Electro-Optical Rangefinding With Adaptive Sampling for Precise TOF
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Solution Overview
Problem
Existing electro-optical distance measurement systems face challenges in achieving high precision and accuracy due to limitations in signal power, temporal resolution, and complexity, leading to measurement errors and ambiguities, particularly with pulsed lasers and high background interference.
Innovation Solution
A method and device utilizing a frequency comb laser with a free-running, unstabilized pulse rate, coupled with a sampling rate set at least ten times the pulse rate, and a phase-locked or asynchronously adjusted sampling process to resolve ambiguities, enabling precise distance measurement with simple components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pulsed laser operation is used to achieve high peak power for detectable signal intensity, then signal-to-noise ratio is improved, but temporal resolution and measurement precision deteriorate due to pulse duration of several hundred picoseconds
Solution Approach 1:
The patent changes the pulse duration parameter from conventional hundreds of picoseconds to approximately 200 picoseconds or less, and adjusts the pulse rate to several MHz. This parameter optimization allows achieving both sufficient peak power for detectable signals and reduced temporal uncertainty for improved measurement precision of 1 mm or better.
Solution Approach 2:
The patent introduces dynamic adjustment of pulse rate with controlled temporal noise (1% to 5% of pulse interval) and implements complex evaluation methods that adapt to pulse rate variations. This dynamic approach allows the system to maintain high peak power while compensating for temporal jitter through sophisticated signal processing.
2Measurement precision
If Q-switched solid state lasers with short pulses are used to reduce pulse duration, then measurement precision is improved, but device complexity and cost increase due to required pulse rate stabilization
Solution Approach 1:
The patent extracts and removes the complex pulse rate stabilization system and CEP stabilization mechanisms from the laser setup. By accepting and compensating for pulse rate temporal noise through evaluation algorithms rather than eliminating it through hardware stabilization, the system achieves simplified device architecture while maintaining measurement precision.
Solution Approach 2:
The patent employs relatively inexpensive Q-switched solid state lasers without costly stabilization systems. The approach treats the pulse rate variations as acceptable temporary conditions that can be handled through software evaluation rather than requiring expensive hardware corrections, making the system more cost-effective.
3Measurement precision
If stabilized frequency comb lasers with tunable resonators are used to achieve ppm accuracy, then measurement precision is improved, but device complexity and manufacturing cost increase significantly
Solution Approach 1:
The patent removes the tunable resonator and CEP stabilization components from the frequency comb laser system. By using a simpler frequency comb laser without these stabilization mechanisms and compensating through evaluation methods, the system achieves significantly reduced device complexity and manufacturing cost while maintaining adequate measurement precision.
Solution Approach 2:
The patent employs an inexpensive frequency comb laser configuration without costly stabilization systems. The approach uses relatively simple laser hardware that can be manufactured at lower cost, accepting pulse rate variations that are handled through evaluation algorithms rather than expensive hardware stabilization.
4Productivity
If high pulse rate is used to increase measurement frequency, then productivity is improved, but temporal noise and measurement ambiguity increase
Solution Approach 1:
The patent implements feedback mechanisms in the evaluation method that monitor and compensate for pulse rate temporal noise. By continuously adjusting the evaluation parameters based on actual pulse rate measurements, the system can operate at high pulse rates for improved productivity while maintaining measurement precision through active compensation of temporal variations.
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
Enables precise distance measurements with resolutions in the micrometer or nanometer range, even at large distances, using cost-effective components and reducing complexity, jitter, and speckle effects, while maintaining high accuracy and low cost.
Implementation Method 1
A method and device utilizing a frequency comb laser with a free-running, unstabilized pulse rate
Implementation Method 2
coupled with a sampling rate set at least ten times the pulse rate, and a phase-locked or asynchronously adjusted sampling process
Implementation Method 3
a sampling rate set at least ten times the pulse rate, and a phase-locked or asynchronously adjusted sampling process
Implementation Method 4
enabling precise distance measurement with simple components
Data Source
Figure 1a~1b
Figure 2~3
Figure 4
AI summary
The invention relates to an electro-optical rangefinder (1) and a distance measurement method, wherein a distance to a target (100) is measured based on the time of flight using radiation pulses (12, 13) which are emitted at a pulse rate. Received radiation pulses (13) are digitized by sampling, wherein the sampling rate (S) is set depending on the pulse rate (P, 22), and a digitized signal (13D) is generated by sampling over the received signals (13a, 13b, 13c ... 13x) of a plurality x of received radiation pulses (13).