SiPM LIDAR Receiver Spatial Filter for Ambient Light Saturation
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Solution Overview
Problem
Silicon photomultiplier (SiPM) cells in LIDAR systems face challenges in detecting signal photons due to saturation from ambient light, resulting in a low probability of capturing signal photons as they are constantly bombarded with ambient photons, leading to reduced effectiveness in distance and depth measurements.
Innovation Solution
Incorporating a spatial filter with an aperture in the receiver optics to spread the laser beam across an array of single-photon avalanche diode (SPAD) pixels, reducing the impact of ambient photons and increasing the chances of detecting signal photons by distributing the photon flux over a larger area, and using a spatial light modulator to direct the laser beam effectively towards the SiPM pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a SiPM cell is used to detect signal photons, then the detection capability for single photons is improved, but the cell becomes saturated by ambient light photons resulting in near-zero probability to catch signal photons
Solution Approach 1:
The SiPM cell is divided into multiple independent SPAD pixels arranged in an array. Each SPAD pixel can be independently controlled and its saturation state monitored. By segmenting the detector, the system can identify and exclude saturated pixels from signal detection, thereby maintaining reliable signal photon detection despite ambient light saturation of individual pixels.
Solution Approach 2:
Different regions or individual SPAD pixels within the SiPM cell are treated with different characteristics. The system selectively activates or weights specific pixels based on their saturation status, signal strength, or spatial position. This local differentiation allows the detector to maintain high detection probability for signal photons by focusing on non-saturated or less-saturated regions while ignoring saturated ones.
2Quantity of substance
If the SPAD is constantly bombarded with ambient photons, then the ambient light detection increases, but the SPAD becomes blind to signal photons for the predetermined time period
Solution Approach 1:
The system employs periodic gating or pulsed activation of SPAD pixels, synchronizing detection windows with the expected arrival times of signal photons. By periodically enabling and disabling pixel groups, the system captures signal photons during active periods while minimizing ambient light accumulation during inactive periods, thereby extending the effective operational time for signal detection.
Solution Approach 2:
The system performs preliminary identification and exclusion of saturated or heavily ambient-light-affected SPAD pixels before they can blind to signal photons. By pre-monitoring pixel states and proactively managing which pixels are active for signal detection, the system prevents the transition to blind state, thereby maximizing the operational time available for signal photon detection.
3Measurement precision
If the laser beam is concentrated on a small area, then the signal photon density increases, but the ambient light saturation effect is intensified
Solution Approach 1:
The system transitions from a single-point or small-area detection approach to a two-dimensional array of SPAD pixels. By spreading the detection area across multiple pixels in spatial dimensions, the system maintains signal photon density through coherent detection across the array while distributing ambient light saturation across many pixels, allowing selective use of non-saturated regions.
Solution Approach 2:
The system combines signals from multiple SPAD pixels that have not reached saturation, effectively merging their detection capabilities. By summing or coherently combining outputs from multiple non-saturated pixels, the system achieves high signal photon detection probability while avoiding the saturation problem that would occur in a single concentrated detector, thereby reducing the impact of ambient light.
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 configuration enhances the detection probability of signal photons, reducing saturation and increasing the operational time of SPAD pixels, thereby improving the accuracy of distance and depth measurements in LIDAR systems.
Implementation Method 1
the spatial filter including an aperture located at a focal point of the receiver optics that is configured to permit a passage of the at least one laser beam therethrough and spread the at least one laser beam in at least one direction orthogonal to the receiver path
Implementation Method 2
Each SiPM cell of a SiPM array comprises an array of single-photon avalanche diodes (SPADs), and each SPAD is configured to detect one photon at a time
Implementation Method 3
single-photon avalanche diode (SPAD) pixels, the at least one SiPM pixel configured to generate at least one electrical signal
Data Source
AI summary
A Light Detection and Ranging (LIDAR) receiver includes a receiver optics configured to receive at least one laser beam and direct the at least one laser beam along a receiver path; at least one silicon photomultiplier (SiPM) pixel including an array of single-photon avalanche diode (SPAD) pixels, the at least one SiPM pixel configured to generate at least one electrical signal based on the at least one laser beam; and a spatial filter arranged between the receiver optics and the at least one SiPM pixel, the spatial filter including an aperture located at a focal point of the receiver optics that is configured to permit a passage of the at least one laser beam therethrough and spread the at least one laser beam across the array of SPAD pixels in at least one direction.