TOF Distance Sensor Using Four-Phase Correlation Signals
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Solution Overview
Problem
Current 2-tap TOF distance sensors using sinusoidal signals face limitations in accurately measuring distances due to hardware complexity, signal-to-noise ratio, and dynamic range issues, particularly when dealing with varying light sources and object distances.
Innovation Solution
A TOF distance sensor that generates 4 phase-shifted correlation signals with the same period length, using a semiconductor radiation source and a receiving device to correlate the received radiation, forming differential correlation values for linear dependence-based distance calculation, optimized for improved signal-to-noise ratio and dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If 2-tap TOF distance sensors use sinusoidal signals for distance measurement, then the measurement capability is provided, but hardware complexity and computation effort increase
Solution Approach 1:
The patent divides the correlation process into 4 discrete correlation values (C0, C1, C2, C3) corresponding to four phase-shifted correlation signals instead of continuous sinusoidal correlation. This segmentation transforms the continuous measurement problem into discrete steps, reducing computational complexity while maintaining measurement capability through differential correlation values.
Solution Approach 2:
The patent replaces complex sinusoidal signal generation and continuous correlation computation with simpler rectangular correlation signals and discrete correlation values. The computation is simplified to basic arithmetic operations on 4 correlation values, significantly reducing processing requirements while achieving the same distance measurement function.
2Measurement precision
If 2-tap TOF distance sensors use sinusoidal signals, then distance measurement is enabled, but signal-to-noise ratio and dynamic range are limited
Solution Approach 1:
The patent skips the intermediate steps of continuous sinusoidal correlation and directly computes 4 discrete correlation values at specific phase points (0°, 90°, 180°, 270°). This approach rushes through the correlation process at critical sampling points, capturing essential phase information while rejecting noise through differential calculation of correlation values.
Solution Approach 2:
The patent combines 4 correlation values measured at different phase shifts to form differential correlation values, creating a composite measurement that is more robust to noise and varying light conditions. This composite approach leverages multiple measurements to extract accurate distance information while canceling out noise components.
3Measurement precision
If complex correlation calculations are performed continuously, then measurement accuracy is maintained, but processing speed and frame rate decrease
Solution Approach 1:
The patent uses periodic rectangular correlation signals with four distinct phase shifts (0°, 90°, 180°, 270°) to sample the reflected light. This periodic sampling at critical phase points captures all necessary information for distance calculation in a single modulation period, enabling fast computation and high frame rates while maintaining accuracy.
Solution Approach 2:
The patent replaces complex continuous mathematical correlation operations with simple discrete arithmetic calculations on 4 correlation values. The continuous sinusoidal correlation is substituted with discrete rectangular pulse correlation followed by basic differential calculations, dramatically reducing processing time and enabling real-time distance measurement at high frame rates.
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 reduces hardware complexity, enhances signal-to-noise ratio, increases processing speed, and improves frame rate while reducing computation effort and sensor size, enabling more accurate and efficient distance measurements across different light sources and object distances.
Implementation Method 1
The radiation source is preferably a semiconductor radiation source, preferably an LED (light emitting diode) or multiple LEDs
Implementation Method 2
TOF distance sensor for measuring a distance to an object
Implementation Method 3
a receiving device which is in a predetermined spatial relationship to the radiation source for receiving radiation reflected from the object
Data Source
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Figure 3
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AI summary
A time-of-flight (TOF) distance sensor is proposed for measuring the distance to an object, comprising an electronic device for generating a modulation signal and for generating four correlation signals which are phase-shifted relative to each other and have the same period as the modulation signal; a radiation source for emitting radiation modulated by the modulation signal; a receiving device positioned in a predetermined spatial relationship to the radiation source for receiving radiation reflected from the object; a correlation device for correlating the received radiation or a corresponding quantity with each of the four correlation signals to generate four corresponding correlation values; and a difference calculation device for generating two difference correlation values from the difference between any two of the correlation values.a calculating device designed to calculate the distance in a predetermined linear relationship to the two difference correlation values.