SPAD Array Ambient Light Suppression for Solid-State LiDAR
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Solution Overview
Problem
Solid-state LiDAR devices face challenges with ambient light interference, which affects signal-to-noise ratios and energy efficiency due to the high photon sensitivity of SPADs, and traditional methods like histogram binning require multiple illuminations to generate usable data.
Innovation Solution
The LiDAR device configures laser pulses to incident on one column of macro-pixels at a time, turning off the rest, and uses a multi-level digital signal with a threshold for noise reduction by concatenating outputs from multiple SPADs, allowing for increased resolution through multiple scans at different angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If SPADs are used to achieve high photon sensitivity, then detection capability is improved, but ambient light interference increases
Solution Approach 1:
The photodetector array is divided into multiple columns of macro-pixels, with only one column activated at a time. This temporal and spatial segmentation allows the system to distinguish between signal photons (incident on the active column) and ambient light photons (which would randomly activate any column), thereby suppressing ambient light interference while maintaining high photon sensitivity.
Solution Approach 2:
A timing signal synchronized with the laser pulse transmission acts as an intermediary mechanism. The timing signal enables the system to correlate detected photons with the expected signal arrival time, allowing discrimination between true signal photons and ambient light photons, thus resolving the contradiction between sensitivity and ambient light rejection.
2Measurement precision
If histogram binning is used to remove ambient light, then signal-to-noise ratio is improved, but energy consumption increases
Solution Approach 1:
The system performs preliminary action by activating only one column of macro-pixels at a time in synchronization with laser pulse transmission. This pre-planned selective activation pattern allows the system to expect signal photons at specific times and locations, enabling ambient light suppression without requiring energy-intensive post-processing histogram binning of multiple illuminations.
3Adaptability or versatility
If multiple columns are activated simultaneously, then field of view is improved, but ambient light suppression decreases
Solution Approach 1:
The photodetector array is divided into multiple columns of macro-pixels, with only one column activated at a time. This temporal and spatial segmentation allows the system to distinguish between signal photons (incident on the active column) and ambient light photons (which would randomly activate any column), thereby suppressing ambient light interference while maintaining high photon sensitivity.
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 effectively suppresses ambient light, improves signal-to-noise ratios, and enhances the resolution of LiDAR images while reducing energy consumption by selectively turning on columns and using a threshold to filter noise.
Implementation Method 1
Solid State LiDAR devices tend to use single photon avalanche diodes (SPAD), which has high photon sensitivity
Implementation Method 2
single photon avalanche diodes (SPAD)
Data Source
AI summary
In various embodiments, described herein are systems and methods for ambient light suppression on a photodetector of a LiDAR device. The LiDAR device can be configured to scan laser pulses in such a manner that reflected laser pulses are incident on one column of macro-pixels at a time in a macro-pixel array on the photodetector, where only that column is turned on, and the rest of the columns are turned off. The LiDAR device can further be configured to scan at different angles such that laser pulses from a same portion of a target object can be incident on the turned-on column multiple times to increase the resolution of a LiDAR image. Further, outputs from multiple SPADs in a max-pixel are concatenated to form a multi-level digital signal, and a threshold can be used for discarding or registering the multi-level digital signal for further noise reduction.