Laser Return Pulse Discrimination for Long-Range Pixel Detectors
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Solution Overview
Problem
Conventional laser ranging systems face challenges in detecting poorly reflective objects at long distances, requiring high laser pulse energy and sensitive photoreceivers to accommodate large dynamic ranges, while also ensuring safety and reducing ocular damage.
Innovation Solution
A photonic integrated circuit (ROIC) with safety features, such as ASIL compliance, is developed to validate the signal path by generating photons directly and applying electrical stimulation, allowing for pulse validation and alert generation based on response analysis, thereby enhancing detection accuracy and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high laser pulse energy is used to detect poorly reflective objects at long distances, then detection capability is improved, but ocular damage risk increases
Solution Approach 1:
The system performs preliminary validation of the returned pulse characteristics (shape, amplitude, timing) before processing the range measurement. By checking these parameters in advance, the system can identify and reject false pulses from spurious sources, allowing safe operation at lower laser energies while maintaining detection accuracy for legitimate targets.
Solution Approach 2:
The system implements feedback mechanisms where the detected pulse characteristics are continuously monitored and compared against expected patterns. This feedback loop enables the system to adaptively distinguish between genuine target returns and spurious pulses, improving detection reliability without requiring increased laser energy that would raise safety concerns.
2Measurement precision
If sensitive photoreceivers are used to accommodate large dynamic ranges, then detection sensitivity is improved, but system complexity increases
Solution Approach 1:
Rather than using highly sensitive photoreceivers that would detect all possible signals including noise, the system employs a validation approach that processes only pulses meeting specific criteria. This partial action strategy maintains adequate detection sensitivity for legitimate targets while filtering out spurious signals through pulse characteristic validation, avoiding the need for excessively sensitive (and complex) receiver hardware.
Solution Approach 2:
The system changes the operational parameters of pulse validation dynamically, adjusting the thresholds and criteria for accepting pulse returns based on operating conditions. This allows the system to maintain optimal detection sensitivity across large dynamic ranges without requiring hardware that can handle every possible signal level, thereby reducing overall system complexity.
3Reliability
If pulse validation and alert generation are implemented, then false pulse rejection is improved, but processing time increases
Solution Approach 1:
The validation checks for pulse shape, amplitude, and timing characteristics are performed as preliminary steps in the signal processing chain, before full range measurement calculation. By establishing acceptance criteria early in the process, the system can quickly reject invalid pulses without committing to full processing, thereby maintaining high false pulse rejection while minimizing time loss for valid signals.
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
The solution improves the detection of poorly reflective objects at long distances by validating signal responses and reducing false pulses, ensuring accurate range measurement and safety in automotive applications.
Implementation Method 1
A photodiode converts the optical energy to current
Implementation Method 2
a LED is located proximate the detector pixel to generate a photon in response to an electrical signal
Data Source
AI summary
Methods and apparatus for receiving a return laser pulse at a detector system having pixels in a pixel array and analyzing a response of the pixels in the pixel array including comparing the response to at least one threshold corresponding to decay of photonic energy of the laser pulse over distance and target reflectivity, wherein the at least one threshold comprises a first threshold corresponding to a low trigger for a pulse generated by a first type of laser and a second threshold corresponding to a high trigger for the pulse generated by the first type of laser. Embodiments can further include generating an alert signal based on the response of the pixels in the pixel array.