Time-of-Flight Camera Cyclic Error Correction via Fourier Analysis
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Solution Overview
Problem
Time-of-flight cameras face cyclic errors due to frequency aliasing, which affect the accuracy of depth or distance measurements, and existing calibration techniques are not optimal for all correlation waveform sampling schemes.
Innovation Solution
An electronic device with circuitry that samples differential mode measurements during calibration using a known time-of-flight, determines Fourier coefficients, and calculates cyclic errors based on these coefficients, allowing for improved cyclic error correction at runtime using aliasing weights and look-up tables.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If frequency aliasing occurs in time-of-flight cameras, then cyclic errors appear in depth measurements, but measurement precision deteriorates
Solution Approach 1:
The patent applies preliminary action by performing calibration before actual depth measurements to determine cyclic error characteristics. The system pre-determines cyclic error values for different time-of-flight ranges and stores them for later correction, preventing the harmful effect from impacting measurement precision.
Solution Approach 2:
The patent implements feedback by using the determined cyclic error values to correct depth measurements. The system continuously refines depth accuracy by applying correction based on the relationship between time-of-flight and cyclic error, creating a closed-loop correction mechanism.
2Reliability
If separate calibration acquisitions are performed for different sampling schemes, then cyclic error correction can be optimized for each scheme, but device complexity increases
Solution Approach 1:
The patent applies universality by creating a calibration method that works across different sampling schemes (e.g., 4-tap, 5-tap, 6-tap schemes) without requiring separate calibration procedures for each. The determined cyclic error characteristics can be applied universally to correct measurements regardless of the specific sampling scheme used.
Solution Approach 2:
The patent uses parameter changes by adapting the calibration approach to work with different sampling parameters (number of taps, sampling intervals). The system determines cyclic error as a function of time-of-flight that can accommodate various sampling configurations through parameter adjustment rather than requiring complete recalibration.
3Measurement precision
If calibration is performed using known objects at known distances, then cyclic error data can be acquired, but loss of time occurs during calibration acquisition
Solution Approach 1:
The patent applies preliminary action by performing the calibration process during manufacturing or initial setup, so that cyclic error correction data is available before actual depth measurements begin. This shifts the time cost from operational use to setup phase, making the calibration time imperceptible during normal 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
This approach enhances the accuracy of depth measurements by effectively correcting cyclic errors across different sampling strategies, reducing the need for separate calibration acquisitions and improving the reliability of distance estimation in time-of-flight imaging.
Implementation Method 1
A time-of-flight camera is a range imaging camera system that determines the distance of objects measuring the time-of-flight (ToF) of a light signal between the camera and the object for each point of the image
Data Source
AI summary
An electronic device comprising circuitry configured to sample, in a calibration phase using a known time-of-flight τD, a first set of differential mode measurements μcal (nΔτE,τD) according to a first sampling strategy tEcal, and to determine Fourier coefficients Mk of the first set of differential mode measurements μcal(τE,n,τD) based on the known time-of-flight (τD) used in the calibration phase, and to determine a cyclic error (fCE(θ1,μ(τD);x)) based on the Fourier coefficients (Mk).