SPAD Array Ambient Light Suppression via Column Scanning
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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 multi-level digital signals concatenated from multiple SPADs with a threshold for noise reduction, allowing for improved signal processing and increased image resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If SPADs are used for high photon sensitivity, then detection capability is improved, but ambient light interference increases
Solution Approach 1:
The photodetector is divided into multiple macro-pixels arranged in columns, allowing selective activation of specific columns based on the scanning pattern. This segmentation enables the system to distinguish between signal photons and ambient light by spatially separating the detection regions, thereby reducing ambient light interference while maintaining high photon sensitivity in the active columns.
Solution Approach 2:
The patent implements dynamic control of macro-pixel columns, switching between different scanning patterns (e.g., row-by-row, column-by-column, or random patterns) to adapt to varying lighting conditions and target positions. This dynamic activation strategy allows the system to optimize the balance between photon detection sensitivity and ambient light rejection in real-time.
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 spatial separation of signal and noise by activating only the relevant macro-pixel columns before signal processing. By pre-configuring the scanning pattern and corresponding macro-pixel activation, the system avoids the need for extensive post-processing histogram binning, thereby reducing energy consumption while maintaining effective ambient light rejection.
Solution Approach 2:
The patent extracts and removes ambient light interference by spatially separating it from the signal through selective macro-pixel activation. By taking out the ambient light component through spatial filtering rather than temporal processing, the system achieves noise reduction with lower energy consumption compared to traditional histogram binning methods.
3Loss of information
If multiple illuminations are used for histogram binning, then usable data is generated, but time consumption increases
Solution Approach 1:
The patent enables continuous data collection by maintaining a steady scanning pattern that continuously activates relevant macro-pixel columns. This continuous action eliminates the need for repeated illuminations and histogram binning processes, providing uninterrupted usable data while reducing the total time required for data acquisition.
Solution Approach 2:
By pre-establishing the scanning pattern and macro-pixel activation scheme, the system performs the necessary spatial separation of signal and noise before data collection begins. This preliminary configuration allows for continuous, efficient data acquisition without the need for multiple sequential illuminations, thereby reducing time loss while ensuring sufficient usable data.
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 enhances signal-to-noise ratios and reduces energy consumption by selectively turning off macro-pixels to avoid ambient light, improving the resolution and efficiency of LiDAR image processing.
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.