Rectangular Waveform Modulation for Distance Measurement
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Solution Overview
Problem
Existing laser scanners face challenges in achieving high signal/noise ratio and large unambiguity range due to reduced light intensity from amplitude modulation, particularly when measuring objects with low reflectivity, leading to longer measurement times and reduced accuracy.
Innovation Solution
The use of a rectangular-waveform modulation signal with varying temporal intervals and pulse numbers, combined with multiple modulation frequencies, optimizes light power utilization, enabling high accuracy and large unambiguity range in distance measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the emission light beam is amplitude-modulated with a rectangular-waveform modulation signal having a first, relatively high modulation frequency, then the distance measurement accuracy is improved, but the unambiguity range decreases
Solution Approach 1:
The modulation signal is segmented into groups of rectangular pulses with varying temporal intervals and varying numbers of pulses per group. This segmentation creates multiple effective modulation frequencies within a single signal structure, allowing the system to achieve both high measurement accuracy (through high-frequency pulse groups) and large unambiguity range (through low-frequency pulse groups with larger intervals)
Solution Approach 2:
The modulation signal dynamically varies the temporal intervals between pulse groups and the number of pulses within each group. This dynamic variation allows the system to adaptively optimize the balance between measurement accuracy and unambiguity range, effectively resolving the contradiction between high modulation frequency (accuracy) and low modulation frequency (unambiguity range)
2Length of stationary object
If the emission light beam is amplitude-modulated with a lower, second modulation frequency to increase unambiguity range, then the unambiguity range is increased, but the signal/noise ratio is reduced
Solution Approach 1:
The modulation signal is divided into distinct pulse groups where each group contains multiple rectangular pulses. By varying the number of pulses per group and the intervals between groups, the system maintains high peak light intensity (improving signal/noise ratio) while creating effective low-frequency modulation components (expanding unambiguity range)
Solution Approach 2:
The modulation signal employs periodic pulse groups with varying characteristics. The periodic structure ensures sufficient light intensity for reliable detection (maintaining signal/noise ratio) while the varying periods create multiple effective modulation frequencies that expand the unambiguity range without sacrificing measurement reliability
3Length of stationary object
If the emission light beam is modulated alternately with higher and lower modulation frequencies, then the unambiguity range is increased, but the measurement time is lengthened
Solution Approach 1:
Multiple modulation frequencies are merged into a single composite modulation signal rather than applying them sequentially. The signal combines high-frequency pulse groups (for accuracy) and low-frequency pulse groups (for unambiguity range) in one continuous measurement cycle, eliminating the need for separate measurement passes and significantly reducing total measurement time
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 signal/noise ratio and unambiguity range, allowing for precise distance measurement with improved light power utilization and reduced measurement times, even for objects with low reflectivity.
Implementation Method 1
the emission light beam is amplitude-modulated with a rectangular-waveform modulation signal having a first, relatively high modulation frequency
Implementation Method 2
the propagation time is determined on the basis of a phase shift of the modulation signal in the reception light beam relative to the modulation signal in the emission light beam
Implementation Method 3
receives a reception light beam reflected from an object
Implementation Method 4
The distance between the measuring head and the object is determined from the propagation time of the emission light beam and of the reception light beam
Data Source
AI summary
A method for determining a distance from an object may include emitting an emission light beam from a light emitter, receiving a reception light beam at a light receiver, and determining the distance on the basis of a propagation time of the emission and reception light beams. The reception light beam may arise as a result of reflection of the emission light beam at the object. The emission light beam may be amplitude-modulated with a rectangular-waveform modulation signal. The modulation signal may have a multiplicity of rectangular pulses which occur in a multiplicity of groups. The groups may occur at varying temporal intervals with respect to one another and have changing numbers of rectangular pulses.