Alternating Power-Level Scanning for ToF Lidar Safety
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Solution Overview
Problem
Automotive time-of-flight lidar systems face challenges in providing long-range detection while complying with safety regulations on optical power limits, which can constrain detection range and increase hardware complexity or require additional hardware.
Innovation Solution
The implementation of an alternating pattern of power levels in a ToF lidar system, where a transmitter emits signals at different power levels during consecutive frames, effectively limiting the total power level emitted during specific intervals to comply with safety regulations without reducing detection range or scan rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the optical power output is increased to provide long-range detection capability, then the detection range is improved, but the safety regulations on optical power limits are exceeded
Solution Approach 1:
The patent applies periodic action by alternating between high-power and low-power signal transmission in a time-multiplexed manner. During odd frames, high-power signals are transmitted for long-range detection, while during even frames, low-power signals are transmitted. This periodic switching allows the system to achieve long-range detection capability while maintaining compliance with safety regulations on average optical power exposure over time.
Solution Approach 2:
The patent implements dynamics by making the optical power level variable rather than static. The transmitter dynamically adjusts its output power based on the frame number, switching between high and low power levels. This dynamic power adjustment enables the system to optimize detection range when needed while ensuring safety compliance during other periods, resolving the contradiction between detection range and safety limits.
2Object-affected harmful factors
If the optical power is reduced to comply with safety regulations, then the safety requirements are met, but the detection range is constrained
Solution Approach 1:
By implementing periodic high-power transmission interspersed with low-power transmission, the system achieves compliance with safety regulations on average power while maintaining the capability for long-range detection during high-power frames. The time-averaged power remains within safety limits while peak power exceeds them temporarily for detection purposes.
Solution Approach 2:
The patent segments the detection process into discrete time frames, where odd frames use high-power transmission and even frames use low-power transmission. This temporal segmentation allows the system to separate the long-range detection function (performed during high-power frames) from the safety compliance requirement (maintained through low-power frames), thereby resolving the contradiction.
3Length of stationary object
If additional hardware or increased dynamic range photodetectors are used to maintain long-range detection with power limits, then the detection range is preserved, but the hardware complexity increases
Solution Approach 1:
The patent uses periodic action to achieve long-range detection without requiring additional hardware. By alternating between high-power and low-power transmission frames, the system leverages the existing photodetector's full dynamic range during high-power frames while maintaining safety compliance on average. This temporal multiplexing approach eliminates the need for additional hardware components or increased photodetector dynamic range that would otherwise be required.
Solution Approach 2:
The patent changes the power level parameter of the transmitted signal based on frame number, allowing the same hardware to operate in different power states. This parameter change approach enables the system to achieve long-range detection capability when needed while maintaining safety compliance, all using the existing hardware without requiring additional components or increased photodetector capabilities.
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 allows for longer detection ranges without exceeding safety regulations, maintaining high scan rates and frame rates, and does so without requiring additional hardware or increased dynamic range photodetectors.
Implementation Method 1
A transmitter of a time-of-flight lidar system may be configured to maintain an alternating pattern of power levels that includes a first power level and a second power level
Implementation Method 2
Automotive time-of-flight (ToF) 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 alternate power-level scanning for ToF lidar systems. The described lidar system transmits an initial signal having a first power level of an alternating pattern of power levels. The initial signal is associated with an initial pixel of consecutive pixels. The lidar system then transmits a subsequent signal, which is associated with a subsequent pixel of the consecutive pixels, having a second power level. The transmission of the initial signal and the subsequent signal with the alternating pattern of power levels limits a total power level emitted by the lidar system during a time interval to comply with safety regulations. The alternating pattern of power levels also permits the lidar system to switch between a long-detection range and a short-detection range for consecutive pixels.