Time-of-flight rangefinder MTA zone assignment
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Solution Overview
Problem
Modern pulse time-of-flight rangefinders face challenges in accurately assigning received pulses to their corresponding transmission pulses beyond a certain distance range, known as the Multiple Time Around (MTA) zone, leading to incorrect distance measurement results due to overlapping pulses.
Innovation Solution
A method that involves emitting a sequence of transmission pulses with varying intervals, generating candidate distances for each receive pulse based on preceding pulses, and determining a weighting value using distance and amplitude differences to select the most accurate distance measurement value, effectively resolving MTA zone assignment issues even in multi-target situations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high pulse repetition rates are used to quickly create distance measurement points, then productivity is improved, but the MTA zone size decreases causing incorrect pulse assignment beyond a certain distance
Solution Approach 1:
The patent divides the distance measurement process into multiple MTA zones by generating multiple candidate distances for each receive pulse. Each candidate distance is assigned to a specific MTA zone based on transmission pulse timing, allowing the system to handle reflections from different zones separately and correctly identify the valid distance measurement.
Solution Approach 2:
The patent uses feedback mechanisms by evaluating multiple candidate distances and selecting the valid one based on consistency checks with adjacent transmission pulses. The system feeds back the candidate distance information and uses weighting values to determine which candidate is the correct distance measurement, resolving the pulse assignment ambiguity.
2Length of stationary object
If high pulse power is used to extend measurement range, then the maximum measurable distance is improved, but the MTA problem worsens due to overlapping reflections from multiple zones
Solution Approach 1:
The patent adds a temporal dimension to distance measurement by considering multiple candidate distances corresponding to different MTA zones. Instead of measuring only the first reflection, the system evaluates reflections from multiple time-around zones, effectively utilizing the time dimension to extend the measurable distance range while managing interference through candidate evaluation.
Solution Approach 2:
The patent changes the parameter of pulse interval by using varying pulse intervals in the transmission pulse sequence. This variation helps distinguish between reflections from different MTA zones, allowing the system to identify and select the correct distance measurement even when multiple reflections are present.
3Measurement precision
If pulse intervals are varied to resolve MTA zone assignment, then measurement accuracy beyond MTA zone is improved, but device complexity increases due to multiple candidate evaluation
Solution Approach 1:
The patent applies partial action by generating a limited number of candidate distances (typically 2-3 candidates) for each receive pulse instead of evaluating all possible distances. This partial evaluation approach provides sufficient accuracy for most applications while keeping the computational complexity manageable.
Solution Approach 2:
The patent performs preliminary action by pre-calculating and storing transmission pulse timing information before receive pulse processing. This preliminary preparation allows the system to quickly generate and evaluate candidate distances without adding significant processing complexity during the measurement phase.
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 method provides robust and reliable MTA zone assignment and correct distance measurement values, enhancing accuracy and precision by utilizing amplitude information for pulse assignment, especially in situations with multiple reflections and distance jumps.
Implementation Method 1
measuring the time-of-flight of pulses reflected by the target, in particular laser pulses
Implementation Method 2
pulses reflected at the targets... light pulses, in particular laser pulses
Data Source
AI summary
The present disclosed subject matter relates to a method for measuring the distance of targets in the surroundings by way of a time-of-flight measurement of pulses reflected at said targets, in particular laser pulses, said method comprising: emitting a sequence of transmission pulses having varying pulse intervals, and receiving at least one receive pulse after each one of two different transmission pulses; for each receive pulse: generating a group of M candidate distances, each based on a different transmission pulse among M transmission pulses preceding the receive pulse, wherein each candidate distance is assigned to the corresponding transmission pulse on which it is based; for each candidate distance: determining a weighting value on the basis of at least the closest of the candidate distances assigned to such a transmission pulse which is adjacent to the transmission pulse to which the candidate distance being considered in this determining process is assigned; for each group: selecting the candidate distance with the highest weighting value as the distance measurement value of the receive pulse for which the group was generated.