is generated by the sensor with a first phase shift with respect to a beginning of the basis period. No emitted light is generated in a supplemental period following the basis period, and the received signal has a second phase shift with respect to a beginning of the supplemental period. The distance between the sensor and the object is determined according to the first phase shift and the second phase shift.