LiDAR SPAD Array Dynamic Region Actuation
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Solution Overview
Problem
Existing LiDAR sensors face challenges such as background noise from ambient light, low signal-to-noise ratio, and limited operational flexibility due to environmental and manufacturing constraints, leading to bulky designs and restricted use in uncontrolled environments.
Innovation Solution
The implementation of a LiDAR system with a pulsed laser source, beam steering, and a single-photon avalanche diode (SPAD) array, where the sensitivity of each SPAD is controlled to reduce background noise and increase signal-to-noise ratio, allowing for high-resolution depth imaging in uncontrolled environments with adjustable illumination and scanning patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a SPAD array is used to detect single photons with high time-of-arrival resolution, then measurement precision is improved, but background noise from ambient light increases and signal-to-noise ratio deteriorates
Solution Approach 1:
The system performs preliminary actions by predicting the positions of illumination spots before detection occurs. The control circuit determines which SPADs will be illuminated by the scanned beam in advance, and pre-configures the selected region to include only those SPADs. This allows the system to activate only the necessary detectors, reducing background noise accumulation while maintaining high time-of-arrival resolution for the illuminated spots.
Solution Approach 2:
The system applies local quality by creating a dynamic selected region that concentrates detection resources only where illumination spots are expected to appear. Instead of uniformly activating all SPADs or using a fixed region, the selected region adapts its shape, size, and position to match the instantaneous illumination pattern. This localized detection approach reduces background noise from non-illuminated areas while maintaining high measurement precision for the illuminated spots.
2Object-affected harmful factors
If the selected region is kept small to reduce background noise, then signal-to-noise ratio is improved, but the area of the target scene that can be monitored at any instant is reduced
Solution Approach 1:
The system employs dynamics by making the selected region time-varying and adaptive rather than static. As the beam scans across the target scene and illumination spots move, the selected region dynamically updates its position, shape, and size to track the illumination pattern. This dynamic adaptation allows the system to maintain a compact selected region for low noise while still covering the entire target scene area over the course of the scanning period.
Solution Approach 2:
The system uses periodic action through the scanning mechanism that systematically moves the illumination beam across the target scene in a repeating pattern. The selected region is updated periodically synchronized with the scan, allowing different portions of the target scene to be monitored at different times. This periodic scanning approach enables comprehensive area coverage while maintaining a small selected region size at any given instant.
3Device complexity
If a fixed selected region is used to simplify control circuitry, then device complexity is reduced, but the ability to track moving illumination spots and adapt to different scan patterns is limited
Solution Approach 1:
The control circuit implements feedback by continuously monitoring the positions of illumination spots (either directly or through knowledge of beam steering commands) and using this information to update the selected region. The feedback loop ensures that the selected region remains synchronized with the moving illumination spots, enabling accurate tracking without requiring overly complex control circuitry. The feedback mechanism adapts the selected region to match the instantaneous illumination pattern.
Solution Approach 2:
The control circuit achieves universality by designing a flexible selected region update mechanism that can accommodate various scan patterns and target configurations through a unified approach. The same control logic handles different scanning geometries, beam patterns, and target distances by adjusting the selected region parameters accordingly. This multi-functional design provides high adaptability without proportionally increasing device complexity.
4Area of stationary object
If all SPADs are activated to monitor the entire array, then the area of the target scene that can be monitored is maximized, but background noise increases and signal-to-noise ratio deteriorates
Solution Approach 1:
The system performs preliminary action by predicting which SPADs will receive illumination before the actual detection occurs. The control circuit calculates the expected positions of illumination spots based on beam steering commands and optical geometry, then pre-configures the selected region to include only those SPADs. This preliminary configuration allows the system to activate a limited subset of SPADs rather than all SPADs, reducing background noise while ensuring that all illuminated spots are captured.
Solution Approach 2:
The system applies parameter changes by dynamically adjusting the parameters of the selected region (position, size, shape) based on the instantaneous illumination pattern. Instead of using a fixed large region that activates all SPADs, the selected region parameters are continuously updated to match the illumination spots' positions. This parameter adaptation allows the system to expand coverage when needed while maintaining a compact active region to reduce background noise.
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 enables compact, cost-effective LiDAR systems capable of high-resolution depth imaging with improved signal-to-noise ratio and flexibility in environmental operation, overcoming limitations of existing systems by selectively actuating SPADs and adjusting illumination based on the target scene.
Implementation Method 1
At this bias, the electric field is so high that a single charge carrier injected into the depletion layer, due to an incident photon, can trigger a self-sustaining avalanche
Implementation Method 2
a laser light source, which is configured to emit at least one beam of light pulses
Data Source
AI summary
An electro-optical device includes a laser light source, which emits at least one beam of light pulses, a beam steering device, which transmits and scans the at least one beam across a target scene, and an array of sensing elements. Each sensing element outputs a signal indicative of a time of incidence of a single photon on the sensing element. Light collection optics image the target scene scanned by the transmitted beam onto the array. Circuitry is coupled to actuate the sensing elements only in a selected region of the array and to sweep the selected region over the array in synchronization with scanning of the at least one beam.