Time-of-Flight Histogram Correction for SPAD Pile-Up
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current time-of-flight ranging systems face issues with pile-up and cross-talk, which affect distance measurement accuracy and require iterative SPAD selection schemes that reduce event counts and cause spatial subsampling, especially in high ambient light conditions.
Innovation Solution
The implementation of a pile-up corrector and cross-talk detector within a processing device to process histogram data, using adaptive filters and probability-based corrections to mitigate pile-up and cross-talk effects, allowing for more accurate range and parameter extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If iterative SPAD selection schemes are used to mitigate pile-up effects, then distance measurement accuracy is improved, but event counts are reduced and spatial subsampling occurs
Solution Approach 1:
A processing device is introduced as an intermediary between the sensor and the output, which receives histogram data from the sensor and applies pile-up correction algorithms. This mediator processes the raw data to correct pile-up effects without requiring iterative SPAD selection, thereby preserving event counts while improving distance measurement accuracy
Solution Approach 2:
The patent replaces the mechanical/iterative SPAD selection process with a computational approach using probability-based pile-up correction algorithms. Instead of physically selecting and reconfiguring SPADs through iterative schemes, the system uses mathematical models to correct pile-up effects in the histogram data, eliminating spatial subsampling while maintaining accuracy
2Reliability
If iterative SPAD selection schemes are implemented, then pile-up effects are reduced, but device complexity and power consumption increase
Solution Approach 1:
The patent replaces complex iterative control logic and SPAD reconfiguration mechanisms with a simpler computational approach. The processing device applies probability-based correction algorithms to histogram data, eliminating the need for iterative selection schemes and reducing overall system complexity while maintaining pile-up mitigation effectiveness
Solution Approach 2:
The system uses the raw histogram data itself to perform self-correction through pile-up mitigation algorithms. The processing device automatically calculates and applies corrections based on the detected pile-up effects in the data, without requiring external control or iterative reconfiguration, thereby simplifying the system architecture
3Measurement precision
If iterative SPAD selection is used to correct pile-up, then measurement accuracy improves, but processing time increases
Solution Approach 1:
The patent applies pile-up correction algorithms to the histogram data in a single processing pass rather than through iterative cycles. By performing the correction action preliminarily and directly on the collected data, the system achieves high range resolution without the time penalty of repeated measurement and selection cycles
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 proposed solution effectively corrects for pile-up and cross-talk, enhancing distance measurement accuracy and reducing the need for iterative SPAD selection, thereby improving range resolution and reducing power consumption.
Implementation Method 1
A photon may generate a carrier in the SPAD through the photo electric effect
Implementation Method 2
The photo generated carrier may trigger an avalanche current in one or more of the SPADs in an SPAD array
Data Source
Figure 1A
Figure 1B
Figure 2A
AI summary
A method by which histogram distortion from pile-up can be compensated based on the determining a probability of readout saturation, the method comprising: determining a probability of readout saturation; and compensating a histogram based on the determined probability.