Gated DTOF LiDAR Pixel Grouping for Low-Power Depth Accuracy
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Traditional DTOF-based LiDAR systems require multiple passes to achieve high accuracy, leading to inefficient use of optical power and increased power consumption, especially in conditions with strong ambient light or long object distances.
Innovation Solution
A LiDAR system utilizing disparity-based pixel grouping and gated Time-to-Digital Conversion (TDC) circuits, with varying clock rates for different disparity locations, and a reduced-bin histogram technique to optimize power usage and improve depth accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional two-pass solution is used to achieve high accuracy, then measurement precision is improved, but power consumption increases due to multiple laser passes
Solution Approach 1:
The patent segments the sensor array into multiple groups based on disparity locations, with each group having its own gated TDC circuit. This allows selective activation of only the necessary pixel groups for each depth range, avoiding the need to activate all pixels in traditional two-pass solutions, thereby reducing power consumption while maintaining measurement precision.
Solution Approach 2:
The patent implements dynamic gating of TDC circuits based on detected disparity locations. The system adaptively enables or disables specific TDC circuits depending on the current depth range being measured, optimizing power usage in real-time while maintaining high accuracy measurements for the active depth range.
2Reliability
If many laser cycles are used to form reliable histogram in strong ambient light or long distance conditions, then measurement reliability is improved, but power consumption increases
Solution Approach 1:
The patent applies local quality by assigning different clock rates to different gated TDC circuits based on their disparity location groups. Circuits measuring closer objects use higher clock rates for better resolution, while circuits for farther objects use lower clock rates, optimizing power consumption locally for each depth range while maintaining reliable histogram formation.
Solution Approach 2:
The system changes the clock rate parameter of TDC circuits dynamically based on the disparity location and depth range being measured. This parameter adjustment allows the system to achieve reliable measurements with fewer laser cycles by optimizing the time resolution to match the specific measurement requirements of each depth range.
3Measurement precision
If large memory or large counter depth is used to form full histograms, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent segments the histogram formation process into multiple disparity-based groups, each handled by dedicated gated TDC circuits. This segmentation allows each circuit to maintain smaller, more manageable memory and counter depth requirements while collectively achieving comprehensive depth measurement coverage with high precision.
Solution Approach 2:
The system dynamically gates TDC circuits based on detected disparity locations, activating only the necessary circuits for the current measurement range. This dynamic approach reduces the effective memory and counter depth requirements at any given time while maintaining high measurement precision through selective high-resolution measurement of the active depth range.
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 system achieves better range accuracy across an entire measurement range while reducing power consumption by minimizing the number of laser pulses needed, using a one-pass high-resolution depth measurement and background noise cancellation.
Implementation Method 1
DTOF-based LiDAR systems measure distance of an object by sending multiple short laser pulses toward that object (interrogation) and measuring the TOF of the returned pulses
Implementation Method 2
Single Photo Avalanche Diode (SPAD) pixels in a DTOF sensor capture impinging photons and generate digital time codes representing TOF information of a photon
Implementation Method 3
The first gated time-to-digital converter circuit may be configured to generate first timestamp information relating to detection of the first reflection signal in which the first gated time-to-digital converter circuit may be gated to generate the first timestamp information based on the first disparity location
Implementation Method 4
A histogram may be formed using the digital time codes captured over hundreds or thousands of repetitions
Implementation Method 5
An embodiment may include a histogram circuit in which an average ambient light level is subtracted from each bin of a histogram generated by the histogram circuit
Data Source
AI summary
A direct time-of-flight (DTOF) LiDAR system includes a sensor array, a first gated time-to digital converter (TDC) circuit and second TDC circuit. The sensor array includes pixels arranged to detect a first disparity location on the sensor array of a reflection signal received from a first object at a first range with respect to a second disparity location on the sensor array of a reflection signal received from a second object at a second range that is greater than the first range. The first TDC circuit generates first timestamp information relating to detection of the first reflection signal in which the first gated TDC circuit is gated based on the first disparity location. The second gated TDC circuit generates second timestamp information relating to detection of the second reflection signal in which the second gated TDC circuit is gated based on the second disparity location.