LiDAR Readout Circuit Multi-Threshold Detection
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Solution Overview
Problem
Traditional LiDAR systems with analogue SiPMs face challenges in high light conditions, where multiple photons contribute to the output current/voltage beyond a fixed single-photon threshold, leading to loss of single-photon event information, and increasing the threshold results in missed information for both high and low light levels.
Innovation Solution
A LiDAR readout circuit with multiple comparators set to different threshold values, each configured to compare the SiPM analog output signal, allowing for the detection of single, double, and triple photon events, and a time-to-digital converter to timestamp these events, with an amplifier and voltage divider to set these thresholds based on ambient light levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fixed single-photon threshold is used for discrimination, then single-photon detection is enabled, but in high light conditions multiple photons contribute to output current/voltage beyond the threshold leading to loss of single-photon event information
Solution Approach 1:
The patent segments the single threshold discrimination approach into multiple thresholds (first threshold and second threshold). The first threshold is set for single-photon detection in low light conditions, while the second threshold is set higher to detect multi-photon events in high light conditions. This segmentation allows the system to preserve single-photon event information while also capturing multi-photon contributions without saturation.
2Adaptability or versatility
If the threshold is increased to detect multi-photon events, then high light condition detection is improved, but information about single-photon events is lost
Solution Approach 1:
The patent divides the detection range into two segments with different thresholds. The first threshold handles single-photon events, while the second threshold handles multi-photon events. This allows the system to maintain sensitivity to single-photon events while also being adaptable to high light conditions with multi-photon contributions.
Solution Approach 2:
The patent implements dynamic threshold selection where the readout circuit can switch between the first threshold and the second threshold based on operating conditions. This dynamic adaptation allows the system to optimize for single-photon detection when appropriate while also capturing multi-photon events in high light conditions, preventing information loss.
3Device complexity
If a single threshold discriminator is used, then the circuit is simple, but in high light conditions the discriminator limits the number of timestamps of the readout causing saturation
Solution Approach 1:
The patent segments the single discriminator into multiple discriminators with different thresholds. This allows parallel processing of single-photon and multi-photon events, increasing the number of timestamps that can be captured without saturation. While this increases circuit complexity, it significantly improves productivity in high light conditions.
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
This multi-threshold system enables efficient detection of a larger number of events without saturation, reducing acquisition times and improving signal-to-noise ratio, especially in high light conditions, and eliminating the need for feedback loops, making it suitable for fast and high-frame-rate LiDAR systems.
Implementation Method 1
an SiPM sensor for detecting photons and generating an SIPM analog output signal
Implementation Method 2
an amplifier is provided for amplifying the SiPM analog output signal in advance of the SiPM analog signal being received by the comparators
Implementation Method 3
a plurality of comparators each having an associated threshold value and being configured to compare the SiPM analog output signal with their associated threshold value and generate a comparison signal
Implementation Method 4
a voltage divider is configured for setting the respective threshold values of the comparators
Implementation Method 5
a time to digital converter configured to receive the comparison signals from the plurality of comparators
Data Source
AI summary
A LiDAR readout circuit is described. The readout circuit comprises an SiPM sensor for detecting photons and generating an SIPM analog output signal. A plurality of comparators are provided each having an associated threshold value and being configured to compare the SiPM analog output signal with their associated threshold value and generate a comparison signal. A time to digital converter is configured to receive the comparison signals from the plurality of comparators.