Indirect Time of Flight Phase Angle Correction for Harmonic Error Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Indirect Time of Flight (iToF) ranging systems face limitations in distance measurement accuracy due to aliasing errors from harmonic content and are susceptible to motion artifacts, which affect the precision of phase angle calculations and distance determination.
Innovation Solution
A phase angle calculation apparatus that employs a light source and a photonic mixer cell to generate electrical signals at predetermined phase values, with a signal processing circuit that calculates vectors and angles, applies a phase offset, de-rotates signals, and corrects angles to reduce harmonic errors and motion artifacts, using a combination of Digital Fourier Transform and angle correction units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high modulation frequencies are used in iToF systems to achieve low stochastic distance measurement errors, then measurement precision is improved, but the unambiguous distance range that can be measured decreases
Solution Approach 1:
The measurement process is divided into multiple segments by using multiple modulation frequencies. The system performs measurements at different frequencies (e.g., first frequency for short range, second frequency for extended range) and combines the results through frequency mixing or phase unwrapping algorithms to achieve both high precision and extended unambiguous range.
Solution Approach 2:
The system dynamically changes the modulation frequency parameter based on the measurement requirements. By switching between different modulation frequencies or using frequency modulation, the system can optimize the balance between measurement precision and unambiguous range for different scattering scenarios.
2Device complexity
If conventional iToF systems use single frequency modulation, then device complexity is reduced, but susceptibility to multiple reflections and multiple propagation paths increases
Solution Approach 1:
The system employs periodic modulation at multiple frequencies to encode the optical signals. By using orthogonal frequency modulation schemes, the system can distinguish between direct reflections and multiple propagation paths through frequency domain analysis, reducing the impact of multipath effects without significantly increasing device complexity.
3Ease of operation
If amplitude modulated continuous wave systems use standard correlation functions, then ease of operation is maintained, but inherent depth measurement errors due to aliasing occur
Solution Approach 1:
The system introduces an intermediary processing stage that applies advanced correlation functions or phase extraction algorithms between the raw signal acquisition and final depth calculation. This intermediary layer corrects aliasing errors by analyzing phase relationships across multiple frequencies or using iterative optimization methods, maintaining ease of operation while improving measurement precision.
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 solution enhances the accuracy of phase angle calculations, reduces the impact of harmonic errors, and improves immunity to motion artifacts, leading to more precise distance measurements in iToF systems.
Implementation Method 1
a photonic mixer cell to generate a plurality of electrical output signals in respect of a fundamental frequency
Data Source
AI summary
An indirect time of flight range calculation apparatus comprises a light source, a photonic mixer that generates a plurality of output signals corresponding to a first plurality of phase values. A signal processor is also provided to calculate a first vector and a first angle from the first vector. The photonic mixer generates a second plurality of electrical output signals corresponding to a second plurality of phase values. Each phase value of the second plurality of phase values is respectively offset with respect to each phase value of the first plurality of phase values by a predetermined phase offset value. The signal processor processes the second plurality of electrical output signals in order to calculate a second vector, and de-rotates the second vector calculated and calculates a second angle from the de-rotated vector before offsetting the second angle against the first angle, thereby generating a corrected output angle.