Lidar Time-of-Flight Estimation With Wide-Bin Cumulative Deltas
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Solution Overview
Problem
Existing lidar systems face challenges in achieving high resolution and sensitivity for time-of-flight measurements in automotive applications due to memory limitations and the trade-off between bin width and signal-to-noise ratio, leading to reduced sensitivity and accuracy.
Innovation Solution
A method involving wide-bin histogram bins with inter-bin cumulative delta or phase values for real-time range estimation, allowing for reduced memory requirements and maintaining sensitivity by canceling out noise, and using intra-bin cumulative delta or phase values for more accurate range estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If smaller bin width is used in histogram, then time-of-flight resolution is improved, but memory capacity requirements increase
Solution Approach 1:
The patent extracts only the necessary information from the full histogram data by calculating cumulative sums of time differences within bins. Instead of storing and processing complete timestamp data for all photons, the system computes and stores only the cumulative time difference values (inter-bin delta and intra-bin delta) which are sufficient for accurate range estimation. This extraction reduces memory requirements while preserving measurement precision.
Solution Approach 2:
The patent inverts the traditional approach by not directly using histogram bin centers for range estimation, but rather by calculating the cumulative sum of time differences relative to bin references. This inversion allows the system to achieve sub-bin resolution through the cumulative delta calculations, effectively reversing the conventional method of direct bin-based measurement.
2Quantity of substance
If multiple course resolution steps are used before fine resolution steps, then memory requirements are reduced, but signal-to-noise ratio decreases
Solution Approach 1:
The patent performs preliminary calculation of cumulative time differences for all bins during the data acquisition phase, before any range estimation is performed. This preliminary action prepares the data in a form that allows direct, accurate range estimation from any bin without requiring sequential processing steps. The cumulative sums are computed in advance, enabling single-step fine resolution measurement while maintaining high signal-to-noise ratio.
3Measurement precision
If cumulative delta values are calculated for all bins, then range estimation accuracy is improved, but memory requirements increase
Solution Approach 1:
The patent applies local quality by storing different types of cumulative delta values for different bins based on their specific needs. Inter-bin delta values (cumulative sums from previous bins) are stored for all bins, while intra-bin delta values (cumulative sums within the current bin) are calculated only for the bin containing the peak. This selective storage approach maintains high range estimation accuracy while minimizing memory requirements.
4Loss of information
If second central moment of timestamps is calculated, then additional information about material or orientation is obtained, but processing complexity increases
Solution Approach 1:
The patent merges the calculation of the second central moment with the existing cumulative time difference calculations. By computing the sum of squared time differences alongside the cumulative sums, the system obtains both the first and second central moments without requiring separate processing passes. This combining approach extracts additional physical information while avoiding significant increases in processing complexity.
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 method achieves higher accuracy and reduced memory requirements while maintaining sensitivity, enabling precise time-of-flight calculations without significant loss in resolution, even with wider bins.
Implementation Method 1
time of flight calculations for a lidar transceiver
Data Source
AI summary
The disclosure relates to time of flight calculations for a lidar transceiver. Example embodiments include a method of calculating time of flight of a lidar signal, the method comprising: i) transmitting a light pulse to start (502) an acquisition time period having a plurality of successive time portions; ii) for each successive time portion, if a photon is received (503): iia) recording (505) a time at which the photon is received; iib) updating (504) a histogram to record a cumulative count of photons received during the time portion; iic) calculating (505) a time difference between the time at which the photon is received relative to a reference point of the time portion; iid) updating (506) a cumulative total of the calculated time difference for the time portion; iii) repeating steps i) to iid) for a succession of N transmitted light pulses; iv) identifying (509) a peak in a time portion of the histogram; and v) estimating (510) a time of flight from the cumulative total of the calculated time difference for the time portion of the histogram containing the identified peak.