Integrated TOF Sensor Dual Modulation Phase Estimation
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Solution Overview
Problem
Existing 3D Time-of-Flight (TOF) systems face limitations in range and accuracy due to phase wrapping, requiring a trade-off between distance measurement range and accuracy, and are often bulky and expensive, with interference from other light sources being a significant issue.
Innovation Solution
The implementation of an integrated TOF sensor with dual modulation frequencies and a CORDIC Rotator for phase estimation, along with a maximal length sequence (MLS) generator for improved signal processing, allows for unambiguous distance measurement and reduced interference, enhancing accuracy and range without increasing system complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high frequency modulation is used to improve distance measurement accuracy, then measurement precision is improved, but the measurable distance range is reduced due to phase wrapping
Solution Approach 1:
The patent employs dual periodic modulation frequencies (first and second modulation frequencies) to simultaneously achieve high measurement precision and extended range. The first modulation frequency provides high precision for close objects, while the second modulation frequency enables measurement of distant objects, resolving the phase wrapping limitation of single-frequency systems.
Solution Approach 2:
The patent transitions from single-frequency modulation to dual-frequency modulation, adding a temporal dimension to the measurement system. By combining measurements at two different frequencies, the system achieves unambiguous distance measurement over an extended range while maintaining high precision, effectively solving the trade-off between range and accuracy.
2Device complexity
If square wave modulation is used to simplify implementation, then device complexity is reduced, but measurement precision deteriorates due to greater ambiguity and depth error
Solution Approach 1:
The patent changes the modulation waveform parameter from square wave to sinusoidal wave. Sinusoidal modulation provides smoother phase transitions and reduces distortion compared to square wave modulation, thereby improving depth measurement accuracy while maintaining implementation feasibility through standard signal generation techniques.
3Device complexity
If integrated TOF sensor is used to reduce system size, then device complexity is reduced, but interference from other light sources increases
Solution Approach 1:
The patent introduces a correlation processor as an intermediary that compares the reflected signal against the original modulated signal. This correlation analysis enables the system to distinguish between the target object's reflection and interference from other light sources, filtering out spurious signals while maintaining the compact integrated sensor design.
Solution Approach 2:
The system employs feedback mechanisms where the correlation processor continuously analyzes the reflected signal characteristics and adjusts measurements accordingly. By comparing expected signal patterns with actual reflections, the system can identify and reject interference from other light sources, maintaining measurement accuracy in complex lighting environments.
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 accurate and unambiguous distance measurement over a wider range while minimizing interference from other light sources, improving the overall performance and reducing the need for bulky and expensive systems.
Implementation Method 1
a photodetector device (e.g. photodiode, photomultiplier tube, avalanche photodiode, or single photon avalanche diode) capable of producing an image and responsive to the same spectrum
Implementation Method 2
The light source is pulsed or modulated by a continuous-wave (CW), source, typically a sinusoid or square wave
Data Source
AI summary
A time of flight sensor includes a time of flight (TOF) processor having a digital TOF port, a digital input port, and a digital output port, the TOF processor comprising a phase detector including cyclically rotating demultiplexer (DEMUX), a first summer coupled to a first DEMUX output, a second summer coupled to a second DEMUX output, a third summer coupled to a third DEMUX output, a fourth summer coupled to a fourth DEMUX output, and a phase estimator coupled to outputs of the first summer, the second summer, the third summer and the fourth summer and having a phase estimate output; a driver having a digital driver port coupled to the digital TOF port and a driver output port; and an analog-to-digital converter (ADC) having an output port coupled to the digital input port of the digital TOF processor.