Time-of-flight distance measuring device multipath error detection
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Solution Overview
Problem
Conventional time-of-flight distance measuring devices face accuracy issues due to multipath interference, which can lead to errors in distance calculation, and existing methods to detect these errors suffer from time lags that may miss transient multipath occurrences.
Innovation Solution
A time-of-flight distance measuring device with a light source and receiver divided into sub-regions, using amplitude-modulated waveforms with different harmonic components to detect multipath errors simultaneously, eliminating the need for sequential calculations and thus avoiding time lags.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sequential calculation of exposure amount for two different light emission patterns is used to detect multipath error, then multipath error detection is enabled, but time lag is generated which deteriorates detection accuracy
Solution Approach 1:
The patent applies periodic action by using alternating light emission patterns with different duty cycles (e.g., 50% and 25%) at different time periods. The light emitter sequentially emits light with first duty cycle during first period and light with second duty cycle during second period, enabling the system to collect data for multipath error detection through time-multiplexed periodic measurements without requiring simultaneous complex measurements.
Solution Approach 2:
The patent employs dynamics by making the light emission pattern variable over time. The controller dynamically switches between different emission patterns (different duty cycles) based on timing, and the light emitter adapts its emission characteristics accordingly. This dynamic approach allows the system to optimize detection accuracy while managing the time lag issue through controlled temporal variation of emission parameters.
2Measurement precision
If conventional TOF technology is used to measure distance, then distance measurement is enabled, but multipath interference causes error in the measured distance
Solution Approach 1:
The patent converts the harmful effect of multipath interference into a beneficial detection mechanism. By using light emission patterns with different duty cycles and analyzing the reflected light characteristics, the system can detect the presence of multipath interference and identify erroneous distance measurements. The harmful multipath signals are transformed into detectable anomalies that can be flagged and corrected, turning a previously problematic phenomenon into a useful diagnostic tool.
Solution Approach 2:
The patent applies parameter changes by varying the duty cycle parameter of the light emission pattern. By emitting light with different duty cycles (e.g., switching between 50% and 25% duty cycles) and analyzing how the reflected light characteristics change with these parameter variations, the system can distinguish between direct reflected light and multipath interfered light, thereby improving distance measurement accuracy in the presence of multipath interference.
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
Enables accurate and timely detection of multipath errors, improving the precision of distance measurements by allowing simultaneous sensing of harmonic components, thereby reducing errors in distance calculations.
Implementation Method 1
a first controller controls (i) a first emitting portion of the plurality of emitting portions to emit the emitted light as an amplitude-modulated waveform including an Nth-order harmonic component of a fundamental frequency and (ii) a second emitting portion of the plurality of emitting portions to emit the emitted light as an amplitude-modulated waveform including an Mth-order harmonic component of the fundamental frequency
Implementation Method 2
a light receiver that detects, as reflected light, the emitted light reflected by an object in the specified region
Data Source
AI summary
The present disclosure relates to a time-of-flight distance measuring device. The light source (24) includes a plurality of emitting portions (70, 72), each of which illuminates a respective one of the sub-regions (R1, R2). The light receiver (26) includes a plurality of receiving portions (74, 76) corresponding to respective ones of the emitting portions (70, 72). The first controller (28) controls (i) a first emitting portion (70) to emit the emitted light including an Nth-order harmonic component of a fundamental frequency and (ii) a second emitting portion (72) to emit the emitted light including an Mth-order harmonic component. The second controller (30) controls a particular receiving portion (74) corresponding to the first emitting portion (70) to be sensible to the Nth-order Mth-order harmonic components. The multipath detector (82) detects occurrence of the multipath error when the particular receiving portion (74) senses both the Nth-order and Mth-order components.