LiDAR Interpolation Filtering to Prevent Ringing in Distance Waveforms
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Solution Overview
Problem
Conventional lidar distance measurement apparatuses face accuracy issues due to waveform distortion caused by ringing during upsampling, particularly when dealing with saturated waveforms, leading to erroneous distance detection.
Innovation Solution
A distance measurement apparatus that includes a light emitter, a light receiver, an AD converter, and an interpolation processor with a low-pass filter that suppresses waveform distortion by inserting interpolation data and using a moving average filter to smooth the data series, preventing ringing and maintaining accurate distance detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional upsampling methods are used to increase sampling rate, then distance measurement resolution is improved, but waveform distortion occurs due to ringing
Solution Approach 1:
The patent changes the parameter of the low-pass filter from a conventional design to one with specific characteristics where ringing does not occur. By modifying the filter's impulse response parameters and using a moving average filter with specific coefficients, the system achieves upsampling while preventing waveform distortion caused by ringing, thus maintaining both measurement precision and waveform accuracy.
Solution Approach 2:
The patent introduces a specially designed low-pass filter as an intermediary component between the AD converter and the distance calculation unit. This filter acts as a mediator that smooths the upsampled data while preventing ringing distortion, thereby protecting the waveform accuracy while still enabling high-resolution distance measurement.
2Reliability
If high-order low-pass filters are used to reduce ringing, then waveform accuracy is improved, but circuit complexity and power consumption increase
Solution Approach 1:
The patent replaces complex high-order filters with a simpler moving average filter that uses basic arithmetic operations (addition and division). This simpler filter structure consumes less power and has lower circuit complexity while achieving the same waveform accuracy through optimized filtering coefficients and a specific filtering approach that avoids ringing without requiring complex hardware.
3Reliability
If high-order low-pass filters are used to reduce ringing, then waveform accuracy is improved, but power consumption increases
Solution Approach 1:
The patent employs a moving average filter that relies on simple addition and division operations rather than complex multiplication and accumulation required by high-order filters. This reduces the computational burden and power consumption while maintaining waveform accuracy through optimized filter coefficients that prevent ringing without requiring excessive processing power.
4Stability of the object's composition
If conventional filtering is applied after upsampling, then interpolation smoothness is improved, but distance detection accuracy decreases due to ringing distortion
Solution Approach 1:
The patent changes the fundamental parameter of the filter design from conventional approaches to a moving average filter with specific coefficients that prevent ringing. By modifying the filter characteristics to have a gradual frequency response rather than a sharp cutoff, the system achieves data smoothness through interpolation while eliminating the ringing distortion that would compromise distance detection accuracy.
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 effectively suppresses the decrease in distance detection accuracy attributed to waveform distortion after upsampling, ensuring precise distance measurement even with saturated waveforms, while reducing power consumption and circuit complexity.
Implementation Method 1
The light receiver receives reflected light of the light emitted by the light emitter and converts the received light to an electrical signal
Implementation Method 2
smooths the data series in which the interpolation data is inserted using a low-pass filter that has characteristics in which waveform distortion caused by ringing does not occur
Data Source
AI summary
In a distance measurement apparatus, a light emitter emits pulse-like light. A light receiver receives reflected light of the emitted light and converts the received light to an electrical signal. An AD converter converts the electrical signal to a digital value at a predetermined sampling rate to generate a conversion data series. An interpolation processor upsamples the outputted conversion data series by inserting interpolation data therein to generate an up-data series. A distance calculator calculates a distance to an object that reflects light using a signal waveform indicated by the up-data series. The interpolation processor inserts the interpolation data having an interpolation value between pieces of data belonging to the conversion data series, and smooths the data series in which the interpolation data is inserted using a low-pass filter that has characteristics in which waveform distortion caused by ringing does not occur.