Multiple Analog Ramps for LIDAR Range Measurement
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Solution Overview
Problem
LIDAR systems face inaccuracies in determining the range of targets due to noise and ramp droop, which lead to incorrect slope number calculations and subsequent errors in pulse arrival time and range measurement.
Innovation Solution
The use of multiple analog ramps, including a slow ramp and two fast ramps, with fast ramp information to modify the slope number calculation, allowing for an adjusted slope number to be determined, which helps in selecting the correct fast ramp for calculating a more accurate fine time, thereby mitigating inaccuracies caused by noise and ramp droop.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single analog ramp is used for range measurement, then the device complexity is low, but the measurement precision deteriorates due to noise and ramp droop effects
Solution Approach 1:
The patent divides the range measurement process into multiple segments by using separate analog ramps for different distance zones. A first analog ramp handles near-range measurements while a second analog ramp handles far-range measurements, allowing each ramp to be optimized for its specific zone and reducing the impact of noise and droop effects in each segment
Solution Approach 2:
The patent implements dynamic ramp selection based on the detected zone of the target. The system automatically switches between different analog ramps depending on the range zone, adapting the measurement process to the specific measurement requirements of each zone to maintain high precision across the entire measurement range
2Measurement precision
If multiple analog ramps are used to improve measurement precision, then the measurement precision improves, but the device complexity increases
Solution Approach 1:
The patent combines multiple analog ramp generation circuits and their associated control logic into a single integrated readout integrated circuit (ROIC). This integration consolidates the complexity into one unified component rather than requiring separate discrete circuits, making the system more manageable and potentially more reliable
Solution Approach 2:
The readout integrated circuit is designed to perform multiple functions: generating multiple analog ramps, detecting pulse arrival times, determining zones, and controlling ramp switching. This multi-functional design reduces the need for separate dedicated circuits for each function, thereby managing complexity while maintaining measurement precision
Data Source
AI summary
A technology is provided for determining a range of a target using multiple analog ramps. A slow ramp voltage level can be identified that indicates an approximate arrival time for a light pulse to be received as a target reflection after propagating towards the target. A slope number associated with the slow ramp voltage level can be identified, wherein the slope number is an integer ranging from 0 to N. An adjusted slope number can be calculated using the slope number and fast ramp information. A coarse range and a fine range of the target can be determined using the adjusted slope number. The range of the target can be calculated by adding the coarse range and the fine range.