Dynamic Bias Voltage Adjustment for ToF Lidar Dynamic Range
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Solution Overview
Problem
Current time-of-flight (ToF) lidar systems face challenges in increasing their dynamic range without adding complex hardware or readouts, which is necessary for improving low-light detection and maintaining accurate reflectivity measurements for both long-range and short-range objects.
Innovation Solution
The system adjusts the bias voltage of a photodetector based on the energy of the first return pulse for subsequent return pulses, allowing for dynamic range expansion without additional hardware or complex readouts, by transmitting at least two pulses for each object pixel with varying energy levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the dynamic range of a lidar system is increased to improve low-light detection capability, then the ability to detect long-range objects is improved, but the hardware complexity and cost increase
Solution Approach 1:
The patent implements dynamic range extension by adjusting the bias voltage of the photodetector based on the energy level of received return pulses. The system transitions from a static bias voltage configuration to a dynamic one where the bias voltage is modulated according to the detected signal strength, allowing the same hardware to adapt to both low-light long-range detection and high-light short-range detection conditions
Solution Approach 2:
The patent changes the operating parameter (bias voltage) of the photodetector to extend the dynamic range. By varying the bias voltage level in response to different return pulse energies, the system can detect both weak signals from long-range objects and strong signals from short-range objects without requiring multiple photodetectors with different sensitivities
2Measurement precision
If the dynamic range is increased to maintain accurate reflectivity measurements for short-range objects, then measurement accuracy is improved, but the system complexity increases
Solution Approach 1:
The patent employs a feedback mechanism where the energy of the first return pulse is used to adjust the bias voltage for subsequent return pulses. This feedback loop ensures that the photodetector operates at optimal sensitivity levels for the current detection conditions, maintaining accurate reflectivity measurements across varying signal strengths without adding complex hardware
3Adaptability or versatility
If multiple photodetectors with different sensitivities are used to increase dynamic range, then detection capability across different ranges is improved, but the readout complexity increases
Solution Approach 1:
The patent makes a single photodetector perform multiple functions by dynamically adjusting its bias voltage. Instead of requiring one photodetector for long-range detection and another for short-range detection, the same photodetector can adapt its sensitivity to handle both scenarios, simplifying the readout architecture while maintaining versatility
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 enhances the lidar system's ability to detect objects at a wider range of distances and reflectivities, maintaining accurate measurements while reducing hardware and processing complexity.
Implementation Method 1
The transceiver adjusts, based on an energy of a first return pulse, a bias voltage of a photodetector for other return pulses of the object pixel
Implementation Method 2
Automotive lidar systems use laser signals to determine the speed and distance of stationary and moving objects
Data Source
AI summary
This document describes techniques and systems to increase the dynamic range of time-of-flight (ToF) lidar systems. The described lidar system adjusts, based on the energy of a first return pulse, the bias voltage of a photodetector for other return pulses of the object pixel. The bias voltage can be adjusted down for highly-reflective or close-range objects. Similarly, the bias voltage can be increased for low-reflectivity or long-range objects. The ability of the described lidar system to adjust the bias voltage of the photodetector for each object pixel increases the dynamic range of the lidar system without additional hardware or a complex readout. The increased dynamic range allows the described lidar system to maintain a long-range capability, while accurately measuring return-pulse intensity for detecting close-range or highly-reflective objects.