Parallel Photon Detector Array for Lidar Backscatter Suppression
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Solution Overview
Problem
Lidar systems face challenges in accurately detecting targets in environments obscured by rain, fog, smoke, and other scatterers due to false distance measurements caused by backscatter, which limits real-time identification capabilities.
Innovation Solution
A lidar processing system that pulses a scene with light sequences and uses a photo detector array with multiple photon detector elements connected in parallel, defocusing reflected light to cover a light sensing surface, generating a time-resolved histogram to characterize physical features and determine distances, while minimizing the effects of backscatter through parallel detection and composite histogram analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a single-photon avalanche diode (SPAD) is used in Geiger mode to detect photons, then the signal strength is improved, but the detector becomes blind to other photons during dead time
Solution Approach 1:
The invention divides the detection function across multiple parallel SPAD detectors instead of using a single detector. Each SPAD operates independently with its own dead time period, but the parallel arrangement ensures that while one detector is blind, others can still detect photons. This segmentation resolves the contradiction by maintaining high signal strength while eliminating the effective blind period through parallel operation.
2Measurement precision
If the laser is pulsed multiple times to detect photons through fog, then the target photons become detectable over backscatter, but the acquisition time increases
Solution Approach 1:
The invention maintains continuous detection capability by operating multiple SPAD detectors in parallel throughout the pulse sequence. While traditional systems must wait between pulses due to detector dead time, the parallel array ensures continuous photon detection across all pulses. This allows the system to accumulate useful signal data continuously without interruption, resolving the contradiction between achieving sufficient signal-to-noise ratio and minimizing acquisition time.
3Measurement precision
If time-gating is used to remove returns from nearby scatterers, then false distance measurements are reduced, but the benefits are limited
Solution Approach 1:
The invention creates multiple parallel detection channels (copies of the detection function) instead of relying on complex temporal gating of a single detector. Each SPAD in the parallel array independently records photon arrival times, and the collective data from all detectors provides robust distance measurements that are inherently resistant to scatterer interference. This approach achieves improved measurement precision through parallel redundancy rather than complex time-gating processing.
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 significantly improves acquisition speed and signal-to-noise ratio, enabling real-time identification of targets and distance measurement by suppressing backscatter effects, allowing for more precise and efficient lidar imaging in adverse conditions.
Implementation Method 1
the optical detector can be a single-photon avalanche diode (SPAD) configured for operating in Gieger mode. These detectors are ideal for sensitive detectors because they provide a relatively large signal every time they detect a photon. However, due to the avalanche process, these detectors can only detect a single photon at a time.
Implementation Method 2
Reflected light from the target scene passes through receiver optics and is defocused to cover a light sensing surface of a photo detector array. Defocusing may be performed by receiver optics including a lens having a focal plane positioned beyond the light sensing surface of the photo detector array.
Implementation Method 3
Alternatively, the receiver optics may include a collimating lens to collimate defocused light onto the light sensing surface of the photo detector array.
Implementation Method 4
Lidar uses a pulsed laser beam to probe the distance to a reflector by measuring the time it takes for the light to be reflected back to the device.
Data Source
AI summary
A method of lidar processing pulses a scene with laser pulse sequences from a laser light source. Reflected light from the target scene passes through receiver optics and is defocused to cover a light sensing surface of a photo detector array. The photo detector array contains multiple photon detector elements connected in parallel where each photon detector element is configured to generate corresponding photon pulse output signals based on sensing photons in the received reflected light, and each photon detector element is characterized by a non-responsive dead time period immediately after sensing a photon. The photon pulse output signals are combined to form a common real time output signal, which is converted to a digital time resolved histogram. Multiple digital time resolved histograms produced in response to multiple light pulses directed at a scanning location are combined to form a composite time resolved histogram for the scanning location.