LiDAR Receiver Segmentation for Dead Time Blind Spots
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Solution Overview
Problem
Current LiDAR systems face challenges in detecting objects at close ranges due to the dead time of single-photon avalanche diodes (SPADs), which can result in 'blindness' in critical proximity zones, and require high-energy light signals for long-range detection, leading to potential dazzle from small backscattering.
Innovation Solution
The use of two groups of light-receiving elements, where the first group with higher sensitivity (SPADs or SiPMs) and the second group (photodiodes or APDs) compensates for dead time, enabling effective detection at close ranges by employing time-correlated photon counting and sequential sampling methods, respectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If high-energy light signals and very sensitive receiving elements (SPADs) are used for long-range detection, then detection range is improved, but close-range detection becomes impossible due to dead time
Solution Approach 1:
The receiving elements are divided into two distinct groups: first group (SPADs) optimized for long-range detection with high sensitivity, and second group (photodiodes) optimized for close-range detection without dead time. Each group handles different detection scenarios, resolving the contradiction between long-range capability and close-range reliability.
Solution Approach 2:
Different regions of the receiving array are assigned different detection characteristics. The first group of receiving elements provides high sensitivity for distant objects, while the second group provides dead-time-free detection for nearby objects. Each local region specializes in its optimal detection range.
2Measurement precision
If single-photon avalanche diodes (SPADs) are used for detection, then sensitivity is improved, but dead time causes blindness in critical proximity zones
Solution Approach 1:
The receiving elements are segmented into two functional groups: SPADs for high-sensitivity long-range detection, and photodiodes for dead-time-free close-range detection. This segmentation allows each type to operate in its optimal performance regime without the limitations of the other.
Solution Approach 2:
The second group of receiving elements (photodiodes) acts as an intermediary solution for close-range detection where SPADs fail due to dead time. The system seamlessly switches between the two groups based on object distance, ensuring continuous detection capability.
3Productivity
If reflected light pulse triggers light-receiving elements, then detection is enabled, but dead time prevents renewed detection for 10-20 nanoseconds
Solution Approach 1:
The system merges two types of light-receiving elements with complementary characteristics: SPADs that provide high sensitivity but suffer from dead time, and photodiodes that provide continuous detection capability without dead time. The combination ensures uninterrupted detection across all ranges.
Solution Approach 2:
The system changes the operational parameter (which receiving group is active) based on detection needs. For close-range detection where dead time would cause loss, the second group is activated. For long-range detection, the first group is used. This dynamic parameter change optimizes performance for each scenario.
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 approach eliminates blind spots in close-range detection and reduces energy consumption and costs by optimizing signal processing, allowing precise distance determination without the limitations of dead time in SPADs.
Implementation Method 1
first group of light-receiving elements, which convert the light signals into first electrical signals
Implementation Method 2
second group of light-receiving elements, which convert the light signals into second electrical signals
Data Source
AI summary
Light signals are converted into first electric signals by a first group of light-receiving elements, and the light signals are additionally converted into second electrical signals by a second group of light-receiving elements. The second group has a lower degree of sensitivity for converting the photons into an electric current than the first group. The first electric signals are used to ascertain the distance to an object by means of a time-correlated photon counting process depending on a starting time for the emission of the light signals. Furthermore, the second electric signals are used to determine the distance depending on the starting time but using a second signal processing different from the process used for the first electric signals.