Laser Scanner Signal Distortion Compensation

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Solution Overview

Problem

Conventional distance-measuring laser scanners face inaccuracies due to signal distortions and high dynamic range issues, leading to measurement errors, especially in environments with interference like fog, rain, or varying surface reflectivity.

Innovation Solution

The solution involves digitizing and sampling the entire received signal curve to accurately determine the peak position, using preprocessing techniques such as filtering and digital decompression to compensate for distortions, and selecting the relevant peak based on criteria like amplitude, width, and symmetry, allowing for precise distance measurement even in challenging conditions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the entire received signal curve is digitized and sampled to determine peak position, then measurement accuracy is improved, but device complexity increases

Engineering Contradiction:
Improvedistance measurement accuracyVSAvoidsignal processing complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent applies preliminary action by performing preprocessing operations (filtering, decompression) on the received signal before peak position determination. This prepares the signal in advance to remove distortions and artifacts, ensuring that the subsequent peak detection operates on cleaned data, thereby improving measurement accuracy without requiring complex real-time processing during peak detection

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The patent segments the signal processing into distinct stages: filtering to remove noise, digital decompression to correct dynamic range distortions, and peak position determination. This segmentation allows each processing stage to be optimized independently, managing overall system complexity while achieving high measurement precision through cumulative effect of multiple specialized processing steps

Inventive Principle:
Principle #1Segmentation

2Measurement precision

If preprocessing techniques like filtering and digital decompression are applied, then measurement accuracy is improved, but processing time increases

Engineering Contradiction:
Improvepeak position determination accuracyVSAvoidsignal processing time
Core Design Contradiction:
Measurement precisionVSLoss of time

Solution Approach 1:

The patent applies partial action by selectively applying preprocessing techniques only to the necessary portions of the signal. The filtering and digital decompression are applied with specific parameters optimized for the expected signal characteristics, processing only enough of the signal to achieve accurate peak detection without unnecessary additional processing that would waste time

Inventive Principle:
Principle #16Partial or excessive action

3Adaptability or versatility

If the scanner handles high dynamic ranges and environmental interferences, then outdoor capability is improved, but device complexity increases

Engineering Contradiction:
Improveoutdoor capabilityVSAvoidsignal processing complexity
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent uses digital decompression as an intermediary process between the raw received signal and the peak position determination. This intermediary step specifically addresses high dynamic range issues by correcting distortions introduced by limited bandwidth and dynamic range in the analog electronics, enabling the system to handle varying signal strengths from different surface reflectivities without requiring the entire system to be redesigned for extreme conditions

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent applies parameter changes through digital decompression, which transforms the signal parameters to correct for distortions. By changing the signal representation in the digital domain, the system can compensate for analog limitations and handle a wide dynamic range of reflected signal powers, enhancing outdoor capability across various environmental conditions

Inventive Principle:
Principle #35Parameter changes

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 measurement accuracy, reduces errors, and improves the scanner's outdoor capability by effectively handling high dynamic ranges and environmental interferences, enabling precise distance determination with lower statistical errors.

Implementation Method 1

a light receiving element (20), in particular a photodiode, is provided, which converts the received signal into an electrical signal

Methodology Applied
Scientific EffectPhotoelectric Effect: Photoelectric Effect

Implementation Method 2

the light propagation time between the transmission and reception of a light signal is evaluated

Methodology Applied
Scientific EffectTime of Flight: Time of Flight

Implementation Method 3

a laser source (12) is provided, which emits light pulses

Methodology Applied
Scientific EffectLight: Light

Data Source

PatentEP2182378B1Laser scanner to measure distance
Publication Date: 2012.07.18 SICK AG
  • EP2182378B1 patent drawingFigure 1~2b
  • EP2182378B1 patent drawingFigure 3~4
  • EP2182378B1 patent drawingFigure 5a~5b

AI summary

A distance-measuring laser scanner (10) is described, comprising a laser light source for emitting a light signal (12, 32), a light receiving element (20) for receiving a received signal (18, 34), an analog-to-digital converter (24), and a memory (26) for digitizing and recording the received signal (34). The laser scanner (10) further comprises an evaluation unit (30) designed for selecting a peak of the received signal (34) and determining distances from the travel time of the light signal based on the peak.A preprocessing unit (28) is provided which is designed to at least partially compensate for distortions of the shape and/or position of the peak by including a model, wherein the model is calibrated with a transfer function and/or other prior knowledge about a receiving electronics of the light receiving element (20) so that the peak can be reconstructed for more accurate time-of-flight determination.