Time-of-Flight Camera Modulation Signal Harmonic Reduction
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Solution Overview
Problem
Time-of-flight cameras face challenges in achieving high accuracy while complying with electromagnetic compatibility (EMC) standards due to high energy harmonics in their modulation signals, which can limit their accuracy and increase production costs.
Innovation Solution
Applying a periodic frequency perturbation to the base frequency of the modulation signal, spreading the energy over a wider spectrum to reduce peak energy density, thus improving EMC compliance without compromising distance measurement precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sharply defined pulses with limited rise and fall time are used for high accuracy distance measurement, then measurement precision is improved, but electromagnetic compliance deteriorates due to high energy harmonics
Solution Approach 1:
The patent applies frequency perturbation to the modulation signal, changing the frequency parameter from a fixed value to a time-varying value. This spreads the spectral energy density of the modulation signal over a wider frequency range, reducing peak energy density while maintaining the ability to accurately measure time-of-flight for distance calculation
Solution Approach 2:
The patent employs periodic frequency perturbation of the modulation signal. By periodically varying the frequency around a base frequency, the signal maintains its periodic nature which is essential for phase-based distance measurement while simultaneously reducing harmonic energy concentration at any single frequency
2Measurement precision
If high modulation frequency is used to improve distance measurement accuracy, then measurement precision is improved, but electromagnetic compliance deteriorates due to increased harmonic energy
Solution Approach 1:
The patent changes the frequency parameter of the modulation signal by applying periodic perturbation. This transforms the signal from having a single high-frequency component to having a distributed frequency spectrum, thereby reducing the energy concentration in harmonics while preserving measurement accuracy through the maintained base frequency
3Object-affected harmful factors
If EMC requirements are strictly enforced to ensure electromagnetic compliance, then electromagnetic compliance is improved, but measurement precision deteriorates due to limited modulation frequency options
Solution Approach 1:
The patent enables the use of higher base frequencies for modulation while maintaining EMC compliance through frequency perturbation. The periodic frequency variation spreads the spectral energy, allowing the system to operate at frequencies that would otherwise generate excessive harmonics, thus improving both compliance and measurement capability
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 allows for high-accuracy distance information acquisition while enhancing electromagnetic compliance, reducing the spectral energy density and making the devices more cost-effective to produce.
Implementation Method 1
evaluating a time-of-flight information for the received reflections of the modulated light pulse
Implementation Method 2
receiving reflections of the modulated light pulse from the scene
Data Source
AI summary
The invention relates to a method for providing distance information of a scene with a time-of-flight camera, comprising the steps of emitting a modulated light pulse towards the scene, receiving reflections of the modulated light pulse from the scene, evaluating a time-of-flight information for the received reflections of the modulated light pulse, and deriving distance information from the time-of-flight information for the received reflections, whereby a spread spectrum signal is applied to a base frequency of the modulation of the light pulse, and the time-of-flight information is evaluated under consideration of the a spread spectrum signal applied to the base frequency of the modulation of the light pulse. The invention further relates to a time-of-flight camera for providing distance information from a scene, whereby the time-of-flight camera performs the above method.