Programmable Pixel Test Injection for LiDAR Detector Validation
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Solution Overview
Problem
Lidar systems face challenges in detecting poorly reflective objects at long distances, requiring high laser pulse energy and sensitive photodetectors that can handle large dynamic ranges, while also needing to accommodate the focus and blur changes of optical signals with range, and validate the active operation of all pixels in safety-sensitive applications like automotive systems.
Innovation Solution
A photodetection system with a programmable pixel test injection circuit, including a photo-detector, amplifier, differential voltage discriminator, and charge injection circuit, which allows for testing of pixel functionality by mimicking an active photo-current return pulse, enabling validation of pixel sensitivity and safety reporting, and meeting high fault detectability standards.
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 system complexity and safety requirements increase
Solution Approach 1:
The patent applies preliminary action by implementing a test pulse injection circuit that can pre-validate pixel functionality before actual imaging operations. The circuit includes test pulse generation units connected to pixel circuits through selection switches, allowing systematic testing of each pixel's response characteristics without requiring actual high-energy laser illumination. This preliminary validation ensures detection capability while avoiding the complexity of continuous high-power operation.
2Measurement precision
If sensitive photodetectors are used to handle large dynamic ranges, then detection sensitivity is improved, but validation of pixel operation becomes more critical
Solution Approach 1:
The patent implements feedback by creating a closed-loop test system where test pulses are injected into pixel circuits and the resulting signals are read through the same signal path used for actual detection. The test pulse generation unit produces controlled pulses that traverse the photodetector, amplifier, and discrimination circuits, providing feedback on each component's functionality. This ensures reliable operation validation for sensitive photodetectors handling large dynamic ranges.
Solution Approach 2:
The patent applies copying by creating artificial test signals that replicate the characteristics of actual optical return pulses. The test pulse injection circuit generates electrical pulses that mimic the amplitude, duration, and timing characteristics of genuine photodetector outputs from reflected laser light. This allows validation of the entire signal chain without requiring actual optical targets, ensuring reliable pixel operation assessment.
3Measurement precision
If optical signal focus and blur changes are accommodated with range, then imaging accuracy is improved, but pixel validation requirements increase
Solution Approach 1:
The patent implements universality by designing a test pulse injection system that can validate all pixel circuits regardless of their specific optical focusing conditions. The selection switch network allows any pixel in the array to be selected for testing, and the test pulse characteristics can be adjusted to simulate various range conditions. This multi-functional approach validates pixels under different imaging accuracy requirements without increasing overall system complexity.
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 system effectively tests and validates the active imaging functions of pixels, ensuring safety and reliability in applications like automotive lidar systems by mimicking return pulses and allowing for variable charge injection to evaluate sensitivity, thus enhancing the detection of poorly reflective objects and maintaining safety standards.
Implementation Method 1
The photo-detector converts incident photon energy striking the photo-detector into current flow that is proportional to the number of photons striking the photo-detector
Implementation Method 2
the amplifier comprises a transimpedance amplifier that converts photo-current into a corresponding voltage output
Implementation Method 3
the differential voltage discriminator detects when the positive input exceeds the negative input and produces a digital output pulse corresponding to time a duration of the positive input exceedance
Implementation Method 4
The charge injection circuit may provide a moment of charge transfer onto the photo-detector node which is equivalent to a current pulse
Data Source
AI summary
Methods and apparatus for a detector system having a photodetector and an amplifier to amplify the photodetector signal. A discriminator generates an active output signal when the output from the amplifier is greater than a threshold. An injection circuit is coupled to the input of the amplifier. The injection circuit is configured to selectively inject a test pulse that mimics a pulse from the photodetector for verifying operation of the detector system.